JP2002307598A - Gas barrier film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas barrier film or sheet of a polyester stretched film or sheet, with practical characteristics without losing the heat resistance, arom a retention, water resistance or the like being the excellent characteristics of the polyester stretched film or sheet, having good tear properties and twist properties and excellent in gas barrier properties or moisture proofness as important characteristics in a packaging film for perishable foods, processed foods, medicines, medical machinery, electronic parts or the like. SOLUTION: The polyester type gas barrier film is constituted by forming an inorganic vapor-deposition layer on the polyester resin layer (B) of a substrate polyesterf film which is obtained by at least uniaxially stretching a non- stretched laminated film, wherein the polyester resin layer (B) having a melting point higher than that of a polyester resin layer (A) by 10 deg.C or higher and having a thickness of 5-60% of the total thickness is laminated on at least the single surface of the polyester resin layer (A), and heat-treating the stretched laminated film at a temperature lower than the melting point of the polyester resin layer (A) by 10 deg.C but below the melting point of the polyester resin layer (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stretched polyester film. More specifically, fresh foods and processed foods that maintain 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 having excellent gas barrier properties and moisture proof properties, which are important properties in packaging films for foods, medical products, medical devices, electronic components, and the like (hereinafter, these are collectively referred to as gas barrier films).

[0002]

2. Description of the Related Art In recent years, food packaging has been drastically changed due to changes in food distribution and dietary habits, and the characteristics required for packaging films and sheets (hereinafter collectively referred to as films) are increasing. It's getting tougher.

[0003] Temperature, moisture, oxygen,
Deterioration of the quality of products due to ultraviolet rays and the influence of microorganisms such as bacteria and mold is a serious problem not only in terms of sales but also in terms of food hygiene. As a method of preventing such quality deterioration, antioxidants and preservatives have been added directly to foods in the past, but in recent years, regulations on food additives have become stricter from the standpoint of consumer protection. Is required to be reduced or not added.

[0004] That is, in the packaging of fish meat, animal meat, shellfish and the like, it is important to suppress the oxidation and deterioration of proteins and oils and fats, and to maintain the taste and freshness. It is desirable to use a material to block air permeation. In addition, packaging with good gas barrier properties retains the fragrance of the contents and prevents the permeation of moisture. Solidification is suppressed, and fresh flavor during packaging can be maintained for a long time.

For these reasons, kneaded products such as kamaboko, dairy products such as butter and cheese, miso, tea, coffee,
In packaging films for confectionery such as ham and sausage, instant food, castella, biscuit, etc., gas barrier properties and moisture resistance are extremely important properties. These characteristics are not limited to the film for food packaging, but are also extremely important as a packaging film for medical products that need to be handled under aseptic conditions or electronic components that require rust prevention.

As a film having excellent gas barrier properties,
Known are those in which a metal foil such as aluminum is laminated on a plastic film, and those in which vinylidene chloride or an ethylene vinyl alcohol copolymer is coated.

In actual use, a sealant layer is provided on the above-mentioned gas barrier film by a dry lamination method via a printing layer and an adhesive, or a sealant layer is provided by an extrusion lamination method. After forming a laminate, filling the contents with the bag and filling the contents, the opening is heat-sealed, for example, a seasoning such as miso or soy sauce, or a water-containing food or chemical such as soup or retort food. It is packaged and provided to general consumers.

The following problems have been pointed out in the conventional gas barrier laminated films as described above. Although a metal foil laminated as a gas barrier layer is excellent in economy and gas barrier properties, it is opaque, so that its contents cannot be seen when packaged, and does not transmit microwaves, so that it cannot be processed by a microwave oven. Also,
Those coated with vinylidene chloride or ethylene vinyl alcohol copolymer do not have sufficient gas barrier properties against water vapor, oxygen and the like, and the performance is particularly deteriorated by high-temperature treatment. In addition, there is a concern that vinylidene chloride may cause air pollution due to generation of chlorine gas at the time of incineration.

