Method for selecting packaging material, packaging material, and retort container

Abstract

Provided is a method for sorting packaging materials that can impart a beautiful metallic luster without using a metal layer and can suppress changes in appearance during distribution. [Solution] A method for sorting packaging materials having a structure in which at least a plastic film, a glossy printing layer, and a sealant layer are laminated in this order from the outer layer side, in which, when the printing layer contains a luster pigment and inorganic particles with an average primary particle diameter of 1 to 100 nm, the angle at which the reflection intensity of the packaging material is half the regular reflection intensity of the reflected light satisfies specific conditions.

Description

Technical Field

[0001] The present invention relates to a method for selecting a packaging material, a packaging material, and a retort container.

Background Art

[0002] From the viewpoint of producing a high-class and luxurious feeling for the object to be packaged and creating an aesthetic appearance, the packaging material may be decorated with a high-brightness metallic luster. As such a decorative means, for example, forming a metal layer such as a metal vapor deposition film or a metal foil is generally performed.

[0003] However, there is a problem that the cost of the packaging material using a metal layer increases. Further, among the metal layers, the metal vapor deposition film has a problem that it cannot be produced inline with other layers constituting the packaging material, so the production efficiency is poor, and among the metal layers, the metal foil has a problem that it is difficult to handle. Furthermore, when the packaging material using a metal layer is heated in a microwave oven, the microwave in the microwave oven is reflected on the surface of the metal layer, generating sparks, which may cause malfunctions and accidents of the microwave oven, and there is also a problem that the contents in the packaging container cannot be sufficiently heated.

[0004] For this reason, for example, Patent Document 1 proposes a packaging material in which a gloss layer is formed with an ink agent containing a high-brightness aluminum paste having a predetermined concentration instead of a metal layer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, although the number of occurrences of packaging materials that impart a metallic luster without using a metal layer is small, there have been cases where problems such as changes in appearance occur during the distribution process of the packaging materials have been pointed out.

[0007] The present invention has been made to solve the above technical problems, and an object thereof is to provide a method for selecting a packaging material that can produce an aesthetic appearance with a metallic luster without using a metal layer and can suppress changes in appearance during the distribution process. Another object of the present invention is to provide a packaging material that can produce an aesthetic appearance with a metallic luster without using a metal layer and can suppress changes in appearance during the distribution process, and a packaging container using the packaging material.

Means for Solving the Problems

[0008] As a result of earnestly studying the cause of the change in the appearance of the packaging material during the distribution process, the present inventors have found that the appearance of the packaging material changes when the intensity of the retort treatment is increased more than usual (specifically, retort treatment in a high temperature region of 130 ° C or higher) in the retort treatment for pressure heating sterilization. Then, the present inventors further repeated the study and completed the present invention.

[0009] That is, the present invention provides the following [1] to [3]. [1] A method for selecting a packaging material having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, When the printing layer has a glossy printing layer containing a bright pigment, and the bright pigment is a metal flake or a pearl pigment, the angle showing half the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 1 is d1, and the angle showing half the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d2, a method for selecting a packaging material, in which the following formula (1) is satisfied, is used as a pass line. |(d1 - d2) / d1|×100 ≦ 8.0% (1) <Measurement Condition 1> A black plate is bonded to the surface of the packaging material on the sealant layer side via a transparent adhesive layer, and a sample A is prepared by laminating the packaging material, the transparent adhesive layer, and the black plate. Visible light inclined 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side, and the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle with the specular reflection direction of the incident light as 0 degrees of the reference angle. <Measurement condition 2> The packaging material is subjected to retort treatment at 135 ° C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface of the retort-treated packaging material on the sealant layer side via a transparent adhesive layer, and a sample B is prepared by laminating the retort-treated packaging material, the transparent adhesive layer, and the black plate. Visible light inclined 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the retort-treated packaging material side, and the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle with the specular reflection direction of the incident light as 0 degrees of the reference angle.

[0010] [2] A packaging material having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, The printing layer has a glossy printing layer containing a phosphorescent pigment and inorganic particles having an average primary particle diameter of 1 to 100 nm, When the angle indicating half the intensity of the specular reflection direction of the packaging material measured under the above measurement condition 1 is d1, and the angle indicating half the intensity of the reflected light in the specular reflection direction of the packaging material measured under the above measurement condition 2 is d2, a packaging material that satisfies the following formula (1). |(d1 - d2) / d1| × 100 ≦ 8.0% (1) [3] A retort container at least partially formed of the packaging material described in [2] above.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a method for selecting a packaging material that can produce an aesthetic appearance with a metallic luster without using a metal layer and can suppress changes in appearance during the distribution process. Further, according to the present invention, it is possible to provide a packaging material that can produce an aesthetic appearance with a metallic luster without using a metal layer and can suppress changes in appearance during the distribution process, and a packaging container using the packaging material.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Modes for Carrying Out the Invention

[0013] Hereinafter, the packaging material of the present invention, as well as the packaging container and the lid using the packaging material, will be described in detail. In the present specification, the numerical range notation of "AA to BB" means "AA or more and BB or less". Further, hereinafter, the "intensity of reflected light" may be referred to as "reflection intensity".

[0014] [Selection method of packaging material] The selection method of the packaging material of the present invention is at least a selection method of a packaging material having a structure in which a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side. When the printing layer has a glossy printing layer containing a bright pigment, the angle showing half the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 1 is d1, and the angle showing half the reflection intensity in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d2. When the following formula (1) is satisfied, it is regarded as a passing line. |(d1 - d2) / d1|×100 ≦ 8.0% (1)

[0015] <Measurement condition 1> A black plate is bonded to the surface on the sealant layer side of the packaging material via a transparent adhesive layer to produce a sample A in which the packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side. With the specular reflection direction of the incident light as the reference angle of 0 degrees, the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle. <Measurement condition 2> The packaging material is subjected to retort treatment at 135°C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface on the sealant layer side of the retort-treated packaging material via a transparent adhesive layer, and a sample B in which the retort-treated packaging material, the transparent adhesive layer, and the black plate are laminated is produced. Visible light inclined 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the side of the retort-treated packaging material, and the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle with the specular reflection direction of the incident light as the reference angle of 0 degrees.

[0016] In the method for selecting the packaging material of the present invention, when having a glossy printing layer containing a glitter pigment as the printing layer, the angle showing the reflection intensity of 1 / 2 of the reflection intensity in the specular reflection direction of the packaging material measured under the above measurement condition 1 is d1, and the angle showing the reflection intensity of 1 / 2 of the reflection intensity in the specular reflection direction of the packaging material measured under the above measurement condition 2 is d2. A packaging material satisfying the above formula (1) is recognized as a passing line and selected. Hereinafter, each measurement condition and formula (1) will be described.

[0017] <<Measurement Conditions>> FIG. 8 is a diagram for explaining a method of measuring the reflection intensity of a packaging material. To measure the reflection intensity of a packaging material, first, a sample 100 in which a black plate 50 is bonded to the surface on the sealant layer 4 side of the packaging material 1 via a transparent adhesive layer 40 is produced. Next, visible light inclined 45 degrees from the normal direction of the sample 100 is incident on the surface of the sample 100 on the side of the packaging material 1. The solid arrow in FIG. 8 indicates the incident light. Then, with the specular reflection direction of the incident light (the direction of the broken arrow in FIG. 8) as the reference angle, the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle. The plus direction means the direction away from the incident light, and the minus direction means the direction approaching the incident light.

[0018] Under measurement condition 1, as the packaging material constituting sample A, a packaging material that has not been subjected to retort treatment or high retort treatment is used. Under measurement condition 2, as the packaging material constituting sample B, a packaging material that has been subjected to high retort treatment is used. Note that the packaging materials used for sample A and sample B may be cut out from the packaging container. For example, a pouch may be produced using a packaging material, the pouch may be subjected to high retort treatment, and the packaging material may be cut out from the treated pouch and used as the packaging material constituting sample B.

[0019] For the refractive index of the transparent adhesive layer 40 of sample 100, one with a refractive index difference within 0.05 from the refractive indices of the adherend 10 and the black plate 50 can be used, and preferably the refractive index difference is 0.00. In this specification, the refractive index means the refractive index at a wavelength of 589 nm. There are no particular restrictions on the apparatus for measuring the reflection intensity, and a general variable-angle photometer (goniophotometer) can be used. In the present invention, as the variable-angle photometer, the product number GP-200 (with an incident beam inclination angle within 0.5 degrees) manufactured by Murakami Color Research Laboratory was used, the scale of the light-receiving aperture was set to "4", and the scale of the light beam aperture was set to "3".

[0020] The high retort treatment under measurement condition 2 is performed for 30 minutes at a hot water temperature of 135°C using a batch-type hot water shower type retort apparatus. It is preferable to follow the conditions of the examples for further conditions of the high retort treatment.

[0021] <<Formula (1)>> The light reflected by the packaging material having a glossy printing layer containing a phosphorescent pigment has a strong intensity in the specular reflection direction and exhibits a metallic luster. Also, humans generally do not recognize the difference in intensity (brightness) within the range of the maximum intensity to 1 / 2 of the maximum intensity under normal attention. Therefore, the range of the maximum intensity to 1 / 2 of the maximum intensity can be said to be an important angular range for humans to feel the metallic luster. For this reason, it can be said that formula (1) shows the change rate of the important angular range for humans to feel the metallic luster before and after the high retort treatment.

[0022] When "|(d1 - d2) / d1|×100" in formula (1) exceeds 8.0%, it means that after high retort treatment, the range of angles at which humans feel a metallic luster will become significantly wider or significantly narrower. Therefore, packaging materials that do not satisfy formula (1) will change to a design unintended by the manufacturer when subjected to high retort treatment. Also, even if packaging materials that do not satisfy formula (1) have the same metallic luster feeling (the same appearance) at the time of manufacture, the metallic luster feeling of those subjected to high retort treatment and those not subjected to high retort treatment will be different during the distribution process, which may cause problems in product management or give consumers a sense of discomfort when the two are displayed side by side. For this reason, by using those that satisfy formula (1) as the pass line and selecting packaging materials that satisfy this, it is possible to suppress changes in the metallic luster feeling (changes in appearance) of the packaging material during the distribution process and stably supply packaging materials with a stabilized level of designability.

[0023] Also, when using metal flakes as the glitter pigment, not satisfying formula (1) indicates the possibility that the arrangement of the metal flakes in the gloss printing layer will fluctuate due to high retort treatment. For example, when the absolute value of formula (1) is removed and "((d1 - d2) / d1)×100" is less than -8.0%, it indicates the possibility that the arrangement of the metal flakes will be disrupted and the distance between the metal flakes will become narrower due to high retort treatment. And when the distance between the metal flakes becomes narrower, sparks may occur or local overheating may occur and holes may be generated when heating with a microwave oven. Therefore, by using those that satisfy formula (1) as the pass line and selecting packaging materials that satisfy this, it is possible to suppress the occurrence of sparks or the generation of holes due to local overheating when heating with a microwave oven after high retort treatment, and stably supply packaging materials with excellent safety. That is, the method for selecting the packaging material of the present invention is also useful as a method for selecting packaging materials for microwave ovens.

