JPWO2014208519A1 - Biaxially oriented polyester film - Google Patents

Abstract

An object of the present invention is to provide a biaxially oriented polyester film that is excellent in moldability and uniformity in physical properties in the width direction and can be suitably used for molding and optics. The biaxially oriented polyester film of the present invention has a 10% elongation stress in the film MD direction at 150 ° C. of 5 MPa or more and 30 MPa or less, a thermal shrinkage rate in the film MD direction at 150 ° C. of 5% or less, and a film orientation at a width of 1000 mm. It is a biaxially oriented polyester film having a maximum value of the angle (the smaller one of the angles formed by the main orientation axis and the film TD direction or the film MD direction) of 20 ° or less.

Description

The present invention relates to a biaxially oriented polyester film and relates to a biaxially oriented polyester film that is particularly suitable for use in molding and optical applications.

  In recent years, due to increasing environmental awareness, there has been an increasing demand for solventless painting, plating replacement, etc. for building materials, automobile parts, mobile phones, electrical appliances, etc., and the introduction of decoration methods using films is progressing.

  Several proposals have been made as molding polyester films used in such decoration methods. For example, a molding polyester film that exhibits low mold stress and low storage modulus even at low temperatures and that satisfies high moldability has been proposed (see, for example, Patent Document 1).

In addition, a polyester film having both high heat resistance and moldability, which has a high storage elastic modulus at low temperatures and low molding stress at high temperatures, has been proposed (see, for example, Patent Document 2).
In addition, liquid crystal displays are used in large TV sets, personal computers, tablets, smartphones, etc., and stable demand is expected in the future. Various films such as surface protective films, release films, retardation films, and process films are used for polarizing plates that make up liquid crystal displays. Uniformity of physical properties in the width direction is very important. Several proposals have been made for stretched polyester films. For example, in order to satisfy the uniformity in the width direction, a polarizing film laminating polyester film with a reduced orientation angle and thickness unevenness has been proposed (see, for example, Patent Document 3). In addition, with the expansion of smart devices such as smartphones and tablet terminals, there is an increasing demand for thinning liquid crystal displays, and high definition and thinning are also progressing in polarizing plates and retardation layers. For this reason, in order to achieve high definition and thinning of the retardation layer, the retardation layer is applied to the process film and molded together with the process film to achieve high definition and thinning of the retardation layer. Process development is progressing.

JP-A-2005-290354 International Publication No. 2012-005097 JP 2002-40249 A

  However, although the films described in Patent Documents 1 and 2 are excellent in moldability, the physical properties in the width direction are not uniform. Therefore, when used for decorative molding of large members, molding unevenness and distortion after molding. Unevenness may occur. Moreover, when it is going to be used as a process film of a polarizing plate / retardation layer, since the physical properties are not uniform, characteristic unevenness may occur.

  Moreover, although the film of patent document 3 is excellent in the uniformity of the width direction, since a moldability is inadequate, it is the polarizing plate and phase difference which shape | mold the decoration shape to a deep shape, and shape | mold the whole process film Difficult to use for.

  An object of the present invention is to eliminate the above-described problems of the prior art. That is, the present invention is to provide a biaxially oriented polyester film that is excellent in moldability and uniformity in physical properties in the width direction and can be suitably used for molding and optical use.

The gist of the present invention for solving this problem is as follows.
Orientation of a film having a 10% elongation stress in the direction of film MD (hereinafter referred to as MD) at 150 ° C. of 5 to 30 MPa, a thermal shrinkage in the direction of film MD at 150 ° C. of 5% or less, and a width of 1000 mm. Biaxially oriented polyester whose maximum value of the angle {(the smaller one of the angles formed by the main orientation axis and the film TD (Transverse Direction)) or the film MD direction) is 20 ° or less. the film. However, the orientation angle of the film having a width of 1000 mm is the width of 1100 mm by taking the main orientation axis direction at an arbitrary position of the film as the TD direction, taking 550 mm width in each of the two directions along the TD direction with the position as the center. The orientation angle is measured at the positions (1000 mm width) of 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, and 500 mm from the arbitrary point to the both ends in the TD direction, and the maximum value is obtained. Moreover, let the direction orthogonal to the TD direction be the MD direction within the same film plane.

Since the biaxially oriented polyester film of the present invention has a low molding stress at 150 ° C., it has good moldability, and since the thermal shrinkage at 150 ° C. is low, the film deformation during coating drying is small, Furthermore, since the maximum value of the orientation angle of a 1000 mm wide film is small, it has excellent uniformity of physical properties in the width direction, and is used for decorative decorations for building materials, mobile devices, electrical products, automobile parts, game machine parts, etc., polarizing plates It can use suitably for optical films etc., etc.

  The polyester constituting the biaxially oriented polyester film of the present invention is a general term for polymer compounds in which main bonds in the main chain are ester bonds. The polyester resin can be usually obtained by polycondensation reaction of dicarboxylic acid or its derivative with glycol or its derivative.

  In the present invention, from the viewpoint of moldability, appearance, heat resistance, dimensional stability and economy, 60 mol% or more of the glycol units constituting the polyester is a structural unit derived from ethylene glycol, and 60 mol% of the dicarboxylic acid unit. The above is preferably a structural unit derived from terephthalic acid. Here, the dicarboxylic acid unit (structural unit) or the diol unit (structural unit) means a divalent organic group from which a portion to be removed by polycondensation has been removed. It is represented by

Dicarboxylic acid unit (structural unit): —CO—R—CO—
Diol unit (structural unit): —O—R′—O—
(Where R and R ′ are divalent organic groups)
In addition, when a trivalent or higher carboxylic acid or alcohol such as trimellitic acid unit or glycerin unit or a derivative thereof is included, the trivalent or higher carboxylic acid or alcohol unit (structural unit) is similarly obtained by polycondensation. The trivalent or higher valent organic group from which the part to be removed is removed is meant.

  Glycols or derivatives thereof that give polyester for use in the present invention include, in addition to ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, Aliphatic dihydroxy compounds such as 1,5-pentanediol, 1,6-hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, 1,4-cyclohexanedimethanol , Alicyclic dihydroxy compounds such as spiroglycol, aromatic dihydroxy compounds such as bisphenol A and bisphenol S, and derivatives thereof. Of these, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol are preferably used from the viewpoint of moldability and handleability.

  In addition to terephthalic acid, the dicarboxylic acid or derivative thereof that provides the polyester used in the present invention includes isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid. Acids, aromatic dicarboxylic acids such as 5-sodiumsulfone dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid, etc. Alicyclic dicarboxylic acids, oxycarboxylic acids such as paraoxybenzoic acid, and derivatives thereof. Examples of dicarboxylic acid derivatives include dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, diethyl maleate, and dimethyl dimer. An esterified product can be mentioned. Among these, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and esterified products thereof are preferably used from the viewpoint of moldability and handleability.

  The biaxially oriented polyester film of the present invention has a shape stress to a complex shape and an easy moldability when molding the entire process film, so that the stress at 10% elongation in the MD direction at 150 ° C. is 5 MPa or more and 30 MPa or less. There must be.