In order to solve such a problem, a gas barrier film having an inorganic vapor-deposited layer made of silicon oxide, aluminum oxide or the like as a gas barrier layer has been proposed.
As a substrate film on which silicon oxide, aluminum oxide, or the like is deposited, a polyester film having good dimensional stability has been used.

[0010] However, it is difficult to open the bag with ordinary polyester film due to lack of cutability and twisting property when the bag is used as a packaging bag, or it is difficult to bend the bag once opened and store it. .

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a polyester stretched film having excellent transparency, gas barrier properties and adhesiveness. An object of the present invention is to provide a polyester-based gas barrier film having good tearability and twistability while maintaining practical properties without losing its properties such as heat resistance, fragrance retention, and water resistance.

[0012]

(1) A polyester resin layer (A) is provided on at least one surface of the polyester resin layer (A).
The polyester resin layer (B) having a melting point of 10% or more higher than the melting point of the polyester resin layer (B) having a thickness of 5% or more and 60% or less with respect to the total thickness is subjected to at least uniaxial stretching. The formation of the inorganic vapor-deposited layer on one or both B layers of the base polyester film heat-treated at a temperature of at least 10 ° C. lower than the melting point of A) and lower than the melting point of the polyester resin layer (B). Characteristic gas barrier film. (2) 1 in the width direction of the base polyester film
The gas barrier film according to claim 1, wherein the maximum value of the heat shrinkage in the longitudinal direction at 50 ° C is 5.0% or less. (3) 1 in the width direction of the base polyester film
3. The gas barrier film according to claim 1, wherein the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction at 50 ° C. is 1.0% or less. (4) The gas barrier film according to any one of claims 1 to 3, wherein the inorganic vapor-deposited layer is a layer containing silicon oxide, aluminum oxide, or a mixture thereof. (5) The content of aluminum oxide in the inorganic vapor deposition layer is 5
The gas barrier film according to claim 4, wherein the content is not less than 45% by weight and not more than 45% by weight.

The gas barrier film of the present invention having the above-described structure is a polyester-based gas barrier film having excellent gas barrier properties and adhesive properties in actual use, and excellent in cut properties and twisting properties.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the gas barrier film of the present invention will be described in detail.

(Polyester Ester-Based Film) In the present invention, the polyester-based film as the base material according to the present invention is formed on at least one surface of the polyester resin layer (A) by 10 ° C. below the melting point of the polyester resin layer (A). An unstretched laminated film having a polyester resin layer (B) having a high melting point and having a thickness of 5% or more and 60% or less of the total thickness is at least 10% lower than the melting point of the polyester resin layer (A) after uniaxial stretching. A polyester film excellent in tearing property and twisting property, which has been heat-treated at a temperature not lower than 0 ° C. and lower than the melting point of the polyester resin layer (B).

That is, in the present invention, after stretching a polyester laminated film having a different melting point, the polyester (B) having a higher melting point than the polyester (A) having a lower melting point by 10 ° C. or more than the melting point of the polyester (A) having a lower melting point. By performing the heat treatment at a temperature lower than the melting point, the polyester (A) layer loses its orientation in the stretching step, and tearing and twisting while maintaining properties of the polyester resin such as heat resistance, transparency, water resistance and fragrance retention. A laminated film that constitutes a layer having a fixed property, and the polyester (B) layer constitutes a layer having two kinds of different properties such as a layer having excellent properties such as heat resistance and the like, which is a polyester film maintaining the orientation. Has the contradictory properties of having excellent tearability and twist fixability while maintaining the excellent properties inherent in polyester film. It found that polyester film is obtained, and have completed the present invention.

The polyester used in the polyester resin layer (B) of the present invention is not particularly limited. For example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and copolymers containing these components as main components Etc. The polyester used for the polyester resin layer (A) is preferably a copolymer having a melting point lower than the melting point of the polyester used for the polyester resin layer (B) by 10 ° C. or more, preferably 20 ° C. or more.

