JP2022138299A - Laminate film - Google Patents

Abstract

To provide a laminate film capable of simplifying a manufacturing process and reducing the cost while maintaining high gas barrier property.SOLUTION: A laminate film having gas barrier property comprises an ink reception layer, a substrate layer, a gas barrier layer, and a low melting point resin layer in this order. The substrate layer involves a polyolefin-based resin. The gas barrier layer involves a gas barrier resin. The low melting point resin layer involves a low melting point resin having a melting point of 135°C or under. The ink reception layer involves a component derived from an emulsion of a resin particle, and a volume average particle diameter of the resin particle is 0.01-3.0 μm.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a laminated film having gas barrier properties.

Conventionally, gas barrier films that suppress the permeation of water vapor, oxygen gas, and the like have been widely used as packaging materials for foods, cosmetics, and the like in order to suppress deterioration of the contents. A gas barrier film is generally a laminated film having a gas barrier layer, a substrate layer, a heat seal layer, and the like. As the gas barrier layer, a resin film having high gas barrier properties such as vinyl alcohol resin (PVA), ethylene-vinyl alcohol copolymer (EVOH), vinylidene chloride resin, etc. is used (see, for example, Patent Documents 1 and 2).

International Publication No. 2014/104237 International Publication No. 2017/209212

Among them, ethylene-vinyl alcohol copolymer is excellent in gas barrier properties, but it is known that the gas barrier properties are easily deteriorated under the influence of water. In order to maintain a high gas barrier property, it was necessary to provide a water barrier layer by laminating a polyolefin resin film or the like on both sides of the gas barrier layer.

However, such multi-layering increases the number of materials and manufacturing steps, resulting in an increase in cost. In addition, since the water barrier layer having low hydrophilicity has low ink adhesion, it also reduces the printability of the laminated film. In order to prevent the ink from peeling off, it was necessary to provide a protective layer by coating after printing.

An object of the present invention is to provide a laminated film capable of simplifying the manufacturing process and reducing costs while maintaining high gas barrier properties.

As a result of intensive studies conducted by the present inventors to solve the above problems, it was found that the above problems can be solved by arranging the layers in a laminated film in a specific order and providing a specific ink-receiving layer on the film surface. , completed the present invention.
That is, the present invention is as follows.

(1) A laminated film having gas barrier properties,
having an ink receiving layer, a substrate layer, a gas barrier layer and a low melting point resin layer in this order,
The base material layer contains a polyolefin resin,
The gas barrier layer contains a gas barrier resin,
The low melting point resin layer contains a low melting point resin having a melting point of 135° C. or less,
The laminated film, wherein the ink-receiving layer contains an emulsion-derived component of resin particles, and the resin particles have a volume average particle size of 0.01 to 3.0 μm.

(2) The laminated film according to (1), wherein the laminated film has an oxygen permeability of 15 cm ³ /(m ² ·24 h·atm) or less at a temperature of 23°C and a relative humidity of 90% RH.

(3) The laminated film according to (1) or (2), wherein the gas barrier resin is an ethylene-vinyl alcohol copolymer or a polyvinyl alcohol resin.

(4) The laminated film according to any one of (1) to (3) above, wherein the resin particles are a urethane resin or an olefin copolymer.

(5) The laminated film according to any one of (1) to (4), wherein the low-melting resin is low-density polyethylene or metallocene-catalyzed polyolefin.

(6) The laminated film according to any one of (1) to (5), further comprising adhesive layers on both sides of the gas barrier layer.

(7) The base material layer is a resin film containing at least one of a polypropylene resin and a polyethylene resin as the polyolefin resin, and a filler. laminated film.

(8) The laminated film according to (7), wherein the substrate layer is a porous stretched film stretched in at least one axial direction.

ADVANTAGE OF THE INVENTION According to this invention, the laminated|multilayer film which can simplify a manufacturing process and can reduce cost can be provided, maintaining high gas-barrier property.

It is a cross-sectional view showing an example of a laminated film.

The laminated film of the present invention will be described in detail below. The following are examples (representative examples) of the present invention, and the present invention is not limited thereto.

In the following description, the description of "(meth)acrylic" indicates both acrylic and methacrylic.

[Laminated film]
The laminated film of the present invention has an ink receiving layer, a substrate layer, a gas barrier layer and a low melting point resin layer in this order. Specifically, a substrate layer is provided on one side of the gas barrier layer, and an ink receiving layer is provided thereon. A low melting point resin layer is provided on the other surface of the gas barrier layer.

In general, the gas barrier properties of the gas barrier layer are likely to deteriorate under the influence of water. However, in the laminated film of the present invention, the gas barrier layer is arranged between the substrate layer and the low melting point resin layer. Since the base material layer and the low-melting-point resin layer shield the gas barrier layer from coming into contact with water, it is possible to obtain a laminated film whose gas barrier properties are less likely to deteriorate even under high humidity conditions. By covering both sides of the gas barrier layer with the base material layer and the low-melting resin layer which are usually provided in the laminated film, it is unnecessary to add a new water barrier layer, so that the layer structure can be simplified.

Further, in the present invention, an ink receiving layer is provided on the substrate layer. The ink-receiving layer contains an emulsion-derived component of resin particles having a volume average particle size of 0.01 to 3.0 μm. This component not only has high adhesion to the ink, but also has high adhesion to the substrate layer, and can be directly laminated on the substrate layer without using an adhesive. Since the substrate layer contains a polyolefin resin and has low adhesion to ink, it is necessary to form a protective layer after printing when printing on the substrate layer. However, the ink-receiving layer makes it possible to eliminate the need for such a protective layer.

Thus, the laminated film of the present invention has a specific layer structure that does not require multi-layering to maintain high gas barrier properties. Since raw materials and manufacturing equipment for multilayering are not required, manufacturing costs can be reduced. Furthermore, it was found that the ink-receiving layer improves the gas barrier properties of the laminated film, and the utility of the laminated film as a gas barrier film can be further enhanced.
Each layer will be described below.

(Gas barrier layer)
The gas barrier layer contains a gas barrier resin and suppresses permeation of gas such as oxygen gas, water vapor, carbon dioxide gas, or nitrogen gas. The gas barrier layer may be one layer, or two or more layers may be provided. From the viewpoint of flexibility, impact resistance, or pinhole resistance, the gas barrier layer is preferably a thermoplastic resin film having gas barrier properties.

Gas barrier resins include, for example, polyvinyl alcohol resin (PVA), ethylene-vinyl alcohol copolymer (EVOH), acrylonitrile resin (AN), vinylidene chloride resin (PVDC), nylon 6 (PA6), and the like. These 1 type(s) or 2 or more types can be used.

Among them, vinyl alcohol-based resins containing at least one of polyvinyl alcohol resins and ethylene-vinyl alcohol copolymers, which have high gas barrier properties and good moldability, are preferred, and ethylene-vinyl alcohol copolymers are preferred due to their high moldability. more preferred.

The ethylene-vinyl alcohol copolymer preferably has an ethylene content of 30 mol % or more, more preferably 40 mol % or more, from the viewpoint of lowering the melting point that affects moldability. From the viewpoint of enhancing gas barrier properties, the ethylene content is preferably 60 mol % or less, and preferably 50 mol % or more. Here, the ethylene content means the ratio of the number of ethylene units to the total number of monomer units of the ethylene/vinyl alcohol copolymer.

<Ethylene/vinyl alcohol copolymer>
The ethylene-vinyl alcohol copolymer used for the gas barrier layer is a polymer mainly having ethylene-derived structural units and vinyl alcohol structural units. The ethylene/vinyl alcohol copolymer can contain one or more structural units other than ethylene and vinyl alcohol as long as the effects of the present invention are not impaired.

Ethylene/vinyl alcohol copolymers can usually be produced by polymerizing ethylene and vinyl esters and saponifying the obtained ethylene/vinyl ester copolymers. Ethylene-vinyl alcohol copolymers produced in this manner may contain a small amount of residual vinyl ester structural units that have not been saponified.

