Microwave oven package

• US 5,213,902 A
• Filed: 02/19/1991
• Issued: 05/25/1993
• Est. Priority Date: 02/19/1991
• Status: Expired due to Term

• Current Assignee: Graphic Packaging International Incorporated
• Original Assignee: Beckett Industries, Inc.
• Inventors: Beckett, D. Gregory
• Primary Examiner(s): Lewis, Michael
• Assistant Examiner(s): LUND, VALERIE A
• Application Number:
  US07/656,736
• Time in Patent Office: 826 Days
• Field of Search: 426/107, 426/243, 428/596, 428/597
• US Class Current: 428/597
• CPC Class Codes: B32B 15/043 of metal B32B15/01 takes precedence
• CPC Class Codes: B32B 15/08 of synthetic resin
• CPC Class Codes: B32B 15/12 of paper or cardboard
• CPC Class Codes: B32B 15/20 comprising aluminium or copper B32B15/016 and B32B15/017 take precedence
• CPC Class Codes: B32B 2311/24 Aluminium
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 3/10 characterised by a discontinuous layer, i.e. formed of separate pieces of material
• CPC Class Codes: B32B 3/266 characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: B65D 2581/3406 Pizza or bread
• CPC Class Codes: B65D 2581/344 Geometry or shape factors influencing the microwave heating properties
• CPC Class Codes: B65D 2581/3452 Packages having a plurality of microwave reactive layers, i.e. multiple or overlapping microwave reactive layers
• CPC Class Codes: B65D 2581/3454 Microwave reactive layer having a specified optical density
• CPC Class Codes: B65D 2581/3466 Microwave reactive material applied by vacuum, sputter or vapor deposition
• CPC Class Codes: B65D 2581/3467 Microwave reactive layer shaped by delamination, demetallizing or embossing
• CPC Class Codes: B65D 2581/3472 Aluminium or compounds thereof
• CPC Class Codes: B65D 2581/3478 Stainless steel
• CPC Class Codes: B65D 2581/3489 Microwave reflector, i.e. microwave shield B65D2581/3487 takes precedence
• CPC Class Codes: B65D 2581/3494 Microwave susceptor B65D2581/3487 takes precedence
• CPC Class Codes: B65D 81/3446 specially adapted to be heated by microwaves
• CPC Class Codes: Y10T 428/12361 : having aperture or cut
• CPC Class Codes: Y10T 428/12368 : Struck-out portion type

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

Claims

1. A laminate structure, useful for forming a food package for a microwave oven, which comprises:

a polymeric film layer,

a layer of material adhered to the polymeric film layer and defining a grid, the grid having an electroconductive surface surrounding transmissive apertures,

a thin layer of electroconductive material of sufficient thickness that a portion of incident microwave energy is converted to thermal energy, said thin layer of electroconductive material overlaying said grid layer and being in abutting contact with and directly adhered to said electroconductive surface and to said polymeric film layer in said apertures, and

a substrate layer of microwave transparent material adhered to the electroconductive material layer.

2. The structure of claim 1, wherein said microwave transparent material is paper or paperboard.

3. The structure of claim 1, wherein said microwave transparent material is polymeric material.

4. The structure of claim 1, wherein said layer of material defining the grid is formed of aluminum foil.

5. The structure of claim 4 wherein said aluminum foil has a thickness of about 1 to about 15 microns.

6. The structure of claim 5 wherein said thin layer of electroconductive material is formed of aluminum having a thickness corresponding to an optical density of about 0.1 to about 0.4.

7. The structure of claim 5 wherein said aluminum foil has a thickness of about 3 to about 10 microns.

8. The structure of claim 4 wherein said thin layer of electroconductive material is formed of aluminum.

9. The structure of claim 8 wherein said aluminum layer has a thickness corresponding to an optical density of about 0.08 to about 1.0.

10. The structure of claim 4 wherein said transmissive apertures each has a square outline.

11. The structure of claim 10 wherein said apertures have a width of about 0.125 to about 2 inches.

12. The structure of claim 11 wherein said width is about 0.375 to about 0.875 inch.

13. A laminate structure, useful for forming a food package for a microwave oven, which comprises:

a polymeric film layer,

a layer of material adhered to the polymeric film layer and defining a grid, the grid having an electroconductive surface surrounding transmissive apertures,

said electroconductive surface of said grid having a layer of etchant-resistant material thereon,

a thin layer of electroconductive material of sufficient thickness that a portion of incident microwave energy is converted to thermal energy, said thin layer of electroconductive material overlying said grid layer and being adhered to said etchant-resistant material on said electroconductive surface and to said polymeric film in said apertures, and

a substrate layer of microwave transparent material adhered to the electroconductive material layer.