JP4163010B2 - Laminated biaxially stretched polyester film with excellent hand cutting properties - Google Patents

Description

【００５３】
【発明の効果】
本発明においては、非晶性ポリエステル樹脂層と結晶性ポリエステル樹脂層の厚み構成比により引張強度をコントロールすることができ、強度と厚みのバランスのよいフィルムを得ることができる。また結晶性ポリエステル樹脂の固有粘度を特定の範囲に限定することにより、結晶性ポリエステル樹脂層および非晶性ポリエステル樹脂層間の層間剥離強度が改善され、さらに固有粘度の小さい結晶性ポリエステル単独の場合と比較して溶融加工性が改善される。その結果、手切れ性のみならず開封時のカットラインの安定性にすぐれ、かつ加工性のバランスに優れたポリエステルフィルムを得ることができる。本発明の方法によれば、食品をはじめとする、医薬品、日用品、コスメティックスなどの包装材料や粘着テープとして有用な手切れ性に優れたフィルムを工業的かつ容易に提供することが可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film having excellent hand cutting properties useful as a packaging material for foods, pharmaceuticals, daily necessities, cosmetics and the like.
[0002]
[Prior art]
The biaxially stretched polyester film has excellent durability, moisture resistance, mechanical strength, heat resistance, and oil resistance, and uses a tubular method, a flat simultaneous biaxial stretching method, a flat sequential biaxial stretching method, etc. Manufactured and widely used in various fields. However, biaxially stretched polyester films generally have high mechanical strength and are difficult to cut. For example, when used as various packaging materials or adhesive tapes, they cannot be easily opened or cut by hand.
[0003]
On the other hand, cellophane is known as a film with excellent hand cutting properties, but cellophane is highly hygroscopic and its dimensions are likely to change due to moisture absorption. It was difficult. On the other hand, cellophane has good hand cutting properties, but on the other hand, there are many troubles such as film cutting in the secondary processing step. Therefore, a hand cutting film excellent in balance with mechanical strength has been desired.
[0004]
As a method for imparting hand cutting properties to the biaxially stretched polyester film, a method for imparting a notch to the film end can be mentioned. However, since such a method cannot be torn from a place other than the notch, there is a problem that the degree of freedom of the opening method is low, and hand tearability is lost when tearing from the notch fails.
[0005]
As a method of improving the hand cutting property of a biaxially stretched polyester film, a method of copolymerizing a predetermined amount of diethylene glycol with polyethylene terephthalate (hereinafter referred to as PET) (Patent Document 1), a low molecular weight compared to a relatively high molecular weight PET A method of mixing PET (Patent Document 2), a method of imparting a specific refractive index distribution with an intrinsic viscosity in the range of 0.35 to 0.58 (Patent Document 3), and a crosslinked polyester copolymerized with a polyfunctional monomer Method used (Patent Document 4), Biaxially stretching a multilayer film composed of a high melting point polyester and a low melting point polyester, and then heat-treating at a temperature lower than the melting point of the low melting point layer by 10 ° C. 5) etc. are disclosed.
[0006]
However, since the copolymerization amount of diethylene glycol is relatively large in the method described in Patent Document 1, there is a problem that the heat resistance of PET is impaired due to a melting point drop, and the tensile strength (about 170 MPa) of the obtained film is cellophane. There was a problem that the film was very large as compared with a general tensile strength of about 50 to 70 MPa, and the hand cutting property of this film was not comparable to cellophane.
In the method described in Patent Document 2, since it is necessary to mix a relatively high amount of low molecular weight PET resin with high molecular weight PET in order to provide sufficient hand cutting properties, the melt tension of the resin is significantly reduced. However, there are problems that it is difficult to form a stable unstretched film and that a low molecular weight body tends to bleed out.
When the intrinsic viscosity of the film obtained by the method described in Patent Document 3 is very small, the film shows closeness to cellophane, but a resin having a low intrinsic viscosity, that is, a low melt tension is used. However, there are problems that it is difficult to form an unstretched film and that the film is easily broken during stretching because of its low strength.