The degree of saponification of the ethylene-vinyl alcohol copolymer is preferably 80 mol% or more, more preferably 95 mol% or more, more preferably 99 mol% or more, from the viewpoint of melt moldability, gas barrier properties, color resistance or moisture resistance. Especially preferred. The upper limit of the degree of saponification of the ethylene-vinyl alcohol copolymer may be 100 mol%, but since a sufficient gas barrier property can be obtained even if it is less than 100 mol%, 99.99 mol% or less is preferable from the viewpoint of cost. The degree of saponification means the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in the ethylene-vinyl alcohol copolymer. The degree of saponification of the ethylene/vinyl alcohol copolymer can be measured according to JIS-K-6726:1994.

The ethylene/vinyl alcohol copolymer may be used in combination with other gas barrier resins as described above as long as the high gas barrier properties of the ethylene/vinyl alcohol copolymer are not impaired.

From the viewpoint of moldability, the melting point of the ethylene-vinyl alcohol copolymer is preferably 175°C or lower, more preferably 170°C or lower, and even more preferably 165°C or lower.

The gas barrier layer may contain additives as necessary, but from the viewpoint of gas barrier properties, it is preferably a film made of a gas barrier resin.

<Oxygen permeability>
The oxygen permeability, which means the gas barrier property of the gas barrier layer, is preferably 15 cm ³ /(m ² ·24 h·atm) or less, more preferably 10 cm ³ /(m ² · 24 h·atm) or less is more preferable.
In addition, the oxygen permeability of the gas barrier layer is preferably 50 cm ³ /(m ² ·24 h·atm) or less, more preferably 30 cm ³ /(m ² ·24 h·atm) in a high humidity environment with a temperature of 23 ° C. and a relative humidity of 90%. ) or less, and more preferably 11 cm ³ /(m ² ·24 h·atm) or less.
Under any humidity, the lower limit of oxygen gas permeability may be 0 cm ³ /(m ² ·24 h·atm), but considering appropriate thickness etc., it is usually 0.001 cm ³ /(m ² ·24 h·atm). atm) or more.

(Base material layer)
The substrate layer is a resin film containing a polyolefin resin having excellent mechanical strength, and is provided as a support for the laminated film. Polyolefin resin has excellent moisture resistance, so it can block water from entering the gas barrier layer, and also has the function of suppressing the effect of humidity on the gas barrier layer. The base material layer can be formed by film forming a resin composition containing a polyolefin resin. From the viewpoint of mechanical strength, the substrate layer is preferably a biaxially stretched film of polyolefin resin.

<Polyolefin resin>
Specific examples of polyolefin-based resins include polypropylene-based resins, polyethylene-based resins, polymethyl-1-pentene, and the like.

The polypropylene-based resin is not particularly limited as long as propylene is used as the main monomer. Examples include isotactic and syndiotactic polymers obtained by homopolymerizing propylene. Also, a copolymer of propylene as a main component and an α-olefin such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, or 1-octene Certain propylene-α-olefin copolymers and the like can also be used. The copolymer may be a binary system or a multi-component system having three or more monomer components, and may be a random copolymer or a block copolymer. Also, a propylene homopolymer and a propylene copolymer may be used in combination.

Examples of polyethylene-based resins include high density polyethylene with a density of 0.940 to 0.965 g/cm ³ , medium density polyethylene with a density of 0.920 to 0.935 g/cm ³ , and density of 0.900 g/cm ³ or more. Linear low-density polyethylene of less than 0.920 g/cm ³ , a copolymer mainly composed of ethylene, etc., and copolymerized with an α-olefin such as propylene, butene, hexene, heptene, octene, 4-methylpentene-1, etc. , maleic acid-modified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, ethylene-methacrylic acid alkyl ester copolymer, ethylene- Examples include metal salts of methacrylic acid copolymers (metals include zinc, aluminum, lithium, sodium, potassium, etc.), ethylene-cyclic olefin copolymers, maleic acid-modified polyethylene, and the like.

Further, as the polyolefin resin, a graft-modified product thereof can be used as needed from the viewpoint of improving the adhesiveness or moldability of the resin film.
A known technique can be used for graft modification. Specifically, a graft-modified product using an unsaturated carboxylic acid or a derivative thereof as a graft monomer can be mentioned. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid. Examples of the unsaturated carboxylic acid derivative include an acid anhydride, an esterified product, an amidated product, an imidized product, and a metal salt of the unsaturated carboxylic acid.

Specific grafting monomers include maleic anhydride, itaconic anhydride, citraconic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, glycidyl (meth)acrylate, and maleic acid. monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, (meth)acrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide , maleic acid-N,N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-N , N-diethylamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium (meth)acrylate, or potassium (meth)acrylate etc. can be mentioned.

The graft monomer can be used in an amount of usually 0.005 to 10% by mass, preferably 0.01 to 5% by mass, based on the polyolefin resin.

As the polyolefin resin used for the substrate layer, one of the above may be used alone, or two or more may be used in combination. From the viewpoint of moisture resistance, moldability, mechanical strength, cost, etc., the substrate layer is preferably a resin film of polypropylene resin or polyethylene resin, more preferably polypropylene resin. Among them, a propylene homopolymer is preferable because it is easy to handle as a main raw material for the base material layer.

From the viewpoint of film moldability, it is possible to use a polypropylene resin film in combination with a resin having a melting point equal to or lower than that of a propylene homopolymer. Such resins include polyethylene-based resins, specifically high density or low density polyethylene. The blending amount of the polyethylene-based resin can be, for example, 2 to 25% by mass.

As the polyolefin-based resin used for the base layer, it is preferable to use one having a moisture permeability of the obtained laminated film at a temperature of 38° C. and a relative humidity of 90% RH in the range of 0.01 to 10 g/(m ² ·24 h). can be done. When the moisture permeability of the laminated film is equal to or less than the above upper limit, it is easy to suppress changes in the gas barrier performance of the laminated film due to external humidity. In addition, even when highly hygroscopic contents are packaged and stored, it is easy to suppress changes in the physical properties of the contents due to moisture absorption. On the other hand, if the thickness of the base layer is increased in order to lower the moisture permeability of the laminated film, the flexibility of the laminated film will decrease, making it less suitable for printing and die-cutting, making it more difficult to process into bags or containers. There is Therefore, from the viewpoint of practical use, the moisture permeability is preferably equal to or higher than the lower limit.

The substrate layer may be a resin film using only a polyolefin resin as the thermoplastic resin, or may contain a thermoplastic resin other than the polyolefin resin within a range that does not impair the effects of the present invention. Examples of thermoplastic resins that can be used in combination include polyamide resins such as nylon-6 and nylon-6,6; polyethylene terephthalate or copolymers thereof; aliphatic polyesters such as polybutylene terephthalate, polybutylene succinate, and polylactic acid. thermoplastic polyester resin; polycarbonate; styrene resin such as atactic polystyrene or syndiotactic polystyrene.

<Filler>
The base material layer may contain a filler. Examples of usable fillers include inorganic fillers and organic fillers. Fillers facilitate adjusting the whiteness or opacity of the film. In addition, voids are likely to be formed inside the film, making it possible to reduce the weight of the base material layer and thus the laminated film. When the substrate layer is porous, the heat insulating properties of the laminated film are likely to be improved. If the base material layer is a resin film in which a polyethylene resin is blended with a polypropylene resin, fibril-like pores are easily formed by blending the filler, which is preferable.

<<Inorganic filler>>
Examples of inorganic fillers include calcium carbonate, calcined clay, silica, diatomaceous earth, clay, talc, titanium oxide, barium sulfate, barium titanate, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, dolomite, wax. Inorganic particles such as lastonite or glass fibers can be used. The average particle size of the inorganic filler as measured by a particle size distribution meter based on laser diffraction is usually 0.01 to 15 μm, preferably 0.1 to 5 μm.

<<Organic filler>>
As the organic filler, it is preferable to select a type of resin different from the polyolefin-based resin that is the main component of the base material layer. Examples of such organic fillers include polymers such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, cyclic polyolefin, polystyrene, or polymethacrylate. Organic particles that have a high melting point (eg, 170-300° C.) or a high glass transition temperature (eg, 170-280° C.) and are immiscible can be used.

As the filler, the above inorganic filler and organic filler can be used alone or in combination.
The content of the filler in the base material layer (the total amount when an inorganic filler and an organic filler are used together) is preferably 0 to 60% by mass, more preferably 0 to 50% by mass.