[0024] "|(d1 - d2) / d1| × 100" in formula (1) is preferably 6.0% or less, more preferably 4.0% or less.

[0025] Figure 9 is a diagram showing the reflection intensity distribution of the packaging material of Example 1. The solid line indicates the reflection intensity before the high retort treatment, and the dotted line indicates the reflection intensity after the high retort treatment. Further, Figure 10 is a diagram showing the reflection intensity distribution of the packaging material of Comparative Example 1. The solid line indicates the reflection intensity before the high retort treatment, and the dotted line indicates the reflection intensity after the high retort treatment. However, in Figures 9 and 10, the reflection intensity at the reference angle is set to 100, and the reflection intensity at each angle is normalized. From the comparison between Figures 9 and 10, it can be confirmed that the reflection intensity of the packaging material of Comparative Example 1 changes before and after the high retort treatment, while the reflection intensity of the packaging material of Example 1 hardly changes before and after the high retort treatment. The value of "|(d1 - d2) / d1| × 100" is 3.4% for Example 1 and 12.5% for Comparative Example 1.

[0026] The sorting method of the packaging material of the present invention is preferably applied to a packaging material excellent in metallic luster with d1 being 2.0 degrees or less. This is because in a packaging material that exhibits such a high degree of metallic luster, the stability of the design is highly regarded. d1 is more preferably 1.8 degrees or less, and even more preferably 1.7 degrees or less. In addition, when d1 is too small, the reflected light may be dazzling. Therefore, d1 is preferably 1.0 degrees or more, and more preferably 1.2 degrees or more.

[0027] In this specification, when the angle in the positive direction that first reaches an intensity of 1 / 2 or less of the intensity of the reflected light at the reference angle is "α1" and the angle in the negative direction that first reaches an intensity of 1 / 2 or less of the intensity of the reflected light at the reference angle is "α2", d1 and d2 refer to the angle calculated by the formula "(α1 + |α2|) / 2".

[0028] The method for selecting the packaging material of the present invention preferably uses, as the pass line, those that satisfy the following formula (2), where the angle indicating 1 / 20 of the intensity of the reflected light in the specular reflection direction of the packaging material measured under the above measurement condition 1 is d3, and the angle indicating 1 / 20 of the intensity of the reflected light in the specular reflection direction of the packaging material measured under the above measurement condition 2 is d4. |(d3 - d4) / d3|×100 ≦ 15.0% (2)

[0029] When a human observes a visual object from the specular reflection direction, the human can detect the brightness up to 1 / 20 of the reflection intensity of the reference angle. Therefore, by setting those that satisfy the above formula (2) as the pass line, the effects of the present invention can be further enhanced.

[0030] "|(d3 - d4) / d3|×100" in formula (2) is preferably 12.0% or less, more preferably 10.0% or less, and even more preferably 8.0% or less.

[0031] In this specification, when the angle in the positive direction that first reaches an intensity of 1 / 20 or less of the intensity of the reflected light at the reference angle is "η1", and the angle in the negative direction that first reaches an intensity of 1 / 20 or less of the intensity of the reflected light at the reference angle is "η2", d3 and d4 refer to the angles calculated by the formula "(η1 + |η2|) / 2".

[0032] Examples of the lustrous pigment of the gloss printing layer include metal flakes and pearl pigments. Regarding metal flakes and pearl pigments, they will be described in the embodiments of the packaging material of the present invention described later. The plastic film, printing layer, and sealant layer constituting the packaging material will also be described in the embodiments of the packaging material of the present invention described later.

[0033] [Packaging Material] The packaging material of the present invention is a packaging material having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, and has a glossy printing layer containing a bright pigment as the printing layer. When the angle indicating half of the reflection intensity in the specular reflection direction of the packaging material measured under the following measurement condition 1 is d1, and the angle indicating half of the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d2, it satisfies the following formula (1). |1 - (d2 / d1)|×100 ≦ 8.0% (1)

[0034] <Measurement condition 1> A black plate is bonded to the surface of the sealant layer side of the packaging material via a transparent adhesive layer to produce a sample A in which the packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side, and the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle with the specular reflection direction of the incident light as the reference angle of 0 degrees. <Measurement condition 2> The packaging material is subjected to retort treatment at 135°C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface of the sealant layer side of the retort-treated packaging material via a transparent adhesive layer to produce a sample B in which the retort-treated packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the retort-treated packaging material side, and the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle with the specular reflection direction of the incident light as the reference angle of 0 degrees.

[0035] Details of Measurement Conditions 1 and 2 are the same as those of the above-described method for selecting the packaging material of the present invention. Also, the embodiments of formula (1), the embodiments of d1, the technical objections to formula (1), and the technical objections to d1 are the same as those of the above-described method for selecting the packaging material of the present invention.

[0036] Further, with respect to the packaging material of the present invention, when the angle at which the intensity of the reflected light in the specular reflection direction of the packaging material measured under the above measurement condition 1 is 1 / 20 of the intensity is defined as d3, and the angle at which the intensity of the reflected light in the specular reflection direction of the packaging material measured under the above measurement condition 2 is 1 / 20 of the intensity is defined as d4, it preferably satisfies the following formula (2). |(d3 - d4) / d3|×100 ≦ 15.0% (2)

[0037] The embodiments of formula (2) and the technical objections to formula (2) are the same as those of the above-described method for selecting the packaging material of the present invention.

[0038] <Laminated structure> Figs. 1 to 4 show schematically the laminated structure in the thickness direction of the packaging material of the present invention. In Figs. 1 to 4, the upper side is the outer layer side and the lower side is the inner layer side. The packaging material 1 only needs to have at least a plastic film 2, a gloss printing layer 3a, and a sealant layer 4 laminated in this order from the outer layer side, and may include other layers as constituent layers. For example, as shown in Figs. 1 to 4, an intermediate base material layer 5 laminated via an adhesive layer 6 on both sides may be provided between the gloss printing layer 3a and the sealant layer 4. Further, as shown in Fig. 2, a pattern printing layer 3b may be provided on the outer layer side of the gloss printing layer 3a, or as shown in Fig. 4, a pattern printing layer 3b may be provided in parallel with the gloss printing layer 3a. Further, as shown in Fig. 3, a black background printing layer 3c may be provided in contact with the inner layer side of the gloss printing layer 3a. Further, as shown in Fig. 4, a white background printing layer 3d may be provided on the inner layer side of the gloss printing layer 3a. Although not shown, a white background printing layer 3d may be provided on the inner layer side of the gloss printing layer 3a in Figs. 1 to 3 Further, a gas barrier layer (not shown) may be formed between the plastic film 2 and the gloss printing layer 3a or between the gloss printing layer 3a and the sealant layer 4. Specifically, the laminated structure of the packaging material of the present invention can be exemplified as follows in order from the outer layer side. Note that " / " means the boundary of each layer. (1) Plastic film / Gloss printing layer / Intermediate base material layer / Sealant layer (2) Plastic film / Gas barrier layer / Gloss printing layer / Sealant layer (3) Plastic film / gas barrier layer / gloss printing layer / intermediate base material layer / sealant layer (4) Plastic film / gloss printing layer / gas barrier layer / intermediate base material layer / sealant layer From the viewpoint of making the gloss printing layer 3 visible from the outside, the layer formed on the outer layer side of the gloss printing layer 3a shall have light transmissibility.

[0039] <Plastic film> The plastic film 2 serves as a base material on the outer layer side of the packaging material 1 and is composed of a material having light transmissibility so that the gloss printing layer 3a can be visually recognized from the appearance. Specifically, for example, polyolefin resins such as polyethylene (PE) - based and polypropylene (PP) - based resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile - styrene copolymer (AS) resins, acrylonitrile - butadiene - styrene copolymer (ABS) resins, poly (meth) acrylic resins, polycarbonate resins, polyvinyl alcohol resins, ethylene - vinyl alcohol copolymer (EVOH), saponified ethylene - vinyl ester copolymer, polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyamide resins such as various nylons (Ny), polyurethane resins, acetal resins, cellulose resins, polyvinylidene chloride resins (PVDC), etc. may be mentioned. The plastic film may be uniaxially stretched or biaxially stretched. Also, a composite film in which two or more of the above resin films are laminated may be used. These plastic films may be formed by an inflation method or a melt extrusion coating method.

[0040] From the viewpoints of heating in a microwave oven and retort treatment, the plastic film preferably has excellent heat resistance. Examples of the resin constituting the plastic film with excellent heat resistance include polyester resins and polyamide resins. Specific examples of the plastic film excellent in heat resistance include a single polyester film, a single polyamide film such as nylon, and a composite film containing one or more of a polyester film and a polyamide film. Examples of the composite film include a co-extruded stretched film having a PET / Ny configuration from the outer layer side, such as PET / Ny / PET. Further, as the composite film, it is also preferable to combine one or more of a polyester film and a polyamide film with one or more of an ethylene-vinyl alcohol copolymer film and a polyvinylidene chloride film.

[0041] The thickness of the plastic film 2 is not particularly limited and can be appropriately set according to the use of the packaging material 1. Usually, it is preferably about 5 to 50 μm, more preferably 10 to 40 μm, and even more preferably 12 to 25 μm.

[0042] <Gloss printing layer> The packaging material of the present invention has a gloss printing layer containing a glitter pigment between the plastic film and the sealant layer. As shown in FIGS. 1 to 3, the gloss printing layer 3a may be provided on the entire surface of the packaging material, or as shown in FIG. 4, it may be provided only on a part of the packaging material. Further, as shown in FIG. 2, a pattern printing layer 3b may be provided on a part of the outer layer side of the gloss printing layer 3a. Further, as shown in FIG. 4, the gloss printing layer 3a and the pattern printing layer 3b may be provided in parallel at the same position in the thickness direction of the packaging material. Further, a pattern such as a character, a figure, a symbol, a pattern, or a pattern may be formed by the gloss printing layer 3a.

[0043] Examples of the glitter pigment include a pearl pigment and metal flakes. Among these, a pearl pigment that can be easily inked without using a high-boiling solvent such as mineral spirit is preferable. Further, the pearl pigment can easily impart resistance to a microwave oven, and is also preferable in that its shape and the like are less likely to change even by a high retort treatment and it is easy to satisfy formulas (1) and (2). More specifically regarding microwave resistance, when the packaging material is processed by heat sealing, if the pearlescent pigment is a metallic flake, during heat sealing, the distance between the metallic flakes tends to become close. In the case of a packaging material for a microwave oven, the risk of spark generation due to microwaves in the microwave oven increases. On the other hand, in the case of a pearl pigment, even when the distance between the pearl pigments becomes close during heat sealing, the above-mentioned risk does not occur during heating in a microwave oven.

