Packaging material, packaging bag, and package

Abstract

A packaging material 10 includes a first base material 1, an aqueous ink layer 2, an adhesive layer 3, and a second base material 4 in said order. A phase image obtained by observing a cross section in a thickness direction of the adhesive layer 3 in a tapping mode of a scanning probe microscope has a microphase separation structure having a sea part and a plurality of island parts scattered in the sea part.

Description

Packaging materials, packaging bags and packaging bodies

[0001] The present disclosure relates to a packaging material, a packaging bag, and a packaging body.

[0002] Conventionally, as packaging materials used for packaging bags (e.g., flexible packaging bags) that undergo heat treatment such as boiling or retort treatment or heat and pressure treatment, laminates having a laminated structure made of materials that provide the preservation properties of the contents, heat resistance, pressure resistance, durability (strength) against external stress, printability, etc., while taking cost-effectiveness into consideration, have been used.

[0003] In the field of packaging materials, efforts are being made to eliminate VOCs (volatile organic compounds) in order to address environmental concerns. Specifically, for forming printed layers of letters, pictures, patterns, etc., oil-based inks containing solvents (toluene, methyl ethyl ketone, etc.), which are volatile organic compounds (VOCs), are being replaced with water-based inks. The use of water-based inks has the advantage of improving the production environment and eliminating the problem of residual organic solvents in packaging materials. For example, Patent Document 1 discloses a heat-sterilizable packaging laminate using water-based ink.

[0004] Japanese Patent Application Laid-Open No. 2001-79986

[0005] When a packaging material includes a printed layer formed with an aqueous ink (aqueous ink layer), delamination and lifting are likely to occur between the layers constituting the packaging material after retort treatment.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a packaging material that is less likely to cause peeling and lifting between layers after retort treatment, as well as a packaging bag and a package using the packaging material.

[0007] Some aspects of the present disclosure provide the following [1] to

[12] .

[0008] [1] A packaging material comprising a first substrate, an aqueous ink layer, an adhesive layer, and a second substrate, in this order, wherein a phase image obtained by observing a cross section of the adhesive layer in the thickness direction using a scanning probe microscope in tapping mode shows a microphase-separated structure having a sea region and a plurality of island regions scattered within the sea region.

[0009] [2] The packaging material according to [1], wherein the adhesive layer is formed of a urethane adhesive containing polyisocyanate and polyol.

[0010] [3] The packaging material according to [1] or [2], wherein the microphase-separated structure has islands having a maximum Feret diameter of 0.1 to 1.0 μm.

[0011] [4] The number of the island portions is 0.1 to 100 / μm ２ The packaging material according to any one of [1] to [3],

[0012] [5] The packaging material according to any one of [1] to [4], wherein the ratio (n1 / n2) of the number n1 of the island portions present on the aqueous ink layer side of the center in the thickness direction of the adhesive layer to the number n2 of the island portions present on the second substrate side of the center in the thickness direction of the adhesive layer is less than 1.

[0013] [6] The packaging material according to any one of [1] to [5], wherein the aqueous ink layer is formed from an aqueous flexographic ink.

[0014] [7] The packaging material according to any one of [1] to [6], wherein the adhesive layer is formed of a dry lamination adhesive.

[0015] [8] The packaging material according to any one of [1] to [7], wherein the first substrate comprises at least one selected from the group consisting of a stretched polyethylene terephthalate film, a stretched polypropylene film, a stretched nylon film, and a stretched polyethylene film.

[0016] [9] The packaging material according to any one of [1] to [8], wherein the first substrate includes a water vapor barrier layer.

[0017]

[10] The packaging material according to any one of [1] to [9], wherein the adhesive strength between the first substrate and the second substrate, as measured by the following procedures (1) to (5), is 1.0 N / 15 mm or more. (1): Two sheets measuring 140 mm wide and 100 mm long are cut out from the packaging material, and the second substrate-side surfaces of the two sheets are placed face to face so that the four edges overlap. Three of the four edges are heat-sealed to produce a packaging bag with one opening. (2): 50 g of water is added to the packaging bag, and the opening edge of the packaging bag is heat-sealed to produce a test pouch. (3): The test pouch produced in (2) is subjected to a retort treatment at 121°C for 30 minutes. (4): After the retort treatment in (3), a test piece measuring 15 mm wide and 200 mm long is cut out from one of the two sheets constituting the test pouch. (5): A T-peel test is performed on the test piece at 20°C and 30% RH in accordance with JIS K 6854, with a peel rate of 300 mm / min and a width of 15 mm, to measure the adhesive strength between the first substrate and the second substrate.

[0018]

[11] A packaging bag made from the packaging material according to any one of [1] to

[10] .

[0019]

[12] A package comprising the packaging bag according to

[11] and contents contained in the packaging bag.

[0020] According to the present disclosure, it is possible to provide a packaging material that is less likely to cause peeling and lifting between layers after retort treatment, as well as a packaging bag and a package that use the packaging material.

[0021] Fig. 1 is a cross-sectional view schematically showing one embodiment of a packaging material according to the present disclosure. Fig. 2 is a partially enlarged cross-sectional view showing an enlarged area indicated by A in Fig. 1. Fig. 3 is a cross-sectional view schematically showing another embodiment of a packaging material according to the present disclosure. Fig. 4 is a plan view schematically showing one embodiment of a packaging bag using a packaging material according to the present disclosure. Fig. 5 is an SPM phase image of a cross section of an adhesive layer obtained in an example and a comparative example.

[0022] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​written before and after "to" are the same. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limit values ​​individually described can be combined arbitrarily. Furthermore, "A or B" may include either A or B, or may include both.

[0023] Hereinafter, embodiments of the present disclosure will be described in detail, with reference to the drawings where necessary. Note that the present disclosure is not limited to the following embodiments. In the drawings, the same or equivalent parts are designated by the same reference numerals, and duplicate explanations will be omitted. The dimensional ratios of the drawings are not limited to those shown in the drawings.

[0024] <Packaging Material> One embodiment of the present disclosure is a packaging material including a first substrate, an aqueous ink layer, an adhesive layer, and a second substrate, in this order. The packaging material is, for example, a sheet-like laminate (packaging material 10) shown in FIG. 1. The packaging material 10 in FIG. 1 is composed of a first substrate 1, an aqueous ink layer 2, an adhesive layer 3, and a second substrate 4, and the adhesive layer 3 bonds the aqueous ink layer 2 and the second substrate 4. In FIG. 1, 2a indicates a pigment in the aqueous ink layer. The thickness (total thickness) of the packaging material is not particularly limited, but is, for example, 20 to 300 μm.

[0025] The packaging material is characterized in that, in a phase image (hereinafter also referred to as "SPM phase image of adhesive layer cross section") obtained by observing a cross section of the adhesive layer in the thickness direction using a tapping mode (AC mode) of a scanning probe microscope (hereinafter also referred to as "SPM phase image of adhesive layer cross section"), a microphase-separated structure having a sea region (3a in Figure 2) and a plurality of island regions (3b in Figure 2) scattered within the sea region is observed (i.e., the phase image has a microphase-separated structure having a sea region and a plurality of island regions scattered within the sea region). The SPM phase image of the adhesive layer cross section can be obtained by the following steps (1) to (5).

[0026] (1) After corona treatment of the front and back surfaces of the packaging material, the packaging material is cut into 2 x 3 mm strips. (2) The resulting strip-shaped packaging material is embedded in a photocurable resin, and the resin is cured by irradiating it with light to obtain a block piece consisting of the packaging material and the cured resin that embeds the packaging material. (3) The resulting block piece is fixed in an insert for an SPM sample holder, and at room temperature (25°C), the block piece is trimmed and the cross section of the packaging material (cross section perpendicular to the layer interface) is cut. (4) While the block piece after the cross section is still fixed in the insert for the SPM sample holder, phase image measurement is performed on the block piece using an SPM (scanning probe microscope) under the following conditions. [Conditions] Under an environment of 25°C, shape measurement is performed using the SPM's AC mode (tapping mode) with a field of view of 6 μm × 6 μm and a scanning speed of 2 Hz, so that the cross-sectional layer interface is parallel to the scanning direction of the fast scan, and a phase image, height image, and amplitude image are acquired. The typical characteristic values ​​of the SPM cantilever (measurement probe) are a tip curvature radius of 7 nm and a spring constant of 26 N / m. The resolution during measurement is 256 × 256, and the setpoint, drive amplitude, and integral gain are adjusted so that the island portion is clearly observed in the phase image. Specifically, in the phase image, the phase during measurement is set to be smaller than the phase before contact (engagement) between the sample and the cantilever, in the height image, the trace and retrace signals are matched, and in the amplitude image, the trace and retrace signals are inverted. (5) The above measurements are carried out at three locations, and the resulting phase image is analyzed using the following procedure. [Procedure] First, a binary image of the brightness of the adhesive layer is obtained from an image in which the magnitude of the phase is represented by brightness on a grayscale. Next, in the binary image, the midpoints in the thickness direction of the adhesive layer are found at both ends of the image parallel to the thickness direction of the adhesive layer, and a straight line is drawn between the midpoints of both ends to divide the image along the line. From the adhesive layer divided by the straight line, island-like regions with low brightness are extracted on the water-based ink layer side of the adhesive layer and on the substrate side opposite the water-based ink layer. The area of ​​the extracted region is limited to a minimum of 5 pixels (0.0027 μm) to distinguish it from noise. ２Next, the minimum Feret diameter of each of the extracted island-like regions with low brightness is calculated, and among these, regions with a minimum Feret diameter of 0.1 μm or more are determined to be "islands."

[0027] The island and sea regions are clearly distinguished by the magnitude of the phase in the SPM phase image. The measurements specified herein are performed under conditions in which the phase during measurement is smaller than the phase before contact (engagement) between the sample and the cantilever. These conditions are suitable for measuring polymeric materials. In SPM phase images acquired under these conditions, regions with higher elastic modulus generally display a smaller phase, and regions with lower elastic modulus generally display a larger phase. Therefore, the island and sea regions can also be described as regions with relatively higher (or lower) elastic modulus and regions with relatively lower (or higher) elastic modulus. In SPM phase images in which the magnitude of the phase is displayed as grayscale brightness, regions with higher elastic modulus generally appear darker and regions with lower elastic modulus generally appear brighter, allowing the distribution of elastic modulus to be determined by brightness. Note that, depending on the acquisition conditions, SPM phase images of the adhesive layer cross section may contain shapes that cannot be determined to be noise or not. Therefore, in this specification, in a sea-island structure that can be clearly distinguished from noise under the specified SPM phase image measurement conditions and that can be determined to have a significant distribution of elastic modulus, among the regions observed as islands, those with a minimum Feret diameter of 0.1 μm or more are defined as "islands." The "Feret diameter" is defined as the distance between two parallel lines arbitrarily drawn to sandwich the image to be measured (islands). In this specification, the minimum value of the Feret diameters is referred to as the minimum Feret diameter, and the maximum value of the Feret diameters is referred to as the maximum Feret diameter. The minimum Feret diameter can be obtained by drawing two parallel lines so that the above distance is minimized. Similarly, the maximum Feret diameter can be obtained by drawing two parallel lines so that the above distance is maximized.

