Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TransEer Elements and Process for Making Same
Background of the Invention
The use of fluorescent liquid inks is well-known for the application
of information to various types oE documents which are intended to be exposed
to ultraviolet radiation and then processed or read by means of detection
machines. Such inks are widely used for the application of data information to
checks for the indication of amounts, dates, banks involved, etc., enabling the
checks to be sorted and routed automatically by processing machines.
The conventional fluorescent inks are liquid inks which are applied
to the intended documents by means of fabric printing ribbons or ink pads. In
many cases, different images and data are applied to the same document using
different inks to provide information which is automatically sensible by
optical, magnetic or other sensing devices. In such cases the fluorescing im-
ages frequently are applied over said Gther images such as over black optical
or magnetic images.
Different fluorescing dyes have different colors and emit different
wave-length radiation when exposed to and excited by ultraviolet radiation.
The processing machines are quite sensitive and can be adjusted to detect and
recognize either strong or weak signals within the emitted wave-length range.
This adjustment requirement is necessitated by the fact that some detectible
images are relatively poor in mass and/or quality or are absorbed and broadened
when applied
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as liquid inks to porous copy papers so as to provide rela-
tively weak signals while other detectible images are of
good mass and quality and emit strong signals. The process-
ing machine can be adjusted to read strong or weak signals
but cannot reliably read both strong and weak signals emitted
by images present on -the same document. If the images cannot
be read by the processing machine, the document is rejected
and must be processed manually. In some cases,'the imperfect
images will be misread by the processing machine, causing
errors. These defects frustrate the entire purpose of the
system.
One of the most common causes of defective results in
the system arises from the fact that the fluorescent inks
frequently are typed or printed in overlapping relation over
pre-applied images of con-trasting color, i.e., over black images
or bar codes comprising magnetic or optical inks. The fluor-
escing images, or portions thereof, applied directly to the
light-colored paper stock emit strong signals under irradia-
tion while the fluorescing images, or portions thereof,
applied over the black images or bar codes, provide substan-
tially weaker signals under irradiation. The sensitivity of
the processing machine can be adjusted for the accurate recog-
nition of the weak signals but such adjustment results in a
loss of reliability with respect to the sensing of the strong
signals, and vice-versa.
Summary of the Invention
The present invention relates to novel pressure-
sensitive transfer elements having a plastic film foundation
supporting a frangible, complete-release transfer layer of a
solid, non-penetrating, volatile-vehicle-applied composition
comprising a synthetic thermoplastic resinous binder material
containing at least one dissolved fluorescing dyestuff and a
small amount of a finely divided lamelliform pigment such as
a bronze powder.
The present transfer elements provide solid, pressure-
transferable compositions which have good affinity for copy
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shee~s and do not penetrate substantially within even porous paper copy sheets
when transferred thereto under the effects of imaging pressure. The present
compositi.ons contain fluorescing dyes in the form of solid solutions, in which
form the dyes have the greatest ability to emit strong radiation under exposure
to ultraviolet radiation. The present compositions also contain opaque lamelli-
orm particles in amounts which do not unduly mask the radiation emitted by the
excited dyestuffs but which do provide a selective barrier between the dye im-
ages and the background on which they are supported so that such background has
a substantially reduced effect upon the strength of the signals emitted by the
dye images under irradiation, ~hereby providing more uniform signals regardless
of background.
Since the images produced by the present transfer elements should be
as sharp and dense as possible, the transfer elements have a smooth inert film
foundation such as polyethylene, polypropylene, polyethylene terephthalate or
other thin film which has the ability to sharply and completely release the
transfer composition in a stencilling manner lmder the effects of imaging pres-
sure such as typing or printing pressure.
