JP2003300272A - Easily tearable film excellent in gas barrier properties - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily tearable film excellent in transparency and gas barrier properties suitably utilizable as a packing material, especially a food packaging material. <P>SOLUTION: The easily tearable film excellent in gas barrier properties is constituted by forming a vapor deposition thin film layer comprising an inorganic oxide on at least one surface of a laminated biaxially stretched polyester film which has at least one amorphous polyester resin layer and at least one crystalline polyester resin layer and characterized in that the thickness of the amorphous polyester resin layer is 20-95% with respect to the total thickness of the laminated film and the edge tear resistance thereof is 5-70 N. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film having excellent transparency, gas barrier property and easy tearability, which is suitable for use as a packaging material for packaging, especially food packaging.

2. Description of the Related Art In order to preserve food for a long period of time, in order to block oxygen and water vapor from the outside air, which promotes spoilage and deterioration,
It is necessary to use packaging materials with excellent gas barrier properties. Aluminum foil, aluminum vapor-deposited film, polyvinylidene chloride coated film, etc. are known as materials having a gas barrier property, but due to recent environmental problems, the use of polyvinylidene chloride is being restricted, and aluminum foil and Aluminum vapor-deposited film exhibits a high degree of gas barrier property, but it has the drawbacks that it is opaque and its contents cannot be seen from the outside, and it cannot be heat-treated by a microwave oven.

Therefore, as a transparent film having a high oxygen barrier property, polyvinyl alcohol films such as polyvinyl alcohol films, coated films thereof, and ethylene-vinyl alcohol copolymer films have been used. However, the polyvinyl alcohol-based film is inferior in water vapor barrier property and has a property that the oxygen barrier property is rapidly lowered under the condition of high humidity.
Further, since polyvinyl alcohol is eluted in the high temperature region, it has a drawback that it is not suitable for sterilization treatment for boiling or retort.

As a packaging material, Japanese Patent Publication No. 63-28
No. 017, Japanese Patent Application Laid-Open No. 1-176069, Japanese Patent Application Laid-Open No. 1-20
A film in which a vapor-deposited thin film layer made of an inorganic oxide is laminated on at least one surface of a plastic substrate film described in Japanese Patent No. 2435 or the like is used. This film is transparent and has the advantage that it can be sterilized by boiling or retort, and in recent years, its production amount and usage amount have increased. A biaxially stretched polyester film is often used as a base film for forming a vapor-deposited thin film layer made of an inorganic oxide, because heat resistance and mechanical strength are required.

The biaxially stretched polyester film is excellent in durability, moisture resistance, mechanical strength, heat resistance and oil resistance, and is a tubular method, a flat simultaneous biaxial stretching method, a flat sequential biaxial stretching method, etc. It is manufactured by using and is widely used in various fields. However, since the biaxially stretched polyester film generally has high mechanical strength, it is difficult to cut, and there is a problem that it cannot be easily opened and cut by hand when used as various packaging materials or adhesive tapes.

By the way, cellophane is known as a film having excellent tearability. For example, cellophane is used in the structure of cellophane / polyethylene. However, since cellophane has a high hygroscopic property, it tends to change in size and its characteristics vary depending on the season. It was difficult to supply products of varying and constant quality. Further, while cellophane has good tearability, there are many problems such as film cutting in secondary processing steps such as printing and laminating, and a film having an excellent balance of easy tearability and mechanical strength has been desired. Further, polyvinylidene chloride coated cellophane is used as cellophane having a barrier property, but an alternative film has been demanded due to recent environmental problems.

[0006] Further, as a material having easy tearability,
A laminate of a polystyrene film having a highly syndiotactic structure and a polyolefin film is disclosed
No. 3,380,895. However, since the main structure of this film is polystyrene, the film itself is fragile and easily cut in a secondary processing step. In addition, the laminate has problems such as sharp wrinkles that are likely to remain clearly and poor appearance, and the heat resistance is inferior. Due to its low strength, bag breakage occurs during transportation, and the performance required as a packaging material is not fully satisfied.

