JPH0438166Y2 - - Google Patents

Description

[Detailed explanation of the idea]

Purpose of invention

[Industrial application field]

The present invention relates to a food container for cooking in a microwave oven.
To provide a container capable of efficiently heating food and browning the surface of the food.

[Conventional technology]

When you heat food in a microwave, it usually does not brown. However, gratin
When cooking foods such as pizza and dumplings, it is desirable to brown the surface to give them a crisp texture. To achieve this, a coating of electrically conductive material may be provided so that a specific surface in contact with the food container is heated strongly. However, the methods known so far cannot be applied to containers such as paper cartons because the temperature of the coating becomes too high. The inventor of the present invention considered limiting the amount of heat generated so that the portion of the conductive material coating does not reach an excessively high temperature. As one measure, we proposed forming a layered film by printing using inks containing far-infrared emitting ceramics, reduced potassium titanate, and conductive materials (Japanese Patent Application No. 250346/1983). . Another method is to print using an ink containing a mixture of reduced potassium titanate and non-metallic conductive substance powder, which we also proposed (Japanese Patent Application No. 1983-
No. 250347). This means that even containers with poor heat resistance, such as paper cartons, will not be damaged. If the heat-generating coating made of conductive material is transparent,
It is convenient to be able to print explanatory text or designs such as cooking methods under the coating. Furthermore, it is convenient to form a bag by providing this heat-generating coating on a transparent packaging material, since the degree of scorching can be observed from the outside.
Therefore, there is a need to develop a container having a heat-generating coating of a transparent conductive material.

[Problem that the invention attempts to solve]

The purpose of the present invention is to meet the above demands, to be able to properly brown food without causing damage even if the container has poor heat resistance, and to have a transparent heat-generating coating with printing underneath. It is possible,
Another object of the present invention is to provide a food container for cooking in a microwave oven in which the degree of burntness can be observed from the outside if desired. Structure of the idea

[Means to solve the problem]

The food container for microwave cooking of the present invention is a container for cooking food in a microwave oven.
As shown in FIG. 1, a thin film layer 3 of indium tin oxide having a transparent protective layer 2 is partially adhered to a part of the container body or lid 1 using an adhesive 4. . There can be various forms of partial adhesion, but typically, as shown in Figure 2, the non-adhesive surface is a square with side a in the range of 2 to 5 mm, and the width b of the adhesive surface is 1 mm. It is made into a grid pattern. To partially apply the adhesive, a method such as gravure coating using a grid-like gravure plate may be used. In addition to lattice shapes, striped shapes, polka dot shapes, diamond shapes,
Of course, it can be made into any shape such as a hexagon. Adhesives include thermosetting resins such as polyisocyanates, epoxy resins, phenolic resins, and urea resins, or thermosetting resins such as ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, polyamides, acrylic resins, and methacrylic acid esters. Use plastic resin. For both the container body and the lid, paper, a composite material of paper and plastic film, or a laminated material of plastic film can be used. The thin film layer of indium tin oxide may be formed on the transparent protective layer by any method such as vacuum evaporation, sputtering, or ion plating.
Prior to vapor deposition, printing may be performed on the transparent protective layer by any means such as gravure printing, or
After deposition, printing may be performed on the thin film layer. As the transparent protective layer, a film of relatively heat-stable plastic, such as polyester, polyethylene, nylon, cellophane, polysulfone, etc. is used.

[Effect]

The thin film layer of indium tin oxide absorbs microwaves and generates heat, and also generates heat due to eddy currents generated inside. Since this heat flows through the adhesive layer to the container body or lid, if the area of the adhesive is large, the temperature of the thin film layer will not rise to an effective level. On the other hand, if the thin film layer is insufficiently fixed to the container body or lid by adhesive, the thin film layer curls and wrinkles occur due to heat generation. By appropriately adjusting the adhesion area, it became possible to control the amount of heat dissipated and to reach a suitable high temperature without curling the thin film layer. The effects are shown below based on experimental data. A thin film layer of indium tin oxide having a surface resistance of 5×10 ⁻² Ω/cm ² was provided on a polyester film having a thickness of 12 μm by vapor deposition. A polyethylene layer with a thickness of 20 μm was provided on pure white roll paper with a basis weight of 65 g/m ² by extrusion coating. On the indium tin oxide thin film layer of the above film, apply a urethane adhesive consisting of the base agent "Takerak A-515" (Takeda Pharmaceutical Co., Ltd.) and the curing agent "Takenate A-50" (Takeda Pharmaceutical Co., Ltd.) as shown below. .1～
8 various grid-like and solid gravure plates (plate depth
70μ) to form a laminate by gluing the polyethylene layer of the sheet. This laminated material was cut into 10cm x 10cm pieces and placed in a 500W household microwave oven, and the rise in surface temperature of the indium oxide thin film layer was measured using a fluorescent fiber thermometer (ASEA). The results are shown below.

【table】

[Table] It can be seen from the above results that if the area ratio of the adhesive part is too small, the fixation of the thin film is insufficient, and if it is too large, it is difficult to increase the temperature.

【Example】

A pizza carton was prepared by punching out the laminated material No. 4 above. When pizza ingredients were placed in this carton and heated for 3 minutes in a household microwave oven, the surface temperature of the thin layer of indium tin oxide reached 150°C, allowing the pizza to be cooked with just the right amount of browning. Effects of the invention The food container of the invention can give food an appropriate browning even when applied to containers made of paper or plastic molded products with low heat resistance. The thin layer of indium tin oxide is transparent, so it is possible to print cooking instructions or other graphics underneath. Furthermore, if a bag is formed by providing this layer on a transparent packaging material such as nylon, the degree of charring can be observed from the outside.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of the material of the food container for microwave cooking of the present invention. FIG. 2 is a plan view showing a partial adhesive pattern corresponding to FIG. 1; 1... Container body or lid, 2... Transparent protective layer, 3... Thin film layer of indium tin oxide, 4...
Adhesive, a...one side, b...width.

Claims (1)

[Claims for Utility Model Registration] (1) In a container for cooking food in a microwave oven, a thin film layer 3 of indium tin oxide having a transparent protective layer 2 is provided on a part of the container body or lid 1. A food container for cooking in a microwave oven, characterized in that it is partially bonded using adhesive 4. (2) When partial adhesion occurs, the non-adhesive surface has 2 to 5 a sides.
The food container for microwave cooking according to claim 1, which is a grid-like square with an adhesive surface width b of 1 mm. (3) A thin film layer of indium tin oxide increases the surface resistance.
10 ^-1 - 10 ³ Ω/cm ² The food container for microwave cooking according to claim 1, which is a utility model.