Metalized microwave interactive laminate and process for mechanically deactivating a selected area of microwave interactive laminate

A present invention provides a microwave interactive laminate and a process for brush deactivation of such a laminate. A film, coated with a microwave interactive layer is provided. A desired portion of the microwave interactive layer is coated with a mask layer and the entire assembly is then exposed to abrasion means. The coated and un-coated areas are subjected to the application of mechanical forces to form discontinuities in the microwave interactive layer. That portion of the microwave interactive layer that was coated remains interactive with microwave radiation and is a heating area while the un-coated area is deactivated.

BACKGROUND 
1. Field of the Invention 
The present invention relates to a process for brush deactivation of the 
microwave interactive layer of a microwave interactive laminate to reduce 
or eliminate the capacity of the microwave interactive layer to generate 
heat in response to microwave energy. The present invention also relates 
to brush deactivated microwave interactive films and brush deactivated 
microwave interactive laminates which include a brush deactivated 
microwave interactive layer. 
2. Background of the Invention 
A characteristic of microwave cooking is that the exterior of foods cooked 
in a microwave oven, such as breads, do not have a brown or crisp texture 
desired by consumers. An objective of those concerned with microwave 
cooking has therefore been to provide ways of browning or crisping the 
exterior of foods cooked in a microwave oven. 
One technique developed to brown or crisp the exterior of foods during 
microwave cooking has been the incorporation of a microwave interactive 
laminate into packages that contain foods. In response to microwave 
energy, a microwave interactive layer of the laminate generates heat which 
browns or crisps the surface of food. 
Typically, a microwave interactive laminate includes a thin film which has 
a microwave interactive layer of lossy material deposited onto one side of 
the film. The layer of material generates heat in response to microwave 
energy. Film with a microwave interactive layer deposited on one side is a 
microwave interactive film. 
To form a microwave interactive laminate, the microwave interactive film is 
commonly bonded to a substrate with the substrate serving as a support 
structure. The microwave interactive layer is disposed between the film 
and the substrate. The laminate may subsequently be cut into a shape that 
approximates the shape of a particular food product or the size of a 
particular package. 
Commercially, a microwave interactive laminate can most conveniently be cut 
into rectangles for use in packages. When the food product which is being 
heated is circular, triangular or some other shape which does not conform 
to a rectangle, heat-generating areas of the microwave interactive 
laminate will not be covered by the food product. The exposed areas of 
conventional microwave interactive laminate can produce excessive heat 
which can scorch the food or the container. Also, the efficiency of the 
microwave interactive laminate is diminished when heat-generating areas 
are not covered by the food product since the exposed heat-generating 
areas absorb microwave radiation that would otherwise brown or crisp the 
food. 
In addition, the heat-generating areas of a microwave interactive laminate 
can overlap each other when a package is assembled. A consequence of such 
an overlap is that excessive heat, which can scorch the package, is 
generated at the areas of overlap. 
Finally, in packages where the microwave interactive laminate covers only a 
portion of a package or container, adhesive used to bond the microwave 
interactive laminate to the package or container can extend outside the 
area covered by the microwave interactive laminate. Adhesive outside the 
area of a package surface covered by the microwave interactive laminate 
can cause packages to stick together during production and handling. 
U.S. Pat. Nos. 4,398,994 and 4,552,614 both to Beckett disclose continuous 
methods for forming decorative patterns of a metallized film and the use 
of such films in packaging. Both methods involve removing selected 
portions of a metal layer which has been deposited on a strip of polymer 
film. The '614 patent provides that the metallized surface is overprinted 
with an etchant-resistant material. The thus overprinted film is exposed 
to jets of aqueous etchant solution which is then washed. A scraper is 
provided to assist in the removal of etched metal and the spent etchant 
solution from the surface of the film. 
While the foregoing apparatuses and methods of the prior art do succeed in 
producing a de-metalized film, they employ caustic chemicals in a complex 
washing and drying process. In addition, the methods and apparatus 
disclosed in the prior art apply to the producing of decorative metallized 
films, not to the production of microwave interactive laminates. 