As a method of imparting easy tearability to the above-mentioned biaxially stretched polyester film, a method of imparting a notch to the end portion of the film can be mentioned. However, with such a method, it is not possible to tear from a place other than the notch, so there is a problem that the degree of freedom of the opening method is low, and if tearing from the notch fails, easy tearability is lost.

As a method for improving the easy tearing 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) (JP-A-50-103574), a comparatively high method. Low molecular weight PET compared to low molecular weight PET
A method of mixing (JP-A-51-104618),
A method of imparting a specific refractive index distribution having an intrinsic viscosity of 0.35 to 0.58 (Japanese Patent Publication No. 62-20016), and a method of using a crosslinked polyester copolymerized with a polyfunctional monomer (JP-A-2- No. 47038), a method of biaxially stretching a multilayer film composed of high-melting point polyester and low-melting point polyester, and then heat-treating at a temperature 10 ° C. lower than the melting point of the low-melting point layer and lower than the melting point of the high-melting point layer (Japanese Patent Laid-Open No. Hei 5 (1999) -58)
No. 104618) is disclosed.

However, JP-A-50-103574
In the method described in the publication, since the copolymerization amount of diethylene glycol is relatively large, there is a problem that the heat resistance of PET is impaired by a decrease in melting point, and the breaking strength (about 170 MPa) of the obtained film is common to that of cellophane. The breaking strength was very large as compared with about 50 to 70 Mpa, and there was a problem that the easy tearing property of this film was completely inferior to that of cellophane.

In 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 easy tearability. However, there has been a problem that it is difficult to form an unstretched film in which the melt tension of the resin is remarkably lowered and bleed-out of a low molecular weight substance is likely to occur.

The film obtained by the method described in Japanese Examined Patent Publication No. 62-20016 shows easy tearing similar to cellophane when the intrinsic viscosity is very small,
When a resin having a low intrinsic viscosity, that is, a resin having a low melt tension is used, there are problems that it is difficult to form an unstretched film and that the strength of the unstretched film is low, so that the film is likely to break during stretching.

According to the method described in JP-A-2-47038, although a film showing good easy tearability is obtained when a crosslinkable comonomer and another comonomer component are used in combination, the gel formed during polymerization causes There are problems that fish eyes are likely to occur on the film and that problems such as film breakage tend to occur during stretching due to the brittleness of the film.

According to the method described in JP-A-5-104618, a film having a very good easy tearing property can be obtained. However, since the orientation of the low melting point layer is relaxed, a crystal having a relatively large size is formed. However, there is a problem in that the transparency is deteriorated and the dimensional stability is impaired due to a dimensional change caused by crystallization. Further, since it is difficult to uniformly cause the orientation relaxation of the low melting point layer, there is a problem that the flatness of the film is easily impaired.

As described above, it is difficult for the conventional technique to provide a packaging material having a gas barrier property as well as easy tearability, mechanical strength and heat resistance, and its improvement has been desired.

[0015]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems, and in particular, a machine which is suitable as a food packaging material and which is excellent in transparency and gas barrier property and is required as a packaging material. An object of the present invention is to provide a plastic film which has good strength and heat resistance, and also has good easy tearability like cellophane.

[0016]

Means for Solving the Problems As a result of intensive studies to solve such problems, the present inventors have found that a crystalline polyester resin layer and an amorphous polyester resin layer are laminated at a specific thickness composition ratio. By providing a vapor-deposited thin film layer made of an inorganic oxide on the laminated film, a film that can be easily torn by hand is obtained while maintaining strength and processability as a packaging material, and the obtained laminated film is They have found that they are transparent and have excellent gas barrier properties and have reached the present invention.