<Other ingredients>
The substrate layer may further contain a heat stabilizer (antioxidant), light stabilizer, dispersant, lubricant, nucleating agent, or the like, if necessary.
As the heat stabilizer, for example, a sterically hindered phenolic antioxidant, a phosphorus antioxidant, an amine antioxidant, or the like can be used, usually within the range of 0.001 to 1% by mass.
As the light stabilizer, for example, a sterically hindered amine light stabilizer, a benzotriazole light stabilizer, or a benzophenone light stabilizer can be used within the range of 0.001 to 1% by mass.
Examples of dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, and salts thereof. For the purpose of dispersing fillers, for example, these can be used within the range of 0.01 to 4% by mass.

<Structure of Base Material Layer>
The substrate layer may have a single-layer structure, or may have a multi-layer structure of two or more layers. Multilayering enables the base material layer to have various functions such as mechanical properties, writability, abrasion resistance, and suitability for secondary processing.

<Stretched film>
The substrate layer preferably contains a stretched film that is stretched in at least one axial direction, and more preferably contains a porous stretched film having pores therein. Since the substrate layer containing the stretched film has high moisture resistance and mechanical strength and excellent thickness uniformity, it is possible to obtain a laminated film having excellent post-processing properties.
When the substrate layer has a multilayer structure, the number of stretching axes of each layer is 1 axis/1 axis, 1 axis/2 axes, 2 axes/1 axis, 1 axis/1 axis/2 axes, 1 axis/2 axes/ It may be 1-axis, 2-axis/1-axis/1-axis, 1-axis/2-axis/2-axis, 2-axis/2-axis/1-axis, or 2-axis/2-axis/2-axis.

<Porosity>
From the viewpoint of weight reduction or improvement of whiteness, etc., the porosity of the substrate layer preferably exceeds 0%, but is preferably 50% or less, and more preferably 40% or less. If the porosity is 50% or less, adjacently formed pores are less likely to be connected to each other, and it is easy to suppress deterioration of the moisture resistance of the base material layer due to communicating pores.
The porosity can be obtained from the ratio of the area occupied by pores in a certain region of the cross section of the film observed with an electron microscope.

(Ink receiving layer)
The ink-receiving layer is provided on the substrate layer and positioned on the outermost surface of the laminated film of the present invention. Ink is transferred onto the ink-receiving layer by printing. From the viewpoint of avoiding multi-layering, the ink-receiving layer is preferably provided adjacent to the substrate layer.

The ink-receiving layer contains a component derived from an emulsion of resin particles (hereinafter sometimes simply referred to as an emulsion). The ink-receiving layer can be formed by applying a coating liquid containing an emulsion to the surface of the substrate layer and drying it.

Here, the emulsion-derived component is a residual component after volatilization of the dispersion medium of the emulsion in the coating liquid for the ink receiving layer. For example, the residual ingredients are the resin particles in the emulsion and other optional ingredients. These components may contain modified substances modified during the process of forming the ink-receiving layer. The resin particles in the residual component exist as particles in the ink-receiving layer, but may be melted and deformed by overheating during printing.

<Emulsion>
An emulsion is a liquid in which fine resin particles are emulsified or dispersed in a dispersion medium. In the present invention, the term "resin particles" refers to a fine particle resin that forms an emulsion by being dispersed in a dispersion medium. From the viewpoint of ease of handling, an O/W emulsion in which resin particles are emulsified or dispersed in an aqueous dispersion medium is preferred.

By including a component derived from an emulsion in the ink-receiving layer, it is possible to obtain good ink adhesion and stability of printed images over time in various printing methods such as offset printing, fusion heat transfer printing, and electrophotographic printing. can.

It is presumed that this is because the emulsion imparts hydrophobicity to the ink-receiving layer and suppresses excessive hydrophilicity. Due to such action, it is possible to prevent the moisture around the ink-receiving layer from coming into contact with the ink transferred onto the ink-receiving layer, resulting in an over-emulsified state, thereby improving the ink adhesion and the stability of the printed image over time. be. As a result, since the peeling of the ink is suppressed as described above, the formation of a protective layer after printing becomes unnecessary. In addition, it becomes easier to manage the conditions of the printing press.

In a printing method that heats, such as a fusion heat transfer printing method or an electrophotographic printing method, part of the resin particles contained in the ink-receiving layer is melted and compatible with the fusion heat transfer ink or toner, and the fusion heat transfer ink or toner is dissolved. Easily fixed to the ink-receiving layer. This point is also presumed to be one of the factors for improving the ink adhesion.

<<Volume average particle diameter of resin particles>>
In the present invention, the volume average particle size of the resin particles contained in the emulsion is 0.01 to 3.0 μm. The volume average particle diameter of the resin particles is measured using a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation: SALD-2200).

If the volume average particle diameter is 3.0 μm or less, it is possible to form a dense film depending on the heat drying conditions when providing the ink-receiving layer, and the smoothness of the ink-receiving layer is enhanced to improve the adhesion to the ink. do. Moreover, when the volume average particle diameter is 0.01 μm or more, it is easy to prepare an emulsion having a suitable viscosity, and the handleability is easily improved.

The volume average particle size of the resin particles is preferably 0.05 μm or more, preferably 2.0 μm or less, and more preferably 1.6 μm or less.

<<type of resin>>
Examples of resin types that can be used as the resin particles in the emulsion include urethane-based resins, olefin-based copolymers, and styrene-based resins. Among these, urethane resins or olefin copolymers are preferable, and urethane resins are more preferable, from the viewpoint of adhesion with ink.

<<<Urethane Resin>>>
As the urethane-based resin, a cationic urethane-based resin can be preferably used. A cationic urethane resin is a copolymer in which a cationic group is introduced into the polyurethane resin skeleton. This copolymer is produced by reacting a tertiary amino group-containing polyol obtained by reacting a compound having two epoxy groups in one molecule with a secondary amine, with polyisocyanate to produce a polyurethane resin. can be generated by quaternizing with a quaternizing agent. Alternatively, N,N-dialkylalkanolamines; N-alkyl-N,N-dialkanolamines such as N-methyl-N,N-diethanolamine and N-butyl-N,N-diethanolamine; and trialkanolamines It is also produced by adding one or more selected from the group consisting of to a part of the polyol, reacting it with polyisocyanate to produce a polyurethane resin, and quaternizing it with a quaternizing agent. be able to.

<<<olefin-based copolymer>>>
As the olefin-based copolymer, those containing a carboxyl group or a salt thereof as a copolymerization component, which have good emulsifiability, are preferred. Typical examples of olefinic copolymers containing a carboxyl group or a salt thereof as a copolymerization component include copolymers of olefinic monomers and unsaturated carboxylic acids or anhydrides thereof, salts thereof, and the like. These olefinic copolymers may be used singly or in combination of two or more.

Among the olefinic copolymers containing a carboxyl group or a salt thereof as a copolymerization component, it is preferable to use an olefinic copolymer obtained by copolymerizing the unsaturated carboxylic acid or its anhydride. Specific examples of such copolymers include ethylene-(meth)acrylic acid copolymers, ethylene-methyl acrylate copolymers (EMA), ethylene-methyl methacrylate copolymers (EMMA) and the like. - (meth) acrylic acid alkyl ester copolymer, ethylene - (meth) acrylic acid copolymer alkali (earth) metal salt, ethylene - (meth) acrylic acid ester - (anhydrous) maleic acid copolymer, ( meth)acrylic acid-grafted polyethylene, (anhydrous) maleic acid-grafted polyethylene, (anhydrous) maleic acid-grafted ethylene-vinyl acetate copolymer, (anhydrous) maleic acid-grafted (meth)acrylate-ethylene copolymer, (anhydrous) Maleic acid-grafted polypropylene, (anhydrous) maleic acid-grafted ethylene-propylene copolymer, (anhydrous) maleic acid-grafted ethylene-propylene-butene copolymer, (anhydrous) maleic acid-grafted ethylene-butene copolymer, or (anhydrous) A maleic acid-grafted propylene-butene copolymer and the like can be mentioned.

