JP5055660B2 - Gas barrier film - Google Patents

Description

【００６０】
表１から明らかなように、実施例１〜５で得られたガスバリア性フィルムは、いずれも蒸着後の平面性、引裂き性、ガスバリア性が実用上問題ないレベル以上であり、その中でも実施例１、２、４は良好であり、特に実施例1は非常に良好なフィルムであった。しかし、比較例１、２、３、４では製膜時に破断が多発したり、得られたガスバリア性フィルムは蒸着後の平面性、引裂き性が不良であった。
【００６１】
【発明の効果】
以上の説明で明らかなように、本発明のポリエステル系ガスバリア性フィルムは、蒸着後の平面性、引裂き性およびガスバリア性が良好であり、生鮮食品、加工食品、医療品、医療機器、電子部品等の包装用フィルムに有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stretched polyester film. More specifically, fresh foods and processing that maintain good practical properties without losing the excellent properties of stretched polyester film such as heat resistance, fragrance retention, and water resistance, and have good tearing and twisting properties. The present invention relates to a gas barrier film or sheet (hereinafter, collectively referred to as a gas barrier film) having excellent gas barrier properties and moisture resistance, which are important characteristics in packaging films for foods, medical products, medical devices, electronic parts and the like.
[0002]
[Prior art]
In recent years, food packaging has changed dramatically due to changes in food distribution and eating habits, and the required characteristics of packaging films and sheets (hereinafter collectively referred to as films) have become increasingly severe. Yes.
[0003]
Degradation of product quality due to the effects of temperature, moisture, oxygen, ultraviolet rays, and microorganisms such as bacteria and fungi in the distribution and sales process not only causes a loss in sales but is also a major problem from the viewpoint of food hygiene. Conventionally, antioxidants and preservatives have been added directly to food as a method to prevent such quality degradation. Recently, however, regulations on food additives have become stricter from the standpoint of consumer protection. Reduction or no addition is required.
[0004]
In other words, in the packaging of fish meat, livestock meat, shellfish, etc., it is important to maintain the taste and freshness by suppressing the oxidation and alteration of proteins and fats and oils. To that end, use packaging materials with good gas barrier properties. Therefore, it is desirable to block air permeation. In addition, packaging with a packaging material with good gas barrier properties retains the aroma of the contents and also prevents moisture permeation, so moisture absorption deterioration is suppressed in dry products, and in the case of water-containing products, alteration due to moisture volatilization and Solidification is suppressed, and a fresh flavor during packaging can be maintained for a long time.
[0005]
For these reasons, paste films such as kamaboko, dairy products such as butter and cheese, miso, tea, coffee, ham and sausages, instant foods, instant foods, castella, biscuits and other confectionery packaging films have gas barrier properties and moisture resistance. This is an extremely important characteristic. These properties are not limited to food packaging films, but are also extremely important as packaging films for medical products that require aseptic handling or electronic components that require rust prevention.
[0006]
As a film excellent in gas barrier properties, a film obtained by laminating a metal foil such as aluminum on a plastic film, or a film coated with vinylidene chloride or an ethylene vinyl alcohol copolymer is known.
[0007]
As a form actually used, the above-mentioned gas barrier film is provided with a print layer and further a sealant layer on the printed layer by an adhesive, by a dry laminate method, or a sealant layer by an extrusion laminate method, etc. Create a laminate and use it to create a bag and fill the contents, then heat-sealing the opening and packaging, for example, seasonings such as miso and soy sauce, water-containing foods such as soup and retort foods, and medicines Provided to general consumers.
[0008]
The following problems have been pointed out in the conventional gas barrier laminate films as described above. A metal foil laminated as a gas barrier layer is excellent in economic efficiency and gas barrier properties, but is opaque, so that the contents cannot be seen when it is packaged, and it cannot be processed by a microwave oven because it does not transmit microwaves. Also, those coated with vinylidene chloride or an ethylene vinyl alcohol copolymer do not have sufficient gas barrier properties against water vapor, oxygen, etc., and the performance deterioration due to high temperature treatment is particularly remarkable. Moreover, regarding vinylidene chloride, there is a concern that air pollution may be caused by generation of chlorine gas during incineration.
