JP5682073B2 - Packaging container and inspection method for packaging container - Google Patents

Description

  The present invention relates to a packaging container that can heat and cook food by containing the food in a sealed state and heating it in a microwave oven, and more specifically, an inspection method for the packaging container. The present invention relates to a packaging container that has a vapor venting mechanism and can exhibit hermeticity and high gas barrier properties when not heated, and an inspection method for the packaging container.

DESCRIPTION OF RELATED ART Conventionally, the packaging container which can heat-cook a foodstuff by accommodating a foodstuff inside in a sealed state and heating it with a microwave oven is known.
Such a packaging container for cooking by heating in a microwave oven is usually provided with a steam venting mechanism in order to prevent the container from bursting, because the internal pressure of the container rises due to steam generated from the food during heating.

Patent Documents 1 and 2 below disclose a packaging container for cooking by heating with a microwave oven provided with a steam release mechanism.
Patent Document 1 discloses a packaging bag that is made using a synthetic resin film and stores foodstuffs in a sealed state. This packaging bag is made of a material made of a resin having a melting point lower than that of the layer located on the outer side of the layer constituting the inner surface side, and forms a gas vent part in a part of the bag. ing. This degassing part forms a notch in the packaging bag material, and at least the layers constituting the packaging bag material from the inner surface side to the inner surface side melt in the range including the notch portion, but constitutes this inner surface side. Heated at a temperature at which the layer located outside the layer to be melted does not melt, and only the cut portion of the layer constituting the inner surface side is opened by the increase in the internal pressure of the packaging bag during cooking in the microwave oven Closed by melting.

According to the packaging bag disclosed in Patent Document 1, when cooking the food stored in the sealed packaging bag in a microwave oven, the inner surface side of the gas venting portion is configured by increasing the internal pressure of the packaging bag. The cut portion of the layer to be pressed is pushed open from the inside, and the degassing portion can be easily opened.
However, in this packaging bag, since the layer constituting the inner surface side is made of polyolefin having low gas barrier properties, the gas filled in the bag (nitrogen gas) permeates the layer constituting the inner surface side before heating. As a result, there is a problem of leakage from the cut portion of the outer layer to the outside of the bag.
Therefore, it has been difficult to store food materials for a long period of time with this packaging bag.

  In Patent Document 2, a low-melting point heat sealant is applied to a required portion of a synthetic resin stretched film, and a cut line is formed on the synthetic resin stretched film by a line or a broken line passing through the portion where the heat sealant is applied. Further, a packaging bag using a film that is engraved and further bonded with a synthetic resin unstretched film having heat sealing properties on the synthetic resin stretched film is disclosed.

According to the packaging bag disclosed in Patent Document 2, when the pressure inside the bag rises due to microwave heating, the unstretched film extends in a direction perpendicular to the cutting line while spreading the stretched film, and the heat sealant melts. Peeling of the stretched film and the unstretched film begins, the cutting line at the application site of the heat sealant is cut, and the stretched film begins to open. Even after the stretched film starts to open, the unstretched film tries to stretch, but only the part where the heat sealant is applied is stretched, and the other parts not coated are not stretched. Stress concentrates at the boundary point between the part that is applied and the part that is not applied, and a small hole is opened in the unstretched film at both ends of the part where the cutting line is opened, and this small hole functions as a steam release mechanism.
However, since this packaging bag uses a polyethylene film having a low gas barrier property as an unstretched film placed inside the bag, it is filled in the bag in the state before heating as in the technology disclosed in Patent Document 1. The gas (nitrogen gas) permeated the unstretched film and leaked out of the bag from the cut line of the stretched film.
Therefore, it has been difficult to store food materials for a long time even in this packaging bag.

Japanese Patent No. 3148160 WO01 / 082011 Publication

  The present invention has been made to solve the above-mentioned problems of the prior art, and is a package for cooking food by containing the food in a sealed state and heating it in a microwave oven. The container for use has a steam venting mechanism for preventing the container from bursting when the internal pressure of the container rises due to steam generated from food during heating, and nitrogen filled in the container from the steam venting mechanism during non-heating. The present invention provides a packaging container that can prevent gas and the like from leaking and enables the long-term storage of food contained in the container, and an inspection method for the packaging container.

The invention according to claim 1 is a packaging container for containing foodstuffs in a sealed state, and is made of a bag formed of a synthetic resin film, and the film is on the inner surface side of the bag Is a laminated film having an inner layer film having heat-sealability and an outer layer film constituting the outer surface side of the bag body, and the outer layer film has a slit, and the slit is formed by a microwave oven. Opening occurs when the internal pressure of the container rises due to the steam generated from the food during heating, and the inner layer film generates a pinhole by stretching along with the opening of the slit, and without tearing along the slit. The vapor is released from the pinhole, the melting point of the inner layer film is lower than the melting point of the outer layer film, and the slit shape of the outer layer film The slit is formed to reach the inner layer film, and the slit formed in the inner layer film includes the slit at a temperature higher than the melting point of the inner layer film and lower than the melting point of the outer layer film. The film is closed by heating a part of the film, and the outer layer film is a gas barrier film having a gas barrier coat layer on the surface of the base film, and is made of a film having a property of improving the gas barrier property by heating. The present invention relates to a packaging container.