Among olefin copolymers, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl ester copolymer, ethylene-(meth) ) Ethylene-(meth)acrylic acid copolymer such as acrylic acid ester-(anhydrous) maleic acid copolymer, (anhydrous) maleic acid-grafted ethylene-vinyl acetate copolymer, (anhydrous) maleic acid-grafted (meth) Acrylic acid ester-ethylene copolymer, (anhydrous) maleic acid-grafted ethylene-propylene-butene copolymer, (anhydrous) maleic acid-grafted ethylene-butene copolymer, or (anhydrous) maleic acid-grafted propylene-butene copolymer is more preferred, ethylene-(meth)acrylic acid alkyl ester copolymer is more preferred, and ethylene-methyl acrylate copolymer (EMA) is particularly preferred. From the viewpoint of ink adhesion, the melting point or softening point of these resins is more preferably 130° C. or less.

<<Content of resin particles in emulsion>>
The content of the resin particles in the emulsion is preferably 5% by mass or more, more preferably 10% by mass or more. The content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. If the content is at least the above lower limit value or below the above upper limit value, it becomes easy to prepare an emulsion in which the volume average particle diameter of the resin particles is 0.01 to 3.0 μm.

<<Content of components derived from emulsion in ink-receiving layer>>
The solid content of the components derived from the emulsion in the ink-receiving layer is preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 30% by mass or more relative to the total solid content of the ink-receiving layer. More preferred. The content is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less. When it is at least the above lower limit, the printability of the laminated film tends to be enhanced, and when it is at most the above upper limit, preparation of the emulsion is facilitated.

<<Dispersant>>
A dispersant may be added to the emulsion as needed. As a result, the olefinic copolymer can be uniformly dispersed in the dispersion medium, and the smoothness of the surface of the ink-receiving layer can be easily improved.
As the dispersant, it is preferable to use at least one selected from nonionic surfactants, nonionic water-soluble polymers, cationic surfactants and cationic water-soluble polymers.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene-polyoxypropylene block polymers, polyethylene glycol fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and the like.
Examples of the nonionic water-soluble polymer include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol and modified products thereof, and hydroxyethyl cellulose.
Examples of cationic surfactants include stearylamine hydrochloride, lauryltrimethylammonium chloride, trimethyloctadecylammonium chloride, and the like.
Examples of the cationic water-soluble polymer include polymers having a quaternary ammonium salt structure or phosphonium salt structure, nitrogen-containing (meth)acrylic polymers, and nitrogen-containing (meth)acrylic polymers having a quaternary ammonium salt structure. .
Among these, cationic water-soluble polymers such as nitrogen-containing (meth)acrylic polymers or nitrogen-containing (meth)acrylic polymers having a quaternary ammonium salt structure are used from the viewpoint of adhesion to the substrate layer. is particularly preferred.

The amount of the dispersant added to the emulsion is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more based on 100 parts by mass of the resin component of the resin particles in terms of solid content. . The amount added is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less.

When the amount of the dispersant added is within the above range, the resin particles can be easily dispersed uniformly so that the volume average particle diameter is 0.01 to 3.0 μm. Further, when the amount added is at least the lower limit, a sufficient effect as a dispersant can be easily obtained. Conversely, if the amount added is equal to or less than the upper limit, the ink adhesion is likely to be improved in a high-temperature, high-humidity environment.

<<Aqueous dispersion medium>>
As the aqueous dispersion medium for the emulsion, an aqueous dispersion medium that does not dissolve or hardly dissolves the resin particles to be used can be used. Specific examples of such an aqueous dispersion medium include, in addition to water, a mixture of water and a solvent such as ethanol, isopropanol, or acetone.

<Ethyleneimine resin>
The ink-receiving layer preferably contains a component derived from an ethyleneimine-based resin. Ethyleneimine-based resins have a high affinity with various inks, and are presumed to have the effect of increasing the adhesion of the surface of the ink-receiving layer to the inks.
The content of the ethyleneimine-based resin in the coating liquid is preferably 1 part by mass or more, more preferably 2 parts by mass or more based on 100 parts by mass of the solid content of the emulsion, and is 25 parts by mass or less in terms of solid content. is preferred, and 15 parts by mass or less is more preferred. When the content is at least the above lower limit, the ink adhesion is likely to be improved, and when it is at most the above upper limit, blocking of the laminated film is likely to be reduced.

<Other ingredients>
The ink-receiving layer may contain other additives such as an antistatic agent, if necessary, as long as the printability is not impaired.

<<Antistatic agent>>
The antistatic agent can reduce problems such as adhesion of dust due to static charge on the film surface or problems caused by static electricity during printing.
The antistatic agent is not particularly limited, and cationic, anionic, amphoteric, or nonionic antistatic agents can be used. Further, it may be a low-molecular-weight antistatic agent or a high-molecular-weight (polymer) antistatic agent.

Examples of cationic antistatic agents include antistatic agents having an ammonium salt structure, a phosphonium salt structure, or the like.
Examples of anionic antistatic agents include antistatic agents having an alkali metal salt structure such as sulfonic acid, phosphoric acid, or carboxylic acid. Examples of alkali metal salts of these acids include lithium salts, sodium salts, potassium salts, and the like. The anionic antistatic agent may have an alkali metal salt structure such as acrylic acid, methacrylic acid, (anhydrous) maleic acid, etc. in the molecular structure.

Examples of amphoteric antistatic agents include antistatic agents containing structures of both a cationic antistatic agent and an anionic antistatic agent in the same molecule. The amphoteric antistatic agent may be a betaine antistatic agent.
Examples of nonionic antistatic agents include ethylene oxide polymers having an alkylene oxide structure and polymers having an ethylene oxide polymerization component in the molecular chain.
As other antistatic agents, polymer type antistatic agents having boron in the molecular structure can be exemplified.

As the antistatic agent, a nitrogen-containing polymer type antistatic agent is preferably used, and a tertiary nitrogen- or quaternary nitrogen-containing acrylic resin is more preferably used.
One type of these antistatic agents may be used alone, or two or more types may be used in combination.

The amount of the antistatic agent added to the coating liquid is preferably 2 parts by mass or more, preferably 30 parts by mass or less, and 20 parts by mass or less with respect to 100 parts by mass of the solid content of the emulsion. is more preferred. If the amount of the antistatic agent added is within the above range, sufficient ink transferability can be easily obtained during printing.

(Low melting point resin layer)
The low-melting-point resin layer imparts heat-sealing properties to the laminated film, facilitating adhesion to adherends and molding of packaging materials such as bags or containers. The low-melting-point resin layer may be provided on the entire surface of the base material layer, or may be provided on a portion of the entire surface that requires sealing.

The laminated film of the present invention is processed into a shape such as a sealable bag, a container, or a lid material for a container, in order to effectively utilize its gas barrier property and minimize contact between the contents to be stored and the outside air. It is desirable to use A typical example of such a processing method is heat sealing. By providing the low-melting-point resin layer in the laminated film of the present invention, it is possible to easily form a bag or a container by heat-sealing, thereby shortening the processing time.

The low-melting-point resin layer contains a low-melting-point resin having a melting point of 135° C. or lower. The melting point of the low melting point resin is preferably 120° C. or lower, more preferably 115° C. or lower. If the melting point is 135° C. or lower, the amount of heat required for heat-sealing is small, and the low-melting-point resin layers can be easily brought into close contact with each other in a short period of time. From the viewpoint of suppressing the softening of the low-melting-point resin layer under high-temperature conditions in the summer, blocking during storage of the laminated film, and the deterioration of the heat-sealing strength of heat-sealed products, the use of low-melting-point resin It is preferable that the melting point is 60° C. or higher.

As long as the melting point is 135° C. or lower, the usable low-melting resin is not particularly limited, but specific examples include olefins represented by ethylene, propylene, butene, pentene, hexene, methylpentene, or octene. homopolymers, copolymers of two or more of these olefins, copolymers of one or more of these olefins and one or more of comonomers copolymerizable with olefins, or metal salts thereof. . Examples of comonomers copolymerizable with olefins include styrenes such as styrene and α-methylstyrene; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl laurate, vinyl stearate, and benzoin. vinyl carboxylates such as vinyl acid or vinyl butyl benzoate; and acrylic acids such as acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, acrylonitrile, and the like.

The low-melting-point resin layer contains a low-melting-point resin having a melting point of 135° C. or lower as a main component, and may contain a thermoplastic resin whose melting point is not 135° C. or lower. A main component means a component whose content in the layer is 50% by mass or more. From the viewpoint of heat sealing, the low melting point resin layer is preferably a resin film made of a low melting point resin having a melting point of 135° C. or lower.