Here, in the present invention, a 1000 mm wide film is evaluated with the main orientation axis direction at an arbitrary position of the film as the TD direction and the position as the center (hereinafter also referred to as the TD direction center) along the TD direction. In each of the two directions, a width of 550 mm is sampled, and a 500 mm width (1000 mm width) is evaluated in two directions along the TD direction from the center in the TD direction of the film having a width of 1100 mm. 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.
In addition, the stress at 10% elongation in the MD direction at 150 ° C. means that a film sample cut into a rectangular shape with a test length of 50 mm is set in a constant temperature layer set in advance at 150 ° C., and after preheating for 90 seconds, When a tensile test is performed at a strain rate of 300 mm / min, the stress applied to the film when the sample is stretched by 10% is shown. The evaluation was performed by taking a 550 mm width in each of the two directions along the TD direction, with the main orientation axis direction at any position of the film as the TD direction, and the position as the center (hereinafter also referred to as the TD direction center). TD direction center of a film having a width of 1100 mm, 500 mm position in any one direction (A direction) from the TD direction center to the TD direction, 500 mm in the direction opposite to the A direction (B direction) from the TD direction center The measurement was performed 5 times at each of the three points, and the average value of the 15 values was defined as the stress at 10% elongation in the film MD direction at 150 ° C. From the viewpoint of moldability and dimensional stability, the stress at 10% elongation in the film MD direction at 150 ° C. is more preferably from 6 MPa to 20 MPa, and most preferably from 7 MPa to 15 MPa.

  In the biaxially oriented polyester film of the present invention, as a method of setting the stress in the MD direction 10% elongation of the film at 150 ° C. in the above range is not particularly limited, for example, as a glycol component constituting the polyester film of the present invention, Contains at least 60 mol% of an ethylene glycol component, and at least one glycol 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 It is preferable to include a component. Especially, it is preferable that at least 1 or more types of a diethylene glycol component, a 1, 4- cyclohexane dimethanol component, and a neopentyl glycol component are contained. Moreover, as a dicarboxylic acid component which comprises the polyester film of this invention, a terephthalic acid component is contained 60 mol% or more, and at least 1 or more types of dicarboxylic acid component of an isophthalic acid component and a 2, 6- naphthalene dicarboxylic acid component is included. Is preferred.

  In the biaxially oriented polyester film of the present invention, as a particularly preferable constitution in which the stress at 10% elongation in the film MD direction at 150 ° C. is in the above range, the glycol component contains an ethylene glycol component of 85 mol% or more and less than 97 mol%. , Containing at least one kind of diethylene glycol component, 1,4-cyclohexanedimethanol component, neopentyl glycol component in an amount of 3 mol% to less than 15 mol%, and 85 mol% or more as a dicarboxylic acid component is a terephthalic acid component Is preferred. More preferably, the glycol component contains an ethylene glycol component of 90 mol% or more and less than 95 mol%, and at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and a neopentyl glycol component is 5 mol% or more and 10 mol%. The dicarboxylic acid component is contained in an amount of less than mol%, and 90 mol% or more is preferably a terephthalic acid component, and more preferably 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component.

  Moreover, in the biaxially oriented polyester film of the present invention, in order to make the stress at 10% elongation in the film MD direction at 150 ° C. within the above range, the above composition is used, and the higher one of the plane orientation coefficients on both sides of the film. The plane orientation coefficient is preferably from 0.111 to 0.17.

  Of the surface orientation coefficients on both sides of the film, the method in which the higher surface orientation coefficient is 0.111 or more and 0.17 or less is not particularly limited. For example, the above composition is used, and the surface magnification is 9.8 times or more and 13.5 times. The method of extending | stretching is mentioned below. The stretching temperature is preferably 70 ° C. or higher and 150 ° C. or lower, and the heat treatment temperature after biaxial stretching is preferably 200 ° C. or higher and 240 ° C. or lower at the highest temperature.

  In addition, the biaxially oriented polyester film of the present invention needs to have a heat shrinkage rate in the film MD direction at 150 ° C. of 5% or less. Here, the thermal shrinkage rate in the MD direction at 150 ° C. means that a line is drawn at intervals of 100 mm on a sample obtained by cutting a film into a rectangle 150 mm long × 10 mm wide in the MD direction (positions at 50 mm from the center to both ends). ) This refers to the rate of change in the distance between the marked lines before and after performing heat treatment by suspending a 3 g weight in a hot air oven heated to 150 ° C. for 30 minutes. The evaluation was performed by taking a 550 mm width in each of the two directions along the TD direction, with the main orientation axis direction at any position of the film as the TD direction, and the position as the center (hereinafter also referred to as the TD direction center). 3 points of TD direction center of the film having a width of 1100 mm, a position of 500 mm in any one direction (A direction) from the center to the TD direction, and a position of 500 mm from the center in the direction opposite to the A direction in the TD direction (B direction) The average value of the 15 values was taken as the thermal shrinkage in the film MD direction at 150 ° C. The biaxially oriented polyester film of the present invention has a thermal shrinkage rate at 150 ° C. in the MD direction of 5% or less, and a functional coating such as a hard coat layer, a decorative layer, or a retardation layer is applied to the film. When drying, problems such as a decrease in the functionality of the coating film and a decrease in the flatness of the film due to film shrinkage can be suppressed. The thermal shrinkage at 150 ° C. in the MD direction is more preferably 4% or less, and most preferably 3% or less.

  Examples of the method of setting the thermal shrinkage rate in the MD direction at 150 ° C. to 5% or less include a method of adjusting the heat treatment conditions of the film after biaxial stretching. When the treatment temperature is high, orientation relaxation occurs and the thermal shrinkage tends to be reduced, but the heat treatment temperature after biaxial stretching is 200 ° C. to 240 ° C. from the viewpoint of dimensional stability and film quality. It is preferable if it is 210 ° C to 235 ° C, more preferably 215 ° C to 230 ° C. The heat treatment temperature of the biaxially oriented polyester film of the present invention is a minute value resulting from the thermal history in the DSC curve when measured at a temperature increase rate of 20 ° C./min in a nitrogen atmosphere with a differential scanning calorimeter (DSC). It can be determined from the endothermic peak.

  Moreover, as preferable heat processing time, although it can set arbitrarily in 5 to 60 second, it is preferable to set it as 10 to 40 second from a viewpoint of a moldability, dimensional stability, a color tone, and productivity, and 15-30. Preferably it is seconds. Further, the heat shrinkage can be reduced by performing the heat treatment while relaxing in the longitudinal direction and / or the width direction. The relaxation rate (relaxation rate) when relaxing during heat treatment is preferably 1% or more. From the viewpoint of dimensional stability and productivity, it is preferably 1% or more and 10% or less, and may be 1% or more and 5% or less. Is most preferable.

  Also, a method of heat treatment under two or more conditions is very preferable. After heat treatment at a high temperature of 200 ° C. to 240 ° C., the heat shrinkage rate can be further reduced by performing heat treatment at a temperature lower than the heat treatment temperature while relaxing in the longitudinal direction and / or the width direction. The heat treatment temperature in the second stage at this time is preferably 120 ° C. to less than 200 ° C., more preferably 150 ° C. to 180 ° C.

  The biaxially oriented polyester film of the present invention has a maximum film orientation angle (the smaller one of the angles formed by the main orientation axis and the film TD direction or the film MD direction) from the viewpoint of uniformity of physical properties. The value needs to be 20 ° or less. Here, the maximum value of the orientation angle of a film having a width of 1000 mm means that the main orientation axis direction at an arbitrary position of the film is the TD direction, and the 550 mm width is sampled in each of the two directions along the TD direction with the position at the center. As a film having a width of 1100 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm (1000 mm) from the arbitrary point to both ends in the TD direction (one direction is A direction and the other is B direction) The orientation angle is measured at the position of (width) (21 points), and the maximum value is obtained.

