Note: Descriptions are shown in the official language in which they were submitted.
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Inventors: William D. Swiercz
Robert W. Brunea
George E. Maalouf
Title: Self-Contained Pressure-Sensitive
Carbonless Recording Sheet Having
Anti-Scuff Protective Overcoating
Background of the Invention
The present invention relates to providing a
self-contained pressure sensitive carbonless recording sheet with
a protective coating for improving the scuff-resistance and other
handling qualities of the product.
Pressure-sensitive carbonless recording sheets are
generally available in two different types, namely complementary
and self-contained.
In manufacturing the complementary type, a first kind of
coating is applied on the back of a sheet which wlll be used as an
overlying sheet, and a second kind of coating is applied to a
sheet which will be used as an underlying sheet. In use, these
sheets are placed ln an overlying/underlying relation. As the
averlying sheet is written-upon or printed-upon using pressure,
for instance by means of a ballpoint pen or impact-type of
printer, some material in the coating on the back of the overlying
sheet is transferred onto tor into) the coating on the front of
the underlying sheet, causing a chemical and/or physical reaction
at the situs of and in the pattern of the applied pressure,
resulting in a visible mark being produced c,n the front of the
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underlying sheet in correspondance with the situs and pattern of
pressure applied to the front of the overlying sheet.
In manufacturing self-contained pressure-sensitive
carbonless recording sheets, of the kind most frequently
manufactured at Moore Business Forms, Inc., the manufacturlng
process best known to the present inventors, quanta of the coating
slurries conventionally used for respectively coating the backs
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and fronts of the coated back ("CB"~ and coated front ("CF"~
members of the complementary-type of pressure-sensitive carbonless
recording sheets mentioned above, are blended together.
Conventionally, the CB coating slurry comprises
microencapsulated color-former solution dispersed in an emulsifer/
binder medium, and the CF coating slurry comprises a color
developer, such as zinc-modified novolac polymer particles dispersed
in a binder medium.
When this blend is coated onto a paper substrate, the
resultant sheet will produce a visible mark in the area where the
impact is applied to the sheet with no transfer of materials
required. This has great utility in imaging systems where impact
alone is used to impart information on the sheet without the
benefit of transfer of any materials such as ink, carbon, toner,
color former or such. Such a system generally requires a high
degree of sensitivity to imaging pressure. As a result, since the
sheet is always active, it is prone to premature imaging caused by
normal handling operations such as printing, winding, collating,
filing, copying, the imaging process ltself, distribution,
collection, and scanning.
There is considerable prior art disclosing using
latexes, polyvinyl alcohols, or cellulose gums and ethers in
carbonless systems, either as binders for the capsules or as an
inherent carry-over material from the capsule-making process.
Summary of the Invention
A protective overcoat is provided for a self-contained
pressure-sensitive carbonless recording sheet. The sheet is
initially coated with a blend of a microencapsulated color former
and a colox developer in a binder medium. The purpose of the
overcoat is to prevent premature color formation through acci-
dental rupture of the microcapsules and reaction of the color
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former and color developer. The overcoat compxises a film ~orming
material dissolved, dispersed or otherwise distributed in an
essentially aqueous medium. These materials can be prepared in an
aqueous medium from the dry state prior to use or supplied in a
pre-dissolved or dispersed state by a manufacturer.
It is an object of this disclosure to provide a method
for improvement of the general handling qualities of a self-
contained sheet by overcoating the self-contained coated sheet
with a barrier comprised of a film forming material in an essen-
tially aqueous medium. That the film former be carried in an
essentially aqueous medium is relatively important for several
reasons. The first deals with the microcapsules contained in the
self-contained coating. The majority of microcapsule shells are
composed of materials which are permeable to organic solvents,
particularly polar ones, to various degrees and allow removal of
the core material. If an amount of core material is extracted by
application of an organic solvent, premature color formation will
occur when the core color former contacts the color developing
material. Another reason deals primarily with phenolic or zinc-
modified phenolic polymer based systems. These materials all
exhibit various degrees of solubility in organic solvents, polar
and non-polar. Under application of such they can lose signifi-
cant amounts of their color developing capability. Nei~her of
these problems occur when a substantially water based system is
employed.
Since many industrially prepared emulsions, solutions
and dispersions of film forming materials can contain additives or
in themselves hold properties which may be harmful in some way to
the imaging characteristics of a carbonless self-contained system
without the user's knowledge, it is necessary to screen them by
application to the self-contained coated sheet as an overcoat
followed by testing to determine acceptability. Suitab~e
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materials which have been found include synthetic latexes,
polyvinylalcohols (PVA) and polyvinylalcohol-acetate copolymers
(PVAc), cellulose gums and ethers, acrylic resins, polyethylene
oxide ethers, polyvinylpyrrolidone (PVP) and copolymers of
styrene, ethylene and methylvinylether with maleic anhydride.
