JP6960782B2 - Heat seal film for packaging and packaging containers using the heat seal film - Google Patents

Description

The present invention relates to a heat-sealing film for packaging and a packaging container using the heat-sealing film. More specifically, the heat-sealing film used for making a heat-sealing bag and an opening of a packaging tray are covered. A packaging container such as a heat-sealing film used for packaging, the above-mentioned heat-sealing bag manufactured by using the heat-sealing film, or a packaging tray covered with the heat-sealing film, such as a heat-sealing film. The present invention relates to a packaging container suitable for heating using a microwave oven while containing food inside.

Packaging containers such as heat-sealed bags used for packaging retort-packed foods and frozen foods, and packaging trays whose openings are covered with a heat-sealing film are used for packaging various foods.

Foods packaged in such packaging are distributed in a state of being sealed and sealed in the packaging by heat sealing, and consumers who purchase the food are heated as necessary before making it edible. However, with the spread of microwave ovens, heating using microwave ovens is becoming the mainstream as such a heating method.

Here, when the food contained in the package container sealed by heat sealing is heated in a microwave oven, the water contained in the food becomes vapor due to the dielectric heating by microwaves, and the pressure inside the sealed package container rises. The packaging container may explode and the food inside may be scattered.

Therefore, in order to prevent such food scattering, when heating by a microwave oven is started, a steam vent hole is automatically formed in a part of the packaging container so that the increased pressure inside the packaging container can be released. Various packaging containers constructed in the above have been proposed.

As an example of such a packaging container 100, in Patent Document 1 described later, as shown in FIG. 9, metal is vapor-deposited at a predetermined position of the heat seal film 104 that seals the opening of the food packaging tray 105. When a conductive heating material 107 that generates heat by microwaves such as a layer is provided and heated in a microwave oven, the heat seal film 104 at the position where the conductive heating material 107 is provided is heated and melted to form a steam vent hole 130. The constructed packaging container 100 has been proposed (the scope of the claim of Patent Document 1).

Further, Patent Document 2 described later proposes a packaging container 100 which is a heat-sealed bag 110 as shown in FIG. 10, and is connected to a peripheral welding portion 106 of the heat-sealed bag 110 to form an inner side of the bag. Discloses a configuration in which an overhanging seal portion 135 having an overhanging portion 135a is provided, and a microwave absorbing layer 107'is provided on a film in an unsealed region 136 formed in the overhanging seal portion 135 (Patent). Claim 1 of Document 2 and others).

Unlike Patent Document 1 and Patent Document 2 described above, the steam vent hole 130 is not formed by a material that absorbs microwaves and generates heat, but the applicant of the present application has shown in FIG. As a packaging container for food packaging, a packaging bag 110 formed of a laminated film 104 having at least two layers of an inner layer 102 and an outer layer 103 made of a synthetic resin film, the outer layer 103 having a slit 137 formed therein, and the above. We have proposed a package 110 in which a heat-sealing portion 138 formed in a width covering the slit 137 is provided in the inner layer 102, and a plurality of uneven stripes facing the slit 137 are mixed in the inner layer 102 (Patent Document 3). Claim 1).

Jikkenhei 1-110175 Japanese Unexamined Patent Publication No. 2011-116440 Japanese Patent No. 5899155

Among the packaging containers 100 described above as the prior art, in the packaging container 100 (see FIG. 9) described in Patent Document 1, when heated by a microwave oven, the conductive heat generating material 107 of the heat seal film 104 which is a lid material The formed range is heated and melted by microwaves, and a steam vent hole 130 is generated in the heat seal film 104 in this portion, so that the steam of the packaging container 100 can be released and the packaging container 100 can be prevented from bursting. There is.

However, in the packaging container 100 having the above configuration, since food is stored under the melted heat-sealing film 104, when the heat-sealing film 104 in the formation range of the conductive exothermic material 107 melts and falls, it becomes food. It will be mixed as a foreign substance.

In this way, in order to prevent the molten resin from being mixed into the food as a foreign substance, the heat-sealed bag 110 (see FIG. 10) described in Patent Document 2 described above has an unsealed region in the overhanging seal portion 135. By providing the microwave absorbing layer 107'on the 136 film, even if the film in this portion melts, the melted resin does not exceed the overhanging seal portion 135 and is mixed into the food, and after that, When the heat seal bag expands due to the pressure rise in the heat seal bag 110, the overhanging seal portion 135 starts peeling from the protruding portion 135a, so that the pressure can be released through the steam vent hole 130. ing.

However, in the heat seal bag 110 having the above configuration, it is necessary not only to provide the microwave absorbing layer 107', but also to provide the overhanging seal portion 135 connected to the peripheral welding portion 106, which increases the number of steps during bag making. Therefore, the work becomes complicated.

Further, since the overhanging seal portion 135 is provided in connection with the peripheral welding portion 106, the microwave absorbing layer 107', and therefore the steam vent hole 130, is formed in the vicinity of the peripheral welding portion 106. When the heat seal bag 110 is heated while lying down, the contents may be blown out through the steam vent hole 130 in foods, especially liquid foods such as curry and stew. A packaging container such as a heat-sealed bag 110 that can be heated in an upright state like a pouch, in which the peripheral welding portion 106 of the portion where the steam vent hole 130 is provided is arranged at a higher place than food. The application is limited to.

