JP2003211608A - Packaging polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a packaging polyester film excellent in adhesion, oligomer sealability, shaving resistance, and gas barrier properties. <P>SOLUTION: The packaging polyester film is a biaxially oriented laminated polyester film manufactured by a continuous film forming method and has a multilayered structure comprising two or more layers. The center line average roughness (Ra) of the surface of the film is at least 1-8 nm on the single surface of the film and at least 2-20 nm in the average of both surfaces of the film. Further, when the film is continuously heated from 180°C to 220°C, the dimensional change speed of the film in the direction vertical to a continuous film forming direction is always -0.05%-below 0.10%/°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester film for packaging. More specifically, the present invention relates to a polyester film which has excellent adhesion to metals and metal oxides and is useful as a packaging material that requires gas barrier properties.

[0002]

2. Description of the Related Art Polyester films, especially polyethylene terephthalate films, have been used as a constituent of many flexible packaging films because of their advantages such as mechanical strength and thermal dimensional stability. Among them, foods and chemicals have a so-called gas barrier property, which has the effect of blocking the invasion of oxygen and water vapor from the outside air for long-term storage, since decomposition and deterioration are promoted by oxygen and water vapor. The material needs to be wrapped. As a film having excellent gas barrier properties, a film in which polyvinylidene chloride or ethylene vinyl alcohol copolymer is laminated is known, and a film in which a metal or metal oxide is formed on a polymer film substrate is known. . For example, the one in which aluminum oxide is formed on a polyester film is known from Japanese Patent Publication No. 62-179935.

However, a laminate of polyvinylidene chloride and an ethylene vinyl alcohol copolymer has poor heat resistance, and has a problem that the gas barrier property is deteriorated by high temperature wet heat treatment such as retort treatment. Further, polyvinylidene chloride generates chlorine gas when incinerated, and there is a concern that it may affect the global environment.

On the other hand, the gas barrier performance of a film having a metal or metal oxide film formed on a polyester film is much better than that of the polyester film itself, but a metal or metal oxide film is formed on the polyester film. Regarding the gas barrier property of the formed film,
The detailed theoretical analysis has not been sufficiently conducted, and studies are being conducted in this field for the purpose of further improving the gas barrier performance. For example, Japanese Patent Application Laid-Open No. 10-315420 proposes the composition and constitution of a polyester film as a base material.

Further, when forming a metal oxide on a polyester film, it is known from JP-A-2000-108285 that the gas barrier property is improved by reducing the amount of low molecular weight compounds and oligomers deposited on the surface by heat treatment. There is.

[0006]

However, when a polyester film is used as a substrate, the polyester film generally has poor adhesiveness to a metal oxide, causing peeling at the interface and degrading gas barrier properties. .

JP-A-11-198326, JP-A-11-198327, and JP-A-11-334010.
In the gazette, a polyester film having an easy-adhesive film on the polyester film is proposed, but the gas barrier property after metal oxide vapor deposition is insufficient due to poor oligomer encapsulation properties particularly in applications with severe performance requirements. There are
In addition, since the easily-adhesive film has defects due to poor abrasion resistance in the film manufacturing process and processing process, and peeling of the interface between the substrate and the metal oxide deposition film occurs, gas barrier after metal oxide deposition It was a problem that the property deteriorated.

An object of the present invention is to solve the above problems and to obtain a polyester film for packaging which is excellent in adhesion to a metal or a metal oxide and is excellent in gas barrier property after vapor deposition of a metal or a metal oxide.

[0009]

The polyester film for packaging of the present invention is a biaxially oriented laminated polyester film having a multilayer structure of two or more layers, which is produced by a continuous film forming method, and has a center line on the film surface. The average roughness (Ra) is 1 nm or more and 8 nm or less on at least one side of the film, and 2 nm or more and 20 nm or less on average on both sides of the film, and when the film is continuously heated from 180 ° C. to 220 ° C., it is perpendicular to the continuous film formation direction. The dimensional change rate of the film in the direction is always −0.05% / ° C. or more and less than 0.10% / ° C.

<Polyester Film> In the present invention, the polyester constituting the polyester film is a linear saturated polyester composed of a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid and the like. . Among these dicarboxylic acid components, terephthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferable from the viewpoint of the mechanical properties of the film.

As the glycol component, ethylene glycol, diethylene glycol, propylene glycol,
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, 1,6-hexanediol,
Examples thereof include cyclohexanedimethanol and polyethylene glycol. Of these glycol components, ethylene glycol, 1,3-
Propanediol is particularly preferred.

The polyester in the present invention may be a copolyester obtained by copolymerizing the above-mentioned dicarboxylic acid component or glycol component as the third component, and the polyester obtained is a trifunctional or higher polyvalent carboxylic acid component or polyol component. Range that is substantially linear (for example, 5
It may be a polyester copolymerized in a small amount (mol% or less).

Among the above polyesters, a particularly preferred polyester is mainly composed of ethylene terephthalate units,
A copolymer containing less than 40% by weight, more preferably less than 35% by weight and particularly preferably less than 30% by weight of ethylene-2,6-naphthalate units and / or trimethylene terephthalate units and / or trimethylene-2,6-naphthalate units. It comprises a polymerized polymer or a mixture of polymers.

