KR20160026846A - Biaxially oriented polyester film - Google Patents

Abstract

The object of the present invention is to provide a biaxially oriented polyester film that is excellent in moldability and uniformity in the direction of width and can be preferably used for molding and optical applications.
The biaxially oriented polyester film of the present invention has a stress at 10% elongation in the film MD direction at 150 DEG C of 5 to 30 MPa, a heat shrinkage rate at 150 DEG C in the film MD direction of 5% The maximum value of the orientation angle of the film at a width of 1000 mm (the smaller angle of the angle formed by the main alignment axis with the film TD direction or the film MD direction) is 20 degrees or less.

Description

Biaxially oriented polyester film {BIAXIALLY ORIENTED POLYESTER FILM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film, and more particularly to a biaxially oriented polyester film which is particularly suitably used for molding and optical applications.

In recent years, as environmental consciousness has increased, there has been an increasing demand for solventless painting, plating substitution, and the like in construction materials, automobile parts, cellular phones, and electric appliances.

Several proposals have been made for a polyester film for molding used in such decorative methods. For example, there has been proposed a polyester film for molding that satisfies a high-range moldability indicating a low molding stress and a low storage elastic modulus even at a low temperature (see, for example, Patent Document 1).

Further, a polyester film which has both a high storage modulus at low temperature and a low heat stress at low temperature and moldability has been proposed (for example, see Patent Document 2).

In addition, since liquid crystal displays are used in large-sized televisions, personal computers, tablets, smart phones, and the like, stable demand is expected in the future. Various films such as a surface protective film, a release film, a retardation film and a process film are used for the polarizing plate constituting the liquid crystal display, but since the uniformity of physical properties in the width direction is very important, some proposals have been made as biaxially stretched polyester films have. For example, there has been proposed a polyester film for polarizing film bonding in which the orientation angle and the thickness unevenness are reduced in order to satisfy the uniformity in the width direction (see, for example, Patent Document 3). In addition, with the expansion of smart devices such as smart phones and tablet terminals, the demand for thinning of liquid crystal displays is increasing, and the polarizers and phase difference layers are also becoming higher quality and thinner. For this reason, in order to attain high definition and thin film formation of the retardation layer, a process of developing a process for achieving high definition and thinning of the retardation layer by applying a retardation layer to the process film and forming the retardation layer together with the process film is under development.

Japanese Patent Application Laid-Open No. 2005-290354 International Publication No. 2012-005097 Japanese Patent Application Laid-Open No. 2002-40249

However, although the films described in Patent Documents 1 and 2 are excellent in moldability, since the physical properties in the width direction are not uniform, when used for decorative molding of a large member or the like, unevenness in molding and unevenness in deformation after molding may occur. Further, when it is intended to be used as a process film of a polarizing plate / retardation layer, the physical properties are not uniform, and characteristic irregularities may occur.

Further, the film described in Patent Document 3 is excellent in uniformity in the width direction, but has insufficient moldability. Therefore, it is difficult to use it for decorating a deep shape or for forming a polarizing plate and a phase plate together with a process film.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the problems of the prior art described above. That is, it is an object of the present invention to provide a biaxially oriented polyester film that is excellent in moldability and uniformity in the direction of width, and can be suitably used for molding and optical applications.

In order to solve these problems, the gist of the present invention is as follows.

A stress at 10% elongation in the machine direction (hereinafter referred to as MD) of the film at 150 ° C of 5 to 30 MPa, a heat shrinkage of 5% or less at 150 ° C in the film MD direction, (The angle between the main orientation axis and the direction of the film TD (Transverse Direction, hereinafter referred to as TD) or the direction of the film MD) of 20 占 or less is 20 占 or less, Ester film. However, the orientation angle of the film having a width of 1000 mm is the direction of the main alignment axis at an arbitrary position of the film in the TD direction, and a width of 550 mm in each of the two directions along the TD direction around the above position is taken as 1100 mm Wherein the film has a width of 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm ), And the maximum value among them is obtained. The direction perpendicular to the TD direction in the same film plane is the MD direction.

(Effects of the Invention)

Since the biaxially oriented polyester film of the present invention is low in molding stress at 150 占 폚 and therefore has a good anti-wetting property and has a low heat shrinkage rate at 150 占 폚, film deformation during coating and drying is small, Can be suitably used for shaping and decorating purposes of construction materials, mobile devices, electric appliances, automobile parts, and organic parts, and optical films such as polarizing plates, because the maximum value of the orientation angle of the polarizer is small.

The polyester constituting the biaxially oriented polyester film of the present invention is a generic name of a polymer compound having ester bond as a principal bond in the main chain. The polyester resin is usually obtained by polycondensation reaction of a dicarboxylic acid or a derivative thereof and a glycol or a derivative thereof.

In the present invention, at least 60 mol% of the glycol units constituting the polyester are structural units derived from ethylene glycol from the viewpoints of moldability, appearance, heat resistance, dimensional stability and economical efficiency, and 60 mol% or more of the dicarboxylic acid units are terephthalic acid Derived structural units. Herein, the dicarboxylic acid unit (structural unit) or the diol unit (structural unit) means a divalent organic group excluding a part to be removed by polycondensation, and in summary, it is represented by the following general formula.

Dicarboxylic acid unit (structural unit): -CO-R-CO-

Diol unit (structural unit): -O-R'-O-

(Wherein R and R 'are divalent organic groups)

When a tri- or higher-valent carboxylic acid or an alcohol such as a trimellitic acid unit or a glycerin unit, or an alcohol or a derivative thereof is contained, a carboxylic acid or an alcohol unit (structural unit) having three or more valences is also removed by polycondensation Quot; means a trivalent or more organic group in which a moiety is excluded.

Examples of the glycol or derivative thereof to be used in the present invention include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, , Aliphatic dihydroxy compounds such as 5-pentanediol, 1,6-hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, 1,4 - alicyclic dihydroxy compounds such as cyclohexane dimethanol and spiroglycol, aromatic dihydroxy compounds such as bisphenol A and bisphenol S, and derivatives thereof. Among them, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol and 1,4-cyclohexanedimethanol are preferably used from the viewpoints of moldability and handleability.

Examples of dicarboxylic acids or derivatives thereof to be used in the present invention include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfone dicar Aliphatic dicarboxylic acids such as benzoic acid, succinic acid, adipic acid, sebacic acid, dimeric acid, maleic acid, and fumaric acid; aromatic dicarboxylic acids such as benzoic acid, Alicyclic dicarboxylic acids such as dicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, oxycarboxylic acids such as paraoxybenzoic acid, and derivatives thereof. Examples of derivatives of dicarboxylic acids include dimethyl terephthalate, diethyl terephthalate, terephthalic acid 2-hydroxyethyl methyl ester, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, maleic acid Diethyl, dimer acid dimethyl and the like. Among them, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and esterified products thereof are preferably used from the viewpoints of moldability and handleability.

The biaxially oriented polyester film of the present invention has a stress at 10% elongation in the film MD direction at 150 占 폚 of not less than 5 MPa and not more than 30 MPa at 150 占 폚 in order to satisfy the formation of a complicated shape, MPa or less.

Here, in the present invention, the evaluation of the 1000 mm wide film is carried out in such a manner that the main alignment axis direction at an arbitrary position of the film is the TD direction and the position is defined as the center (hereinafter also referred to as the TD direction center) And 500 mm width (1000 mm width) in two directions along the TD direction from the TD direction center of the film having the width of 1100 mm was evaluated. The polyester film of the present invention preferably has a size of 10 m or more in the MD direction and 1100 mm or more in the TD direction.

