U.S. patent application number 14/153810 was filed with the patent office on 2014-05-08 for partially metallized film having barrier properties.
This patent application is currently assigned to Frito-Lay North America, Inc.. The applicant listed for this patent is Frito-Lay North America, Inc.. Invention is credited to Edward Anthony BEZEK, Anthony Robert KNOERZER, Steven Kenneth TUCKER.
Application Number | 20140124400 14/153810 |
Document ID | / |
Family ID | 41799540 |
Filed Date | 2014-05-08 |
United States Patent
Application |
20140124400 |
Kind Code |
A1 |
BEZEK; Edward Anthony ; et
al. |
May 8, 2014 |
PARTIALLY METALLIZED FILM HAVING BARRIER PROPERTIES
Abstract
A partially metallized packaging film and method of making is
disclosed. In one aspect, at least one portion of a vaporized metal
stream is shielded from contacting a sheet of packaging film during
the metallization process. The shield is a rigid plate and can be
shaped to provide a sharp transition from transparent film to
opaque film, or it can provide a gradual transition from
transparent film to opaque film. The partially metallized packaging
film can be used with a form, fill and seal machine or other
packaging machine to create a food package with a product viewing
window. In one aspect, the barrier web comprises a bio-based
film.
Inventors: |
BEZEK; Edward Anthony;
(Frisco, TX) ; KNOERZER; Anthony Robert; (Parker,
TX) ; TUCKER; Steven Kenneth; (Hurst, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Frito-Lay North America, Inc. |
Plano |
TX |
US |
|
|
Assignee: |
Frito-Lay North America,
Inc.
Plano
TX
|
Family ID: |
41799540 |
Appl. No.: |
14/153810 |
Filed: |
January 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12207010 |
Sep 9, 2008 |
8663758 |
|
|
14153810 |
|
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Current U.S.
Class: |
206/459.5 ;
118/720; 427/251 |
Current CPC
Class: |
B32B 27/36 20130101;
B32B 2307/412 20130101; B32B 2307/7244 20130101; B32B 2307/7265
20130101; B32B 2307/40 20130101; B32B 5/142 20130101; B65D 33/04
20130101; B32B 2307/7246 20130101; B32B 2307/41 20130101; Y10T
428/24942 20150115; B32B 2255/10 20130101; Y10T 428/1334 20150115;
B32B 27/32 20130101; B32B 2307/414 20130101; B32B 2307/75 20130101;
B32B 2439/70 20130101; B32B 27/06 20130101; B65D 75/522 20130101;
B32B 2255/205 20130101; B65D 33/004 20130101 |
Class at
Publication: |
206/459.5 ;
427/251; 118/720 |
International
Class: |
B65D 33/00 20060101
B65D033/00; B65D 33/04 20060101 B65D033/04 |
Claims
1. A food package made from a partially metallized packaging film
comprising: product viewing window comprising a section of
transparent packaging film and defined by at least one translucent
film strip or at least one opaque film strip, and at least one
product package graphic.
2. The food package of claim 1 wherein said translucent film strip
comprises an outer edge, an inner edge, and a width generally
running between said outer and inner edges, and a degree of
transmittance that varies across its width.
3. The food package of claim 1 wherein said degree of transmittance
varies linearly across its width.
4. The food package of claim 1 wherein said product viewing window
is further defined by two translucent film strips on opposite sides
of said product viewing window, and two package graphics on
opposite sides of said product viewing window.
5. The food package of claim 1 further comprising at least one
metallized target shape on said section of transparent packaging
film.
6. A method of making a partially metallized packaging film
comprising: providing a vaporized metal stream and a sheet of
packaging film; moving said sheet of packaging film through said
vaporized metal stream; during said moving, shielding at least one
portion of said vaporized metal stream from contacting said
packaging film.
7. The method of claim 6 further wherein said shielding further
comprises disposing a shield between said vaporized metal stream
and said sheet of packaging film without allowing said shield to
contact said packaging film.
8. The method of claim 7 wherein said shielding further comprises
intermittently allowing at least one portion of said vaporized
metal stream to contact said sheet in at least one product logo
shape.
9. The method of claim 7 wherein said disposing said shield further
comprises disposing a rigid plate.
10. An apparatus for creating a partially metallized packaging film
comprising: a vaporized metal sprayer that produces a vaporized
metal stream; a shield disposed within the vaporized metal stream
such that any packaging film sheet used with the apparatus will
have at least one portion of the vaporized metal stream shielded
from contacting it.
11. The apparatus of claim 10 wherein said shield is disposed such
that it does not touch any packaging film sheet used with the
apparatus.
12. The apparatus of claim 10 wherein said shield further comprises
a rigid plate.
13. The apparatus of claim 12 wherein said shield further comprises
a length, a major width, and a minor width.
14. The apparatus of claim 10 wherein said shield is disposed
generally co-planar with any packaging film sheet used with the
apparatus.
