JP2021152094A - Polyester film - Google Patents

Abstract

To provide a polyester film having low heat shrinkage at 90°C in a main shrinkage direction, and high heat shrinkage with high tensile force at 150°C.SOLUTION: A polyester film is such that: a heat shrinkage rate at 150°C in a main shrinkage direction is 25% or more and 45% or less; a heat shrinkage rate at 150°C in a direction orthogonal to the main shrinkage direction is -6% or more and 10% or less; a heat shrinkage rate at 90°C in the main shrinkage direction is 14% or less; a heat shrinkage rate at 90°C in the direction orthogonal to the main shrinkage direction is 5% or less; a rigid amorphous rate is 42% or more and 60% or less; and a refraction index in the direction orthogonal to the main shrinkage direction is 1.64 or more and 1.67 or less.SELECTED DRAWING: None

Description

The present invention relates to a polyester film.

In recent years, in order to print and apply special inks, coating agents, etc., the raw film has heat resistance that does not deform such as shrinkage at a low temperature of about 90 ° C., and at a high temperature of about 150 ° C., which is the subsequent shrinkage process. There is an increasing demand for heat-shrinkable films having the characteristic of shrinking significantly. For example, packaging applications centered on bottle containers for tea and soft drinks, decorative applications that use film shrinkage to give highly designed members to members with complex shapes, and unevenness using film shrinkage. For example, a pattern creation application having the above. In these applications, there is an increasing need to achieve both flexibility such as secondary processing in which the product is stretched in a direction orthogonal to the contraction direction after contraction. As a heat-shrinkable film that solves such needs, it is described in a wide film obtained by stretching in the horizontal direction as represented by Patent Document 1 and then sequentially biaxially stretching in the vertical direction, and in Patent Document 2. There is a film obtained by sequentially biaxially stretching including a step of stretching in the longitudinal direction, then stretching in the horizontal direction, and then stretching in the vertical direction.

International Publication No. 2014/021120 International Publication No. 2017/022742

As a heat-shrinkable film, commercialization in a wide width is required from the viewpoint of increasing mass productivity, but it can be obtained by stretching in the horizontal direction as represented by Patent Document 1 and then sequentially biaxially stretching in the vertical direction. When the wide film is heat-shrinked due to variations in heat shrinkage in the width direction, for example, the difference in heat-shrinkage in the 45 ° and 135 ° directions is large, with the width direction (hereinafter referred to as the TD direction) being 0 °. There is a problem that the heat is distorted. Further, as described in Patent Document 2, the film obtained by sequentially biaxially stretching including a step of stretching in the vertical direction, then stretching in the horizontal direction, and then stretching in the vertical direction is obtained by the above-mentioned heat shrinkage. Although the variation in the rate is small, there is a problem that it is torn in the secondary processing step such as stretching in the TD direction after high temperature shrinkage. Therefore, the subject of the present invention is flexibility in which the variation in the heat shrinkage rate in the width direction is small when the film shrinks significantly when heated to a high temperature, and the film is not broken in the stretching step in the TD direction at a high temperature in the subsequent secondary processing. It is an object of the present invention to provide a polyester film having a property.

In order to solve the above problems, the polyester film of the present invention has a heat shrinkage rate of 150 ° C. in the main shrinkage direction of 25% or more and 45% or less, and a heat shrinkage rate of 150 ° C. in the direction orthogonal to the main shrinkage direction of -6% or more and 10%. % Or less, 90 ° C. heat shrinkage in the main contraction direction is 14% or less, 90 ° C. heat shrinkage in the direction orthogonal to the main contraction direction is 5% or less, and the proportion of rigid amorphous is 42% or more and 60% or less. The polyester film having a refractive index of 1.64 or more and 1.67 or less in the direction orthogonal to the main contraction direction can provide the films listed above.

The polyester film of the present invention has a heat shrinkage rate of 150 ° C. in the main shrinkage direction of 25% or more and 45% or less, a heat shrinkage rate of 150 ° C. in the direction orthogonal to the main shrinkage direction of -6% or more and 10% or less, and a heat shrinkage rate in the main shrinkage direction. The 90 ° C. heat shrinkage rate is 14% or less, the 90 ° C. heat shrinkage rate in the direction orthogonal to the main shrinkage direction is 5% or less, the ratio of rigid amorphous is 42% or more and 60% or less, and orthogonal to the main shrinkage direction. It has a feature that the refractive index in the direction of heat is 1.64 or more and 1.67 or less. As a result, the variation in the heat shrinkage in the width direction (difference in heat shrinkage in the 45 ° and 135 ° directions with the TD direction as 0 °) is small when the heat shrinks significantly when heated to a high temperature, and the subsequent high temperature. Since it has flexibility not to be torn in a secondary process such as stretching in the TD direction, it can be preferably used for packaging, molding and decoration, and optical applications.

Hereinafter, the polyester film of the present invention will be described in detail.
The polyester film of the present invention has a heat shrinkage rate of 150 ° C. in the main shrinkage direction determined by a measurement method described later of 25% or more and 45% or less. By setting the heat shrinkage rate at 150 ° C. in the main shrinkage direction to 25% or more and 45% or less, excellent shrinkage characteristics can be exhibited when used in packaging applications, molding decoration applications, optical applications, and the like. The method of setting the heat shrinkage rate at 150 ° C. in the main shrinkage direction to 25% or more and 45% or less as in the present invention is not particularly limited, and examples thereof include a method of stretching in the main shrinkage direction. For example, if it is intended to shrink by 25% or more at 150 ° C., it must be stretched at least 1.25 times or more, and the orientation should be such that the refractive index in the main shrinkage direction is 1.58 or more and 1.64 or less. It is preferable to give it. However, when the refractive index in the main contraction direction is oriented beyond 1.64, the heat contraction rate at 150 ° C. in the main contraction direction is set to 25% or more, and the heat at 150 ° C. in the direction orthogonal to the main contraction direction is set. It may be difficult to reduce the shrinkage rate to 10% or less. Further, the main shrinkage direction in the present invention is defined as 0 ° in any one direction of the film, and the heat shrinkage rate of 150 ° C. is measured in each direction from there to 180 ° at 5 ° intervals, and the most heat shrinkage rate is obtained. Points to the higher direction.

