JP2906284B2 - Microwave absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microwave absorber that absorbs microwaves and generates heat in a microwave oven.

2. Description of the Related Art Microwave cooking in a microwave oven can heat food efficiently in a short time, but it is difficult to brown the food due to its characteristics.

For this reason, it is necessary to provide a brown plate that absorbs microwaves and generates heat. As shown in FIG. 2, the browning plate generally has a non-adhesive surface-treated metal plate 11, a microwave absorber 12 that absorbs microwaves and generates heat, and a support 15 from the side in contact with the food 10. And was composed of As the microwave absorber 12, one in which a ferrite 13 is dispersed and held in a silicon rubber 14 or the like is partially commercialized (using magnetic loss).

Problems to be Solved by the Invention However, the conventional browning plate using the microwave absorber has a problem that a long remaining heating time is required before heating the food or a low heat generation temperature. On the principle of the heat generation mode, for example, the use of dielectric loss of a dielectric material such as barium titanate can be considered. Was not practical.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a practical microwave absorber having a very high microwave absorbing ability even with a dielectric material.

Means for Solving the Problems To achieve the above object, the microwave absorber of the present invention is a convergent material having a high dielectric constant material having a relative dielectric constant of 50 or more and a dielectric tangent of 0.01 or less as a dispersoid. , And a damping material having a high dielectric loss tangent material having a relative dielectric constant of 50 or less and a dielectric loss tangent of 0.01 or more as a dispersoid.

The microwave absorber according to the present invention having the above-described structure has a structure in which the convergent material having a high dielectric constant material as a dispersoid concentrates microwaves, and the microwave concentrator has a microscopic structure in a direction perpendicular to the attenuating material having a high dielectric tangent material as a dispersoid. Irradiate waves. Then, the microwave is absorbed by the attenuating material, and the microwave that cannot be completely absorbed proceeds in the direction of the converging material but is reflected on the surface of the converging material. In this way, multiple reflections occur until the microwaves are absorbed in the attenuating material. Therefore, it is considered that the attenuating material has a function of efficiently absorbing the microwave.

Embodiment An embodiment of the present invention will be described below with reference to FIG.

The convergence material 1 having a high dielectric constant material having a relative dielectric constant of 50 or more and a dielectric loss tangent of 0.01 or less as a dispersoid is a strontium titanate powder (relative dielectric constant 25
5, dielectric loss tangent 0.001), for example, 40
The mixture kneaded by wt% was heated and formed into a sheet-like molded product having a thickness of 2 mm. The attenuating material 3 containing a high dielectric loss tangent material having a relative dielectric constant of 50 or less and a dielectric loss tangent of 0.01 or more as a dispersoid is used as a high dielectric loss tangent material 4 such as a silicon carbide-titanium carbide solid solution 1 mm chop (trade name “Tyranno fiber”). , Ube Industries, Ltd.
The mixture was kneaded with, for example, 40% by weight of silicone resin in a dielectric material having a relative dielectric constant of 10 and a dielectric loss tangent of 1). Then, a sheet-shaped attenuation material 3 and a convergence material 1 were arranged in contact with each other in this order on a metal plate 5 for an experiment. 15 is a support. For evaluation, this was placed in a microwave oven and microwaves (μ waves) were
The irradiation was carried out at a temperature immediately after irradiation for one minute. As a comparative example A, a damping material 3 of a sheet-like molded product having a thickness of 4 mm, and as a comparative example B, a composite mixture of the high dielectric constant material 2 and the high dielectric loss tangent material 4 (each concentration is 50% of the convergent material and the damping material). %) Was kneaded with a silicone resin, and a 4 mm-thick sheet-like molded product obtained by heating and molding was subjected to the experiment.

In addition, as the high dielectric constant material 2, besides strontium titanate, potassium titanate, titania, Sr—Sn oxide, Ba—Sm—Ti oxide, and the like are given. As the high dielectric loss tangent material 4, other than the examples, alkali titanate (metal; L
i, Na, K), synthetic resin and conductive material (carbon black,
(Metal powder, conductive ceramic).