SUMMARY OF THE INVENTION 
The present invention overcomes the problems and disadvantages of the prior 
art by providing a microwave interactive laminate wherein the microwave 
interactive layer in such a laminate has an area of any desired shape. 
Excessive heat generation caused by exposed or overlapping microwave 
interactive laminates can thus be avoided by the present invention. The 
microwave interactive laminate can be easily and inexpensively produced. 
To achieve the objects and in accordance with the purpose of the invention, 
as embodied and broadly described herein, the microwave interactive film 
of this invention comprises: a film layer; and a microwave interactive 
layer deposited onto one side of the film layer having a heating area and 
a deactivated area, the deactivated area having discontinuities produced 
by application of mechanical forces whereby the capability of the 
deactivated area to generate heat in response to microwave energy has been 
reduced. 
Further, to achieve the objects and in accordance with the purpose of the 
invention, as embodied and broadly described herein, a microwave 
interactive laminate of the present invention comprises: a microwave 
interactive film having a film layer and a microwave interactive layer 
deposited onto one side of the film layer, the microwave interactive layer 
having a heating area and a deactivated area, the deactivated area having 
discontinuities produced by abrasion, whereby the capability of the 
deactivated area to generate heat in response to microwave energy has been 
reduced; and a substrate layer bonded to the microwave interactive film to 
form a microwave interactive laminate, wherein the microwave interactive 
layer is between the film layer and the substrate layer. 
A further embodiment of the present invention is a process for making a 
microwave interactive laminate having a substrate layer and a microwave 
interactive film, comprising: providing a microwave interactive film 
having a film layer and a microwave interactive layer deposited onto one 
side of the film layer; coating a selected area of said microwave 
interactive layer with a coating layer to form a coated area and an 
uncoated area; and abrading said coated area and the uncoated area, the 
uncoated area of the microwave interactive layer being sufficiently 
abraded to form discontinuities in the microwave interactive layer and 
convert the uncoated area into a deactivated area with reduced capability 
of generating heat in response to microwave energy and the coated area of 
the microwave interactive layer remaining microwave interactive.

DETAILED DESCRIPTION OF THE INVENTION 
I. Microwave Interactive Film and Laminate 
One embodiment of the present invention, illustrated with reference to FIG. 
1, is a microwave interactive laminate 10 having a heating area 12 and a 
deactivated area 14. Mechanical abrasion has reduced or eliminated the 
ability of a selected area of a microwave interactive layer (not shown in 
FIG. 1), corresponding to deactivated area 14, to generate heat in 
response to microwave energy. Only heating area 12 remains fully capable 
of generating heat in response to microwave energy without impairment 
since the area of the microwave interactive layer corresponding to heating 
area 12 has not been abraded. 
In the embodiment of the invention illustrated in FIG. 1 the heating area 
12 is circular to approximate the shape of a circular food product, such 
as a pizza. The food product will cover heating area 12 when the food is 
placed in a package into which the microwave interactive laminate 10 has 
been bonded. The area of the microwave interactive layer corresponding to 
heating area 12 will generate heat in response to microwave energy, 
preferably sufficient heat to brown or crisp the surface of food product 
placed in or on the package. While the heating area 12 of FIG. 1 is shown 
as being circular it should be understood that the present invention 
contemplates providing a heating area 12 of any desired shape, 
configuration and/or size. 
The present invention is not limited by the location of the heating area in 
a package or container. The heating area of a laminate formed in 
accordance with the present invention could be disposed on any surface of 
a package or container where heat for browning or crisping the food is 
desired. The heating area may therefore be at the bottom interior surface, 
the top interior surface, vertical interior surfaces or top exterior 
surface of a container, depending on where the heat for browning or 
crisping food is desired and the kind of container involved. 
FIG. 2 illustrates the layers making up microwave interactive laminate 10. 
It will be understood, of course, that the sizes of layers illustrated in 
FIG. 2 are exaggerated for purposes of illustration and are not 
necessarily in correct proportion to each other. 
