Note: Descriptions are shown in the official language in which they were submitted.
~_ 2 1 5 1 7 8 0 50704U~A
REMOVABLE NONPOROUS OPAQUE THIN FILM LAYER
Background of the Invention
Field of the Invention
The present invention relates to transparent imaging
sheets for use in printers and copiers. More
specifically, the present invention relates to a
composite sheet having a releasable non porous opaque
thin film layer attached to an edge portion of the
transparent imageable sheet.
Description of the Art
Copiers and printers usually employ sophisticated
mechanisms to allow them to select a single imaging sheet
from a stack of such sheets and, by means of rollers,
wheels, belts, and the like, cause each such sheet to be
rapidly and precisely moved past various points in the
machine which image and process the sheet. In this way,
large numbers of copies can be made in a short time.
Further, the automated feeding means that an operator
need not tend the copier during such process. A large
number of sheets is stacked in the feeding tray of the
copier or printer, and combinations of optical sensing
mechanisms (which may be transmissive or reflective), and
mechanical methods are used to detect the passage of
sheets. These sensing mechanisms will halt the operation
if jamming occurs to avoid any damage to the machine.
Transparent films~ by their nature, cannot be
detected by optical sensors. In order for such sensing
mechanisms to operate, the sheets need to be at least
partially opaque to interrupt the light beams employed in
the photosensing mechanisms. Otherwise, transparent
sheets will not operate in such machines.
In order to render transparent sheets useful in
these machines, two different solutions have been used to
form an opaque area readable by the sensor. Most
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commonly, a paper backing has been used; however,
synthetic paper and some thicker films have been
disclosed. The paper or other opaque body is typically
releasably adhered to the transparent imaging sheet by
means of a thin line of adhesive. The paper may cover
only a portion of the sheet, e.g., it may be a stripe
along the leading edge portion of a plane opposite to the
image transfer plane of the transparent film such as that
disclosed in Sho 58-187743, or for machines requiring
larger opaque areas, a full sheet of paper substantially
coextensive with the imaging sheet, such as described in
CA 1184951. When the transparent sheet has been imaged,
the operator removes the paper from the transparent sheet
and discards the paper.
Paper backings and thick film backings work quite
well for opacity, and may be designed to be easily
releasable from the imaging sheets after imaging;
however, the backings disclosed insulate the sheets from
contact with the heated fuser which can result in
insufficient fusing in copier machines. Further, the
paper used for such stripes is usually quite thick and
therefore the edge portion bearing the paper backing is
much thicker than the portion of the sheet not bearing
the paper backing. When a large number of sheets are put
into the feeding tray, the thickness of the combination
of paper stripes at one edge of the sheet causes one side
of the stack to be almost twice as tall as the other
side. This results i~n feeding problems, as well as
substantially limiting the number of sheets which can be
stacked at one time. Another problem occurs in imaging
machines which pick up a sheet in the center of the sheet
stack. In these machines, the sensor for the stack will
give a false reading and the mechanical means will not
lower to the correct height to select a sheet.
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Color copiers have two problems with transparent
imaging sheets. First, most color copiers require that
such sheets be bypass fed rather than tray fed. In some
models, this means single sheet bypass feeding by an
operator. The bypass feeding causes a slower trip
through the fuser, increasing the fuser contact time,
thus ensuring complete fusing of the transparent imaging
sheet. Second, tray feeding, possible only if the
imaging sheet can simulate a sheet of paper to the
sensor, causes a faster trip through the fuser, which
reduces the fuser contact time. This makes the fusing
much more heat transfer limited, and may result in
incomplete fusing of the color image. If the imaging
sheet has a backing or stripe, the insulative property
thereof reduces fusing even further, typically resulting
in visible degradation of color image quality.
The other alternative, useful where only a small
portion of the transparent sheet need be opaque is the
printing of a dark line along the top or side of such
sheet such as that disclosed in Sho 56-204005.
U.S. Patent No. 5,126,762 discloses a recording
sheet having a mark for permitting the determination of
sheet feeding as well as differentiating between front
and back surfaces of the sheet. The sheet comprises an
optical functional portion disposed along at least one
edge of the sheet and arranged asymmetrically with
respect to the center of the edge and having a functional
feature regarding ligh~t different from that of an image
forming portion of the sheet.
These composite sheets can be stacked into a tray
without causing feeding problems as the thinness of the
printed line or lines does not cause stacking problems.
However, such thin printed lines are not removable after
imaging and are visible when projected during a
presentation which is not aesthetically pleasing.
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Imaging sheets constructed to have an attached
overlay, at least a portion of which is an opaque sensing
strip, are disclosed in U.S. Patent No. 5,208,093. Such
an article preferably comprises a second opaque region,
or a tab, underlying the transparent sheet and spaced
away from the first opaque strip leaving a transparent
window to signal the fuser that a transparency has been
fed, so that the fusing speed can be reduced for better
fusing. However, this reference prefers porous materials
to be used as opaque strips and tabs, and such porous
materials are known to be good insulators. Also, porous
materials must be relatively thick to have sufficient
tensile strength required for clean removal without
tearing.
It would therefore be desirable to create a
composite imaging sheet having a thin easily-releasable
layer, which can be applied in differing positions and
sizes during, or immediately after manufacture of the
imaging sheet. Such a sheet would provide good automated
stacking and feeding in state of the art machines.
It would further be desirable for such thin layer
not to having such large insulating effects on the film
during fusing, as such insulation reduces the
effectiveness of the fusing. Effective fusing is
especially important for good image quality in the case
of color copiers, but may impact toner adhesion and image
quality in black and white copiers as well.
Finally, it would~ be highly desirable to have a film
which would tray feed effectively~in a color copier,
especially in those copiers which only allow single sheet
bypass feeding of transparency films.
It has now been discovered that the use of a
nonporous opaque thin film layer provides improved
multiple sheet feeding, while minimizing the insulative
characteristics. These sheets therefore, exhibit more
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complete fusing, and attendant improved image quality and
have sufficient opacity to be tray fed.
Summary of the Invention
The present invention provides a composite imaging
sheet for use in copying and printing devices which has a
nonporous opaque thin film layer which allows a
transparent imaging sheet to be used in machines having
optical sensors. The nonporous opaque thin film layer
provides such benefit without insulating the sheets,
which allows full fusing in copier machines. The
composite sheet stacks easily in such machines and large
numbers may be fed both from side selecting and midpoint
selecting machinery. The nonporous opaque thin film is
easily removable after imaging so that the final imaged
transparency has no distracting dark line or area when
projected during a presentation.
Specifically, the composite imaging sheet of the
invention comprises a transparent imageable sheet having
a machine direction and a transverse direction, said
sheet having two major surfaces, each surface having four
edges with edge portions coextensive therewith, said
sheet bearing a releasable nonporous opaque thin film
layer having a total thickness of from 5 to 60 ~Im and a
film thickness of no greater than 30 ~m on at least one
edge portion of one surface of said imageable sheet said
thin film layer having an opacity of at least 70%, and a
tensile energy to brea~k of at least 0.1 joule, said film
layer being cleanly released from said imageable sheet.