  From the viewpoint of uniformity in physical properties in the width direction, the maximum value of the orientation angle of a 1000 mm wide film is more preferably 15 ° or less, and most preferably 10 ° or less.

  Here, the method of setting the maximum value of the orientation angle of a film having a width of 1000 mm to 20 ° or less is not particularly limited, and examples thereof include a method of reducing bowing during film formation. Specifically, a method of performing heat treatment after once cooling to below the glass transition temperature of the polyester after stretching in the width direction, a method of providing a nip roll after stretching in the width direction, and a method of raising the temperature stepwise by dividing the stretching in the width direction into a plurality of zones There are a method in which heat treatment is divided into a plurality of zones and the temperature is raised and lowered stepwise, a method in which a temperature distribution is provided in the width direction and the heat treatment zone is guided, and a method in which a heat treatment chamber is finely stretched in the width direction.

  In addition, 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, and ensures the functionality of the coating film when it is dried. From the viewpoint of ensuring, it is preferable that the thermal shrinkage rate in the film MD direction and the TD direction at 190 ° C. is 5% or less. Even at temperatures as high as 190 ° C, by reducing the thermal shrinkage in the MD and TD directions, it is possible to maintain high dimensional stability even when the drying temperature of the functional coating film needs to be increased. It is.

  As a method of setting the thermal shrinkage rate in the film MD direction and TD direction at 190 ° C. to 5% or less, for example, the method after biaxial stretching in the same manner as the method of setting the thermal shrinkage rate in the film MD direction at 150 ° C. to 5% or less. The method of adjusting the heat processing conditions of a film is mentioned. Further, it is preferable to perform relaxation during the heat treatment stepwise. For example, the first heat treatment is 230 ° C., the second heat treatment is 200 ° C. with a relaxation rate of 3%, and the third heat treatment is 180 ° C. with a relaxation rate of 2%. It is a method. The thermal shrinkage ratio in the film MD direction / TD direction at 190 ° C. is preferably 5% or less / 4% or less, and most preferably 5% or less / 3% or less.

  In addition, 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, from the viewpoint of heat resistance when performing drying, and easy moldability, It is preferable that the minimum temperature of the glass transition temperature calculated | required by the temperature modulation | alteration DSC of the film in 1000 mm width is 80 degreeC or more and 110 degrees C or less. Here, the glass transition temperature obtained by the temperature modulation DSC of the film at a width of 1000 mm means that the main orientation axis direction at an arbitrary position of the film is the TD direction, and the width is 550 mm width in each of the two directions along the TD direction. As a film with a width of 1100 mm, the glass transition temperature was measured at 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, and 500 mm positions (1000 mm width) at both ends in the TD direction from the arbitrary point. , Refers to the lowest temperature in it. The glass transition temperature obtained by temperature modulation DSC is measured in a sine wave shape with a temperature modulation amplitude of 1 ° C. with a temperature modulation period of 60 seconds in a nitrogen flow atmosphere at a temperature modulation period of 2 ° C./min in the range of 0 ° C. to 200 ° C. In the stepwise change portion of the obtained reversible component temperature modulation DSC chart, the method described in “9.3 Determination of glass transition temperature (1) Intermediate glass transition temperature Tmg” in JISK7121 (1987) is used as the glass transition temperature. It is the temperature obtained by the same method. From the viewpoint of heat resistance and moldability, the glass transition temperature obtained by temperature modulation DSC is more preferably 85 ° C. or higher and 110 ° C. or lower, and most preferably 85 ° C. or higher and 100 ° C. or lower.

In the present invention, the method of setting the minimum glass transition temperature required by temperature-modulated DSC of the film at a width of 1000 mm to 80 ° C. or higher and 110 ° C. or lower is not particularly limited. A method in which the time stress is set to a preferred composition of 5 MPa or more and 30 MPa or less and a fine stretching of 2% or more is preferably used in the heat treatment step after stretching in the width direction.
In addition, 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, and ensures the functionality of the coating film when it is dried. From the viewpoint of securing and functional uniformity in the width direction, it is preferable to satisfy the following formula (I).

_{(SA MD + SB MD) /} (SC MD × 2) ≦ 1.2 (I)
However, from the center in the TD direction of SA _MD : 1100 mm width film, 190 ° C. heat shrinkage in the MD direction at a position of 500 mm in any one direction (A direction) in the TD direction SB _MD : Center in the width direction of the 1100 mm width film From 190 ° C. heat shrinkage in the MD direction at a position of 500 mm in the direction opposite to the A direction in the TD direction (B direction) SC _MD : 190 ° C. heat shrinkage in the MD direction at the center of the TD direction of the 1100 mm width film is there.
1100 mm wide film (the main orientation axis direction at an arbitrary position of the film is taken as the TD direction, the position is the center (hereinafter also referred to as the center of the TD direction), and a 550 mm width is sampled in each of the two directions along the TD direction. 3 of the center in the TD direction of the width of the film), a position of 500 mm in any one direction (A direction) from the center to the TD direction, and a position of 500 mm in the direction opposite to the A direction in the TD direction (B direction) from the center. It is the average value which measured the thermal contraction rate in 190 degreeC 5 times, respectively about the sample cut out into the rectangle of length 150mm (A direction or B direction) x width 10mm about the point.

  Satisfying the formula (I) indicates that the difference in MD thermal shrinkage in the TD direction of the 1000 mm wide film is small, and the functional coating in the direction when the functional coating is applied to the film and dried. It is possible to suppress film unevenness and film unevenness. From the viewpoint of uniformity in physical properties in the TD direction, it is more preferable to satisfy the formula (I) ′, and it is most preferable to satisfy the formula (I) ″.

(SA _MD + SB _MD ) / SC _MD × 2 ≦ 1.15 (I) ′
(SA _MD + SB _MD ) / SC _MD × 2 ≦ 1.1 (I) ″
The method by which the biaxially oriented polyester film of the present invention satisfies the formula (I) is not particularly limited, but the maximum value of the orientation angle of the above-mentioned 1000 mm wide film is 20 ° or less.

  Furthermore, in thermomechanical analysis (TMA), the elongation peak temperature in the film MD direction when the temperature is raised from 25 ° C. to 200 ° C. at a rate of temperature rise of 5 ° C./min with a load of 19.6 mN should be 60 ° C. or higher. Is also effective. Here, the stretching peak temperature in the film MD direction refers to a temperature at which the stretched film shifts to shrinkage behavior as the temperature rises. There is a case where the film once shrinks and then shifts to the stretching behavior again. In the present invention, the temperature at which the stretching behavior first shifts to the shrinking behavior when the temperature is raised from 25 ° C. to 200 ° C. is the direction of the film MD. The extension peak temperature of The measurement is 1100 mm wide film (the main orientation axis direction at an arbitrary position of the film is the TD direction, and the position is the center (hereinafter also referred to as the center of the TD direction), and the 550 mm width is sampled in each of the two directions along the TD direction. The center of the TD direction of the film having a width of 1100 mm), a position of 500 mm in any one direction (A direction) from the center to the TD direction, and a distance of 500 mm from the center in the direction opposite to the A direction of the TD direction (B direction) For each of the three points, MD and TD are each performed three times, and an average value of nine values measured for MD and TD is adopted. In order to set the elongation peak temperature in the longitudinal direction of the film when the temperature is raised from 25 ° C. to 200 ° C. at a heating rate of 5 ° C./min at a load of 19.6 mN, It is effective to set the draw ratio to 2.8 to 3.4 times, preferably 2.9 to 3.3 times. The film draw ratio is not a special condition. However, as a result of various studies, the inventors have made the film draw ratio in the longitudinal direction to be within the above range, specifically at a load of 19.6 mN at 25 ° C. It was found that the elongation peak temperature in the longitudinal direction of the film when the temperature was raised from 1 to 200 ° C. at a temperature raising rate of 5 ° C./min could be 60 ° C. or higher.

