Note: Descriptions are shown in the official language in which they were submitted.
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SHEETING HAVING AN OPTICAL CORE LAMINATED TO A VINYL
FILM, RETROREFLECTIVE ARTICLES, AND METHODS
Field of the Invention
The invention relates to retroreflective articles and other articles useful
for various applications, such as graphic designs and retroreflective products
that
include a vinyl film.
Background
Articles containing polymer films have wide utility in such applications
as commercial graphics for advertising and for retroreflective products.
Specifically, retroreflective products (e.g., bead-based and prismatic-type
(e.g.
cube corner) retroreflective sheeting) have been developed to provide
increased
safety, especially during periods of reduced visibility. These articles may
encounter demanding environments, such as extremes in temperature, chemical
challenges from atmospheric pollution and road salt, and photo-reaction
involving infrared, visible, and ultraviolet radiation from sunlight.
One conventional retroreflective base sheeting includes a monolayer of
optical elements typically in the form of glass microspheres (i.e., beads)
embedded in a polymeric binder layer and a specularly reflective layer
covering
the polymeric layer. Transparent cover films are used to provide protection
(e.g.,
weather-resistance) to such articles, particularly retroreflective articles
such as
license plates, signage, and the like. Such cover films have been made by dip
coating the base material or by attaching a preformed cover film. For example,
preformed cover films can include poly(methyl methacrylate) and polyethylene
terephthalate). Although these cover films function well when the
retroreflective
sheeting has a rigid, flat support such as a highway sign, they are not very
conformable or stretchable, and thus, not useable for products that require
embossing such as license plates. Furthermore, these cover films typically
require a pressure sensitive adhesive layer for adhering them to the base
sheeting.
Other cover films are known that are more flexible, and thus, useful for
products that require embossing. For example, U.S. Pat. No. 4,767,659 (Bailey.
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et al.) discloses an extruded thermoplastic film that includes aliphatic
urethanes,
copolymers of ethylene or propylene, or homopolymers of ethylene and
propylene. A preferred cover film includes a copolymer of ethylene and acrylic
acid (EAA). Such cover films are extremely effective cover films for
retroreflective sheeting, particularly license plates. One drawback, however,
is
their poor receptivity to ink jet and hot foil stamping processes.
Thus, there is a desire to provide retroreflective articles and other articles
useful for various applications, such as graphic designs and retroreflective
products, that are more receptive to, for example, ink jet, thermal mass
transfer,
and hot foil stamping processes.
Summary of the Invention
One approach to fulfilling the desire for cover films for retroreflective
articles, for example, that are more receptive to printing using ink jet,
thermal
mass transfer, and hot foil stamping processes is to use vinyl films, such as
those
used in commercial graphics products. However, such vinyl films are not
readily
bonded to conventional preformed optical cores, which include optical elements
such as glass microspheres or prismatic elements. The present invention is
directed to a solution to this problem, which involves the use of a primer
that
includes a urethane polymer and optionally an olefinic copolymer such as a
copolymer of ethylene and acrylic acid (EAA).
Thus, in one embodiment of the present invention, there is provided a
sheeting (preferably, retroreflective sheeting) that includes: a vinyl film
having
two major surfaces; a preformed optical core laminated to a first major
surface of
the vinyl film; and a primer disposed between the vinyl film and the preformed
optical core, preferably at a (dry) thickness of no greater than about 12.5
micrometers, wherein the primer includes a urethane polymer; and optionally,
graphics positioned between the primer and the optical core or between the
primer and the vinyl film.
The urethane polymer of the primer can be provided by a water-based
urethane resin or a solvent-based urethane resin. For embodiments in which the
urethane is mixed with an olefinic copolymer such as an EAA copolymer, a
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water-based urethane resin is typically used. Typically, the urethane polymer
has
a weight average molecular weight of about 8000 to about 500,000..
For certain preferred embodiments, the primer also includes a copolymer
of an olefinic monomer and a second monomer containing a pendant carboxyl
group, such as an ethylene/acrylic acid (EAA) copolymer. This can be mixed
(e.g., blended) with the urethane polymer (typically, which is formed from a
water-based urethane resin). Alternatively, the primer can include two
distinct
layers, for example, one of the urethane polymer and one of the EAA copolymer.
A mixture (e.g., blend) of urethane polymer and EAA copolymer, for example,
can also be used in a primer that includes several layers (typically, two
layers)..
In a preferred mixture of the urethane polymer and olefinic copolymer, an
olefinic copolymer is present in an amount of about 7 weight percent (wt-%) to
about 87 wt-%, based on polymer solids, and a urethane polymer is present in
an
amount of about 13 wt-% to about 93 wt-%, based on polymer solids. Whether
used in mixtures or in layers, a urethane polymer is preferably proximate the
vinyl film.
In another embodiment of the invention, there is provided a sheeting
(preferably, a retroreflective sheeting) that includes: a vinyl film having
two
major surfaces; a preformed optical core laminated to a first major surface of
the
vinyl film; a primer disposed between the vinyl film and the preformed optical
core, wherein the primer consists essentially of a urethane polymer; and
optionally, graphics positioned between the primer and the optical core or
between the primer and the vinyl film.
In still another embodiment of the invention, there is provided a sheeting
(preferably, a retroreflective sheeting) that includes: a vinyl film having
two
major surfaces; a preformed optical core laminated to a first major surface of
the
vinyl film; a primer disposed between the vinyl film and the preformed optical
core, wherein the primer includes a first layer that includes a urethane
polymer
proximate the vinyl film and a second layer that includes an ethylene/acrylic
acid
copolymer; and optionally, graphics positioned between the primer and the
optical core or between the primer and the vinyl film. Preferably, either or
both
layers can include a mixture of an ethylene/acrylic acid copolymer and a
urethane
polymer.
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In a further embodiment, there is provided a sheeting (preferably, a
retroreflective sheeting) that includes: a vinyl film having two major
surfaces; a
preformed optical core laminated to a first major surface of the vinyl film; a
primer disposed between the vinyl film and the preformed optical core, wherein
the primer is formed from a solvent-based urethane resin; and optionally,
graphics positioned between the primer and the optical core or between the
primer and the vinyl film.
In another embodiment, the present invention provides a retroreflective
sheeting that includes: a vinyl film having two major surfaces; a preformed
optical core laminated to a first major surface of the vinyl film; a primer
disposed between the vinyl film and the preformed optical core at a thickness
of
no greater than about 12.5 micrometers, wherein the primer includes a urethane
polymer; and optionally, graphics positioned between the primer and the
optical
core or between the primer and the vinyl film.
The present invention also provides methods of making such sheeting
(preferably, retroreflective sheeting). In general, these methods involve
laminating a vinyl film to a preformed optical core. The vinyl film, the
preformed optical core, or both are primed with a primer that includes a
urethane
primer before laminating them together. Also, graphics can optionally be
applied
to the vinyl film, the preformed optical core, or both prior to lamination.