Film layer 22 is a heat tolerant and heat stable material. Immediately 
below film layer 22 is microwave interactive layer 24 which is a thin 
layer of material capable of generating heat in response to microwave 
energy, if it is not abraded to reduce or eliminate its ability to 
generate heat in response to microwave energy. In the embodiment 
illustrated in FIG. 2, a selected area of the microwave interactive layer 
has been abraded to form deactivated area 14. By converting the selected 
area into deactivated area 14 with abrasion in accordance with the present 
invention, the shape of heating area 12 can be precisely controlled. The 
microwave interactive layer 24 is usually vacuum vapor deposited onto one 
side of film layer 22 to form microwave interactive film 26 consisting of 
layers 22 and 24. Other processes for depositing microwave interactive 
layer 24 onto film layer 22, such as sputtering or transferring, may be 
used. Abrasion of the surface of the microwave interactive layer 24 
corresponding to the inactive area 14 acts to convert that area of the 
microwave interactive layer 24 selected for abrasion into deactivated area 
14. After the abrasion, the microwave interactive film 26, is bonded to 
substrate layer 28 with an appropriate adhesive disposed as an adhesive 
layer 25 between substrate layer 28 and microwave interactive film 26. 
Substrate layer 28 provides laminate 10 with structural rigidity and a 
fixed shape which conforms to the shape of a package into which the 
microwave interactive laminate 10 will be incorporated. 
FIGS. 3A, 3B and 3C illustrate the manner in which the microwave 
interactive film 26 of FIG. 2 is produced. As shown in FIG. 3A a film 
layer 22 is provided and a microwave interactive layer 24 is deposited on 
it. FIG. 3B shows the microwave interactive film 26 with a coating layer 
38 deposited on that portion of the microwave interactive layer 24 that is 
desired as a heating area. The coating layer 38 acts as a mask to protect 
the desired portion of the microwave interactive layer 24 from abrasion 
during the step of abrasion as illustrated in FIG. 3C. Suitable materials 
for the coating layer 38 are those useful for lamination such as binder 
resins or laminating adhesives. 
As illustrated in FIG. 3C the coating layer 38 and that portion of the 
microwave interactive layer 24 not underlaying the coating layer has been 
mechanically abraded. As discussed in the Examples that follow a variety 
of coating layer material and mechanical abrasion device combinations can 
be used to accomplish the objects of the present invention. While FIG. 3C 
shows the coating layer 38 as having been substantially abraded some 
combinations of coating layer and abrasion device may produce an effect 
whereby the coating layer 38 is not abraded. To accomplish the objects of 
the present invention, however, the continuity of the microwave 
interactive layer 24 must be broken in those areas where an deactivated 
area is desired. FIG. 3C illustrates the manner in which the continuity of 
the microwave interactive layer 24 is broken in accordance with the 
present invention. In order to deactivate the metal layer it is necessary 
that continuity of the microwave interactive layer 24 be broken by removed 
areas 41 that extend to the film layer 22. 
The film layer 22 serves as a stock material onto which microwave 
interactive layer 24 is deposited to form microwave interactive film 26 
consisting of layers 22 and 24. Film layer 22 can also separate a food 
product resting on top of laminate 10 from the microwave interactive layer 
24 or the substrate 28. The film layer 22 must be sufficiently stable at 
high temperatures when laminated to substrate layer 28 so that it will not 
degrade during the operation of a microwave oven at temperatures selected 
for cooking the desired food. Suitable materials for use as a film layer 
include, but are not limited to, films such as polyesters, polyolefins, 
nylon, cellophane, polysulphone, biaxially oriented polyester and other 
relatively stable plastics. It has been found that biaxially oriented 
polyester is a preferred material for most food containers because of its 
heat stability and its surface smoothness. 
The microwave interactive layer 24 is preferably deposited onto one side of 
film layer 22 by a vacuum vapor deposition technique. The side of film 
layer 22 onto which the microwave interactive material is deposited will 
face away from the food product in a container. Sputtering, transferring 
or other techniques, which are known to those skilled in the art, may also 
be used to deposit a layer of lossy material which interacts with 
microwave energy onto one side of protective film 22. 