[0028] Packaging materials having the above characteristics are less likely to experience peeling or lifting between layers after retort processing. Therefore, the packaging material is suitable for retort packaging, and this packaging material makes it possible to obtain retort packaging bags that are less likely to experience peeling or lifting between layers and are less likely to experience problems such as deterioration of the aqueous ink layer surface, reduced barrier properties, and increased risk of bag breakage due to these factors. Here, "for retort packaging" refers to packaging bags that are to be subjected to retort processing or are used to produce such packaging bags. Furthermore, retort processing is a moist heat sterilization treatment defined by the Food Sanitation Act, and refers to moist heat sterilization treatment performed at a temperature of 100°C or higher. Retort processing may also be performed under pressure (e.g., 0.2 Pa or higher).

[0029] Packaging materials having the above characteristics tend to be less susceptible to interlayer peeling and lifting after retort treatment, and also tend to exhibit good laminate strength before and after retort treatment. The laminate strength of the packaging material before retort treatment is, for example, the adhesive strength between the first substrate and the second substrate, measured by the following procedures (1a) to (2a). The laminate strength of the packaging material after retort treatment is, for example, the adhesive strength between the first substrate and the second substrate, measured by the following procedures (1b) to (5b).

[0030] (1a): A test piece 15 mm wide and 200 mm long is cut out from the packaging material. (2a): A T-peel test is performed on the test piece at 20°C and 30% RH in accordance with JIS K 6854 at a peel rate of 300 mm / min over a width of 15 mm to measure the adhesive strength between the first substrate and the second substrate.

[0031] (1b): Two sheets measuring 140 mm wide and 100 mm long are cut out from the packaging material, and the second substrate sides of the two sheets are placed face to face so that their four sides overlap, and three of the four sides are heat-sealed to produce a packaging bag with one opening. (2b): 50 g of water is added to the packaging bag, and the opening side of the packaging bag is heat-sealed to produce a test pouch. (3b): The test pouch produced in (2b) is subjected to a retort treatment at 121°C for 30 minutes. (4b): After the retort treatment in (3b), a test piece measuring 15 mm wide and 200 mm long is cut out from one of the two sheets constituting the test pouch. (5b): A T-peel test is performed on the test piece at a peel rate of 300 mm / min and a width of 15 mm in accordance with JIS K 6854 under conditions of 20°C and 30% RH to measure the adhesive strength between the first substrate and the second substrate. Note that if the layer constituting the surface of the packaging material facing the second substrate (i.e., the surface opposite the first substrate from the aqueous ink layer) does not have heat-sealability, the measurement is performed after placing a sealant layer on the surface of the packaging material facing the second substrate. Furthermore, the heat sealing of (b1) and (b2) is performed using a 15 mm wide seal bar at 150°C and 3 kg / cm on each side. ２ This may be done by applying heat and pressure at 500 kJ / min for 0.5 seconds.

[0032] The adhesive strength measured by the above procedure (lamination strength before and after retort treatment) is, for example, 1.0 N / 15 mm or more, and can also be 1.5 N / 15 mm or more, 2.5 N / 15 mm or more, or 3.5 N / 15 mm or more. The upper limit of the adhesive strength measured by the above procedure is, for example, 10 N / 15 mm.

[0033] The first substrate, the aqueous ink layer, the adhesive layer, and the second substrate that constitute the packaging material, as well as the microphase separation structure observed in the SPM phase image of the cross section of the adhesive layer, will be described in detail below.

[0034] (First substrate) The first substrate is a support for the aqueous ink layer, and can also be referred to as a printing substrate on which the aqueous ink is printed. The first substrate includes, for example, a resin film. Examples of resins constituting the resin film include polyester-based resins, polyamide-based resins, polyaramid-based resins, polypropylene-based resins, polyethylene-based resins, polyvinyl chloride-based resins, polystyrene-based resins, polycarbonate-based resins, polyacetal-based resins, and fluorine-based resins. The resin constituting the resin film may be one type or two or more types.

[0035] As the resin film, from the viewpoint that the interlayer lamination strength (adhesion strength) before and after retort treatment is likely to be higher, it is preferable to use a resin film containing at least one resin selected from the group consisting of polyester-based resins, polyamide-based resins, polyethylene-based resins, and polypropylene-based resins, and it is more preferable to use a resin film containing at least one resin selected from the group consisting of polyethylene terephthalate, polypropylene, and polyamide (nylon) polyethylene-based resins.

[0036] The resin film may be an unstretched resin film or a uniaxially or biaxially stretched resin film (stretched film). From the viewpoints of printability, dimensional stability, and puncture resistance, the resin film is preferably a biaxially stretched resin film (biaxially stretched resin film). From the viewpoint of increasing the interlayer lamination strength (adhesion strength) before and after retort treatment, it is preferable to use at least one selected from the group consisting of stretched polyethylene terephthalate (PET) film, stretched polypropylene (OPP) film, stretched nylon (ONY) film, and stretched polyethylene film, and it is more preferable to use at least one selected from the group consisting of biaxially stretched polyethylene terephthalate film, biaxially stretched polypropylene film, biaxially stretched nylon film, uniaxially stretched polyethylene film, and biaxially stretched polyethylene film.

[0037] The first substrate may include two or more types of resin films. That is, the first substrate may be a substrate (laminate) with a multilayer structure. When the first substrate has a multilayer structure, it is preferable that the resin film constitutes the outermost layer of the first substrate and is in contact with the aqueous ink layer, and it is more preferable that the resin film of the above-mentioned preferred embodiment constitutes the outermost layer of the first substrate and is in contact with the aqueous ink layer.

[0038] The thickness of the resin film may be a thickness that satisfies the strength, rigidity, etc. required for heat and pressure treatment, and may be, for example, 5 μm to 100 μm or 8 μm to 50 μm. If the thickness of the resin film is 100 μm or less, the flexible packaging bag is easily torn by hand when opened, and production costs can be reduced. If the thickness of the resin film is 8 μm or more, sufficient strength, rigidity, etc. can be easily obtained.

[0039] The first substrate may consist of only a resin film, or may include layers other than the resin film. For example, the first substrate may include a water vapor barrier layer in addition to the resin film. The water vapor barrier layer may be provided on the surface of the resin film facing the water-based ink layer, or on the surface of the resin film opposite the water-based ink layer. When the first substrate includes a water vapor barrier layer, the resin film may be in contact with the water-based ink layer, or the water vapor barrier layer may be in contact with the water-based ink layer.

[0040] The water vapor barrier layer may include an inorganic thin film layer and a water vapor barrier coating layer, as shown in Fig. 3. In the packaging material 20 shown in Fig. 3, the first substrate 1 is made of a resin film 1a and a water vapor barrier layer 1b, and the water vapor barrier layer 1b is made of an inorganic thin film layer 1c and a water vapor barrier coating layer 1d. As shown in Fig. 3, the inorganic thin film layer and the water vapor barrier coating layer may be provided in this order on the resin film.

[0041] The inorganic thin film layer is formed by film formation (e.g., vacuum film formation) of, for example, a metal, or an oxide, nitride, or nitride oxide of silicon or the like. Specific examples of materials that can be used for the inorganic thin film layer include metals such as aluminum, titanium, copper, indium, and tin, or oxides thereof (e.g., alumina), silicon, silicon oxide, and even nitrides or nitride oxides of metals or silicon. The inorganic thin film layer may be a thin film layer containing a plurality of these metals. In particular, inorganic thin film layers containing oxides, nitrides, or nitride oxides of aluminum, titanium, copper, indium, or silicon tend to have both excellent transparency and barrier properties, and inorganic thin film layers containing oxides or nitride oxides of silicon tend to have even better barrier properties.

[0042] The inorganic thin film layer can be formed by vacuum deposition (resistance heating vacuum deposition, electron beam heating vacuum deposition, induction heating vacuum deposition), sputtering (reactive sputtering, dual magnetron sputtering), and PECVD (plasma generation methods include direct current (DC), radio frequency (RF), middle frequency (MF), DC pulse, RF pulse, and DC+RF superposition). The method for forming the inorganic thin film layer can be appropriately selected depending on the purpose and application. For example, sputtering may be selected from the viewpoint of film uniformity, and vacuum deposition may be selected from the viewpoint of cost.

[0043] The thickness of the inorganic thin film layer may be, for example, 5 nm or more and 100 nm or less. When the thickness of the inorganic thin film layer is 5 nm or more, good barrier properties are easily obtained, and when it is 100 nm or less, the occurrence of cracks is suppressed, the deterioration of the water vapor and oxygen barrier properties is small, and costs can be reduced due to a reduction in the amount of material used and a shortened formation time, etc.

[0044] The inorganic thin film layer may be a metal foil such as an aluminum foil, and in this case, the thickness of the metal foil may be 6 to 9 μm.

[0045] The water vapor barrier coating layer can be formed by applying a coating liquid containing, for example, a polar compound such as polyvinyl alcohol, polyvinylpyrrolidone, or ethylene vinyl alcohol, a chlorine-containing compound such as polyvinylidene chloride, a compound containing a Si atom, a compound containing a Ti atom, a compound containing an Al atom, a compound containing a Zr atom, etc., onto the inorganic thin film layer, drying, and curing the liquid. By laminating the water vapor barrier coating layer, various secondary damages in later processes can be prevented and high barrier properties can also be imparted.

[0046] The thickness of the water vapor barrier coating layer may be, for example, 50 nm or more and 1000 nm or less. More preferably, it may be 200 nm or more and 500 nm or less. When the thickness of the water vapor barrier coating layer is 50 nm or more, good water vapor barrier properties are easily obtained, and when it is 1000 nm or less, defects in the water vapor barrier coating layer due to insufficient conformability can be suppressed.

[0047] The total thickness of the first substrate may be, for example, from 5 μm to 100 μm or from 8 μm to 50 μm.

[0048] (Aqueous Ink Layer) The aqueous ink layer is a layer formed with an aqueous ink. The aqueous ink layer is formed by printing an aqueous ink on the first substrate. The aqueous ink layer may be, for example, an aqueous colored ink layer formed with an aqueous colored ink, or an aqueous colorless ink layer formed with an aqueous colorless ink (medium).

[0049] The water-based colored ink contains, for example, a pigment, a binder resin (also called a "vehicle"), and a solvent (dispersion medium).