As described in Patent Document 1 and Patent Document 2, in the configuration in which the steam vent hole 130 is formed by applying the conductive exothermic material 107 or forming the microwave absorbing layer 107', the vapor absorbing hole 130 accompanies the absorption of microwaves. Since the conductive exothermic material 107 and the microwave absorbing layer 107'heat heat and the heat seal film 104 in this portion melts down to form the steam vent hole 130, the shape of the conductive exothermic material 107 and the microwave absorbing layer 107' As many steam vent holes 130 having a shape corresponding to the above are formed at the positions where the conductive heating material 107 and the microwave absorbing layer 107'are provided.

Further, even when a plurality of vapor vent holes 130 are formed by applying a conductive heating material 107 or forming a microwave absorbing layer 107'at a plurality of locations of the packaging container 100, each vapor vent hole 130 is a microwave oven. After starting the heating by, it will be formed almost at the same time.

Therefore, once the air release is started, the opening area of the entire steam vent hole 130 becomes substantially constant. Therefore, the size and number of the steam vent holes 130 to be formed are based on the relatively low pressure at the start of the air release. When set to, the packaging container 100 may burst or food may be scattered because it cannot cope with the subsequent further pressure increase, while the size and number of the vapor vent holes 130 to be formed are generated in the packaging container 100. When set according to the maximum pressure, when the pressure inside the packaging container 100 is relatively low, such as immediately after the start of heating, it takes a relatively long time for the pressure inside the packaging container 100 to rise, so the food is "steamed". It becomes difficult to exert an action such as ".

On the other hand, in the packaging container 100 (packaging bag 110) described in Patent Document 3 described above, a slit 137 is formed in the outer layer 103, and at least a plurality of uneven stripes facing the slit 137 are mixed on the surface of the inner layer 102. By adopting this configuration, when the inner layer 102 of the slit 137 portion is stretched in response to the increase in the internal pressure of the packaging bag 110, a pinhole is generated in the concave portion of the interior 102 of this portion, and the internal pressure rises. Along with this, the number of pinholes formed or the hole diameter of the already formed pinholes gradually increases, so that the pressure inside the packaging bag 110 can be increased at an early stage, and the pressure inside the packaging bag 110 is further increased. Even if it rises, it is possible to prevent the packaging bag 110 from bursting while maintaining the internal pressure by increasing the amount of air released, and it is possible to add an element of "steaming" during heating. Even foods such as sushi, which are preferable, can be preferably heated.

However, in the packaging bag 110 described in Patent Document 3 having the above configuration, since the slit 137 is provided in the outer layer 103, which is generally higher in strength than the inner layer 102, the strength of the slit-forming portion is lowered. If pressure is applied to the packaging bag 110 by stacking a large number of them during transportation, storage, or display at a store, there is a risk of damage and leakage of the contents.

Therefore, the present invention has been made in order to eliminate the above-mentioned drawbacks in the prior art, and a plurality of packaging containers are expanded at appropriate intervals due to expansion of the packaging container due to an increase in internal pressure without causing a significant decrease in the strength of the packaging container. A packaging container that gradually forms fine holes and starts releasing steam little by little, and prevents damage by increasing the number of holes or the area of holes as the internal pressure rises. Packaging such as heat seal bags and heat seal trays that can maintain high internal temperature and pressure for high-pressure cooking and high-temperature cooking, and also exerts a sufficient steaming effect for foods that require steaming. It is an object of the present invention to provide a container for use, a heat seal film for packaging used as a bag for the heat seal bag, or a lid for the heat seal tray.

The means for solving the problem are described below together with the reference numerals used in the embodiment of the invention. This reference numeral is for clarifying the correspondence between the description of the claims and the description of the form for carrying out the invention, and needless to say, it is used in a restrictive manner in the interpretation of the technical scope of the present invention. It's not a thing.

In order to achieve the above object, the heat-sealing film 4 for packaging of the present invention is used.
A laminated film provided with an outer layer 3 made of a thermoplastic resin and a heat seal layer 2 made of a thermoplastic resin having a melting point lower than that of the outer layer 3, and is used for packaging which is sealed by heat seal and becomes a part of a packaging container. In the heat seal film 4 of
A microwave absorption layer 7 is partially formed on the inner surface of the outer layer 3, and the microwave absorption layer 7 is partially formed.
A plurality of recesses 8 are formed in the heat seal layer 2 at least at the position where the microwave absorption layer 7 is formed (claim 1).

The microwave absorbing layer 7 can be formed into a circular shape, a triangular shape, a quadrangle, other polygonal shapes, or various geometric shapes, but is preferably linear with a width of 0.5 to 3.0 mm. Form (claim 2).

When the microwave absorbing layer 7 is formed as a linear one in this way, its length is preferably 5 to 200 mm, more preferably 30 to 70 mm (claim 3).

In the heat seal film 4 having any of the above configurations, it is preferable that the outer layer 3 is formed of a biaxially stretched film and the heat seal layer 2 is formed of a non-stretched film (claim 4).

It is preferable that the recess 8 is formed not only at the position where the microwave absorbing layer 7 is formed, but also at least in a region having a width of 3 mm outside the recess 8 and, for example, a region having a width of 3 mm to 20 mm (claim 5).