The polyester film of the present invention has a heat shrinkage rate of 150 ° C. or more and 10% or less in a direction orthogonal to the main shrinkage direction determined by a measurement method described later. Within this range, the occurrence of wrinkles in the heat shrinkage process can be suppressed. Normally, in the case of a biaxially stretched film such as a shrink film, the film shrinks significantly in both the longitudinal direction and the width direction. A method in which the heat shrinkage in the main shrinkage direction is 25% or more and 45% or less and the heat shrinkage at 150 ° C. in the direction orthogonal to the main shrinkage direction is -6% or more and 10% or less as in the polyester film of the present invention is particularly applicable. Although not limited, in the step of manufacturing the polyester film, after the stretching step (I) in which the stretching ratio in the direction orthogonal to the main shrinkage direction is at least 3.0 times or more, the polyester film is stretched in the direction of the main shrinkage direction. It is preferable to include the stretching step (II) in which the magnification is more than 1.1 times and 2.2 times or less. From the viewpoint of improving uniformity such as thickness unevenness, a stretching step in the main contraction direction may be included before stretching in a direction orthogonal to the main contraction direction in the stretching step (I), but it is orthogonal to the main contraction direction. From the viewpoint of reducing the heat shrinkage rate at 150 ° C. in the direction of 10% or less, the stretching ratio of the stretching step is preferably more than 1.0 times and 2.8 times or less, and preferably 1.6 times or less. Is the most preferable. Further, the heat shrinkage rate can be further controlled by providing a heat treatment step (I) between the stretching step (I) and the stretching step (II) or by providing a heat treatment step (II) after the stretching step (II). Can be done.

In the present invention, at least in the stretching step (I), the stretching ratio in the direction orthogonal to the main contraction direction is set to 3.0 times or more so that the drawing is oriented and crystallized in the stretching direction, and then the stretching step (II). ), The resin constituting the film is oriented and crystallized by stretching more than 1.0 times and 2.2 times or less in the direction orthogonal to the stretching direction (main contraction direction) in the stretching direction (I). It is possible to obtain a film that suppresses and largely heat-shrinks in the stretching direction (main contraction direction) of the stretching step (II). That is, it is considered that the shrinkage component is obtained by slightly stretching in a direction orthogonal to the stretching direction of the stretching step (I) as the stretching step (II) in a state of being largely oriented and crystallized in the stretching direction of the stretching step (I). It is presumed that the amorphous component can be selectively distorted in the stretching direction in the stretching step (II). Therefore, in order to control the heat shrinkage rate at 150 ° C. in the direction orthogonal to the main shrinkage direction to -6% or more and 10% or less, it is important to use a crystalline resin as the resin composition to the extent that it can be oriented and crystallized. .. The degree of orientation crystallization can be grasped by using the refractive index and the plane orientation coefficient as indexes. In the present invention, the plane orientation coefficient is preferably more than 0.06, and the plane orientation coefficient is preferably 0.14 or less in that the amorphous component is distorted without crystallizing.

The polyester film of the present invention has a 90 ° C. heat shrinkage rate of 14% or less in the main shrinkage direction. In the present invention, since it is required to suppress shrinkage deformation in the drying step after printing and coating various functional layers, the shrinkage rate in the main shrinkage direction at 90 ° C. needs to be 14% or less. When the 90 ° C. heat shrinkage rate in the main shrinkage direction exceeds 14%, the functional layers are shrink-deformed in the drying step after printing and coating, and the flatness is deteriorated. On the other hand, when the coefficient of thermal expansion at 90 ° C. in the main shrinkage direction is larger than -2% (that is, thermal expansion such as -3% or -4%), the transportability of the film deteriorates and the productivity deteriorates. In some cases, the 90 ° C. thermal shrinkage in the main shrinkage direction is preferably greater than -2%. The method for setting the heat shrinkage rate in the main shrinkage direction at 90 ° C. to 14% or less is not particularly limited. For example, the refractive index in the main shrinkage direction is set to 1.58 or more and 1.64 or less, and the plane orientation coefficient. Is preferably 0.08 or more and 0.14 or less.

The polyester film of the present invention has a 90 ° C. heat shrinkage rate of 5% or less in the direction orthogonal to the main shrinkage direction. Within this range, for example, wrinkles during thermal laminating in packaging applications can be suppressed. The 90 ° C. thermal shrinkage rate in the direction orthogonal to the main shrinkage direction can be controlled under the stretching conditions described later.

The polyester film of the present invention has a refractive index of 1.64 or more and 1.67 or less in the direction orthogonal to the main contraction direction. A heat-shrinkable film is required to have a uniform heat-shrinkability in the width direction when heated at a high temperature. However, if the refractive index in the direction orthogonal to the main shrinkage direction is less than 1.64, the film orientation is weak and heat is generated. The variation in shrinkage rate increases. Further, when the refractive index in the direction orthogonal to the main shrinkage direction is oriented beyond 1.67, the heat shrinkage rate at a low temperature becomes high and shrinkage deformation occurs. By setting the refractive index in the direction orthogonal to the main shrinkage direction within the above range, it is possible to suppress the variation in the heat shrinkage rate when heated at a high temperature and suppress the shrinkage deformation at a low temperature.