[0044] The pearl pigment is a thin-plate-shaped fine particle having a coating layer made of a high refractive index material such as titanium dioxide on the surface of scaly fine particles of mica, and has light transmissibility. Therefore, when the thin-plate-shaped fine particles are arranged in layers, light is multiply reflected, and a luster similar to that of metal or pearl can be produced. As described above, the pearl pigment is not a metal itself, but is mainly composed of metal oxides, and is a colorant that can produce a metallic luster.

[0045] There are several types of the pearl pigments, and they can be mainly classified into three types: white pearl pigment, interference pearl pigment, and colored pearl pigment. The white pearl pigment has a coating layer of mica made of a colorless high refractive index material such as titanium dioxide, and the thickness of the coating layer is relatively small, about 0.1 to 0.15 μm. Since it reflects almost all wavelengths of light, it appears white or silver. The interference pearl pigment has a coating layer of mica made of a colorless high refractive index material such as titanium dioxide, and the thickness of the coating layer is larger than that of the white pearl pigment and exceeds 0.15 μm. Due to this thickness, the reflected light and the transmitted light change, producing various interference colors. It may also be called an iridescent pearl. The colored pearl pigment is colored, and examples include those having a coating layer of mica made of a colored high refractive index material such as ferric oxide, those having the periphery of the white pearl pigment further coated with a colored high refractive index material such as ferric oxide or other colored pigments, or those having a pigment or other colorant added to the coating layer of mica.

[0046] The pearl pigment may be any of the above types. From the perspective of obtaining a pearl coating color with higher brightness and a sense of luxury when viewed from any direction, it preferably contains one or more selected from white pearl pigments and interference pearl pigments, and one or more selected from colored pearl pigments. As one or more selected from white pearl pigments and interference pearl pigments, a white pearl pigment is preferred. As one or more selected from colored pearl pigments, those in which the coating layer of mica is a colored high refractive index material such as ferric oxide and those in which the periphery of the white pearl pigment is coated with a colored high refractive index material are preferred. In this case, particularly, in order to obtain a deep golden luster when viewed from any direction, as the colored pearl pigment, it is preferable to use a colored pearl pigment in which the periphery of the white pearl pigment is coated with ferric oxide or a colored pearl pigment in which the coating layer of mica is ferric oxide. Furthermore, as one or more selected from white pearl pigments and interference pearl pigments, it is more preferable to use a white pearl pigment.

[0047] When one or more (A) selected from white pearl pigments and interference pearl pigments and one or more (B) selected from colored pearl pigments are used in combination, A:B is preferably 1:0.2 to 1:20 by mass ratio, more preferably 1:0.5 to 1:15, and even more preferably 1:1 to 1:10.

[0048] The particle size of the pearl pigment is not particularly limited, and the average particle size is preferably 5 to 60 μm, more preferably 5 to 30 μm. In this specification, the average particle size refers to the average value of the major axis lengths of any 20 particles observed with an optical microscope.

[0049] The content of the pearl pigment in the gloss printing layer is preferably 40% by mass or more and 90% by mass or less of the total solid content of the gloss printing layer, more preferably 50% by mass or more and 85% by mass or less, and even more preferably 60% by mass or more and 80% by mass or less. Pearl pigments are suitable in that even when added in a large amount, they can suppress the generation of sparks and local overheating when heated in a microwave oven. Further, as described above, by adding a large amount of pearl pigment, it is possible to make the pearl pigment difficult to flow during high retort treatment, and it is easy to satisfy formulas (1) and (2).

[0050] Examples of the material of the metal flakes include metals and alloys such as aluminum, gold, silver, brass, titanium, chromium, nickel, nickel chromium, and stainless steel. The metal flakes can be obtained, for example, by (i) peeling a metal thin film formed by vacuum-depositing the above metal or alloy on a plastic film from the plastic film and pulverizing and stirring the peeled metal thin film, (ii) mixing the powder of the above metal or alloy and a solvent, and spreading and / or pulverizing the powder with a medium stirring mill, a ball mill, an attritor, etc.

[0051] When using metal flakes as the lustrous pigment, from the viewpoint of facilitating satisfaction of formulas (1) and (2), those produced by the method (i) above are preferred. On the other hand, the metal flakes produced by the method (ii) above are disadvantageous materials from the viewpoint of satisfying formulas (1) and (2). Specifically, in this regard, the metal flakes produced by the method (ii) above are made into a flaky shape by stretching the metal powder, so wrinkles are likely to occur on the surface of the metal flakes, and strain accumulates in the metal flakes. Then, when the metal flakes produced by the method (ii) above are subjected to high heat during high retort treatment, the strain is released, and the shape changes due to the restoration of the wrinkles generated on the surface. For this reason, the metal flakes produced by the method (ii) above are likely to have a change in the intensity distribution of reflected light due to high retort treatment. That is, the metal flakes produced by the method (ii) above are difficult to satisfy formulas (1) and (2).

[0052] The metal flakes preferably have an average length of 1 to 50 μm, more preferably 2 to 30 μm, and even more preferably 5 to 20 μm. By setting the average length to 1 μm or more, aggregation can be easily suppressed, and by setting the average length to 50 μm or less, when the metal flakes are tilted in the gloss printing layer, it is possible to make it difficult for them to come into contact with other metal flakes.

[0053] The metal flakes preferably have an average thickness of 0.01 to 5 μm, more preferably 0.02 to 3 μm, and even more preferably 0.05 to 1 μm. By setting the average thickness to 0.01 μm or more, it is easy to improve the handleability and metallic luster, and by setting it to 5 μm or less, it is possible to suppress the narrowing of the distance between the metal flakes due to the tilting of the metal flakes in the gloss printing layer. Also, the metal flakes preferably have an aspect ratio defined by [average length / average thickness] of 50 to 500, more preferably 60 to 450, and even more preferably 70 to 400.

[0054] The average length and average thickness of the metal flakes are the average values of 20 metal flakes. The length and thickness of each individual metal flake can be measured by using a laser interference type three-dimensional shape analyzer in a state where the metal flakes are scattered on a smooth substrate. The length of each individual metal flake means the maximum diameter when observing each individual metal flake from a plane in an arbitrary direction, and the thickness of each individual metal flake means the maximum thickness when observing each individual metal flake from the cross-sectional direction. Note that the maximum diameter when observing each individual metal flake from a plane in an arbitrary direction is for the purpose of unifying the direction in which the maximum diameter of each individual metal flake is measured. For example, when the X-axis direction on the screen obtained by image processing the measurement result of the three-dimensional shape analyzer is set as an arbitrary direction (measurement direction), the maximum diameter is measured in a direction parallel to the X-axis. Even if there is a maximum diameter in a direction not parallel to the X-axis, it is not regarded as the maximum diameter. Examples of the laser interference type three-dimensional shape analyzer include the product name "Shape Analysis Laser Microscope VK-X Series" manufactured by Keyence Corporation.

[0055] From the perspective of suppressing the generation of sparks and local overheating when heating in a microwave oven, the content of metal flakes in the glossy printing layer is preferably 3% by mass or more and less than 40% by mass of the total solid content of the glossy printing layer, more preferably 10% by mass or more and 30% by mass or less.

[0056] The glossy printing layer preferably contains 0.5% by mass or less of a black pigment. By including a small amount of black pigment in the glossy printing layer, the light that is not reflected by the pearlescent pigment present near the surface layer can be absorbed by the black pigment, suppressing the diffuse reflection on the inner layer side compared to the glossy printing layer, and improving the metallic luster. In particular, when the pearlescent pigment is a pearl pigment, by including a small amount of black pigment in the glossy printing layer, the complementary color transmitted through the pearl pigment is suppressed from being reflected on the inner layer side compared to the glossy printing layer, so that a deep pearl coating color can be obtained.

[0057] The content of carbon black in the glossy printing layer is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less. Also, from the perspective of facilitating the obtaining of a deep pearl coating color, the lower limit of the content of carbon black in the glossy printing layer is preferably 0.0001% by mass or more.

[0058] Examples of the black pigment include carbon black and titanium black. Also, a black pigment having near-infrared reflectivity or near-infrared transmissivity, which will be described later, can be used.

[0059] From the perspective of enhancing the absorbability in the visible light region, the average primary particle size of the black pigment is preferably 0.1 μm or more, more preferably 0.2 μm or more. The upper limit of the average primary particle size of the black pigment is not particularly limited, but is preferably 3.0 μm or less, more preferably 2.0 μm or less, and even more preferably 1.0 μm or less. The average primary particle size of the black pigment is determined as the mass average value d50 in the particle size distribution measurement by the laser light diffraction method.

[0060] In the gloss printing layer, in order to enhance the design property, it is preferable to contain a colorant other than the black pigment. As the colorant, general-purpose dyes and pigments (for example, inorganic pigments such as lead yellow, titanium yellow, Indian red, cadmium red, ultramarine blue, cobalt blue, etc., organic pigments or dyes such as quinacridone red, isoindolinone yellow, phthalocyanine blue, etc.) can be used.

[0061] The content of the colorant is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and even more preferably 30 to 50 parts by mass with respect to 100 parts by mass of the metal flakes.

[0062] It is preferable that the gloss printing layer contains inorganic particles having an average primary particle diameter of 1 to 100 nm (hereinafter sometimes referred to as "inorganic fine particles"). By containing inorganic fine particles in the gloss printing layer, it is possible to make it difficult to flow the bright pigment in the gloss printing layer during the high retort treatment, and it is possible to easily satisfy formulas (1) and (2). In particular, when the bright pigment is metal flakes, the inorganic fine particles are effective. The average primary particle diameter of the inorganic fine particles is more preferably 2 to 50 nm, and even more preferably 5 to 30 nm. The average primary particle diameter of the inorganic fine particles is determined as the mass average value d50 in the particle size distribution measurement by the laser light diffraction method.

[0063] The content of the inorganic fine particles in the gloss printing layer is preferably 10 to 70 parts by mass, more preferably 15 to 50 parts by mass, and even more preferably 20 to 35 parts by mass with respect to 100 parts by mass of the bright pigment.

[0064] Examples of the inorganic fine particles include silica, alumina, zirconia, and titania. Among these, silica having excellent transparency is preferable. Further, since silica and alumina have excellent insulating properties, they are also preferable in terms of improving the electron range resistance.