  Moreover, it is preferable that the biaxially oriented polyester film of the present invention satisfies the following formula (II).

(SA _TD + SB _TD ) / SC _TD × 2 ≦ 1.2 (II)
However, SA _TD : 1100 mm width film (the main orientation axis direction at an arbitrary position of the film is the TD direction, and the position is the center (hereinafter also referred to as the TD direction center), and the two directions along the TD direction are 550 mm wide. From the center in the TD direction of the film (1100 mm width) from the center in the TD direction at a position of 500 mm in any one direction (A direction) in the TD direction _{TD TD} : TD direction of the 1100 mm width film 190 ° C. thermal shrinkage in the TD direction at a position 500 mm in the direction opposite to the A direction (B direction) in the TD direction from the center of the film SC _TD : 190 ° C. heat shrinkage in the TD direction at the center in the TD direction of the 1100 mm width film .
Satisfying the formula (II) indicates that the difference in TD heat shrinkage in the TD direction of a 1000 mm wide film is small, and the functional coating in the direction when applying a functional coating film to the film and drying is applied. It is possible to suppress film unevenness and film unevenness. From the viewpoint of uniformity of physical properties 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 × 2 ≦ 1.15 (II) ′
(SA _TD + SB _TD ) / SC _TD × 2 ≦ 1.1 (II) ″
The method by which the biaxially oriented polyester film of the present invention satisfies the formula (II) is not particularly limited, but the maximum value of the orientation angle of the above-mentioned 1000 mm wide film is 20 ° or less. Furthermore, in thermo-mechanical analysis (TMA), the elongation peak temperature in the film TD direction is 70 ° C. or higher when the temperature is increased from 25 ° C. to 200 ° C. at a heating rate of 5 ° C./min with a load of 19.6 mN. Therefore, it becomes easy to satisfy the formula (II). Here, the stretching peak temperature in the film TD direction refers to a temperature at which the stretched film shifts to shrinkage behavior as the temperature rises. The measurement is 1100 mm wide film (the main orientation axis direction at an arbitrary position of the film is the TD direction, and the position is the center (hereinafter also referred to as the center of the TD direction), and the 550 mm width is sampled in each of the two directions along the TD direction. The center of the TD direction of the film having a width of 1100 mm), a position of 500 mm in any one direction (A direction) from the center to the TD direction, and a distance of 500 mm from the center in the direction opposite to the A direction of the TD direction (B direction) For each of the three points of the position, MD and TD are each performed three times, and an average value of nine points measured for MD and TD is adopted. In some cases, the film is once shrunk and then shifted to the stretching behavior again. In the present invention, when the temperature is raised from 25 ° C. to 200 ° C., the temperature at which the stretching behavior first shifts to the shrinking behavior is set in the film TD direction. The extension peak temperature of In thermo-mechanical analysis (TMA), in order to obtain a stretching peak temperature of 70 ° C. or more in the film TD direction when the temperature is raised from 25 ° C. to 200 ° C. at a heating rate of 5 ° C./min with a load of 19.6 mN, It is effective to reinforce the fine stretching in the heat treatment step after stretching in the width direction, in addition to a method in which the stretching ratio in the longitudinal direction during film formation is 2.8 times to 3.4 times.

  Moreover, it is also effective to perform off-annealing as a method in which the biaxially oriented polyester film of the present invention satisfies the formulas (I) and (II). That is, it is a method in which the polyester film once wound is subjected to heat treatment again. The off-annealing temperature is set to 140 ° C or higher and 200 ° C or lower, and the width direction is free so that there is no difference in thermal shrinkage in the width direction, so it is possible to satisfy the formulas (I) and (II). It becomes. The off-annealing treatment temperature is preferably 150 ° C. or higher and 200 ° C. or lower, and most preferably 160 ° C. or higher and 200 ° C. or lower.

The biaxially oriented polyester film of the present invention has a stress at 10% elongation in the film MD direction at 150 ° C. of 5 MPa or more and 30 MPa or less, a thermal shrinkage rate in the film MD direction at 150 ° C. of 5% or less, and an orientation angle of 1000 mm width film. It is very important to satisfy the physical properties of the maximum value of 20 ° or less at the same time. If the stress at 10% elongation in the MD direction at 150 ° C. is set to 5 MPa or more and 30 MPa or less, the thermal shrinkage rate in the MD direction at 150 ° C. may increase, and the maximum value of the film orientation angle of 1000 mm width may be increased. There are cases where it is difficult to control to 20 ° or less. As a method for solving this dilemma, the biaxially oriented polyester film of the present invention has a laminated film configuration having a polyester A layer and a polyester B layer, and the polyester A layer is positioned in at least one outermost layer. Is preferred.
In the present invention, in the case of a laminated film having a polyester A layer and a polyester B layer, the layer having the higher melting point is the polyester A layer.

  The polyester film of the present invention has a layer A having a high melting point and a layer B having a melting point lower than that of the layer A, so that the layer A is a rigid layer, and the thermal shrinkage rate in the film MD direction at 150 ° C. is 5% or less. It can be kept low, and the maximum value of the orientation angle of a film having a width of 1000 mm can be easily set to 20 ° or less, and fulfills the role of satisfying the physical property uniformity in the width direction, while the B layer is a layer having high mobility, The stress at 10% elongation in the film MD direction at 150 ° C. can be easily set to 5 MPa or more and 30 MPa or less, and by fulfilling the role of achieving easy moldability, it is possible to satisfy characteristics that are difficult to achieve with a single film configuration. . The layer A in the polyester film of the present invention preferably has a plane orientation coefficient of 0.111 or more and 0.17 or less, preferably 0.13 or more and 0.17 or less, from the viewpoints of dimensional stability and width direction physical property uniformity. More preferably, it is more preferably 0.145 or more and 0.17 or less.

  Further, from the viewpoint of curling suppression of the film, the biaxially oriented polyester film of the present invention has a three-layer configuration of A layer / B layer / A layer in the case of a laminated polyester film having a polyester A layer and a polyester B layer. It is preferable.

  In the biaxially oriented polyester film of the present invention, in the case of a laminated film having a polyester A layer and a polyester B layer, the stress at 10% elongation in the film MD direction at 150 ° C. is 5 MPa or more and 30 MPa or less, and in the film MD direction at 150 ° C. Preferred embodiments of the polyester A layer and the polyester B layer for simultaneously satisfying physical properties such as a thermal shrinkage rate of 5% or less and a maximum orientation angle of a film having a width of 1000 mm of 20 ° or less include the following configurations. It is done.

  As a glycol component of the polyester A layer, an ethylene glycol component is contained in an amount of 90 mol% to less than 99 mol%, and at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and neopentyl glycol is 1 mol% to 10 mol. It is preferable that 90 mol% or more is a terephthalic acid component as a dicarboxylic acid component. More preferably, the glycol component contains an ethylene glycol component of 95 mol% or more and less than 99 mol%, and at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component and a neopentyl glycol component is 1 mol% or more and 5 mol%. The dicarboxylic acid component is preferably contained in an amount of less than 95% by mole, more preferably 95% by mole or more, more preferably terephthalic acid component, more preferably 98% by mole or more of the dicarboxylic acid component in the glycol component.

