TWI632053B - Biaxially oriented polyester film - Google Patents

Abstract

An object of the present invention is to provide a biaxially-oriented polyester film which is excellent in moldability and uniformity in physical properties in the width direction and can be suitably used for molding processing and optical applications.

The solution of the present invention is a biaxially oriented polyester film, which has a stress of 5 MPa or more and 30 MPa or less when stretched at 10% of the MD (machine direction) direction of the film at 150 ° C, and thermal shrinkage of the film in the MD direction at 150 ° C. The ratio is 5% or less, and the maximum value of the alignment angle (the angle of the smaller of the angle formed by the main alignment axis and the TD (transverse direction) direction or the MD direction of the film) of the film is 20 ° or less.

However, the alignment angle of a film with a width of 1000 mm is to set the main alignment axis direction of any position of the film to the TD direction. With this position as the center, take a width of 550 mm in two directions along the TD direction to make a film with a width of 1100 mm , From the arbitrary point to the two ends in the TD direction at 50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, and 500mm (1000mm width), measure the alignment angle, and find the maximum value ; In the same film plane, the direction orthogonal to the TD direction is set to the MD direction.

Description

Biaxially oriented polyester film

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

In recent years, due to the rise in environmental awareness, there is a strong demand for solvent-free coating, plating replacement, etc. in building materials, automotive parts, mobile phones, and electrical products. The introduction of decorative methods using thin films is progressing.

As a polyester film for molding used in this decoration method, several proposals have been made. For example, there is a proposal for a polyester film for molding that exhibits low molding stress, low modulus of storage elasticity, and satisfies high moldability even at low temperatures (for example, refer to Patent Document 1).

There is also a proposal for a polyester film that exhibits a high storage elastic modulus at a low temperature, a low molding stress at a high temperature, and a combination of heat resistance and moldability (for example, refer to Patent Document 2).

In addition, liquid crystal displays are used in large TVs, personal computers, tablets, and smartphones, and stable demand is expected in the future. The polarizing plate constituting the liquid crystal display uses various films such as a surface protection film, a release film, a retardation film, and an engineering film. The uniformity of the physical properties in the width direction is very important. As a biaxially stretched polyester film, There are also several proposals. For example, there are proposals to satisfy the uniformity in the width direction A polyester film for polarizing film bonding that reduces unevenness in alignment angle and thickness (for example, refer to Patent Document 3). In addition, with the expansion of smart devices such as smart phones and tablet terminals, the demand for thin filming of liquid crystal displays has increased, and high-definition and thin-filming has also progressed in polarizing plates and retardation layers. Therefore, in order to achieve high-definition and thin-film formation of the retardation layer, a process retardation layer is coated on the engineering film and molded together with the engineering film, and the process development system for achieving high-definition and thin-film formation of the retardation layer is progressing.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-290354

[Patent Document 2] International Publication No. 2012-005097

[Patent Document 3] Japanese Patent Laid-Open No. 2002-40249

However, although the films described in Patent Documents 1 and 2 are excellent in moldability, they are uneven in physical properties in the width direction, and when they are used for decorative molding of large members, uneven molding or uneven strain after molding may occur. Moreover, if it is used as an engineering film of a polarizing plate and a retardation layer, uneven physical properties may cause uneven characteristics.

Moreover, although the film described in Patent Document 3 is excellent in uniformity in the width direction, it is difficult to use it because it has insufficient moldability for deep-shaped decorative molding or polarizing plates and phase differences formed with an engineering film.

The object of the present invention is to eliminate the problems of the conventional techniques described above. point. That is, a biaxially-oriented polyester film is provided, which is excellent in moldability and uniformity in physical properties in the width direction, and is suitable for use in molding and optical applications.

To solve this problem, the gist of the present invention is as follows.

A biaxially oriented polyester film having a thermal contraction rate of 150 MPa or more and a stress of 5 MPa or less at 10% of the MD (Machine direction, hereinafter referred to as MD) direction of the film at 150 ° C, and the MD direction of the film at 150 ° C The maximum value of the alignment angle of a film with a width of less than 5% and a thickness of 1000 mm {(the angle of the smaller of the angle formed by the main alignment axis and the film in the TD (Transverse Direction, transverse direction) or MD direction of the film)} Is 20. the following. However, the alignment angle of a film with a width of 1000 mm is to set the main alignment axis direction of any position of the film to the TD direction. With this position as the center, take a width of 550 mm in two directions along the TD direction to make a film with a width of 1100 mm. , From the arbitrary point to the two ends in the TD direction at 50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, and 500mm (1000mm width), measure the alignment angle, and find the maximum value ; In the same film plane, the direction orthogonal to the TD direction is set to the MD direction.

The biaxially oriented polyester film of the present invention has low forming stress at 150 ° C and good moldability, and because of the low thermal shrinkage at 150 ° C, the film deformation during coating and drying is small, and because of the 1000mm width film, The maximum value of the alignment angle is small, and the physical property uniformity in the width direction is excellent. It can be applied to building materials, mobile machines, electrical products, automotive parts, and tourism. It is used for molding and decoration of theater parts, and for optical films such as polarizing plates.

[Form of Implementing Invention]

The polyester constituting the biaxially oriented polyester film of the present invention is a general term for a polymer compound whose main bond in the main chain is an ester bond. The polyester resin is usually obtained by subjecting a dicarboxylic acid or a derivative thereof to a polycondensation reaction with a diol or a derivative thereof.

In the present invention, from the aspects of moldability, appearance, heat resistance, dimensional stability, and economy, more than 60 mol% of the diol units constituting the polyester are preferably structural units derived from ethylene glycol. 60 mol% or more of the carboxylic acid unit is preferably a structural unit derived from terephthalic acid. Here, the so-called dicarboxylic acid unit (structural unit) or diol unit (structural unit) means a divalent organic group in which a portion removed by polycondensation has been removed, and if necessary, it is represented by the following general formula .

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

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

(Here, R and R 'are divalent organic groups)

In addition, when a trivalent or higher carboxylic acid or alcohol and a derivative thereof including a trimellitic acid unit or a glycerol unit are included, the same applies to a trivalent or higher carboxylic acid or alcohol unit (structural unit). The trivalent or more organic group after removing the part removed by polycondensation has been removed.

Examples of the diol or its derivative to be used for the polyester used in the present invention include diethylene glycol, 1,2-propylene glycol, and Aliphatic dihydroxy compounds such as 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, etc. Polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., cycloaliphatic diene such as 1,4-cyclohexanedimethanol, spirodiol, etc. Aromatic dihydroxy compounds such as hydroxy compounds, bisphenol A, bisphenol S, and their derivatives. Among these, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol are more preferably used in terms of moldability and operability.

Also, as a dicarboxylic acid to be used for the polyester used in the present invention Or its derivative, in addition to terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfodicarboxylic acid, dibenzene Fatty acids such as oxyethanedicarboxylic acid, 5-sodium disulfonic acid, etc., oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid, etc. Alicyclic dicarboxylic acids such as dicarboxylic acids, 1,4-cyclohexanedicarboxylic acids, hydroxycarboxylic acids such as parahydroxybenzoic acid, and their derivatives. Examples of the dicarboxylic acid derivatives include dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, and dimethyl 2,6-naphthalene dicarboxylate. Esters, esters of dimethyl isophthalate, dimethyl adipate, diethyl maleate, dimethyl dimer, etc. Among them, in terms of moldability and operability, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and their esterified products are more preferably used.