15. The apparatus of claim 13 wherein said shield further comprises
a transition from said major width to said minor width comprising
at least one of, a linear transition, a concave transition, a
convex transition, a stepped transition and a saw tooth transition.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional patent application of
co-pending U.S. patent application Ser. No. 12/207,010 entitled
"Partially Metallized Film Having Barrier Properties" filed Sep. 9,
2008, the technical disclosure of which is hereby incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to customizable, metallized,
flexible packaging material that can be used to balance product
visibility with barrier protection in packaged food products and a
method of making the customized packaging material.
[0004] 2. Description of Related Art
[0005] Multi-layered flexible film structures made from polymers
are often used in flexible packages where there is a need for its
advantageous barrier, sealant, and graphics-capability properties.
Barrier properties in one or more layers are important in order to
protect the product inside the package from light, oxygen or
moisture. Such a need exists, for example, for the protection of
foodstuffs, which may run the risk of flavor loss, staling, or
spoilage if insufficient barrier properties are present to prevent
transmission of such things as light, oxygen, or moisture into the
package.
[0006] In addition, barrier properties also prevent undesirable
leaching of the product to the outside of the bag. For example,
oily foods such as potato chips have the potential for some oil to
leach out into the film of the bag. The sealant properties are
important in order to enable the flexible package to form an
airtight or hermetic seal. Without a hermetic seal, any barrier
properties provided by the film are ineffective against oxygen,
moisture, or aroma transmission between the product in the package
and the outside.
[0007] A graphics capability is needed because it enables a
consumer to quickly identify the product that he or she is seeking
to purchase, allows food product manufacturers a way to label the
nutritional content of the packaged food, and enables pricing
information, such as bar codes to be placed on the product. At the
same time, consumers also desire to actually view some products,
such as potato chips or tortilla chips, through the packaging film
in order generally inspect the food products' physical condition
and ensure that most of the product has not been broken into small
pieces during transport and handling.
[0008] One prior art packaging film used for packaging potato chips
and like products is metallized film. Metallized film is typically
a polymer film, such as oriented polypropylene (OPP) or
polyethylene terephthalate (PET), coated with a thin layer of
metal. The thin layer of metal is typically applied using a
physical vapor deposition process whereby the metal used for the
coating is vaporized and deposited onto a sheet of polymer film,
all under vacuum conditions. Prior art metallized film has a shiny,
opaque appearance and excellent barrier properties against moisture
and oxygen transmission.
[0009] FIG. 1 depicts a simplified representation of a prior art
apparatus for creating metallized film. Inside a vacuum chamber
100, unmetallized polymer film 202 is disposed on a first roll 208
on one side of the vacuum chamber 100. The unmetallized film 202 is
unrolled from the first roll 208, travels through a vapor
deposition apparatus 206 where it becomes metallized film 204. As
stated previously, the vaporized metal 200 is deposited onto one
surface of the film. During the process, the film is continuously
unrolled from the first roll 208 and rolled onto a second roll 210
disposed on the side of the vapor deposition apparatus 206 opposite
the first roll 208. At the conclusion of the process, the second
roll 210 will contain a roll of metallized film 204, while the
first roll will be empty.
[0010] While metallized film provides food packagers with a
relatively inexpensive barrier layer, as mentioned previously, the
barrier is opaque. This property can be problematic when used for
packages of breakable foodstuffs, such as potato chips or tortilla
chips. When shopping for such breakable foodstuffs, some consumers
may want to view the contents of the food package before actually
purchasing the food package to make sure its contents have not been
broken to an undesirable degree. Even for non-breakable foodstuffs,
consumers may still want to inspect the contents of a food package
before deciding whether to purchase it. Particularly colorful or
delicious looking foods may even entice a consumer to purchase them
if viewed by the consumer. It would be desirable, therefore, to
provide a metallized food packaging film with a viewing window
through which the contents of the food package can be viewed.
[0011] As described in U.S. Pat. No. 5,530,231, a pattern of oil
can be deposited on the polymer film before the vaporized metal is
deposited on the film to prevent the deposition of metal on the
film in the areas masked by the oil. This masking oil pattern can
then be washed off to reveal unmetallized portions of the film
underneath. This method suffers from several disadvantages,
including substantial increases in processing time and capital
expense. Furthermore, this method does not provide any way to
control the degree of metallization that occurs on different
portions of the film. In other words, a particular portion of film
metallized using this method will be either fully metallized or
completely unmetallized.
[0012] A need exists, therefore, to finely control the degree of
metallization over the entire surface of the film, and to do so
economically.