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% with respect to the total thickness of the laminated polyester film, and the end is torn. An easily tearable film having excellent gas barrier properties, characterized in that a vapor-deposited thin film layer made of an inorganic oxide 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 composed of a dibasic acid component mainly containing terephthalic acid and a diol component containing 10 to 70 mol% of 1,4-cyclohexanedimethanol. (1) The easily tearable film described. (3) The easily tearable film according to (1) or (2), which has a transparent primer layer between the laminated biaxially stretched polyester film and the vapor deposited thin film layer made of an inorganic oxide. (4) Any one of (1) to (3), wherein a resin layer is laminated and formed on a vapor-deposited thin film layer made of an inorganic oxide formed on at least one surface of the laminated biaxially stretched polyester film. The easily tearable film described in Crab. (5) The easily tearable film according to any one of (1) to (4), wherein the inorganic oxide is aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof. (6) A laminate comprising at least one layer of the easily tearable film according to any one of (1) to (5). (7) A packaging bag using the laminate according to (6).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The amorphous polyester resin used in the present invention refers to a polyester resin that does not substantially show crystallinity. That is, when the resin is left in the temperature range from the glass transition temperature to the melting point, the crystallinity is 5
% Or less of resin. As such an amorphous polyester resin, for example, an amorphous copolymerized polyester obtained by subjecting polyethylene terephthalate to acid modification and / or diol modification is preferable.

The acid modifying component used in the copolymerization is
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,
Dicarboxylic acids such as itaconic acid, citraconic acid, mesaconic acid and cyclohexanedicarboxylic acid, oxycarboxylic acids such as 4-hydroxybenzoic acid, ε-caprolactone and lactic acid, and polyfunctional compounds such as trimellitic acid, trimesic acid and pyromellitic acid. A compound etc. are mentioned. These acid-modified components may be used alone or in combination of two or more.

As the diol-modifying component 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, trimethylolpropane,
Examples thereof include polyfunctional compounds such as glycerin and pentaerythritol. These diol modifying components may be used alone or in combination of two or more.

Among these amorphous polyester resins, from the viewpoints of heat resistance, mechanical properties, transparency, etc., dibasic acid components mainly containing terephthalic acid and 1,4-cyclohexanedimethanol are used in an amount of 10 to 10%. A polyester resin composed of a diol component containing 70 mol% is preferable.

The amorphous 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.

The intrinsic viscosity of the amorphous polyester resin used in the present invention is not particularly limited,
It is preferable to use one having an intrinsic viscosity of about 0.5 to 0.8 at a temperature of 20 ° C. When the intrinsic viscosity is smaller than this, the mechanical properties of the film are deteriorated and drawdown occurs during extrusion molding, which is not preferable. On the other hand, if the intrinsic viscosity is larger than this, the load during extrusion molding becomes large, which is not preferable.

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 the crystalline polyester resin, heat resistance, mechanical properties, good stretchability, and thickness accuracy which cannot be obtained by only the amorphous polyester resin are provided.

As such a crystalline polyester resin, one having a melting point of 230 ° C. or higher is usually used.
A polyester resin having ET as a main skeleton is preferably used. Such a crystalline polyester resin may be copolymerized with other copolymerization components as long as the required properties are not impaired.

As the copolymerization component, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, anhydrous Examples thereof include dicarboxylic acids such as maleic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid and cyclohexanedicarboxylic acid. Further, 4-hydroxybenzoic acid, ε-caprolactone, oxycarboxylic acid such as lactic acid, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,3- Cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,
Examples thereof include glycols such as 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. These copolymerization components may be used alone or in combination of two or more.

The crystalline polyester resin layer 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.

The intrinsic viscosity of the crystalline polyester resin used in the present invention at a temperature of 20 ° C. is not particularly limited, but it is usually preferable to use one having an intrinsic viscosity of about 0.5 to 0.9. When the intrinsic viscosity is smaller than this, the mechanical properties of the film are deteriorated, and the melt viscosity during extrusion molding becomes 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.

In the present invention, the laminated biaxially stretched polyester film must have at least one amorphous polyester resin layer (A) and at least one crystalline polyester resin layer (B). Specific layer structures of the laminated biaxially stretched polyester film include A / B, B / A / B, A / B / A, B / A / B / A / B, and the like. B / A / B is mentioned as a preferable structure.
In addition to the above-mentioned amorphous polyester resin layer and 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 adhesiveness.