The invention according to claim 2 is a packaging container for containing a foodstuff inside in a sealed state, and is a cover made of a synthetic resin container body and a synthetic resin film covering the opening of the container body. The film is a laminated film having a heat-sealing inner layer film constituting the inner surface side of the lid member and an outer layer film constituting the outer surface side of the lid member. Have slits formed therein, and the slits are opened when the internal pressure of the container is increased by steam generated from the food during heating by a microwave oven, and the inner layer film is pinned by extending along with the opening of the slits. holes are generated, the vapor from the pinholes without tearing along the slit is released, the melting point of the inner layer film is the outer layer fill When forming the slit of the outer layer film, the slit is formed to reach the inner layer film, and the slit formed in the inner layer film is higher than the melting point of the inner layer film and the melting point of the outer layer film. It is closed by heating a partial region of the laminated film including the slit at a lower temperature, and the outer layer film is a gas barrier film having a gas barrier coat layer on the surface of the base film , It is related with the packaging container characterized by consisting of a film which has the characteristic which property improves .

The invention according to claim 3 relates to the packaging container according to claim 1 or 2 , wherein the heating of the partial region is performed at least from the inner layer film side.

The invention according to claim 1 is characterized in that the outer layer film is a film having a characteristic that gas barrier properties are improved by heating .

The invention according to claim 4 relates to the packaging container according to claim 1 or 2 , wherein the outer layer film has the base film made of polyethylene terephthalate and the gas barrier coat layer made of an acrylic resin. .
The invention according to claim 5 relates to packaging containers according to 請 Motomeko 1 to 4 or wherein the length of said slit is 10mm or more.

  The invention according to claim 6 is the inspection method of the packaging container according to any one of claims 1, 2, 3 and 5, in the region including the slit formed in the inner layer film and closed by heating. After disposing a discharge electrode on one surface of the laminated film and disposing a ground electrode on the other surface of the laminated film, discharging from the discharge electrode and grounding from the discharge electrode during this discharge The present invention relates to a method for inspecting a packaging container, wherein the presence or absence of a pinhole in the closed slit is determined by measuring the amount of current applied to an electrode.

According to the first and second aspects of the invention, the slit formed in the outer layer film can function as a vapor venting mechanism for preventing the container from bursting when the container internal pressure is increased by the steam generated from the food during heating. it can. In addition, since the outer layer film is made of a gas barrier film having a gas barrier coat layer on the surface of the base film, the gas barrier property of the outer layer film is increased. Leakage is prevented, and food stored in the container can be stored for a long time.
Furthermore, by heating a partial region of the laminated film including the slit at a temperature higher than the melting point of the inner layer film and lower than the melting point of the outer layer film, only the inner layer film melts without melting the outer layer film. Since the formed slit is closed, a laminated film in which the slit is formed only in the outer layer film is obtained.
Since a coat-type barrier film is used as the outer layer film, when the laminated film is heated and only the inner layer film is melted, the gas barrier coat layer moves together with the melted inner layer film to block the slit of the outer layer film. The effect of narrowing the slit width is produced, and the gas barrier property of the laminated film can be improved.
Moreover, since the inner layer film is once formed with a slit and then closed, it becomes easy to generate a pinhole starting from the closed slit portion when heated in a microwave oven, and it is possible to surely vent the vapor. .
Then, without inner layer film is torn along the slit, the extent vapor from the pinholes is released, the pressure inside the container is reduced, bulging small laminate film Kunar. Thus, the vapor released is suppressed by the pinhole is reduced, container is moderate pressure (above atmospheric pressure) is maintained. Also, more liquid leakage is prevented by the surface tension of the liquid adhering to the pinhole. Moreover, further pinholes is reduced after heating, by the surface tension of the liquid even chance container is turned upside down or leakage is unlikely to occur.
Further, the outer layer film is a film der Rukoto having the property of improving the gas barrier property by heating, during heating of a partial area including the slit, pressurized thermal region including the slit portion of the outer layer film (partial region) gas barrier Improves. Therefore, to improve the gas barrier properties of the laminate fill beam in the non-heated, gas leakage from the slit is suppressed.

  According to the invention according to claim 3, since the heating of a partial region including the slit is performed at least from the inner layer film side, the slit formed in the outer layer film is closed by heating (there is no gap) Thus, a high gas barrier property can be obtained.

According to the invention according to claim 1 , since the outer layer film is a film having a characteristic that the gas barrier property is improved by heating, when the partial region including the slit is heated, the heating region including the slit portion of the outer layer film ( Gas barrier properties in some areas) are improved. Therefore, the gas barrier property of the laminated film during non-heating is improved, and gas leakage from the slit is suppressed.