Further, the packaging container 1 of the present invention is
A heat-sealing film 4 provided with an outer layer 3 made of a thermoplastic resin and a heat-sealing layer 2 made of a thermoplastic resin having a melting point lower than that of the outer layer 3 is provided, and the peripheral edge of the heat-sealing film 4 is heat-sealed to the peripheral edge. In the packaging container 1 in which the packaging area 30 in which the object to be packaged is packaged is formed on the inner peripheral side of the peripheral heat-sealing portion 6 by forming the heat-sealing portion 6.
A microwave absorption layer 7 is partially formed on the inner surface of the outer layer 3 at a position other than the peripheral heat seal portion 6 of the heat seal film 4.
A plurality of recesses 8 are formed in the heat seal layer 2 at least at the position where the microwave absorption layer 7 is formed (claim 6).

The microwave absorbing layer 7 is preferably formed in a linear shape having a width of 0.5 to 3.0 mm (claim 7).

In this case, the microwave absorbing layer 7 is preferably formed to have a length of 5 to 200 mm, more preferably 30 to 70 mm (claim 8).

In any of the above configurations, it is preferable to use the heat seal film 4 in which the outer layer 3 is made of a biaxially stretched film and the heat seal layer 2 is made of a non-stretched film (claim 9).

Further, it is preferable that the recess 8 is formed not only in the formation range of the microwave absorption layer 7, but also in a region having a width of at least 3 mm outside the concave portion 8 and, for example, a region having a width of 3 mm to 20 mm (claim 10). ..

Based on the configuration of the present invention described above, in the packaging heat-sealing film 4 of the present invention and the packaging container 1 using the same, when the food is dielectrically heated by a microwave oven in a state of being packaged, the microwave absorbing layer 7 is used. Heats and heats the heat seal film 4 in this portion.

When the heating of the heat seal film 4 in the formed portion of the microwave absorbing layer 7 is continued in this way, the recess 8 which is thinner than the other portions melts, and the central portion thereof is torn and the pin is broken. A hole 21 is created and steam emission is started.

The pinhole 21 formed in this way expands the hole diameter by heat shrinkage, but the convex portion 22 is formed because the peripheral portion of the concave portion 8 is thicker than the concave portion 8. The expansion of the pinhole diameter due to heat shrinkage is unlikely to occur beyond the above, and the expansion of the hole diameter is suppressed, so that the state of the hole having a relatively small diameter, that is, the pinhole 21 is maintained.

The heat-sealing film 4 of the present application in which the holes are formed in this manner is packaged while maintaining the state in which the pinholes 21 described above are formed without melting the entire formed portion of the microwave absorbing layer 7. The internal pressure of the packaging container 1 is maintained by increasing the number of pinholes 21 generated in the formed portion of the microwave absorbing layer 7 and / or expanding the opening area of the pinholes 21 in response to the increase in pressure in the container 1. While doing so, I was able to remove the steam little by little.

On the other hand, unlike the packaging bag of Patent Document 3, the outer layer 3 of the heat-sealing film 4 is not provided with a slit or the like, so that the heat-sealing film 4 has a large strength until it is heated by a microwave oven. No deterioration occurred, and even when pressure was applied to the packaging container 1 during transportation, storage, display, etc., it was possible to prevent the packaging container 1 from bursting or the like.

Further, as for the pressure release in the packaging container 1, as described above, the pinhole 21 is first formed in the formed portion of the recess 8, and then the pinhole 21 gradually expands and / or the number of the pinhole 21 increases. Since it is designed to respond to pressure rise, there is no bursting noise at the start of air release, and it is possible to prevent the molten resin from falling into the food and being mixed in as foreign matter. ..

In particular, when a configuration such as the overhanging seal portion in the heat-sealed bag of Patent Document 2 is not provided in order to prevent the molten resin from falling onto food, the number of steps during bag making can be reduced.

Further, the microwave absorbing layer 7 is formed in a linear shape having a width of 0.5 to 3.0 mm, more preferably the length of the microwave absorbing layer 7 is 5 to 200 mm, more preferably 30 to 70 mm. In the configuration formed in the range, the pressure inside the container could be maintained for a longer period of time by increasing the opening area of the pinhole more slowly.

Further, in the configuration in which the outer layer 3 is a biaxially stretched film and the heat seal layer 2 is a non-stretched film, the outer layer 3 can be strengthened and the heat seal layer 2 can be easily stretched to form a recess 8. It was possible to make the pinhole 21 more easily formed.

By forming the recess 8 in the forming range of the microwave absorbing layer 7 and outside the forming range of the microwave absorbing layer 7 with a width of at least 3 mm, as the internal pressure increases, not only the forming position of the microwave absorbing layer 7 but also the peripheral portion thereof. By expanding the range of pinhole formation, it was possible to respond to a wider range of pressure changes in the container.

