JPH03205016A - Exothermic material for microwave oven - Google Patents

Abstract

PURPOSE:To enable the application of a burn trace on a food, and adjustment of heating and heat radiation by laminating a thin paper layer on the exothermic layer or heat resisting sheet side of a heat resisting sheet, and further laminating a thick sheet layer having many holes onto the aforesaid thin paper layer. CONSTITUTION:A thin sheet layer 3 comprising high quality paper having weight of 15 to 200g/mm<2> is pasted to the side of a heat resisting sheet 2 of the laminate of an exothermic layer 1 and the heat resisting sheet 2 via a heat resisting adhesive layer 6 made of an urethane adhesive, thereby constituting an exothermic material body. A paper layer 4 comprising 0.3 to 2mm thickness cardboard has many circular holes 5 over the entire surface thereof and the numerical aperture of the holes 5 is set at 3 to 80%. The aforesaid paper layer 4 is pasted to the side of the thin paper layer 3 of the exothermic material body via a heat resisting adhesive layer 7 made of a urethane adhesive, thereby forming an exothermic material for a microwave oven. This exothermic material is placed within a microwave oven and a food, for example, a rice cake is placed thereon for heating and drying. Then, it is ensured to apply a trace of burn on the food. Also, the thickness of the thick paper layer 4 and the numerical aperture of the holes 5 can freely be selected and set, thereby enabling the arbitrary adjustment of heating and heat radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat-generating material for microwave ovens, and more specifically, to heating the food and simultaneously imparting browning and aroma to the food when cooking or heating the food using a microwave oven. This relates to heat-generating materials that can generate heat.

BACKGROUND OF THE INVENTION Microwave ovens that use microwaves to quickly heat food have recently become rapidly popular.

The heating principle of a microwave oven is to heat the food itself by the vibrational friction of the water contained in the food (the container itself does not have microwave absorption properties, so it does not generate heat directly), so it cannot be heated using normal cooking methods. Therefore, in order to brown foods, many efforts have been made to use materials that give heat-generating properties to containers. In this case, although it is effective to impart heat-generating properties to a container made of heat-resistant glass or the like, imparting heat-generating properties to a lightweight container has a wider range of applications.

Among the ideas for imparting heat generation properties to lightweight containers, for example, Japanese Patent Laid-Open No. 63-96075 discloses a microwave cooking container with a transparent protective layer/ITO layer/7-paper structure. It is shown. Jitsukai 1986-530
Publication No. 83 discloses a heating packaging material for microwave cooking having a seven-layer structure of paper (heat-resistant protective layer/(ink layer containing ferroelectric material and conductive material as main components)). Jitsukai Showa 64-5
No. 5818 discloses a heating packaging material for microwave cooking having a layered structure of heat-resistant protective layer/ferroelectric layer/conductive layer/paper. JP-A-63-12478 discloses a food container with a microwave heating element having a layer structure of polyethylene terephthalate film/conductive metal thin film layer/paper layer. In Special Publication No. 60-15548,
A food container for microwave cooking is shown having a layer configuration of protective layer/conductive element metal layer/base material such as paper.

JP-A No. 63-12479 discloses that a microwave heating element made of a polyester film/aluminum layer/paper layer is attached to a container body made of a heat-resistant material so that the peripheral edge of the microwave heating element is placed so that the paper layer is on the side of the container body. A food container with a fixed microwave heating element is shown.

Japanese Utility Model Application Publication No. 63-70329 discloses that a microwave heating sheet (for example, a polyester film/aluminum evaporated thin scrap/paper layer) mainly consisting of a microwave heating substance layer having a large number of pores is coated with a water-absorbing material. A laminated material is shown in which sheets of paper (for example, water-resistant, water-absorbing paper, sizeless paper) are partially bonded and laminated.

Problems to be Solved by the Invention According to the studies of the present inventors, microwave heating sheets typified by aluminum vapor-deposited layer/polyester film have the following problems:
The M-deposited layer shrinks during heating in a microwave oven, making it unusable. If aluminum foil is used instead of the aluminum vapor-deposited layer, sparks will occur during microwave irradiation.
It is a danger.

