JP7764733B2 - Resin films and laminated films - Google Patents

Description

The present invention relates to a resin film and a laminated film.

When packaging metallic contents such as medical devices, industrial materials, and electronic components, the contents must be dried before packaging to prevent rust and other problems from forming on the contents. If the contents are not completely dry, they must be dried after packaging, but to do this, the film used to package the contents must be moisture-permeable.

Highly moisture-permeable base films have been known in the past (for example, Patent Document 1). However, these conventional highly moisture-permeable base films cannot ensure gas barrier properties, and there is a risk of the contents deteriorating due to oxidation. Furthermore, to prevent the contents from deteriorating, it is necessary to seal in an inert gas such as carbon dioxide or nitrogen. However, conventional highly moisture-permeable base films also allow inert gases to pass through, making it impossible to seal in the inert gas, and making it difficult to prevent the packaged contents from deteriorating.

Japanese Patent Application Laid-Open No. 2019-163357

The present invention was made in consideration of the above circumstances, and aims to provide a resin film that, when laminated to a highly moisture-permeable substrate layer, can impart gas barrier properties to the substrate layer while suppressing a decrease in the moisture permeability of the substrate layer.

Another objective of the present invention is to provide a laminated film that has excellent moisture permeability and gas barrier properties.

To achieve the above objectives, the present invention adopts the following configuration.

[1] The water vapor permeation amount measured by the cup method specified in JIS Z 0208 under conditions of 30°C and 97% RH is 7000 g/ ^m2 ·day or more,
A resin film having an air permeability resistance of 5000 seconds or more at 23°C and 50% RH, measured by the Oken method specified in JIS P 8117:2009.
[2] The resin film according to [1], wherein the thickness of the resin film is 0.1 μm or more and 5.0 μm or less.
[3] The resin film according to [1] or [2], wherein the resin film comprises an anchor coat layer and a gas barrier layer provided on one surface of the anchor coat layer.
[4] The resin film according to [3], wherein the anchor coat layer contains a 1,2-polybutadiene modified product.
[5] The resin film according to [3] or [4], wherein the gas barrier layer contains at least one selected from the group consisting of a saponified ethylene vinyl acetate copolymer, polyvinyl alcohol, modified polyvinyl alcohol, polyether, and polyurethane.
[6] The resin film according to [1] or [2], wherein the resin film comprises a single layer containing at least one selected from the group consisting of a saponified ethylene vinyl acetate copolymer, polyvinyl alcohol, modified polyvinyl alcohol, polyether, and polyurethane, and a modified 1,2-polybutadiene.
[7] A laminated film comprising the resin film according to any one of [1] to [6] and a base material layer provided on the resin film.

The resin film of the present invention has a water vapor transmission rate of 7000 g/ ^m2 ·day or more at 30°C and 97% RH, measured by the cup method specified in JIS Z 0208, and an air resistance of 5000 seconds or more at 23°C and 50% RH, measured by the Oken method specified in JIS P 8117:2009. Therefore, when laminated on a substrate film, it is possible to impart gas barrier properties to the substrate layer while suppressing a decrease in the moisture permeability of the substrate layer.

Furthermore, the laminate film of the present invention comprises the above-mentioned resin film and a substrate layer provided on the resin film, and therefore has excellent moisture permeability and gas barrier properties.

1 is a cross-sectional view showing the configuration of a laminated film having a single-layer resin film, which is one embodiment of the present invention. 1 is a cross-sectional view showing the structure of a laminated film having two layers of resin films, which is one embodiment of the present invention.

The following provides a detailed description of a resin film, which is one embodiment of the present invention, and a laminate film incorporating this resin film. Note that the drawings used in the following description may show characteristic portions enlarged for ease of understanding, and the dimensional proportions of each component element may not necessarily be the same as in reality.

<<Resin film>>
The resin film of the present embodiment has a water vapor transmission rate of 7000 g/ ^m2 ·day or more at 30°C and 97% RH, measured by the cup method specified in JIS Z 0208, and an air resistance of 5000 seconds or more at 23°C and 50% RH, measured by the Oken method specified in JIS P 8117:2009.
The resin film of the present embodiment has a water vapor transmission rate of 7000 g/ ^m2 ·day or more at 30°C and 97% RH, measured by the cup method specified in JIS Z 0208, and an air resistance of 5000 seconds or more at 23°C and 50% RH, measured by the Oken method specified in JIS P 8117:2009. Therefore, it is possible to impart gas barrier properties to the base layer while suppressing a decrease in the moisture permeability of the base layer.

By laminating the resin film of this embodiment to a highly moisture-permeable substrate layer, it is possible to impart gas barrier properties to the substrate layer while suppressing a decrease in the moisture permeability of the substrate layer. This means that even if the contents are packaged without being completely dried, they can be dried after packaging. Furthermore, because the resin film of this embodiment can impart gas barrier properties to the substrate layer, deterioration of the contents can be prevented by sealing in an inert gas after packaging. Therefore, for example, metal items such as medical devices, industrial materials, and electronic components can be packaged without being dried, and by sealing in an inert gas after packaging, they can be dried after packaging. This allows packaging to be completed in a short time and prevents deterioration due to rust and other factors.

The resin film contains at least a gas barrier resin component. The resin film may also contain an adhesive resin component. When the resin film contains an adhesive resin component, the gas barrier resin component and the adhesive resin component may be contained in the same layer or in separate layers. When the gas barrier resin component and the adhesive resin component are contained in separate layers, the gas barrier layer containing the gas barrier resin component is laminated to the base layer via an anchor coat layer containing the adhesive resin component.

<Gas barrier resin>
The gas barrier resin is a resin that suppresses gas permeation and imparts gas barrier properties to the base layer. The type of gas is not particularly limited as long as it does not affect the contents packaged in the laminate film described below, and examples thereof include carbon dioxide and nitrogen.

Preferably, the gas barrier resin component is one that can impart gas barrier properties to the base layer and prevent a decrease in the moisture permeability of the base layer. Specific examples include saponified ethylene vinyl acetate copolymer, polyvinyl alcohol, modified polyvinyl alcohol in which polyvinyl alcohol is partially modified, polyether, polyurethane, polyamide, cellophane, cellulose, polysaccharides such as starch, polyhydroxyethyl (meth)acrylate, etc.