It is explanatory drawing which showed the structural example of the packaging bag which is an example of the packaging container of this invention. The explanatory view which showed the structural example of the heat seal tray which is an example of the packaging container of this invention. It is explanatory drawing of the recess formation method with respect to a heat seal film, (A) is a formation example using a letterpress, and (B) is a formation example using a letterpress roll. It is explanatory drawing of the packaging container (four-way seal bag) of this invention provided with a linear microwave absorption layer, (A) is an overall view, (B) is an enlarged view of a recess formation region, (C) is (B). ) CC line sectional view. It is explanatory drawing of the packaging container (four-way seal bag) of this invention provided with a circular microwave absorption layer, (A) is an overall view, (B) is an enlarged view of a recess formation region. It is an explanatory view of the formation principle (prediction) of a pinhole, (A) is an enlarged view of the broken line circle part of FIG. (D) is a plan enlarged view of the heat seal film at the time of pinhole formation. It is a photograph of the formation state of a hole when a heat seal film provided with a linear microwave absorbing layer is heated in a microwave oven, and (A) is a heat seal film of the present application in which a recess is provided in the heat seal layer. (Example 1) and (B) are heat seal films of Comparative Example in which the heat seal layer is not provided with a recess (Comparative Example 1). It is a photograph of the formation state of a hole when a heat seal film provided with a circular microwave absorption layer is heated in a microwave oven, and (A) is a heat seal film of the present application in which a recess is provided in the heat seal layer (A). Examples 2) and (B) are heat-sealing films of Comparative Example in which the heat-sealing layer is not provided with a recess (Comparative Example 2). Explanatory drawing of a conventional packaging container (corresponding to Patent Document 1). Explanatory drawing of a conventional packaging container (corresponding to Patent Document 2). It is explanatory drawing (corresponding to patent document 3) of the conventional packaging container, (A) is a front view, (B) is a sectional view of the heat seal film in the BB line portion of (A).

Next, an embodiment of the present invention will be described below with reference to the accompanying drawings.

[Overall composition of packaging container]
1 and 2 show a configuration example of the packaging container for heating a microwave oven of the present invention.

The packaging container 1 of FIG. 1 is a packaging bag 10 made by using the heat-sealing film 4 of the present invention, and FIG. A four-sided seal bag formed by heat-sealing four sides in total, FIG. 1 (B) is folded in half so that the heat-seal layer 2 of one heat-seal film 4 overlaps, and the three sides are heat-sealed. FIG. 1 (C) is a so-called "gassho-pasted" heat-sealing bag formed by folding and sealing in three so that the heat-sealing layer 2 of one heat-sealing film 4 overlaps. All of these heat-sealed bags are the objects of the packaging container in the present application, and in addition to the illustrated packaging bag, the so-called "standing pouch" packaging bag, and the food packaging tray 5 and cup as shown in FIG. The heat-sealing tray 10', which is obtained by superimposing the heat-sealing layer 2 of the heat-sealing film 4 on the opening edge of the heat-sealing film 4, etc. Can be contained in container 1.

In the heat-sealing film 4 constituting such a packaging container 1, the peripheral portion that is heat-sealed between the films or the opening edge of the tray 5 by heat-sealing is referred to as the peripheral heat-sealing portion 6 in the present specification. However, in FIGS. 1 and 2, the portion indicated by “shading” corresponds to the peripheral heat seal portion 6.

[Heat seal film]
(1) Overall Structure As shown in FIG. 4C, the packaging heat-sealing film 4 of the present invention has an outer layer 3 made of a thermoplastic resin and a heat-sealing layer made of a thermoplastic resin having a melting point lower than that of the outer layer 3. A film having a laminated structure provided with 2 and used for welding by heat sealing, even if the film has one or more intermediate layers (not shown) between the outer layer 3 and the heat sealing layer 2. good.

The inner surface (the surface on the heat-sealing layer 2 side) of the outer layer 3 at any position of the heat-sealing film 4 excluding the portion serving as the peripheral heat-sealing portion 6 has a microwave absorbing layer 7 as a part thereof. At least at the position where the microwave absorption layer 7 is formed, the heat seal layer 2 is formed with a plurality of recesses 8.

(2) Outer layer It is preferable to use a synthetic resin film having heat resistance and airtightness for the outer layer 3 of the heat seal film 4, and examples of such synthetic resin include nylon (NY) and polyethylene terephthalate. (PET) and the like can be mentioned.

Further, in order to strengthen the stress, it is preferable to use a uniaxially stretched or biaxially stretched film for the outer layer 3, for example, biaxially stretched nylon (ONY), biaxially stretched polyethylene terephthalate (OPET), and biaxially stretched polypropylene (OPP). ) Etc., all biaxially stretched films can be preferably used.

Further, the above-mentioned biaxially stretched film may be subjected to barrier processing such as silica vapor deposition, alumina vapor deposition, and barrier coating agent coating.

The outer layer 3 needs to have heat resistance that does not melt even when heated during heat sealing, and a resin having a high melting point is used in comparison with the resin of the heat sealing layer 2 described later, and is used for the outer layer 3 as an example. As a material for the synthetic resin film, biaxially stretched nylon (ONY) having a melting point of 215 to 225 ° C. or polyethylene terephthalate (PET) having a melting point of 265 ° C. is preferably used. It was used.

(3) Heat Sealing Layer As the heat sealing layer 2 described above, a resin having a melting point lower than that of the outer layer described above is used in order to impart heat sealing properties, and an olefin-based non-stretched film can be preferably used as an example. ..

Synthetic resins having such heat-sealing properties include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE) and other polyethylene, and unstretched polypropylene (unstretched polypropylene). CPP) and the like.

Further, the synthetic resin film used for the heat seal layer 2 is preferably a film that easily stretches due to stress, and is preferably, for example, an unstretched film, but is not limited thereto.

As the synthetic resin used for the heat seal layer 2, it is necessary to use a resin having a melting point lower than that of the synthetic resin used for the outer layer 3 described above, and preferably the melting point difference between the resin of the outer layer 3 and the heat seal layer 2 is large. It is preferably 50 ° C. or higher.