[0065] From the perspective of being able to sufficiently impress metallic luster, the thickness of the glossy printing layer is preferably 1 to 10 μm, more preferably 1.5 to 5 μm.

[0066] The glossy printing layer 3a, as well as the pattern printing layer 3b, black background printing layer 3c, and white background printing layer 3d (hereinafter, these may be collectively referred to as "printing layers") can be formed, for example, on the plastic film 2, the sealant layer 4, etc., by using a known printing method such as a gravure printing method, an offset printing method, a relief printing method, or a silk screen printing method and using a known ink. The printing layer is preferably formed by reverse printing on the inner surface of the plastic film 2 or the inner layer side of the gas barrier layer. Alternatively, it may also be formed by surface printing on the outer surface of the intermediate base material layer 5 or the sealant layer 4 and then being bonded to the plastic film 2 or the gas barrier layer through an adhesive layer. Also, it may be full-surface printing or partial printing on the packaging material 1.

[0067] The ink of the printing layer usually has a vehicle composed mainly of a binder resin and a solvent, and a colorant such as a dye or a pigment is added and mixed therein (the glossy printing layer 3a contains a bright pigment as an essential component). The colorant of the printing layer may be used alone or in combination of two or more.

[0068] Examples of the binder resin include polyolefin resins such as polyethylene resins and chlorinated polypropylene resins, poly(meth)acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymers, polystyrene resins, styrene-butadiene copolymers, vinylidene fluoride resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyvinyl butyral resins, polybutadiene resins, polyester resins, polyamide resins, alkyd resins, epoxy resins, unsaturated polyester resins, thermosetting poly(meth)acrylic resins, melamine resins, urea resins, polyurethane resins, phenol resins, xylene resins, maleic resins, cellulose resins such as nitrocellulose, ethyl cellulose, acetyl butyl cellulose, and ethyl oxyethyl cellulose, rubber resins such as chlorinated rubber and cyclized rubber, petroleum resins, natural resins such as rosin and casein, and the like.

[0069] Further, from the viewpoint of suppressing the flow of the pearlescent pigment in the gloss printing layer during high retort and facilitating the satisfaction of formulas (1) and (2), the binder resin of the gloss printing layer preferably has a melting point of 130°C or higher. More preferably, the melting point of the binder resin of the gloss printing layer is 140°C or higher, and even more preferably 150°C or higher. In the present specification, the resin having a melting point of AA°C or higher includes not only resins whose melting points are observed at AA°C or higher, but also resins whose melting points are not observed below AA°C and at AA°C or higher.

[0070] In the printing layer-forming ink, optionally, for example, fillers, stabilizers, plasticizers, antioxidants, light stabilizers such as ultraviolet absorbers, dispersants, thickeners, desiccants, lubricants, antistatic agents, crosslinking agents, and other arbitrary additives can be added as necessary.

[0071] As the solvent contained in the ink of the printing layer, solvents used in ordinary pigment inks can be applied. For example, alcohol-based solvents such as methanol, ethanol, normal propanol, isopropanol, propylene glycol monomethyl ether, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ester-based solvents such as methyl acetate, ethyl acetate, normal propyl acetate, aliphatic hydrocarbon-based solvents such as normal hexane, normal heptane, normal octane, alicyclic hydrocarbon-based solvents such as cyclohexane, methylcyclohexane, cycloheptane, aromatic solvents such as toluene, xylene, and mineral spirit. These may be used alone or in combination of two or more. Among these, from the viewpoints of the working environment during printing and food hygiene, etc., it is preferable not to contain aromatic solvents.

[0072] Also, generally, in inks containing metal flakes such as aluminum paste, mineral spirit is contained in the solvent. However, mineral spirit has a high boiling point of 162 to 192 °C at 1 atm. Even when a heat drying treatment is performed after printing, it is difficult to completely volatilize and remove it. Even with a small residual amount, the produced packaging material may generate a solvent odor. It is not preferable for the packaging material to generate such a solvent odor. In particular, when the packaged product by the packaging material is food, it is required to generate as little solvent odor as possible. Therefore, as the solvent used in the ink for forming the printing layer, it is not preferable to use a high-boiling solvent such as mineral spirit. The boiling point at 1 atm is preferably 150 °C or lower, more preferably 130 °C or lower, and still more preferably 120 °C or lower.

[0073] <Pattern printing layer> The packaging material of the present invention may have a pattern printing layer 3b between the plastic film 2 and the sealant layer 4. The pattern printing layer 3b can be formed, for example, on the outer layer side of the gloss printing layer 3a (Fig. 2), or can be formed in parallel with the gloss printing layer 3a at the same position in the thickness direction of the packaging material (Fig. 4).

[0074] The pattern printing layer 3b may be a printing layer formed from a color distinguishable from that of the gloss printing layer 3a, and is a broad concept including characters, figures, symbols, patterns, designs, solid printing, etc. The colorant for the pattern printing layer 3b may use general-purpose dyes and pigments (for example, inorganic pigments such as lead yellow, titanium yellow, rose pink, cadmium red, ultramarine blue, cobalt blue, etc., organic pigments or dyes such as quinacridone red, isoindolinone yellow, phthalocyanine blue, etc.). The thickness of the pattern printing layer is not particularly limited, and is preferably about 1.5 to 5 μm, more preferably 1.5 to 3 μm.

[0075] <Black background printing layer> When the lustrous pigment is a pearl pigment, from the viewpoint of imparting depth and a sense of solidity to the metallic luster of the pearl pigment, as shown in FIG. 3, it is preferable that a black background printing layer 3c is provided in contact with the inner layer side of the gloss printing layer 3a. The black background printing layer is the L of the International Commission on Illumination (CIE) standard measured in accordance with JIS Z8781-4:2013 * a * b * L in the color system * The value is preferably 20 or less, more preferably 10 or less. The black background printing layer may be formed on the entire surface of the portion having the gloss printing layer, or may be formed only on a part of the portion having the gloss printing layer. When the black background printing layer is formed on the entire surface of the portion having the gloss printing layer, the above-described effect can be obtained on the entire surface of the gloss printing layer. Further, when the black background printing layer is formed on a part of the portion having the gloss printing layer, a change in metallic luster can be imparted in the plane. The black background printing is preferably single-color solid printing.

[0076] The thickness of the black background printing layer is sufficient to enhance the metallic luster of the gloss printing layer 3a by the pearl pigment, is not particularly limited, and is preferably about 1.5 to 5 μm, more preferably 1.5 to 3 μm.

[0077] The method for forming the black background printing layer is not particularly limited, but it can be formed by printing with an ink using a black dye, pigment, or the like as a colorant by the printing method described above. From the viewpoint of developing a stable black as the background color, it is preferable to use a black pigment as the black colorant. As the black pigment for the black background printing layer, a black pigment having near-infrared reflectivity or near-infrared transmissivity is preferable. Examples of the black pigment having near-infrared reflectivity include composite oxides containing manganese as an essential component and at least one metal element other than manganese, and examples of the black pigment having near-infrared transmissivity include azomethine azo pigments and perylene-based pigments.

[0078] Since the composite oxide has near-infrared reflection characteristics, the packaging material 1 provided with the black background printing layer formed thereby can also have the property of heat retention of the packaged product. The metal element other than manganese contained in the composite oxide may be a single species or a combination of two or more species. Examples of the metal element other than manganese contained in the composite oxide include Group 2 elements such as calcium and barium; Group 3 elements such as yttrium, lanthanum, praseodymium, and neodymium; Group 4 elements such as titanium and zirconium; Group 13 elements such as boron, aluminum, gallium, and indium; and Group 15 elements such as antimony and bismuth. Among these, Group 2 elements, Group 4 elements, and Group 15 elements are preferable, calcium, titanium, and bismuth are more preferable, and calcium and titanium are even more preferable. A particularly preferable specific example of the composite oxide is a composite oxide containing manganese, calcium, and titanium. The structure of the composite oxide is not particularly limited, but from the viewpoints of a stable structure and its color development, etc., it is preferably a perovskite structure, an orthorhombic structure, a hexagonal structure, etc., and more preferably a perovskite structure. The manganese-based composite oxide is described, for example, in WO2016 / 125906A1.

[0079] The azomethine azo-based pigment has a diazonium group which is a reaction compound of tetrachlorophthalimide and aminoaniline. The perylene-based pigment is a pigment having a structure in which two oxygen atoms constituting the six-membered ring of perylene tetracarboxylic dianhydride are removed, and examples thereof include perylene black.

[0080] The average particle diameter of the black pigment in the black undercolor printing layer can be in the same range as the average particle diameter of the black pigment in the gloss printing layer.

[0081] From the viewpoints of enhancing the metallic gloss and balancing the coating film strength, the content of the black pigment in the black undercolor printing layer is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and still more preferably 20 to 40% by mass of the total solid content constituting the black undercolor printing layer.

[0082] As the black pigment in the black undercolor printing layer, it is also possible to use general-purpose black pigments such as carbon black and titanium black. However, when the packaging material 1 is for a microwave oven, there is a risk that the portion where carbon black, titanium black, etc. are present may be locally overheated by the microwave of the microwave oven, causing holes in the packaging material. Therefore, when using general-purpose black pigments such as carbon black and titanium black for a microwave oven, attention such as suppressing the content is necessary.

[0083] <White undercolor printing layer> As shown in FIG. 4, the packaging material of the present invention preferably has a white undercolor printing layer 3d on the inner layer side of the gloss printing layer 3a. By forming the white undercolor printing layer, depending on the type of the object to be packaged, etc., the appearance of the object to be packaged can be improved. When having the above-described black undercolor printing layer, it is preferable to form the white undercolor printing layer on the inner layer side of the black undercolor printing layer. The white undercolor printing layer is preferably formed by solid-color solid printing.

[0084] The white background printing layer may be formed only on a part of the surface of the packaging material. However, from the perspective of facilitating the above-described effects, as shown in FIG. 4, it is preferably formed on the entire surface of the packaging material. As the colorant for the white background printing layer, a general-purpose white pigment can be used. In addition, in order to adjust the color tone of the white background printing layer, dyes and pigments other than white pigments may be used as the colorant. The thickness of the white background printing layer is not particularly limited, and is preferably about 1.5 to 5 μm, more preferably 1.5 to 3 μm.

[0085] <Sealant layer> The sealant layer 4 has a role of protecting the packaged product with the inner surface directly contacting the packaged product. In particular, when the packaging material 1 forms a packaging container for a liquid substance, the sealant layer 4 is preferably made of a material that does not allow the liquid substance to penetrate. Also, it is preferable that the innermost layer of the sealant layer 4 has heat sealability for forming a pouch.