Preferred composite imaging sheets of the invention
comprise a nonporous opaque thin film layer having an
opacity of at least 75% and a tensile energy to break of
at least 0.25 joule, said nonporous opaque thin film
layer being cleanly releasable from said imageable sheet.
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For those composite sheets of the invention
specifically designed for use with color copiers, the
projected color image of an imaging sheet of the
invention will exhibit an increased pastel haze (~ Pastel
Haze) of no more than 10% when measured in regions of the
image overlaid by the nonporous opaque thin film layer.
This value is based on a reference sheet having no
attached nonporous opaque thin film layer.
In an especially preferred embodiment of the
invention for color copiers, the nonporous opaque thin
film layer has a machine direction width which is
sufficient in size to simulate paper to the sensor. It
is believed that this is the first time tray feeding of
transparency films has been possible on most color
copiers.
Once formed, the nonporous opaque thin film layer
remains attached to the imaging sheet throughout the
printing and copying process until manually removed.
The opaque thin releasable opaque film layer can
vary in total thickness from 5 ~lm to 60 ~lm, preferably
from 5 to 35 ~m. The film thickness varies, but must be
no greater than 30 ~m, preferably 25 ~m or less. The
thinness of this layer makes it possible to allow from 3
to 10 times as many of these composite sheets to be
stacked into the feeding tray of a printer or copier as
conventional sheets without significant insulating effect
or feeding problems. Because the opaque edge portion of
the composite imaging sheet does n~ot insulate the imaging
sheet, incomplete fusing problems, and resultant
degradation of images are not encountered. This is even
true for images made at tray-feed speeds in color
coplers .
The releasable nonporous thin opaque film layer has
adhesive characteristics, i.e., either the layer is
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directly coated on or it is attached by means of an
adhesive composition. Whichever method is used, the
layer can be cleanly removed from the transparent sheet
even after imaging. Surprisingly, the thin layer
possesses sufficient tensile strength that the layer is
cleanly removable, i.e., no tearing of the layer occurs
during removal.
In another embodiment of the invention, the
nonporous opaque thin film layer is arranged along
multiple, typically two, edge portions of the imaging
sheet, such edge portions can either be in a parallel or
perpendicular relationship to each other. This allows
imaging in either the portrait or landscape positions.
In yet another embodiment of the invention, the
nonporous opaque thin film layer can have varying degrees
of opacity along the transverse direction of the imaging
sheet so that machines having asymmetrically placed
sensors will be able to distinguish the imaging surface
of the imaging sheet from the opposing surface, and thus
prevent jams caused by inverted sheets.
The following terms have the defined meanings when
used herein.
1. The terms "film" and "thin film" mean a
continuous nonporous polymeric sheet having a film
thickness of no greater than 30 ~lm which is substantially
non fiber containing.
2. The term "thickness" refers to the dimension
measured from the subs`trate through the coating to the
surface, also called "coating hèight" or "coating depth".
3. The terms "opaque" and "opacity" as used herein
mean non-transparent, i.e., the thin film layer has
optical properties which cause light blocking, light
reflecting or light scattering or a combination thereof
to such an extent as to prevent transmission of the
majority of light. A majority of light is not
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J transmitted through the edge portion(s) of the
transparency bearing the thin film layer thereon.
The opacity must also be such that the layer is
capable of interrupting the light beams employed in the
5 photosensing mechanisms, i.e., it must be at least 70%.
4. The term "total thickness" when used for the
nonporous opaque thln film layer means the thickness of
the film layer combined with the thickness of the
adhesive used to attach the layer, if any, and the
10 thickness of the opaque paint or dye used to render the
film layer opaque, if any.
5. The term "film thickness" when used for the
nonporous opaque thin film layer means the thickness of
the film only, i.e., the actual dried coating height of
15 the film.
6. The term "edge portion" means a portion smaller
than the entire imageable sheet, said portion being
coextensive with one edge of a major surface. Each major
surface has four edge portions.
7. The term "leading edge" means that edge of the
paper which is the first edge of the sheet to feed into
the copier or printer. Depending on whether a landscape
or portrait oriented image is desired, the leading edge
may be either length edge of a rectangular imaging sheet.
8. The term "stripe" refers to a nonporous opaque
thin film layer having a small machine direction width
and therefore having a line or stripe appearance.
9. The terms "s~triped" and "striped film" mean a
film having an opaque layer thereo~, either a layer
within the scope of invention or a paper layer outside
the scope of the invention, as specified.
10. The term "width" means the amount of space that
the thin film layer overlays proceeding from the edge of
the transparency toward the interior.
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All percents, ratios and parts herein are by weight
unless otherwise specified.
Detailed ~escription of the Invention
This invention describes the use of a nonporous
opaque thin film layer as a sensing layer or stripe for
transparent imaging sheets. Films useful as nonporous
opaque thin film layers must have four characteristics;
they must be strong enough to be cleanly removable, they
must be opaque enough to reliably trip the optical sensor
used in copiers, they must have low enough insulative
effects to allow complete fusing in order to provide
excellent image quality, and they must be thin enough not
to cause a large variation in the stack height from the
edge portion having the overlaid film layer to the edge
portion which does not have a film layer. The top sheet
"slopes" down from one edge portion to the other.
Useful films have a tensile energy to break of at
least 0.1 joule, preferably at least 0.25 joule. Films
or other materials having lower tensile strength than 0.1
joule will have insufficient strength to be cleanly
removable, i.e., they will frequently tear when removal
is attempted.
This thin layer can be selected from a variety of
heat-resistant materials, as long as such materials are
available in the requisite thickness, i.e., less than 30
~m, and possess sufficient structural integrity such that
no tearing of the layer occurs during imaging or removal.
Heat-resistance means that usefùl films must retain
sufficient cohesive strength to be easily removed in one
piece from the imaging sheet when normally fused, and
when a misfeed results in extended contact with hot
fusing rolls. Useful films must have sufficient cohesive
strength to allow a clean removal in most samples from
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the fusing roll should a premature release from the
imaging sheet causes retention in the copier machine.
The nonporous opaque thin film layer can be formed
from heat-resistant polymer films including, but not
limited to, polyolefins such as polyethylene and
polybutylene; polystyrene; polyesters such as
polyethylene terephthalate (PET); polymethylmethacrylate;
cellulose acetate; polyvinylchloride and polyvinylidene
fluoride; polyamides and polyimides; and mixtures
thereof. Polyethylene and PET are preferred, with PET
being highly preferred.
Porous materials, such as those disclosed in U.S.
Patent 5,208,093, are not useful as thin film layers of
the invention. When such layers are used in typical
thicknesses, the stack height variation is on the order
of 2; that is, the edge portion of the imaging sheet
overlaid by the porous material is close to twice the
height of the edge portion having no porous material
overlaid. The thick material also has a very large
insulative effect. If the porous material is formed into
thinner layers, the tensile strength and the opacity
decrease drastically while the insulative effect
decreases more slowly. This means that layers which are
thin enough for the imaging sheets to pass the stack
height variation test fail two or even all three other
requirements; they typically have opacity values of less
than 70%, they have extremely low tensile strength, and
may still have insulative values high enough to prevent
complete fusing. This is seen by ~educed image quality.
