Package for microwave heating with heat-generating ink and high-brightness ink and method for manufacturing same

Abstract

To provide a package for microwave oven heating which is provided with a high-luminance ink layer and a conductive heating layer and can form a steam vent by dielectric breakdown and heat generation during microwave oven cooking.SOLUTION: A package 100 for microwave heating includes a first sheet member 11 in which a base material layer 12, a sealant layer 13, and an automatic steam passage mechanism 5 are formed. A high brightness ink layer 15 and a conductive heat generating layer 16 are formed in an overlapping manner in the automatic steam passing mechanism 5. The high brightness ink layer 15 is an ink composition containing a vapor-deposited aluminum pigment in the form of thin flakes having an aspect ratio of thickness to length of 100 to 3000. In the high luminance ink layer 15, a plurality of non-spark parts composed of island parts and spark parts composed of gap parts separating the non-spark parts from each other or bridge parts narrower than the island parts are formed. The conductive heat generation layer 16 contains a conductive material composed of an organic compound, and is laminated on at least one of the upper and lower sides of the high luminance ink layer 15 so as to cover the spark part in a plan view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a package for microwave heating, and more particularly to a package for microwave heating with heat-generating ink and high-brightness ink, and a method for manufacturing the same. [Background technology]

[0002] Supermarkets, convenience stores, and other stores display foods completely sealed in plastic packaging, some of which are intended to be cooked in a microwave oven. When cooking in a microwave oven, the food inside the packaging heats up and generates steam, so various technologies have been proposed to allow this steam to escape safely, and many of these technologies are now available on the market.

[0003] (Top seal packaging) In recent years, in response to demands for resource reduction, there has been a trend toward switching from the conventional inset lid to a form in which a thinner (approximately 50 to 80 μm) plastic composite film is used to seal (heat seal) the outer edge of the top opening of the container (hereinafter referred to as "top-seal packaging").

[0004] This top-seal packaging has a high level of sealing for food, and it can also be filled with an inert gas instead of air, which has the advantage of extending the expiration date of food. For example, if the expiration dates of boxed lunches and prepared meals, which have traditionally been around one day after the date of manufacture, can be extended by several days or more, food waste can be significantly reduced, and this top-seal packaging technology is already being adopted by convenience stores to package salads and some prepared meals, and is becoming increasingly popular.

[0005] (Challenges with microwave-heated packaging (top-seal packaging)) Foods covered with conventional fitted lids (such as boxed lunches) have perforations on the lid surface, which allow the food's steam to escape when heated, allowing consumers and store staff to heat the food in a microwave oven without any hassle.

[0006] However, in the case of top-sealed packaging with enhanced airtightness, no through-holes are pre-drilled, so a steam vent must be prepared by peeling back a small edge of the lid (film) before heating in the microwave.

[0007] Furthermore, when heating top-seal packaging at a convenience store, store employees are required to peel off part of the film, and as part of infection control measures, they are also required to disinfect their hands beforehand. Not only does this increase the amount of work required for peeling and disinfecting, but it also necessitates a manual to ensure that all store employees perform these tasks correctly. On the other hand, when consumers take food (packaged items) home to heat rather than at a convenience store, they are required to open part of the lid (film) before using the microwave. However, forgetting to do this could lead to accidents such as the packaging bursting or food spilling.

[0008] For these reasons, there is a demand for top-sealed packaging that has an "automatic steaming mechanism" that allows steam to escape automatically during microwave cooking while maintaining the food's airtightness and without the need to peel off the film before microwave cooking.

[0009] (Prior art (Patent document 1: Heat-generating ink)) In response to the above demand for top-sealed packaging, the inventors of the present application have already proposed a technology in which a conductive heat-generating layer containing a conductive material (also called "heat-generating ink") that generates heat when exposed to microwaves from a microwave oven is printed on a film (Patent Document 1). By printing this heat-generating ink partially within the "heat-sealed area" between the tray (container) and the film (lid), the conductive heat-generating layer is heated and weakened during microwave cooking, and the steam pressure generated by the contents causes the heat seal in the weakened area to peel off, opening the film and allowing steam inside the tray to be safely released.

[0010] (Problems with Patent Document 1) However, the package of Patent Document 1 requires the formation of a conductive heating layer (i.e., a weakened portion) in the heat-sealed area where the container and lid come into contact, but because the lid is typically heat-sealed along the outer periphery of the top opening of the container, the location of the weakened portion (steaming opening) is limited to the outer periphery of the lid. When packaging liquid foods such as soups or noodles in a package with a steaming opening formed on the outer periphery of the lid as in Patent Document 1, there is a risk that the liquid will spill out of the steaming opening even if the package is tilted even slightly after cooking in a microwave. Furthermore, if the package is heated at a convenience store, great care must be taken to avoid spilling hot water when taking it home.

[0011] (Prior art (Patent Document 2: Tearable label)) Furthermore, Patent Document 2 discloses a tearable label that can form a desired cut in the lid film of a package by irradiating it with microwaves (see in particular FIG. 9 of the document).

[0012] (Problems with Patent Document 2) However, to realize the package of Patent Document 2, a process of individually and additionally attaching a tear label to the lid film is required, which is not suitable for manufacturing sites that mass-produce packages using gravure printing, and reduces productivity. Also, if the tear label is not securely attached to the surface of the lid film, the effect of forming the cut cannot be achieved, so a label inspection process will also be necessary.

[0013] (Prior art (Patent document 3 metal vapor deposited layer)) Patent Document 3 discloses a package in which a pattern is formed on the surface of a lid film so that a plurality of metal films each having a triangular or rectangular shape in plan view are arranged side by side. It is described that this patterning is preferably achieved by depositing a metal vapor deposition layer on the film surface.