  As a glycol component of the polyester B layer, an ethylene glycol component is contained in an amount of 80 mol% or more and less than 95 mol%, and at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and a neopentylglycol component is 5 mol% or more 20 It is preferable to contain less than mol%, and 90 mol% or more is a terephthalic acid component as a dicarboxylic acid component. More preferably, the glycol component contains an ethylene glycol component of 85 mol% or more and less than 95 mol%, and at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component and a neopentyl glycol component is 5 mol% or more and 15 mol%. The dicarboxylic acid component is preferably contained in an amount of less than 95% by mole, more preferably 95% by mole or more, more preferably terephthalic acid component, more preferably 98% by mole or more of the dicarboxylic acid component in the glycol component.

  Next, although the example of the specific manufacturing method of the biaxially-oriented polyester film of this invention is described, this invention is limited to this example and is not interpreted.

  When a laminated polyester film having a polyester A layer and a polyester B layer is used, first, as polyester A used for the polyester A layer, a polyethylene terephthalate resin (a) and a 1,4-cyclohexanedimethanol copolymer polyethylene terephthalate resin (b ) At a predetermined rate. Moreover, as polyester B used for the polyester B layer, polyethylene terephthalate resin (c) and 1,4-cyclohexanedimethanol copolymerized polyethylene terephthalate resin (d) are weighed 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 resin temperature to 265 ° C. to 295 ° C. under an atmosphere of flowing nitrogen in the extruder, with an oxygen concentration of 0.7% by volume or less. Next, foreign matter is removed and the amount of extrusion is leveled through a filter and a gear pump, respectively, and discharged from the T die onto a cooling drum in a sheet form. At that time, an electrostatic application method in which a cooling drum and the resin are brought into close contact with each other by static electricity using an electrode applied with a high voltage, a casting method in which a water film is provided between the casting drum and the extruded polymer sheet, and the casting drum temperature is set to be equal to that of the polyester resin. The sheet-like polymer is brought into close contact with the casting drum, cooled and solidified by a method of sticking the extruded polymer at a glass transition point to (glass transition point−20 ° C.) or a combination of these methods, and unstretched. Get a film. Among these casting methods, when using polyester, a method of applying an electrostatic force is preferably used from the viewpoint of productivity and flatness.

The biaxially oriented polyester film of the present invention needs to be a biaxially oriented film from the viewpoints of heat resistance and dimensional stability. The biaxially oriented film is obtained by stretching an unstretched film in the longitudinal direction and then stretching in the width direction, or by stretching in the width direction and then stretching in the longitudinal direction, or by the longitudinal direction of the film. It can be obtained by stretching by a simultaneous biaxial stretching method in which the width direction is stretched almost simultaneously.
As the stretching ratio in such a stretching method, 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 is employed in the longitudinal direction. The stretching speed is preferably 1,000% / min or more and 200,000% / min or less. Moreover, it is preferable that the extending | stretching temperature of a longitudinal direction shall be 70 degreeC or more and 90 degrees C or less. Further, the stretching ratio in the width direction is preferably 3.1 times to 4.5 times, and more preferably 3.5 times to 4.2 times. The stretching speed in the width direction is desirably 1,000% / min or more and 200,000% / min or less. Also, stretching in the width direction is divided into a plurality of zones so that the maximum value of the orientation angle of a 1000 mm width film is 20 ° or less while the stress at 10% elongation in the film MD direction at 150 ° C. is 5 MPa or more and 30 MPa or less. A method of stretching while raising the temperature stepwise is preferable, for example, the first half temperature of stretching is 90 ° C. or more and 120 ° C. or less, the middle temperature of stretching is 100 ° C. or more and 130 ° C. or less, and the second half temperature is 110 ° C. or more and 150 ° C. or less, A method of increasing the temperature in the order of the first half-stretching temperature, the middle stretching temperature, and the second half-stretching temperature can be mentioned.

  Furthermore, the film is heat-treated after biaxial stretching. The heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. This heat treatment is performed at a temperature of 120 ° C. or more and below the crystal melting peak temperature of the polyester, preferably 200 ° C. or more and 240 ° C. or less, more preferably 210 ° C. to 235 ° C., and 215 ° C. to 230 ° C. Most preferred. Here, the preferable heat treatment temperature indicates the highest temperature among the heat treatment temperatures performed after biaxial stretching. The heat treatment time can be arbitrarily set within a range not deteriorating the characteristics, and is preferably 5 seconds to 60 seconds, more preferably 10 seconds to 40 seconds, and most preferably 15 seconds to 30 seconds. Good. In addition, the maximum value of the orientation angle of a film having a width of 1000 mm is 20 ° while the stress at 10% elongation in the film MD direction at 150 ° C. is 5 MPa or more and 30 MPa or less and the thermal shrinkage rate in the film MD direction at 150 ° C. is 5% or less. In order to achieve the following, a method in which the heat treatment is divided into a plurality of zones and the temperature is raised or lowered stepwise, or a method of fine stretching in the width direction in the heat treatment step is preferably employed. For example, the first half temperature of the heat treatment is 180 ° C. to 210 ° C. and slightly stretched 1% to 10%, preferably 3% to 10% in the width direction, and the mid-heat treatment temperature is 200 ° C. to 240 ° C. and 1% to the width direction. More than 10%, preferably 3% or more and 10% or less fine stretching, and the latter half temperature of the heat treatment is 150 ° C. or more and less than 200 ° C. It is also preferable to carry out the latter half of the heat treatment while relaxing 1% or more and 10% or less in order to lower the heat shrinkage rate. Furthermore, in order to improve the adhesive force with various processed layers such as a printing layer, an adhesive, a vapor deposition layer, a hard coat layer, and a weathering layer, at least one surface can be subjected to corona treatment or an easy adhesion layer can be coated. As a method of providing the coating layer in-line in the film manufacturing process, at least uniaxially stretched film with a coating layer composition dispersed in water is uniformly applied using a metalling ring bar or gravure roll. Then, a method of drying the coating while stretching is preferable, and in this case, the thickness of the easy adhesion layer is preferably 0.01 μm or more and 1 μm or less. Also, various additives such as antioxidants, heat stabilizers, ultraviolet absorbers, infrared absorbers, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc. may be added to the easy-adhesion layer. Good. The resin preferably used for the easy-adhesion layer is preferably at least one resin selected from an acrylic resin, a polyester resin, and a urethane resin from the viewpoint of adhesiveness and handleability. Furthermore, off-annealing under conditions of 140 to 200 ° C. is also preferably used.

  Since the biaxially oriented polyester film of the present invention has a low molding stress at 150 ° C., it has good moldability, and since the heat shrinkage rate at 150 ° C. is low, the film deformation during coating drying is small, Since the maximum orientation angle of a 1000 mm wide film is small, it has excellent uniformity of physical properties in the width direction. For decorative purposes such as building materials, mobile devices, electrical products, automobile parts, game machine parts, etc. For example, it can be suitably used for a molding process in which a process film such as a film is molded. Above all, because it is very excellent in the uniformity of physical properties in the width direction, in order to achieve optical applications, specifically high-definition and thinning of the retardation layer, a retardation layer is applied to the process film, and the process It is preferably used for applications in which the entire film is molded.