[0009]
In order to solve such a problem, a gas barrier film in which an inorganic vapor deposition layer such as silicon oxide or aluminum oxide is formed as a gas barrier layer has been proposed. Conventionally, a polyester film having good dimensional stability has been used as a base film on which silicon oxide, aluminum oxide or the like is deposited.
[0010]
However, since a normal polyester film does not have cutability or sag when used as a packaging bag, it is difficult to open the bag, or it is difficult to fold and store the opened bag.
[0011]
[Problems to be solved by the invention]
The present invention is intended to solve the above-mentioned problems, and its purpose is to have excellent transparency, gas barrier properties, adhesiveness, and excellent properties of stretched polyester film. Another object of the present invention is to provide a polyester-based gas barrier film that maintains practical properties without losing water resistance and the like, and has good tearability and twistability.
[0012]
[Means for Solving the Problems]
(1) A polyester resin having a melting point higher by 10 ° C. or more than the melting point of the polyester resin layer (A) on at least one surface of the polyester resin layer (A) and having a thickness of 5% or more and 60% or less with respect to the total thickness. Base polyester obtained by heat-treating an unstretched laminated film on which layer (B) is laminated at least uniaxially stretched at a temperature not lower than the melting point of polyester resin layer (A) by 10 ° C or more and lower than the melting point of polyester resin layer (B) A gas barrier film comprising an inorganic vapor-deposited layer formed on one or both B layers of a film.
(2) The gas barrier film according to claim 1, wherein the maximum value of the heat shrinkage in the longitudinal direction at 150 ° C. in the width direction of the base polyester film is 5.0% or less.
(3) The difference between the maximum value and the minimum value of the thermal shrinkage in the longitudinal direction at 150 ° C. in the width direction of the base polyester film is 1.0% or less. Gas barrier film.
(4) The gas barrier film according to any one of claims 1 to 3, wherein the inorganic vapor deposition layer is a layer containing silicon oxide, aluminum oxide or a mixture thereof.
(5) The gas barrier film according to claim 4, wherein the content of aluminum oxide in the inorganic vapor deposition layer is 5% by weight or more and 45% by weight or less.
[0013]
The gas barrier film of the present invention having the above constitution is a polyester-based gas barrier film having excellent gas barrier properties and adhesiveness in an actual use form, and excellent in cutability and sag properties.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the gas barrier film of the present invention will be described in detail.
[0015]
(Base material polyester film)
In the present invention, the polyester film as a substrate has a melting point higher by 10 ° C. or more than the melting point of the polyester resin layer (A) on at least one side of the polyester resin layer (A), and has a total thickness. An unstretched laminated film in which a polyester resin layer (B) having a thickness of 5% or more and 60% or less is laminated is at least 10 ° C. lower than the melting point of the polyester resin layer (A) after uniaxial stretching, and the polyester resin layer (B The polyester film has good tearability and twistability, and is heat-treated at a temperature lower than the melting point.
[0016]
That is, in the present invention, after stretching polyester laminated films having different melting points, the temperature is 10 ° C. lower than the melting point of the polyester (A) having a low melting point and less than the melting point of the polyester (B) having a high melting point. By carrying out heat treatment at a temperature, the polyester (A) layer loses its orientation in the stretching process and maintains the properties of the polyester resin such as heat resistance, transparency, water resistance, fragrance retention, and tearability and twist fixability. The polyester film is formed by forming a layered film having two different characteristics, that is, the polyester (B) layer constitutes a layer having excellent characteristics such as heat resistance inherent in the polyester film with the orientation maintained. Polyester with contradictory properties of having excellent tear properties and twist fixability while having excellent properties Found that film is obtained, and have completed the present invention.
[0017]
The polyester used in the polyester resin layer (B) of the present invention is not particularly limited, and examples thereof include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymers mainly composed of these components. . The polyester used in the polyester resin layer (A) is preferably a copolymer having a melting point that is 10 ° C. or more, preferably 20 ° C. or more lower than the melting point of the polyester used in the polyester resin layer (B).
