JP2019014487A - Packaging heat seal film and packaging container using heat seal film - Google Patents

Abstract

To provide a packaging container causing no rupture even with heating by a microwave oven, and heatable while keeping temperature and pressure in the packaging container high.SOLUTION: A packaging container 1 such as a heat seal bag is formed by heat sealing an outer layer 3 comprising a thermoplastic resin to a heat seal film 4 having a heat seal layer 2 comprising a thermoplastic resin with a lower melting point than the outer layer 3. A microwave absorption layer 7 is partially formed on an inner face of the outer layer 3 out of the heat seal film 4, and multiple recessed parts 8 are formed on the heat seal layer 2 at least at the microwave absorption layer 7 forming position. Thus, when heating by a microwave oven, pinholes 21 are formed at the recessed parts 8 at the microwave absorption layer 7 forming position, and pressure in the container is released little by little to prevent rupture of the packaging container, allowing heating while keeping the inside temperature and pressure high.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a packaging heat-sealing film and a packaging container using the heat-sealing film, and more specifically covers a heat-sealing film used for making a heat-sealing bag and an opening of a packaging tray. A heat-sealing film used for packaging, such as a heat-sealing film, and the above-mentioned heat-sealing bag manufactured using the heat-sealing film, or a packaging container such as a packaging tray covered with 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 sealing bags used for packaging retort foods and frozen foods and packaging trays whose openings are covered with heat sealing films are used for packaging various foods.

  The food packaged in such a packaging container is circulated in a sealed and sealed state in the packaging container by heat sealing, and consumers who have purchased it are heated as necessary before serving food. However, with the widespread use of microwave ovens, heating using microwaves in a microwave oven is becoming the mainstream as such a heating method.

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

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

  As an example of such a packaging container 100, Patent Document 1 described later discloses that a metal is deposited on a predetermined position of a heat seal film 104 that seals an opening of a food packaging tray 105 as shown in FIG. When a conductive heating material 107 that generates heat by microwaves such as a layer is provided and heated by 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 vapor vent hole 130. A structured packaging container 100 has been proposed (Claims of Patent Document 1).

  Further, Patent Document 2 described below proposes a packaging container 100 that is a heat seal bag 110 as shown in FIG. 10. A configuration is disclosed in which a projecting seal portion 135 having a projecting portion 135a is provided, and a microwave absorbing layer 107 ′ is provided on a film in an unsealed region 136 formed in the projecting seal portion 135 (patent) (Claim 1 etc. of literature 2).

  Although the vapor vent hole 130 is not formed by a material that absorbs microwaves and generates heat as in the above-mentioned Patent Document 1 and Patent Document 2, the applicant of the present application is as shown in FIG. , A packaging bag 110 formed of a laminated film 104 of at least two layers of an inner layer 102 and an outer layer 103 made of a synthetic resin film as a packaging container for food packaging, the outer layer 103 having a slit 137 formed thereon, A package 110 is proposed in which a heat seal portion 138 formed with a width covering the slit 137 is provided on the inner layer 102, and a plurality of irregularities facing the slit 137 are mixed in the inner layer 102 (Patent Document 3). Claim 1).

Japanese Utility Model Publication No. 1-110175 JP 2011-116440 A Japanese Patent No. 5899155

  Among the packaging containers 100 described above as the prior art, in the packaging container 100 described in Patent Document 1 (see FIG. 9), when heated by a microwave oven, the conductive heating material 107 of the heat seal film 104 serving as a lid material is used. The formation range is heated and melted by microwaves, and a steam vent hole 130 is formed in this portion of the heat seal film 104, so that it is possible to prevent the packaging container 100 from being ruptured by releasing the steam of the packaging container 100. Yes.

  However, in the packaging container 100 having the above-described configuration, since the food is stored below the melted heat seal film 104, if the heat seal film 104 in the formation range of the conductive heating material 107 melts and falls, It will be mixed as a foreign object.

  Thus, in order to prevent the molten resin from being mixed as a foreign substance in the food, in the heat seal bag 110 (see FIG. 10) described in the above-mentioned Patent Document 2, an unsealed region in the overhang seal portion 135 is obtained. By providing the microwave absorbing layer 107 ′ on the film 136, even if this part of the film melts, the melted resin does not enter the food beyond the overhanging seal part 135, and thereafter When the heat seal bag expands due to an increase in pressure in the heat seal bag 110, the overhanging seal portion 135 starts to peel off 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-described configuration, not only the microwave absorbing layer 107 ′ but also the overhang seal portion 135 connected to the peripheral weld portion 106 needs to be provided, which increases the number of steps during bag making. Therefore, the work becomes complicated.

