Abstract: A self-supporting layer of flexible etchable metal having a thickness of about 1 micron has a plurality of apertures formed therethrough and has a layer of etchant resistant material on each face of the metal layer in a pattern completely overlying the metal layer and the periphery of the plurality of apertures.

Abstract: Selective demetallization of an etchable metal layer supported on a polymeric material or other microwave transparent material, or a self-supporting etchable metal layer, particularly aluminum of thickness at least about 1 micron adhesively joined to a flexible polymeric material substrate, is described. A web of polymeric material bearing the etchable metal layer, or an unsupported etchable metal layer, has a pattern of etchant-resistant material first applied and then the web is immersed in and passed through a bath aqueous etchant, particularly hot aqueous sodium hydroxide solution, for a time at least sufficient completely remove the etchable metal from non-protected areas of the web. The demetallized web is washed and dried. Specific structure incorporating the selectively demetallized etchable metal layer also are described.

Abstract: A novel structure for use in the microwave cooking of foodstuffs for consumption is described. The structure includes an array of individual shapes of flexible electroconductive material normally opaque to microwave radiation supported on a microwave transparent substrate. Each of the individual discrete shapes of flexible electroconductive material has a thickness normally opaque to microwave radiation and is formed in an H-, I- or elongate strip shape. The individual discrete shapes are arranged on the substrate to define a space surrounding the periphery of each individual shape with the spaces defining a continuous aperture extending throughout the array and effective to generate thermal energy in the continuous aperture when the article is exposed to microwave energy and the foodstuff is in contact with or proximate to the aperture. The multiple layer article of manufacture is adapted to be formed into a packaging structure in which a foodstuff may be heated by microwave energy to an edible condition.

Abstract: Selective demetallization of an etchable metal layer supported on a polymeric material or other microwave transparent material, or a self-supporting etchable metal layer, particularly aluminum of thickness at least about 1 micron adhesively joined to a flexible polymeric material substrate, is described. A web of polymeric material bearing the etchable metal layer, or an unsupported etchable metal layer, has a pattern of etchant-resistant material first applied and then the web is immersed in and passed through a bath of aqueous etchant, particularly hot aqueous sodium hydroxide solution, for a time at least sufficient to completely remove the etchable metal from non-protected areas of the web. The demetallized web is washed and dried. Specific structure incorporating the selectively demetallized etchable metal layer also are described.

Abstract: A tray useful for the microwave cooking of prepared foodstuffs, particularly frozen foodstuffs, for consumption is structured to provide a more uniform heating of the foodstuff than has heretofore been possible. The tray comprises an outer layer formed of paperboard or molded plastic to which is laminated an inner polymeric film layer. A layer of microwave-reflective material, usually aluminum foil, is positioned between the outer and inner layers in the location of the peripheral wall of the tray and in a pattern in a portion of the bottom wall.

Abstract: A microwave heating element is described which permits a more uniform microwave cooking of a foodstuff to be achieved. The element comprises a layer of electroconductive material having circular openings formed therethrough and arranged in an array that generates thermal energy when exposed to microwave energy and adjacent a foodstuff. An antenna is provided in at least some of the openings to guide microwave energy to and through the openings. The electroconductive material layer usually is adhered to a paperboard layer with an overlying polymeric film layer.

Abstract: Selective demetallization of an etchable metal film supported on a polymeric material or other microwave transparent material, particularly an etchable metal film, particularly aluminum, of thickness at least about 1 micron adhesively joined to a flexible polymeric material substrate, is described. A web of metallized polymeric material has a pattern of etchant-resistant material first applied and then the web is immersed in and passed through a bath of aqueous etchant, particularly hot aqueous sodium hydroxide solution, for a time at least sufficient to completely remove the etchable metal from non-protected areas of the web. The demetallized web is washed and dried.

Abstract: The structure includes a layer of flexible electroconductive material normally opaque to microwave radiation and having a plurality of apertures therethrough dimensioned to permit microwave energy to pass through to the interior of the foodstuff and to produce thermal energy at the surface of the foodstuff. Both a microwave shielding effect and a combined microwave energy heating and thermal energy heating effect are obtained, enabling close control of the manner and extent of microwave cooking of the foodstuff to be obtained. The plurality of apertures comprises a first plurality of elongate discrete closed-end apertures and a second plurality of continuous apertures, each of which encloses a discrete rectangular island of the electroconductive material.

Abstract: A laminate structure useful for incorporating into a package structure for the microwave cooking of foodstuffs for consumption comprises an outer layer polymeric material, an outer layer of microwave transparent material, a grid layer having an electroconductive surface surrounding transmissive apertures located between the outer layers, and a thin layer of electroconductive material of sufficient thickness so that a portion of incident microwave energy is converted to thermal energy also located between the outer layers. The structure is useful in providing controlled surface heating and microwave transmittance to achieve a more uniformly heated product employing less structural material than the prior art.

Abstract: A laminate structure useful for incorporating into a package structure for the microwave cooking of foodstuffs for consumption comprises an outer layer polymeric material, an outer layer of microwave transparent material, a grid layer having an electroconductive surface surrounding transmissive apertures located between the outer layers, and a thin layer of electroconductive material of sufficient thickness so that a portion of incident microwave energy is converted to thermal energy also located between the outer layers.

Abstract: A lid for a T.V. dinner tray is constructed to provide a more uniform heating of frozen prepared foodstuffs by controlling the flow of microwave radiation to the foodstuff, to effect a decreased flow of microwave energy to the foodstuffs in certain zones of the tray and an enhanced flow of microwave energy to the foodstuffs in the remainder of the tray. The lid comprises a polymeric material layer and a patterned layer of continuous microwave-reflective material adhered thereto.

Abstract: A novel structure for use in the microwave cooking of foodstuffs for consumption is described. The structure includes a layer of flexible electroconductive material normally opaque to microwave radiation and having a plurality of elongate apertures therethrough dimensioned to permit microwave energy to pass through to the interior of the foodstuff and to produce thermal energy at the surface of the foodstuff. Both a microwave shielding effect and a combined microwave energy heating and thermal energy heating effect are obtained, enabling close control of the manner and extent of microwave cooking of the foodstuff to be obtained. The layer of flexible electroconductive material is supported by and adhered to a substrate layer of microwave energy transparent material in a multiple layer article of manufacture adapted to be formed into a packaging structure in which a foodstuff may be heated by microwave energy to an edible condition.

Abstract: A method is described for achieving selective generation of thermal energy from a thin metal film upon exposure to microwave energy. A deactivating material is first applied to a substrate from the thin metal film in a pattern corresponding to the region from which heat is not to be generated. The metal then is applied over the substrate and the pattern in a thickness which normally generates thermal energy upon exposure to microwave energy. Such thermal energy is produced only from those regions where the metal is adhered directly to the substrate.