[0050] The pigment may be an inorganic pigment or an organic pigment. Examples of inorganic pigments include extender pigments such as titanium oxide (white pigment), carbon black (black ink pigment), barium sulfate, and calcium carbonate. Examples of organic pigments include azo pigments, phthalocyanine pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, and dye lake pigments.

[0051] The pigment may be one type of pigment or multiple types of pigments. For example, the aqueous ink layer may contain multiple pigments of different colors or multiple pigments of different particle sizes.

[0052] When the aqueous ink layer is an aqueous colored ink layer, the pigment content may be 30 to 90% by mass, based on the total mass of the aqueous ink layer. A pigment content of 30% by mass or more tends to provide excellent color development and significantly improve lamination strength (adhesion strength). Furthermore, a pigment content of 90% by mass or less reduces the likelihood of delamination between the aqueous ink layer and the adhesive layer. To achieve both excellent color development and enhanced suppression of delamination, the pigment content may be, for example, 35 to 85% by mass, based on the total mass of the aqueous ink layer. When the aqueous ink layer is an aqueous colorless ink layer, such as a medium ink layer, the aqueous ink layer may contain a white pigment, but the pigment content is typically 0% by mass, based on the total mass of the aqueous ink layer. Such colorless inks are used to adjust the color of undercoats and colored inks.

[0053] When the aqueous ink contains a pigment, the pigments contact each other within the aqueous ink layer formed by printing the aqueous ink, forming gaps between the pigments, and these gaps connect in a network-like pattern, forming through holes that connect in a network-like pattern from the surface of the aqueous ink layer. Therefore, when the aqueous ink contains a pigment, the adhesive (especially polyisocyanate) is more likely to penetrate into the aqueous ink layer during the formation of the adhesive layer. This forms a network structure derived from the adhesive within the aqueous ink layer, and this network structure is expected to improve the laminate strength before and after retort treatment.

[0054] The binder resin is, for example, an aqueous binder resin, such as a water-soluble binder resin, an emulsion-type binder resin, or a colloidal dispersion-type binder resin.

[0055] Examples of aqueous binder resins include natural resin-based casein resins, shellac resins, synthetic resin-based rosin-modified maleic acid resins, styrene-maleic acid resins, styrene-acrylic acid resins, α-methylstyrene-acrylic acid resins, styrene-methacrylic acid resins, styrene-maleic acid-acrylic acid resins, acrylic acid-acrylic acid ester resins, acrylic acid-methacrylic acid ester resins, acrylic resins, urethane resins, acrylic-urethane resins, styrene resins, and polyester resins, as well as water-soluble polyamide resins and aqueous polyurethane resins. From the viewpoint of obtaining a more significant effect of improving laminate strength (adhesion strength), the aqueous binder resin may be a resin that does not have a urethane skeleton. From the viewpoint of more easily improving the dispersion stability of the ink, the adhesion of the aqueous ink layer, and the strength of the aqueous ink layer, the water-soluble binder resin may be a resin that has no acid value or a low acid value as the main component, and the resin may be used in combination with a resin with a high acid value.

[0056] When the aqueous ink layer is an aqueous colored ink layer, the content of the aqueous binder resin may be, for example, 15 to 60 mass %, 25 to 55 mass %, or 30 to 50 mass % based on the total mass of the aqueous ink layer. When the aqueous ink layer is an aqueous colorless ink layer, the content of the aqueous binder resin may be, for example, 60 to 100 mass % or 80 to 100 mass % based on the total mass of the aqueous ink layer.

[0057] The solvent (dispersion medium) of the aqueous ink dissolves or disperses the binder resin in the aqueous ink. The solvent (dispersion medium) of the aqueous ink is, for example, water or a hydrophilic solvent. Examples of hydrophilic solvents include alcoholic solvents such as methanol, ethanol, propanol, and butanol. A portion of the solvent (dispersion medium) of the aqueous ink may remain in the aqueous ink layer, but the content of the solvent (dispersion medium) is, for example, 1 mass % or less based on the total mass of the aqueous ink layer.

[0058] Water-based inks may contain auxiliary agents such as dispersants, plasticizers, waxes, lubricants, and antifoaming agents. The water-based ink layer may contain these components. Examples of plasticizers include dioctyl terephthalate. Examples of waxes include polyethylene and polypropylene. Examples of lubricants include calcium carbonate, barium sulfate, and clay. Examples of antifoaming agents include silicone-based and hydrocarbon-based agents.

[0059] In order to improve the solubility or dispersibility of the resin in the solvent, a basic compound such as ammonia, trimethylamine, sodium hydroxide, or potassium hydroxide may be added to the aqueous ink. The aqueous ink layer may contain these components.

[0060] The aqueous ink may be an aqueous flexographic ink used in aqueous flexographic printing, an aqueous inkjet ink used in inkjet printing, or the like. The aqueous ink layer is preferably a layer formed from an aqueous flexographic ink. When the aqueous ink layer is a layer formed from an aqueous flexographic ink, the lamination strength (adhesion strength) between the layers before and after retort treatment is likely to be higher. The reason for this is unclear, but it is presumed that the aqueous ink used in flexographic printing tends to contain a high concentration of pigment to improve color development, which in turn makes it easier for voids to form between the pigments in the aqueous ink layer, making it easier for the adhesive to penetrate into the aqueous ink layer, thereby achieving the above-mentioned effect.

[0061] Within the plane of the aqueous ink layer, thickness and ink type distribution may occur depending on the printed image. The maximum thickness of the aqueous ink layer may be 0.4 μm or more, or may be 0.5 μm or more. When the maximum thickness of the aqueous ink layer is in the range of 0.4 μm or more, the color development of the print tends to be good. In other words, it is desirable that the aqueous ink layer have a region with a thickness in the range of 0.4 μm or more (preferably 0.5 μm or more) depending on the desired image expression. The maximum thickness of the aqueous ink layer is preferably 5.0 μm or less, and may be 3.0 μm or less or 2.0 μm or less. The thinner the aqueous ink layer, the higher the interlayer lamination strength (adhesion strength) before and after retort treatment tends to be. From these perspectives, the maximum thickness of the aqueous ink layer may be, for example, 0.4 to 5.0 μm. The maximum thickness of the aqueous ink layer is the thickness of the aqueous ink layer in the thickest region within the plane of the aqueous ink layer, and is determined by cross-sectional observation. The maximum thickness of the water-based ink layer is measured by cross-sectional observation as follows.

[0062] First, three randomly selected regions measuring 8 mm wide x 8 mm long were cut out from within the surface of the packaging material containing the aqueous ink layer, and three samples were taken from these regions. Next, each of the three samples was embedded and fixed in a photocurable resin, and then cross-sectioned using an ultramicrotome. The resulting cross-sections were then observed using an optical microscope or scanning electron microscope, and 30 cross-sectional images were taken at 1,000 to 5,000 magnifications at approximately 0.2 mm intervals in the width direction. The maximum thickness of the aqueous ink layer was measured in each image. Of the 90 measurement values ​​(maximum thicknesses of the aqueous ink layer) obtained from the above measurement of the three samples, the arithmetic mean of the top 15 was taken as the maximum thickness of the aqueous ink layer.

[0063] 1 and 3 show the aqueous ink layer as a single layer, the aqueous ink layer may have a multi-layer structure of two or more layers. For example, the aqueous ink layer may be formed by forming a first aqueous ink layer containing a pigment with a relatively small particle size on the surface of a first substrate, and then forming a second aqueous ink layer containing a pigment with a relatively large particle size (e.g., a white pigment) on the surface of the first aqueous ink layer, resulting in an aqueous ink layer with a two-layer or more structure. When the packaging material includes a second aqueous ink layer containing a white pigment, the color development of the first aqueous ink layer tends to be further improved.

[0064] (Adhesive Layer) The adhesive layer is formed, for example, from a urethane-based adhesive containing polyisocyanate and polyol. The urethane-based adhesive contains a base agent containing polyol and a curing agent containing polyisocyanate, and the adhesive hardens as the polyol and polyisocyanate react with each other to form the adhesive layer. Therefore, the adhesive layer formed from the urethane-based adhesive contains polyurethane, which is a reaction product of the polyol and polyisocyanate. The type of polyisocyanate that constitutes the polyurethane in the adhesive layer can be analyzed at the monomer level by pyrolysis GC / MS analysis.

[0065] [Polyol] Examples of polyols include polyether polyols such as polyoxypropylene polyol and polyoxytetramethylene glycol, hydrocarbon polyols such as polycarbonate polyol, polybutadiene polyol and polyacrylate polyol, and polyester polyols such as polyadipate polyol and polycaprolactone diol. Among these, polyester polyols are preferably used from the viewpoints of water resistance and heat resistance.

[0066] A polyester polyol is a compound having two or more polyol hydroxyl groups (hydroxyl groups) and a polyester structure as a main skeleton. The polyester structure may be a polyester polyurethane structure. That is, the polyester polyol may be a polyester urethane polyol. The polyester polyol may further have a polyether structure in addition to the polyester structure and polyurethane structure. The polyester polyol may be a single polyester polyol or a combination of two or more polyester polyols.

[0067] The polyester polyol may be a commercially available product, such as Takelac A525 (trade name, "Takelac" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc., or DIC Dry LX-747 manufactured by DIC Corporation.

[0068] [Polyisocyanate] The polyisocyanate is composed of a compound having two or more isocyanate groups. From the viewpoint of generating highly regular hard segments and increasing the cohesive strength of the adhesive, the polyisocyanate preferably contains a diisocyanate having a single structure (i.e., a structure containing no isomers) and a highly regular structure (i.e., a highly symmetric, simple structure), and / or an isocyanate polymer derived from the diisocyanate. Specific examples include hexamethylene diisocyanate, isophorone diisocyanate, and isocyanate polymers derived from these. From the same viewpoint, the polyisocyanate may contain a chain isocyanate having a symmetric structure and / or an isocyanate polymer derived from the chain isocyanate. Hereinafter, the chain isocyanate will be referred to as polyisocyanate (a1), and the isocyanate polymer will be referred to as polyisocyanate (a2), and these will be collectively referred to as polyisocyanate (A).

[0069] The polyisocyanate (a1) is a chain isocyanate having a symmetrical structure. The polyisocyanate (a1) may be linear or branched. The polyisocyanate (a1) may be, for example, an aliphatic isocyanate. The aliphatic isocyanate may have, for example, 4 to 6 carbon atoms. Examples of the aliphatic isocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, and pentamethylene diisocyanate. One type of polyisocyanate (a1) may be used alone, or two or more types may be used in combination.