In one preferred embodiment, a method is provided that includes:
providing a vinyl film that includes a primer disposed on a first major
surface
thereof to form a primed surface, wherein the primer includes a urethane
polymer; providing a preformed optical core having two major surfaces; and
laminating a first major surface of the preformed optical core to the primed
surface of the vinyl film. In this method, the vinyl film can be primed with a
urethane polymer provided from a water-based urethane resin or from a solvent-
based urethane resin.
In another preferred embodiment, a method is provided that includes:
providing a vinyl film having two major surfaces; providing a preformed
optical
core that includes a primer disposed on a first major surface thereof to form
a
primed surface, wherein the primer includes a urethane polymer; and laminating
a first major surface of the vinyl film to the primed surface of the preformed
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optical core. In this method, the optical core is preferably primed with a
urethane polymer provided from a water-based urethane resin.
As discussed above for the sheeting, the primer used in the methods can
also include an olefinic copolymer such as an ethylene/acrylic acid (EAA)
copolymer. This can be mixed (e.g., blended) with the urethane polymer
(typically, which is formed from a water-based urethane resin). Alternatively,
the primer can include two distinct layers - one of the urethane polymer and
one
of the olefinic copolymer, as long as the urethane polymer is proximate the
vinyl
film.
In all the embodiments described herein, a preformed optical core
includes optical elements typically in the form of glass microspheres (i.e.,
beads)
or prisms, for example. Microspheres can be embedded in a polymeric binder
layer or pressed into a polymeric film, for example. Such preformed optical
cores
are well known to those of skill in the art.
The sheeting of the present invention can be used in a variety of products,
including, but not limited to, license plates, reflective graphic articles,
and
pavement markings.
As used herein, the phrase "urethane polymer" refers to a urethane-
containing polymer or copolymer. Such materials may alternatively be referred
to as a "polyurethane." The term "polyurethane" typically includes polymers
having urethane and/or urea linkages, and such is the intended meaning herein.
As used herein, the phrase "primer" or "primer layer" refers to a layer that
adheres two or more other layers, films, and/or sheets to each other, usually
when these would not sufficiently adhere to each other absent the primer
therebetween.
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Brief Description of the Drawings
The invention will be further explained with reference to the drawings,
wherein:
Fig. 1 is a cross-sectional view of an embedded-lens retroreflective
article;
Fig. 2 is a cross-sectional view of an enclosed-lens retroreflective article;
Fig. 3 is a cross-sectional view of an alternative embodiment of an
enclosed-lens retroreflective article;
Fig. 4 is a cross-sectional view of an encapsulated-lens retroreflective
article;
Fig. 5a is a cross-sectional view of an exposed prismatic-type
retroreflective article;
Fig. 5b is a cross-sectional view of an enclosed prismatic-type
retroreflective article; and
Fig. 6 is a cross-sectional view of an encapsulated prismatic-type
retroreflective article.
These figures, which are idealized, are not to scale and are intended to be
merely illustrative and non-limiting.
Detailed Descriution of Preferred Embodiments
The present invention provides sheeting (preferably, retroreflective
sheeting) that includes a vinyl film having two major surfaces and a preformed
optical core in the form of a sheet material laminated to a first major
surface of
the vinyl film. Significantly, a primer that includes a urethane polymer is
used to
enhance the adhesion of the vinyl~film laminated to the preformed optical
core.
Preferably, the primer is present at a dry coating thickness of no greater
than about 12.5 micrometers, more preferably no greater than about 6
micrometers, and most preferably no greater than about 5 micrometers.
Preferably, suitable bonding of an optical core to a vinyl film occurs if the
peel
force using the 180° peel test described in the Examples Section is at
least about
356 grams/centimeter (g/cm) (2.0 pounds/inch (lb/in)), preferably, at least
about
455 g/cm (2.5 lb/in), and more preferably, at least about 535 g/cm (3.0
lb/in).
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Generally, in retroreflective articles, a preformed optical core can include
a monolayer of optical elements typically in the form of glass microspheres
(i.e.,
beads). These microspheres can be embedded in a polymeric binder layer or
pressed into a polymeric film, for example. Alternatively, a preformed optical
core can include prismatic-type optical elements. Such preformed optical cores
(i.e., optical core sheets) are well known to those of skill in the art.
Preferably,
the optical core is an enclosed-lens optical core or an embedded-lens optical
core.
Generally, in retroreflective articles, the vinyl film forms the first major
viewing surface of a retroreflective article. It is often called the face
member,
overlay, cover film, top film, front face, top layer, or top coat, which for
the
purposes of this application are all equivalent terms. Suitable cover films
provide a substantially transparent viewing surface that protects the optical
elements from a variety of possible destructive effects, such as dirt, water,
and
exposure to weather and outdoor conditions. Polymers selected for the cover
films are preferably dimensionally stable, durable, weatherable, and readily
formable into a desired configuration. Herein, the vinyl cover film is also
receptive to inks used in ink jet printing processes, hot foil stamping
processes,
and thermal mass transfer processes, for example.
Primer
The primer comprises (and for certain embodiments, consists essentially
of) a urethane polymer (i.e., a urethane-containing polymer or copolymer,
alternatively referred to as a polyurethane, which includes polymers having
urethane and/or urea linkages).
Preferably, the primer also includes a copolymer of an olefinic monomer
and a second monomer containing a pendant carboxyl group (e.g., a compound
of Formula I below), such as an ethylene/acrylic~acid (EAA) copolymer. This
can be mixed (e.g., blended) with the urethane polymer (typically, which is
formed from a water-based urethane resin). Alternatively, the primer can
include
two distinct layers, for example, one of the urethane polymer and one of the
olefinic copolymer. A mixture (e.g., blend) of urethane polymer and olefinic
copolymer can also be used in a primer that includes several layers
(typically,
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two layers). For example, a mixture of urethane polymer and olefinic copolymer
can form a first layer proximate the vinyl film with a second layer of either
the
urethane polymer, the olefinic copolymer, or a mixture of the two. In a
preferred
mixture of the urethane polymer and olefinic copolymer, an olefinic copolymer
is present in an amount of about 7 wt-% to about 87 wt-%, based on polymer
solids, and a urethane polymer is present in an amount of about 13 wt-% to
about
93 wt-%, based on polymer solids. Such mixtures are described in U.S. Patent
No. 5,468,532 (Ho et al.); however, the primer of the present invention is
preferably not crosslinked. Also, the primer of the present invention
preferably
does not include colorants. Whether used in mixtures or in layers, a urethane
polymer is proximate the vinyl film for desirable adhesion to the optical
core.