Other materials conventionally used for binding, film forming
may also be suitable for use and can easily be identified by
the methods shown in this application.
The principles of the invention will be further
discussed with reference to the drawing wherein a preferred
embodiment is shown. The specifics illustrated in the drawing
are intended to exemplify, rather than limit, aspects of the
invention as defined in the claims.
Brief Description of the Drawing
In the Drawing
Figure 1 is an enlarged fragmentary cross-sectional
view of a sheet of paper, coated with a scuff-protected self-
contained pressure-sensitive carbonless recording material pro-
vided in accordance with the principles of the present invent-
ion, this sheet being covered with an overlying sheet which isshown as it is about to be impacted by an impact printer
member for causing a visible mark to be intentionally made on
the underlying sheet.
Description of the Preferred Embodiment
; Figure 1 shows a sheet of paper 10 on a backing plate
20. The paper is coated with a scuff-protected self-contained
pressure-sensitive carbonless recording material 12 of clay or
resin and microencapsulated dye precursor with a superimposed
layer of overcoat varnish 14. This sheet is covered with an
~ 30 overlying sheet 16 which is shown as it is about to be impacted
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by an impact printer member 22 for causing a visible mark to
be intentionally made on the underlying sheet.
In practicing a best mode of the invention for
laboratory test purposes, a self contained carbonless coating
composition comprised of a blend of microcapsules containing
color former solution designed to provide a black image, zinc
modified novolac phenol polymer particles, filler pigments and
binders are coated on the front surface of a white bond paper
such as Boise Summit Bond, with a basis weight of 12 lbs per
500 sheets, 17 x 22 inches, by means of a wire wound rod to
achieve a dry coating
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weight in the range of 5.0 to lO.O grams/meter, or approximately
1.33 to 2.66 pounds~17 x ~2 in. per 500 sheets.
Therea~ter, this stock of conventional SC product was
divided into nine lots. The first lot was left plain (non-
overcoated) for comparison, and the other eight lots were
overcoated with eight different notionally-potential overcoating
compositions in the research laboratory by flowing a solution of
the respective composition onto a respective SC-coated sheet, and
using a smooth rod to spread the coating to a generally uniform
level of thickness. The coated sheets and control sheets were
then subjected to drying in an oven at a temperat~re of 110
degrees Centigrade for a period of one minute, re~oved, permited
to regain ambient temperature and humidity and then weighed, and
tested for scuff resistance as reported below in connection with
the results tabulated in table I.
TABLE I
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LOT TRADE NAME TrpE OF MATERIAL SOLIDS DEPOS!T IMM. 20 H:'~. 'CUFF
, 1 S/C-no overcoat ~ 55.7 41.E 67.3/71.4
2_Dou 620 _ SBR latex 48 1.1 51.3 L3.c 96.7196.2
VinDI 325 PVA ,10 .7 52.3 42.1 9L.9/96.4
4 Techniflex Atrylic OPV 40 .954.2 L8.~ 98.5/98.
~P
5200 _ - ~ ~
EMA 1103 EMA resin 10 .753.2 L2,C 8B.7/90.1
6 Scriptset 540 Styrene MA resin 10 .5 45.8 _39.7 90.8/90.B
7 Future Acrylie flcor coating 20 .8 L8.2 ~Ø~ 93.4/94.5
8 Rhoplex 6-15 Cationit late~l 45 1.0 67.9 58.7
9 Joncryl 678 ~ Atrylic resin in 20 .7 70.3 60.2
solvent .
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In the DEPOSIT column, the amount recorded is the w~ight
of over-coating, subsequent to drying, given as a value of pounds
per 500 sheets of 17 x 22 inch paper.
As ~or the coa~ing materials, Dow 620 is a styrene-
butadiene rubber, Vinol 325 is polyvinyl alcohol, Techniflex 5200
is an acrylic overprint varnish, EMA 1103 is ethylene-maleic
anhydride, Scriptset 540 is styrene-maleic anhydride, Future is an
acrylic floor coating sold in grocery stores for household use,
Rhoplex B-15 is a cationic latex, and, as a further control,
Joncryl 678 is an acrylic resin, which was dissolved in ethanol/
methyl carbitol, rather than being applied as an a~ueous emulsion
as were lots 2-8.
