U.S. patent application number 10/422385 was filed with the patent office on 2003-12-18 for internally scored film, package and methods of making the same.
Invention is credited to Buelow, Duane H., Hodson, Jay D., Perre, Chad M..
Application Number | 20030231811 10/422385 |
Document ID | / |
Family ID | 29739935 |
Filed Date | 2003-12-18 |
United States Patent
Application |
20030231811 |
Kind Code |
A1 |
Hodson, Jay D. ; et
al. |
December 18, 2003 |
Internally scored film, package and methods of making the same
Abstract
The presently preferred embodiments relate to film structures
that are exposed to focused energy to provide a score line on an
internal layer of the film structure, or on both an internal layer
of a film structure and an outer layer of the film structure. In
addition, the present invention relates to a package that may be
torn along the score line. More specifically, the package may have
a score line provided on an internal layer of barrier material,
such as ethylene vinyl alcohol copolymer, polyvinylidene chloride
copolymer, nylon, or any other laser scorable barrier material. The
score line in an internal layer and/or in the surface of the film
may allow the package to be opened using tearing forces, thereby
exposing a product within the package and allowing a user of the
package to gain access to product that may be contained
therein.
Inventors: |
Hodson, Jay D.; (Greenville,
WI) ; Buelow, Duane H.; (Oshkosh, WI) ; Perre,
Chad M.; (Waupun, WI) |
Correspondence
Address: |
Stephen T. Scherrer
McDermott, Will & Emery
227 West Monroe Street
Chicago
IL
60606-5096
US
|
Family ID: |
29739935 |
Appl. No.: |
10/422385 |
Filed: |
April 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60387198 |
Jun 7, 2002 |
|
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Current U.S.
Class: |
383/208 ;
383/109; 383/203; 383/204; 383/64; 383/9 |
Current CPC
Class: |
B65D 33/2508 20130101;
B29L 2009/00 20130101; B65D 75/5805 20130101; B29C 59/007 20130101;
B29C 2035/0838 20130101; B65D 31/02 20130101 |
Class at
Publication: |
383/208 ;
383/203; 383/204; 383/64; 383/9; 383/109 |
International
Class: |
B65D 033/00 |
Claims
We claim:
1. A film structure comprising: a plurality of layers wherein a
first layer disposed as an internal layer within the film structure
comprises a polymeric material wherein the polymeric material is
scorable by a focused energy source; a score line disposed within
the first internal layer by the focused energy source; and a second
layer of the film structure wherein the second layer is disposed
between the focused energy source and the first layer when the
score line is applied to the first internal layer wherein said
second layer is not scored by said focused energy source.
2. The film structure of claim 1 wherein said first layer is a
barrier material.
3. The film structure of claim 1 wherein said first layer comprises
a polymeric material selected from the group consisting of ethylene
vinyl alcohol copolymer, polyvinylidene copolymer and nylon.
4. The film structure of claim 1 wherein said score line is
provided in the first layer in both the transverse and machine
directions of said film structure.
5. The film structure of claim 1 wherein said score line is a
straight line.
6. The film structure of claim 1 further comprising: an outer layer
comprising a polymeric material that is scorable by a focused
energy source.
7. The film structure of claim 6 wherein said score line is
disposed in both first layer and the outer layer.
8. The film structure of claim 6 wherein said outer layer comprises
a polymeric material selected from the group consisting of
polyethylene terephthalate and biaxially oriented nylon.
9. The film structure of claim 1 further comprising: a third layer
disposed internally within the film structure comprising a
polymeric material that is scorable by the focused energy source;
and a score line in said third layer.
10. The film structure of claim 9 further comprising: an outer
layer comprising a polymeric material that is scorable by the
focused energy source; and a score line in said outer layer.
11. The film structure of claim 1 wherein the focused energy source
is a laser beam.
12. The film structure of claim 7 wherein said second layer is
disposed between the first layer and the outer layer.
13. The film structure of claim 10 wherein said second layer is
disposed between the first layer and the outer layer.
14. The film structure of claim 10 wherein said second layer is
disposed between the third layer and the outer layer.
15. A package for a product comprising: a first film structure
comprising a plurality of layers wherein a first layer disposed
internally within the film structure comprises a polymeric material
wherein said polymeric material is scorable by a focused energy
source and further wherein said film structure comprises a score
line disposed within said first layer by the focused energy source
and further wherein the film structure comprises a second layer
that is disposed between the first layer and the focused energy
source when the score line is applied to said first layer wherein
said second layer is not scored by the focused energy source.
16. The package of claim 15 wherein said first layer is a barrier
material.