[0014] (Problems with Patent Document 3) However, the manufacturing method of laminating a metal film (metal foil) onto the surface of a lid film as in Patent Document 3 is technically difficult and cannot be realized in the mass production process of gravure printing that is normally used in manufacturing packages. While it is possible to vapor-deposit a metal vapor-deposited layer onto the film surface in advance, this is by no means an inexpensive method to manufacture, and the inventors of this application believe that there have been no examples of packages with such a metal film attached that have actually been commercialized. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Patent No. 6709931 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-176805 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-046419 Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention has been proposed in light of the above circumstances, and aims to provide a package for microwave heating in which a steam vent can be formed at any position on the lid (for example, in the center of the lid surface of a top-seal package), which opens due to insulation breakdown (spark) when microwaves are irradiated during microwave cooking, and a method for manufacturing the same. [Means for solving the problem]

[0017] (Invention and use of high-brightness ink layer) The inventors discovered that forming a high-brightness ink layer inside a package using an ink composition containing a specially shaped vapor-deposited aluminum pigment and applying (printing patterning) this high-brightness ink layer so that it has non-sparking areas and sparking areas that have a higher electrical resistance value when irradiated with microwaves than the non-sparking areas makes it more likely that dielectric breakdown (opening) will occur when irradiated with microwaves. Note that a patent application for this invention has already been filed (Patent Application No. 2022-207123), and the application was not yet published at the time of filing this application.

[0018] (Risks when using only high-brightness ink layer) However, with an automatic vaporization mechanism formed from a high-brightness ink layer, if the microwave irradiation energy is set low or if the content of the food (the absorber of the above energy) inside the package is large (i.e., if the environmental conditions change during microwave heating), there is a risk that sufficient energy will not be irradiated to the spark area, and the opening will not be able to occur reliably.

[0019] (Additional use of conductive heating layer) Therefore, the inventors discovered that by additionally using a conductive heat-generating layer containing the heat-generating ink of Patent Document 1 mentioned above and overlaying it on the spark section of the high-brightness ink layer to form an automatic vaporization mechanism, a stable opening phenomenon can be achieved regardless of the set value of microwave irradiation energy or the type and content of food (the absorber of the above energy).

[0020] In short, by providing an automatic steaming mechanism that combines high-brightness ink and heat-generating ink, we have come up with the idea of ​​providing a microwave heating package that not only can be formed anywhere on the lid surface, but also has an automatic steaming mechanism that exhibits stable opening performance.

[0021] That is, the present invention employs, for example, the following configurations and features. (Aspect 1) A microwave heating package comprising a first sheet member having a base layer, a sealant layer, and an automatic steaming mechanism formed thereon, The automatic vaporization mechanism has a high-brightness ink layer and a conductive heat generating layer formed in a superimposed manner, the high-brightness ink layer is an ink composition containing a vapor-deposited aluminum pigment in the form of thin flakes having an aspect ratio of an average thickness to an average length of 100 to 3000; The high-brightness ink layer has formed therein a plurality of non-spark portions each composed of an island portion, and spark portions each composed of a gap portion separating the non-spark portions or a bridge portion narrower than the island portion, The conductive heat generating layer contains a conductive material made of an organic compound, and is laminated on at least one of the upper and lower sides of the high brightness ink layer so as to cover the spark portion in a plan view. A package for microwave heating, characterized by: (Aspect 2) The high-brightness ink layer has a film thickness of 0.1 to 3 μm, and The high-brightness ink layer is laminated with the vapor-deposited aluminum pigment having a plate thickness of 10 to 50 nm. The package for microwave heating according to aspect 1, characterized in that: (Aspect 3) The island portion forms a circle, an ellipse, or a polygon (where n is the number of vertices, n is 3 or more) in a plan view, or the gap of the void portion changes. 3. The package for microwave heating according to claim 1 or 2, (Aspect 4) A dividing layer made of ink or film is formed between the high-brightness ink layer and the conductive heat generating layer. 3. The package for microwave heating according to claim 1 or 2, (Aspect 5) the substrate layer includes a first substrate layer and a second substrate layer, Either the high-brightness ink layer or the conductive heat generating layer is formed between a first substrate layer and a second substrate layer, and the other is formed between the second substrate layer and the sealant layer. 3. The package for microwave heating according to claim 1 or 2, (Aspect 6) a first step of preparing a first sheet member; a second step of preparing a second sheet member or tray container; a step of thermally welding a first sheet member to a second sheet member or the tray container; A method for producing a package for microwave heating, comprising: The first step is Step 1a: preparing a film to be a base layer; a step 1b of applying a high brightness ink composition containing a vapor-deposited aluminum pigment to the inside or inner surface of the base layer to partially form a high brightness ink layer; a step 1c of applying a conductive material made of an organic compound to at least one of the upper and lower surfaces of the high brightness ink layer to form a conductive heat generating layer; a step 1d of preparing a film to be a sealant layer and further adhering and laminating it to the inner surface side of the base material layer; Including, In step 1b, the vapor-deposited aluminum pigment is a thin flake-shaped pigment having an aspect ratio of an average thickness to an average length of 100 to 3000, In step 1b, the ink composition is applied to the high-brightness ink layer so as to form a plurality of non-spark portions each composed of an island portion, and spark portions each composed of a gap portion separating the non-spark portions or a bridge portion narrower than the island portion, and In step 1c, the conductive heat generating layer is laminated so as to cover the spark portion in a plan view. A method for producing a package for microwave heating using a high brightness ink characterized by the above. (Aspect 7) In step 1b, the high brightness ink layer has a film thickness of 0.1 to 3 μm, and the vapor-deposited aluminum pigment has a plate thickness of 10 to 50 nm. 7. A method for producing a package for microwave heating according to claim 6, characterized in that: (Aspect 8) In step 1b, the ink composition is applied so that the island portion forms a circle, an ellipse, or a polygon (where n is the number of vertices, n is 3 or more) in a plan view, or so that the gap of the void portion changes. 8. A method for producing a package for microwave heating according to claim 6 or 7, characterized in that: (Aspect 9) The first step further includes a step 1e of applying ink or laminating a film so as to form a dividing layer between the high-brightness ink layer and the conductive heat generating layer. 8. A method for producing a package for microwave heating according to claim 6 or 7, characterized in that: (Aspect 10) In step 1a, two films are prepared to form the first and second base layers. When the high brightness ink layer is formed between the first and second base layers in step 1b, the conductive heat generating layer is laminated between the second base layer and the sealant layer in step 1c, When the high brightness ink layer is formed between the second base material layer and the sealant layer in step 1b, the conductive heat generating layer is laminated between the first and second base material layers in step 1c. 8. A method for producing a package for microwave heating according to claim 6 or 7, characterized in that: [Effects of the Invention]