The biaxially oriented polyester film of the present invention Due to the heterogeneous shape forming ability and the ease of forming when the engineering film is molded together, the stress must be 5 MPa to 30 MPa when the film is stretched at 10% in the MD direction at 150 ° C.

Here, in the present invention, the evaluation of a film having a width of 1000 mm is to set the main alignment axis direction of an arbitrary position of the film to the TD direction, and use that position as the center (hereinafter also referred to as the TD direction center), and follow the TD direction to A width of 550 mm was taken in each of the two directions, and a 500 mm width (1000 mm width) of the two directions along the TD direction from the center of the TD direction of the 1100 mm film 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.

In addition, the so-called stress at 10% stretching in the MD direction of a film at 150 ° C means that a rectangular film sample cut into a test length of 50 mm is fixed in a thermostatic bath set at 150 ° C in advance, and After a preheating time of 90 seconds, when the tensile test was performed at a strain rate of 300 mm / min, the stress applied to the film when the sample was stretched by 10%. In addition, the evaluation is to set the main alignment axis direction of the arbitrary position of the film to the TD direction, and use this position as the center (hereinafter also referred to as the TD direction center), and take a width of 550 mm in each of two directions along the TD direction, and a width of 1100 mm. TD direction center of the film, 500mm position in any one of the TD directions (A direction) from the center of the TD direction, 500mm position in the TD direction opposite to the A direction (B direction) from the center of the TD direction 3 points were performed 5 times each, and the average value of 15 values was set as the stress at the time of 10% stretching in the MD direction of the film at 150 ° C. From the viewpoint of moldability and dimensional stability, the stress at 10% stretching in the MD direction of a film at 150 ° C. is more preferably 6 MPa to 20 MPa, and most preferably 7 MPa to 15 MPa.

In the biaxially oriented polyester film of the present invention, the stress at the time of 10% stretching in the MD direction of the film at 150 ° C is within the above range. The method is not particularly limited, but, for example, as the diol component constituting the polyester film of the present invention, it contains an ethylene glycol component of 60 mol% or more, and preferably contains a diethylene glycol component and 1,3-propanediol. Component, a 1,4-butanediol component, a 1,4-cyclohexanedimethanol component, and a diol component of at least one type of neopentyl glycol component. Among them, it is preferable to include at least one type of a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and a neopentyl glycol component. The dicarboxylic acid component constituting the polyester film of the present invention contains at least 60 mol% of a terephthalic acid component, and preferably contains at least an isophthalic acid component and a 2,6-naphthalenedicarboxylic acid component. 1 or more types of dicarboxylic acid components.

In the biaxially oriented polyester film of the present invention, as When the film at 150 ° C is stretched at 10% in the MD direction, the stress is in the above-mentioned range. It is preferable that the diol component contains 85 mol% or more and less than 97 mol% of the ethylene glycol component, and contains 3 mol. 1% or more of diethylene glycol component, 1,4-cyclohexanedimethanol component, neopentyl glycol component or more, at least 1 mole%, and 85 mole% of dicarboxylic acid component The above is a terephthalic acid component. More preferably, the diol component contains 90 mol% or more and less than 95 mol% of the ethylene glycol component, 5 mol% or more and less than 10 mol% of the diethylene glycol component, 1 At least one species of 4-cyclohexanedimethanol component and neopentyl glycol component; 90% or more of the dicarboxylic acid component is terephthalic acid component, and more preferably 95% of the dicarboxylic acid component Ears above% are terephthalic acid.

Moreover, in the biaxially oriented polyester film of the present invention, The stress is made into the above-mentioned range when the film is stretched at 10% in the MD direction at 150 ° C, and the composition is more preferably the higher of the surface alignment coefficients on both sides of the film. The surface alignment coefficient is 0.111 or more and 0.17 or less.

The higher of the surface alignment coefficients on both sides of the film The method for setting the alignment coefficient to 0.111 or more and 0.17 or less is not particularly limited. For example, as the composition, a method of stretching to a surface magnification of 9.8 to 13.5 times may be mentioned. The elongation temperature is preferably 70 ° C. or higher and 150 ° C. or lower, and the heat treatment temperature after biaxial stretching is preferably the highest temperature of 200 ° C. or higher and 240 ° C. or lower.

In addition, the biaxially oriented polyester film of the present invention is The thermal shrinkage of the film in the MD direction at 150 ° C must be 5% or less. Here, the thermal shrinkage in the MD direction at 150 ° C means that the film is cut into a rectangular sample having a length of 150 mm by a width of 10 mm in the MD direction, and a reticle is drawn at an interval of 100 mm (from the center) (50mm at both ends), hang a 3g scale weight, and place it in a hot air oven heated to 150 ° C for 30 minutes before and after the heat treatment to change the distance between the marked lines. In addition, the evaluation is to set the main alignment axis direction of the arbitrary position of the film to the TD direction, and use this position as the center (hereinafter also referred to as the TD direction center), and take a width of 550 mm in each of two directions along the TD direction, and a width of 1100 mm. 3 points of the center of the TD direction of the film, a position of 500 mm in any one direction (A direction) from the center, and a position of 500 mm in the direction opposite to the A direction (B direction) from the center, Each of them was performed 5 times, and the average value of 15 values was set as the thermal shrinkage rate of the film MD direction at 150 degreeC. The biaxially oriented polyester film of the present invention is a functional coating film such as a hard coat layer, a decorative layer, a retardation layer, etc., by applying a thermal shrinkage of 150 ° C in the MD direction to 5% or less. When drying is performed, it is possible to suppress the decrease in the function of the coating film caused by the shrinkage of the film, Deterioration such as flatness. The thermal shrinkage at 150 ° C in the MD direction is more preferably 4% or less, and more preferably 3% or less.

The heat shrinkage rate in the MD direction at 150 ° C is As a method of 5% or less, the method of adjusting the heat treatment conditions of the film after biaxial stretching is mentioned, for example. By increasing the processing temperature to reduce the orientation, the thermal shrinkage tends to decrease. However, from the viewpoint of dimensional stability and film quality, the heat treatment temperature after biaxial stretching is 200 ° C to 240 ° C. Preferably, it is more preferably 210 ° C to 235 ° C, and most preferably 215 ° C to 230 ° C. In addition, the heat treatment temperature of the biaxially oriented polyester film of the present invention can be measured in a DSC curve of a differential scanning calorimeter (DSC) in a nitrogen environment at a temperature increase rate of 20 ° C / min. It is obtained by a small endothermic peak due to thermal history.

In addition, the preferred heat treatment time can be arbitrarily selected from 5 to 60 seconds. From the viewpoint of moldability, dimensional stability, color tone, and productivity, it is preferably 10 to 40 seconds, and more preferably 15 to 30 seconds. In addition, the heat treatment is performed while relaxing in the longitudinal direction and / or the width direction, so that the thermal shrinkage can be reduced. The relaxation rate (relaxation rate) at the time of relaxation 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 1% or more. Less than 5% is best.

In addition, the method of heat treatment under the conditions of more than 2 steps is also Very good. After heat treatment at a high temperature of 200 ° C to 240 ° C, at a temperature lower than the heat treatment temperature, heat treatment is performed while relaxing in the length direction and / or width direction, which can further reduce the thermal shrinkage rate. The heat treatment temperature in the second stage at this time is preferably 120 ° C to less than 200 ° C, and more preferably 150 ° C to 180 ° C.