[0018]
Moreover, the thickness of the polyester resin layer (B) is 5% or more and 60% or less, preferably 5% or more and 30% or less, more preferably 5% or more and 15% or less of the total thickness. When the thickness of the polyester resin layer (B) is less than 5% of the total thickness, the strength of the resulting film is lowered, which impedes practical use. On the other hand, when the thickness of the polyester resin layer (B) exceeds 60% of the total thickness, the intended tearability and twistability are lowered. Further, the polyester resin layer (A) and the polyester resin layer (B) may be laminated in a three-layer (B / A / B) or two-layer (B / A) configuration. Further, the thickness of the stretched film is not particularly limited, although the thickness of the film used in the packaging bag or the like which is the intended use of the present invention is 12 to 100 μm.
[0019]
Furthermore, in the present invention, the maximum value of the thermal shrinkage rate at 150 ° C. of the polyester film is preferably 5.0% or less, and more preferably 3.0% or less. When the thermal shrinkage rate at 150 ° C. is larger than 5.0%, the flatness may be disturbed when the inorganic vapor deposition layer is formed, which is not preferable.
[0020]
In the present invention, the difference between the maximum value and the minimum value of the heat shrinkage rate at 150 ° C. in the width direction of the polyester film is preferably 1.0% or less, and more preferably 0.5% or less. If the thermal shrinkage at 150 ° C. in the width direction is larger than 1.0%, the flatness may be disturbed when forming the inorganic vapor deposition layer, which is not preferable.
[0021]
The polyester film of the present invention may be added with various known additives such as lubricants, pigments, antioxidants, antistatic agents, etc., as long as the effects of the present invention are not impaired.
[0022]
The unstretched laminated film here refers to a method of laminating unstretched films that are melted separately at a temperature equal to or higher than the melting point and extruded from a die outlet in a plurality of extruders and the like in a heated state. It is done. As another method, there is a method of melt laminating the other molten film on the surface of one unstretched film. As another method, there is a method of forming an unstretched film by extruding from a die outlet in a state of being laminated by a coextrusion method.
[0023]
Next, an example of the manufacturing method of this invention film is demonstrated. Vacuum-dried polyester resin (A) and polyester resin (B) are supplied to two different extruders, melt extruded at a temperature equal to or higher than their melting points, passed through a composite adapter, and two types and three layers (B / A / B) or 2 types and 3 layers (B / A / B), extruded from the die and cooled and solidified to form an unstretched laminated film.
[0024]
The unstretched laminated film thus obtained is uniaxially stretched or biaxially stretched at a temperature higher than the secondary transition point of the polyester resin (A) and the polyester resin (B) and lower than the melting point of the polyester resin (A). Axial stretching is performed. In the case of uniaxial stretching, it is at least 1.5 times or more, preferably 3 to 5 times, and in the case of biaxial stretching, the stretching area is 2 to 30 times, preferably 9 to 16 times. In the case of biaxial stretching, sequential stretching or simultaneous stretching may be used.
[0025]
This stretched film is heat-treated at a temperature higher than the melting point of the polyester resin layer (A) and lower than the melting point of the polyester resin layer (B). In this heat treatment, it goes without saying that a relaxation treatment may be performed as necessary.
[0026]
The polyester resin layer (A) is almost completely collapsed by stretching due to the previous heat treatment, and the tearing and twisting properties of the present invention are obtained, and the polyester resin layer (B) maintains the molecular orientation. It is believed that a film having the characteristics of the present invention is obtained.
[0027]
As described above, the polyester film used in the present invention is composed of a layer that imparts tearing and twisting properties in which the molecular orientation is almost destroyed by the heat treatment in the film production line, and a layer that has the inherent characteristics of polyester that maintains the molecular orientation. It has the advantage that the desired film properties can be set freely by the balance, and the molecular orientation is maintained.
Due to the presence of the layer, there is an advantage that it is possible to prevent breakage troubles in film formation.
[0028]
However, variation in the relaxed state of alignment in the width direction and longitudinal direction is likely to occur with heat treatment, and tearing and twisting properties are not sufficient, or variation is likely to occur. At the same time, the heat shrinkage rate may not be sufficiently reduced or the variation may increase. Therefore, the heat treatment temperature is not only higher than the temperature lower by 10 ° C. than the melting point of the polyester resin layer (A) and lower than the melting point of the polyester resin layer (B), but also in the tenter from the beginning of the transverse stretching to the end of the heat treatment. It is desirable that the difference in the maximum temperature in the film width direction is 10 ° C. or less, preferably 5 ° C. or less, more preferably 3 ° C. or less.
