JP6044127B2 - Laminated film - Google Patents

Description

  The present invention relates to a packaging material used in the packaging field of foods, pharmaceuticals, and the like, and more specifically, a laminated film in which a coating layer and an inorganic thin film are formed on a plastic substrate, and even when subjected to a retort treatment, It is related with the laminated film excellent in the adhesiveness between and the gas barrier property.

  Packaging materials used for foods, pharmaceuticals, etc. should have the property of blocking gases such as oxygen and water vapor, that is, gas barrier properties, in order to suppress the oxidation of proteins and fats, maintain the taste and freshness, and maintain the efficacy of pharmaceuticals. It has been demanded. In addition, gas barrier materials used in electronic devices such as solar cells, organic EL, and electronic components require higher gas barrier properties than food packaging materials.

  Conventionally, a gas barrier laminate film in which a metal thin film such as aluminum or a thin film of inorganic oxide such as silicon oxide or aluminum oxide is formed on the surface of a base film made of plastic needs to block various gases such as water vapor and oxygen. It is generally used in food applications. Among them, those formed with an inorganic oxide thin film such as silicon oxide, aluminum oxide, and a mixture thereof are widely used because they are transparent and the contents can be confirmed.

  However, the above gas barrier laminate film is an inorganic material due to local high temperature in the formation process, causing damage to the base material, decomposition of low molecular weight parts or additive parts such as plasticizers, degassing, etc. Defects, pinholes, etc. may occur in the thin film layer, and the gas barrier property may be lowered. Furthermore, there is a problem that the inorganic thin film layer is cracked and cracks are generated during post-processing of the packaging material such as printing, laminating, bag making, and the gas barrier property is lowered. In particular, when the inorganic thin film layer is damaged by the above-described process, the gas barrier property is greatly lowered by the subsequent retort treatment, and the interlayer adhesive strength between the inorganic thin film and the resin in contact with the inorganic thin film is lowered, and the contents leak out. There is a problem to do.

  In addition to the above gas barrier laminate film, many gas barrier films have been proposed by coating a resin composition on a base film. In particular, a coating agent using polyvinyl alcohol or ethylene-vinyl alcohol copolymer having a high oxygen barrier property is put into practical use.

  Furthermore, a gas barrier film is also proposed in which a base film made of plastic is coated with a layer having a gas barrier property in which an inorganic layered compound such as montmorillonite is blended with the vinyl alcohol resin. For example, an example in which a layer having a gas barrier property composed of polyvinyl alcohol, a crosslinking agent and an inorganic layered compound is provided on a substrate film, an ethylene-vinyl alcohol copolymer, a water-soluble zirconium crosslinking agent on the substrate film, An example in which a gas barrier property layer made of an inorganic layered compound is provided (for example, see Patent Documents 1 and 2). Since these gas barrier films are cross-linked resin, they can withstand moisture resistance and water resistance such as boiling, but when used for retort, after retort treatment performed under pressure of 120-130 ° C The gas barrier properties and laminate strength were not satisfactory.

  On the other hand, as a method for improving the defects of the gas barrier laminate film having the inorganic thin film formed, an attempt has been made to further provide a layer having gas barrier properties on the inorganic thin film. As an example, a composite of an inorganic and water-soluble polymer containing an inorganic layered compound on an inorganic thin film by coating a water-soluble polymer with an inorganic layered compound and a metal alkoxide or a hydrolyzate thereof on the inorganic thin film. There has been proposed a method of forming (see, for example, Patent Document 3). This method shows excellent characteristics even after retorting, but the stability of the coating liquid is low, and the characteristics at the start and end of coating (that is, the outer peripheral part and inner peripheral part of a roll film that is distributed industrially). However, the characteristics differ due to slight differences in drying and heat treatment in the width direction of the film, and the quality varies greatly depending on the production environment. Furthermore, since the sol-gel coat is poor in flexibility, it has been pointed out that pinholes are easily generated when the film is bent or impacted, and the gas barrier property may be lowered.

  Against this background, there has been a demand for an improvement by a coating method that does not involve a sol-gel reaction or the like on the inorganic thin film layer, that is, a coating method that mainly uses a resin and involves a crosslinking reaction during coating. As a gas barrier laminate of such a method, a gas barrier laminate in which a resin layer containing an inorganic layered compound having a specific particle size and aspect ratio is coated on an inorganic thin film (for example, Patent Document 4), A gas barrier laminate (for example, Patent Document 5) in which a barrier resin containing a silane coupling agent is coated is disclosed.

  In addition, as another method for improving the deterioration of the gas barrier laminated film formed with the inorganic thin film, various aqueous polyurethane resins, polyester resins, or polyurethanes between the polyester base film and the inorganic thin film layer formed by, for example, vapor deposition A method of providing a coating layer made of a mixture of polyester and polyester is known (for example, Patent Document 6). Furthermore, in order to improve the water resistance of the coating layer under wet heat, there is known a method of providing a coating layer composed of various aqueous polyurethane and / or aqueous polyester resins and an oxazoline group-containing water-soluble polymer (for example, Patent Document 7). ). In addition, in order to prevent deterioration of the inorganic thin film layer due to oligomer precipitation from the base film, a method of providing a coating layer composed of a mixture of various aqueous acrylic resins and an oxazoline group-containing water-soluble polymer is known (for example, patents). Reference 8). In this case, water resistance is improved by adding an oxazoline group and crosslinking.

JP 2005-349769 A JP 2008-297527 A JP 2000-43182 A Japanese Patent No. 3681426 Japanese Patent No. 3441594 JP-A-2-50837 JP 2002-301787 A Japanese Patent Laid-Open No. 11-179836

  However, even with these methods, although improvement in characteristics under boiling and high humidity is recognized, a gas barrier film having a stable quality and satisfactory gas barrier properties after retort and laminate strength has not been obtained. Was the current situation.

  The present invention has been made against the background of the problems of the prior art. The purpose of the present invention is to provide a laminated body with an inorganic thin film, which is excellent in oxygen and water vapor barrier properties even after retorting, and delamination after retorting. An object of the present invention is to provide a laminated film that has adhesiveness that does not occur, is easy to manufacture, and is economical.

  As a result of intensive studies to solve the above problems, the present inventor provided a coating layer containing an acrylic resin and a resin having an oxazoline group on at least one surface of the plastic substrate film, and further on the coating layer. It is a laminated film provided with an inorganic thin film layer, and the rate of change of the surface roughness Ra before and after the retorting of the laminated film is 1 to 18%, so that it has a barrier property against oxygen and water vapor even after retorting. The present inventors have found the fact that it is possible to provide an excellent laminated film having adhesion that does not cause delamination after retorting, and have arrived at the present invention.