"For a heat generating sheet with a paper layer attached as a support to the polyester film side or aluminum vapor deposited layer side of two heat generating sheets, if a thin paper layer is used,
The paper layer can become scorched and in extreme cases even burn. On the other hand, if cardboard is used as the paper layer, the cardboard will absorb heat, making it impossible to brown the food.

Japanese Unexamined Patent Publication No. 63-96075, Utility Model Application No. 64-5308
Publication No. 3, Japanese Utility Model Publication No. 1983-55818, Japanese Patent Application Publication No. 1983
The heat-generating materials for microwave cooking described in Japanese Patent Publication No. 12478 and Japanese Patent Publication No. 60-15548 are equivalent to modified examples of the above-mentioned heat-generating sheets. The tolerance range for the thickness of the layers and paper layers is narrow, leaving room for improvement in terms of practicality.

In the food container of JP-A No. 63-12479,
A space is created between the microwave heating element and the container body by fixing the peripheral edge of the microwave heating element made of polyester film/aluminum layer/paper layer to the container body,
Although this method prevents the container itself from melting or burning, a slight change in the width or narrowness of the space can greatly change the state of the food being burnt, so strict control is required to manufacture the food container, which is disadvantageous in that it increases manufacturing costs. Another disadvantage is that there are restrictions on the size and shape of the food to be cooked.

The laminated material described in Japanese Utility Model Application Publication No. 63-70329 has a water-absorbing material that is easily affected by the surrounding humidity atmosphere.
There is a difficulty in cooking in that the microwave irradiation conditions for browning the food change due to the difference in moisture content. Also,
The provision of a water-absorbing material tends to hinder the rise in temperature, and is not necessarily preferable from the standpoint of heating efficiency.

In view of this background, it is an object of the present invention to provide a heat generating material for a microwave oven that does not have the above-mentioned problems.

Means for Solving the Problems The heat generating material for a microwave oven of the present invention is provided on the heat generating layer (1) side of a heat resistant sheet (2) provided with a heat generating layer (1) that generates heat by microwaves or on the heat resistant sheet (2). A thin paper layer (3) is laminated on either side, and a large number of holes (5) are provided on this thin paper layer (3), with an open area ratio of 3 to 80%.
It has a structure in which thick paper layers (0) are laminated, and the surface opposite to the side where the thick paper layer (4) is installed is the surface facing the food.

The present invention will be explained in detail below.

The heat generating layer (1) is made of a thin film of a conductive material formed by means such as vacuum deposition, sputtering, ion blasting, coating, etc. Here, the conductive substance is
Zero heat generation performance, including metals, metal oxides, carbon, etc.
When considering cost and other factors, the most practical one is a vacuum-deposited layer of aluminum with a thickness of about 30 to 1000 A.9The heat-generating layer (1) is a heat-resistant sheet (
2) Usually, it is formed directly or via an anchor coating layer.

As the heat-resistant sheet (2), a film that can withstand heating conditions during microwave cooking, such as a polyester film, a polyolefin film, a polyamide film,
Examples include polycarbonate film and polysulfone film. Among these, polyester film (
Biaxially oriented polyethylene terephthalate film) is the most practical.

The thin paper layer (3) has a basis weight of 15 to 200 g/rn.
', more preferably 20 to 150 g/rn' paper is suitably used. There is no particular limitation on the type of paper, including western paper,
Japanese paper, high-quality paper, kraft paper, parchment paper, etc. are used.

Non-woven fabrics are also included in the term paper referred to here.

A thick paper layer (0 refers to a thickness of 0.3 to 2 layers, especially 0
．． Cardboard of 4 to 1.5 mm, for example, paperboard such as white paperboard or yellow paperboard, is preferably used.

It is necessary to provide this thick paper layer (4) with a large number of holes (5). The shape of the hole (5) is arbitrary, including circular, square, groove, and star shape. The size of the hole (5) is 5~
1000mm'', especially 1O~400mm2, but it is not necessarily limited to this range.
The open area ratio due to holes (5) is 30 to 80%, especially 4 to 60%.
, above all, it is set to 5 to 50%, and if the pores (5) are not present or the porosity is insufficient, the browning will be insufficient.On the other hand, if the porosity is too large, the heat dissipation will be insufficient and the browning will be thin. The paper layer (3) may burn. The holes (5) may be distributed uniformly over the entire surface of the thick paper layer (4), or may be distributed non-uniformly.