Suitable urethane polymers or copolymers for use in the primer include
aliphatic or aromatic urethanes or blends thereof. Preferably, the urethane
polymer is an aliphatic urethane. Typically, many suitable polyurethanes
include
three main components: an aliphatic or aromatic diisocyanate; a chain extender
(such as an ethylene-, propylene- or butane- diol); and a soft segment polyol
(such as polyether, polyester, or polycarbonate, e.g., polyethyleneoxide,
polyadipate, or polycaprolactone). For water-based urethanes, a water-
dispersible segment is also included, such as dimethyl propionic acid or
diethanol amine.
Suitable urethane polymers have a weight average molecular weight of
about 8,000 to about 500,000. The urethane polymer of the primer can be
provided by a water-based urethane resin or a solvent-based urethane resin.
Such
urethane resin (dispersions) are commercially available from a variety of
sources.
They include aliphatic polyester polyurethanes, aliphatic polyether
polyurethanes, aliphatic polycarbonate polyurethanes, and blends thereof.
Examples of suitable dispersion grade urethane polymers include those
commercially available from Avecia (formerly Zeneca), Wilmington, MA, under
the trade designations "Neorez 972," "Neorez 9679," and "Neorez 960," all of
which are water-based aliphatic polyester urethane resins, and a solvent-based
aliphatic polyester urethane resin commercially available from KJ Quinn,
Seabrook, NH under the trade designation "QC 4820." For embodiments in
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which the urethane is mixed with an EAA copolymer, a water-based urethane
resin is typically used.
The primer can also include a copolymer of an olefinic monomer and a
second monomer containing a pendant carboxyl group, for better adhesion to the
optical core. These olefinic copolymers preferably have the following formula
(Formula n:
Rl COOH
I I
X-(CH2-CH)"-(CH2-C)m Y
R2
wherein R1 is either H or a Cl_6 alkyl group; R2 is H, a C1_6 alkyl group, --
CN, an
ester group, or R3-COOH, wherein R3 is any alkyl group; X and Y are
independently a residue of the olefinic monomer or a residue of the second
monomer; n is a number selected such that the olefinic monomer provides from
about 70 mole percent (mol-%) to about 99 mol-% of the copolymeric binder;
and m is a number selected such that the second monomer correspondingly
provides from about 1 mol-% to about 30 mol-% of the copolymeric binder.
Preferred such copolymers include copolymerized ethylene and acrylic acid or
copolymerized ethylene and methacrylic acid.
Suitable copolymers of ethylene with acrylic acid (EAA) include a
dispersion grade EAA commercially available from Michelman Inc., Cincinnati,
OH under the trade designation "Michem 49838." Suitable copolymers of
ethylene and methacrylic acid (EMAA) include a dispersion grade EMAA
commercially available from Morton International, Seabrook, NH under the trade
designation "Adcote 56220."
The primer can optionally include a surfactant (i.e., wetting agent).
A sufficient amount of surfactant is typically used such that a uniform
coating or
film results. Preferably, a primer can include 0 to about 5 wt-% of a
surfactant,
based upon the total weight of the primer (coatable composition or solution
weight). If too much surfactant is included, the resultant laminated sheeting
may
have poor moisture resistivity, which may also result in poor outdoor
durability.
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If too little surfactant is included, the primer will not demonstrate
sufficient
surface wetting upon coating. A surfactant serves to lower the surface tension
and improve the coatability of the primer. The surface tension required
depends
upon the substrate to be coated.
Useful surfactants for water-based compositions include, but are not
limited to, those selected from the group consisting of anionic, nonionic, and
cationic surfactants. Preferred surfactants are nonionic. Examples of
preferred
nonionic surfactants for water-based compositions include, but are not limited
to,
those selected from the group of ethoxylated tetramethyldecynediol available
from Air Products and Chemicals, Allentown, PA under the trade designation
"Surfynol" 440, 420, 465, 104 PA, and 485, and polyether-polysiloxane
copolymer commercially available from Tego Chemie Service USA, Hopewell,
VA, under the trade designation "Foamex" -800, -805, and -810.
For non-water-based compositions useful surfactants also include
nonionic surfactants. In general, nonionic surfactants are organic solvent
reducible and thus useful in the non-water-based compositions of the
invention.
Useful nonionic surfactants include, but are not limited to, those selected
from
the group of cellulose derivatives such as cellulose acetate, cellulose
acetate
butyrate, cellulose acetate propionate cellulose acetate butyrate
butanedioate,
which are commercially available from Eastman Chemical, Kingsport, TN under
the trade designations "CAB" -398-3, -381-0.1, -381-0.5, -531.1, and -482-0.5.
Numerous other surfactants are commercially available.
. The primer can also include various other additives for desired effect.
These include, for example: defoamers, such as that commercially available
from
Byk Chemie, Wilmington, DE under the trade designation "Byk 024";
fungicides, such as that commercially available from Troy Chemical, Troy, MI
under the trade designation "Troysan Polyphase AF-1"; and ultraviolet
protectors, such as hindered amine light stabilizers ("HAL") commercially
available from Ciba-Geigy Corp., Greensboro, NC under the trade designation
"Tinuvin 123," and ultraviolet absorbers, commercially available from Ciba-
Geigy Corp., Greensboro, NC under the trade designation "Tinuvin 1130."
The components of the primer, e.g., urethane dispersion, EAA dispersion,
and the surfactant, include solvents such as water, isopropanol, and N-methyl
to
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pyrrolidone. If desired, additional water and/or organic solvents can be added
to
the primer composition to adjust the solids concentration for effective
coatability
and/or to enhance compatibility of additives. Such organic solvents include
alcohols, methyl isobutyl ketone, diisobutyl ketone, xylene, amyl acetate,
methyl
amyl acetate, propylene glycol monoethyl ether, or mineral spirits solvent, or
combinations thereof. Typically, a suitable solids content for coatability is
within a range of about 20 wt-% to about 35 wt-% for primers containing water-
based urethane resins and about 10 wt-% to about 15 wt-% for primers
containing solvent-based urethane.
A preferred coatable primer composition includes 27.9 wt-% "Neorez
972" water-based urethane polymer resin, 65.2 wt-% "Michem 4983R" EAA, 0.5
wt-% "Surfynol 104 PA" surfactant, 0.3 wt-% "Byk 024" defoamer, and 6 wt-%
of a solution containing 2.8 wt-% "Troysan Polyphase AF-1" fungicide, 4.2 wt-
% "Tinuvin 123" ultraviolet protector, and 12.6 wt-% "Tinuvin 1130"
ultraviolet
absorber in 80.4 wt-% propylene glycol monoethyl ether.
The primer can be prepared by mixing the various components and
coating onto either the vinyl film or the optical core. Such coating
techniques,
such as wire bar coating and gravure coating, that are well known to those of
skill in the art can be used.
Preferably, the primer, whether it includes one layer of more than one
layer, has a total thickness once dry of no greater than about 12.5
micrometers.