The stress at 10% elongation in the film MD direction at 150 占 폚 is the stress at which a film sample cut into a rectangle frame with a test length of 50 mm was set in advance at 150 占 폚 and a film sample was set. After 90 seconds of preheating, / Min < / RTI > at a strain rate of 10%. In addition, the evaluation was performed by taking the main alignment axis direction at an arbitrary position of the film in the TD direction, taking its position as the center (hereinafter also referred to as the TD direction center), and measuring 550 mm width in two directions along the TD direction (A direction) from the center of the TD direction, the direction (B direction) opposite to the A direction in the TD direction from the TD direction center, And the average value of the 15 values was used as a stress at 10% elongation in the film MD direction at 150 ° C. From the viewpoints of moldability and dimensional stability, the stress at 10% elongation in the film MD direction at 150 占 폚 is more preferably 6 MPa or more and 20 MPa or less, and most preferably 7 MPa or more and 15 MPa or less.

In the biaxially oriented polyester film of the present invention, there is no particular limitation on the method of setting the stress in the above range within a range of 10% elongation in the MD direction at 150 DEG C, but for example, And at least 60% by mole of an ethylene glycol component as a glycol component, and at least one of a diethylene glycol component, a 1,3-propanediol component, a 1,4-butanediol component, a 1,4-cyclohexanedimethanol component and a neopentyl glycol component And it is preferable that it contains one or more kinds of glycol components. Among them, it is preferable to contain at least one or more of diethylene glycol component, 1,4-cyclohexane dimethanol component, and neopentyl glycol component. Further, it is preferable that the dicarboxylic acid component constituting the polyester film of the present invention contains a terephthalic acid component in an amount of 60 mol% or more, and at least one of an isophthalic acid component and a 2,6-naphthalenedicarboxylic acid component Component. ≪ / RTI >

In the biaxially oriented polyester film of the present invention, as a particularly preferable constitution wherein the stress at 10% elongation in the film MD direction at 150 DEG C falls within the above range, ethylene glycol component is contained in an amount of 85 mol% or more and less than 97 mol% , At least one of diethylene glycol component, 1,4-cyclohexanedimethanol component and neopentyl glycol component is contained in an amount of 3 mol% or more and less than 15 mol%, and 85 mol% or more as a dicarboxylic acid component Terephthalic acid component. More preferably, at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component and a neopentyl glycol component is contained in an amount of not less than 90 mol% and not more than 95 mol% as an ethylene glycol component, % Or more and less than 10 mol% of the dicarboxylic acid component, and 90 mol% or more of the dicarboxylic acid component is a terephthalic acid component, and more preferably, 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component.

In the biaxially oriented polyester film of the present invention, the above composition is used in order to set the stress at 10% elongation in the film MD direction at 150 ° C within the above-mentioned range, and the higher one of the planar orientation coefficients And a planar orientation coefficient of 0.111 or more and 0.17 or less.

A method of setting the higher plane orientation coefficient of the film between both sides of the film to 0.111 or more and 0.17 or less is not particularly limited. For example, there is a method in which the film is stretched to 9.8 times or more and 13.5 times or less have. The stretching temperature is preferably not lower than 70 ° C and not higher than 150 ° C, and the heat treatment temperature after biaxial stretching is preferably not lower than 200 ° C and not higher than 240 ° C at the highest temperature.

In addition, the biaxially oriented polyester film of the present invention needs to have a heat shrinkage ratio of 5% or less in the film MD direction at 150 ° C. Here, the heat shrinkage ratio in the MD direction at 150 deg. C means a heat shrinkage rate at 150 deg. C, in which the film is cut in a rectangular shape having a length of 150 mm and a width of 10 mm in the MD direction and a line is drawn at intervals of 100 mm ), And the rate of change of the distance between the lines before and after the heat treatment was performed after 30 minutes of installation in a hot air oven heated to 150 캜 by suspending 3 g of weight. In addition, the evaluation was performed by taking the main alignment axis direction at an arbitrary position of the film in the TD direction, taking its position as the center (hereinafter also referred to as the TD direction center), and measuring 550 mm width in two directions along the TD direction (A direction) in the TD direction from the center of the film of 1100 mm width, 500 mm in the direction (B direction) opposite to the A direction in the TD direction from the center, Position, and the average value of the 15 values was defined as the heat shrinkage rate in the film MD direction at 150 deg. When the biaxially oriented polyester film of the present invention is coated with a functional coating film such as a hard coat layer, a decorative layer and a retardation layer on the film by setting the heat shrinkage rate at 150 ° C in the MD direction to 5% or less, Problems such as deterioration of the function of the coating film due to shrinkage of the film and lowering of the flatness of the film can be suppressed. The heat shrinkage rate at 150 占 폚 in the MD direction is more preferably 4% or less, and most preferably 3% or less.

As a method for setting the heat shrinkage ratio at 150 占 폚 in the MD direction to 5% or less, for example, a method of adjusting heat treatment conditions of the film after biaxial stretching can be mentioned. From the viewpoints of dimensional stability and film quality, the heat treatment temperature after biaxially stretching is preferably 200 ° C to 240 ° C, more preferably 210 ° C to 235 ° C , And most preferably from 215 ° C to 230 ° C. In addition, the heat treatment temperature of the biaxially oriented polyester film of the present invention is determined by a DSC curve measured at a heating rate of 20 ° C / minute in a nitrogen atmosphere in a differential scanning calorimeter (DSC) Can be obtained by an endothermic peak.

The preferable heat treatment time is arbitrarily set within a range of 5 to 60 seconds, but it is preferably 10 to 40 seconds, more preferably 15 to 30 seconds from the viewpoints of moldability, dimensional stability, color tone and productivity. Further, the heat treatment can be performed while relaxing in the longitudinal direction and / or the width direction, thereby reducing the heat shrinkage rate. The relaxation rate (relaxation rate) at the time of relaxation in the heat treatment is preferably 1% or more, more preferably 1% or more and 10% or less from the viewpoint of dimensional stability and productivity, and most preferably 1% or more and 5% or less.

Also, a method of performing heat treatment under two or more stages is also highly desirable. It is possible to further reduce the heat shrinkage rate by performing heat treatment after relaxation in the longitudinal direction and / or width direction at a temperature lower than the heat treatment temperature after the heat treatment at a high temperature of 200 ° C to 240 ° C. The second heat treatment temperature at this time is preferably 120 ° C to 200 ° C, more preferably 150 ° C to 180 ° C.

In the biaxially oriented polyester film of the present invention, the maximum value of the orientation angle of the film having a width of 1000 mm (the smaller angle between the main orientation axis and the film TD direction or the film MD direction) is 20 Deg. Here, the maximum value of the orientation angle of a film having a width of 1000 mm is defined as the direction of the main alignment axis at an arbitrary position of the film in the TD direction, and a width of 550 mm 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm from the arbitrary point in the TD direction (one side is referred to as A direction and the other as B direction) , The orientation angle is measured (21 points) at positions of 350 mm, 400 mm, 450 mm, and 500 mm (1000 mm width), and the maximum value among these is obtained.

The maximum value of the orientation angle of the film having a width of 1000 mm is more preferably 15 degrees or less, and most preferably 10 degrees or less, from the viewpoint of uniformity in the widthwise direction.