According to the invention which concerns on Claim 4 , a base film consists of a polyethylene terephthalate, and a gas barrier coating layer consists of acrylic resin based on an outer layer film. Therefore, an outer layer film will have the characteristic that a barrier property improvement part spreads from an edge part (cross-section exposed part) at the time of a heating. As a result, when a partial region including the slit of the laminated film is heated, the slit becomes an end (cross-section exposed portion) and heat is applied thereto, so the heating region including the slit portion of the outer layer film (partial region) The gas barrier property of the laminated film is improved centering on the slit portion, and the gas barrier property of the laminated film when not heated is improved.
Maintained according to the invention of claim 5, since the length of the slit is 10mm or more, the inner layer Fi Lum is will tear the entire length of the slit, thereby suppressing the steam releasing vessel moderate pressure It can be prevented that it becomes impossible to do.

  According to the invention according to claim 6, in the packaging container according to any one of claims 1, 2, 3 and 5, the slit formed in the inner layer film has conditions such as temperature, time, pressure, etc. during heating. When the pinhole is not completely closed due to improperness or the like, and a pinhole is present in the slit, this can be reliably detected. Therefore, it is possible to prevent nitrogen gas or the like filled in the container from leaking out of the pinhole during non-heating, and food can be stored for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st embodiment of the packaging container which concerns on this invention, Comprising: (a) is a perspective view, (b) is the AA part expanded sectional view of (a) figure. It is a figure which shows the example of a change of the shape of a slit. It is explanatory drawing about the method of forming a slit only in an outer layer film. It is a figure which shows 2nd embodiment of the packaging container which concerns on this invention, Comprising: (a) is a perspective view, (b) is the BB part expanded sectional view of (a) figure. It is a figure explaining the effect | action of the packaging container (including both 1st embodiment and 2nd embodiment) which concerns on this invention. It is a figure explaining the difference in an effect | action by the difference in the length of the slit formed in an outer layer film. It is explanatory drawing of the method of the effect confirmation test of the packaging bag which concerns on this invention. It is a figure explaining the inspection method of the packaging container concerning the present invention.

Hereinafter, preferred embodiments of a packaging container according to the present invention will be described with reference to the drawings.
The packaging container according to the present invention is a packaging container in which foodstuffs are contained in a sealed state and can be heated by a microwave oven when the container internal pressure rises due to steam generated from the foodstuffs during heating. It has a steam venting mechanism to prevent bursting.

1A and 1B are views showing a first embodiment of a packaging container according to the present invention, in which FIG. 1A is a perspective view and FIG. 1B is an enlarged cross-sectional view taken along line AA of FIG.
The packaging container of the first embodiment is composed of a bag (1) formed from a synthetic resin film. In addition, the area | region (R) which gave the hatching of FIG. 1 is a "partial area | region containing the slit of a laminated film" mentioned later.
The form of the bag body (1) is shown as a flat bag having heat seal portions (H) on the four sides in the illustrated example, but is not limited to this form. For example, a palm type bag, a gusset type Or a stand-type bag, a two-chamber separation type bag, or the like.

The film is a laminated film having an inner layer film (2) constituting the inner surface side of the bag body and an outer layer film (3) constituting the outer surface side of the bag body.
The inner layer film (2) is a film having heat sealability.
As a material for the inner layer film (2), for example, LLDPE (Linear Low Density Polyethylene), CPP (Unstretched Polypropylene) and the like are preferably used.
The outer layer film (3) is a gas barrier film (hereinafter referred to as “coat type barrier film”) having a gas barrier coat layer (32) on the surface of the base film (31). The gas barrier coat layer (32) is disposed on the inner layer film (2) side of the base film (31).
As the gas barrier film used as the outer layer film (3), for example, those having an oxygen permeability of 10 cc / m ² · day · atm or less are preferably used.

As a material of the outer layer film (3), for example, the following materials can be used.
As the base film (31), OPP (biaxially stretched polypropylene), PET (polyethylene terephthalate), ONY (stretched nylon) or the like can be used, but it is preferable to use PET having high heat resistance. The base film (31) may be manufactured using these materials alone or in combination. When used in combination, for example, a coextruded stretched film of PET and NY (nylon) can be used.
As the gas barrier coat layer (32), PVDC (polyvinylidene chloride), acrylic acid resin, organic material, inorganic compound, or the like can be used.
Specific examples of the outer layer film (3) preferably used in the present invention are shown in Table 1.

In the present invention, the reason for using a coat type barrier film as the outer layer film (3) is as follows.
For example, in the case of a transparent vapor deposition type barrier film, when the film is bent or stress is applied to the film, the vapor deposition layer may crack and the gas barrier property may decrease. On the other hand, in the case of a coat-type barrier film, even if the film is bent or stress is applied to the film, the gas barrier coat layer is not cracked and stable gas barrier properties can be maintained.
In addition, as will be described later, when only the inner layer film (2) is melted by heating the laminated film, the gas barrier coat layer moves together with the melted inner layer film, and the effect of closing the slit (4) is produced. Can be improved.

