JP2020012086A - Polyester-based film roll - Google Patents

Abstract

To provide a film roll consisting of a film mainly containing a polybutylene terephthalate resin good in bag breaking resistance, and less in loss when printing processing or laminate processing since slack is less.SOLUTION: There is provided a polyester-based film roll consisting of a polyester resin composition containing a polybutylene terephthalate resin (A) of 60 to 100 wt.% and satisfying (1) to (5). (1) A film roll winding length is 2000 to 60000 m. (2) A film roll width is 400 to 3000 mm. (3) A thickness of the film is 5 to 40 μm. (4) A location with a thickness pattern of recess exists in a thickness unevenness in a film width direction on a surface layer of the film roll, and thickness unevenness of maximum recess calculated by maximum thickness difference in the maximum recess and film average thickness is 6% or less. (5) A winding hardness of the film roll surface layer is 20 to 80.SELECTED DRAWING: None

Description

  The present invention relates to a film roll formed by winding a polyester film. More specifically, the present invention relates to a roll obtained by winding a polyester film mainly composed of polybutylene terephthalate resin having good bag-breaking resistance and having little slack, so that a loss in printing or laminating is small. .

  Polybutylene terephthalate (hereinafter abbreviated as PBT) resin is more excellent in impact resistance than polyethylene terephthalate (hereinafter abbreviated as PET) resin, so that it is used for food packaging film, drawing film and the like. Applications are also being studied in the field of films (for example, Patent Documents 1, 2, and 3).

However, the roll of the film containing PBT resin as a main component causes loosening when stored, and when performing printing or laminating, the loosened portion may cause misregistration of printing or variation / decrease in laminating strength. There is also a problem that wrinkles may occur, resulting in defective products.
The biaxially stretched PBT film has a problem that the film roll is more likely to be looser than the biaxially stretched PET film because the deformation temperature is low and uniform stretching is difficult, and the thickness unevenness tends to increase. Was.

JP 2017-94746 A JP 2013-256110 A JP 2012-146636 A JP 2001-151907 A

  The present invention has been made in the background of the problems of the related art. That is, an object of the present invention relates to a film roll formed by winding a polyester film. More specifically, an object of the present invention is to obtain a film roll that is a roll made of a film mainly composed of polybutylene terephthalate resin having good bag-breaking resistance and has a small amount of slack, so that loss during printing and lamination is small. .

  In the present invention, as a result of intensive studies to achieve such an object, a PBT resin having excellent bag-breaking resistance is obtained by setting the winding length, width, thickness unevenness in the film width direction and winding hardness of a film roll to specific ranges. It has been found that even with a film roll of a film containing as a main component, a film roll with less slack can be obtained. For this reason, troubles such as defective products in post-processing such as printing and laminating can be reduced.

That is, the present invention has the following configurations.
1. It comprises a polyester resin composition containing 60 to 100% by weight of a polybutylene terephthalate resin (A) and 0 to 40% by weight of a polyester resin (B) other than the polybutylene terephthalate resin (A), and the following requirements (1) to ( 5) A biaxially oriented polyester film roll characterized by satisfying 5).
(1) The roll length of the film roll is 2000 m or more and 60000 m or less.
(2) The film roll width is 400 mm or more and 3000 mm or less.
(3) The thickness of the film is 5 μm or more and 40 μm or less.
(4) In the thickness unevenness in the film width direction in the surface layer of the film roll, there is a portion where the thickness pattern is a concave portion, and in the concave portion having the largest thickness difference (maximum concave portion), the maximum thickness difference in the maximum concave portion and the film The thickness unevenness of the largest concave portion obtained from the average thickness is 6% or less.
(5) The winding hardness of the film roll surface layer is 20 or more and 80 or less.
2. In the thickness unevenness in the width direction of the film of each sample sampled at a winding length of 1000 m from the surface layer of the film roll, all of the thickness unevenness obtained from the maximum thickness difference in the maximum recess and the average thickness of the film are 6% or less. 2. The biaxially oriented polyester film roll according to 1.
3. 3. The biaxially oriented polyester film roll according to claim 1, wherein the thickness unevenness of the entire film roll in the width direction is 10% or less.
4. The biaxially oriented polyester film roll according to any one of claims 1 to 3, wherein the coefficient of kinetic friction measured on the outer surface and the inner surface of the biaxially oriented polyester film is 0.20 or more and 0.60 or less.
5. The biaxially oriented polyester film roll according to any one of claims 1 to 5, wherein the value of the piercing strength of the biaxially oriented polyester film measured by a piercing test according to JIS-Z1707 is 0.5 N / μm or more.
6. The biaxially oriented polyester film roll according to any one of claims 1 to 5, wherein the slit is obtained by setting the slitting tension of the slitter to 100 N / m or more and 160 N / m or less from a wide roll as an intermediate product. Manufacturing method.

  The inventor of the present invention has made it possible to obtain a film roll with little slack, even if the film roll is a film mainly composed of a PBT resin in which slack is easily generated. Since the film roll of the present invention can reduce troubles in post-processing such as printing and lamination, it can be suitably used as a film for food packaging or a film for drawing.

Installation example of shield plate for hot air supply duct in TD stretching zone (plan view) Example of three-stage stretching pattern in TD stretching machine (plan view) Example of measuring uneven thickness of recess

Hereinafter, the present invention will be described in detail.
[Polyester resin composition]
The polyester resin composition used for the film of the present invention contains the PBT resin (A) as a main component, and the content of the PBT resin (A) is preferably at least 60% by weight, more preferably at least 75% by weight. And more preferably 85% by weight or more. If it is less than 60% by weight, the pinhole resistance and the bag-breaking resistance are reduced.
In the PBT resin (A) used as a main constituent, terephthalic acid is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 98 mol% or more as a dicarboxylic acid component. Preferably it is 100 mol%. The glycol component preferably contains 1,4-butanediol in an amount of at least 90 mol%, more preferably at least 95 mol%, even more preferably at least 97 mol%, and most preferably 1,4-butanediol during polymerization. Except for by-products formed by the ether bond of the diol.