Here, a method of setting the maximum value of the orientation angle of the film of 1000 mm width to be 20 DEG or less is not particularly limited, and for example, a method of reducing bowing during film formation can be mentioned. Concretely, there are a method of heat treatment after being cooled to a glass transition temperature or lower of the polyester once in the width direction, a method of providing a nip roll after stretching in the width direction, a method of raising the width in a plurality of zones A method of heating and cooling stepwise by dividing a heat treatment into a plurality of zones, a method of forming a temperature distribution in a width direction and guiding to a heat treatment zone, and a method of fine stretching in a width direction in a heat treatment chamber.

Further, the biaxially oriented polyester film of the present invention can be produced by coating a film with a functional coating film such as a hard coat layer, a decorative layer and a retardation layer and drying the film at 190 ° C It is preferable that the heat shrinkage ratio in the film MD direction and the TD direction is 5% or less. Even at a high temperature such as 190 占 폚, it is possible to maintain high dimensional stability even when the drying temperature of the functional coating film needs to be raised by lowering the heat shrinkage rate in the film MD and TD directions.

As a method of setting the heat shrinkage ratio in the film MD direction and the TD direction at 190 占 폚 to 5% or less, for example, a method of making the heat shrinkage ratio at 150 占 폚 in the MD direction of the film 5% And a method of adjusting the heat treatment conditions. For example, the first heat treatment is performed at 230 占 폚, the second heat treatment is performed at a relaxation rate of 3% at 200 占 폚, the third heat treatment is performed at a relaxation rate of 2% Lt; 0 > C. The heat shrinkage ratio in the film MD direction / TD direction at 190 占 폚 is preferably 5% or less / 4% or less, and most preferably 5% or less / 3% or less.

Further, the biaxially oriented polyester film of the present invention can be produced by coating a functional film such as a hard coat layer, a decorative layer and a retardation layer on a film, and drying the film with a thickness of 1000 mm from the viewpoint of heat resistance and anti- Temperature Modulation of Film The lowest temperature of the glass transition temperature determined by DSC is preferably 80 ° C or more and 110 ° C or less. Here, the glass transition temperature determined by the temperature-modulated DSC of the film at a width of 1000 mm is defined as the direction of the main alignment axis at an arbitrary position of the film in the TD direction, and along the TD direction 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm and 450 mm from the arbitrary point on both ends in the TD direction, The glass transition temperature is measured at a position of 500 mm (1000 mm width), and indicates the lowest temperature in the glass transition temperature. The glass transition temperature determined by the temperature-modulated DSC is obtained by measuring the film in a nitrogen atmosphere at a temperature of 2 占 폚 / min in a range of 0 占 폚 to 200 占 폚 and a temperature modulation period of 60 seconds in a sinusoidal wave with a temperature modulation amplitude of 1 占 폚 (1) mid-point glass transition temperature Tmg " of JIS K 7121 (1987), " 9.3 Determination of glass transition temperature ", in the change part on the step of the reversible component temperature- . From the viewpoint of heat resistance and moldability, the glass transition temperature determined by the temperature-modulated DSC is more preferably 85 ° C or more and 110 ° C or less, and most preferably 85 ° C or more and 100 ° C or less.

In the present invention, a method of controlling the minimum temperature of the glass transition temperature determined by DSC of the temperature-modulated film of a film at a width of 1000 mm is not particularly limited. However, A method of making a preferable composition such that the stress at 10% elongation in the film MD in the film MD is not less than 5 MPa and not more than 30 MPa and the micro-stretching not less than 2% in the heat treatment step after stretching in the transverse direction is preferably used.

In addition, the biaxially oriented polyester film of the present invention can be produced by coating a film with a functional coating film such as a hard coat layer, a decorative layer and a retardation layer, securing the function of the coating film at the time of drying, securing film flatness, It is preferable to satisfy the following formula (I) in view of functional uniformity.

(SA _MD + SB _MD ) / (SC _MD 2)? 1.2 (I)

However, SA _MD : 190 占 폚 heat shrinkage ratio in the MD direction at a position of 500 mm in any one direction (A direction) from the center of the 1100 mm wide film in the TD direction to the TD direction

SB _MD : Heat shrinkage at 190 占 폚 in MD direction at a position of 500 mm in a direction opposite to A direction in the TD direction (from the center in the width direction of the 1100 mm wide film)

SC _MD : 190 占 폚 heat shrinkage rate in the MD direction at the center of the 1100 mm wide film in the TD direction.

A width of 550 mm in each of the two directions along the TD direction was defined as the center of the main alignment axis at any position of the film in the TD direction and its position as the center (hereinafter also referred to as the TD direction center) (A direction) in the TD direction from the center, a position of 500 mm in the TD direction in the direction opposite to the A direction in the TD direction from the center And the heat shrinkage rate at 190 占 폚 is measured five times for each sample cut into a rectangle having a length of 150 mm (A direction or B direction) 占 10 mm width with respect to three points at a position of 500 mm.

(I) is satisfied means that the difference in the MD heat shrinkage ratio in the TD direction of the 1000 mm wide film is small, and it means that the functional coating film is applied to the film to cause unevenness of the functional coating film in the direction of drying, It becomes possible to inhibit it. (I) 'is more preferable from the viewpoint of physical property uniformity in the TD direction, and it is most preferable to satisfy the expression (I)'.

(SA _MD + SB _MD ) / SC _MD x 2? 1.15 (I)

(SA _MD + SB _MD ) / SC _MD x 2? 1.1 (I)

The method of satisfying the formula (I) of the biaxially oriented polyester film of the present invention is not particularly limited, but the maximum value of the orientation angle of the film having a width of 1000 mm is set to 20 ° or less.

It is also effective to set the elongation peak temperature in the film MD direction at 60 ° C or higher when the temperature is raised from 25 ° C to 200 ° C at a heating rate of 5 ° C / min at a load of 19.6mN by thermal mechanical analysis (TMA). Herein, the elongation peak temperature in the film MD direction refers to the temperature at which the elongated film shifts to the shrinkage behavior in accordance with the elevated temperature. In the present invention, the temperature at which the elongation behavior shifts to the shrinkage behavior for the first time when the temperature is elevated from 25 占 폚 to 200 占 폚 is set as the elongation peak temperature in the film MD direction in some cases . The measurement was carried out in the same manner as in the case of the 1100 mm wide film [the direction of the main alignment axis at any position of the film was the TD direction and the position thereof was taken as the center (hereinafter also referred to as the TD direction center) (A direction) in the TD direction from the center, a position of 500 mm in the TD direction in the direction opposite to the A direction in the TD direction (from the center in the B direction ) Is performed three times in each of MD and TD for three points at a position of 500 mm in the longitudinal direction, and an average value of nine values measured for MD and TD is employed. In order to set the elongation peak temperature in the longitudinal direction of the film to 60 ° C or more when the temperature is raised from 25 ° C to 200 ° C at a heating rate of 5 ° C / min at a load of 19.6mN, the stretching magnification in the longitudinal direction at the film- Fold, preferably 2.9 to 3.3 times. As a result of various examinations, the inventors of the present invention have found that when the stretching magnification in the longitudinal direction of the film is in the above-mentioned range, the temperature rise rate from 25 占 폚 to 200 占 폚 at a rate of 5 占 폚 / The elongation peak temperature in the longitudinal direction of the film can be set to 60 DEG C or more.

The biaxially oriented polyester film of the present invention preferably satisfies the following formula (II).