[0022] In the microwave heating packaging of the present invention, a high-brightness ink layer of the above-described configuration is formed within the film (first sheet member). Therefore, when microwaves are irradiated onto the packaging, the thin flake-shaped vapor-deposited aluminum pigments stacked in large numbers within the ink layer become charged, creating a potential difference between adjacent pigments, and an electric current flows within the ink layer, generating Joule heat.

[0023] Furthermore, since the high-brightness ink layer is printed to form the spark portions and non-spark portions of the above-described configuration, when microwaves are continuously irradiated, insulation breakdown occurs in the spark portions, where current does not easily flow, and a vapor vent (vapor escape port) is formed that penetrates the first sheet member.

[0024] In the packaging for microwave heating of the present invention, the conductive heating layer is laminated so as to cover the spark portion of the high-brightness ink layer. Therefore, even if the environmental conditions change during microwave heating (for example, the food inside the packaging is large and the irradiated energy is absorbed by the food), making it difficult for insulation breakdown to occur in the spark portion, the heat generated by the conductive heating layer melts and weakens the spark portion, ensuring the reliable and stable formation of a steam vent (steam release port).

[0025] Furthermore, in a preferred embodiment of the packaging of the present invention, a separating layer made of ink or film is inserted between the high-brightness ink layer and the conductive heat-generating layer, forming a coupling structure in which the layers are close to each other but not in contact with each other. This reduces problems that can occur when the two layers come into direct contact (for example, insulation breakdown due to a decrease in resistance, or poor coating of one layer that is superimposed on the other), and makes it possible to create a base that is easy to form a vapor vent.

[0026] In addition, the coupling structure not only has excellent microwave power transmission properties, but also allows the power required for the steam vent operation to be distributed and supplied to the high-brightness ink layer and the conductive heat generating layer due to the presence of the separating layer, and prevents damage to the contacts when they are directly superimposed. [Brief explanation of the drawings]

[0027] [Figure 1] 1A and 1B are a perspective view and a cross-sectional view showing the overall structure of a package according to the present invention (Example 1), and a partially enlarged cross-sectional view showing the structure of a part of the package (an automatic steaming mechanism at the upper center). [Figure 2] 10 is a partially enlarged cross-sectional view showing a modified example of the stacking arrangement of the first sheet member (laminate layer), and a schematic cross-sectional view showing a bridge portion and a gap portion of the spark portion. FIG. [Figure 3] 1 is a schematic diagram illustrating the shape of the vapor-deposited aluminum pigment of the present invention in comparison with the shape of a conventional pigment. [Figure 4] FIG. 2 is a diagram illustrating print patterns (P1 to P6) of a high-brightness ink layer and a conductive heat generating layer. [Figure 5] 1 is a flowchart showing each step of the method for manufacturing a package of the present invention. [Figure 6] 1A to 1C are diagrams showing detailed steps in the process of forming a high-brightness ink layer. [Figure 7] 10 is an image showing the results of a confirmation test (whether or not a steam vent is formed in the packaging bodies of the example and comparative examples 1 and 2). DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will be described below based on the embodiments shown in the drawings, but the present invention is not limited to the specific embodiments described below. In addition, the same reference numerals are used in each drawing to designate the same or corresponding parts.

[0029] As described above, the microwave oven heating package of the present invention is characterized by the provision of an automatic vaporization mechanism that combines a layer containing a novel high-brightness ink and a layer containing a heat-generating ink (see Patent Document 1). Each ink material is described in detail below.

[0030] (Conductive heating layer material) The material for the conductive heat-generating layer 16 (hereinafter also referred to as "conductive material" or "heat-generating ink") can be, for example, inorganic materials such as indium oxide, aluminum, tin, nickel, and carbon, or conductive organic compounds such as polyanilines and polypyrroles, but is not necessarily limited to these, and any known conductive material that is commonly used in microwave cooking and generates heat when irradiated with microwaves will do. However, from the experience of the inventors, organic compound-based conductive materials are preferred from the perspective of achieving favorable releasability of the sealant layer 13.

[0031] (High brightness ink) In the present invention, a novel ink composition (high-brightness ink) is used to form a steam port (automatic steaming mechanism) for a package for microwave heating. This ink composition contains a vapor-deposited aluminum pigment 15b (see FIG. 3(b)), a thermoplastic resin 15a (see FIG. 3(a)), and a solvent (preferably an organic solvent). The presence of this vapor-deposited aluminum pigment 15b gives the ink composition a silver color.