Examples of modified polyvinyl alcohol include cationically modified polyvinyl alcohol, anionically modified polyvinyl alcohol, nonionically modified polyvinyl alcohol, and vinyl alcohol polymers. Modified polyvinyl alcohols also include vinyl acetate resins (e.g., "Exceval" manufactured by Kuraray Co., Ltd.), polyvinyl acetal resins obtained by reacting polyvinyl alcohol with aldehyde (e.g., "S-LEC" manufactured by Sekisui Chemical Co., Ltd.), silanol-modified polyvinyl alcohols containing silanol groups (e.g., "R-1130" manufactured by Kuraray Co., Ltd.), and modified polyvinyl alcohol resins containing acetoacetyl groups in the molecule (e.g., "GOHSEFIMER® Z/WR series" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).

Examples of anion-modified polyvinyl alcohol include polyvinyl alcohol with anionic groups, such as those described in JP-A-1-206088, copolymers of vinyl alcohol and vinyl compounds with water-soluble groups, such as those described in JP-A-61-237681 and JP-A-63-307979, and modified polyvinyl alcohol with water-soluble groups, such as those described in JP-A-7-285265.

Other examples of nonion-modified polyvinyl alcohol include polyvinyl alcohol derivatives in which polyalkylene oxide groups are added to a portion of vinyl alcohol, as described in JP-A-7-9758 (e.g., "GOHSENEX (registered trademark) WO" manufactured by Mitsubishi Chemical Corporation), block copolymers of vinyl alcohol and a vinyl compound having a hydrophobic group, as described in JP-A-8-25795, silanol-modified polyvinyl alcohol having a silanol group, and reactive group-modified polyvinyl alcohol having a reactive group such as an acetoacetyl group, a carbonyl group, or a carboxy group (e.g., "D Polymer" manufactured by Nippon Vinyl Acetate & Poval Co., Ltd., which is a reactive group-modified polyvinyl alcohol having a carbonyl group).

Cation-modified polyvinyl alcohols include, for example, polyvinyl alcohols having primary, secondary, or tertiary amino groups or quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol, as described in JP-A-61-10483, which are obtained by saponifying a copolymer of vinyl acetate and an ethylenically unsaturated monomer having a cationic group.

Examples of vinyl alcohol polymers include Exeval (mentioned above) and Nichigo G Polymer (product name: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).

Examples of polyethers include polyoxymethylene, chlorinated polyethers, glycol condensates (polyethylene glycol (polyethylene oxide), polypropylene glycol, and copolymer compositions thereof, etc.), and polyethers containing aromatic rings (polyphenylene oxide, polysulfone, etc.).
Among these, glycol condensates are preferred because of their effect of increasing moisture permeability. Examples of components that form glycol condensates include ethylene glycol (the number of carbon atoms between ether bonds in the polymer chain is 2), propylene glycol (the number of carbon atoms between ether bonds in the polymer chain is 3), butylene glycol (the number of carbon atoms between ether bonds in the polymer chain is 4), and derivatives thereof. To achieve high moisture permeability, the number of carbon atoms is preferably 4 or less, more preferably 3 or less, and particularly preferably 2.2 or less. To suppress the moisture absorption of the gas barrier film after film formation and to achieve excellent shape retention, the number of carbon atoms between ether bonds in the polymer chain is preferably 2.01 or more, more preferably 2.05 or more. Here, the number of carbon atoms between ether bonds in the polymer chain refers to an average value calculated from the number of carbon atoms in each repeating unit that forms the polymer and the number of repeating units.
Examples of polyethers include Alcox (trade name: manufactured by Meisei Chemical Industry Co., Ltd.).

Examples of polyurethanes include polyester-based, polycarbonate-based, and polyether-based polyurethanes. In this specification, "polyester-based polyurethane" means "polyurethane having a polyester segment.""Polycarbonate-basedpolyurethane" means "polyurethane having a polycarbonate segment.""Polyether-basedpolyurethane" means "polyurethane having a polyether segment."
In terms of the effect of increasing moisture permeability, polyether polyurethanes having highly hydrophilic polyether segments in the molecular chain are preferred. Specifically, those having polyether segments such as polyoxyethylene glycol or a block copolymer of polyoxyethylene and polyoxypropylene, and having a long length between urethane bonds, are preferred. In addition, to improve moisture permeability, the Tg of the polyurethane is preferably 25°C or less, more preferably -20°C or less, and particularly preferably -50°C or less.
Alternatively, a varnish in which polyurethane is dispersed may be used as the polyurethane. Examples of varnishes include organic solvent solution types and water dispersion types. The use of water dispersion types is preferred in terms of not damaging the environment and being effective in suppressing penetration and erosion of the substrate and anchor coat layer. Examples of varnishes in which polyurethane is dispersed include Hydran (trade name: manufactured by DIC Corporation).

Among these, saponified ethylene vinyl acetate copolymers, resins containing hydrophilic groups such as polyvinyl alcohol and modified polyvinyl alcohol, polyethers, and polyurethanes are particularly preferred because they are highly effective in preventing a decrease in the moisture permeability of the base layer.

The moisture permeability and gas barrier properties of polyvinyl alcohol or modified polyvinyl alcohol can be adjusted by adjusting the molecular weight and degree of saponification. The degree of saponification of polyvinyl alcohol or modified polyvinyl alcohol is preferably 70 to 99 mol%, more preferably 85 to 99 mol% or more, and even more preferably 97 to 99 mol% or more. If the degree of saponification is above the lower limit, water resistance increases and the film is less likely to dissolve even when in contact with water, allowing the strength of the film to be maintained. Furthermore, if the degree of saponification is below the upper limit, water solubility is maintained at an appropriate level, making it possible to prepare a solution with good coatability.
The viscosity of a 4% by mass solution of polyvinyl alcohol or modified polyvinyl alcohol is preferably 3 mPa s or more, more preferably 8.0 mPa s or more, and even more preferably 20 mPa s or more. When the 4% by mass solution of polyvinyl alcohol or modified polyvinyl alcohol has the above viscosity, the water vapor permeability is high, the strength is increased, and the moisture absorption is low.
From the viewpoint of coatability, the viscosity of a 4% by mass solution is preferably 1000 mPa·s or less.