More preferably, the primer, whether in one or more layers, has a total
thickness
of no greater than about 6 micrometers, and most preferably no greater than
about 5 micrometers. Preferably, the thickness is at least about 1 micrometer
for
desirable adhesion.
Vinyl Film
A suitable film includes a vinyl-containing plastic film. Herein, "vinyl
film" and "vinyl-containing film" are used interchangeably and include those
films having vinyl functionality. The vinyl functionality can be provided by a
wide array of polymers, preferably polyvinyl chloride such as that
commercially
available from Union Carbide, Danbury, CT under the trade designation "Geon
178."
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A preferred vinyl film is a transparent vinyl film having a formulation of
about 42 wt-% to about 56 wt-% polyvinyl chloride, about 0 to about 25 wt-%
acrylic resin, about 15 to about 25 wt-% plasticizers, from about 0.5 wt-% to
about 8 wt-% heat stabilizers, and about 0.1 to about 6 wt-% ultraviolet
protectors. Optionally, the vinyl film can include colorants (e.g., dyes or
pigments), such as the pigments described in U.S. Patent No. 5,874,158 (Ludwig
et al.).
The acrylic resin is preferably included in the vinyl film formulation to
provide durability and nonblocking properties. Nonlimiting examples of acrylic
resins include poly(methyl methacrylate) and methyl methacrylate/n-butyl
methacrylate copolymer. Suitable acrylic resins are commercially available
from
Rohn & Haas under the trade designations "Acryloid B66," "Acryloid A11," and
"Acryloid A21," and from DuPont under the trade designations "Elvacite 2008,"
"Elvacite 2010," and "Elvacite 2042."
Nonlimiting examples of ultraviolet protectors include hindered amine
light stabilizers ("HAL") commercially available from Hal-stab Company of
Hammond, IN under the trade designations "Hal-Lub, " "Hal-Base," "Hal-Carb,"
and "Hal-Stab"; or from Ciba-Geigy Corp., Greensboro, NC under the trade
designation "Tinuvin" (e.g., "Tinuvin 123" and "Tinuvin 292") and ultraviolet
light absorbers such as diphenylacrylate protectors commercially available
from
BASF of Williamsburg, VA under the trade designation "Uvinul" (e.g., "Univul
N-539").
Nonlimiting examples of heat stabilizers include CaZn compounds, such
as that commercially available from Witco of Greenwich, CN under the trade
designation "Mark V-1923"; BaZn compounds, such as that commercially
available from Ferro Corp., Cleveland, OH under the trade designation
"Sympron 940"; BaCdZn compounds, such as that commercially available from
Ferro Corp. under the trade designations "Ferro 1237" and "Sympron 856"; and
tin mercaptide compounds, such as that commercially available from M&T
Chemicals of Rahway, NJ under the trade designation "Termolite 31."
Nonlimiting examples of plasticizers include dimethyl terepthalate,
dimethyl isophthalate, dimethyl octyl terephthalate, and a polyester
plasticizes
such as that commercially available from Henkel under the trade designation
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"Plastolein 9777" (combination of hexanedioic acid, 1,3-butanediol, and 2-
ethylhexyl ester).
The vinyl film can be prepared by bar coating on to, for example, a
polyester, presized paper, or presized polyester liner, the film formulation
in
methyl isobutyl ketone, diisobutyl ketone, xylene, amyl acetate, methyl amyl
acetate, or mineral spirits solvent. A film having a dry caliper ranging from
about 20 micrometers to about 80 micrometers is preferred. Coating involves
bar
coating of the organosol onto the liner and obtaining the desired film
thickness
and a smooth, uniform film by placing a smooth, stationary bar at a fixed
distance from a moving web substrate.
Examples of suitable vinyl films include those disclosed in U.S. Pat. No.
5,874,158 (Ludwig et al.). Other films are commercially available vinyl films
including~calendered vinyl from Achilles USA, Everett, WA.
Optical Core
A preformed optical core includes optical elements typically in the form
of glass microspheres (i.e., beads) or prismatic elements, for example.
Microspheres can be embedded in a polymeric binder layer or pressed into a
polymeric film, for example. Herein, "preformed" means that the optical core
was prepared before applying the primer or the vinyl film.
Retroreflective polymeric sheeting in the preferred articles of the present
invention may be, for example, "beaded sheeting" in the form of an enclosed-
lens
sheeting, embedded-lens sheeting, or encapsulated-lens sheeting, as well as
cube
corner retroreflective sheeting. Such articles are described, for example, in
U.S.
Pat. Nos. 2,407,680; 4,511,210; 4,950,525; 3,190,178; 4,025,159; 4,896,943;
5,064,272; 5,066,098; 3,684,348; 4,801,193; 4,895,428; and 4,938,563. The
following are descriptions of illustrative embodiments of such optical core
sheets. Preferred optical cores include the embedded-lens and the enclosed-
lens
optical cores.
The materials of the surface of the optical core to which the vinyl film is
laminated can include a wide variety of polymers. Nonlimiting examples include
polyvinyl butyral), aliphatic polyester polyurethane, aliphatic polyether
polyurethane, aliphatic polycarbonate polyurethane, ethylene acrylic acid
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copolymers, ethylene vinyl acetate copolymers, crosslinked acrylate polymers,
and polycarbonate. Preferred polymers of the optical core surface to which the
vinyl film is laminated include polyvinyl butyral) and polyester polyurethane.
A typical "embedded-lens" retroreflective sheeting 10 is illustrated in Fig.
1. An optical core 17 includes a monolayer of optical elements 11 embedded
between transparent bonding and spacing layers 12 and 13, a specularly
reflective layer 14, which is typically aluminum vapor-deposited on the
spacing
layer 13, and a layer of pressure sensitive adhesive 15 covering the
reflective
layer. A transparent cover film 16, which forms the exterior front surface of
the
sheeting, can be the vinyl film described herein. Light rays incident on the
sheeting travel through the layers 16 and 12 to the optical elements 11, which
act
as lenses focusing the incident light approximately onto the appropriately
spaced
specularly reflective layer 14. Thereupon the light rays are reflected back
out of
the sheeting along substantially the same path as they traveled to the
sheeting.
Embedded-lens sheeting as described has the advantage that, because the
optical
elements are embedded within the sheeting, incident light rays are focused
onto
the specularly reflective layer irrespective of whether the front of the
sheeting is
wet or dry.
Specific examples of embedded-lens optical cores are disclosed in U.S.
Patent Nos. 4,950,525 (Bailey) and 4,511,210 (Tung et al.). For example, the
optical elements can be pressed into an extruded thermoplastic aliphatic
polyurethane film. Alternatively, an extruded ethylene acrylic acid film can
be
used in place of the polyurethane film.
A typical "enclosed-lens" retroreflective sheeting 28 is illustrated in Fig.