The biaxially oriented polyester film of the present invention has uniform physical properties. From a viewpoint, the maximum value of the alignment angle of the film with a width of 1000 mm (the smaller of the angles formed by the main alignment axis and the film TD direction or the film MD direction) must be 20 ° or less. Here, the maximum value of the alignment angle of a film having a width of 1000 mm is to set the main alignment axis direction of an arbitrary position of the film to the TD direction, and use this position as the center to take a width of 550 mm in each of the two directions along the TD direction to make For a film with a width of 1100mm, from this arbitrary point to both ends of the TD direction (one is the A direction and the other is the B direction) 50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm (1000mm Width), the alignment angle (21 o'clock) is measured, and the maximum value is obtained.

From the viewpoint of uniformity of physical properties in the respective width directions, The maximum value of the alignment angle of a film having a width of 1000 mm is preferably 15 ° or less, and more preferably 10 ° or less.

Here, the maximum alignment angle of a film having a width of 1000 mm is maximized. The method for the value to be 20 ° or less is not particularly limited, but examples thereof include a method for reducing bowing in film formation. Specifically, after extending in the width direction, once it is cooled to below the glass transition temperature of the polyester, heat treatment is performed, and a method of setting a nip roll after extending in the width direction to divide the extension in the width direction into a plurality of regions. The method of stepwise heating, dividing the heat treatment into multiple zones, the method of stepwise heating and cooling, setting the temperature distribution in the width direction, and guiding to the heat treatment zone, and the method of slightly extending in the width direction in the heat treatment chamber, etc. .

The biaxially oriented polyester film of the present invention From the viewpoint of ensuring the functional properties and film flatness of the coating film when a functional coating film such as a hard coat layer, a decorative layer, and a retardation layer is applied on drying, the MD direction and TD of the film at 190 ° C The thermal shrinkage in the direction is preferably 5% or less. Since the heat shrinkage of the MD direction and the TD direction of the film is reduced even at a high temperature of 190 ° C, when the drying temperature of the functional coating film needs to be increased, high dimensional stability can be ensured.

As the difference between MD direction and TD direction of the film at 190 ° C The method of making the heat shrinkage rate 5% or less includes, for example, a method of adjusting the heat treatment conditions of the biaxially stretched film in the same manner as the method of making the heat shrinkage rate of the film MD direction of 150 ° C. 5% or less. Furthermore, it is preferable to use a relaxer when performing heat treatment in stages. For example, the first heat treatment is 230 ° C, the second heat treatment is a relaxation rate of 3% at 200 ° C, and the third heat treatment is a relaxation rate of 2% at 180 ° C. The thermal shrinkage of the MD direction / TD direction of the film at 190 ° C is preferably 5% or less / 4%, and most preferably 5% or less / 3% or less.

The biaxially oriented polyester film of the present invention A functional coating film such as a hard coat layer, a decorative layer, and a retardation layer is applied, and from the standpoint of heat resistance and moldability at the time of drying, the thickness of a film in a 1000 mm width is determined by temperature control DSC. The minimum temperature of the obtained glass transition temperature is preferably 80 ° C or higher and 110 ° C or lower. Here, the so-called glass transition temperature of a film in a width of 1000 mm obtained by temperature-modulated DSC means that the main alignment axis direction of an arbitrary position of the film is set to the TD direction, and the position is used as the center to follow the TD Take a width of 550mm in each of the two directions to make a film with a width of 1100mm, and start from this arbitrary point to 50mm, 100mm, 150mm, and 200mm at both ends of the TD direction. , 250mm, 300mm, 350mm, 400mm, 450mm, 500mm (1000mm width), the glass transition temperature was measured, the lowest temperature among them. The glass transition temperature obtained by temperature-modulated DSC is that the film is in a gas flow environment at a range of 0 ° C to 200 ° C at 2 ° C / min, the temperature modulation period is 60 seconds, and the temperature modulation amplitude is 1 Measured in a sine wave shape at ℃, and in the stepwise change portion of the DSC diagram of the reversible component temperature modulation obtained, the method of "9.3 glass transition temperature determination method (1) with intermediate point glass transition temperature" in accordance with JIS K7121 (1987) The method described in "Tmg" is the same method, and the glass transition temperature is determined. From the viewpoint of heat resistance and moldability, the glass transition temperature obtained by temperature-modulated DSC is more preferably 85 ° C to 110 ° C, and most preferably 85 ° C to 100 ° C.

In the present invention, the thickness of a film in a width of 1000 mm The method for the lowest temperature of the glass transition temperature obtained by temperature-modulated DSC to be 80 ° C. to 110 ° C. is not particularly limited, but for example, to make the above-mentioned film have a stress of 5 MPa to 30 MPa when the film is stretched at 10% in the MD direction at 150 ° C. For the following preferred composition, in the heat treatment step after the widthwise stretching, it is more preferable to use a method of performing micro-elongation of more than 2%.

In addition, the biaxially oriented polyester film of the present invention has a functional coating film such as a hard coat layer, a decorative layer, a retardation layer, etc. applied to the film, and the functional film of the coating film at the time of drying is ensured and the film is flat. From the viewpoint of ensuring 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, SA _MD : From the center of the TD direction of a 1100 mm-thick film, the thermal contraction rate at 190 ° C in the MD direction at a position of 500 mm in any one of the TD directions (A direction)

SB _MD : From the center of the width direction of the 1100mm width film, the thermal shrinkage rate at 190 ° C in the MD direction at a position of 500mm in the TD direction opposite to the A direction (B direction)

SC _MD : Thermal shrinkage at 190 ° C in the MD direction at the center of the TD direction of a 1100 mm-thick film.

For a film with a width of 1100 mm (the main alignment axis direction of any position of the film is set to the TD direction, and the position is used as the center (hereinafter also referred to as the TD direction center)), a width of 550 mm is taken in each of the 2 directions along the TD direction, and the width is 1100mm film) in the center of the TD direction, at a position of 500mm in any one of the TD directions (A direction) from the center, at a position of 500mm in the TD direction from the center opposite to the A direction (B direction) At three points, the thermal shrinkage at 190 ° C. was measured five times for each sample cut out into a rectangular shape having a length of 150 mm (A direction or B direction) × width of 10 mm, and the respective average values were obtained.

If the formula (I) is satisfied, it means that the difference in MD thermal shrinkage in the TD direction of a film with a width of 1000 mm is small, and the unevenness of the functional coating film in the direction when the functional coating film is applied to the film and dried is suppressed. , Uneven film. From the viewpoint of uniformity of the physical properties in the TD direction, it is more preferable to satisfy the formula (I) ', and it is more 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 for satisfying the formula (I) of the biaxially oriented polyester film of the present invention is not particularly limited, but the maximum value of the alignment angle of the above-mentioned film having a width of 1000 mm becomes 20 ° or less.

