JP5534083B2 - Packaging container sheet lid - Google Patents

Description

  The present invention relates to a sheet lid of a packaging container used for food cooked in a microwave oven.

For example, various foods that are cooked and cooked in a microwave oven, such as steamed rice bowl and cooking pan, have been conventionally provided. Generally, such food is wrapped in a packaging material, a part of which is opened, put into a microwave oven, and cooked.
In the case of chawanmushi, food is stored in a cup-shaped container, and its upper opening is sealed with a film material. Before putting it into the microwave oven, a hole is made in a part of the film material with a toothpick or the like, or the film material is partially peeled off to be partially opened.

  This is done because the internal pressure of the container is increased by cooking, so that the pressure is released to prevent rupture. By heating in a state where a part of the container is opened, the pressure escapes to the outside and the container can be prevented from bursting.

  However, it is troublesome to partially open the container before putting it into the microwave oven. There is a problem of scattering in the cabinet.

  In the packaging material disclosed in Patent Document 1, a “stretched film” is laminated on a “non-stretched film” via a “low-melting heat sealant”, and a cutting line is provided on the “stretched film”. . When the internal pressure of the package rises due to heating, an opening is formed along the cutting line, from which pressure escapes to the outside.

International Publication No. WO01 / 082011 Pamphlet

  The present invention is a sheet lid of a cup-shaped container used for cooking by heating in a microwave oven, and a sheet in which an opening is automatically formed as the internal pressure increases due to heating without being partially opened in advance. The purpose is to provide a lid.

The seat lid of the present invention is removably bonded to a flange portion around the opening of the cup-shaped container to seal the opening. The sheet lid includes a “thermal adhesive layer bonded to the flange portion” on the back surface of the “base material layer on which the cut line is formed”. And, between the base material layer and the thermal adhesive layer, a “conductive heat generating layer (a layer having a property of generating heat by absorbing microwaves)” is disposed in a region facing at least a part of the flange portion. .
When heated in a state where the cup-shaped container is sealed with the sheet lid, the cut line is first vaporized and then the region of the thermal bonding layer is vaporized as the pressure in the container increases.

The sheet lid of the present invention having the above-described configuration has both a “cut line” and a “conductive heating layer”.
The “cut line” is the one that vaporizes as the internal pressure of the cup-shaped container increases, and releases the internal pressure to the outside. “Conductive heat generation layer” generates heat by absorbing microwaves when cooked in a microwave oven, etc. Under the influence of this heat generation, the thermal adhesive layer softens and deforms slowly, and this is supported The thermal adhesive layer partially peels from the flange and vaporizes in the region on the flange that does.
The “conductive heat generating layer” takes time to generate heat, but the internal pressure is released from the through-hole generated in the cut line part so that the container does not rupture by that time. It takes time to achieve very good steaming.

  Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is an exploded perspective view schematically illustrating the structure of a seat lid 10 according to an embodiment.

The sheet lid 10 has a thermal adhesive layer 40 on the back side of the base material layer 20, and a conductive heat generating layer 30 is disposed between the two. A cross-shaped cut line 21 is formed at the center of the base material layer 20.
The formation position of the cut line 21 is arbitrary, but the cut line 21 is preferably provided in the vicinity of the center of the sheet lid 10 so that the stress acts well when the internal pressure increases.

As shown in FIG. 1, the sheet lid 10 is thermally bonded to the flange portion 6 of the cup-shaped container 5 in the thermal bonding layer 40 to seal it. FIG. 2 is a perspective view of the seat lid 10 as viewed from above, and an annular region with hatching indicates the flange portion 6 of the cup-shaped container 5.
Note that reference numeral 11 indicates a knob that the consumer finally picks when the sheet lid 10 is peeled off from the container 5.

