JP2004025484A - Easy tear film excellent in gas barrier performance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film which is preferably utilized for packaging, in particular for a food packaging material, and is excellent in gas barrier and easy tear performance. <P>SOLUTION: An easy tear film excellent in the gas barrier performance is provided, which is characterized in that at least one layer of an amorphous polyester resin layer and a crystalline polyester resin layer is included there into respectively, the thickness of the amorphous polyester resin layer comprises 20 to 95% in the total thickness of a laminated polyester film, and also an evaporated thin film layer composed of aluminum is formed at least on one side of a laminated twin screw-oriented polyester film having edge tearing resistance of 5 to 70N. <P>COPYRIGHT: (C)2004,JPO

Description

【００６１】
表１に示したように、実施例で得られたフィルムは易裂き性、ガスバリア性に優れ、また製膜及びスリット時、蒸着加工時にも破断等のトラブルは無く生産性も良好であった。一方、比較例のフィルムはガスバリア性を有するものの、引裂き性に劣るものであった。
【００６２】
【発明の効果】
本発明によれば、包装用、特に食品包装の包装材料として好適に利用される、ガスバリア性および易裂き性に優れたフィルムを工業的に容易に提供することが可能である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a film having excellent gas barrier properties and easy tearability, which is suitably used as a packaging material for packaging, particularly for food packaging.
[0002]
[Prior art]
In order to preserve food for a long period of time, it is necessary to use a packaging material having excellent gas barrier properties in order to block external oxygen and water vapor which promote decay and deterioration. Known materials having gas barrier properties include aluminum foil, aluminum-deposited films, polyvinylidene chloride coated films, polyvinyl alcohol films and their coated films, and polyvinyl alcohol-based films such as ethylene-vinyl alcohol copolymer films.
[0003]
However, polyvinylidene chloride generates chlorine gas at the time of incineration, and aluminum foil generates incineration residues, which is an environmental problem. Further, the polyvinyl alcohol-based film has a property of being inferior in the water vapor barrier property, and that the oxygen barrier property is rapidly reduced under high humidity conditions. Furthermore, since polyvinyl alcohol is eluted in a high temperature region, there is a disadvantage that it is unsuitable for sterilizing boil or retort.
[0004]
On the other hand, a film obtained by laminating a vapor-deposited thin film layer made of aluminum does not have the above-mentioned problems and is used as a packaging material. As a base film on which the vapor-deposited thin film layer is formed, a biaxially stretched polyester film is often used because heat resistance and mechanical strength are required.
[0005]
The biaxially stretched polyester film has excellent durability, moisture resistance, mechanical strength, heat resistance, and oil resistance, and is manufactured using a tubular method, a flat simultaneous biaxial stretching method, a flat sequential biaxial stretching method, or the like. Manufactured and widely used in various fields. However, the biaxially stretched polyester film generally has a high mechanical strength and is difficult to be cut. For example, when used as various packaging materials or adhesive tapes, there is a problem that it cannot be easily opened and cut by hand.
[0006]
By the way, cellophane is known as a film having excellent tearability, and is used in a structure such as cellophane / polyethylene. However, cellophane has a high hygroscopicity and thus easily changes its dimensions. It was difficult to supply quality products. In addition, while cellophane has good tearability, there are many troubles such as film cutting in secondary processing steps such as printing and lamination, and a film excellent in balance between easy tearability and mechanical strength has been desired. In addition, polyvinylidene chloride-coated cellophane is used as cellophane having a barrier property, but an alternative film has been demanded due to recent environmental problems.
[0007]
Further, as a material imparted with easy tearing property, a laminate of a polystyrene film and a polyolefin film having a highly syndiotactic structure is disclosed in JP-A-5-3380895. However, since the main structure of this film is polystyrene, there is a problem that the film itself is brittle and easily cut in a secondary processing step or the like. Furthermore, the laminate has problems such as broken wrinkles tending to remain sharply, resulting in poor appearance, and poor heat resistance, resulting in a narrower range of sealing conditions for heat-welding the laminate, The performance required as a packaging material is not sufficiently satisfied, for example, a bag is broken during transportation due to low strength.
[0008]
As a method for imparting easy tearability to the above-described biaxially stretched polyester film, there is a method for imparting a notch to an end of the film. However, since such a method cannot be used to tear from a place other than the notch, there is a problem that the degree of freedom of the opening method is low, and if tearing from the notch fails, easy tearing property is lost.
