Light-shielding package

Abstract

To provide a light-shielding package which has a light-shielding property equivalent to that of an aluminum vapor deposition film by the formation of a light-shielding printed layer, can reduce the whiteness loss in appearance due to the light-shielding printed layer, is excellent in lamination suitability, does not cause the lowering of heat seal strength in a sealed portion, and can be relatively easily manufactured.SOLUTION: A package is manufactured by using a packaging sheet material 10 formed by laminating an outer surface base material film 12, an adhesive layer 18, an intermediate material film 14, an adhesive layer 20 and an inner surface material film 16. Two or more gray colored light-shielding printed layers are formed on the outer surface side of the intermediate material film 14, and a brightness of a light-shielding printed layer 24b located on the outer surface side is made higher than a brightness of a light-shielding printed layer 24a located on the inner surface side. Two or more white colored printed layers are formed on the inner surface side of the outer surface base material film 12, and the content of pigments in a white colored printed layer 22b in contact with the adhesive layer 18 is made smaller than the content of pigments in a white colored printed layer 22a located on the outer surface side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This invention relates to a light-blocking package in which a packaging sheet material is formed into a bag shape, the overlapping edges of the sheet material are heat-sealed together, and the contents are placed inside and sealed, and which has been given light-blocking properties for the purposes of protecting the contents which are sensitive to light and for improving the appearance of the bag packaging, and in particular to a light-blocking package in which light-blocking properties have been given by printing without using metal foil or metal-deposited film. [Background technology]

[0002] Light-shielding packaging materials are used for packaging foods that are easily discolored, oxidized, or deteriorated by light, contents that are dark in color and can be seen through the bag surface, which reduces their appearance, and various personal care products whose active ingredients are degraded by light, etc. As a means for imparting light-shielding properties to packaging materials, it is generally known to use metal foil as part of the material of packaging sheet materials. However, while metal foil has excellent light-shielding properties, it is a different material from the plastic film that is the main material of packaging materials, and from the perspective of protecting the global environment, it is not preferable to use a film laminated with metal foil as a material for packaging materials. Therefore, instead of metal foil, films vapor-deposited with metals such as aluminum have come to be widely used as materials for packaging materials. Although this metal vapor-deposited film is inferior to metal foil, it has sufficient barrier properties and light-shielding properties in terms of protecting the contents and looking good. On the other hand, compared to transparent films, metallized films have limited varieties and range of applications, and the film composition of the sheet material is also limited. Furthermore, there are drawbacks in that they cannot be used for packaging that can be heated in a microwave oven as is, a bag for which demand and consumption have been rapidly increasing in recent years. Instead of such metallized films, packaging that has been given light-blocking properties by using colored films or printing on the film has come to be used. Among these, packaging that uses colored films can provide a light-blocking layer of the film thickness, making it easy to obtain sufficient light-blocking properties, but on the other hand, the variety is more limited than that of metallized films, the film composition of the sheet material is also limited, and the types of contents that can be stored are also limited. For these reasons, in recent years, packaging that has been given light-blocking properties by printing on a versatile film that has few restrictions on the film composition of the sheet material has come to be used frequently.

[0003] A packaging bag for use in a microwave oven has been proposed as a packaging material imparted with light-blocking properties by printing on a film, the bag being made from a laminate comprising, in order, a base layer, a design layer, a white ink layer, an adhesive layer, an intermediate layer, a light-blocking ink layer, an adhesive layer, and a heat-sealable resin layer, with the light-blocking ink layer being formed by gravure printing using a light-blocking ink such as a black ink containing a black pigment such as carbon black, a gray ink containing a black pigment and a white pigment, an ink containing aluminum powder or aluminum paste, or an ink containing aluminum powder or the like and a white pigment or a colored pigment. This packaging bag for use in microwave ovens has a structure in which a white ink layer is provided on the base layer side and a light-blocking ink layer is provided on the heat-sealable resin layer side, with an intermediate layer in between. The provision of the intermediate layer increases the number of layers with different refractive indices of light, thereby increasing the reflected light in each layer above the light-blocking ink layer and making the bag appear whiter, without impairing the design. Furthermore, the white ink layer and the light-blocking ink layer are formed separately by the intermediate layer, so the bag does not become cloudy, achieving both better design and excellent light-blocking properties (see, for example, Patent Document 1).