The resin film may contain only one type of gas barrier resin component, or two or more types. If two or more types are used, the combination and ratio of these components can be selected as desired depending on the purpose.

When the resin film contains a gas barrier resin component and an adhesive resin component in the same layer, the content of the gas barrier resin component relative to the total mass of the resin film is preferably 90% by mass or more, and may be, for example, 95% by mass or more or 97% by mass or more. Having this proportion at or above the lower limit can further improve gas barrier properties and prevent a decrease in moisture permeability.

When the resin film contains a gas barrier resin component and an adhesive resin component in the same layer, the content of the gas barrier resin component relative to the total mass of the resin film is less than 100% by mass, and in order to ensure the content of the adhesive resin component, it is preferable that the content be, for example, 99.5% by mass or less.

When the resin film contains a gas barrier resin component and an adhesive resin component in the same layer, the content ratio of the gas barrier resin component to the total mass of the resin film can be adjusted appropriately within a range set by any combination of any of the above-mentioned lower and upper limits. For example, in one embodiment, the ratio is preferably 90 to 99.5% by mass, and may be, for example, 95 to 99.5% by mass, 97 to 99.5% by mass, or 95 to 99.5% by mass. However, these are just examples of the ratios.

In the resin film, the content ratio of the gas barrier resin component to the total mass of the resin film may be set to a different range in addition to the above-mentioned range, depending on the intended use of the resin film.

<Adhesive resin>
When the gas barrier resin component and the adhesive resin component are contained in the same layer in the resin film, the adhesive resin component is preferably one that does not react with the gas barrier resin component when mixed with the gas barrier resin component. Specific examples include 1,2-polybutadiene modified products, polyester resins, and polyester/urethane mixed resins. Among these, 1,2-polybutadiene modified products are preferred because they are less sticky and easier to handle. Furthermore, 1,2-polybutadiene modified products have low reactivity with saponified ethylene-vinyl acetate copolymers and polyvinyl alcohol, etc., and therefore are prevented from reacting with saponified ethylene-vinyl acetate copolymers and polyvinyl alcohol, etc., prior to coating to form gels. This allows for uniform coating and also prevents a decrease in moisture permeability. Examples of 1,2-polybutadiene modified products include "Titabond T180E" manufactured by Nippon Soda Co., Ltd.

The adhesive resin component contained in the resin film may be one type only, or two or more types. If there are two or more types, the combination and ratio of these can be selected as desired depending on the purpose.

When the resin film contains a gas barrier resin component and an adhesive resin component in the same layer, the content of the adhesive resin component relative to the total mass of the resin film is preferably 0.5 to 10% by mass, and may be, for example, 0.5 to 5% by mass, 0.5 to 3% by mass, or 0.5 to 1% by mass. Having this proportion equal to or greater than the lower limit mentioned above can further improve adhesive strength.

In the resin film, the content ratio of the adhesive resin component to the total mass of the resin film may be set to a different numerical range in addition to the above-mentioned numerical range depending on the application of the resin film.

The thickness of the resin film is not particularly limited, but is preferably 0.1 μm or more and 5.0 μm or less, more preferably 0.3 μm or more and 4.0 μm or less, and may be any of 0.4 μm or more and 3.0 μm or less, and 0.4 μm or more and 2.0 μm or less. When the thickness of the resin film is at least the lower limit, the effect of imparting gas barrier properties to the substrate layer is improved. When the thickness of the resin film is at most the upper limit, the decrease in the moisture permeability of the substrate layer can be further suppressed.

The water vapor transmission rate of the resin film measured by the cup method specified in JIS Z 0208 under conditions of 30°C and 97% RH is 7000 g/ ^m2 ·day or more, preferably 7500 g/ ^m2 ·day or more, more preferably 10000 g/ ^m2 ·day or more, and even more preferably 20000 g/ ^m2 ·day or more, and may be any of 30000 g/ ^m2 ·day or more, 40000 g/ ^m2 ·day or more, 50000 g/ ^m2 ·day or more, 60000 g/ ^m2 ·day or more, or 70000 g/ ^m2 ·day or more. When the gas barrier resin component and the adhesive resin component are contained in the same layer, the water vapor transmission rate can be adjusted by the type or content of the gas barrier resin component and the adhesive resin component, or the thickness of the resin film. Furthermore, when the gas barrier resin component and the adhesive resin component are contained in separate layers, the water vapor permeation amount can be adjusted by the type or content of the gas barrier resin component and the adhesive resin component in each layer, or the thickness of each layer.

The air permeability resistance of the resin film measured at 23°C and 50% RH using the Oken method specified in JIS P 8117:2009 is 5,000 seconds or more, preferably 100,000 seconds or more, more preferably 1,000,000 seconds or more, and may be any of 2,000,000 seconds or more, 3,000,000 seconds or more, 4,000,000 seconds or more, 5,000,000 seconds or more, 8,000,000 seconds or more, and 10,000,000 seconds or more. When the gas barrier resin component and the adhesive resin component are contained in the same layer, the air permeability resistance can be adjusted by the type or content of the gas barrier resin component and the adhesive resin component, or the thickness of the resin film. When the gas barrier resin component and the adhesive resin component are contained in separate layers, the air permeability resistance can be adjusted by the type or content of the gas barrier resin component and the adhesive resin component in each layer, or the thickness of each layer.

The resin film may contain only the gas barrier resin component and adhesive resin component (i.e., it may consist of the gas barrier resin component and adhesive resin component), or it may contain other components that do not fall into either the gas barrier resin component or the adhesive resin component (i.e., it may consist of the gas barrier resin component, the adhesive resin component, and the other components).

<Other ingredients>
The other components contained in the resin film are not particularly limited and can be selected arbitrarily depending on the purpose.

Examples of the other components include additives known in the art.
Examples of the additives include crosslinking agents, antifogging agents, antiblocking agents, antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, inorganic fibers, organic fibers, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers. Among these, crosslinking agents are preferably used because they can improve water resistance and strength. Examples of crosslinking agents include titanium compounds, metal chelate-based, boron-based, isocyanate-based, organic acid, and acid-modified polymers. Examples of titanium compounds include titanium alkoxide compounds and titanium acylate compounds. Antifogging agents are also preferably used because they can improve moisture permeability by making the resin film surface more compatible with water. Examples of antifogging agents include glycerin laurate, diglycerin laurate, decaglycerin laurate, glycerin monostearate, and sorbitan stearate. Inorganic and organic fibers can improve the film strength and water resistance. Examples of organic fibers include cellulose, and cellulose nanofibers (CNF) are preferably used.

