Note: Descriptions are shown in the official language in which they were submitted.
CA 02459589 2004-03-03
HIGH MODULUS THERMOPLASTIC F1LMS
AND THEIR USE AS CASH: REG[STER TAPES
Field of the Invention
The present invention is generally directed to thermoplastic films of
sufficient
stiffness and opacity for use in high speed printing equipment. Specifically,
this
invention describes an improved cash register receipt tape produced from a
thin, niulti-
layer, coextruded, machine direction oriented, heat stabilized thermoplastic
film.
Background of the Invention
Currently, point-of-sale cash register receipts are printed on a paper tape
using
inkjet, thermal image or ribbon printers. Numerous patents describe inventions
of plastic
films to replace these paper tape receipts. The primary focus for many of
these
inventions is to describe a plastic printer register receipt that is "co-
recyclable" with
existing plastic shopping bags.
For example, U. S. Patent 5,229,218 to Dobreski presents a general description
of
plastic materials for use as a register receipt tape that is claimed to be
recyclable. The
concepts embodied in the Dobreski patent were continued in U. S. Patent
6,284,177 to
Ewing, which similarly provides a somewhat general description of a recyclable
plastic
register tape. ln the Backgroutid section, the `177 patent notes that t.he
:Dobreski patent,
"does not provide sufficient details to select a specific thermoplastic
material which is
economical, of sufficient strength and which can be reliably fabricated into a
printable
flm."
U.S. Patent 6,407,034, also to Ewing, discloses a recyclable register tape in
which
the base sheet materials and thermally printed media are combined prior to
production of
the film.
CA 02459589 2004-03-03
The above-described prior art laudably recognizes the benefit of providing a
thin,
thermoplastic register tape as a replacement for prior paper tapes.
Specifically, the
current commonly used paper tape ranges in thickness from 2.1 to 2.5 mils. A.
cash
register paper tape roll 3-inches in diameter wound on a 7/8-in. diameter core
contains
230 feet of paper register tape. A 3 inch diameter roll of a 0.5 rnil thick.
thermoplastic
tape wound on a 7/8 in. diameter core contains 1,077.9 feet of thermoplastic
register tape
or 4.7 times the length included in a similar diameter paper register tape
roll. The
thermoplastic tape therefore should provide numerous economies to firms and
individuals
using cash register printers and receipt printers since the additional tape
length available
in the therinoplastic tape roll should result irt less frequent roil changes
at the cash
register or receipt printer and less storage space for register tape roll
inventory. However,
the prior art to date has failed to yield a thermoplastic tape having adequate
physical
properties to serve as a drop-in replacement for current paper register tapes.
Summary of the I:nvention
I:t is therefore one purpose of the present invention to provide a
thermoplastic
register or receipt tape having sufficient stiffness to run in current receipt
printers. It is a
further purpose of the present invention to provide such a thermoplastic film
with
adequate antistatic properties for printing. Specifically the film must have
sufficient
stiffness in the machine direction and it must also be capable of dissipating
static
electrical charges that accumulate on the film surface as a result of the film
encountering
and separating from printer rollers as it moves through the printer during the
printing
process. Many of the commercial receipt printers are constructed with plastic
cases that
may develop high static electricity charges. If the register film is not
relatively static
free, it may be attracted to the case causing the film to jam during the
printing process.
Similarly a film with insufficient machine direction stiffness will jam during
the printing
process.
Accordingly, the present invention is directed to a multilayer, oriented
thermoplastic composite for use as a. register or receipt tape which includes
a film having
a first outer film surface and a second outer film surface, the film including
a core layer,
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CA 02459589 2004-03-03
and at least a first outer layer having an outermost surFace which is the
first outer film
surface, the first outer layer including a non-migratory anti-static additive,
and a heat
sensitive, thermal image coating on the second outer film surface, wherein at
least one
outer layer includes a pigment and wherein the composite has a I% secant
modul4s in the
machine direction of at least about 150,000 psi, preferably at least about
200,000 psi. In
one embodiment the second outer film surface is the outermost surface of the
core layer
opposite to the first outer layer. However, in a preferred embodiment the film
includes a
second outer layer that has an outermost surface and that outermost surface is
the second
outer film surface bearing the heat sensitive, thermal image coating. The
composite has a
thickness of from about 0.35 mils to about 1.5 mils, preferably from about
0.50 mils to
about 0.75 mils. If the core layer is sandwiched between first and second
outer layers, as
is preferred, the core layer may include a cavitation promoting additive. At
least one of
the layers includes a polymer such as polyethylene, polypropylene, linear low
density
polyethylene, polystyrene or polyester. In one embodiment the film may be
biaxially
oriented. In a preferred embodiment the film is uniaxially oriented in the
machine
direction. Either way, following orientation the film is rendered essentially
non-heat
shrinkable by a heat treatment such as annealing.