  Further, since the overhang seal portion 135 is provided in connection with the peripheral weld portion 106, the microwave absorbing layer 107 ′, and hence the vapor vent hole 130, is formed in the vicinity of the peripheral weld portion 106. When the heat-sealed bag 110 is heated while being laid, the food, particularly liquid food such as curry or stew, may blow out the contents through the vapor vent hole 130. A packaging container in which the peripheral weld portion 106 of the portion where the steam vent hole 130 is provided is arranged at a higher position than the food, such as the heat seal bag 110 that can be heated in a standing state like a pouch. Application is limited.

  Note that, as described in Patent Document 1 and Patent Document 2, in the configuration in which the vapor vent hole 130 is formed by applying the conductive heating material 107 or forming the microwave absorption layer 107 ′, the microwave absorption is accompanied. The conductive heat generating material 107 and the microwave absorbing layer 107 ′ generate heat, and the heat seal film 104 in this portion melts down to form a vapor vent hole 130, so that the shape of the conductive heat generating material 107 and the microwave absorbing layer 107 ′ is formed. Vapor vent holes 130 having a shape corresponding to the above are formed in the provided number at the positions where the conductive heating material 107 and the microwave absorption layer 107 ′ are provided.

  Further, even when the plurality of vapor vent holes 130 are formed by applying the conductive heat generating material 107 or forming the microwave absorbing layer 107 ′ at a plurality of locations on the packaging container 100, each vapor vent hole 130 is provided in the microwave oven. After heating is started, they are formed almost simultaneously.

  For this reason, once venting 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 a relatively low pressure at the start of venting. If it is set to, the packaging container 100 may not be able to cope with the subsequent increase in pressure and the packaging container 100 may burst or the food may be scattered, while the size and number of the steam vent holes 130 to be formed are generated in the packaging container 100. If the pressure is set corresponding to the maximum pressure, it takes a relatively long time for the pressure in the packaging container 100 to rise when the pressure in the packaging container 100 is relatively low, such as immediately after the start of heating. It becomes difficult to exert an action such as “.

  In contrast, in the packaging container 100 (packaging bag 110) described in the above-mentioned Patent Document 3, a slit 137 is formed in the outer layer 103, and a plurality of concave and convex strips facing the slit 137 are mixed at least 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 an 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, which increases the internal pressure. Along with this, the number of pinholes to be formed or the hole diameter of the pinholes that have already been formed gradually increases, so that the pressure in the packaging bag 110 can be increased quickly, and further pressure in the packaging bag 110 can be increased. Even when it rises, the amount of air released increases, so that the internal pressure can be maintained and the wrapping bag 110 can be prevented from bursting. It has become one that can be preferably, for example, even in foods such as dumplings suitably heated adding an element of "steaming".

  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 reduced. If the pressure is applied to the packaging bag 110 during transportation, storage, or display in a store and pressure is applied to the packaging bag 110, the contents may leak.

  Accordingly, the present invention has been made to solve the above-described disadvantages of the prior art, and without causing a significant decrease in strength of the packaging container, the present invention can be applied to a plurality of containers at appropriate intervals by expansion of the packaging container due to an increase in internal pressure. Containers for packaging are formed by gradually forming fine holes and starting to release steam little by little, and by preventing the breakage etc. by increasing the number or area of holes as the internal pressure increases. Packaging such as heat-sealing bags and heat-sealing trays that can maintain high temperature and pressure in the interior and perform high-pressure cooking and high-temperature cooking, and also exert sufficient steaming effect on foods that require steaming It is an object of the present invention to provide a heat seal film for packaging and a packaging for use as a lid for the heat seal bag or the heat seal bag.

  Hereinafter, means for solving the problem will be described together with reference numerals used in the embodiment for carrying out the invention. This code is used to clarify the correspondence between the description of the scope of claims and the description of the mode for carrying out the invention. Needless to say, it is used in a limited manner for the interpretation of the technical scope of the present invention. It is not a thing.