In the present invention, as the outer layer film (3), it is preferable to use a coat type barrier film having a characteristic that the gas barrier property is improved when heated. More specifically, it is preferable to use a coat-type barrier film having a property that a barrier property-enhancing portion spreads from an end portion (cross-section exposed portion) of the film when heated.
Among the specific examples of the outer layer film (3) shown in Table 1, those having these characteristics are those in which the gas barrier coat layer is an acrylic resin and the base film is PET or ONY (hereinafter referred to as barrier film A). ).
Table 2 shows the physical properties of the barrier film A.

As shown in Table 2, both the oxygen permeability and the water vapor permeability are lower when the base film is PET than when it is ONY. Moreover, since PET has higher heat resistance than ONY, barrier film A in which the base film is PET is particularly preferably used.
Table 3 shows oxygen permeability (cm ³ / m ² · d · atm) before and after heating (retort) of the barrier film A whose base film is PET. The heating conditions are 120 ° C. and 30 minutes, and the measurement conditions are 20 ° C. and 80% RH.

As shown in Table 3, the barrier film A has a low oxygen permeability by heating at 120 ° C. or higher.
Although details will be described later, in the present invention, the outer layer film is heated when the slit is formed only in the outer layer film (3), and therefore, by utilizing this characteristic, the gas barrier property of the packaging bag can be improved. It becomes possible.

In the present invention, among the specific examples of the outer layer film (3) shown in Table 1, those in which the gas barrier coat layer is an inorganic compound are also preferably used.
For example, a film (hereinafter referred to as “barrier film B”) in which an inorganic fine particle nanocomposite resin is provided as a gas barrier coat layer on both surfaces of a base film made of PET or ONY is preferably used. In this case, the gas barrier coat layer preferably has a structure in which an inorganic compound (particle size of 5 nm or less) is uniformly dispersed in an organic polymer.
Table 4 shows the oxygen permeability (ml / m ² · d · MPa) before and after heating (retort) of the barrier film B and the transparent vapor deposition type film. In addition, the used barrier film B is PET, and the (lami film) in the table is a film in which CPP is laminated on the barrier film B.

As shown in Table 4, the barrier film B has a very low oxygen permeability after heating as compared with the transparent vapor deposition type film. That is, the oxygen permeability does not increase by heating as in a transparent vapor deposition type film.
In this invention, when forming a slit only in an outer layer film (3), an outer layer film is heated, but high gas barrier property is maintained by this characteristic.

  In the present invention, the barrier film A and the barrier film B are particularly preferably used as the coating type barrier film, but any coating type barrier film having the same properties as these can be used preferably. .

  Specific examples of the combination (laminate structure) of the inner layer film (2) and the outer layer film (3) include barrier film A / DL (dry laminate) / CPP, barrier film B / DL / CPP, barrier film A / DL / LLDPE, barrier film B / DL / LLDPE, etc. are mentioned.

The melting point of the inner layer film (2) is lower than the melting point of the outer layer film (3).
As will be described later, when the slit (4) is formed, the slit is once formed so as to penetrate both the inner layer film (2) and the outer layer film (3), and then only the inner layer film (2) is melted. This is because the slit formed in the inner layer film (2) can be closed.

The film forming the bag (1) is separated between the inner layer film (2) and the outer layer film (3) in addition to the laminated film having the two-layer structure of the inner layer film (2) and the outer layer film (3). It is possible to use a laminated film having a three-layer structure or more with an intermediate film.
Specific examples of laminated films having a three-layer structure or more include barrier film A / DL / ONY / DL / CPP, barrier film B / DL / ONY / DL / CPP, barrier film A / DL / LLDPE, barrier film B / DL / LLDPE and the like.

A slit (4) is formed in the outer layer film (3).
The formation method of a slit (4) is not specifically limited, For example, you may form with a blade and may form with a laser.
The length of the slit (4) is not particularly limited, but is preferably longer (the reason will be described later). Specifically, it is preferably at least 5 mm or more, more preferably 10 mm or more, and further preferably 50 mm or more. The upper limit of the length is appropriately set depending on the size of the packaging container, the slit forming method, and the like, but about 80 mm is preferable in consideration of the size of a general packaging container. Therefore, the length of the slit (4) is preferably set to, for example, 50 to 80 mm.

The shape of the slit (4) may be linear, but may be other shapes such as a curved line or a combination of a straight line and a curved line.
FIG. 2 is a diagram showing a modification of the shape of the slit (4).
2A is an example of a substantially S-shaped slit, FIG. 2B is an example of crossing three linear slits at one point (center), and FIG. 2C is an illustration of two C-shaped slits reversed from each other. (D) is an example in which slits are wavy, (e) is an example in which two arc-shaped slits are arranged in line symmetry in opposite directions, and (f) is substantially S-shaped. This is an example in which a straight slit intersects the center of the slit.
(A), (c), (d) and (e) have a function of preventing the outer layer film from spreading apart, and (b) has a function of allowing the outer layer film to tear from the center so that vapor can be easily removed. f) has these two functions together.
By forming the slit (4) with a laser, it is possible to easily form slits having such various shapes.