The thickness of the polyester resin layer (B) is at least 5% and at most 60%, preferably at least 5% of the total thickness.
The thickness is preferably 30% or less, more preferably 5% or more and 15% or less. If the thickness of the polyester resin layer (B) is less than 5% of the total thickness, the strength of the obtained film will be low, which will hinder practical use. If the thickness of the polyester resin layer (B) exceeds 60% of the total thickness, the desired tearing property and twisting property decrease. The polyester resin layer (A) and the polyester resin layer (B) are laminated in three layers (B
/ A / B) or two layers (B / A). Further, the thickness of the stretched film is set to 1 in the use intended for the purpose of the present invention, such as a packaging bag.
It is 2 μm to 100 μm, but is not particularly limited.

Further, in the present invention, the maximum value of the thermal shrinkage at 150 ° C. of the polyester film is preferably 5.0% or less, more preferably 3.0% or less. If the heat shrinkage at 150 ° C. is more than 5.0%, planarity may be disturbed when forming the inorganic vapor deposition layer, which is not preferable.

In the present invention, the difference between the maximum value and the minimum value of the heat shrinkage at 150 ° C. in the width direction of the polyester film is preferably 1.0% or less, more preferably 0.5% or less. . If the heat 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.

The polyester film of the present invention may contain various known additives such as a lubricant, a pigment, an antioxidant, an antistatic agent and the like as long as the effects of the present invention are not impaired.

The term "unstretched laminated film" as used herein refers to a laminate of unstretched films that are separately melted at a temperature equal to or higher than the melting point in a plurality of extruders or the like, extruded from a die outlet, and formed. Method. As another method, there is a method in which the other molten film is melt-laminated on the surface of one unstretched film. As still another method, there is a method in which an unstretched film is formed by extruding from a die outlet in a state of being laminated by a co-extrusion method.

Next, an example of a method for producing the film of the present invention will be described. The vacuum-dried polyester resin (A) and polyester resin (B) are supplied to two separate extruders, respectively, extruded at a temperature not lower than their melting points, passed through a composite adapter, and passed through a composite three-layer (B). / A / B) or two types and three layers (B / A / B), extruded from a die, cooled and solidified to form an unstretched laminated film.

The unstretched laminated film obtained in this manner is uniaxially heated at a temperature higher than the second transition point of the polyester resin (A) and the polyester resin (B) and lower than the melting point of the polyester resin (A). Stretching or biaxial 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.

The 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.

By the heat treatment, the molecular orientation of the polyester resin layer (A) is almost destroyed by stretching, and the tearing property and twisting property of the present invention are obtained. The polyester resin layer (B) maintains the molecular orientation. Therefore, it is considered that a film having the characteristics of the present invention can be obtained.

As described above, the polyester film used in the present invention has, as described above, a layer that imparts tearing and twisting properties in which the molecular orientation has almost collapsed due to heat treatment in the film-forming line, and a polyester characteristic maintaining the molecular orientation. It has the advantage that the desired film properties can be freely set by the balance of the layers that it has, and also has the advantage that it is possible to prevent breakage troubles in film formation due to the presence of the layer maintaining the molecular orientation.

However, variations in the relaxation state of the orientation in the width direction and the longitudinal direction are apt to occur due to the heat treatment, and the tearing and twisting properties are not sufficient, and the variations are likely to occur. At the same time, the heat shrinkage rate may not be sufficiently reduced, or the dispersion may increase. Therefore, the heat treatment temperature is not less than 10 ° C. lower than the melting point of the polyester resin layer (A) and lower than the melting point of the polyester resin layer (B). The difference in the maximum temperature in the film width direction is 10 ° C or less, preferably 5 ° C.
C. or lower, more preferably 3 ° C. or lower.

