JP2009154936A - Packaging material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging material which is a packaging material which can be used for heat cooking by a microwave oven, and can form automatically an opening with an increase in inner pressure by heating without partially unsealing in advance. <P>SOLUTION: A sheet-like packaging material 10 has a heat bonding layer on the back surface of a substrate layer, and a cut line 21 is formed on a part of the substrate layer. Between the substrate layer and the heat bonding layer, an electrically conductive exothermic layer 30 is arranged in a region covering at least a part of the cut line 21. When heat cooking is performed by a microwave oven or the like, the electrically conductive exothermic layer generates heat, and the heat bonding layer is softened and is gradually deformed by this influence, and eventually, a part corresponding to the cut line is penetrated through, and steam is vented from here. That is, as the electrically conductive exothermic layer exists, the heat bonding layer is gradually deformed to form a steam hole. As there exists no possibility of unsealing at a breath so that the packaging material may burst (or explode), it is possible to prevent such a problem as splashing of the content from occurring. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a packaging material used for food that is 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 it is put into the microwave oven, and if this is forgotten and cooked, the container bursts during heating and the food is stored in 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 provides a packaging material that can be used for cooking by a microwave oven, and automatically opens as the internal pressure increases due to heating without being partially opened in advance. With the goal.

  The packaging material of the present invention is a sheet-shaped packaging material having a thermal adhesive layer on the back surface of a base material layer, and a cut line is formed on a part of the base material layer. And, between the base material layer and the thermal adhesive layer, a conductive heating layer (a layer having physical properties that absorbs microwaves and generates heat) is disposed in a region covering at least a part of the cut line. Yes.

  When the packaging material of the present invention having the above-described configuration is cooked in a microwave oven or the like with food stored therein, the conductive heating layer absorbs microwaves and generates heat. Under the influence of this heat generation, the thermal adhesive layer is softened and gently deformed, finally the portion corresponding to the cut line penetrates, and the steam escapes from here. That is, due to the presence of the conductive heat generating layer, the vapor hole is formed while the thermal adhesive layer is gently deformed. Since the packaging material is not opened at a stretch so as to rupture (or explode), problems such as scattering of contents can be prevented.

  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 sheet-like packaging material (lid material) 10 according to an embodiment.

The packaging material 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 packaging material 10 so that the stress acts well when the internal pressure increases.

As shown in FIG. 1, the packaging material 10 is thermally bonded to the flange portion 6 of the cup-shaped container 5 to seal it. FIG. 2 is a perspective view of the packaging material 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 packaging material 10 is peeled off from the container 5.

The conductive heating layer 30 is configured as a circular layer that covers the entire cross-shaped cut line 21. 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 finally the portion corresponding to the cut line 21 penetrates and the steam escapes from here.
Even if the conductive heat generating layer 30 does not exist, the portion corresponding to the cut line 21 penetrates due to the increase in the container internal pressure. However, in that case, since the above-mentioned action of “gradual deformation of the thermal adhesive layer 40 caused by the conductive heat generating layer 30” cannot be obtained, the contents are opened at a stretch so as to burst (or explode). Problems such as splashing. In the present invention, by interposing the conductive heat generating layer 30, the deformation at the time of opening is moderated to prevent such a problem.

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。 ≪Conductive heating layer 30≫
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, but is not limited to carbon black, silver, 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. Is less than 10 [Omega / □, reduces the amount of heat generated because the microwave is reflected and more than 10 ⁷ Ω / □, since heating value resistor is too large drops, both undesirable.

<< 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.

<< The shape of the conductive heat generating layer 30 and the cut line 21 >>
In the example of FIG. 2, the conductive heat generating layer 30 is configured as a circular layer that covers the entire cross-shaped cut line 21. However, in the present invention, the specific shape of the conductive heat generation layer 30 is not limited as long as the deformation at the time of opening can be moderated by interposing the conductive heat generation layer 30. It is only necessary that the conductive heat generating layer 30 is disposed in a region covering at least a part of the cut line 21.
Further, the shape of the cut line 21 is not limited to a cross shape, and a single character, a spiral shape, or any other appropriate shape can be employed.
The cut line 21 is not only slit-like formed through the entire thickness of the base material layer 20, but also half-cut partially cut or perforated when heated in a microwave oven. Any material that breaks the material layer 20 may be used. 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 packaging material 10 itself is lowered, so that it is preferable to be within an area 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.

  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 circular conductive heating layer as shown in FIG. 1 was printed at a coating amount of about 1.4 g / m ^{2 on} the back surface of PET (polyethylene terephthalate) having a thickness of 12 μm by gravure printing.
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 packaging material produced as described above was punched into a substantially circular shape to form a sheet-like 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≫
Except for omitting the conductive heat generating layer, the same structure as described above was prepared and used as a comparative sample.

≪Range heating evaluation≫
Three “practical products” and “comparative samples” were prepared and heated in a 500 W microwave oven for 1 minute 30 seconds to compare the states. The results were as shown in Table 2 below.

  In the embodiment illustrated and described, the packaging material of the present invention is configured as a sheet lid for a cup-shaped container. However, the packaging material of the present invention can be configured, for example, as a packaging bag for packaging cooking bread. In that case, the packaging material is folded with the thermal adhesive layer inside, and the surroundings are thermally bonded. To form a bag.

The isolation | separation perspective view explaining the packaging material which concerns on one Embodiment of this invention. The perspective view which looked at the packaging material of FIG. 1 from upper direction.

Explanation of symbols

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

Claims (1)

A sheet-like packaging material (10) having a thermal adhesive layer (40) on the back surface of the base material layer (20), wherein a cut line (21) is formed on a part of the base material layer,
A packaging material, characterized in that a conductive heating layer (30) is disposed in a region covering at least a part of the cut line (21) between the base material layer (20) and the thermal bonding layer (40). .

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