(SA _TD + SB _TD ) / SC _TD 2? 1.2 (II)

However, SA _TD : 1100 mm wide film [having a main alignment axis direction at an arbitrary position of the film in the TD direction and a center thereof (hereinafter also referred to as the TD direction center) 190 占 폚 heat shrinkage ratio in the TD direction at a position of 500 mm in any one direction (A direction) in the TD direction from the center in the TD direction of the film obtained by taking a width of 550 mm each and having a width of 1100 mm

SB _TD : 190 占 폚 in the TD direction at the position of 500 mm in the direction opposite to the direction A in the TD direction (direction B) from the center in the TD direction of the 1100 mm width film

SC _TD : 190 ° C heat shrinkage in the TD direction at the center of the 1100 mm wide film in the TD direction.

(II) is satisfied means that the difference of the TD heat shrinkage ratio in the TD direction of the 1000 mm wide film is small, and the functional coating film is applied to the film and the non-uniformity of the functional coating film in the direction when the film is dried, It becomes possible to inhibit it. From the viewpoint of physical property uniformity in the TD direction, it is more preferable to satisfy the formula (II), and it is most preferable to satisfy the formula (II).

(SA _TD + SB _TD ) / SC _TD x 2? 1.15 (II)

(SA _TD + SB _TD ) / SC _TD x 2? 1.1 (II) "

The method for satisfying the formula (II) of the biaxially oriented polyester film of the present invention is not particularly limited, but the maximum value of the orientation angle of the film having a width of 1000 mm is set to 20 ° or less. Further, when the temperature is elevated from 25 占 폚 to 200 占 폚 at a heating rate of 5 占 폚 / min at a load of 19.6 mN by thermal mechanical analysis (TMA), the elongation peak temperature in the TD direction of the film becomes 70 占 폚 or more, It becomes easier to do. Here, the elongation peak temperature in the film TD direction refers to the temperature at which the elongated film shifts to the shrinkage behavior in accordance with the temperature rise. The measurement was carried out on a 1100 mm wide film (the main alignment axis direction at an arbitrary position of the film is referred to as the TD direction, and its position is defined as the center (hereinafter also referred to as the TD direction center) (A direction) in the TD direction from the center, a position of 500 mm in the TD direction in the direction opposite to the A direction in the TD direction (from the center in the B direction ), Three times for MD and TD for three points, respectively, and an average value of nine points measured for MD and TD is adopted. In the present invention, the temperature at which the elongation behavior shifts to the shrinkage behavior for the first time when the temperature is elevated from 25 占 폚 to 200 占 폚 is set as the elongation peak temperature in the film TD direction, although there is a case where the film is once shifted to the elongation behavior after shrinkage. In order to set the elongation peak temperature in the TD direction of the film when the temperature is raised from 25 DEG C to 200 DEG C at a heating rate of 5 DEG C / min at a load of 19.6 mN by thermal mechanical analysis (TMA) at 70 DEG C or higher, Is 2.8 times to 3.4 times, and further it is effective to enhance the micro-stretching in the heat treatment step after the stretching in the width direction.

It is also effective that the biaxially oriented polyester film of the present invention is subjected to off-annealing as a method of satisfying the formulas (I) and (II). That is, the polyester film once wound is subjected to heat treatment again. Since the off-annealing temperature is 140 占 폚 or higher and 200 占 폚 or lower and the transverse direction is free, the difference in thermal shrinkage in the width direction is eliminated, thereby satisfying the expressions (I) and (II). The temperature for the off-annealing treatment is preferably 150 占 폚 to 200 占 폚, and most preferably 160 占 폚 to 200 占 폚.

The biaxially oriented polyester film of the present invention has a stress at 10% elongation in the film MD direction at 150 占 폚 of 5 to 30 MPa, a heat shrinkage rate at 150 占 폚 in the film MD direction of 5% It is very important that the maximum value of the orientation angle of the film of width is equal to or less than 20 degrees. If the stress at 10% elongation in the film MD direction at 150 占 폚 is set to 5 MPa or more and 30 MPa or less, the heat shrinkage rate in the MD direction at 150 占 폚 may become high and the film orientation angle It may be difficult to control the maximum value to 20 DEG or less. As a method for solving this dilemma, the biaxially oriented polyester film of the present invention is a laminated film structure having a polyester A layer and a polyester B layer, and the polyester A layer is a structure having at least one outermost layer .

Further, in the case of a laminated film having a polyester A layer and a polyester B layer in the present invention, the layer having a higher melting point is referred to as a polyester A layer.

The polyester film of the present invention has an A-layer having a high melting point and a B-layer having a melting point lower than that of the A-layer so that the A-layer is a rigid layer and the heat shrinkage rate in the film MD direction at 150 캜 is maintained at 5% And the maximum value of the orientation angle of the film of 1000 mm width can be easily set to 20 or less so as to satisfy the uniformity of physical properties in the transverse direction while the layer B serves as a layer having high mobility of 150 The stress at 10% elongation in the MD direction of the film can be easily set to 5 MPa or more and 30 MPa or less, and it is possible to satisfy the characteristics that are difficult to be compatible with each other in the single-layer structure . The A layer in the polyester film of the present invention preferably has a planar orientation coefficient of 0.111 or more and 0.17 or less, more preferably 0.13 or more and 0.17 or less, and most preferably 0.145 or more and 0.17 or less, from the viewpoints of dimensional stability and physical properties uniformity in the transverse direction Do.

From the viewpoint of curl suppression of the film, the biaxially oriented polyester film of the present invention has a three-layer structure of layer A / layer B / layer A in the case of a laminated polyester film having a polyester A layer and a polyester B layer .

In the case of the laminated film having the polyester A layer and the polyester B layer in the biaxially oriented polyester film of the present invention, the stress at 10% elongation in the film MD direction at 150 ° C is not less than 5 MPa and not more than 30 MPa, A polyester A layer for satisfying the properties such that the heat shrinkage rate in the MD direction of the film at 150 ° C is 5% or less and the maximum value of the orientation angle of the film of 1000 mm width is 20 ° or less at the same time, Examples of the form are as follows.

At least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and neopentyl glycol is contained in an amount of 1 mol% or more, and a glycol component of the polyester A layer is contained in an amount of 90 mol% or more and less than 99 mol% Or more and less than 10 mol%, and at least 90 mol% of the dicarboxylic acid component is a terephthalic acid component. More preferably, at least one of the diethylene glycol component, the 1,4-cyclohexanedimethanol component and the neopentyl glycol component is contained in an amount of not less than 95 mol% and not more than 99 mol%, as an ethylene glycol component, % Or more and less than 5 mol% of the dicarboxylic acid component and 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component, and more preferably 98 mol% or more of the dicarboxylic acid component is the terephthalic acid component.

At least one of the diethylene glycol component, the 1,4-cyclohexanedimethanol component and the neopentyl glycol component is contained in an amount of not less than 5 mol % Or more and less than 20 mol%, and 90 mol% or more as a dicarboxylic acid component is a terephthalic acid component. More preferably, at least one of a diethylene glycol component, a 1,4-cyclohexane dimethanol component, and a neopentyl glycol component is contained in an amount of not less than 85 mol% and not more than 95 mol% as an ethylene glycol component, more preferably not less than 5 mol% By mole or more and less than 15% by mole of the dicarboxylic acid component and 95% by mole or more of the dicarboxylic acid component is a terephthalic acid component, and more preferably 98% by mole or more of the dicarboxylic acid component is the terephthalic acid component.

Next, an example of a specific production method of the biaxially oriented polyester film of the present invention is described, but the present invention is not limited to these examples.