The present invention uses a resin having an oxazoline group for the coating layer of the laminated film, and further uses an acrylic resin, so that the deformation of the coating layer surface can be reduced even after the retort treatment. It is a laminated film based on a technical idea that does not exist in the prior art that can reduce damage to the laminated inorganic thin film layer, and as a result, can maintain the gas barrier property of the laminate formed with the inorganic thin film layer even during retort processing.

The above-described problem can be achieved by the following solution means.
1. A coating film comprising an acrylic resin and a resin having an oxazoline group is provided on at least one surface of a plastic substrate film, and further, an inorganic thin film layer is provided on the coating layer. The amount of carboxyl groups [mmol] with respect to the amount of oxazoline groups [mmol] in the constituent resin composition is 20 mmol% or less, the periphery of the laminated film is fixed with a metal frame, and pressurized hot water at a temperature of 130 ° C. A laminated film characterized in that the change rate of the surface roughness Ra before and after the retort treatment held therein for 30 minutes is 1 to 18%.
2. 1 above. It is a laminated film of description, Comprising: The average thickness of a coating layer is 5-150 nm, The laminated film characterized by the above-mentioned.
3. 2. It is a laminated film of description, Comprising: The amount of oxazoline groups of resin which has an oxazoline group is 5.1-9.0 mmol / g, The laminated film characterized by the above-mentioned.
4). 3 above. It is a laminated film of description, Comprising: The laminated | multilayer film characterized by including a urethane resin in a coating layer.
5. 4. above. It is a laminated film of description, Comprising: The urethane resin in a coating layer has a carboxylic acid group, The acid value is 10-40 mgKOH / g, The laminated film characterized by the above-mentioned. 6). 5. above. It is a laminated film of description, Comprising: The acrylic resin in a coating layer has a carboxylic acid group, The acid value is 40 mgKOH / g or less, The laminated film characterized by the above-mentioned.
7). 6. above. The laminated film described above, wherein the coating layer is formed by curing a resin mixture containing 20 to 70% by weight of a resin having an oxazoline group, 10 to 60% by weight of an acrylic resin, and 10 to 60% by weight of a urethane resin. A laminated film characterized by
8). Said 7. 2. The laminated film according to claim 1, wherein the inorganic thin film layer is a composite oxide layer of alumina and silica.

The laminated body in which the inorganic thin film layer is formed on the laminated film of the present invention is excellent in oxygen barrier property and water vapor barrier property and excellent in laminate strength even after retorting.
Further, the laminate is excellent in production stability and economy, and uniform characteristics are easily obtained.

Hereinafter, embodiments of the laminated film and the manufacturing method thereof of the present invention will be described.
[Base film]
The base film used in the present invention is, for example, a film obtained by melt-extrusion of plastic and stretching, cooling, and heat setting in the longitudinal direction and / or width direction as necessary. 6, represented by polyamide 6, polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and the like represented by nylon 6, nylon 6, 6 and nylon 12, polyester, polyethylene, polypropylene, polybutene, etc. In addition to polyolefins, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, polystyrene, polylactic acid and the like can be mentioned. Polyester, especially polyethylene terephthalate or polyethylene terephthalate copolymerized with other components is preferred in terms of heat resistance, step stability, and transparency.

As the substrate film in the present invention, those having an arbitrary film thickness can be used according to desired purposes such as mechanical strength and transparency. Although not particularly limited, it is usually recommended to be 5 to 250 μm, and when used as a packaging material, it is preferably 10 to 60 μm.
The transparency of the base film is not particularly limited, but when used as a packaging material that requires transparency, a film having a light transmittance of 50% or more is desirable.

In addition, the base film in the present invention may be a laminated film of one kind or two or more kinds of plastic films. There are no particular limitations on the type of laminate, the number of laminations, the lamination method, and the like in the case of a laminated film, and any one of known methods can be selected according to the purpose.
Further, the base film may be subjected to surface treatment such as corona discharge treatment, glow discharge, flame treatment, surface roughening treatment, etc., as long as the object of the present invention is not impaired. Processing, printing, decoration and the like may be performed.

[Coating layer]
The laminated film of the present invention is a laminated film in which a coating layer containing an acrylic resin and a resin having an oxazoline group is provided on at least one surface of a plastic substrate film, and an inorganic thin film layer is provided on the coating layer. It is important to satisfy that the change rate of the surface roughness Ra before and after the retort treatment of the laminated film is 1 to 18%.
More preferably, it is 1.5-15%, More preferably, it is 2-12%. By providing the coating layer of the present invention, the rate of change can be within the above range, the inorganic thin film layer is not deteriorated due to the deformation of the coating layer, and the gas barrier property can be maintained.
If the rate of change of the surface roughness is less than 1%, the degree of freedom of deformation of the coating layer is too small and the flexibility is lacking. As a result, there is a concern that stress is applied to the inorganic thin film layer. On the other hand, when it is 18% or more, the deformation of the coating layer becomes large, the deformation also affects the inorganic thin film, and as a result, sufficient gas barrier properties may not be obtained.

  The surface roughness Ra of the laminated film obtained by laminating the coating layer and the inorganic thin film layer in the present invention is preferably 0.5 nm to 10 nm, more preferably 1.0 nm to 9.5 nm, still more preferably 2.0 nm to 9.0 nm. When Ra is 0.5 nm or less, the unevenness is too fine, and there is a possibility that the film lacks the density of the inorganic substance at the interface between the coating layer and the inorganic thin film layer. On the other hand, when Ra is 10 nm or more, the inorganic thin film layer is not uniformly deposited due to the unevenness of the surface of the coating layer, and the normal barrier property may be deteriorated.

The coating layer in the present invention uses a resin having an oxazoline group. In particular, it is preferable that an unreacted oxazoline group is present in the coating layer.
The oxazoline group has high affinity with inorganic thin films such as metal oxides, and can react with oxygen deficient portions of inorganic oxides and metal hydroxides generated during the formation of inorganic thin film layers, thus providing strong adhesion to inorganic thin film layers. Indicates. Further, the unreacted oxazoline group present in the coating layer can react with the carboxylic acid terminal generated by hydrolysis of the base film and the coating layer to form a crosslink, and the water resistance of the coating layer can be maintained. .

In addition, an unreacted oxazoline group portion and a reacted cross-linked portion coexist in the coating layer, thereby forming a film having water resistance and flexibility, and even when retorted, the coating layer As a result, the gas barrier property can be maintained without damaging the inorganic thin film layer.