[0009]
As a method of improving the tearability of a biaxially stretched polyester film, a method of copolymerizing a predetermined amount of diethylene glycol with polyethylene terephthalate (hereinafter referred to as PET) (Japanese Patent Application Laid-Open No. 50-103574), a method of relatively high molecular weight PET A method of mixing low molecular weight PET (JP-A-51-104618), a method of imparting a specific refractive index distribution with an intrinsic viscosity in the range of 0.35 to 0.58 (Japanese Patent Publication No. 62-20016). JP-A-2-47038), a method of biaxially stretching a multilayer film composed of a high-melting polyester and a low-melting polyester, and then obtaining a film having a melting point of 10% from the melting point of the low-melting layer. A method of performing heat treatment at a temperature lower than the lower temperature of ℃ and lower than the melting point of the high melting point layer (JP-A-5-104618) is disclosed. .
[0010]
However, in the method described in JP-A-50-103574, since the copolymerization amount of diethylene glycol is relatively large, there is a problem that the heat resistance of PET is impaired due to a decrease in melting point, and the breaking strength of the obtained film (about 170 MPa) is much higher than the general breaking strength of cellophane of about 50 to 70 MPa, and there is a problem that the tearability of this film is far lower than that of cellophane.
[0011]
According to the method described in JP-A-51-104618, it is necessary to mix a relatively large amount of a low-molecular-weight PET resin with a high-molecular-weight PET in order to impart sufficient tearability. There is a problem that it is difficult to form an unstretched film having a remarkably reduced melt tension, and that bleed-out of a low-molecular-weight substance easily occurs.
[0012]
When the film obtained by the method described in JP-B-62-20016 is extremely low in intrinsic viscosity, it exhibits a tearing property close to cellophane, but has a small intrinsic viscosity, that is, a resin having a low melt tension. In the case where is used, there are problems that it is difficult to form an unstretched film and that the film is easily broken during stretching due to low strength.
[0013]
According to the method described in JP-A-2-47038, a film exhibiting good tearability is obtained when a crosslinkable comonomer is used in combination with another comonomer component. There is a problem that an eye is easily generated and a problem that a film is fragile and a trouble such as a film breakage during stretching is likely to occur.
[0014]
According to the method described in JP-A-5-104618, a film having very good tearability can be obtained, but relatively large crystals are generated together with the relaxation of the orientation of the low melting point layer. And dimensional stability is impaired due to dimensional change accompanying crystallization. Furthermore, since it is difficult to uniformly relax the orientation of the low-melting point layer, there is a problem that the flatness of the film is easily impaired.
[0015]
As described above, it is difficult to provide a packaging material having gas barrier properties, and at the same time, having both easy tearability, mechanical strength, and heat resistance, and improvement thereof has been desired.
[0016]
[Problems to be solved by the invention]
The present invention is intended to solve the above-mentioned problems, and is particularly suitable as a food packaging material, has excellent gas barrier properties, and has the mechanical strength and heat resistance required as a packaging material, as well as cellophane. It is an object of the present invention to provide a plastic film having such good tearability.
[0017]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve such problems, and as a result, laminated a crystalline polyester resin layer and an amorphous polyester resin layer at a specific thickness composition ratio, and deposited a laminated film of aluminum on the laminated film. By providing a thin film layer, it is possible to obtain a film that can be easily torn by hand while maintaining strength and processability as a packaging material, and has also found that the obtained laminated film has excellent gas barrier properties. Reached.
[0018]
That is, the gist of the present invention is as follows.
(1) It has at least one amorphous polyester resin layer and at least one crystalline polyester resin layer, the thickness of the amorphous polyester resin layer is 20 to 95% of the total thickness of the laminated polyester film, and An easily tearable film having excellent gas barrier properties, wherein a deposited thin film layer made of aluminum is formed on at least one surface of a laminated biaxially stretched polyester film having a resistance of 5 to 70 N.
(2) The amorphous polyester resin is a polyester resin comprising a dibasic acid component mainly containing terephthalic acid and a diol component containing 10-70 mol% of 1,4-cyclohexanedimethanol. The easily tearable film according to (1).
(3) The easily tearable film according to (1) or (2), further comprising a transparent primer layer between the laminated biaxially stretched polyester film and the vapor-deposited thin film layer made of aluminum.
(4) A laminate comprising at least one layer of the easily tearable film according to any one of (1) to (3).
(5) A packaging bag using the laminate according to (4).