The polyester resin composition used in the film of the present invention contains a polyester resin (B) other than the PBT resin (A) for the purpose of adjusting the film forming property when performing biaxial stretching and the mechanical properties of the obtained film. be able to.
Polyester resin (B) other than PBT resin (A) is a polyester resin such as PET, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, or isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid PBT resin, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol copolymerized with at least one dicarboxylic acid selected from the group consisting of, adipic acid, azelaic acid and sebacic acid , 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate. PBT resin copolymerized with at least one diol component selected from the group, selected from the group consisting of isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid PBT resin obtained by copolymerizing at least one dicarboxylic acid, or 1,3-butanediol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, At least one diol component selected from the group consisting of 2,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate. At least one resin.

  Above all, PET resin has a high melting point and is excellent in heat resistance, so it is difficult to change its dimensions, and because it has excellent compatibility with PBT resin, it is excellent in transparency. Therefore, it is copolymerized as a polyester resin (B) other than PBT resin (A). PET resin is preferred, and PET is particularly preferred.

The lower limit of the intrinsic viscosity of the PBT resin (A) used in the film of the present invention is preferably 0.8 dl / g, more preferably 0.95 dl / g, and still more preferably 1.0 dl / g.
When the intrinsic viscosity of the PBT resin (A) is less than 0.9 dl / g, the intrinsic viscosity of a film obtained by forming a film may decrease, and the breaking strength or piercing strength may decrease.
The upper limit of the intrinsic viscosity of the PBT resin (A) is preferably 1.3 dl / g. If the ratio exceeds the above range, the stress at the time of stretching the film becomes too high, and the film forming property may be deteriorated. Furthermore, when a PBT resin having a high intrinsic viscosity is used, the extrusion temperature needs to be high because the melt viscosity of the resin is high. However, when the PBT resin is extruded at a higher temperature, a decomposition product may be easily generated. .

  The upper limit of the addition amount of the polyester resin (B) other than the PBT resin (A) is preferably 40% by weight or less, more preferably 35% by weight or less, and particularly preferably 15% by weight or less. When the addition amount of the polyester resin (B) other than the PBT resin (A) exceeds 40% by weight, the pinhole resistance and the bag breakage resistance are impaired, and the transparency and the gas barrier property may be reduced.

  If necessary, the polyester resin composition may contain conventionally known additives such as a lubricant, a stabilizer, a coloring agent, an antioxidant, an antistatic agent, and an ultraviolet absorber.

  As the lubricant species for adjusting the dynamic friction coefficient of the film of the present invention, silica, calcium carbonate, in addition to inorganic lubricants such as alumina, organic lubricants are preferable, silica, calcium carbonate is more preferable, and silica reduces haze. It is particularly preferred in that With these, transparency and slipperiness can be exhibited.

  The lower limit of the content of the lubricant in the polyester resin composition is preferably 100 ppm by weight, more preferably 800 ppm by weight, and if it is less than 100 ppm by weight, the slipperiness is reduced, and the amount of air involved during slitting is large. When the film is rolled, looseness and wrinkles may be easily formed due to air bleeding from the concave portion. The upper limit of the content of the lubricant is preferably 20,000 ppm by weight, more preferably 1,000 ppm by weight, particularly preferably 1800 ppm by weight. The end face may shift due to slippage.

[Production method of biaxially oriented polyester film]
As a suitable method for obtaining the biaxially oriented polyester film of the present invention, a T-die method is preferable from the viewpoint of thickness accuracy in the width direction. In the inflation method, the draw ratio is hardly increased due to the manufacturing method, and a thickness defect in the width direction may occur.
Further, as a preferred method for obtaining the biaxially oriented polyester film of the present invention, when casting the molten polyester resin composition on a cooling roll, a polyester resin composition raw material having the same composition may be multilayered and cast.
Since the PBT resin has a high crystallization rate, crystallization proceeds during casting. At this time, if a single layer is cast without forming a multilayer, these crystals grow into large spherulites because there is no barrier that can suppress the growth of the crystals. As a result, the yield stress of the obtained unstretched sheet increases, and the sheet tends to break during stretching in the longitudinal direction.
Not only that, since the crystallization proceeds during the stretching in the longitudinal direction, the film is easily broken during the stretching in the width direction, and the obtained biaxially oriented polyester film has insufficient bag breaking strength and piercing strength. Will be.
Furthermore, a large variation occurs in crystal growth according to the thickness of the film in the width direction, resulting in a density difference. As a result, during the subsequent stretching in the longitudinal direction and the width direction, unevenness in the stretching stress occurs, the thickness accuracy of the obtained biaxially oriented polyester film is reduced, and the film roll may be loosened.

Specifically, the method for producing a biaxially oriented PBT film of the present invention comprises a molten fluid formed in the step (1) of melting a polyester resin composition containing at least 60% by weight of a PBT resin to form a molten fluid. Discharging the layered fluid formed in the step (2) of forming a layered fluid having 60 or more layers from a dice, contacting with a cooling roll and solidifying to form a layered body (3); At least a step (4) of axial stretching is provided.
Other steps may be inserted between step (1) and step (2), and between step (2) and step (3). For example, a filtration step, a temperature changing step, and the like may be inserted between step (1) and step (2). Further, between the step (2) and the step (3), a temperature changing step, a charge adding step and the like may be inserted. However, between the step (2) and the step (3), there must be no step of destroying the laminated structure formed in the step (2).

  In the step (1), a method of melting the polyester resin composition to form a molten fluid is not particularly limited, but a preferred method is a method of heating and melting using a single-screw extruder or a twin-screw extruder. Can be.

  The method of forming the layered fluid in the step (2) is not particularly limited, but a static mixer and / or a multilayer feed block are more preferable in terms of facility and maintainability. Further, from the viewpoint of uniformity in the sheet width direction, those having a rectangular melt line are more preferable. It is further preferred to use a static mixer or a multilayer feedblock having a rectangular melt line. In addition, the resin composition composed of a plurality of layers formed by joining a plurality of polyester resin compositions may be passed through any one or more of a static mixer, a multilayer feed block, and a multilayer manifold.

  The theoretical number of stacked layers in the step (2) needs to be 60 or more. The lower limit of the theoretical number of layers is preferably 200, and more preferably 500. If the theoretical number of laminations is too small, the distance between the layer interfaces will be too long and the crystal size will be too large, and the above-described breakage during stretching, reduction in mechanical strength, and slackening of the film roll due to reduction in thickness accuracy will occur. Further, the degree of crystallinity in the vicinity of both ends of the sheet increases, the film formation becomes unstable, and the transparency after molding may decrease. The upper limit of the theoretical lamination number in the step (2) is not particularly limited, but is preferably 100,000, more preferably 10,000, and further preferably 7000. Even if the theoretical number of layers is extremely increased, the effect may be saturated.