  Conventionally, when the adhesion between an inorganic thin film layer and a laminated film provided with a base film or a coating layer is insufficient, when the laminated film on which the inorganic thin film layer is formed is retorted, water enters between the layers, and the inorganic thin film Peeling occurs at the interface between the layer and the substrate film. As a result of the peeled portion as a trigger, the inorganic thin film layer is cracked or floated, resulting in a decrease in barrier properties and laminate strength.

  Moreover, delamination at the time of retorting also occurs between the base film and the coating layer. That is, at the time of the retort treatment, the plastic in the base film, for example, a plastic such as a polyester resin or the resin in the coating layer is hydrolyzed to break the bond. As a result, poor adhesion between the base film and the coating layer occurs, and the gas barrier property and laminate strength are reduced as described above.

  Moreover, even if a coating layer with good interlayer adhesion is provided, if the coating layer itself is too soft, the coating layer itself is deformed during retorting, and the inorganic thin film laminated thereon is also deformed. This causes a decrease in gas barrier properties. On the other hand, if the coating layer itself is too hard, the coating layer cracks and deforms due to the stretching stress of the base film when it is retorted, and accordingly, the inorganic thin film laminated on the coating layer is also deformed. This also causes a decrease in gas barrier properties.

  That is, the coating layer in the present invention contains a resin containing an oxazoline group, and preferably has an unreacted oxazoline group, so that the adhesion between the layers is strong even during retort and the coating layer is not deformed. As a result, cracking and deterioration of the inorganic thin film can be prevented, and gas barrier properties and laminate strength can be maintained.

  Even a coating layer consisting only of a resin having an oxazoline group can exhibit retort resistance, but the coating layer itself has a slightly insufficient cohesive force when subjected to severe retort treatment for a longer time and at a higher temperature. Damage to the inorganic thin film layer due to deformation of itself is inevitable. Therefore, in the present invention, it is preferable to mix the acrylic resin so that the coating layer can sufficiently withstand the severer retort treatment. By mixing the acrylic resin, the cohesive force of the coating layer itself is improved, and as a result, the water resistance is increased. When the acrylic resin has a carboxylic acid group, it can have a partially crosslinked structure with the oxazoline group, and further improvement in water resistance can be expected.

In the present invention, the retort resistance of the coating layer can be further improved by mixing a urethane resin having a carboxyl group. That is, by reacting the carboxyl group and the oxazoline group in the urethane resin, the coating layer becomes a layer having the flexibility of the urethane resin while being partially crosslinked, and the stress relaxation of the inorganic thin film is performed at a higher level. be able to.
Although the laminated film of the present invention is a laminated body provided with an inorganic thin film layer, the gas barrier property and interlayer adhesion of the inorganic thin film layer can be maintained even after retorting according to the above embodiment.

Next, the configuration of the coating layer will be described in detail.
(Resin having an oxazoline group)
In the present invention, it is necessary to contain a resin having an oxazoline group in the coating layer. Examples of the resin having an oxazoline group include a polymer having an oxazoline group, for example, a polymerizable unsaturated monomer having an oxazoline group, and other polymerizable unsaturated monomers as required, and a conventionally known method (for example, solution polymerization). And a polymer obtained by copolymerization by emulsion polymerization or the like.

  Examples of the polymerizable unsaturated monomer having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2- Examples thereof include isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

  Examples of the other polymerizable unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meta ) Acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate and other (meth) acrylic acid alkyl or cycloalkyl esters having 1 to 24 carbon atoms; 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate (Meth) acrylic acid hydroxyalkyl esters such as (meth) acrylic acid, etc .; vinyl aromatic compounds such as styrene and vinyltoluene; (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl Addition product of meth) acrylate, glycidyl (meth) acrylate and amines; polyethylene glycol (meth) acrylate; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, (meth) acrylonitrile, etc. . These may be selected singly or in appropriate combination of two or more.

  The composition molar ratio of the copolymer of the polymerizable unsaturated monomer having an oxazoline group and another polymerizable unsaturated monomer is such that the polymerizable unsaturated monomer having an oxazoline group is 30 to 70 mol%. It is preferable that it is 40 to 65 mol%.

  The resin having an oxazoline group used in the present invention is preferably a water-soluble resin because it improves compatibility with other resins, improves wettability, improves the crosslinking reaction efficiency, and the transparency of the coating layer.

  In order to make the resin having an oxazoline group water-soluble, it is preferable to contain a hydrophilic monomer as another polymerizable unsaturated monomer. As the hydrophilic monomer, a monomer having a polyethylene glycol chain such as 2-hydroxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, a monoester compound of (meth) acrylic acid and polyethylene glycol, (Meth) acrylic acid 2-aminoethyl and its salts, (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, (meth) acrylonitrile, sodium styrenesulfonate, etc. Can be mentioned. Especially, it is preferable to contain the monomer which has polyethyleneglycol chains, such as (meth) acrylic-acid methoxypolyethylene glycol with high solubility to water, and the monoester compound of (meth) acrylic acid and polyethyleneglycol. The molecular weight of the polyethylene glycol chain to be introduced is preferably 200 to 150, more preferably 300 to 700.

  Moreover, it is preferable that oxazoline group content of resin which has an oxazoline group in the resin composition for coating layers which comprises the coating layer of this invention is 5.1-9.0 mmol / g. More preferably, it is in the range of 6.0 to 8.0 mmol / g. There are examples in which resins having an oxazoline group up to about 5.0 mmol / g have been used so far (see, for example, Patent Document 8), but in the present invention, by using a resin having a large amount of oxazoline groups, The coating layer has a crosslinked structure, and at the same time, the oxazoline group can be left in the coating layer, so that an effect of easily controlling the balance between water resistance and flexibility can be expected.

  In addition, the number average molecular weight of the resin having an oxazoline group in the resin composition for a coating layer constituting the coating layer of the present invention is in the range of 20000 to 50000 in order to develop the flexibility and cohesion of the coating layer. It is preferable. More preferably, it is 25000-45000. When the molecular weight is less than 20000, the binding force when the crosslinked structure is taken increases, so that the flexibility of the coating layer at the time of retort treatment cannot be obtained sufficiently, and the stress load on the inorganic thin film layer increases. On the other hand, when the molecular weight is 50000 or more, the water resistance is lowered because the cohesive force of the coating layer is not sufficient.

  The content ratio of the resin having an oxazoline group in the coating layer resin composition constituting the coating layer is 100% of all resin components in the composition (for example, the total of the resin having the oxazoline group, the acrylic resin, and the urethane resin described later). It is preferable that it is 20-70 mass% in mass%, More preferably, it is 30-60 mass%, More preferably, it is good that it is 40-50 mass%. When the content ratio of the resin having oxazoline is less than 20% by mass, the water-resistant adhesion and flexibility effects due to the oxazoline group tend not to be sufficiently exhibited. On the other hand, when it exceeds 70% by mass, the cohesive strength of the coating layer May be insufficient, and the water resistance may be reduced.