They can also be arranged in five patterns.

The heat-generating material for microwave ovens of the present invention is composed of: (1) heat-generating layer (1)/heat-resistant sheet (2)/thin paper layer (3)/thick paper layer (0), or (2) heat-resistant sheet (2)/ Heat generating layer (1)/thin paper layer (
3)/Thick paper layer (The layer structure of 0 is the basic layer structure.

Between the heat-resistant sheet (2) and the thin paper layer (3) (above ■
) or thin paper layer (3) and heat-resistant sheet (2)
A heat-resistant adhesive layer (6) is often interposed between the two (in the case of (1) above).

A heat-resistant adhesive layer (7) is often interposed between the thin paper layer (3) and the thick paper layer (0).

In the case of (2) above, it is also possible to provide a heat-resistant protective layer (8) on the surface of the heat generating layer (1).

The above heat-resistant adhesive layers (8) and (7) include urethane adhesive, epoxy adhesive, polyester adhesive, acrylic adhesive, polyamide adhesive, silicone adhesive, and polyolefin adhesive. Thermosetting, thermoplastic, active energy ray-curable, hot-melt, and pressure-sensitive adhesives, including adhesives, phenolic resin adhesives, and urea resin adhesives, as long as they can withstand the heating conditions during microwave cooking. Various adhesives can be used regardless of the adhesive.

Examples of the protective layer (8) include a coating layer of a heat-resistant resin or a film similar to the heat-resistant sheet (2).

The heat generating material having the above structure is used in the form of a sheet, or as all or a part of a tray or a deep-bottomed container (including a lid material). It can also be used by being inserted or placed in another container.

Function In the heat generating material for microwave ovens of the present invention, the main roles of each layer are as follows.

The heat generating layer (1) generates heat by microwave irradiation, and has the function of heating the food and imparting browned color and aroma to the food.

The heat-resistant sheet (2) is a base material layer for forming the heat generating layer (1).

With only the layer structure of the heat generating layer (1) and the heat resistant sheet (2),
The thin paper layer (3) is a layer to prevent the heating layer (1) from shrinking due to microwave irradiation. Act as a support group.

Heat generating layer (1) l Heat resistant sheet (2) / Thin paper layer (3)
The layer structure of (2)/heat-generating layer (1)/thin paper layer (3) constitutes the main body of the heat-generating material, but even in this layer structure, there is no possibility of browning the food. If this is the case, the thin paper layer (3) itself may become burnt. A thick paper layer (4) with a large number of holes (5) is
It plays the role of an adjustment layer that adjusts heating and heat dissipation.

When using the heat generating material for microwave ovens of the present invention,
Thick paper layer (0) The side opposite to the installation side is the food side.

Examples Example 1 FIG. 1 is a sectional view showing an example of the heat generating material for a microwave oven of the present invention, and FIG. 2 is a bottom view thereof.

(1) is a heat-generating layer made of an aluminum vapor-deposited layer with a thickness of 80λ, and (2) is a heat-resistant sheet made of a polyester film (biaxially oriented polyethylene terephthalate film) with a thickness of 12 h. The film is directly deposited on the heat-resistant sheet (2) by vacuum evaporation.

(3) is a thin paper layer made of high-quality paper with a basis weight of 63 g/m'', and a heat-resistant adhesive layer (63 g/m'') made of urethane adhesive.
), the heat generating layer (1) is attached to the heat resistant sheet (2) side of the laminate of the heat resistant sheet (2).

Fever J! (1) Heat-resistant sheet (2)/thin paper layer (3)
) constitutes the main body of the heat generating material.

(4) is a thick paper layer made of cardboard with a recommended thickness of 1.2 m, and circular holes (5) with a diameter of 7 layers are provided on the entire surface.

The open area ratio was set at 18.6%. This thick paper layer (
4) is a heat-resistant adhesive layer (7) made of urethane adhesive.
), it is attached to the thin paper layer (3) side of the heat generating material main body.