When an adhesive is employed for attaching the thin
film layer to the imaging sheet, its adhesive properties
need to be carefully balanced. The thin film opaque
layer needs to adhere firmly to the imaging sheet so that
the composite sheet will not be separated during routine
handling and packaging, or during imaging in the copier
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or printer. However, the adhesive must also allow the
thin film opaque layer to be readily removed from the
imaging sheet without leaving adhesive residues. This
must also be true of the adhesive properties of directly
coated thin film opaque layers.
Useful adhesives include inherently-tacky,
elastomeric copolymer microspheres such as disclosed in
U.S. Patents 3,691,140 and 4,166,152; removable adhesives
such as disclosed in U.S. patents 4,599,265, 4,855,170,
and 5,283,092.
Preferably, the adhesive composition comprises:
1) from 50 to 90 parts by weight of at least one
lower alkyl acrylate having an alkyl group comprising
from 4 to 12 carbon atoms; and
2) from 10 to 50 parts by weight of at least one
higher alkylacrylate having an alkyl group comprising
from 12 to 26 carbon atoms.
Photocrosslinker may be added if necessary improve
the cohesive strength of the adhesive in order to prevent
substantial adhesive transfer to the imaging sheet. The
photocrosslinker is preferably present from 0.05% to 1
by weight of the adhesive composition.
This preferred adhesive has high cohesive strength,
high tack and high peel strength along with good
removability. The adhesive further possesses low melt
viscosity and can be easily used as a hot melt adhesive
thereby allowing it to be used in an continuous
processing line forming~the composite imaging sheet.
The total thickness of the nonporous opaque thin
film layer (film plus adhesive) ranges from 5 ~lm to 60
~m, preferably from 5 ~m to 50 ~m. The film thickness is
no greater than 30 ~m, preferably from 5 ~m to 25 ~m.
The adhesive layer ranges in thickness from 2.5 ~m to 30
~m, preferably from 5 ~m to 15 ~Im. At these thicknesses,
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the films have good tensile strengths, opacity values,
and do not cause stack height variation.
The opacity can be accomplished either by casting a
pigment filled composition into a film and attaching the
film onto the imaging sheet, or by coating or printing a
pigment filled composition or ink. The pigment filled
composition can be coated onto a substrate and then
attached onto the imaging sheet, or coated directly onto
the imaging sheet. A transparent nonporous thin film can
also be printed with an opaque ink after attachment to
the imaging sheet, if desired.
The degree of opacity needed will depend on the
detection methods used in the copier or printer. However,
the opacity of the stripe should be at least 70%,
preferably, greater than 75~ for ease and reliability of
detection by the optical sensor.
In one embodiment where opacity is introduced by
direct printing of a thin film and attachment of the
printed film to the imaging sheet, the degree of opacity
is varied along the transverse direction of the thin film
layer. This permits the copier or printer to distinguish
between the imageable and nonimageable surfaces of the
imaging sheet while still sensing that a sheet has been
fed when fed in the proper orientation. This permits the
coating of only one surface of the transparency, if
desired, or coating a different coat on the opposing
surface, e.g., a feed facilitation coat, without fear of
inverted feeding. Pref~erably, the opacity of the layer
should drop to a level beyond which the opacity will no
longer be detected by the sensing device at the center of
the transverse direction width. However, since certain
machines have centered sensing devices, and others have
asymmetrically placed sensing devices, this embodiment of
the invention may have an opacity gradient specifically
designed for a certain model or series of copiers or
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=_ ^ 2151 78~
printers. Since inverted sheets result in machine jams
and possibly, deposits of imageable coatings onto
portions of the machine, requiring manual removal and
possible down time for cleaning, this embodiment allows
multiple worry free feeding, as an inverted sheet will
simply not be sensed by the machine, and thus will not
feed.
If the nonporous opaque thin film layer is coated or
painted directly onto the imageable sheet, the
composition must be chosen to permit removability without
leaving any unwanted residue on the imageable sheet.
Useful compositions for coating directly onto the
imaging sheet include such binders as hot-melt binders,
and W-curable binders, including but not limited to
water-soluble polymers such as poly(vinyl alcohol),
poly(vinyl pyrrolidone), and gelatini solvent-soluble
binders such as poly(bisphenol-A-ester), e.g., those
available under the trade name Atlac~ from Reichold
Chemical; acrylic resins, urethanes, and the like.
These compositions may contain pigments or dyes for
coloring purposes, with the pigment to binder ratio being
preferably less than one. Lower ratios of binder in the
composition tend to produce brittle layers, whereas
higher ratios tend to excessively soften the layers.
Preferred pigments include conventional pigments and
dyes such as titanium dioxide, carbon black, metallic
oxides, metal powders lead chromates, natural and
synthetic dyes and pigments used in~inks, fabrics and the
like.
The surface of the substrate may be treated to
better receive or retain the nonporous opaque thin film
layer. However, any treatment to improve adhesion of the
stripe to the substrate should not interfere with the
removability of the stripe.
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The transparency film is generally coated with an
imaging layer on at least one major surface. The imaging
layer can be any toner-receptive or ink-receptive
composition imageable in a copier or printer.
Compositions suitable for the imaging layer include a
variety of known compositions depending on the machine(s)
with which the film is intended for use. Useful imaging
compositions include thermoplastic resins such as
polyester resins, styrene resins, polymethylmethacrylate
resins, epoxy resins, polyurethane resins, vinyl chloride
resins, and vinyl chloride-vinyl acetate resins.
If the image-receptive sheet is to be used in a
plain paper copier, the imaging coating typically
comprises from 65 parts to 99.9 parts of a film forming
polymer, which can be any polymer, copolymer or polymer
blend capable of water-based emulsion coating or aqueous
solution coating, using conventional coating techniques.
Such polymers can be made from any ethylenically
unsaturated monomers and can include acrylates and
methacrylates, styrenes, substituted styrenes and
vinylidine chlorides.
In this embodiment, the film forming polymer
contains from 80 parts to 100 parts of at least one
monomer selected from the group consisting of bicyclic
alkyl (meth)acrylates, aliphatic alkyl (meth)acrylates
having from one to twelve carbon atoms, and aromatic
(meth)acrylates.
Useful bicyclic (m~eth)acrylates include, but are not
limited to, dicyclopentenyl (meth)acrylate, norbornyl
(meth)acrylate, 5-norborene-2-methanol, and isobornyl
(meth)acrylate. Preferred bicyclic monomers include
dicyclopententyl (meth)acrylate, and isobornyl
(meth)acrylate.
Useful aliphatic alkyl (meth)acrylates include, but
are not limited to, methyl acrylate, ethyl acrylate,
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methyl (meth)acrylate, isobutyl (meth)acrylate, isodecyl
~meth)acrylate, cyclohexyl (meth)acrylate, and the like.
Preferred aliphatic monomers include methyl
(meth)acrylate, ethyl (meth)acrylate, and isodecyl
(meth)acrylate.
Useful aromatic (meth)acrylates include, but not
limited to benzyl(meth)acrylate and styrene
(meth)acrylate.
The polymer can also contain from 0 to 20 parts of a
polar monomer having the formula:
CH2=C--C--O--( CH2 ) n~N~R2
ll l
O Rl
wherein R is hydrogen or methyl, Rl and R is selected
from the group consisting of hydrogen, identical, and
differing alkyl groups having up to 8 carbon atoms,
preferably up to 2 carbon atoms; the N-group can also
comprise a cationic salt thereof.