Any suitable lossy substance that will heat in a microwave oven can be used 
as the microwave interactive material. These materials fall primarily into 
four groups: conductors, semi-conductors, ferromagnetic materials and 
dielectic materials. Any of these materials which convert microwave 
radiation into heat energy may be used in the present invention. Preferred 
microwave interactive materials used in the present invention to form 
microwave interactive layer 24 are compositions containing metals or other 
materials such as aluminum, iron, nickel, copper, silver, carbon, 
stainless steel, nichrome, magnetite, zinc, tin, iron, tungsten and 
titanium. These materials may be used in a powder, flake or fine particle 
form. The microwave interactive materials can be used alone or in 
combination with each other. The most preferred material for many 
applications of the present invention is aluminum metal. 
The microwave interactive layer 24 is very thin. In general, the thickness 
of vacuum vapor deposited layers of electrically conductive material is 
measured in terms of the optical density of the conductive layer itself. 
Microwave interactive layers used in microwave cooking are so thin that 
after they are deposited on transparent film, the microwave interactive 
film made up of film layer 22 and microwave interactive layer 24 may be 
seen through by the human eye. 
The substrate layer 28 may be made of a variety of materials but is 
preferably formed of a low density material having a relatively high 
insulating capacity and a heat stability sufficient to withstand cooking 
temperatures in a microwave oven. Suitable substrate materials include, 
but are not limited to, paperboard, papers, plastics, plastic films, 
ceramics and a wide variety of composite materials such as fiber/polymer 
composites. A preferred material for use in disposable packages for 
prepared foods is paperboard. 
A process, illustrated with reference to FIG. 4, used to make microwave 
interactive laminates in accordance with the present invention, may be 
conducted by first providing a continuous roll of microwave interactive 
film 26 comprising film layer 22 and microwave interactive layer 24. As 
explained above, microwave interactive film 26 can be formed by depositing 
microwave interactive material in a layer onto one side of the film. 
Next, a mask coating layer 38 is deposited on the microwave interactive 
layer 24 over that area in which microwave interactivity is desired to be 
maintained. The printed pattern can include very fine detail, including 
the printing of instructions, information or decoration. 
Conventional printing techniques such as rotogravure, flexography or 
lithography may be used to coat the selected area of the microwave 
interactive layer with the coating layer 38. The printing techniques used 
may be conducted with equipment which is well known to those of ordinary 
skill in the art. Flexographic printing, however, is preferred for many 
applications of the present invention. 
As embodied herein, the coating operation is carried out at the coating 
station 30 as shown in FIG. 4. The coating 31 used for the coating layer 
38 is contained in a recepticle 39. The surface of a roller 32 is coated 
by rotating it through the coating 31 in the recepticle 39. The thickness 
of the coating 31 that clings to the surface of the roller 32 is 
controlled by roller 32 and a doctor blade 37. A printing roller 34 is 
provided that rotates in a direction counter to that of the roller 32. The 
printing roller 34 carries on its surface one or more printing plates, 
such as, for example, plates 33 and 35. The printing plates 33 and 35 are 
brought into rotating contact with the coating 31 clinging to the 
counter-rotating surface roller 32 to transfer the coating 31 to the 
printing plates 33 and 35. The printing plates 33 and 35 then continue to 
rotate until they contact the microwave interactive film 26 to transfer 
the coating 31 from the plate to the film. In this way, the image formed 
on the printing plates 33 and 35 can be transferred to the microwave 
interactive film 26. The roller 36 is disposed opposite the film 26 from 
the printing roller 34 to ensure that sufficient pressure is brought to 
bear between the film 26 and the printing plates 33 and 35 to transfer the 
coating 31 to the film 26. 
It should be noted that deactivated area 14 of the microwave interactive 
layer 24 need not be visibly scratched to be deactivated. Accordingly, a 
colored coating 31 for use in the coating layer 38 can be used to provide 
a visual indication of the demarcation between deactivated area 14 and 
heating areas 12 of the microwave interactive layer 24 in applications of 
the present invention wherein the deactivated area 14 is deactivated 
without being visibly scratched. 
After the coating layer 38 has been printed onto the microwave interactive 
layer, the coating layer 38 and the microwave interactive film is dried at 
drying station 40 with any conventional drier or driers, such as hot air 
driers, infrared heating driers, or internally heated rolls. 