In the method described in Patent Document 4, although a film having improved hand cutting properties is obtained when a crosslinkable comonomer and another comonomer component are used in combination, fish eyes are generated in the film by the gel generated during polymerization. There was a problem that it was easy, and there was a problem that the effect of improving hand cutting was not sufficient.
According to the method described in Patent Document 5, a film with improved hand cutting properties can be obtained. However, since the relatively large size crystals are formed with the relaxation of the orientation of the low melting point layer, the transparency of the film deteriorates. There was a problem that the dimensional stability was impaired by the dimensional change accompanying crystallization. Furthermore, since it is difficult to uniformly relax the orientation of the low melting point layer, there has been a problem that the flatness of the film is easily impaired. Further, such a problem is likely to occur when heat sealing is performed in the bag making process, and there is a problem in terms of commercialization.
[0007]
[Patent Document 1]
JP 50-103574 A [Patent Document 2]
Japanese Patent Laid-Open No. 51-104618 [Patent Document 3]
Japanese Patent Publication No. 62-20016 [Patent Document 4]
JP-A-2-47038 [Patent Document 5]
Japanese Patent Laid-Open No. 5-104618
[Problems to be solved by the invention]
The present inventors have previously described a laminated polyester film having at least one amorphous polyester resin layer and a crystalline polyester resin layer, wherein the thickness of the amorphous polyester resin layer is relative to the total thickness of the laminated polyester film. It has been found that a laminated biaxially stretched polyester film of 20 to 95% is excellent in hand cutting properties (Japanese Patent Application No. 2002-155889).
However, this laminated film may have a low interfacial peel strength between the crystalline polyester resin layer and the amorphous polyester resin layer. For example, a bag product using a film obtained by laminating a sealant film on this laminated film may be used. When produced, the seal strength of the bag-made product may decrease, or when the bag-made product is torn by hand, the cut line may become unstable and the contents may easily scatter. .
The present invention solves the above problems and realizes a film having excellent mechanical properties, heat resistance, moisture resistance, transparency and secondary processability of a polyester film while realizing good hand cutting properties of cellophane. The purpose is to provide a stable supply.
[0009]
[Means for Solving the Problems]
As a result of studies conducted by the present inventors to solve the above problems, in a biaxially stretched polyester film in which an amorphous polyester resin layer is laminated on a crystalline polyester resin layer, the crystalline polyester resin layer and the amorphous polyester film are laminated. Biaxial with excellent hand cutting property and improved delamination strength by making the polyester resin layer have a specific thickness configuration and defining the intrinsic viscosity of the crystalline polyester resin within a specific range The inventors have found that a stretched polyester film can be obtained, and have reached the present invention.
That is, the gist of the present invention is as follows.
(1) A laminated biaxially stretched polyester film in which the amorphous polyester resin layer (A) and the crystalline polyester resin layer (B) have a three-layer structure of B / A / B, and the amorphous polyester resin Laminated biaxially excellent in hand cutting characteristics, wherein the layer thickness is 50 to 95% of the total thickness of the laminated polyester film, and the intrinsic viscosity of the crystalline polyester resin is 0.30 to 0.57 Stretched polyester film.
(2) The amorphous polyester resin is a polyester resin composed of a dibasic acid component mainly containing terephthalic acid and a diol component containing 10 to 70 mol% of 1,4-cyclohexanedimethanol. The laminated biaxially stretched polyester film according to (1).
(3) The laminated biaxially stretched polyester film according to (1) or (2), wherein the film has an end tear resistance of 5 to 70 N and a tensile strength of 40 to 170 MPa.
(4) The laminated biaxial stretching according to any one of (1) to (3), wherein the delamination strength between the amorphous polyester resin layer and the crystalline polyester resin layer is 0.7 N / cm or more. Polyester film.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The amorphous polyester resin used in the present invention refers to a polyester resin that does not substantially exhibit crystallinity. That is, it means a resin having a crystallinity of 5% or less when the resin is sufficiently crystallized in an arbitrary temperature range between the glass transition temperature and the melting point. As such an amorphous polyester resin, for example, an amorphous copolymer polyester obtained by acid-modifying and / or diol-modifying polyethylene terephthalate is preferable.