[0029]
(Inorganic vapor deposition layer)
An inorganic vapor deposition layer which is a gas barrier layer is formed on one or both A layers of the base ester film. The said inorganic vapor deposition layer contains a silicon oxide, aluminum oxide, magnesium oxide, these mixtures, etc. In the present invention, silicon oxide is composed of a mixture of various silicon oxides such as SiO and SiO2, aluminum oxide is composed of a mixture of various aluminum oxides such as AlO and Al2O3, and magnesium oxide is various materials such as MgO. It consists of a mixture of magnesium oxide. The amount of oxygen bound in each oxide varies depending on the respective production conditions.
[0030]
In particular, an inorganic vapor deposition layer containing a mixture of aluminum oxide and silicon oxide is transparent, and can impart excellent gas barrier properties that can withstand a boil treatment, a retort treatment, or a gelbo test (flexibility test). Particularly preferred as a gas barrier layer. In this case, the content of aluminum oxide in the inorganic vapor deposition layer is preferably 20% by weight to 90% by weight, more preferably 25% by weight to 80% by weight, and particularly preferably 30% by weight to 75% by weight. is there. If the aluminum oxide content is less than 20% by weight, lattice defects may occur in the inorganic vapor deposition layer and sufficient gas barrier properties may not be obtained. Conversely, if it exceeds 90% by weight, the flexibility of the inorganic vapor deposition layer When the gas barrier film is boiled, the dimensional change of the base polyester film tends to cause destruction (cracking or peeling) of the inorganic vapor-deposited layer, which may reduce the gas barrier property.
[0031]
In the above case, a trace amount (up to 3% by weight) of other oxides may be included in addition to aluminum oxide and silicon oxide as long as the characteristics are not impaired.
[0032]
The thickness of the inorganic vapor deposition layer is usually 10 to 5000 mm, preferably 50 to 2000 mm. If the film thickness is less than 10 mm, it is difficult to obtain satisfactory gas barrier properties, and even if the thickness exceeds 5000 mm, the corresponding gas barrier property improvement effect cannot be obtained, but in terms of bending resistance and manufacturing cost, Disadvantageous.
[0033]
For the production of the inorganic vapor deposition layer, a vacuum vapor deposition method, a sputtering method, a physical vapor deposition method such as an ion plating method, or a chemical vapor deposition method such as CVD is appropriately used. For example, when the vacuum deposition method is employed, a mixture of SiO2 and Al2 O3 or a mixture of SiO2 and Al is used as a deposition material. For heating, resistance heating, induction heating, electron beam heating, etc. can be adopted, oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor, etc. are introduced as reaction gases, ozone addition, ion assist, etc. It is also possible to employ reactive vapor deposition using these means. Further, the film forming conditions can be arbitrarily changed, such as applying a bias to the base polyester film, heating, or cooling. The vapor deposition material, reaction gas, substrate bias, heating / cooling, and the like can be similarly changed when a sputtering method or a CVD method is employed.
[0034]
The gas barrier property of the gas barrier film is greatly related to the adhesion strength between the base polyester film and the inorganic vapor-deposited layer. The greater the adhesion strength, the better the gas barrier property. And according to the results of the study by the present inventors, in order to have an excellent gas barrier property and maintain the excellent gas barrier property even after the boil treatment, after the boil treatment for 30 minutes in 95 ° C. hot water. It has been confirmed that the adhesion strength should be 100 g / 15 mm or more, preferably 150 g / 15 mm or more, more preferably 200 g / 15 mm or more, and particularly preferably 250 g / 15 mm or more. When the adhesion strength is less than 100 g / 15 mm, the gas barrier property tends to deteriorate due to the boil treatment or the retort treatment. The reason for this is considered to be that if the adhesion strength is high, the inorganic vapor-deposited layer is unlikely to peel even if the base polyester film is slightly shrunk by the boil treatment or retort treatment.
[0035]
As a means for obtaining such excellent adhesion strength, the surface of the base polyester film is subjected to corona treatment, flame treatment, plasma treatment, glow discharge treatment, reverse sputtering treatment, rough surface before the formation of the inorganic vapor deposition layer. There are methods such as applying a treatment or forming an adhesion-modified layer on the base polyester film, and among these, formation of the adhesion-modified layer is preferable from the viewpoint of durability of the adhesive force.