When the slit (4) is formed by a blade, the slit direction (direction in which the slit extends) is the film flow direction (MD direction) during slit formation. This is because tension in the flow direction is applied to the film at the time of slit processing, so if the slit direction is a direction perpendicular to the film flow (TD direction), the slit width increases and the slit may not close after the slit is formed. Because.
When the slit (4) is formed by a laser, such a problem does not occur, and therefore the slit direction can be set to either the MD direction or the TD direction.

In the present invention, the slit (4) is formed only in the outer layer film (3) of the laminated film forming the bag (1) (see FIG. 1 (b)).
Hereinafter, a method for forming the slit (4) only in the outer layer film (3) will be described.
When forming a slit with a cutter, first, a slit (4) is formed so as to penetrate all layers (total thickness) of the laminated film (see FIG. 3A). Next, only the partial region (R) including the slits of the laminated film is sandwiched and heated by the hot plate (5) from above and below (see FIG. 3B). At this time, a film in which the melting point of the inner layer film (2) is lower than the melting point of the outer layer film (3) is used, the heating temperature by the hot plate (5) is higher than the melting point of the inner layer film (2) and the outer layer film (3) The temperature is lower than the melting point (for example, 120 to 200 ° C.). Thereby, since only the inner layer film (2) is melted, the slit (4) is closed at the portion of the inner layer film (2), but is not closed at the portion of the outer layer film (3). Therefore, a laminated film in which the slit (4) is formed only in the outer layer film (3) is obtained (see FIG. 3 (c)).

When forming a slit with a laser, it is only necessary to irradiate a laser whose intensity is adjusted so as to penetrate all layers or only the outer layer film (3) from the outer layer film side of the laminated film.
However, even when slits are formed by laser, after forming the slits so as to penetrate the entire layer (total thickness) of the laminated film, as in the above-described method using the blade, a partial region including the slits of the laminated film Only the inner layer film may be sandwiched from above and below, the inner layer film alone may be melted, and the slit may be closed at the inner layer film portion, and the slit may not be closed at the outer layer film portion.

In the present invention, heating is performed from at least the inner layer film (2) side (from both upper and lower sides or only from the inner layer film side) when heating by sandwiching only a partial region including the slit of the laminated film from above and below with a hot plate (5). It is preferable to do.
When this is heated only from the outer layer film (3) side, the slit formed in the outer layer film (3) is in a widened state (a state in which a gap is left), and there is a concern about a decrease in gas barrier properties. This is because when the heating is performed from the inner layer film (2) side, the slit formed in the outer layer film (3) is closed (there is no gap), and high gas barrier properties are obtained.

  In the slit forming method described above, by using a coat-type barrier film as the outer layer film (3), when the laminated film is heated and only the inner layer film (2) is melted, together with the melted inner layer film (2) In addition, the gas barrier coat layer moves and the slit (4) is blocked, so that the gas barrier property can be improved.

  Further, as the outer layer film (3), by using a coat-type barrier film having a property of improving the gas barrier property when heated, only a partial region including the slit of the laminated film is sandwiched from above and below by the hot plate (5). When heated at, the gas barrier property of the heating region (partial region) including the slit portion of the outer layer film (3) is improved. Therefore, the gas barrier property of the laminated film when not heated is improved.

Furthermore, when a coat-type barrier film having the property that the barrier property-enhancing part spreads from the end (cross-section exposed part) of the film when heated is used as the outer layer film (3), only a partial region including the slit of the laminated film Is heated between the upper and lower plates with the hot plate (5), and the slit becomes an end (exposed section) and heat is applied thereto, so that the heating region including the slit portion of the outer layer film (3) (partial region) ) Gas barrier property is improved centering on the slit portion. Therefore, the gas barrier property of the laminated film when not heated is further improved.
In this case, even when the slit is formed by the laser, since the end of the slit is heated by the laser, the gas barrier property of the heating region (partial region) including the slit portion of the outer layer film (3) is centered on the slit portion. improves.

  For example, the barrier film A shown in Table 1 is a coating type barrier film having a characteristic that the gas barrier property is improved when heated, and a property that the barrier property improving part spreads from the end portion (cross-section exposed portion) of the film when heated. .

4A and 4B are views showing a second embodiment of the packaging container according to the present invention, in which FIG. 4A is a perspective view, and FIG.
The packaging container of 2nd embodiment consists of a synthetic resin container main body (10) and the cover material (11) which consists of a synthetic resin film which covers the opening part of a container main body (10). The lid (11) is thermally bonded to the upper peripheral surface of the container body (10) in the heat seal part (H).
In addition, the area | region (R) which gave the hatching of FIG. 4 is "the partial area | region containing the slit of a laminated film" mentioned above.

