WO2024075588A1

WO2024075588A1 - Multilayered film

Info

Publication number: WO2024075588A1
Application number: PCT/JP2023/034853
Authority: WO
Inventors: 奈津美横田; 敦史山崎
Original assignee: 東洋紡株式会社
Priority date: 2022-10-04
Filing date: 2023-09-26
Publication date: 2024-04-11

Abstract

A multilayered film which comprises a base film and an aluminum oxide layer disposed on at least one side of the base film and satisfies the following requirements (A) and (B). (A) When the multilayered film is etched from the surface of the aluminum oxide layer by time-of-flight secondary ion mass spectrometry and when a position at which the intensity for a fragment ion having a mass number of 102 is 80% of a maximum intensity is taken as the boundary between the aluminum oxide layer and the base film, then the ratio between the intensity a for the mass number 102 (derived from Al₂O₃) and the intensity b for mass number 119 (derived from Al₂O₄H), b/a, is 0.10 or less. (B) When a 15-μm, biaxially stretched nylon film and a 70-μm, unstretched polypropylene film are bonded to the surface of the aluminum oxide layer with a polyurethane-based two-pack curable adhesive applied in a dry thickness of 4 μm and the laminate is aged at a temperature of 40°C for 4 days and then subjected to a wet heat treatment at 130°C for 30 minutes, then the resultant wet laminate has a strength of 1.5 N/15 mm or greater and a water vapor permeability of 2.5 g/m²·day or less.

Description

Laminated Film

The present invention relates to a laminate film used in the packaging fields of foods, medicines, industrial products, etc. More specifically, the present invention relates to a gas barrier laminate film having an aluminum oxide layer and a protective layer, which, by controlling the physical properties of the film, can ultimately exhibit good gas barrier properties and adhesion.

Packaging materials used for food, medicines, etc. are required to have gas barrier properties, that is, properties that block gases such as oxygen and water vapor, in order to inhibit oxidation of proteins and fats and oils, preserve flavor and freshness, and maintain the efficacy of medicines. In addition, gas barrier materials used for electronic devices and electronic components such as solar cells and organic electroluminescence (EL) devices require even higher gas barrier properties than packaging materials for food, etc.

Conventionally, for food applications that require blocking various gases such as water vapor and oxygen, gas barrier laminate films have been commonly used, which have a thin metal film made of aluminum or a thin inorganic film made of inorganic oxides such as silicon oxide or aluminum oxide formed on the surface of a plastic base film. Among these, those with a thin film of inorganic oxides such as silicon oxide, aluminum oxide, or mixtures of these are widely used because they are transparent and allow the contents to be checked.

Silicon oxide (hereafter referred to as silica) and aluminum oxide (hereafter sometimes referred to as alumina) are often used as materials for inorganic thin films. However, silica, which has good gas barrier properties, has a slightly brown color and is insufficient as a transparent gas barrier film. In addition, the evaporation temperature of the raw material for alumina is high, and the evaporation rate during the deposition process is slow. As a result, in order to deposit a film of sufficient thickness to exhibit gas barrier properties, the film formation time is long, which reduces production efficiency and increases costs.

Against this background, Patent Document 1 proposes a technology that suppresses the production of alumina hydroxide and improves hot water resistance by removing moisture contained in the reaction space where the oxidation reaction between evaporated aluminum and oxygen gas occurs during deposition. However, there is no specific description of what properties have been improved in terms of hot water resistance and to what extent.

Patent Document 2 also proposes a technology that allows the gas barrier properties to be maintained even after bending by specifying the depth ratio of SiOH and Si in the inorganic layer.

However, there are many cases where adhesion of laminated bodies is reduced after hot water treatment, such as delamination, but these documents make no mention of adhesion.

Patent No. 6547946 JP 2018-140552 A

The inventors have found that alumina hydroxide is formed near the interface between the plastic film and the alumina vapor deposition, resulting in a problem of reduced moist heat resistance. The present invention aims to provide a gas barrier film having an alumina layer with excellent moist heat resistance.

The inventors discovered that by carefully examining the plasma treatment and thin film thickness during the formation of the aluminum oxide layer, it is possible to provide a gas barrier film with moisture and heat resistance.

That is, the present invention comprises the following:
(1) A laminate film having gas barrier properties, comprising a base film and an aluminum oxide layer laminated on at least one side of the base film, and characterized in that the laminate film satisfies the following requirements (A) and (B):
(A) When the aluminum oxide layer is etched from the surface side by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the position at which the intensity of the fragment ion of mass number 102 (Al ₂ O ₃ ) is 80% of the maximum intensity is defined as the interface with the substrate film, and at that interface, the ratio b/a of the intensity a of mass number 102 (derived from Al ₂ O ₃ ) to the intensity b of mass number 119 (derived from Al ₂ O ₄ H) is 0.10 or less.
(B) A 15 μm biaxially oriented nylon film and a 70 μm unoriented polypropylene film are laminated by a dry lamination method using a polyurethane-based two-component curing adhesive applied to the surface of the aluminum oxide layer of the laminated film so that the thickness after drying is 4 μm, and the film is aged at a temperature of 40° C. for 4 days and then subjected to a wet heat treatment at 130° C. for 30 minutes. After this, the water-exposed laminate strength is 1.5 N/15 mm or more and the water vapor permeability is 2.5 g/ ^m2 ·day or less.
(2) The laminate film according to (1), wherein the aluminum oxide layer has a thickness of 5 to 30 nm.
(3) having a protective layer;
The laminate film according to (1) or (2), wherein the base film, the aluminum oxide layer, and the protective layer are laminated in this order, and the protective layer contains at least one type of urethane resin or ester resin.
(4) The laminate film according to (3), wherein the protective layer contains a silane coupling agent.
(5) A laminate comprising a heat seal layer laminated on the surface of the protective layer of the laminate film according to any one of (1) to (4) above.
(6) A packaging bag, comprising at least a portion of the laminate according to (5).