[0032] The vapor-deposited aluminum pigment 15b is preferably contained in the ink composition at 0.5 to 15% by mass. If the content is less than the lower limit (0.5% by mass), the pigments 15b in the ink composition are less likely to come into contact with each other, and the effects of the present invention (electric charging and dielectric breakdown during microwave irradiation, as described below) are not fully achieved. On the other hand, if the content is more than the upper limit (15% by mass), the ink composition contains an excess of pigment 15b, which not only reduces the fluidity of the ink composition during production of the ink composition and during subsequent production of the package 100 (when applying the high-brightness ink layer 15, as described below), but also increases production costs.

[0033] (vapor-deposited aluminum pigment) Here, the vapor-deposited aluminum pigment 15b is an aluminum powder that is "thin flake-like (scale-like)" in cross section as shown in Figures 3(a) and (b). More specifically, the average thickness t p and the average length L p Aspect ratio (AR=L p / tp) is molded so that AR=100 to 3000. p Therefore, the average thickness t p When is 10 nm, the corresponding average length L p is 1 to 30 μm, and the average thickness t p When is 50 nm, the corresponding average length L p is 5 to 150 μm.

[0034] The pigment 15b has an extremely high aspect ratio AR compared to the same type of conventional pigment (aluminum paste) described below, and therefore each pigment 15b is likely to be oriented so as to line up orderly in the same direction in the ink layer 15 after printing on the film (substrate layer 12). The pigments 15b lined up orderly in the same direction have more contact points (larger contact area) and are more uniformly packed, so that when microwaves are applied, current tends to flow uniformly through the pigments 15b (the ink layer 15 containing them).

[0035] (conventional pigments) On the other hand, the shape of a conventional pigment (e.g., aluminum paste) is shown as 150b in Figure 3(c). Reference numeral 150a denotes a resin surrounding the pigment 150b. This conventional pigment 150b is used when manufacturing ordinary aluminum paste-type silver ink. This pigment 150b is clumped compared to the pigment 15b of the present invention, and has an aspect ratio AR of 100 or less. As a result, it is difficult for each pigment 150b to be oriented in the same direction within the ink layer 150 after film printing, resulting in a non-uniform pigment loading state, which makes it difficult for current to flow uniformly through the pigment 150b (or the ink layer 150 containing the pigment 150b) when exposed to microwaves.

[0036] (resin) Examples of thermoplastic resin 15a include resins used in ordinary gravure printing inks, but it is more preferable that the resin is at least one resin selected from among shellac resin, rosins, urethane resin, acrylic resin, polyvinylidene chloride resin, polyester resin, fibrous resin such as nitrocellulose, vinyl chloride-vinyl acetate copolymer resin, polyamide resin, and chlorinated olefin resin, and gravure printing ink or flexographic printing ink containing one or a combination of two or more of these resins may also be used.

[0037] (solvent) The ink composition of the present invention may contain a solvent. In particular, in the case of gravure printing ink or flexographic printing ink, the solvent may be any solvent that dissolves or disperses the thermoplastic resin 15a in the solvent. Examples of the solvent include the following organic solvents and / or water that are commonly used in gravure printing ink or flexographic printing ink.

[0038] Examples of the organic solvent include aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as hexane, cyclohexane, methylcyclohexane and ethylcyclohexane; alcohol solvents such as methanol, ethanol, isopropyl alcohol, normal propyl alcohol, 1-butanol, 2-butanol, isobutanol and tert-butanol; ester solvents such as ethyl acetate, n-propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate and tert-butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether and propylene glycol monobutyl ether; and esters thereof. [Example]

[0039] Fig. 1(a) is a perspective view showing a package 100 for microwave heating according to Example 1. Fig. 1(b) is a schematic cross-sectional view of the package 100. Fig. 1(c) is a partially enlarged cross-sectional view showing the part surrounded by circle C (broken line) in Fig. 1(b).

[0040] (Outline of top-seal package (tray pack) according to Example 1) The packaging body 100 shown in Example 1 is in the form of a tray pack including a first sheet member 1 and a tray container 2. The first sheet member 1 and the tray container 2 are heat-sealed to each other at their peripheral edges 11, 21 to form an internal space 4 in which foodstuffs 3 and the like are enclosed.

[0041] (Cross-sectional structure of first sheet member) 1(c) shows an enlarged cross-sectional structure of a portion having this automatic steaming mechanism 5 (5A). The first sheet member 1 includes a heat-resistant film-like base material layer 12, a film-like sealant layer 13, an adhesive layer 14 that connects the base material layer 12 and the sealant layer 13 with an adhesive, and a printed layer (not shown). From the perspective of product sales, the base material layer 12 may be formed of multiple layers (for example, first and second base material layers 12a and 12b as shown).

[0042] Before the base layer 12 is bonded to the sealant layer 13, a printing layer, a conductive heat-generating layer 16, and a high-brightness ink layer 15 (not shown) are applied to one side of the base layer 12 (the inner side facing the sealant layer 13).

[0043] 1(c), before the first substrate layer 12a and the second substrate layer 12b are connected by the adhesive layer 14', a printing layer (not shown) and a conductive heat-generating layer 16 are applied (printed) in advance on the inner surface (on the film) of the first substrate layer 12a, and high-brightness ink layers 15, 15 are applied (printed) in advance on the inner surface (on the film) of the second substrate layer 12b so as to be spaced apart from each other. The first and second substrate layers 12a, 12b thus integrated are then connected to the sealant layer 13 by the adhesive (adhesive layer 14) to form the final laminate.