2. An optical core sheet (often referred to as a retroreflecting base
material) 20
includes a binder layer 21, substantially a monolayer of optical elements 22,
a
specularly reflective layer 24, and a pressure sensitive adhesive layer 26
covered
by a removable liner 27. In this embodiment, the optical elements are
substantially fully embedded in the binder layer. A transparent cover film 29,
which forms the exterior front surface of the sheeting, can be the vinyl film
described herein. An example of such sheeting is commercially available from
Minnesota Mining and Manufacturing Company (."3M"), St. Paul, MN under the
trade designation "Scotchlite Reflective License Plate Sheeting No. 3750".
14
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Another example of a typical "enclosed-lens" retroreflective sheeting 38
is illustrated in Fig. 3. In this embodiment, the optical core 30 includes a
binder
layer 3 l, substantially a monolayer of optical elements 32, a specularly
reflective
layer 34, and a pressure sensitive adhesive layer 36 covered by a removable
liner
37. In this embodiment, the optical elements are generally embedded about 50
percent in the binder layer. A transparent cover film 39, which forms the
exterior
front surface of the sheeting, can be the vinyl film described herein.
In the illustrative embodiments shown in Figs. 2 and 3, the thickness of
the binder layer typically is about 20 micrometers to about 120 micrometers.
It
typically includes a crosslinked polyvinyl butyral) resin or a synthetic
polyester
resin crosslinked with a butylated melamine resin. The optical elements are
typically microspheres made of glass, having refractive indices of about 2.1
to
about 2.3, with diameters ranging from about 30 micrometers to about 200
micrometers, preferably averaging about 60 micrometers in diameter. The
reflective material may be a layer of metal flakes or vapor or chemically
deposited metal layer such as aluminum or silver. As such, the sheeting will
have a silver or gray appearance caused by the metallic appearance of the
reflective material. However, colored sheeting can be prepared by placing dyes
or pigments, which are preferably light transmissible, in the spacing layer,
bead
bond layer, cover film, and/or primer layers.
Alternative embodiments of "enclosed-lens" retroreflective sheeting
include a bead bond layer and a space coat layer in place of the binder layer
illustrated in Figs. 2 and 3. The reflective layer is held in a cooperative
position
with respect to the optical elements by the space coat layer. That is, the
optical
elements have a first hemispherical portion enclosed by the bead bond and a
second opposing hemispherical portion spaced at the cooperative position from
the reflective coating by the space coat layer. The space coat layer typically
has a
thickness extending from the surface of the microspheres approximately one
fourth the average diameter of the microspheres. An example of such an optical
core is disclosed in the context of a license plate in U.S. Pat. No. 5,882,771
(Klein et al.).
Fig. 4 illustrates an "encapsulated-lens" retroreflective article 48. An
optical core sheet 40 includes transparent beads 41 having a first
hemispherical
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air exposed portion, and a second opposing hemispherical portion having the
reflective coating 44 thereon. A sealing member 46, having a second major
surface 45 opposed from the viewing surface 43, is bonded to portions of the
cover film 49 to form a pattern of seal legs (such as the ones shown as 42),
wherein the cover film 49, the sealing member 46, and the seal legs 42 form a
plurality of encapsulated air cells 47, with the cover film 49 in spaced
relation to
the sealing member 46, and the air-exposed portions of the beads within the
cells.
The bonding portions between the face member and sealing member
form seal legs. These legs have a height sufficient to provide an air
interface for
the unbonded portion of the face member. The seal legs may be formed, for
example, by application of heat and pressure to the sealing member and the
cover
film as disclosed in U.S. Pat. No. 3,190,178 (McI~enzie). In this embodiment,
the seal legs may form a sealing pattern of individual air-tight cells each
having a
small area on the viewing surface 43. Seal legs may also be called sealing
walls,
bonds, bond lines, septa, or seal leg members, which for the purposes of this
application are all equivalent terms.
Fig. 5a illustrates a reflector-coated prismatic-type retroreflective article
50 having a cover film 52 (the vinyl film described herein) with a major
viewing
surface 53, and a retroreflective member 54. The retroreflective member 54 has
a first major surface in contact with the face member and a second opposing
microstructured surface having retroreflective elements 56, such as prisms,
with
a reflective coating thereon.
The total thickness of retroreflective members having cube corner
retroreflective elements is typically between about 0.2 mm and 0.7 mm, but may
be more or less depending on the polymers used. As the thickness of the
retroreflective member decreases, the flexibility of the member may also be
expected to increase.
Polymers are selected for the retroreflective member 54 in view of the
properties desired of the resultant article, the methods used for forming the
retroreflective surface, the desired bondability to the sealing member, and
the
nature of any other members of the retroreflective article. Polymers selected
for
the microstructured layer preferably should form cube corner elements that are
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dimensionally stable so that precise geometry desired for retroreflection is
maintained. The polymeric materials selected for the microstructured surface
tend to be relatively inflexible, hard, and rigid materials with a high Vicat
softening temperature relative to other polymers. Thus, these polymers may be
brittle or easily fractured when at room temperature or lower temperatures.
Notably, however, many of these polymers retain their transparency and their
shape under adverse conditions. Suitable polymers include thermoplastic or
thermosetting materials, as desired. The polymer forming the retroreflective
surface preferably is substantially optically clear, though it may be colored
as
desired. These polymers are often selected for one or more of the following
reasons: thermal stability, dimensional stability, environmental stability,
clarity,
excellent release from the tooling or mold, and capability of receiving a
reflective coating.
Suitable microstructured surfaces include, for example, cube corner
elements that can be of various geometric designs. The optical elements may
also be called cube corners, prisms, microprisms, or triple mirrors, which for
the
purposes of his application are all equivalent terms. The basic cube corner
retroreflective element is generally a tetrahedral structure having, for
example, a
base triangle and three mutually substantially perpendicular optical faces
that
cooperate to retroreflect incident light. The optical faces preferably
intersect at
an apex, with the base triangle lying opposite the apex. Each cube corner
element
also has an optical axis, which is the axis that extends through the cube
corner
apex and trisects the internal space of the cube corner element. Light
incident on
the first major viewing surface enters the base triangle and is transmitted
into the
internal space of the cube, is reflected from each of the three optical faces,
and is
redirected back in the same general direction as the incoming incident light.
It is
optional whether the faces of the cubes are exposed to an air interface or
coated
with a reflective coating, such as aluminum. Fig. 5a illustrates a
microstructured
surface that is spectrally coated with metal or other suitable reflective
coatings as
a means for altering the optical performance of the retroreflective member. In
this embodiment, an optional sealing member (not shown) may be in complete
contact with the microstructured surface without loss in retroreflection.
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The height of the cube corner elements, defined as the length of the
optical axis, is preferably as small as manufacturable for ease of sealing but
may
be as large as necessary while recognizing the desirability of avoiding waste
of
material and of increasing the thickness of the article. The minimum height is
preferably about 0.01 mm and the maximum height is preferably less than 1 mm.