According to the present invention, regardless of the surface condition of the substrate, by introducing oxygen gas when forming the aluminum oxide layer or by making the thin film layer thicker and increasing the energy of the thin film itself, it is possible to provide a gas barrier film with excellent resistance to moist heat without forming aluminum hydroxide near the substrate film interface.

The laminated film of the present invention is a laminated film comprising a substrate film and an aluminum oxide layer laminated on at least one side of the substrate film, and when etching is performed from the surface side of the aluminum oxide layer by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the position at which the intensity of the fragment ion of mass number 102 (Al ₂ O ₃ ) is 80% of the maximum intensity is defined as the interface with the substrate film, and at the interface, the intensity a of the fragment ion of mass number 102 (derived from Al ₂ O ₃ ) and the intensity b of the fragment ion of mass number 119 (derived from Al ₂ O ₄ and the ratio b/a of the strength b of the aluminum oxide layer of the laminated film to the strength b of the aluminum oxide layer of the laminated film (derived from H) is 0.10 or less, and a 15 μm biaxially oriented nylon film and a 70 μm unoriented polypropylene film are laminated by a dry lamination method using a polyurethane-based two-component curing adhesive applied to the surface of the aluminum oxide layer of the laminated film so that the thickness after drying is 4 μm, and the laminated film is aged at a temperature of 40° C. for 4 days and then subjected to a wet heat treatment at 130° C. for 30 minutes, after which the water-added lamination strength is 1.5 N/15 mm or more, preferably 2.0 N/15 mm or more, and the water vapor permeability is 2.5 g/ ^m2 ·day or less, preferably 2.0 g/ ^m2 ·day or less. First, the plastic substrate film will be described, and then the aluminum oxide layer and protective layer, and other layers to be laminated thereon will be described.

[Base film]
The substrate film used in the present invention may be, for example, a stretched film obtained by melt-extruding a plastic and, if necessary, stretching the plastic in the longitudinal direction (MD direction) and/or the transverse direction (TD direction), cooling, and heat setting. In terms of obtaining mechanical strength, a biaxially stretched film stretched in the longitudinal direction and the transverse direction is preferred. Examples of plastics include polyamides such as nylon 4.6, nylon 6, nylon 6.6, and nylon 12; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate; polyolefins such as polyethylene, polypropylene, and polybutene; as well as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, polystyrene, and polylactic acid. Among these, polyesters are preferred in terms of heat resistance, dimensional stability, and transparency, and in particular polyethylene terephthalate and copolymers obtained by copolymerizing polyethylene terephthalate with other components are preferred.

Plastic resins may be made from biomass-derived or recycled materials.

The base film can be of any thickness depending on the desired purpose and application, such as mechanical strength and transparency. There are no particular limitations on the thickness, but a thickness of 5 to 250 μm is usually recommended, and when used as a packaging material, a thickness of 10 to 60 μm is desirable. From the viewpoints of handling during processing, post-processing, and machine costs, the width of the base film is preferably 1000 mm or more and 5,000 mm or less, more preferably 3,000 mm or less, and even more preferably 2,000 mm or less. There are no particular limitations on the transparency of the base film, but when used as a packaging material requiring transparency, it is desirable for the film to have a light transmittance of 50% or more.

The base film may be a monolayer film made of one type of plastic, or a laminated film in which two or more types of plastic films are laminated. When a laminated film is used, the type of laminated film, the number of layers, the lamination method, etc. are not particularly limited, and can be arbitrarily selected from known methods depending on the purpose. In addition, the base film may be subjected to surface treatments such as corona discharge treatment, glow discharge, flame treatment, surface roughening treatment, etc., as long as they do not impair the purpose of the present invention, and may also be subjected to known anchor coat treatment, printing, decoration, etc.

[Aluminum oxide layer]
The laminate film of the present invention has an aluminum oxide layer on the substrate film.

The thickness of the aluminum oxide layer is usually 1 to 100 nm, preferably 3 to 50 nm, and more preferably 5 to 30 nm. If the thickness of the aluminum oxide layer is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties. On the other hand, even if the thickness is made excessively thick, exceeding 100 nm, the corresponding improvement in gas barrier properties cannot be obtained, and it is actually disadvantageous in terms of flex resistance and manufacturing costs.