 The results are shown in the following table.

As is clear from these results, according to the embodiment of the present invention, there is a remarkable heat generation characteristic (microwave absorption ability). It can be seen that this characteristic is caused by the state of lamination of the convergence material 1 and the attenuation material 3.

Physical properties related to the microwave absorption capacity of dielectric materials include:
There are a relative dielectric constant ε and a dielectric loss tangent tan δ, and the product of the two and tan δ are called a loss coefficient, which is an index for absorbing microwaves to generate heat. Naturally, this requires a material having a large relative dielectric constant and a large dielectric loss tangent, but such a material is the only material other than water (the food is heated by microwaves). That is, there is only a capacitor material having a very high relative dielectric constant and a small dielectric loss tangent, such as a capacitor material, or a material having a small relative dielectric constant and a large dielectric loss tangent, such as a recent ceramic dielectric material.
Therefore, a combination of such materials, that is, a combination of a material having a high relative dielectric constant and a material having a high dielectric loss tangent can be considered, but as a result of intensive studies, the physical properties of a composite of such materials are considered to be intermediate between the two, or In many cases, the value will be lower. In particular, it was found that the dielectric loss tangent was greatly reduced, and there was a problem in practical use.

In general, in existing materials, the dielectric tangent has a larger difference between materials than the relative dielectric constant (the dielectric tangent ranges from about two digits to four orders of magnitude). Although a material having a large dielectric loss tangent is used even if it is small, it does not absorb microwaves unless it has an appropriate thickness (generally, it is said that a thickness that is half the wavelength of microwaves is necessary).

Based on this background, the present invention has been achieved, but there are still many unknown reasons for the effects. The convergent material 1 made of the high dielectric constant material 2 concentrates the microwave and irradiates the microwave to the attenuating material 3 made of the high dielectric loss tangent material 4 from a perpendicular direction, and converges until the attenuating material 3 absorbs the microwave. Multiple reflection occurs between the material 1 and the metal plate 5. Therefore, it is considered that the attenuation member 3 efficiently absorbs the microwave.

In one embodiment of the present invention, the high dielectric constant material 2
And a high dielectric loss tangent material 4 dispersed in a silicone resin,
Although only this is shown by heat molding, it goes without saying that a structural reinforcing material (for example, paper, film, nonwoven fabric, woven fabric, synthetic resin sheet, ceramic molding, foam) may be covered and impregnated. Further, the filling amount (wt%) of each material may be arbitrarily adjusted between 10 and 80 depending on the heat generation temperature and the use form.

As described above, according to the microwave absorber of the embodiment of the present invention, the thickness can be reduced and the heat generation temperature can be increased by the combination of the existing high dielectric material and low dielectric material.

Effects of the Invention As apparent from the above description, according to the microwave absorber of the present invention, a convergent material having a high dielectric constant material having a relative dielectric constant of 50 or more and a dielectric tangent of 0.01 or less as a dispersoid, By laminating an attenuating material with a high dielectric loss tangent material having a non-dielectric constant of less than 0.01 and a dielectric loss tangent of 0.01 or more, even if it is a dielectric material, and a combination of existing materials, the microwave absorption capacity is high. A practical microwave absorber can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a browning plate to which one embodiment of the microwave absorber of the present invention is applied, and FIG. 2 is a sectional view of a browning plate to which a conventional microwave absorber is applied. 1 ... converging material, 2 ... high dielectric constant material, 3 ... attenuating material, 4
…… High dielectric loss tangent material.

Claims (2)

(57) [Claims] 1. A convergent material comprising a high dielectric constant material having a relative dielectric constant of 50 or more and a dielectric tangent of 0.01 or less as a dispersoid, and a high dielectric tangent material having a relative dielectric constant of 50 or less and a dielectric tangent of 0.01 or more. A microwave absorber obtained by laminating an attenuating material having a dispersoid. 2. The high dielectric constant material is strontium titanate;
The microwave absorber according to claim 1, wherein the high dielectric loss tangent material is a silicon carbide-titanium carbide solid solution.