The thus-coated film is then abraded at station 50. As embodied herein, 
this abrasion is accomplished by bringing a rotating brush 52 into contact 
with the microwave interactive film 26 opposite roller 54. The brush 52 
rotates so that its bristles move relative to the film 26. The brush 52, 
coating layer 38, and microwave interactive layer 24 are selected in the 
manner explained in reference to FIGS. 3B and 3C such that the coating 
layer is not fully removed by the brush action and the microwave 
interactive layer 24 is abraded by the action of the brush sufficiently to 
produce dicontinuities in it to reduce or eliminate its microwave 
interactive qualities. It should be understood that, depending on the 
coating layer 38 and the microwave interactive film 26 chosen, it will be 
sufficient to move the coated microwave interactive film over a stationary 
surface to sufficiently abrade the un-coated area of the microwave 
interactive film 26 to de-activate it. 
The abrasion of the microwave interactive film 26 sufficiently to cause 
deactivation is dependent upon several factors including: the abrasion 
device chosen, such as a brush or a metal cylinder; the force with which 
the abrasion device is exerted against the microwave interactive film 26; 
and the speed at which the abrasion device moves relative to the microwave 
interactive film. 
Adhesive 61 is preferably applied to the treated microwave interactive film 
26 at station 60 by equipment illustrated by rollers 62 and 64. The 
thickness of the adhesive layer is controlled by roller 62 and a doctor 
blade 63. The adhesive 61, however, may be applied to substrate 56 rather 
than, or in addition to, the treated microwave interactive film 26. A 
variety of adhesives may be used to bond the microwave interactive film to 
the substrate. Adhesives found useful in the present invention include 
water based acrylic emulsions and casein neoprene emulsions. 
After adhesive has been applied, the treated microwave interactive film 26 
can be continuously bonded to substrate 56 at station 70 by equipment 
illustrated by rollers 74 and 76 to form microwave interactive laminate 10 
of the present invention. Although the process as depicted shows in-line 
lamination, the invention does not preclude separate stages of treating 
and out-of-line lamination. 
Preferably, only selected areas of the microwave interactive layer have 
been deactivated by abrading, forming a shaped heating area, such as 
heating area 12 illustrated in FIGS. 1 and 2. The heating area may 
generally conform to the shape of the food product to be placed in a 
package. By selecting the area or areas of the microwave interactive layer 
which are mechanically abraded, it is possible to control the shape of the 
heating area. This control over the shape of the heating area can be used 
to prevent overlap of heat-generating areas of a laminate used in 
assembled packages, to provide heat generating areas of laminate that are 
fully covered by a food product, and/or to form a printed message or 
decoration. 
The microwave interactive film and the process of making it in accordance 
with the present invention are further illustrated with the following 
examples. 
Example 1 
A mask coating layer 38 comprising acrylic adhesive was applied to the 
metal side of an aluminum metalized polyester. The coating rate was 0.9 
lb/ream. The brush used was a swine bristle brush, 11/2 inches in diameter 
driven by an electric drill at 1300 rpm. The brush rotated in a direction 
opposite to its direction of travel over the microwave interactive film. 
The bristles had nominal diameters in the range of 0.005 to 0.006 inches. 
A section of the sample was microwaved at 600 watts for 5 seconds. In the 
heating area, where heating was desired, the polyester was destroyed - 
indicating that the desired heating had been achieved. The remaining 
intact polyester corresponding to the deactivated area, indicated minimal 
or no heating. 
EXAMPLE 2 
The same materials and conditions as followed in Example 1 were followed in 
Example 2 with the exception that a 3/4" diameter brush with swine 
bristles having nominal diameters in the range of 0.007-0.008 being used. 
Again, the desired results were obtained since the inactivation of the 
unmasked portion of the microwave interactive layer was achieved while the 
masked portion retained its microwave interactive qualities. 
EXAMPLES 3-6 
In these examples the same mask coating layer 38 was used as in Example 1. 
The brushes used were as set forth in the following table: 
______________________________________ 
Brush Bristle 
Example Brush Material Diam. Diam. 