From the viewpoint of adhesion to the substrate layer, among the above, polyolefin resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, or metallocene-catalyzed polyolefins such as metallocene-catalyzed polypropylene are preferable. From the viewpoint of low melting point and good moldability, low-density polyethylene or metallocene-catalyzed polyolefin is more preferable.

The low-melting-point resin can be selected depending on the object to be adhered to the laminated film. For example, when a laminated film is adhered to a polyester resin such as polyethylene terephthalate (PET) via a low-melting resin layer, the density (g/cm ³ ) of the low-melting resin is 0.900 or more and less than 0.920. It is preferred to use polyethylene (LDPE) or metallocene-catalyzed polyethylene. Metallocene-catalyzed polypropylene is preferably used as the low-melting-point resin for adhering the laminated film to the polyolefin-based resin. When the low-melting-point resin layers of the laminated film are brought into close contact with each other as in the case of sealing in the form of a bag, high adhesion can be obtained regardless of the type of low-melting-point resin used.

The laminated film of the present invention may have layers other than the ink receiving layer, substrate layer, gas barrier layer and low melting point resin layer described above. For example, an adhesive layer may be provided to suppress peeling of each layer.

FIG. 1 shows an example of a laminated film provided with an adhesive layer.
In the laminated film 10A illustrated in FIG. 1, an ink receiving layer 3, a substrate layer 1, a gas barrier layer 2 and a low melting point resin layer 4 are laminated in this order. A printed layer 7 may be formed on the ink receiving layer 3 by printing.
The laminated film 10A can have adhesive layers 6 on both sides of the gas barrier layer 2 . Adhesiveness between the gas barrier layer 2 and the base layer 1 and the low melting point resin layer 4 adjacent to the gas barrier layer 2 can be enhanced by the adhesive layer 6 .

(adhesive layer)
The adhesive layer is optionally provided for the purpose of improving adhesion between the gas barrier layer and the base material layer and the low melting point resin layer adjacent to the gas barrier layer. The adhesive layer can prevent the gas barrier layer from peeling off and exposing the gas barrier layer, thereby suppressing deterioration of the gas barrier properties. As the content of the gas barrier resin in the gas barrier layer increases, the adhesion between the gas barrier layer and the adjacent layer decreases, so an adhesive layer is preferably interposed between the two.

The lamination method of the adhesive layer is not particularly limited. For example, a co-extrusion method can be used in which resin melted by a plurality of extruders and a hot-melt adhesive are laminated in one die by means of a feed block or a multi-manifold. Also, a dry lamination method can be used in which a solvent-based adhesive is applied or sprayed to form an adhesive layer, and then the other layer is adhered via the adhesive layer. Alternatively, a melt extrusion lamination method can be used in which a hot-melt adhesive is melt-extruded on the surface of one layer to form an adhesive layer, and the other layer is adhered via the adhesive layer. Furthermore, a hot-melt type adhesive film is laminated on one layer, melted by heat to form an adhesive layer, and the other layer is bonded through this adhesive layer. A lamination method can be used. Among them, it is preferable to laminate the adhesive layers using a co-extrusion method that can reduce the number of steps.

Examples of hot-melt adhesives include low-density polyethylene, ethylene/vinyl acetate copolymer, metal salts of ethylene/(meth)acrylic acid copolymer, polyolefin resins such as chlorinated polyethylene and chlorinated polypropylene, and malein. Functional group-containing polyolefin-based resins such as acid-modified polypropylene, polyamide-based resins, polybutyral-based resins, urethane-based resins, and the like are included. Among these, functional group-containing polyolefin resins such as maleic acid-modified polypropylene are preferable from the viewpoint of adhesion to the substrate layer.

[Characteristics of laminated film]
(thickness of each layer)
The thickness of the gas barrier layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. When the thickness of the gas barrier layer is at least the above lower limit, the gas barrier property of the gas barrier layer tends to be easily obtained, and the laminated film with the desired performance tends to be easily obtained. The thickness of the gas barrier layer is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the thickness of the gas barrier layer is equal to or less than the above upper limit, the rigidity of the same layer can be reduced, so the flexibility of the laminated film is likely to be increased, and it is easy to use as a packaging material. Moreover, the effect of cost reduction is also acquired.

The thickness of the substrate layer is preferably 5 µm or more, more preferably 10 µm or more, and even more preferably 20 µm or more. If the thickness of the base material layer is at least the above lower limit, the rigidity and stiffness of the base material can be easily obtained, the moisture resistance of the base material layer can be easily obtained, and the laminated film with the desired gas barrier performance can be easily obtained. Tend. The thickness of the substrate layer is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. If the thickness of the base material layer is equal to or less than the above upper limit value, the rigidity of the same layer can be reduced, so the flexibility of the laminated film is likely to be increased, and the laminated film can be easily used as a packaging material.

The thickness of the ink-receiving layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, still more preferably 0.1 μm or more, while it is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. If the thickness is within this range, it is possible to obtain a laminated film with a texture similar to that of general printing paper.

The thickness of the low melting point resin layer is preferably 0.5 μm or more, more preferably 1 μm or more. When the thickness of the low-melting-point resin layer is at least the above lower limit, it is easy to obtain adhesive strength, and it is easy to mold into a bag-like or container-like shape. In addition, the moisture permeability of the low-melting-point resin layer can be lowered to easily enhance the water barrier property. The thickness of the low melting point resin layer is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. When the thickness of the low-melting-point resin layer is equal to or less than the above upper limit, stickiness is reduced and the laminate film is easier to cut, so the laminate film tends to be more easily processed.

The thickness of the adhesive layer is preferably 0.5 μm or more, more preferably 1 μm or more. When the thickness of the adhesive layer is at least the above lower limit, the uniformity of the adhesive layer is enhanced, the lamination processability of each layer is easily improved, and deterioration of the gas barrier performance of the laminated film is easily suppressed. On the other hand, the thickness of the adhesive layer is preferably 10 μm or less, more preferably 5 μm or less. When the thickness of the adhesive layer is equal to or less than the above upper limit, the cohesive force of the adhesive layer is less likely to be impaired, and the layers are less likely to separate.

As for the solid content of the adhesive layer, the basis weight of the adhesive layer is preferably 0.5 to 30 g/m ² , more preferably 1 to 25 g/m ² . The adhesive layer is preferably provided by coating or melt extruding the adhesive so as to have the above thickness or basis weight.

(oxygen permeability)
The oxygen permeability, which means the gas barrier property of the laminated film, is preferably 15 cm ³ /(m ² · 24 h · atm) or less, more preferably 10 cm ³ /(m ² ·) in a high humidity environment with a temperature of 23 ° C. and a relative humidity of 90%. 24 h·atm) or less is more preferable.
The oxygen permeability can be 0 cm ³ /(m ² ·24 h·atm), but is usually 0.001 cm ³ /(m ² ·24 h·atm) or more in consideration of appropriate thickness and the like.
The oxygen permeability is measured according to JIS-K-7126-2.

(moisture permeability)
The moisture permeability of the laminated film is preferably 10 g/(m ² ·24 h) or less at a temperature of 38° C. and a relative humidity of 90% RH. It can be evaluated that the lower the moisture permeability, the higher the gas barrier property of the laminated film. The moisture permeability may be 0 g/(m ² ·24 h), but is usually 0.01 g/(m ² ·24 h) or more in consideration of appropriate thickness and the like.
The moisture permeability is measured according to JIS-K-7129-B.

[Method for producing laminated film]
The laminated film of the present invention can be produced by laminating an ink receiving layer, a substrate layer, a gas barrier layer and a low melting point resin layer in this order, and the production method is not particularly limited. For example, the laminated film of the present invention can be produced by forming and laminating a gas barrier layer, a substrate layer and a film of a low-melting resin, and coating the substrate layer with a coating liquid for forming an ink-receiving layer to obtain an ink-receiving layer. can be manufactured by forming

(Film molding and lamination)
As a method for forming the film, for example, cast molding, calendar molding, rolling molding, inflation molding, etc., in which a molten resin is extruded into a sheet by a single-layer or multi-layer T die, I die, etc. connected to a screw type extruder can be used. can be done. A film may be formed by casting or calendering a mixture of a thermoplastic resin and an organic solvent or oil, followed by removal of the solvent or oil.