In the laminated biaxially stretched polyester film, the thickness composition ratio of the amorphous polyester resin layer must be 20 to 95% of the total thickness, and 30 to 8
It is preferably 5%. The thickness composition ratio here is the 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, the heat resistance, mechanical properties, good stretchability, and thickness accuracy obtained by the contribution of the crystalline polyester layer are impaired, which is not preferable. Further, if 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.

In the present invention, the laminated biaxially stretched polyester film has an edge tear resistance (average value) of 5 to 70 measured according to JIS C 23186.3.4.
N, preferably 10 to 60 N, more preferably 15 to
It is preferably 50N. If the edge tear resistance is larger than this, it becomes difficult to obtain the easy tearing property of the target film, and if it is smaller than this, the strength of the film is too low,
It is not preferable because cutting troubles are likely to occur in the drawing step and the secondary processing steps such as slitting, printing and bag making.

In the present invention, the thickness of the laminated biaxially stretched polyester film is not particularly limited, and as a result, the edge 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 10 to 4
The range of 0 μm is preferable.

In the present invention, the laminated biaxially stretched polyester film is a known various additives such as other polymers, slip agents, inorganic fillers, antioxidants, antistatic agents, etc. within a range that does not impair the effects of the present invention. May be included. From the viewpoint of the anti-blocking property and transparency of the film, the slip agent is 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 mass%.

In the present invention, as a method for producing a laminated biaxially stretched polyester film, an amorphous polyester resin and a crystalline polyester resin are separately melted in a plurality of extruders and the like, and the unstretched film is extruded from a die outlet. The method may include a method in which the unstretched films are laminated to each other 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 another method, there is a method of extruding from a die outlet to form a film in a state of being laminated by a coextrusion method.

Next, an example of a method for producing a laminated biaxially stretched polyester film will be described. Sufficiently dried amorphous polyester resin (A) and crystalline polyester resin (B) are supplied to two separate extruders, melt-extruded, passed through a composite adapter, and passed through a two-layer, two-layer (A / B) or 2
A seed 3 layer (B / A / B) is extruded and discharged in a sheet form from the die orifice of the T die. The softened sheet discharged from the die orifice is closely wound around the cooling drum and cooled. Subsequently, the obtained unstretched sheet is biaxially stretched at a temperature of 90 to 140 ° C. and usually at a stretching ratio of 3.0 to 5.0 times in each length and width. If the stretching temperature is less than 90 ° C, a homogeneous stretched film may not be obtained, and if it exceeds 140 ° C, crystallization of the crystalline polyester resin (B) may be promoted and transparency may deteriorate. . Further, if the stretching ratio is less than 3.0 times, the strength is low, and pinholes are likely to occur when the bag is made into a bag, and if it exceeds 5.0 times, stretching 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 and it is not preferable.

The biaxial stretching method may be either a tenter simultaneous biaxial stretching method, a sequential biaxial stretching method using a roll and a tenter, or a tubular method.

The easily tearable film having excellent gas barrier properties of the present invention is a laminated biaxially stretched polyester film having a vapor-deposited thin film layer formed of an inorganic oxide formed on at least one surface thereof.

Examples of the inorganic oxide constituting the vapor-deposited thin film layer include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof, which has transparency and has a gas barrier property against oxygen, water vapor and the like. The inorganic oxide is not limited as long as it expresses.

The thickness of the vapor-deposited thin film layer made of inorganic oxide is
Optimum conditions vary depending on the type and composition of the inorganic compound used, but it is generally desirable to select in the range of 5 to 500 nm. When the thickness of the thin film layer is less than 5 nm, a uniform thin film may not be obtained or the film thickness may not be sufficient, and the gas barrier property may be insufficient. Also, the film thickness is 5
If it exceeds 00 nm, the film may be curled,
External factors such as bending and pulling tend to cause cracks in the thin film layer. More preferable film thickness is 10 to 150
It is in the range of nm. Examples of the method for forming the above-mentioned vapor-deposited thin film layer include physical vapor deposition methods such as vacuum vapor deposition method, EB vapor deposition method, sputtering method and ion plating method (PV
D) and chemical vapor deposition (CV) such as plasma vapor deposition
D) etc. are mentioned.