[0036]
When a coating solution is applied to the biaxially stretched base polyester film to form the above-mentioned adhesion modified layer, the adhesion modification between the base polyester film and the adhesive modified layer is further improved. The base polyester film may be subjected to surface treatment by corona treatment, flame treatment, electron beam irradiation or the like before the formation of the quality layer.
[0037]
The adhesion modified layer has good adhesion to various materials, and in the present invention, an inorganic vapor deposition layer may be formed thereon, but in order to further improve the adhesion, before forming the inorganic vapor deposition layer, The adhesion modified layer may be further subjected to surface treatment by corona treatment, flame treatment, electron beam irradiation or the like.
[0038]
In actual use, on the surface of the inorganic vapor-deposited layer, a heat seal layer made of a polyolefin resin mainly for imparting thermal adhesiveness is formed. Examples of the polyolefin resin constituting the heat seal layer include LDPE, LLDPE, and CPP. The heat seal layer does not necessarily have to be a single layer, and may be a multilayer. The resin constituting each layer in the multilayer structure is not only a combination of the same type of resin, but also a copolymer of different polymers, It may be a laminate of a modified product, a blended product, or the like. For example, in order to improve the laminating property and heat sealing property, a polymer having a glass transition temperature (Tg) or a melting point lower than that of the thermoplastic polyolefin-based resin as a base is blended. It is also possible to blend high polymers.
[0039]
In the resin composition constituting the heat seal layer, various additives as necessary, for example, plasticizer, heat stabilizer, ultraviolet absorber, antioxidant, colorant, filler, antistatic agent, antibacterial agent, It is also possible to blend a lubricant, an anti-blocking agent, other resins and the like.
[0040]
The heat sheet layer may be formed as a heat seal layer on the inorganic resin layer by a dry lamination method or a wet lamination method using an adhesive, or a melt extrusion lamination method or a coextrusion lamination method. The layer also has a function as a protective layer for the inorganic vapor-deposited layer, and in order to effectively perform the function, it is extremely effective to increase the adhesive force between the inorganic vapor-deposited layer and the heat seal layer. As a means, it is extremely effective to provide an adhesive layer between the inorganic vapor deposition layer and the heat seal layer.
[0041]
As a resin constituting the adhesive layer, a resin having a glass transition temperature in the range of −10 ° C. to 50 ° C., for example, polyurethane resin, polyester resin, epoxy resin, vinyl chloride resin, vinyl acetate resin, polyethylene resin Polypropylene resin, melamine resin, acrylic resin and the like are preferable, and these may be used alone or in combination of two or more. In addition, a carboxyl group, an acid anhydride group, a compound having a (meth) acrylic acid or (meth) acrylic acid ester skeleton; an epoxy compound having a glycidyl group or a glycidyl ether group; an oxazoline group, an isocyanate group, an amino group, a hydroxyl group, etc. It is also effective to use an adhesive composition containing a curing agent or a curing accelerator having a reactive functional group.
[0042]
The gas barrier film of the present invention thus obtained makes use of its excellent gas barrier property, cut property, and hineri property, and is made with miso, pickles, prepared dishes, baby food, boiled, konjac, chikuwa, rice cake, processed fishery products, meatballs, hamburger steak , Genghis Khan, ham, sausage, other processed meat products, tea, coffee, tea, bonito, kelp, potato chips, butter peanuts, etc., rice crackers, biscuits, cookies, cakes, buns, castella, cheese, butter, It can be effectively used as a packaging material for chopped rice cakes, soups, sauces, ramen, wasabi, etc., medicines, toothpastes, etc., for pet food, agricultural chemicals, fertilizers, infusion packs, semiconductors and precision materials Effective use for materials and packaging materials for industrial materials such as medicine, electronics, chemistry, and machinery Door can be.
[0043]
The form of the packaging material is not particularly limited, and can be widely applied to bags, lid materials, cups, tubes, standing packs, and the like.
[0044]
【Example】
Next, the present invention will be specifically described with reference to examples. The present invention is of course not limited by the following examples, and can of course be implemented with appropriate modifications within a range that can be adapted to the gist of the preceding and following descriptions, all of which are within the technical scope of the present invention. Is included. Moreover, the various performance tests employ | adopted by the following Example were done with the following method.