[0004] Also, as a package imparted with light-shielding properties by printing on a film, a pouch made of a laminate including a base resin layer, a light-shielding printed layer, and a heat-sealable resin layer has been proposed, in which the light-shielding printed layer is made of a white ink layer having a weight ratio of white pigment to resin content in the range of 3.5 to 4.2 and a thickness in the range of 4 to 11 μm, and a gray ink layer obtained by blending 2 to 4 parts by weight of black ink and 1 to 3 parts by weight of yellow ink with respect to 100 parts by weight of white ink. In this pouch, since the thickness of the white ink layer constituting the light-shielding printed layer is in the range of 4 to 11 μm, it is possible to effectively prevent cracks in the ink layer while maintaining high whiteness, and by using a gray ink of the above composition for the light-shielding printed layer, it is possible to block visible light without impairing whiteness, and high light-shielding properties can be ensured (for example, see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-203716 A (Pages 5-6, FIG. 3) [Patent Document 2] Patent No. 6308024 (pages 4-5, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0006] The packaging bag for microwave ovens disclosed in Patent Document 1 has a light-shielding ink layer adjacent to a heat-sealing resin layer with an adhesive layer between them, so that when a force is applied to peel off the sealed portion of the packaging bag, the light-shielding ink layer breaks before the sealing portion peels off, resulting in a problem that the heat seal strength is lower than that of a packaging bag using a laminate with a layered structure that does not have an ink layer. To improve this, it is possible to provide a second intermediate layer between the light-shielding ink layer and the heat-sealing resin layer, but this would increase the manufacturing cost and would result in a packaging bag with an excessively multi-layered structure, which is not preferable.

[0007] In the pouch disclosed in Patent Document 2, cracks do not occur in the white ink layer in the light-shielding printing layer, but the white ink layer is set to a thickness far beyond the general range, such as 4 to 11 μm, in order to obtain a high degree of whiteness, and in order to form the white ink layer to that thickness, it is essential to print the white ink over and over again. Furthermore, in order to form the gray ink layer to a thickness that provides sufficient light-shielding properties, it is necessary to overprint the gray ink. In this case, since a large number of printing units are required to print the white ink or gray ink multiple times, the manufacturing cost increases, and since the number of printing units is limited in a gravure rotary printing machine that prints on a plastic film, there are problems such as a very narrow choice of patterns when printing a pattern on a packaging bag in multiple colors. Furthermore, if multiple printing processes are to be performed for light-shielding printing or pattern printing, in reality, the same film will be passed through two printing machines for printing, which is not preferable because it leads to a decrease in quality and an increase in the loss rate.

[0008] This invention has been made in consideration of the above-mentioned circumstances, and aims to provide a light-blocking packaging body that can be relatively easily manufactured by forming a light-blocking printed layer on a film to impart light-blocking properties equivalent to those of an aluminum vapor-deposited film, reduces the loss of whiteness in appearance due to the light-blocking printed layer, and has excellent design properties, and does not cause poor appearance due to the generation of air bubbles when laminating a film on which a white printed layer has been formed, and has good lamination suitability, and does not cause a decrease in heat seal strength at the sealed portion even though it has a layer structure including a light-blocking printed layer, and further eliminates various problems that arise from the inclusion of printing processing in the manufacturing process. [Means for solving the problem]

[0009] In this invention, the packaging sheet material, which is the material for forming the packaging body, has a film laminate structure in which an intermediate film made of a resin material is sandwiched between an outer base film made of a resin material and an inner film made of a heat-adhesive resin material, and a light-blocking printed layer is formed on the outer side of the intermediate film, creating a layer structure in which the light-blocking printed layer is not adjacent to the inner film.In addition, the light-blocking printed layer and white printed layer each have two or more layers, and the brightness of each light-blocking printed layer and the pigment content of each white printed layer are each appropriately set, thereby solving the above problem. That is, the invention according to claim 1 provides a packaging sheet material comprising at least an outer base material film made of a resin material, an intermediate material film made of a resin material, and an inner material film made of a heat-adhesive resin material, the outer base material film and the intermediate material film, and the intermediate material film and the inner material film are laminated via adhesive layers to form a sheet-like packaging sheet material, the inner material film being on the inner side, and the overlapping edge portions of the packaging sheet material being heat-sealed in a strip shape to form a sealed bag having a content storage portion. The light-shielding packaging body has a configuration in which a gray light-shielding printed layer is formed on the outer surface side of the intermediate film, and a white printed layer is formed on the inner surface side of the outer base film, the light-shielding printed layer and the white printed layer each have two or more layers, the lightness of the light-shielding printed layer located on the outer surface side of the two or more light-shielding printed layers is higher than the lightness of the light-shielding printed layer located on the inner surface side thereof, and the pigment content of the white printed layer in contact with the adhesive layer of the two or more white printed layers is lower than the pigment content of the white printed layer located on the outer surface side thereof.