Further, the present invention is directed to an oriented thermoplastic
composite
for use as a register or receipt tape which includes a film having a first
outer film surface
and a second outer film surface, the film having at leas t a core layer, with
an anti-static
coating on the first outer film surface and a heat sensitive, thermal image
coating on the
second outer film surface, wherein at least one composite component includes a
pigment
and wherein the composite has a 1% secant modulus in the machine direction of
at least
150,000 psi, preferably at least 200,000 psi. In one embodiment the film
includes an
outer layer having an outermost surface which is the first outer film surface
bearing the
anti-static coating. In one enibodiment the film includes an outer layer
having an
outermost surface which is the second outer film surface bearing the heat
sensitive,
thermal image coating. The overall composite has a thickness of from about
0.35 mils to
about 1.5 mils, preferably from about 0.50 mils to about 0.75 mils. At least
one layer of
the film includes a polymer such as polyethylene, polypropylene, linear low
density
polyethylene, polystyrene or polyester. In one embodiment the film is
biaxially oriented.
3
CA 02459589 2006-03-10
However, in a preferred embodiment the film is uniaxially oriented in the
machine
direction. Either way, the following orientation the film is rendered
essentially non-
heat shrinkable by a heat treatment such as annealing.
The present invention also is directed to a method for making a thermoplastic
composite suitable for use as a register or receipt tape, which includes the
steps of:
a) coextruding a multilayer film having a first outer film surface and a
second outer film surface, the film including a core layer, and at least a
first outer layer having an outermost surface which is the first outer
film surface, the first outer layer having a non-migratory anti-static
additive, and at least one outer layer having a pigment;
b) orienting the film;
c) annealing the film; and
d) applying a heat sensitive, thermal image layer to the second outer film
surface.
In one embodiment the step of orienting involves biaxially orienting. For such
embodiment it is preferred that the product of the machine direction and
transverse
direction stretch ratios is from about 2.OX to about 50X. However, it is
preferred that
the step of orienting is performed by uniaxially orienting the film in the
machine
direction, preferably wherein the machine direction stretch ratio is in the
range of
from about 1.5X to about 10.OX. In one embodiment the step of coextruding is
performed in a blown film process. In another embodiment the step of
coextruding is
performed in a cast film process.
According to an aspect, there is provided a multilayer, oriented thermoplastic
composite for use as a register or receipt tape comprising:
a film having a first outer film surface and a second outer film surface, the
film comprising a core layer, and at least a first outer layer having an
outermost
surface comprising the first outer film surface;
the first outer layer comprising a non-migratory anti-static additive; and
a heat sensitive, thermal image coating on the second outer film surface;
wherein at least one outer layer comprises a pigment and wherein the
composite has a 1% secant modulus in the machine direction of at least about
150,000
psi.
4
CA 02459589 2007-03-06
According to another aspect, there is provided an oriented thermoplastic
composite for use as a register or receipt tape comprising:
a film having a first outer film surface and a second outer film surface, the
film comprising at least a core layer;
an anti-static coating on the first outer film surface; and
a heat sensitive, thermal image coating on the second outer fihn surface;
wherein at least one composite component comprises a pigment and wherein
the composite has a 1% secant modulus in the machine direction of at least
150,000
psi.
According to a further aspect, there is provided a method for making a
thermoplastic composite suitable for use as a register or receipt tape,
comprising the
steps of
a. coextruding a multilayer film having a first outer film surface and a
second
outer film surface, the film comprising a core layer, and at least a first
outer layer
having an outermost surface comprising the first outer film surface, the first
outer
layer comprising a non-migratory anti-static additive, and at least one outer
layer
comprising a pigment;
b. orienting the film;
c. annealing the film; and
d. applying a heat sensitive, thermal image layer to the second outer film
surface.
According to another aspect, there is provided an oriented, thermoplastic
composite for use as a register or receipt tape, comprising:
a) a monolayer film having a first outer film surface and a second
outer film surface;
b) an anti-static coating on the first outer film surface; and
c) a heat sensitive, thermal image coating on the second outer film
surface;
wherein the composite is essentially non-heat shrinkable and has a 1%
secant modulus in the machine direction of at least 150,000 psi; and
wherein at least one structural component has a pigment blended
therein.