≪Cut line 21≫
The cut line 21 is not only a slit-like one formed through the entire thickness of the base material layer 20 but also a half-cut partly cut or perforated when heated in a microwave oven along the base material layer. It is sufficient if 20 is broken.
By providing such a cut line 21, when the internal pressure rises with the temperature rise in the container during cooking with a microwave oven, the location of the cut line 21 is broken and steamed (a hole is formed). From here, the internal pressure escapes to the outside.
Therefore, the specific shape of the cut line 21 is not limited to the cross shape as illustrated, and a single character, a spiral shape, or other appropriate shapes can be employed. Moreover, about the formation method of the cut line 21, an appropriate method can be employ | adopted, such as using a cutter or a laser.
The size of the cut line is not particularly limited, but if the cut line is formed in a very wide range, the strength of the sheet lid 10 itself is lowered, so that it is preferable to fit within a region of about 5 cm × 5 cm.
On the other hand, if the cut line is too small, good steaming is hindered, so it is preferable to form the cut line in a region exceeding 1 cm × 1 cm.

≪Conductive heating layer 30≫
In the illustrated example, the conductive heat generating layer 30 is substantially positioned along the outer periphery of the sheet lid over a 180 ° angle range with the position (A) facing the knob portion 11 of the sheet lid 180 ° as the center. It extends in an arc shape.
Due to the presence of the conductive heat generating layer 30, the following effects can be obtained. That is, when cooking with a microwave oven or the like, the conductive heating layer 30 absorbs microwaves and generates heat. Under the influence of this heat generation, the thermal adhesive layer 40 is softened and gently deformed, and the thermal adhesive layer 40 is partially peeled from the flange 6 and vaporized in a region on the flange 6 corresponding thereto.
Therefore, the conductive heat generating layer 30 is not limited to the substantially arcuate shape as shown, and is disposed in a region facing at least a part of the flange portion 6 between the base material layer 20 and the heat bonding layer 40. If it is, it is enough. For example, the extending angular range may be an arcuate region of 180 ° or more, or a plurality of conductive heating layers that are discretely arranged at intervals may be employed.

なお、導電性発熱層の表面抵抗率としては１０Ω／□以上１０^７Ω／□以下であることが望ましい。１０Ω／□未満では、マイクロ波が反射するため発熱量が低下し、１０^７Ω／□を超えると、抵抗が大きすぎて発熱量が低下するため、いずれも好ましくない。 The “conductive heat generating layer” used in the present invention is not particularly limited as long as it has a property of generating heat by absorbing microwaves during cooking in a microwave oven. A layer containing aluminum, ITO (indium tin oxide) or the like is preferable.
An example of the composition of the conductive heat generating layer 30 is shown in Table 1 below.

Note that the surface resistivity of the conductive heat generating layer is preferably 10 Ω / □ or more and 10 ⁷ Ω / □ or less. If it is less than 10 Ω / □, the amount of heat generated is reduced because the microwave is reflected, and if it exceeds 10 ⁷ Ω / □, the resistance is too large and the amount of heat generation is reduced.

≪Advantages of providing both the cut wire 21 and the conductive heating layer 30≫
In the present invention, by providing both the “cut line 21” and the “conductive heating layer 30” on the sheet lid 10, extremely stable vaporization is achieved. This will be described.
(1)
As described above, the cut line 21 is provided in order to break the pressure and release the pressure as the internal pressure increases. However, if the cut line 21 is present alone, the steaming is unstable, or the open holes are too small to follow the amount of steam generated, which may eventually burst.
(2)
On the other hand, if the conductive heat generating layer 30 is present alone, the following inconvenience may occur.
In the case of a high-output microwave oven for business use, the temperature in the container rises rapidly and the internal pressure also rises rapidly. However, since it takes time for the conductive heat generating layer to warm up, if the internal pressure rapidly increases, the heat generated by the conductive heat generating layer may not catch up with it and may eventually burst.
In addition, in the case of a food that has a large dielectric loss coefficient and is easily heated, the temperature of the food surface suddenly rises and the internal pressure of the container also rises sharply.
(3)
Therefore, by having both the cut line 21 and the conductive heat generating layer 30 coexist, extremely satisfactory vaporization can be achieved as described below.
As the pressure in the container increases, the cut line first partially vaporizes. As a result, the increased internal pressure escapes to the outside. After this, even if the steam discharge cannot catch up during the heating until the contents are sufficiently warmed, the conductive heat generating layer is sufficiently heated by that time, so the corresponding thermal adhesive layer This region is sufficiently softened and peeled off from the flange portion 6, from which steam escapes to the outside and does not rupture.