The resin film may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

[0033] When the gas barrier resin component and the adhesive resin component are contained in the same layer in the resin film, the ratio of the total content of the gas barrier resin component and the adhesive resin component to the total mass of the resin film is preferably 90% by mass or more, and may be, for example, 95% by mass or more, 97% by mass or more, or 99% by mass or more. When the ratio is equal to or more than the lower limit, the effect of using the resin is more pronounced, and the gas barrier property of the resin film is further improved.
There is no particular upper limit to the ratio, and the ratio may be 100% by mass or less.

The resin film may comprise a single layer containing a gas barrier resin component and an adhesive resin component, or it may comprise two layers: an anchor coat layer containing an adhesive resin component and a gas barrier layer containing a gas barrier resin component provided on one side of the anchor coat layer.

<Anchor coat layer>
The anchor coat layer is a resin layer provided to increase the adhesive strength between the substrate layer and a gas barrier layer, which will be described later.

Specific examples of adhesive resin components contained in the anchor coat layer include 1,2-polybutadiene modified products, polyester resins, and polyester/urethane mixed resins. Of these, 1,2-polybutadiene modified products are preferred because they are less sticky and easier to handle. Furthermore, 1,2-polybutadiene modified products have low reactivity with saponified ethylene vinyl acetate copolymers and polyvinyl alcohol, and are therefore less likely to react with saponified ethylene vinyl acetate copolymers and polyvinyl alcohol before coating, resulting in gelation. This allows for uniform coating, and is also preferred because it can prevent a decrease in moisture permeability.

The anchor coat layer may contain only one adhesive resin component, or two or more adhesive resin components. If two or more adhesive resin components are used, the combination and ratio of these components can be selected as desired depending on the intended purpose.

The anchor coat layer may contain only an adhesive resin component (i.e., it may consist of an adhesive resin component), or it may contain other components that do not fall under the category of adhesive resin components (i.e., it may consist of the adhesive resin component and the other components).

The anchor coat layer may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

The other components include film-forming aids to impart film-forming properties. Examples of film-forming aids include ethylene glycol monobutyl ether.

In the anchor coat layer, the content of the adhesive resin component relative to the total mass of the anchor coat layer is preferably 70 to 99.5% by mass, and may be, for example, 75 to 99% by mass or 75 to 95% by mass. Having this proportion equal to or greater than the lower limit can further improve adhesive strength.

In the anchor coat layer, the ratio of the adhesive resin component content to the total mass of the anchor coat layer may be set to a different range in addition to the above-mentioned range, depending on the application of the anchor coat layer.

The thickness of the anchor coat layer is not particularly limited as long as it can bond the substrate layer and the gas barrier layer described below with the required adhesive strength, but is preferably 0.01 μm or more and 1.0 μm or less, more preferably 0.02 μm or more and 0.5 μm or less, and may be any of 0.04 μm or more and 0.2 μm or less, and 0.04 μm or more and 0.1 μm or less. When the thickness of the anchor coat layer is at least the lower limit, the adhesive strength with the substrate layer is further improved. When the thickness of the anchor coat layer is at most the upper limit, the decrease in the moisture permeability of the substrate layer can be further suppressed.

<Gas barrier layer>
The gas barrier layer is a resin layer that suppresses gas permeation and is provided to impart gas barrier properties to the base layer. The type of gas is not particularly limited as long as it does not affect the contents packaged in the laminate film described below, and examples thereof include carbon dioxide and nitrogen.

The gas barrier resin component contained in the gas barrier layer is preferably one that can impart gas barrier properties to the base layer and suppress a decrease in the moisture permeability of the base layer. Specific examples include saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, modified polyvinyl alcohol, polyurethane, polyether, polyamide, cellophane, cellulose, polysaccharides such as starch, and polyhydroxyethyl (meth)acrylate. Among these, resins containing hydrophilic groups, such as saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, and modified polyvinyl alcohol, as well as polyethers and polyurethanes, are particularly preferred because they are effective in suppressing a decrease in the moisture permeability of the base layer. Examples of modified polyvinyl alcohol include those listed above.

The water vapor permeability and gas barrier properties of polyvinyl alcohol or modified polyvinyl alcohol can be adjusted by adjusting the molecular weight and degree of saponification. The degree of saponification of polyvinyl alcohol or modified polyvinyl alcohol is preferably 70 to 99 mol%, more preferably 85 to 99 mol% or more, and even more preferably 97 to 99 mol% or more. If the degree of saponification is above the lower limit, water resistance increases and the film is less likely to dissolve even when in contact with water, allowing the strength of the film to be maintained. Furthermore, if the degree of saponification is below the upper limit, water solubility is maintained at an appropriate level, making it possible to prepare a solution with good coatability.
The viscosity of a 4% by mass solution of polyvinyl alcohol or modified polyvinyl alcohol is preferably 3 mPa s or more, more preferably 8.0 mPa s or more, and even more preferably 20 mPa s or more. When the 4% by mass solution of polyvinyl alcohol or modified polyvinyl alcohol has the above viscosity, the water vapor permeability is high, the strength is increased, and the moisture absorption is low.
From the viewpoint of coatability, the viscosity of a 4% by mass solution is preferably 1000 mPa·s or less.

The resin film may contain only one type of gas barrier resin component, or two or more types. If two or more types are used, the combination and ratio of these components can be selected as desired depending on the purpose.

The gas barrier layer may contain only a gas barrier resin component (i.e., it may consist of a gas barrier resin component), or it may contain other components that do not fall under the category of gas barrier resin components (i.e., it may consist of the gas barrier resin component and the other components).

The gas barrier layer may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

Examples of the other components include additives known in the art.
Examples of the additives include crosslinking agents, antifogging agents, antiblocking agents, antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, inorganic fibers, organic fibers, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers. Among these, crosslinking agents are preferably used because they can improve water resistance and strength. Examples of crosslinking agents include titanium compounds, metal chelate-based, boron-based, isocyanate-based, organic acid, and acid-modified polymers. Examples of titanium compounds include titanium alkoxide compounds and titanium acylate compounds. Antifogging agents are also preferably used because they can improve moisture permeability by making the resin film surface more compatible with water. Examples of antifogging agents include glycerin laurate, diglycerin laurate, decaglycerin laurate, glycerin monostearate, and sorbitan stearate. Inorganic and organic fibers can improve the film strength and water resistance. Examples of organic fibers include cellulose, and cellulose nanofibers (CNF) are preferably used.