In order to improve the adhesion between the vapor-deposited thin film layer and the laminated biaxially stretched polyester film and prevent deterioration of the laminate strength with the passage of time after filling the contents when used as a packaging bag, A transparent primer layer may be provided between the laminated biaxially stretched polyester film.

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, Resins such as ethylene-ethylene 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 0.0
The range of 1 to 2 μm is preferable.

As a method for forming the transparent primer layer, a solution of a primer resin is prepared by a known printing method such as a gravure printing method, an offset printing method, a gravure coating method, or a gravure coating method.
Examples thereof include a method in which a laminated biaxially stretched polyester film is coated using a known coating method such as reverse coating and then dried. The coating and drying conditions may be generally used conditions as long as the performance of the primer resin is not impaired. The solvent that dissolves the primer resin may be any solvent that can dissolve the primer resin, and an organic solvent, an aqueous solvent, or the like can be used alone or as a mixed liquid. Further, the solution of the primer resin may contain other polymer components, curing agents, crosslinking agents, reaction accelerators, silane coupling agents, antioxidants, leveling agents, etc., as long as the required properties are not impaired. Additives may be added. Furthermore, the laminated biaxially stretched polyester film is
In order to improve the adhesion to the transparent primer layer, pretreatment such as corona treatment or low temperature plasma treatment may be performed, and further chemical treatment or solvent treatment may be performed.

In the present invention, it is preferable to provide a resin layer on the vapor-deposited thin film layer from the viewpoint of protecting the vapor-deposited thin film layer from scratches and cracks due to secondary processing and imparting printability.

The resin constituting the resin layer is not particularly limited as long as the above properties are not impaired, and examples thereof include polyester resin, polyurethane resin or polyurethane polyurea resin, ethylene-ethylene vinyl alcohol copolymer, polyvinyl alcohol. And the like.
The thickness of the resin layer is not particularly limited, but is generally in the range of 0.001 to 10 μm, particularly 0.01 to 5
The range of μm is preferred.

As a method for forming the resin layer, a resin solution is deposited by a well-known printing method such as a gravure printing method and an offset printing method, or a known coating method such as a gravure coating and a reverse coating. A method of coating on and drying. The coating and drying conditions are
The conditions generally used may be used as long as the performance of the resin is not impaired. The solvent that dissolves the resin may be any solvent that can dissolve the resin, and an organic solvent, an aqueous solvent, or the like can be used alone or as a mixed liquid. In addition, other polymer components, curing agents, crosslinking agents, reaction accelerators, silane coupling agents, antioxidants, leveling agents, etc. are added to the resin solution as long as the required properties are not impaired. Agents may be added.

The easily tearable film of the present invention can be used as a laminate by printing or laminating, if necessary. The laminated body includes at least one layer of the 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-sealable resin layer can be mentioned.

The heat-sealable resin may be made of the same material as that which has been conventionally used as a sealant layer for packaging materials, for example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer,
An ionomer or the like can be used. The thickness of the heat-sealable resin layer is not particularly limited and can be appropriately selected as needed.

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 a paper.

The laminating method is not particularly limited as long as the easy tearability is not impaired, but a dry laminating method, an extrusion laminating method and the like can be used.

As the constitution of the laminate of the present invention, for example,
The following configurations are available. When the easily tearable film of the present invention is (C), other stretched film or paper is (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 etc. However, in the above configuration, S is S / S
Or an S layer may be present as an adhesive layer between C / D, D / C, C / A and D / D.

At least one easily tearable film of the present invention is used.
A laminated bag including layers can be used to form a packaging bag. The form of the packaging bag is not particularly limited, for example,
Examples include three-sided bags, four-sided bags, pillow bags, gusset bags, stick bags, and the like.