  In other words, the conductive heat generating layer takes time to generate heat, but in order to prevent the container from rupturing by that time, by letting the internal pressure escape from the somewhat formed steam hole, It can be considered that time is being saved.

<< Base Layer 20 and Thermal Adhesive Layer 40 >>
The base material layer 20 uses an appropriate material such as one constituting the top surface of a sheet lid used for general cup soup. As the thermal bonding layer 40, a generally known layer is used for bonding and fixing the sheet lid to the flange portion of the cup-shaped main body.

  In order to verify the effectiveness of the present invention, as described below, “implemented products” and “comparative samples” were prepared and subjected to comparative evaluation.

<Products>
A conductive heating layer having a shape as shown in FIG. 1 was printed on the back surface of PET (polyethylene terephthalate) having a thickness of 12 μm by a gravure printing method at a coating amount of about 1.4 g / m ² .
After that, using a two-component curable urethane adhesive, 15 μm thick ONY (stretched nylon) and 50 μm easy peel sealant (manufactured by Tosero Co., Ltd., CMPS022C) are sandwiched by dry lamination so that the conductive heat generating layer is sandwiched Laminated.
The laminated sheet lid produced as described above was punched into a substantially circular shape to form a sheet-shaped lid material, and the upper opening of the cup-shaped container was sealed with this. The cup-shaped container was filled with 150 g of corn potage. Thereafter, the top surface of the lid member was irradiated with a carbon dioxide laser, and a cross-shaped half cut of approximately 3 cm × 3 cm was placed in the center of the lid member.
The cup-shaped container is made of polypropylene and has the following dimensions.
(1) Flange inner diameter: 90 mm
(2) Outer diameter of flange: 104mm
(3) Container height: 75 mm
(4) Outer diameter of container bottom: 55 mm

≪Comparative sample 1≫
A sample having the same structure as that described above was prepared except that the conductive heat generating layer was omitted, and this was designated as Comparative Sample A.

≪Comparative sample 2≫
A sample having the same structure as that described above was prepared except that the half-cut was omitted.

≪Range heating evaluation≫
Three “practical products”, “comparative samples A”, and “comparative samples B” were prepared and heated in a 1800 W microwave oven for 40 seconds to compare the states. The results were as shown in Table 2 below.

The separation perspective view explaining the sheet lid concerning one embodiment of the present invention. The perspective view which looked at the sheet | seat cover of FIG. 1 from upper direction.

DESCRIPTION OF SYMBOLS 5 Cup-shaped container 6 Flange part 10 Sheet lid 11 Knob part 20 Base material layer 21 Cut wire 30 Conductive heat generating layer 40 Thermal adhesive layer

Claims (2)

A sheet lid that is removably bonded to the flange portion (6) around the opening of the cup-shaped container and seals the opening,
The sheet lid has a thermal adhesive layer (40) bonded to the flange portion (6) on the back surface of the base material layer (20) on which the cut line (21) is formed.
Between the base material layer (20) and the thermal adhesive layer (40), the conductive heating layer (30) is disposed in a region facing at least a part of the flange portion (6) ,
When heated in a state where the cup-shaped container is sealed with the sheet lid, the cut line (21) is first steamed as the pressure in the container increases, and then the region of the thermal adhesive layer (40) is A sheet lid characterized by steaming .
  The sheet lid according to claim 1, wherein the conductive heating layer (30) includes at least a position (A) opposite to the knob (11) and extends along an outer periphery of the sheet lid. .

Images