The polyester in the present invention can be produced by a conventionally known method. For example, a method of directly obtaining a low degree of polymerization polyester by the reaction of dicarboxylic acid and glycol,
Using a conventionally known transesterification catalyst for lower alkyl ester of dicarboxylic acid and glycol, for example, one or more compounds containing sodium, potassium, magnesium, calcium, zinc, strontium, titanium, zirconium, manganese, cobalt are used. After the reaction, the polymerization is carried out in the presence of a polymerization catalyst.

As the polymerization catalyst, antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds represented by germanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraphenyl titanate or partial hydrolysates thereof, oxalic acid Titanium compounds such as titanyl ammonium, potassium titanyl oxalate, and titanium trisacetylacetonate may be mentioned.

When the polymerization is carried out via a transesterification reaction, phosphorus compounds such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate and orthophosphoric acid are used for the purpose of deactivating the transesterification catalyst before the polymerization reaction. Is added. At that time, the content of polyethylene in the polyethylene-2,6-naphthalene dicarboxylate as a phosphorus element is preferably 20 ppm by weight or more and 100 ppm by weight or less from the viewpoint of the thermal stability of the polyester.

The polyester may be melt-polymerized and then formed into chips, which may be solid-phase polymerized under reduced pressure with heating or in an inert gas stream such as nitrogen.

The intrinsic viscosity of such polyester (in orthochlorophenol, 35 ° C.) is 0.45 dl / g or more,
It is more preferably 0.47 dl / g or more, and particularly preferably 0.50 dl / g or more, since mechanical properties such as high rigidity of the film are improved, which is preferable.

The polycondensation metal catalyst residue of the polyester used in the film of the present invention is less than 150 ppm by weight, and when antimony is used as a catalyst, the amount of antimony is 10 mmol% or less per 1 mol of all acid components. It is preferable because the transparency of the film becomes high.

In the present invention, the thickness of the biaxially oriented polyester film is preferably 1 μm or more and 500 μm or less.
When the thickness is 1 μm or less, the film is often cut when it is formed, which is not preferable. On the other hand, when the thickness is 500 μm or more, the film tends to be too stiff and the film-forming property tends to deteriorate, which is not preferable. And it is more preferably 5 μm or more, and particularly preferably 9 μm or more and 350 μm or less.

The polyester film has a multilayer structure of two or more layers formed by a coextrusion method or the like, and the means for forming the multilayer structure is not limited as long as no peeling occurs between the layers in the subsequent handling of the film.

<Additives> The polyester film of the present invention may contain additives such as lubricants, stabilizers, and hue adjusters. A small amount of inert fine particles such as inorganic particles, organic particles, and crosslinked polymer particles is used as a lubricant for imparting lubricity to the film for the purpose of improving the running property and handling property during the production, processing and use of the film. It is preferable to contain it in a ratio.

As the inorganic particles, calcium carbonate, porous silica, spherical silica, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, Titanium oxide,
Examples thereof include zirconium oxide and lithium fluoride.

Examples of the organic salt particles include calcium oxalate and terephthalates such as calcium, barium, zinc, manganese and magnesium.

Examples of the crosslinked polymer particles include divinylbenzene, styrene, acrylic acid, methacrylic acid, homopolymers or copolymers of vinyl monomers of acrylic acid or methacrylic acid, and the like, polytetrafluoroethylene, silicone. Organic fine particles such as resin, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin are also used.

It is particularly preferable that the packaging polyester film of the present invention contains porous silica particles, spherical silica particles, kaolin particles, aluminum oxide particles, or silicone resin particles among the above examples.

The average particle size of these lubricants is 0.05.
It is not less than μm and not more than 5 μm. The average particle size is more preferably 0.07 μm or more and 4 μm or less, and 0.1 μm or less.
Particularly preferred is m or more and 3 μm or less. If the thickness is less than 0.05 μm, the effect of improving the slipperiness is small, so that it is necessary to make the added concentration extremely high, and the transparency of the film becomes insufficient, which is not preferable. On the other hand, if it exceeds 5 μm, the number of defects on the film surface due to the falling of particles increases, which is not preferable. Further, in the laminated polyester film of the present invention, at least one outermost layer required to have a smooth surface property has an average particle diameter of 0.05 μm or more and 0.8 μm or less, more preferably 0.05 μm or more and 0.5 μm or less. Is preferably added. The amount of the inert fine particles added to each layer is 0.001% by weight or more and 2.0% by weight or less, more preferably 0.002% by weight or more and 1.0% by weight or less.
It is particularly preferable that the amount is 004% by weight or more and 0.5% by weight or less. 0.
If it is less than 001% by weight, the improvement of the slipperiness is insufficient, and 2
If it exceeds 5% by weight, the transparency of the film becomes insufficient, which is not preferable.

The inert fine particles added to the film may be a single component selected from the examples given above, or may be a multi-component containing two or more components.

When a coating film containing fine particles is provided on the surface of the laminated polyester film for the purpose of imparting a slip property to the film, and the running property and handling property of the film can be sufficiently secured, a lubricant is provided inside the polyester film. Need not be added.

The polyester film of the present invention may contain a crystal nucleating agent, an antioxidant, a heat stabilizer, a slippery agent, a hue adjusting agent, a flame retardant, an antistatic agent, a polysiloxane and the like depending on its use. it can.