SUMMARY OF THE INVENTION
[0013] The present invention is directed towards a metallized
packaging film having variable barrier properties. In one aspect,
the packaging film of the present invention is partially metallized
such that when the film is used on a form-fill-seal packaging
machine, a clear product window is provided to the consumer. In
another aspect of one embodiment, the packaging film gradually
transitions from at least one opaque, metallized area to at least
one transparent, non-metallized area. In another embodiment, the
product viewing window is not transparent, but is translucent. In
still another aspect of the invention, the metallized and
non-metallized areas are provided such that product logos and
graphics are not obscured. The present invention thereby provides a
partially metallized packaging film with barrier properties that
approximate fully metallized packaging films. The above as well as
additional features and advantages of the present invention will
become apparent in the following written detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The novel features believed characteristic of the invention
are set forth in the appended claims. The invention itself,
however, as well as a preferred mode of use, further objectives and
advantages thereof, will be best understood by reference to the
following detailed description of illustrative embodiments when
read in conjunction with the accompanying drawings, wherein:
[0015] FIG. 1 depicts a perspective view of a prior art apparatus
used to make metallized polymer film;
[0016] FIG. 2 is a cross-sectional view of prior art multi-layered
packaging film;
[0017] FIG. 3 depicts a schematic view of a prior art apparatus
used to make multi-layered packaging film;
[0018] FIG. 4 depicts a vertical form, fill, and seal machine that
is known in the prior art;
[0019] FIG. 5 depicts an apparatus used to make the partially
metallized film of the present invention;
[0020] FIG. 6 depicts one embodiment of the vapor shield of the
present invention; and
[0021] FIG. 7 depicts one embodiment of the partially metallized
film of the present invention;
[0022] FIG. 8 depicts one embodiment of the food product of the
present invention having a transparent product viewing window;
[0023] FIG. 9 depicts one embodiment of the vapor shield of the
present invention;
[0024] FIG. 10 depicts one embodiment of the partially metallized
film of the present invention;
[0025] FIG. 11 depicts one embodiment of the vapor shield of the
present invention;
[0026] FIG. 12 depicts one embodiment of the vapor shield of the
present invention;
[0027] FIG. 13A depicts one embodiment of the vapor shield of the
present invention;
[0028] FIG. 13B depicts one embodiment of the vapor shield of the
present invention;
[0029] FIG. 14 depicts one embodiment of the vapor shield of the
present invention;
[0030] FIG. 14A depicts one embodiment of the vapor shield of the
present invention;
[0031] FIG. 14B depicts one embodiment of the vapor shield of the
present invention;
[0032] FIG. 14C depicts one embodiment of the vapor shield of the
present invention;
[0033] FIG. 15 depicts one embodiment of the partially metallized
film of the present invention;
[0034] FIG. 16 depicts one embodiment of the partially metallized
film of the present invention;
[0035] FIG. 17A depicts one embodiment of the vapor shield of the
present invention in a first position;
[0036] FIG. 17B depicts one embodiment of the vapor shield of the
present invention in a second position;
[0037] FIG. 18A depicts one embodiment of the vapor shield of the
present invention;
[0038] FIG. 18B depicts one embodiment of the vapor shield of the
present invention in a first position;
[0039] FIG. 18C depicts one embodiment of the vapor shield of the
present invention in a second position; and
[0040] FIG. 19 is a cross sectional view of one embodiment of the
packaging film of the present invention.
DETAILED DESCRIPTION
[0041] One embodiment of the present invention is directed towards
an apparatus and a method of making a partially metallized
packaging film that can be used on a vertical form, fill and seal
machine to create a product package with a viewing window. As used
herein, the terms "fully metallized packaging film" or "metallized
film" mean a polymer film with at least one surface that has been
coated with a thin metal layer using a vapor deposition process or
similar process known in the art. The most common metal used to
coat metallized film is aluminum, but other metals such as nickel
or chromium can also be used. The typical thickness of the metal
layer on metallized film is approximately 0.5 microns. Metallized
PET film can provide about 30 times the moisture barrier and about
400 times the oxygen barrier of a non-metallized PET film. Other
metallized polymer films provide similar gains in barrier
properties. Metallized film also provides its barrier properties at
a unit cost far below the unit cost for clear films that provide
similar barrier properties.
[0042] Metallized films are virtually opaque to visible light and
UV light. While this property may be desirable from a product
preservation perspective, it may not be desirable from a consumer
perspective depending on the types of foodstuffs inside the
package.
[0043] One prior art multi-layer or composite metallized film used
for packaging foodstuffs and like products is illustrated in FIG. 2
which is a schematic of a cross section of a multi-layer film 500
illustrating each individual substantive layer. Each of these
layers functions in some way to provide the needed barrier,
sealant, and graphics capability properties. For example, the
graphics layer 114 is typically used for the presentation of
graphics that can be reverse-printed and viewed through a
transparent outer base layer 112. Like numerals are used throughout
this description to describe similar or identical parts, unless
otherwise indicated. The outer base layer 112 is typically oriented
polypropylene ("OPP") or polyethylene terephthalate ("PET"). A
metal layer 120, as described above, is disposed upon an inner base
layer 118 to provide barrier properties. A sealant layer 119
disposed upon the inner base layer 118 enables a hermetic seal to
be formed at a temperature lower than the melt temperature of the
inner base layer. A lower melting point sealant layer 119 is
desirable because melting a metallized OPP to form a seal could
have an adverse effect on the barrier properties. Typical prior art
sealant layers 119 include an ethylene-propylene co-polymer and an
ethylene-propylene-butene-1 ter-polymer. A glue or laminate layer
115, typically a polyethylene extrusion, is required to adhere the
outer base layer 112 with the inner, product-side base layer 118.