Useful examples include N,N-dialkyl monoalkyl amino
ethyl (meth)acrylate, and N,N-dialkyl monoalkyl amino
methyl (meth)acrylate, N-butyl amino ethyl
(meth)acrylate, and the like for emulsion polymers, and
quaternary ammonium salts thereof for solution polymers.
Preferred monomers include N,N'-diethylamino-
ethyl(meth)acrylate, and N,N'-dimethyl-
aminoethyl(meth)acrylate for emulsion polymers andbromoethanol salts of N,N'-dimethylaminoethyl
(meth)acrylate, and N,N'-diethylaminoethyl(meth)acrylate
for solution polymers.
The presence of these polar monomers improves the
adhesion of the coating to the transparent film substrate
or backing.
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Preferred film forming polymers comprise at least
two monomers selected from aliphatic alkyl (meth)acrylate
monomers, bicyclic alkyl (meth)acrylates monomers and
aromatic (meth)acrylates.
In one preferred embodiment of the invention
especially useful with color copiers, the nonporous
opaque thin film layer is selected such that the
projected color image has an increase in pastel haze in
regions of the image overlying the nonporous opaque thin
film layer of no more than 10% when compared to a similar
reference sheet without a nonporous opaque thin film
backing. This provides an imaged sheet having much
better image color quality in the areas of the imaging
sheet which overlay the opaque area when compared to a
sheet having a more conventional removable paper backing
for feed facilitation.
In a highly preferred embodiment for color copiers,
the nonporous opaque thin film layer or stripe has a
sufficient machine direction width to simulate a piece of
paper to the copier sensor. The copier then processes
the imaging sheets of the invention at the same speed as
paper, and allows tray feeding of the imaging sheets.
This is a great advantage in machines such as the "Canon
CLC" series color copiers, which only allow single bypass
feeding of transparent imaging sheets at one per minute.
This occupies an operator continually during imaging of
multiple sheets.
However, this embodiment of the invention, which
preferably bears a nonporous opaque thin film layer
having a machine direction width of at least 1.75 cm,
preferably at least 1.9 cm, may be fed in the paper tray
in these copiers, allowing several hundred imaging sheets
to be imaged without an operator present, and causes the
imaging sheets to be imaged at the much faster paper rate
rather than at the slower bypass rate.
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Preferred imaging coatings for use with color
copiers include polyester resins, e.g., polyesters based
on bisphenol A, such as ATLAC~382E, (also sold as
ATLAC~R 32-629), available from Reichold Chemical as well
as bisphenol A monomers and their derivatives, (e.g., the
dipropylene glycol ether of bisphenol A). A suitable
carrier binder such as ~itel~ PE 222 polyester resin,
available from The Goodyear Tire and Rubber Company, is
also present when bisphenol A monomers or their
derivatives are used to facilitate coating. The
thickness of this imaging coating is preferably between
0.5 to 10 ~m, more preferably from 1 to 6.5 ~m.
Where use in color copiers is desirable, the imaging
coating may also contain polymeric, silica or starch
particles to reduce pooling of the fusing oil at the
edges of the sleeves and inhibit transfer of the oil to
the stage of a projection device when the transparency is
used. Useful particles are from 5 to 25 ~m in diameter,
more preferably from 10 to 20 ~m in diameter. Larger
particles are effective to reduce the oil pooling, but
have the problem of being visible when projected.
Smaller particles, i.e., less that 5 ~m, in diameter may
be used, but a higher loading is required to effectively
reduce the oil pooling. This often results in higher
haze of the final image. Also, the smaller particles are
not effective in regions of the transparency where the
thickness of the toner layer exceeds the extent to which
the particles normally protrude from the imaging layer.
This is especially important when multiple toner layers
are present, e.g., in color electrophotography. For
example, after fusing a two layer green (cyan plus
yellow) toner layer on a Canon CLC 200, the toner
thickness can be from 3.5 to 11 ~m.
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Preferred particles include Syloid~ 620 particles,
available from Davison Chemical.
When it is desirable to use the transparency with an
ink-jet printer, the imaging coating the ink-receptive
layer comprises a crosslinked semi-interpenetrating
network, hereinafter referred to as an SIPN, formed from
polymer blends comprising a) at least one crosslinkable
polymeric component, b) at least one liquid-absorbent
polymer comprising a water-absorbent polymer, and (c)
optionally, a crosslinking agent. The SIPNs are
continuous networks wherein the crosslinked polymer forms
a continuous matrix. The SIPN is generated by
crosslinking a copolymer containing from 3 to 20%
ammonium acrylate groups with a crosslinking agent and
then combining the copolymer with a liquid absorbent
polymer or an uncrosslinked blend of the polymer.
Such crosslinked systems have advantages for dry
time, as disclosed in U.S. Patent 5,134,198 (Iqbal).
The water-absorbing hydrophilic polymeric material
comprises homopolymers or copolymers of monomeric units
selected from vinyl lactams, alkyl tertiary amino alkyl
acrylates or methacrylates, alkyl quaternary amino alkyl
acrylates or methacrylates, 2-vinylpyridine and 4-
vinylpyridine. Polymerization of these monomers can be
conducted by free-radical techniques with conditions such
as time, temperature, proportions of monomeric units, and
the like, adjusted to obtain the desired properties of
the final polymer.
Hydrophobic polymeric materials are preferably
derived from combinations of acrylic or other hydrophobic
ethylenically unsaturated monomeric units copolymerized
with monomeric units having acid functionality. The
hydrophobic monomeric units are capable of forming water-
insoluble polymers when polymerized alone, and contain no
pendant alkyl groups having more than 10 carbon atoms.
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They also are capable of being copolymerized with at
least one species of acid-functional monomeric unit.
Preferred hydrophobic monomeric units are preferabiy
selected from certain acrylates and methacrylates, e.g.,
methyl(meth)acrylate, ethyl(meth)acrylate, acrylonitrile,
styrene or a-methylstyrene, and vinyl acetate. Preferred
acid functional monomeric units for polymerization with
the hydrophobic monomeric units are acrylic acid and
methacrylic acid in amounts of from 2% to 20%.
The crosslinking agent is preferably selected from
the group of polyfunctional aziridines possessing at
least two crosslinking sites per molecule, such as
trimethylol propane-tris-(~-(N-aziridinyl)propionate)
CH3--CH2--C-(CH2--O C--CH2--CH2--N~Cl )
pentaerythritol-tris-(~-(N-aziridinyl)propionate)
8 ,CH2
OH--CH2--C--(CH2--O C-CH2--CH2--N~ ¦ )
trimethylolpropane-tris-(~-(N-methylaziridinyl
propionate)
Cl H3
1l / Cl H
CH3--CH2--C-(CH2--O C--CH2--CH2--N~
and so on. Crosslinking can also be brought by means of
metal ions, such as provided by multivalent metal ion
salts, provided the composition containing the
crosslinkable polymer is made from 80 to 99 parts by
--19--
2151780
weight of monomer and from 1 to 20 parts by weight of a
chelating compound.