In order to achieve the above object, the packaging heat seal film 4 of the present invention comprises:
A laminated film comprising 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 sealed by heat sealing to become a part of a packaging container In the heat seal film 4 of
A microwave absorbing layer 7 is partially formed on the inner surface of the outer layer 3, and
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 absorption layer 7 can be formed in a planar shape of a circle, triangle, quadrangle, other polygons, and various geometric shapes, but preferably in a linear shape with a width of 0.5 to 3.0 mm. (Claim 2).

  Thus, when forming the microwave absorption layer 7 as a linear thing, the length becomes like this. Preferably it is 5-200 mm, More preferably, it is 30-70 mm.

  In any of the heat seal films 4 having the above-described configuration, it is preferable that the outer layer 3 is formed of a biaxially stretched film and the heat seal layer 2 is formed of an unstretched film.

  The concave portion 8 is preferably formed not only in the formation position of the microwave absorption layer 7, but also in at least the outer 3 mm width region, for example, the 3 mm to 20 mm width region.

The packaging container 1 of the present invention is
A heat seal film 4 including 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 is provided. In the packaging container 1 in which a packaging region 30 in which an article to be packaged is packaged is formed on the inner peripheral side of the peripheral heat seal part 6 by forming the heat seal part 6.
In the heat seal film 4, a microwave absorbing layer 7 is partially formed on the inner surface of the outer layer 3 at a position excluding the peripheral heat seal portion 6,
A plurality of recesses 8 are formed at least in the heat seal layer 2 at the position where the microwave absorption layer 7 is formed (Claim 6).

  The microwave absorption layer 7 is preferably formed in a linear shape having a width of 0.5 to 3.0 mm.

  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.

  In any of the above configurations, it is preferable to use a 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 an unstretched film.

  Further, the recess 8 is preferably formed not only in the formation range of the microwave absorption layer 7, but also in at least the outer 3 mm wide region, for example, the 3 mm to 20 mm wide region (claim 10). .

  Due to the configuration of the present invention described above, in the packaging heat seal film 4 of the present invention and the packaging container 1 using the same, when the food is packaged and dielectrically heated by a microwave in the microwave, the microwave absorbing layer 7 Generates heat and heats the heat seal film 4 in this portion.

  When the heating of the heat seal film 4 in the portion where the microwave absorption layer 7 is formed in this way is continued, the concave portion 8 which is thinner than the other portions is melted, and the central portion is broken and the pin is broken. Hole 21 is created and the release of vapor begins.

  The pinhole 21 formed in this way expands its hole diameter due to thermal contraction, but since the peripheral portion of the concave portion 8 is thicker than the concave portion 8, the convex portion 22 is formed. It is difficult for the pinhole diameter to expand due to thermal contraction beyond this, and the state of the relatively small diameter hole, that is, the pinhole 21 is maintained by suppressing the expansion of the hole diameter.

  In the heat seal film 4 of the present application in which the holes are formed in this way, the state in which the above-described pinhole 21 is formed is maintained without melting the entire portion where the microwave absorption layer 7 is formed. The internal pressure of the packaging container 1 is maintained by increasing the number of pinholes 21 generated in the formation portion of the microwave absorption layer 7 and / or increasing the opening area of the pinhole 21 in accordance with the pressure increase in the container 1. I was able to remove steam little by little.

  On the other hand, since the outer layer 3 of the heat seal film 4 is not provided with a slit or the like unlike the packaging bag of Patent Document 3, the heat seal film 4 has a great strength until it is heated by a microwave oven. No drop occurred, and even when pressure was applied to the packaging container 1 during transportation, storage, display, etc., it was difficult to cause rupture or the like.

  In addition, as described above, the pressure release in the packaging container 1 is such that the pinhole 21 is first formed in the portion where the recess 8 is formed, and then the pinhole 21 gradually widens and / or the number of pinholes 21 increases. Therefore, it is possible to prevent the occurrence of a popping sound at the start of air release and prevent the molten resin from falling into the food and entering as a foreign object. .

  In particular, in order to prevent the molten resin from falling on the food, when the configuration such as the overhang sealing portion in the heat seal bag of Patent Document 2 is not provided, the number of steps at the time of bag making could 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. With the configuration formed in the range, the pressure in the container could be maintained for a longer time by increasing the pinhole area more gradually and gently.

