Abuse-tolerant metallic packaging materials for microwave cooking

• US 6,552,315 B2
• Filed: 03/20/2002
• Issued: 04/22/2003
• Est. Priority Date: 09/20/1999
• Status: Expired due to Term

• Current Assignee: Graphic Packaging International Incorporated
• Original Assignee: Graphic Packaging Corporation
• Inventors: Zeng, Neilson, Lai, Laurence M. C., Russell, Anthony
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US10/103,052
• Publication Number:
  US 20020144996A1
• Time in Patent Office: 398 Days
• Field of Search: 219/725, 219/728, 219/729, 219/730, 219/735, 219/734, 219/759, 426/107, 426/109, 426/234, 426/243, 426/241, 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 microwave energy reflective material segments disposed on a substrate. Each set of reflective segments is arranged to define a perimeter having a length equal to a predetermined fraction of the 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 plurality of a first set of segments formed of a microwave energy reflective material, each first set of segments supported on a substrate in a repeated pattern, wherein each first set of segments defines a first perimeter having a length approximately equal to a first predetermined fraction of an effective wavelength of microwaves in an operating microwave oven, wherein each segment in each first set of segments is spaced apart from adjacent segments, and wherein the first perimeter comprises at least one shape selected from the group of shapes comprising:

a circle, an oval, a curvilinear shape, a symmetrical curvilinear shape, a triangle, a square, a rectangle, a polygon, a right polygon, and an equilateral polygon.

2. An abuse-tolerant microwave packaging material as described in claim 1, further comprising a plurality of a second set of segments formed of a microwave energy reflective material, each second set of segments supported on the substrate in a repeated pattern, wherein each second set of segments defines a second perimeter enclosing at least one first set of segments, the second perimeter having a length approximately equal to a second predetermined fraction of the effective wavelength of microwaves in the operating microwave oven, wherein each segment of each second set of segments is spaced apart from adjacent segments, and wherein the second perimeter comprises at least one shape selected from the group of shapes comprising:

a circle, an oval, a curvilinear shape, a symmetrical curvilinear shape, a triangle, a square, a rectangle, a polygon, a right polygon, and an equilateral polygon.

3. An abuse-tolerant microwave packaging material as described in claim 2, further comprising a plurality of a third set of segments formed of a microwave energy reflective material, each third set of segments supported on the substrate in a repeated pattern, wherein each third set of segments defines a third perimeter enclosing at least one second set of segments, the third perimeter having a length approximately equal to a third predetermined fraction of the effective wavelength of microwaves in the operating microwave oven, wherein each segment of each third set of segments is spaced apart from adjacent segments, and wherein the third perimeter comprises at least one shape selected from the group of shapes comprising:

a circle, an oval, a curvilinear shape, a symmetrical curvilinear shape, a triangle, a square, a rectangle, a polygon, a right polygon, and an equilateral polygon.

4. The abuse-tolerant microwave packaging material of claim 2, wherein each second set of segments is nested with at least one adjacent second set of segments.

5. The abuse-tolerant microwave packaging material of claim 3, wherein each third set of segments is nested with at least one adjacent third set of segments.

6. The abuse-tolerant microwave packaging material of claim 1, 2, or 3, wherein each segment has an area less than 5 mm².

7. The abuse-tolerant microwave packaging material of claim 1, 2, or 3, wherein the substrate includes a susceptor film.

8. The abuse-tolerant microwave packaging material of claim 1, 2, or 3, wherein the substrate is microwave transparent.

9. The abuse-tolerant microwave packaging material of claim 8, wherein the substrate is a paper based material.

10. The abuse-tolerant microwave packaging material of claims 1, 2, or 3, wherein the microwave energy reflective material comprises a metal material comprised of at least one of the following:

metal foil and a deposition of a high optical density evaporated material on the substrate.

11. The abuse-tolerant microwave packaging material of claim 10, wherein the metal comprises aluminum.

12. The abuse-tolerant microwave packaging material of claims 1, 2, or 3 wherein the equilateral polygon is a hexagon.

13. The abuse-tolerant microwave packaging material of claims 1, 2, or 3 wherein the first predetermined fraction of the effective wavelength is an integer multiple of the effective wavelength, such that the length of the first perimeter is resonant with the effective wavelength.

14. The abuse-tolerant microwave packaging material of claims 1, 2, or 3 wherein the first predetermined fraction of the effective wavelength is an integer multiple of one-half the effective wavelength, such that the length of the first perimeter is quasi-resonant with the effective wavelength.

15. The abuse-tolerant microwave packaging material of claims 2 or 3 wherein the second predetermined fraction of the effective wavelength is an integer multiple of the effective wavelength, such that the length of the second perimeter is resonant with the effective wavelength.

16. The abuse-tolerant microwave packaging material of claims 2 or 3 wherein the second predetermined fraction of the effective wavelength is an integer multiple of one-half the effective wavelength, such that the length of the second perimeter is quasi-resonant with the effective wavelength.