17. The package of claim 15 wherein said first layer comprises a
polymeric material selected from the group consisting of ethylene
vinyl alcohol copolymer, polyvinylidene copolymer and nylon.
18. The package of claim 15 wherein said score line is provided in
the first layer in both the transverse and machine directions of
said film structure.
19. The package of claim 15 wherein said score line is a straight
line.
20. The package of claim 15 wherein said first film structure
further comprises an outer layer comprising a polymeric material
that is scorable by the focused energy source.
21. The package of claim 20 wherein said score line is disposed in
both the first layer and the outer layer.
22. The package of claim 20 wherein the outer layer comprises a
polymeric material selected from the group consisting of
polyethylene terephthalate and biaxially oriented nylon.
23. The package of claim 15 wherein the film structure further
comprises a third layer disposed internally within the film
structure comprising a polymeric material that is scorable by a
focused energy source and a score line in said third layer.
24. The package of claim 23 wherein said film structure further
comprises an outer layer comprising a polymeric material that is
scorable by a focused energy source and a score line in said outer
layer.
25. The package of claim 15 wherein said focused energy source is a
laser beam.
26. The package of claim 21 wherein said second layer is disposed
between the first layer and the outer layer.
27. The package of claim 24 wherein said second layer is disposed
between the first layer and the outer layer.
28. The package of claim 24 wherein said second layer is disposed
between the third layer and the outer layer.
29. The package of claim 15 further comprising: a second film
structure heat sealed to said first film structure thereby forming
a cavity within the package for a product.
30. The package of claim 15 wherein said first film structure forms
a first package wall and further wherein a second package wall is
heat sealed to said first film structure to form a cavity within
the package for a product.
31. A method of making a laser-scored film structure comprising the
steps of: providing a multilayer film structure comprising a
plurality of layers wherein a first layer comprises a polymeric
material wherein the polymeric material is scorable by a focused
energy source; exposing said film structure to the focused energy
source; scoring said first layer with said focused energy source;
providing a second layer disposed between the first layer and the
focused energy source when the focused energy source scores the
first layer; and not scoring said second layer when said first
layer is scored.
32. The method of claim 31 wherein said first layer is a barrier
material.
33. The method of claim 31 wherein the first layer is a polymeric
material selected from the group consisting of ethylene vinyl
alcohol copolymer, polyvinylidene chloride copolymer and nylon.
34. The method of claim 31 further comprising the step of:
coextruding said plurality of layers to form said film
structure.
35. The method of claim 31 further comprising the step of:
laminating said plurality of film layers to form said film
structure.
36. The method of claim 31 further comprising the step of: scoring
said first layer in both the machine and transverse directions of
said film structure.
37. The method of claim 31 further comprising the step of:
providing an outer layer of said film structure wherein said outer
layer comprises a material scorable with the focused energy source;
and scoring said outer layer with the focused energy source when
the first internal layer is scored.
38. The method of claim 31 further comprising: providing a third
layer disposed internally within said film structure wherein said
third layer comprises a polymeric material that is scorable by the
focused energy source; and scoring said third layer with the
focused energy source.
39. The method of claim 37 wherein said second layer is disposed
between said first layer and said outer layer.
40. The method of claim 38 wherein said second layer is disposed
between said third layer and said outer layer.
41. The method of claim 31 wherein said focused energy source
comprises a laser beam.
42. A film structure comprising: a plurality of layers wherein at
least one of the plurality of layers has a score line disposed
therein, wherein the film structure has a tensile strength across
the score line of less than about 6.5 lb/in.
43. The film structure of claim 42 wherein the tensile value of the
film structure has a tensile strength across the score line of less
than about 4 lb/in.
44. The film structure of claim 42 further comprising: an internal
layer wherein the score line is disposed in the internal layer.
45. The film structure of claim 42 further comprising: a first
internal layer; and an outer layer, wherein the score line is
disposed in both the internal layer and the outer layer.
46. The film structure of claim 45 further comprising: a second
internal layer disposed between the first internal layer and the
outer layer wherein said score line is not disposed within the
second internal layer.
47. The film structure of claim 42 wherein said score line is
disposed in said film structure via a focused energy source.
48. The film structure of claim 47 wherein said focused energy
source is a focused laser beam.
49. The film structure of claim 42 wherein said film structure is
between about 2 mils and about 10 mils thick.