[0044] That is, the base material layer 12 is integral with these multiple layers and connected to the sealant layer 13 via the adhesive layer 14. A laminate of films 12 and 13 made of different materials in this way is also called a "multilayer laminate film" or simply a "laminate layer."

[0045] (Material for base layer) It is desirable to use stretched film materials such as nylon, polypropylene, polyethylene terephthalate, polybutylene terephthalate, and transparent vapor-deposited PET as the material for the base layer 12 (12a, 12b), but the material is not limited to these.

[0046] (Sealant layer material) Furthermore, it is desirable to use a non-stretched film material such as non-stretched polypropylene as the material for the sealant layer 13, but the material is not necessarily limited to this.

[0047] (Modifications regarding the lamination arrangement of the conductive heat generating layer and the high brightness ink layer) The layer structure of the automatic vaporization mechanism 5 for the high-brightness ink layer 15 is not limited to the example (5A) shown in FIG. 1(c). It is also possible to prepare only one film (layer) as the base layer 12, and form various layers between this base layer 12 and the sealant layer 13. For example, as shown in modified example 5 (5B) of FIG. 2(a), before bonding the base layer 12 (12a) to the sealant layer 13 with the adhesive layer 14, the high-brightness ink layer 15 and a printed layer (not shown) may be applied to the inner surface of the base layer 12a (the surface facing the sealant layer 13), and then a third ink layer 17 may be applied using a known ink, followed by the application of the conductive heat-generating layer 16. It is also possible to reverse the arrangement of the high-brightness ink layer 15 and the conductive heat-generating layer 16, without being limited to the example shown in FIG. 2(a).

[0048] (Overview of high-brightness ink layer) As described above, it should be noted that in this embodiment, the high-brightness ink layer 15 is formed in the center of the first sheet member 1 in a plan view (between the base layer 12 and the sealant layer 13 in a cross-sectional view). Here, as shown in FIG. 3(a), the high-brightness ink layer 15 is an ink composition containing a vapor-deposited aluminum pigment (hereinafter also simply referred to as "pigment") 15b in a thermoplastic resin 15a. In addition to this pigment 15b, the ink composition is prepared by blending a thermoplastic resin 15a (e.g., shellac resin) and an organic solvent (e.g., toluene).

[0049] (thin flake pigment) In addition, the vapor-deposited aluminum pigment 15b of the present invention has an average thickness t p and the average length L p Aspect ratio (AR=L p / t pIt should be noted that the high brightness ink layer 15 is formed in the form of a thin flake with an AR of 100 to 3000. i The ink layer 15 has a thickness t of 10 to 50 nm. p It is preferable that the vapor-deposited aluminum pigment 15b having the above structure is laminated.

[0050] (Formation of spark and non-spark parts) The high-brightness ink layer 15 is printed (preferably by gravure printing) to form a plurality of non-spark portions NSP and spark portions SP that connect these non-spark portions NSP, NSP. The spark portions SP are formed to form bridge portions 151 (see FIGS. 2(b) and 4(b)) with reduced vapor-deposited aluminum pigment 15b (in other words, a cross-sectional area in a direction perpendicular to the connection (coupling) direction between the non-spark portions NSP) compared to the non-spark portions NSP, or void portions 152 (no connection between the non-spark portions NSP, see FIG. 2(c)). Note that this results in the spark portions SP having a higher electrical resistance when irradiated with microwaves than the non-spark portions NSP.

[0051] (Shape and arrangement of non-sparking and sparking parts) The non-spark portions NSP of the high-brightness ink layer 15 may be island-shaped objects (islands) containing pigment 15b in a plan view, and may be selected to be circular, elliptical, polygonal such as triangular or quadrangular (where n is the number of vertices, n is 3 or more), as shown in Figures 4(a) to 4(d), or rectangular with a partially curved surface (see Figure 4(e)). The non-spark portions NSP are multiple islands spaced apart from each other with one spark portion SP between them, but are not limited to two in number, and three or more may be arranged as shown in Figure 4(f), and the number of spark portions SP is also not limited to one, but multiple may be arranged.

[0052] According to the inventors' experience through trial and error, it is preferable that the distance between the non-spark portions NSP (in other words, the gaps in the gaps 152 and the width of the bridge portions 151) varies rather than being constant, and it is even more preferable that it varies so as to have a minimum value (see print patterns P1 to P3 and P5 to P6 other than P4 in FIG. 4(d)). This causes highs and lows in the electrical resistance value within the gaps 152, and sparks are reliably generated at points with higher electrical resistance values ​​(i.e., more specific points), and the vapor port can be expanded from there as a base point.

[0053] (Principle of charging and heat generation in high-brightness ink layer) In the packaging body 100 of the present invention (this embodiment), the high-brightness ink layer 15 having the above-described configuration is formed within the first sheet member 1. Therefore, when microwaves are irradiated onto the packaging body 100, the thin flake-shaped pigments 15b stacked in large numbers within the ink layer 15 become charged, creating a potential difference between adjacent pigments 15b, 15b, and causing an electric current to flow within the high-brightness ink layer 15, generating Joule heat.

[0054] (Insulation breakdown at the spark point) Furthermore, the high-brightness ink layer 15 is printed to form the spark portions SP and non-spark portions NSP of the above-described configuration, so that when microwaves are continuously irradiated onto the packaging body 100 by microwave heating, insulation breakdown occurs in the spark portions SP, which are difficult for current to flow through, and a vapor vent (vapor escape port) is formed that penetrates the first sheet member 1.