In addition, the thermomechanical analysis (TMA) was performed at 19.6 mN. It is also effective that the stretch peak temperature in the MD direction of the film when the temperature rises from 25 ° C to 200 ° C at a temperature increase rate of 5 ° C / min becomes 60 ° C or higher. Here, the stretching peak temperature in the MD direction of the film refers to a temperature at which the stretched film transitions to a shrinking behavior as the temperature increases. Once the film shrinks, it may shift to the stretching behavior again. However, in the present invention, the temperature at which the transition from the stretching behavior to the shrinking behavior is initially set as the stretching peak in the MD direction of the film when the temperature rises from 25 ° C to 200 ° C. temperature. The measurement system is for a 1100 mm wide film (the main alignment axis direction of any position of the film is set to the TD direction, and the position is used as the center (hereinafter also referred to as the TD direction center)). Film with a width of 1100 mm) in the center of the TD direction, at a position of 500 mm in any one of the TD directions (A direction) from the center, at a position of 500 mm in the TD direction from the center (direction B) For each of the three points, three times were performed in MD and TD, and the average of the nine values measured for MD and TD was used. In order to increase the stretching peak temperature in the length direction of the film when the temperature is increased from 25 ° C to 200 ° C and a temperature increase rate of 5 ° C / min from 25 ° C to 200 ° C, the stretching rate in the lengthwise direction during film formation is set Effective from 2.8 to 3.4 times, preferably from 2.9 to 3.3 times. Although there are no special conditions for the stretch ratio of the film, the inventors conducted various reviews and found that by setting the stretch ratio in the longitudinal direction of the film to be in the above range, it is possible to specifically set the stretch ratio to 25 ° C under a load of 19.6 mN. When the temperature was raised up to 200 ° C at a temperature increase rate of 5 ° C / min, the stretching peak temperature in the longitudinal direction of the film became 60 ° C or higher.

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 : From the 1100mm width film (the main alignment axis direction of any position of the film is set to the TD direction, with this position as the center (hereinafter also referred to as the TD direction center), 550mm in each of the 2 directions along the TD direction Width, as the center of the TD direction of a film with a width of 1100 mm), at a temperature of 190 ° C in the TD direction at a position of 500 mm in any one of the TD directions (A direction)

SB _TD : From the center of the TD direction of a 1100mm wide film, the thermal shrinkage of 190 ° C in the TD direction at a position of 500mm in a direction opposite to the A direction (B direction)

SC _TD : Thermal shrinkage of 190 ° C in the TD direction at the center of the TD direction of a 1100 mm-thick film.

If the formula (II) is satisfied, it means that the difference in TD thermal shrinkage in the TD direction of a film having a width of 1000 mm is small, and the unevenness of the functional coating film in the direction when the functional coating film is applied to the film and dried is suppressed. , Uneven film. From the viewpoint of uniformity of the physical properties in the TD direction, it is more preferable to satisfy the formula (II) ', and it is more 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 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 alignment angle of the film having a width of 1000 mm described above is 20 ° or less. In addition, in a thermomechanical analysis (TMA), a temperature of 5 ° C / min was raised from 25 ° C to 200 ° C under a load of 19.6mN. The stretching peak temperature of the film in the TD direction at the time of temperature increase becomes 70 ° C. or higher, and it becomes easy to satisfy the formula (II). Here, the stretch peak temperature in the TD direction of the film refers to a temperature at which the stretched film transitions to a shrinking behavior as the temperature increases. The measurement system is for a 1100 mm wide film (the main alignment axis direction of any position of the film is set to the TD direction, and the position is used as the center (hereinafter also referred to as the TD direction center)). Film with a width of 1100 mm) in the center of the TD direction, at a position of 500 mm in any one of the TD directions (A direction) from the center, at a position of 500 mm in the TD direction from the center (direction B) Each of the three points was performed three times in MD and TD, and the average value of nine points measured for MD and TD was used. Once the film has shrunk, it may shift to the stretching behavior again. However, in the present invention, the temperature at which the transition from the stretching behavior to the shrinking behavior is initially taken as the stretching peak in the TD direction of the film when the temperature rises from 25 ° C to 200 ° C. temperature. In order to increase the peak temperature in the TD direction of the thin film during thermomechanical analysis (TMA) with a load of 19.6mN and a temperature increase rate of 5 ° C / min from 25 ° C to 200 ° C to 70 ° C or higher, the film was formed. The method of setting the stretching ratio in the length direction at the time of 2.8 times to 3.4 times is more effective, and the micro-elongator that strengthens the heat treatment step after stretching in the width direction is effective.

In addition, as a result of satisfying the biaxially oriented polyester film of the present invention, The methods of formulas (I) and (II) are also effective for off-annealing. That is, the polyester film which has been wound once is subjected to a heat treatment method. The off-line annealing treatment temperature is 140 ° C. to 200 ° C., and the width direction is a free state. Since the difference in heat shrinkage in the width direction disappears, the formulas (I) and (II) can be satisfied. The off-line annealing treatment temperature is preferably 150 ° C or higher. Above 200 ° C, preferably 160 ° C to 200 ° C.

It is very important that the biaxially oriented polyester film of the present invention is the same as It meets the following physical properties: 10% of the MD direction of the film at 150 ° C, the stress is 5 MPa or more and 30 MPa or less, the thermal shrinkage of the film at 150 ° C in the MD direction is less than 5%, and the maximum orientation angle of the film with a width of 1000 mm is the largest. The value is 20 ° or less. If the stress in the MD direction of a film at 150 ° C is stretched to 10 MPa or more and the stress is 5 MPa or more and 30 MPa or less, the thermal shrinkage in the MD direction at 150 ° C may become high, and it may be difficult to align the film with a film width of 1,000 mm. When the maximum value is controlled below 20 °. As a method to solve this difficulty, the biaxially oriented polyester film of the present invention is preferably a laminated film structure having a polyester A layer and a polyester B layer, and the polyester A layer is the outermost layer on at least one side.

In the present invention, when the laminated film has 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 an A layer having a high melting point and a B layer having a lower melting point than the A layer, and the A layer becomes a rigid layer, and the heat shrinkage rate of the film in the MD direction at 150 ° C is kept below 5%. It is low, and it is easy to make the maximum value of the alignment angle of a film with a width of 1000 mm be 20 ° or less, to achieve the task of satisfying the uniformity of physical properties in the width direction. On the other hand, layer B is a layer with high mobility, which can It is easy to make the stress at 10% of the MD direction of the film at 150 ° C to be 5 MPa or more and 30 MPa or less, and the task of achieving formability can be achieved, which can meet the characteristics that are difficult to take into consideration with a single film configuration. In the polyester film of the present invention, from the viewpoint of dimensional stability and uniformity of physical properties in the width direction, the surface alignment coefficient is preferably 0.111 or more and 0.17 or less, and more preferably 0.13 or more and 0.17 or less. It is preferably at least 0.145 and at most 0.17.

Also, from the viewpoint of curl suppression of the film, when the present invention When Mingzhi's biaxially oriented polyester film is a laminated polyester film having a polyester A layer and a polyester B layer, it is preferably composed of three layers of A layer / B layer / A layer.

In the biaxially oriented polyester film of the present invention, when When a polyester A layer and a polyester B layer are laminated, in order to satisfy the 10% MD of the film at 150 ° C, the tensile stress is 5 MPa or more and 30 MPa or less, and the thermal shrinkage of the film at 150 ° C in the MD direction is 5%. Below, the maximum value of the alignment angle of a film having a width of 1000 mm is 20 ° or less. As a preferable aspect of the polyester A layer and the polyester B layer, the following configuration can be mentioned.