The height of the cube elements is more preferably 0.02 mm to 0.5 mm. This
microstructured surface is molded to yield a cube layer using any of a variety
of
techniques known to those skilled in the art.
Fig. 5b illustrates an enclosed prismatic-type retroreflective article 50
having a cover film 52 with a major viewing surface 53, and a retroreflective
member 54. The retroreflective member 54 has a first major surface in contact
with the face member and a second opposing microstructured surface having
retroreflective elements 56, such as prisms, with a reflective coating
thereon. An
underlying layer 55 lies against the reflective coating, thereby enclosing the
prisms. The face member preferably comprises a transparent multilayer film, as
previously discussed for Fig. 5a.
Fig. 6 illustrates a cross-sectional view of an encapsulated prismatic-type
retroreflective article 60 having a cover film 62 with major viewing surface
63,
retroreflective member 64 with retroreflective elements 56 forming a
microstructured surface, and sealing member 66 having a major surface 67. The
sealing member 66 is bonded to the microstructured surface or to the
retroreflective member 64 to form seal legs (42 in Fig. 6). The
microstructured
surface, the sealing member, and the seal legs form a plurality of
encapsulated air
cells 65.
Typically, the seal legs have a height sufficient to provide an air interface
for the unbonded portion of the microstructured surface. The width of the seal
legs suitably may vary between about 0.2 mm to 4 mm, preferably between about
0.4 mm to 1 mm, and most preferably is at a width sufficiently narrow to
maximize retroreflectivity while maintaining a satisfactory bonding strength
of
the sealing member to the microstructured surface. The seal legs may be formed
by application of heat and pressure to the retroreflective member and the
sealing
member as disclosed in U.S. Pat. No. 3,190,178 (McKenzie).
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The thickness of the sealing member is sufficient to protect the
microstructured surface from exposure to factors, such as dirt and water that
lower their optical efficiency and to bond the article to a substrate. The
thickness
of the sealing member is preferably at least 0.02 mm, more preferably at least
0.06 mm, but generally the thickness does not exceed about 0.3 mm.
The seal legs typically form a sealing pattern on the viewing surface of
the face member. Patterns, such as hexagonal, rectangular, square, circular,
hexagonal, or chain link, may be employed as desired. The seal legs do not
retroreflect as much light as the area within the cells, which results in the
pattern
on the viewing surface. Typically, each individually sealed air cell has
length
and width dimensions A and B. Dimension A and B preferably range from about
4 mm to about 50 mm. Dimensions A and B determine the area of each cell on
the viewing surface. The area of the cells is preferably small. For example,
the
surface area of each cell is less than 5 square centimeters, preferably less
than 4
centimeters, more preferably less than 1 square centimeters, and most
preferably
less than 0.5 square centimeters, although area may vary from cell to cell.
Dimensions of a cell may be measured using a metric ruler and the area of a
cell
calculated by formulas known to those skilled in the art.
Some illustrative examples of materials for the sealing member include
thermoplastic, heat-activated, ultraviolet cured, and electron beam cured
polymer
systems. Preferably, the Vicat softening temperature of the sealing member is
at
least about 30°C less than that of the microstructured surface.
Other optical cores can include raised-ridge prismatic-type retroreflective
articles having a pattern of raised ridges with retroreflective elements
forming a
microstructured surface on the retroreflective member.
Optional Graphics
Optionally, graphics can be applied to the optical core or the vinyl film
before the primer is applied and before lamination of the optical core and
vinyl
film. When images are embedded in this way within the sheeting, the images are
generally more durable. Such images can be formed using gravure coating, for
example. Alternatively, images can be formed in the reflective layer of an
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optical core sheet through the use of lasers as disclosed in U.S. Pat Nos.
4,634,220 (Hicks et al.) and 4,688,894 (Hockert).
If graphics are applied using commercially available inks, such as vinyl
based inks, a primer can optionally be used between the graphics and the
optical
core or vinyl film. The primer described herein, optionally crosslinked with,
for
example, an aziridine crosslinker (such as that commercially available from
Zeneca, Wilmington, MA under the trade designation "Neocryl CX-100") can be
used. Other inks, such as EAA-based inks, can be used with a primer that
includes a copolymer of an olefinic monomer and a second monomer containing
a pendant carboxylic group described herein, either alone or mixed with the,
urethane polymer described herein. Other suitable covalent crosslinkers are
described in U.S. Patent No. 5,468,532 (Ho et al.).
Methods of Making Sheeting
Methods of making the sheeting of the present invention (preferably,
retroreflective sheeting) involve laminating a vinyl film to a preformed
optical
core. The vinyl film, the preformed optical core, or both are primed with a
primer that includes a urethane primer before laminating them together.
In one preferred embodiment, a method is provided that includes:
providing a vinyl film that includes a primer disposed on a first major
surface
thereof to form a primed surface, wherein the primer includes a urethane
polymer; providing a preformed optical core having two major surfaces; and
laminating a first major surface of the preformed optical core to the primed
surface of the vinyl film. In this method, the vinyl film can be primed with a
urethane polymer provided from a water-based urethane resin or from a solvent-
based urethane resin.
In another preferred embodiment, a method is provided that includes:
providing a vinyl film having two major surfaces; providing a preformed
optical
core that includes a primer disposed on a first major surface thereof to form
a
primed surface, wherein the primer includes a urethane polymer; and laminating
a first major surface of the vinyl film to the primed surface of the preformed
optical core. In this method, the optical core is preferably primed with a
urethane polymer provided from a water-based urethane resin.
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The optical core sheet and vinyl film, at least one of which is primed with
a urethane polymer-containing primer, can be directly laminated together using
a
typical thermal/mechanical method. Typically, the lamination temperature is
sufficiently hot to thermally bond the optical core to the vinyl film.
Typically,
opposing nip rolls are used, which may both be smooth, or one may be smooth
and one embossed for the formation of the seal legs described in certain of
the
desired embodiments disclosed herein. In addition to thermoforming techniques,
other techniques, such as ultrasonic welding, radio frequency welding, thermal
fusion, and reactive welding, may be used.
In a preferred lamination process, the application of temperature and
pressure occurs through the use of a nip roll process. Typically, the nip
force is
about 17 kg/cm width to about 21 kg/cm width; the hot can temperature is about
140°C to about 200°C; and the line speed is about 5
meters/minute to about 50
meters/minute. Those skilled in the art will optimize the line speed, nip
force
and other lamination conditions (e.g., hot can temperature) to obtain the
desired
properties in finished laminated sheeting, preferably retroreflective
sheeting, of
the invention.
Prior to the lamination process, it may be desirable to apply an adhesion-
promoting treatment to the surface of the optical core sheet and/or vinyl
film.
This can include a corona or plasma treatment. Such treatment is typically
applied to the surface of the optical core and/or vinyl film and then
optionally the
primer is applied to the treated surface.