SIPNs to be used for forming ink-receptive layers of
the present invention typically comprise from 0.5 to 6.0
percent crosslinking agent, preferably from 1.0 to 4.5
percent, when crosslinking agents are needed. The
crosslinkable polymer can comprise from 25 to 99 percent,
preferably from 30 to 60 percent of the total SIPNs. The
liquid-absorbent component can comprise from 1 to 75
percent, preferably from 40 to 70 percent of the total
SIPNs.
Any imaging coating useful herein, e.g., whether
designed for use with plain paper copiers, color copiers,
or printers, may also contain polymeric particles.
Useful polymeric particles range from 1 ~m to 15 ~m in
diameter and include such polymers as
poly(methylmethacrylate) (PMMA), modified
poly(methylmethacrylate), poly(tetrafluorethylene),
polyethylene, and particles produced from diol
di(meth)acrylate homopolymers which impart antifriction
characteristics when coated on image recording sheets.
These diol di(meth)acrylates can be reacted with long-
chain fatty alcohol esters of (meth)acrylic acid.
Preferred water based imaging coatings contain
particles selected from PMMA, modified PMMA, and
particles produced from diol-di(meth)acrylate
homopolymers or copolymers of diol di(meth)acrylates
reacted with long-chain fatty alcohol esters of
(meth)acrylic acid.
Specifically such microspheres comprise at least 20
percent by weight polymerized diol di(meth)acrylate
having a formula
CH2=CR2COOCnH2nOOCCR2=CH2
wherein R2 is hydrogen or a methyl group, and n is an
integer from 4 to 18. Examples of these monomers include
-20-
2151780
-
those selected from the group consisting of 1,4-
butanediol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,10-
decanediol di(meth)acrylate, 1,12-dodecanediol
di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate,
and mixtures thereof.
Preferred monomers include those selected from the
group consisting of 1,4-butanediol di(meth~acrylate, 1,6
hexanediol di(meth)acrylate, 1,12-dodecanediol
di(meth)acrylate, and 1,14-tetradecanediol
di(meth)acrylate.
The microspheres may contain up to 80 weight percent
of at least one copolymerized vinyl monomer having the
formula
lS CH2=CR2COocmH2m+l
wherein R2 is hydrogen or a methyl group and m is an
integer of from 12 to 40.
Useful long-chain monomers include, but are not
limited to lauryl (meth)acrylate, octadecyl
(meth)acrylate, stearyl (meth)acrylate, and mixtures
thereof, preferably stearyl (meth)acrylate.
The microspheres may optionally contain up to 30
percent by weight of at least one copolymerized
ethylenically unsaturated monomer selected from the group
consisting of vinyl esters such as vinyl acetate, vinyl
propionate, and vinyl pivalate; acrylic esters such as
methacrylate, cyclohexylacrylate, benzylacrylate,
isobornyl acrylate, hydroxybutylacrylate and glycidyl
acrylate; methacrylic esters such as methyl methacrylate,
butyl methacrylate, cyclohexyl methacrylate, benzyl
methacrylate, ~-methacryloxypropyl trimethoxysilane, and
glycidyl methacrylate; styrene; vinyltoluene; a-methyl
styrene, and mixtures thereof.
-21-
2151780
-
Most preferred microspheres include 50/50
poly(hexanediol-diacrylate/stearyl methacrylate), and
50/50 poly(butanediol-diacrylate)/lauryl(meth)acrylate,
80/20 poly(hexanediol-diacrylate)/stearyl(meth)acrylate,
50/50 polymethylmethacrylate/ 1,6 hexanedioldiacrylate,
C14 dioldiacrylate, and C12 dioldi(meth)acrylate.
In addition to the above, useful microspheres may
also comprise additives which are not ethylenically
unsaturated, but which contain functional groups capable
of reacting with materials containing reactive groups
which may also be coated on the substrate along with the
microspheres. Such additives are useful in modifying the
degree of interaction or bonding between the microspheres
and the imaging polymer. Suitable examples include
organosilane coupling agents having alkyl groups with 1
to 8 carbon atoms, such as glycidoxy trimethoxysilanes
such as ~-glycidoxypropyltrimethoxysilane, and
(aminoalkylamino) alkyl trimethoxysilanes such as 3-(2-
amino ethyl amino) propyl trimethoxysilane.
For good feedability, the mean particle size
preferably ranges from 0.25 ~m to 15 ~m. Particles
smaller than 0.25 ~m would require the use of more
particles to produce an effective coefficient of
friction, this would tend to also produce more haze.
Larger particles than 15 ~m would require thicker
coatings to anchor the particles firmly in the coatings,
which would increase haze and coating cost. For good
performance, the particles preferably have narrow
particle size distributions, i.e., a standard deviation
of up to 20~ of the average particle size. These ranges
are preferably 0.1-0.7 ~m, 1-6 ~m, 3-6 ~m, 4-8 ~m, 6-10
~m, 8-12 ~m, 10-15 ~m. More preferred particles are
those having bimodal particle size distributions. This
is made by mixing particles having 2 different particle
-22-
2151780
size distributions. When bimodal particles are used,
both particles can be selected from the preferred
polymeric beads described above, or one of the particles
can be a preferred microsphere and the other may be
selected from other particles such as PMMA and
polyethylene particles. If so, the second type of
particle also preferably has a narrow particle size
distribution.
Most preferably, both bimodal particles are selected
from particles produced from the copolymer of
hexanedioldiacrylate and stearylmethacrylate, having
particle size distributions of from 1 to 4 ~m and from 6
to 10 ~m, or from 2 to 6 ~m and from 8 to 12 ~m, or from
0.20 to 0.5 ~m and from 1-6 ~m.
An antistatic agent may be present in any imaging
coating. Useful agents are selected from the group
consisting of nonionic antistatic agents, cationic
agents, anionic agents, and fluorinated agents. Useful
agents include such as those available under the trade
name AMTERTM, e.g., AMTERTM 110, 1002, 1003, 1006, and the
like, derivatives of JeffamineT~ ED-4000, 900, 2000 with
FX8 and FX10, available from 3M, LarostatTM 60A, and
MarkastatTM AL-14, available from Mazer Chemical Co., with
the preferred antistatic agents being steramido-
propyldimethyl-~-hydroxy-ethyl ammonium nitrate,
available as CyastatTM SN, N,N'-bis(2-hydroxyethyl)-N-(3'-
dodecyloxy-2'2-hydroxylpropyl) methylammonium
methylsulfate, available as CyastatTM 609, both from
American Cyanamid.
When the antistatic agent is present, amounts of up
to 20% (solids/solids) may be used. Preferred amounts
vary, depending on coating weight. When higher coating
-23-
2151780
-
weights are used, 1-10% is preferred; when lower coating
weights are used, 5-15% is preferred.
Where emulsion polymerization of the polymer is
desired, an emulsifier is also present. The emulsifiers
include nonionic, or anionic emulsifiers, and mixtures
thereof, with nonionic emulsifiers being preferred.
Suitable emulsifiers include those having a HLB of at
least 10, preferably from 12 to 18.
Useful nonionic emulsifiers include C11 to C18
polyethylene oxide ethanol, such as TergitolTM, especially
those designated series "S" from Union Carbide Corp.,
those available as TritonTM from Rohm and Haas Co., and
the TweenTM series available from ICI America.