The preferred compositions of the present invention are applied to
the film foundation as liquid coating compositions comprising a major amount by
weight of a volatile solvent such as methyl ethyl ketone, ethyl acetate,
toluene and/or other solven~s depending upon the specific other ingredients of
the composition, a film-forming resinous binder material which is soluble in
said solvent and which is a solvent for the particular fluorescing dyes used
: therewith, one or more fluorescing dyes which are soluble in both said solvent
:~ and in said resinous binder material, a wax which is mainly insoluble but pre-
ferably partially solub].e to a minor extent in said solvent so as to provide,
: on drying and solidification of said composition, substantially discontinuous
wax particles preferably associated with a continuous wax phase, a non-volatile
: oil plasticizer for said wax
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324
which is compatible with said wax and is a solvent for said
dye so as to form a solid solution of said dye in said wax,
and a minor amount by weight of a finely divided lamelliform
pigment, preferably a bronze powder.
Suitable ~ilm-forming binder materials will vary to
some extent depending upon the specific fluorescing dyes used
therewith. However, the generally suitable resin binder
materials include vinyl chloride-vinyl acetate copolymers such
as Vinylite VYHH, acrylic polymers such as Elvacite (copolymer
of methyl methacrylate and ethyl acrylate), linear polyesters
such as Vitel (terephthalic acid-aliphatic acid copolyester),
and similar resins which are solvents for~ the dyes, soluble
in the coating solvent and which do not mask or unduly impede
the fluorescence of the dyes.
Preferred waxes for use in the present compositions
are the hard waxes which can be pulverized to the form of fine
particulate powders which can readily be mixed with the plasti-
cizer and melted to form the plasticized wax. The required
adhesion of the coating to the film foundation and the required
stencilling or complete transfer properties of the coating are
improved in cases where the wax is present in both dissolved
and dispersed form. Preferably, the wax is present in at least
about 80% by weight particulate form and at least 20% by weight
continuous form in the final transfer layer bu-t these percen-
tages are difficult to establish since it appears that some of
the dissolved wax precipitates during drying of the coated
composition. ~ preferred wax is carnauba wax but other waxes
such as ouricury wax, microcrystalline wax, candelilla wax,
montan wax and the like can also be used with the proper selec-
tion of coating solvent and compatible softener or plasticizer.
Soft waxes such as beeswax, petroleum wax and the like are
unsuitable.
The selection of the appropriate softener or plasticizer
oil will depend upon the particular wax used. In all cases9
the plasticizer must be non-volatile, compatible with the wax
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and a solvent for the fluorescing dye. A preferred plasticizer for use with
carnauba wax is a sorbitan ester such as sorbitan monolaurate. In general, the
petroleum oils are unsatisfactory since they are not solvents for the conven-
tional fluorescing pigments. Esters, such as butyl stearate and dioctyl phtha-
late, vegetable oils, animal oils and related non-volatile oily materials, may
be selected depending upon their solvent properties for the dye and their com-
patibility with the ~ax.
The fluorescing dyes useful according to the present invention are
those which are capable of emitting intense radiation within the range of from
about 300 m~ to about 700 m~ when exposed to a light source rich in ultraviolet
radiation. Suitable dyes include the flavins and thioflavins which have a
bright yellow color and emit a high signal in the area of about 600 m~ and
Rhodamine B which has a reddish color and emits a signal in the area of between
400 m~ and 50Q m~. Preferably, a combination of the yellow and red dyes is used
in order to obtain the strong signal of the yellow dye and the coloration of the
red dye which makes the formed images more easily readable by the naked eye.
The preferred lamelliform pigments for use according to the present
invention are the so-called bronze powders which include fine powders of metals
such as aluminum, copper, zinc, manganese, and others. Such materials provide a
selective masking property whereby they substantially increase the hiding power
of the transfer composition while not unduly masking the fluorescing dyes from
the applied radiation or preventing the image signals from being sensed. The
end result is that the present compositions emit a weaker signal than correspond-
ing compositions which do not contain any lamelliform pigment, but the present
compositions emit a more uniform or level signal whether applied over a light or
a dark background so that they can be sensed more accurately than similar com-
positions which do not contain any lamelliform pigment.