  When the lamination in the step (2) is performed by a static mixer, the theoretical number of laminations can be adjusted by selecting the number of elements of the static mixer. The static mixer is generally known as a static mixer (line mixer) having no drive unit, and fluids in the mixer are sequentially stirred and mixed by the elements. However, when a high-viscosity fluid is passed through a static mixer, division and lamination of the high-viscosity fluid occur, and a laminated fluid is formed. Each time one element of the static mixer passes, the high-viscosity fluid is divided into two parts and then merged and laminated. Therefore, when the high-viscosity fluid is passed through a static mixer having n elements, a laminated fluid having a theoretical lamination number N = 2 to the nth power is formed.

  A typical static mixer element has a structure in which a rectangular plate is twisted by 180 degrees, and there are a right element and a left element depending on the direction of the twist, and the size of each element is 1.5 times as long as the diameter. It is based on The static mixer that can be used in the present invention is not limited to such a mixer.

When the lamination in the step (2) is performed using a multilayer feed block, the theoretical number of laminations can be adjusted by selecting the number of divisions and laminations of the multilayer feed block. A plurality of multilayer feed blocks can be installed in series. Further, the high-viscosity fluid itself supplied to the multilayer feed block can be used as a layered fluid. For example, when the number of layers of the high-viscosity fluid supplied to the multilayer feed block is p, the number of divisions / layers of the multilayer feed block is q, and the number of layers of the multilayer feed block is r, the number N of layers of the multilayer fluid is N = p × (q to the power of r).
In the case where the polyester resin composition having the same composition is multilayered as in the present invention, using only one extruder, the above-described multilayering apparatus can be introduced into a melt line from the extrusion to the die. .

  In the step (3), the layered fluid is discharged from the die, and is contacted with a cooling roll to be solidified.

The lower limit of the die temperature is preferably 255 ° C., more preferably 260 ° C., and particularly preferably 265 ° C. If it is lower than the above, the ejection may not be stable and the thickness may be uneven.
Further, the PET resin retained in the resin melt extrusion step may become an unmelted substance and be mixed into the film, thereby deteriorating the quality of the film. The upper limit of the resin melting temperature is preferably 285 ° C, more preferably 280 ° C, and most preferably 275 ° C. If the ratio exceeds the above range, the decomposition of the resin proceeds, and the film becomes brittle.
The upper limit of the die temperature is preferably 320 ° C, more preferably 300 ° C or less, and further preferably 280 ° C or less. If the thickness exceeds the above range, the thickness becomes non-uniform, the film roll is loosened, the resin is deteriorated, and the appearance becomes poor due to die lip stain or the like.

  The upper limit of the cooling roll temperature is preferably 40 ° C, and more preferably 20 ° C or less. If the ratio exceeds the above range, the crystallinity of the molten polyester resin composition upon cooling and solidification becomes too high, and stretching may be difficult. The lower limit of the cooling roll temperature is preferably 0 ° C. If it is lower than the above, the effect of suppressing crystallization when the molten polyester resin composition is cooled and solidified may be saturated. When the temperature of the cooling roll is in the above range, it is preferable to lower the humidity of the environment near the cooling roll in order to prevent dew condensation.

When the molten polyester resin composition is cast on the surface of the cooling roll, the temperature of the surface of the cooling roll increases because the high-temperature resin comes into contact with the surface. Normally, chill rolls are cooled by flowing cooling water through piping inside the chill rolls.However, ensure a sufficient amount of cooling water, devise piping arrangements, perform maintenance so that sludge does not adhere to piping, etc. It is necessary to reduce the temperature difference in the width direction. In particular, care must be taken when cooling at a low temperature without using a method such as multilayering.
At this time, the thickness of the unstretched sheet is preferably in the range of 15 to 2500 μm. It is more preferably 500 μm or less, and further preferably 300 μm or less.

  The above-described casting with a multilayer structure is performed with at least 60 layers or more, preferably 250 layers or more, and more preferably 1000 layers or more. When the number of layers is small, the spherulite size of the unstretched sheet increases, and not only the effect of improving the stretchability is small, but also the distortion of the film roll due to a decrease in mechanical strength and a decrease in thickness accuracy of the obtained biaxially stretched film is reduced. May occur.

  Next, the stretching method in the step (4) will be described. The stretching method can be simultaneous biaxial stretching or sequential biaxial stretching, but it is easy to increase the plane orientation coefficient from the viewpoint of pinhole resistance and bag breakage resistance, and it is easy to increase the uniformity of the film thickness in the width direction. From the viewpoint of high film forming speed and high productivity, sequential biaxial stretching is most preferable.

  The lower limit of the stretching temperature in the longitudinal direction (hereinafter, MD) is preferably 55 ° C, more preferably 60 ° C. When the temperature is lower than 55 ° C., not only breakage is liable to occur, but also stretching at a low temperature increases longitudinal orientation, so that contraction stress at the time of heat-setting increases, thereby causing molecular orientation in the width direction. May increase, and as a result, the straight-line tearability in the longitudinal direction may decrease. The upper limit of the MD stretching temperature is preferably 100 ° C, more preferably 95 ° C. If the temperature exceeds 100 ° C., the orientation is not applied, and the mechanical properties may be reduced.

The lower limit of the MD stretching ratio is preferably 2.5 times, and particularly preferably 2.7 times. When it is less than the above, the orientation is not easily applied, so that the mechanical properties are reduced, and the film roll may be loosened due to uneven thickness.
The upper limit of the MD stretching ratio is preferably 3.8 times, more preferably 3.4 times, and particularly preferably 3.0 times. If the ratio exceeds the above range, the effect of improving mechanical strength and thickness unevenness may be saturated.

  The lower limit of the stretching temperature in the width direction (hereinafter abbreviated as TD) is preferably 60 ° C., and if it is less than the above, breakage may easily occur. The upper limit of the TD stretching temperature is preferably 100 ° C. If it exceeds the above range, the orientation is not applied and the mechanical properties may be reduced.

  In the TD stretching, it is preferable to install a shielding plate at a center position with respect to the hot air supply duct in the stretching zone. Normally, the film after MD stretching has a greater thickness at the end than at the center. This difference in thickness in the width direction causes thickness unevenness in the width direction. By installing a shielding plate at the center position with respect to the hot air supply duct in the TD stretching zone, a large amount of hot air is supplied to the ends, so that the difference in stretching behavior in the width direction is reduced and uneven thickness is less likely to occur. . FIG. 1 shows an example of installation of the shielding plate.