As described above, in the present embodiment, as the synthetic resin used for the outer layer 3, biaxially stretched nylon (ONY) having a melting point of 215 to 225 ° C. and polyethylene terephthalate (PET) having a melting point of 265 ° C. are used. As the synthetic resin used for the heat seal layer 2, low density polyethylene (LDPE) having a melting point of 105 to 115 ° C., medium density polyethylene (MDPE) having a melting point of 110 to 130 ° C., and a linear chain having a melting point of 105 to 130 ° C. Low-density polyethylene (LLDPE), high-density polyethylene (HDPE) having a melting point of 135 to 150 ° C., and unstretched polypropylene (CPP) having a melting point of 135 to 165 ° C. can be used.
In this embodiment, an LLDPE film having a thickness of 50 μm was used as an example.

(4) Microwave Absorption Layer Of the above-mentioned outer layer 3, the inner surface (the surface on the heat seal layer 2 side) at any position excluding the portion that will later become the peripheral heat seal portion 6 is covered with a microwave absorption layer. 7 is formed in a predetermined shape.

The microwave absorbing layer 7 is a layer that absorbs microwaves in the band used in a microwave oven, and is coated with ink or paint to which fine particles having microwave absorption or other materials having microwave absorption are added. As long as it is a layer formed by vapor deposition of a metal or the like having microwave absorption, or if it is possible to form a layer having the above-mentioned property of absorbing microwaves and generating heat. , It may be formed by using various known materials and lamination techniques.

When the microwave absorbing layer 7 is formed by applying an ink or paint to which a material having a microwave absorbing property is added, the material having the microwave absorbing property to be added includes metal powder such as aluminum, graphite or carbon black. Non-metal powders such as carbon and various salts can be used, and the microwave absorbing layer 7 may be formed by vapor deposition of a metal such as aluminum.

The microwave absorbing layer 7 may be formed by applying ink or paint in a predetermined shape at a predetermined position on the inner surface of the outer layer 3 from the beginning, or by depositing a metal or the like, but for example, as in paster processing. The microwave absorbing ink may be applied to the entire surface of the film to be the outer layer 3 in advance, and then the ink other than the portion left as the microwave absorbing layer 7 may be removed to form the film.

The planar shape of the microwave absorbing layer 7 is not particularly limited, and in addition to being formed in a circular shape as shown in FIG. 5, various shapes such as a triangle, a quadrangle, and other polygons and geometric shapes can be adopted. The size and the number of formations can also be set as appropriate in relation to the size of the packaging container and the amount of steam generated.

When the microwave absorbing layer 7 is formed in the above shape except for the linear shape described later, the diameter or the long side can be formed to have a size of about 3 to 20 mm as an example, although not limited to this.

The microwave absorbing layer 7 can be preferably formed linearly as shown in FIG. 4, and in this case, the microwave absorbing layer 7 is formed linearly with a width of 0.5 to 3.0 mm.

When the microwave absorbing layer 7 is formed linearly in this way, the length of the formation can be set according to the size of the packaging container and the amount of steam generated, but the microwave absorbing layer 7 is formed in such a linear shape. When formed in, the length thereof is in the range of about 5 to 200 mm, preferably 30 to 70 mm. In the present embodiment, the linear microwave absorbing layer 7 provided in a four-way seal bag having a width of 125 mm and a length of 200 mm is provided. A microwave absorbing layer 7 having a width of 1 mm and a length of 50 mm is provided.

(5) Recesses A plurality of recesses are formed in the heat seal layer 2 at a position corresponding to the formation position of the microwave absorption layer 7 described above by debossing (concave processing) or embossing (concavo-convex processing). 8 is formed.

The formation of the recess 8 with respect to the formation position of the microwave absorption layer is performed by forming a letterpress roll on a portion of the film to be the heat seal layer 2 that is arranged at a position corresponding to the formation position of the microwave absorption layer 7 at least during lamination. Even if the recess 8 is formed in advance by contact with or the like, and the film to be the heat seal layer 2 is laminated on the film to be the outer layer 3 after the microwave absorption layer 7 is formed. good.

Alternatively, the film to be the heat seal layer 2 is laminated on the film to be the outer layer 3 on which the microwave absorption layer 7 is formed to form the heat seal film 4, and then at least the microwave of the heat seal film 4 is formed. The recess 8 may be formed ex post facto in the heat seal layer 2 at the position where the absorption layer 7 is formed.

In the present embodiment, a configuration is adopted in which the recess 8 is formed in the heat seal layer after the heat seal film 4 is formed.

As shown in FIG. 3A as an example, such a recess 8 is formed by forming a heat seal layer 2 between a letterpress 12 having a convex portion formed on the surface and a facing plate 13 having a flat surface. The heat seal film 4 is arranged so that the outer layer 3 faces the facing plate 13 on the 12 side, the heat seal film 4 is sandwiched between the letterpress 12 and the facing plate 13, and the softening temperature and melting temperature of the heat sealing layer 2 are formed. The convex portion formed on the surface of the letterpress 12 may be transferred to the heat seal layer 2 to form the concave portion 8 in the heat seal layer 2, or as shown in FIG. 3 (B). The heat seal layer 2 faces the letterpress roll 12'side and the outer layer 3 faces the facing roll 13'side between the heated letterpress roll 12'with the convex portion formed on the surface and the facing roll 13' having a flat surface. By sandwiching and passing the heat seal film 4 in this way, the convex portion formed on the surface of the letterpress roll 12'may be continuously transferred to the heat seal layer 2 to form the concave portion 8. The recess 8 can be formed in the heat seal layer 2 by various known methods.