There are no particular limitations on the method for forming the aluminum oxide layer, and any known deposition method may be used, such as physical deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, or chemical deposition (CVD). A typical method for forming an aluminum oxide layer is described below. For example, when vacuum deposition is used, aluminum is preferably used as the deposition raw material. Particles are usually used as these deposition raw materials, and in this case, it is desirable that the size of each particle is large enough that the pressure during deposition does not change, and the preferred particle diameter is 1 mm to 5 mm. Heating can be performed by resistance heating, high-frequency induction heating, electron beam heating, laser heating, or other methods. In addition, oxygen is preferable as a reactive gas, and it is also possible to introduce nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc., or to use means such as adding ozone or ion assist. Furthermore, the film formation conditions can be changed arbitrarily, such as applying a bias to the deposition target (laminated film to be subjected to deposition) or heating or cooling the deposition target. The deposition material, reaction gas, bias of the deposition target, heating/cooling, etc. can be changed in the same way when using sputtering or CVD methods.

A plasma treatment may be carried out before forming the thin film layer. Known pretreatment methods such as bipolar sputtering, magnetron sputtering, DC (direct current) sputtering, RF (radio frequency) sputtering, dual magnetron, hollow cathode, hollow anode, etc. may be appropriately adopted. During these treatments, an atmospheric gas is required for discharging, and oxygen is most preferable, but nitrogen, hydrogen, carbon dioxide, etc. may also be introduced.
The amount of the introduced gas is preferably 500 sccm or more, more preferably 750 sccm or more, and even more preferably 1000 sccm or more. If it is less than 500 sccm, plasma discharge does not occur. Furthermore, the plasma output is preferably 15 A or more, more preferably 20 A or more, and even more preferably 25 A or more. If it is less than 15 A, plasma discharge does not occur.
It is preferable to combine all of the above-mentioned preferable types of gases to be introduced, amounts of gases to be introduced, and plasma output.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is one method for analyzing aluminum oxide layers. In this method, the surface of the aluminum oxide layer on the substrate film is etched with sputtered ions, and primary ions are irradiated onto the area, and secondary ions generated by collisions between the ions and the solid surface are detected by a mass spectrometer. By repeating etching and detection, information on the depth direction can be obtained.

When etching is performed from the surface of the aluminum oxide layer, fragment ions with mass numbers of 86 (Al ₂ O ₂ ), 102 (Al ₂ O ₃ ), 118 (Al ₂ O ₄ ), and 145 (Al ₃ O ₄ ) that can be assumed to be derived from Al oxide are detected. In addition, fragment ions with mass numbers of 103 (Al ₂ O ₃ H) and 119 (Al ₂ O ₄ H) that can be assumed to be derived from Al hydroxide are detected. The fragment ions derived from the complete oxide of Al detected near the surface of the aluminum oxide layer attenuate as they approach the interface with the substrate film. The inventors have found that the position where the maximum intensity of the fragment ion with mass number 102 (Al ₂ O ₃ ), which is representative of the complete oxide of Al, becomes 80% when etching is performed from the thin film surface is defined as the interface with the substrate film, and that the intensity ratio between the Al hydroxide and the Al oxide, which have a mass number difference of 17, at that portion can be correlated with the moist heat resistance.

In the present invention, the ratio b/a of the intensity a of mass number 102 ( _derived from _Al2O3 ) to the intensity b of mass _number 119 (derived from _Al2O4H ) is preferably 0.10 or less, more preferably 0.80 or less, and even more preferably 0.60 or less. If it is 0.10 or less, there is almost no Al hydroxide in the vicinity of the interface, and water cannot be present at the interface when a wet heat treatment is performed, improving adhesion.

[Protective Layer]
In the present invention, it is preferable to have a protective layer on the aluminum oxide layer. The aluminum oxide layer laminated on the plastic film is not a completely dense film, but has minute defects scattered therein. By forming a protective layer by applying a specific resin composition for protective layer, which will be described later, on the aluminum oxide layer, the resin in the resin composition for protective layer penetrates into the defective parts of the aluminum oxide layer, resulting in an effect of stabilizing the gas barrier properties. In addition, by using a material having gas barrier properties for the protective layer itself, the gas barrier performance of the laminated film is also greatly improved.

In the present invention, the coating amount of the protective layer is preferably 0.05 to 0.60 g/m ^2. This reduces unevenness and defects in the coating due to uniformity, while enhancing adhesion due to the anchor effect. In addition, the cohesive force of the protective layer itself is improved, and the adhesion between the aluminum oxide layer and the protective layer is strengthened, and water resistance can also be enhanced. The coating amount of the protective layer is preferably 0.08 g/m ² or more, more preferably 0.10 g/m ² or more, and even more preferably 0.15 g/m ² or more, and is preferably 0.50 g/m ² or less, more preferably 0.45 g/m ² or less, and even more preferably 0.40 g/m ² or less. If the coating amount of the protective layer exceeds 0.60 g/m ² , the gas barrier property is improved, but the cohesive force inside the protective layer becomes insufficient, and adhesion may decrease. In addition, unevenness or defects may occur in the appearance of the coat, and gas barrier property and adhesion after wet heat treatment may not be fully exhibited. On the other hand, if the thickness of the protective layer is less than 0.10 g/m ² , sufficient gas barrier properties, interlayer adhesion, and ink permeability may not be obtained.

As the component of the protective layer, either a solvent-dispersed resin or a water-dispersed resin may be used. In particular, a solvent-dispersed resin is preferred for improving adhesion to the aluminum oxide layer. Furthermore, in order to obtain high gas barrier properties, a resin composed of a polyester polyol component obtained by reacting a dicarboxylic acid with a polyhydric alcohol, and a polyisocyanate component is preferred.

(A) Polyester Component The polyester component is obtained by reacting a polyvalent carboxylic acid with a polyhydric alcohol.