(1) Composition of polyester A polyester resin and a film are dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue component and by-product diethylene glycol can be quantified using ¹ H-NMR and ¹³ C-NMR. it can. In the case of a laminated film, the components constituting each layer can be collected and evaluated by scraping off each layer of the film according to the laminated thickness. In addition, about the film of this invention, the composition was computed by calculation from the mixing ratio at the time of film manufacture.

(2) Intrinsic viscosity of polyester The intrinsic viscosity of the polyester resin and the film was measured at 25 ° C. using an Ostwald viscometer after dissolving the polyester in orthochlorophenol. In the case of a laminated film, the intrinsic viscosity of each layer can be evaluated by scraping each layer of the film according to the laminated thickness.

(3) Film thickness, layer thickness The film was embedded in an epoxy resin, and the film cross section 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) Using a melting point differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., RDC220), measurement and analysis were performed in accordance with JIS K7121-1987 and JIS K7122-1987. Using 5 mg of a polyester film as a sample, the temperature at the apex of the endothermic peak obtained from the DSC curve when the temperature was raised from 25 ° C. to 300 ° C. at 20 ° C./min was defined as the melting point. In the case of a laminated film, the melting point of each layer alone can be measured by scraping each layer of the film according to the laminated 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 was measured, and a layer having a higher melting point was a polyester A layer and a lower layer was a polyester B layer.

(5) Minute endothermic peak temperature (Tmeta) before crystal melting
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., RDC220), measurement and analysis were performed in accordance with JIS K7121-1987 and JIS K7122-1987. Using 5 mg of a polyester film as a sample, a minute endothermic peak temperature appearing before the crystal melting peak when the temperature was raised from 25 ° C. to 300 ° C. at 20 ° C./min was read as Tmeta.
(6) A sample with a dimension of 100 mm × 100 mm at an arbitrary point on the main orientation axis and orientation angle maximum value film of a 1000 mm wide film, and a microwave molecular orientation meter MOA-2001A (manufactured by KS Systems (current Oji Scientific Instruments)) Using a frequency of 4 GHz), the in-plane main orientation axis of the polyester film was determined and taken as the TD direction. In addition, with this arbitrary point as the center in the TD direction of the film, between 50 mm to 500 mm in any one direction (A direction) of the TD direction every 50 mm (50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm) , 450 mm, 500 mm) and the center of the film in the TD direction from the center of the TD direction in the direction opposite to the A direction (B direction) between 50 mm and 500 mm at the position of every 50 mm, the above-mentioned microwave molecular orientation meter MOA- Using 2001A (frequency 4 GHz), the orientation angle (the smaller of the angles formed by the main orientation axis and the film TD direction or the film MD direction) was measured, and the maximum value was obtained.
(7) Glass transition temperature obtained from temperature-modulated DSC In the same manner as (6), a sample was cut out with a size of 100 mm × 100 mm at an arbitrary point of the film, 5 mg was taken therefrom, put into an aluminum standard container, and differential Using a scanning calorimeter (Q100 manufactured by TA Instrument), in a nitrogen flow atmosphere (flow rate 50 mL / min), in the range of 0 ° C. to 200 ° C., 2 ° C./min, with a temperature modulation period of 60 seconds and a temperature modulation amplitude of 1 Measurements were performed in a sine wave form at ° C. The specific heat calibration was performed with sapphire, and “Universal Analysis 2000” manufactured by TA Instrument was used for data analysis. The method described in “9.3 Determination of Glass Transition Temperature (1) Intermediate Glass Transition Temperature Tmg” in JISK7121 (1987) in the step-like change portion of the temperature-modulated DSC chart of the obtained reversible component The glass transition temperature of the temperature-modulated DSC was obtained by the same method as above (the point where the straight line equidistant from the straight line extending from each base line in the vertical axis direction and the curve of the step-like change part of the glass transition intersect) Was the glass transition temperature of the temperature-modulated DSC). Further, with this arbitrary point as the center in the TD direction of the film, every 50 mm to 500 mm in any one direction (A direction) of the TD direction (50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm) and glass transition using the above-described differential scanning calorimeter at a position of 50 mm to 500 mm in the direction opposite to the A direction (B direction) from the center in the TD direction of the film at every 50 mm. The temperature was measured and the minimum temperature was determined. (8) Stress at 10% elongation in the film MD direction at 150 ° C. The film was cut into a rectangle 150 mm long × 10 mm wide in the MD direction and used as a sample. Using a tensile tester (Orientec Tensilon UCT-100), the tensile test was performed in the MD direction of the film at an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. For the measurement, a film sample was set in a constant temperature layer set in advance at 150 ° C., and a tensile test was performed after 90 seconds of preheating. Read the load applied to the film when the sample is stretched 10% (when the distance between chucks is 55 mm), and divide by the cross-sectional area (film thickness x 10 mm) of the sample before the test. did. Note that the measurement was performed by taking a main orientation axis direction at an arbitrary position of the film as a TD direction, taking the position as a center (center in the TD direction), collecting a width of 550 mm in each of two directions along the TD direction, and setting the width as 1100 mm. 5 times for each of the three points at the center in the TD direction, at a position of 500 mm in any one direction (A direction) from the center to the TD direction, and at a position of 500 mm in the direction opposite to the A direction (B direction) from the center The average value of the 15 values was defined as the stress at 10% elongation in the film MD direction at 150 ° C.

(9) Thermal shrinkage (150 ° C, 190 ° C)
The film was cut into rectangles each having a length of 150 mm and a width of 10 mm in the MD direction and the TD direction as samples. Draw a marked line on the sample at an interval of 100 mm (positions at 50 mm from the center to both ends) and suspend a 3 g weight and place it in a hot air oven heated to the specified temperature (150 ° C, 190 ° C) for 30 minutes and heat treatment Went. The distance between the marked lines after the heat treatment was measured, and the thermal contraction rate was calculated from the change in the distance between the marked lines before and after heating by the following formula. The evaluation was performed with the main orientation axis direction at an arbitrary position of the film as the TD direction, the position (center in the TD direction) as a center, and a 550 mm width in each of the two directions along the TD direction. 5 times for each of the three points at the center of the direction, 500 mm from the center to any one direction (A direction) in the TD direction, and 500 mm from the center in the direction opposite to the A direction in the TD direction (B direction) The average value of the 15 values was defined as the thermal shrinkage in the film MD direction and the TD direction at a predetermined temperature (150 ° C., 190 ° C.).
Thermal shrinkage (%) = {(distance between marked lines before heat treatment) − (distance between marked lines after heat treatment)} / (distance between marked lines before heat treatment) × 100.

(10) Formula (I), Formula (II) Calculation Method In the same manner as in (9), the MD of the center value in the TD direction of the 1100 mm wide film, the heat shrinkage rate at 190 ° C. in the TD direction (SC _MD , SC _TD ) From the center in the width direction of the 1100 mm width film, MD at a position of 500 mm in any one direction (A direction) in the TD direction, heat shrinkage rate at 190 ° C. in the TD direction (SA _MD , SA _TD ) From the center of the TD direction, the MD at a position of 500 mm in the direction opposite to the A direction of the TD direction (B direction) and the heat shrinkage rate at 190 ° C. (SB _MD , SB _TD ) in the TD direction are measured (each 5 times) The value on 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 Using sodium D line (wavelength 589 nm) as a light source and using an Abbe refractometer, the MD refractive index (n _MD ), TD refractive index (n _TD ), and refractive index in the thickness direction of the film The ratio (n _ZD ) was measured, and the plane orientation coefficient (fn) was calculated from the following formula.
fn = (n _MD + n _TD ) / 2-n _ZD
The plane orientation coefficient was measured on both sides of the film, and the value of the higher plane orientation coefficient was listed in the table.