A container main body (10) is a cup shape which has an opening part in an upper surface, Comprising: Foodstuffs are accommodated in the inside.
The material of the container body (10) may be any material as long as it can thermally bond the inner layer of the synthetic resin film constituting the lid material (11). For example, PP, PE, APET or the like is preferably used.

As shown in FIG. 4B, the film constituting the lid member (11) constitutes the inner layer film (12) constituting the inner surface side of the lid member (11) and the outer surface side of the lid member (11). A laminated film having an outer layer film (13).
This laminated film can have the same configuration as the laminated film forming the bag (1) described above. Therefore, the outer layer film (13) is a gas barrier film (coat type barrier film) having a gas barrier coat layer (132) on the surface of the base film (131). The only difference is that an easy peel film with heat sealability is used as the inner layer film (12). The reason for using the easy peel film is to make it easier to peel the lid (11) from the container body (10). However, other than the easy peel film (for example, CPP, LLDPE, etc.) can be used as the inner layer film (12).
As the easy peel film, a polypropylene-based easy peel film, a polyethylene-based easy peel film or the like (hereinafter collectively referred to as “EASY”) can be preferably used.

As a specific example of the combination (laminated structure) of the inner layer film (12) and the outer layer film (13), in the case of a two-layer structure, barrier film A / DL / EASY, barrier film B / Examples thereof include DL / EASY, barrier film A / DL / CPP, barrier film B / DL / CPP, barrier film A / DL / LLDPE, barrier film B / DL / LLDPE.
In the case of a three-layer structure or more, barrier film A / DL / ONY / DL / EASY, barrier film B / DL / ONY / DL / EASY, barrier film A / DL / ONY / DL / CPP, barrier film B / DL / ONY / DL / CPP, barrier film A / DL / ONY / DL / LLDPE, barrier film B / DL / ONY / DL / LLDPE, and the like.

Of the laminated film forming the lid member (11), the slit (14) is formed only in the outer layer film (13) (see FIG. 4B).
The configuration (material etc.) of the outer layer film (13) of the laminated film that forms the lid material (11), and the configuration and formation method of the slit (14) are the outer layer film (3) of the laminated film that forms the bag (1). Since the configuration (material etc.) and the configuration and forming method of the slit (4) are the same, the description thereof is omitted.

FIG. 5 is a diagram for explaining the operation of the packaging container according to the present invention (including both the first embodiment and the second embodiment), wherein (A) to (D) are partially enlarged plan views, a)-(d) is a partial expanded sectional view.
The packaging container according to the present invention is heated by a microwave oven in a state where food is contained inside and sealed.
In the state before heating, the laminated film forming the bag body (1) or the laminated film forming the lid (11) (hereinafter simply referred to as the laminated film) receives pressure (vapor pressure) from the inside of the container. The slits (4, 14) formed in the outer layer films (3, 13) are in a closed state (see FIGS. 5A and 5A).
In this state, the nitrogen gas filled in the bag body (1) tries to leak through the inner layer films (2, 12) to the outside through the slits (4, 14). However, since a coat-type barrier film is used as the outer layer film (3), excellent gas barrier properties are exhibited, and gas leakage from the slits (4, 14) to the outside hardly occurs. Therefore, it becomes possible to stably store the food stored in the container over a long period of time.

When the food is heated, the pressure inside the container is increased by the steam generated from the food, and the laminated film swells outward. Thereby, the slits (4, 14) formed in the outer layer films (3, 13) are opened, and the inner layer films (2, 12) are elongated accordingly (see FIGS. 5B and 5B).
When the pressure (vapor pressure) inside the container further increases, the inner layer film (2, 12) further expands, and a pinhole (6) is generated at the opening of the slit (4, 14), from the pinhole (6). Steam (S) is discharged to the outside (see FIGS. 5C and 5C). In addition, the inner layer films (2, 12) are in a state in which pinholes are likely to be generated by using a closed film after forming a slit once.
When the vapor is released to some extent, the pressure inside the container is lowered, so that the swelling of the laminated film is reduced (see FIGS. 5D and 5D). Thereby, a pinhole (6) becomes small and vapor | steam discharge | release is suppressed and a moderate pressure (pressure higher than atmospheric pressure) is maintained in a container. Moreover, the liquid leakage is prevented by the surface tension of the liquid adhering to the pinhole (6). Further, after heating, the pinhole (6) is further reduced, and even if the container is turned upside down, liquid leakage hardly occurs due to the surface tension of the liquid.