Thus, at least two base layers of polymer film are typically
required in a composite or multi-layered film.
[0044] FIG. 3 demonstrates schematically the formation of material,
in which the outer base layer 112 and metallized inner base layer
118 of the packaging material are separately manufactured, then
formed into the final material 500 on an extrusion laminator 400.
The outer base layer 112 having graphics 114 previously applied by
a known graphics application method such as flexographic or
rotogravure is fed from roll 212 while metallized inner base layer
118 is fed from roll 218. At the same time, resin for the laminate
layer 115 is fed into hopper 215a and through extruder 215b, where
it will be heated and extruded at die 215c as molten polymer
laminate 115. This molten polymer laminate 115 is extruded at a
rate that is congruent with the rate at which the base layer
materials 112, 118 are fed, becoming sandwiched between these two
layers. The layered material 500 then runs between chill drum 220
and nip roller 230, ensuring that it forms an even layer as it is
cooled. The pressure between the laminator rollers is generally in
the range of 0.5 to 5 pounds per linear inch across the width of
the material. The large chill drum 220 is made of stainless steel
and is cooled to about 50-60.degree. F., so that while the material
is cooled quickly, no condensation is allowed to form. The smaller
nip roller 230 is generally formed of rubber or other resilient
material. Note that the layered material 500 remains in contact
with the chill drum 220 for a period of time after it has passed
through the rollers, to allow time for the resin to cool
sufficiently. The material can then be wound into rolls (not
specifically shown) for transport to the location where it will be
used in packaging.
[0045] Once the material is formed and cut into desired widths, it
can be loaded into a vertical form, fill, and seal machine to be
used in packaging the many products that are packaged using this
method. FIG. 4 shows an exemplary vertical form, fill, and seal
machine that can be used to package snack foods, such as snack
chips. This drawing is simplified, and does not show the cabinet
and support structures that typically surround such a machine, but
it demonstrates the general workings of the machine. Packaging film
500 is taken from a roll 512 of film and passed through tensioners
514 that keep it taut. The film then passes over a former 516,
which directs the film as it forms a vertical tube around a product
delivery cylinder 518. This product delivery cylinder 518 normally
has either a round or a somewhat oval cross-section. As the tube of
packaging material is pulled downward by drive belts 520, the edges
of the film are sealed along its length by a vertical sealer 522,
forming a back seal 524. The machine then applies a pair of
heat-sealing jaws 526 against the tube to form a transverse seal
528. This transverse seal 528 acts as the top seal on the bag 530
below the sealing jaws 526 and the bottom seal on the bag 532 being
filled and formed above the jaws 526. After the transverse seal 528
has been formed, a cut is made across the sealed area to separate
the finished bag 530 below the seal 528 from the partially
completed bag 532 above the seal. The film tube is then pushed
downward to draw out another package length. Before the sealing
jaws form each transverse seal, the product to be packaged is
metered through the product delivery cylinder 518 and is held
within the tube above the transverse seal 528.
[0046] The present invention is thus directed towards a method for
making a partially metallized packaging film base layer, and the
packaging film itself, that can be used in conjunction with a
co-extrusion machine to create a multi-layered partially metallized
packaging film which in turn can be used with a vertical form, fill
and seal machine to create a metallized product package with a
product viewing window. In one embodiment, at least one metallized
target shape in the form of a logo or graphic can be included on
the packaging film.
[0047] As used herein, the term "partially metallized packaging
film" means a polymer film with at least one surface that has at
least one area fully coated with a thin metal layer and at least
one area that is either not coated with a thin metal layer or that
is partially coated with a thin metal layer. FIG. 5 is a
representative depiction of one embodiment of the apparatus of the
present invention used to create the partially metallized film of
the present invention. As shown therein, inside a vacuum chamber
100, unmetallized polymer film 202 is disposed on a first roll 208
on one side of the vacuum chamber 100. The unmetallized film 202 is
unrolled from the first roll 208, travels through a vapor
deposition apparatus 206 where it becomes partially metallized.
Inside the vapor deposition apparatus 206, the vaporized metal
stream 200 is sprayed towards one surface of the film. A vapor
shield 300 is disposed between the vaporized metal stream 200 and
the surface of the film to be metallized. The vapor shield 300
blocks at least one portion of the vaporized metal stream 200 from
reaching the film surface, thereby leaving at least one area of the
film unmetallized or partially metallized. During the process, the
film is continuously unrolled from the first roll 208 and rolled
onto a second roll 210 disposed on the side of the vapor deposition
apparatus 206 opposite the first roll 208. At the conclusion of the
process, the second roll 210 will contain a roll of partially
metallized film 220, while the first roll will be empty.