50. The film structure of claim 42 wherein said film structure is
between about 4 mils and about 8 mils thick.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a film structure that is
irradiated by a focused laser beam or other focused energy source
to provide a score line on an internal layer of the film structure,
or on both the internal layer of a film structure and an outer
layer of the film structure. In addition, the present invention
relates to a package that may be torn along the score line. More
specifically, the package may have a score line provided on an
internal layer of barrier material, such as ethylene vinyl alcohol
copolymer, polyvinylidene chloride copolymer, nylon, blends thereof
or any other laser scorable barrier polymeric material. In
addition, the package may have a recloseable feature to open and
then reclose the package, such as, for example, a zipper or an
adhesive. The score line on an internal layer and/or on the surface
of the film may allow the package to be more easily opened using
pull-apart forces, thereby exposing a product within the package
and allowing a user of the package to gain access to product that
may be contained therein.
BACKGROUND OF THE INVENTION
[0002] It is generally known to provide a line of weakness on a
surface of a film structure via a focused laser beam. The focused
laser beam is typically applied to the film in a first direction,
such as in the machine direction of the web after extrusion or
after being unwound from a roll. As a web of polymeric film, made
via conventional extrusion or extrusion laminating methods, moves
in the machine direction, the focused laser beam vaporizes the
outer layer of the web thereby leaving a very thin line of weakness
in the web material. Typically, the focused laser beam may vaporize
the polymeric material of a single layer of material, such as a
surface layer of the material, so that the web may be torn using
digital pull-apart forces.
[0003] Many conventional polymeric materials are known to be very
receptive to absorbing focused laser energy, typically focused
infrared radiation. These polymeric materials include, for example,
biaxially oriented polyethylene terephthalate (PET), biaxially
oriented nylon (BON), nylon, paper, cellophane, polyvinylidene
chloride copolymer (PVdC), or ethylene vinyl alcohol copolymer
(EVOH). However, certain other thermoplastic polymers are not as
susceptible to infrared laser energy at the energy level exposure
of the presently preferred embodiments, such as polyolefins like
low density polyethylene (LDPE) and polypropylene.
[0004] Score lines are typically applied to a film structure in a
first direction, as noted above, such as in the machine direction
of a web of film. However, score lines may also be applied in two
different directions, such as in the machine direction of the web
and the transverse direction of the web.
[0005] Typically, score lines applied to film structures useful for
packages allow a user to gain access to a recloseable feature
disposed on the package. Recloseable features are utilized on
flexible plastic packaging to allow an individual to gain access to
a product contained therein, and to then seal the product within
the packaging for later use. For example, a recloseable plastic
zipper can be incorporated into the plastic packaging. The plastic
zipper typically is attached on an end of the packaging and
utilized to provide an opening in the end of the package.
Alternatively, the plastic zipper is attached to inside surfaces of
the package and is exposed when a portion of the plastic packaging
is removed from the plastic packaging.
[0006] The flexible plastic packaging may be provided with a
feature that allows the portion of the plastic packaging to be
removed from the plastic packaging thereby exposing the recloseable
feature. This feature is typically a score line that is used to
allow the portion of the plastic packaging to be removed, thereby
exposing the recloseable feature.
[0007] Packages are known that contain a product, such as, for
example, a cheese product. A typical package consists of two flat
multilayer films that are heat sealed on three sides to provide a
compartment therein. For example, a single multilayer film is
folded and sealed on its sides to provide the package. On the
fourth side, a resealable feature is provided for opening and
closing the package to add and/or remove the product from the
package. The recloseable feature may be a zipper that opens or
closes the package when the slider is moved laterally over the open
end of the package. However, the open end of the package containing
the recloseable feature must be initially hermetically sealed to
keep and store the product that is contained therein. A typical
hermetic seal is provided below the zipper, which is separated by
pull-apart forces when the package is opened for the first
time.
[0008] Alternatively, the zipper is provided on inside surfaces of
the package. The outer surfaces of the package therefore extend
over the zipper and are hermetically sealed at a position over the
zipper thereby providing a sheath over the zipper. Not only does
this configuration provide a hermetic seal for the package, but
also the sheath further protects the zipper. To remove the sheath,
straight line or patterned score lines (i.e. two dimensional, or
provided in both the machine and transverse directions of the film)
are provided so that the sheath can be torn and the zipper
exposed.
[0009] FIG. 1 illustrates a prior art package 500 with a sheath 501
extending over a zipper 504 and having a one-dimensional score line
502 that extends horizontally across the sheath 501 at a position
below the zipper 504. When the sheath 501 is torn at the score line
502, made easier by the use of a notch 506 in the side of the
package 500, the zipper 504 is exposed, and the package 500 may be
opened or closed by the zipper 504.