With each of these layers, (1)/(2)/(8)/(3)
A heat generating material for a microwave oven having a layer structure of /(7)/(4) is formed.

Note that a heat-resistant protective layer (for example, a coating layer of a urethane resin liquid containing a curing agent or a polyester film) may be provided over the heat-generating layer (1) of the heat-generating material. Shown in Figure 1 by a dashed line (8)
is this protective layer.

When the heat-generating material having the above-described layered structure was placed on a tray, and pizza ingredients were placed thereon and cooked in a household microwave oven, the desired browned color and aroma could be imparted.

Note that when the thick paper layer (0) was omitted, the thin paper layer (3) was inevitably burnt when heated to the point where the pizza ingredients were browned.

When the thick paper layer (4) was laminated but the holes (5) were not provided, the heat dissipation was excessive and it was not possible to brown the pizza.

Example 2 FIG. 3 is a sectional view showing another example of the heat generating material for a microwave oven of the present invention, and FIG. 4 is a bottom view thereof.

(2) is a heat-resistant sheet made of a polyester film having a thickness of 12 degrees centigrade, and (1) is a heat-generating layer made of an aluminum vapor-deposited layer having a thickness of 80λ.

(3) is a thin paper layer made of parchment paper with a basis weight of 50 g/rry', and is made of heat-resistant adhesive layer (6) made of urethane adhesive. ) is attached to the heat generating layer (1) side of the laminate.

(4) is a thick paper layer made of cardboard with a thickness of 0.71 mm, and a square hole (5) of 8 mm square is provided on the entire surface.

The open area ratio was set at 25%. This thick paper layer (4)
is a heat-resistant adhesive layer (7) made of polyester adhesive.
), it is attached to the above-mentioned thin paper layer (3) side.

With each of these layers, (2)/(1)/(θ)/(3)/
A heat generating material for a microwave oven having a layer structure of (7)/(4) is formed.

When the heat-generating material having the above-mentioned layered structure was placed in a microwave oven and a rice cake was placed on top of it and heated, it was possible to impart the desired browned color and aroma.

Effects of the Invention The heat-generating material for microwave ovens of the present invention can reliably brown and has good mechanical strength. In addition, the thickness of the thick paper layer (4) and the porosity of the holes (5) provided in it can be freely selected and set, so heating and heat radiation can be adjusted as desired, making it suitable for a variety of foods. can do.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the heat generating material for a microwave oven of the present invention, and FIG. 2 is a bottom view thereof. FIG. 3 is a sectional view showing another example of the heat generating material for a microwave oven of the present invention, and FIG. 4 is a bottom view thereof.

Claims (1)

[Claims] 1. Thin paper on either the heat-generating layer (1) side or the heat-resistant sheet (2) side of the heat-resistant sheet (2) provided with the heat-generating layer (1) that generates heat by microwaves. A layer (3) is laminated, and on this thin paper layer (3), a thick paper layer (4) with a porosity of 3 to 80% with a large number of holes (5) is laminated. A heat generating material for a microwave oven, characterized in that the surface opposite to the side on which the thick paper layer (4) is installed is the surface facing the food. 2. The heat generating material according to claim 1, wherein the heat generating layer (1) is a metal vapor deposited layer. 3. The heat generating material according to claim 1, wherein the heat-resistant sheet (2) is a polyester film. 4. The heat generating material according to claim 1, wherein the thin paper layer (3) is paper with a basis weight of 15 to 200 g/m^2. 5. The heat generating material according to claim 1, wherein the thick paper layer (4) is a cardboard having a thickness of 0.3 to 2 mm. 6. The heat generating material according to claim 1, wherein the heat generating layer (1) or the heat resistant sheet (2) and the thin paper layer (3) are laminated with a heat resistant adhesive layer (6) interposed therebetween. 7. The heat generating material according to claim 1, wherein the thin paper layer (3) and the thick paper layer (4) are laminated with a heat-resistant adhesive layer (7) in between. 8. When a thin paper layer (3) is laminated on the heat-resistant sheet (2) side of a heat-resistant sheet (2) provided with a heat-generating layer (1), a heat-resistant The heat-generating material according to claim 1, further comprising a protective layer (8) having properties.