[0011]
Examples of acid-modifying components used for copolymerization include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid , Maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid and other dicarboxylic acids, 4-hydroxybenzoic acid, ε-caprolactone, lactic acid and other oxycarboxylic acids, and trimellitic acid And polyfunctional compounds such as trimesic acid and pyromellitic acid. These acid-modifying components may be used alone or in combination of two or more.
[0012]
Further, as diol-modifying components used for copolymerization, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2- Cyclohexanedimethanol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycols such as ethylene oxide adducts of bisphenol A and bisphenol S, and polyfunctional compounds such as trimethylolpropane, glycerin, pentaerythritol Etc. These diol-modified components may be used alone or in combination of two or more.
[0013]
Among such amorphous polyester resins, from the viewpoint of heat resistance, mechanical properties, transparency, etc., 10 to 70 mol% of a dibasic acid component mainly composed of terephthalic acid and 1,4-cyclohexanedimethanol. The polyester resin which consists of a diol component to contain is preferable.
[0014]
The amorphous polyester resin used in the present invention may contain other polymer components as long as required properties are not impaired. These polymer components may be molecularly compatible or incompatible.
[0015]
The intrinsic viscosity of the amorphous polyester resin layer used in the present invention is not particularly limited, but in the present invention, a crystalline polyester resin layer having a low molecular weight and a low melt tension is laminated on the amorphous polyester resin layer. The amorphous polyester resin layer needs to have sufficient melt tension, that is, intrinsic viscosity as a support layer at the time of melt molding. Therefore, the intrinsic viscosity of the amorphous polyester resin is preferably 0.6 or more, and more preferably 0.7 or more. If the intrinsic viscosity is smaller than this, an effect as a support layer cannot be obtained at the time of extrusion molding, and it becomes difficult to form an unstretched film. The upper limit of the intrinsic viscosity is not particularly limited, but in general, the intrinsic viscosity is preferably 0.9 or less for the purpose of preventing overload during melt extrusion and excessive shearing heat generation. In addition, the intrinsic viscosity here means a value at a temperature of 20 ° C. and phenol / 1,1,2,2-tetrachloroethane.
[0016]
The laminated polyester film of the present invention is composed of an amorphous polyester resin layer and a crystalline polyester resin layer. By using crystalline polyester resin, it is characterized in that heat resistance, mechanical properties and good stretchability, thickness accuracy, heat shrink stability, which cannot be obtained by stretched film of amorphous polyester resin only, are provided. is there.
As such a crystalline polyester resin, those having a melting point of 220 ° C. or higher are usually used, and among them, a polyester resin having PET as the main skeleton is preferably used. Such a crystalline polyester resin may be copolymerized with other copolymerization components as long as required properties are not impaired.
[0017]
Examples of acid-modifying components used for copolymerization include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid , Maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid and other dicarboxylic acids, 4-hydroxybenzoic acid, ε-caprolactone, lactic acid and other oxycarboxylic acids, and trimellitic acid And polyfunctional compounds such as trimesic acid and pyromellitic acid. These acid-modifying components may be used alone or in combination of two or more.
[0018]
Further, as diol-modifying components used for copolymerization, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2- Cyclohexanedimethanol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycols such as ethylene oxide adducts of bisphenol A and bisphenol S, and polyfunctional compounds such as trimethylolpropane, glycerin, pentaerythritol Etc. These diol-modified components may be used alone or in combination of two or more.
[0019]
The crystalline polyester resin used in the present invention may contain other polymer components as long as the required properties are not impaired. These polymer components may be molecularly compatible or incompatible.
[0020]
The intrinsic viscosity of the crystalline polyester resin used in the present invention needs to be 0.30 to 0.57. More preferably, it is in the range of 0.40 to 0.55. By limiting the intrinsic viscosity of the crystalline polyester resin to this range, the delamination strength between the crystalline polyester resin layer and the amorphous polyester resin layer is improved. By this, when the laminated film of the present invention is processed as a package, the cut line when torn by hand is stabilized, and a more practical product can be provided. If the intrinsic viscosity is less than this range, the mechanical properties of the film are too low, or the melt tension becomes too low during extrusion molding, which is not preferable. Further, if the intrinsic viscosity is larger than this, the delamination strength is lowered, which is not preferable.