In the gas barrier layer, the content of the gas barrier resin component relative to the total mass of the gas barrier layer is preferably 60 to 100% by mass, and may be, for example, 80 to 100% by mass, 90 to 100% by mass, or 95 to 100% by mass. Having this proportion at or above the lower limit imparts stronger gas barrier properties to the base layer. Having this proportion at or below the upper limit prevents a decrease in the moisture permeability of the base film.

In the resin film, the content ratio of the gas barrier resin component to the total mass of the resin film may be set to a different range in addition to the above-mentioned range, depending on the intended use of the resin film.

The gas barrier layer may consist of one layer (single layer), or two or more layers. When the gas barrier layer consists of multiple layers, these layers may be the same or different, and there are no particular restrictions on the combination of these layers as long as it does not impair the effects of the present invention.

The thickness of the gas barrier layer is not particularly limited, but is preferably 0.1 μm or more and 5.0 μm or less, more preferably 0.3 μm or more and 4.0 μm or less, and may be any of 0.4 μm or more and 3.0 μm or less, and 0.4 μm or more and 2.0 μm or less. When the thickness of the gas barrier layer is equal to or more than the lower limit, the effect of imparting gas barrier properties to the base layer is improved. When the thickness of the gas barrier layer is equal to or less than the upper limit, the decrease in moisture permeability of the base layer can be further suppressed.
Here, the "thickness of the gas barrier layer" means the thickness of the entire gas barrier layer, and for example, the thickness of a gas barrier layer consisting of multiple layers means the total thickness of all layers that make up the gas barrier layer.

<Method of manufacturing resin film>
When the resin film has a single layer containing a gas barrier resin component and an adhesive resin component (the resin film is a single layer containing a gas barrier resin component and an adhesive resin component), for example, a resin composition containing the gas barrier resin component, the adhesive resin component, and optionally the other components can be applied to one side of a layer (hereinafter sometimes referred to as an "adjacent layer") that will be adjacent to the resin film in the laminate film described below (for example, a substrate layer described below), and dried as necessary to form a resin film on the adjacent layer. In this case, the desired laminate film itself or a part thereof can be immediately obtained.

When the resin film comprises two layers: an anchor coat layer containing an adhesive resin component; and a gas barrier layer containing a gas barrier resin component provided on one side of the anchor coat layer (the resin film is a two-layer structure consisting of the anchor coat layer and the gas barrier layer), for example, a resin composition containing the adhesive resin component and, if necessary, the other components can be applied to one side of the adjacent layer and dried as necessary to form an anchor coat layer on the adjacent layer. Then, a resin composition containing the gas barrier resin component and, if necessary, the other components can be applied to the exposed surface of the anchor coat layer and dried as necessary to form a resin film comprising an anchor coat layer and a gas barrier layer provided on one side of the anchor coat layer on the adjacent layer. In this case, the desired laminate film itself or a portion thereof can be immediately obtained.

The resin composition may contain a solvent in order to improve its applicability for coating.
Examples of the solvent include water, 2-propanol (IPA), ethanol, methanol, methyl ethyl ketone (MEK), ethyl acetate, toluene, and acetone.

The resin composition may contain only one type of solvent, or two or more types. If two or more types are used, the combination and ratio of these solvents can be selected as desired depending on the purpose.

This method of producing the resin film by coating the resin composition is particularly effective when the desired resin film contains components that decompose, ignite, or vaporize at relatively low temperatures. Examples of such components that are unsuitable for handling at high temperatures include potassium sorbate and sodium lactate.

The resin composition can be applied using a known method. For example, the resin composition can be applied using various coaters.

There are no particular restrictions on the drying conditions for the resin composition, but if the resin composition contains a solvent, as described below, it is preferable to heat-dry it. In this case, it is preferable to dry it at a temperature of, for example, 40 to 120°C.

<<Laminated film>>
The structure of a laminate film according to one embodiment of the present invention will be described. FIG. 1 is a cross-sectional schematic diagram of a laminate film 1 according to one embodiment of the present invention. As shown in FIG. 1, the laminate film 1 of this embodiment is generally configured to include a resin film 2 of the present invention and a substrate layer 3 provided on the resin film 2. As shown in FIG. 2, the laminate film 1 of this embodiment may also be generally configured to include an anchor coat layer 20, a gas barrier layer 21 provided on one side of the anchor coat layer 20, and a substrate layer 3 provided on the other side of the anchor coat layer 20. The laminate film 1 of this embodiment can be used as a package, particularly as a film for packaging metal articles such as medical devices, industrial materials, and electronic components.

<Base material layer>
The substrate layer (also referred to as core layer) 3 is a resin layer provided on the above-mentioned resin film 2. The substrate layer 3 can impart flexibility to the multilayer film 1. Resins that can be used for the substrate layer 3 are not particularly limited as long as they are capable of imparting the above-mentioned functions and have moisture permeability, and examples thereof include polyolefin-based resins, polyester-based resins, nylon-based resins, ethylene-vinyl acetate copolymers, and olefin-based elastomers. The substrate layer may or may not be porous as long as it has moisture permeability.

Examples of polyolefin resins include polyethylene copolymers, polypropylene copolymers, and butene copolymers, and among these, polyethylene copolymers and polypropylene copolymers are preferred.
From the viewpoint of improving adhesiveness, the copolymer may be in the form of a random copolymer, a graft copolymer, a block copolymer or a graft copolymer, with a random copolymer being particularly preferred.

The polyolefin resin is an olefin copolymer.
The polyethylene copolymer is a copolymer of ethylene and a monomer other than ethylene.
The polypropylene copolymer is a copolymer of propylene and a monomer other than propylene.
The butene copolymer is a copolymer of butene and a monomer other than butene.

Polyethylene copolymers include, but are not limited to, copolymers of ethylene and vinyl group-containing monomers.