(Inorganic Vapor Deposition Layer) An inorganic vapor deposition layer as a gas barrier layer is formed on one or both A layers of the base ester film. The inorganic vapor-deposited layer contains silicon oxide, aluminum oxide, magnesium oxide, a mixture thereof, or the like. In the present invention, silicon oxide is a mixture of various silicon oxides such as SiO and SiO2, aluminum oxide is a mixture of various aluminum oxides such as AlO and Al2 O3, and magnesium oxide is a mixture of various oxides such as MgO. It consists of a mixture of magnesium oxide. The amount of oxygen in each oxide varies depending on the production conditions.

In particular, an inorganic vapor-deposited layer containing a mixture of aluminum oxide and silicon oxide is transparent and can impart excellent gas barrier properties that can withstand boil treatment, retort treatment, or gelbo test (flex resistance test). Particularly preferred as the gas barrier layer in the present invention. in this case,
The content of aluminum oxide in the inorganic vapor deposition layer is preferably 20% by weight or more and 90% by weight or less, more preferably 25% by weight or less.
% By weight to 80% by weight, particularly preferably 30% by weight
Not less than 75% by weight. When the content of aluminum oxide is less than 20% by weight, sufficient gas barrier properties may not be obtained due to lattice defects in the inorganic vapor-deposited layer. When the gas barrier film is boiled, the inorganic polyester layer is likely to be broken (cracked or peeled) due to a dimensional change of the base polyester film, and the gas barrier property may be deteriorated.

In the above case, other oxides and the like may be contained in trace amounts (up to 3% by weight) in addition to aluminum oxide and silicon oxide as long as the characteristics are not impaired.

The thickness of the inorganic vapor-deposited layer is usually from 10 to 50.
00 °, preferably 50 to 2000 °. The film thickness is 1
If it is less than 0 °, it is difficult to obtain a satisfactory gas barrier property, and if it exceeds 5,000 °, the effect of improving the gas barrier property cannot be obtained, and it is disadvantageous in terms of bending resistance and manufacturing cost. .

For the preparation of the inorganic vapor deposition layer, a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method or an ion plating method, or a chemical vapor deposition method such as a CVD method is appropriately used. For example, when a 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, and oxygen, nitrogen, hydrogen, argon, carbon dioxide gas,
It is also possible to adopt reactive vapor deposition using a means such as introduction of water vapor, addition of ozone, or ion assist. Further, the film forming conditions such as applying a bias, heating or cooling the base polyester film can be arbitrarily changed. The above-mentioned deposition material, reaction gas, substrate bias, heating / cooling, and the like can be similarly changed when a sputtering method or a CVD method is adopted.

The gas barrier property of the gas barrier film is largely related to the adhesion strength between the base polyester film and the inorganic vapor-deposited layer, and the gas adhesion property increases as the adhesion strength increases. According to the study results of the present inventors, in order to have excellent gas barrier properties and to maintain the excellent gas barrier properties even after the boil treatment, it is necessary to use 9
Adhesion strength after boiling for 30 minutes in hot water at 5 ° C is 1
00g / 15mm or more, preferably 150g / 15mm
As described above, it has been confirmed that the thickness should be 200 g / 15 mm or more, 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 be deteriorated by boil treatment or retort treatment. It is considered that the reason for this is that if the adhesion strength is high, the inorganic vapor-deposited layer hardly peels off even when the base polyester film slightly shrinks due to the boil treatment or the retort treatment.

Means for obtaining such excellent adhesion strength include corona treatment, flame treatment, plasma treatment, glow discharge treatment, and reverse sputtering treatment on the surface of the base polyester film before forming the inorganic vapor-deposited layer. Or a method of forming an adhesion-modified layer on a base polyester-based film. Among them, the formation of an adhesion-modified layer is preferred from the viewpoint of the durability of the adhesive force.

When the coating liquid is applied to the biaxially stretched base polyester film to form the above-mentioned adhesion-modified layer, the adhesiveness between the base polyester film and the adhesion-modified layer is further improved. Before the formation of the adhesion modifying layer, the base polyester film may be subjected to a surface treatment such as a corona treatment, a flame treatment, and an electron beam irradiation.