Polycarboxylic acids include aromatic polycarboxylic acids, alicyclic polycarboxylic acids, aliphatic polycarboxylic acids, etc. From the viewpoint of gas barrier properties, aromatic polycarboxylic acids are preferred. Examples include orthophthalic acid, isophthalic acid, terephthalic acid, 1,2-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, anthracene-1,2-dicarboxylic acid, and anthraquinone-2,3-dicarboxylic acid.

As polyhydric alcohols, glycols ranging from low molecular weight to high molecular weight can be used, but from the standpoint of gas barrier properties and flexibility due to the amorphous portion, low molecular weight glycols such as alkylene glycols (e.g., linear or branched C2-10 alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, neopentyl glycol, heptanediol, octanediol, etc.), (poly)oxy C2-4 alkylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, etc.) are used. Preferred glycol components are C2-8 polyol components [e.g., C2-6 alkylene glycol (particularly, ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol), etc.], di- or trioxy C2-3 alkylene glycol (diethylene glycol, triethylene glycol, dipropylene glycol, etc.), and particularly preferred diol components are C2-8 alkylene glycol (particularly, C2-6 alkylene glycol).

These diol components can be used alone or in combination of two or more. If necessary, low molecular weight diol components such as aromatic diols (e.g., bisphenol A, bishydroxyethyl terephthalate, catechol, resorcinol, hydroquinone, 1,3- or 1,4-xylylenediol or mixtures thereof, etc.) and alicyclic diols (e.g., hydrogenated bisphenol A, xylylenediol, cyclohexanediol, cyclohexanedimethanol, etc.) may be used in combination. If necessary, trifunctional or higher polyol components such as glycerin, trimethylolethane, trimethylolpropane, polyester polyol, polycarbonate polyol, and polyether polyol may also be used in combination. The polyol component preferably contains at least a C2-8 polyol component (especially a C2-6 alkylene glycol).

(B) Polyisocyanate Component The polyisocyanate component includes aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, etc. As the polyisocyanate compound, a diisocyanate compound is usually used.

Examples of aromatic diisocyanates include tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or a mixture thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or a mixture thereof), 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof) (MDI), 4,4'-toluidine diisocyanate (TODI), 4,4'-diphenyl ether diisocyanate, etc. Examples of aromatic aliphatic diisocyanates include xylylene diisocyanate (1,3- or 1,4-xylylene diisocyanate or a mixture thereof) (XDI), tetramethyl xylylene diisocyanate (1,3- or 1,4-tetramethyl xylylene diisocyanate or a mixture thereof) (TMXDI), ω,ω'-diisocyanate-1,4-diethylbenzene, etc.

Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorodiisocyanate, IPDI), methylene bis(cyclohexyl isocyanate) (4,4'-, 2,4'-, or 2,2'-methylene bis(cyclohexyl isocyanate)) (hydrogenated MDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanatomethyl)cyclohexane (1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof) (hydrogenated XDI), etc.

Examples of aliphatic diisocyanates include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), hexamethylene diisocyanate, pendanthemethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl caferate, etc.

A urethane resin is obtained by reacting the polyester component (A) with the polyisocyanate component (B). The weight ratio of the polyester component to the polyisocyanate component is 9:1 to 1:9 on a solids basis. It is preferably 8:2 to 2:8, and more preferably 6:4 to 4:6.

The resin composition for the protective layer of the present invention preferably contains a silane coupling agent as described below, but various additives may be added as necessary to the extent that the gas barrier properties are not impaired. Examples of additives include layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, ultraviolet absorbers, etc.), plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, crystal nucleating agents, etc.

Silane coupling agents are effective in improving the adhesion of the protective layer to the aluminum oxide layer. Examples of silane coupling agents include hydrolyzable alkoxysilane compounds, such as halogen-containing alkoxysilanes (chloro C2-4 alkyl tri C1-4 alkoxysilanes such as 2-chloroethyl trimethoxysilane, 2-chloroethyl triethoxysilane, 3-chloropropyl trimethoxysilane, and 3-chloropropyl triethoxysilane), alkoxysilanes having epoxy groups [glycidyloxy C2-4 alkyl tri C1-4 alkoxysilanes such as 2-glycidyloxyethyl trimethoxysilane, 2-glycidyloxyethyl triethoxysilane, 3-glycidyloxypropyl trimethoxysilane, and 3-glycidyloxypropyl triethoxysilane, glycidyloxy di C such as 3-glycidyloxypropyl methyl dimethoxysilane and 3-glycidyloxypropyl methyl diethoxysilane]. 2-4 alkyl di C1-4 alkoxy silanes, (epoxy cycloalkyl) C2-4 alkyl tri C1-4 alkoxy silanes such as 2-(3,4-epoxy cyclohexyl) ethyl trimethoxy silane, 2-(3,4-epoxy cyclohexyl) ethyl triethoxy silane, 3-(3,4-epoxy cyclohexyl) propyl trimethoxy silane, etc.], alkoxy silanes having amino groups [amino C2-4 alkyl tri C1-4 alkoxy silanes such as 2-aminoethyl trimethoxy silane, 3-aminopropyl trimethoxy silane, 3-aminopropyl triethoxy silane, etc., amino di C2-4 alkyl di C1-4 alkoxy silanes such as 3-aminopropyl methyl dimethoxy silane, 3-aminopropyl methyl diethoxy silane, etc., 2-[N-(2-aminoethyl) amino] ethyl trimethoxy silane, 3-[N- (2-amino C2-4 alkyl)amino C2-4 alkyl tri C1-4 alkoxysilanes such as (2-aminoethyl)amino]propyl trimethoxysilane and 3-[N-(2-aminoethyl)amino]propyl triethoxysilane; (amino C2-4 alkyl)amino di C2-4 alkyl di C1-4 alkoxysilanes such as 3-[N-(2-aminoethyl)amino]propyl methyl dimethoxysilane and 3-[N-(2-aminoethyl)amino]propyl methyl diethoxysilane; alkoxysilanes having a mercapto group (mercapto C2-4 alkyl tri C1-4 alkoxysilanes such as 2-mercaptoethyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane and 3-mercaptopropyl triethoxysilane; 3-mercaptopropyl methyl dimethoxysilane and 3-mercaptopropyl methyl Examples of the silane coupling agent include mercaptodiC2-4 alkyldiC1-4 alkoxysilanes such as diethoxysilane, etc.), alkoxysilanes having a vinyl group (vinyltrimethoxysilane, vinyltriethoxysilane, etc., vinyltriC1-4 alkoxysilanes, etc.), alkoxysilanes having an ethylenically unsaturated bond group [(meth)acryloxyC2-4 alkyltriC1-4 alkoxysilanes such as 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, etc., (meth)acryloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, etc.], etc. Among the above-mentioned silane coupling agents, alkoxysilane compounds having an amino group are preferred, and aminopropyltrimethoxysilane is particularly preferred. These silane coupling agents can be used alone or in combination.