Examples of copolymers of ethylene and vinyl group-containing monomers include maleic anhydride-grafted linear low-density polyethylene (hereinafter referred to as "LLDPE-g-MAH"), ethylene-vinyl acetate copolymer (hereinafter referred to as "EVA resin"), ethylene-methyl methacrylate copolymer (hereinafter referred to as "EMMA resin"), ethylene-ethyl acrylate copolymer (hereinafter referred to as "EEA resin"), ethylene-methyl acrylate copolymer (hereinafter referred to as "EMA resin"), ethylene-ethyl acrylate-maleic anhydride copolymer (hereinafter referred to as "E-EA-MAH resin"), ethylene-acrylic acid copolymer (hereinafter referred to as "EAA resin"), ethylene-methacrylic acid copolymer (hereinafter referred to as "EMAA resin"), ionomer (hereinafter referred to as "ION resin"), and ethylene-based thermoplastic elastomer. In this specification, ION resin refers to a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid, which has an ionically crosslinked structure formed by salt formation between the acid moiety and metal ions.

Specific examples of polyester resins include polyethylene terephthalate resin, polytrimethylene terephthalate resin, polytetramethylene terephthalate resin, and polyhexamethylene terephthalate resin.

Examples of nylon resins include 4-nylon, 6-nylon, 7-nylon, 11-nylon, 12-nylon, 46-nylon, 66-nylon, 69-nylon, 610-nylon, 611-nylon, 612-nylon, 6T-nylon, 6I-nylon, copolymer of 6-nylon and 66-nylon (nylon 6/66), copolymer of 6-nylon and 610-nylon, copolymer of 6-nylon and 611-nylon, copolymer of 6-nylon and 12-nylon (nylon 6/12), copolymer of 6-nylon and 612-nylon, 6-nylon Examples of such nylon include copolymers of nylon and 6T-nylon, copolymers of nylon 6 and 6I-nylon, copolymers of nylon 6, 66-nylon and 610-nylon, copolymers of nylon 6, 66-nylon and 12-nylon (nylon 6/66/12), copolymers of nylon 6, 66-nylon and 612-nylon, copolymers of nylon 66 and 6T-nylon, copolymers of nylon 66 and 6I-nylon, copolymers of nylon 6T-nylon and 6I-nylon, copolymers of nylon 66, 6T-nylon and 6I-nylon, and amorphous nylon. Among these, from the standpoints of heat resistance, mechanical strength, and ease of availability, 6-nylon, 12-nylon, 66-nylon, nylon 6/66, nylon 6/12, and nylon 6/66/12 are preferred, with 6-nylon being more preferred.

The base layer 3 may consist of a single layer, or two or more layers. For example, by making the base layer 3 out of multiple layers made of different materials, it is possible to adjust the properties of the base layer 3, such as its hardness and moisture permeability.

The thickness ratio of the base layer 3 to the total layers of the laminate film 1 is preferably 75 to 99.9%, more preferably 90 to 99.9%, even more preferably 95 to 99.9%, and particularly preferably 97 to 99.5%. When this thickness ratio is equal to or greater than the above-mentioned lower limit, flexibility can be imparted to the multilayer film 1. When this thickness ratio is equal to or less than the above-mentioned upper limit, a decrease in moisture permeability when a resin film is laminated is suppressed.

The thickness of the substrate layer 3 is preferably 10 to 100 μm, and more preferably 15 to 50 μm. If the thickness is at or above the lower limit of the preferred range, the decrease in moisture permeability when a resin film is laminated is suppressed, and if the thickness is at or below the upper limit, flexibility is achieved.

<Method of manufacturing laminated film>
Next, a method for producing the laminated film 1 will be described.
The method for producing the laminated film 1 of this embodiment is not particularly limited, but for example, when the resin film is a single layer, it can be produced by coating and laminating the resin film on one side of the base layer. When the resin film is a two-layer film consisting of an anchor coat layer and a gas barrier layer, it can be produced by coating and laminating the anchor coat layer on one side of the base layer, and then coating and laminating the gas barrier layer on the side of the anchor coat layer opposite to the base layer.

<<Packaging body and manufacturing method thereof>>
A package can be produced by using the laminated film, placing the resin film on the packaging object side, and packaging the packaging object.
The packaging body including the resin film allows the contents in the packaging body to be dried after packaging, and the inert gas sealed in the packaging body prevents deterioration of the contents, thereby preventing deterioration due to rust, etc., of metal items such as medical devices, industrial materials, and electronic components.

During packaging, for example, the object to be packaged is wrapped with one sheet of the laminate film, and the remaining portion of the laminate film (the portion not wrapping the object to be packaged) is overlapped with another portion of the laminate film and sealed, thereby packaging the object to be packaged. At this time, the resin films in the laminate film may be overlapped with each other, or the resin film and the base material layer may be overlapped.
In addition, during packaging, for example, the object to be packaged can be sandwiched between two sheets of the laminate film, and these laminate films can be overlapped and sealed to package the object to be packaged. At this time, the resin films in the laminate film can be overlapped, or the resin film and the base material layer can be overlapped.
Furthermore, the object to be packaged can be packaged by placing the object on a tray and sealing the resin film in the laminated film with the periphery of the tray.

The effects of the present invention will be explained in detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[Example 1]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 2:8), and the diluted solution was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), and dried at 100°C to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
A saponified ethylene vinyl acetate copolymer ("Soarnol 16DX" manufactured by Mitsubishi Chemical Corporation) (solid content concentration: 16% by mass) diluted with a dilution solvent (a mixed solvent of water and 2-propanol at a ratio of 5:5) to a solid content concentration of 9% by mass was applied to the exposed surface of this anchor coat layer using a 12 μm bar and dried at 100°C, thereby forming a gas barrier layer (thickness: 1.04 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 2]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 2:8), and the diluted solution was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), and dried at 100°C to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
A saponified ethylene vinyl acetate copolymer ("Soarnol 16DX" manufactured by Mitsubishi Chemical Corporation) (solid content concentration: 16% by mass) diluted with a dilution solvent (a mixed solvent of water and 2-propanol at a ratio of 5:5) to a solid content concentration of 3% by mass was applied to the exposed surface of this anchor coat layer using a 12 μm bar and dried at 100°C, thereby forming a gas barrier layer (thickness: 0.36 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 3]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Polyvinyl alcohol (Kuraray Poval 60-98 manufactured by Kuraray Co., Ltd.) (solid content: 100% by mass, viscosity of 4% by mass aqueous solution at 20°C: 60 mPa s, degree of saponification: 98-99 mol%) diluted with water to a solid content of 2% by mass was applied to the exposed surface of this anchor coat layer using a 54 μm bar, and dried at 100°C to form a gas barrier layer (thickness: 1.04 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 4]
<<Production of Resin Films and Laminated Films>>
A laminated film was obtained in the same manner as in Example 3, except that the thickness of the anchor coat layer was 0.04 μm and the thickness of the gas barrier layer was 0.36 μm, and the base film (thickness: 20 μm), the anchor coat layer (thickness: 0.04 μm), and the gas barrier layer (thickness: 0.36 μm) were laminated in this order.