The adhesion-modified layer has good adhesion to various materials, and in the present invention, an inorganic vapor-deposited layer may be formed thereon. Before the formation, the adhesion modified layer may be further subjected to a surface treatment such as a corona treatment, a flame treatment, and an electron beam irradiation.

In actual use, on the surface of the above-mentioned inorganic vapor-deposited layer, a heat seal layer mainly composed of a polyolefin-based resin for providing thermal adhesion is formed. Examples of the polyolefin resin constituting the heat seal layer include LDPE, LLDPE, CPP and the like. The heat seal layer does not necessarily have to be a single layer and may be a multilayer, and the resin constituting each layer when forming a multilayer structure, not only a combination of resins of the same kind, but also a copolymer of a different polymer or Modified products, blended products and the like may be laminated. For example, a polymer having a glass transition temperature (Tg) or a melting point lower than that of the thermoplastic polyolefin resin as a base is blended in order to enhance laminating property and heat sealing property, and conversely, a Tg or melting point is added to impart heat resistance. It is also possible to incorporate high polymers.

Various additives such as a plasticizer, a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, a filler,
It is also possible to blend antistatic agents, antibacterial agents, lubricants, antiblocking agents, other resins, and the like.

The heat sheet layer can 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, a melt extrusion lamination method, a coextrusion lamination method, or the like. ,
The heat seal layer also has a function as a protective layer of the inorganic vapor-deposited layer, and in order to effectively perform the function, increasing the adhesive force between the inorganic vapor-deposited layer and the heat seal layer is extremely effective. It is extremely effective to provide an adhesive layer between the inorganic vapor deposition layer and the heat seal layer as a means for achieving this.

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, a polyurethane resin, a polyester resin, an epoxy resin,
Preference is given to vinyl chloride resins, vinyl acetate resins, polyethylene resins, polypropylene resins, melamine resins, acrylic resins and the like, and these may be used alone or in combination of two or more. A compound having a carboxyl group, an acid anhydride group, a (meth) acrylic acid or a (meth) acrylate 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.

The thus obtained gas barrier film of the present invention makes use of its excellent gas barrier properties, cut properties and twisting properties, and is made of miso, pickles, prepared dishes, baby food, boiled tsukudani, konjac, chikuwa, kamaboko, processed fishery products, meat Ball, hamburger, Genghis Khan, ham, sausage,
Other processed meat products, tea, coffee, black tea, bonito, kelp, potato chips, butter peanuts and other oil confections, rice crackers, biscuits, cookies, cakes, buns, castella,
Cheese, butter, rice cake, soup, sauce, ramen,
It can be effectively used as a packaging material for wasabi and other foods, medicines, toothpastes, etc.
It can be effectively used as a fertilizer, an infusion pack, a packaging material for semiconductors and precision materials, and a packaging material for industrial materials such as medical, electronic, chemical, and mechanical.

There is no particular limitation on the form of the packaging material.
It can be widely applied to bags, lid materials, cups, tubes, standing packs and the like.

[0044]

Next, the present invention will be described in detail with reference to examples. The present invention is naturally not limited by the following examples, and it is of course possible to implement the present invention with appropriate modifications within a range that can be adapted to the spirits of the preceding and the following. Is included. Also,
Various performance tests employed in the following Examples were performed by the following methods.

1. Oxygen permeability Oxidation permeability measurement device (“OX-TRAN 10/50”
The measurement was performed at a temperature of 23 ° C. and a humidity of 65% RH.