The polyester film of the present invention preferably has a refractive index of 1.58 or more and 1.64 or less in the main contraction direction. By setting the refractive index in the main contraction direction to such a range, the heat shrinkage rate at 150 ° C. in the main contraction direction is set to 25% or more, and the heat shrinkage rate at 150 ° C. in the direction orthogonal to the main contraction direction is set to 10% or less. It becomes easy to do.

The polyester film of the present invention has a rigid amorphous ratio of 42% or more and 60% or less. The ratio of rigid amorphous can be calculated by the method described in (5) Measurement of bulk composition of polyester film (5-3) Rigid amorphous amount (fraction) described later. The ratio of rigid amorphous is an index for measuring the uniformity of heat shrinkage and the formability of uneven patterns. If the proportion of rigid amorphous is less than 42%, it becomes difficult to achieve both uniformity of heat shrinkage at high temperature and flexibility in high temperature shrinkage step. On the other hand, when the ratio of rigid amorphous exceeds 60%, the heat shrinkage rate in the drying step becomes large and shrinkage deformation occurs. By setting the ratio of rigid amorphous to the above range, it is possible to suppress shrinkage deformation in the drying step while achieving both uniformity of the heat shrinkage rate at high temperature and flexibility in the high temperature shrinkage step. The proportion of rigid amorphous is more preferably 45% or more and 55% or less. As a method of controlling to this range, it can be achieved by stretching the homopolyester in the main contraction direction at a predetermined magnification, but to reach this range, polyethylene terephthalate is the main component and the copolymerization component is the diol component or the glycol component. On the other hand, it is preferable to introduce 6 mol% or more in total, but the film orientation is lowered as the crystallinity is lowered by introducing the copolymerization component, so that the conventional film forming method is used. Then, the variation in the heat shrinkage rate at a high temperature in the width direction becomes large. Therefore, in the present invention, in order to reduce the proportion of rigid amorphous to 42% or more and 60% or less, a copolymerization component is introduced, and then the heat treatment step (I) is carried out after the stretching step (I) described above. The heat treatment temperature HS-1 [° C.] in the heat treatment step (I) is set to be 80 ° C. or higher and 110 ° C. or lower lower than the melting point Tm1 [° C.] of the resin constituting the film ((ΔmS [° C.] = Tm1 [° C.]. ] -HS-1 [° C.]), 80 ≤ ΔmS [° C.] ≤ 110). For example, in the case of polyethylene terephthalate, HS-1 [° C.] is preferably 140 ° C. or higher and 170 ° C. or lower. Next, by carrying out stretching in the main shrinkage direction in the stretching step (II), a film having flexibility capable of suppressing film tearing in the shrinking step at a high temperature can be obtained. If HS-1 is set to be 80 ° C. or higher and 110 ° C. or lower using a highly crystalline resin such as a homopolymer and film formation is performed, crystallization of the film may proceed and film tearing may occur. be. Therefore, it is important to reduce the crystallinity of the resin by introducing a copolymerization component or the like. When the polyester resin constituting the film has a melting point of 2 or more, the lowest melting point is Tm1.

The polyester film of the present invention has a crystallinity of 10% or more and 20% from the viewpoint of achieving both drying heat resistance after coating various functional layers and flexibility in the secondary processing step in the TD direction after heat shrinkage. The following is preferable. When the crystallinity is less than 10%, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction increases, and when the crystallinity exceeds 20%, film tear occurs in the secondary processing step in the TD direction after heat shrinkage. May be done. The method for setting the crystallinity within this range is not particularly limited, but the crystallinity is determined by the conditions at the time of film formation in addition to the crystallinity of the raw material used, and is sequentially biaxial. Examples thereof include a method in which the area stretching ratio at the time of stretching is 6.0 times or more, and a method in which the above-mentioned ΔmS is 80 ° C. or higher and 110 ° C. or lower. Further, it can be controlled by adjusting the stretching method and the stretching temperature.

The glycol or derivative thereof that gives the polyester used in the present invention preferably contains 80 mol% or more of ethylene glycol, but other components include 1,2-propanediol, 1,3-propanediol, and 1,3. -Butandiol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4: 3,6-dianhydro-D-glucitol (generic name: isosorbide), neopentyl glycol, etc. Polyoxyalkylene glycols such as aliphatic dihydroxy compounds, diethylene glycols, polyethylene glycols, polypropylene glycols and polytetramethylene glycols, alicyclic dihydroxy compounds such as 1,4-cyclohexanedimethanol and spiroglycols, and fragrances such as bisphenol A and bisphenol S. Group dihydroxy compounds and derivatives thereof can be mentioned.

The dicarboxylic acid or derivative thereof that gives the polyester used in the present invention preferably contains 80 mol% or more of terephthalic acid, but other components include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and the like. Aromatic dicarboxylic acids such as diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid and diphenoxyetanedicarboxylic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid and fumaric acid, 1, Examples thereof include alicyclic dicarboxylic acids such as 4-cyclohexanedicarboxylic acid, oxycarboxylic acids such as paraoxybenzoic acid, and derivatives thereof. Examples of the derivative of the dicarboxylic acid include dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethylmethyl ester terephthalate, dimethyl 2,6-naphthalenedicarboxylic acid, dimethyl isophthalate, dimethyl adipate, diethyl maleate, and dimethyl dimerate. Can be mentioned.