The polyester A layer preferably contains 90 moles as a diol component. At least 1 type of ethylene glycol component, less than 99 mol%, diethylene glycol component, 1,4-cyclohexane dimethanol component, and neopentyl glycol contains at least 1 mol% and Less than 10 mole%; as the dicarboxylic acid component, preferably 90 mole% or more is a terephthalic acid component. More preferably, as the diol component, 95 mol% or more and less than 99 mol% of a glycol component, a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and a neopentyl glycol component are contained. At least one type or more contains 1 mol% or more and less than 5 mol%; as a dicarboxylic acid component, 95 mol% or more is a terephthalic acid component, and more preferably, among the above diol components, dicarboxylic acid At least 98 mol% of the acid component is preferably a terephthalic acid component.

Polyester B layer preferably contains 80 moles as a diol component At least 1 type of ethylene glycol component, less than 95 mol%, diethylene glycol component, 1,4-cyclohexanedimethanol component, and at least one type of neopentyl glycol component It contains 5 mol% or more and less than 20 mol%; as the dicarboxylic acid component, 90 mol% or more is preferably a terephthalic acid component. More preferably, as the diol component, 85 mol% or more and less than 95 mol% of a glycol component, a diethylene glycol component, a 1,4-cyclohexanedimethanol component, and a neopentyl glycol component are contained. At least one type or more contains 5 mol% or more and less than 15 mol%; as the dicarboxylic acid component, 95 mol% or more is a terephthalic acid component, and more preferably, among the above diol components, dicarboxylic acid At least 98 mol% of the acid component is preferably a terephthalic acid component.

Next, an example of a specific manufacturing method of the biaxially-oriented polyester film of the present invention is described, but the present invention is not limited to the explanation of such an example.

When forming a laminated polyester film having a polyester A layer and a polyester B layer, first as the polyester A used for the polyester A layer, measure the polyethylene terephthalate resin (a) and 1 at a specified ratio. , 4-cyclohexanedimethanol copolymerized polyethylene terephthalate resin (b). In addition, as the polyester B used in the polyester B layer, polyethylene terephthalate resin (c) was copolymerized with 1,4-cyclohexanedimethanol at a specified ratio to measure polyethylene terephthalate. Ester resin (d).

Then, the mixed polyester resin was supplied to a vented biaxial extruder and melt-extruded. At this time, it is preferable to control the resin temperature at 265 ° C to 295 ° C in an extruder under an atmosphere of flowing nitrogen, with an oxygen concentration of 0.7% by volume or less. Next, a filter or a gear pump is used to remove foreign matter and homogenize the amount of extrusion, respectively, and spit out a sheet on a cooling drum through a T die. In this case, by using an electrostatic application method in which an electrode to which a high voltage is applied and the cooling roller and the resin are brought into close contact with each other by static electricity, a casting method in which a water film is provided between the casting roller and the extruded polymer sheet is used. The method of casting the roller temperature to the glass transition point of polyester resin (glass transition point -20 ° C), the method of making the extruded polymer adhere, or a combination of these methods, to make the sheet polymer tight. It was affixed to a casting drum and cooled and solidified to obtain an unstretched film. Among these casting methods, when polyester is used, a method of applying static electricity is more preferable from the viewpoint of productivity or flatness.

The biaxially oriented polyester film of the present invention From the viewpoint of inch stability, it must be a biaxial alignment film. The biaxially oriented film can be a sequential biaxially stretching method in which the unstretched film is stretched in the lengthwise direction and then in the widthwise direction, or after being stretched in the widthwise direction and in the lengthwise direction, or by almost simultaneously It can be obtained by performing a biaxial stretching method while simultaneously extending the ground in the length direction and the width direction of the film.

As the stretching magnification in this stretching method, it is preferable to use 2.8 times to 3.4 times in the longitudinal direction, and it is more preferable to use 2.9 times to 3.3 times. The elongation speed is preferably 1,000% / minute or more and 200,000% / minute or less. The stretching temperature in the longitudinal direction is preferably 70 ° C or higher and 90 ° C or lower. 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 extension speed in the width direction is preferably 1,000% / minute or more and 200,000% / minute or less. In addition, in order to make the maximum value of the alignment angle of a film having a width of 1,000 mm to 20 ° or less while the stress at a stretch of 10% in the MD direction of the film at 150 ° C. is 5 MPa to 30 MPa, the extension system in the width direction is preferably divided The method of stretching in a plurality of zones while gradually heating up includes, for example, a temperature of 90 ° C or higher and 120 ° C or lower during the first half of stretching, and 100 ° C or higher and 130 ° C or lower, and the second half stretching temperature is 110 ° C or higher and 150 ° C or lower, the method is to increase the temperature in the order of the first half of the temperature, the temperature during the middle of the stretching, and the second half of the stretching.

After the biaxial stretching, the film is heat-treated. The heat treatment can be performed in an oven, on a heated roll, or the like, by any conventional method. This heat treatment is performed at a temperature of 120 ° C or higher and below the crystal melting peak temperature of the polyester, but preferably 200 ° C to 240 ° C, more preferably 210 ° C to 235 ° C, and most preferably 215 ° C to 230 ° C. The so-called preferred heat treatment temperature means the highest temperature among the heat treatment temperatures performed after biaxial stretching. The heat treatment time may be arbitrarily selected within a range that does not deteriorate the characteristics, 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. In addition, the orientation angle of a film having a width of 1000 mm was set to make the thermal shrinkage of the film in the MD direction at 150 ° C less than 5% while the stress in the MD direction of the film being stretched at 10% at 150 ° C was 5 MPa to 30 MPa. The maximum value is less than 20 °. It is more appropriate to use a method of dividing the heat treatment into multiple zones and gradually raising and lowering the temperature, or a method of slightly extending in the width direction during the heat treatment step. For example, the temperature before the heat treatment can be 180 ° C or higher and 210 ° C or lower, and slightly stretched in the width direction by 1% or higher and 10% or lower, preferably 3% or higher and 10% or lower. A method of slightly extending in the width direction by 1% or more and 10% or less, preferably 3% or more and 10% or less, so that the half temperature after the heat treatment is 150 ° C or more and 200 ° C or less. At the half temperature after the heat treatment, in order to reduce the thermal shrinkage, it is also preferable to carry out while relaxing 1% to 10%. Moreover, in order to improve the printing layer or adhesive, The adhesion of various processed layers, such as a vapor-deposited layer, a hard coat layer, and a weather-resistant layer, can also be corona-treated on at least one side to apply an easy-adhesive layer. As a method for providing a coating in a line in a film manufacturing process, it is preferable to uniformly coat the film that has been subjected to at least uniaxial stretching with a metering ring bar or a grooved roller and disperse it in water. In the case of a coating composition, the method of drying the coating agent while applying extension is preferable. In this case, the thickness of the easy-adhesive layer is preferably 0.01 μm or more and 1 μm or less. Various additives such as an antioxidant, a heat-resistant stabilizer, an ultraviolet absorber, an infrared absorber, a pigment, a dye, organic or inorganic particles, an antistatic agent, and a nucleating agent may be added to the easy-adhesive layer. As the resin preferably used for the easy-adhesion layer, at least one resin selected from the group consisting of acrylic resin, polyester resin, and urethane resin is preferred from the viewpoint of adhesiveness and handling properties. Furthermore, it is more suitable to use offline annealing at 140 ~ 200 ℃.