In the case of a laminated polyester film having a polyester A layer and a polyester B layer, it is preferable that the polyester A used in the polyester A layer is composed of a polyethylene terephthalate resin (a) and a 1,4-cyclohexanedimethanol copolymer polyethylene terephthalate The phthalate resin (b) is weighed at a predetermined ratio. Further, the polyester terephthalate resin (c) and the 1,4-cyclohexane dimethanol copolymerized polyethylene terephthalate resin (d) as the polyester B to be used for the polyester B layer are metered at a predetermined ratio.

Then, the mixed polyester resin is supplied to a vent type twin-screw extruder and melt-extruded. At this time, it is preferable to control the oxygen concentration in the extruder to 0.7% by volume or less and the resin temperature to be 265 to 295 DEG C in a circulating nitrogen atmosphere. Subsequently, foreign matters are removed through the filter and the gear pump, and the amount of extrusion is homogenized, and the sheet is discharged onto the cooling drum from the T die. At that time, an electrostatic application method in which a cooling drum and a resin are adhered to each other by electrostatic using a high voltage electrode, a casting method in which a water film is formed between a casting drum and a polymer sheet to be extruded, a casting drum temperature, (Glass transition point -20 占 폚), or by a method in which a plurality of these methods are combined, the sheet-like polymer is brought into close contact with the casting drum and cooled and solidified to obtain an unstretched film. Among these casting methods, when polyester is used, a method of applying a static electricity from the viewpoint of productivity and planarity is preferably used.

The biaxially oriented polyester film of the present invention needs to be a biaxially oriented film in view of heat resistance and dimensional stability. The biaxial oriented film can be obtained by a sequential biaxial stretching method in which an unoriented film is stretched in the longitudinal direction, followed by stretching in the width direction, or stretching in the width direction, and stretching in the longitudinal direction, Direction and a simultaneous biaxial stretching method in which the stretching direction is substantially simultaneous.

The draw ratio in this stretching method is preferably 2.8 times or more and 3.4 times or less, more preferably 2.9 times or more and 3.3 times or less, in the longitudinal direction. The stretching speed is preferably 1,000% / min to 200,000% / min or less. The stretching temperature in the longitudinal direction is preferably 70 占 폚 or more and 90 占 폚 or less. The stretching magnification in the width direction is preferably 3.1 to 4.5 times, more preferably 3.5 to 4.2 times. The stretching speed in the width direction is preferably not less than 1,000% / min and not more than 200,000% / min. Further, in order to make the maximum value of the orientation angle of the film of 1000 mm width 20 degrees or less while keeping the stress at 10% elongation at 150 deg. C in the film MD in the range of 5 MPa to 30 MPa, For example, a method in which the overall stretching temperature is 90 占 폚 or more and 120 占 폚 or less, the stretching middle temperature is 100 占 폚 or more and 130 占 폚 or less, and the stretching second half temperature is 110 占 폚 or more and 150 占 폚 or less , A method of raising the temperature in the order of the overall stretching temperature, the middle stretching temperature, and the latter half of the stretching temperature.

After the biaxial stretching, the film is subjected to heat treatment. The heat treatment can be carried out by an arbitrary method known in the art, such as heating in an oven or the like. The heat treatment is carried out at a temperature of not less than 120 ° C and not higher than the crystal melting peak temperature of the polyester but is preferably 200 ° C to 240 ° C, more preferably 210 ° C to 235 ° C, and most preferably 215 ° C to 230 ° C Do. Here, the preferable heat treatment temperature refers to the temperature at which the highest temperature among the heat treatment temperatures is performed after the biaxial stretching. The heat treatment time can be arbitrarily set within a range that does not deteriorate the characteristic, and is preferably 5 seconds or more and 60 seconds or less, more preferably 10 seconds or more and 40 seconds or less, and most preferably 15 seconds or more and 30 seconds or less . Further, it is preferable that the stress at 10% elongation in the film MD direction at 150 占 폚 is 5 to 30 MPa and the heat shrinkage rate at 150 占 폚 in the film MD direction is 5% A method of raising or lowering the temperature stepwise by dividing the heat treatment into a plurality of zones or a method of finely stretching in the width direction in the heat treatment step is preferably adopted. For example, it is possible to finely stretch the overall heat treatment temperature in a range of from 1% to 10%, preferably from 3% to 10% in the transverse direction at 180 ° C or more and 210 ° C or less, In the width direction is 1% or more and 10% or less, preferably 3% or more and 10% or less in the transverse direction, and the temperature of the latter half of the heat treatment is set to be 150 占 폚 or more and less than 200 占 폚. It is also preferable that the latter half of the heat treatment is carried out with a relaxation of 1% or more and 10% or less in order to lower the heat shrinkage rate. Further, in order to improve the adhesive strength to various processing layers such as the printing layer, the adhesive, the vapor deposition layer, the hard coat layer and the inner layer, at least one surface may be subjected to corona treatment or a reverse adhesion layer may be coated. As a method for forming the coating layer in inline in the film production process, there is a method in which the coating layer composition is dispersed in water on at least one uniaxially stretched film by uniformly applying the dispersion with water using a metal ring bar or a gravure roll, , And the thickness of the reverse adhesive layer is preferably 0.01 m or more and 1 m or less. Various additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, a pigment, a dye, an organic or inorganic particle, an antistatic agent, a nucleating agent and the like may be added to the backside adhesive layer. As the resin preferably used for the reverse adhesive layer, at least one resin selected from an acrylic resin, a polyester resin and a urethane resin is preferable from the viewpoint of adhesiveness and handleability. It is also preferable to use off-annealing under the condition of 140 to 200 ° C.

Since the biaxially oriented polyester film of the present invention is low in molding stress at 150 占 폚 and therefore has a good anti-wetting property and has a low heat shrinkage rate at 150 占 폚, film deformation during coating and drying is small, Is excellent in the uniformity of physical properties in the width direction. Therefore, it is possible to perform molding with the use of molding films such as building materials, mobile devices, electric appliances, automobile parts, and organic parts and optical films such as polarizing plates And can be suitably used in molding and processing applications. In particular, it is advantageously used for applications such as application of a phase difference layer to a process film and molding together with a process film in order to attain an optical application, specifically, a high definition and thinning of the phase difference layer.

Example

(1) Composition of polyester

The polyester resin and the film are dissolved in hexafluoroisopropanol (HFIP), and the content of the polyester resin and the film relative to each monomer residue component and by-product diethylene glycol can be quantified by ¹ H-NMR and ¹³ C-NMR. In the case of a laminated film, components constituting each layer can be collected and evaluated by shaving each layer of the film according to the lamination thickness. For the film of the present invention, the composition was calculated from the mixing ratio at the time of film production.

(2) intrinsic viscosity of polyester

The intrinsic viscosity of the polyester resin and the film was measured by dissolving the polyester in o-chlorophenol and using an Oswald viscometer at 25 ° C. In the case of a laminated film, the intrinsic viscosity of each layer can be evaluated by shaving each layer of the film according to the lamination thickness.

(3) Film thickness, layer thickness

The film was embedded in an epoxy resin, and the cross section of the film was cut out with a microtome. The cross section was observed with a transmission electron microscope (TEM H7100, manufactured by Hitachi, Ltd.) at a magnification of 5000 times to determine the film thickness and the thickness of the polyester layer.

(4) Melting point

Measurement and analysis were carried out in accordance with JIS K7121-1987 and JIS K7122-1987 using a differential scanning calorimeter (RDC220, manufactured by Seiko Denshi Kogyo Co., Ltd.). 5 mg of the polyester film was used as a sample, and the temperature at the apex of the endothermic peak obtained by DSC curve when the temperature was raised from 25 캜 to 20 캜 / min to 300 캜 was taken as the melting point. In the case of a laminated film, the melting point of each layer can be measured by shaving each layer of the film according to the lamination thickness. In the present invention, in the case of a laminated polyester film having a polyester A layer and a polyester B layer, the melting point of each layer is measured to determine the polyester A layer having a higher melting point and the polyester B layer did.