[0048] FIG. 6 depicts one embodiment of the vapor shield 300 of the
present invention. In this embodiment, the vapor shield of the
present invention is a single plate comprising a top surface 302
and a bottom surface 204, a width 306, a length 308, and a
thickness. As depicted in FIG. 5 (although the specific shield
depicted therein is the embodiment of FIG. 9), during the
metallization process the shield 300 is disposed in an
approximately co-planar arrangement with the film being metallized,
but without touching or contacting the film. The shield is also
arranged such that the length 308 of the shield is approximately
parallel to the film's direction of travel and the width 306 of the
shield is parallel to the width of the film sheet. The embodiment
depicted in FIG. 5 is simplified and does not depict the support
structures which would dispose the shield inside the metallization
apparatus in a coplanar relationship with the film sheet. Such
support structures would be known to one skilled in the art.
[0049] The shield embodiment depicted in FIG. 6 is the most basic
embodiment of the present invention. It has a constant width 306
throughout its length 308, and its length 308 is long enough to
shield the entire portion of film behind the shield 300 from being
metallized inside the metallization apparatus 206.
[0050] FIG. 7 depicts a perspective view of a partially metallized
film 220 created using the shield embodiment of FIG. 6. When
initially transparent polymer film 202 is used with this embodiment
of the shield 300, the resulting partially metallized film 220
comprises a strip of transparent film 234 (or fully unmetallized
film) disposed between two strips of opaque film 230 (or fully
metallized film). This embodiment is not a preferred embodiment
because the transition from the transparent film strip 234 to the
opaque film strips 230 in this embodiment is a sharp one. The sharp
transition is not preferred because, ultimately, the partially
metallized film 220 will be combined with an outer base layer that
has graphics and/or logos printed on it. When the sharp transition
from opaque to transparent film is present in the partially
metallized film layer 220, a distinct line corresponding to the
transition can be discerned through the graphics layer, especially
where light pigments are used in the graphics layer. Therefore,
some graphics can be obscured or made less attractive due to the
presence of this distinct line. An example of a product bag 600
with a distinct line is shown in FIG. 8. The preferred embodiments
described below overcome this problem by providing a gradual
transition from opaque to transparent film. The gradual transition
region is less distinct, if not completely invisible, through most
graphics and logo prints.
[0051] FIG. 9 depicts another embodiment of the vapor shield of the
present invention. The FIG. 9 embodiment is shown in use in FIG. 5.
FIG. 10 depicts a perspective view of a partially metallized film
sheet made using the shield embodiment of FIG. 9. As can be seen
therein, it comprises a transparent strip 234, which is bordered on
both sides by a translucent strip 232, each of which are bordered
by an opaque strip 230. In this embodiment, as depicted in FIG. 9,
the shield comprises a single plate with a top surface 302, a
bottom surface 304, a length 308, major width 314 and a minor width
312. The major width is found at one end of the plate and the minor
width is found at the opposite end. The resulting cross section of
the plate when viewed looking directly at the top or bottom surface
302, 304 is that of an isosceles trapezoid, with the transition
between the major and minor widths being approximately linear. In
one embodiment, the length 308 of the vapor shield is such that
when an initially transparent polymer film sheet undergoes
metallization, it has the following characteristics, as depicted in
FIG. 10: (a) one strip of the film sheet having a width 222
approximately equal to the minor width 312 of the shield receives
no vaporized metal, and as such is a transparent film strip 234;
(b) two strips of the film sheet, one on either side of the
transparent film strip 234, each of which, having reduced exposure
time to the vaporized metal stream 200, is partially metallized,
and thereby a translucent strip 232, with each translucent strip
232 having a width 224 approximately equal to half the difference
between the shield's major width 314 and minor width 312, an inner
edge adjacent to said transparent film strip 234, and an outer edge
opposite said transparent film strip 234; and (c) two strips of the
film sheet that are fully metallized, or opaque film strips 230,
with an inner edge adjacent to said translucent film strip 232, an
outer edge coterminous with one edge of said film sheet and a width
226 equal to the distance between said inner and outer edges.
[0052] It will be appreciated by one skilled in the art, in view of
the teachings herein, that the shield can be disposed relative to
the film sheet such that the transparent, translucent, and opaque
film strips can be located at different places laterally along the
width of the film sheet. For example, in one embodiment, the shield
can be disposed with one edge coterminous with an edge of the film
sheet. In this embodiment, either a translucent film strip or a
transparent film strip will comprise one edge adjacent to the film
strip edge. Different embodiments of the shield can be used in this
way to provide a variety of different partially metallized
packaging films. All embodiments of the partially metallized film
sheets produced by this invention, regardless of where the
particular strips are located, will comprise at least one opaque
film strip, and at least one of a transparent film strip or a
translucent film strip.
[0053] Referring back to FIG. 10, the degree of metallization of
the translucent film strip 232 gradually varies from almost fully
unmetallized at its inner edge to almost fully metallized at its
outer edge. Thus, the transition from the opaque film strip 230 to
the transparent film strip 234 is a gradual transition. This
gradual transition from opaque to transparent is one of the novel
features of the partially metallized film of the present invention.
The opaque strips of the film 230 provide excellent oxygen and
moisture barrier properties.