  Note that the measurement was performed by taking a main orientation axis direction at an arbitrary position of the film as a TD direction, taking the position as a center (center in the TD direction), collecting a width of 550 mm in each of two directions along the TD direction, and setting the width as 1100 mm. 5 times for each of three points at the center in the TD direction, at a position of 500 mm in any one direction (A direction) from the center to the TD direction, and at a position of 500 mm in the direction opposite to the A direction in the TD direction (B direction) from the center The average value of the 15 values was adopted.

(12) Thermomechanical analysis (TMA)
The film was cut into a rectangular shape with a length of 50 mm and a width of 4 mm in the MD direction and the TD direction as a sample, and the temperature was raised under the following conditions using a thermomechanical analyzer (manufactured by Seiko Instruments, TMA EXSTAR6000). The extension peak temperature at 200 ° C. was calculated.

Test length: 15 mm, load: 19.6 mN, heating rate: 5 ° C./min,
Measurement temperature range: 25-200 ° C
In the present invention, the stretching peak temperature from 25 ° C. to 200 ° C. refers to the temperature at which the stretched film shifts to shrinkage behavior as the temperature rises. There is a case where the film once shrinks and then shifts to the stretching behavior again. In the present invention, the temperature at which the stretching behavior first shifts to the shrinking behavior when the temperature is raised from 25 ° C. to 200 ° C. is the direction of the film MD. And the extension peak temperature in the TD direction.

  Note that the measurement was performed by taking a main orientation axis direction at an arbitrary position of the film as a TD direction, taking the position as a center (center in the TD direction), collecting a width of 550 mm in each of two directions along the TD direction, and setting the width as 1100 mm. MD at three points, the center in the TD direction, the 500 mm position in any one direction (A direction) from the center to the TD direction, and the 500 mm position in the direction opposite to the A direction (B direction) from the center in the TD direction. The measurement was performed three times for each TD, and an average value of nine values measured for MD and TD was adopted.

(13) Dimensional stability Polyarylate / MEK dispersion was coated and dried on a 1100 mm wide polyester film surface with a die coater (drying temperature: 150 ° C., drying time: 1 minute, unwinding tension: 200 N). / M, winding tension: 100 N / m). The width of the polyester film after drying was measured and evaluated according to the following criteria (polyarylate thickness after drying was 25 μm).
A: The width shrinkage was less than 5 mm (the width of the polyester film after drying was 995 mm or more).
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).

  In addition, the width shrinkage is evaluated by selecting any 10 locations of the 1000 mm wide film after coating and drying, and measuring the width, and the (1000 mm width-film width average value at 10 optional locations) is used as the width shrinkage amount. Adopted.

(14) Molding processability The polyester film coated with the polyarylate obtained in (13) was put into a hot air oven and uniaxially stretched in the longitudinal direction (oven temperature: 150 ° C., free in the width direction). The stretchability (moldability) of the film was evaluated according to the following criteria.
A: The stretching tension was less than 1200 N / m, and 1.1-fold stretching was possible.
B: The film was stretched 1.1 times with a stretching tension of 1200 N / m or more and less than 1500 N / m.
C: The film could not be stretched 1.1 times at a stretching tension of 1500 N / m.

(15) Functional coating film width direction uniformity The polyarylate layer is peeled from the polyarylate-coated uniaxially stretched polyester film obtained in (14), and the center in the width direction and any one direction in the width direction from the center (A The in-plane retardation was measured at three points, the position of 500 mm in the direction) and the position of 500 mm in the direction (B direction) opposite to the A direction in the width direction from the center, and evaluated according to the following criteria. The retardation was measured using an automatic birefringence meter (KOBRA-21ADH) manufactured by Shin-Oji Scientific Instruments.
A: The difference between the maximum value and the minimum value of the retardation measured at 3 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 and minimum retardation values measured at three points was 20 nm or more.

(Manufacture of polyester)
The polyester resin used for film formation was prepared as follows.

(Polyester A)
Polyethylene terephthalate resin (intrinsic viscosity 0.65) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component and the ethylene glycol component is 100 mol% as the glycol component.

(Polyester B)
Copolyester (GN001 manufactured by Eastman Chemical Co., Ltd.) obtained by copolymerizing 33 mol% of 1,4-cyclohexanedimethanol with respect to the glycol component was used as cyclohexanedimethanol copolymerized polyethylene terephthalate (inherent viscosity 0.75).

(Polyester C)
A neopentyl glycol copolymer polyethylene terephthalate resin (intrinsic viscosity of 0.75) having a terephthal component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 70 mol% as a glycol component, and a neopentyl glycol component of 30 mol%.

(Polyester D)
A diethylene glycol copolymer polyethylene terephthalate resin (intrinsic viscosity 0.65) in which the terephthalic component is 100 mol% as the dicarboxylic acid component, the ethylene glycol component is 85 mol%, and the diethylene glycol component is 15 mol% as the glycol component.

(Polyester E)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 82.5 mol% of terephthalic component as dicarboxylic acid component, 17.5 mol% of isophthalic component, and 100 mol% of ethylene glycol component as glycol component.

(Polyester F)
2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate resin (specifically 85 mol% of terephthalic component as dicarboxylic acid component, 15 mol% of 2,6-naphthalenedicarboxylic acid component, and 100 mol% of ethylene glycol component as glycol component) Viscosity 0.7).

(Particle Master)
Polyethylene terephthalate particle master (intrinsic viscosity 0.65) containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester A at a particle concentration of 2 mass%.

Example 1
The composition is as shown in the table, and the raw materials are supplied to separate bent co-directional twin-screw extruders each having an oxygen concentration of 0.2% by volume, the A-layer extruder cylinder temperature is 270 ° C., and the B-layer extruder cylinder temperature is After melting at 277 ° C., the short tube temperature after joining the A layer and B layer was 277 ° C., the die temperature was 280 ° C., and discharged from a T die onto a cooling drum controlled to 25 ° C. At that time, a wire electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched sheet. Next, the film temperature was raised with a heating roll before stretching in the longitudinal direction, and the film was stretched 3.1 times in the longitudinal direction at a stretching temperature of 85 ° C. and immediately cooled with a metal roll whose temperature was controlled at 40 ° C.

  Next, the film was stretched 3.9 times in the width direction at a first half temperature of 95 ° C., a middle stretching temperature of 105 ° C. and a second half stretching temperature of 140 ° C. in a tenter-type transverse stretching machine, and the first half temperature of the first half of the heat treatment was maintained at 200 ° C. in the tenter. A heat treatment was performed at a temperature of 230 ° C., and a heat treatment was performed while applying a relaxation of 3% in the width direction at a heat treatment latter half temperature of 180 ° C. 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 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 3)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

Example 4
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 3 except that 5% fine stretching was performed in the width direction in the first half of the heat treatment.

(Example 5)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 6)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 7)
A three-layer film of A / B / A was obtained. The composition of each layer is as shown in the table, and the raw material for layer A and the raw material for layer B are supplied to separate vented co-directional twin screw extruders each having an oxygen concentration of 0.2% by volume. Cooling with temperature controlled at 270 ° C, B layer extruder cylinder temperature at 277 ° C, short tube temperature after merging with A layer and B layer at 277 ° C, die temperature at 280 ° C, 25 ° C from T die The sheet was discharged onto the drum. At that time, a wire-like electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain a three-layer laminated unstretched film composed of A layer / B layer / A layer.
Thereafter, a biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the mid-heat treatment temperature was 225 ° C.