[0019]
BEST MODE FOR CARRYING OUT 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, the resin has a crystallinity of 5% or less when the resin is left in a temperature range from a glass transition temperature to a melting point. As such an amorphous polyester resin, for example, an amorphous copolymer polyester obtained by acid-modified and / or diol-modified polyethylene terephthalate is preferable.
[0020]
Acid-modified components used in the copolymerization include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecane diacid, dimer acid Dicarboxylic acids such as maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, and cyclohexanedicarboxylic acid; oxycarboxylic acids such as 4-hydroxybenzoic acid, ε-caprolactone, and lactic acid; and trimellitic acid. And polyfunctional compounds such as trimesic acid and pyromellitic acid. These acid-modified components may be used alone or as a mixture of two or more.
[0021]
The diol-modified components used for the copolymerization include 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,2-cyclohexanedimethanol. Glycols such as cyclohexanedimethanol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, and polyfunctional compounds such as trimethylolpropane, glycerin and pentaerythritol And the like. These diol-modified components may be used alone or in combination of two or more.
[0022]
Among such amorphous polyester resins, from the viewpoint of heat resistance, mechanical properties, transparency, etc., a dibasic acid component mainly composed of terephthalic acid and 1,4-cyclohexanedimethanol are 10 to 70 mol%. A polyester resin comprising a diol component is preferred.
[0023]
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.
[0024]
The intrinsic viscosity of the amorphous polyester resin used in the present invention is not particularly limited, but it is preferable to use one having an intrinsic viscosity of about 0.5 to 0.8 at a temperature of 20 ° C. If the intrinsic viscosity is lower than this, it is not preferable because the mechanical properties of the film deteriorate or drawdown occurs during extrusion molding. On the other hand, if the intrinsic viscosity is higher than this, the load during extrusion molding increases, which is not preferable.
[0025]
In the present invention, the laminated biaxially stretched polyester film is composed of an amorphous polyester resin layer and a crystalline polyester resin layer. By using a crystalline polyester resin, heat resistance, mechanical properties, good stretchability, and thickness accuracy that cannot be obtained by using only an amorphous polyester resin are imparted.
[0026]
As such a crystalline polyester resin, those having a melting point of 230 ° C. or higher are usually used, and among them, a polyester resin having PET as a main skeleton is preferably used. Other copolymer components may be copolymerized in such a crystalline polyester resin as long as the required properties are not impaired.
[0027]
As copolymerization components, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecane diacid, dimer acid, maleic anhydride, Examples thereof include dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, and cyclohexanedicarboxylic acid. Also, oxycarboxylic acids such as 4-hydroxybenzoic acid, ε-caprolactone, and lactic acid, and 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3- Glycols such as cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, trimethylolpropane, and glycerin And polyfunctional compounds such as pentaerythritol. These copolymer components may be used alone or as a mixture of two or more.
[0028]
The crystalline polyester resin layer 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.
[0029]
The intrinsic viscosity of the crystalline polyester resin used in the present invention at a temperature of 20 ° C. is not particularly limited, but usually it is preferably about 0.5 to 0.9. If the intrinsic viscosity is lower than this, the mechanical properties of the film are lowered and the melt viscosity during extrusion molding is too low, which is not preferable. On the other hand, if the intrinsic viscosity is higher than this, the melt viscosity becomes too high and extrusion becomes difficult, which is not preferable.
[0030]
In the present invention, the laminated biaxially stretched polyester film needs to have at least one amorphous polyester resin layer (A) and at least one crystalline polyester resin layer (B). Specific layer configurations of the laminated biaxially stretched polyester film include A / B, B / A / B, A / B / A, B / A / B / A / B, and the like. Preferred configurations include B / A / B. Further, in addition to the amorphous polyester resin layer and the crystalline polyester resin layer, an adhesive layer or the like may be laminated on the laminated polyester film of the present invention in order to impart interlayer adhesion.
[0031]
In the laminated biaxially stretched polyester film, the thickness ratio of the amorphous polyester resin layer needs to be 20 to 95% of the total thickness, and preferably 30 to 85%. The term “thickness composition ratio” as used herein refers to a percentage of the thickness of the amorphous polyester resin layer with respect to the total thickness of the film. If the thickness of the amorphous polyester resin layer exceeds 95% of the total thickness, heat resistance, mechanical properties, good stretchability, and thickness accuracy obtained by the contribution of the crystalline polyester layer are undesirably impaired. When the thickness of the amorphous polyester resin layer is less than 20% of the total thickness, it is difficult to obtain the desired easy tearability, which is not preferable.