[Example 5]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Polyvinyl alcohol (Kuraray Poval 44-88 manufactured by Kuraray Co., Ltd.) (solid content: 100% by mass, viscosity of 4% by mass aqueous solution at 20°C: 44 mPa s, degree of saponification: 87-89 mol%) diluted with water to a solid content of 2% by mass was applied to the exposed surface of this anchor coat layer using a 35 μm bar, and dried at 100°C to form a gas barrier layer (thickness: 0.70 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 6]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Modified polyvinyl alcohol ("Exceval RS-2117" manufactured by Kuraray Co., Ltd.) (solids concentration: 100% by mass, viscosity of 4% by mass aqueous solution at 20°C: 26.5 mPa s, degree of saponification: 97.5-99 mol%) was diluted with a solvent (a mixed solvent of water:2-propanol = 9:1) to a solids concentration of 6% by mass and applied to the exposed surface of this anchor coat layer using a 35 μm bar, and dried at 100°C to form a gas barrier layer (thickness: 2.10 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 7]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Polyvinyl alcohol ("Exceval RS-2117" manufactured by Kuraray Co., Ltd.) (solids concentration: 100% by mass, viscosity of 4% by mass aqueous solution at 20°C: 26.5 mPa s, degree of saponification: 97.5-99 mol%) diluted with a solvent (a mixed solvent of water:2-propanol = 9:1) to a solids concentration of 2% by mass was applied to the exposed surface of this anchor coat layer using a 52 μm bar and dried at 100°C to form a gas barrier layer (thickness: 1.04 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 8]
<<Production of Resin Films and Laminated Films>>
A laminated film was obtained in the same manner as in Example 7, except that the thickness of the anchor coat layer was 0.04 μm and the thickness of the gas barrier layer was 0.70 μm, and the base film (thickness: 20 μm), the anchor coat layer (thickness: 0.04 μm), and the gas barrier layer (thickness: 0.70 μm) were laminated in this order.

[Example 9]
<<Production of Resin Films and Laminated Films>>
A laminated film was obtained in the same manner as in Example 7, except that the thickness of the anchor coat layer was 0.04 μm and the thickness of the gas barrier layer was 0.36 μm, and the base film (thickness: 20 μm), the anchor coat layer (thickness: 0.04 μm), and the gas barrier layer (thickness: 0.36 μm) were laminated in this order.

[Example 10]
<<Production of Resin Films and Laminated Films>>
A laminated film was obtained in the same manner as in Example 7, except that the thickness of the anchor coat layer was 0.04 μm and the thickness of the gas barrier layer was 0.25 μm, and the base film (thickness: 20 μm), the anchor coat layer (thickness: 0.04 μm), and the gas barrier layer (thickness: 0.25 μm) were laminated in this order.

[Example 11]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Polyvinyl alcohol ("Exceval RS-4104" manufactured by Kuraray Co., Ltd.) (solids concentration: 100% by mass, viscosity of 4% by mass aqueous solution at 20°C: 4 mPa s, degree of saponification: 98-99 mol%) diluted with a mixed solvent of water and 2-propanol at a ratio of 9:1 to a solids concentration of 2% by mass was applied to the exposed surface of this anchor coat layer using a 35 μm bar and dried at 100°C to form a gas barrier layer (thickness: 0.70 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 12]
<<Production of Resin Films and Laminated Films>>
A laminated film was obtained in the same manner as in Example 7, except that a solution containing 0.3 mass% of cellulose nanofiber (manufactured by KRI) (sulfuric acid ester treated) and 2 mass% of modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., "Exceval RS-2117") (solvent: mixed solvent of water:2-propanol = 9:1) was used instead of modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., "Exceval RS-2117"), and the thickness of the gas barrier layer was set to 0.81 μmμm.

[Example 13]
<<Production of Resin Films and Laminated Films>>
Five parts by mass of a 1,2-polybutadiene modified material ("TITABOND T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration: 10% by mass) and 95 parts by mass of an ethylene-vinyl alcohol copolymer ("SOARNOL 16DX" manufactured by Mitsubishi Chemical Corporation) (solid content concentration: 16% by mass) were diluted 7 times with a dilution solvent (a mixed solvent of water:2-propanol = 5:5). This was then coated on one side of a substrate film ("BREATHLAYER" manufactured by Kurabo Industries, Ltd., thickness: 20 μm) and dried at 100°C to form a resin film (thickness: 0.81 μm) on the substrate film.
In this way, a laminated film was obtained in which the resin film was laminated on the base film.

[Example 14]
<<Production of Resin Films and Laminated Films>>
A laminated film was obtained in the same manner as in Example 13, except that the thickness of the resin film was 0.34 μm, in which a substrate film and a resin film (thickness: 0.34 μm) were laminated.