4a
CA 02459589 2007-03-06
According to a further aspect, there is provided a method for making a
thermoplastic composite suitable for use as a register or receipt tape,
comprising the
steps of:
a) extruding a monolayer film having a first outer film surface and
a second outer film surface, said monolayer film comprising a
pigment blended therein;
b) orienting the film;
c) annealing the film;
d) surface treating each of the first and second outer film surfaces,
thereby preparing each surface for subsequent coating;
e) applying an anti-static coating to the first outer film surface;
and
f) applying a heat sensitive, thermal image coating to the second
outer film surface.
Brief Description of the Fieure of the Drawin~
The present invention will be described with reference to the following
drawing:
Figure 1 is a schematic, cross-sectional view of a thermoplastic printing or
register tape in accordance with the present invention.
4b
CA 02459589 2006-10-20
Detailed Description of the Preferred Embodiments
Generally, the present invention is directed to a multilayer, oriented
thermoplastic composite for use as a register or receipt tape. Figure 1 of the
drawing
illustrates a preferred embodiment wherein the composite 10 is formed of a
film 12
having at least one outer coating 20. As shown in the embodiment of Figure 1,
film
12 includes a core layer 14, a first outer layer 16, and a second outer layer
18. First
outer layer 16 has an outermost surface which is a first outer film surface 17
and
second outer layer 18 has an outermost surface which is a second outer film
surface
19. In this embodiment, outer coating 20 has been applied to second outer film
surface 19. The overall composite preferably has a thickness in the range of
from
about 0.35 mils to about 1.5 mils, preferably from about 0.50 mils to about
0.75 mils.
Turning to the specific function of each composite component, the core layer
of the film provides the film bulk, the first outer layer provides anti-static
properties,
and the outer coating 20 provides a printable surface. The second outer layer
18 of
the film is preferred but optional. Outer coating 20 may be applied directly
to an
outer surface of the core layer. If outer layer 18 is present it preferably
includes a
pigment which renders the film opaque in order to enhance the visibility of
the
printing. If outer layer 18 is not present at least one of the remaining film
components
should include a pigment. A preferred pigment for use in accordance with the
present
invention is titanium dioxide.
The core layer may be formed of any of a number of thermoplastic polymers
or polymer blends. Preferred polymers for use in the core layer include
polyethylene
homopolymers and copolymers, including low density polyethylene and high
density
polyethylene, polypropylene homopolymers and copolymers, linear low density
polyethylene, polystyrene or polyester. However, any suitable thermoplastic
polymer
or polymers may be employed. The core layer preferably comprises from about
50%
to about 85% of the overall film thickness.
Thus, core layer 14 preferably includes a cavitation promoting additive such
as AmpacetTM 110881, supplied by AmpacetTM Corp., Tarrytown, NY, which is
calcium carbonate and titanium dioxide in a high density polyethylene carrier.
With
such an additive a relatively thick core layer may be formed with a reduced
volume of
polymer. However, a cavitation promoting additive only may be employed if both
outer film layers are present. Otherwise, the additive would render the outer
surface
CA 02459589 2006-10-20
of the core layer, which would comprise an outer film surface, unsuitable for
receiving a coating.
Optionally, the core layer may include a pigment. Inclusion in at least one of
the composite components of a sufficient amount of a pigment to render the
overall
composite opaque is required. However, a reduced amount of pigment may be
employed if it is incorporated into one of the thinner layers or a thin
coating. Thus,
from an economic perspective, if the core layer is the thickest layer, it may
be the
least preferred composite component for carrying the pigment.
The first outer layer 16 provides anti-static properties to the film.
Generally,
there are two classes of anti-static agents, migratory and non-migratory, that
can be
used to dissipate static electricity charges that accumulate on the surfaces
of plastic
films. Each class has advantages and disadvantages. Migratory additives,
either
amine or non-amine, are inexpensive compared to non-migratory additives and
work
by diffusing to the film surface after the film is blown or cast. Once on the
surface,
they attract atmospheric moisture to the film surface to dissipate static
electricity
charges. This type of additive is not effective in very dry climates or in
conditions
where there is insufficient moisture in the air. Accordingly, non-migratory
additives,
which work by forming a continuous matrix that is electrically conductive
within the
film structure, are preferred for use in accordance with the present
invention. A
preferred non-migratory anti-static additive for use in accordance with the
present
invention is AntistatTM PE MB 101710, a polyethylene-based antistatic additive
supplied by AmpacetTM Corp., Tarrytown, NY. In order for a non-migratory
additive
to be economically viable, it becomes necessary to minimize the amount of
additive
employed by limiting the inclusion of this additive to a thin surface layer.