2. Heat shrinkage A sample of 10 mm in width and 250 mm in length was cut out in the longitudinal direction of the film, marked at 200 mm intervals, and 5 g
The interval A is measured at a constant tension of. Then, it was left in an oven in an atmosphere of 150 ° C. for 30 minutes without load. Remove from oven and cool to room temperature.
Was determined, and the heat shrinkage was determined by the following equation. For the measurement, samples were cut out from five places at equal intervals in the width direction of the film and measured, and the maximum value and the variation (difference between the maximum value and the minimum value) were determined. Heat shrinkage = (AB) / A × 100 (%)

3. Flatness after evaporation The film is sent to a vacuum evaporation device, and the inside of the chamber is 1 × 1
The pressure is maintained at 0-5 Torr, and 70% by weight of SiO2 and A
30% by weight of a mixed oxide of l2 O3 was evaporated by heating with an electron beam of 15 kW, and a colorless and transparent inorganic vapor-deposited layer having a thickness of 200 DEG was formed on the adhesion reforming layer. The film after vapor deposition was unwound from a roll, and the flatness of the film was visually observed, and the following four-stage evaluation was performed based on the state of lamination of the heat sealable resin in the evaluation of tearability. : The flatness is good even without tension, and there is no problem in laminating. ：: Good flatness when a slight tension is applied to the film,
There is no problem with lamination. : Even if tension is applied, the flatness is slightly disturbed, but there is no problem with lamination. X: Even if tension is applied, the flat surface is disturbed and there is a problem in practical use.

4. Tearability A linear low-density polyethylene film (40 μm in thickness, L4102 manufactured by Toyobo Co., Ltd.) is used as a heat-sealing resin on an inorganic vapor-deposited layer of a polyester-based gas barrier film having a thickness of 20 μm. Morton's TM590 / CAT56) was applied at a dry thickness of 3 g / m2 and adhered. After aging at 40 ° C. for 3 days, the obtained laminate was heat-sealed (sealing conditions:
160 ° C × 1kg × 2 seconds) to make 80 × 120mm
Created a packaging bag. The cutability when the bag was torn by hand without notching was sensory evaluated.

Example 1 A copolymer (A) of polyethylene isophthalate and polyethylene terephthalate having a melting point of 218 ° C. and silica particles having an average particle diameter of 1.5 μm were used.
2,000 ppm of polyethylene terephthalate (B) having a melting point of 265 ° C. is melted by a separate extruder at a temperature of 285 ° C., and the melts are combined by a composite adapter, extruded from a T-die, and quenched by a cooling drum at 30 ° C. Thus, a three-layer unstretched laminated film having a (B / A / B) configuration was obtained.

The unstretched laminated film was first preheated to 95 ° C. using a metal roll, further heated using three infrared heaters having a surface temperature of 750 ° C., and stretched 1.5 times in the longitudinal direction at 115 ° C. After cooling with a roll and a film temperature of 95 ° C., the film was stretched three times in the machine direction. The film is then preheated to 110 ° C. in a tenter,
Stretched 4.0 times while raising the temperature to 150 ° C., stretched 1.1 times while raising the temperature to 223 ° C., and heat-treated at 223 ° C. while keeping the width in a constant length. ℃ to 1
Perform a 3% relaxation treatment in the width direction while lowering the temperature to 50 ° C.
A 20 μm film was obtained. The blowing amount of hot air in the width direction in the tenter was adjusted, and the difference in the maximum temperature in the width direction in the tenter from the horizontal stretching to the relaxation treatment was 3 ° C.
The thickness ratio of each layer of B / A / B of this film is 4
/ 92/4. This film was free from troubles such as breakage during film formation and slitting, and had good productivity. Table 1 shows the obtained films, and the evaluation results after vapor deposition and processing.

Example 2 In Example 1, B / A /
B Except that only the thickness ratio of each layer was changed to 8/84/8,
By carrying out exactly the same as in Example 1, a gas barrier film was obtained.

Example 3 In Example 1, B / A /
Except that only the thickness ratio of each layer B was changed to 16/68/16, the same procedure was performed as in Example 1 to obtain a gas barrier film.

(Comparative column 1) In Example 1, B / A /
Except that only the thickness ratio of each layer B was changed to 40/20/40, the procedure was exactly the same as in Example 1 to obtain a gas barrier film.