[0010] The invention of claim 2 is characterized in that, in the light-blocking packaging body described in claim 1, the light-blocking printed layer is two-layered, and the brightness of the light-blocking printed layer located on the outer surface is higher than the brightness of the light-blocking printed layer located on the inner surface.

[0011] The invention of claim 3 is characterized in that, in the light-shielding packaging material described in claim 1, the white printed layer is made of two layers, and the pigment content of the white printed layer located on the inner surface side is less than the pigment content of the white printed layer located on the outer surface side.

[0012] The invention according to claim 4 is characterized in that in the light-shielding packaging material according to claim 1, another white printed layer is formed on the outer surface side of the light-shielding printed layer.

[0013] The invention of claim 5 is characterized in that, in the light-shielding packaging material described in claim 1, the pigment content of the white printed layer in contact with the adhesive layer among two or more white printed layers is less than 40%.

[0014] The invention according to claim 6 is characterized in that in the light-shielding packaging material according to any one of claims 1 to 5, the packaging sheet material has an optical density (OD value) of 1.9 or more. Effect of the Invention

[0015] In the light-shielding package of the invention according to claim 1, a gray light-shielding printed layer is formed on the outer surface side of the intermediate film, which provides light-shielding properties, and a white printed layer is formed on the inner surface side of the outer substrate film, which reduces the loss of whiteness in appearance due to the light-shielding printed layer. In addition, since the light-shielding printed layer is formed on the outer surface side of the intermediate film and is not adjacent to the inner material film, when a force is applied to peel off the sealed part of the package, the light-shielding printed layer is not destroyed before the bonding surfaces of the inner material films are peeled off, and there is no concern that the heat seal strength will be reduced due to the formation of the light-shielding printed layer. In addition, since the light-shielding printed layer is two or more layers, and the lightness of the light-shielding printed layer located on the outer surface side of the two or more light-shielding printed layers is higher than the lightness of the light-shielding printed layer located on the inner surface side, the loss of whiteness in appearance due to the light-shielding printed layer is more effectively reduced. Since the white printing layer contains a pigment, fine irregularities are formed on the surface of the white printing layer, and the degree of the irregularities increases as the pigment content increases. If the surface of the white printing layer is uneven, fine air bubbles will be generated due to the unevenness of the surface of the white printing layer after laminating the outer substrate film on which the white printing layer is provided and the intermediate material film on which the light-shielding printing layer is provided via the adhesive layer. However, in this light-shielding packaging body, the white printing layer is made to have two or more layers, and the pigment content of the white printing layer in contact with the adhesive layer among the two or more white printing layers is made lower than the pigment content of the white printing layer located on the outer surface side thereof, thereby suppressing the generation of fine air bubbles after lamination. As a result, the lamination suitability of the sheet material is improved, and a packaging body with excellent appearance can be obtained by using the packaging sheet material. Therefore, the present invention can provide a light-shielding package which is excellent in light-shielding properties and design, has good suitability for lamination, has excellent heat seal strength, and can be produced relatively easily.

[0016] The light-shielding packages of the invention according to claims 2 and 3 have two light-shielding printed layers and two white printed layers, and reliably achieve the above-mentioned effects of the invention according to claim 1.

[0017] According to the invention of claim 4, by forming another white printed layer on the outer surface side of the light-blocking printed layer, the whiteness of the package when viewed from the outer surface side is improved, resulting in a light-blocking package with superior design in appearance.

[0018] According to the invention of claim 5, by appropriately setting the pigment content of the white printing layer on the side in contact with the adhesive layer to less than 40%, the degree of unevenness on the surface of the white printing layer is reduced, the generation of fine air bubbles after lamination is reliably suppressed, the lamination suitability of the sheet material is improved, and a packaging body with a superior appearance is obtained.