The timing of addition of the inert fine particles and other additives is not particularly limited as long as it is a stage until the polyester film is formed, and for example, it may be added at the polymerization stage.
It may also be added during film formation. From the viewpoint of uniform dispersion, it is preferable to add to ethylene glycol at a high concentration at the time of polymerization to prepare a master chip and dilute it with an additive-free chip.

<Surface Roughness> The center line average roughness (Ra) of at least one surface of the film of the present invention is from 1 nm to 8 nm.
It is the following. This is more preferably 1 nm or more and 6 nm
It is particularly preferably 1 nm or more and 4 nm or less. Further, the average of the center line average roughness on both sides of the film ((Ra1 +
Ra2) / 2) is 2 nm or more and 20 nm or less. The average value on both sides is more preferably 2 nm or more and 17 n or more.
m or less, particularly preferably 2 nm or more and 15 nm or less.

Regardless of whether or not a coating film is provided on the surface of the film, if Ra on at least one side is less than 1 nm, the scratch resistance in the film manufacturing process and the processing process may be poor. On the other hand, when it exceeds 8 nm, surface defects of the transparent vapor deposition layer are likely to occur, and the gas barrier property may deteriorate. In addition, the average centerline average roughness on both sides of the film is 2n.
When it is less than m, the running property of the film is deteriorated. on the other hand,
If the thickness exceeds 20 nm, the flatness of the smooth surface may be disturbed by the imprint of the protrusions on the opposite surface after the film is wound up, resulting in surface defects.

<Dimensional change rate> When the biaxially oriented laminated polyester film of the present invention is continuously heated from 180 ° C. to 220 ° C., the dimensional change rate is the direction perpendicular to the continuous film forming direction, that is, the lateral direction ( In TD)-
0.05% / ° C or more and less than 0.10% / ° C, more preferably -0.04% / ° C or more and less than 0.10% / ° C, and particularly preferably -0.04% / ° C or more and 0.08. % / ° C.

The dimensional change rate when the film is continuously heated from 100 ° C. to 190 ° C. is always −0 in the continuous film forming direction of the film, that is, the machine direction (MD).
It is preferably at least 05% / ° C and less than 0.03% / ° C, and more preferably at least -0.04% / ° C and less than 0.02% / ° C.

If the dimensional change rate is out of the above range, the metal film or the metal oxide film is formed on the biaxially oriented laminated polyester film, and the gas barrier property of the packaging film after the post-processing is insufficient. There is.

<1% Strain Strength> The biaxially oriented laminated polyester film of the present invention has a 1% strain strength in the machine direction (MD) of preferably 40 MPa or more, more preferably 42 MPa or more, and particularly 45 MPa or more. It is preferable. 1% strain strength in the machine direction (MD) is 40 MPa
If it is less than the above range, the metal film or the metal oxide film formed on the film may be distorted in some cases because the film is likely to stretch in the longitudinal direction during processing. The 1% strain strength in the machine direction (MD) is 65 MPa.
The following is preferable in the production of the polyester film.

<Absolute value of difference in surface orientation coefficient between front surface and back surface>
In the biaxially oriented laminated polyester film of the present invention, the absolute value of the difference in surface orientation coefficient between the front surface and the back surface is preferably less than 0.050, more preferably less than 0.040,
It is particularly preferably less than 0.035. If the absolute value of the difference in the surface orientation coefficient between the front surface and the back surface of the film is 0.050 or more, the film tends to curl in the production of the laminated polyester film and wrinkles (flutes) are likely to occur on the film surface, which is not preferable. Further, when used as a base material for a packaging film, curling of the film may occur more significantly in the processing step.

<Coating film> In the present invention, the oligomer sealing coating film provided on at least one side of the polyester film is a solid binder resin composed of an acrylic-polyester resin and inert particles having an average particle size of 20 nm to 100 nm. A coating liquid containing 1% by weight or more and 20% by weight or less is applied, dried and stretched.

The acrylic-polyester resin used in the present invention is meant to include an acrylic-modified polyester resin and a polyester-modified acrylic resin, in which the polyester resin component (A) and the acrylic resin component (B) are bonded to each other. Is. This bond includes, for example, a graft type and a block type. Such an acrylic-polyester resin is obtained by adding a radical initiator to both ends of a polyester resin component to polymerize an acrylic monomer, or adding a radical initiator to a side chain of a polyester resin component to form an acrylic monomer. Polymerization of
Alternatively, it can be produced by attaching a hydroxyl group to the side chain of the acrylic resin component and reacting it with a polyester resin component having an isocyanate group or a carboxyl group at the terminal.

The polyester resin component (A) constituting the acrylic-polyester is a linear polyester having a dicarboxylic acid component and a glycol component as constituent components.
As the dicarboxylic acid component, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid,
Examples thereof include 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, phenylindanedicarboxylic acid and dimer acid. Two or more kinds of these components can be used. Further, in combination with these components, unsaturated polybasic acids such as maleic acid, fumaric acid and itaconic acid, and hydroxycarboxylic acids such as p-hydroxybenzoic acid and p- (β-hydroxyethoxy) benzoic acid are used in small proportions. You can The ratio of the unsaturated polybasic acid component and the hydroxycarboxylic acid component is at most 10 mol%, preferably 5 mol% or less.