The polyester film of the present invention is preferably a laminated film having at least two or more layers composed of a resin layer A containing resin A as a main component and a resin layer B containing resin B as a main component. In the present invention, a film forming method in which ΔmS is 80 ° C. or higher and 110 ° C. or lower is preferable in order to reduce the variation in the heat shrinkage rate at high temperature in the width direction, but the film at this time is very brittle and the film tears frequently. However, the film formation stability is poor. However, it is preferable to provide the resin layer B as the protective layer because the film tearing is suppressed and the film forming stability is improved. In addition to the two layers of A / B, the three layers of A / B / A, and the five layers of A / B / A / B / A, the laminated structure may be a multi-layer laminated structure of more than five layers. Further, an A / B / C laminated structure in which the resin layer C is further provided may be used as long as the effect of the present invention is not impaired.

When the polyester film of the present invention is composed of two or more laminated films having a resin layer A and a resin layer B, the melting heat absorption peak temperature TmA of the resin A constituting the resin layer A is a resin constituting the resin layer B. It is preferable that the temperature is 10 ° C. or higher lower than the melting heat absorption peak temperature TmB of B. In the present invention, in order to make the ratio of rigid amorphous and the refractive point orthogonal to the main contraction direction within the range of the present invention, the lowest melting point Tm1 [° C.] (resin A, resin A, of the melting points of the resins constituting the film). In a polyester film made of resin B, when the melting point Tm of resin A is lower than that of resin B, Tm1 [° C.] = TmA [° C.]) to HS-1 [° C.], which is the set temperature of the heat treatment step (I). ] Is subtracted, the value ΔmS is preferably 80 ° C. or higher and 110 ° C. or lower, and the main purpose is to relax the orientation given by the stretching in the stretching step (I). That is, although it is desired to relax the orientation of only the resin layer A as much as possible in the heat treatment step (I), if HS-1 is set to a condition close to the melting point TmA of the resin A, the film forming stability becomes low. Therefore, the film forming stability is improved by providing the resin B having a melting point higher than that of the resin A. From the viewpoint of film formation stability, the melting endothermic peak temperature TmA of the resin A is preferably 15 ° C. or higher lower than the melting endothermic peak temperature Tmb of the resin B, and more preferably 20 ° C. or higher.

In the present invention, the crystal melting energy ΔHmA of the resin A is preferably 25 J / g or less, and the film tear in the heat treatment step (I) is suppressed from the viewpoint of suppressing the film tear in the shrinkage step at a high temperature. From the viewpoint, the crystal melting energy ΔHmA is preferably 10 J / g or more. The method for controlling ΔHmA to 10 J / g or more and 25 J / g or less is not particularly limited, and for example, it is preferable to introduce a copolymerization component into the polyester resin. From the viewpoint of suppressing film tearing in the heat treatment step (I) and suppressing film tearing in the shrinkage step at a high temperature, the dicarboxylic acid component and the diol component of the polyester resin (resin A) constituting the resin layer A include terephthalic acid. After using 80 mol% or more of each of ethylene glycol, 2,6-naphthalenedicarboxylic acid, isophthalic acid, 1,4-cyclohexanedimethanol, neopentyl glycol, spiroglycol, 1,4: 3, as copolymerization components. It is mentioned as a preferable method to use 6-dianhydro-D-glucitol (generic name: isosorbide).

The polyester film of the present invention has hard coat property, self-healing property, antiglare property, and antireflection property on at least one surface for the purpose of surface smoothing when the film surface is slightly scratched by biaxial stretching. It may have a surface layer exhibiting one or more functions selected from the group consisting of low reflectivity, ultraviolet shielding property, and antistatic property. The surface layer is preferably soft enough to be deformed following the shrinkage from the viewpoint of followability due to the shrinkage of the original film.

The polyester film of the present invention is preferably biaxially oriented from the viewpoint of heat shrinkage characteristics. A preferable manufacturing method for obtaining such a biaxially oriented polyester film will be described below by taking a sequential biaxial stretching method as an example. The present invention is not construed as being limited to such examples.

As a method for producing the polyester film of the present invention, at least after forming a sheet by a melt extrusion step and a casting step, the steps are performed in the order of stretching step (I), heat treatment step (I), stretching step (II), and heat treatment step (II). A method for producing a passing film is mentioned as a preferable method. In the stretching step (I), biaxial stretching may be performed sequentially, and the stretching ratio in the film forming direction (film flow direction: MD direction (longitudinal direction)) is 1.1 times or more and 2.2 times or less, and the film forming direction. It is preferable that the draw ratio in the direction orthogonal to (film width direction: TD direction (horizontal direction)) is 3.0 times or more and 6.0 times or less. In the stretching step (I), the stretching ratio in the film forming direction (film flow direction: MD direction (longitudinal direction)) is 2.0 times or less from the viewpoint of suppressing the heat shrinkage rate in the direction orthogonal to the main shrinkage direction. It is preferable that the amount is 1.5 times or less, and most preferably 1.5 times or less. Further, from the viewpoint of setting the heat shrinkage rate in the main shrinkage direction to 25% or more, the integrated stretch ratio in the film-forming direction in the stretching steps (I) and (II) is 2.0 times or less, and the stretching step (II). It is preferable that the stretching ratio in the film-forming direction of) is higher than the stretching ratio in the film-forming direction of the stretching step (I). Further, the temperature (HS-1) in the heat treatment step (I) is preferably −80 ° C. or higher and −110 ° C. or lower with respect to the melting point Tm1 of the resin constituting the film from the viewpoint of controlling the ratio of rigid amorphous. .. Further, in a method for producing a film having a heat treatment step (II) after the stretching step (II), the heat treatment temperature (HS-2) is not less than the glass transition temperature of the resin and not more than the glass transition temperature + 40 ° C. preferable. When there are a plurality of glass transition temperatures, the temperature at which the glass transition temperature is higher is used as a reference.