(acrylic resin)
The resin composition constituting the coating layer contains an acrylic resin. As the acrylic resin, an aqueous acrylic resin containing an alkyl acrylate and / or an alkyl methacrylate (hereinafter sometimes collectively referred to as “alkyl (meth) acrylate”) as a main component is used. Specifically, the aqueous acrylic resin contains an alkyl (meth) acrylate component usually in a content of 40 to 95 mol%, and, if necessary, a vinyl monomer component that can be copolymerized and has a functional group. Examples thereof include water-soluble or water-dispersible resins usually contained at a content of 5 to 60 mol%. By making the content rate of the alkyl (meth) acrylate in water-based acrylic resin 40 mol% or more, especially applicability | paintability, the intensity | strength of a coating film, and blocking resistance become favorable. On the other hand, the content ratio of alkyl (meth) acrylate is 95 mol% or less, and a compound having a specific functional group as a copolymerization component is introduced into an aqueous acrylic resin by 5 mol% or more to achieve water-solubilization or water dispersion. It can be made easy and the state can be stabilized over a long period of time. As a result, the adhesion between the coating layer and the base film, the strength of the coating layer due to the reaction in the coating layer, water resistance, chemical resistance Etc. can be improved.

Examples of the alkyl group in the alkyl (meth) acrylate include a methyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group and the like.
Examples of the functional group in the vinyl monomer that is copolymerizable and has a functional group include a carboxyl group, an acid anhydride group, a sulfonic acid group or a salt thereof, an amide group, an alkylolated amide group, an amino group ( A substituted amino group), an alkylolated amino group or a salt thereof, a hydroxyl group, an epoxy group, and the like. Particularly preferred are a carboxyl group, an acid anhydride group, and an epoxy group. These functional groups may be used alone or in combination of two or more.

Examples of the compound having a carboxyl group or an acid anhydride group that can be used as a vinyl monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, alkali metal salts thereof, and alkaline earth metals. Examples thereof include salts and ammonium salts, and further maleic anhydride and the like.
Examples of the compound having a sulfonic acid group or a salt thereof that can be used as a vinyl monomer include vinyl sulfonic acid, styrene sulfonic acid, metal salts (such as sodium) and ammonium salts of these sulfonic acids.

Examples of the compound having an amide group or an alkylolated amide group that can be used as a vinyl monomer include acrylamide, methacrylamide, N-methylmethacrylamide, methylol acrylamide, methylol methacrylamide, and ureido vinyl ether. , Β-ureido isobutyl vinyl ether, ureido ethyl acrylate and the like.
Examples of the compound having an amino group, an alkylolated amino group, or a salt thereof that can be used as the vinyl monomer include diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2- Examples thereof include aminobutyl vinyl ether, dimethylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, and those obtained by converting these amino groups to methylol, and those quaternized with alkyl halide, dimethyl sulfate, sultone, or the like.

Examples of the compound having a hydroxyl group that can be used as a vinyl monomer include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyvinyl ether, 5- Examples thereof include hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, and polypropylene glycol monomethacrylate.
Examples of the compound having an epoxy group that can be used as the vinyl monomer include glycidyl acrylate and glycidyl methacrylate.

  In addition to the alkyl (meth) acrylate and the compound having the functional group described above as a vinyl monomer, the water-based acrylic resin includes, for example, acrylonitrile, styrenes, butyl vinyl ether, maleic acid mono- or dialkyl ester, fumaric acid mono- or dialkyl Esters, itaconic acid mono- or dialkyl esters, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, vinyl trimethoxysilane, and the like may be used in combination.

  The acrylic resin preferably has a carboxyl group and has an acid value of 40 mgKOH / g or less. Thereby, the oxazoline group and the carboxyl group described above react, and the coating layer can maintain flexibility while partially cross-linking, and can further improve the cohesive force and relieve the stress of the inorganic thin film. A more preferable acid value is 20 mgKOH / g or less, and a more preferable acid value is 10 mgKOH / g or less. If the acid value exceeds 40 mgKOH / g, the crosslinking layer is too soft due to excessive crosslinking, and the stress on the inorganic thin film layer during retort treatment may increase.

  The content ratio of the acrylic resin in the resin composition for the coating layer constituting the coating layer is 100% by mass of all resin components in the composition (for example, the total of the resin having the oxazoline group, the acrylic resin, and the urethane resin described later). 10 to 60% by mass, more preferably 15 to 55% by mass, and still more preferably 20 to 50% by mass. If the content of the acrylic resin is less than 10% by mass, the effects of water resistance and solvent resistance may not be sufficiently exhibited. On the other hand, if the content exceeds 60% by mass, the coating layer becomes too hard, so that the retort treatment There is a tendency for the stress load to the inorganic thin film layer to increase.

(Urethane resin)
It is preferable that the resin composition which comprises a coating layer contains a urethane resin.
As the urethane resin, for example, a water-soluble or water-dispersible resin obtained by reacting a polyhydroxy compound and a polyisocyanate compound according to a conventional method can be used. In particular, as the aqueous polyurethane resin, one containing a carboxyl group or a salt thereof is preferably used in order to increase the affinity with an aqueous medium. The components of these urethane resins can be specified by nuclear magnetic resonance analysis or the like.

  Examples of the polyhydroxy compound that is a component of the urethane resin include polyethylene glycol, polypropylene glycol, polyethylene / propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, and triethylene. Glycol, neopentyl glycol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, glycerin and the like.

  Examples of the polyisocyanate compound as a constituent component of the urethane resin include isomers of toluylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, and isophorone diisocyanate. , Cycloaliphatic diisocyanates such as 4,4-dicyclohexylmethane diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, or these And polyisocyanates obtained by adding a single compound or a plurality of these compounds in advance with trimethylolpropane or the like.

  In order to introduce a carboxyl group or a salt thereof into a urethane resin, for example, as a copolymer component by using a polyol compound (polyhydroxy compound) having a carboxyl group such as dimethylolpropionic acid and dimethylolbutanoic acid. It may be introduced and neutralized with a salt forming agent. Specific examples of the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, tri-n-butylamine, N such as N-methylmorpholine and N-ethylmorpholine. -N-dialkylalkanolamines such as alkylmorpholines, N-dimethylethanolamine, N-diethylethanolamine and the like. These may be used alone or in combination of two or more.