As the glycol component, ethylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, diethylene glycol. Examples thereof include methylolpropionic acid, glycerin, trimethylolpropane, poly (ethyleneoxy) glycol, poly (tetramethyleneoxy) glycol, an alkylene oxide adduct of bisphenol A, and an alkylene oxide adduct of hydrogenated bisphenol A.
These can use 2 or more types.

Among such glycol components, ethylene glycol, ethylene oxide adduct of bisphenol A and polypropylene oxide adduct, and 1,4-butanediol are preferable, and ethylene glycol and bisphenol A ethylene oxide adduct and propylene oxide are more preferable. It is an adjunct.

The polyester resin may be copolymerized with a small amount of a compound having a sulfonate group or a compound having a carboxylate group in order to facilitate aqueous liquefaction, and this is preferred. .

Examples of the compound having this sulfonate group include 5-Nasulfoisophthalic acid, 5-ammoniumsulfoisophthalic acid, 4-Nasulfoisophthalic acid, 4-methylammoniumsulfoisophthalic acid, 2-
Na sulfoisophthalic acid, 5-K sulfoisophthalic acid,
Preferable examples include sulfonic acid alkali metal salt-based compounds such as 4-K sulfoisophthalic acid, 2-K sulfoisophthalic acid and Na sulfosuccinic acid, or sulfonic acid amine salt-based compounds.

Examples of the compound having a carboxylic acid group include trimellitic anhydride, trimellitic acid, pyromellitic dianhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, dimethylolpropionic acid, and the like, or monos thereof. Examples thereof include alkali metal salts. After the copolymerization, the free carboxyl group is reacted with an alkali metal compound or an amine compound to form a carboxylate group.

The acrylic resin component (B) constituting the acrylic-polyester is acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, sodium acrylate, ammonium acrylate, 2-hydroxyethyl acrylate, methacrylic acid. , Methyl methacrylate, ethyl methacrylate, butyl methacrylate, sodium methacrylate, ammonium methacrylate, 2-hydroxyethyl methacrylate, acrylonitrile, acrylamide, methacrylamide, N-methylol methacrylamide, and the like. These monomers can be used in combination with other unsaturated monomers such as styrene, vinyl acetate, vinyl chloride, vinylidene chloride, divinylbenzene, sodium styrenesulfonate, sodium vinylsulfonate and sodium methallylsulfonate. .

The molar ratio of the polyester resin component / acrylic resin component of the acrylic-polyester resin is preferably 1/9 or more and 5/5 or less, more preferably 2/8 or more and 4 /.
It is 6 or less. If this ratio is less than 1/9, the adhesion of the coating film to the polyester film is insufficient, and if it exceeds 5/5, the coating film is inferior in abrasion resistance and oligomer sealing property.

The acrylic resin component constituting the acrylic-polyester resin is the alkyl methacrylate component 5
It is preferable that the main component is a component consisting of 0 mol% or more and 95 mol% or less, an epoxy group-containing acrylic monomer component of 3 mol% or more and 30 mol% or less, and an alkyl acrylate component of 3 mol% or more and 30 mol% or less.

The proportion of the acrylic methacrylate component is preferably 50 mol% or more and 95 mol% or less, more preferably 60 mol% or more and 90 mol% or less. If this ratio is less than 50 mol%, it becomes difficult to polymerize the acrylic-polyester resin. On the other hand, when it exceeds 96 mol%, the ratio of the epoxy group-containing acrylic monomer component and the alkyl acrylate component decreases, and the abrasion resistance deteriorates.

In the coating liquid for forming the oligomer-encapsulating coating film in the present invention, a binder resin other than the above may be blended in order to adjust the adhesiveness between the coating film and the polyester film. Examples of such resin include polyurethane resin, epoxy resin, vinyl resin, polyether resin,
The water-soluble resin and the like can be increased.

The coating film of the present invention has an average particle size of 20.
It is indispensable to contain the inert particles having a size of 1 nm to 100 nm inclusive in an amount of 1% by weight to 20% by weight as a solid content in the coating liquid. Examples of the inert particles include calcium carbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesium oxide, silicon oxide, sodium silicate, aluminum hydroxide, iron oxide, zirconium oxide, barium sulfate, titanium oxide, tin oxide, carbon black. Examples thereof include inorganic particles such as molybdenum disulfide, acrylic cross-linked polymers, styrene cross-linked polymers, silicone resins, fluororesins, benzoguanamine resins, phenol resins, nylon resins and polyethylene wax.

The average particle size of the inert particles is 20 nm or more 1
00 nm or less is necessary, preferably 25 nm
It is above 80 nm. If it is less than 20 nm, the abrasion resistance in the film manufacturing process and the processing process is poor, and the gas barrier property after metal oxide deposition is deteriorated. On the other hand, when it exceeds 100 nm, the transparency is impaired. Further, it is necessary that the amount of the inert particles is 1% by weight or more and 20% by weight or less as a solid content in the coating liquid. If it is less than 1% by weight, the abrasion resistance in the film manufacturing process or processing process is poor, and if it exceeds 20% by weight, the transparency is impaired.

The coating liquid for forming the oligomer-encapsulating coating film in the present invention is to improve the stability of the coating liquid, especially the aqueous coating liquid, and to improve the wettability when the coating liquid is applied to the polyester film. , A surfactant can be added. Examples of the surfactant include nonionic surfactants such as alkylene oxide homopolymers, alkylene oxide copolymers, aliphatic alcohol / alkylene oxide adducts, polyhydric alcohol fatty acid esters, long-chain aliphatic amide alcohols, and quaternary surfactants. Examples thereof include cationic or anionic surfactants such as a compound having an ammonium salt, a compound having an alkylpyridinium salt, and a compound having a sulfonate, and a nonionic surfactant is particularly preferable.