Useful anionic emulsifiers include sodium salts of
alkyl sulfates, alkyl sulfonates, alkylether sulfates,
oleate sulfates, alkylarylether sulfates, alkylaryl
polyether sulfates, and the like. Commercially available
examples include such as those available under the trade
names SiponateTM and SiponicTM from Alcolac, Inc.
When used, the emulsifier is present at levels of
from 1% to 7%, based on polymer, preferably from 2% to
5~.
Additional wetting agents with HLB values of from 7
to 10 may be present in the emulsion to improve
coatability. These additional surfactants are added
after polymerization is complete, prior to coating onto
the polymeric substrate. Preferred additional wetting
agents include fluorochemical surfactants such as
C8F175O2N-c2H5
(C2H40) nR
wherein n is from 6 to 15 and R can be hydrogen or
methyl. Useful examples include FC-170C and FC-171,
available from 3M. Another useful wetting agent is
TritonTM X-100, available from Union Carbide.
-24-
2151780
_
Addition of a coalescing agent is also preferred for
emulsion based coatings to insure that the coated
material coalesces to form a continuous and integral
layer and will not flake in conventional printing
process. Compatible coalescing agents include
propylcarbitol, the CarbitolTM series, as well as the
CellusolveTM series, and PropasolveT~ series, from Union
Carbide, and the EktasolveTM series, available from
Eastman Chemical. Other useful agents include the
acetate series from Eastman Chemicals Inc., the DowanolTM
E series, DowanolTM E acetate series, DowanolTM PM series
and their acetate series from Dow Chemical, N-methyl-2-
pyrrolidone from GAF, and 3-hydroxy-2,2,4-trimethyl
pentyl isobutryate, available as TexanolTM, from Eastman
Chemicals Inc. These coalescing agents can be used
singly or as a mixture.
Other optional ingredients may be present in the
imaging coating. Useful additives include such as
crosslinking agents, catalysts, thickeners, adhesion
promoters, glycols, defoamers and the like.
The desired imaging coating formulation can be
prepared by dissolving the components in a common
solvent, or dispersing therein in the case of a latex.
Well-known methods for selecting a common solvent make
use of Hansen parameters, as described in U.S. 4,935,307.
The imaging layer can be applied to the film backing
by any conventional coating technique, e.g., deposition
from a solution or dispersion of the resins in a solvent
or aqueous medium, or blend thereof, by means of such
processes as Meyer bar coating, knife coating, reverse
roll coating, rotogravure coating, extrusion coating, and
the like.
Drying of the imaging layer can be effected by
conventional drying techniques, e.g., by heating in a hot
21517~0
air oven at a temperature appropriate for the specific
film backing and coating chosen.
The imaging sheet of the invention may also comprise
an ink-permeable protective layer such as polyvinyl
alcohol, and the like, to insure faster drying.
Film substrates may be formed from any polymer
capable of forming a self-supporting sheet, e.g., films
of cellulose esters such as cellulose triacetate or
diacetate, polystyrene, polyamides, vinyl chloride
polymers and copolymers, polyolefin and polyallomer
polymers and copolymers, polysulfones, polycarbonates,
polyesters, and blends thereof. Suitable films may be
produced from polyesters obtained by condensing one or
more dicarboxylic acids or their lower alkyl diesters in
which the alkyl group contains up to 6 carbon atoms,
e.g., terephthalic acid, isophthalic, phthalic, 2,5-,
2,6-, and 2,7-naphthalene dicarboxylic acid, succinic
acid, sebacic acid, adipic acid, azelaic acid, with one
or more glycols such as ethylene glycol, 1,3-propanediol,
1,4-butanediol, and the like.
Preferred film substrates for the imaging sheet are
cellulose triacetate or cellulose diacetate, polyesters,
especially polyethylene terephthalate, and polystyrene
films. Polyethylene terephthalate is most preferred. It
is preferred that film substrates have a caliper ranging
from 50 ~m to 150 ~m. Films having a caliper of less
than 50 ~m are difficult to handle using conventional
methods for graphic materials. Films having calipers
over 150 ~m are very stiff, and present feeding
difficulties in certain commercially available copying
machines.
When polyester film substrates are used, they can be
biaxially oriented to impart molecular orientation before
the imaging layer is coated thereon, and may also be heat
set for dimensional stability during fusion of the image
-26-
r 2151780
to the support. These films may be produced by any
conventional extrusion method.
In some embodiments, the polyester film forming the
imaging sheet is extruded or cast, and uniaxially
oriented in the machine direction. The imaging layer is
then coated thereon. The composite can then undergo
further orientation in the transverse direction to
produce a finished product. When this process is used,
the coated layer exhibits evidence of such stretching
under optical microscopy, but surprisingly, the coating
remains transparent, and the polymer, whether emulsion or
solution polymerized, exists in a continuous coated layer
without voids, thus showing the high integrity and
cohesiveness of the coated layer. In these embodiments,
the nonporous opaque thin film layer may be coated before
or after orientation, but if coated before orientation,
the film layer must be chosen such that it can withstand
the subsequent processing without adverse affects.
To promote adhesion of the imaging layer to the film
substrate, it may be desirable to treat the surface of
the film substrate with one or more primers, in single or
multiple layers. Useful primers include those known to
have a swelling effect on the substrate polymer.
Examples include halogenated phenols dissolved in organic
solvents. Alternatively, the surface of the film
substrate may be modified by treatment such as corona
treatment or plasma treatment.
The primer layer, when used, should be relatively
thin, e.g., preferably less than 2 ~m, most preferably
less than 1 ~m, and may be coated by conventional coating
methods.
Imaging sheets or "transparencies" of the invention
are particularly useful in the production of imaged
transparencies for viewing in a transmission mode or a
2151780
reflective mode, i.e., in association with an overhead
projector.
The following examples are for illustrative purposes
only, and are not meant to be limiting. One skilled in
the art will easily think of variations within the scope
of the invention, which is solely that defined by the
claims.
Test Methods
Image Transparency
Image transparency or "Pastel Haze" measures how
much light is scattered by a fused toner layer. Higher
quality images have lower pastel haze values. The haze
of a yellow halftone was measured using a Gardner Model
XL-211 Hazeguard hazemeter. First, the machine is zeroed
with no film in place, the Reference/Open switch set to
"Open". Next, the film is placed at the entrance port,
and set the switch to "Reference" and record the reading.
Again set the Ref/Open switch to "Open" and record
reading. The percent Haze is computed according to the
following formula.
Image Transparency
% Haze = (Open Reading x 100~)
Reference Reading
Increased Pastel Haze (~ Pastel Haze) is determined
by first determining the Pastel Haze of a reference film
having no overlaid layer of any type. The Pastel Haze of
overlaid films is then measured, and the Pastel Haze
value of the reference film is subtracted therefrom to
determine the ~ Pastel Haze.
-28-
215178D
Tensile Energy to Break
The Tensile Energy to Break is defined using the
procedure of ASTM D882-91. A constant rate of grip
separation method is employed. The rate of grip
separation for all samples was 20 inch/minute. The
sample length was approximately 4 inches. The initial
spacing between grips was 2 inches, so the initial strain
rate was (20 in/min)/(2 in)= 10/min.