In the above operation, when the length of the slit (4) formed in the outer layer film (3) is short (see FIG. 6 (a)), the slit (4) cannot be greatly expanded. When the pressure is excessive, the pinhole (6) formed in the inner layer film (2, 12) cannot be enlarged. Therefore, the inner layer films (2, 12) are torn over the entire length of the slit (4), and it becomes impossible to keep the inside of the container at an appropriate pressure by suppressing vapor discharge.
On the other hand, when the length of the slit (4) is long (see FIG. 6 (b)), the slit (4) can be greatly expanded, so that the pressure (vapor pressure) inside the container becomes excessive. The pinhole (6) formed in the inner layer film (2, 12) becomes larger. Therefore, it is prevented that the inner layer films (2, 12) are torn over the entire length of the slit (4), and the inside of the container can be maintained at an appropriate pressure by suppressing vapor discharge.
Therefore, as described above, it is preferable that the length of the slit (4) is as long as possible in the design. Specifically, in order to avoid a problem as shown in FIG. 6A, it is preferably at least 5 mm, more preferably 10 mm, and even more preferably 50 mm.

Hereinafter, the test results conducted to confirm the effect of the packaging bag according to the present invention will be shown.
<1. Test sample>
A laminated film having a laminated structure of “besaler / adhesive / PE-based EASY” using Besera (thickness 13 μm) made by Kureha Chemical Co., Ltd. corresponding to barrier film A as an outer layer film, and a polyethylene-based easy peel film as an inner layer film. Produced.
A slit having a length of 80 mm was formed only in the outer layer film by the method shown in FIG. 3 with respect to the manufactured laminated film. The heating conditions with the hot plate were 150 to 220 ° C. × 1 second, and the size of the heating zone with the hot plate (partial region including the slit) was 15 mm × 80 mm.

<2. Test method>
(2-1) Test 1
As shown in FIG. 7 (a), from the laminated film original fabric, the test target area including the slit (4) (area including the heating area (R) by the hot plate) (A area) and the comparison area not including the slit. (Area other than area A) (area B) was cut out, and oxygen permeability was measured at 20 ° C. and 80% RH for 24 hours using a gas barrier test apparatus (manufactured by Mocon).
(2-2) Test 2
As shown in FIG. 7 (b), the periphery of the film including the region A is fixed to a square frame-shaped frame (F) using a pin (P), and the bottom surface is placed in a square box. A weight (500 g, 1 kg) of weight was placed on the upper part of area A and pressed. The area of the bottom of the box containing the weight and the contact portion of the film (the region (W) surrounded by the phantom line) was 10 cm × 10 cm = 100 cm ² . After maintaining this pressurized state for 1 day and 7 days in an environment of 25 ° C. and 50% RH, an oxygen permeability measurement was performed for 24 hours at 20 ° C. and 80% RH using a gas barrier test apparatus (manufactured by Mocon). .
It should be noted that the state where the weight 500g is placed assumes a state in which the lunch boxes equipped with the film are stacked in two stages, and the state where the weight 1kg is placed assumes a state where the lunch boxes equipped with the film are stacked in three stages. It is assumed that the lunch box is stored for the longest expiration date for 7 days.

<3. Test results>
Table 5 shows the measurement results. The values in the table are oxygen permeability (cm ³ / m ² · d · atm).

As shown in Table 5, although the oxygen permeability of the test target region in which the slit was formed was higher than that in the comparative region in which the slit was not formed, the average value was 1.26 or less, which was a value that was not problematic in use. . From this result, the laminated film used in the packaging container according to the present invention has a high gas barrier property when not heated (before heating in the microwave oven) despite having a slit as a vapor venting mechanism. I understand that
In addition, even after storing in a pressurized state, the oxygen permeability is the same as when no pressure is applied. Therefore, store it in the pressurized state (the state where the lunch boxes are stacked) that is assumed as the storage state of the lunch box. However, it was confirmed that the gas barrier property was not lowered. From this, it can be said that according to the packaging container according to the present invention, the food contained in the packaging container can be stably stored for a long period (seven days or more).

Next, the inspection method for packaging containers according to the present invention will be described.
As described above, the packaging container according to the present invention (including all the above embodiments) has the slit formed in the inner layer film (2, 12) higher than the melting point of the inner layer film (2, 12) and the outer layer film. It is closed by heating a partial region (R) of the laminated film including the slit formed in the inner layer film (2, 12) at a temperature lower than the melting point of (3, 13). (See Figure 3)
However, when conditions such as temperature, time, and pressure during heating are inappropriate, the slits formed in the inner layer films (2, 12) may not be completely closed and pinholes may exist. If there is a pinhole, nitrogen gas or the like filled in the container leaks out from the pinhole when not heated, which causes a problem that the food cannot be stored for a long time.

  Although it is very difficult to visually find a pinhole that exists in such a closed slit, according to the inspection method according to the present invention, the presence or absence of a pinhole can be easily and reliably found. it can. The inspection method according to the present invention will be specifically described below.

FIG. 8 is a diagram for explaining an inspection method according to the present invention.
In the inspection method according to the present invention, first, in the region including the slit formed in the inner layer film (2, 12) and closed by heating (the same region as the partial region (R)), one of the laminated films The discharge electrode (15) is disposed on the side surface, and the ground electrode (16) is disposed on the other surface of the laminated film. As a device having such a discharge electrode (15) and a ground electrode (16), a voltage type pinhole tester can be used.
In addition, regarding the arrangement of the discharge electrode (15) and the ground electrode (16), in the illustrated example, the discharge electrode (15) is arranged on the surface on the outer layer film (3, 13) side, and the inner layer film (2, 12). Although the ground electrode (16) is arranged on the side surface, the arrangement may be reversed.