The solid content concentration of the coating liquid in the present invention is 0.5.
It is preferable that the content is not less than 30% by weight and not more than 30% by weight. When the solid content concentration is less than 0.5% by weight, the wettability to the polyester film is insufficient, and when it exceeds 30% by weight, the coating appearance tends to be deteriorated.

In the present invention, the coating liquid containing each of the above-mentioned components is applied to at least one surface of the polyester film, and the polyester film is preferably a polyester film before the completion of oriented crystals. As the polyester film before the oriented crystals are completed, an unstretched film formed by heat-melting polyester to form a film as it is, a uniaxially stretched film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction, Examples thereof include those which are stretched and oriented in a low-magnification direction in both the machine direction and the transverse direction (a biaxially stretched film before being finally re-stretched in the machine direction and the transverse direction to complete the oriented crystallization). .

As a method of applying the coating liquid to the polyester film, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a micro gravure coating method, a reverse coating method, a roll brush method, a spray coating method, an air knife coating method, an impregnation method and a curtain coating method may be applied alone or in combination. When an aqueous coating liquid is used, a small amount of organic solvent may be included for the purpose of helping the stability of the coating liquid.

The coating amount is preferably 0.5 g or more and 50 g or less, and more preferably 5 g or more and 30 g or less per 1 m ² of the running film. The thickness of the final dry coating film is preferably 0.02 μm or more and 1 μm or less, and more preferably 0.02 μm or more and 0.8 μm or less. If the thickness of the coating film is less than 0.02 μm, the oligomer sealing property becomes insufficient, while if it exceeds 1 μm, the blocking resistance tends to decrease. The coating can be performed on only one side or both sides depending on the application of the film. After coating, a uniform coating film is obtained by drying.

In the present invention, at least two kinds of polyesters are melted by respective extruders and extruded from a die slit onto a rotating cooling drum in a state of being laminated by a coextrusion method (manifold type, feed block type, etc.). After applying the coating liquid to the obtained unstretched polyester sheet or uniaxially stretched polyester film,
It is preferable to perform drying, preferably stretching treatment, but it is preferable to perform drying at 90 ° C. or higher and 130 ° C. or lower for 2 seconds or more and 20 seconds or less. Drying can also serve as a residual heat treatment of the stretching treatment or a heat treatment during the stretching. The stretching treatment of the polyester film is carried out at a temperature of 70 ° C. or higher and 140 ° C. or lower, 2.5 times or more and 7 times or less in the longitudinal direction, 2.5 times or more and 7 times or less in the transverse direction, and 8 times or more, further 9 times in area magnification. It is preferable to stretch at a stretch ratio of 28 times or less. When re-stretching,
It is preferable to stretch at a draw ratio of 1.05 times or more and 3 times or less (however, the area magnification is the same as above). The film is stretched by a known roll longitudinal stretching machine, an infrared heating longitudinal stretching machine, a tentercrib type transverse stretching machine, a multi-stage stretching machine that performs these stretching steps in multiple stages, a tubular stretching machine, and an oven type longitudinal stretching machine. It can be performed using a simultaneous biaxial stretching machine, but is not particularly limited. The heat setting treatment after stretching is performed at a temperature higher than the final stretching temperature and lower than the melting point for 1 second or more 3
It is preferable to perform the heating in 0 second or less. For example, in the case of a polyethylene terephthalate film, it is preferable to perform heat setting at a temperature of 170 ° C. or more and 240 ° C. or less for a time of 2 seconds or more and 30 seconds or less. Further, after the heat-setting treatment, heat relaxation treatment is performed in the longitudinal direction and / or the transverse direction at a relaxation rate of 0.5 to 15% for the purpose of imparting dimensional stability to the film. At the time of the cooling treatment, it is preferable to cut the film from the gripping tool and perform the relaxation treatment. In order to bring the dimensional change rate of the film into a desired range, it is necessary to optimize the balance between the stretching temperature and the stretching ratio, and further the balance between the heat setting temperature and the heat relaxation rate.

The biaxially oriented polyester film thus obtained is excellent in adhesiveness with metals and metal oxides, and is also excellent in oligomer encapsulation and abrasion resistance, and has gas barrier properties after vapor deposition of metals and metal oxides. It is excellent and is extremely useful especially as a film for packaging materials.

The present invention will be described in detail with reference to Examples below, but the evaluation in the present invention was performed by the following methods.

1. Dimensional change rate Seiko Electronics Co., Ltd. measurement module TMA / SS
A 120C type and a thermal analysis system SSC / 5200H type manufactured by the same company were used as a data analysis device. A film sample is sampled into a strip with a width of 4 mm, and the measurement original length is 1
5 mm, a constant load of 2.0 MPa in the direction of the measured original length
The temperature is increased from room temperature at a heating rate of 5 ° C./min. The rate of dimensional change with respect to the measurement original length was recorded in a predetermined temperature range. The amount of change in the dimensional change rate when the temperature increased by 1 ° C was defined as the dimensional change rate (% / ° C). That is, the temperature T
The dimensional change rate (% / ° C) at (° C) is (T + 1)
It is the value obtained by subtracting the value of the dimensional change rate at T ° C from the dimensional change rate at ° C. In the measurement in the machine direction (MD), a sample slit along the machine direction of the film with a width of 4 mm was used, and in the measurement in the transverse direction (TD), a sample similarly slit along the transverse direction was used.