______________________________________ 
3 Stainless Steel 1 in. .005 
4 Stainless Steel 1 in. .003 
5 Brass 1 in. .005 
6 Brass 1 in. .003 
______________________________________ 
In each of examples 3-6 the brush did not perform satisfactorially as it 
was too stiff and abraded the mask coating layer and the underlying 
microwave interactive layer. Thus the microwave interactive layer 
underlying the mask coating layer was deactivated. 
______________________________________ 
Examples 7-10 
Brush Nominal Bristle 
Example Diameter Diameter 
______________________________________ 
7 1.5 0.010 
8 1.0 0.006 
9 1.0 0.0035 
10 4.0 0.0035 
______________________________________ 
In each of examples 7-10 the methodology of example 1 was followed whereby 
the brushes were driven at 1300 rpm by an electric drill and rotated in a 
direction opposite to the brush's direction of travel across the microwave 
interactive film. No mask coating layer was used in these examples. Both 
examples 7 and 8 were sufficiently abraded in the brushed areas to 
deactivate the microwave interactive film. Example 9 exhibited only slight 
scratching in the brushed area and approximately 20% of its surface area 
was deactivated. Example 10 exhibited faint scratching and approximately 
5% of its brushed area was deactivated. 
EXAMPLE 11 
The technique of example 1 was followed using a mask coating layer 38 of 
ink binder WBB-17592, available from CZ Ink, Co., of St. Louis, Missouri. 
The ink binder was applied by flexography in a suitable pattern. A 3 3/4" 
diameter horsehair brush with 1/2" bristle extension was applied at 390 
RPM counter-rotating to the direction of travel of the web travelling at 
50 ft/min. The metalized film was thoroughly scratched while the masked 
area was protected. The protected or coated area was microwave interactive 
while that area that was uncoated was deactivated. 
EXAMPLE 12 
The technique of Example 1 was followed using a mask coating layer 38 of 
human skin oil (squalene). A 1 1/2 swine bristle brush was used. The 
surface covered with squalene was protected from abrasion. 
This example illustrates how the present invention can be used to provide a 
permanent record of a print of human skin such as a handprint, a 
fingerprint, or the like. Such a print can be produced by pressing, for 
example, a finger against a metallized film. Squalene will be deposited on 
the film in those areas where the finger contacted the film. The film is 
then mechanically abraded and those areas coated with squalene will not be 
abraded thus producing a permanent record of the fingerprint. 
II. A CONTAINER INCORPORATING A MICROWAVE INTERACTIVE FILM OR LAMINATE 
Because the microwave interactive layer or laminates formed in accordance 
with the present invention generate heat only at the area or areas 
selected as the heating area or areas, the microwave interactive laminate 
does not have to be cut to the approximate shape of the food product prior 
to bonding to a package. This can lower package production time, 
complexity and cost. Moreover, the control provided by the present 
invention over the shape of the heating area can be used to provide areas 
of heat-generating microwave interactive laminate where it is desired for 
a particular end use. In addition, overlap between heat-generating 
microwave interactive layers, which can ocur when a package or container 
is assembled, can be avoided by deactivating selected areas of the 
microwave interactive layer that will overlap when the package or 
container is assembled. 
A variety of improved packages or containers can incorporate microwave 
interactive laminates made in accordance with the present invention. With 
the present invention, for instance, pizza packages or pizza trays may be 
provided with a microwave interactive laminate having all areas of the 
microwave interactive layer of the laminate, which are not to be covered 
by the pizza, deactivated. This focuses the heat from the microwave 
interactive layer where it is needed to brown and crisp the pizza crust. 
In accordance with the present invention a container is provided for 
storing, supporting and microwave cooking food. The container includes a 
package having a surface or surfaces for enclosing and/or supporting a 
food product and a microwave interactive laminate, as, for example, shown 
in FIG. 2, that forms the surface or surfaces of the package to heat the 
food product in response to microwave energy. As embodied herein such a 
container 80, as shown in FIG. 5 includes a top surface 82, a bottom 
surface 84, a first side surface 86 and a second side surface 88. The 
microwave interactive laminate 10 is bonded in any convenient manner to 
the bottom surface 84. As shown in FIG. 5 a food product 11 is placed on 
the microwave interactive laminate 10. Alternatively, the food product 11 
may be placed directly n the bottom surface 84 and the microwave 
interactive laminate 10 may be bonded to the top surface 82 or to the 
first and second side surfaces 86 and 88, respectively. 