[0032]
In the present invention, the laminated biaxially stretched polyester film has an edge crack resistance (average value) of 5 to 70 N, preferably 10 to 60 N, more preferably 15 to 70 N, as measured according to JIS C 23186.3.4. Preferably it is 50N. If the end tear resistance is greater than this, the desired tearability of the target film becomes difficult to obtain, and if it is less than this, the strength of the film is too low, and the secondary processing such as stretching, slitting, printing, and bag making is performed. It is not preferable because a cutting trouble easily occurs in the process.
[0033]
In the present invention, the thickness of the laminated biaxially stretched polyester film is not particularly limited, and consequently the end tear resistance of the film may be within the range specified in the present invention. Usually, it is in the range of 5 to 50 μm, and preferably in the range of 10 to 40 μm.
[0034]
In the present invention, the laminated biaxially stretched polyester film includes various known additives, for example, other polymers, slip agents, inorganic fillers, antioxidants, antistatic agents, and the like, as long as the effects of the present invention are not impaired. It may be. From the viewpoint of the anti-blocking property and transparency of the film, the slip agent contains 0.005 to 1.0% by mass, preferably 0.01 to 0.5% by mass of inert particles having an average particle size of 0.1 to 4 μm, such as silica. It is preferable to add by mass%.
[0035]
In the present invention, as a method for producing a laminated biaxially stretched polyester film, in a plurality of extruders, etc., the amorphous polyester resin and the crystalline polyester resin are separately melted, extruded from a die outlet and formed into an unstretched film. Then, there is a method of laminating unstretched films in a heated state. As another method, there is a method in which the surface of one unstretched film is melt-laminated with the other molten film. As still another method, there is a method of forming a film by extruding from a die outlet in a state of being laminated by a co-extrusion method.
[0036]
Next, an example of a method for producing a laminated biaxially stretched polyester film will be described. The sufficiently dried amorphous polyester resin (A) and the crystalline polyester resin (B) are supplied to two separate extruders, respectively, melt-extruded, passed through a composite adapter, and subjected to two types and two layers (A / A). B) or extruded and discharged as a sheet from a die orifice of a T-die as two or three layers (B / A / B). The softened sheet discharged from the die orifice is closely wound around a 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 each in the length and width directions. If the stretching temperature is lower than 90 ° C., a uniform stretched film may not be obtained, and if the stretching temperature is higher than 140 ° C., crystallization of the crystalline polyester resin (B) may be promoted and transparency may be deteriorated. . When the stretching ratio is less than 3.0 times, the strength is low, and when the bag is formed, pinholes are easily generated, and when it exceeds 5.0 times, stretching becomes difficult.
[0037]
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 is melted, which is not preferable.
[0038]
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.
[0039]
The easily tearable film having excellent gas barrier properties of the present invention is obtained by forming a vapor-deposited thin film layer made of aluminum on at least one surface of the laminated biaxially stretched polyester film.
[0040]
The thickness of the evaporated thin film layer made of aluminum is preferably 20 to 80 nm, and more preferably 40 to 60 nm. When the thickness of the thin film layer is less than 20 nm, sufficient barrier properties cannot be obtained, and the light reflectivity of aluminum vapor deposition is low, so that sufficient metallic luster may not be obtained. On the other hand, if the film thickness exceeds 80 nm, the adhesiveness of the ink may become unstable during printing on the aluminum vapor-deposited surface.
Examples of a method for forming the above-described deposited thin film layer include a method such as a vacuum deposition method, an EB deposition method, and a sputtering method. It is preferable to use a vacuum deposition method from the viewpoint of productivity and cost.
[0041]
In order to increase the adhesion between the deposited thin film layer and the laminated biaxially stretched polyester film, and to prevent the deterioration of the lamination strength over time after filling the contents when used as a packaging bag, the laminated biaxially stretched polyester film is used. A transparent primer layer may be provided between the stretched polyester film.
[0042]
The resin constituting the primer layer is not particularly limited as long as it is a resin which can enhance the adhesion to the thin film layer and does not impair the above-mentioned properties, and examples thereof include polyester-based, polyurethane-based or polyurethane-polyurea resins, and ethylene-ethylene. Resins such as vinyl alcohol copolymer and polyvinyl alcohol are preferred.
The thickness of the transparent primer layer is not particularly limited, but is generally in the range of 0.001 to 5 μm, and particularly preferably in the range of 0.01 to 2 μm.
[0043]
As a method for forming the transparent primer layer, the primer resin solution is laminated and biaxially stretched using a known printing method such as a gravure printing method or an offset printing method, or a known coating method such as a gravure coat or a reverse coat. A method of applying to a polyester film and drying. The application and drying conditions may be generally used conditions as long as the performance of the primer resin is not impaired.