[0070] The polyisocyanate (a2) is an isocyanate polymer derived from a chain isocyanate having a symmetric structure. The polyisocyanate (a2) may be a polymer (multimer) obtained by reacting (polymerizing) chain isocyanates with each other, or may be a polymer obtained by further reacting (polymerizing) such polymers with each other. The polyisocyanate (a2) may also be a copolymer obtained by reacting (polymerizing) a chain isocyanate with a monomer capable of reacting with the isocyanate (for example, an active hydrogen-containing compound such as a polyol).

[0071] Examples of the polyisocyanate (a2) include an isocyanurate of the polyisocyanate (a1), a uretdione of the polyisocyanate (a1), a biuret of the polyisocyanate (a1), an allophanate of the polyisocyanate (a1), an adduct of the polyisocyanate (a1) (for example, a polyhydric alcohol adduct such as a trimethylolpropane adduct), and a compound having a urethane bond, which is a reaction product of the polyisocyanate (a1) and a polyhydric alcohol. One type of polyisocyanate (a2) may be used alone, or two or more types may be used in combination. The polyisocyanate (a2) may be an isocyanate polymer derived from multiple types of polyisocyanate (a1). The polyisocyanate (a2) may be an isocyanate polymer derived from the polyisocyanate (a1) through multiple reactions (polymerizations).

[0072] From the viewpoint of increasing the interlayer laminate strength (adhesion strength) before and after retort treatment, the polyisocyanate (A) preferably contains hexamethylene diisocyanate (HDI) or an isocyanate polymer derived from the hexamethylene diisocyanate, more preferably contains an isocyanate polymer derived from hexamethylene diisocyanate, and even more preferably contains an isocyanurate of hexamethylene diisocyanate (HDI isocyanurate) or a biuret of hexamethylene diisocyanate (HDI biuret). From the viewpoint of water resistance, the polyisocyanate (A) particularly preferably contains an isocyanurate of hexamethylene diisocyanate.

[0073] The content of polyisocyanate (a1) may be 3% by mass or more, 15% by mass or more, or 25% by mass or more, based on the total solid content of the adhesive, from the viewpoint of likely increasing the interlayer lamination strength (adhesion strength) before and after retort treatment. From the viewpoint of cost, the content of polyisocyanate (a1) may be 35% by mass or less, or 15% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (a1) may be 3 to 35% by mass or 3 to 15% by mass, based on the total solid content of the adhesive. In this specification, the total solid content of the adhesive refers to the amount obtained by excluding the amount of the solvent from the total amount of the adhesive when the adhesive contains a solvent, or refers to the total amount of the adhesive when the adhesive does not contain a solvent.

[0074] The content of polyisocyanate (a2) may be 3% by mass or more, 15% by mass or more, or 25% by mass or more, based on the total solid content of the adhesive, from the viewpoint of easily increasing the interlayer lamination strength (adhesion strength) before and after retort treatment. From the viewpoint of cost, the content of polyisocyanate (a2) may be 35% by mass or less, or 15% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (a2) may be 3 to 35% by mass, or 3 to 15% by mass, based on the total solid content of the adhesive.

[0075] The content of polyisocyanate (A) may be 3 to 70 mass%, 3 to 50 mass%, 3 to 35 mass%, or 3 to 15 mass%, or may be 15 to 70 mass%, 25 to 70 mass%, or 50 to 70 mass%, based on the total solid content of the adhesive, from the viewpoint of easily increasing the interlayer laminate strength (adhesive strength) before and after retort treatment and easily forming an islands-in-a-sea microphase-separated structure.

[0076] When polyisocyanate (A) is used in combination with polyisocyanate (B) described below, the content of polyisocyanate (A) may be 3% by mass or more, 15% by mass or more, 25% by mass or more, or 50% by mass or more, based on the total solid content of the adhesive, from the viewpoint of easily increasing the interlayer laminate strength (adhesion strength) before and after retort treatment and easily forming a sea-island microphase-separated structure. In the above case, from the viewpoint of cost, the content of polyisocyanate (A) may be 70% by mass or less, 50% by mass or less, 35% by mass or less, or 15% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (A) may be 3 to 70% by mass, 3 to 50% by mass, 3 to 35% by mass, or 3 to 15% by mass, or may be 15 to 70% by mass, 25 to 70% by mass, or 50 to 70% by mass, based on the total solid content of the adhesive.

[0077] When polyisocyanate (A) is used alone as the polyisocyanate, the content of polyisocyanate (A) may be 8% by mass or more, 11% by mass or more, 22% by mass or more, or 50% by mass or more, based on the total solid content of the adhesive, from the viewpoint of easily increasing the interlayer lamination strength (adhesion strength) before and after retort treatment and easily forming a sea-island microphase-separated structure. In the above case, from the viewpoint of cost, the content of polyisocyanate (A) may be 70% by mass or less, 50% by mass or less, or 41% by mass or less, based on the total solid content of the adhesive. From these viewpoints, the content of polyisocyanate (A) may be 8 to 70% by mass, 8 to 50% by mass, or 8 to 41% by mass, or may be 11 to 70% by mass, 22 to 70% by mass, or 50 to 70% by mass, based on the total solid content of the adhesive.

[0078] The polyisocyanate may contain a polyisocyanate other than the polyisocyanate (A) (hereinafter referred to as "polyisocyanate (B)") in addition to the polyisocyanate (A) or instead of the polyisocyanate (A).

[0079] Examples of the polyisocyanate (B) include aromatic polyisocyanates such as phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate (meta-xylylene diisocyanate and para-xylylene diisocyanate), alicyclic polyisocyanates such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate, and isocyanate polymers derived from these polyisocyanates. Examples of the isocyanate polymer include isocyanurates of the above-mentioned aromatic polyisocyanates or alicyclic polyisocyanates, biurets of the above-mentioned aromatic polyisocyanates or alicyclic polyisocyanates, and polyhydric alcohol adducts (e.g., trimethylolpropane adducts) of the above-mentioned aromatic polyisocyanates or alicyclic polyisocyanates.

[0080] Commercially available products may be used as the polyisocyanate (B), including Takenate D-140N, Takenate D-110N, and Takenate A52 (trade names, "Takenate" is a registered trademark (hereinafter the same)) manufactured by Mitsui Chemicals, Inc., and KX-75 manufactured by DIC Corporation.

[0081] The content of the polyisocyanate (B) may be 8 to 62 mass%, 8 to 14 mass%, or 18 to 62 mass%, based on the total solid content of the adhesive, from the viewpoints of the crosslinking density with the polyol, the film cohesive strength, and the ease of forming an islands-in-a-sea microphase-separated structure.

[0082] When polyisocyanate (B) is used in combination with polyisocyanate (A), the content of polyisocyanate (B) may be 8% by mass or more, or 14% by mass or more, based on the total solid content of the adhesive, from the viewpoints of crosslink density with the polyol, film cohesive strength, and ease of forming a sea-island microphase-separated structure. In the above case, the content of polyisocyanate (B) may be 14% by mass or less, based on the total solid content of the adhesive, from the viewpoint of more easily increasing interlayer lamination strength (adhesion strength) before and after retort treatment. From these viewpoints, the content of polyisocyanate (B) may be 8 to 14% by mass, based on the total solid content of the adhesive.

[0083] When polyisocyanate (B) is used alone as the polyisocyanate, the content of polyisocyanate (B) may be 18% by mass or more, or 34% by mass or more, based on the total solid content of the adhesive, from the viewpoint of easily increasing the interlayer lamination strength (adhesion strength) before and after retort treatment and easily forming a sea-island microphase-separated structure. In the above case, the content of polyisocyanate (B) may be 62% by mass or less, based on the total solid content of the adhesive, from the viewpoint of cost. From these viewpoints, the content of polyisocyanate (B) may be 18 to 62% by mass or 34 to 62% by mass, based on the total solid content of the adhesive.

[0084] The NCO value (unit: mol / g) of the polyisocyanate is set to 1.0×10 －３ or more, and may be 2.0 × 10 －３ or more or 5.0 x 10 －３ When the NCO value of the polyisocyanate is large, segregation of the urethane bond proceeds more, and island portions with high cohesive strength are more likely to be formed. The NCO value (unit: mol / g) of the polyisocyanate may be, for example, 1.0 × 10 －３ ~3.0 x 10 －１ The NCO value may be measured in accordance with JIS K 6806 (potentiometric titration method).

[0085] The ratio (NCO / OH) of the number of moles of all isocyanate groups (NCO groups) in the isocyanate group-containing compound (e.g., polyisocyanate) to the number of moles of all active hydrogen groups in the active hydrogen group-containing compound (e.g., polyol) contained in the adhesive may be 2.0 or more, 11.5 or less, 8.1 or less, or may be 2.0 to 11.5, from the viewpoint of the crosslink density of the adhesive layer and the viewpoint of further promoting segregation of urethane bonds and facilitating the formation of island portions with high cohesive force.

[0086] In addition to the active hydrogen-containing compound and polyisocyanate, the adhesive may further contain additives such as a solvent, a dispersant, an antifoaming agent, a leveling agent, a stabilizer, a filler, a lubricant, a slip agent, and a wax. These components may be contained in the adhesive layer.

[0087] The adhesive may be a dry laminating adhesive or a non-solvent laminating adhesive.

[0088] The adhesive layer may contain a portion of the solvent (diluent, etc.) contained in the adhesive, but the content of the solvent is, for example, 1 mass % or less based on the total mass of the adhesive layer. Examples of the solvent include ethyl acetate and methyl ethyl ketone.

[0089] The thickness of the adhesive layer is, for example, 0.5 to 5.0 μm. The thickness of the adhesive layer refers to the shortest distance from the surface on the aqueous ink layer side to the surface on the opposite side of the aqueous ink layer, and does not include the thickness of the area in the aqueous ink layer where the adhesive has soaked in. The thickness of the adhesive layer can be measured using the top 15 cross-sectional images used to calculate the maximum thickness of the aqueous ink layer described above. Specifically, the thickness of the adhesive layer can be measured in the above 15 cross-sectional images, and the arithmetic average of these measurements can be used as the thickness of the adhesive layer.

[0090] The ratio of the thickness (maximum thickness) of the aqueous ink layer to the thickness of the adhesive layer (thickness of aqueous ink layer / thickness of adhesive layer) may be 0.1 or more, or may be 0.3 or more, 0.5 or more, or 1.0 or more, from the viewpoint of increasing interlayer adhesion strength. The ratio of the thickness (maximum thickness) of the aqueous ink layer to the thickness of the adhesive layer (thickness of aqueous ink layer / thickness of adhesive layer) may be 2.5 or less, or may be 2.0 or less, 1.5 or less, 1.0 or less, or 0.5 or less, from the viewpoint of material cost and coating process suitability. From these viewpoints, the ratio of the thickness (maximum thickness) of the aqueous ink layer to the thickness of the adhesive layer (thickness of aqueous ink layer / thickness of adhesive layer) may be 0.1 to 2.5.