[0086] Examples of the material constituting the sealant layer 4 include polyolefin resins such as low-density PE (LDPE), linear low-density PE (LLDPE), medium-density PE (MDPE), high-density PE (HDPE), ethylene-vinyl acetate copolymer, propylene homopolymer, ethylene-propylene block copolymer, and ethylene-propylene random copolymer. One or more of these resins can be used. The sealant layer 4 may be composed of a single layer or multiple layers of two or more layers. Note that the sealant layer is preferably an unstretched film made of the above-described resin in order to suppress shrinkage during heat sealing.

[0087] From the viewpoints of heating in a microwave oven and retort processing, in order to enhance heat resistance, the sealant layer is preferably composed of a resin having excellent heat resistance. Specifically, propylene-based resins such as propylene homopolymer, ethylene-propylene block copolymer, and ethylene-propylene random copolymer, and HDPE are preferable. Also, it is preferable to use the above propylene-based resin appropriately according to the purpose. Specifically, when emphasizing cold resistance performance (for example, packaging material for frozen foods), an ethylene-propylene block copolymer is preferable; when emphasizing transparency, an ethylene-propylene random copolymer is preferable; when emphasizing heat resistance, a propylene homopolymer is preferable. Also, in the case of a container equipped with an automatic steam venting mechanism, an ethylene-propylene block copolymer is preferable from the viewpoint that steam can easily escape due to a decrease in seal strength at high temperatures.

[0088] Also, when the lid of the container with a lid is formed of the packaging material 1, the sealant layer 4 preferably has easy peelability. Easy peelability means, for example, when the sealant layer 4 of the packaging material 1 of the lid of the container with a lid is joined to the container body, the lid can be easily peeled from the container body when opening the container with a lid. A sealant layer having easy peelability can be formed by mixing two or more resins, one resin (a resin having good adhesion to the container body) and another resin (a resin having poor adhesion to the container body and being incompatible with the one resin). Such resins vary depending on the material of the container and cannot be generally stated. However, when the container is formed of PP, a resin obtained by mixing PP, which is one resin (a resin having good adhesion to the container body), with one or more selected from PE, polybutene, and polystyrene, which are other resins (resins having poor adhesion to the container body and being incompatible with the one resin), can impart easy peelability to a PP container. Note that the sealant layer may have a multilayer structure, and easy peelability may be imparted only to the side of the sealant layer joined to the container body (the innermost layer in the packaging material).

[0089] The thickness of the sealant layer 4 is not particularly limited and is appropriately set according to the use of the packaging material 1 and the type and properties of the packaged product, etc. Usually, it is preferably about 10 to 200 μm. In the case of a pouch (especially a retort pouch), the thickness of the sealant layer 4 is more preferably 20 to 150 μm, and even more preferably 30 to 100 μm. In the case of a container with a lid, the thickness of the sealant layer 4 is more preferably 15 to 80 μm, and even more preferably 20 to 60 μm.

[0090] <Gas barrier layer> The gas barrier layer can be provided between the plastic film 2 and the sealant layer 4 as needed. The gas barrier layer plays a role of blocking the permeation of oxygen, water vapor, etc. between the packaged product by the packaging material 1 and the external environment of the packaging material 1. Further, it may also impart light-shielding properties that block the permeation of visible light, ultraviolet light, etc. The gas barrier layer may be composed of only one layer or may be composed of a plurality of two or more layers. When the gas barrier layer is formed on the outer layer side of the gloss printing layer 3a, like the plastic film 2, it is composed of a material having light transmissivity so that the gloss printing layer 3a can be visually recognized from the outside.

[0091] The gas barrier layer can be formed as a vapor deposition film or a coating film by a known method. Note that the surface on which the gas barrier layer is formed may be subjected to surface treatment in advance from the viewpoint of improving the adhesion of the gas barrier layer. Examples of the surface treatment include corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas, nitrogen gas, etc., glow discharge treatment, oxidizing agent treatment, application of an anchor coat agent, etc.

[0092] 〔Vapor deposition film〕 As an example of the vapor deposition film which is a gas barrier layer, for example, it can be formed of an inorganic substance such as silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr), yttrium (Y), or an oxide thereof. Among these, when the packaging material is for a microwave oven, from the viewpoint of enabling the food or the like of the packaged product to be sufficiently heated by the microwave of the microwave oven, inorganic oxides such as silicon oxide, aluminum oxide, magnesium oxide are preferable. Examples of the method for forming the vapor deposition film include physical vapor deposition (PVD) methods such as vacuum vapor deposition, sputtering, ion plating, and chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photo chemical vapor deposition.

[0093] The film thickness of the vapor deposition film varies depending on the forming material, the required gas barrier performance, etc., but usually, it is preferably about 5 to 200 nm, more preferably 5 to 150 nm, and even more preferably 10 to 100 nm. In the case of inorganic oxides such as silicon oxide and aluminum oxide, it is preferably about 5 to 100 nm, more preferably 5 to 50 nm, and even more preferably 10 to 30 nm.

[0094] 〔Gas barrier coating film〕 As an example of the gas barrier coating film which is a gas barrier layer, for example, at least one or more alkoxides represented by the general formula R 1 n M(OR 2 ) m (In the formula, R 1 , R 2 are organic groups having 1 to 8 carbon atoms, and M is a metal atom. n represents an integer of 0 or more, m represents an integer of 1 or more, and n + m is the valence of M.) and a polyvinyl alcohol-based resin and / or an ethylene-vinyl alcohol copolymer are polycondensed by the sol-gel method in the presence of a sol-gel method catalyst, an acid, water, and an organic solvent, and the obtained coating liquid is applied and heat-treated at 50 to 300 ° C for 0.05 to 60 minutes to form it. As the coating method, for example, it can be carried out by coating means such as roll coating with a gravure roll coater, spray coating, spin coating, dipping, brush, bar coating, applicator, etc. It is preferable that the dry film thickness of the coating film is about 0.01 to 30 μm by one or more coatings, more preferably 0.05 to 20 μm, and still more preferably 0.1 to 10 μm. From the viewpoint of improving the gas barrier property, the gas barrier coating film is preferably formed on the surface of the vapor deposition film.

[0095] Considering the specific configuration of the gas barrier layer, as the packaging material of the present invention, the following laminated structures (1') to (4') can be exemplified in order from the outer layer side. Note that " / " means the boundary of each layer. (1') Plastic film / Vapor deposition film / Glossy printing layer / Sealant layer (2') Plastic film / Vapor deposition film / Gas barrier coating film / Glossy printing layer / Sealant layer (3') Plastic film / Glossy printing layer / Vapor deposition film / Intermediate base material layer / Sealant layer (4') Plastic film / Glossy printing layer / Gas barrier coating film / Vapor deposition film / Intermediate base material layer / Sealant layer

[0096] <Intermediate base material layer> The intermediate base material layer is a layer provided as needed for the purpose of improving the strength of the packaging material 1, improving the processability, changing the texture of the packaging material, or using it as a base material for forming other layers. Examples of the constituent material of the intermediate base material layer include plastic films and paper. In the case of a plastic film, the same one as the above-mentioned plastic film formed on the outer layer side of the glossy printing layer 3a can be used. In the case of paper, characteristics such as formability, bend resistance, and rigidity can also be imparted to the packaging material 1. For example, high-sizing bleached or unbleached kraft paper, pure white roll paper, paperboard, various processed papers, etc. can be used. The basis weight of the paper is usually preferably about 50 to 600 g / m 2 and more preferably 60 to 500 g / m 2, more preferably 70 to 450 g / m 2 . When the packaging material 1 is for flexible packaging use, it is preferably less than 150 g / m 2 . When it is for paper container use such as paper cups and liquid paper containers, it is preferably 200 g / m 2 or more.

[0097] From the viewpoints of heating in a microwave oven and retort processing, in order to enhance heat resistance, the intermediate base material layer is preferably one having excellent heat resistance. Specific examples of the intermediate base material layer having excellent heat resistance include the plastic films exemplified as the packaging material plastic films for microwave ovens and retort containers, and paper.

[0098] <Adhesive layer> In the packaging material 1, each constituent layer may be laminated via an adhesive layer 6 from the viewpoint of improving the bonding strength between the layers. The adhesive layer can be formed by a method using a known adhesive for dry lamination. Examples of the adhesive for dry lamination include polyvinyl acetate-based adhesives, polyacrylate-based adhesives, cyanoacrylate-based adhesives, ethylene copolymer-based adhesives, cellulose-based adhesives, polyester-based adhesives, polyamide-based adhesives, polyimide-based adhesives, amino resin-based adhesives such as urea resins and melamine resins, phenol resin-based adhesives, epoxy-based adhesives, polyurethane-based adhesives (for example, cured products of polyols and isocyanate compounds), reactive (meth)acrylic acid-based adhesives, rubber-based adhesives such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber, silicone-based adhesives, and inorganic-based adhesives such as alkali metal silicates and low melting point glasses.

[0099] <Thermoplastic resin layer> As shown in FIG. 11, the packaging material 1 may have a thermoplastic resin layer 7 in a part of the region between the plastic film and the sealant layer. As shown in Fig. 11, the heat-softening resin layer 7 is formed in a part near the edge of the packaging material 1, and the heat-softening resin layer is composed of a resin that has a predetermined strength in a temperature environment of room temperature or lower but whose strength decreases in a high-temperature environment. By heating it in a microwave oven, when the pressure inside the packaging container rises, a part of the sealant layer is broken, and a part of the heat-softening resin layer undergoes interfacial peeling or cohesive failure, allowing steam to escape. Specifically, it will be described in the second embodiment of the automatic steam venting mechanism.

[0100] Examples of the heat-softening resin, that is, a resin that has a predetermined strength in a temperature environment of room temperature or lower but whose strength decreases in a high-temperature environment, include resins with a melting point of 60 to 110°C, preferably 60 to 90°C. Specifically, ethylene-vinyl acetate copolymer resins, polyamides, nitrocellulose, and polyethylene waxes, etc. can be mentioned, and a mixed resin of polyamide, nitrocellulose, and polyethylene wax is preferred. As the resin containing polyamide, nitrocellulose, and polyethylene wax, MWOP varnish (softening point: 105°C) manufactured by DIC Graphics Co., Ltd. can be used, etc.

[0101] The thickness of the heat-softening resin layer is preferably 1 to 5 μm. By setting the thickness of the heat-softening resin layer to 1 μm or more, when heated in a microwave oven, the heat-softening resin layer and the sealant layer can be easily broken. Also, by setting the thickness of the heat-softening resin layer to 5 μm or less, when the film-like packaging material is wound into a roll, bulging in a part can be suppressed, and the stretching of the packaging material in that part can be inhibited.