[0019] In the light-blocking packaging of the invention according to claim 6, the packaging sheet material satisfies the condition of an optical density of 1.9 or more, thereby achieving light-blocking properties comparable to those of sheet materials using aluminum vapor-deposited film, and providing sufficient performance to protect the contents against light. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an enlarged cross-sectional view of a portion of a packaging sheet material constituting a light-shielding packaging body according to an embodiment of the present invention. [Diagram 2] 2 is a partially enlarged cross-sectional view for explaining a manufacturing process of the packaging sheet material shown in FIG. 1. FIG. [Diagram 3] FIG. 4 is an enlarged cross-sectional view of a portion of a packaging sheet material constituting a light-shielding packaging body according to another embodiment of the present invention. [Figure 4] FIG. 2 shows an example of a light-shielding package produced using the packaging sheet material shown in FIG. 1, and is a plan view of a vertical pillow-type package seen from the back side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. This light-shielding packaging body is produced by forming a packaging sheet material 10, a partial enlarged cross-sectional view of which is shown in Fig. 1, into a bag shape. The packaging sheet material 10 includes an outer substrate film 12 made of a resin material, an intermediate substrate film 14 made of a resin material, and an inner substrate film 16 made of a heat-adhesive resin material (sealant), and has a configuration in which the outer substrate film 12 and the intermediate substrate film 14 are laminated together via an adhesive layer 18, and the intermediate substrate film 14 and the inner substrate film 16 are laminated together via an adhesive layer 20. The light-shielding packaging body is produced by forming the packaging sheet material 10 into a bag shape with the inner substrate film 16 facing inward, and heat-sealing the overlapping edge portions of the packaging sheet material 10 into a strip shape.

[0022] As shown in FIG. 2, the outer substrate film 12 of the packaging sheet material 10 has multiple layers, two layers in the illustrated example, of white printed layers 22a and 22b formed on its inner surface (the surface that will be the inner surface of the bag when the package is produced). The white printed layer 22b located on the inner surface side is printed (solid printing) using an ink with a lower pigment content than the white printed layer 22a located on the outer surface (the surface that will be the outer surface of the bag when the package is produced). In this case, it is preferable that the pigment content of the white printed layer 22b located on the inner surface side is less than 40%. In addition, the intermediate material film 14 has multiple layers, two layers in the illustrated example, of light-shielding printed layers 24a and 24b that exhibit a gray color formed on its outer surface side. The gray ink used for printing on the intermediate material film 14 can be easily obtained by simply mixing general-purpose white and black inks, but it may also be prepared by mixing colored inks with the white and black inks as necessary. At this time, the ink used for printing the light-shielding printed layer 24b located on the outer surface side is prepared to have a higher brightness than the ink for the light-shielding printed layer 24a located on the inner surface side. The outer substrate film 12 and the intermediate material film 14, each of which has been printed, are then laminated together by various lamination methods with their printed surfaces facing each other, and the inner material film 16 is further laminated to the inner surface side of the intermediate material film 14, i.e., the surface side on which no printing has been performed, by various lamination methods, thereby producing the packaging sheet material 10.

[0023] The materials of the outer substrate film 12, intermediate film 14, and inner film 16 of the packaging sheet material 10 are not particularly limited, and may be appropriately selected from petroleum-derived, plant-derived, or composite materials containing non-plastic components to reduce petroleum-derived components that are generally used as raw materials for packaging bodies. For example, as plastic films forming the outer substrate film 12 and intermediate film 14, biaxially oriented nylon films, biaxially oriented polyethylene terephthalate films, biaxially oriented polybutylene terephthalate films, biaxially oriented polypropylene films, and biaxially oriented films of ethylene-vinyl alcohol copolymers may be used. In addition, those plastic films may be vapor-deposited or coated with alumina, silica, or both alumina and silica, or biaxially oriented films formed of multiple materials by coextrusion to form a multilayer structure. In addition, the material for the inner surface film 16 may be a thermoplastic synthetic resin such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or ionomer. Alternatively, these thermoplastic synthetic resins may be blended with elastomers or various additives, or a non-oriented film material formed into a multi-layer structure using multiple materials by co-extrusion may be used.