[0091] [Microphase-separated structure] The microphase-separated structure observed in an SPM phase image of the cross section of the adhesive layer has a sea region and a plurality of island regions scattered within the sea region.

[0092] The island portions are, for example, aggregates of components in the adhesive layer, and exhibit a higher elastic modulus than the sea portion in phase measurement by the tapping mode (AC mode) of the SPM.

[0093] The sea-island microphase separation structure can be formed, for example, by adding a certain amount or more of the polyisocyanate. When the urethane-based adhesive is used, both the sea portion and the island portion may contain polyurethane, but the island portion (e.g., an area with low brightness in a phase image) tends to contain a large amount of urethane bonds. Therefore, for example, when the polyol component of the urethane-based adhesive is polyester polyol, the ratio of urethane bonds to ester bonds (urethane bonds / ester bonds) confirmed by IR analysis tends to be larger in the island portion than in the sea portion. The larger the amount of polyisocyanate added, the larger the size of the island portion and the larger the number of island portions.

[0094] The microphase-separated structure preferably has island portions with a maximum Feret diameter of 0.1 to 1.0 μm, and more preferably has a maximum Feret diameter of 1.0 μm or less for all island portions (i.e., the maximum value of the maximum Feret diameter of the island portions is 1.0 μm or less). When island portions with a maximum Feret diameter within the above range are present, the laminate strength (adhesive strength) before and after retort treatment tends to be higher. From the same viewpoint, the microphase-separated structure may have island portions with a maximum Feret diameter of 0.8 μm or less, 0.5 μm or less, or 0.35 μm or less, and all of the island portions may have a maximum Feret diameter of 0.8 μm or less, 0.5 μm or less, or 0.35 μm or less. When there is a thickness distribution in the plane of the aqueous ink layer due to a pattern, from the viewpoint of reducing the variation in laminate strength (adhesive strength) in the plane, the maximum Feret diameter of the island portions is preferably 0.11 μm or more. That is, the microphase-separated structure preferably has islands with a maximum Feret diameter of 0.11 μm or more (e.g., 0.11 to 1.0 μm), and more preferably, all of the islands have a maximum Feret diameter of 0.11 μm or more (e.g., 0.11 to 1.0 μm). The maximum Feret diameter of the islands may be 0.15 μm, 0.2 μm or more, or 0.3 μm or more. The maximum value of the maximum Feret diameter of the islands is determined by acquiring cross-sectional phase images (field of view of 6 μm × 6 μm) at any three locations and measuring the maximum Feret diameter of all of the islands included in these locations by particle analysis using image analysis software.

[0095] The number of islands is, for example, 0.1 to 100 / μm ２ When the number of island portions is within the above range, the laminate strength (adhesion strength) before and after retort treatment tends to be higher. From the same viewpoint, the number of island portions may be 0.5 pieces / μm ２ or more than 0.7 / μm ２ It may be 40 or more per μm ２ Below, 10 pieces / μm ２ Less than or 6 pieces / μm ２ The number of island portions may be, for example, the number n1 (unit: pieces / μm) of island portions present on the water-based ink layer side from the center in the thickness direction of the adhesive layer. ２ ) and the number n2 (unit: pieces / μm ２ The number n1 of islands is obtained by measuring the number of islands of 1 μm at three arbitrary points (within a visual field of 6 μm×6 μm) on the water-based ink layer side from the center in the thickness direction of the adhesive layer, for example. ２ Similarly, the number n2 of islands can be obtained by measuring the number of islands per 1 μm at any three locations (within a field of view of 6 μm×6 μm) on the second substrate side from the center in the thickness direction of the adhesive layer and calculating the average of these. ２ The number of islands per square meter is measured and the average is calculated.

[0096] The size and number of the island portions tend to vary depending on the amount of polyisocyanate added, as well as the type of polyisocyanate, the type of aqueous ink layer, the thickness of the aqueous ink layer, the thickness of the adhesive layer, and the ratio of the thickness of the aqueous ink layer to the thickness of the adhesive layer. For example, when a polyhydric alcohol adduct of polyisocyanate (a1) (e.g., a trimethylolpropane adduct) is used as the polyisocyanate, the size of the island portions tends to increase. Furthermore, when an aqueous ink layer through which an adhesive easily penetrates is used, when the thickness of the aqueous ink layer is increased, or when the thickness of the adhesive layer is decreased, the size of the island portions tends to decrease and the number of island portions tends to decrease.

[0097] The ratio (n1 / n2) of the number of island portions n1 present closer to the aqueous ink layer than the center of the adhesive layer in the thickness direction to the number of island portions n2 present closer to the second substrate than the center of the adhesive layer in the thickness direction may be less than 1, or may be 0.95 or less, or 0.80 or less. When the ratio (n1 / n2) is less than 1, the laminate strength (adhesion strength) tends to be higher before and after retort treatment. The reason for this effect is unclear, but it is thought that the adhesive penetrates into the aqueous ink layer, causing a gradient in the number of island portions in the thickness direction of the adhesive layer, resulting in the ratio (n1 / n2) being less than 1. It is presumed that the adhesive that penetrates into the aqueous ink layer forms a network structure, thereby improving the laminate strength before and after retort treatment. From the viewpoint of maintaining uniformity in the thickness direction of the laminate, the ratio (n1 / n2) may be 0.1 or more, or 0.4 or more, or 0.5 or more. From these viewpoints, the ratio (n1 / n2) may be, for example, 0.1 or more and less than 1.

[0098] (Second Substrate) The second substrate may include a sealant layer. The sealant layer is composed of, for example, a resin that can be melted and mutually fused by heat. Examples of the resin that constitutes the sealant layer include polyolefin resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer, methylpentene polymer, polyethylene, and polypropylene, as well as acid-modified polyolefin resins obtained by modifying these with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, and the like. The resin that constitutes the sealant layer may be one type or two or more types.

[0099] The thickness of the sealant layer may be, for example, 5 to 300 μm, or may be 10 to 100 μm.

[0100] The second substrate may consist of only the sealant layer, or may include layers other than the sealant layer. For example, the second substrate may include a water vapor barrier layer in addition to the sealant layer. The details of the water vapor barrier layer are the same as those of the water vapor barrier layer that may be included in the first substrate.

[0101] The total thickness of the second substrate may be, for example, 5 to 300 μm, 10 to 200 μm, or 10 to 100 μm.

[0102] The packaging material may consist only of a first substrate, an aqueous ink layer, an adhesive layer, and a second substrate, or may include other substrates or layers. For example, the packaging material may further include another substrate different from the first substrate and the second substrate on at least one of the surface of the first substrate opposite the aqueous ink layer and the surface of the second substrate opposite the aqueous ink layer. The other substrate may be the substrate described as the first substrate or the substrate described as the second substrate. The other substrate may be laminated via an adhesive layer. Details of the adhesive layer are the same as those of the adhesive layer described above.

[0103] The outermost layer of the packaging material may be a sealant layer. Details of the sealant layer are the same as those of the sealant layer that the second substrate may include. The second substrate may include a sealant layer that serves as the outermost layer of the packaging material, or a substrate other than the second substrate may include a sealant layer that serves as the outermost layer. For example, if the packaging material further includes another substrate (e.g., a third substrate) on the surface of the second substrate opposite the aqueous ink layer, the other substrate may include a sealant layer. In this case, the second substrate may not include a sealant layer. The second substrate that does not include a sealant layer may be a substrate exemplified as the first substrate.

[0104] <Method for manufacturing packaging material> Another embodiment of the present disclosure is a method for manufacturing a packaging material, including the steps of: (A) printing an aqueous ink on a surface of a first substrate to form an aqueous ink layer; (B) applying an adhesive to the surface of the aqueous ink layer opposite the first substrate to form an adhesive layer; and (C) laminating a second substrate on the surface of the adhesive layer opposite the aqueous ink layer. In the following description, details common to the packaging material of the above embodiment will be omitted.

[0105] The aqueous ink contains, for example, a pigment, a binder resin, and a solvent (dispersion medium). The aqueous ink used to form the aqueous ink layer described above can be used. The content of the solvent in the aqueous ink is, for example, 40 to 80 mass % based on the total mass of the aqueous ink.

[0106] The printing of the aqueous ink can be carried out by known methods such as gravure printing, flexographic printing, inkjet printing, etc. In step (A), the aqueous ink layer may be formed by solid printing, or the aqueous ink layer may be formed by pattern printing of letters, figures, symbols, pictures, or other desired patterns, or a first aqueous ink layer may be formed by solid printing, and then a desired pattern may be printed on the first aqueous ink layer to form a second aqueous ink layer. As described above, it is preferable to use an aqueous flexographic ink as the aqueous ink, and it is preferable to print the aqueous ink by flexographic printing using the aqueous flexographic ink.

[0107] The adhesive contains, for example, an active hydrogen-containing compound and a polyisocyanate. The adhesive may be any of the adhesives used to form the adhesive layer described above. The adhesive components (e.g., the active hydrogen-containing compound and the polyisocyanate) may be mixed immediately before coating. The adhesive may be applied using a conventionally known method such as commonly used casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metaling bar coating, chamber doctor combined coating, or curtain coating.

[0108] When the adhesive contains a solvent (for example, when the adhesive is a dry laminating adhesive), the coating may be dried by carrying out a drying treatment after coating in order to remove the solvent. The drying of the coating may be carried out at, for example, 25 to 120°C.

[0109] The lamination of the second substrate (e.g., formation of a sealant layer) may be carried out by applying a coating liquid containing the above-mentioned resin that can be melted and fused to each other by heat using a conventionally known method such as dipping, roll coating, screen printing, spraying, etc. Alternatively, the sealant layer can be formed by attaching a film or sheet made of the above-mentioned resin.

[0110] In the manufacturing method of this embodiment, the size and number of the island portions observed in a cross section in the thickness direction of the adhesive layer can be adjusted, for example, by adjusting the type and amount of polyisocyanate used in the adhesive, the type and thickness of the aqueous ink layer, etc. In other words, in the manufacturing method of this embodiment, the packaging material of the above embodiment can be obtained by adjusting, for example, the type and amount of polyisocyanate used in the adhesive, the type and thickness of the aqueous ink layer, etc.