The thickness of the polyester film of the present invention is not particularly limited as long as the object can be achieved, and may be about 3 μm to 300 μm as generally used as a biaxially stretched film. The thickness may be varied as needed.

The polyester film of the present invention may be further reinforced with a backing material or the like. Examples of the backing material include biaxially oriented polyester film and biaxially oriented polypropylene.

The polyester film of the present invention has a low heat shrinkage rate in a low temperature region and exhibits uniform heat shrinkage in a high temperature region, and is therefore preferably used for packaging. Since it has heat resistance that does not shrink in the drying process after coating various functional layers such as a printing layer, a weather resistant layer, an adhesive layer, an adhesive layer, and a vapor deposition layer, it can be used as a coating agent for an aqueous solvent. Further, since it exhibits high heat shrinkage when heated at a high temperature, it is excellent in mountability to a container such as a bottle, and is therefore preferably used for various packaging applications mainly for labels.

Further, the polyester film of the present invention can also be preferably used for decorative purposes. Various functional layers such as printing layer, weather resistant layer, adhesive layer, adhesive layer, vapor deposition layer, scratch resistant layer, fingerprint resistant layer, etc. It has excellent heat resistance in the drying process after coating various functional layers, and exhibits high heat shrinkage when heated at high temperature, so it can be applied to highly designed decorations on members with complicated shapes. Is.

(Characteristic measurement method and effect evaluation method)
The method for measuring the characteristics and the method for evaluating the effect in the present invention are as follows.

(1) Polyester composition
The polyester film can be 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.} In the case of a laminated film, by scraping off each layer of the film according to the laminated thickness, the components constituting each layer alone can be collected and evaluated. The composition of the film of the present invention was calculated from the mixing ratio at the time of film production.

(2) Film thickness, thickness of each layer 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 film thickness and the thickness of each layer in the case of a laminated structure were determined.

(3) Film main contraction direction
A sample cut into a size of 150 mm (measurement direction) x width 10 mm (direction orthogonal to the measurement direction) in the direction from there to 180 ° at 5 ° intervals, with 0 ° in any one direction of the film, is 100 mm (100 mm). Marks (marked lines) were placed at both ends of the interval of L0), and a 3 g weight was hung and placed in a hot air oven heated to 150 ° C. for 30 minutes for heat treatment. The distance between the marked lines (L1) after the heat treatment was measured, and the heat shrinkage rate was calculated by the following formula from the change in the distance between the marked lines before and after the heating.
Heat shrinkage rate (%) = 100 × (L0-L1) / L0
The measurement was performed 5 times in each direction, and the direction having the highest heat shrinkage rate was defined as the main shrinkage direction.

(4) Thermal Shrinkage at 90 ° C. and 150 ° C. Measurements were carried out in the main shrinkage direction and the direction orthogonal to the main shrinkage direction of the film. Marks (marked lines) are placed at both ends of a 100 mm (L0) interval on a sample cut into a size of 150 mm (measurement direction) x width 10 mm (direction orthogonal to the measurement direction), and a 3 g weight is hung for measurement. It was placed in a hot air oven heated to a temperature for 30 minutes and heat-treated. The distance between the marked lines (L1) after the heat treatment was measured, and the heat shrinkage rate was calculated by the following formula from the change in the distance between the marked lines before and after the heating. Five samples were measured in each direction, and the average value was used for evaluation.
Heat shrinkage rate (%) = 100 × (L0-L1) / L0.

(5) Measurement of bulk composition of polyester film (5-1) Movable non-crystalline amount Using a temperature-modulated DSC manufactured by TA Instruments, 5 mg of a sample was heated from 0 ° C. to 150 ° C. at a heating rate of 2 ° C./min under a nitrogen atmosphere. , The temperature modulation amplitude was ± 1 ° C., and the temperature modulation cycle was 60 seconds. The specific heat difference at the glass transition temperature obtained by the measurement was calculated and calculated from the following formula.
Movable amorphous amount (%) = (specific heat difference) / (theoretical value of specific heat difference of polyester completely amorphous) x 100
Theoretical value of specific heat difference of polyethylene terephthalate completely amorphous material = 0.4052J / (g ℃)
Further, in the present invention, for the polyethylene terephthalate unit having a content of 80 mol% or more, the theoretical value of the specific heat difference of the completely amorphous material of polyethylene terephthalate was referred to.
For the theoretical values of the specific heat difference of the other completely amorphous polyesters, the values described in Advanced thermal analysis system (ATHAS) polymer heat capacity data bank were used.

(5-2) Crystallinity
According to JIS K7122 (1987), Hitachi High-Tech Co., Ltd. differential scanning calorimetry robot DSC 6220 ASD-2 is used, and thermal analysis software standard analysis Mouse Version: 9.0 is used for data analysis, and film sample 5 mg. Was heated from room temperature to 300 ° C. at a heating rate of 20 ° C./min on an aluminum saucer, and held at 300 ° C. for 5 minutes. At that time, it was calculated by the following formula from the endothermic peak heat amount ΔHm, the cold crystallization heat amount ΔHc, and the melting heat amount ΔHm0 (140.1 J / g) of the perfect crystal PET obtained by the measurement.
Crystallinity (%) = (ΔHm−ΔHc) / ΔHm0 × 100
For the heat capacity for melting the other polyesters in the perfect crystal state, the values described in Advanced thermal analogy system (ATHAS) polymer heat capacity data bank were used.