[0024] The method for laminating the outer substrate film 12 and the intermediate material film 14, and the inner substrate film 16 and the intermediate material film 14, is not particularly limited, but for example, dry lamination and extrusion lamination are suitably used, and adhesive layers 18, 20 are formed by the adhesive or molten resin used in these lamination methods.

[0025] The packaging sheet material 10 having the above-mentioned configuration is provided with light-shielding properties by forming the light-shielding printed layers 24a, 24b on the outer surface side of the intermediate material film 14, and the loss of whiteness in appearance due to the light-shielding printed layers 24a, 24b is reduced by forming the white printed layers 22a, 22b on the inner surface side of the outer substrate film 12. In addition, since the intermediate material film 14 is interposed between the light-shielding printed layers 24a, 24b and the inner material film 16, and the light-shielding printed layers 24a, 24b and the inner material film 16 are not adjacent to each other, when a force is applied to peel off the sealed portion of the package, the light-shielding printed layers 24a, 24b are not destroyed before the bonding surfaces of the inner material films 16 are peeled off, and a decrease in heat seal strength can be prevented. And, by making the lightness of the light-shielding printed layer 24b located on the outer surface side higher than that of the light-shielding printed layer 24a located on the inner surface side, the loss of whiteness in the appearance caused by the light-shielding printed layers 24a, 24b is more effectively reduced. Also, by making the pigment content of the white printed layer 24b in contact with the adhesive layer 18 lower than that of the white printed layer 24a located on the outer surface side, the generation of fine air bubbles after lamination is suppressed, the lamination suitability of the sheet material is improved, and a package with excellent appearance is obtained.

[0026] Next, a packaging sheet material 26, a partially enlarged cross-sectional view of which is shown in Fig. 3, is an example in which a white printed layer 28 separate from the white printed layers 22a, 22b is formed on the outer surface side of the light-shielding printed layers 24a, 24b. In Fig. 3, the parts denoted with the same reference numerals as those used in Fig. 1 are the same components as those explained with reference to Fig. 1. By providing a separate white printed layer 28 on the outer surface side of the light-shielding printed layers 24a, 24b in this way, the whiteness of the package when viewed from the outer surface side is improved, and a light-shielding package with superior appearance design can be obtained.

[0027] In the configuration of the packaging sheet material 10 described above, in order to achieve light-blocking properties comparable to those of sheet materials using aluminum vapor-deposited films, the light-blocking printed layers 24a, 24b may be formed so that the optical density (OD value) of the packaging sheet material 10 is 1.9 or higher.

[0028] The packaging sheet material 10 according to the present invention may have a layered structure including the outer substrate film 12, the adhesive layer 18, the intermediate substrate film 14, the adhesive layer 20, and the inner substrate film 16, and may be laminated with paper on the outer surface of the outer substrate film 12 to provide a design, or with a plastic film on the outer surface of the outer substrate film 12 to improve pinhole resistance from the outside. The white printed layers 22a, 22b and the light-shielding printed layers 24a, 24b may satisfy predetermined conditions, and may be appropriately adjusted, such as by making the white printed layers and the light-shielding printed layers three or more layers, depending on the whiteness and light-shielding properties required for the package, or taking into account the number of prints (number of printing units) possible in one printing machine used for printing. In this case, when there are three or more white printed layers, the pigment content of the white printed layer in contact with the adhesive layer is made less than the pigment content of the white printed layer located on the outer side thereof, and when there are three or more light-blocking printed layers, the brightness of the light-blocking printed layer located on the outer side is made higher than the brightness of the light-blocking printed layer located on the inner side thereof.

[0029] 4 shows a vertical pillow-type packaging bag in which the left and right sides of a single sheet of packaging material 10 are folded back, the folded edges are heat-sealed in a strip shape to form a back seal 30, and the overlapping edges on the bottom side are heat-sealed in a strip shape to form a bottom seal 32. Contents are inserted into this packaging body with the top side open through the opening, and then the overlapping edges on the top side are heat-sealed to form a packaged product in which the contents are sealed in a content-accommodating section 36 closed by the top seal 34, bottom seal 32 and back seal 30. In addition to this vertical pillow-type packaging bag, the present invention can be applied to various types of packaging bodies, such as a packaging bag formed by folding one sheet of packaging sheet material 10 in half and overlapping the two sheets, and then heat-sealing the overlapping edges to form a sealed bag, and a packaging bag formed by overlapping two sheets of packaging sheet material 10 and heat-sealing the overlapping edges to form a sealed bag. EXAMPLES

[0030] Next, the present invention will be explained in more detail with reference to examples, and tests conducted to compare and evaluate the light-shielding packages of the examples with packages of comparative examples and the results thereof will be described.