[0111] The manufacturing method of this embodiment may further include step (B') of applying a second adhesive to the surface of the second substrate opposite the aqueous ink layer to form a second adhesive layer, and may further include step (C') of laminating a third substrate on the surface of the second adhesive layer opposite the second substrate. The manufacturing method of this embodiment may further include step (B'') of applying a third adhesive to the surface of the first substrate opposite the aqueous ink layer to form a third adhesive layer, instead of or in addition to step (B'), and may further include step (C'') of laminating a fourth substrate on the surface of the third adhesive layer opposite the first substrate, instead of or in addition to step (C'). Steps (B') and (B'') can be performed in the same manner as step (B) described above. Steps (C') and (C'') can be performed in the same manner as step (C) described above. Furthermore, the third substrate and the fourth substrate may be the same as the first substrate described above, and the second adhesive and the third adhesive may be the same as the adhesive described above.

[0112] <Packaging Bag> Another embodiment of the present disclosure is a packaging bag made from the packaging material of the above embodiment. For example, as shown in FIG. 4 , the packaging bag is formed by heat-sealing three sides L1, L2, and L3 of two overlapping rectangular packaging materials to form a bag. After placing the contents (e.g., food, medicine, etc.) through the unheat-sealed opening 30a, the opening 30a can also be heat-sealed to hermetically seal the packaging bag 30. Note that the form of the packaging bag is not limited to this. Other examples of packaging bags include pillow packaging, three-sided seal packaging, and gusset packaging.

[0113] <Packaging> Another embodiment of the present disclosure is a packaging body including a packaging bag and a content accommodated in the packaging bag, wherein the laminate constituting the packaging bag includes, from the outside, a first substrate, an aqueous ink layer, an adhesive layer, and a second substrate, and a phase image obtained by observing a cross section of the adhesive layer in the thickness direction using a scanning probe microscope in tapping mode shows a microphase-separated structure having a sea portion and a plurality of island portions scattered within the sea portion.

[0114] The packaging bag of the above-mentioned packaging body may be the packaging bag of the above-mentioned embodiment (i.e., a packaging body obtained by manufacturing the packaging material of the above-mentioned embodiment). That is, another embodiment of the present disclosure may be a packaging body including the packaging bag of the above-mentioned embodiment and contents accommodated in the packaging bag. The packaging bag of the above-mentioned embodiment may be retort-treated. That is, the packaging body may be a retort-treated packaging body. Although the reason is not clear, when the packaging material of the above-mentioned embodiment is retort-treated, the size and number of island portions observed in the SPM phase image of the cross section of the adhesive layer may change.

[0115] When the package is a retort-treated package, the maximum Feret diameter of the island portions is preferably, for example, 0.1 to 1.0 μm. That is, the microphase-separated structure preferably has island portions with a maximum Feret diameter of 0.1 to 1.0 μm, and more preferably, the maximum Feret diameter of all island portions is 1.0 μm or less (i.e., the maximum value of the maximum Feret diameter of the island portions is 1.0 μm or less). When island portions with a maximum Feret diameter within the above range are present, from the same viewpoint, the microphase-separated structure may have island portions with a maximum Feret diameter of 0.8 μm or less, 0.5 μm or less, or 0.35 μm or less, and all island portions may have a maximum Feret diameter of 0.8 μm or less, 0.5 μm or less, or 0.35 μm or less. When there is a thickness distribution in the plane of the aqueous ink layer due to the pattern, from the viewpoint of reducing variation in the laminate strength (adhesion strength) in the plane, the maximum Feret diameter of the island portions is preferably 0.11 μm or more. That is, the microphase-separated structure preferably has islands with a maximum Feret diameter of 0.11 μm or more (e.g., 0.11 to 1.0 μm), and more preferably, the maximum Feret diameter of all the islands is 0.11 μm or more (e.g., 0.11 to 1.0 μm). The maximum Feret diameter of the islands may be 0.15 μm, 0.2 μm or more, or 0.3 μm or more. The method for measuring the maximum value of the maximum Feret diameter of the island parts is the same as the method for measuring the maximum value of the maximum Feret diameter of the island parts in the packaging material.

[0116] When the package is a package that has been retorted, the number of islands is, for example, 0.1 to 100 / μm ２ When the number of island portions is within the above range, the laminate strength (adhesion strength) before and after retort treatment tends to be higher. From the same viewpoint, the number of island portions may be 0.5 pieces / μm ２ or more than 0.7 / μm ２ It may be 40 or more per μm ２ Below, 10 pieces / μm ２ Less than or 6 pieces / μm ２ The method for measuring the number of island portions is the same as the method for measuring the number of island portions in the packaging material.

[0117] When the package is a retort-treated package, the ratio (n1 / n2) of the number of island portions n1 located closer to the aqueous ink layer than the center of the adhesive layer in the thickness direction to the number of island portions n2 located closer to the second substrate than the center of the adhesive layer in the thickness direction may be less than 1, or may be 0.95 or less, or 0.80 or less. When the ratio (n1 / n2) is less than 1, the laminate strength (adhesive strength) before and after the retort treatment tends to be higher. From the viewpoint of maintaining uniformity in the thickness direction of the laminate, the ratio (n1 / n2) may be 0.1 or more, or may be 0.4 or more, or 0.5 or more. From these viewpoints, the ratio (n1 / n2) may be, for example, 0.1 or more and less than 1.

[0118] When the package is a retort-treated package, the adhesive strength between the first substrate and the second substrate measured by the following procedures (1') to (2') may be 1.0 N / 15 mm or more, and may also be 1.5 N / 15 mm or more, 2.5 N / 15 mm or more, or 3.5 N / 15 mm or more. The upper limit of the adhesive strength measured by the following procedures is, for example, 10 N / 15 mm. (1'): A test piece 15 mm wide and 200 mm long is cut out from the laminate. (2'): A T-peel test is performed on the test piece at a peel rate of 300 mm / min and a width of 15 mm in accordance with JIS K 6854 under conditions of 20°C and 30% RH, and the adhesive strength between the first substrate and the second substrate is measured.

[0119] The contents of the package are not particularly limited, but may be, for example, food, medicine, etc.

[0120] The above-mentioned package can be obtained, for example, by placing the contents (food, medicine, etc.) into the package through the opening of the packaging bag of the above-mentioned embodiment, closing the opening to seal the package, and optionally performing a retort process.

[0121] The present disclosure will be described below based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0122] Example 1-1 (Manufacturing of packaging material) [Step (A)] A 12 μm thick biaxially oriented polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name: Toyobo Ester Film (Type: 5102), "Toyobo Ester" is a registered trademark, "PET" in the table) was prepared as a first substrate, and a red water-based flexographic ink (Aquariona TPN3 Red, manufactured by Toyo Ink Co., Ltd.) was printed on the surface of the first substrate by flexographic printing to form a 0.7 μm thick water-based ink layer ("ink" in the table). This resulted in a laminate consisting of the first substrate and the water-based ink layer. Note that the thickness of the water-based ink layer in this example is the "maximum thickness" measured by the method described above.

[0123] [Step (B) and Step (C)] Takelac A626 (polyester polyol, solid content: 60% by mass, OH value: 2.2 × 10) manufactured by Mitsui Chemicals, Inc. －４ (mol / g), acid value: 3.0×10 －５ (mol / g)) and Takenate A52 (a polyisocyanate containing xylylene diisocyanate (XDI) and isophorone diisocyanate (IPDI), solid content: 75% by mass, NCO value: 2.5×10 manufactured by Mitsui Chemicals, Inc. －３ mol / g) were blended in a mass ratio (solid content ratio) of 4.80:0.75 to prepare a mixed solution. Then, to the mixed solution obtained above, Duranate 24A-100 (polyisocyanate containing hexamethylene diisocyanate (HDI) biuret, solid content: 100 mass%, NCO value: 5.9 × 10) manufactured by Asahi Kasei Corporation was added. －３ An adhesive was prepared by adding and mixing 24A-100 (mol / g). The amount of 24A-100 added was such that the mass ratio (solid content ratio) of A626:A52:24A-100 was 4.80:0.75:1.00. The content (solid content) of the HDI biuret compound in the adhesive was 15.3 mass% based on the total solid content of the adhesive.

[0124] Next, using a dry laminator, an adhesive layer and a second substrate were laminated onto the aqueous ink layer of the laminate obtained in step (A). Specifically, first, in the coating section of the dry laminator, the adhesive (solid content concentration: 30% by mass) obtained above was applied to the surface of the aqueous ink layer and dried at 80°C for 1 minute to form a 3.1 μm thick adhesive layer (dry laminate adhesive layer, "DL" in the table). Next, a 60 μm thick unstretched polypropylene film (manufactured by Toray Industries, Inc., product name: Pylen ZK207, "CPP" in the table) was prepared as a second substrate (sealant layer), and the second substrate was laminated onto the adhesive layer formed above in the laminating section of the dry laminator. After lamination, the packaging material of Example 1-1 was obtained by aging at 50°C for 72 hours.

[0125] [Preparation of Package] Two sheets measuring 140 mm wide and 100 mm long were cut out from the packaging material, and the second substrate sides of the two sheets were placed face to face so that the four sides overlapped each other. Three of the four sides were heat-sealed to prepare a packaging bag with one opening. 50 g of water was added to the packaging bag, and the opening side of the packaging bag was heat-sealed to prepare a packaging body (pouch). The prepared packaging body was subjected to a retort treatment at 121°C for 30 minutes. This resulted in a retort-treated packaging body.

[0126] <Example 1-2 and Comparative Example 1-1> Packaging materials of Example 1-2 and Comparative Example 1-1 were produced in the same manner as Example 1-1, except that the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, packaging bodies of Example 1-2 and Comparative Example 1-1 were produced in the same manner as Example 1-1, except that the packaging materials of Example 1-2 and Comparative Example 1-1, respectively, were used as the packaging materials.

[0127] Example 1-3: Instead of Duranate 24A-100, Duranate P301-75E (a polyisocyanate containing an HDI adduct (a trimethylolpropane adduct of HDI), solid content: 75% by mass, NCO value: 3.0 × 10) manufactured by Asahi Kasei Corporation was used. －３The packaging material of Example 1-3 was produced in the same manner as in Example 1-1, except that a cellulose ester resin (polysiloxane diacrylate) having a viscosity of 1000 MPa (1000 psi) of 1000 MPa (1000 psi) was used, and that the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. The content (solid content) of the HDI adduct in the adhesive was 15.3 mass% based on the total solid content of the adhesive. Furthermore, the packaging body of Example 1-3 was produced in the same manner as in Example 1-1, except that the packaging material of Example 1-3 was used as the packaging material.

[0128] Example 1-4: Instead of Duranate 24A-100, Duranate TPA-100 (polyisocyanate containing HDI isocyanurate, solid content: 100% by mass, NCO value: 5.9 × 10) manufactured by Asahi Kasei Corporation was used. －３ The packaging material of Example 1-4 was produced in the same manner as in Example 1-1, except that a 100% acrylic acid acrylate acrylate (polymer of 100% acrylic acid acrylate ...