(5) The small endothermic peak temperature (Tmeta) before crystal melting

Measurement and analysis were carried out in accordance with JIS K7121-1987 and JIS K7122-1987 using a differential scanning calorimeter (RDC220, manufactured by Seiko Denshi Kogyo Co., Ltd.). 5 mg of the polyester film was used as a sample, and the temperature of the endothermic peak of the minute appearing before the crystal melting peak when the temperature was raised from 25 캜 to 300 캜 at 20 캜 / min was read as Tmeta.

(6) The main orientation axis of a 1000 mm wide film, the maximum orientation angle value

A sample was cut out at a size of 100 mm x 100 mm at an arbitrary point of the film, and a sample was cut out using a microwave molecular alignment system MOA-2001A (frequency 4 GHz) manufactured by KS Systems Co., The principal orientation axis in the plane was obtained, and the direction was the TD direction. This arbitrary point is defined as the center of the film in the TD direction, and 50 mm to 500 mm in any one direction (A direction) in the TD direction is recorded every 50 mm (50 mm, 100 mm, 150 mm, 50 mm to 500 mm in the direction opposite to the A direction in the TD direction from the center of the film in the TD direction (The smaller angle of the angle between the main alignment axis and the film TD direction or the film MD direction) using the above-described microwave molecular alignment system MOA-2001A (frequency 4 GHz) And the maximum value thereof was obtained.

(7) Temperature Modulation The glass transition temperature

(6), a sample was cut out at a size of 100 mm x 100 mm at an arbitrary point on the film, and 5 mg was taken therefrom. The sample was placed in a standard container made of aluminum and subjected to a differential scanning calorimeter (TA Instrument Q100) And the measurement was carried out in a sinusoidal wave with a temperature modulation amplitude of 1 占 폚 at a rate of 2 占 폚 / min in a temperature range of 0 占 폚 to 200 占 폚 and a temperature modulation cycle of 60 seconds under a nitrogen atmosphere (flow rate: 50 ml / min). In addition, non-thermal calibration was performed with sapphire, and "Universal Analysis 2000" made by TA Instrument was used for data analysis. The glass transition temperature of the obtained reversible component was measured in the same manner as described in "9.3 Method for Determining the Glass Transition Temperature (1) Mid-point Glass Transition Temperature Tmg" of JIS K7121 (1987) The glass transition temperature of the temperature-modulated DSC was obtained (the point at which the straight line extending equidistant from the extended straight line of each base line and the curve of the changing portion on the step of the glass transition intersected the glass transition temperature of the temperature-modulated DSC ). This arbitrary point is defined as the center of the film in the TD direction and is measured every 50 mm to 500 mm (50 mm, 100 mm, 150 mm, 200 mm, 250 mm, And 50 mm to 500 mm in the direction opposite to the direction A in the TD direction (direction B) from the center of the film in the TD direction at intervals of 50 mm The glass transition temperature was measured using the above differential scanning calorimeter and its minimum temperature was determined.

(8) Stress at 10% elongation in the film MD direction at 150 ° C

The film was cut into a rectangle having a length of 150 mm and a width of 10 mm in the MD direction, and a sample was obtained. A tensile test was conducted in the MD direction of the film using a tensile tester (Orientech Tensilon UCT-100) at an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. The film sample was set in a constant temperature layer set at 150 占 폚 in advance, and a tensile test was performed after preheating for 90 seconds. The load applied to the film when the sample was elongated by 10% (when the distance between the chucks became 55 mm) was read, and the value obtained by dividing by the cross-sectional area (film thickness x 10 mm) of the sample before testing was taken as the stress at 10% elongation . In addition, the measurement was performed such that the main alignment axis direction at an arbitrary position of the film was the TD direction, and a 550 mm width in each of the two directions along the TD direction was taken as the center (center of TD) A position of 500 mm in a certain direction (A direction) in the TD direction from the center of one film of the film, a position of 500 mm in a direction (B direction) opposite to the A direction in the TD direction from the center, , And the average value of the 15 values was used as a stress at 10% elongation in the film MD direction at 150 占 폚.

(9) Heat shrinkage (150 DEG C, 190 DEG C)

The film was cut into a rectangle having a length of 150 mm and a width of 10 mm in the MD direction and the TD direction, respectively. The sample was placed in a hot-air oven heated at a predetermined temperature (150 DEG C, 190 DEG C) for 30 minutes by hanging 3 g of a weight and spaced 100 mm from the center (50 mm from both ends) . The distance between the lines after the heat treatment was measured and the heat shrinkage rate was calculated from the change in the distance between the lines before and after the heating by the following formula. In addition, the evaluation was carried out by taking a 550 mm width in two directions along the TD direction with the center in the direction of the center (TD direction) with the main alignment axis direction at an arbitrary position of the film in the TD direction, At a position of 500 mm in one arbitrary direction (A direction) in the TD direction from the center in the TD direction, and 500 mm in a direction opposite to the A direction in the TD direction (from the center) The average value of the 15 values was determined as the heat shrinkage rate in the film MD direction and the TD direction at the predetermined temperature (150 DEG C, 190 DEG C).

Heat shrinkage percentage (%) = [(distance between marks before heat treatment) - (distance between markings after heat treatment)] / (distance between markings before heat treatment) 占 100.

(10) Calculation method of formula (I) and formula (II)

The MD of the center value of the 1100 mm wide film in the TD direction, the heat shrinkage rate (SC _MD , SC _TD ) at 190 deg. C in the TD direction, the TD direction from the center in the width direction of the 1100 mm wide film (SA _MD , SA _TD ) at 190 ° C in the MD and TD directions at a position of 500 mm in any one direction (A direction) of the TD direction, the heat shrinkage ratio The heat shrinkage rate (SB _MD , SB _TD ) at 190 ° C in the MD and TD directions at the position of 500 mm in the direction opposite to the direction A (direction B) was measured ) The value of the left side of the formula (I) and the formula (II) was calculated.

(SA _MD + SB _MD ) / SC _MD 2? 1.2 (I)

(SA _TD + SB _TD ) / SC _TD 2? 1.2 (II).

(11) Plane orientation coefficient

The refractive index (n _MD ) of the film in the MD direction, the refractive index (n _TD ) in the TD direction and the refractive index (n _ZD ) in the thickness direction of the film were measured using an Abbe's refractometer using a sodium D line (wavelength: 589 nm) The plane orientation coefficient fn was calculated from the following equation.

fn = (n _MD + n _TD ) / 2-n _ZD

The surface orientation coefficient is measured on both sides of the film, and the table shows the value of the higher surface orientation coefficient.

In addition, the measurement was performed such that the main alignment axis direction at an arbitrary position of the film was the TD direction, and a 550 mm width in each of the two directions along the TD direction was taken as the center (center of TD) A position of 500 mm in a certain direction (A direction) in the TD direction from the center of one film of the film, a position of 500 mm in a direction (B direction) opposite to the A direction in the TD direction from the center, , And the average value of the 15 values was employed.

(12) Thermomechanical analysis (TMA)

The film was cut into a rectangle having a length of 50 mm and a width of 4 mm in the MD and TD directions to obtain a sample. Using a thermomechanical analyzer (TMA EXSTAR6000 manufactured by Seiko Instruments Inc.), the temperature was raised under the following conditions, The elongation peak temperature was calculated.