Referring briefly to the drawing figure, in each
instance, the sheet of paper lO with its SC coating 12, overcoated
with an overcoating composition and dried to provide an overcoat
14, was covered with a sheet of 12-pound bond paper 16, and
typed-on using an I~M Selectric typewriter. The IMAGE column in
Table I tabulates the results of such testing in terms of a
darXness of intentionally-created image in comparison to back-
ground. As is conventional for such testing, results are
tabulated both from immediate (IMM.) readings, and ones made 20
minutes after impact printing. The testing was conducted using a
Bausch & Lomb opacimeter further described below.
Scuff resistance was measured by scuffing the coated
side of each sheet using a Scott C-fold paper towel No. 150, under
3-4 psi weight, with scuffing being performed both with and cross-
wise of the coating application direction.
In the SCUFF column, the two numbers separated by the
slash indicates the direction of the scuff. The first number,
before the slash, in the scuff column is the r~ading for scuffs
with the web, and the second number, after the slash, is for
scuffs across the web. These two readings were taken because a
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doctor blade or similar device spreads the coating material over
the paper surface as the paper is drawn through the coater.
Because of irregularities in the particle sizes, in the blade, or
in the paper, striations occur in the coating. When the scuff
occurs with the striations, it may give one reading which might be
biased. Accordingly, to ef~ect a more true reading, two scuffs at
right angles to each other are made, and a reading of each is
made.
In Table I, the numbers in the SCUFF column ara
separated by a slash, e.g. the first entry is 67.3/71.4. These
are readings from a Bausch ~ Lomb opacimeter. The opacimeter
reads re~lectance, and the opacimeter is calibrated by setting the
re~lectance o~ the substrate at 100. The substrate is usually
white paper. Thus, the first reading of 67.3/7104 indicates poor
reflectance ~color resulting from broken capsules rep~esenting a
mark absorbed some of the light). The second reading of 96.7/96.2
indicates good r~flectance (very little c~lor from br~ken
capsules), i.e. just a few points below the white substrate
reading of 100. No scuff value was generated ~or l~ts 8 and 9 due
to poor imaging intensity results.
Further interpreting the test results which are
tabulated in Table X, the present inventors have concluded that in
many instances, paper having a sel~-contained pressure-sensitive
carbonless recording coating can ~e improved by having that
coating overcoated using an aqueous-based film-forming material so
as to dramatically improve scuff resistance, without signifi-
cantly deteriorating the image-providing capability in comparison
with the non-overcoated control (Lot 1). The application of an
overcoat film-forming material dissol~ed in a non-a~ueous solvent
was seen to have a significant detrimental effect, as did the
cationic latex overcoat.
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Aqueous based overcoats can be applied during the
coating phase of manufacture of the conventional self-contained
pressure-sensitive carbonless recording sheet product by a coating
fountain of various available types, or during the finishing phase
by a flexo print deck on the printing press or collator. This
produces a self-contained sheet with the advantages of high
imaging sensitivity and extended form life during use.
Overcoats also o~fer the opportunity to include
additives for better performance which may not be as useful or
compatible with the blended self-contained system itself. For
instance, a U.V. absorber can be include in the overcoat to give
resistance to U.V. exposure. A surface~modifying agent may be
included to give an overcoat with a more recepti~e surface for
printing or scanning, or to produce a glossy or matte finish.
Suitable aqueous-based film-forming material found for
use as the overcoat of the present invention include emulsions,
dispersions or solutions of synthetic latexes, polyvinylalcohols
and poly~inylalcohol-acetate copolymers, cellulose gums a~d
ethers, acrylic resins, polyethylene oxide ethers, polyvinyl-
pyrrolidone, copolymers of styrene, ethylene and ~ethylvinylether
with maleic anhydride, and other materials variously
conventionally used for bindi~g, film-forming and the like.
Self-contained carbonless coatings with protective
overcoating could be used in many products and applications where
improved scuff resistance and reduced discoloration are required.
These overcoats provide improved protection of the image against
weather and abrasion. Enhanced security aspects, indelibility,
and alterat~on resistance of the image is obtained with these
overcoatings.
Some examples of products which may benefit from
overcoatings are business forms, airline ticXets, lottery tickets,
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shipping labels, and other similar items. Generally, any document
having carbonless microcapsules, or more particularly,
self-contained carbonless coatings will be improved by an overcoat
according to the present invention.
It should now be apparent that the self-contained
pressure-sensitive carbonless recoxding sheet having anti-scuff
protective overcoating as described hereinabove, possesses each of
the attributes set forth in the specification under the heading
"Summary of the Invention" hereinbefore. Because it can be
modified to some extent without departing from the principles
thereof as they have been outlined and explained in this
specification, the present invention should be understood as
encompassing all such modifications as are within the spirit and
scope of the following claims.
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