[Example 15]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Modified polyvinyl alcohol (Gohsenol WO-320N manufactured by Mitsubishi Chemical Corporation, modified polyvinyl alcohol having ethylene oxide chains in the side chains) (solids concentration: 100% by mass, 4% by mass aqueous solution viscosity at 20°C: 8.5 mPa s, saponification degree: 98.5 mol%) was diluted with a solvent (100% water) to a solids concentration of 2% by mass and applied to the exposed surface of this anchor coat layer using a 52 μm bar, and dried at 100°C to form a gas barrier layer (thickness: 1.1 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 16]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Modified polyvinyl alcohol ("D Polymer DF-20" manufactured by Japan Vinyl Acetate & Poval Co., Ltd., a modified polyvinyl alcohol having carbonyl groups in the side chains) (solids concentration: 100% by mass, 4% by mass aqueous solution viscosity at 20°C: 28 mPa s, saponification degree: 98-99 mol%) was diluted with a solvent (100% water) to a solids concentration of 2% by mass and applied using a 52 μm bar to the exposed surface of this anchor coat layer. The coating was then dried at 100°C to form a gas barrier layer (thickness: 1.1 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Example 17]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
Polyurethane (DIC Corporation's "Hydran WLS-230") (solid content: 35% by mass) diluted with a solvent (100% water) to a solid content of 6% by mass was applied to the exposed surface of this anchor coat layer using a 32 μm bar, and dried at 100°C to form a gas barrier layer (thickness: 1.9 μm) on the anchor coat layer.

[Example 18]
<<Production of Resin Films and Laminated Films>>
A 1,2-polybutadiene modified material ("Titabond T180E" manufactured by Nippon Soda Co., Ltd.) (solid content concentration 10% by mass) was diluted 10 times with a dilution solvent (a mixed solvent of water:2-propanol = 7:3), and the diluted material was applied to one side of a corona-treated substrate film ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), followed by drying at 100°C, to form an anchor coat layer (thickness 0.04 μm) on the substrate film.
A polyether ("ALKOX CP-A1H" manufactured by Meisei Chemical Industry Co., Ltd.) (solid content: 100% by mass) diluted with a solvent (100% water) to a solid content of 2% by mass was applied to the exposed surface of this anchor coat layer using a 52 μm bar, and dried at 100°C to form a gas barrier layer (thickness: 1.1 μm) on the anchor coat layer.
As a result, a laminated film was obtained in which the base film, anchor coat layer, and gas barrier layer were laminated in this order.

[Comparative Example 1]
Instead of the laminated films of Examples 1 to 14, a biaxially oriented polypropylene film (OPP film, "FOR" manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) was used.

[Comparative Example 2]
Instead of the laminated films of Examples 1 to 14, a microporous film (a porous film manufactured by 3M, thickness 20 μm) was used.

<<Measurement of water vapor transmission rate of resin film>>
The water vapor permeation rates of the laminate films of Examples 1 to 18 obtained above, the substrate films used in the examples ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), and the films used in Comparative Examples 1 and 2 were each measured at 30°C and 97% RH using the cup method specified in JIS Z 0208. The measurements were carried out by placing 10 g of dried calcium chloride in a container with a diameter of 60 mm. Next, for the laminate films of Examples 1 to 18, the water vapor permeation rate of a resin film not including a substrate layer was calculated from the measured water vapor permeation rate of the laminate film using the following formula. The results are shown in Table 1.

<<Measurement of Air Resistance of Resin Film>>
The air permeability resistance of the laminate films of Examples 1 to 18 obtained above, the base film used in the examples ("Breathlayer" manufactured by Kurabo Industries, Ltd., thickness 20 μm), and the films used in Comparative Examples 1 and 2 was measured at 23°C and 50% humidity using the Oken method specified in JIS P 8117:2009. Next, for the laminate films of Examples 1 to 18, the air permeability resistance of the resin film of each Example was calculated by subtracting the air permeability resistance of the laminate film of each Example from the air permeability resistance of the base film. The results are shown in Table 1.

<<Evaluation of the Deterioration Prevention Effect of Laminated Film>>
A 0.2 cm (iron plate) piece measuring 5 cm x 5 cm was immersed in water for 10 minutes, and then placed in a bag made by laminating a 12 cm x 12 cm laminated film or films one on top of the other and welding them at a temperature of 160°C, which was produced in each of the above examples and comparative examples, and carbon dioxide was sealed inside to form a package.
After storing the package under normal pressure at 23° C. for 5 days, the iron pieces in storage were taken out of the package as test pieces, and the occurrence of rust on the surface of the iron pieces was visually confirmed.
<Evaluation criteria>
A: No rust was observed on the surface of the metal piece.
B: Rust is present on part of the metal surface.
C: Rust is present on the entire metal piece.

As is clear from the above results, the laminate films of Examples 1 to 18 had water vapor permeation rates of 7000 g/ ^m² -day or more and air resistance rates of 5000 seconds or more, so rusting of metal pieces was suppressed. In contrast, the film of Comparative Example 1 had a water vapor permeation rate of less than 7000 g/ ^m² -day, so rusting of metal pieces was not suppressed. Furthermore, the film of Comparative Example 2 had an air resistance rate of less than 5000 seconds, so rusting of metal pieces was not suppressed, just like Comparative Example 1.

This invention can be used to package metal items such as medical equipment, industrial materials, and electronic components.

DESCRIPTION OF SYMBOLS 1...Laminated film 2...Resin film 3...Base material layer 20...Anchor coat layer 21...Gas barrier layer

Claims (6)

The water vapor transmission rate measured by the cup method specified in JIS Z 0208 under conditions of 30°C and 97% RH is 7000 g/m2·day or more,
A resin film having an air permeability resistance of 5000 seconds or more at 23°C and 50% RH , as measured by the Oken method specified in JIS P 8117:2009,
The resin film comprises an anchor coat layer and a gas barrier layer provided on one surface of the anchor coat layer,
The resin film, wherein the gas barrier layer comprises at least one selected from the group consisting of a saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, modified polyvinyl alcohol, polyether, and polyurethane . The resin film according to claim 1, wherein the thickness of the resin film is 0.1 μm or more and 5.0 μm or less. The resin film according to claim 1 or 2 , wherein the anchor coat layer contains a modified 1,2-polybutadiene. The water vapor transmission rate measured by the cup method specified in JIS Z 0208 under conditions of 30°C and 97% RH is 7000 g/m2·day or more,
A resin film having an air permeability resistance of 5000 seconds or more at 23°C and 50% RH, as measured by the Oken method specified in JIS P 8117:2009,
The resin film has a single layer containing at least one selected from the group consisting of a saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, modified polyvinyl alcohol, polyether, and polyurethane, and a modified 1,2-polybutadiene. The resin film according to claim 4, wherein the resin film has a thickness of 0.1 μm or more and 5.0 μm or less. A laminated film comprising the resin film according to any one of claims 1 to 5 and a substrate layer provided on the resin film.