[0031] [Packaging sheet material according to Example 1] A biaxially oriented polyethylene terephthalate film having a thickness of 12 μm and having been corona-treated on one side was used as the outer substrate film 12 (see FIG. 1; the same applies below). The corona-treated surface was the laminate side, and two white printed layers 22a and 22b were formed on the laminate side (inner side). Of the two white printed layers, the outer white printed layer 22a was printed using a white ink containing 40% pigment, and the inner white printed layer 22b was printed using a white ink containing 35% pigment, with the pigment content of the inner white printed layer 22b set to be less than that of the outer white printed layer 22a. The white ink containing 40% pigment is a high-grade ink with extremely excellent whiteness, and the white ink containing 35% pigment is a general-purpose grade with a slightly higher pigment content than the standard. For the intermediate material film 14, a biaxially oriented nylon film with a thickness of 15 μm, which was subjected to corona treatment on both sides, was used, and the outer surface side was printed with a gray ink prepared by mixing white ink and black ink, forming two light-shielding printed layers 22a and 22b. For the formation of the outer light-shielding printed layer 24b of the two light-shielding printed layers, a mixture of white ink and about 5% black ink was used, and for the formation of the inner light-shielding printed layer 24a, a mixture of white ink and about 40% black ink was used, so that the brightness of the outer light-shielding printed layer 24b was set higher than that of the inner light-shielding printed layer 24a. For the inner material film 16, a non-oriented polypropylene film with a thickness of 40 μm was used. Then, the outer substrate film 12, the intermediate material film 14, and the inner material film 16 were bonded together by a dry lamination method to form a packaging sheet material 10.

[0032] [Packaging sheet material according to Example 2] In the above-mentioned packaging sheet material 10 according to Example 1, a white ink containing 40% pigment was used for printing on the outer surface side of the light-shielding printed layers 24a and 24b to form another white printed layer 28 (see FIG. 3; the same applies below). A packaging sheet material 26 was produced in the same manner as in Example 1 except for the above.

[0033] [Comparative packaging sheet material] In the above-mentioned packaging sheet material 10 of Example 1, the white ink used to form the inner white printed layer 22b of the two white printed layers applied to the outer base film 12 was changed to a white ink containing 40% pigment, the same as the white ink used to form the outer white printed layer 22a, and the ink used to form the two light-shielding printed layers 24a, 24b applied to the intermediate film 14 was changed to a gray ink consisting of a mixture of white ink and approximately 25% black ink, and a packaging sheet material was produced in a similar manner. In addition, in order to ensure that the thickness of the printed layer was consistent for both sheet materials in Examples 1 and 2 and the comparative example, all of the plates onto which ink was applied to form the white printed layer and the light-shielding printed layer were standardized to the engraved plate "150 lines / stylus angle 130 degrees / compressed."

[0034] [Evaluation 1 - Surface roughness of the white printed layer of the outer substrate film] The surface roughness of the white printed layer 22b applied to the outer substrate film 12 was measured using a laser microscope (Keyence Corporation's "VK-X260"), and the arithmetic mean roughness "Ra" was used as an index of the surface roughness. The results are shown in Table 1.

[0035] [Table 1]

[0036] As shown in Table 1, the surface of the printed layer becomes rougher as the pigment content in the ink increases, such as in the comparative example against Example 1, and the white ink single layer containing 40% pigment against the white ink single layer containing 35% pigment. When the outer substrate film 12 and the intermediate material film 14 are laminated, an adhesive layer 18 is formed on the surface of the white printed layer 22b, and the rougher the surface of the white printed layer 22b in contact with the adhesive layer 18, the more likely it is that poor appearance will occur due to the generation of air bubbles. In a past actual example, the surface roughness Ra of the printed layer of a film that had poor appearance due to the generation of air bubbles was 0.353. Comparing this example with the results shown in Table 1, the numerical value of the surface roughness of the comparative example (0.376) is close to the numerical value (0.353), and this shows that the pigment content in the white printed layer 22b on the inner side must be kept below 40%. Furthermore, it can be said that making the pigment content of at least the white printing layer in contact with the adhesive layer, among the two or more white printing layers applied to the outer base film 12, less than the pigment content of the white printing layer located on the outer side thereof is effective in obtaining a printing layer with a surface roughness suitable for lamination.