[0054] The term opaque, as used herein, means a degree of
transmittance of less than about 5% of incident visible light. In
other words, an opaque film 230 allows less than about 5% of
incident visible light pass through. The translucent strips 232
provide improved oxygen and moisture barrier properties. The term
translucent, as used herein to describe a particular polymer based
film, means a degree of transmittance between about 5% and the
degree of transmittance for that particular film in its
non-metallized condition. In other words, a translucent film allows
more than about 5% of incident visible light to pass through, but
less than the percentage of visible light that would pass through
the same particular film in its non-metallized condition. The
transparent strip of film 234 provides the same barrier properties
as the unmetallized polymer film. The term transparent, as used
herein to describe a particular polymer based film, means the
degree of transmittance of incident visible light for that
particular film when it is in a completely non-metallized
condition. In other words, a transparent film is a film that allows
approximately as much incident visible light to pass through it as
that particular film would in a completely non-metallized
condition. The term "degree of transmittance" as used herein, when
used to describe a film, means the percentage of incident visible
light allowed to pass through the film. When a food package is made
utilizing the partially metallized film of this embodiment of
present invention, it has excellent barrier properties, along with
a transparent product viewing window.
[0055] In the embodiment of the shield depicted in FIG. 9, the
widths of the transparent strip 234, the translucent strips 232,
and the opaque strips 230, as well as the degree of gradation of
the translucent strips 232, can all be controlled by varying the
major 314 and minor 312 widths of the shield. The width of the
transparent strip 222 is approximately equal to the minor width 312
of the shield. When the shield 300 is symmetrical around its
lengthwise axis, the width of each translucent strip 224 is
approximately equal to half the difference between the major 314
and minor 312 widths of the shield. Furthermore, the rate of change
in the degree of transmittance across the width of each translucent
strip 224 can be controlled by controlling the difference between
the major 314 and minor 312 widths of the shield 300. The greater
the difference between the major and minor widths of the shield,
the more gradual the transition from the opaque strip to the
transparent strip. However, in this embodiment, the degree of
control a practitioner has over the transition region is restricted
to some extent in that the amount of metal deposited onto the
translucent film strip varies approximately linearly across its
width due to the trapezoidal shape of the shield plate. The width
of each opaque strip 226 is approximately equal to the distance
between an outer edge of each translucent strip 232 and the edge of
the film sheet closest in proximity to said outer edge of said
translucent strip 232.
[0056] In another embodiment of the shield depicted in FIG. 9, the
major width 314 of the shield is made greater than or equal to the
width of the film sheet. In this embodiment, no opaque strips 230
are formed during the metallization process. A transparent strip
222 will be formed, again with a width approximately equal to the
minor width 312 of the shield. Two translucent strips 232 will be
formed on opposite sides of said transparent strip 222. In this
embodiment, the width of each translucent strip 224 is equal to the
distance between one edge of the transparent strip 222 and the edge
of the film sheet 220 closest in proximity to said transparent
strip 222 edge. The degree of transmittance will gradually vary
from almost transparent at the translucent strip edge adjacent to
said transparent strip, to almost opaque at the edge of the film
sheet.
[0057] In FIG. 11 is depicted another embodiment of the vapor
shield of the present invention. In this embodiment, the vapor
shield comprises a single plate with a length, a major width and a
minor width. The plate in this embodiment has a plurality of saw
teeth 330 along its length. Preferably, in one embodiment all of
the saw teeth 330 protrude from the plate to approximately equal
distances. In another embodiment, depicted in FIG. 12, the saw
teeth protrude from the plate at varying distances. In one
embodiment, referring back to FIG. 11, the major width of the
shield comprises the distance from the tips of the saw teeth on one
side of the shield to the tips of the saw teeth on the opposite
side of the shield, the minor width of the shield comprises the
distance from the base of the saw teeth on one side of the shield
to the base of the saw teeth on the opposite side of the shield,
and the transition between its major and minor widths is a saw
tooth transition. As with the embodiment depicted in FIG. 9, a film
sheet metallized behind this shield will be similar to the film
strip depicted in FIG. 10, and will comprise a transparent strip
234, two graduated translucent strips 232, and two opaque strips
230. The width of the translucent strip 224 is approximately equal
to the height of the saw teeth 332. Higher saw teeth also provide a
more gradual transition from transparent to opaque. In this
embodiment, the degree of metallization in the translucent strip
again varies approximately linearly across its width due to the
linear shape of the saw tooth edges.
[0058] FIGS. 13A and 13B depict two variations of another
embodiment of the vapor shield of the present invention. This
embodiment is a single plate with edges that curve convexly, as in
FIG. 13B, or concavely, as in FIG. 13A, within the plate's major
plane, along the entire length 308 of the plate. The longest width,
or major width 314, of this embodiment is found at one end, while
the minor width 312, or shortest width, is found at the opposite
end, and the transition between its major and minor widths is
convex or concave, respectively. The widths of the transparent,
translucent, and opaque film strips created using this embodiment
of the vapor shield will again be defined by the major 314 and
minor 312 widths of the shield, and the width of the film sheet.
