Abuse-tolerant metallic packaging materials for microwave cooking

• US 6,433,322 B2
• Filed: 01/19/2001
• Issued: 08/13/2002
• Est. Priority Date: 09/20/1999
• Status: Expired due to Term

• Current Assignee: Graphic Packaging International Incorporated
• Original Assignee: Graphic Packaging Corporation
• Inventors: Russell, Anthony, Zeng, Neilson, Lai, Laurence
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US09/765,851
• Publication Number:
  US 20010017297A1
• Time in Patent Office: 571 Days
• Field of Search: 219/725, 219/728, 219/730, 219/734, 219/745, 219/759, 219/729, 426/107, 426/234, 426/243, 99D/IG.14
• US Class Current: 219/728
• CPC Class Codes: B65D 2581/344 Geometry or shape factors influencing the microwave heating properties
• CPC Class Codes: B65D 2581/3466 Microwave reactive material applied by vacuum, sputter or vapor deposition
• CPC Class Codes: B65D 2581/3472 Aluminium or compounds thereof
• CPC Class Codes: B65D 2581/3487 Reflection, Absorption and Transmission [RAT] properties of the microwave reactive package
• 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

Abstract

An abuse-tolerant microwave food packaging material includes repeated sets of metallic foil or high optical density evaporated material segments disposed on a substrate. Each set of metallic segments is arranged to define a perimeter having a length equal to a predetermined fraction of the operating or effective wavelength of an operating microwave oven. The repeated sets of segments act both as a shield to microwave energy and as focusing elements for microwave energy when used in conjunction with food products, while remaining electrically safe in the absence of the food products.

Claims

1. An abuse-tolerant microwave packaging material comprising:

a repeated first set of metallic segments on a substrate, wherein each first set of metallic segments defines a perimeter of a multi-lobe shape with a center, the perimeter having a length approximately equal to a predetermined fraction of an effective wavelength of microwaves in an operating microwave oven, and wherein each metallic segment in each first set of metallic segments is spaced apart from adjacent metallic segments; and

a repeated second set of metallic segments on the substrate, wherein the metallic segments of each second set of metallic segments are arranged between and within the lobes of the multi-lobe shape defined by each first set of metallic segments, and wherein each metallic segment in each second set of metallic segments is spaced apart from adjacent segments of each first set of metallic segments.

2. An abuse-tolerant microwave packaging material as described in claim 1 wherein each metallic segment of each second set of metallic segments defines a triangular shape, and wherein a vertex of each triangular shape points toward the center of the multi-lobe shape defined by each first set of metallic segments.

3. The abuse-tolerant microwave packaging material of claim 1 wherein each metallic segment has an area less than 5 mm².

4. The abuse-tolerant microwave packaging material of claim 1 wherein the substrate includes a susceptor film.

5. The abuse-tolerant microwave packaging material of claim 1 wherein the substrate is microwave transparent.

6. The abuse-tolerant microwave packaging material of claim 5 wherein the substrate is a paper based material.

7. The abuse-tolerant microwave packaging material of claim 1 wherein the metallic segments are formed of metallic foil.

8. The abuse-tolerant microwave packaging material of claim 7 wherein the metallic foil comprises aluminum.

9. The abuse-tolerant microwave packaging material of claim 1 wherein the metallic segments are formed by the deposition of a high optical density evaporated material on the substrate.

10. The abuse-tolerant microwave packaging material of claim 9 wherein the high optical density evaporated material comprises aluminum.

11. The abuse-tolerant microwave packaging material of claim 1 wherein the predetermined fraction of the effective wavelength is an integer multiple of the effective wavelength, such that the length of the perimeter is resonant with the effective wavelength.

12. The abuse-tolerant microwave packaging material of claim 1 wherein the predetermined fraction of the effective wavelength is an integer multiple of one-half the effective wavelength, such that the length of the perimeter is quasi-resonant with the effective wavelength.