Browse Prior Art Database

Variable Resistivity Films for Use in Microwave Ovens

IP.com Disclosure Number: IPCOM000120963D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Braslau, N: AUTHOR [+4]

Abstract

Disclosed is a packaging material which attains a particular temperature in a microwave oven, and then stops absorbing the microwave energy. Microwave ovens do not brown baked goods. Resistive film packages which absorb the microwave energy and are heated to a temperature where they can radiate infrared energy to the food and heat the surrounding air depend on the non-uniform distribution of microwave energy in the oven and do not have uniform temperature.

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Variable Resistivity Films for Use in Microwave Ovens

      Disclosed is a packaging material which attains a particular
temperature in a microwave oven, and then stops absorbing the
microwave energy.  Microwave ovens do not brown baked goods.
Resistive film packages which absorb the microwave energy and are
heated to a temperature where they can radiate infrared energy to the
food and heat the surrounding air depend on the non-uniform
distribution of microwave energy in the oven and do not have uniform
temperature.

      This article discloses that a film packaging material with a
conversion of microwave energy to heat which varies as the
temperature in a way given by the figure 1 will assume the
temperature at the step (i.e. good baking temperature) uniformly, as
the energy absorbed by the film will drop as soon as the film reaches
baking temperature.

      Ferrite materials will absorb microwave radiation until the
material reaches its Curie temperature, and then the absorption will
crop and the temperature will remain constant in the microwave oven.
These materials can be made with a wide variety of Curie temperatures
and resistivities depending on the material composition.

      The material can also be one of a class of materials which
suffers a phase at the correct temperature.  For example, the
martensitic transition in a nickel titanium alloy would have a
resistivity vs temp curve as sketched in figure 2.  The precise
temperature at which the...