(Example 8)
The composition was changed as shown in the table, and a biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 7 except that 2% fine stretching was performed in the width direction in the first half of the heat treatment.

Example 9
The composition was changed as shown in the table, and a biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 17 except that 5% fine stretching was performed in the width direction in the first half of the heat treatment.

(Example 10)
The film thickness was 75 μm in the same manner as in Example 7 except that the composition was changed as shown in the table, and the film was slightly stretched 5% in the width direction in the first half of the heat treatment, and was further slightly stretched 3% in the width direction in the middle of the heat treatment. A biaxially oriented polyester film was obtained.

(Example 11)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 7 except that the composition was changed as shown in the table and the mid-heat treatment temperature was set to 205 ° C.

(Example 12)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 7 except that the composition was changed as shown in the table and the mid-heat treatment temperature was 230 ° C.

(Example 13)
The film thickness was changed to 50 μm in the same manner as in Example 7 except that the composition was changed as shown in the table, and the film was slightly stretched 5% in the width direction in the first half of the heat treatment, and further 3% stretched in the width direction in the middle of the heat treatment. A biaxially oriented polyester film was obtained.

(Example 14)
The film thickness was 75 μm in the same manner as in Example 7 except that the composition was changed as shown in the table, and the film was slightly stretched 5% in the width direction in the first half of the heat treatment, and was further slightly stretched 3% in the width direction in the middle of the heat treatment. A biaxially oriented polyester film was obtained.

(Example 15)
The biaxially oriented polyester film obtained in Example 14 was subjected to an off-annealing treatment in a hot air oven at 180 ° C. while reducing the winding speed in the width direction and the longitudinal direction by 1% from the unwinding speed.

(Example 16)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table and heat treatment was performed at a mid-heat treatment temperature of 235 ° C.

(Example 17)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 10 except that the composition was changed as shown in the table.

(Comparative Example 1)
The composition was changed as shown in the table, and the first half, the middle, and the second half of the horizontal stretching were both 120 ° C. and stretched 3.4 times. In the tenter, heat treatment was performed at the first half of the heat treatment and the middle heat treatment at 230 ° C. A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 7 except that the heat treatment was performed while applying a 3% relaxation in the width direction at a heat treatment latter half temperature of 180 ° C.

(Comparative Example 2)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was as shown in the table and the mid-heat treatment temperature was 220 ° C.

(Comparative Example 3)
The composition was as shown in the table, and a biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the mid-heat treatment temperature was 195 ° C.

The meanings of the 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-naphthalenedicarboxylic acid

Since the biaxially oriented polyester film of the present invention has a low molding stress at 150 ° C., it has good moldability, and since the thermal shrinkage at 150 ° C. is low, the film deformation during coating drying is small, Furthermore, since the maximum value of the orientation angle of a 1000 mm wide film is small, it has excellent uniformity of physical properties in the width direction, and is used for decorative decorations for building materials, mobile devices, electrical products, automobile parts, game machine parts, etc., polarizing plates It can use suitably for optical films etc., etc.

Claims (12)

The stress at 10% elongation in the film MD direction at 150 ° C. is 5 MPa or more and 30 MPa or less, the thermal shrinkage rate in the film MD direction at 150 ° C. is 5% or less, and the orientation angle of the film at 1000 mm width (main orientation axis and film TD direction or A biaxially oriented polyester film having a maximum value of 20 ° or less of the smaller angle formed by the film MD direction.
However, the orientation angle of the film having a width of 1000 mm is the width of 1100 mm by taking the main orientation axis direction at an arbitrary position of the film as the TD direction, taking 550 mm width in each of the two directions along the TD direction with the position as the center. The orientation angle is measured at the positions (1000 mm width) of 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, and 500 mm from the arbitrary point to the both ends in the TD direction, and the maximum value is obtained. Moreover, let the direction orthogonal to the TD direction be the MD direction within the same film plane. The biaxially oriented polyester film according to claim 1, which is a film having a MD direction of 10 m or more and a TD direction of 1100 mm or more. The biaxially oriented polyester film according to claim 1 or 2, wherein the minimum glass transition temperature obtained by temperature-modulated DSC of the film at a width of 1000 mm is 80 ° C or higher and 110 ° C or lower.
However, the glass transition temperature obtained by temperature-modulated DSC of the film at a width of 1000 mm is 550 mm in width in each of the two directions along the TD direction with the main orientation axis direction at the arbitrary position of the film as the TD direction. As a film having a width of 1100 mm, the glass transition temperature was measured at 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, and 500 mm positions (1000 mm width) from both points to the TD direction. Find the minimum temperature. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the thermal shrinkage in the film MD direction and the TD direction at 190 ° C is 5% or less. The biaxially oriented polyester film according to any one of claims 1 to 4, which satisfies the following formula (I).
_{(SA MD + SB MD) /} (SC MD × 2) ≦ 1.2 (I)
However, from the center in the TD direction of the SA _MD : 1100 mm width film, the thermal shrinkage of 190 ° C. in the MD direction at a position of 500 mm in any one direction (A direction) in the TD direction SB _MD : the center in the TD direction of the 1100 mm width film To 190 ° C. heat shrinkage in the MD direction at a position of 500 mm in the direction opposite to the A direction in the TD direction (B direction) SC _MD : 190 ° C. heat shrinkage in the MD direction at the center in the TD direction of the 1100 mm width film The biaxially oriented polyester film according to any one of claims 1 to 5, which satisfies the following formula (II).
(SA _TD + SB _TD ) / (SC _TD × 2) ≦ 1.2 (II)
However, SA _TD : 190 ° C. heat shrinkage ratio in the TD direction at a position of 500 mm in any one direction (A direction) of the TD direction from the center in the TD direction of the 1100 mm width film SB _TD : the center in the TD direction of the 1100 mm width film To 190 ° C. heat shrinkage in the TD direction at a position of 500 mm in the direction opposite to the A direction (B direction) of the TD direction SC _TD : 190 ° C. heat shrinkage in the TD direction at the center in the TD direction of the 1100 mm wide film. The biaxially oriented polyester film according to any one of claims 1 to 6, wherein the plane orientation coefficient on the higher side of the plane orientation coefficients on both sides of the film is 0.111 or more and 0.17 or less. The biaxially oriented polyester film according to claim 1, which is a laminated polyester film having a polyester A layer and a polyester B layer having a melting point lower than that of the polyester A layer, wherein the polyester A layer is located in at least one outermost layer. 2. The elongation peak temperature in the film TD direction is 70 ° C. or higher when the temperature is raised from 25 ° C. to 200 ° C. at a rate of temperature increase of 5 ° C./min by thermomechanical analysis (TMA). The biaxially-oriented polyester film in any one of -8. The elongation peak temperature in the film MD direction when the temperature is raised from 25 ° C to 200 ° C at a rate of temperature rise of 5 ° C / min at a load of 19.6 mN by thermomechanical analysis (TMA) is 60 ° C or higher. The biaxially oriented polyester film according to any one of 1 to 9. The biaxially oriented polyester film according to any one of claims 1 to 10, which is used for molding processing. The biaxially oriented polyester film according to any one of claims 1 to 11, which is used for optical applications.