  The urethane resin preferably has a carboxyl group and has an acid value in the range of 10 to 40 mgKOH / g. Thereby, the oxazoline group and the carboxyl group described above react, and the coating layer can maintain flexibility while partially cross-linking, and can further improve the cohesive force and relieve the stress of the inorganic thin film. More preferably, it is in the range of 15 to 35 mgKOH / g, and further preferably in the range of 20 to 30 mgKOH / g.

  When the urethane resin is contained in the coating layer, the content ratio of the urethane resin in the resin composition constituting the coating layer is the total resin component in the composition (for example, the resin having an oxazoline group, the acrylic resin, and the urethane described later) It is preferable that it is 10-60 mass% in 100 mass% of (total of resin), More preferably, it is 15-55 mass%, More preferably, it is good that it is 20-50 mass%. By including a urethane resin in the above range, improvement in water resistance can be expected. The aqueous polyurethane resin is used together with the aqueous acrylic resin.

  In the coating layer resin composition, the carboxyl group amount [mmol] relative to the oxazoline group amount [mmol] in the composition is preferably 20 mmol% or less, more preferably 15 mmol% or less. is there. If the amount of carboxyl groups exceeds 20 mmol%, the cross-linking reaction proceeds too much during the formation of the coating layer, resulting in the consumption of a large amount of oxazoline groups, which decreases the adhesion with the inorganic thin film layer and the flexibility of the coating layer. As a result, there is a possibility that the gas barrier property and adhesion after the retort treatment may be impaired.

  In the present invention, the thickness of the coating layer is preferably 5 to 150 nm. Thereby, the thickness of the coating layer can be controlled uniformly, and as a result, the inorganic thin film layer can be densely deposited. Moreover, since the cohesion force of coating layer itself improves and the adhesive force between each layer of an inorganic thin film layer-coating layer-base film becomes dense, the water resistance of a coating film can also be improved. The film thickness of the coating layer is preferably 10 nm or more, more preferably 30 nm or more, further preferably 50 nm or more, preferably 140 nm or less, more preferably 110 nm or less, and still more preferably 100 nm or less. If the film thickness of the coating layer exceeds 150 nm, the cohesive force of the coating layer becomes insufficient, and the uniformity of the coating layer also decreases, so that the oxygen barrier property and the water vapor barrier property during retort processing may not be sufficiently exhibited. In addition, not only the gas barrier property is lowered, but also the production cost is increased, which is economically disadvantageous. On the other hand, if the film thickness of the coating layer is less than 5 nm, sufficient interlayer adhesion to the substrate film cannot be obtained.

The method for providing the coating layer on at least one surface of the base film is not particularly limited, and for example, a coating method can be employed.
Among the coating methods, preferred examples include an off-line coating method and an in-line coating method. For example, in the case of an in-line coating method performed in the process of producing a base film,
The conditions for drying and heat treatment during coating depend on the thickness of the coat and the conditions of the apparatus, but it is preferable that the coating is sent to the stretching step in the perpendicular direction immediately after coating and dried in the preheating zone or stretching zone of the stretching step. In such a case, it is normally performed at about 50 to 250 ° C.
The base film may be subjected to corona discharge treatment or other surface activation treatment.

  Further, if necessary, the coating layer may contain a small amount of other resin or various known inorganic and organic additives such as an antistatic agent, a slip agent, and an antiblocking agent. It is optional as long as it does not inhibit.

[Inorganic thin film layer]
In the laminated film of the present invention, an inorganic thin film layer is further laminated on the coating layer. The inorganic thin film layer is a thin film made of a metal or an inorganic oxide. The material for forming the inorganic thin film layer is not particularly limited as long as it can be formed into a thin film, but inorganic oxides such as silicon oxide, aluminum oxide, and a mixture of silicon oxide and aluminum oxide are preferable from the viewpoint of gas barrier properties. In particular, a composite oxide of silicon oxide and aluminum oxide is preferable from the viewpoint that both flexibility and denseness of the thin film layer can be achieved. In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably such that Al is in the range of 20 to 70% by mass ratio of metal. More preferably, it is 25 to 65% of range. If the Al concentration is less than 20%, the water vapor barrier property may be lowered. On the other hand, if the Al concentration exceeds 70%, the inorganic thin film layer tends to be hard, and the film is formed during secondary processing such as printing or lamination. There is a possibility that the barrier property is lowered due to the destruction. Here, silicon oxide is various silicon oxides such as SiO and SiO ₂ or a mixture thereof, and aluminum oxide is various aluminum oxides such as AlO and Al ₂ O ₃ or a mixture thereof.

The mixing ratio of silicon oxide and aluminum oxide in this composite oxide can be determined by a monitor that measures the composition using fluorescent X-rays. The measured object is irradiated with X-rays, the intensity of characteristic X-rays generated from atoms contained in the measured object is measured, converted into a composition, and a value is output. Conversion is based on a calibration curve prepared by measuring a measured object having a known film thickness composition and the relationship with the obtained fluorescent X-rays.
When the plastic substrate film contains the same atoms as those contained in the inorganic oxide layer, for example, when the inorganic oxide layer is SiOx, and the plastic film contains silica powder as a lubricant, Si atoms are commonly used. When it contains, the film which formed the inorganic oxide layer of a different known film thickness beforehand on the plastic base film containing the said atom of the same density | concentration is created, and it measures with this monitor. An unknown inorganic oxide layer thickness can be obtained by a calibration curve prepared by obtaining the relational expression between the obtained fluorescent X-ray intensity and the thickness.

  The film thickness of the inorganic thin film layer is preferably 1 nm or more, more preferably 5 nm or more, preferably 800 nm or less, more preferably 500 nm or less. If the film thickness of the inorganic thin film layer is less than 1 nm, satisfactory gas barrier properties may be difficult to obtain. On the other hand, even if the thickness exceeds 800 nm, the corresponding gas barrier property improvement effect is obtained. However, it is disadvantageous in terms of bending resistance and manufacturing cost.

There is no restriction | limiting in particular as a method of forming an inorganic thin film layer, What is necessary is just to employ | adopt well-known thin film formation methods, such as a vapor deposition method. Hereinafter, a typical method for forming the inorganic thin film layer will be described by taking a silicon oxide / aluminum oxide thin film as an example. As an inorganic thin film forming method by a vapor deposition method, a vacuum vapor deposition method, a sputtering method, a physical vapor deposition method such as an ion plating method (PVD method), a chemical vapor deposition method (CVD method), or the like is appropriately used. For example, when a vacuum deposition method is employed, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al is preferably used as a deposition material. As these vapor deposition raw materials, particles are usually used. At this time, the size of each particle is desirably such that the pressure during vapor deposition does not change, and the preferred particle diameter is 1 mm to 5 mm. For heating, methods such as resistance heating, high frequency induction heating, electron beam heating, and laser heating can be employed. It is also possible to introduce reactive vapor deposition using oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor or the like as a reactive gas, or using means such as ozone addition or ion assist. Furthermore, the film forming conditions can be arbitrarily changed, such as applying a bias to the base film or heating or cooling the base film. Such 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.