[0010] Typically, barrier materials are utilized in film structures
and packages that contain products that can be damaged by oxygen,
moisture or other gases. Typical barrier materials may include
polyvinylidene chloride copolymer (PVdC) and ethylene vinyl alcohol
copolymer (EVOH), nylon, blends thereof, or any other laser
scorable barrier material known to one having ordinary skill in the
art. Many of these materials have limitations, however.
Polyvinylidene chloride copolymer is susceptible to yellowing
during cross-linking of the films by irradiation, which also tends
to break down the barrier properties of the polyvinylidene
chloride. In addition, EVOH has a relatively low melting
temperature, and may be damaged if extruded with polymers having
relatively high temperature melting points.
[0011] A known process of coextruding and laminating heat sensitive
materials is described in U.S. Pat. Nos. 5,106,562, 5,108,844,
5,190,711 and 5,236,642 and 6,500,514, which are hereby
incorporated by reference in their entireties. Various methods are
disclosed for reducing the impact of higher temperature polymeric
meltstream elements on a lower temperature polymeric meltstream.
The methods may include super-cooling the hotter meltstream element
below the melting temperature but above the crystallization
temperature, exposing one or more meltstream elements to an
undesirable thermal condition for a limited period of time, and/or
using one or more layers as a heat sink via encapsulation.
[0012] Specifically, these patents describe methods of
encapsulating one film layer by another material. The '562 and '844
patents specifically relate to PVdC or, preferably, PVdC-MA core
materials with ethylene vinyl acetate copolymer ("EVA") or ethylene
methyl acrylate copolymer ("EMA") or blend's thereof encapsulating
the core material. The encapsulated PVdC or PVdC-MA is, therefore,
protected from the high temperatures of the coextrusion process.
Generally, the encapsulation method uses an encapsulator having a
crosshead mandrel with a central bore to receive a first meltstream
element from an extruder. A second polymeric meltstream is fed
through a sleeve via an inlet passage into the encapsulator. As the
second meltstream enters the encapsulator, it splits and flows
around the first meltstream. Consequently, the second meltstream
completely surrounds the first meltstream, thereby forming a
combined meltstream. The second meltstream forms a continuous layer
about the circumference of the first meltstream completely
surrounding the first meltstream. Thus, the first and second
meltstreams maintain their individual identities while the first
meltstream is completely surrounded by and encapsulated within the
second meltstream. The combined meltstream may then be fed through
a transport pipe to a feedblock for coextrusion with one or more
other layers to produce a multilayer film.
[0013] In addition, other film structures containing barrier layers
may be utilized in the present invention, such as those film
structures described in U.S. Pat. Nos. 6,068,933 and 09/411,671 to
Shepard et al., entitled "Thermoformable Multilayer Polymeric
Films", which are expressly incorporated herein by reference. These
films may include alternating layers of nylon and adhesive, with
one or more layers of EVOH as internal barrier layers.
[0014] Typically, film structures having barrier materials, such as
polyvinylidene chloride, ethylene vinyl and alcohol, nylon, blends
thereof, or any other laser scorable barrier material which are
susceptible to being vaporized by a focused laser beam, are
carefully scored via the laser beam so that the barrier layers are
not damaged via the focused laser beam, such that the barrier
characteristics of a package made from these film structures are
not affected by the scoring of the film structure. However, it has
been found that laser scoring one or more internal barrier layers
does not appreciably decrease the barrier properties of packages
made from the films because the area of scoring is so small.
Typical laser score lines are 0.003-0.006 inches thick.
[0015] If only surface layers of a film structure are scored and
internal layers of film structures are left intact, it may be
difficult to tear a package made from the film structure cleanly,
evenly or easily. When tearing forces are applied to tear a package
along a laser scored tear line wherein the surface layer is the
only layer that is scored, the tensile strength of the film
structure may be relatively high making it difficult to tear the
package cleanly.
[0016] A need exists, therefore, for a film structure having a
plurality of layers wherein an internal layer of the film
structure, or both the internal layer of the film structure and an
outer surface layer of the film structure is scored via a focused
laser beam so that the film structure may more easily be torn using
tearing forces. A need further exists for internal scoring of a
film structure via a focused laser beam or other focused energy
source wherein the film structure is useful as a package so that
the package retains or mostly retains its barrier properties and/or
hermetic properties. Still further, a need exists for methods of
making the film structures and packages made therefrom.
SUMMARY OF THE INVENTION
[0017] The present invention relates to flexible film structures
having a plurality of layers wherein one or more of the internal
layers, such as a layer of EVOH copolymer, PVdC copolymer, nylon,
blends thereof, or other laser scorable barrier materials is scored
via a focused laser beam or other focused energy source. Further,
the present invention relates to flexible film structures having a
plurality of layers wherein one or more of the internal layers and
an outer surface layer of the film structure are scored via a
focused laser beam or other focused energy source. In addition, the
present invention relates to packages made therefrom, and methods
of making the film structures.