  Further, in the configuration in which the outer layer 3 is a biaxially stretched film and the heat seal layer 2 is an unstretched film, the outer layer 3 can be strengthened and the heat seal layer 2 can be easily stretched to form a recess 8. Thus, the pinhole 21 can be more easily formed.

  In addition, since the concave portion 8 is formed at least 3 mm wide on the outer side of the microwave absorbing layer 7 and on the outer side thereof, not only the formation position of the microwave absorbing layer 7 but also the peripheral portion thereof with the increase in internal pressure. Up to now, it was possible to cope with a wider range of pressure changes in the container by expanding the pinhole formation range.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which showed the structural example of the packaging bag which is an example of the packaging container of this invention, (A) is a 4-way seal bag, (B) is a 3-way seal bag, (C) is a lap-wrapping packaging bag. Explanatory drawing 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 recessed part formation method with respect to a heat seal film, (A) is the formation example which uses a relief printing plate, (B) is the formation example which uses a relief printing roll. It is explanatory drawing of the packaging container (four-side seal bag) of this invention provided with a linear microwave absorption layer, (A) is a general view, (B) is an enlarged view of a recessed part formation area, (C) is (B CC sectional view taken on the line of FIG. It is explanatory drawing of the packaging container (four-side seal bag) of this invention provided with a circular microwave absorption layer, (A) is a general view, (B) is an enlarged view of a recessed part formation area. It is explanatory drawing of the formation principle (prediction) of a pinhole, (A) is an enlarged view of the broken-line circle | round | yen part of FIG.4 (C), (B) is the heating start initial stage, (C) is heating. (D) is an enlarged plan view of the heat seal film when the pinhole is formed. It is the photograph which image | photographed the formation state of the hole at the time of heating the heat seal film which provided the linear microwave absorption layer with the microwave oven, (A) is the heat seal film of this application which provided the recessed part in the heat seal layer (Example 1) and (B) are heat seal films of a comparative example in which no recess is provided in the heat seal layer (Comparative Example 1). It is the photograph which image | photographed the formation state of the hole at the time of heating the heat seal film which provided the circular microwave absorption layer with the microwave oven, (A) is the heat seal film of this application which provided the recessed part in the heat seal layer ( Examples 2) and (B) are comparative heat seal films in which no recesses are provided in the heat seal layer (Comparative Example 2). Explanatory drawing of the conventional packaging container (corresponding to patent document 1). Explanatory drawing of the 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 sectional drawing of the heat seal film in the BB line part of (A).

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

[Overall structure of packaging container]
1 and 2 show a configuration example of a microwave heating packaging container according to the present invention.

  The packaging container 1 of FIG. 1 is a packaging bag 10 made using the heat seal film 4 of the present invention, and FIG. 1 (A) is a stack of heat seal layers 2 of two heat seal films 4 on each other. A four-side sealed bag formed by heat-sealing four sides together, FIG. 1 (B) is folded in two so that the heat-sealing layer 2 of one heat-sealing film 4 overlaps, and the three sides are heat-sealed. FIG. 1 (C) is a heat sealing bag formed as a so-called “gap-sticking” in which the heat sealing layer 2 of one heat sealing film 4 is folded and sealed so as to overlap, These heat seal bags are all objects of the packaging container in the present application, and in addition to the illustrated packaging bag, a so-called “standing pouch”, a food packaging tray 5 as shown in FIG. Any packaging that includes the heat seal film 4 as a component, such as a heat seal tray 10 'that is heat sealed by superimposing the heat seal layer 2 of the heat seal film 4 on the opening edge, etc. It can be contained in the container 1.

  In addition, in the heat seal film 4 constituting such a packaging container 1, the peripheral portion that is heat sealed with the films or the opening edge of the tray 5 by heat sealing is described as the peripheral heat seal portion 6 in this specification. In FIG. 1 and FIG. 2, the portion indicated by “shaded” corresponds to the peripheral heat seal portion 6.

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

  In the heat seal film 4, the microwave absorbing layer 7 is partially formed on the inner surface (surface on the heat seal layer 2 side) of the outer layer 3 at any position excluding the peripheral heat seal portion 6. In addition, 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.