  The lower limit of the TD stretching ratio is preferably 3.8 times, more preferably 3.9 times, and particularly preferably 4.0 times. If it is less than the above, the degree of orientation in the width direction is reduced, so that the mechanical strength is reduced, and the film roll may be loosened due to uneven thickness. The upper limit of the TD stretching ratio is preferably 5 times, more preferably 4.6 times, and particularly preferably 4.3 times. If the ratio exceeds the above range, the effect of improving mechanical strength and thickness unevenness may be saturated.

  In the TD stretching, it is preferable to perform multi-stage stretching in two or more stages and five or less stages. Multi-stage stretching is preferable because the stretching stress can be changed by changing each stretching temperature and thickness unevenness in the width direction can be reduced. Preferably, it is at least three-stage stretching. FIG. 2 shows an example of a stretching pattern (three-stage stretching) of the TD stretching apparatus. As shown in FIG. 2, in the multi-stage stretching, it is preferable to provide a pattern that maintains a constant length after the completion of the stretching in each stage. In addition, it is preferable that a temperature pattern in which a temperature difference of 2 ° C. or more is applied in each stage of stretching and the temperature is lowered from the first stage stretching to the final stage stretching.

  The lower limit of the TD heat setting temperature is preferably 185 ° C, more preferably 190 ° C. If it is less than the above, the heat shrinkage may increase. The upper limit of the TD heat setting temperature is preferably 210 ° C. If it exceeds the above range, the film may be melted, and even if it does not melt, the film may be extremely brittle.

  The lower limit of the TD relaxation rate is preferably 0.5%, and if it is less than the above, breakage may easily occur during heat fixing. The upper limit of the TD relaxation rate is preferably 10%. If the TD relaxation rate exceeds the above range, slack or the like may occur, resulting in thickness unevenness. As a result, not only the film roll may be loosened, but also in the longitudinal direction during heat setting. As a result, the distortion of the molecular orientation at the end is increased, and the dimensional stability and the like in the width direction may become non-uniform.

[Properties of biaxially oriented polyester film]
In the biaxially oriented polyester film of the present invention, the lower limit of the film thickness is preferably 5 μm, more preferably 7 μm, and still more preferably 9 μm. If it is less than 5 μm, the strength as a film may be insufficient.
The upper limit of the film thickness is preferably 40 μm, more preferably 30 μm, and even more preferably 20 μm. If it exceeds 40 μm, it may be too thick and it may be difficult to improve the slack for the purpose of the present invention.

The lower limit of the intrinsic viscosity of the biaxially oriented PBT film of the present invention is preferably 0.80 dl / g, more preferably 0.85 dl / g, further preferably 0.90 dl / g, and particularly preferably 0. .95 dl / g. Above the above, impact strength and piercing resistance are improved.
The upper limit of the intrinsic viscosity of the biaxially oriented PBT film is preferably 1.2 dl / g, and more preferably 1.1 dl / g. If the ratio exceeds the above range, the stress at the time of stretching becomes too high, and the film forming property deteriorates.

  In the biaxially oriented PBT film of the present invention, it is preferable that a resin having the same composition exist over the entire area of the film.

The lower limit of the degree of plane orientation (ΔP) of the biaxially oriented polyester film of the present invention is preferably 0.145, more preferably 0.148, and still more preferably 0.151. If it is less than the above, the plane orientation is weak, the piercing strength is reduced, and the bag breaking resistance may be reduced.
The upper limit of ΔP of the biaxially oriented polyester film of the present invention is preferably 0.200. If it exceeds the above, the effect of improvement may be saturated.

  The upper limit of the heat shrinkage of the biaxially oriented polyester film of the present invention after heating at 150 ° C. for 15 minutes in the MD direction is 5.0%, preferably 4.0%, and more preferably 3.3%. is there. If it exceeds 5.0%, the film may be greatly shrunk when heat is applied in post-processing, and processing may be difficult.

  The lower limit of the piercing strength of the biaxially oriented polyester film of the present invention is preferably 0.5 N / μm. If it is less than the above, the strength may be insufficient when used as a bag. The upper limit of the piercing strength is preferably 1.4 N / μm. Above the above, the effect of the improvement may be saturated.

  The coefficient of static friction and the coefficient of kinetic friction between the outer and inner film surfaces of the biaxially oriented polyester film of the present invention are preferably 0.20 or more and 0.60 or less, more preferably 0.23 or more and 0. 57 or less, and most preferably 0.26 or more and 0.54 or less. If it is lower than 0.20, the end face may be misaligned due to slippage. On the other hand, when it is larger than 0.60, the amount of air entrained at the time of slitting is increased, and loosening and wrinkles may be easily caused by air leakage from the concave portion at the time of film roll.

  The upper limit of the haze per thickness of the biaxially oriented polyester film of the present invention is preferably 0.66% / μm, more preferably 0.60% / μm, and still more preferably 0.53% / μm. . Exceeding the above, when printing is performed on the film, the quality of printed characters and images may be impaired.

  The winding length of the biaxially oriented polyester film roll of the present invention is preferably from 2,000 m to 60,000 m. In processing such as printing, the longer the winding length, the less frequently the rolls are replaced, and the higher the work efficiency. It is preferably at least 3,000 m, more preferably at least 4,000 m, particularly preferably at least 5,000 m. There is no particular upper limit, and a longer winding length is preferable. However, since the inventors have confirmed only a winding length of up to 60000 m, the winding length was set to 60000 m as the upper limit. In addition, since the area of the film increases as the winding length of the film roll increases, and the chance of the occurrence of the defect of loosening increases, the longer winding length of the film roll is more difficult in the embodiment of the present invention. .

  The width of the biaxially oriented polyester film roll of the present invention is preferably 400 mm or more and 3000 mm or less. There is no particular upper limit, and it is preferable that the width of the film roll is long because the loss in the printing process is small. However, since the inventors have confirmed only up to 3000 mm, the upper limit is 3000 mm. Also, the wider the film roll, the better the efficiency in processing such as printing as described above. The preferred width is at least 500 mm, more preferably at least 600 mm, particularly preferably at least 800 mm. It should be noted that the longer the width of the film roll, the greater the area of the film and the greater the chance of occurrence of the defect of loosening. Therefore, in the embodiment of the present invention, the longer the width of the film roll involves more difficulty.