[0021]
In the laminated polyester film of the present invention, it is necessary that the amorphous polyester resin layer (A) and the crystalline polyester resin layer (B) have a three-layer structure of B / A / B.
[0022]
In the laminated polyester film of the present invention, the thickness constitution ratio of the amorphous polyester resin layer needs to be 50 to 95% of the total thickness, and preferably 50 to 90%. The thickness constitution ratio here is a percentage of the thickness of the amorphous polyester resin layer to the total thickness of the film. If the thickness of the amorphous polyester resin layer exceeds 95% of the total thickness, the heat resistance, mechanical properties, good stretchability, and thickness accuracy obtained by the contribution of the crystalline polyester layer are impaired. Moreover, when the thickness of the amorphous polyester resin layer is less than 20% of the total thickness, it is not preferable because it is difficult to obtain the desired hand cutting property.
[0023]
The laminated polyester film of the present invention has an end tear resistance (average value) of 5 to 70 N, preferably 10 to 60 N, more preferably 15 to 50 N, measured according to JIS C 2318 6.3.4. Preferably there is. If the tear resistance is higher than this, it will be difficult to obtain the desired film cutting ability, and if it is lower than this, the strength of the film will be too low, and secondary processing such as stretching, slitting, printing, bag making, etc. This is not preferable because a cutting trouble is likely to occur in the process.
[0024]
The laminated polyester film of the present invention preferably has a tensile strength of 40 to 170 MPa, preferably 40 to 160 MPa, more preferably 40 to 150 MPa, measured according to JIS K 6732. If the tensile strength is greater than 170 MPa, it will be difficult to obtain the desired hand cutting property, or the film must be made thin in order to improve the hand cutting property, which makes handling difficult in secondary processing, etc. It is not preferable. On the other hand, if the tensile strength is less than 40 MPa, it is not preferable because a cutting trouble is likely to occur in the stretching process and the secondary processing processes such as slitting, printing, and bag making. In the present invention, a film having a good balance between strength and thickness can be obtained by controlling the tensile strength by the thickness constitution ratio of the amorphous polyester resin layer and the crystalline polyester resin layer. As a result, a feature of the present invention is that a polyester film having an excellent balance between hand cutting properties and processability can be obtained.
The tensile elongation of the laminated polyester film of the present invention is not particularly specified, but the tensile elongation of the film measured according to JIS K 6732 is usually preferably 20 to 150%.
[0025]
In the present invention, the delamination strength between the amorphous polyester resin layer and the crystalline polyester resin layer is preferably 0.7 N / cm or more, more preferably 1.0 N / cm or more. When the delamination strength is smaller than this, peeling between layers constituting the laminated film is likely to occur when the film is torn by hand, and the cut line is not stable, which is not preferable. The delamination strength here refers to the peel strength measured when a sample piece having a width of 15 mm is T-shaped peeled in an environment of a temperature of 20 ° C. and a humidity of 65% RH (a peel strength converted per 1 cm width of the sample piece). Unit (N / cm).
[0026]
The thickness of the laminated polyester film of the present invention is not particularly limited, and as a result, the end tear resistance of the film only needs to be within the range defined in the present invention. Usually, it is in the range of 5 to 50 μm, preferably 7 to 40 μm, more preferably 9 to 30 μm. If the film is too thick, it is difficult to obtain the desired hand cutting property, and if it is too thin, handling becomes difficult, which is not preferable.
[0027]
The laminated polyester film of the present invention may contain various known additives such as other polymers, slip agents, inorganic fillers, antioxidants, antistatic agents and the like as long as the effects of the present invention are not impaired. . The slip agent is 0.005 to 1.0% by mass, preferably 0.01 to 0.5% by weight of inert particles having an average particle size of 0.1 to 4 μm, for example, silica, from the viewpoint of antiblocking property and transparency of the film. It is preferable to add mass%.