[0102] [Packaging container] The packaging container of the present invention is at least partially formed of the said packaging material. By being formed of the said packaging material, a packaging container with a high-class feeling due to a metallic luster can be obtained even if metal itself is not used. The said packaging material may be applied to a desired part where a high-class feeling due to a metallic luster is to be imparted, and the entire packaging container may be formed of the said packaging material, or alternatively, only a part of it may use the said packaging material.

[0103] The type and use of the packaging container of the present invention are not particularly limited, but when selling the contents contained in the packaging container, it is possible to impress the purchaser with a sense of luxury of the contents. For example, it can be suitably used for food containers, cosmetic containers, and the like. Examples of the packaging container include a pouch and a container with a lid, and also include a cup and a tray. These packaging containers partially contain the packaging material described above. That is, these packaging containers may be formed of a packaging material containing paper as an intermediate base material layer. Specific examples of the shape of the pouch include the shape of the pouch for a microwave oven shown in FIG. 5 described later. The pouch may be a retort container (a container sterilized at high temperature and high pressure), and furthermore, it may be a packaging container for a microwave oven or a container other than a retort container. As a specific shape of the container with a lid, it has a configuration including a container body having a storage portion and a lid body joined to the container body so as to seal the storage portion, and an example is that the lid body is formed of the packaging material. The packaging container can be suitably used for a microwave oven as described above. Also, the packaging container can be used as a retort container. Of course, the packaging container can also be used as a retort container for a microwave oven.

[0104] When the packaging container is a container for a microwave oven or a retort container, the packaging material constituting the container preferably has any of the laminated structures (1) to (4) described above. At this time, as the plastic film, it is preferable to use a single polyester film, a single polyamide film such as nylon, or a composite film containing one or more of a polyester film and a polyamide film. At this time, as the intermediate base material, it is preferable to use a single polyester film, a single polyamide film such as nylon, a composite film containing one or more of a polyester film and a polyamide film, and paper. Also, at this time, as the sealant layer, propylene-based resins such as propylene homopolymer, ethylene-propylene block copolymer, ethylene-propylene random copolymer, and HDPE are preferable. More specifically, in the case of a retort container or a container for a microwave oven, the packaging material constituting the container preferably has any of the following laminated structures (A1) to (A12). Note that " / " means the boundary of each layer. In (A1) to (A12), PET and Ny are preferably stretched films.

[0105] (A1) PET / Glossy printing layer / Ny / Ethylene-propylene block copolymer (A2) PET / Gas barrier layer / Glossy printing layer / Ny / Ethylene-propylene block copolymer (A3) PET / Glossy printing layer / Gas barrier layer / Ny / Ethylene-propylene block copolymer (A4) PET / Glossy printing layer / PET / Ethylene-propylene block copolymer (A5) PET / Gas barrier layer / Glossy printing layer / PET / Ethylene-propylene block copolymer (A6) PET / Glossy printing layer / Gas barrier layer / PET / Ethylene-propylene block copolymer (A7) Coextruded stretched film (PET / Ny / PET) PET / Glossy printing layer / PET / Ethylene-propylene block copolymer (A8) Coextruded stretched film (PET / Ny / PET) / Gas barrier layer / Glossy printing layer / PET / Ethylene-propylene block copolymer (A9) Coextruded stretched film (PET / Ny / PET) / Glossy printing layer / Gas barrier layer / PET / Ethylene-propylene block copolymer (A10) PBT / Glossy printing layer / Ny / Ethylene-propylene block copolymer (A11) PBT / Gas barrier layer / Glossy printing layer / Ny / Ethylene-propylene block copolymer (A12) PBT / Glossy printing layer / Gas barrier layer / Ny / Ethylene-propylene block copolymer

[0106] In the case of a container for a microwave oven, the ethylene-propylene block copolymer, which is the sealant layer of the above (A1) to (A12), can also be a polyethylene resin such as LDPE, LLDPE, MDPE, or HDPE. In addition, when adopting the configuration of the automatic steam penetration mechanism of the second embodiment described later in a container for a microwave oven, a heat-softening resin layer described above may be formed in part between the plastic film and the sealant layer.

[0107] (Pouch) FIG. 5 shows an example of a pouch which is an embodiment of the packaging container of the present invention. The pouch 10 in FIG. 5 is for a microwave oven and is a standing pouch formed by heat-sealing a body portion 11 and a bottom portion 12. As shown in FIG. 5, the body portion 11 includes a pair of main surface sheets 13 composed of a front main surface sheet 13a and a back main surface sheet 13b arranged to face each other, and the side edges 14 of the pair of overlapped main surface sheets 13 are heat-sealed to each other in the vicinity. A bottom surface sheet 16 forming the bottom portion 12 is arranged between the lower edges 15 of the pair of main surface sheets 13. And an accommodation space 17 for accommodating the content is formed in the region surrounded by the pair of main surface sheets 13 and the bottom surface sheet 16. The bottom surface sheet 16 is bent convexly toward the accommodation space 17 side, and the vicinity of its periphery is heat-sealed together with the lower part of the overlapping main surface sheets 13. By the bottom surface sheet 16 holding the shape of the lower ends of the pair of main surface sheets 13, the pouch 10 is given self-standing property and can be a standing pouch. In the pouch 10 of FIG. 5, an opening 19 is formed between the upper edges 18 of the front main surface sheet 13a and the back main surface sheet 13b, and the content can be accommodated through the opening 19. After accommodating the content, the packaging container can be sealed by heat-sealing the vicinity of the upper edge 18 where the opening 19 is formed. When taking out the content from the pouch 10, it is unsealed by tearing the vicinity of the upper edge 18 from the notch 23.

[0108] The front main surface sheet 13a, the back main surface sheet 13b, and the bottom surface sheet 16 of this pouch 10 can be formed by the packaging material 1. All of these sheets may be formed of the packaging material 1 having a gloss printing layer 3a containing a pearl pigment, or only any one of the sheets that requires metallic luster may be formed of the packaging material 1. FIG. 5 shows that the front main surface sheet 13a is formed to have a gloss printing layer 3a and a pattern printing layer 3b with the packaging material 1 having a laminated structure as shown in FIG. 2. In addition, as the sheets other than the sheet on which the packaging material 1 is used, for example, in the packaging material 1, those without a gloss printing layer 3a containing a pearl pigment, those without a printing layer, etc. can be used.

[0109] (Automatic steam venting mechanism) When the container is for a microwave oven, when the pressure inside the pouch rises due to steam generated by heat cooking of food or the like as the contents, it preferably has an automatic steam venting mechanism that automatically vents the steam in the accommodation space to the outside to prevent the pouch from bursting. The automatic steam venting mechanism is preferably formed near the peripheral edge of the container.

[0110] A first embodiment of the automatic steam venting mechanism will be described with reference to FIG. 5. The pouch for a microwave oven shown in FIG. 5 has a first unsealed region 21 that is not heat-sealed near the side edge 14 closer to the upper side of the container (pouch). The first unsealed region 21 reaches the side edge 14 and has an opening 22. Further, the first unsealed region 21 projects toward the accommodation space 17 side. Also, a heat-sealed portion 25 projects toward the accommodation space 17 side so as to surround the first unsealed region 21 that projects toward the accommodation space 17 side, and a projecting portion 25a is formed. More specifically, the first unsealed region 21 and the accommodation space 17 are isolated, and the projecting portion 25a is formed so as to be continuously provided to the heat-sealed portion 25 for sealing the pouch. The pouch for a microwave oven shown in Fig. 5 forms an automatic steam venting mechanism 20 by means of the opening 22, the first unsealed area 21, and the heat-sealing part (overhanging part 25a) that projects toward the accommodating space 17 as described above. Specifically, when the pressure inside the container rises due to heating, the overhanging part 25a of the heat-sealing part 25 is subjected to a strong load, and the area of the overhanging region 25 peels off first, so that the accommodating space 17 and the first unsealed area 21 communicate with each other, and steam can be released to the outside. Further details of the automatic steam venting mechanism of the type shown in Fig. 5 are described in JP-A-2015-120550, JP-A-2016-74457, and JP-A-2016-74458.

[0111] In the container 10 shown in Fig. 5, a second unsealed area 23 is formed at the side edge 14 on the side opposite to the first unsealed area 21. The second unsealed area 23 is formed from the viewpoint of improving the yield of the formation of the opening 22 of the first unsealed area 21 when a plurality of retort containers 10 are continuously formed and then cut one by one, and it does not necessarily have to be formed.

[0112] A second embodiment of the automatic steam venting mechanism will be described with reference to Figs. 11 to 13. The packaging container (pouch) 10 shown in Fig. 12 is formed by heat-sealing the periphery of the edge of the packaging material (a packaging material having a heat-softening resin layer in a part near the edge between a plastic film and a sealant layer) shown in Fig. 11 to form a pouch. Fig. 13 is a cross-sectional view taken along XI-XI of the heat-sealing part 25 at the periphery of the edge of the packaging container 10 shown in Fig. 12. As shown in Fig. 12, the heat-softening resin layer 7 needs to be formed from the inner edge to the outer edge of the heat-sealing part 25 for sealing the pouch in at least a part of the area of the heat-sealing part 25 of the packaging container 10. The heat-softening resin layer 7 provided at such a position has its strength reduced when heated in a microwave oven to a high temperature. As shown in Fig. 13, when the heat-softening resin layer 7 is heated in a microwave oven or the like and the internal pressure rises due to the expansion of the air in the packaging container 10 or the water vapor contained in the contents, starting from an arbitrary point "A" of the sealant layer 4 near the inner edge of the heat-sealing portion 25, a part of the sealant layer 4 is broken, and a part of the heat-softening resin layer 7 undergoes interfacial peeling or cohesive failure. (The broken line at symbol B indicates a virtual line where the sealant layer 4 is broken and a virtual line where the heat-softening resin layer 7 undergoes interfacial peeling or cohesive failure.) As a result, air and water vapor can escape from the broken portion, and the internal pressure of the packaging container 10 can be reduced. In addition, the automatic steam ventilation mechanism of the second embodiment can also be applied to a container with a lid described later.

[0113] As the packaging material constituting the container provided with the second embodiment of the automatic steam ventilation mechanism, it is preferable to select a resin that is easily collapsible as the resin constituting the sealant layer. Specifically, LLDPE is preferable. Further, the packaging material constituting the container provided with the second embodiment of the automatic steam ventilation mechanism preferably has a laminated structure of any of the following (B1) to (B6). Note that " / " means the boundary of each layer. Also, in (B1) to (B6), PET and Ny are preferably stretched films.