[0129] Examples 1-5 to 1-6 The packaging materials of Examples 1-5 to 1-6 were each produced in the same manner as Example 1-1, except that a white aqueous flexographic ink (Aquariona TPN3 White, manufactured by Toyo Ink Co., Ltd.) was used as the aqueous ink instead of the red aqueous flexographic ink, and the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, the packages of Examples 1-5 to 1-6 were each produced in the same manner as Example 1-1, except that the packaging materials of Examples 1-5 to 1-6 were used as the packaging materials.

[0130] Example 2-1 A packaging material of Example 2-1 was produced in the same manner as Example 1-1, except that a 12 μm thick barrier film (manufactured by Toppan Printing Co., Ltd., product name: GL-ARH, designated "GL-ARH" in the table) comprising a biaxially oriented polyethylene terephthalate film and a water vapor barrier layer (alumina vapor deposition layer and water vapor barrier coating layer) on the first substrate was used instead of the biaxially oriented polyethylene terephthalate film, and the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, a packaged body of Example 2-1 was produced in the same manner as Example 1-1, except that the packaging material of Example 2-1 was used as the packaging material.

[0131] Example 3-1 A packaging material of Example 3-1 was produced in the same manner as Example 1-3, except that a 15 μm thick biaxially oriented nylon film (manufactured by Unitika Ltd., product name: Emblem ONM (type: RT); "Emblem" is a registered trademark, and "ONY" in the table) was used as the first substrate instead of the biaxially oriented polyethylene terephthalate film, a white water-based flexographic ink (Aquariona TPN3 White, manufactured by Toyo Ink Co., Ltd.) was used instead of the red water-based flexographic ink, and the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, a package of Example 3-1 was produced in the same manner as Example 1-1, except that the packaging material of Example 3-1 was used as the packaging material.

[0132] Example 3-2 Instead of Duranate P301-75E, Takenate D-140N (a polyisocyanate containing an IPDI adduct (a trimethylolpropane adduct of IPDI), solid content: 75% by mass, NCO value: 2.5 × 10) manufactured by Mitsui Chemicals, Inc. was used. －３ The packaging material of Example 3-2 was produced in the same manner as in Example 3-1, except that a cellulose ester resin (wt. mol / g) was used and the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. In addition, the packaging body of Example 3-2 was produced in the same manner as in Example 1-1, except that the packaging material of Example 3-2 was used as the packaging material.

[0133] Example 3-3: Instead of Duranate P301-75E, Takenate D-110N (a polyisocyanate containing an XDI adduct (a trimethylolpropane adduct of XDI), solid content: 75% by mass, NCO value: 2.7 × 10) manufactured by Mitsui Chemicals, Inc. was used. －３ The packaging material of Example 3-3 was produced in the same manner as in Example 3-1, except that a cellulose ester resin (wt. mol / g) was used and the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. In addition, the packaging body of Example 3-3 was produced in the same manner as in Example 1-1, except that the packaging material of Example 3-3 was used as the packaging material.

[0134] <Comparative Examples 1-2 to 1-3> Packaging materials of Comparative Examples 1-2 to 1-3 were each produced in the same manner as Example 1-1, except that Duranate 24A-100 was not used and that the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, packaging bodies of Comparative Examples 1-2 to 1-3 were each produced in the same manner as Example 1-1, except that the packaging materials of Comparative Examples 1-2 to 1-3 were each used as the packaging materials.

[0135] <Comparative Examples 1-4 to 1-6> Packaging materials of Comparative Examples 1-4 to 1-6 were each produced in the same manner as Example 1-5, except that Duranate 24A-100 was not used and that the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, packaging bodies of Comparative Examples 1-4 to 1-6 were each produced in the same manner as Example 1-1, except that the packaging materials of Comparative Examples 1-4 to 1-6 were each used as the packaging materials.

[0136] <Comparative Example 2-1> A packaging material of Comparative Example 2-1 was produced in the same manner as in Example 2-1, except that Duranate 24A-100 was not used and that the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, a package of Comparative Example 2-1 was produced in the same manner as in Example 1-1, except that the packaging material of Comparative Example 2-1 was used as the packaging material.

[0137] <Comparative Example 3-1> A packaging material of Comparative Example 3-1 was produced in the same manner as in Example 3-1, except that Duranate P301-75E was not used and that the thickness of the adhesive layer and the thickness of the ink layer were adjusted to the values ​​shown in Table 1. Furthermore, a package of Comparative Example 3-1 was produced in the same manner as in Example 1-1, except that the packaging material of Comparative Example 3-1 was used as the packaging material.

[0138] Example 4-1 Preparation of Solvent-Free Adhesive TSN4864A (polyester polyol, OH value: 1.8×10) manufactured by Toyo-Morton Co., Ltd. was used as the polyol base. －３ mol / g, acid value: 3.8×10 －３ mol / g), and a polyisocyanate (A), an HDI biuret compound (BASONATE HB-100 manufactured by BASF, NCO value: 5.3 × 10 －３ mol / g) and HDI nurate (Takenate D177N manufactured by Mitsui Chemicals, Inc., NCO value: 4.8 × 10 －３ mol / g) were mixed together. The mixing ratio of the polyol base, HDI biuret, and HDI nurate was 60:20:80 by mass (solid content ratio). In this way, solventless adhesive 1 was prepared. The HDI component in the adhesive (total amount (solid content) of HDI biuret and HDI nurate) was 62.5 mass% based on the total solid content of the adhesive.

[0139] (Production of packaging material) [Step (A)] A 20 μm thick biaxially oriented polypropylene film (manufactured by Mitsui Chemicals Tohcello, product name: U-1), indicated as "OPP1" in the table) was prepared as a first substrate, and a white aqueous flexographic ink (Aquariona TPN3 White, manufactured by Toyo Ink Co., Ltd.) was printed on the surface of the first substrate by flexographic printing to form a 2.8 μm thick aqueous ink layer (indicated as "ink" in the table). This resulted in a laminate (A) consisting of the first substrate and the aqueous ink layer.

[0140] [Step (B) and Step (C)] The solventless adhesive 1 was applied onto the aqueous ink layer of the laminate (A) using a non-solvent laminator (SuperSimplex SL, manufactured by Nordmechanika) at a coating roll temperature of 70°C, a coating speed of 200 m / min, and a coating amount of 1.6 g / m２ The resulting mixture was applied at a rate of 1000 kJ / min to form a 1.4 μm thick adhesive layer (non-solvent adhesive layer, "NS1" in the table). Next, a 20 μm thick biaxially oriented polypropylene film (manufactured by Mitsui Chemicals Tohcello, product name: U-1, "OPP2" in the table) was prepared as a second substrate, and the second substrate was laminated onto the adhesive layer formed above in the laminating section of a non-solvent laminator. After lamination, the laminate was aged at 40°C for 72 hours to obtain a laminate (B).

[0141] [Steps (B') and (C')] The solventless adhesive 1 was applied to the second substrate of the laminate (B) under the same conditions as in step (B) to form a 2 μm thick adhesive layer (non-solvent adhesive layer, "NS2" in the table). Next, a 60 μm thick unstretched polypropylene film (manufactured by Toray Industries, Inc., product name: Pylen ZK207, "CPP" in the table) was prepared as a third substrate, and the third substrate was laminated onto the adhesive layer formed above in the laminating section of a non-solvent laminator. After lamination, the product was aged at 40°C for 72 hours to obtain the packaging material of Example 4-1.

[0142] Example 4-2 Preparation of Solvent-Free Adhesive In addition to HDI biuret and HDI nurate, IPDI (VESTANAT T 1890 / 100 manufactured by Evonik, NCO value: 4.1 × 10) was used as the isocyanate to be mixed with the polyol base. －３ A solventless adhesive 2 was prepared in the same manner as in Example 4-1, except that a polyol base, HDI biuret, HDI nurate, and IPDI were used (mol / g) and the mixing ratio of the polyol base, HDI biuret, HDI nurate, and IPDI was set to a mass ratio (solid content ratio) of 100:35:15:50.

[0143] (Production of packaging material) The solvent-free adhesive 2 was used instead of the solvent-free adhesive 1, and the amount of adhesive applied in step (B) was 1.8 g / m. ２ A packaging material of Example 4-2 was produced in the same manner as in Example 4-1, except that the thickness of the adhesive layer (non-solvent adhesive layer, "NS1" in the table) was changed to 1.5 μm.

[0144] <Comparative Example 4-1> A packaging material of Comparative Example 4-1 was produced in the same manner as in Example 4-2, except that in step (A), the thickness of the aqueous ink layer was changed to 9.0 μm, and in step (B), the thickness of the adhesive layer (non-solvent adhesive layer, "NS1" in the table) was changed to 0.5 μm.

[0145]

[0146]

[0147] <SPM Observation> [Packaging Material] SPM phase images of the cross section of the adhesive layer in the packaging material of each Example and Comparative Example were obtained. Specifically, first, the front and back surfaces of the packaging material were corona-treated, and then the packaging material was cut into 2 x 3 mm strips. Next, the resulting strip-shaped packaging material was embedded in a photocurable resin (Aronix LCRD-800 visible light-curable resin manufactured by Toa Gosei Co., Ltd.), and the resin was cured by irradiation with light to obtain a block piece consisting of the packaging material and the cured resin embedding the packaging material. Next, the resulting block piece was fixed in an SPM sample holder insert (AFM sample holder insert manufactured by Leica Microsystems). At room temperature (25°C), the block piece was trimmed and the cross section of the packaging material (cross section perpendicular to the layer interface) was cut with a glass knife, and then the cross section was cut with a diamond knife until it obtained a mirror finish. The cross-section cutting device used was a Leica Microsystems EM UC7 ultramicrotome. The cutting speed was set to 3 mm / s, and the cutting thickness was set to 500 nm. The cutting direction was parallel to the layer interface. Next, while the block piece after the cross-section was fixed in the SPM sample holder insert, phase image measurement was performed on the block piece using an SPM (scanning probe microscope). Specifically, in an environment of 25°C, shape measurement was performed using the SPM's AC mode (tapping mode) with a field of view of 6 μm × 6 μm and a scanning speed of 2 Hz, so that the layer interface of the cross section was parallel to the scanning direction of the Fast Scan, and phase, height, and amplitude images were obtained. The SPM used was a JupiterXR (trade name) manufactured by Oxford Instruments. The SPM cantilever (measurement probe) used was an Olympus AC160TS (trade name), with typical characteristic values ​​of a tip curvature radius of 7 nm and a spring constant of 26 N / m. The resolution during measurement was set to 256 x 256, and the setpoint, drive amplitude, and integral gain were adjusted so that the island portion could be clearly observed in the phase image. Specifically, the phase during measurement in the phase image was set to be smaller than the phase before contact (engagement) between the sample and the cantilever, the trace and retrace signals were matched in the height image, and the trace and retrace signals were inverted in the amplitude image.