Test length: 15 mm, load: 19.6 mN, temperature raising rate: 5 캜 /

Measuring temperature range: 25 ~ 200 ℃

In the present invention, the elongation peak temperature at 25 ° C to 200 ° C indicates the temperature at which the elongated film shifts to the shrinkage behavior in accordance with the elevated temperature. In the present invention, the temperature at which the elongation behavior shifts to the shrinkage behavior for the first time when the temperature is elevated from 25 占 폚 to 200 占 폚 is set as the elongation peak in the film MD direction and the elongation peak in the TD direction Temperature.

In addition, the measurement was performed such that the main alignment axis direction at an arbitrary position of the film was the TD direction, and a 550 mm width in each of the two directions along the TD direction was taken as the center (center of TD) A position of 500 mm in a certain direction (A direction) in the TD direction from the center of one film of the film, a position of 500 mm in a direction (B direction) opposite to the A direction in the TD direction from the center, , The average of nine values measured for MD and TD was employed.

(13) Dimensional stability

The polyarylate / MEK dispersion was coated and dried on the surface of a polyester film having a width of 1100 mm by a die coater (drying temperature: 150 占 폚, drying time: 1 minute, winding tension: 200 N / m, 100 N / m). The width of the polyester film after drying was measured and evaluated according to the following criteria (the thickness of the polyarylate after drying was 25 占 퐉).

A: The width shrinkage was less than 5 mm (the width of the polyester film after drying was not less than 995 mm).

B: The width shrinkage was 5 mm or more and less than 10 mm (the width of the polyester film after drying was 990 mm or more and less than 995 mm).

C: The width shrinkage was 10 mm or more (the width of the polyester film after drying was less than 990 mm).

The evaluation of the width shrinkage was carried out by selecting 10 arbitrary positions of a 1000 mm width film after coating and drying, and measuring the width thereof (1,000 mm width - 10 film width average values) as the width shrinkage amount.

(14) Moldability

The polyarylate-coated polyester film obtained in (13) was put into a hot air oven and uniaxially stretched in the longitudinal direction (oven temperature: 150 캜, width direction free). The extensibility (molding processability) of the film was evaluated according to the following criteria.

A: The stretching tension was less than 1200 N / m, and the stretching was 1.1 times.

B: Drawing tension of 1200 N / m or more and less than 1500 N / m, and 1.1 times of drawing was possible.

C: The stretching tension was 1500 N / m, and 1.1 times stretching was impossible.

(15) Functional coating film Width direction uniformity

The polyarylate layer was peeled off from the polyarylate-coated uniaxially stretched polyester film obtained in (14), and the polyarylate layer was peeled off from the center in the width direction, the position of 500 mm in one arbitrary direction in the width direction (A direction) Plane retardation was measured with respect to three points at a position of 500 mm in a direction opposite to the direction A (direction B), and evaluation was performed based on the following criteria. The retardation was measured using an automatic birefringence meter (KOBRA-21ADH) manufactured by Shin-Oji Keiki Co., Ltd.

A: The difference between the maximum value and the minimum value of the retardation measured at three points was less than 10 nm.

B: The difference between the maximum value and the minimum value of the retardation measured at three points was 10 nm or more and less than 20 nm.

C: The difference between the maximum value and the minimum value of the retardation measured at three points was 20 nm or more.

(Production of polyester)

The polyester resin provided in the film formation was prepared as follows.

(Polyester A)

A polyethylene terephthalate resin (intrinsic viscosity: 0.65) having 100 mol% of a terephthalic acid component as a dicarboxylic acid component and 100 mol% of an ethylene glycol component as a glycol component.

(Polyester B)

Copolymer polyester (GN001, manufactured by Eastman Chemical Company) having 1,4-cyclohexanedimethanol copolymerized in an amount of 33 mol% based on the glycol component was used as cyclohexane dimethanol copolymerized polyethylene terephthalate (intrinsic viscosity: 0.75).

(Polyester C)

A neopentyl glycol-copolymerized polyethylene terephthalate resin (inherent viscosity: 0.75) having 100 mole% of a terephthalic component as a dicarboxylic acid component, 70 mole% of an ethylene glycol component as a glycol component and 30 mole% of a neopentyl glycol component.

(Polyester D)

(Intrinsic viscosity: 0.65) having 100 mol% of a terephthalic component as a dicarboxylic acid component, 85 mol% of an ethylene glycol component as a glycol component and 15 mol% of a diethylene glycol component.

(Polyester E)

An isophthalic acid copolymerized polyethylene terephthalate resin (intrinsic viscosity: 0.7) having a terephthalic component of 82.5 mol% as a dicarboxylic acid component, an isophthalic component of 17.5 mol%, and an ethylene glycol component of 100 mol% as a glycol component.

(Polyester F)

Naphthalenedicarboxylic acid copolymerized polyethylene having 85 mol% of a terephthalic component as a dicarboxylic acid component, 15 mol% of a 2,6-naphthalenedicarboxylic acid component and 100 mol% of an ethylene glycol component as a glycol component Terephthalate resin (intrinsic viscosity 0.7).

(Particle master)

A polyethylene terephthalate particle master (intrinsic viscosity: 0.65) containing 2% by mass of a coagulated silica particle having a number average particle diameter of 2.2 占 퐉 in the polyester A at a particle concentration of 2% by mass.

(Example 1)

The mixture was supplied to respective twin-screw extruders in the venting directions of 0.2% by volume of oxygen as the raw materials, melted at a cylinder temperature of the A-layer extruder cylinder of 270 ° C and a B-layer extruder cylinder temperature of 277 ° C, The sheet was then discharged onto a cooling drum having a single-tube temperature of 277 deg. C and a separating temperature of 280 deg. C controlled by a T die at 25 deg. C after the joining of the A layer and the B layer. At this time, electrostatic force was applied using a wire-shaped electrode having a diameter of 0.1 mm, and the sheet was brought into close contact with a cooling drum to obtain an unstretched sheet. Then, before stretching in the longitudinal direction, the film temperature was elevated by a heating roll, stretched 3.1 times in the longitudinal direction at a stretching temperature of 85 캜, and then cooled with a metal roll controlled at 40 캜.

Subsequently, the film was stretched by 3.9 times in the transverse direction at a stretching front temperature of 95 캜, a middle stretching temperature of 105 캜 and a stretching latter half temperature of 140 캜 by a tenter type transverse stretching machine, ° C, and heat treatment was performed at a temperature of 180 ° C at the end of the heat treatment while applying a relaxation of 3% in the width direction to obtain a biaxially oriented polyester film having a film thickness of 75 μm.

(Example 2)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 1.

(Example 3)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 1.

(Example 4)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 3 except that the 5% microstretch was performed in the width direction throughout the entire heat treatment.

(Example 5)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 1.

(Example 6)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 1.

(Example 7)

A / B / A. The composition of each layer was fed to each vent-directional twin-screw extruder having an oxygen concentration of 0.2% by volume as the raw material for the A-layer and the raw material for the B-layer as shown in the table, and the temperature of the A- The extruder cylinder temperature was melted at 277 占 폚 and discharged as a sheet on a cooling drum whose temperature was controlled at 277 占 폚 for the single-tube temperature after joining the A and B layers and at 25 占 폚 by the T-die at 280 占 폚. At that time, electrostatic force was applied by using a wire-shaped electrode having a diameter of 0.1 mm, and the film was brought into close contact with the cooling drum to obtain a three-layer laminated undrawn film consisting of layer A / layer B / layer A.