[0053]

〔material〕

PET: Polyethylene terephthalate resin manufactured by Unitika Ltd., intrinsic viscosity 0.67, melting point 256 ° C. AP: Ethylene glycol as a glycol component, terephthalic acid as an acid component, trimellitic acid having a copolymerization ratio of 1 mol%, and isophthalic acid having a copolymerization ratio of 5 mol% were charged in an esterification tank and reacted at 240 ° C. for 4 hours to prepare an ester. The compound was obtained. Next, under antimony trioxide catalyst,
Melt polymerization was carried out at 300 ° C. under a reduced pressure of 1.3 hPa 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, 1,4-cyclohexanedimethanol 31.5 mol% and terephthalic acid, intrinsic viscosity 0.75. APET: Polyester obtained by copolymerizing ethylene glycol, 1,4-cyclohexanedimethanol 3.4 mol% and terephthalic acid, intrinsic viscosity 0.80, melting point 23
4 ° C. IPET: Copolymerized polyester resin IP- manufactured by Unitika Ltd.
11 (terephthalic acid / isophthalic acid 11 mol% and polyester copolymerized with ethylene glycol), intrinsic viscosity 0.67, melting point 211 ° C.

[Primer Layer] Primer (P): Aqueous polyester resin (Besresin AD100 manufactured by Takamatsu Yushi Co., Ltd.) and a melamine crosslinking agent, and an aqueous polyester resin / melamine crosslinking agent = 80.
A mixture of / 20 (mass ratio).

[Resin Layer] Resin (T): Copolyester-based resin (UE-3220 manufactured by Unitika Ltd.) and silane coupling agent, copolyester-based resin / silane coupling agent = 98/2
(Mass ratio) mixed.

[Measurement of Edge Tear Resistance] The edge tear resistance is JIS
It was measured according to C 2318 6.3.4 and the average value was shown. [Measurement of Oxygen Permeability] Using a gas permeability meter (OX-TRAN2 / 20) manufactured by MOCON, measurement was performed at a temperature of 20 ° C. and a humidity of 90% RH. [Evaluation of Easy Tearability] The tearability of the film was evaluated in three stages by tearing the ends of the film sample cut into 100 mm square with both hands. Those that were easily torn by hand were marked with "○", those that were somewhat resistant but could be torn were marked with "△", and those that were very difficult to tear by hand were marked with "x".

Examples 1 to 3 PETG as the resin (A) constituting the amorphous polyester resin layer and PET as the resin (B) constituting the crystalline polyester resin layer were melted by separate extruders at respective temperatures of 270 ° C. Then, the melts are combined with a composite adapter, then extruded from a T die, and rapidly cooled with a cooling drum to produce B.
A three-layer unstretched laminated film having a structure of / A / B was obtained. At this time, in the final laminated polyester film, PET
And the discharge rate of each extruder was adjusted so that the thickness composition ratio of PETG was as shown in Table 1. The unstretched laminated film is first subjected to 3.5 by a roll stretching method at about 90 ° C in the machine direction.
The film was then stretched in the transverse direction at a temperature of about 110 ° C. to 3.8 times by a tenter stretching method, and then heat-treated at a temperature of 225 ° C. while being relaxed by 3% in the transverse direction. After further cooling the film, it is wound into a roll by a winder to obtain a thickness of 12
A laminated biaxially stretched polyester film having a thickness of μm was obtained. Silicon oxide was vapor-deposited on one surface of the obtained laminated biaxially stretched polyester film to a thickness of 50 nm by a vacuum vapor deposition method to form an inorganic oxide thin film layer to obtain an easily tearable film.

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 the temperature was 140 ° C.
And dried for 30 seconds. Silicon oxide was vapor-deposited on the primer P by a vacuum vapor deposition method to a thickness of 50 nm to form an inorganic oxide thin film layer, and an easily tearable film was obtained.