Products
The sheeting of the present invention can be used in a variety of products,
including, but not limited to, a license plate, a reflective graphic article
(e.g.,
traffic sign), a pavement marking article, a road sign, vehicle conspicuity
sheeting, an article of clothing (e.g., a warning vest), footwear (e.g.,
running
shoes), an accessory bag, a backpack, a protective cover, a sheet, a tarpaulin
(e.g., a truck trailer cover), a warning tape, a decorative webbing, a
structural
webbing, or tapes, piping, patches and emblems for attachment to such items.
In many applications, the retroreflective article having a vinyl film is
mounted via an adhesive to a rigid substrate, such as an aluminum plate for a
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highway sign or for a license plate, or to a highway surface, such as concrete
or
asphalt. Typically, for signage and license plates, the vinyl film forms the
outermost surface of each of the articles.
An exemplary license plate in which the vinyl cover film and primer of
the present invention could be used is described in U.S. Pat. No. 5,882,771,
which includes a substrate (e.g., metal or plastic) having characters embossed
therein and a retroreflective sheeting adhered thereto. An exemplary graphics
article in which the vinyl film and primer of the present invention could be
used
is a roll-up sign, which includes a vinyl film mounted on a flexible scrim-
reinforced backing, as disclosed in U.S. Pat. Application Serial No.
09/393,369
(Atty. Docket No. 55056 USA 2A), filed on September 10, 1999, entitled
"Retroreflective Articles Having Multilayer Films and Methods of
Manufacturing Same." Exemplary pavement marking articles or other traffic
control articles in which the vinyl cover film and primer of the present
invention
could be used are disclosed in U.S. Pat. No. 5,981,033 (Haunschild et al.) and
International Publication Nos. WO 98/40562, WO 97/01677, and WO 97/01678.
For example, the vinyl film and primer of the present invention can be used
with
conventional optical core sheets used in: vertical applications, such as on
Jersey
barricades or guard rails; curved surface applications, such as traffic
barrels,
tubes, and cones; vehicle surfaces; road surfaces; signage; license plates;
reflective graphics; etc.
Examples
Features and advantages of the invention are further explained in the
following illustrative examples. All parts and percentages herein are by
weight
unless otherwise specified. The constructions cited in the Examples and
Comparative Examples were evaluated by the following tests.
180° Peel Force Test
The peel force was performed on each laminated construction on a test
panel by clamping the panel in the lower jaw of a Sintech 1 tensile testing
apparatus (MTS, Eden Prairie, MN) and the filament tape tab of the laminated
construction in the upper jaw. The laminated construction was separated at a
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180° peel back angle using a crosshead speed of 30.5 cm/minute. The
peel force
was recorded in grams/cm (lb/in) or, if the vinyl film could not be peeled
apart
from the remainder of the laminated construction, rated as "Could Not Be
Separated (CS)."
EXAMPLES 1- 2
Peel Force Between Primed Enclosed-Lens Optical Core
and Unprimed Vinyl Film
A first construction was made by casting 0.06 mm (2.5 mil) thick vinyl
film from organosol on a polyester (PET) carrier prepared according to Example
5 of U.S. Pat. No. 5,874,158 (Ludwig et al.), except that no pigments were
added
and an acrylic resin commercially available under the trade designation
"Elvacite
2013" from DuPont was substituted for "Acryloid B66" acrylic resin.
A second construction consisted of an enclosed-lens optical core
commercially available from Minnesota Mining and Manufacturing Company
("3M"), St. Paul, MN under the trade designation "Scotchlite Reflective
License
Plate Sheeting No. 3750." The surface of the optical core was corona treated
in
an air atmosphere at 1.4 kilowatts per meter width. Each corona treated
optical
core construction was independently coated with a primer solution prepared by
combining the primer listed in TABLE I with a 0.05 wt-% wetting agent (i.e.,
surfactant) commercially available from Air Products, Allentown, PA under the
trade designation "Surfynol 104 PA" to provide a primer solution of 99.95:0.05
(by weight).
The primer solution was coated on the optical core using a #8 wire bar to
provide a 0.018 mm (0.72 mil) wet coating thickness. The primer was dried for
5 minutes in a 121 °C (250°F) oven.
The exposed surfaces of both the primed optical core and the unprimed
vinyl film were air corona treated as described above for the optical core. A
5.1
cm wide by 25.4 cm long strip of green tape commercially available from 3M
under the trade designation "3M #8402" was placed crossweb between the first
and second constructions and aligned with both edges of the constructions. The
two constructions with the green tape therebetween were laminated together at
9.1 meters per minute using a hot can surface temperature of 154°C
(310°F).
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The resultant laminated constructions were stored at room temperature for
about
24 hours.
The PET carrier on the vinyl film was removed and then a razor blade
was used to cut the laminated construction down the center of the green tape
to
form two portions. From one portion of the laminated construction was cut a
2.5
cm wide by 12.7 cm long strip, the strip having the green tape on one edge.
The
release liner was removed from the adhesive of the optical core portion of the
construction (i.e., the second construction). The exposed adhesive surface of
the
strip was applied to a 7 cm wide by 28 cm long aluminum panel (6061T6 alloy
with etch and desmut surface from Q Panel Company, Cleveland, OH) aligning
the edge of the green tape portion of the strip with the edge of the aluminum
panel. The strip was applied to the panel by running a rubber coated, 5 cm
wide
roller back and forth along the length of the strip twice using hand pressure.
The vinyl film was lifted from the remainder of the laminated
construction in the area of the green tape area and a strip of filament tape
commercially available from 3M under the trade designation "Scotch 898 Tape,"
2.5 cm wide by 20 cm long, was wrapped around and adhered to the vinyl film in
the area of its separation from the remainder of the construction (i.e., at
the area
of the green tape) to form a tab of about 10 cm in length. The Peel Force Test
was performed immediately to provide the peel force data in TABLE I.
The 180° Peel Force Test data in TABLE I show that a strong bond
was
formed between the primed optical core and the unprimed vinyl film. The peel
force between the primed optical core and the unprimed vinyl film was of such
high strength that the optical core broke, i.e., the two constructions could
not be
separated.
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TABLEI
Ex. Primer Primer Peel Force
No. (w/w solution (w/w solid ratio)(g/cm; lb/in)
ratio)
1 100 % Neorez 9721---- CS
2 Neorez 972/lVIichem36.7!63.3 CS
498382 (30170)
1 A 34 wt-% solids dispersion of polyurethan in water commercially
available from Avecia (Formerly Zeneca Resins), Wilmington,
MA under the trade designation "Neorez 972."
2 A 25 wt-% solids dispersion of EAA commercially available from
Michelman Inc., Cincinnati, OH under the trade designation
"Michem 49838."