The biaxially oriented polyester film of the present invention Low molding stress and good moldability. Due to the low thermal shrinkage at 150 ° C, the film deformation during coating and drying is small, and because the maximum alignment angle of a film with a width of 1000 mm is small, the physical properties in the width direction are excellent. It is suitable for molding and processing applications such as building materials, mobile equipment, motor products, automobile parts, game machine parts, and other decorative films, or optical films such as polarizing plates. Among them, since the uniformity of the physical properties in the width direction is very excellent, it is more suitable for optical applications. Specifically, in order to achieve high definition and thin film of the retardation layer, the retardation layer is coated on the engineering film, and the engineering film is molded together. use.

[Example]

(1) Composition of polyester

Polyester resin and film can be dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue component or by-product diethylene glycol can be quantified using ¹ H-NMR and ¹³ C-NMR. When laminating a film, each layer of the film can be cut out according to the thickness of the layer, and the components constituting each element of the layer can be collected and evaluated. The composition of the film of the present invention is calculated from the mixing ratio at the time of film production.

(2) inherent viscosity of polyester

The limiting viscosity of polyester resins and films is that polyester is dissolved in o-chlorophenol and measured at 25 ° C using an Oshwa viscosity meter. When the film is laminated, each layer of the film can be cut out according to the thickness of the laminate, and the inherent viscosity of each element of the layer can be evaluated.

(3) film thickness, layer thickness

The film was embedded in 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, and the thickness of the film and the thickness of the polyester layer were determined.

(4) Melting point

Measurement and analysis were performed using a differential scanning calorimeter (RDC220 manufactured by SEIKO Electronics Industries) in accordance with JIS K7121-1987 and JIS K7122-1987. A 5 mg polyester film was used in the sample, and the temperature of the vertex 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 set as the melting point. In addition, when the film is laminated, each layer of the film can be cut out according to the thickness of the laminated layer, and the melting point of each element of the layer can be measured. Yu Benfa In the Ming Dynasty, 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, the layer with the higher melting point is referred to as the polyester A layer, and the lower layer is referred to as the polyester B. Floor.

(5) Tiny endothermic peak temperature before crystal melting (Tmeta)

Measurement and analysis were performed using a differential scanning calorimeter (RDC220 manufactured by SEIKO Electronics Industries) in accordance with JIS K7121-1987 and JIS K7122-1987. A 5 mg polyester film was used in the sample, and the tiny endothermic peak temperature that appeared 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) The main alignment axis and the maximum value of the alignment angle of the 1000mm width film

At any point of the film, cut out a sample with a size of 100 mm × 100 mm, and use the microwave molecular alignment meter MOA-2001A (frequency 4 GHz) manufactured by KS Systems (now Oji measuring equipment) to determine the main alignment in the plane of the polyester film. Axis as the TD direction. Also, using this arbitrary point as the center of the TD direction of the film, every 50mm (50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 50mm to 500mm) between 50mm and 500mm in any one of the TD directions (A direction). 450mm, 500mm), and from the center of the TD direction of the film, every 50mm between 50mm and 500mm in the TD direction opposite to the A direction (B direction), using the above-mentioned microwave molecular alignment meter MOA-2001A (Frequency 4 GHz), the alignment angle (the smaller of the angles formed by the main alignment axis and the film TD direction or the film MD direction) was measured, and the maximum value was obtained.

(7) Glass transition temperature determined by temperature-modulated DSC

As in (6), cut out a sample at any point of the film with a size of 100mm × 100mm, take 5mg from it, and place it in an aluminum standard container Within the range, a differential scanning calorimeter (Q100, manufactured by TA Instrument) was used in an airflow environment (flow rate: 50 mL / min) in the range of 0 ° C to 200 ° C, at a temperature of 2 ° C / min, with a temperature adjustment cycle of 60 seconds, and temperature adjustment. The measurement was performed in a sine wave shape with a variable amplitude of 1 ° C. The specific heat correction is performed using sapphire, and "Universal Analysis 2000" manufactured by TA Instrument was used for data analysis. In the step-like change portion of the temperature-modulated DSC chart of the obtained reversible component, the glass transition temperature was determined in accordance with JIS K7121 (1987), "9.3 Method for Determining Glass Transition Temperature. "The method described in the same way, to determine the glass transition temperature of the temperature-modulated DSC (take the intersection of a straight line at an equal distance in the vertical axis direction from the extended straight line of each baseline with the curve of the step-shaped change portion of the glass transition as Temperature-modulated DSC glass transition temperature). In addition, this point is used as the center of the TD direction of the film, and every 50mm to 500mm (50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm) in any one of the TD directions (A direction). , 500mm), and from the center of the TD direction of the film, every 50mm between 50mm and 500mm in the TD direction opposite to the A direction (B direction), using the above differential scanning calorimeter to measure the glass Transfer the temperature to find its minimum temperature.

(8) Tensile stress at 10% of MD direction of film at 150 ° C

A rectangle with a length of 150 mm and a width of 10 mm was cut out in the MD direction as a sample. A tensile tester (Tensilon UCT-100 manufactured by ORIENTEC) was used, and the initial tensile chuck distance was 50 mm and the tensile speed was 300 mm / min. The tensile test was performed in the MD direction of the film. The measurement is based on a film sample fixed in a constant temperature bath set at 150 ° C at 90 ° C. After a second warm-up, a tensile test was performed. The load applied to the film when the sample was stretched at 10% (when the distance between the chucks was 55mm) was divided by the cross-sectional area of the sample before the test (thickness of the film × 10mm). The stress was set at 10%. . In addition, the measurement is based on the main alignment axis direction of the arbitrary position of the film as the TD direction, with the position as the center (the center of the TD direction), and a width of 550 mm in each of two directions along the TD direction. The center of the direction, the position of 500 mm in any one of the TD directions (A direction) from the center, and the position of 500 mm in the TD direction opposite to the A direction (B direction) from the center are each performed 5 points Next, the average value of 15 values was set as the stress at the time of 10% stretching in the MD direction of the film at 150 ° C.

(9) Thermal shrinkage (150 ° C, 190 ° C)

A rectangle having a length of 150 mm and a width of 10 mm was cut out of the film in the MD direction and the TD direction, respectively, and used as samples. Draw a marking line on the sample at 100mm intervals (50mm from the center to both ends), hang a 3g scale weight, and place in a hot air oven heated to the specified temperature (150 ° C, 190 ° C) for 30 minutes For heat treatment. The distance between the graticules after the heat treatment was measured, and the change in the distance between the graticules before and after heating was measured, and the thermal shrinkage was calculated by the following formula. In addition, the evaluation is based on the main alignment axis direction at any position of the film as the TD direction, with the position as the center (the center of the TD direction), and the width of 550 mm in each of the two directions is collected along the TD direction. The three positions of 500 mm in any one of the TD directions (A direction) from the center and 500 mm in the TD direction opposite to the A direction (B direction) from the center are performed 5 times each, and An average of 15 values is set to a film at a specified temperature (150 ° C, 190 ° C) Thermal shrinkage in MD and TD directions.

Thermal shrinkage (%) = {(distance between graticules before heat treatment)-(distance between graticules after heat treatment)} / (distance between graticules before heat treatment) × 100.

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

As in (9), the MD of the center value of the 1100 mm-thick film in the TD direction and the thermal shrinkage rate (SC _MD , SC _TD ) of 190 ° C in the TD direction are performed from the center of the width direction of the 1100 mm-thick film in the TD direction. MD at 500mm in either direction (A direction), thermal shrinkage (SA _MD , SA _TD ) of 190 ° C at TD direction, from the center of the TD direction of the 1100mm-thick film in the TD direction The heat shrinkage (SB _MD , SB _TD ) of the MD at 500 mm in the opposite direction (B direction) and 190 ° C in the TD direction was measured (using the average of 5 measurements each), and formula (I) was performed. Calculate the value on the left side of formula (II).