[0055] (Placement of a conductive heating layer on the spark part) In addition, it should be noted that in the present invention, the conductive heat generating layer 16 is arranged so that, in plan view, it is projected onto the spark portion SP of the high-brightness ink layer 15. As a result, when microwaves are irradiated, the conductive heat generating layer 16 generates heat, which softens the spark portion SP in the vicinity, making it easier for the steam opening to open.

[0056] Preferably, an intervening material (separating layer) made of ink or film is formed between the high-brightness ink layer 15 and the conductive heat-generating layer 16. In the embodiment shown in FIG. 1(c), the film of the second base material layer 12b is interposed so as to separate the layers 15 and 16. On the other hand, in the modified example shown in FIG. 2, instead of using a film as in the embodiment, a separating layer (third ink layer 17) is formed by applying a separate ink (a known ink that can be used for gravure printing on packaging (for example, but not limited to, white ink (LAMITECC 630 R White B manufactured by Tokyo Ink Co., Ltd.)).

[0057] (Advantages of inserting a dividing layer) The insertion of such a separating layer 17 forms a "coupling structure" that brings the layers 15, 16 close to each other without contacting each other. This reduces problems that can occur when the layers 15, 16 are in direct contact with each other (for example, insulation breakdown at the spark portion SP due to a decrease in resistance (difficulty in current flow), and coating defects of one layer 16 that is superimposed on the other layer 15), making it possible to create a base material that is easy to form a vapor vent hole.

[0058] In addition, the coupling structure not only has excellent microwave power transmission properties, but also, due to the presence of the separating layer 17, the power required for the steam port operation can be distributed and supplied to the high-brightness ink layer 15 and the conductive heat generating layer 16, and damage to the contacts that can occur when the two are directly superimposed on each other can be prevented. [Example]

[0059] (Outline of packaging manufacturing method) FIG. 5 is a flowchart showing the steps constituting the manufacturing method of the packaging body 100 of the present invention. First, a first sheet member 1 that will form one side (e.g., the front side) of the packaging body 100 is prepared (first step S1). Then, as shown in steps S2 to S4 on the left side of FIG. 5, a tray container 2 is prepared on the other side (e.g., the back side) of the packaging body 100 (step S2). Then, food ingredients 3 are packed into the tray container 2 (packing step S3). Thereafter, by thermally welding the peripheral edge 11 of the first sheet member 1 to the peripheral edge 21 of the tray container 2, the food ingredients 3 can be completely sealed within the packaging body 100 (sealing step S4). When performing steps S1, S2, S4, etc., among the above, it is preferable to use a known gravure printing technique.

[0060] On the other hand, when manufacturing a package (not shown) that uses a second sheet member (not shown) instead of the tray container 2, after the first step S1 is completed, the process proceeds to steps S2a, S2b, S3a, and S4a shown on the right side of Fig. 5. Specifically, a regular second sheet member (not shown) made of a laminate layer is prepared (step S2a), and the peripheral edge 11 of the first sheet member 1 and a part of the peripheral edge of the second sheet member are heat-sealed (step S2b).

[0061] When step S2b is completed, a package is produced in which a portion of the periphery (e.g., three sides) is heat-sealed. Thereafter, the desired ingredients are stuffed into the interior space of the package from the remaining open periphery (e.g., one side) (packing step S3a). After the ingredients have been stuffed, the remaining periphery is also heat-sealed to completely seal the ingredients in the interior space of the package (sealing step S4a).

[0062] The method for producing the package 100 of the present invention is characterized by the treatment in the first step S1 as shown in FIG. 5, and will be described in detail below.

[0063] (Formation of base layer, conductive heat-generating layer and high-brightness ink layer) In the first step S1, a stretched film that will become the aforementioned base layer 12 is first prepared (step S11). One layer (e.g., layer 16) of the conductive heat-generating layer 16 or the high-brightness ink layer 15 is formed on the inner surface side (i.e., the sealant layer 13 side) of this base layer 12 (step S12). In the former case, the heat-generating ink is applied to the inner surface side of the base layer 12 (film), and in the latter case, the high-brightness ink is applied to the inner surface side of the base layer 12 (film).

[0064] (Formation of a dividing layer) Thereafter, a film or ink is superimposed on the inner surface of the base material layer 12 to further form a dividing layer (step S13). More specifically, the second base material layer 12b may be used as the dividing layer film and adhered to the base material layer 12 so as to sandwich one of the layers. Alternatively, a known film applicable to packaging materials may be used. The ink used in step S13 may be a known ink that can be printed on packaging materials (for example, the white ink described above).

[0065] In addition, the other of the conductive heat generating layer 16 and the high brightness ink layer 15 (the other layer for the one layer selected in step S12) is formed on the inner surface side of the dividing layer (step S14). For example, in the case of the cross-sectional configuration shown in Figure 1(a), the conductive heat generating layer 16 is formed in step S12, so the high brightness ink layer 15 is formed in this step S14.

[0066] (Preparing the sealant layer) Furthermore, an unstretched film that will become the sealant layer 13 is prepared and adhered to the inner surface of the base material layer 12 and laminated (step S15). This forms a laminate layer (first sheet member 1) that incorporates the high-brightness ink layer 15. Note that adhesive layers 14, 14' made of adhesive or a printed layer (not shown) that will become the package surface may be inserted (laminated) between the base material layer 12, the dividing layer (in the case of a film such as the second base material layer 12b), and the sealant layer 13.