The biaxially oriented polyester film roll of the present invention has a portion where the thickness pattern is concave in the thickness unevenness in the width direction of the film roll, and the concave portion having the largest thickness difference (the maximum concave portion) has the maximum concave portion. It is preferable that the thickness unevenness of the largest concave portion obtained from the following formula (1) from the maximum thickness difference and the average thickness of the film is 6% or less (an example is shown in FIG. 3).
Thickness unevenness of concave portion = (maximum height of concave portion−minimum height of concave portion) ÷ average thickness × 100 (%) Expression (1)

  The concave portion in the present invention refers to a point in the thickness unevenness in the film width direction measured using a continuous contact thickness gauge as described later, where a point where the thickness decreases in both directions of the measurement direction with the point as a peak. When a point at which the thickness increases in both directions of the measurement direction with the point as a boundary is defined as a valley, it is a portion of a thickness pattern that is a peak-valley-peak. It should be noted that a film having no such a thickness pattern, that is, a film having no concave portions is not included in the present invention. In the two peaks and one valley in the concave portion, a larger value of the thickness difference between each peak and the valley (both values in the case of the same ground) is referred to as a maximum thickness difference in the concave portion.

  If the thickness unevenness of the largest concave portion is higher than 6%, when slitting the position of the concave portion and winding it up as a film roll, air is trapped and air accumulates, and then the air escapes when storing the film roll. It is undesirable because it causes wrinkles and looseness. Further, since the concave portion is thinner than other portions in the width direction, the concave portion is elongated in the longitudinal direction by the tension when slit and wound as a film roll. Therefore, the length of the concave portion in the film roll becomes longer in the longitudinal direction than in the other position in the width direction, and the portion becomes slack. In particular, it has been found by the present inventors that this phenomenon becomes apparent when the thickness difference between the concave portion and both ends is large. The thickness unevenness of the maximum concave portion is preferably 4% or less, more preferably 2% or less. The thickness unevenness of the largest concave portion is preferably as low as possible, and in the test of the present inventors, 0.8% was the lowest.

  The thickness unevenness of the concave portion as described above should be measured using a continuous contact thickness gauge as shown in the examples. For example, as shown in Patent Document 4, when the thickness is measured at intervals of 30 mm to 500 mm in the measurement direction, the maximum thickness difference of the concave portion may not be measured, It is difficult to seek. The thickness unevenness in the present invention refers to a value measured using a continuous contact thickness gauge.

The overall thickness unevenness of the biaxially oriented polyester film roll of the present invention in the width direction is 10% or less according to the following expression (2). If the thickness unevenness is poor, wrinkles are likely to occur, which is not preferable. It is preferably at most 7%, more preferably at most 4%. The smaller the value of the thickness unevenness, the more preferable. As described above, the cause of the loosening is a larger factor due to the thickness unevenness in the maximum concave portion.
｛(Maximum thickness−minimum thickness) ÷ average thickness｝ × 100 (%) Expression (2)

The obtained biaxially oriented polyester film is wound as a wide roll (jumbo roll) as an intermediate product, then slit into a specified width and length using a slitter, and wound on a winding core (core). An oriented polyester film roll is obtained. As the winding core, a plastic core such as 3 inches, 6 inches, or 8 inches, a metal core, or a paper tube can be used. The preferred winding length and width of the film roll are as described above.
In addition, it is preferable to reduce the slack generated at the time of slitting by adopting the following slit conditions.

  As specific slit conditions, the winding tension is preferably from 100 to 160 N / m, and more preferably from 120 to 140 N / m. The initial surface pressure when starting the slit is preferably 50 to 90 N / m, more preferably 60 to 80 N / m. If the winding tension is higher than 160 N / m, the uneven thickness portion of the concave portion is slightly stretched by the tension at the time of slitting, which is not preferable because it causes loosening. Further, when the winding tension is 100 N / m or less, the winding becomes soft. For example, when the film roll is stored in a warehouse for a long time (for example, half a year), the air taken in at the time of slitting escapes from between the films, and the film roll is rolled. This is not preferable because the file is distorted and the file is loosened. In addition, when the film is wound by the slit, the tension is insufficient, and the end faces of the film roll are displaced and irregular (so-called end face shift), which is not preferable. The final surface pressure is preferably from 550 to 950 N / m, and more preferably from 650 to 850 N / m.

  Further, the winding hardness of the film roll surface layer slit as described above is preferably 20 or more and 80 or less. If the winding hardness of the surface layer of the film roll is less than 20, for example, when the film roll is stored in a warehouse for half a year, the air caught at the time of slitting escapes and the film roll is loosened. On the other hand, if the winding hardness of the surface layer of the film roll is higher than 80, the film roll becomes hard-wound, and the above-described recesses are compressed to cause loosening, which is not preferable. The winding hardness of the surface layer of the film roll is preferably 30 or more and 70 or less, and more preferably 40 or more and 60 or less. In addition, the winding hardness in the present invention refers to the winding hardness measured according to the description in the examples described later.

A printed layer may be laminated on the biaxially oriented polyester film of the present invention.
As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks can be preferably used. Here, examples of the resin used for the printing ink include an acrylic resin, a urethane resin, a polyester resin, a vinyl chloride resin, a vinyl acetate copolymer resin, and a mixture thereof. Printing inks include known antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, antioxidants, etc. May be added.

  The printing method for providing the printing layer is not particularly limited, and a known printing method such as an offset printing method, a gravure printing method, and a screen printing method can be used. Known drying methods such as hot air drying, hot roll drying, and infrared drying can be used for drying the solvent after printing.

  Further, the biaxially oriented polyester film of the present invention may be subjected to a corona discharge treatment, a glow discharge treatment, a flame treatment, a surface roughening treatment as long as the object of the present invention is not impaired, An anchor coat treatment, printing, decoration, etc. may be applied.

  A gas barrier layer such as an inorganic thin film layer or a metal foil such as an aluminum foil can be provided on at least one surface of the biaxially oriented polyester film of the present invention.