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

  In order to strengthen the stress, it is preferable to use a uniaxially or biaxially stretched film for the outer layer 3, for example, biaxially stretched nylon (ONY), biaxially stretched polyethylene terephthalate (OPET), biaxially stretched polypropylene (OPP). Biaxially stretched films such as) can be suitably used.

  Further, the above-described biaxially stretched film may be used after being subjected to a barrier process such as silica vapor deposition, alumina vapor deposition, and coating of a barrier coating agent.

  The outer layer 3 needs to have heat resistance that does not melt even when heated at the time of heat sealing. 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, it is preferable to use biaxially stretched nylon (ONY) having a melting point of 215 to 225 ° C. or polyethylene terephthalate (PET) having a melting point of 265 ° C. In this embodiment, ONY having a thickness of 25 μm It was used.

(3) Heat seal layer As the heat seal 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 seal properties, and as an example, an olefin-based unstretched film can be suitably used. .

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

  Further, the synthetic resin film used for the heat seal layer 2 is preferably a film that is easily stretched by stress, 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 lower melting point than the synthetic resin used for the outer layer 3 described above. Preferably, there is a difference in melting point between the resin of the outer layer 3 and the heat seal layer 2. It is preferable that the temperature is 50 ° C or higher.

As described above, in this embodiment using biaxially stretched nylon (ONY) having a melting point of 215 to 225 ° C or polyethylene terephthalate (PET) having a melting point of 265 ° C as a synthetic resin used for the outer layer 3, 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., straight chain having a melting point of 105 to 130 ° C. as a synthetic resin used for the heat seal layer 2 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 is used as an example.

(4) Microwave absorption layer Of the outer layer 3 described above, the microwave absorption layer is formed on the inner surface (surface on the heat seal layer 2 side) at any position other than the portion that will later become the peripheral heat seal portion 6. 7 is formed in a predetermined shape.

  This microwave absorption layer 7 is a layer that absorbs microwaves in a band used in a microwave oven, and is applied with ink or paint to which fine particles having microwave absorption properties and other materials having microwave absorption properties are added. Or a layer formed by vapor-depositing a metal or the like having microwave absorption properties, and can form a layer having the property of generating heat by absorbing microwaves as described above. These may be formed using various known materials and lamination techniques.

  When the microwave absorbing layer 7 is formed by application of ink or paint to which a material having microwave absorbing properties is added, the microwave absorbing material to be added includes powder of metal such as aluminum, graphite or carbon black. Non-metallic powders such as carbon and various salts can be used, and the microwave absorption 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 on the inner surface of the outer layer 3 from the beginning, or by depositing metal or the like. The film may be formed by applying the microwave absorbing ink to the entire surface of the film to be the outer layer 3 in advance and then removing the ink other than the portion to be left as the microwave absorbing layer 7.

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

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

  The microwave absorption layer 7 can be preferably formed in a linear shape as shown in FIG. 4, and in this case, it is formed in a linear shape having a width of 0.5 to 3.0 mm.

  Thus, when forming the microwave absorption layer 7 in linear form, the formation length can be set according to the size of a packaging container and the amount of generated steam, but the microwave absorption layer 7 is formed in such a linear form. In the present embodiment, the length of the linear microwave absorbing layer 7 provided in a four-way sealing bag having a width of 125 mm and a length of 200 mm is approximately 5 to 200 mm, preferably 30 to 70 mm. A microwave absorbing layer 7 having a width of 1 mm and a length of 50 mm is provided.

(5) Concave portion The heat seal layer 2 at a position corresponding to the formation position of the microwave absorbing layer 7 described above is subjected to a plurality of concave portions by performing debossing (concave processing) or embossing (concave processing). 8 is formed.

  The concave portion 8 is formed at the position where the microwave absorbing layer is formed. The relief roll 8 is formed at least in a portion of the film which becomes the heat seal layer 2 at a position corresponding to the position where the microwave absorbing layer 7 is formed at the time of lamination. It is also possible to form the recess 8 in advance by contact with, etc., and laminate the film to be the heat seal layer 2 on the film to be the outer layer 3 after forming the microwave absorbing layer 7. good.

  Alternatively, after forming a heat seal film 4 by laminating a film to be the heat seal layer 2 on a film to be the outer layer 3 on which the microwave absorption layer 7 is formed, at least the microwave of the heat seal film 4 is formed. It is good also as what forms the recessed part 8 later in the heat seal layer 2 of the position in which the absorption layer 7 is formed.