(5-3) Rigid amorphous amount The rigid amorphous amount is described in (5-1) Movable amorphous amount obtained by the measuring method described in (5-1) Movable amorphous amount and (5-2) Crystallinity. From the crystallinity obtained by the measuring method, it was calculated by the following formula.
Rigid amorphous amount (%) = 100- (movable amorphous amount + crystallinity).
Theoretical value of specific heat difference of polyethylene terephthalate completely amorphous material = 0.4052J / (g ℃)
Further, in the present invention, for the polyethylene terephthalate unit having a content of 80 mol% or more, the theoretical value of the specific heat difference of the completely amorphous material of polyethylene terephthalate was referred to.
For the theoretical values of the specific heat difference of the other completely amorphous polyesters, the values described in Advanced thermal analysis system (ATHAS) polymer heat capacity data bank were used.

(6) Glass transition temperature, melting endothermic peak temperature Tm, crystal melting energy ΔHm
In accordance with JIS7122 (1987), a differential scanning calorimeter (EXSTAR DSC6220 manufactured by Seiko Instruments Inc.) is used to raise the temperature of 3 mg of resin from 30 ° C. to 300 ° C. at 20 ° C./min in a nitrogen atmosphere. Then, after holding at 300 ° C. for 5 minutes, the temperature is lowered to 30 ° C. under the condition of 40 ° C./min. Further, after holding at 30 ° C. for 5 minutes, the temperature is raised from 30 ° C. to 300 ° C. under the condition of 20 ° C./min. The glass transition temperature obtained at the time of this temperature rise was calculated by the following formula (i).
Glass transition temperature = (extrapolation glass transition start temperature + extrapolation glass transition end temperature) / 2 ... (i)
Here, the extra glass transition start temperature is the intersection of the straight line extending the baseline on the low temperature side to the high temperature side and the tangent line drawn at the point where the slope of the curve of the stepwise change part of the glass transition is maximized. Let it be the temperature. The outer glass transition end temperature is the temperature at the intersection of the straight line extending the baseline on the high temperature side to the low temperature side and the tangent line drawn at the point where the slope of the curve of the stepwise change part of the glass transition is maximized. do. Moreover, the peak top of the endothermic peak was defined as the melting point.

(7) Refractive index, plane orientation coefficient fn
Using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting solution, and using an Abbe refractometer at 25 ° C., the film main shrinkage direction, the direction orthogonal to the main shrinkage, and the thickness specified in (3). The refractive index in the direction (nMD, nTD, nZD, respectively) was determined. The plane orientation coefficient (fn) was calculated from the obtained refractive index by the following formula.
Planar orientation coefficient fn = (nMD + nTD) /2-nZD
(8) Uniformity of heat shrinkage (8-1) Heat shrinkage rate Heat in the main shrinkage direction and the direction orthogonal to the main shrinkage direction, and in the 45 ° and −45 ° directions when the main shrinkage direction is 0 °. The shrinkage rate was measured. A circle with a diameter of 50 mm (L0) and a main contraction direction and main A sample is created by marking a total of four straight lines in the direction orthogonal to the contraction direction and the 45 ° direction and the −45 ° direction when the main contraction direction is 0 ° so as to intersect the circle. The prepared samples were sandwiched between papers and placed in a hot air oven heated to 150 ° C. for 30 minutes for heat treatment. The distance between the marked lines (L1) in each direction (4 directions) after the heat treatment was measured, and the heat shrinkage rate was calculated by the following formula from the change in the distance between the marked lines before and after the heating. Three samples were measured for each width direction position, and the average value was used for evaluation.
Heat shrinkage rate (%) = 100 × (L0-L1) / L0
A: The range of the heat shrinkage difference between the 45 ° direction and the −45 ° direction of less than 3.0% was the range of the width of 1000 mm or more.
B: The range of the heat shrinkage rate difference of less than 3.0% in the 45 ° direction and the −45 ° direction was a range of a width of 500 mm or more and less than 1000 mm.
C: The range of the heat shrinkage rate difference of less than 3.0% in the 45 ° direction and the −45 ° direction was the range of the width of 200 mm or more and less than 500 mm.
D: The range of the heat shrinkage difference of less than 3.0% in the 45 ° direction and the −45 ° direction was the range of less than 200 mm in width.
A, B, and C are pass levels.

(8-2) Circular area reduction Similar to (8-1), cut out to a size of 60 mm in the main contraction direction × 60 mm in the direction orthogonal to the main contraction direction, centered at a position at intervals of 50 mm from the center in the film width direction to the film edge. Using the inner circle area of the sample in which a circle with a diameter of 50 mm was drawn, the reduction in the circular area before and after the heat treatment based on the center position in the width direction of the film was evaluated as an index of variation. Each sample image before and after the heat treatment is read with a gray scale with a scanner, and the image analysis software Image-Pro Plus The Proven Solution version 4.5.0.24 for windows 98 / NT / 2000 Count / Size is used to fill the image including the boundary line. The area of the part (dark color) is automatically extracted, the area inside the circle painted in black is calculated (the area before heat treatment is S0, the area after heat treatment is S1), the circle area reduction is calculated by the following formula, and heat shrinkage is performed. It was used as an index of the variation of. The method of painting the inside of the circle in black may be either before or after scanning with a scanner, and the method of painting the sample with black oil-based magic or the method of painting the captured image in black with paint software is not particularly limited. Three samples were measured for each width direction position, and the average value was used for evaluation.
Circle area reduction (%) = 100 × (S0-S1) / S0
A: The range in which the difference from the reduction in the circular area at the center position was 5.0% or less was the range in which the width was 1000 mm or more.
B: The range in which the difference from the reduction in the circular area at the center position was 5.0% or less was the range in which the width was 500 mm or more and less than 1000 mm.
C: The range in which the difference from the reduction in the circular area at the center position was 5.0% or less was the range in which the width was 200 mm or more and less than 500 mm.
D: The range in which the difference from the reduction in the circular area at the center position was 5.0% or less was less than 200 mm in width.