  When the inorganic thin film layer is used as the gas barrier layer, the inorganic thin film layer is a thin film made of a metal or an inorganic oxide. The material for forming the inorganic thin film layer is not particularly limited as long as it can be formed into a thin film, but from the viewpoint of gas barrier properties, inorganic oxides such as silicon oxide (silica), aluminum oxide (alumina), and a mixture of silicon oxide and aluminum oxide are used. Thing is mentioned preferably. In particular, a composite oxide of silicon oxide and aluminum oxide is preferable from the viewpoint of achieving both flexibility and denseness of the thin film layer.

In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably such that Al is in the range of 20 to 70% by weight of metal. If the Al concentration is less than 20%, the water vapor gas barrier properties may be low. On the other hand, if it exceeds 70%, the inorganic thin film layer tends to be hard, and the film may be broken at the time of secondary processing such as printing or laminating, and the gas barrier property may be reduced. Here, silicon oxide refers to various silicon oxides such as SiO and SiO ₂ or a mixture thereof, and aluminum oxide refers to various aluminum oxides such as AlO and Al ₂ O ₃ or a mixture thereof.

  The thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 5 to 50 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain a satisfactory gas barrier property. On the other hand, if the thickness exceeds 100 nm, the effect of improving the gas barrier property is obtained. This is disadvantageous in terms of bending resistance and manufacturing cost.

The method for forming the inorganic thin film layer is not particularly limited, and is, for example, a known vapor deposition method such as a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a chemical vapor deposition method (CVD method). The method may be appropriately adopted. Hereinafter, a typical method for forming an inorganic thin film layer will be described by taking a silicon oxide / aluminum oxide-based thin film as an example. For example, when a vacuum deposition method is employed, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al is preferably used as a deposition material. Particles are usually used as these vapor deposition raw materials. At this time, it is desirable that the size of each particle is such that the pressure during vapor deposition does not change, and a preferable particle diameter is 1 mm to 5 mm. For heating, a method such as resistance heating, high-frequency induction heating, electron beam heating, or laser heating can be employed. It is also possible to introduce oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor, or the like as a reaction gas, or to employ reactive vapor deposition using means such as ozone addition or ion assist. Further, the film formation conditions can be arbitrarily changed, such as applying a bias to the object to be deposited (a laminated film to be subjected to evaporation), or heating or cooling the object to be deposited. Such deposition material, reaction gas, bias of the object to be deposited, heating / cooling, and the like can be similarly changed when a sputtering method or a CVD method is adopted. Further, a printing layer may be laminated on the inorganic thin film layer.

  In the present invention, it is preferable to provide a protective layer on the gas barrier layer. The gas barrier layer made of a metal oxide is not a completely dense film, but has minute defects. By coating a specific protective layer resin composition described later on the metal oxide layer to form a protective layer, the resin in the protective layer resin composition penetrates into the defective portion of the metal oxide layer, As a result, an effect that the gas barrier property is stabilized can be obtained. In addition, by using a material having gas barrier properties for the protective layer itself, the gas barrier performance of the laminated film is also greatly improved.

  Examples of the protective layer include urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, and polybutadiene-based resins, and epoxy-, isocyanate-, and melamine-based hardeners. . Solvents (solvents) used for forming the protective layer include, for example, aromatic solvents such as benzene and toluene; alcohol solvents such as methanol and ethanol; ketone solvents such as acetone and methyl ethyl ketone; ethyl acetate and acetic acid. Ester solvents such as butyl; polyhydric alcohol derivatives such as ethylene glycol monomethyl ether;

In the urethane resin, the polar group of the urethane bond interacts with the inorganic thin film layer, and also has flexibility due to the presence of the amorphous portion. Therefore, even when a bending load is applied, the damage to the inorganic thin film layer is suppressed. It is preferable because it can be performed.
The acid value of the urethane resin is preferably in the range of 10 to 60 mgKOH / g. More preferably, it is in the range of 15 to 55 mgKOH / g, and still more preferably in the range of 20 to 50 mgKOH / g. When the acid value of the urethane resin is in the above range, the liquid stability is improved when an aqueous dispersion is formed, and the protective layer can be uniformly deposited on the highly polar inorganic thin film, so that the coat appearance is good. Becomes

  The urethane resin preferably has a glass transition temperature (Tg) of 80 ° C. or higher, more preferably 90 ° C. or higher. By setting Tg to 80 ° C. or higher, swelling of the protective layer due to molecular motion in the wet heat treatment process (heating to warming to cooling) can be reduced.

As the urethane resin, it is more preferable to use a urethane resin containing an aromatic or araliphatic diisocyanate component as a main component from the viewpoint of improving gas barrier properties.
Among them, it is particularly preferable to contain a meta-xylylene diisocyanate component. By using the above resin, the cohesive force of urethane bonds can be further increased due to the stacking effect between aromatic rings, and as a result, good gas barrier properties can be obtained.

  In the present invention, the proportion of the aromatic or araliphatic diisocyanate in the urethane resin is preferably in the range of 50 mol% or more (50 to 100 mol%) based on 100 mol% of the polyisocyanate component (F). The proportion of the total amount of the aromatic or araliphatic diisocyanate is preferably from 60 to 100 mol%, more preferably from 70 to 100 mol%, even more preferably from 80 to 100 mol%. As such a resin, the “Takelac (registered trademark) WPB” series commercially available from Mitsui Chemicals, Inc. can be suitably used. If the proportion of the total amount of the aromatic or araliphatic diisocyanate is less than 50 mol%, good gas barrier properties may not be obtained.

  The urethane resin preferably has a carboxylic acid group (carboxyl group) from the viewpoint of improving the affinity with the inorganic thin film layer. In order to introduce a carboxylic acid (salt) group into the urethane resin, for example, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid and dimethylolbutanoic acid may be introduced as a polyol component as a copolymerization component. Further, if the carboxylic acid group-containing urethane resin is synthesized and then neutralized with a salt-forming agent, a water-dispersed urethane resin can be obtained. Specific examples of the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and tri-n-butylamine, and N-methylmorpholine and N-ethylmorpholine. -Alkylmorpholines, N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone or in combination of two or more.

  A layer of another material may be laminated on the biaxially oriented polyester film of the present invention. As a method for the lamination, the biaxially oriented polyester film can be laminated after production or can be laminated during film formation.

  The biaxially oriented polyester film of the present invention can be used as a packaging material, for example, by providing an inorganic vapor-deposited layer on the biaxially oriented polyester film of the present invention and further forming a heat sealable resin layer called a sealant. The formation of the heat-sealable resin layer is usually performed by an extrusion lamination method or a dry lamination method. The thermoplastic polymer forming the heat-sealable resin layer is not limited as long as it can sufficiently exhibit sealant adhesiveness. Examples thereof include polyethylene resins such as HDPE, LDPE and LLDPE, and polypropylene resins. Ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, ionomer resin and the like can be used.