  In this embodiment, the structure which forms the recessed part 8 afterward in the said heat seal layer after forming the heat seal film 4 was employ | adopted.

  As shown in FIG. 3 (A) as an example, the concave portion 8 is formed between the relief plate 12 having a convex portion formed on the surface and the counter plate 13 having a flat surface. The heat seal film 4 is arranged so that the outer layer 3 faces the side 12 and the outer plate 3, the heat seal film 4 is sandwiched between the relief plate 12 and the counter plate 13, and the softening temperature or melting temperature of the heat seal layer 2. The concave portion 8 may be formed in the heat seal layer 2 by transferring the convex portion formed on the surface of the relief plate 12 to the heat seal layer 2 or as shown in FIG. Between the heated relief printing roll 12 ′ having a convex portion formed on the surface and the opposed roll 13 ′ having a flat surface, the heat seal layer 2 faces the relief printing roll 12 ′ side, and the outer layer 3 faces the opposed roll 13 ′ side. Heatsea The film 4 may be sandwiched and passed to form the recesses 8 by continuously transferring the protrusions formed on the surface of the relief roll 12 ′ to the heat seal layer 2, and the heat seal layer 2 can be formed by various known methods.

  In the description with reference to FIG. 3 (A) and FIG. 3 (B), the case where the above-described recess 8 is formed only on the heat seal layer 2 side of the heat seal film 4 is described as an example. However, in the above-described example, the surface of the counter plate 13 and the counter roll 13 ′ formed on the flat surface may be uneven and the unevenness may be formed on the outer layer 3 side.

  It is preferable to form a large number of relatively small recesses 8, and as an example, each of the recesses 8 having a diameter or a long side of about 0.1 to 2 mm in plan view is about 0.1 to 2 mm apart. Thus, a repeating pattern can be formed at a depth of about 10 to 90% with respect to 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 using a relief plate 12 having a convex portion.

  The concave portion 8 described above may be formed in the same range as the formation range of the microwave absorption layer 7, but preferably the formation of the microwave absorption layer 7 as shown in FIG. 1, FIG. 4 and FIG. In addition to the range, it is preferable to use the above-described recess forming region 9 in which the above-described recess 8 is formed in a range of at least 3 mm width on the outer peripheral side.

  The recess formation region 9 may be formed as having a certain width and length as shown in FIGS. 4 and 5, but in this embodiment, as shown in FIG. A strip-shaped recess forming region 9 having a width of about 10 mm is formed continuously with the MD of the heat seal film 4 at a position overlapping with the layer 7, and one side of the recess forming region 9 is about 0.1 mm in plan view. Were formed continuously at equal intervals of about 0.4 mm on MD and TD.

[Action etc.]
The heat seal film 4 configured as described above is manufactured by overlapping the heat seal layer 2 so that the heat seal layer 2 side is inside and heat-sealing the peripheral heat seal portion 6 as shown in FIGS. Or the packaging container 1 is formed by heat-sealing the peripheral heat-seal part 6 with the heat-seal layer 2 superimposed on the periphery of the opening part 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 as described above, when heating is performed using a microwave oven in a state where food is packaged inside, the pressure in the packaging container 1 is increased by steam generated by heating the food contained therein. As the packaging container 1 begins to swell, the microwave absorbing layer 7 absorbs the microwave emitted from the microwave oven and generates heat, and heats and softens the heat seal film 4 at the position where the microwave absorbing layer 7 is formed. Let

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

  Since the pinholes 21 formed in this way are small in size, the release of water vapor in the container is started, but the amount of air released is small, so the inside of the packaging container 1 When the pressure in the packaging container 1 rises, the number of pinholes 21 to be formed increases or the size of each pinhole 21 increases to include the pressure of the rise, The pressure inside the packaging container 1 can be relieved well, thereby preventing the packaging container 1 from rupturing and scattering of food accompanying the rupture, and heating while maintaining the pressure inside the packaging container 1 at a relatively high level. It can be performed.