2. 1% strain strength (F1 value) A film is cut into a sample width of 10 mm (direction perpendicular to the continuous film forming direction) and a length of 150 mm (continuous film forming direction of the film), and the chuck distance is set to 100 mm and the pulling speed is 10 mm /
Min, chart speed is 500 mm / min and is pulled by an Instron type universal tensile tester. Read the strength at 1% elongation from the obtained load-elongation curve, divide by the original cross-sectional area,
It is 1% strain strength (MPa) in the continuous film forming direction.

3. Intrinsic viscosity ([η]) A value (unit: dl / g) measured at 35 ° C. using o-chlorophenol as a solvent.

4. Center line average roughness (Ra) According to the method specified in JIS B-6601, using a surface roughness meter (Surfcom 3B type manufactured by Tokyo Seimitsu Co., Ltd.) with a cutoff of 0.25 mm and a measuring stylus with a radius of 3 μm. taking measurement.

5. Haze Measured according to JIS K-6714 and converted to a thickness of 12 μm. The haze is preferably 2.5% or less.

6. Absolute value of the difference in surface orientation coefficient between the front surface and the back surface of the film Using an Atsube refractometer (manufactured by Atago Co., Ltd.), 2
Longitudinal direction of the film (M
The refractive index was obtained for each of D), the lateral direction (TD), and the thickness direction (z). Then, for each of the front surface and the back surface of the film, the plane orientation coefficient (ns) was calculated by the following formula. In the formula, nMD is the refractive index in the vertical direction, nTD is the refractive index in the horizontal direction, and nz is the refractive index in the thickness direction. ns = {(nMD + nTD) / 2} -nz From the thus obtained surface orientation coefficients of the front surface and the back surface, the absolute value of the difference between the two is obtained.

7. Scrap resistance Using a film sample cut into a width of 20 mm, the coated surface of the film was applied to a cylindrical stainless steel fixed bar with a diameter of 10 mm, run for 80 m under a load of 200 g, and then adhered to the bar. The white powder of the coated film was observed and the abrasion resistance was evaluated according to the following criteria. A: No white powder adhered to the bar (good abrasion resistance) B: White powder slightly adhered to the bar (slight abrasion resistance slightly good) C: Large amount of white powder adhered to the bar (poor abrasion resistance)

8. After the sample film cut into the oligomer sealing property of 150 mm × 100 mm was heat-treated at 150 ° C. for 1 hr in a dryer,
The sample film was cooled down to room temperature by allowing it to stand still, being careful not to touch the surface of the sample film with fingers. The surface of the obtained sample film was observed under a microscope (reflection, magnification: 50 times,
200 times) and the oligomer sealing property was evaluated according to the following criteria. A: No oligomer is generated (good oligomer sealing property) B: Some oligomer is generated (some oligomer sealing property is good) C: A large amount of oligomer is generated (poor oligomer sealing property)

9. Oxygen permeability film is supplied to the vacuum evaporation system and 5 × 10 ^-5 Torr
Under vacuum of 10kw by electron beam heating method
And SiO ₂ were heated and evaporated to obtain a vapor deposition film in which a transparent thin film of SiO _x having a thickness of 52 nm was formed on the side having the coating film of the film. A tension of 8 kg / m is applied to the obtained film in the machine direction, and the film is kept at 180 ° C. for 1
Heat treatment was performed for 1 minute. Then, on the vapor deposition surface of this film,
A urethane adhesive (manufactured by Dainippon Ink and Chemicals, a two-component adhesive in which Dick Dry LX-703A and KR-90 were mixed in a ratio of 15: 1) was applied to a thickness of 3 μm and then a thickness of 5
0 μm low density polyethylene film (Tamapoly, V
-1) was pasted by the dry lamination method. The obtained film was measured with a gas permeability measuring device (manufactured by Toyo Seiki, MC-1 type) in accordance with JIS K-7126 to 2
The oxygen transmission rate at 5 ° C was measured. Oxygen permeability is 3c
The ^{m 3 / (m 2 / 24hr} / atom) or less was evaluated as acceptable.

10. Comprehensive evaluation Comprehensive evaluation was based on the following criteria after considering each evaluation result. ⊚: Very good result, extremely useful as a polyester film for packaging ○: Good result, preferable as a polyester film for packaging ×: Poor evaluation result, impossible to use as a packaging film is there.

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EXAMPLES Example 1 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, germanium oxide as a polymerization catalyst, phosphorous acid as a stabilizer, and an average particle size of 0 as aggregated particles as a lubricant. 80 μm porous silica particles to polymer 80
Polymerization was carried out by a conventional method by adding so that the concentration became 0 weight ppm,
Intrinsic viscosity (o-chlorophenol, 35 ° C) 0.65d
1 / g of polyethylene terephthalate A (Tg: 78
C) was obtained.