  According to the present invention, it is possible to obtain a laminated film having excellent oxygen barrier properties and water vapor barrier properties after retorting, high interlayer adhesion, and excellent laminate strength.

[Heat sealable resin layer]
Since the laminated film of the present invention is usually used as a packaging material, a heat sealable resin layer called a sealant is often formed on an inorganic thin film layer. The heat-sealable resin layer is usually formed by an extrusion lamination method or a dry lamination method. The thermoplastic polymer for forming the heat-sealable resin layer may be any one that can sufficiently exhibit sealant adhesive properties, such as polyethylene resins such as HDPE, LDPE, and LLDPE, PP resin, and ethylene-vinyl acetate copolymer. , Ethylene-α-olefin random copolymer, ionomer resin, and the like can be used.

  The laminate of the present invention further comprises at least one layer of a printing layer, another plastic substrate and / or a paper substrate between or outside the inorganic thin film or substrate plastic film and the heat-sealable plastic film. May be. As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks can be used. Here, examples of the resin used in the printing ink include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. In addition to printing inks, antistatic agents, light blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, antifoaming agents, crosslinking agents, antiblocking agents, antioxidants, etc. Known additives may be added.

  The printing method for providing the printing layer is not particularly limited, and a known printing method such as an offset printing method, a gravure printing method, or a screen printing method can be used. For drying the solvent after printing, known drying methods such as hot air drying, hot roll drying, and infrared drying can be used.

  As other plastic substrates and paper substrates, paper, polyester resin, polyamide resin and biodegradable resin are preferable from the viewpoint of obtaining sufficient rigidity and strength of the laminate. Moreover, it is preferable to laminate | stack a biaxially stretched polyester film and a biaxially stretched nylon film as a film excellent in mechanical strength.

  In particular, when the laminated film of the present invention is used as a packaging material, it is preferable to laminate a nylon film between the inorganic thin film and the heat-sealable plastic film in order to improve mechanical properties such as pinhole properties.

  As a kind of nylon, nylon 6, nylon 66, metaxylene adipamide and the like are usually mentioned. Moreover, the thickness of a nylon film is 10-30 micrometers normally, Preferably it is 15-25 micrometers. If it is thinner than 10 μm, the strength is insufficient, and if it exceeds 30 μm, the waist is too strong to be suitable for processing. As the nylon film, a biaxially stretched film having a stretching ratio in each direction of vertical and horizontal is usually 2 times or more, preferably about 2.5 to 4 times. Such a nylon film has good pinhole properties and good piercing strength.

  According to the present invention, it is possible to obtain a laminated film having excellent oxygen barrier properties and water vapor barrier properties after retorting, high interlayer adhesion, and excellent laminate strength.

  EXAMPLES Next, although this invention is demonstrated in detail using an Example and a comparative example, naturally this invention is not limited to a following example. Unless otherwise specified, “%” means “% by mass”, and “part” means “part by mass”.

The evaluation method used in the present invention is as follows.
(1) Preparation of laminated laminate On the inorganic thin film layers of the laminated films obtained in Examples and Comparative Examples, urethane two-component curable adhesives ("Takelac A525S" and "Takenate A50" manufactured by Mitsui Chemicals, Inc.) 13.5: 1) and a 15 μm-thick nylon film (N1100, manufactured by Toyobo Co., Ltd.) was bonded together by a dry laminating method. A non-stretched polypropylene film (P1147 manufactured by Toyobo Co., Ltd.) having a thickness of 70 μm was bonded as a resin and aged at 40 ° C. for 4 days to obtain laminated gas barrier laminated films of Examples 1 to 5 and Comparative Examples 1 to 3. It was. The thickness of the adhesive layer was about 4 μm after drying.

(2) Evaluation method of water vapor permeability About the laminate laminate for evaluation prepared in (1) above, according to the JIS-K7129-B method, a water vapor permeability measuring device ("PERMATRAN-W 3 / 33MG" manufactured by MOCON) ) Was used to measure the water vapor permeability under normal conditions in an atmosphere at a temperature of 40 ° C. and a humidity of 100% RH. In the measurement, the humidity of the film was adjusted in such a direction that water vapor permeates from the plastic film side toward the gas barrier resin composition layer side.
On the other hand, the laminate laminate for evaluation was subjected to a retort treatment that was held in pressurized hot water at a temperature of 130 ° C. for 30 minutes, and then dried at 40 ° C. for 24 hours. The water vapor permeability (after retort treatment) was measured in the same manner as above.

(3) Oxygen permeability evaluation method Oxygen permeability measuring device according to JIS K7126 B method JIS-K7126-2 electrolysis sensor method (Appendix A) for the laminate laminate for evaluation created in (1) above ("CON-TRAN 2/20" manufactured by MOCON) was used, and the oxygen permeability in a normal state was measured in an atmosphere of a temperature of 23 ° C and a humidity of 65% RH.
On the other hand, the laminate laminate for evaluation was subjected to a retort treatment that was held in pressurized hot water at a temperature of 130 ° C. for 30 minutes, and then dried at 40 ° C. for 24 hours, and the resulting laminate laminate after the retort treatment was obtained. In the same manner as above, oxygen permeability (after retort treatment) was measured.

(4) Laminate Strength Evaluation Method The laminate laminate A produced in (1) above was cut into a test piece with a width of 15 mm and a length of 200 mm, and a Tensilon universal material test under the conditions of a temperature of 23 ° C. and a relative humidity of 65%. The laminate strength (normal state) was measured using a machine (“Tensilon UMT-II-500 type” manufactured by Toyo Baldwin). The laminate strength was measured by setting the tensile speed to 200 mm / min and adding water between the inorganic thin film layer (gas barrier laminate film layer) and the nylon film layer of each laminate film obtained in the examples and comparative examples. Then, the strength when peeled at a peel angle of 90 degrees was measured.
On the other hand, the laminate laminate A produced above was subjected to a retort treatment that was held in pressurized hot water at a temperature of 130 ° C. for 30 minutes, and then immediately after the obtained laminate laminate after the retort treatment was Similarly, a test piece was cut out and the laminate strength (after retort treatment) was measured in the same manner as described above.