Next, a high voltage (for example, 0.1 kV to 10 kV) is applied to the discharge electrode (15) to discharge (corona discharge) toward the ground electrode (16) (at the time of this discharge). The amount of current (voltage between the discharge electrode (15) and the ground electrode (16)) from the discharge electrode (15) to the ground electrode (16) is measured.
When there is no pinhole, the discharge from the discharge electrode (15) is blocked by the inner layer film (2, 12) even though it passes through the slits (4, 14) formed in the outer layer film (3, 13). Therefore, as shown in FIG. 8A, the measured value of the energization amount (voltage) to the ground electrode (16) is 0 V, and it is determined that the current is normal (no pinhole).
When there is a pinhole, the discharge from the discharge electrode (15) passes through the slit (4, 14) formed in the outer layer film (3, 13) and the pinhole of the inner layer film (2, 12). As shown in FIG. 8B, the measured value of the energization amount (voltage) to the ground electrode (16) does not become 0V, and is judged to be abnormal (with a pinhole).

  INDUSTRIAL APPLICABILITY The present invention can be widely used as a packaging container for cooking food by containing the ingredients inside and heating them in a microwave oven, and a method for inspecting the packaging containers. For example, retort food It is suitably used as a packaging container such as a box lunch or a method for inspecting this packaging container.

DESCRIPTION OF SYMBOLS 1 Bag body 2 Inner layer film 3 Outer layer film 31 Base film 32 Gas barrier coat layer 4 Slit 5 Hot plate 6 Pinhole 10 Container body 11 Cover material 12 Inner layer film 13 Outer layer film 14 Slit 131 Base film 132 Gas barrier coat layer 15 For discharge Electrode 16 Ground electrode R Partial region S of laminated film including slit S Vapor

Claims (6)

A packaging container for containing foods in a sealed state inside,
It consists of a bag formed from a synthetic resin film,
The film is a laminated film having an inner layer film having heat sealing properties constituting the inner surface side of the bag body and an outer layer film constituting the outer surface side of the bag body,
A slit is formed in the outer layer film,
The slit is opened by increasing the internal pressure of the container by steam generated from the food during heating by the microwave oven,
The inner layer film generates a pinhole by extending along with the opening of the slit, and the vapor is released from the pinhole without tearing along the slit ,
The melting point of the inner layer film is lower than the melting point of the outer layer film,
At the time of slit formation of the outer layer film, the slit is formed to reach the inner layer film,
The slit formed in the inner layer film is closed by heating a partial region of the laminated film including the slit at a temperature higher than the melting point of the inner layer film and lower than the melting point of the outer layer film.
The packaging container, wherein the outer layer film is a gas barrier film having a gas barrier coat layer on the surface of the base film and has a characteristic that the gas barrier property is improved by heating. A packaging container for containing foods in a sealed state inside,
Consists of a synthetic resin container body and a cover made of a synthetic resin film covering the opening of the container body,
The film is a laminated film having an inner layer film having a heat sealing property constituting the inner surface side of the lid member and an outer layer film constituting the outer surface side of the lid member,
A slit is formed in the outer layer film,
The slit is opened by increasing the internal pressure of the container by steam generated from the food during heating by the microwave oven,
The inner layer film generates a pinhole by extending along with the opening of the slit, and the vapor is released from the pinhole without tearing along the slit ,
The melting point of the inner layer film is lower than the melting point of the outer layer film,
At the time of slit formation of the outer layer film, the slit is formed to reach the inner layer film,
The slit formed in the inner layer film is closed by heating a partial region of the laminated film including the slit at a temperature higher than the melting point of the inner layer film and lower than the melting point of the outer layer film.
The packaging container, wherein the outer layer film is a gas barrier film having a gas barrier coat layer on the surface of the base film and has a characteristic that the gas barrier property is improved by heating.   The packaging container according to claim 1 or 2, wherein the heating of the partial area is performed at least from the inner layer film side.   3. The packaging container according to claim 1, wherein the outer layer film includes the base film made of polyethylene terephthalate and the gas barrier coat layer made of an acrylic resin. The length of the slit is 10 mm or more, according to any one of claims 1 to 4. The packaging container as described. A method for inspecting a packaging container according to any one of claims 1 to 5 ,
In the region including the slit formed in the inner layer film and closed by heating, the discharge electrode is disposed on one surface of the laminated film, and the ground electrode is disposed on the other surface of the laminated film, A method for inspecting a packaging container, comprising: discharging from the discharge electrode; and determining the presence or absence of a pinhole in the closed slit by measuring an energization amount of the ground electrode during the discharge.

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