The content of the silane coupling agent in the protective layer is 5.0% by weight or less, preferably 2.0 to 4.5% by weight, and more preferably about 3.0 to 4.0% by weight.

When forming a protective layer using a resin composition for a protective layer, a coating liquid (applied liquid) consisting of the composition and an organic solvent is prepared, applied to a substrate film, and dried. The organic solvent may be a single or mixed solvent selected from alcohols such as methanol, ethanol, isopropyl alcohol (IPA), etc.; ketones such as acetone and methyl ethyl ketone, etc.; ethers such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, etc.; and esters such as ethyl acetate and propyl acetate, and from the viewpoints of coating film processing and odor, methyl ethyl ketone and ethyl acetate are preferred.

The coating method for the resin composition for the protective layer is not particularly limited as long as it is a method that coats the film surface to form a layer. For example, conventional coating methods such as gravure coating, reverse roll coating, wire bar coating, and die coating can be used. From the viewpoints of productivity and coating stability, wire bar coating and gravure coating are preferably used.

When forming the protective layer, it is preferable to apply the resin composition for the protective layer and then heat-dry it. The drying temperature is preferably 110 to 210°C, more preferably 115 to 205°C, and even more preferably 120 to 200°C. If the drying temperature is less than 110°C, the protective layer may not be sufficiently dried or may not be sufficiently cohesive due to heat, and the surface hardness may be outside the specified range. As a result, the adhesion and water resistance of the protective layer when subjected to boiling treatment or retort treatment may decrease. On the other hand, if the drying temperature exceeds 210°C, the protective layer may be too cohesive, the film may become hard, the barrier layer may be destroyed, and the barrier performance may decrease. In addition, the film itself, which is the base material, may be too heated, making the film brittle or shrinking, resulting in poor processability. In addition to drying, adding an additional heat treatment (for example, 150 to 190°C) is also effective in promoting the drying of the protective layer.

The drying time for the protective layer is preferably within 30 seconds. If the drying time exceeds 30 seconds, not only will the protective layer not dry, but the base film will shrink, causing cracks in the gas barrier layer and reducing the gas barrier performance. On the other hand, if the drying time is shorter than 5 seconds, the protective layer will not harden, resulting in reduced adhesion and barrier properties. From the viewpoint of productivity, it is more preferably 5 to 25 seconds, and more preferably 10 to 20 seconds. If the film is heated suddenly, it will shrink significantly, causing compressive stress in the gas barrier layer and reducing the barrier performance. It is preferable to increase the temperature at a rate of 50°C/sec or less. It is more preferably 30°C/sec or less, and more preferably 20°C/sec or less.

The surface temperature during heating in the process of forming the protective layer is preferably 100 to 150°C, more preferably 105 to 145°C, and even more preferably 110 to 140°C.

The film tension during heating in the process of forming the protective layer is preferably 30 to 90 N/m. More preferably, it is 40 to 80 N/m, and even more preferably, it is 50 to 70 N/m. If it is less than 20 N/m, winding defects will occur, and if it exceeds 100 N/m, tensile stress will be generated in the gas barrier layer, reducing the barrier performance.

[Heat seal layer]
When the gas barrier laminate film having an inorganic thin film layer is used as a packaging material, it is preferable to form a heat seal layer called a sealant. The heat seal layer is usually provided on the aluminum oxide layer, but may also be provided on the outside of the base film (the surface opposite to the surface on which the protective layer is formed). When a protective layer is provided, the heat seal layer may be laminated on the surface of the protective layer.
The heat sealable resin is usually formed by extrusion lamination or dry lamination. The thermoplastic polymer forming the heat sealable resin layer may be any polymer capable of sufficiently exhibiting sealant adhesiveness, and may be polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, ionomer resin, or the like. When a moist heat treatment such as retort treatment is to be performed, it is preferable to form the heat sealable resin by the dry lamination method using a polypropylene resin. The heat seal layer is usually recommended to be 20 to 250 μm, and when used as a packaging material, it is desirable to be 40 to 100 μm.