Thus, it is
preferred that first outer layer 16 which carries the non-migratory additive
comprises
from about 7.5% to about 25% of the overall thickness of film 12.
In a less preferred embodiment the composite may include an anti-static
coating. Such coating may be applied to the outer film surface 17 or the first
outer
layer 16 may be omitted and the anti-static coating may be applied directly to
an
outermost surface of the core layer.
In accordance with the present invention, outer coating 20, which provides a
printable surface to the composite, is opposite to the anti-static layer or
coating
because
6
CA 02459589 2004-03-03
the "back," or non-printing, surface of the composite is subjected to the
higher degree of
friction as the tape passes through the printer. Coating 20 is a heat
sensitive, thermal
image coating such as Protecoat 8468, supplied by NuCoat, Inc., Plymouth, MN.
The
thermal image coating may be applied directly to an outer surface of the core
layer.
However, preferably film 12 includes second outer layer 18 and the coating is
applied to
outer film surface 19. Preferably, second outer layer 18 comprises from about
7.5% to
about 25% of the overall film thickness. Preferably, second outer layer 18
includes a
pigment in su .fficient quantity to render the composite opaque. However, the
pigment
may be incorporated into the composite in any component including coating 20.
Che present composite is preferably made by forming the film, orienting the
film,
and then applying the thermal image coating and, if one is employed, an anti-
static
coating. Preferably, the film is formed by coextrusion of the layers. If the
film only
comprises a monolayer core then preferably it is extruded. Although
coextrusion is the
preferred means for forming the present preferred multilayer film, other means
of film
formation also are within the scope of the present invention, such as
lamination, coating
or extrusion coating. The film may be coextruded by any conventional means
such as a
blown film process or a cast film process.
Thereafter, the film is oriented. Orientation is necessary to the present
invention
in order to render the film sufficiently stiff to run through a register or
printer. It should
be noted that as ttie film thickness is decreased to a level that is
commercially cost
effective, the film stiffhess decreases substantially. Thus, although a 1-mil
thick static
free film may have sufficient machine direction stiffness, a thermoplastic
film with this
thickness is not economically viable as a regi5ter tape. I:t is therefore
necessary to reduce
the film thickness to reach a film cost per unit area which is economically
viable and
which has sufficient machine direction stiffness to function in commercial
register
printers. Accordingly, the present film, which preferably has a thickness of
from about
0.50 mils to about 0.75 mils, must have a 1% secant modulus in the machine
direction of
at least about 1.50,000 psi, preferably at least about 200,000 psi. - In order
to achieve this
stiffness, preferably the film is uniaxially oriented in the machine direction
with a
machine direction stretch ratio in the range of from about 1. 5X to about
1Ø0X. This
degree of orientation improves machine direction stiffness by 2 to 5 times as
compared to
7
CA 02459589 2004-03-03
a non-oriented film. Alternatively, the film may be biaxially oriented such
that the
product of the machine direction and transverse direction stretch ratios is
from about
2.OX to-about 50X. In accordance with the present invention, orientation may
take place
in one step or in a series of stretching steps. Regardless of the type of
orientation,
thereafter the film must be thermally stabilized, i.e., annealed or heat set,
in order to
render it essentially non-heat shrinkable. Orientation and annealing may be
performed
either in-line out-of-line with coextrusion.
Following orientation and heat stabilization, the outer film surface 19
preferably
is subjected to a surface treatment such as, preferably, corona discharge,
flame or
chemical treatment, prior to application of the thermal image coating. Tf an
anti-static
coating is employed, the surface onto which it is applied preferably is
subjected to a
surface treatment prior to coating as well. Such surface treatment is employed
to ensure
adherence of the coating to the outer surface of the film.
Thereafter, outer coating 20 and, optionalty, an anti-static coating are
applied in a
conventional manner.
Following extrusion, orientation, heat stabilization, surface adhesion
treatment
and coating, the film is slit and wound into roll sizes useful in commercial
register
printers. All process steps may be performed either in-line or out-of-line
with the
preceding step.
In making the present composite matting compound is not included in any layer.
The materials for each film layer are preferably dry or melt blended prior to
extrusion to
improve uniformity. Although not required, intermediate layers, such as tie
layers or
other structural layers, may be included in the present film structure.