Film lamination methods include a coextrusion method, an extrusion lamination method, a coating method, and the like, and these methods can also be combined. In the coextrusion method, resin compositions for each layer melted and kneaded in separate extruders are laminated and extruded in a feed block or multi-manifold, and film formation and lamination are performed in parallel. Extrusion lamination processes laminate a film by extruding a resin composition onto a preformed film. In the coating method, a film is formed and laminated by coating a resin solution, emulsion or dispersion on a film and drying it.

From the viewpoint of interlayer adhesion, the gas barrier layer is preferably laminated with the substrate layer and the low melting point resin layer via an adhesive layer. For example, in the case of the laminated film 10A illustrated in FIG. Each layer of film can be laminated by extrusion. Lamination is also possible by extruding the substrate layer and then successively forming an adhesive layer, a gas barrier layer, an adhesive layer and a low melting point resin layer on one surface by a coating method.

(stretching)
Each layer may be stretched individually prior to lamination or may be stretched together after lamination. Alternatively, the unstretched layer and the stretched layer may be laminated and then stretched again.

Examples of stretching methods for stretching a film include a longitudinal stretching method utilizing a peripheral speed difference between rolls, a transverse stretching method utilizing a tenter oven, a sequential biaxial stretching method combining these methods, a rolling method, and a tenter oven. A simultaneous biaxial stretching method using a combination of pantographs, a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor, and the like. A simultaneous biaxial stretching (inflation molding) method can also be used, in which a circular die connected to a screw extruder is used to extrude a molten resin into a tubular shape, and then air is blown into the tubular shape.

When the thermoplastic resin used for the film is a non-crystalline resin, the stretching temperature at which the film is stretched is preferably in the range of the glass transition temperature of the thermoplastic resin or higher. Also, when the thermoplastic resin is a crystalline resin, the stretching temperature should be above the glass transition point of the non-crystalline portion of the thermoplastic resin and below the melting point of the crystalline portion of the thermoplastic resin. is preferred, and specifically, a temperature lower than the melting point of the thermoplastic resin by 2 to 60°C is preferred.

The stretching speed is not particularly limited, but from the viewpoint of stable stretching molding, it is preferably in the range of 20 to 350 m/min.
In addition, the draw ratio can also be appropriately determined in consideration of the properties of the thermoplastic resin to be used. For example, when a resin film containing a propylene homopolymer or a copolymer thereof is stretched in one direction, the lower limit of the draw ratio is usually 1.2 times or more, preferably 2 times or more. The upper limit is usually 12 times or less, preferably 10 times or less. The draw ratio in the case of biaxial stretching is an area draw ratio, and the lower limit is usually 1.5 times or more, preferably 10 times or more, while the upper limit is usually 60 times or less, preferably 50 times. It is below.

(surface treatment)
From the viewpoint of enhancing adhesion to the ink-receiving layer, the substrate layer is preferably surface-treated to activate its surface.
Surface treatments include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, ozone treatment, and the like, and these treatments can be combined. Among them, corona discharge treatment or flame treatment is preferable, and corona treatment is more preferable.

The amount of discharge when performing corona discharge treatment is preferably 600 J/m ² (10 W·min/m ² ) or more, more preferably 1,200 J/m ² (20 W·min/m ² ) or more. On the other hand, it is preferably 12,000 J/m ² (200 W·min/m ² ) or less, more preferably 10,800 J/m ² (180 W·min/m ² ) or less. The discharge amount when flame treatment is performed is preferably 8,000 J/m ² or more, more preferably 20,000 J/m ² or more, and preferably 200,000 J/m ² or less. It is preferably 100,000 J/m ² or less.

(Formation of ink receiving layer)
The ink-receiving layer can be formed by preparing a coating liquid for forming the ink-receiving layer and coating it on the substrate layer.

<Preparation of coating solution>
The coating liquid for forming the ink-receiving layer can be prepared by adding additives to the emulsion of the resin particles described above, if necessary.

When resin particles of a cationic urethane resin are used, an emulsion can be prepared by dispersing in water a copolymer having a cationic hydrophilic group introduced into the polyurethane resin skeleton. Specifically, a method of emulsifying and dispersing the monomers constituting the target polymer in water for polymerization, obtaining the target polymer by bulk polymerization, etc., and then using a twin-screw extruder to melt-knead the raw material resin. and emulsification sequentially.

A method for preparing an emulsion when using resin particles of an olefinic copolymer is not particularly limited, but for example, the following method (1) or (2) can be used.

(1) An olefinic copolymer is added to an aromatic hydrocarbon solvent and dissolved by heating to prepare a resin solution. A dispersant is added to this resin solution, mixed and stirred, and then water is added to effect phase change. Thereafter, the aromatic hydrocarbon solvent is distilled off, and the resulting aqueous dispersion is used as an emulsion.

(2) An olefinic copolymer is melted using a twin-screw extruder. Then, an aqueous solution of a dispersant is added and kneaded to obtain an aqueous dispersion, which is used as an emulsion (see Japanese Patent Publication No. 62-29447).

When an emulsion is prepared by these methods, it is preferable to use a polymer emulsifier such as a cationic water-soluble polymer as a dispersant, and it is more preferable to use the dispersion method using a twin-screw extruder in (2) above. Thereby, the volume average particle diameter of the resin particles of the olefinic copolymer in the emulsion can be easily adjusted to 0.01 to 3.00 μm. In the method (2) above, the volume-average particle size of the resin particles of the olefin copolymer in the emulsion is determined, for example, by the operating conditions of the twin-screw extruder, for example, the amount of water relative to the olefin copolymer, the cylinder temperature It can be adjusted by controlling the and its profile, the residence time of the resin in the extruder, the barrel rotation speed of the extruder, and the like.

The solid content concentration of the coating liquid is preferably 0.1% by mass or more, more preferably 1.5% by mass or more, and 20% by mass or less with respect to the total amount of the coating liquid. is preferred, and 15% by mass or less is more preferred.

The coating liquid can be applied using a coating device such as a roll coater, a blade coater, a bar coater, an air knife coater, a size press coater, a gravure coater, a die coater, a lip coater, and a spray coater. .

The coating amount of the coating liquid is preferably 0.05 g/m ² or more, more preferably 0.10 g/m ² or more, and more preferably 0.15 g/m ² or more as a solid content after drying. It is particularly preferably 1.40 g/m ² or less, more preferably 0.50 g/m ² or less, more preferably 0.30 g/m ² or less, and 0 0.24 g/m ² or less is particularly preferred.
When the coating amount is at least the above lower limit value, the adhesiveness to the UV-curable ink for offset printing, which is generally considered to be poor, is likely to be improved. On the other hand, since the emulsion does not have high adhesiveness, it is possible to suppress deterioration in adhesiveness of the ink for offset printing due to an excessive coating amount.

Formation of the ink-receiving layer is preferably carried out continuously by a roll-to-roll method. Thereby, the productivity of the laminated film can be improved. In addition, since the thickness of the ink-receiving layer can be adjusted relatively easily with the roll-to-roll method, the thickness of the ink-receiving layer can be reduced while maintaining printability. Films can be easily manufactured.
The formation of the ink-receiving layer may be performed on the same line as the line for forming each layer other than the ink-receiving layer, or may be performed on a separate line.

(printing)
A printed layer can be formed by printing on the surface of the ink-receiving layer of the laminated film of the present invention.
Usable printing methods include offset printing, gravure printing, flexographic printing, letterpress printing, screen printing, inkjet recording, thermal recording, thermal transfer recording, electrophotographic recording, and other known methods. It is possible. Among these, offset printing, gravure printing, or flexographic printing is preferable because it is easy to obtain printed matter having excellent weather resistance and water resistance, and gravure printing is preferable for packaging applications. Furthermore, as the printing ink, it is possible to use an oil-based ink, a water-based ink, an ultraviolet curable ink, or the like.

(Processing of laminated film)
The laminated film of the present invention can effectively utilize its gas barrier properties by processing it into a bag shape or a container shape and using it as a packaging material for filling and sealing contents such as food or cosmetics.
For example, by heat-sealing the low-melting-point resin layers of the laminated film to each other, the gas barrier is processed into a bag shape having an opening, and after filling the contents, the low-melting-point resin layers at the opening are further heat-sealed to form a gas barrier. A flexible packaging bag is obtained.