[0037] [Evaluation 2 - Heat seal strength] In a laminate film, when a printed layer and a heat-adhesive resin film (sealant film) are laminated next to each other, when a force is applied in the direction of peeling off the heat-sealed portion (the joint between the heat-adhesive resin films), the printed layer breaks before the film joint peels off, resulting in a lower heat-seal strength than a laminate film with a layered structure that does not include a printed layer. A test was conducted to verify this phenomenon. As a sample for verification, a biaxially oriented nylon film with a thickness of 15 μm, which has a white printed portion with a white printed layer and a plain portion without a printed layer, was dry-laminated on the printed surface with a non-oriented polypropylene film with a thickness of 60 μm to prepare a laminate film. Two types of non-oriented polypropylene film were prepared, one with low strength and one with high strength, with different heat-seal strengths. The laminate film was then formed into a bag shape with the unstretched polypropylene film on the inside, and the overlapping edges of the film were heat sealed together so that the edges included the white printed and plain areas, to produce a packaging bag. The heat seal strength of the white printed and plain areas of this packaging bag was measured using a tensile tester (Shimadzu Corporation's "Autograph AG-500NXPlus") in accordance with JIS Z1707 "General Rules for Food Packaging Plastic Films." The measurement direction was MD. The results are shown in Table 2.

[0038] [Table 2]

[0039] As shown in Table 2, when the printed layer and the heat adhesive resin film are laminated next to each other, the heat seal strength is lower than that of a plain part without a printed layer, and this tendency becomes more pronounced as the heat seal strength increases. From this result, it was confirmed that it is necessary to provide the printed layer (light-shielding printed layer) at an appropriate position relative to the lamination position of the heat adhesive resin film (inner surface material film), as in the packaging sheet material according to the present invention.

[0040] [Evaluation 3 - Lightness (L value) and optical density (OD value)] The brightness and optical density (transmission density) of the film were measured to verify the effect of making the brightness of the outer light-shielding printed layer 24b higher than that of the inner light-shielding printed layer 24a for the two light-shielding printed layers applied to the outer surface of the intermediate film 14. For each of Example 1 and Comparative Example, an intermediate film (biaxially oriented nylon film with a thickness of 15 μm) provided with two light-shielding printed layers was prepared as a verification sample to eliminate the influence of other factors. In addition, the effect of providing another white printed layer 28 on the outer surface side of the light-shielding printed layers 24a and 24b applied to the intermediate film 14 in the packaging sheet material according to Example 2 was also verified. This verification sample had the same configuration as the verification sample described above, except that another white printed layer was provided on the outer surface side of the two light-shielding printed layers. A transmission densitometer (Ihac-T5, manufactured by Ihara Electronics Co., Ltd.) was used to measure the optical density. The brightness was measured using a spectrophotometer (Nippon Denshoku Industries Co., Ltd. "SD7000") in accordance with JIS Z8722 "Method of measuring color - Reflection and transmission object color." The detailed measurement conditions were [measurement method: reflection, regular reflection processing: SCE, light source: D65, viewing angle: 10°, sample holder: black]. The results are shown in Table 3.

[0041] [Table 3]

[0042] From the results shown in Table 3, it can be seen that the film according to Example 1 has excellent brightness on the outer surface side while maintaining the same optical density as the film according to the comparative example, and reduces the loss of whiteness in appearance due to the light-shielding printed layer. Also, as shown in the results for Example 2, by providing another white printed layer on the outer surface side of the light-shielding printed layer, the effect of reducing the loss of whiteness in appearance due to the light-shielding printed layer is greater. Also, the sample films according to Examples 1 and 2 have an optical density of 1.9 or more, and have light-shielding properties equal to or greater than those of aluminum vapor-deposited films.