Packages made with the microwave interactive film integral to all of the 
interior vertical surfaces may have ends of the vertical surfaces which 
form tabs or flaps which overlap the ends of adjacent vertical surface 
when the package is assembled. The overlapping tabs or flaps can result in 
overlapping areas of the microwave interactive layer 26 of the laminate. 
The overlapping areas of the microwave interactive layer generate 
excessive heat which can result in scorching. Other package constructions, 
of course, can result in overlapping layers of microwave interactive 
layers. In some packages, for instance, overlapping occurs at glued seams 
or on dust flaps. Again, excessive heat is generated at the areas of 
overlap. The overlap problem can be avoided with the present invention by 
deactivating selected areas of the microwave interactive layer 26 of the 
laminate which will overlap each other when the package is assembled. 
In accordance with the present invention the container shown in FIG. 6 has 
deactivated areas of microwave interactive layer that correspond to areas 
of the package wherein the microwave interactive layers overlap when the 
package is assembled. As embodied herein, the microwave interactive 
laminate 10 is bonded to the sides 86, 88, 90, and 92 of the container. 
The microwave interactive laminate 10 includes a first end 96 and a second 
end 98 that overlap to form an overlap portion 94. That portion of the 
first end 96 of the microwave interactive laminate 10 that overlaps with 
the second end 98 in the overlap portion 94 is deactivated in the manner 
described in reference to FIGS. 3A-3C. 
Also as embodied herein a container in accordance with the present 
invention is provided wherein the microwave interactive laminate forms the 
structure of the container. 
As shown in FIGS. 7 and 8 a container 81 is formed having the microwave 
interactive laminate 10, including the microwave interactive layer 26 and 
the substrate layer 28. In the embodiment of FIG. 5 food 11 is disposed on 
the bottom surface 84. Accordingly, the microwave interactive film 26 
corresponding to the bottom surface 84 is microwave interactive, while the 
remaining surfaces 82, 86 and 88 are deactivated. 
As shown in FIG. 8, the microwave interactive laminate 10, including the 
microwave interactive layer 26 and the substrate layer 28, forms the sides 
86, 88, 90 and 92 of the container. The microwave interactive laminate has 
a first end 100 and a second end 102 that overlap to form an overlap 
portion 104. That portion of the first end 100 of the microwave 
interactive laminate 10 that overlaps with the second end 102 in the 
overlap portion 104 has a microwave layer 26 that is deactivated. 
It is also sometimes desirable to provide pressed trays and plates which 
are not microwave interactive at the brim, sides or selected areas of the 
bottom of a tray or plate for performance or handling reasons. With the 
present invention, pressed trays and plates can be provided with a 
microwave interactive laminate in which deactivated areas of the microwave 
interactive layer correspond only to areas at which heating is not 
desired. 
In addition, portions of the microwave interactive layer may be deactivated 
to provide a grid pattern of alternating discrete activated and 
deactivated areas. This grid pattern decreases the amount of heat that 
will be generated over the grid area as a whole. 
It will be apparent to those skilled in the art that various modifications 
and variations can be made in the products and processes of the present 
invention without departing from the scope or spirit of the invention. For 
example, the present invention discusses the abrasion of a microwave 
interactive film 26 to deactivate it. It should be understood, however, 
that to deactivate a microwave interactive film 26 in accordance with the 
present invention, one need only cause minute discontinuities in the 
microwave interactive layer 24 that may or may not be visible to the 
unaided eye. Such discontinuities 39 can be formed by abrasion in the 
conventional sense or through abrasion by drawing the microwave 
interactive film 26 over a surface, such as, for example, a metal 
cylinder. Thus, it is intended that the present invention cover 
modifications and variations thereof provided they come within the scope 
of the appended claims and their equivalents.