For bonding the protective layer and the heat seal layer, polyurethane resin, polyisocyanate resin, polyester resin, ether resin, etc. are used. When performing a wet heat treatment such as retort treatment, it is preferable to use a reaction product of polyurethane resin and polyisocyanate resin as an adhesive. The amount of application varies depending on the material of the film to be laminated, but is preferably 1 to 20 g/ ^m2 , more preferably 2 to 10 g/ ^m2 , and more preferably 3 to 6 g/ ^m2 . The adhesion temperature is set depending on the thickness of the heat seal layer and the thickness of the adhesive, but is preferably 50 to 120°C, more preferably 55 to 100°C, and more preferably 60 to 80°C.

As described above, the laminate film of the present invention has excellent water vapor barrier properties and appearance both in its normal state and after retort treatment, and has good adhesion even when processed by printing, lamination, etc., and is a gas barrier laminate film (laminate film) that is easy to manufacture and has excellent economical properties.

[Other layers]
In the gas barrier laminate film having an aluminum oxide layer formed by using the laminate film of the present invention, in addition to the above-mentioned base film, aluminum oxide layer, and protective layer, various layers that are provided in known gas barrier laminate films can be provided as necessary. For example, a polyamide resin can be provided as an intermediate layer between the gas barrier laminate film and the heat seal layer to improve the adhesion and flexibility of the laminate. In addition, a coating layer may be provided to react with oxygen-deficient parts of inorganic oxides and metal hydroxides generated during the formation of the aluminum oxide layer to improve adhesion.

Furthermore, the gas barrier laminate film having an aluminum oxide layer may have at least one or more layers of a printed layer, other plastic substrate, and/or paper substrate laminated between or on the outside of the aluminum oxide layer or substrate film and the heat sealable resin layer.

As the printing ink for forming the printing layer, water-based and solvent-based resin-containing printing inks can be preferably used. Examples of resins used in the printing ink include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, light blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. There are no particular limitations on the printing method for providing the printing layer, and known printing methods such as offset printing, gravure printing, and screen printing can be used. To dry the solvent after printing, known drying methods such as hot air drying, hot roll drying, and infrared drying can be used.

On the other hand, as other plastic and paper substrates, from the viewpoint of obtaining sufficient rigidity and strength of the laminated film, paper, polyester resin, polyamide resin, biodegradable resin, etc. are preferably used. Also, in order to obtain a film with excellent mechanical strength, oriented films such as biaxially oriented polyester film and biaxially oriented nylon film are preferred.

In particular, when a gas barrier laminate film with an aluminum oxide layer is used as a packaging material, it is preferable to laminate a nylon film between the aluminum oxide layer and the heat sealable resin layer in order to improve mechanical properties such as pinhole resistance and puncture strength. The types of nylon typically used here include nylon 6, nylon 66, and metaxylene adipamide. The thickness of the nylon film is usually 10 to 30 μm, preferably 15 to 25 μm. If the nylon film is thinner than 10 μm, it may lack strength, while if it exceeds 30 μm, it may be too stiff and unsuitable for processing. As the nylon film, a biaxially oriented film with a stretch ratio in both the length and width directions is usually 2 times or more, preferably about 2.5 to 4 times.

The laminated film of the present invention also includes embodiments having the above-mentioned layers other than the substrate layer, aluminum oxide layer, and protective layer.

The water vapor permeability of the laminated film of the present invention is preferably 2.5 g/ ^m2 ·day or less, more preferably 2.0 g/ ^m2 ·day or less, and even more preferably 1.5 g/ ^m2 ·day or less. The water vapor permeability after retort treatment is preferably 2.5 g/ ^m2 ·day or less, more preferably 2.0 g/ ^m2 ·day or less, and even more preferably 1.5 g/ ^m2 ·day or less.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and can be modified as appropriate within the scope of the above and below-mentioned aims, and all such modifications are included in the technical scope of the present invention. Unless otherwise specified, "%" means "% by mass."

The processing methods and evaluation/physical property measurement methods used in each example and comparative example are as follows:

(1) Film Thickness of Aluminum Oxide Layer A wavelength dispersive small-sized fluorescent X-ray analyzer (Rigaku Corporation, "Supermini 200") was used to measure the film thickness of the aluminum oxide layer. The density of the aluminum oxide layer was calculated as 0.74 times (2.94/cm ³ ) the bulk density (3.97 g/cm ³ ). The reason for using 0.74 times is that it closely matches the actual film thickness calculated by TEM or the like. In order to calculate the film thickness using a fluorescent X-ray analyzer, it is necessary to measure a sample with a known film thickness in advance, calculate the amount of fluorescent X-rays emitted from the sample, and create a calibration curve of film thickness and fluorescent X-ray intensity. The sample used for creating the fluorescent X-ray calibration curve was one in which the amount of aluminum attached per unit area was identified by inductively coupled plasma emission spectroscopy, and the film thickness was measured by converting the density of the aluminum oxide layer into a film thickness.