[0028]
If necessary, the laminated polyester film of the present invention may have other polymer materials such as high-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin, modified polyethylene resin, polypropylene resin, modified polypropylene resin, polyamide. You may laminate | stack at least one layer of resin, polyester resin, and / or the film which consists of them in the presence or absence of an adhesive bond layer. As a method for laminating, any known method such as a dry laminating method, an extrusion laminating method, or a thermal laminating method may be mentioned.
[0029]
Moreover, you may laminate | stack the layer which consists of inorganic films, for example, a silicon dioxide, an alumina, a zinc dioxide, or these mixtures as needed on the lamination | stacking polyester film of this invention. As a lamination method, any known method such as physical vapor deposition or chemical vapor deposition may be used.
[0030]
Furthermore, you may laminate | stack the layer which consists of a metal film, for example, aluminum, as needed to the lamination | stacking polyester film of this invention. As a lamination method, for example, any known method such as a vapor deposition method or a dry lamination method may be used.
[0031]
Furthermore, you may laminate | stack the layer which consists of papers on the laminated polyester film of this invention as needed. As a method of laminating, for example, any known method such as a dry laminating method, an extrusion laminating method, or a thermal laminating method may be mentioned.
[0032]
As a method of laminating an amorphous polyester resin layer and a crystalline polyester resin layer, in a plurality of extruders, etc., the resin is melted separately, extruded from the die outlet and formed into an unstretched film, and then unstretched A preferred example is a method of laminating films in a heated state. Another method includes a method of melt laminating the other molten film on the surface of one unstretched film. Still another method includes a method of forming a film by extruding from a die outlet in a state of being laminated by a co-extrusion method.
[0033]
Next, an example of a method for producing the laminated polyester film of the present invention will be described. The sufficiently dried amorphous polyester resin (A) and the crystalline polyester resin (B) are supplied to two different extruders, melt-extruded, passed through a composite adapter, and two kinds of two layers (A / B) or two types and three layers (B / A / B) are extruded from a die orifice of a T die into a sheet and discharged. The softened sheet discharged from the die orifice is tightly wound around the cooling drum and cooled. Subsequently, the obtained unstretched sheet is biaxially stretched at a temperature of 90 to 140 ° C., usually at a stretch ratio of 3.0 to 5.0 times in the vertical and horizontal directions. When the stretching temperature is less than 90 ° C, a homogeneous stretched film may not be obtained. When the stretching temperature exceeds 140 ° C, crystallization of the crystalline polyester resin is promoted and transparency may be deteriorated. Further, when the draw ratio is less than 3.0 times, the strength is low, and pinholes are easily generated when the bag is formed, and when it exceeds 5.0 times, drawing becomes difficult.
The biaxially stretched film is subsequently heat treated at a temperature below the melting point of the crystalline polyester layer. If the heat treatment temperature is too high, the film will melt, which is not preferable. The biaxial stretching method may be any of a tenter simultaneous biaxial stretching method, a sequential biaxial stretching method using a roll and a tenter, or a tubular method.
[0034]
【Example】
Hereinafter, the present invention will be described by way of examples.
In addition, the raw material and measurement method which were used for evaluation of an Example and a comparative example are as follows.
〔material〕
PET1:
Unitika polyethylene terephthalate resin CG0BRD, intrinsic viscosity 0.54, melting point 256 ° C.
PET2:
Unitika polyethylene terephthalate resin DABR, intrinsic viscosity 0.47, melting point 256 ° C.
PET3:
Unitika polyethylene terephthalate resin DHCBR, intrinsic viscosity 0.67, melting point 256 ° C.
AP:
Ethylene glycol as a glycol component, terephthalic acid as an acid component, trimellitic acid with a copolymerization ratio of 1 mol%, and isophthalic acid with a copolymerization ratio of 5 mol% are charged in an esterification tank and reacted at 240 ° C. for 4 hours to obtain an esterified product. Obtained. Next, melt polymerization was performed at 300 ° C. under a reduced pressure of 1.3 hPa under an antimony trioxide catalyst to obtain a polyester resin AP having an intrinsic viscosity of 0.51 and a melting point of 232 ° C.