[0018] In addition, the present invention relates to film
structures containing one or more barrier layers of, preferably,
ethylene vinyl alcohol copolymer, although other barrier layers are
contemplated by the present invention. The film structures may be
coextruded or extrusion laminated to other film layers, including
an outer layer of a laser scorable polymeric material, such as PET
or BON. A focused laser beam, or other focused energy source, can
be applied to a film structure in a first direction, such as the
machine direction, in a second direction, such as the transverse
direction, or both the machine and transverse directions to provide
a package having a score line on the internal barrier layer or both
an internal layer and an outer layer of the film structure. Of
course, film structures made with barrier layers may be made
according to any method known in the art, via extrusion lamination
or coextrusion, for example, such as via encapsulation as described
in U.S. Pat. Nos. 5,106,562, 5,108,844, 5,190,711 and 5,236,642 and
6,500,514.
[0019] To this end, in an embodiment of the present invention, a
film structure is provided having a plurality of layers wherein a
first internal layer is a barrier material. The film structure has
a score line on the internal layer of barrier material, and
optionally includes a score line on both an internal layer of the
film structure and an outer surface layer of the film structure. A
preferred film structure includes a first layer of EVOH, and
various other layers, in the following structure:
PET or BON/Ink/LDPE/PE/tie/EVOH/tie/heat sealant
[0020] The tie layers may be any polymeric material that may be
useful to bond the EVOH layers to the heat sealant layer or the
layer of polyethylene. The heat sealant layer is comprised of any
polymeric material useful to provide a seal when heat is applied to
the film structure. Typical materials include ethylene vinyl
acetate copolymer and/or linear low density polyethylene, for
example.
[0021] In an alternate embodiment of the present invention, a
package is provided comprising a first side wall; a second side
wall wherein the first side wall and the second side wall are
bonded together on edges to form a pouch having a space therein for
storing a product; a recloseable feature disposed on inside
surfaces of the side walls wherein the side walls are sealed
together on an end of the package; and a score line in at least one
side wall from a first edge to a second edge of the at least one
side wall. The package comprises an internal layer of a barrier
material of EVOH copolymer. The score line may be a straight score
line or may be a patterned score line, i.e., a score line disposed
in both the machine and transverse directions of the film structure
utilized as a package wall. The score line creates a line of
weakness on the EVOH layer disposed as an internal layer in the
package.
[0022] In an alternate embodiment of the present invention, a
method of making a scored film wherein said score line is applied
via a focused laser beam or other focused energy source on an
internal layer is provided. The method includes providing a film
structure having a plurality of layers wherein a first internal
layer comprises a barrier material. The method further includes
applying a focused laser beam or other focused energy source to the
film structure wherein the focused laser beam or other focused
energy source produces a line of weakness in the barrier layer. In
addition, the film layer may comprise an outer layer of PET or BON
that may be scored via the laser beam or other focused energy
source as well.
[0023] In an alternate embodiment of the present invention, a
method of making a package is provided comprising the steps of
providing a first wall and a second wall; laser scoring a line of
weakness in at least one side wall; providing a recloseable feature
attached at a first end of the side walls; attaching the
recloseable feature to inside surfaces of the side walls; and
sealing the first wall and the second wall together on edges of the
walls to form a pouch having a space therein for a product, wherein
said score line is disposed above the recloseable feature at edges
of the side walls and further wherein said score line is a straight
line or traces a path to below the recloseable feature between the
edges of the side walls. The package further comprises an internal
layer of a barrier material. Further, the score line may create a
line of weakness on the internal barrier layer.
[0024] It is, therefore, an advantage of the present invention to
provide a film structure having a plurality of layers wherein one
or more of the layers is an internal layer of laser scorable
barrier material wherein a focused laser beam imparts a line of
weakness in the internal barrier layer. The barrier properties of a
package made from the film structure remain relatively unchanged
after scoring the barrier layer with the focused laser beam.
[0025] In addition, it is an advantage of the present invention to
provide a film structure having a plurality of layers wherein an
outer layer of the film structure comprises a laser scorable
polymer such as PET or BON, and further wherein an internal layer
is made from a barrier material of ethylene vinyl alcohol
copolymer. A focused laser or other focused energy source applied
to the film structure creates a line of weakness in both the outer
layer of laser scorable polymer and the internal layer of EVOH. The
line of weakness aids in tearing the film structure when pulled
apart by digital pull-apart forces.