[0045]
1. Oxygen permeability
An oxidative permeability measuring device (“OX-TRAN 10/50” manufactured by Modern Controls) was used, and the measurement was performed at a temperature of 23 ° C. and a humidity of 65% RH.
[0046]
2. Heat shrinkage
A sample with a width of 10 mm and a length of 250 mm is cut out in the longitudinal direction of the film, marked at intervals of 200 mm, and the interval A is measured with a constant tension of 5 g. Subsequently, it was left in an oven in an atmosphere at 150 ° C. for 30 minutes with no load. After taking out from the oven and cooling to room temperature, the interval B was obtained with a constant tension of 5 g, and the thermal shrinkage rate was obtained by the following equation. The measurement was performed by cutting out samples from five locations at equal intervals in the width direction of the film, and determining the maximum value and variation (difference between the maximum value and the minimum value).
Thermal contraction rate = (A−B) / A × 100 (%)
[0047]
3. Flatness after deposition
The film was sent to a vacuum deposition apparatus, the inside of the chamber was maintained at a pressure of 1 × 10 −5 Torr, and a mixed oxide of 70% by weight of SiO 2 and 30% by weight of Al 2 O 3 was evaporated by heating with an electron beam of 15 kw. A colorless and transparent inorganic vapor deposition layer was formed on the adhesion modified layer. The film after vapor deposition was unwound from a roll, the flatness of the film was visually observed, and from the state of lamination of the heat-sealable resin in the evaluation of tearability, the following four-step evaluation was performed.
: Even when tension is not applied, the flatness is good, and there is no problem with bonding.
○: When a slight tension is applied to the film, the flatness is good, and there is no problem with the bonding.
: Even if tension is applied, the flatness is slightly disturbed, but there is no problem with the bonding.
X: Even if tension is applied, there is a problem in practical use because there is a disorder in flatness.
[0048]
4). Tearability
A linear low density polyethylene film (thickness 40 μm, L4102 manufactured by Toyobo Co., Ltd.) is used as a heat-sealable resin on the inorganic vapor-deposited layer of a polyester-based gas barrier film having a thickness of 20 μm, and an isocyanate adhesive (Toyo Morton Co., Ltd.). TM590 / CAT56) manufactured was applied with a dry thickness of 3 g / m 2 and adhered. After aging at 40 ° C. for 3 days, the resulting laminate was heat-sealed (sealing conditions: 160 ° C. × 1 kg × 2 seconds) to prepare an 80 × 120 mm packaging bag. Sensory evaluation was conducted on the cut ability when the bag was torn by hand without making a notch.
[0049]
Example 1
A copolymer of polyethylene isophthalate and polyethylene terephthalate (A) having a melting point of 218 ° C. and polyethylene terephthalate (B) having a melting point of 265 ° C. containing 1000 ppm of silica particles having an average particle diameter of 1.5 μm at a temperature of 285 ° C. After being melted by separate extruders, this melt is joined by a composite adapter, extruded from a T die, and rapidly cooled by a cooling drum at 30 ° C. (B / A / B) to obtain a three-layer unstretched laminated film It was.
[0050]
The unstretched laminated film is first preheated to 95 ° C. using a metal roll, further heated using three infrared heaters having a surface temperature of 750 ° C., stretched 1.5 times at 115 ° C. in the longitudinal direction, and further rolled. After cooling and a film temperature of 95 ° C., the film was stretched 3 times in the machine direction. Next, the film was preheated to 110 ° C. in a tenter, stretched 4.0 times while raising the temperature from 110 ° C. to 150 ° C., and then stretched 1.1 times while raising the temperature to 223 ° C. Then, heat treatment was performed while keeping the width direction constant, and then a relaxation treatment of 3% was performed in the width direction while cooling from 223 ° C. to 150 ° C. to obtain a 20 μm film. The amount of hot air blown in the width direction in the tenter was adjusted, and the difference in the maximum temperature in the width direction in the tenter in the stretching process from the lateral stretching was 3 ° C. The thickness ratio of each B / A / B layer of this film was 4/92/4. This film was free of troubles such as breakage during film formation and slitting, and the productivity was good.
Table 1 shows the obtained film, the evaluation results after vapor deposition and processing.
[0051]
(Example 2)
In Example 1, except having changed only the thickness ratio of B / A / B each layer into 8/84/8, it carried out exactly like Example 1 and the gas barrier film was obtained.