However, the curved edges allow a practitioner of the present
invention to more finely control the variability of the
metallization within the translucent strip because the width of the
plate does not vary linearly along its length. Using the convex
arrangement depicted in FIG. 13B, the transition from opaque film
to transparent film across the width of the translucent strip
begins by gradually allowing more visible light through nearer the
outer edge of the translucent strip and then accelerates the rate
of increase in the degree of transmittance towards the inner edge
of the translucent strip. The concave arrangement depicted in FIG.
13A does the opposite; the transition from the opaque film to the
transparent film across the width of the translucent strip begins
at the outer edge of the translucent strip as a more severe
transition and then decelerates the rate of increase in the degree
of transmittance towards the inner edge of the translucent
strip.
[0059] FIG. 14 depicts another embodiment of the vapor shield of
the present invention. This embodiment of the shield 300 comprises
a single plate with a length 308, a major width 314, a minor width
312, and at least one stepped change, or transition, in width 340
between said major width 314 and said minor width 312. The widths
of the transparent, translucent, and opaque film strips created
using this embodiment of the vapor shield will again be defined by
the major and minor widths of the shield, and the width of the film
sheet. However, the degree of transmittance in the translucent
strip will undergo at least one step change which corresponds to
the at least one step change 340 in the width of the shield. This
embodiment gives practitioners of the present invention an
alternative way of controlling the transition from opaque film to
transparent film.
[0060] FIGS. 14A through 14C depict other embodiments of the vapor
shield of the present invention. Each of these embodiments comprise
a single plate with a length 388 and a width 306 that remains
constant throughout its length 388. These embodiments, when
considered in comparison to each other and FIG. 6, demonstrate that
these embodiments of the shield have varying lengths 388 that are
shorter than the shield length 308 depicted in FIG. 6. Whereas the
length 308 of the shield in FIG. 6 is long enough to completely
shield the strip of film below it from receiving any metal during
the metallization process (thus making it transparent), the shorter
length 388 shields of FIGS. 14A through 14C are short enough allow
the area of film underneath to receive some metal during the
metallization process, but prevent it from becoming fully
metallized, thereby making the strip of film directly underneath
the shield translucent. Furthermore, as the length of the shield
388 is shortened in these embodiments, the degree of transmittance
for the translucent strip directly underneath the shield will
decrease. An example of a sheet of partially metallized film using
an embodiment of the shields depicted in FIGS. 14A through 14C is
depicted in FIG. 15, and has the following characteristics: (a) one
translucent strip 236 with a width 228 equal to the width 306 of
the shield; and (b) two opaque strips, each having a width 226
corresponding to the length between an outer edge of the
translucent strip 236 and the corresponding edge of the film
sheet.
[0061] Other embodiments of the present invention are possible by
varying the length of the embodiments of the vapor shields depicted
in FIGS. 9, 11, 12, 13A and 13B. In a similar manner to that
described with reference to FIGS. 14A through 14C above, a shorter
length 388 will allow the film strip underneath the shield's minor
width to receive some metal during the metallization process,
thereby making it translucent. For example, if the length 308 of
the embodiment in FIG. 9 is shortened, and its major width 314 is
less than the width of the film sheet being metallized, it will
produce a film sheet with the following characteristics, as
depicted in FIG. 16: (a) one translucent strip 236 having a width
228 approximately equal to the minor width 312 of the shield and
having an approximately constant degree of transmittance throughout
its width 228; (b) two translucent strips 232, each having a width
224 approximately equal to half the difference between the major
314 and minor 312 widths of the shield 300, and each having a
degree of transmittance that varies along its width 224; and (c)
two opaque strips 230, each having a width 226 from the outer edge
of the translucent strip 232 to the corresponding edge of the film
sheet.
[0062] FIG. 17A and 17B depict still another embodiment of the
present invention. This shield in this embodiment comprises two
plates 302, 304 each with two faces and an edge, disposed adjacent
to one another, face to face. Furthermore, the plates are movably
disposed such that one or both plates are able to move in the
lengthwise axial direction relative to one another. Each plate is
similar to the embodiment of FIG. 11, having saw teeth 330 along
its length. In a first position, depicted in FIG. 17A, all of the
saw teeth 330 on each plate are fully aligned with one another.
When the shield is used in the first position, the width of the
translucent strip of film will be approximately equal to the height
of the saw teeth 332, and the width of the transparent strip of
film will be approximately equal to the minor width 312 of the
shield. As described previously, the plates are movably disposed
such that one or both plates can be shifted in the direction of the
plates' longitudinal axes to a second position. In the second
position, depicted in FIG. 17B, none of the saw teeth 330 on either
plate are fully aligned with the saw teeth 330 of the other plate.
In the second position, the minor width 312 of the shield is
increased, and the effective height 332 of the saw teeth is
decreased. A sheet of film that is metallized using this embodiment
of the shield in the second position will have narrower translucent
strips and a wider transparent strip, than a sheet of film
metallized using this shield in the first position. In addition,
when the shield is used in the second position the translucent
strip will have a more rapid change in transmittance across its
width. This arrangement gives a practitioner of the present
invention the ability to finely tune the properties of the
partially metallized film sheet, in that the widths of the
transparent strip and the translucent strips can be changed to suit
different applications without the need to replace one shield with
another.