3 CS = Could Not Be Separated.
EXAMPLES 3 - 6
Peel Force Between Primed Vinyl Film and
Unprimed Enclosed-Lens Optical Core
The constructions of Examples 3-6 were prepared as detailed for
Examples 1-2 with the exception that the primer solutions (prepared by
combining the primer listed in TABLE II with 0.05% "Surfynol 104PA"
surfactant to provide a primer solution of 99.95:0.05 (by weight)) were
independently coated on the vinyl film instead of the optical core.
For Example 5, a second coat of primer solution was applied atop the
first coat after the first coat was dried. The second coat of primer solution
consisted of "Michem 49838" EAA dispersion and "Surfynol 104PA" surfactant
in a 99.95:0.05 weight ratio. The application, wet coating thickness and
drying
conditions of the second coat were the same as that described for the first
coat.
First and second constructions were prepared, air corona treated,
laminated together, sample laminated constructions prepared as described in
Examples 1-2 and tested according to the 180° Peel Force Test. The
Peel Force
Test values are provided in TABLE II.
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The 180° Peel Force Test data in TABLE II show that a strong bond
was
formed between the primed vinyl film and the unprimed optical core. The peel
force between the primed vinyl film and the unprimed optical core was of such
high strength that the optical core broke, i.e., the two constructions could
not be
separated.
TABLE II
Ex. Primer Primer Peel Force
No. First Coat Second Coat (g/cm; lb/in)
3 100 % Neorez 972 No CS
4 Neorez 972/MichemNo CS
49838 (30170)
5 100% Neorez 972 Michem 49838 CS
diluted with
0.05%
Surfynol 104PA
6 QC4820* No CS
* An aliphatic polyester urethane diluted to 12 wt-% with 1:1 (wt. ratio)
xylene/ethanol commercially available from K. J. Quinn & Co., Inc.,
Seabrook, NH under the trade designation "QC4820."
EXAMPLES 7 - 8
Peel Force Between Primed Embedded-Lens Optical Core
and Unprimed Vinyl Film
The constructions of Examples 7-8 were prepared as detailed for
Examples 1-2 with the exception that an embedded-lens optical core was
substituted for the enclosed-lens optical core. The embedded-lens optical core
was prepared according to Example 2 of U.S. Pat. No. 4,511,210 (Tung et aL).
First and second constructions were prepared, air corona treated,
laminated together, sample laminated constructions prepared as described in
Examples 1-2 and tested according to the 180° Peel Force Test. The
Peel Force
Test values are provided in TABLE I>I.
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The Peel Force Test data in TABLE III show that the peel force between
the primed optical core and the unprimed vinyl film was high and provided
constructions that did not easily peel apart.
TABLE III
Ex. Primer Primer Peel Force
No. (w/w solution ratio)(w/w solid ratio)(g/cm; Ib/in)
7 100 % Neorez 972 ---- 981; 5.5
8 Neorez 972/Michem 36.7/63.3 998; 5.6
49838 (30/70)
EXAMPLES 9 -11
Peel Force Between Primed Vinvl Film and
Unprimed Embedded-Lens Optical Core
The constructions of Examples 9-11 were prepared as detailed for
Examples 3-6 with the exception that an embedded-lens optical core was
substituted for the enclosed-lens optical core. The embedded-lens optical core
was prepared according to Example 2 of U.S. Pat. No. 4,511,210 (Tung et al.).
First and second constructions were prepared, air corona treated,
laminated together, sample laminated constructions prepared as described in
Examples 1-2 and tested according to the 180° Peel Force Test. The
Peel Force
Test values are provided in TABLE IV.
The Peel Force Test data in TABLE IV show that the peel force between
the primed vinyl film and the unprimed optical core was high and provided
constructions that did not easily peel apart.
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TABLE IV t~
Ex. Primer Primer Peel Force
No. (w/w solution ratio)(w/w solid ratio)(g/cm; lb/in)
9 100 % Neorez 972 ---- 1159; 6.5
Neorez 972/Michem 36.7/63.3 1017; 5.7
49838 (30/70)
11 QC4820 diluted ---- 1213; 6.8
to 12
wt-% with 1:1 (wt.
ratio) xylene/ethanol
5 EXAMPLES 12 -13
Peel Force Between Primed Vinyl Film and
Unprimed Embedded-Lens Optical Core
The constructions of Examples 12-13 were prepared as detailed for
Examples 3-6 with the exception that an embedded-lens optical core was
10 substituted for the enclosed-lens optical core. Then embedded-lens optical
core
was prepared according to Example 1 of U.S. Pat. No. 4,950,525 with the
exception that "Primacor 3440" (ethylene acrylic acid resin from Dow Chemical,
Midland, Mn instead of aliphatic polyurethane was used to extrude the film.
First and second constructions were prepared, air corona treated,
laminated together, sample laminated constructions prepared as described in
Examples 1-2, except that all the corona treatments were conducted in an air
atmosphere at 0.2 kilowatts per meter width and the first and second
constructions were laminated together at 1.5 meters per minute using a hot can
surface temperature of 157°C (315°F). The test samples were
tested according to
the 180° Peel Force Test and the values provided in TABLE V.
The Peel Force Test data in TABLE V show that the peel force between
the primed vinyl film and the unprimed optical core was high and provided
constructions that did not easily peel apart.
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TABLE V
Ex. Primer Primer Peel Force
No. (w/w solution ratio)(w/w solid ratio)(g/cm; lb/in)
12 100 % Neorez 972 ---- 838; 4.7
13 Neorez 972/Michem 36.7/63.3 820; 4.6
49838 (30/70)
COMPARATIVE EXAMPLE A
Peel Force Between Unprimed Vinyl Film and
Unprimed Enclosed-Lens Optical Core
The construction of Comparative Example A was prepared as detailed for
Examples 1-2 with the exception that the enclosed-lens optical core was not
primed.
First and second constructions were prepared, air corona treated,
laminated together, a sample laminated construction prepared as described in
Examples 1-2 and tested according to the 180° Peel Force Test. The
Peel Force
Test value was 53.5 g/cm (0.3 lb/in).
COMPARATIVE EXAMPLE B
Peel Force Between Unprimed Vinyl Film and
Unprimed Embedded-Lens Optical Core
The construction of Comparative Example B was prepared as detailed for
Examples 7-8 with the exception that the embedded-lens optical core was not
primed.
First and second constructions were prepared, air corona treated,
laminated together, a sample laminated construction prepared as described in
Examples 1-2 and tested according to the 180° Peel Force Test. The
Peel Force
Test value was 410.2 g/cm (2.3 lb/in).
The complete disclosure of all patents, patent documents, and
publications are incorporated herein by reference as if individually
incorporated.
Various modifications and alterations of this invention will become apparent
to
29
CA 02417728 2003-O1-28
WO 02/21167 PCT/US00/24363
those skilled in the art without departing from the scope and spirit of this
invention.