PETG:
Eastman Chemical Co., Ltd. EASTER 6763 (amorphous polyester copolymerized with ethylene glycol and 1,4-cyclohexanedimethanol 31.5 mol% and terephthalic acid), intrinsic viscosity 0.75, no melting point.
APET:
Eastman Chemical Co. EASTER 9921 (polyester copolymerized with ethylene glycol, 1,4-cyclohexanedimethanol 3.4 mol% and terephthalic acid), intrinsic viscosity 0.80, melting point 234 ° C.
IPET:
Unitika Copolyester Resin IP-11 (polyester copolymerized with 11 mol% terephthalic acid and isophthalic acid and ethylene glycol), inherent viscosity 0.67, melting point 211 ° C.
[0035]
(Measurement of end resistance)
The end resistance was measured in the MD direction of the laminated film according to JIS C 2318 6.3.4.
[0036]
(Measurement of tensile strength)
The tensile strength was measured in the MD direction of the laminated film according to JIS K 6732.
[0037]
[Measurement of delamination strength]
Adhesive on one side of the laminated film (main agent a: Dick Dry LX63F manufactured by Dainippon Ink & Chemicals, Inc., curing agent b: KP-90 manufactured by Dainippon Ink & Chemicals, Inc., ethyl acetate c, a / b / c = 1/12 / 10 (mass ratio) was applied and dried with hot air at 80 ° C. for 15 seconds to evaporate the solvent, followed by dry lamination with a linear low density polyethylene sealant (TUXFCS # 50, manufactured by Tosero Co., Ltd., thickness 50 μm). A sample having a width of 15 mm and a length of 140 mm was cut out from the dry laminate sample, T-shaped peeling was performed at a tensile rate of 300 mm / min in an environment of 20 ° C. and 65% RH, and the peeling strength was measured (unit: N / cm). By measuring the sample thickness after peeling, the peeling interface of the sample was determined, and peeling occurred between the amorphous polyester resin layer and the crystalline polyester resin layer in all the samples of this example and the comparative example, The peel strength was defined as the peel strength.
[0038]
[Evaluation of hand cutting properties]
The hand cut performance of the film was evaluated in three stages by tearing a laminated film sample cut into a 100 mm square with both hands in the TD direction of the film. Those that were easily torn by hand were rated as ◯, those that were slightly resistant but could be torn were marked as Δ, and those that were very difficult to tear by hand were marked as ×.
[0039]
[Opening stability of bag products]
Adhesive on one side of the laminated film (main agent a: Dick Dry LX63F manufactured by Dainippon Ink & Chemicals, Inc., curing agent b: KP-90 manufactured by Dainippon Ink & Chemicals, Inc., ethyl acetate c, a / b / c = 1/12 / 10 (mass ratio) was applied and dried with hot air at 80 ° C. for 15 seconds to evaporate the solvent, followed by dry lamination with a linear low density polyethylene sealant (TUXFCS # 50, manufactured by Tosero Co., Ltd., thickness 50 μm). The obtained laminate film was aged at 40 ° C. for 48 hours. Two 100 mm × 100 mm sample pieces were cut out from the obtained laminate film and aligned in the MD and TD directions to produce a four-side heat-sealed bag. When this seal bag is torn by hand in the TD direction, the one opened by the linear cut line is ○, and the delamination occurs between the amorphous polyester layer and the crystalline polyester layer, and the cut line is disturbed. X.
[0040]
Example 1
PETG as a resin constituting the amorphous polyester resin layer A and PET1 as a resin constituting the crystalline polyester resin layer B were melted by separate extruders at a temperature of 270 ° C., and the melts were joined by a composite adapter. Later, it was extruded from a T-die and quenched with a cooling drum to obtain a three-layer unstretched laminated film having a B / A / B configuration. At this time, the discharge amount of each extruder was adjusted so that the thickness of PET and PETG in the laminated polyester film after stretching was in the ratio of 2 μm / 8 μm / 2 μm.