(2) Time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurement conditions The time-of-flight secondary ion mass spectrometer TOF.SIMS5 manufactured by ION-TOF was used. The surface of aluminum oxide was the measurement target. The conditions were as follows:
Primary ion: _Bi3 ⁺⁺ approx. 0.2 pA (100 μsec.)
Primary ion irradiation area: 150 μm square Sputter ions: Cs 1 kV approx. 60 nA
Sputter ion irradiation area: 600 μm square Sputter time: 10 sec./cycle

(3) Preparation of Laminated Film for Evaluation On each laminated film, a 15 μm thick biaxially oriented nylon film (Toyobo Co., Ltd.'s "Harden Film N1102") and a 70 μm thick non-oriented polypropylene film (Toyobo Co., Ltd.'s "P1146") as a heat sealable resin layer were laminated in this order by dry lamination using a polyurethane-based two-component curing adhesive (Mitsui Chemicals'"Takelac (registered trademark) A525S" and "Takenate (registered trademark) A50" were blended in a ratio of 13.5:1 (mass ratio)) and aged at 40 ° C for 4 days to obtain a laminated gas barrier laminated film for evaluation. The thickness of the adhesive layer formed with the urethane-based two-component curing adhesive after drying was about 4 μm in each case.

(4) Retort Treatment Method The laminate obtained in (2) above was subjected to a retort treatment at 130° C. for 30 minutes using a hot water spray type retort sterilizer ("RCS-60SPXTG" manufactured by Hisaka Works, Ltd.) and then dried for 1 day in a 40° C. room to obtain a laminate.

(5) Evaluation method of laminate strength (before and after moist heat treatment) The laminates obtained in (3) and (4) above were cut into test pieces with a width of 15 mm and a length of 200 mm in the MD direction of the base film, and the laminate strength was measured using a tabletop precision universal testing machine (Shimadzu Corporation's "Autograph AGS-X") under conditions of a temperature of 23°C and a relative humidity of 65%. The laminate strength was measured at a tensile speed of 200 mm/min, and the strength was measured when the laminate film and the heat-sealable resin layer obtained in the examples and comparative examples were peeled off at peel angles of 90° and 180° after soaking in water. The measurement was carried out before and after the treatment in (3).

(6) Evaluation method for water vapor permeability (before and after moist heat treatment) The water vapor permeability of the laminates obtained in (3) and (4) above was measured in accordance with JIS-K7129 using a water vapor permeability measuring device ("PERMATRAN-3/33MW" manufactured by MOCON Corp.) in an atmosphere at a temperature of 40° C. and a relative humidity of 90%. The water vapor permeability was measured in the direction in which water vapor permeated from the substrate film side on which no aluminum oxide layer was laminated to the aluminum oxide layer side.

(7) Evaluation method of oxygen permeability (before and after moist heat treatment) The oxygen permeability of the laminates obtained in (3) and (4) above was measured in accordance with JIS-K7126-2 using an oxygen permeability measuring device ("OXTRAN-2/20" manufactured by MOCON Corp.) in an atmosphere at a temperature of 23° C. and a relative humidity of 65%. The oxygen permeability was measured in the direction in which oxygen permeates from the substrate film side on which no aluminum oxide layer is laminated to the aluminum oxide layer side.

The materials used to form the protective layer in each of the examples and comparative examples were prepared as follows.

<Preparation of material used to form protective layer A (coating liquid a)>
30% of polyester resin having a number average molecular weight of 450 to 3,000 (polyester mainly composed of a polyvalent carboxylic acid component containing at least one of ortho-oriented aromatic dicarboxylic acid or its anhydride, and a polyhydric alcohol component) was dissolved in 70% methyl ethyl ketone (polyester solution). A solution of a silane coupling agent ("KBM-603" manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in acetone and a trimethylolpropane adduct of meta-xylylene diisocyanate ("Takenate D-110N" manufactured by Mitsui Chemical Co., Ltd.: solid content concentration 75%) were mixed and stirred for 10 minutes using a magnetic stirrer. The obtained mixture was diluted with methyl ethyl ketone, and the polyester solution was further added to obtain polyester urethane coating solution a having a solid content concentration of 5%.
<Preparation of material used to form protective layer B (coating liquid b)>
25% of a polyester resin having a weight average molecular weight of 35,000 (a polyester mainly composed of terephthalic acid, isophthalic acid, ethylene glycol, and propylene glycol) was dissolved in 35% propyl acetate and 40% ethyl acetate (polyester solution). 14.00% of the solution was mixed with 41.40% ethyl acetate, 43.10% propyl acetate, 1.30% of a polyisocyanate having an isocyanate group (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.), and 0.2% of a silane coupling agent ("KBM-903" manufactured by Shin-Etsu Chemical Co., Ltd.) to obtain a polyester urethane coating solution b having a solid content concentration of 5%.
<Preparation of material used in forming protective layer C (coating liquid c)>
Polymethacrylic acid having a weight average molecular weight of 30,000 was diluted with a mixed solvent of ethyl acetate/isopropyl alcohol (ethyl acetate/isopropyl alcohol=1:1 (mass ratio)) to obtain polymethacrylic acid coating solution c having a solid content concentration of 5%.