[0026] It is further an advantage of the present invention to
provide a package made from a film structure that may keep and
store a product, such as a product that may have a limited
shelf-life. For example, the product may be a food product, such as
cheese. The package may be hermetically sealed on all sides and may
further restrict the movement of moisture and/or oxygen through the
walls of the package, thereby keeping the product contained therein
fresh. The package may further have a score line in at least an
internal layer of said film structure or on both an internal layer
and an outer layer of said film structure.
[0027] Still further, it is an advantage of the present invention
to provide a straight line or patterned score line on an internal
layer of a film structure or on both an internal layer and an outer
layer of a film structure thereby allowing a portion of the film
structure to be removed by tearing forces. The removable portion
may allow access to an internal space within a package made by the
film structure or to expose a recloseable feature disposed on the
package.
[0028] Additional features and advantages of the present invention
are described in, and will be apparent from, the detailed
description of the presently preferred embodiments and from the
drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0029] FIG. 1 illustrates a plan view of a prior art package having
a zipper that does not extend to the edges of the package and a
one-dimensional score line provided across the package.
[0030] FIG. 2 illustrates a cross-sectional view of a film
structure having a plurality of layers wherein the film structure
has a score line wherein a first outer layer is vaporized, and an
internal layer of a barrier material is partially or completely
vaporized.
[0031] FIG. 3 illustrates a plan view of a flexible pouch having a
zipper and further having a patterned score line provided on the
flexible pouch in an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0032] The present invention relates to a film structure that is
scored by a focused laser beam or other focused energy source to
provide a line of weakness or score line on an internal layer of
the film structure, or on both the internal layer of a film
structure and an outer layer of the film structure. In addition,
the present invention relates to a package made from the film
structure that may be torn along the score line. More specifically,
the package may have a score line provided on an internal layer of
EVOH copolymer, PVdC copolymer, nylon, blends thereof, or any other
laser scorable barrier polymeric material. In addition, the package
may have a recloseable feature to open and then reclose the
package, such as, for example, a zipper or an adhesive. The score
line on an internal layer and/or on the surface of the film may
allow the package to be opened using tearing forces, thereby
exposing a product within the package and allowing a user of the
package to gain access to product that may be contained
therein.
[0033] Although the present description of the presently preferred
embodiments describes the film layers as being "laser scorable" and
that the internal layers and outer layers of the film structures
are scored by a focused laser beam, it should be noted that any
focused energy source that provides a score line or otherwise
provides a line of weakness on an internal layer or on both an
internal layer and an outer layer is contemplated by the present
invention.
[0034] The present invention generally relates to a film structure
having a plurality of layers, wherein a first layer comprises a
laser scorable polymeric material that is disposed as an outer
layer of the film structure. Said laser scorable polymeric material
may include, for example, PET or BON, although any other polymeric
material that is laser scorable is contemplated by the present
invention. In addition, the film structure comprises an internal
layer of a barrier material, such as, for example, EVOH copolymer,
PVdC copolymer, nylon, blends thereof, or any other laser scorable
barrier material. In addition, the film structure comprises a
polymeric material that is not laser scorable with the laser beam
that scores the internal layer or both the internal layer and the
outer layer, such as polyolefin or the like. The non-scorable
internal layer may preferably be disposed between the laser
scorable internal layer and the laser scorable outer layer. Of
course, however, the non-scorable internal layer may be disposed at
any position within the film structure.
[0035] A film structure having an outer layer of PET or BON, or
other laser scorable outer layer, and further having a barrier
layer, such as a layer made from EVOH copolymer, PVdC copolymer,
nylon, blends thereof, or any other laser scorable barrier
material, will readily vaporize when a focused laser beam is
applied to the film structure at the appropriate energy level.
Specifically, a focused laser beam will vaporize most, if not all,
of the outer layer of PET or BON, while not vaporizing layers of
polyolefinic material, such as polyethylene or polypropylene that
may be utilized as adhesive or tie layers or heat sealant layers.
The barrier layer, however, may readily vaporize via the focused
laser beam, and may vaporize within the film to form a bubble or
void in the film structure. Typically, sufficient laser energy will
vaporize up to 100% of the outer layer of laser scorable polymeric
material and up to 100% of laser scorable barrier material disposed
as an internal layer of the film structure. It should be noted,
however, that the laser energy need not vaporize 100% of the laser
scorable internal layer or 100% of either or both of the laser
scorable internal layer and the laser scorable outer layer. Partial
scoring of each of these layers, as well as any other laser
scorable layer within the film structure, may impart sufficient
weakness to provide an easily tearable film structure and,
consequently, a package made therefrom.