Thus, the present invention advantageously provides a thermoplastic register
or
receipt tape of sufficiently reduced thickness to be commercially desirable
for
replacement of a conventional paper tape, which is of sufficient stiffness to
run through a
conventional printer and which has adequate anti-static properties for
printing. However,
it should be noted that if a non-migratory anti-static additive is included in
the first outer
layer 16, as is preferred, one might expect that the subsequent orientation,
which is
necessary to improve stiffness and to reduce the film thickness, might disrupt
the non-
migratory anti-static additive matrix structure such that the anti-static
properties of the
K
CA 02459589 2004-03-03
film would be lost. It has been unexpectedly found in accordance with the
present
invention that this is not the case. For example, the 2.5-mi) thick high
density
polyethylene film of Example 1, below, was produced with a non-migratory
antistatic
additive in the outer layer in a conventional blown film process. The layer
thickness
ratios for this structure were 10% for the first outer layer, 80% for the core
layer, and
10% for the second outer layer. The surface resistivity of the first outer
layer of this film
was 1010 ohms. The surface resistivity of the second outer layer that did not
contain an
anti-static additive was 101-2 ohms. This film was stretched in the machine
direction 5X
to reach a final film thickness of 0.5 mils. There was no transverse direction
stretch.
The surface resistivity of the tirst outer layer after stretching was 10i0
ohms while the
second outer layer remained at 1012 ohms. The machine direction stretch
therefore did
not disrupt the anti-static additive matrix in the first outer layer and did
not disturb the
overall anti-static property of the film.
Further illustrations of the present invention are provided in the two
examples
cited below.
Example 1
A first outer layer, a core layer, and a second outer layer were coextruded
through
a circular die and blown to form a three layer self-supporting film having a
thickness of
2.5 mils. The layer percent thickness ratio was 10:80:10, respectively. The
first outer
layer was comprised of 58% high density polyethylene, 2% titanium dioxide and
40%
non-migratory anti-static additive. The core layer was comprised of 100% high
density
polyethylene. The second outer layer was comprised of 98% high density
polyethylene
and 2% titanium dioxide. The structure was coextruded on a conventional blown
film
line using a 4:1 blow up ratio.
Wound film from the above extrusion operation was then stretched in a
conventional roll-to-roll stretching unit where it was subjected to a 5:1.
machine direction
stretch ratio. Following stretching, the second outet- layer was corona
treated prior to
winding the now 0.5 mil thick machine direction oriented film. There was no
transverse
9
CA 02459589 2004-03-03
stretch employed. Corona treated wound film from the stretching operation was
then
coated with a heat sensitive, thermal image coating on the corona treated
second outer
layer surface. Following coating, the film was then slit into roll sizes
suitable for use in
commercial register printers.
The resulting film structure had the following parameters and characteristics:
Nominal thickness: 0.5 mils
1% secant modulus in the machine direction: approx. 400,000 psi
Area factor: approx. 60,000 sq. in./pound
Surface resistivity:
First outer layer: 1010 ohms
Second outer layer: > I 012 ohms
A film-produced according to this example was tested in an NCR point of sale
printer, Class 7193, Model 3205-9001, where it ran through repeated printing
cycles
without jamming. A. non-oriented film, also having a 0.5 mil thickness and
produced
using the same materials and additives, was tested in the same printer. This
film, which
had a 1% machine direction secant modulus of approximately 200,000, psi jammed
repeatedly after less than five printing cycles.
Example 2
A 4.0 mi) thick high density polyethylene film in accordance with the present
invention was produced with a non-migratory anti-static additive in the first
outer layer in
a conventional blown film process. The film had the same layer-by-layer
composition
and percent layer thicknesses as the film of Example 1. The surface
resistivity of the first
layer was 1010 ohms. The surface resistivity of the second outer layer that
did not contain
an anti-static additive was 1.012 ohms. This film was stretched in the machine
direction
8X to reach a final film thickness of 0.5 mils. There was no transverse
direction stretch.
The surface resistivity of first outer layer after stretching was 101 ' ohms
while the second
outer layer remained at 1012 ohms. Even at this higher level machine direction
stretch,
CA 02459589 2004-03-03
the anti-static additive matrix in the first outer layer was not disrupted to
the point where
the anti-static property of the film was lost.
While the disclosed process has been described according to its preferred
embodiments, those of ordinary skill in the art will understand that numerous
other
embodiments have been enabled by the foregoing disclosure. Accordingly, the
foregoing
embodiments are merely exemplary of the present invention. Modifications,
omissions,
substitutions and rearrangements may be made to the foregoing embodiments
without
departing from the invention as set forth in the appended claims.
it