  Here, as described in the above-mentioned Patent Documents 1 and 2, in a conventional packaging container in which a vapor vent hole is formed by forming a microwave absorption layer (see FIGS. 7 and 8). The heat seal film 4 is melted into a shape corresponding to the shape of the microwave absorption layer 7 by heating using a microwave oven, so that a vapor vent hole having a shape corresponding to the shape of the microwave absorption layer 7 is formed. (Patent Document 1, description, page 3, lines 8-10, 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 absorption layer 7 is melted, and therefore the steam vent hole having the shape corresponding to the shape of the microwave absorption layer 7 is not formed. Thus, the pinhole 21 is formed in the thinned portion of the formation range of the microwave absorption layer 7 due to the formation of the recess 8, and the entire formation region of the microwave absorption layer 7 is formed without melting. In addition, by maintaining the pinhole 21, it is possible to obtain a unique effect that cannot be predicted from the prior art that the pressure in the packaging container 1 can be maintained at a relatively high level.

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

  Thus, in the packaging container 1 of the present invention, the entire formation range of the microwave absorption layer 7 in the heat seal film 4 is not melted, and the portion where the recess 8 is formed in the formation range of the microwave absorption layer 7. 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 packed with food is put into a microwave oven and microwave irradiation is started, the pressure in the packaging container 1 increases due to the generation of steam accompanying the heating of the food, Before heating, the heat seal film 4 which was in a flat state as shown in FIG. 6 (A) bulges outward as a whole as shown in FIG. 6 (B), and the microwave absorption layer 7 is formed. Heat generation starts, and 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, the heat sealing film 4 in the formation range of the microwave absorbing layer 7 is softened by the heating of the heat sealing film 4 accompanying the heat generation of the microwave absorbing layer 7, and the concave portion is thinner than the other portions. As the pinhole formed in the concave portion 8 on the right side of the paper surface in FIGS. 6 (C) and 6 (D), the formed portion 8 is melted before other portions and coupled with the pressure increase in the container. , The center of the recess 8 is broken to form the pinhole 21.

  The pinhole 21 formed in this manner enlarges its hole diameter by heat shrinkage of the heat seal film 4 like the pinhole 21 on the left side of FIG. 6C and FIG. 6D. Is difficult to expand beyond the convex portion 22 formed at the periphery of the concave portion 8, and as a result, the pinhole 21 generated in one concave portion 8 is connected to the pinhole 21 generated in the adjacent concave portion 8. As a result, it is difficult to spread over the entire formation range of the microwave absorption layer 7, and as a result, the state of the pinhole 21 that is a relatively small-diameter hole is maintained, so that the amount of vapor released can be controlled. It is done.

  As a result, in the packaging container 1 of the present invention, the inside of the packaging container 1 is continuously maintained at a relatively high pressure state from the relatively early stage after the heating by the microwave oven is started until the heating is completed. In addition, as described above, the pinhole 21 is maintained in the formation state, and the entire portion of the heat seal film 4 where the microwave absorption layer 7 is formed does not melt, so it melts away. It is considered that the resin could be prevented from entering the food as a foreign substance without providing a structure for receiving the resin.

  Both the heat seal film of the present invention and the heat seal film of the comparative example were heated in a microwave oven to confirm the hole formation state.

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

  As Example 1, a rectangular recess 8 having a side of 0.3 mm was formed on the heat seal layer of the heat seal film on which the linear microwave absorption layer 7 was formed, at a position overlapping with the microwave absorption layer. The one formed continuously at intervals of 1 mm (width of the convex portion 22) was used.

  As Example 2, a rectangular recess 8 having a side of 0.3 mm was formed on the heat seal layer of the heat seal film on which the circular microwave absorption layer was formed, at a position overlapping with the microwave absorption layer by 0.1 mm. What was formed continuously by the space | interval (width | variety of the convex part 22) was used.

  Comparative Example 1 is a heat seal film (not provided with a recess 8) in which the microwave absorption layer 7 having the immediately preceding shape is formed.

  Comparative Example 2 is a heat seal film (not provided with recesses 8) on which the above-described circular microwave absorption layer 7 is formed.

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

  The formation state of the holes after heating by the microwave oven is shown in FIGS. 7A and 7B and FIGS. 8A and 8B, respectively.