In the description with reference to FIGS. 3 (A) and 3 (B), the case where the recess 8 described above is formed only on the heat seal layer 2 side of the heat seal film 4 has been described as an example. However, in the above-described example, the surface of the facing plate 13 and the facing roll 13'formed on a flat surface may also be provided with irregularities, and the outer layer 3 may also be provided with irregularities.

It is preferable to form a large number of relatively small recesses 8, and as an example, each recess 8 has a diameter of about 0.1 to 2 mm or a long side at an interval of about 0.1 to 2 mm in a plan view. Therefore, it can be formed as a repeating pattern at a depth of about 10 to 90% of the thickness of the heat seal layer. In this embodiment, as shown in FIG. A rectangular recess 8 was transferred and formed on the heat seal layer 2 by using a letterpress 12 having a convex portion of the shape.

The recess 8 described above may be formed in the same range as the microwave absorbing layer 7, but preferably, as shown in FIGS. 1, 4 and 5, the microwave absorbing layer 7 is formed. In addition to the range, it is preferable that the recess forming region 9 in which the recess 8 described above is formed is also formed in a range having a width of at least 3 mm on the outer peripheral side thereof.

The recessed region 9 may be formed as having a constant width and length as shown in FIGS. 4 and 5, but in the present embodiment, microwave absorption is performed as shown in FIG. 1 (A). A band-shaped recess forming region 9 having a width of about 10 mm is continuously formed in the MD of the heat seal film 4 at a position overlapping the layer 7, and the recess forming region 9 has a side of about 0.1 mm in a plan view. The rectangular recesses of the above were continuously formed in MD and TD at equal intervals of about 0.4 mm.

[Action, etc.]
The heat-sealing film 4 configured as described above is manufactured by superimposing the heat-sealing film 4 so that the heat-sealing layer 2 side is on the inside and heat-sealing the peripheral heat-sealing portion 6 as shown in FIGS. 1 (A) to 1 (C). The packaging container 1 is formed by heat-sealing the peripheral heat-sealing portion 6 in a state where the heat-sealing layer 2 is superposed on the peripheral edge of the opening of the food packaging tray 5 as shown in FIG. The heat seal film 4 described above constitutes a part of the packaging container 1.

In the packaging container 1 configured in this way, when heating is performed with a microwave oven while the food is packaged inside, the pressure inside the packaging container 1 rises due to the steam generated by heating the food contained inside. As the packaging container 1 begins to swell, the microwave absorbing layer 7 absorbs the microwave emitted from the microwave oven to generate heat, and heats and softens the heat seal film 4 at the position where the microwave absorbing layer 7 is formed. Let me.

Due to the softening of the heat seal film 4, pinholes 21 are formed in the portion where the recess 8 is formed in the position where the microwave absorbing layer 7 is formed, and the water vapor in the packaging container 1 is released.

Since the size of each pinhole 21 formed in this way is very small, the release of water vapor in the container is started, but the amount of air released is small, so that the inside of the packaging container 1 is used. When the pressure inside the packaging container 1 rises, the number of pinholes 21 formed increases, or the size of each pinhole 21 increases, so that the increased pressure is included. The pressure inside the packaging container 1 can be released well, which prevents the packaging container 1 from bursting and the food from scattering due to the burst, and heats the packaging container 1 while maintaining a relatively high pressure. It can be performed.

Here, as described in Patent Documents 1 and 2 described above, in the conventional packaging container (see FIGS. 7 and 8) in which a steam vent hole is formed by forming a microwave absorbing layer. , The heat seal film 4 is melted into a shape corresponding to the shape of the microwave absorbing layer 7 by heating using a microwave oven, so that a steam vent hole having a shape corresponding to the shape of the microwave absorbing layer 7 is formed. (Patent Document 1, page 3, lines 8 to 10, Patent Document 2 [0026] column).

On the other hand, in the configuration of the present application, the heat seal film 4 corresponding to the shape of the microwave absorbing layer 7 is melted, and therefore, the steam vent hole having a shape corresponding to the shape of the microwave absorbing layer 7 is not formed, as described above. As described above, the pinhole 21 is formed in the portion of the microwave absorbing layer 7 that has become thin due to the formation of the recess 8, and the entire forming region of the microwave absorbing layer 7 is formed without melting. By maintaining the pinhole 21, the pressure inside the packaging container 1 can be maintained in a relatively high state, which is a peculiar effect that cannot be predicted from the prior art.

Further, in the packaging container 1 of the present invention, as described above, only the pinhole 21 is formed, and the heat seal film 4 over the entire formation range of the microwave absorbing layer 7 is not melted. Therefore, the melted resin is used. It is possible to prevent the melt of the outer layer 3 and the heat seal layer 2 from falling and being mixed into the food without separately providing a structure for receiving the heat seal layer 2.

As described above, in the packaging container 1 of the present invention, the formed portion of the recess 8 in the formed range of the microwave absorbing layer 7 without melting the entire forming range of the microwave absorbing layer 7 in the heat seal film 4. Although the principle of forming the pinhole 21 is not clear, it is presumed that the pinhole 21 is formed by the following principle.