The sealant layer may be a single-layer film or a multilayer film, and may be selected according to a required function. For example, in terms of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cycloolefin copolymer or polymethylpentene is interposed can be used. The sealant layer may contain various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer, and a tackifier.
The thickness of the sealant layer is preferably from 10 to 100 μm, more preferably from 20 to 60 μm.

  The biaxially oriented polyester film of the present invention can be used as a base film of a laminate for packaging materials. Examples of the layer structure of the laminate include a base layer / gas barrier layer / protective layer, a base layer / gas barrier layer / protective layer / sealant layer, a base layer / gas barrier layer / protective layer / resin layer / sealant layer, and a base layer. Material layer / resin layer / gas barrier layer / protective layer / sealant layer, base layer / gas barrier layer / protective layer / print layer / sealant layer, base layer / print layer / gas barrier layer / protective layer / sealant layer, base layer / Gas barrier layer / protective layer / resin layer / print layer / sealant layer, base layer / resin layer / print layer / gas barrier layer / protective layer / sealant layer, base layer / print layer / gas barrier layer / protective layer / resin layer / Sealant layer, base layer / print layer / resin layer / gas barrier layer / protective layer / sealant layer, base layer / resin layer / gas barrier layer / protective layer / print layer / sealant layer, and the like.

  The laminate using the biaxially oriented polyester film of the present invention can be suitably used for applications such as packaging products, various label materials, lid materials, sheet molded products, and laminated tubes. In particular, it is used for packaging bags (for example, pouches such as pillow bags, standing pouches and 4-way pouches). The thickness of the laminate can be appropriately determined according to its use. For example, it is used in the form of a film or sheet having a thickness of about 5 to 500 μm, preferably about 10 to 300 μm.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. In addition, the evaluation of the film was performed by the following measuring methods.
[Thickness unevenness in the entire width direction]
The roll was set on a slitter. Then, after removing 1 m from the roll surface layer, the film roll was sampled to a full width in the width direction and 40 mm in the longitudinal direction, and was continuously measured at a thickness of 5 m / sec in the width direction using a film thickness tester manufactured by Fuji Work Co., Ltd. Was measured. The maximum thickness at the time of measurement is defined as Tmax. , The minimum thickness is Tmin. , The average thickness is Tave. The thickness unevenness in the film width direction was calculated from the following equation (2).
Thickness unevenness = ｛(Tmax.−Tmin.) / Tave. ) × 100 (%) ・ ・ ・ Equation (2)

[Thickness unevenness of recess]
The continuous thickness in the width direction described above was obtained, and a portion having a maximum concave portion was searched for as shown in FIG. The thickness unevenness of the largest concave portion was determined by the following equation (1). Further, when the heights at both ends of the maximum concave portion were different, the higher value was selected and obtained.
Thickness unevenness of the largest concave portion = (maximum height thickness of the largest concave portion−minimum height thickness of the largest concave portion) ÷ average thickness × 100 (%) Formula (1)

[Thickness unevenness of the largest concave portion in the roll width direction at the roll winding length]
The roll was set on a slitter. Then, after removing 1 m from the roll surface layer, the thickness unevenness of the largest concave portion in the roll width direction was measured by the method described above. After the measurement, the slit was wound 1000 m, and the thickness unevenness of the concave portion in the roll width direction was measured by the method described above. The measurement of the thickness unevenness of the largest concave portion in the roll width direction was repeated by rewinding 1000 m.

[Film thickness]
The measurement was performed using a dial gauge according to JIS K7130-1999 A method.

[Stab strength]
The piercing strength of the polyester film was calculated from the value measured by the test method described in JIS-Z1707 in terms of 1 μm using the calculation formula of Expression (4).
Puncture strength (N / μm) = Puncture strength measured value / Film thickness (4)

[Coefficient of friction]
Based on JIS K-7125, using a tensile tester (Tensilon RTG-1210 manufactured by A & D), the static friction coefficient and the dynamic friction coefficient when the film surface and the back surface are joined at 23 ° C. and 65% RH environment. I asked. The weight of the thread (weight) around which the upper film was wound was 1.5 kg, and the size of the bottom area of the thread was 39.7 mm ² . The tensile speed at the time of friction measurement was 200 mm / min. Met.

[Evaluation of slack]
Twelve hours after the slit film roll, the rolls with a slit roll width of 3000 mm and 1140 mm are sampled at 1140 mm in the width direction and 5 m in the longitudinal direction, and the roll with a 400 mm width is sampled with a film of 400 mm in the width direction and 5 m in the longitudinal direction. Then, each was placed on a flat table. At this time, if a band-shaped portion having a flatness worse than other portions continuously in the longitudinal direction was visually confirmed, it was regarded as slack. The evaluation was performed as follows.
No looseness: ○
There is one or more slack: ×

[Evaluation of winding hardness]
Using a SCH type hammer LR manufactured by Proseq, measurement was performed at three points at both ends and a center position in the roll width direction. The average value of the values measured in the roll width direction was used as the measured value.

[Evaluation of bag resistance]
A urethane-based two-component adhesive (blended with "Takelac (registered trademark) A525S" and "Takenate (registered trademark) A50" at a ratio of 13.5: 1 (weight ratio)) manufactured by Mitsui Chemicals, Inc. on a polyester film. A laminated laminate was obtained by laminating a 70 μm-thick unstretched polypropylene film (“P1147” manufactured by Toyobo Co., Ltd.) as a heat-sealing resin layer using a dry lamination method and aging at 40 ° C. for 4 days. Was. The thickness of the adhesive layer formed of the urethane two-component curable adhesive after drying was about 4 μm in all cases.
Cut the above-mentioned laminate to a size of 15 cm square, superimpose two sheets so that the sealant is on the inside, and heat seal the three sides at a sealing temperature of 160 ° C and a seal width of 1.0 cm. A three-sided seal bag having a size of 13 cm was obtained.
After filling 250 mL of water into the obtained three-side seal bag, the fourth mouth was closed by heat sealing, and a four-side seal bag filled with water was produced.
The resulting four-side sealed bag was subjected to a wet heat treatment for 30 minutes in hot water at 130 ° C., and then at room temperature of 5 ° C. and a humidity of 35% R.C. H. Was dropped on a concrete plate from a position having a height of 100 cm under the above environment, and the number of drops until breakage occurred was counted.
30 or more drops: ○
Less than 30 drops: ×