Also, an in-mold label can be formed by printing on the laminated film. A gas barrier packaging container can be formed by performing in-mold molding such as vacuum/pressure molding (differential pressure molding) or injection molding using this in-mold label. The in-mold label is integrated with the molded body on the surface of the molded body. The contents can be sealed by closing the opening of the container after filling the contents. The laminated film of the present invention can also be used as a cover material for closing the opening. By heat-sealing the laminated film of the present invention so as to cover the opening of the container, it can be easily adhered to the container.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Descriptions of "parts", "%", etc. in the examples are based on mass unless otherwise specified.

[material]
Raw materials used in Examples and Comparative Examples are as follows.
(polyolefin resin)
<A1> Propylene homopolymer (trade name: Novatec PP FY-4, manufactured by Japan Polypropylene Corporation, MFR: 5.0 g/10 min (230°C, 2.16 kg load), melting point: 164°C (DSC peak temperature), density : 0.9g/ ^cm3 )
(filler)
<A2> Heavy calcium carbonate (trade name: Softon 1800 (manufactured by Bihoku Fun Chemical Industry Co., Ltd.), average particle size: 1.2 μm)
(Gas barrier resin)
<B> Ethylene-vinyl alcohol copolymer (trade name: EVAL E105B (manufactured by Kuraray Co., Ltd.), ethylene content: 44 mol%, melting point: 165°C)
(glue)
<C> Maleic acid-modified polypropylene (trade name: Admer QF500 (manufactured by Mitsui Chemicals, Inc.))
(Low melting point resin)
<D> Low-density polyethylene (trade name: Novatec LDLC540 (manufactured by Japan Polyethylene), melting point: 112°C)

Table 1 below provides a list of the above materials.

Materials for the ink-receiving layer were prepared as follows.
(Dispersant (H))
40 kg of isopropanol (manufactured by Tokuyama Co., Ltd.: trade name Tokuso IPA) was charged into a reactor having an internal volume of 150 L equipped with a cooler, a nitrogen inlet tube, a stirrer, a monomer dropping funnel, and a jacket for heating. Next, while stirring, 12.6 kg of N,N-dimethylaminoethyl methacrylate (manufactured by Sanyo Chemical Industries, Ltd.; trade name: Methacrylate DMA) and 12.6 kg of butyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd.; trade name: Acryester B) were added. 6 kg, and 2.8 kg of a higher alcohol methacrylate (Mitsubishi Rayon Co., Ltd.; product name: Acryester SL, a mixture of lauryl methacrylate and tridecyl methacrylate). After nitrogen substitution, the internal temperature was raised to 80° C., and 0.3 kg of azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.: trade name V-60 (AIBN)) was added as a polymerization initiator. to initiate polymerization.

After polymerization was carried out for 4 hours while maintaining the reaction temperature at 80° C., the obtained copolymer was neutralized with 4.3 kg of glacial acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.). Then, while isopropanol is distilled off, 48.3 kg of ion-exchanged water is added to replace the inside of the system, and an aqueous solution (solid content concentration 35% by weight) was obtained as a dispersant (H). The weight average molecular weight of the obtained polymer emulsifier was 40,000.

(Urethane resin emulsion (E1))
A cationic polyurethane aqueous dispersion (trade name: Hydran CP-7050, manufactured by DIC Corporation) was used as emulsion (E1). The solid content of this emulsion (E1) was 25% by mass, and the volume average particle size of the resin particles in the emulsion (E1) was 0.07 μm.

(Olefin copolymer emulsion (E2))
Using a twin-screw extruder (TEX30HSS, manufactured by Japan Steel Works, Ltd.), melt-kneading and emulsification of the raw material resin were performed according to the following procedure to produce an emulsion containing resin particles having an average particle size of 1.5 μm.
Specifically, pellet-shaped ethylene/methacrylic acid/acrylic acid ester copolymer resin (manufactured by Mitsui DuPont Polychemicals, Nuclell N035C, 2.0 kg) was supplied from a hopper to an extruder as an olefin copolymer. , a screw rotation speed of 270 rpm, and a cylinder temperature of 160°C to 250°C. Subsequently, the dispersant (H) was supplied from the injection port in the middle of the cylinder so that the solid content of the emulsion was 45% by mass. Then, emulsification/dispersion treatment was performed to obtain an emulsion (E2) of white resin particles composed of an olefin copolymer from the extruder outlet.
The solid content of this emulsion (E2) was 45% by mass, and the volume average particle size of the resin particles in the emulsion (E2) was 1.5 μm.

(Olefin copolymer emulsion (E3))
An olefinic co-polymer was prepared in the same manner as emulsion (E2) except that the screw speed of the extruder was set to 300 rpm, the amount of resin supplied was tripled, and the amount of dispersant (H) used was reduced to 75%. An emulsion (E3) of polymer resin particles was prepared.
The resulting emulsion (E3) had a solid content of 45% by mass and a volume average particle size of 5.0 μm.

<Volume average particle size>
The volume average particle diameter was measured using a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation: SALD-2200).

(Ethyleneimine resin solution (F))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet is charged with 100 parts by mass of a 25% by mass aqueous solution of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., trade name: Epomin P-1000). - 10 parts by mass of chlorobutane (manufactured by Wako Pure Chemical Industries, Ltd., reagent) and 10 parts by mass of propylene glycol monomethyl ether (manufactured by Wako Pure Chemical Industries, Ltd., reagent) were introduced. Then, the mixture was stirred under a nitrogen stream, and a modification reaction was carried out at a temperature of 80° C. for 20 hours. Water was added to this solution to adjust the solid content concentration to 20% by mass to obtain an ethyleneimine resin solution (F).

(Antistatic agent (G))
N,N-dimethylaminoethyl methacrylate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) 35 parts by mass, ethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd., reagent) 20 parts by mass, cyclohexyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) , reagent) 20 parts by mass, stearyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd., reagent) 25 parts by mass, ethyl alcohol 150 parts by mass, and 2,2′-azobis(isobutyronitrile) (Wako Pure Chemical Industries ( 1 part by mass of Reagent) was introduced into a four-necked flask equipped with a stirrer, a reflux condenser (condenser), a thermometer, and a dropping funnel. The inside of the system was replaced with nitrogen, and a polymerization reaction was carried out at 80° C. for 6 hours under a nitrogen stream. Then, 85 parts by mass of a 50% by mass aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride (reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added. After further reacting at 80° C. for 15 hours, ethyl alcohol was distilled off while water was added dropwise to obtain a solution of an antistatic agent comprising a quaternary ammonium salt type copolymer with a solid content concentration of 20% by mass.

Table 2 below shows a list of materials for each coating liquid.

(Coating liquid (1))
An aqueous solution containing 13% by mass of the urethane resin emulsion (E1), 0.5% by mass of the ethyleneimine resin solution (F), and 0.5% by mass of the antistatic agent (G) was prepared and coated. It was used as liquid (1). The concentration of each component described above represents the solid content concentration of each component with respect to the entire coating liquid.

(Coating liquids (2) and (3))
Coating Liquid (1) was prepared in the same manner as Coating Liquid (1), except that olefin copolymer emulsions (E2) and (E3) were used instead of urethane resin emulsion (E1). Coating solutions (2) and (3) were prepared respectively.

(Coating liquid (4))
The ethyleneimine resin solution (F) was used as the coating liquid (4).

[Production of laminated film]
(Example 1)
A resin composition consisting of 80 parts by mass of polyolefin resin (A1) (Novatec PP FY-4) and 20 parts by mass of ground calcium carbonate (A2) (Softon 1800) was extruded at 230°C in an extruder. Melt-kneaded. Then, it was supplied to an extrusion die set at 250° C. and extruded into a sheet, which was cooled to 60° C. by a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 135° C. and stretched 5 times in the longitudinal direction by utilizing the difference in peripheral speed of the roll group to form a substrate layer.