[0052]
(Example 3)
In Example 1, except having changed only the thickness ratio of each B / A / B layer into 16/68/16, it carried out exactly like Example 1 and the gas-barrier film was obtained.
[0053]
(Comparison column 1)
In Example 1, except having changed only the thickness ratio of each B / A / B layer into 40/20/40, it carried out exactly like Example 1 and the gas-barrier film was obtained.
[0054]
(Comparative Example 2)
In Example 1, it carried out exactly like Example 1 except having changed only the thickness ratio of each B / A / B layer into 1/98/1. This film had poor productivity due to frequent breakage during film formation and slitting. Therefore, a film was not obtained, and vapor deposition processing and evaluation could not be performed.
[0055]
(Comparative Example 3)
A 25 μm film was obtained in the same manner, with the same conditions and thickness ratio as in Example 1, except that the copolymer (A) of polyethylene isophthalate and polyethylene terephthalate having a melting point of 245 ° C. was used. This film was free of troubles such as breakage during film formation and slitting, and the productivity was good.
[0056]
(Comparative Example 4)
Stretched 4.0 times while raising the temperature from 110 ° C to 150 ° C in the transverse direction, then stretched 1.1 times while raising the temperature to 200 ° C, and heat-treated at 200 ° C while keeping the width direction constant. After that, a gas barrier film was obtained in exactly the same manner as in Example 1 except that a 3% relaxation treatment was performed while lowering the temperature from 200 ° C to 150 ° C. Here, the difference in the maximum temperature in the width direction was 3 ° C. This film was free of troubles such as breakage during film formation and slitting, and the productivity was good.
[0057]
Example 4
Except that the amount of hot air blown out in the width direction in the tenter was adjusted, and the difference in the maximum temperature in the width direction in the tenter in the stretching process from the lateral stretching was changed to 6 ° C., it was carried out in exactly the same manner as in Example 1. This film was free of troubles such as breakage during film formation and slitting, and the productivity was good.
[0058]
(Example 5)
The same procedure as in Example 1 was performed except that the amount of hot air blown in the width direction in the tenter was adjusted, and the difference in the maximum temperature in the width direction in the tenter between the transverse stretching and the relaxation treatment was 12 ° C. This film was free of troubles such as breakage during film formation and slitting, and the productivity was good.
[0059]
[Table 1]

[0060]
As is apparent from Table 1, the gas barrier films obtained in Examples 1 to 5 are all at or above the level at which there is no practical problem in flatness, tearability, and gas barrier properties after vapor deposition. 2, 4 were good, and in particular, Example 1 was a very good film. However, in Comparative Examples 1, 2, 3, and 4, breakage occurred frequently during film formation, and the obtained gas barrier film had poor flatness and tearability after vapor deposition.
[0061]
【Effect of the invention】
As is clear from the above description, the polyester-based gas barrier film of the present invention has good flatness, tearability and gas barrier properties after vapor deposition, such as fresh foods, processed foods, medical products, medical devices, electronic parts, etc. It is useful for packaging films.

Claims (4)

A polyester resin layer (B) having a melting point higher by 10 ° C. or more than the melting point of the polyester resin layer (A) on at least one surface of the polyester resin layer (A) and a thickness of 5% or more and 60% or less with respect to the total thickness. ) Is a temperature not lower than the melting point of the polyester resin layer (A) by 10 ° C. and lower than the melting point of the polyester resin layer (B) , and the difference in the maximum temperature in the film width direction. Is formed on one or both polyester resin layers (B) of the base polyester film heat-treated at a temperature of 10 ° C. or lower, and the base polyester film at 150 ° C. in the width direction is formed. A gas barrier film, wherein a difference between a maximum value and a minimum value of heat shrinkage in the longitudinal direction is 1.0% or less.   2. The gas barrier film according to claim 1, wherein the maximum value of the thermal shrinkage in the longitudinal direction at 150 ° C. in the width direction of the base polyester film is 5.0% or less. . 3. The gas barrier film according to claim 1, wherein the inorganic vapor deposition layer is a layer containing silicon oxide, aluminum oxide or a mixture thereof.   4. The gas barrier film according to claim 3, wherein the content of aluminum oxide in the inorganic vapor deposition layer is 20% by weight or more and 90% by weight or less.