  In the packaging bag using the heat seal film of Comparative Example 1 and Comparative Example 2 in which no recess is formed in the heat seal layer, the pressure in the bag rises due to the generation of water vapor accompanying heating, but the microwave absorbing layer When the heat seal film in the forming portion melts and a pinhole is generated, in the case where a linear microwave absorbing layer is provided as in Comparative Example 1, this pinhole is formed in the direction in which the microwave absorbing layer is formed By expanding the hole diameter in a short time and connecting pinholes together to form a slit-shaped hole [FIG. 7B], and also provided with a circular microwave absorbing layer as in Comparative Example 2 Then, by increasing the hole diameter in the direction transverse to the width direction of the microwave absorbing layer to form coarse holes [FIG. 8 (B)], a heat seal formed using any heat seal film In also the pressure in the bag simultaneously with the formation of the holes had at once opened by the bag deflated.

  On the other hand, in the packaging bag using the heat seal film of the present invention in which the concave portion is formed in the heat seal layer, the linear microwave absorption layer of Example 1 is formed (FIG. 7A), and the example. In any of the two circular microwave absorption layers [FIG. 8 (A)], the formed pinholes are formed as independent holes without greatly increasing the hole diameter. It was possible to maintain the state in which the packaging bag was inflated, and thus the pressure was applied to the inside, even after the formation.

  According to the packaging container of the present invention, cooking at high temperature and high pressure is possible, so the time required for cooking is shortened, energy can be saved, and the taste of nutrients and ingredients such as vitamins and minerals of foods・ It is difficult to damage the scent.

  In addition, because it is cooked by both microwave dielectric heating 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 amount of steam, the packaging container is filled with steam, the high-pressure steam is in contact with the surface of the stored food, and the steam adhered to the film. Since it drops to the bottom as water droplets, drying can be prevented, no extra moisture is required, and water vapor attached to the bag surface returns to the bottom again, so it is a product that requires steaming or rehydration. However, it becomes possible to cook only with the moisture of the material, and you can enjoy the umami and nutrients of the material as they are.

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

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

  Examples of the miscellaneous goods include, for example, those that want to be heated in a microwave oven without soiling the hands, and that the volatile cleaning agent is filled in the microwave oven together with steam to make it easier to remove dirt. As a medical use, for example, there is a use in which a medicine is accommodated in the packaging bag of the present invention and heated and heated in a microwave oven without opening the packaging bag.

DESCRIPTION OF SYMBOLS 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 Concave part 9 Concave formation area 10 Packaging bag 10 'Heat seal tray 12 Letter plate 12' Convex roll 13 Opposing plate 13 'Opposing roll 21 Pinhole 22 Protruding portion 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 Portion 107 Conductive Heating Material 107 ′ Microwave Absorbing Layer 110 Packaging Bag (Heat Seal Bag)
130 Vapor vent 135 Overhang seal part 135a Protrusion part 136 Unsealed area 137 Slit 138 Heat seal part

Claims (10)

A laminated film comprising an outer layer made of a thermoplastic resin and a heat seal layer made of a thermoplastic resin having a melting point lower than that of the outer layer, and is a heat for packaging which is sealed by heat seal and becomes at least a part of a packaging container. In the seal film,
Forming a microwave absorption layer partially on the inner surface of the outer layer;
A heat seal film for packaging, wherein a plurality of recesses are formed in at least the heat seal layer at the formation position of the microwave absorption layer.   The packaging heat seal film 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 seal 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 seal layer is made of an unstretched film.   The heat-sealing film for a packaging container according to any one of claims 1 to 4, wherein the concave portion is formed at a position where the microwave absorbing layer is formed and at least in a range of 3 mm width outside thereof. A heat seal film having an outer layer made of a thermoplastic resin and a heat seal layer made of a thermoplastic resin having a melting point lower than that of the outer layer is provided, and a peripheral heat seal portion is formed by heat sealing the peripheral portion of the heat seal film. In a packaging container in which a packaging region in which an article to be packaged is packaged is formed on the inner circumferential side of the peripheral heat seal portion,
Of the heat seal film, a microwave absorption layer is partially formed on the inner surface of the outer layer at a position excluding the peripheral heat seal portion,
A packaging container, wherein a plurality of recesses are formed at least in the heat seal layer at a position where the microwave absorption layer is formed.   The packaging container according to claim 6, wherein the microwave absorption 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 with 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 an unstretched film. The packaging container according to any one of claims 6 to 9, wherein the concave portion is formed in a formation range of the microwave absorption layer and at least an outer 3 mm width range.