(SA _MD + SB _MD ) / SC _MD × 2 ≦ 1.2 (I)

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

(11) Surface alignment coefficient

Using the sodium D-line (wavelength 589nm) as the light source, using an Abbe refractometer to measure the refractive index in the MD direction (n _MD ), the refractive index in the TD direction (n _TD ), and the refractive index in the thickness direction (n _ZD ), The surface alignment coefficient (fn) was calculated from the following formula.

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

The surface alignment coefficient is measured on both sides of the film, and the value of the higher surface alignment coefficient is described in the table.

In addition, the measurement is performed by setting the main alignment axis direction of an arbitrary position of the film to the TD direction, and using the position as the center (the center of the TD direction) along the Collect 550mm widths in two directions in the TD direction. For the center of the TD direction of a film with a width of 1100mm, the position of 500mm in any one direction (A direction) from the center, and the TD direction from the center is opposite to the A direction. Three points at a position of 500 mm in the direction (direction B) were performed 5 times each, and an average of 15 values was used.

(12) Thermomechanical analysis (TMA)

A rectangle with a length of 50 mm and a width of 4 mm was cut out of the film in the MD direction and the TD direction. As a sample, a thermomechanical analysis device (TMAEXSTAR 6000 manufactured by SEIKO Instruments) was used, and the temperature was raised under the following conditions to calculate the temperature at 25 to 200 Stretch peak temperature.

Sample length: 15mm, load: 19.6mN, heating rate: 5 ° C / min, measurement temperature range: 25 ~ 200 ° C

In the present invention, the stretching peak temperature at 25 ° C to 200 ° C refers to the temperature at which the stretched film is stretched to shrinkage behavior with increasing temperature. Once the film has shrunk, it can transition to the stretching behavior again. However, in the present invention, the temperature at which the transition from the stretching behavior to the shrinking behavior is initially set as the MD direction and TD direction of the film when the temperature rises from 25 ° C to 200 ° C. Spike temperature.

In addition, the measurement is performed by setting the main alignment axis direction of the arbitrary position of the film to the TD direction, and using this position as the center (TD direction center), collecting the width of 550 mm in each of the two directions along the TD direction, and the TD direction of the film having a width of 1100 mm 3 points of the center, 500mm position in any one of the TD directions (A direction) from the center, and 500mm position in the TD direction opposite to the A direction (B direction) from the center, both MD and TD are Each measurement was performed 3 times, and the average value of 9 values measured for MD and TD was used.

(13) Dimensional stability

On the surface of a polyester film with a width of 1100 mm, the polyarylate / MEK dispersion was coated and dried 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 (thickness of the polyarylate after drying was 25 μm).

A: The width shrinkage is less than 5 mm (the width of the polyester film after drying is 995 mm or more).

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

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

In addition, the evaluation of width reduction is selected after coating and drying Measure the width at any 10 places of the 1000mm width film, and use it (1000mm width-the average value of the film width at any 10 places) as the width shrinkage.

(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 ° C, width direction free). The stretchability (moldability) of the film was evaluated based on the following criteria.

A: With an extension tension of less than 1200 N / m, it can be extended 1.1 times.

B: It can be extended 1.1 times with an extension tension of 1200 N / m or more and less than 1500 N / m.

C: It cannot be extended by 1.1 times with an extension tension of 1500 N / m.

(15) Functional uniformity in width direction

From the polyarylate coated uniaxially stretched polyester film obtained in (14), the polyarylate layer is peeled off, and from the center of the width direction, at a position of 500 mm in any direction (A direction) from the center, from the center The in-plane hysteresis value was measured at three points at a position of 500 mm in a direction opposite to the A direction (B direction) in the width direction, and evaluated based on the following criteria. In addition, the hysteresis value was measured using the automatic birefringence meter (KOBRA-21ADH made by Shin-Oji Measurement Instruments).

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

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

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

(Production of polyester)

The polyester resin for film formation is prepared as follows.

(Polyester A)

A polyethylene terephthalate resin (inherent viscosity 0.65) having a terephthalic acid component as a dicarboxylic acid component of 100 mole% and a glycol component as a glycol component of 100 mole%.

(Polyester B)

Copolymerized polyester (GN001, manufactured by Eastman Chemical Co., Ltd.) by copolymerizing 1,4-cyclohexanedimethanol with 33 mol% of the diol component, and copolymerized polyethylene terephthalate as cyclohexanedimethanol. Used (inherent viscosity 0.75).

(Polyester C)

Copolymerization of neopentyl glycol with a terephthalic acid component as a dicarboxylic acid component of 100 mol%, a glycol component as a diol component of 70 mol%, and a neopentyl glycol component of 30 mol% Ethylene terephthalate resin (inherent viscosity 0.75).

(Polyester D)

Diethylene glycol copolymerized with 100% by mole of terephthalic acid as dicarboxylic acid component, 85% by mole of ethylene glycol as diol component, and 15% by mole of diethylene glycol. Ethylene terephthalate resin (inherent viscosity 0.65).

(Polyester E)

The terephthalic acid component as the dicarboxylic acid component is 82.5 mole%, the isophthalic acid component is 17.5 mole%, and the ethylene glycol component as the diol component is 100 mole%. Ethylene terephthalate resin (inherent viscosity 0.7).

(Polyester F)

The terephthalic acid component as the dicarboxylic acid component is 85 mol%, the 2,6-naphthalenedicarboxylic acid component is 15 mol%, and the ethylene glycol component as the diol component is 2,6 of 100 mol%. -Naphthalenedicarboxylic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7).

(Particle Masterbatch)

A polyethylene terephthalate particle masterbatch (intrinsic viscosity 0.65) made of agglomerated silica particles having a number average particle diameter of 2.2 μm in a polyester concentration of 2% by mass.

(Example 1)

The composition system is as shown in the table. The raw materials are supplied to each exhaust biaxial extruder in the same direction with an oxygen concentration of 0.2% by volume, and the barrel temperature of the layer A extruder is 270 ° C. The barrel temperature is 277 ° C. The short tube temperature after layer A and B are merged is 277 ° C, and the nozzle temperature is 280 ° C. The sheet is ejected by a T die on a cooling roller controlled by temperature at 25 ° C. shape. In this case, static electricity was applied using a linear electrode with a diameter of 0.1 mm, and it was brought into close contact with a cooling drum to obtain an unstretched sheet. Secondly, before stretching in the longitudinal direction, the film temperature was raised on a heating roller, the stretching temperature was 85 ° C, and the film was stretched 3.1 times in the longitudinal direction, and immediately cooled by a metal roller whose temperature was controlled at 40 ° C.

Secondly, the tenter type horizontal stretcher stretches 3.9 times in the width direction at the first half temperature of 95 ° C, the middle temperature of 105 ° C, and the second half temperature of 140 ° C. It is directly in the tenter at 200 °. The heat treatment was performed at a temperature of half before the heat treatment at 230 ° C and a temperature halfway through the heat treatment at 230 ° C. The heat treatment was performed at a temperature half after the heat treatment at 180 ° C while applying 3% relaxation 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 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)

Except for the first half of the heat treatment, 5% micro-elongation in the width direction to A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 3.