[0067] (Details of the high-brightness ink layer formation process) The step S5 of forming the high brightness ink layer 15 in the above step S12 or S14 will be described in more detail with reference to FIG. 6. An ink composition containing a vapor-deposited aluminum pigment 15b is applied to a part of the inner surface side (see FIG. 1(c) and FIG. 2(a)) of the base layer 12 (12a) to partially form the high brightness ink layer 15. The ink composition applied in this step contains a vapor-deposited aluminum pigment 15b having a thickness of 10 to 50 nm. p It is preferable to use a vapor-deposited aluminum pigment 15b having the following structure.

[0068] (Use of special pigments) The pigment to be added to the ink composition has an average thickness of t p and the average length L p Aspect ratio (AR=L p / t p Note that thin flake vapor-deposited aluminum pigments 15b (see also FIG. 3(b)) having an AR of 100 to 3000 are used (step S51). As a result, when the package 100 is heated in a microwave oven and the ink layer 15 is also irradiated with microwaves, the thin flake vapor-deposited aluminum pigments 15b become charged, creating a potential difference between adjacent pigments 15b, 15b, causing a current to flow within the high-brightness ink layer 15, generating Joule heat.

[0069] (Application with special printing pattern) Furthermore, it should be noted that in step S5, when forming the high-brightness ink layer 15, the ink composition is applied so as to form a plurality of non-spark portions NSP and spark portions SP that connect the non-spark portions NSP, NSP (step S52) (see the print patterns P1 to P6 shown in FIG. 4). When microwaves are continuously irradiated onto the high-brightness ink layer 15 having such print patterns P1 to P6, insulation breakdown occurs in the spark portions SP, through which current does not easily flow, and vapor holes (vapor escape holes) are formed that penetrate the first sheet member 1 (i.e., the laminate layer).

[0070] (Formation of spark and non-spark parts) It should also be noted that the ink composition is applied to the non-spark portions NSP so as to form multiple islands, and to the spark portions SP so as to form bridge portions 151 with reduced vapor-deposited aluminum pigment 15b (in other words, the cross-sectional area in the direction perpendicular to the connecting direction between the non-spark portions NSP) compared to the non-spark portions NSP, or void portions 152 with no pigment 15b at all (step S53). This reliably increases the electrical resistance in the spark portions SP, eventually causing dielectric breakdown.

[0071] In addition, it is preferable to form the island portions so that the gaps between the non-spark portions NSP (the width of the spark portions SP) vary (preferably gradually vary to have an extremely small width) (step S53a). For example, the high-brightness ink layer 15 can be printed (laminated) on the base material layer 12 using print patterns P1 to P3, P5, and P6 as shown in Fig. 4. This creates high and low electrical resistance values ​​even within the gap portions 152, ensuring that sparks are generated at locations with higher electrical resistance values ​​(i.e., more specific points), and the steam opening can be expanded from these points.

[0072] Furthermore, when observing the package 100 in a plan view, it is preferable to position the spark portion SP so that it overlaps (is projected onto) the conductive heating layer 16 (step S54). As a result, when the conductive heating layer 16 generates heat during microwave irradiation, the spark portion SP arranged nearby also becomes soft, making it easier for the vapor vent to open in the event of insulation breakdown in the spark portion SP. [Example]

[0073] (Test to confirm the formation of steam vents) The present inventors fabricated an automatic vaporization mechanism 5 having the cross-sectional structure shown in FIG. 1(c) and the print pattern P1 shown in FIG. 4(a) using a high-brightness ink layer 15 and a conductive heat-generating layer 16 as this example (see FIG. 7(a)). Note that an ink composition was applied to the high-brightness ink layer 15 so that it was composed only of circular non-spark portions NSP, with the conductive heat-generating layer 16 formed outside the non-spark portions NSP, to prepare Comparative Example 1 (see FIG. 7(b)). Furthermore, similar to the above-described example, the high-brightness ink layer 15 was applied in the print pattern P1, but the conductive heat-generating layer 16 was superimposed on the non-spark portions NSP, rather than on the spark portions SP, to prepare Comparative Example 2 (see FIG. 7(c)).

[0074] The comparative example and example packages prepared in this manner were heated in a microwave oven to check for the presence or absence of a steam vent. Figures 7(a)-(c) show images of each sample before heating, and Figures 7(d)-(f) show images of the corresponding samples after heating. As shown in Figure 7(d), in the example sample, a steam vent is clearly formed along the overlapping portion of the spark portion SP and the conductive heating layer 16. On the other hand, in the samples of comparative examples 1 and 2 shown in Figures 7(e) and 7(f), no steam vent is clearly formed.

[0075] In this way, the packaging body 100 of the present invention combines the characteristics of the high brightness ink layer 15 (dielectric breakdown) and the characteristics of the conductive heat generating layer 16 (heat generation) so as to exhibit their full potential.

[0076] Although the embodiments and examples of the present invention have been described above with reference to the drawings, the scope of application of the present invention is not limited to the packaging form of the top-sealed package shown in the drawings. The same advantages can be obtained even if the above-mentioned automatic steaming mechanism is formed in other packaging forms (for example, pillow packaging film, back-sealed bags, standing pouches, three-side sealed bags). [Industrial Applicability]

[0077] In the microwave heating packaging of the present invention, a high-brightness ink layer of the above-described configuration is formed within the film (first sheet member). Therefore, when microwaves are irradiated onto the packaging, the thin flake-shaped vapor-deposited aluminum pigments stacked in large numbers within the ink layer become charged, creating a potential difference between adjacent pigments, and an electric current flows within the ink layer, generating Joule heat.

[0078] Furthermore, since the high-brightness ink layer is printed to form the spark portions and non-spark portions of the above-described configuration, when microwaves are continuously irradiated, insulation breakdown occurs in the spark portions, where current does not easily flow, and a vapor vent (vapor escape port) is formed that penetrates the first sheet member.