Similarly, as a lubricant, the average particle size is 0.1 μm.
Spherical silica particles of m were added so as to be 110 ppm with respect to the polymer and polymerized by a conventional method to obtain an intrinsic viscosity (o-
Chlorophenol, 35 ° C) 0.65 dl / g polyethylene terephthalate B (Tg: 78 ° C) was obtained.

These two types of polyethylene terephthalate pellets were each dried at 170 ° C. for 3 hours, then separately melted from two extruders at a melting temperature of 295 ° C., filtered with a non-woven fabric type filter, and combined and laminated with a feed block. Then, it was extruded from a slit die onto a rotary cooling drum having a surface temperature of 20 ° C. to obtain an unstretched film. Subsequently, this unstretched film was preheated to 80 ° C., heated between a low-speed roller and a high-speed roller to stretch 3.5 times in the longitudinal direction, and rapidly cooled, and then a 1.5% by weight aqueous solution having the following solid content composition was used. The coating liquid was applied to the surface of the above film on the polyethylene terephthalate B side with a roll coater.

<Solid Content Composition of Aqueous Coating Liquid> The aqueous coating liquid is 90% by weight of acrylic-polyester resin and has an average particle size of 80.
5% by weight of inactive particles made of silica fine particles and 5% by weight of a surfactant made of polyoxyethylene alkyl ether. Here, the acrylic-polyester resin is a graft copolymer in which the molar ratio of the polyester component as the trunk polymer to the acrylic component as the branch polymer is 3: 7. Further, the polyester component here is terephthalic acid (18 mol%) / isophthalic acid (70 mol%) / 5-sodium sulfoisophthalic acid (12 mol%) / ethylene glycol (92 mol%) /
It consists of diethylene glycol (8 mol%). The acrylic component is composed of methyl methacrylate (80 mol%) / glycidyl methacrylate (15 mol%) / n-butyl acrylate (5 mol%).

Subsequently, the mixture was supplied to a stenter and stretched 3.8 times in the transverse direction at 120 ° C. The obtained biaxially oriented film was heat-set at a temperature of 233 ° C. for 5 seconds, during which 3.5
% Width was relaxed, and when the film temperature was lowered to around 100 ° C., the polyester film was cut off from the gripping tool. The thickness of the laminated polyester film was 12 μm, the polyethylene terephthalate A layer was 5 μm, and the polyethylene terephthalate B layer was 7 μm. Also,
The film thickness of the coating film after drying was 0.02 μm. Table 1 shows the evaluation results of the obtained film.

Example 2 A film was produced in the same manner as in Example 1 except that the longitudinal stretching ratio was 3.7 times, the transverse stretching ratio was 3.7 times, and the heat setting temperature was 238 ° C. I went. Table 1 shows the evaluation results of the obtained film.

Example 3 In the production of the film of Example 1, polyethylene terephthalate A had an average particle size of 1.
A laminated polyethylene terephthalate film was formed in the same manner except that spherical silica of 2 μm was added in an amount of 900 ppm by weight and porous silica having an average particle size of 0.3 μm was added in an amount of 40 ppm to polyethylene terephthalate B. Table 1 shows the evaluation results of the obtained film.

Example 4 In the production of the film of Example 1, polyethylene terephthalate A had an average particle size of 0.
40 weight ppm of 3 μm porous silica was added, while
A polyethylene terephthalate B was added with no lubricant, and 1.5% by weight aqueous coating liquid was used in the same manner except that the amount of inert particles in the solid composition of the aqueous coating liquid was 10% by weight and the acrylic-polyester resin was 85% by weight. Was prepared, and a film was formed in the same manner except that polyethylene terephthalate B was coated. Table 1 shows the evaluation results of the obtained film.

[Comparative Example 1] In the production of the film of Example 1, the film was formed in the same manner except that the transverse stretching ratio was 4.5 times. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 2] In the production of the film of Example 1, polyethylene terephthalate B had an average particle size of 0.
Film formation was performed in the same manner except that 60 wt ppm of 5 μm porous silica was added. Table 2 shows the evaluation results of the obtained film.

COMPARATIVE EXAMPLE 3 Polyethylene terephthalate was added with 500 weight parts of porous silica having an average particle diameter of 2.3 μm.
After adding m to obtain a single-layer unstretched film of polyethylene terephthalate, the film was formed in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 4] In the production of the film of Example 1, the film formation was carried out in the same manner except that the longitudinal stretching ratio was 3.1 times, the transverse stretching ratio was 3.3 times, and the heat setting temperature was 240 ° C. I went. Table 2 shows the evaluation results of the obtained film.

Comparative Example 5 In the production of the film of Example 1, polyethylene terephthalate B was uniformly mixed with polyethylene-2,6-naphthalate shown below in a proportion of 43% by weight, and dried at 170 ° C. for 6 hours. , Melting temperature 3
Melts at 00 ℃, and preheat temperature of unstretched film to 1
Film formation was performed in the same manner except that the value was set to 00. Table 2 shows the evaluation results of the obtained film. The biaxially oriented laminated polyester film thus formed had a strong curl with the mixed polymer side inward and had a problem in handleability.