Thereafter, a biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the mid-temperature of the heat treatment was changed to 225 캜.

(Example 8)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 7 except that the composition was changed as shown in Table 1 and 2% microstretching was performed in the width direction in the entire heat treatment.

(Example 9)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 17 except that the composition was changed as shown in Table 1 and the 5% microstretch was performed in the width direction in the entire heat treatment.

(Example 10)

Except that the composition was changed as shown in Table 1 and 5% microstretching was performed in the width direction in the entire heat treatment and 3% microstretching was performed in the width direction in the middle of the heat treatment. Axis oriented polyester film.

(Example 11)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 7 except that the composition was changed as shown in Table 1 and the mid-temperature of the heat treatment was changed to 205 캜.

(Example 12)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 7 except that the composition was changed as shown in Table 1 and the mid-temperature of the heat treatment was changed to 230 캜.

(Example 13)

Except that the composition was changed as shown in Table 1 and 5% microstretching was performed in the width direction in the entire heat treatment and 3% microstretching was performed in the width direction in the middle of the heat treatment. Axis oriented polyester film.

(Example 14)

Except that the composition was changed as shown in Table 1 and 5% microstretching was performed in the width direction in the entire heat treatment and 3% microstretching was performed in the width direction in the middle of the heat treatment. Axis oriented polyester film.

(Example 15)

Off-annealing was performed on the biaxially oriented polyester film obtained in Example 14 while reducing the winding speed in the width direction free direction and the length direction in the hot air oven at 180 DEG C by 1% from the winding speed.

(Example 16)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 1 and the heat treatment was carried out at 235 캜 at the middle temperature of the heat treatment.

(Example 17)

A biaxially oriented polyester film having a film thickness of 75 占 퐉 was obtained in the same manner as in Example 10 except that the composition was changed as shown in Tables.

(Comparative Example 1)

The composition was changed as shown in Table 1, and the entirety of the transverse stretching, the middle and the rear half temperatures were all stretched 3.4 times at 120 占 폚, and heat treatment was carried out in the tenter at the overall heat treatment temperature and the middle heat treatment temperature of 230 占 폚, A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 7 except that the heat treatment was carried out while applying a relaxation of 3% in the width direction at a temperature of 180 캜.

(Comparative Example 2)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was as shown in Table 1 and the mid-temperature of the heat treatment was changed to 220 캜.

(Comparative Example 3)

A biaxially oriented polyester film having a film thickness of 75 탆 was obtained in the same manner as in Example 1 except that the composition was as shown in the table and the mid-temperature of the heat treatment was 195 캜.

The meanings of abbreviations in the table are as follows.

EG: ethylene glycol

CHDM: 1,4-cyclohexanedimethanol

DEG: diethylene glycol

NPG: neopentyl glycol

TPA: terephthalic acid

IPA: isophthalic acid

NDC: 2,6-naphthalene dicarboxylic acid

≪ Industrial Availability >

Since the biaxially oriented polyester film of the present invention is low in molding stress at 150 占 폚 and therefore has a good anti-wetting property and has a low heat shrinkage rate at 150 占 폚, film deformation during coating and drying is small, Can be suitably used for shaping and decorating purposes of construction materials, mobile devices, electric appliances, automobile parts, and organic parts, and optical films such as polarizing plates, because the maximum value of the orientation angle of the polarizer is small.

Claims (12)

A stress at 10% elongation in the film MD direction at 150 占 폚 of 5 to 30 MPa at a temperature of 150 占 폚 and a heat shrinkage rate of 5% or less in the film MD direction at 150 占 폚; (The smaller angle of the angle formed by the main alignment axis with the film TD direction or the film MD direction) is 20 DEG or less.
However, the orientation angle of the film having a width of 1000 mm is the direction of the main alignment axis at an arbitrary position of the film in the TD direction, and a width of 550 mm in each of the two directions along the TD direction around the above position is taken as 1100 mm Wherein the film has a width of 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm ), And the maximum value among them is obtained. The direction perpendicular to the TD direction in the same film plane is the MD direction. The method according to claim 1,
Wherein the film is at least 10 m in the MD direction and at least 1100 mm in the TD direction. 3. The method according to claim 1 or 2,
Temperature Modulation of Film at 1000 mm Width The lowest temperature of the glass transition temperature determined by DSC is 80 占 폚 or more and 110 占 폚 or less.
However, the glass transition temperature determined by the temperature-modulated DSC of the film at a width of 1000 mm is defined as the direction of the main alignment axis at any position of the film in the TD direction, and the two directions along the TD direction 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, and 450 mm from the arbitrary point on both ends in the TD direction, , The glass transition temperature is measured at a position of 500 mm (1000 mm width), and the lowest temperature in the glass transition temperature is determined. 4. The method according to any one of claims 1 to 3,
And the heat shrinkage ratio in the film MD direction and the TD direction at 190 占 폚 is 5% or less. 5. The method according to any one of claims 1 to 4,
Wherein the biaxially oriented polyester film satisfies the following formula (I).
(SA _MD + SB _MD ) / (SC _MD 2)? 1.2 (I)
However, SA _MD : 190 占 폚 heat shrinkage ratio in the MD direction at a position of 500 mm in any one direction (A direction) from the center of the 1100 mm wide film in the TD direction to the TD direction
SB _MD : 190 占 폚 heat shrinkage ratio in MD direction at a position of 500 mm in a direction opposite to A direction in the TD direction (from the center in the TD direction of the 1100 mm wide film)
SC _MD : 190 占 폚 heat shrinkage ratio in the MD direction at the center of the 1100 mm wide film in the TD direction 6. The method according to any one of claims 1 to 5,
Satisfies the following formula (II).
(SA _TD + SB _TD ) / (SC _TD 2)? 1.2 (II)
However, SA _TD : 190 占 폚 heat shrinkage ratio in the TD direction at a position of 500 mm in any one direction (A direction) from the center of the 1100 mm wide film in the TD direction to the TD direction
SB _TD : 190 占 폚 in the TD direction at the position of 500 mm in the direction opposite to the direction A in the TD direction (direction B) from the center in the TD direction of the 1100 mm width film
SC _TD : 190 占 폚 heat shrinkage rate in the TD direction at the center of the 1100 mm wide film in the TD direction 7. The method according to any one of claims 1 to 6,
Wherein a plane orientation coefficient on the higher plane of the plane orientation coefficients on both surfaces of the film is 0.111 or more and 0.17 or less. 8. The method according to any one of claims 1 to 7,
And a polyester B layer having a lower melting point than the polyester A layer and the polyester A layer, wherein the polyester A layer is located on at least one outermost layer. 9. The method according to any one of claims 1 to 8,
Wherein the stretching peak temperature in the film TD direction when the temperature is raised from 25 占 폚 to 200 占 폚 at a heating rate of 5 占 폚 / min at a load of 19.6 mN by thermal mechanical analysis (TMA) is 70 占 폚 or higher. . 10. The method according to any one of claims 1 to 9,
Characterized in that the stretching peak temperature in the film MD direction when the temperature is raised from 25 占 폚 to 200 占 폚 at a heating rate of 5 占 폚 / min at a load of 19.6 mN by thermal mechanical analysis (TMA) is 60 占 폚 or more . 11. The method according to any one of claims 1 to 10,
A biaxially oriented polyester film characterized by being used for forming processing. 12. The method according to any one of claims 1 to 11,
A biaxially oriented polyester film characterized by being used for optical applications.