Example 1
A 12 μm thick biaxially oriented polyester film was used, and the roll was set in an electron gun heating type deposition apparatus having a roll-to-roll type film running system so that deposition was performed on the corona-treated surface, to prepare a barrier film. As a pre-deposition treatment, a plasma treatment was performed in a vacuum system. During the treatment, oxygen gas was introduced at 1000 sccm, the current was set to 30 A, and plasma was generated. Thereafter, aluminum was evaporated by electron gun heating, oxygen gas was introduced, and deposition of an aluminum oxide layer was performed. The deposited plastic film (a laminated film of "substrate film/aluminum oxide layer") was moved to an optical film thickness meter in the deposition machine, and the total light transmittance was measured. After the measurement, the laminated film was wound up on a take-up roll. After the vacuum was released, the film thickness of the aluminum oxide layer and the fragment ion intensity in the depth direction were measured by TOF-SIMS. The results were as shown in Table 1. A laminated laminate was prepared from the obtained laminated film as described in (3) above. The laminated body was subjected to a retort treatment at 130°C for 30 minutes, and the laminate strength, water vapor permeability, and oxygen permeability after the treatment were evaluated. Furthermore, the obtained plastic film on which the aluminum oxide layer was formed (laminated film of "substrate film/aluminum oxide layer") was used to apply the coating liquid a by a roll method, and the temperature was raised and lowered at a temperature rise rate of 20°C/sec or less so that the residence time in the oven was 10 seconds, and the film was dried so that the film surface temperature reached 130°C, thereby obtaining a protective layer. The coating amount after drying was 0.3 g/ ^m2 . The tension after passing through the dryer was set to 50 N/m by adjusting the rotation speed ratio of the rolls before and after the oven. In this manner, a laminated film having a substrate film/aluminum oxide layer/protective layer was produced. A laminated film having the obtained laminated film (laminated film having a substrate film/aluminum oxide layer/protective layer) was produced as described in (3) above. The laminate was subjected to a retort treatment at 130° C. for 30 minutes, and the laminate strength, water vapor permeability, and oxygen permeability after the treatment were evaluated.

(Examples 2 to 3)
A laminate was produced and evaluated in the same manner as in Example 1, except that the amount of gas introduced and the output during the plasma treatment were changed and the thickness of the aluminum oxide layer was changed as shown in Table 1.

Example 4
A laminate was produced and evaluated in the same manner as in Example 1, except that a biaxially oriented polyester film that had not been subjected to corona treatment was used and the amount of gas introduced and the output during the plasma treatment were changed as shown in Table 1.

Example 5
A laminate was produced and evaluated in the same manner as in Example 21, except that the amount of gas introduced and the output during the plasma treatment and the coating material of the protective layer were changed as shown in Table 1.

(Comparative Example 1)
A laminate was produced and evaluated in the same manner as in Example 1, except that Ar gas was introduced during the plasma treatment.

(Comparative Examples 2 to 3)
A laminate was produced and evaluated in the same manner as in Example 1, except that the amount of gas introduced and the output during the plasma treatment were changed and the thickness of the aluminum oxide layer was changed as shown in Table 1.

(Comparative Example 4)
A laminate was produced and evaluated in the same manner as in Example 1, except that the thickness of the aluminum oxide layer was changed as shown in Table 1.

(Reference Example 1)
A laminate was produced and evaluated in the same manner as in Example 1, except that the coating material of the protective layer was changed as shown in Table 1.

The present invention has made it possible to provide a laminate film that has excellent adhesiveness not only under normal conditions but also after retort treatment. Therefore, the gas barrier laminate film of the present invention can be widely used not only for food packaging for retort treatment, but also for packaging various foods, pharmaceuticals, industrial products, etc., as well as industrial applications such as solar cells, electronic paper, organic EL elements, and semiconductor elements.

Claims

A laminate film having gas barrier properties, comprising a base film and an aluminum oxide layer laminated on at least one side of the base film, and characterized in that the laminate film satisfies the following requirements (A) and (B):
(A) When the aluminum oxide layer is etched from the surface side by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the position at which the intensity of the fragment ion of mass number 102 (Al 2 O 3 ) is 80% of the maximum intensity is defined as the interface with the substrate film, and at that interface, the ratio b/a of the intensity a of mass number 102 (derived from Al 2 O 3 ) to the intensity b of mass number 119 (derived from Al 2 O 4 H) is 0.10 or less.
(B) A 15 μm biaxially oriented nylon film and a 70 μm unoriented polypropylene film are laminated by a dry lamination method using a polyurethane-based two-component curing adhesive applied to the surface of the aluminum oxide layer of the laminated film so that the thickness after drying is 4 μm, and the film is aged at a temperature of 40° C. for 4 days and then subjected to a wet heat treatment at 130° C. for 30 minutes. After this, the water-exposed laminate strength is 1.5 N/15 mm or more and the water vapor permeability is 2.5 g/ m2 ·day or less.
The laminated film according to claim 1, wherein the thickness of the aluminum oxide layer is 5 to 30 nm.
Provided with a protective layer;
2. The laminate film according to claim 1, wherein the base film, the aluminum oxide layer, and the protective layer are laminated in this order, and the protective layer contains at least one type of urethane resin or ester resin.
The laminated film according to claim 3, wherein the protective layer contains a silane coupling agent.
A laminate in which a heat seal layer is laminated on the surface of the protective layer of the laminate film according to any one of claims 1 to 4.
A packaging bag characterized in that at least a portion of the bag is made of the laminate described in claim 5.