(Production of Polyethylene-2,6-naphthalate) Dimethyl 2,6-naphthalenedicarboxylate 100
To a mixture of 60 parts of ethylene glycol and 60 parts of ethylene glycol, 0.03 parts of manganese acetate tetrahydrate was added, and the temperature was 150 to 240 ° C.
The transesterification reaction was carried out while gradually raising the temperature. When the reaction temperature reached 170 ° C. on the way, 0.024 part of antimony trioxide was added, and porous silica particles having an average particle size of 0.9 μm, which were agglomerated particles as a lubricant, became 800 ppm by weight with respect to the polymer. , Then 2
When the temperature reached 20 ° C., 0.042 parts of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt (2
equivalent to mmol%) was added. Subsequently, a transesterification reaction was carried out, and after completion of the transesterification reaction, 0.023 part of trimethyl phosphate was added. After that, the reaction product is transferred to a polymerization reactor, heated to 290 ° C., and subjected to polycondensation reaction under a high vacuum of 0.2 mmHg or less to give an intrinsic viscosity of 0.61 dl.
/ G (o-chlorophenol, 35 ° C) polyethylene-2,6-naphthalenedicarboxylate polymer (T
g: 122 ° C.) was obtained.

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[Table 1]

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[Table 2]

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EFFECTS OF THE INVENTION According to the present invention, the adhesiveness with a metal or a metal oxide is excellent, the oligomer sealing property and the abrasion resistance are excellent, and the gas barrier property after metal oxide deposition is excellent. It is possible to provide a biaxially oriented laminated polyester film which is useful as a packaging material that requires

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 133/14 C09D 133/14 167/00 167/00 // C08L 67:00 C08L 67:00 (72) Inventor Okuyama Shunsuke 3-37-19 Oyama, Sagamihara City, Kanagawa Teijin DuPont Films Co., Ltd. Sagamihara Research Center (72) Inventor, Koji Kubo 3-37-19 Oyama, Sagamihara City, Kanagawa Teijin DuPont Films Co., Ltd. Sagamihara Research Center centers in the F-term (reference) 3E086 AB01 AC06 AC22 BA04 BA15 BA24 BA33 BA35 BB05 BB22 BB54 BB55 BB57 BB85 BB90 4F006 AA35 AA55 AB24 AB35 AB37 AB74 AB75 AB76 BA01 BA05 CA07 DA04 4F100 AB22A AB22H AK25B AK25C AK41A AK41B AK41C AK42A AL01B AL01C AL05B AL05C AS00B AS00C BA02 BA03 BA06 BA07 BA10B BA10C BA25 DE01B DE01C EH20 EH202 EH46 EH462 EJ37 EJ372 EJ38A GB15 JA20 JD02 JK14A JL11 JM02B JM02C YY00A YY00D HA2DHA2CH02 DB211CH02 DB211CH02 DB211CH02DB02Q11QD02Q11CP02 CH07CP02 CP07 CH02CP07 CH02CP07 CH02CP07 HA216 HA286 HA376 HA446 KA20 MA08 MA10 NA08 NA12 PC08

Claims (8)

[Claims] 1. A biaxially oriented laminated polyester film having a multilayer structure of two or more layers, which is produced by a continuous film forming method, and has a center line average roughness (Ra) of the film surface of 1 nm or more on at least one side of the film. 8 nm or less, and 2 nm or more and 20 nm or less on average on both sides of the film, and when the film is continuously heated from 180 ° C. to 220 ° C., the dimensional change rate of the film in the continuous film forming direction and the vertical direction is always −0. A polyester film for packaging, which is at least 0.05% / ° C and less than 0.10% / ° C. 2. When the film is continuously heated from 100 ° C. to 190 ° C., the rate of dimensional change of the film in the continuous film forming direction is always −0.05% / ° C. or more and less than 0.03% / ° C. The polyester film for packaging according to claim 1, wherein: 3. A coating film prepared by applying a coating liquid, drying and stretching is provided on at least one of the film surfaces, and the coating liquid contains a binder resin composed of an acrylic-polyester resin and an average coating film. Particle size is 20 nm or more and 100 nm
The following inert particles are contained, and the ratio of the inert particles in the coating liquid is 1% by weight or more and 20% by weight or less as a solid content. The described polyester film for packaging. 4. The acrylic-polyester resin in the coating liquid has a molar ratio of polyester resin component / acrylic resin component of 1/9 or more and 5/5 or less, and the acrylic resin component is an alkyl methacrylate component and an epoxy-containing acrylic monomer. Component and an alkyl acrylate component as main components, the alkyl methacrylate component in the acrylic resin component is 50 mol% or more and 95 mol% or less, and the epoxy-containing acrylic monomer component in the acrylic resin component is 3 mol%
The polyester film for packaging according to claim 3, wherein the content is 30 mol% or less and the alkyl acrylate component in the acrylic resin component is 3 mol% or more and 30 mol% or less. 5. The 1% strain strength of the film in the continuous film forming direction is 40 MPa or more.
The polyester film for packaging according to any one of 4 above. 6. The packaging polyester film according to claim 1, wherein the absolute value of the difference between the surface orientation coefficients of the front surface and the back surface of the film is less than 0.05. 7. The packaging polyester film according to claim 1, wherein the amount of antimony in the film is 10 mmol% or less per 1 mol of all acid components. 8. Each layer constituting the biaxially oriented laminated polyester film is mainly composed of ethylene terephthalate units, and less than 40% by weight of ethylene-2,6-naphthalate units and / or trimethylene terephthalate units and / or trimethylene-2. 2. A polymer or mixture of polymers containing 6,6-naphthalate units.
The polyester film for packaging according to any one of to 7.