[0114] (B1) PET / Glossy printing layer / Heat-softening resin layer / LLDPE (B2) PET / Gas barrier layer / Glossy printing layer / Heat-softening resin layer / LLDPE (B3) PET / Glossy printing layer / Gas barrier layer / Heat-softening resin layer / LLDPE (B4) Ny / Glossy printing layer / Heat-softening resin layer / LLDPE (B5) Ny / Gas barrier layer / Glossy printing layer / Heat-softening resin layer / LLDPE (B6) Ny / Glossy printing layer / Gas barrier layer / Heat-softening resin layer / LLDPE

[0115] (Container with lid) Figures 6 and 7 show an example of an embodiment of the container with a lid according to the present invention. Figure 6 is a top view, and Figure 7 is a sectional view taken along line IV-IV of Figure 6. The container with a lid 30 shown in Figures 6 and 7 includes a container body 32 in which a storage portion 31 is formed, and a lid body 33 joined to the container body 32 so as to seal the storage portion 31 of the container body 32. In Figure 6, the shape of the container body 32 is substantially rectangular, but it is not particularly limited. Also, the forming method of the container body 32 is not particularly limited either, and for example, it may be a tray formed by injection molding or a container formed by deep drawing molding. In addition, since the material of the container body 32 is to be joined to the lid body 33, it is usually a thermoplastic resin such as PP or PET, etc. In particular, in the case of a container with a lid for a microwave oven, from the viewpoint of heat resistance, etc., PP is preferably used.

[0116] It is preferable that the lid body 33 of this container with a lid 30 is formed of the packaging material 1 of the present invention. According to such a lid body 30, it is possible to produce an aesthetic appearance due to the metallic luster, and it is possible to obtain a container with a lid that suppresses the glare of the reflected light under sunlight. In Figure 6, it is shown that the lid body 33 is formed to have a gloss printing layer 3a and a pattern printing layer 3b with the packaging material 1 having a laminated structure as shown in Figure 2.

[0117] From the viewpoint of facilitating the opening of the container with a lid 30 by peeling the lid body 33 from the container body 32, as described in the explanation of the sealant layer 4 of the above packaging material 1, it is preferable that the lid body 33 has easy peelability. The joining of the lid body 33 and the container body 32 is specifically made at a joining line 35 of the flange portion 34 of the container body 32. The joining line 35 may be formed, for example, by heat sealing between the lid body 33 and the flange portion 34, or may be formed of a separate component such as an adhesive layer.

[0118] When the covered container 30 is used for a microwave oven, when the pressure inside the covered container 30 rises due to steam generated by heat-cooking food or the like, which is the content stored in the container body 32, the steam inside the covered container 30 is automatically released to the outside, and it is preferable to be provided with an automatic steam venting mechanism (the third embodiment of the automatic steam venting mechanism) for preventing the covered container 30 from bursting. For example, the flange portion 34 has a protruding portion 34a protruding toward the center of the container body 32, and along this protruding portion 34a, the joining line 35 also has a protruding line 35a formed in a convex shape toward the center of the container. By forming the joining line 35 in such a form, as the pressure inside the covered container 30 rises due to heating, among the above-mentioned joining lines 35, it becomes easier to peel off from the portion of the protruding line 35a, the storage portion 31 of the container body 32 can be communicated with the outside, and the steam inside the covered container 30 can be released to the outside. In addition, in the covered container 30 shown in FIGS. 6 and 7, the protruding portions 34a are respectively formed on the opposing long sides of the flange portion 34, but the protruding portions 34a do not necessarily have to be formed in two.

[0119] Further, as the lid body 33 constituting the covered container 30, by using the packaging material shown in FIG. 11 (a packaging material having a heat-softening resin layer in a part near the edge between a plastic film and a sealant layer), for the same reason as described in the second embodiment of the above-mentioned automatic steam venting mechanism, steam can be released when heated in a microwave oven.

[0120] <Lid body> The lid body of the present invention is formed of the above-mentioned packaging material of the present invention.

[0121] The packaging material constituting the lid body is preferably configured in any of the laminated configurations of (1) to (4) described above. Also, when the lid body is used for a microwave oven or a retort container, as the plastic film, it is preferable to use a single polyester film, a single polyamide film such as nylon, or a composite film containing one or more of a polyester film and a polyamide film. In addition, when the lid is used for a microwave oven or a retort container, as the intermediate base material layer, it is preferable to use a single polyester film, a single polyamide film such as nylon, a composite film containing one or more of a polyester film and a polyamide film, or paper. In addition, when the lid is used for a microwave oven or a retort container, as the sealant layer, it is preferable to use a film made of a resin having both heat resistance and easy peelability. Such a film varies depending on the type of container. When the container is a propylene-based resin which is a general-purpose resin, it is preferable to use a film made of a resin obtained by mixing PP with one or more selected from PE, polybutene, and polystyrene. Note that the sealant layer may have a multilayer structure, and easy peelability may be imparted only to the side joined to the container body of the sealant layer (the innermost layer in the packaging material).

[0122] More specifically, the packaging material constituting the lid preferably has any of the following laminated structures (C1) to (C11). Note that " / " means the boundary between each layer. In addition, in (C1) to (C11), PET and Ny are preferably stretched films. (C1) PET / Glossy printing layer / Ny / Sealant layer having easy peelability (C2) PET / Gas barrier layer / Glossy printing layer / Ny / Sealant layer having easy peelability (C3) PET / Glossy printing layer / Gas barrier layer / Ny / Sealant layer having easy peelability (C4) PET / Glossy printing layer / PET / Sealant layer having easy peelability (C5) PET / Gas barrier layer / Glossy printing layer / PET / Sealant layer having easy peelability (C6) PET / Glossy printing layer / Gas barrier layer / PET / Sealant layer having easy peelability (C7) Ny / Glossy printing layer / Ny / Sealant layer having easy peelability (C8) Ny / Gas barrier layer / Glossy printing layer / Ny / Sealant layer having easy peelability (C9) Ny / Gloss printing layer / Gas barrier layer / Ny / Sealant layer with easy peelability (C10) Ny / Gloss printing layer / EVOH / Sealant layer with easy peelability (C11) Ny / EVOH / Gloss printing layer / Sealant layer with easy peelability

[0123] In addition, when adopting the configuration of the second embodiment of the automatic steam penetration mechanism described above for the lid body, a heat-softening resin layer described above may be formed in part between the plastic film and the sealant layer.

[0124] This disclosure includes the following [1] to [6]. [1] A method for sorting packaging materials having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, When having a gloss printing layer containing a bright pigment as the printing layer, the angle indicating half the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 1 is d1, and the angle indicating half the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d2. A method for sorting packaging materials, in which those satisfying the following formula (1) are taken as the pass line. |(d1 - d2) / d1|×100 ≦ 8.0% (1) <Measurement condition 1> A black plate is bonded to the surface on the sealant layer side of the packaging material via a transparent adhesive layer, and a sample A in which the packaging material, the transparent adhesive layer, and the black plate are laminated is produced. Visible light inclined 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle. <Measurement condition 2> The packaging material is subjected to retort treatment at 135°C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface of the retort-treated packaging material on the sealant layer side via a transparent adhesive layer, and a sample B in which the retort-treated packaging material, the transparent adhesive layer, and the black plate are laminated is produced. Visible light inclined at 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the retort-treated packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, in the range of ±15.0 degrees centered on the reference angle, the intensity of the reflected light is measured every 0.1 degree. [2] The method for selecting a packaging material according to [1], wherein the phosphorescent pigment is a metal flake or a pearl pigment. [3] The method for selecting a packaging material according to [1] or [2], wherein the packaging material is a packaging material for a microwave oven. [4] A packaging material having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, having a glossy printing layer containing a phosphorescent pigment as the printing layer, and when the angle indicating half the intensity of the specular reflection direction of the packaging material measured under the following measurement condition 1 is d1, and the angle indicating half the intensity of the specularly reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d2, a packaging material satisfying the following formula (1). |(d1 - d2) / d1| × 100 ≦ 8.0% (1) <Measurement condition 1> A black plate is bonded to the surface of the packaging material on the sealant layer side via a transparent adhesive layer, and a sample A in which the packaging material, the transparent adhesive layer, and the black plate are laminated is produced. Visible light inclined at 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, in the range of ±15.0 degrees centered on the reference angle, the intensity of the reflected light is measured every 0.1 degree. <Measurement condition 2> The packaging material is subjected to retort treatment at 135°C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface on the sealant layer side of the retort-treated packaging material via a transparent adhesive layer, and a sample B in which the retort-treated packaging material, the transparent adhesive layer, and the black plate are laminated is produced. Visible light inclined 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the side of the retort-treated packaging material, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, the intensity of the reflected light is measured every 0.1 degree in the range of ±15.0 degrees centered on the reference angle. [5] A retort container at least a part of which is formed of the packaging material described in [4]. [6] The retort container according to [5], which is for a microwave oven.

Example

[0125] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

[0126] 1. Production of packaging material [Example 1] A packaging material laminated in the order of plastic film / vapor deposition film / gas barrier coating film / gloss printing layer / white base color printing layer / adhesive layer / intermediate base material layer / adhesive layer / sealant layer was obtained from the outer layer side. The configuration of each layer is as follows. · Plastic film: PET (thickness 12 μm) · Gas barrier layer: After subjecting one surface of the plastic film to corona discharge treatment, a vapor deposition film of silicon oxide with a thickness of 10 nm was formed. Further, after subjecting to plasma treatment with a mixed gas of oxygen and argon, a coating liquid mainly composed of ethyl silicate and polyvinyl alcohol was applied with a gravure roll coater to form a gas barrier coating film with a dry film thickness of 300 nm. · Gloss printing layer: The following gold ink 1 for gloss printing layer was gravure-printed on the entire surface of the gas barrier layer and dried to form a gloss printing layer with a dry film thickness of 3 μm. · White base printing layer: Further, white pigment ink was gravure printed on the entire surface of the gloss printing layer and dried to form a white base printing layer with a dry film thickness of 3 μm. · Intermediate substrate layer: A stretched Ny (thickness 15 μm) was laminated on the surface of the white base printing layer by a dry lamination method using a polyurethane-based adhesive. · Sealant layer: A CPP (single-layer film of ethylene-propylene block copolymer, thickness 70 μm) was laminated on the surface of the intermediate substrate layer by a dry lamination method using a polyurethane-based adhesive.

[0127] <Gold ink 1 for gloss printing layer> · 10 parts by mass of white pearl pigment (Average particle size 15 μm) · 20 parts by mass of colored pearl pigment (Colored pearl pigment with a mica coating layer of ferric oxide, average particle size 15 μm) · 0.001 parts by mass of carbon black · 0.1 parts by mass of inorganic fine particles (Silica, average primary particle diameter: 20 nm) · 10 parts by mass of binder resin (Polyurethane-based resin, melting point 140 °C) · 60 parts by mass of solvent 1 (Mixed solvent of propylene glycol monomethyl ether, normal propyl acetate, ethyl acetate, and isopropanol)

[0128] [Example 2] A packaging material was obtained in the same manner as in Example 1, except that Gold ink 1 for gloss printing layer was changed to the following Gold ink 2 for gloss printing layer.