[0079] In the packaging of the present invention, the conductive heating layer is laminated in a superimposed manner, particularly covering the spark portion of the high-brightness ink layer. Therefore, even if the environmental conditions change during microwave heating (for example, the food inside the packaging is large and the irradiated energy is absorbed by the food), making it difficult for insulation breakdown to occur in the spark portion, the heat generated by the conductive heating layer melts and weakens the spark portion, ensuring the reliable and stable formation of a steam vent (steam release port).

[0080] The packaging material and its manufacturing method of the present invention, which exhibit such remarkable effects, are not found in the packaging industry or on the market, and have extremely high industrial value and applicability. [Explanation of symbols]

[0081] 1. First sheet member 2 Tray containers 3. Ingredients 4. Interior space 5,5A,5B Automatic steaming mechanism 11,21 Periphery 12,12a,12b Base material layer (1st and 2nd base material layer) 13 Sealant layer 14,14' adhesive layer 15, 15a, 15b High-brightness ink layer, resin, vapor-deposited aluminum pigment 16 Conductive heating layer 17 Third ink layer 100 packages 150, 150a, 150b Conventional ink layer, resin, pigment 151,152 Bridge section, gap section AR,L p ,t p Pigment aspect ratio, average length, and average thickness NSP, SP Non-spark part, spark part Printing patterns when printing ink compositions P1, P2, P3, P4, P5, and P6 t i High-brightness ink layer thickness

Claims

1. A microwave oven heating package including a first sheet member having a base layer, a sealant layer, and an automatic steaming mechanism formed thereon, The automatic vaporization mechanism has a high-brightness ink layer and a conductive heat generating layer formed in a superimposed manner, the high-brightness ink layer is an ink composition containing a vapor-deposited aluminum pigment in the form of thin flakes having an aspect ratio of an average thickness to an average length of 100 to 3000; The high-brightness ink layer has formed therein a plurality of non-spark portions each composed of an island portion, and spark portions each composed of a gap portion separating the non-spark portions or a bridge portion narrower than the island portion, The conductive heat generating layer contains a conductive material made of an organic compound, and is laminated on at least one of the upper and lower sides of the high brightness ink layer so as to cover the spark portion in a plan view. A package for microwave heating, characterized by:

2. The high-brightness ink layer has a film thickness of 0.1 to 3 μm, and The high-brightness ink layer is laminated with the vapor-deposited aluminum pigment having a plate thickness of 10 to 50 nm.

2. The package for microwave heating according to claim 1, wherein:

3. The island portion has a circular, elliptical or polygonal shape in plan view (where n is the number of vertices, n is 3 or more), or the gap of the void portion varies.

3. The package for microwave heating according to claim 1 or 2, wherein:

4. A dividing layer made of ink or film is formed between the high-brightness ink layer and the conductive heat generating layer.

3. The package for microwave heating according to claim 1 or 2, wherein:

5. the substrate layer includes first and second substrate layers, Either the high-brightness ink layer or the conductive heat generating layer is formed between a first substrate layer and a second substrate layer, and the other is formed between the second substrate layer and the sealant layer.

3. The package for microwave heating according to claim 1 or 2, wherein:

6. a first step of preparing a first sheet member; a second step of providing a second sheet member or tray container; a step of thermally welding a first sheet member to a second sheet member or the tray container; A method for producing a package for microwave heating, comprising: The first step is Step 1a: preparing a film to be a base layer; a step 1b of applying a high brightness ink composition containing a vapor-deposited aluminum pigment to the inside or inner surface of the base layer to partially form a high brightness ink layer; a step 1c of applying a conductive material made of an organic compound to at least one of the upper and lower surfaces of the high brightness ink layer to form a conductive heat generating layer; a step 1d of preparing a film to be a sealant layer and further adhering and laminating the film to the inner surface side of the base material layer; Including, In step 1b, the vapor-deposited aluminum pigment is a thin flake-shaped pigment having an aspect ratio of an average thickness to an average length of 100 to 3000, In step 1b, the ink composition is applied to the high-brightness ink layer so as to form a plurality of non-spark portions each composed of an island portion, and spark portions each composed of a gap portion separating the non-spark portions or a bridge portion narrower than the island portion, and In step 1c, the conductive heat generating layer is laminated in a superposed manner so as to cover the spark portion in a plan view. A method for producing a package for microwave heating using a high brightness ink characterized by the above.

7. In step 1b, the high brightness ink layer has a film thickness of 0.1 to 3 μm, and the vapor-deposited aluminum pigment has a plate thickness of 10 to 50 nm.

7. The method for producing a package for microwave heating according to claim 6,

8. In step 1b, the ink composition is applied so that the island portion has a circular, elliptical or polygonal shape in plan view (where n is the number of vertices, n is 3 or more), or the gap of the void portion changes.

8. A method for producing a package for microwave heating according to claim 6 or 7, characterized by:

9. The first step further includes a step 1e of applying ink or laminating a film so as to form a dividing layer between the high brightness ink layer and the conductive heat generating layer.

8. A method for producing a package for microwave heating according to claim 6 or 7, characterized by:

10. In step 1a, two films are prepared to serve as first and second base layers; When the high brightness ink layer is formed between the first and second base layers in step 1b, the conductive heat generating layer is laminated between the second base layer and the sealant layer in step 1c, When the high brightness ink layer is formed between the second substrate layer and the sealant layer in step 1b, the conductive heat generating layer is laminated between the first and second substrate layers in step 1c.

8. A method for producing a package for microwave heating according to claim 6 or 7, characterized by:

Images