[0148] The above measurement was performed on three independent regions on the cross section. The obtained phase images were digitized using JupiterXR analysis software, and then image analysis was performed.

[0149] Image analysis was performed using ImageJ (manufactured by the National Institutes of Health, USA). Specifically, first, the magnitude of the phase was displayed as a grayscale image, and the entire adhesive layer was selected by a polygon. Next, a binarized image of the adhesive layer's brightness was obtained using Auto Local Threshold. Next, island-like regions were extracted using ANALYZE PARTICLES. The area of ​​the extracted region was set to a lower limit of 5 pixels or more (0.0027 μm ) in order to distinguish it from noise. ２ (or more). Next, the minimum Feret diameter of each extracted island-like region was determined, and regions with a minimum Feret diameter of 0.1 μm or more were determined to be "islands." The number of islands at the three measured locations was added up, and regions with at least two or more island regions were determined to have a microphase-separated structure in which the regions other than the island regions were sea regions. In this way, it was determined whether the SPM phase image of the adhesive layer cross section had a microphase-separated structure having a sea region and multiple island regions scattered within the sea region. Note that the island regions may be regions with lower brightness than the surrounding area or regions with higher brightness than the surrounding area. However, when ANALYZE PARTICLES is used to compare the cases where low-brightness regions are extracted with the cases where high-brightness regions are extracted, the region with the larger number of extracted regions is considered to be an island region, and when the number is the same, the region with the smaller total area is considered to be an island region. Furthermore, an island region may contain one or more regions with different brightnesses within it. In this case, the contained regions with different brightnesses are also considered to be a single island region. Furthermore, the island portion may contact at least one of the boundaries of the image, top, bottom, left, and right, within the range selected as the image analysis target.

[0150] Next, the minimum Feret diameter of each extracted island region was determined, and regions with a minimum Feret diameter of 0.1 μm or more were determined as "islands." The maximum Feret diameter of the islands, the number of islands (n1, n2, total), and the ratio (n1 / n2) of the number of islands n1 present on the aqueous ink layer side of the thickness center of the adhesive layer to the number of islands n2 present on the second substrate side of the thickness center of the adhesive layer were determined. Of the adhesive layers divided by straight lines, island regions were extracted using ANALYZE PARTICLES on the aqueous ink layer side of the adhesive layer and on the substrate side opposite the aqueous ink layer. At this time, for islands overlapping with the line drawn for division, if the area of ​​the substrate side opposite the aqueous ink layer was 50% or more of the total area of ​​the islands, it was counted as the substrate side opposite the aqueous ink layer.

[0151] The maximum Feret diameter of the island portion was determined by measuring the maximum Feret diameter of each island portion. The maximum value of the maximum Feret diameter of the island portion was determined at three arbitrary points (a visual field of 6 μm×6 μm). The number of islands n1 was determined by measuring the maximum Feret diameter of the island portion at three arbitrary points (a visual field of 6 μm×6 μm) on the aqueous ink layer side from the center in the thickness direction of the adhesive layer. ２ The number of islands n2 was measured at three arbitrary locations (within a visual field of 6 μm×6 μm) on the second substrate side from the center in the thickness direction of the adhesive layer, and the average was calculated. ２ The total number of islands was obtained by averaging the number of islands n1 and the number of islands n2.

[0152] As a result of the measurement, in the packaging material of the example, the above-mentioned "island portion" was observed in the SPM phase image of the cross section of the adhesive layer (i.e., a microphase-separated structure having a sea portion and a plurality of island portions scattered within the sea portion was observed). On the other hand, in the packaging material of the comparative example, the above-mentioned "island portion" was not observed in the SPM phase image of the cross section of the adhesive layer. The measurement results of the examples are shown in Table 3.

[0153] [Packages] SPM phase images of the cross section of the adhesive layer in the packages of each Example and Comparative Example were obtained. Specifically, the packages of each Example and Comparative Example were first stored at 25°C and 50% RH for 6 months. Next, the packages were disassembled, and the sheets (laminates) constituting the packaging bags were cut out. Next, SPM phase images of the cross section of the adhesive layer in the obtained sheets were obtained and image analyzed using the same method as for obtaining SPM phase images of the cross section of the adhesive layer in the packaging material and the image analysis method. The above-mentioned "islands" were observed in the packages of the Examples (i.e., a microphase-separated structure having a sea portion and multiple islands scattered within the sea portion was observed). On the other hand, the above-mentioned "islands" were not observed in the packages of the Comparative Examples. The results of the Examples are shown in Table 4. For reference, phase images obtained for Comparative Example 1-2, Example 1-1, Example 1-3, and Example 1-4 are shown in Figure 5. (a), (b), (c), and (d) in FIG. 5 correspond to Comparative Example 1-2, Example 1-1, Example 1-3, and Example 1-4, respectively.

[0154]

[0155]

[0156] <Evaluation (A): Peeling and Lifting Evaluation> The packages of each Example and Comparative Example were visually inspected after retorting. If large linear peeling was observed, including at the seal edge, it was evaluated as "X." If no peeling was observed, including at the seal edge, but small point-like lifting was observed, it was evaluated as "△." If neither large linear peeling nor small point-like lifting was observed, it was evaluated as "O." The results are shown in Table 5.

[0157] <Evaluation (B): Laminate Strength> The laminate strength of the packaging materials of each of the Examples and Comparative Examples was evaluated before and after retort treatment by the following method.

[0158] [Before retort treatment] Test pieces measuring 15 mm wide and 200 mm long were cut from the packaging materials of each Example and Comparative Example. A T-peel test was performed on the test pieces at 20°C and 30% RH in accordance with JIS K 6854, with a width of 15 mm and a peel rate of 300 mm / min, to measure the adhesive strength between the first substrate and the second substrate. In this evaluation, if the adhesive strength was less than 1.0 N / 15 mm, the laminate strength was judged to be insufficient (evaluated as ×); if the adhesive strength was 1.0 N / 15 mm or greater, the laminate strength was judged to be sufficiently high (evaluated as △); and if peeling was not possible (measurable), the laminate strength was judged to be excellent (evaluated as ◯). The results are shown in Table 5.

[0159] [After Retort Treatment] The lamination strength (adhesion strength) between the first substrate and the second substrate of each packaging material in each Example and Comparative Example after (immediately after) retort treatment was measured using the following procedures (1) to (5). The evaluation criteria were the same as those before retort treatment. The results are shown in Table 5. (1): Two sheets measuring 140 mm wide and 100 mm long were cut out from the packaging material. The second substrate-side surfaces of the two sheets were placed facing each other so that their four edges overlapped, and three of the four edges were heat-sealed to produce a packaging bag with one opening. (2): 50 g of water was added to the packaging bag, and the opening edge of the packaging bag was heat-sealed to produce a test pouch. (3): The test pouch produced in (2) was subjected to retort treatment at 121°C for 30 minutes. (4): After the retort treatment in (3), a test piece measuring 15 mm in width and 200 mm in length was cut out from one of the two sheets constituting the test pouch. (5): A T-peel test was performed on the test piece at a width of 15 mm at a peel rate of 300 mm / min in accordance with JIS K 6854 under conditions of 20°C and 30% RH to measure the adhesive strength between the first substrate and the second substrate. Note that the heat sealing in (1) and (2) was performed using a 15 mm wide seal bar at 150°C and 3 kg / cm on each side. ２ The test was carried out by applying heat and pressure at 1000 kJ / min for 0.5 seconds.

[0160] <Evaluation (C): Printing condition> The condition of the ink layer in the packaging material of each Example and Comparative Example was evaluated according to the following criteria: ◯ (Excellent): Excellent color tone reproducibility × (Poor): Poor color tone reproducibility

[0161]

[0162] REFERENCE SIGNS LIST 1...first substrate, 2...water-based ink layer, 2a...pigment, 3...adhesive layer, 3a...sea portion, 3b...island portion, 4...second substrate, 10, 20...packaging material, 30...packaging bag

Claims

1. A packaging material comprising a first substrate, an aqueous ink layer, an adhesive layer, and a second substrate in this order, wherein a phase image obtained by observing a cross-section in the thickness direction of the adhesive layer in tapping mode of a scanning probe microscope has a microphase separation structure having a sea portion and a plurality of island portions scattered within the sea portion.

2. The packaging material according to claim 1, wherein the adhesive layer is formed of a urethane-based adhesive containing a polyisocyanate and a polyol.

3. The packaging material according to claim 1, wherein the microphase separation structure has island portions with a maximum Feret diameter of 0.1 to 1.0 μm.

4. The number of the island portions is 0.1 to 100 pieces / μm ２ The packaging material according to claim 1, which is such that 5. The packaging material according to claim 1, wherein the ratio (n1 / n2) of the number n1 of the island portions present on the side of the aqueous ink layer rather than the center in the thickness direction of the adhesive layer to the number n2 of the island portions present on the side of the second substrate rather than the center in the thickness direction of the adhesive layer is less than 1.

6. The packaging material according to claim 1, wherein the aqueous ink layer is formed of an aqueous flexographic ink.

7. The packaging material according to claim 1, wherein the adhesive layer is formed of an adhesive for dry lamination.

8. The packaging material according to claim 1, wherein the first substrate includes at least one selected from the group consisting of a stretched polyethylene terephthalate film, a stretched polypropylene film, a stretched nylon film, and a stretched polyethylene film.

9. The packaging material according to claim 1, wherein the first substrate includes a water vapor barrier layer.

10. The packaging material according to claim 1, wherein the adhesive strength between the first substrate and the second substrate measured by the following procedures (1) to (5) is 1.0 N / 15 mm or more. (1): Cut out two sheets of a size of 140 mm in width and 100 mm in length from the packaging material, face the surfaces on the second substrate side of the two sheets so that the four sides of each other overlap, and heat-seal three of the four sides to produce a packaging bag with one side open. (2): After adding 50 g of water to the packaging bag, heat-seal the open side of the packaging bag to produce a test pouch. (3): Perform a retort treatment on the test pouch produced in (2) at 121° C. for 30 minutes. (4): After the retort treatment in (3), cut out a test piece of a size of 15 mm in width and 200 mm in length from one of the two sheets constituting the test pouch. (5): Perform a T-peel test with a peel rate of 300 mm / min and a width of 15 mm on the test piece under the conditions of 20° C. and 30% RH in accordance with JIS K 6854, and measure the adhesive strength between the first substrate and the second substrate.

11. A packaging bag formed by making a bag from the packaging material according to any one of claims 1 to 10.

12. A package comprising the packaging bag according to claim 11 and the contents contained in the packaging bag.

Images