[0129] <Gold ink 2 for gloss printing layer> · 7 parts by mass of aluminum flakes (Non-leafing type metal flakes produced by the method of (i) in the specification text) (Average length 4 μm, average thickness 0.04 μm, aspect ratio 100) · 3 parts by mass of organic yellow pigment · 2 parts by mass of inorganic fine particles (Silica, average primary particle diameter: 20 nm) ·Binder resin 20 parts by mass (Polyurethane resin, melting point 140 °C) ·Solvent 1 70 parts by mass (Mixed solvent of propylene glycol monomethyl ether, normal propyl acetate, ethyl acetate, and isopropanol) ·Solvent 2 (mineral spirit) 7 parts by mass

[0130] [Comparative Example 1] A packaging material was obtained in the same manner as in Example 1, except that the gold ink 1 for the gloss printing layer was changed to the following gold ink 3 for the gloss printing layer.

[0131] <Gold ink 3 for gloss printing layer> ·Aluminum flakes 7 parts by mass (Non-leafing type metal flakes manufactured by the method of (ii) in the specification text) (Average length 20 μm, average thickness 0.1 μm, aspect ratio 200) ·Organic yellow pigment 3 parts by mass ·Inorganic fine particles 2 parts by mass (Silica, average primary particle diameter: 20 nm) ·Binder resin 20 parts by mass (Polyurethane resin, melting point 140 °C) ·Solvent 1 70 parts by mass (Mixed solvent of propylene glycol monomethyl ether, normal propyl acetate, ethyl acetate, and isopropanol) ·Solvent 2 (mineral spirit) 7 parts by mass

[0132] 2. Preparation of samples 2-1. Sample A On the CPP side surface of the packaging materials of Examples 1 to 2 and Comparative Example 1, a black plate was bonded through a transparent adhesive layer, and Sample A in which the packaging materials of Examples 1 to 2 and Comparative Example 1, the transparent adhesive layer, and the black plate were laminated was prepared. For Sample A, those with a refractive index difference of 0.05 or less among CPP, the transparent adhesive, and the black plate were used.

[0133] 2 - 2. Sample B Pouches with the structure shown in Fig. 5 were produced and sealed using the packaging materials of Examples 1 - 2 and Comparative Example 1. Using a batch - type hot - water spray sterilizer manufactured by Nisaka Seisakusho Co., Ltd., the produced pouches were subjected to retort treatment (high - retort treatment) at 135°C for 30 minutes. The specifications of the tester are shown below. Also, the packaging material was cut out from the retort - treated pouch, and a black plate was bonded to the CPP - side surface of the cut - out packaging material via a transparent adhesive layer to produce Sample B, which was a laminate of the retort - treated packaging materials of Examples 1 - 2 and Comparative Example 1, the transparent adhesive layer, and the black plate. For Sample B, those with a refractive index difference of 0.05 or less among CPP, the transparent adhesive, and the black plate were used.

[0134] <Specifications of the hot - water spray sterilizer> · Processing capacity: 20 kg · Maximum operating pressure: 0.5 MPa · Maximum operating temperature: 140°C · Wetted part material: SUS316 · Sterilization tank dimensions: Inner diameter = 600 mm, straight body part = 735 mm · Effective liquid volume: 20 L · Heating method: Hot - water spray heating · Cooling method: Spray cooling · Pressure control: Constant pressure, gas - containing method · Processing mechanism: Static type · Heating - up capacity: 20 - 130°C in 11 minutes · Temperature distribution in the tank: Within ±0.5°C · Equipment dimensions: W1,330×L2,130×H1,800 mm · Equipment weight: 1,600 kg · Utilities: Steam = 150 kg / h, Cooling water = 360 L / once (2 m 3 / h), Equipment power = 5.4 kW

[0135] 3. Measurement The sample prepared in 2-1 and 2-2 was set in a variable-angle photometer (product number GP-200 manufactured by Murakami Color Technology Research Institute, with the beam internal inclination angle within 0.5 degrees), and visible light inclined 45 degrees from the normal direction of the sample was incident on the surface on the packaging material side of the sample. With the specular reflection direction of the incident light as the reference angle of 0 degrees, the intensity of the reflected light was measured every 0.1 degrees in the range of ±15.0 degrees centered on the reference angle. During the measurement, the scale of the light-receiving aperture was set to "4" and the scale of the beam aperture was set to "3". Based on the obtained reflection intensity for each angle, d1 (degrees), |(d1 - d2) / d1|×100 in Equation (1), and |(d3 - d4) / d3|×100 in Equation (2) were calculated.

[0136] 4. Evaluation 4-1. Aesthetic appearance due to metallic luster Under the illumination of indoor fluorescent lamps, the packaging materials (packaging materials before high retort treatment) of Examples 1 to 2 and Comparative Example 1 were observed from the plastic film side, and the aesthetic appearance due to metallic luster was evaluated. Those with good aesthetic appearance due to metallic luster were rated 3 points, those for which neither could be said were rated 2 points, and those with inferior aesthetic appearance due to metallic luster were rated 1 point. Twenty subjects conducted the evaluation and the average score was calculated. The results are shown in Table 1. <Evaluation criteria> A: The average score is 2.5 or more B: The average score is 1.5 or more and less than 2.5 C: The average score is less than 1.5

[0137] 4-2. Change in metallic luster (change in appearance) Under the illumination of indoor fluorescent lamps, the above Sample A and Sample B were observed from the plastic film side, and the difference in metallic luster between the two samples was evaluated. Those who did not feel the difference in metallic luster between the two samples were rated 3 points, those for which neither could be said were rated 2 points, and those who felt the difference in metallic luster between the two samples were rated 1 point. Twenty subjects conducted the evaluation and the average score was calculated. The results are shown in Table 1. <Evaluation criteria> A: The average score is 2.5 or more B: The average score is 1.5 or more and less than 2.5 C: The average score is less than 1.5

[0138] [Table 1]

[0139] From the results in Table 1, it was confirmed that by selecting a packaging material that satisfies formula (1), it is possible to provide a packaging material that can produce an aesthetic appearance with a metallic luster without using a metal layer and can suppress changes in appearance during the distribution process. Note that the packaging material of Comparative Example 1 did not satisfy formula (1) because the wrinkles on the surface of the metal flakes were restored by the high retort treatment, the reflection intensity diffused at a wide angle decreased, and the reflection intensity near the specular reflection direction increased.

Explanation of Reference Numerals

[0140] 1 Packaging material 2 Plastic film 3a Gloss printing layer 3b Pattern printing layer 3c Black background printing layer 3d White background printing layer 4 Sealant layer 5 Intermediate substrate layer 6 Adhesive layer 7 Thermoplastic resin layer 10 Packaging container 11 Body 12 Bottom 13 Main surface sheet 14 Side edge 15 Lower edge 16 Bottom surface sheet 17 Accommodation space 18 Upper edge 19 Opening 20 Automatic steaming mechanism 21 First unsealed area 22 Opening 23 Second unsealed area 24 Notch 25 Heat seal part 25a Overhanging part 30 Container with lid 31 Accommodation part 32 Container body 33 Cover 34 Flange portion 35 Joint line 100 Sample

Claims

1. A method for selecting a packaging material having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, having a glossy printing layer containing a lustrous pigment as the printing layer, and when the lustrous pigment is a metal flake or a pearl pigment, the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 1 is 1 / 2. The angle indicating the intensity is d １ The angle indicating 1 / 2 of the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d ２ When this is done, a method for selecting a packaging material, in which those satisfying the following formula (1) are defined as the pass line. |(d １ - d ２ ) / d １ |×100 ≦ 8.0% (1) <Measurement condition 1> A black plate is bonded to the surface on the sealant layer side of the packaging material via a transparent adhesive layer to produce a sample A in which the packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, in the range of ±15.0 degrees centered on the reference angle, the intensity of the reflected light is measured every 0.1 degree. <Measurement condition 2> The packaging material is subjected to retort treatment at 135°C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface on the sealant layer side of the retort-treated packaging material via a transparent adhesive layer to produce a sample B in which the retort-treated packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the retort-treated packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, in the range of ±15.0 degrees centered on the reference angle, the intensity of the reflected light is measured every 0.1 degree.

2. The method for selecting a packaging material according to claim 1, wherein the packaging material is a packaging material for a microwave oven.

3. A packaging material having a structure in which at least a plastic film, a printing layer, and a sealant layer are laminated in this order from the outer layer side, The printing layer has a glossy printing layer containing a bright pigment and inorganic particles having an average primary particle diameter of 1 to 100 nm, The bright pigment is a metal flake, The inorganic particles having an average primary particle diameter of 1 to 100 nm are at least one selected from silica and alumina, The angle indicating half of the reflection intensity in the specular reflection direction of the packaging material measured under the following measurement condition 1 is d １ The angle indicating half of the intensity of the reflected light in the specular reflection direction of the packaging material measured under the following measurement condition 2 is d ２ A packaging material for a microwave oven that satisfies the following formula (1) when |(d １ - d ２ ) / d １ | × 100 ≤ 8.0% (1) <Measurement condition 1> A black plate is bonded to the surface of the packaging material on the sealant layer side via a transparent adhesive layer to produce a sample A in which the packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample A is incident on the surface of the sample A on the packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, in the range of ±15.0 degrees centered on the reference angle, the intensity of the reflected light is measured every 0.1 degree. <Measurement condition 2> The packaging material is subjected to retort treatment at 135°C for 30 minutes in a batch-type hot water shower type retort apparatus to obtain a retort-treated packaging material. A black plate is bonded to the surface of the retort-treated packaging material on the sealant layer side via a transparent adhesive layer to produce a sample B in which the retort-treated packaging material, the transparent adhesive layer, and the black plate are laminated. Visible light inclined 45 degrees from the normal direction of the sample B is incident on the surface of the sample B on the retort-treated packaging material side, and with the specular reflection direction of the incident light as the reference angle of 0 degrees, in the range of ±15.0 degrees centered on the reference angle, the intensity of the reflected light is measured every 0.1 degree.

4. The packaging material according to claim 3, wherein the content of the inorganic particles is 10 to 70 parts by mass with respect to 100 parts by mass of the luminescent pigment.

5. The packaging material according to claim 3 or 4, having a gas barrier layer between the plastic film and the printing layer.

6. The packaging material according to claim 3 or 4, having a gas barrier layer between the printing layer and the sealant layer.

7. The packaging material according to any one of claims 3 to 6, having an intermediate base material layer between the printing layer and the sealant layer.

8. A retort container at least a part of which is formed of the packaging material according to any one of claims 3 to 7.

Images