That is, as described above, when the packaging container 1 in which the food is packaged is put into the microwave oven and microwave irradiation is started, the pressure in the packaging container 1 rises due to the generation of steam accompanying the heating of the food. The heat seal film 4, which was in a flat state as shown in FIG. 6 (A) before heating, swells outward as a whole as shown in FIG. 6 (B), and the microwave absorbing layer 7 is formed. When heat generation is started, the heat seal film 4 at a position corresponding to the formation range of the microwave absorption layer 7 is heated and softened.

As described above, by heating the heat seal film 4 due to the heat generation of the microwave absorption layer 7, the heat seal film 4 in the formation range of the microwave absorption layer 7 is softened and the recess is thinner than the other parts. The formed portion of 8 melts before the other portions, and together with the increase in pressure inside the container, like a pinhole formed in the recess 8 on the right side of the paper surface in FIGS. 6 (C) and 6 (D). , The center of the recess 8 is torn to form a pinhole 21.

The pinhole 21 formed in this way expands its hole diameter due to heat shrinkage of the heat seal film 4 like the pinhole 21 on the left side of the paper surface in FIGS. 6 (C) and 6 (D). Is difficult to extend beyond the convex portion 22 formed on the peripheral edge of the concave portion 8 to the outside, and as a result, the pinhole 21 generated in the concave portion 8 of 1 is connected to the pinhole 21 formed in the adjacent concave portion 8. As a result of being difficult to spread over the entire formation range of the microwave absorption layer 7, it is considered that the amount of steam released could be controlled by maintaining the state of the pinhole 21 having a relatively small diameter. Be done.

As a result, in the packaging container 1 of the present invention, after the heating by the microwave oven is started, the inside of the packaging container 1 is continuously maintained in a relatively high pressure state from a relatively early stage until the heating is completed. Moreover, as described above, the formation state of the pinhole 21 is maintained, and the entire portion of the heat seal film 4 on which the microwave absorption layer 7 is formed does not melt down, so that the pinhole 21 melts down. It is probable that it was possible to prevent the resin from being mixed into food as a foreign substance without providing a structure for receiving the resin.

The state of pore formation was confirmed by heating both the heat-sealing film of the present invention and the heat-sealing film of the comparative example in a microwave oven.

The heat-sealing film used was a biaxially stretched nylon (thickness 25 μm) for the outer layer and unstretched low-density polyethylene (thickness 50 μm) for the inner heat-seal layer, and the inner surface side (heat seal) of the outer layer. Two types of heat seal films are prepared: one with a linear microwave absorbing layer 7 having a width of 1.0 mm and a length of 30 mm formed on the layer side), and one with a microwave absorbing layer 7 having a diameter of 7.5 mm. bottom.

As the first embodiment, a rectangular recess 8 having a side of 0.3 mm is formed in the heat seal layer of the heat seal film on which the linear microwave absorption layer 7 is formed, at a position overlapping the microwave absorption layer. The ones formed continuously at intervals of 1 mm (width of the convex portion 22) were used.

As the second embodiment, 0.1 mm of a rectangular recess 8 having a side of 0.3 mm is formed in the heat seal layer of the heat seal film on which the above-mentioned circular microwave absorption layer is formed at a position overlapping the microwave absorption layer. Those formed continuously at intervals (width of the convex portion 22) were used.

Comparative Example 1 is a heat-sealing film (without the recess 8) on which the above-mentioned microwave absorbing layer 7 in the immediately preceding state is formed.

Comparative Example 2 is a heat-sealing film (without the recess 8) on which the above-mentioned circular microwave absorbing layer 7 is formed.

Wet tissue paper was sandwiched between each of the above heat-sealing films (125 mm x 200 mm) and a heat-sealed film (125 mm x 200 mm) in which the outer layer was biaxially stretched nylon and the heat-sealed layer was unstretched low-density polyethylene. In this state, the four sides are heat-sealed to a width of about 5 mm to form a four-sided heat-sealing bag, and the heat-sealing film provided with the microwave absorbing layer 7 described above is placed in the microwave oven so as to be on the upper side. It was heated at 1000 W for 60 seconds.

The formation states of the holes after heating by the microwave oven are shown in FIGS. 7 (A) and 7 (B), and FIGS. 8 (A) and 8 (B), respectively.

In the packaging bag using the heat-sealing film of Comparative Example 1 and Comparative Example 2 in which the heat-sealing layer does not have a recess, the pressure inside the bag rises due to the generation of water vapor due to heating and swells, but the microwave absorbing layer When the heat seal film is melted and pinholes are formed in the formed portion of the above, in the case where a linear microwave absorbing layer is provided as in Comparative Example 1, the pinholes are formed in the direction of forming the microwave absorbing layer. By expanding the hole diameter in a short time and connecting the pinholes to form a slit-shaped hole [Fig. 7 (B)], a circular microwave absorbing layer is provided as in Comparative Example 2. Then, by expanding the pore diameter in the direction crossing the width direction of the microwave absorbing layer to form coarse pores [Fig. 8 (B)], any heat seal bag formed by using any heat seal film can be used. ， At the same time as the hole was formed, the pressure inside the bag was released at once and the bag deflated.