A, B, and C are pass levels.

(9) Suitable for packaging (9-1) Dry heat resistance
Screen printing was performed on the film surface. Printing was performed using an ink U-PET (517) manufactured by Mino Group Co., Ltd. and a screen SX270T under the conditions of a squeegee speed of 300 mm / sec and a squeegee angle of 45 °, and then in a hot air oven under 90 ° C. conditions for 5 minutes. It was dried to obtain a printed layer laminated film. The appearance of the obtained printed layer laminated film was evaluated according to the following criteria.
A: No wrinkles were confirmed even after drying, and the appearance was good.
B: Some wrinkles were confirmed after drying, but the appearance was good.
C: Wrinkles were confirmed after drying, but there was no problem in practical use.
D: Wrinkles were confirmed after drying, which was not at a practical level.
A, B, and C are pass levels.

(9-2) Heat shrinkage
With respect to the print layer laminated film prepared in (9-1), both ends of the film were bonded with a fusing sticker to prepare a cylindrical label. The label was placed on the body of a cylindrical aluminum bottle (bottom diameter: 150 mm), passed through a tunnel oven in an atmosphere of 150 ° C. with a passing time of 3 seconds, attached to the bottle, and the shrinkage appearance was evaluated according to the following criteria. ..
A: No wrinkles, distortions, or insufficient shrinkage occurred, and the appearance was excellent in design.
B: At least one of wrinkles, distortion, and insufficient shrinkage can be confirmed, but the appearance was excellent in design.
C: At least one of wrinkles, distortion, and insufficient shrinkage can be confirmed, but there was no problem in practical use.
D: At least one of wrinkles, distortion, and insufficient shrinkage was confirmed, which was not at a practical level.
A, B, and C are pass levels.

(10) Formability of Concavo-convex Pattern Acrylic resin having a glass transition temperature of 128 ° C. is diluted with toluene, and a paint for forming a hard layer (solid content concentration: 8% by mass) is applied onto a film so that the thickness after drying is 2 μm. It was coated with a bar coater and dried in a hot air oven under 90 ° C. conditions for 5 minutes to obtain a laminate. The prepared laminate was contracted in the main contraction direction in an oven at 150 ° C., and then slightly stretched in a direction orthogonal to the main contraction direction to form a wavy fine uneven pattern. The moldability at that time was evaluated according to the following criteria.
◯: No breakage of the film occurred, and fine irregularities could be formed.
X: ◯, in which the film was broken in the fine stretching step after shrinkage, is the pass level.

(Manufacturing of polyester)
The polyester resin used for film formation was prepared as follows.
(Polyester A)
A polyethylene terephthalate resin (intrinsic viscosity 0.65) containing 100 mol% of a terephthalic acid component as a dicarboxylic acid component and 100 mol% of an ethylene glycol component as a glycol component.

(Polyester B)
A polyester resin having a terephthalic acid component of 94 mol% as a dicarboxylic acid component, an isophthalic acid component of 6 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).
(Polyester C)
A polyester resin having a terephthalic acid component of 92 mol% as a dicarboxylic acid component, an isophthalic acid component of 8 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).
(Polyester D)
A polyester resin having a terephthalic acid component of 88 mol% as a dicarboxylic acid component, an isophthalic acid component of 12 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).
(Polyester E)
A polyester resin having a terephthalic acid component of 86 mol% as a dicarboxylic acid component, an isophthalic acid component of 14 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).
(Polyester F)
A polyester resin having an terephthalic acid component of 82 mol% as a dicarboxylic acid component, an isophthalic acid component of 18 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).
(Polyester G)
A polyester resin having a terephthalic acid component of 91 mol% as a dicarboxylic acid component, a 2,6-naphthalenedicarboxylic acid component of 9 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).
(Polyester H)
A polyester resin having a terephthalic acid component of 88 mol% as a dicarboxylic acid component, a 2,6-naphthalenedicarboxylic acid component of 12 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).

(Polyester I)
A polyester resin having a terephthalic acid component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 88 mol% as a glycol component, and a 1,4-cyclohexanedimethanol component of 12 mol% (intrinsic viscosity 0.75).

(Polyester J)
A polyester resin having a terephthalic acid component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 85 mol% as a glycol component, and a 1,4-cyclohexanedimethanol component of 15 mol% (intrinsic viscosity 0.75).

(Polyester K)
A polyester resin (intrinsic viscosity 0.75) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component, the ethylene glycol component is 82 mol% as the glycol component, and the 1,4-cyclohexanedimethanol component is 18 mol%.

(Polyester L)
A polyester resin (intrinsic viscosity 0.75) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component, the ethylene glycol component is 92 mol% as the glycol component, and the spiroglycol component is 8 mol%.

(Polyester M)
A polyester resin having a terephthalic acid component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 88 mol% as a glycol component, and a spiroglycol component of 12 mol% (intrinsic viscosity 0.75).

(Polyester N)
A polyester resin having a terephthalic acid component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 84 mol% as a glycol component, and a spiroglycol component of 16 mol% (intrinsic viscosity 0.75).

(Polyester O)
A polyester resin having a terephthalic acid component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 88 mol% as a glycol component, and a neopentyl glycol component of 12 mol% (intrinsic viscosity 0.75).