(5) Surface roughness measurement of laminated film The surface roughness (Ra) of the inorganic thin film layer of the laminated film obtained by laminating the coating layer and the inorganic thin film layer obtained in Examples and Comparative Examples is the scanning probe microscope (SPM). Was used to evaluate. SPM used was SPA 300 manufactured by SII Nano Technology (probe station: Nanonavi). The observation area was 2 μm × 2 μm, and the number of x data was 1024 and the number of y data was 512. The observation place was a place where there was no protrusion or depression due to a lubricant or filler in the film. For observation, a cantilever DF20 (available from SII Nano Technology) was used. The obtained SPM image was subjected to a flattening process in software attached to the apparatus to obtain a surface roughness Ra value. The flattening process is basically a quadratic inclination correction, and the flat process is performed as necessary. SPM observation was carried out at 10 or more locations in one sample, and the average value was used for the Ra value. Under the above conditions, the surface roughness Ra in a normal state of the laminated film in which the coating layer and the inorganic thin film layer were laminated was measured.
On the other hand, for the laminated film in which the coating layer and the inorganic thin film layer are laminated, the periphery of the laminated body is fixed with a metal frame and subjected to a retort treatment for 30 minutes to be held in pressurized hot water at a temperature of 130 ° C. The surface roughness Ra (after retort treatment) was measured in the same manner as described above for the laminated film after retort treatment obtained by drying at 40 ° C. for 24 hours.
The surface roughness change rate X before and after retorting is calculated by dividing the absolute value of the difference between "surface roughness before retort" and "surface roughness after retort" by "surface roughness before retort". did.

X = (| (surface roughness before retorting) − (surface roughness after retorting) |) × 100
/ (Surface roughness before retort)

(6) Measuring method of film thickness of coating layer In each example and comparative example, the laminated film in the stage where only the coating layer was laminated on the base film was used as a sample, the sample was obliquely cut, and the obtained oblique cutting surface The thickness of the coating layer was determined by measuring the height from the coating layer surface to the coating layer / base film interface.

  The sample was obliquely cut using “SAICAS NN04” manufactured by Daipla Wintes Co., Ltd., using a diamond knife as a cutting edge under the conditions of a horizontal speed of 500 nm / second and a vertical speed of 20 nm / second. Since the physical properties of the coating layer and the base film are different at the coating layer / base film interface, the cutting angle changes at the interface, the contrast changes between the coating layer and the base film in the SPM phase image, It was possible to easily recognize from the fact that the uneven state of the cutting surface changed between the layer and the base film.

  The oblique cutting surface is observed using a scanning probe microscope (SPM) (“SPA300 (Nonavi probe station)” manufactured by SII Nano Technology Co., Ltd.) (cantilever: DF3 or DF20 provided by the company, Observation mode: DFM mode). Specifically, observation was performed so that the surface of the coating layer and the oblique cutting surface were within one field of view, and the inclination of the observed image was corrected by performing a flattening process on the surface of the coating layer. In the flattening process, manual tilt correction, which is a function of software attached to the SPM, was used to perform tilt correction in the X direction and the Y direction. The coating layer / substrate film interface was determined by the method described in the section of the cutting method from an image obtained by performing flattening processing (secondary tilt correction, which is a software function) on the entire observation field.

(7) Amount of Oxazoline Group of Resin Having Oxazoline Group A resin having an oxazoline group was freeze-dried and analyzed by ¹ H-NMR analysis using a nuclear magnetic resonance analyzer (NMR) (“Gemini-200” manufactured by Valian). The absorption peak intensity derived from the oxazoline group and the absorption peak intensity derived from other monomers were determined, and the amount of oxazoline group (mmol / g) was calculated from the peak intensity.

<Preparation of each material used for resin composition for coating layer>
(Resin having an oxazoline group (A-1))
A flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube and a thermometer was charged with 460.6 parts of isopropyl alcohol and heated to 80 ° C. while gently flowing nitrogen gas. A monomer mixture consisting of 126 parts of methyl methacrylate, 210 parts of 2-isopropenyl-2-oxazoline and 84 parts of methoxypolyethylene glycol acrylate prepared in advance, and 2,2′-azobis as a polymerization initiator. An initiator solution consisting of 21 parts of (2-methylbutyronitrile) (“ABN-E” manufactured by Nippon Hydrazine Kogyo Co., Ltd.) and 189 parts of isopropyl alcohol was dropped from the dropping funnel over 2 hours, and reacted. The reaction was continued for 5 hours after completion. During the reaction, nitrogen gas was kept flowing, and the temperature in the flask was kept at 80 ± 1 ° C. Thereafter, the reaction solution was cooled, and the obtained polymer was dissolved in ion-exchanged water to obtain a resin (A-1) having an oxazoline group having a solid content concentration of 25%. The obtained resin (A-1) having an oxazoline group had an oxazoline group amount of 4.3 mmol / g, and the number average molecular weight measured by GPC (gel permeation chromatography) was 20,000.

(Resin having an oxazoline group (A-2))
A resin (A-2) having an oxazoline group with a solid content concentration of 10% having a different composition (the amount of oxazoline group and the molecular weight) was obtained in the same manner as the synthesis of the resin (A-1) having an oxazoline group. The amount of oxazoline groups of the obtained resin (A-2) having an oxazoline group was 7.7 mmol / g, and the number average molecular weight measured by GPC was 40000.

(Acrylic resin (B-1))
As an acrylic resin, a commercially available 25% by weight emulsion of an acrylic ester copolymer (“MOVINY (registered trademark) 7980” manufactured by Nichigo Movinyl Co., Ltd.) was prepared. The acid value of this acrylic resin (B-1) ( Theoretical value) was 4 mg KOH / g.

(Urethane resin (C-1))
In a four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube and a thermometer, 72.96 parts of 1,3-bis (isocyanatomethyl) cyclohexane and 12.60 parts of dimethylolpropionic acid And 11.74 parts of neopentyl glycol, 112.70 parts of polyester diol having a number average molecular weight of 2000, and 85.00 parts of acetonitrile and 5.00 parts of N-methylpyrrolidone as a solvent were added under a nitrogen atmosphere. The mixture was stirred at 0 ° C. for 3 hours, and it was confirmed that the reaction solution reached a predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 9.03 parts of triethylamine was added to obtain a polyurethane prepolymer solution (isocyanate group-terminated prepolymer).
Next, 450 parts of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, adjusted to 25 ° C., stirred and mixed at 2000 min−1, and the polyurethane prepolymer solution obtained above (isocyanate group). The total amount of the terminal prepolymer was added and dispersed in water. Then, water-soluble polyurethane resin (C-1) with a solid content concentration of 30% was prepared by removing a portion of acetonitrile and water under reduced pressure. The acid value (theoretical value) of the obtained urethane resin (C-1) was 25 mgKOH / g.