On the other hand, in the packaging bag using the heat-sealing film of the present application in which recesses are formed in the heat-sealing layer, the linear microwave absorbing layer of Example 1 is formed [FIG. 7 (A)], and Examples. In any of the two circular microwave absorption layers [FIG. 8 (A)], the formed pinholes are formed as independent holes without greatly expanding the hole diameter, so that the holes are formed. It was possible to maintain the inflated state of the packaging bag, and therefore the state in which pressure was applied to the inside, even after the formation of the bag.

According to the packaging container of the present invention, cooking under high temperature and high pressure is possible, so that the time required for cooking is shortened, energy can be saved, and nutrients such as vitamins and minerals of foods and the taste of foodstuffs can be tasted.・ Difficult to spoil the scent.

In addition, since it is cooked by both dielectric heating by microwaves and steam, even frozen foods can be finished without uneven heating.

In particular, since the packaging bag of the present invention emits only the minimum necessary steam, the packaging container is filled with steam, the surface of the contained food is exposed to high-pressure steam, and the steam adhering to the film. Is a product that requires steaming and refilling because it becomes water droplets and falls to the bottom, preventing drying, eliminating the need for extra water, and returning the steam adhering to the bag surface to the bottom again. However, it can be cooked only with the water content of the ingredients, and you can enjoy the taste and nutrients of the ingredients as they are.

In addition, microwaves have little effect on frozen parts, and it is difficult for heat to pass through the center of the frozen material. However, high-temperature and high-pressure cooking using the packaging bag and packaging of the present invention can minimize heating unevenness. ， This makes it possible to develop products that are cooked from raw frozen ingredients, that are heated only once, and have a fresh texture.

Further, the packaging bag 1 of the present invention having the above-mentioned special steam venting function can be used for miscellaneous goods, pharmaceuticals, and industrial applications in addition to foods.

The miscellaneous goods include, for example, those who want to heat in a microwave oven without getting their hands dirty, and those who want to fill the microwave oven with a volatile cleaning agent together with steam to make it easier to remove stains. As a pharmaceutical use, for example, there is an application in which a medicine is stored in the packaging bag of the present invention and heated in a microwave oven without opening the packaging bag.

1 Packaging container 2 Heat seal layer 3 Outer layer 4 Heat seal film 5 Food packaging tray 6 Peripheral heat seal part 7 Microwave absorption layer 8 Recess 9 Recess formation area 10 Packaging bag 10'Heat seal tray 12 Convex plate 12' Convex roll 13 Opposing plate 13'Opposite roll 21 Pinhole 22 Convex part 30 Packaging area 100 Packaging container 102 Inner layer 103 Outer layer 104 Heat seal film (laminated film)
105 Food packaging tray 106 Peripheral welding part 107 Conductive exothermic material 107'Microwave absorption layer 110 Packaging bag (heat seal bag)
130 Steam vent hole 135 Overhang seal part 135a Overhang part 136 Unsealed area 137 Slit 138 Heat seal part

Claims (10)

A laminated film having an outer layer made of a thermoplastic resin and a heat-sealing layer made of a thermoplastic resin having a melting point lower than that of the outer layer, and is a heat for packaging that is sealed by heat-sealing and becomes at least a part of a packaging container. In the seal film
A microwave absorption layer is partially formed on the inner surface of the outer layer, and the microwave absorption layer is partially formed.
A heat-sealing film for packaging, characterized in that a plurality of recesses are formed in the heat-sealing layer at least at a position where the microwave absorbing layer is formed. The heat-sealing film for packaging according to claim 1, wherein the microwave absorbing layer is formed in a linear shape having a width of 0.5 to 3.0 mm. The heat-sealing film for a packaging container according to claim 2, wherein the microwave absorbing layer is formed in a range of 5 to 200 mm in length. The heat-sealing film for a packaging container according to any one of claims 1 to 3, wherein the outer layer is made of a biaxially stretched film, and the heat-sealing layer is made of a non-stretched film. The heat-sealing film for a packaging container according to any one of claims 1 to 4, wherein the recess is formed at a position where the microwave absorbing layer is formed and at least within a width of 3 mm outside the microwave absorbing layer. A heat-sealing film provided with an outer layer made of a thermoplastic resin and a heat-sealing layer made of a thermoplastic resin having a melting point lower than that of the outer layer is provided, and the peripheral edge portion of the heat-sealing film is heat-sealed to form a peripheral heat-sealing portion. By doing so, in a packaging container in which a packaging area in which an object to be packaged is packaged is formed on the inner peripheral side of the peripheral heat-sealed portion.
A microwave absorption layer is partially formed on the inner surface of the outer layer at a position other than the peripheral heat seal portion of the heat seal film, and the microwave absorption layer is partially formed.
A packaging container characterized in that a plurality of recesses are formed in the heat seal layer at least at the position where the microwave absorption layer is formed. The packaging container according to claim 6, wherein the microwave absorbing layer is formed in a linear shape having a width of 0.5 to 3.0 mm. The packaging container according to claim 7, wherein the microwave absorbing layer is formed to have a length of 5 to 200 mm. The packaging container according to any one of claims 6 to 8, wherein the outer layer is made of a biaxially stretched film, and the heat seal layer is made of a non-stretched film. The packaging container according to any one of claims 6 to 9, wherein the recess is formed in a range in which the microwave absorbing layer is formed and at least in a range having a width of at least 3 mm outside the microwave absorbing layer.

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