Comparative Example 2 In Example 1, B / A /
Except that the thickness ratio of each layer B was changed to 1/98/1, the procedure was exactly the same as in Example 1. This film frequently suffered breakage during film formation and slitting, resulting in poor productivity. Therefore, a film could not be obtained, and vapor deposition processing and evaluation could not be performed.

Comparative Example 3 The same method as in Example 1 was used except that the copolymer (A) was a copolymer of polyethylene isophthalate and polyethylene terephthalate having a melting point of 245 ° C.
A film having a thickness and a thickness ratio of 25 μm was obtained. This film was free from troubles such as breakage during film formation and slitting, and had good productivity.

Comparative Example 4 150 ° C. to 150 ° in the horizontal direction
Stretched 4.0 times while raising the temperature to 200 ° C, stretched 1.1 times while raising the temperature to 200 ° C, and heat-treated at 200 ° C while keeping the width direction constant. A gas barrier film was obtained in exactly the same manner as in Example 1, except that a 3% relaxation treatment was performed while the temperature was lowered to 150 ° C.
Here, the difference in the maximum temperature in the width direction was 3 ° C. This film was free from troubles such as breakage during film formation and slitting, and had good productivity.

Example 4 Example 4 was repeated 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 from transverse stretching to relaxation treatment was 6 ° C. Performed exactly as in 1. This film was free from troubles such as breakage during film formation and slitting, and had good productivity.

Example 5 Example 5 was repeated 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 from the transverse stretching to the relaxation treatment was 12 ° C. Performed exactly as in 1. This film was free from troubles such as breakage during film formation and slitting, and had good productivity.

[0059]

[Table 1]

As is evident from Table 1, the gas barrier films obtained in Examples 1 to 5 all have a flatness, a tearing property and a gas barrier property after vapor deposition which are above practically acceptable levels. Examples 1, 2 and 4 were good, especially Example 1 was a very good film. However, in Comparative Examples 1, 2, 3, and 4, rupture frequently occurred during film formation, and the obtained gas barrier film had poor flatness and tearability after vapor deposition.

[0061]

As is apparent from the above description, the polyester gas barrier film of the present invention has good flatness, tearability and gas barrier properties after vapor deposition, and is suitable for fresh foods, processed foods, medical products, and medical care. It is useful for packaging films for equipment and electronic components.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29L 7:00 B29L 7:00 9:00 9:00 (72) Inventor Kiyoji Iseki Ozu Kizu, Inuyama City, Aichi Prefecture 344, Maebata, Toyobo Co., Ltd., Inuyama Plant F-term (reference) 4F100 AA01C AA01D AA19C AA19D AA20C AA20D AK41A AK41B AK42 AK42J AL01 BA03 BA04 BA05 BA10A BA10B BA10C BA10D EH66B EJ66EJB EJA JK15 YY00C YY00D 4F210 AA24 AG01 AG03 AR06 QC06 QG01 QG15 QG18 QW12 4K029 AA11 BA44 BA46 BC00 CA01 JA10 KA03

Claims (5)

[Claims] At least one side of the polyester resin layer (A) has a melting point of 10 ° C. lower than the melting point of the polyester resin layer (A).
Has a high melting point and at least 5%,
% At least a temperature lower than the melting point of the polyester resin layer (A) by at least 10 ° C. and lower than the melting point of the polyester resin layer (B) after at least uniaxial stretching of the unstretched laminated film laminated with the polyester resin layer (B) having a thickness of not more than 10%. A gas barrier film, wherein an inorganic vapor-deposited layer is formed on one or both polyester resin layers (B) of the base polyester film heat-treated in the step (a). 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%.
A gas barrier film having the following characteristics. 3. The gas barrier film according to claim 1, wherein the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction at 150 ° C. in the width direction of the base polyester film is 1.0. % Gas barrier film. 4. The gas barrier film according to claim 1, wherein the inorganic vapor-deposited layer comprises silicon oxide,
A gas barrier film, which is a layer containing 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-deposited layer is 20% by weight or more and 90% by weight or less.