First, the unstretched laminated film is stretched 3.5 times at about 90 ° C in the machine direction by roll stretching, then 3.8 times at about 110 ° C in the transverse direction by the tenter stretching method, and then relaxed by 3% in the transverse direction. Heat treatment was performed at a temperature of 225 ° C. Further, after the film was cooled, it was wound into a roll by a winder to obtain a laminated biaxially stretched polyester film having the thickness configuration shown in Table 1. The evaluation results of this film are shown in Table 1.
[0041]
Example 2
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the thickness configuration was 3/6/3 (μm). The evaluation results of this film are shown in Table 1.
[0042]
Example 3
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 1 except that PET2 was used as the crystalline polyester resin. The evaluation results of this film are shown in Table 1.
[0043]
Example 4
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 2 except that PET2 was used as the crystalline polyester resin. The evaluation results of this film are shown in Table 1.
[0044]
Example 5
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 3 except that the thickness configuration was changed to 1/10/1 (μm). The evaluation results of this film are shown in Table 1.
[0045]
Example 6
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 3 except that the thickness configuration was 1.5 / 22 / 1.5 (μm). The evaluation results of this film are shown in Table 1.
[0046]
Example 7
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 1 except that AP was used as the crystalline polyester resin. The evaluation results of this film are shown in Table 1.
[0047]
Comparative Example 1
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 1 except that PET3 was used as the crystalline polyester resin. The evaluation results of this film are shown in Table 1.
[0048]
Comparative Example 2
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 2 except that PET3 was used as the crystalline polyester resin. The evaluation results of this film are shown in Table 1.
[0049]
Comparative Example 3
A laminated biaxially stretched polyester film was obtained in the same manner as in Example 3 except that the thickness configuration was 5/2/5 (μm). The evaluation results of this film are shown in Table 1.
[0050]
Comparative Example 4
A laminated biaxially stretched polyester film was obtained in the same manner as in Comparative Example 2 except that APET was used as the amorphous polyester resin. The evaluation results of this film are shown in Table 1.
[0051]
Comparative Example 5
A laminated biaxially stretched polyester film was obtained in the same manner as in Comparative Example 2 except that IPET was used as the amorphous polyester resin. The evaluation results of this film are shown in Table 1.
[0052]
[Table 1]

[0053]
【The invention's effect】
In the present invention, the tensile strength can be controlled by the thickness constitution ratio of the amorphous polyester resin layer and the crystalline polyester resin layer, and a film having a good balance between strength and thickness can be obtained. In addition, by limiting the intrinsic viscosity of the crystalline polyester resin to a specific range, the delamination strength between the crystalline polyester resin layer and the amorphous polyester resin layer is improved, and the crystalline polyester having a low intrinsic viscosity is used alone. In comparison, the melt processability is improved. As a result, it is possible to obtain a polyester film that is excellent not only in hand cutting properties but also in the stability of the cut line at the time of opening and excellent in workability balance. According to the method of the present invention, it is possible to provide industrially and easily a film having excellent hand cutting properties useful as packaging materials such as foods, pharmaceuticals, daily necessities, cosmetics, and adhesive tapes.

Claims (4)

The amorphous polyester resin layer (A) and the crystalline polyester resin layer (B) are laminated biaxially stretched polyester films having a three-layer structure of B / A / B, and the thickness of the amorphous polyester resin layer Is a laminated biaxially stretched polyester film excellent in hand cutting characteristics, characterized in that it is 50 to 95% of the total thickness of the laminated polyester film and the intrinsic viscosity of the crystalline polyester resin is 0.30 to 0.57 .   The amorphous polyester resin is a polyester resin comprising a dibasic acid component mainly containing terephthalic acid and a diol component containing 10 to 70 mol% of 1,4-cyclohexanedimethanol. The laminated biaxially stretched polyester film described.   The laminated biaxially stretched polyester film according to claim 1 or 2, wherein the film has an end tear resistance of 5 to 70 N and a tensile strength of 40 to 170 MPa.   The laminated biaxially stretched polyester film according to any one of claims 1 to 3, wherein the delamination strength between the amorphous polyester resin layer and the crystalline polyester resin layer is 0.7 N / cm or more.