While ASTM D882-91 defines Tensile Energy to Break
as the energy per unit of volume to pull a sample to
failure, this quantity is not useful in this application.
The volume (i.e. thickness) of a particular sample is
critically important to the sample's performance. We
define Tensile Energy to Break as the integral under the
stress/strain curve, WITHOUT dividing by the original
volume.
Opacity Measurement
The opacity was measured using a Photovolt Model 575
Reflection Meter. The procedure is fully described in
the user's manual.
1) The reference is set by turning the REF
knob until neither the HI nor the LO light is lit.
2) The zero is set by placing a black
standard over the opening, turning the COARSE
sensitivity knob fully clockwise and setting the
FINE sensitivity knob at it's midpoint. The ZERO
knob is then adjusted until the PERCENT REFLECTANCE
shows 00Ø
3) The sample to be measured is placed over
the white reflection standard (furnished by the
manufacturer for opacity measurements.) The sensor
unit is placed on top of the sample and the
sensitivity is set to 100%.
-29-
2151780
4) The sample is then placed on the black
reflection standard (black felt) and the sensor
placed on top of the sample. The value shown by the
unit is the opacity.
Allowable Stack Height
Because striped film is thicker on the striped edge,
a stack of film develops a wedge shape as the number of
sheets increases. Thus as the wedge develops, part of
the gravitational force (Fslip) acts in the direction down
the slope, and so there is a tendency for the film to
slip down the "slope" of the wedge. Frictional forces
(Ffriction)between sheets resist slippage, but as the stack
height increases, the wedge angle (~) reaches a critical
value (~crlt) the frictional force is overcome and the
sheets begin to slide. This is illustrated in Figures 1
and 2. The film will slip at lower angles if the stack
is jarred or subjected to vibrations. Both of these are
common in copying machines. Figure 3 shows the force of
gravity resolved into two forces, one normal to the plane
of the film (Fnor~l) ~ and one parallel to the plane of the
film (Fslip). At wedge angles up to the critical angle the
normal force is balanced by a reaction force applied by
the underlying sheet. The slipping force is balanced by
a frictional force whose magnitude is equal to the
slipping force. At the critical angle the film is on the
verge of slipping and the magnitude of the frictional
force is: Ffriccion= ~staCic mg cos (~crie) . This is shown in
Figure 4.
The height mismatch of the striped side to the
unstriped side is determined by the thickness of the
stripe (t) and the number of sheets. To a first
approximation, the angle ~ can be calculated by treating
-30-
21517~0
the width (w) of the film as the hypotenuse and then
calculating the height mismatch (h) as:
h = f#sheets) * (t)
Thus from Figure 5:
c~ = sin~l (h/w)
And the maximum number of sheets (Allowable Stack Height)
in a stack is given by:
acrit = sin~1 [ (#sheetsmax) * t/w]
or:
#sheets maX = sin(~C~it) * w/t
For a given transparency film the quantity sin (~criC) * W
is a constant, so the maximum number of sheets is
inversely proportional to stripe thickness. For 3M
PP2200 transparency film, the maximum number of sheets
15 that can be stacked is approximately 100, w = 215.9 mm,
and t = 0.108 mm. From the definition, acrit = 2.8,and
sin(~xcrit)* w = 10.8 ~un..
The Allowable Stack Height was calculated based on
the above equation with the data from PP2200 transparency
film.
Examples
Example 1
An opaque, thin stripe was formed by coating a white
coating having a thickness of 3.25 ~m (0.13 mil) onto 10
~m (0.42 mil) PET film and slitting the film to 3.15 cm
(1.25 inch) width in the machine direction. The
thickness and the opacity of the stripe were measured.
The Tensile Energy to Break of this stripe was
determined. All of these measurements are summarized in
Table 1.
A spray coating of #6065 adhesive, available from
Minnesota Mining and Manufacturing Company (3M) was
215178~
applied to the stripe. A transparency film was prepared
by applying the coatings of 3M PP2270 Transparency film
to 75 ~m (3 mil) PET backing. The thin stripe was
applied to the transparency film and imaged in a Canon
CLC 200 copier. The stripe had a sufficient machine
direction width to simulate a paper sheet, allowing tray
feeding. The stripe was removed and the Pastel Haze of a
part of the image that overlay the stripe was measured.
The image quality of the same portion of the image was
noted upon projection. The results of the imaging are
summarized in Table 1.
Example 2
An opaque, thin stripe was formed by slitting 3M 25
~m (1 mil) TiO2 filled PET film to 2.54 cm width.
Processing and testing was done as in Example 1, and the
results are summarized in Table 1.
Comparative Example 3C
An opaque, thin stripe was formed by slitting 3M 50
~m (2 mil) TiO2 filled PET film to 2.54 cm width.
Processing and testing was done as in Example 1, and the
results are summarized in Table 1.
Comparative Example 4C
An opaque stripe was formed by slitting 3M 100 ~m ~4
mil) TiO2 filled PET film to a 2.54 cm width. Processing
and testing was done as in Example 1, and the results are
summarized in Table 1.
Comparative Example 5C
A thin stripe was formed by slitting Dietzgen 340-M
graph paper to 2.54 cm width. Processing and testing was
~ 2151780
done as in Example 1, and the results are summarized in
Table 1.
This Example demonstrates that when porous materials
such as paper are formed thin enough to attempt to
minimize stacking variation, that the tensile strength,
and opacity decrease drastically while the insulative
effect decreases more slowly. As shown in Table 1, the
strength to break is drastically reduced, 0.07 joule,
which would not be cleanly removable; the opacity is also
inadequate at 62% and the image quality is poor due to
the insulative properties remaining.
Comparative Example 6C
A stripe was formed by slitting the paper backing of
3M PP2410 transparency film to a 2.54 cm width.
Processing and testing was done as in Example l, and the
results are summarized in Table 1. This Example uses the
same paper as Examples 4 and 11-13 of U. S. Patent
5,208,093 in the original thickness.
This Example demonstrates that porous materials used
in typical thickness have 888
Reference Example 7
A sample of the transparency film described in
Example 1 was prepared to serve as a reference. The
pastel haze of an identical image not overlying the
stripe was measured and image quality noted.
2151780
Table 1
Example StripeStripe Tensile ~ Pastel Image
No.ThicknessOpacityEnergy to Haze (%)Quality
(~m) ~%)Break
(joules)
1 12.7 72.9 4.98 5.6 very
good
2 22.9 79.9 10.52 9.3 good
3C 45.7 92.7 1.20 30.7 poor
4C 106.7 95.4 7.46 69.4 poor
5C 45.7 62.0 0.07 45.4 poor
6C 81.3 85.0 0.09 61.9 poor
7 - - - Ref. very
good
Example 8
An opaque, thin stripe was formed as in Example l. A
W cured acrylic hot melt adhesive was applied to the
stripe and the stripe was laminated to 3M PP2500
Transparency Film. The average film thickness, the
average thickness of the striped part of the film, and
the Thickness Ratio are tabulated in Table 2. Six
hundred sheets of this film were loaded at one time in a
Xerox 1090 copier. The sheets fed and imaged reliably.
The stripe was easily removed without tearing even over a
wide range of removal speeds and geometries.
Example 9
A striped film was made by using the stripe material
and adhesive from Example 1 and adhering it to 3M PP2500.