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The amount of included lamelliforrn pigrnent may be
varied between about 0.25% and 5% by weight9 based upon the
solids content of the transfer composition. Amounts at the
lower end of -the range have a smaller blocking effect upon
the strength of -the signal emitted by the irradiated composi-
-tion but also have a smaller masking effect upon the bac~-
ground on which the images are suppor~ted. Amounts at the
upper end of the range provide better masking of the back-
ground and more uniform signal strength but the signal
strength is uniformly diminished to a greater degree. How-
ever, as mentioned supra, the processing or sensing equip-
ment can be adjusted to reliably read images of uniform low
or weak signal strength. The most preferred range of bronze
powder content is from about 0.8% to 1.5% of the total solids
content.
The present lamelliform pigments have the ability to
float towards the surface of the present fluid solvent coat-
ing compositions during the application of such compositions
to the film foundation and to be isolated a~s a surface stratum
when the coating solvent is evaporated tos~idify the transfer
layer. Thus, when the -transfer layer is pressure-transferred
to a copy sheet, the lamelliform stratum forms a barrier layer
adjacent the surface of the copy sheet and the fluorescing dye
composition is mainly above said barrier stratum and not masked
thereby to an unacceptable degree. Moreover, the concentration
of the lamelliform pigment in a barrier stratum renders said
pigment more effective in masking the u~derlying color of the
copy sheet and reducing the effect of contrasting underlying
colors upon the intensity of the signal generated by the irra-
diated images. Another advantage of suoh barrier layer, adja-
cent the copy sheet surface, is that such a layer substantially
reduces the possibility of images, produced by means of the pre-
sent transfer elements, being sensed through the copy sheet.
m is is important in the case of copy sheets which carry fluor-
escing images on both the front and rear surfaces thereof, which
images comprise different bits of information which arP sensed
at different timesO Images sensible through the copy sheet can
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cause the sensing device to misread or reject the imaged copy
sheet, thereby frustrating the system.
Such migration and concentration of the lamelliform
pigment depends upon the fluidity of the applied coating com-
position and the period of time during which the coating
remains fluid before the volatile solvent is evaporated.
The selection of suitable coating solvents will depend
upon the particular ingredients present in the composition and
such selec-tion will be obvious to one skilled in the art.
Generally, the solids content of the coating composition will
be within the range of from about 13% to about 20%, most pre-
ferably between 15% and 18%. Thus the volatile solvent con-
tent will range between about 80% and 87%.
While the proportions of the ingredients of the pre-
ferred compositions may be varied somewhat, depending upon the
specific material used, the following table is illustrative of
such proportions:
Ingredient % b~ Weight (solids) % b~ Weight (total)
Resin binder20 to 30 2.6 to 6
Hard wax20 to 30 2.6 to 6
Plasticizer30 to 45 4.3 to 9
D~e(s) 3 to 30 0.5 to 5
Bronze Powder(s) 0.25 to 5 0.065 to 1
Solvent(s) --- 80 to 87
The following example illustrates the preparation of
transfer elements according to one embodiment of the present
invention:
Example
In~redient Parts by ~ei~ht
Vinyl chloride-vinyl
acetate copolymer 4.0
Carnauba wax 4.o
Sorbitan monolaurate 6.0
Flavine dye 1.0
Rhodamine B dye 1.O
Bronze Powder 0.2
Methyl ethyl ketone 8400
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The vinyl resin is dissolved in the methyl ethyl ketone
and a hot melt of the wax and plasticizer is slowly added
there-to with stirring to cause a portion of the plasticized
wax to be dissolved by the solvent. Thereafter, the dyes are
added and dissolved, the bronze powder is added and -the compo-
sition is mixed in a ball mill for several hours.
m e solvent composition is coated as a thin layer over
the film founda~ion and the solvent is evaporated to solidify
the imaging layer having a thickness of from about 0.0002 inch
to 0 a 001 inchO
Finally, the coated web is cut into sheet lengths and
widths or ribbon lengths and widths depending-upon thé desired
end use.
Variations and modifications will be apparent to those
skilled in the art within the scope of the appended claims.