(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 laminated film of A / B / A. The composition of each layer is as shown in the table. The raw material for layer A and the raw material for layer B are supplied to each exhaust co-axial biaxial extruder with an oxygen concentration of 0.2% by volume, and the material is extruded in layer A. The barrel temperature is 270 ° C. The melting of the extruder barrel temperature is 277 ° C. The short tube temperature after layer A and B merge is 277 ° C and the nozzle temperature is 280 ° C. The sheet was discharged on a cooling drum controlled by temperature at 25 ° C. In this case, a static electrode was applied using a linear electrode having a diameter of 0.1 mm, and it was brought into close contact with a cooling drum to obtain a three-layer laminated unstretched film including A layer / B layer / A layer.

Then, 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 temperature during the heat treatment was 225 ° C.

(Example 8)

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 2% of micro-elongation was performed in the width direction in the first half of the heat treatment.

(Example 9)

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 5% micro-elongation was performed in the width direction in the first half of the heat treatment.

(Example 10)

Except changing the composition as shown in the table, in the first half of the heat treatment, 5% micro-elongation was performed in the width direction, and during the heat treatment, 3% micro-elongation was performed in the width direction. In the same manner as in Example 7, a film thickness of 75 μm was obtained. Shaft alignment polyester film.

(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 temperature during the heat treatment was 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 temperature during the heat treatment was changed to 230 ° C.

(Example 13)

Except for changing the composition as shown in the table, in the first half of the heat treatment, 5% micro-elongation was performed in the width direction, and in the middle of the heat treatment, 3% micro-elongation was performed in the width direction. In the same manner as in Example 7, a film thickness of 50 μm was obtained. Shaft alignment polyester film.

(Example 14)

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, 5% micro-elongation was performed in the width direction in the first half of the heat treatment, and 3% micro-elongation was performed in the width direction during the heat treatment. Biaxially oriented polyester film.

(Example 15)

The biaxially oriented polyester film obtained in Example 14 was subjected to off-line annealing while leaving the width direction free in a hot air oven at 180 ° C. and making the winding speed in the longitudinal direction lower than the unwinding speed by 1%.

(Example 16)

A biaxially oriented polyester film with 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 the temperature was 235 ° C. during the heat treatment.

(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)

Except for changing the composition as shown in the table, the temperature of the first half, halfway, and second half of the horizontal stretching is 120 ° C, which is 3.4 times longer. Directly in the tenter, heat treatment is performed at the first half of the heat treatment and the midway temperature of 230 ° C, and the second half of the heat treatment is 180 ° 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 heat treatment was performed while applying 3% relaxation in the width direction.

(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 temperature during the heat treatment was 220 ° C.

(Comparative 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 as shown in the table and the temperature during the heat treatment 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

[Industrial availability]

The biaxially oriented polyester film of the present invention has good moldability due to low forming stress at 150 ° C, and small deformation of the film during coating and drying due to low thermal shrinkage at 150 ° C, and moreover, due to a film having a width of 1000 mm The maximum value of the alignment angle is small and the physical property uniformity in the width direction is excellent. It can be applied to the molding and decoration of building materials, mobile equipment, motor products, automobile parts, game machine parts, and optical films such as polarizing plates.

Claims (12)

A biaxially oriented polyester film having a tensile stress of 5 MPa or more and 30 MPa or less at 10% of the MD (machine direction) direction of the film at 150 ° C, and a thermal shrinkage of 5% or less at the MD direction of the film at 150 ° C. And the maximum value of the alignment angle of the film in the 1000 mm width (the angle between the main alignment axis and the film TD (transverse direction) direction or the angle formed by the film MD direction) is less than 20 °; The alignment angle is to set the main alignment axis direction of the arbitrary position of the film to the TD direction, with this position as the center, and take a width of 550mm in 2 directions along the TD direction to make a film with a width of 1100mm. Point the two ends in the TD direction at 50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, and 500mm (1000mm width), and measure the alignment angle to find the maximum value. The direction orthogonal to the TD direction in the plane is referred to as the MD direction. For example, the biaxially oriented polyester film of claim 1, which is a film of 10 m or more in the MD direction and 1100 mm or more in the TD direction. For example, if the biaxially oriented polyester film of claim 1 or 2 is used, the minimum temperature of the glass transition temperature of the film in 1000mm width determined by temperature modulation DSC is 80 ° C or higher and 110 ° C or lower; The glass transition temperature of the thin film obtained by temperature-modulated DSC is set to the main alignment axis direction of any position of the film as the TD direction, with this position as the center, and a width of 550 mm in each of the two directions along the TD direction ， Make a film with a width of 1100mm, and from the point to the end of the TD direction at 50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm (1000mm width), and measure the glass transition temperature , Find the lowest temperature among them. For example, the biaxially oriented polyester film of claim 1 or 2 has a thermal shrinkage ratio of the film in the MD direction and the TD direction at 190 ° C of 5% or less. For example, the biaxially oriented polyester film of claim 1 or 2 satisfies the following formula (I), (SA _MD + SB _MD ) / (SC _MD × 2) ≦ 1.2 (I), where SA _{MD is} from 1100mm width Thermal shrinkage at 190 ° C from the center of the TD direction of the film in the MD direction at a position of 500mm in any one of the TD directions (A direction); SB _MD : from the center of the TD direction of the 1100mm film in TD Thermal shrinkage at 190 ° C in the MD direction at a position of 500 mm opposite to the direction A (B direction); SC _MD : Thermal shrinkage at 190 ° C in the MD direction at the center of the TD direction of a 1100 mm-thick film. If the biaxially oriented polyester film of claim 1 or 2 satisfies the following formula (II), (SA _TD + SB _TD ) / (SC _TD × 2) ≦ 1.2 (II) Among them, SA _TD : from 1100mm width Thermal shrinkage of 190 ° C in the TD direction from the center of the TD direction of the film at a position of 500mm in any one of the TD directions (A direction); SB _TD : Starting from the center of the TD direction of a 1100mm-thick film, at the TD The thermal shrinkage rate of 190 ° C in the TD direction at a position of 500 mm opposite to the A direction (B direction); SC _TD : the thermal shrinkage rate of 190 ° C in the TD direction at the center of the TD direction of a 1100 mm-thick film. For example, the biaxially oriented polyester film of claim 1 or 2, wherein among the surface alignment coefficients of the two surfaces of the film, the surface alignment coefficient of the higher surface is 0.111 or more and 0.17 or less. If the biaxially oriented polyester film of claim 1 or 2 is a laminated polyester film having a polyester A layer and a polyester B layer having a lower melting point than the polyester A layer, the polyester A layer is located on at least one side Outermost. If the biaxially oriented polyester film of claim 1 or 2 is used, the film is TD when the temperature is raised in a thermomechanical analysis (TMA) with a load of 19.6mN from 25 ° C to 200 ° C at a temperature rise rate of 5 ° C / min. The stretching peak temperature in the direction is 70 ° C or higher. If the biaxially oriented polyester film of claim 1 or 2 is used, the film MD when heated at a temperature of 5 ° C / min from 25 ° C to 200 ° C at a load of 19.6mN in thermomechanical analysis (TMA) The stretching peak temperature in the direction is 60 ° C or higher. If the biaxially oriented polyester film of claim 1 or 2 is used for molding processing. If the biaxially oriented polyester film of claim 1 or 2 is used for optical applications.