[0036] A film having both an external score line (such as a score
line within the PET or BON layer as described above) and an
internal score line will have at least two layers that are weakened
or scored, thereby providing lower tensile values and an easier
opening package. In addition, the barrier characteristics of a
package made from the film are not drastically reduced by scoring
the internal layer of barrier material.
[0037] Tensile values may typically be about 7 lbs/in or greater
for similar films as described above only having the outer layer of
the film structure scored. However, with higher energies, scoring
an internal layer can lower tensile values to 6.5 lbs/in or
lower.
[0038] Focused laser energy useful for the present invention may be
any apparent to one having ordinary skill in the art to score
polymeric material or otherwise vaporize polymeric material. A
typical laser energy source is a CO.sub.2-based infrared energy
laser having a power range of between about 10 and about 50 watts.
Since typical laser beams may be split, such as by a partially
reflective mirror or the like, the wattage of each focused laser
beam from a single laser source that is between about 10 and 50
watts is about 5 to about 25 watts. Of course, the power level
sufficient to score both the outer layer of laser scorable
polymeric material and an internal barrier layer depends on a
number of factors, including the proper focusing of the lens and
the speed of the web. For example, web speeds may range between
about 50 ft/min and about 1000 ft/min, depending on the complexity
of the score line. A straight line score in the machine direction
of the web may be run at relatively fast speeds. However, laser
energy should be relatively high for fast web speeds. For example,
if a web is moving at about 1000 ft/min, then the focused laser
beam may be about 25 watts in order to score both the outer layer
and the internal layer. Of course, the precise wattage necessary
should be determined via experimentation.
[0039] A preferred film structure of the present invention is as
follows:
48ga PET or 60 gauge BON/Ink/LDPE/PE/tie/EVOH/tie/heat sealant
[0040] Specifically, the film structure may have an outer layer of
48 gauge polyethylene terephthalate or 60 gauge biaxially oriented
nylon followed by a printed layer of ink, with a layer of LDPE and
another layer of PE. Next to the layer of PE is a tie layer that
ties the PE layer to a layer of a barrier material comprising EVOH
copolymer. A heat sealant layer is provided as a surface of the
film structure wherein said heat sealant layer is bonded to said
EVOH layer with another tie layer. Although the PET or BON layer is
described as 48 gauge and 60 gauge, respectively, any layer
thickness may be utilized and is contemplated by the present
invention. In addition, the thicknesses of all layers of the
present invention may be any thickness for making a film structure
useful for packaging products, and which may be laser scorable.
[0041] FIG. 2 illustrates a cross-sectional view of a film
structure 100 having an outer layer 102 of a laser scorable
polymeric material such as PET or BON and an internal layer 104 of
EVOH copolymer that has been laser scored via a focused infrared
laser beam. As shown, the outer layer 102 of PET (or BON) is 100%
vaporized to expose layers of polyethylene, such as low density
polyethylene. The internal layer 104 of EVOH is also scored and a
void is shown that pushes or bubbles toward the bottom of the film
structure because of the relative thinness of the bottom of the
film structure. The remaining layers, an LDPE layer 106, a PE layer
108, a tic layer 110, another tie layer 112, and a sealant layer
114, all remain intact and unscored by the focused laser beam.
[0042] Any film structure containing an internal layer of EVOH, or
any other internal layer that may be laser scorable, may be used.
For example, film structures as described in U.S. Pat. Nos.
5,106,562, 5,108,844, 5,190,711 and 5,236,642 and 6,500,514 are
contemplated as being laser scorable in both an internal layer and
an outer layer of the film structures described therein.
[0043] In addition, those film structures described in U.S. Pat.
No. 6,068,933 and U.S. patent application Ser. No. 09/411,671
entitled "Thermoformable Multilayer Polymeric Film" may be
utilized. The film structure described in U.S. Pat. No. 6,068,933
and U.S. patent application Ser. No. 09/411,671 includes seven
layer film structures having alternating layers of nylon and
adhesive, with an outer layer of a laser scorable polymeric
material, such as nylon, and zero to one or more internal layers of
EVOH. A laser beam may be applied to a film structure thereby
scoring one or more internal layers of nylon, and the EVOH layers
or layers, if present.
[0044] The following describes an example of a particular package
that may be made from the film structures described above. Although
the packages and pouches are written in terms of having a score
line provided in two dimensions (i.e., the transverse and machine
directions of the film structures), or otherwise having a patterned
laser score, any type of score line may be provided in the film
structure, such as straight score lines or patterned score
lines.