The solvent for dissolving the primer resin may be any solvent capable of dissolving the primer resin, and an organic solvent / aqueous solvent or the like may be used alone or as a mixture. In addition, the solution of the primer resin includes other polymer components, a curing agent, a cross-linking agent, a reaction accelerator, a silane coupling agent, an antioxidant, a leveling agent, and the like, as long as the required properties are not impaired. Additives may be added. Further, the laminated biaxially stretched polyester film may be subjected to a pretreatment such as a corona treatment or a low-temperature plasma treatment in order to improve the adhesion with the transparent primer layer, and further subjected to a chemical treatment, a solvent treatment, etc. Is also good.
[0044]
The easily tearable film of the present invention can be printed and laminated as necessary to be used as a laminate. The laminate includes at least one easily tearable film, and may have any number of layers such as two layers and three layers. For example, as a laminate having a two-layer structure, a laminate composed of an easily tearable film and a heat-sealing resin layer is exemplified.
[0045]
The heat-sealable resin can be composed of the same material as that conventionally used as a sealant layer of a packaging material. For example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer, or the like is used. be able to. Further, the thickness of the heat-sealing resin layer is not particularly limited, and can be appropriately selected as needed.
[0046]
Further, the easily tearable film of the present invention can be laminated by laminating another stretched film such as a biaxially stretched polyester film, a biaxially stretched nylon film, a biaxially stretched polypropylene film, or paper.
[0047]
The lamination method is not particularly limited as long as the easy tearing property is not impaired, but a method such as a dry lamination method or an extrusion lamination method can be used.
[0048]
Examples of the configuration of the laminate of the present invention include the following configurations. When the easily tearable film of the present invention is (C), other stretched films or papers are (D), and the heat seal layer is (S), C / S, C / D / S, D / C / S, C / C / S, C / D / C / S, C / C / D / S, D / C / C / S, D / C / D / S, D / D / C / S, and the like. However, in the above configuration, S may be S / S, and an S layer may be present as an adhesive layer between C / D, D / C, C / A, and D / D. Good.
[0049]
A packaging bag can be formed using a laminate including at least one layer of the easily tearable film of the present invention. The form of the packaging bag is not particularly limited, and examples thereof include a three-sided bag, a four-sided bag, a pillow bag, a gusset bag, and a stick bag.
[0050]
【Example】
Hereinafter, the present invention will be described with reference to examples.
In addition, the raw materials used for the evaluation of the examples and the comparative examples and the measuring methods are as follows.
〔material〕
PET:
Unitika polyethylene terephthalate resin, intrinsic viscosity 0.67, melting point 256 ° C.
AP:
Ethylene glycol as a glycol component, terephthalic acid as an acid component, trimellitic acid at a copolymerization ratio of 1 mol%, and isophthalic acid at a copolymerization ratio of 5 mol% were charged into 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 0.63 and a melting point of 232 ° C.
PETG:
Polyester obtained by copolymerizing ethylene glycol, 31.5 mol% of 1,4-cyclohexanedimethanol and terephthalic acid, intrinsic viscosity 0.75.
APET:
Polyester obtained by copolymerizing ethylene glycol, 3.4 mol% of 1,4-cyclohexanedimethanol and terephthalic acid, intrinsic viscosity 0.80, melting point 234 ° C.
IPET:
Unitika Co. polyester resin IP-11 (polyester obtained by copolymerizing terephthalic acid and isophthalic acid 11 mol% and ethylene glycol), intrinsic viscosity 0.67, melting point 211 ° C.
[0051]
(Primer layer)
Primer (P):
An aqueous polyester-based resin (manufactured by Takamatsu Yushi Co., Ltd., Bethresin AD100) mixed with a melamine-based crosslinking agent in an aqueous polyester-based resin / melamine-based crosslinking agent = 80/20 (mass ratio).
[0052]
(Measurement of end crack resistance)
The end tear resistance was measured according to JIS C 2318 6.3.4, and the average value was shown.
(Measurement of oxygen permeability)
The measurement was carried out at a temperature of 20 ° C. and a humidity of 90% RH using a gas permeability measuring instrument (OX-TRAN 2/20) manufactured by MOCON.
(Evaluation of easy tearability)
The tearability of the film was evaluated on a three-point scale by tearing the end of the film sample cut into a square of 100 mm with both hands. A sample that was easily torn by hand was marked with “○”, a sample with slightly high resistance but capable of tearing was marked with “、”, and one that was very difficult to tear by hand was marked with “×”.