The average film thickness, the thickness of the striped
part of the film, and the Thickness Ratio are tabulated
in Table 2. The Allowable Stack Height is calculated and
tabulated in Table 2. The stripe was easily removed
without tearing even over a wide range of removal speeds
and geometries.
-34-
2151780
Example 10
A striped film was made by using the stripe material
and adhesive from Example 2 and adhering it to 3M PP2500.
The average film thickness, the thickness of the striped
part of the film, and the Thickness Ratio are tabulated
in Table 2. The Allowable Stack Height is calculated and
tabulated in Table 2. The stripe was easily removed
without tearing even over a wide range of removal speeds
and geometries.
Comparative Example llC
A striped film was made by using the stripe material
and adhesive from Comparative Example 3C and adhering it
to 3M PP2500. The average film thickness, the thickness
of the striped part of the film, and the Thickness Ratio
are tabulated in Table 2. The Allowable Stack Height is
calculated and tabulated in Table 2. The stripe was
easily removed without tearing even over a wide range of
removal speeds and geometries.
Comparative Example 12C
A striped film was made by using the stripe material
and adhesive from Example 4 and adhering it to 3M PP2500.
The average film thickness, the thickness of the striped
part of the film, and the Thickness Ratio are tabulated
in Table 2. The Allowable Stack Height is calculated and
tabulated in Table 2. The stripe was easily removed
without tearing.
Comparative Example 13C
A striped film was made by using the stripe material
and adhesive from Example 5 and adhering it to 3M PP2500.
The average film thickness, the thickness of the striped
part of the film, and the Thickness Ratio are tabulated
in Table 2. The Allowable Stack Height is calculated and
2151780
tabulated in Table 2. The stripe had to be removed
carefully to prevent tearing.
Comparative Example 14C
A striped film was made by using the stripe material
and adhesive from Example 6 and adhering it to 3M PP2500.
The average film thickness, the thickness of the striped
part of the film, and the Thickness Ratio are tabulated
in Table 2. The Allowable Stack Height is calculated and
tabulated in Table 2. The stripe had to be removed
carefully to prevent tearing.
Reference Example 15
3M PP2200 Paper Striped Transparency Film was used as
a reference example of a striped film. The average film
thickness, the thickness of the striped part of the film,
and the Thickness Ratio are tabulated in Table 2. The
Allowable Stack Height is calculated and tabulated in
Table 2. The stripe had to be removed carefully to
prevent tearing.
This Example uses the same paper as Examples 1-3 and
5-10 of U. S. Patent 5,208,093 in the original thickness.
Table 2
Example Average Film Striped Film Thickness Allowed Stack
No. Thickness Thickness RatioHeight (No.
(~m) (~m) sheets)
8 98.6 119.6 1.21 524
9 98.6 121.5 1.23 478
98.6 129.1 1.31 355
llC 98.6 154.5 1.57 193
12C 98.6 215.4 2.18 93
13C 98.6 153.2 1.55 200
14C 98.6 185.0 1.88 125
98.6 206.8 2.10 100
-36-
215178~
Example 16
An opaque, thin stripe was formed by taking a
composition comprising Atlac 382E, 4 g, dissolved in 6 g
of a 50/50 weight/weight MEK/Toluene mix, into which had
been dispersed 2 g of TiO2 pigment, and coating it 150 ~m
(6 mils) wet on unprimed Mylar PET film. When dry, the
coating could be removed by adhering a strip of Filament
Tape and pulling. The coating came away as a coherent
strip. This illustrates use of an organic solvent
formulation.
Example 17
Examples 17-20 demonstrate the removability of a
printed layer coated directly onto the imaging sheet.
The thickness of the dry coating thickness ranges from
10% to 33% of the wet thicknesses mentioned, depending on
the percent solids of the coating solution made. These
examples are provided simply to exhibit removability or
lack thereof for a variety of coatings. Opaque layers
coated in this manner must be within the thickness range
claimed in order to provide the imaging benefits
previously described. The coatings were tested for
removeability by lifting a corner with masking tape, and
filament tape. The former removes coatings with
relatively low adhesion, and the latter removes coatings
with higher adhesions. Coatings not removable with
filament tape are considered useless for this
application.
A 33% solution of poly(vinylpyrrolidone), grade K17,
considered a low viscosity grade, had dispersed in it 4 g
of TiO2 pigment. This was coated at 150 ~m (6 mils) wet
thickness, on a variety of substrates and air dried.
-37-
2151780
Table 3
Substrate Removeabillty
Unprimed Mylar PET Clean removal with Masking Tape
Polyester N2 primed Poor removal, even with
Filament Tape
PP2500, improved 95% removal with Masking Tape;
100% removal with Filament Tape
PP2500, original- No removal with Filament Tape
Polyester, PVDC prime 30% removal with Masking Tape;
75% removal with Filament Tape
An addition to the above formulation of 2 drops of a
10% solution of FC19OC, a Fluorocarbon surfactant, and
coating as above on unprimed Mylar produced a smoother
coating that was easier to remove.
This example illustrates the effect of the substrate
treatment on the coated layer removal, and the
improvements that may be brought by minor additives.
Example 18
1 gram of TiO2 pigment was dispersed in 10 g of a 20~
gelatin solution. The composition was coated at 40C, 250
~m (10 mils) wet onto 100 ~m (4 mil) unprimed PET film.
When dry, a corner could be lifted with a finger nail,
and the whole film removed as an integral layer. It was
noticed that the dryness of the coating influenced the
adhesion to the film, suggesting that the addition of a
humectant could be used to control adhesion properties.
Example 19
A variety of commercially available poly
vinylalcohols were coated, without pigment, onto unprimed
PET, and the dried film tested for peelability. Among
the materials examined were AirvolTM and GohsenolTM
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products. It was observed that the coatings when removed
exhibited "static cling", and it is anticipated that an
antistatic agent, such as a Cyastat~ SN or 609, available
from American Cyanimid would reduce or eliminate this
problem.
Example 20
8 g of Gohsenol KP06, a commercial polyvinylalcohol
were dissolved in 28 ml of water, and subsequently, 4 g
TiO2 dispersed in that solution. This formulation was a
thick, slow-flowing paste, somewhat like a lithography
ink. It was coated 250 ~m (10 mils) thick onto 100 ~m (4
mil) unprimed PET using a Baker Bar coater. When dry,
the coating had an opacity of 72.3%, as measured with a
Photovolt unit, and could be cleanly peeled with Masking
Tape, or by loosening a corner carefully and pulling.
Example 21
Composite imageable sheets were prepared by applying
an opaque stripe 2.54 cm wide to a sheet of 3M PP2500
transparency film, and then cutting the stripe so that
the final machine direction width of the stripe was 1.9
cm. The films were fed in Canon CLC 200 and Xerox 5765
color copiers. In each case the 1.9 cm stripe was
sufficient in machine direction width to simulate a paper
sheet, and the film was fused at the paper speed.
Samples of identical 3M PP2200 film bearing a 1.4 cm
machine direction width stripe were fed into the Canon
CLC 200 and Xerox 5765 color copiers, and were not
sufficient to simulate a paper sheet in the copiers. The
films were fused at (the slower) transparency speed.
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