(Polyester P)
A polyester resin having a terephthalic acid component of 100 mol% as a dicarboxylic acid component, an ethylene glycol component of 82 mol% as a glycol component, and a neopentyl glycol component of 18 mol% (intrinsic viscosity 0.75).

(Polyester Q)
Polyester resin containing 100 mol% of terephthalic acid component as dicarboxylic acid component, 42 mol% of ethylene glycol component as glycol component, 15 mol% of isosorbide component, and 43 mol% of 1,4-cyclohexanedimethanol (intrinsic viscosity 0. 75).

(Polyester R)
A polyester resin having a terephthalic acid component of 96 mol% as a dicarboxylic acid component, an isophthalic acid component of 4 mol%, and an ethylene glycol component of 100 mol% as a glycol component (intrinsic viscosity 0.75).

(Manufacturing of particle master)
(Particle Master A)
Polyester terephthalate particle master (intrinsic viscosity 0.63) containing aggregated silica having a number average particle diameter of 0.2 μm in polyester A at a particle concentration of 5% by mass.

(Examples 1 to 56, Comparative Examples 1 to 6)
The composition of the polyester and the particle master resin used is as shown in the table, and the raw material is supplied to a vent isodirectional twin-screw extruder having an oxygen concentration of 0.2% by volume, the extruder cylinder temperature is melted at 270 ° C., and a short tube is used. The temperature was 275 ° C., the base temperature was 280 ° C., and the particles were discharged in the form of a sheet on a cooling drum whose temperature was controlled to 25 ° C. from the T die. At that time, an unstretched sheet was obtained by electrostatically applying static electricity using a wire-shaped electrode having a diameter of 0.1 mm and bringing it into close contact with a cooling drum. 1 longitudinal stretching, 1 transverse stretching, heat treatment, 2 longitudinal stretching, 2 transverse stretching, and heat treatment were carried out in this order to obtain a polyester film as the stretching ratio, stretching temperature, and heat treatment temperature shown in the table, respectively.

In all the examples, the heat shrinkage rate of 150 ° C. in the main shrinkage direction is 25% or more and 45% or less, the heat shrinkage rate of 150 ° C. in the direction orthogonal to the main shrinkage direction is -6% or more and 10% or less, and the heat shrinkage rate of 90 ° C. in the main shrinkage direction is 90 ° C. The rate is 14% or less, the heat shrinkage rate at 90 ° C. in the direction orthogonal to the main shrinkage direction is 5% or less, the ratio of rigid amorphous is 42% or more and 60% or less, and the refractive index in the direction orthogonal to the main shrinkage direction is It was 1.64 or more and 1.67 or less, and was excellent in drying suitability after coating various functional layers, and was suitable for shrinkability and secondary processability in which it was subsequently greatly shrunk at 150 ° C.

On the other hand, in Comparative Example 1, since the magnification of one longitudinal stretching was 3.3 times, the shrinkage component was deflected and distorted by one transverse stretching, so that the final heat shrinkage rate of 150 ° C. in the longitudinal direction of the film was obtained. Was less than 15%.
Further, in Comparative Example 2, since ΔmS exceeded 110 ° C., the amount of rigid amorphous material was out of the range of the present application, and the shape followability was inferior.
In Comparative Example 3, the heat shrinkage rate at 90 ° C. became 14% or more due to the high 2 longitudinal stretching ratio, and shrinkage deformation occurred in the drying step.
In Comparative Example 4, since ΔmS exceeded 110 ° C., the refractive index in the direction orthogonal to the main shrinkage direction was less than 1.64, and the thermal shrinkage uniformity in the width direction was inferior.
In Comparative Example 5, since the crystal melting energy exceeded 25 J / g, TM1-HS-1 was in the range of 80 ° C. to 110 ° C. or lower, but a film could not be obtained by crystallization.
In Comparative Example 6, since homopolyester was used, the amount of rigid amorphous was less than 42%, and the film was broken in the shrinkage processing step at high temperature.

The polyester film of the present invention has a special heat shrinkage property that suppresses shrinkage at about 90 ° C. and shrinks significantly at a high temperature of about 150 ° C., and also has the characteristics of uniformity of heat shrinkage rate and flexibility in the width direction. Have both. As a result, it is possible to dry after applying various functional layers while suppressing shrinkage and deformation at about 90 ° C., and then for packaging and various mold release applications that require secondary processing after being greatly shrunk at about 150 ° C. , Can be used in process films, etc.

Claims (5)

The 150 ° C. heat shrinkage rate in the main shrinkage direction is 25% or more and 45% or less, the 150 ° C. heat shrinkage rate in the direction orthogonal to the main shrinkage direction is -6% or more and 10% or less, and the 90 ° C. heat shrinkage rate in the main shrinkage direction is 14. % Or less, the 90 ° C. thermal shrinkage in the direction orthogonal to the main shrinkage direction is 5% or less, the proportion of rigid amorphous is 42% or more and 60% or less, and the refractive index in the direction orthogonal to the main shrinkage direction is 1. A polyester film of .64 or more and 1.67 or less. The polyester film according to claim 1, wherein the crystallinity is 10% or more and 20% or less. The polyester film according to claim 1 or 2, wherein the refractive index in the main contraction direction is 1.58 or more and 1.62 or less. In a laminated film having at least two or more layers having a resin layer A and a resin layer B, the melting heat absorption peak temperature TmA of the resin A constituting the resin layer A is the melting heat absorption peak temperature TmB of the resin B constituting the resin layer B. The polyester film according to any one of claims 1 to 3, which has a temperature lower than 10 ° C. or higher. The polyester film according to any one of claims 1 to 4, wherein the crystal melting energy ΔHmA of the resin A constituting the resin layer A is 10 J / g or more and 25 J / g or less.