Next, 100 parts by mass of the gas barrier resin (B), the adhesive (C), and the low-melting resin (D) are respectively melt-kneaded in three extruders set at 250°C, and each resin is added to the adhesive ( C), the gas barrier resin (B), the adhesive (C), and the low melting point resin (D) were stacked in this order and co-extruded into a four-layer sheet, and extruded into a sheet on the substrate layer. As a result, an adhesive layer made of the adhesive (C), a gas barrier layer made of the gas barrier resin (B), an adhesive layer made of the adhesive (C), and a low melting point resin layer made of the low melting point resin (D) are formed. and laminated in this order on the substrate layer so that the adhesive layer side was in contact with the substrate layer. As a result, a five-layer sheet was obtained in which the substrate layer/adhesive layer/gas barrier layer/adhesive layer/low melting point resin layer were laminated in this order.

After cooling the obtained five-layer sheet to 60° C. using a cooling device, the laminated sheet was heated to about 150° C. using a tenter oven and stretched 8.5 times in the transverse direction. After heat treatment by heating to 160° C., cooling to 60° C., slitting of the ear portions was performed.

Next, using continuous coating equipment, the surface of the base material layer of the five-layer sheet was subjected to corona discharge treatment. A corona discharge treatment apparatus (HF400F manufactured by Kasuga Denki Co., Ltd.) was used for the corona discharge treatment. The gap between the aluminum discharge electrode having a length of 0.8 m and the insulating roll was set to 5 mm, the line processing speed was set to 15 m/min, and the applied energy density was set to 4200 J/m ² . Next, the coating liquid (1) was applied onto the substrate layer and dried in a hot air drying facility at 60° C. to form an ink receiving layer. The solid content of the ink-receiving layer after drying was 0.23 g/m ² .

Next, it was wound up by a roll winder, and a six-layer laminated film (thickness of all layers: 72 μm, thickness of all layers: 72 μm, Each layer thickness: -/55 μm/2 μm/10 μm/2 μm/3 μm) and the number of stretching axes of each layer: -/2 axes/1 axis/1 axis/1 axis/1 axis) were obtained.

(Example 2 and Comparative Examples 1 to 3)
Laminated films of Example 2 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1, except that the coating solution (1) forming the ink-receiving layer was changed to the coating solutions (2) to (4). got Also, a laminate film of Comparative Example 3 was obtained without providing the ink-receiving layer in Example 1. All the layers of the laminated films of Example 2 and Comparative Examples 1 to 3, the thickness of each layer, and the number of stretching axes are the same as in Example 1.

(Comparative Example 4)
100 parts by mass of gas barrier resin (B), adhesive (C) and low melting point resin (D) were melt-kneaded in three extruders set at 250°C. Next, the gas barrier resin (B), the adhesive (C), and the low melting point resin (D) were stacked in this order, and three layers were co-extruded into a sheet.

After cooling the resulting three-layer sheet to 60° C. with a cooling device, the laminated sheet was heated to about 150° C. using a tenter oven and stretched 8.5 times in the transverse direction. After heat treatment by heating to 160° C., cooling to 60° C., slitting of the ear portions was performed. Next, it was wound up by a roll winder, and a three-layer laminated film (thickness of all layers: 15 μm, thickness of each layer: 10 μm/2 μm/3 μm) in which gas barrier layer/adhesive layer/low-melting resin layer were laminated in this order, and each layer number of stretching axes: 1 axis/1 axis/1 axis).

[evaluation]
The gas barrier properties and ink adhesion properties of the laminated films of Examples and Comparative Examples were evaluated as follows.

(Gas barrier properties)
The oxygen permeability of the laminated film was measured and evaluated as the gas barrier property of the laminated film.

<Evaluation in normal environment>
The laminated film obtained in each example and comparative example was placed in an environment of 23° C. temperature and 50% RH for 48 hours to condition the humidity. Using a humidity-conditioned laminate film sample, using MOCONOX-TRAN2/2 2L manufactured by Modern Control Co., Ltd., the oxygen permeability was measured according to the method described in JIS-K7126 (isobaric method). (Unit: cm ³ /m ² · 24 h · atm).

<Evaluation in high humidity environment>
The laminated films obtained in each of Examples and Comparative Examples were placed in an environment of 23° C. and 90% RH for 48 hours to condition the humidity. Using the humidity-conditioned sample, the oxygen permeability was measured in the same manner as the evaluation under low humidity.

(Ink adhesion)
Solid printing was performed on the surface of the ink-receiving layer of each of the laminated films of Examples and Comparative Examples with an ink coverage of 2.0 g/m ² . For printing, a flexo printer (manufactured by MT Tech, machine name: FC11B) and UV flexographic ink (manufactured by T&KTOKA, product name: flexo 500) were used. Next, UV irradiation was performed using a UV irradiation machine so that the irradiation intensity was 100 mJ/cm ² to obtain a sample for ink adhesion evaluation.

<Evaluation in normal environment>
The obtained sample was conditioned at 23° C. and 50% RH for 1 day. A cellophane tape of 18 mm (manufactured by Nichiban Co., Ltd., product name: CT-18) was pasted on the printed image of the sample after humidity conditioning, and adhered with a finger. The tape was then peeled off with a peel angle of 180 degrees and a peel speed of 50 m/min. The peeling of the ink after peeling was observed, and the ink adhesion before promoting humidification was evaluated according to the following criteria.
○: No ink peeling ×: Ink peels off, exposing the film surface

<Evaluation after promotion of humidification>
The above samples were placed in an environment of 60° C. and 90% RH for 7 days, and then conditioned at 23° C. and 50% RH for 1 day. Using this humidity-conditioned sample, the adhesion of the ink was evaluated in the same manner as in the evaluation under the normal environment.

Table 3 shows the evaluation results.

Examples 1 and 2 maintain excellent gas barrier properties even under high humidity as in normal environments. Further, according to Examples 1 and 2 in which the ink-receiving layer was formed using an emulsion of resin particles, a laminated film having good ink adhesion even under high humidity and excellent printability was obtained. Comparing Examples 1 and 2 with Comparative Examples 2 and 3, it can be seen that the gas barrier property is also improved by the ink receiving layer formed using the emulsion of resin particles.

On the other hand, in Comparative Example 4, in which the gas barrier layer was positioned on the outermost surface, the gas barrier layer was not covered, and the gas barrier properties were greatly reduced in a high-humidity environment. Further, in Comparative Example 1, the resin particles in the emulsion had a large particle size, and the ink adhesion was low. Comparative Example 2, in which the ink-receiving layer was formed from an ethyleneimine-based resin solution instead of an emulsion, exhibited good ink adhesion under normal conditions, but failed to maintain such ink adhesion under high humidity conditions. Further, unlike the ink-receiving layer formed using an emulsion of resin particles, Comparative Example 2 did not provide an effect of improving gas barrier properties. On the other hand, Comparative Example 3, which does not have a print-receiving layer, not only has low ink adhesion, but also has a low gas barrier property.

10A... laminated film, 1... base layer, 2... gas barrier layer, 3... ink receiving layer, 4... low melting point resin layer, 6... adhesive layer

Claims (8)

A laminated film having gas barrier properties,
having an ink receiving layer, a substrate layer, a gas barrier layer and a low melting point resin layer in this order,
The base material layer contains a polyolefin resin,
The gas barrier layer contains a gas barrier resin,
The low melting point resin layer contains a low melting point resin having a melting point of 135° C. or less,
The laminated film, wherein the ink-receiving layer contains an emulsion-derived component of resin particles, and the resin particles have a volume average particle size of 0.01 to 3.0 μm. The laminated film according to claim 1, wherein the laminated film has an oxygen permeability of 15 cm ³ /(m ² ·24 h·atm) or less at a temperature of 23°C and a relative humidity of 90% RH. The laminated film according to claim 1 or 2, wherein the gas barrier resin is an ethylene-vinyl alcohol copolymer or a polyvinyl alcohol resin. The laminated film according to any one of claims 1 to 3, wherein the resin particles are a urethane resin or an olefin copolymer. The laminated film according to any one of claims 1 to 4, wherein the low-melting resin is low-density polyethylene or metallocene-catalyzed polyolefin. The laminated film according to any one of claims 1 to 5, further comprising adhesive layers on both sides of the gas barrier layer. The laminated film according to any one of claims 1 to 6, wherein the base material layer is a resin film containing at least one of a polypropylene resin and a polyethylene resin as the polyolefin resin, and a filler. The laminated film according to claim 7, wherein the substrate layer is a porous stretched film stretched in at least one axial direction.

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