[Example 1]
Using a single screw extruder, an intrinsic viscosity composed of PBT resin (1100-211XG (CHANG CHUN PLASTICS CO., LTD., Intrinsic viscosity 1.28 dl / g) and terephthalic acid // ethylene glycol = 100 // 100 (mol%)) A mixture of 0.62 dl / g PET resin and silica particles having an average particle size of 2.4 μm as inert particles at a silica concentration of 0.16% by weight was melted at 290 ° C. The melt was divided and laminated to obtain a multilayer melt made of the same raw material, which was cast from a T-die at 270 ° C. and electrostatically applied to a cooling roll at 15 ° C. An unstretched sheet was obtained by close contact with a contact method.
Subsequently, the film is roll-stretched 2.9 times in the machine direction (MD) at 60 ° C., and then stretched 4.3 times in the width direction (TD) through a tenter at a temperature and magnification shown in Table 1 in three steps. Next, after performing a tension heat treatment at 200 ° C. for 3 seconds and a relaxation treatment of 9% for 1 second, the grips at both ends were cut and removed by 10% to obtain mill rolls of films having thicknesses of 10 μm, 15 μm, and 30 μm. Table 1 shows the raw material composition, film forming conditions, and slit conditions of the obtained film. Table 2 shows the physical properties and evaluation results of the obtained film and film roll.

[Examples 2 to 4]
In Example 1, a biaxially stretched film was formed in the same manner as in Example 1 except that the raw material composition, film forming conditions, and slit conditions were changed as described in Table 1, and films having thicknesses of 10 μm, 15 μm, and 30 μm were formed. Of a mill roll. The shielding plate was installed at the center of the tenter-stretched hot air supply duct as shown in FIG. 1, and 75% of the center of the air supply duct was shielded so that hot air did not directly hit it. Table 2 shows the physical properties and evaluation results of the obtained film and film roll.

[Comparative Examples 1 to 6]
Using a single screw extruder, a biaxially stretched film was obtained according to the raw material composition, film forming conditions, and slit conditions shown in Table 1. Table 2 shows the physical properties and evaluation results of the obtained film and film roll.

(Comparative Example 1)
The procedure was performed in the same manner as in Example 1 except that the TD stretching ratio was changed to the value shown in Table 1. Although the bag breaking property of the obtained film was good, loosening was poor because the thickness unevenness of the largest concave portion of the roll surface layer was large. The results are shown in Table 2.

(Comparative Example 2)
The procedure was performed in the same manner as in Example 2 except that the TD stretching ratio was changed to the value shown in Table 1. Although the bag breaking property of the obtained film was good, loosening was poor because the thickness unevenness of the largest concave portion of the roll surface layer was large. The results are shown in Table 2.

(Comparative Example 3)
The procedure was performed in the same manner as in Example 3 except that the TD stretching ratio was changed to the value shown in Table 2. The obtained film had poor bag-breaking properties and also had poor slackness due to large thickness unevenness of the largest concave portion of the roll surface layer. The results are shown in Table 2.

(Comparative Example 4)
The procedure was performed in the same manner as in Example 1 except that the compositions of the PBT resin and the PET resin were changed to the values shown in Table 1. Although the obtained film had good slackness, the composition of the PBT resin was small, so that the bag breaking property was poor. The results are shown in Table 2.

(Comparative Example 5)
The procedure was performed in the same manner as in Example 1 except that the slit conditions were changed to the values shown in Table 1. Although the obtained film had good bag-breaking properties, looseness was poor due to the large winding hardness of the roll surface layer. The results are shown in Table 2.

(Comparative Example 6)
The procedure was performed in the same manner as in Example 1 except that the slit conditions were changed to the values shown in Table 1. Although the bag breaking property of the obtained film was good, the winding hardness of the roll surface layer was small, but the looseness was poor because the thickness unevenness of the largest concave portion of the roll surface layer was large. The results are shown in Table 2.

  According to the present invention, since there is little slack in a roll composed of a film mainly composed of polybutylene terephthalate resin having good bag-breaking resistance, loss during printing or laminating can be reduced. Therefore, it can be widely used as a base film for packaging bags for food packaging and the like.

Claims (6)

It comprises a polyester resin composition containing 60 to 100% by weight of a polybutylene terephthalate resin (A) and 0 to 40% by weight of a polyester resin (B) other than the polybutylene terephthalate resin (A), and the following requirements (1) to ( 5) A biaxially oriented polyester film roll characterized by satisfying 5).
(1) The roll length of the film roll is 2000 m or more and 60000 m or less.
(2) The film roll width is 400 mm or more and 3000 mm or less.
(3) The thickness of the film is 5 μm or more and 40 μm or less.
(4) In the thickness unevenness in the film width direction in the surface layer of the film roll, there is a portion where the thickness pattern is a concave portion, and in the concave portion having the largest thickness difference (maximum concave portion), the maximum thickness difference in the maximum concave portion and the film The thickness unevenness of the largest concave portion obtained from the average thickness is 6% or less.
(5) The winding hardness of the film roll surface layer is 20 or more and 80 or less.   In the thickness unevenness in the width direction of the film of each sample sampled at a winding length of 1000 m from the surface layer of the film roll, all of the thickness unevenness obtained from the maximum thickness difference in the largest concave portion and the average thickness of the film are 6% or less. 2. The biaxially oriented polyester film roll according to 1.   3. The biaxially oriented polyester film roll according to claim 1, wherein the thickness unevenness of the entire film roll in the width direction is 10% or less.   The biaxially oriented polyester film roll according to any one of claims 1 to 3, wherein the coefficient of kinetic friction measured on the outer surface and the inner surface of the biaxially oriented polyester film is 0.20 or more and 0.60 or less.   The biaxially oriented polyester film roll according to any one of claims 1 to 5, wherein the value of the piercing strength of the biaxially oriented polyester film measured by a piercing test according to JIS-Z1707 is 0.5 N / μm or more.   The biaxially oriented polyester film roll according to any one of claims 1 to 5, wherein the slit is obtained by setting the slitting tension of the slitter to 100 N / m or more and 160 N / m or less from a wide roll as an intermediate product. Manufacturing method.