[0053]
Examples 1-3
PETG as the resin (A) constituting the amorphous polyester resin layer and PET as the resin (B) constituting the crystalline polyester resin layer are each melted at a temperature of 270 ° C. by separate extruders. Then, the mixture was extruded from a T-die and rapidly cooled with a cooling drum to obtain a three-layer unstretched laminated film having a B / A / B configuration. At this time, the discharge rate of each extruder was adjusted so that the thickness composition ratio of PET and PETG in the final laminated polyester film was as shown in Table 1.
The unstretched laminated film is first stretched 3.5 times in the longitudinal direction at about 90 ° C. by the roll stretching method, then 3.8 times in the transverse direction at about 110 ° C. by the tenter stretching method, and then relaxed by 3% in the transverse direction. While performing the heat treatment at a temperature of 225 ° C. After the film was further cooled, it was wound into a roll by a winder to obtain a laminated biaxially stretched polyester film having a thickness of 12 μm.
Aluminum was evaporated to a thickness of 50 nm on one surface of the obtained laminated biaxially stretched polyester film by a vacuum evaporation method to form a thin film layer, and an easily tearable film was obtained.
[0054]
Example 4
An aqueous solution of the primer P was applied to one surface of the laminated biaxially stretched polyester film of Example 2 by a gravure coating method so that the thickness after drying was 0.5 μm, and dried at 140 ° C. for 30 seconds. Aluminum was evaporated to a thickness of 50 nm on the primer P by a vacuum evaporation method to form a thin film layer, and an easily tearable film was obtained.
[0055]
Example 5
A laminated biaxially stretched polyester film having a thickness of 12 μm was obtained in the same manner, conditions and thickness configuration as in Example 2 except that PET was changed to AP. Aluminum was vapor-deposited on one side of this film to a thickness of 50 nm by a vacuum vapor deposition method to form a thin film layer, and an easily tearable film was obtained.
[0056]
Comparative Example 1
A laminated biaxially stretched polyester film having a thickness of 12 μm was obtained using the same raw materials and method as in Example 1, except that the thickness configuration of each layer of B / A / B was changed to 5/2/5. Aluminum was evaporated to a thickness of 50 nm on one side of the film by a vacuum evaporation method to form a thin film layer.
[0057]
Comparative Example 2
A laminated biaxially oriented polyester film having a thickness of 12 μm was obtained in the same manner, conditions and thickness configuration as in Example 2 except that PETG was changed to APET. Aluminum was evaporated to a thickness of 50 nm on one side of the film by a vacuum evaporation method to form a thin film layer.
[0058]
Comparative Example 3
A laminated biaxially stretched polyester film having a thickness of 12 μm was obtained in the same manner, conditions and thickness configuration as in Example 2 except that PETG was changed to IPET. Aluminum was evaporated to a thickness of 50 nm on one side of the film by a vacuum evaporation method to form a thin film layer.
[0059]
Table 1 shows the thickness structure and evaluation results of each layer of B / A / B of the obtained film.
[0060]
[Table 1]

[0061]
As shown in Table 1, the films obtained in the examples had excellent tearability and gas barrier properties, and had no trouble such as breakage during film formation, slitting, and vapor deposition, and also had good productivity. On the other hand, the film of the comparative example had gas barrier properties, but was poor in tearability.
[0062]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it is easy to industrially provide the film excellent in gas barrier property and easy tearing property suitably used for packaging, especially as packaging material of food packaging.

Claims (5)

It has at least one amorphous polyester resin layer and at least one crystalline polyester resin layer, the thickness of the amorphous polyester resin layer is 20 to 95% of the total thickness of the laminated polyester film, and the end crack resistance is 5%. An easily tearable film having excellent gas barrier properties, wherein a deposited thin film layer made of aluminum is formed on at least one surface of a laminated biaxially stretched polyester film having a thickness of from 70 to 70 N. 2. The amorphous polyester resin is a polyester resin comprising a dibasic acid component mainly composed of terephthalic acid and a diol component containing 10-70 mol% of 1,4-cyclohexanedimethanol. An easily tearable film according to the above. 3. The easily tearable film according to claim 1, further comprising a transparent primer layer between the laminated biaxially stretched polyester film and a vapor-deposited thin film layer made of aluminum. A laminate comprising at least one layer of the easily tearable film according to claim 1. A packaging bag using the laminate according to claim 4.