[0063] FIGS. 18A, 18B and 18C depict another embodiment of the
present invention. This shield in this embodiment comprises two
plates, each with two faces and an edge, disposed adjacent to one
another, face to face. Furthermore, the plates are movably disposed
such that one or both plates are able to move in the lengthwise
axial direction relative to one another. Each plate is a solid
plate that contains at least one opening 390 comprising at least
one target shape 398. The target shape can be, for example, a
product logo, as depicted in FIG. 18C, or a graphic design shape.
The at least one target shape 398 is the same for both plates. In a
first position, depicted in FIG. 18B, the plates are arranged such
that the at least one opening 390 in one plate is not aligned with
the at least one opening 390 in the bottom plate. Therefore, in the
first position, during metallization no vaporized metal 200 passes
through the at least one opening 390 and the entire strip of film
beneath the shield remains transparent. In a second position,
depicted in FIG. 18C, the plates are arranged such that the at
least one opening 390 in each plate is aligned with the other.
Therefore, in the second position, during metallization vaporized
metal 200 is allowed to pass through the at least one opening and
mark 394 the film with the target shape 398. During metallization,
the plates are periodically shifted from the first position to the
second position and rapidly back to the first position. If the
plates are left in the second position too long, the target shape
398 will bleed in the direction of the film's travel. In one
embodiment, the partially metallized film will have a transparent
strip underneath the plates with periodic target shapes 398 marked
394 within the transparent strip. In this embodiment, opaque strips
will border the transparent strip. Also note that features of
previously discussed embodiments, such as the saw teeth of the FIG.
11 embodiment, or the trapezoid of FIG. 9, can be incorporated into
this embodiment to provide a gradual transition from opaque film to
transparent film.
[0064] As stated previously, FIG. 10 depicts one embodiment of a
partially metallized film sheet of the present invention with a
gradual transition from opaque film to transparent film, which is
made using one embodiment of shield of the present invention. This
partially metallized film strip can, in turn, be used with the
machine depicted in FIG. 3 to create a multi-layered packaging film
sheet. FIG. 19 depicts a cross section of one embodiment of a
partially metallized, multi-layered packaging film sheet utilizing
one embodiment of a shield of the present invention and the
laminate machine depicted in FIG. 3. Most of the layers depicted
therein are similar to the prior art multi-layered packaging film
sheet, except for the metallized layer 116 and the graphics layer
114. (The importance of the graphics layer will be discussed
further below.) As can be seen, the thin metal layer 116 is dense
nearer to the edges of the film sheet, which corresponds to the
opaque strip discussed previously. The dense metal layer then
gradually becomes less dense towards the center of the film sheet,
which corresponds to the translucent strip discussed previously.
The metal layer then disappears altogether near the center of the
film sheet, which corresponds to the transparent strip discussed
previously.
[0065] As discussed previously, the transparent strip runs the
entire length of the partially metallized film sheet. If no
graphics layer 114 were included in the multi-layered packaging
film, the resulting package would have a transparent window that
runs longitudinally along the entire length of the product package.
A transparent product viewing window can thus be framed by
carefully choosing the contents and placement of the graphics
layer. As depicted in FIG. 8, the graphics layer can mask the
transparent, translucent and opaque strips in a transverse
direction across at least one area of the product package, thereby
providing a transparent product viewing window in the unmasked
area. The transparent product window on the food package is thus
defined by at least one longitudinal opaque or translucent strips
and at least one transverse graphic strip, or, preferably, two
transverse graphic strips and/or product logos. Alternatively, a
translucent window can be provided as described previously.
Foodstuffs inside the package can then be easily viewed by
consumers through the window.
[0066] As used herein, the term "package" should be understood to
include any container including, but not limited to, any food
container made up of multi-layer thin films. The partially
metallized film described herein is particularly suitable for
forming packages for snack foods such as potato chips, corn chips,
tortilla chips and the like. However, while the layers and films
discussed herein are contemplated for use in processes for the
packaging of snack foods, such as the filling and sealing of bags
of snack foods, the layers and films can also be put to use in
processes for the packaging of other low moisture products.
[0067] Product packages made using partially metallized films,
wherein approximately 80% of the area of the film used in the
package was metallized, resulted in vastly improved barrier
properties over unmetallized films. For example, in one embodiment
of a package utilizing such partially metallized film, moisture
vapor transmission rates were reduced by about 68% below the MVTR
for the same size package created using unmetallized film. In
another embodiment of a package utilizing such partially metallized
film, the oxygen transmission rate through the package walls was
reduced by about 80% below the OTR for the same size package
created using unmetallized film. In another embodiment, a package
utilizing such partially metallized film and containing 13 ounces
of tortilla chips was able to maintain product freshness (less than
2% product moisture, by weight) for more than eight weeks, whereas
a package made using unmetallized film kept the product fresh for
less than two weeks.
[0068] While this invention has been particularly shown and
described with reference to a preferred embodiment, it will be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and scope of the invention.
* * * * *