[0043] In order to obtain the performance (brightness and optical density) shown in Table 3, the number of printing layers applied to the film (intermediate film) is a maximum of three layers (two light-shielding printing layers and one white printing layer), and the number of times the ink is overprinted is three times, and the ink is not printed many times. Here, the number of times that can be applied with one general printing machine is 4 to 8 times as a standard, and is 10 times at most. Therefore, for the printing sheet material according to this invention, the light-shielding printing layer and the white printing layer can be easily processed and formed on the intermediate film using a general printing machine. And, since the light-shielding printing layer (and the white printing layer) is applied to the intermediate film, the number of printing layers applied to the outer substrate film, and therefore the number of times the ink is overprinted, is reduced accordingly. Therefore, in the printing process on the outer substrate film, the number of times (the number of printing units) that can be printed with one printing machine is not exceeded. In addition, it becomes possible to allocate many printing times for the design applied to the outer substrate film, and the options for the design applied to the packaging bag are expanded. Furthermore, for example, in the case where design printing, white printing, and light-shielding printing are all performed on the outer substrate film, general design printing requires at least four colors excluding white, so the total number of printings is 8 to 9 times, but considering that design printing very often requires an additional one or two colors, it is expected that even a printing machine that can coat a large number of times will not be able to cover it, and it will be necessary to pass the same outer substrate film through two printing machines for printing processing, which will lead to problems such as a decrease in quality and an increase in loss rate. In contrast, the configuration of the printing sheet material according to the present invention eliminates such concerns and allows easy printing processing. [Industrial Applicability]

[0044] This invention relates to a light-blocking packaging body that has been given light-blocking properties by printing, without using metal foil or metal-deposited film, and can be effectively used in fields such as the manufacture of packaging bodies that protect contents that are sensitive to light or that visually block the contents inside the bag, the processed food field in which foods that are prone to deterioration due to fading or oxidation caused by light are manufactured and packaged, and the cosmetics field in which various personal care products are manufactured and packaged, for example, for contents that are dark in color and can be seen through the bag surface, thereby reducing their appearance, or for contents whose efficacy as active ingredients decreases due to deterioration caused by light. [Explanation of symbols]

[0045] 10, 26 Packaging sheet materials 12 Outer substrate film 14 Intermediate film 16 Inner film 18, 20 Adhesive layer 22a, 22b white printing layer 24a, 24b Light-shielding printing layer 28 Another white printing layer 30 Back seal of packaging bag 32 Bottom seal of packaging bag 34 Top seal of packaging bag 36 Contents storage section

Claims

1. A packaging sheet material comprising at least an outer substrate film made of a resin material, an intermediate film made of a resin material, and an inner substrate film made of a heat-adhesive resin material, the outer substrate film and the intermediate film, and the intermediate film and the inner substrate film are laminated via adhesive layers to form a sheet, The light-shielding packaging body is formed into a bag shape with the inner surface film facing inward, and the overlapping edges of the packaging sheet material are heat-sealed in a strip shape to form a sealed bag having a content storage section, A gray light-shielding printed layer is formed on the outer surface side of the intermediate material film, and a white printed layer is formed on the inner surface side of the outer substrate film; A light-shielding packaging body characterized in that the light-shielding printed layer and the white printed layer each have two or more layers, the lightness of the light-shielding printed layer located on the outer surface side of the two or more light-shielding printed layers is higher than the lightness of the light-shielding printed layer located on the inner surface side thereof, and the pigment content of the white printed layer in contact with the adhesive layer of the two or more white printed layers is lower than the pigment content of the white printed layer located on the outer surface side thereof.

2. 2. The light-shielding package according to claim 1, wherein the light-shielding printed layer is two-layered, and the lightness of the light-shielding printed layer located on the outer surface side is higher than the lightness of the light-shielding printed layer located on the inner surface side.

3. 2. The light-shielding package according to claim 1, wherein the white printed layer is two-layered, and the pigment content of the white printed layer located on the inner surface side is less than the pigment content of the white printed layer located on the outer surface side.

4. 2. The light-shielding package according to claim 1, wherein a separate white printed layer is formed on the outer surface side of the light-shielding printed layer.

5. 2. The light-shielding packaging body according to claim 1, wherein the pigment content of the white printed layer in contact with the adhesive layer among the two or more white printed layers is less than 40%.

6. 6. The light-shielding package according to claim 1, wherein the packaging sheet material has an optical density of 1.9 or more.

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