(Polymerization of polyester resin (D-1))
Production Example of Copolyester Resin A stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser was charged with 466 parts of dimethyl terephthalate, 466 parts of dimethyl isophthalate, 401 parts of neopentyl glycol, 443 parts of ethylene glycol, and tetra -0.52 part of n-butyl titanate was charged, and a transesterification reaction was performed from 160 ° C to 220 ° C over 4 hours. Next, 23 parts of fumaric acid was added and the temperature was raised from 200 ° C. to 220 ° C. over 1 hour to carry out an esterification reaction. Next, the temperature was raised to 255 ° C., the pressure of the reaction system was gradually reduced, and the mixture was reacted for 1 hour and 30 minutes under a reduced pressure of 0.2 mmHg. The mixture was stirred to obtain a water-soluble polyester resin having a solid content of 25%. The obtained polyester was light yellow and transparent and had a weight average molecular weight of 12,000.

Example 1
(1) Adjustment of coating liquid Each material was mixed with the following compounding ratio, and the coating liquid (resin composition for coating layers) was produced. The mass ratio in terms of solid content of the resin having an oxazoline group, the acrylic resin, and the urethane resin in the obtained coating solution is as shown in Table 1.
67.53% by mass of water
Isopropanol 5.00% by mass
Resin having oxazoline group (A-2) 20.00% by mass
Acrylic resin (B-1) 4.80 mass%
Urethane resin (C-1) 2.67% by mass

(2) Production of polyester base film and coating of coating solution Polyethylene terephthalate resin having an intrinsic viscosity of 0.62 (30 ° C., phenol / tetrachloroethane = 60/40) is pre-crystallized and then dried to have a T-die Extrusion was carried out at 280 ° C. using an extruder, and rapidly solidified on a drum having a surface temperature of 40 ° C. to obtain an amorphous sheet. Next, the obtained sheet was stretched 4.0 times at 100 ° C. in the longitudinal direction between the heating roll and the cooling roll. And the said coating liquid was coated by the fountain bar coating method on the single side | surface of the obtained uniaxially stretched film. Biaxially stretched polyester with a thickness of 12 μm, led to a tenter while drying, preheated at 100 ° C., stretched 4.0 times transversely at 120 ° C., heat-treated at 225 ° C. while relaxing 6% in the transverse direction A laminated film in which a 50 nm coating layer was formed on the film was obtained.

(3) Formation of inorganic thin film layer A composite oxide layer of silicon dioxide and aluminum oxide was formed as an inorganic thin film layer on the coating layer forming surface of the film obtained in (2) above by an electron beam evaporation method. As the evaporation source, particulate SiO2 (purity 99.9%) and A1 ₂ O ₃ (purity 99.9%) of about 3 mm to 5 mm were used. Here, the composition of the composite oxide layer was SiO ₂ / A1 ₂ O ₃ (mass ratio) = 60/40. The film thickness of the inorganic thin film layer (SiO ₂ / A1 ₂ O ₃ composite oxide layer) in the film thus obtained (inorganic thin film layer / coating layer-containing film) was 13 nm. Thus, the film provided with the coating layer and the inorganic thin film layer was obtained.
As described above, a laminated film provided with a coating layer / inorganic thin film layer on a base film was produced. About the obtained laminated | multilayer film, the surface roughness measurement before and behind a retort process was performed. The results are shown in Table 1.
Further, the oxygen permeability, water vapor permeability, and laminate strength were evaluated according to the evaluation method described above. The results are shown in Table 2.

(Examples 2-5, Comparative Examples 1-3)
In preparing the coating solution for forming the coating layer, the amount of each material used and the amount of each material used were changed so that the mass ratio in terms of solid content is as shown in Table 1 (at this time, the total amount of coating solution The proportion of isopropanol occupying was set to 5.00% by mass as in Example 1), or it was carried out except that the coating amount was changed so that the film thickness of the coating layer was as shown in Table 1. A laminated film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Reference Example 1)
A laminated film was produced and evaluated in the same manner as in Example 1 except that the coating layer was not provided. The results are shown in Table 2.

  According to the present invention, even after retorting, the inorganic thin film exhibits excellent gas barrier properties against oxygen and water vapor, and even when subjected to retorting while being a laminated film having an inorganic thin film layer. The interlayer film adhesion between the resins in contact therewith is high, and a laminated film having good laminate strength can be obtained. Such a laminated film is a gas barrier laminated film that is excellent in production stability and economical efficiency and that can easily obtain uniform characteristics. Therefore, the laminated film of the present invention is not limited to food packaging for retort, but also widely used for industrial applications such as solar cells, electronic paper, organic EL elements, semiconductor elements as well as various foods, pharmaceuticals, and industrial products. Can be used.

Claims (8)

A coating film comprising an acrylic resin and a resin having an oxazoline group is provided on at least one surface of a plastic substrate film, and further, an inorganic thin film layer is provided on the coating layer. The amount of carboxyl groups [mmol] with respect to the amount of oxazoline groups [mmol] in the constituent resin composition is 20 mmol% or less, the periphery of the laminated film is fixed with a metal frame, and pressurized hot water at a temperature of 130 ° C. A laminated film characterized in that the change rate of the surface roughness Ra before and after the retort treatment held therein for 30 minutes is 1 to 18%.   It is a laminated film of Claim 1, Comprising: The average thickness of a coating layer is 5-150 nm, The laminated body characterized by the above-mentioned.   3. The laminated film according to claim 2, wherein the amount of oxazoline groups of the resin having an oxazoline group is 5.1 to 9.0 mmol / g.   It is a laminated film of Claim 3, Comprising: The laminated film characterized by including a urethane resin in a coating layer.   It is a laminated film of Claim 4, Comprising: The urethane resin in a coating layer has a carboxylic acid group, The acid value is 10-40 mgKOH / g, The laminated film characterized by the above-mentioned. A laminated film according to claim 5, wherein the acrylic resin in the coating layer has a carboxylic acid group, laminated film, wherein the acid value is below 40 mg KOH / g.   7. The laminated film according to claim 6, wherein the coating layer is a resin mixture containing 20 to 70% by weight of a resin having an oxazoline group, 10 to 60% by weight of an acrylic resin, and 10 to 60% by weight of a urethane resin. A laminated film characterized by comprising:   8. The laminated film according to claim 7, wherein the inorganic thin film layer is a composite oxide layer of alumina and silica.