Example 5 Silicon oxide was deposited on one surface of the laminated biaxially stretched polyester film of Example 2 to a thickness of 50 nm by a vacuum deposition method to form an inorganic oxide thin film layer. A resin T solution was applied onto the thin film layer by a gravure coating method so that the thickness after drying was 1.0 μm, and dried at 120 ° C. for 30 seconds to obtain an easily tearable film.

Example 6 A laminated biaxially stretched polyester film having a thickness of 12 μm was obtained by the same method, conditions and thickness constitution as in Example 2 except that PET was changed to AP. Silicon oxide was vapor-deposited on one surface of this film to a thickness of 50 nm by a vacuum vapor deposition method to obtain an easily tearable film having an inorganic oxide thin film layer formed thereon.

Comparative Example 1 Using the same raw materials and method as in Example 1, the thickness constitution of each B / A / B layer was changed to 5/2/5 to obtain a laminated biaxially stretched polyester film having a thickness of 12 μm. Silicon oxide was vapor-deposited to a thickness of 50 nm on one surface of this film by a vacuum vapor deposition method to form an inorganic oxide thin film layer.

Comparative Example 2 A laminated biaxially stretched polyester film having a thickness of 12 μm was obtained under the same method, conditions and thickness constitution as in Example 2, except that PETG was changed to APET. Silicon oxide is vapor-deposited on one side of this film to a thickness of 50 nm by a vacuum vapor deposition method,
An inorganic oxide thin film layer was formed.

Comparative Example 3 A laminated biaxially stretched polyester film having a thickness of 12 μm was obtained under the same method, conditions and thickness constitution as in Example 2, except that PETG was changed to IPET. Silicon oxide is vapor-deposited on one side of this film to a thickness of 50 nm by a vacuum vapor deposition method,
An inorganic oxide thin film layer was formed.

Table 1 shows the thickness constitution of each B / A / B layer of the obtained film and the evaluation results.

[0065]

[Table 1]

As shown in Table 1, the films obtained in the examples are excellent in easy tearing property and gas barrier property, and have no trouble such as breakage during film formation, slitting, vapor deposition processing, and good productivity. there were. On the other hand, the film of Comparative Example had a gas barrier property, but was inferior in tearability.

[0067]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to industrially easily provide a film excellent in transparency, gas barrier property and easy tearability, which is suitably used as a packaging material for packaging, particularly food packaging. It is possible.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 14/08 C23C 14/08 A D // C08L 67:00 C08L 67:00 F term (reference) 3E086 AB02 AC22 AD30 BA04 BA15 BA33 BA40 BB05 BB22 BB90 CA01 4F006 AA35 AB74 BA05 CA07 DA01 4F100 AA17C AA19C AA20C AA28C AK41A AK41E EJ42 JA38EJ3838 EJ41BEJB38E20EBAE E38E20EBAE EBAE EBAE EBAE EBAHBA10CBA10D JA11E JA12A JA12D JD02 JJ03 JK01 JK03 JM02C JM02E JN01 4K029 AA11 AA25 BA43 BA44 BA47 BA64 BC00 BD00

Claims (7)

[Claims] 1. At least one amorphous polyester resin layer and at least one crystalline polyester resin layer, wherein the thickness of the amorphous polyester resin layer is 20 to 95% of the total thickness of the laminated polyester film, and Edge tear resistance is 5
An easily tearable film having excellent gas barrier properties, wherein a vapor-deposited thin film layer made of an inorganic oxide is formed on at least one surface of a laminated biaxially stretched polyester film of 70N. 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 easily tearable film according to claim 1. 3. A laminated biaxially stretched polyester film,
The easily tearable film according to claim 1 or 2, which has a transparent primer layer between the vapor-deposited thin film layer made of an inorganic oxide and the transparent primer layer. 4. The resin layer is laminated on a vapor-deposited thin film layer made of an inorganic oxide formed on at least one surface of the laminated biaxially stretched polyester film. The easily tearable film described in Crab. 5. The easily tearable film according to claim 1, wherein the inorganic oxide is aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof. 6. A laminate comprising at least one layer of the easily tearable film according to claim 1. 7. A packaging bag using the laminate according to claim 6.