[0045] Now referring to the figures, wherein like numerals refer to
like parts, FIG. 3 illustrates a food pouch 1 in an embodiment of
the present invention. The food pouch 1 may have two side walls 10,
12 made from multilayer flexible film that are heat sealed together
to form a space 14 wherein a food product 16, or any other product
16, may be stored. The food product may preferably be a dairy
product, such as a cheese product, that may be stored within the
pouch 1. The multilayer flexible film of the food pouch 1 may
preferably have the following film structure:
48ga PET or 60ga BON/Ink/LDPE/PE/Tie/EVOH/Tie/heat sealant
[0046] The edges of the side walls 10, 12 are heat sealed together
to form seals 18, 20, 22 and 24. The seals may be hermetically
sealed to provide a barrier for the movement of oxygen or moisture
through the edges of the pouch 1. On one end 28 of the pouch 1 may
be provided a recloseable feature that may preferably comprise a
zipper system 30. Of course, however, other recloseable features
may be utilized in this invention without detracting from the
present invention. The zipper system 30 may comprise a first zipper
portion 32 that is bonded to an inside surface of the side wall 10.
In addition, the zipper system 30 may comprise a second zipper
portion 34 that is bonded to an inside surface of the side wall
12.
[0047] The first zipper portion 32 may comprise a zipper track
portion 36 that is attached to a film extender 38. The film
extender 38 may be attached to the inside surface of the side wall
10 at seal 40. Similarly, the second zipper portion 34 may comprise
a zipper track portion 42 that is attached to a film extender 44.
The film extender 44 may be attached to the inside surface of the
side wall 12 at seal 46. The seals 40, 46 may extend over an entire
width of the pouch 1, including within the seals 20, 24. The zipper
track portions 36, 42 may be connectable together when a slider 48
is moved along tracks that may be provided on the zipper track
portions 36, 42. The slider 48 may close the zipper track portions
36, 42 together to form a tight seal between the seals 20, 24.
[0048] A score line 50 is provided in at least one of the side
walls 10, 12. In a preferred embodiment, the score line 50 may be
provided in both of the side walls 10, 12. The score line 50 may
have a first curved portion 52a that may start on an edge of the
pouch 1 and be disposed above the zipper track portions 36, 42,
when the pouch is oriented so that the zipper system 30 is at the
top of the pouch 1. The curved portion 52a may trace a path that
travels below the zipper track portions 36, 42 until the curved
portion 52a meets a generally straight portion 52b that traces a
path across the face of the pouch 1 until the score line 50 reaches
the proximity of the other end of the pouch 1. The score line 50
then meets a second curved portion 52c that traces a path from
below the zipper track portions 36, 42 to above the zipper track
portions 36, 42 to the edge of the pouch 1. Of course, the score
line 50 may be any shape that may be apparent to one having
ordinary skill in the art including tracing a path that goes below
and above the zipper track portions 36, 42 a plurality of times
between the ends of the pouch 1. To facilitate the tearing of the
score line 50 when digital pull-apart forces are applied, notches
54, 56 may be provided on edges of the pouch to allow a tear to
form in the side walls when pulled by digital pull apart
forces.
[0049] The score line 50 is provided in the side wall 10 and/or 12
so as to allow an individual to grip the end 28 of the pouch 1 and
tear the end 28 from the pouch 1 along the path of the score line
50. Because the zipper track portions 36, 42 extend from one edge
of the pouch 1 to the other edge of the pouch 1, the portion of the
pouch 1 that is removed must clear the portions of the zipper track
portions 36, 42 that are heat sealed within the heat seals 20, 24.
However, the portion of the pouch 28 that is removed extends below
the zipper track portions 36, 42 so as to allow an individual to
have easy access to, the slider 48 to move the slider 48 back and
forth along the zipper track portions 36,42.
[0050] The score line 50 may be scored via, preferably, a laser
beam, as described above. The score line has a tensile value
measured across the line of weakness of between about 3 and about
10 lbs/in. In addition, and further as described above, the film
structure having the score line 50 may have one or more internal
barrier layers that are internally scored via the laser beam to
provide a film structure having an internal score line and,
optionally, a score line on both the internal layer, such as the
barrier layer, and an outer layer of the film structure to decrease
the tensile value of the film structure. Preferably, the film
structure has a tensile value measured across the line of weakness
of about 6.5 lbs/in or lower.
[0051] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein would be apparent to those skilled in the art. Such changes
and modifications may be made without departing from the spirit and
scope of the present invention and without diminishing its
attendant advantages. It is, therefore, intended that such changes
and modifications be covered by the appended claims.
* * * * *