Note: Descriptions are shown in the official language in which they were submitted.
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RECORDING SHEET WITH IMPROVED IMAGE DRY TIME
BACKGROUND OF THE INVENTION
1. Field of the Invention: This invention relates to recording sheets.
More particularly, this invention relates to recording sheets having improved
image dry time, and in particular to a paper based recording sheet, which is
suitable as a recording sheet for use in any printing or recording process.
While
suitable for use in any printing process, the recording sheets of this
invention are
especially useful in ink jet printing processes.
2. Prior Art: Recording sheets for printing are known. See for
example US Patent numbers 6207258; 6123760; 6162328; 4554181; 4381185;
6880928; 6207258; 6123760; 6162328; 6485139; 6686054; 6761977; 6764726;
and European Patent numbers EP0999937 and EP0999937.
SUMMARY OF THE INVENTION
One aspect of this invention is directed to a recording sheet for use in
printing comprising a substrate which comprising ligno cellulosic fibers and a
water soluble divalent metal salt preferably on at least one surface of the
substrate;
wherein the Hercules Sizing Test Value ("HST") of the substrate and the amount
of
divalent salt are selected such that the recording sheet has a percent ink
transferred
("IT%") equal to or less than about 60. In the preferred embodiments of the
invention, the water soluble divalent metal salt is in a mixture which also
comprises one or more starches, one or more polymer emulsion additives, one or
more nitrogen containing compounds, or a combination thereof.
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Tti61iCording sheets of this invention exhibit one or more advantages over
conventional printing recording sheets. For example, the recording sheets of
this
invention exhibit one or more improved image dry time properties. These
improve
properties include reduced ink transfer immediately after printing, improved
image
black density, and improved edge acuity when printed with pigment-based inks.
Still another aspect of this invention relates to a process of forming the
recording sheet of this invention which comprises:
(a) applying a liquid composition comprising a volatile liquid such as
water, methanol or the like having dissolved or dispersed therein one or more
water soluble divalent metal salts, and one or more starches, one or more
polymeric emulsion additives, one or more nitrogen containing compounds, or a
combination thereof, to a surface of a substrate formed from ligno cellulosic
fibers
and having in contact with at least one surface of the substrate a water
soluble
divalent metal salt wherein the Hercules Sizing Test Value ("HST") of the
substrate and the amount of divalent salt are selected such that the recording
sheet
has a percent ink transferred ("IT%") equal to or less than about 60 to folin
a
wetted, treated substrate having said species or said mixture in contact with
said
surface; and
(b) drying said surface of said wetted, treated substrate to form said
recording sheet.
Yet another aspect of this invention relates to a method of generating
images on a surface of a recording sheet in a printing apparatus which
comprises:
(a) incorporating into said apparatus a recording sheet
comprising a
substrate which comprises ligno cellulosic fibers and a water soluble divalent
metal
salt, wherein the Hercules Sizing Test Value ("HST") of the substrate and the
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amount of divalent salt are selected such that the recording sheet has a
percent ink
transferred ("IT%") equal to or less than about 60; and
(b) forming an image upon at least one surface of said recording
sheet. In
the preferred embodiments, the printing apparatus is an ink jet printer and
the
image is formed by causing ink to be expelled from said apparatus onto a
surface of
the recording sheet..
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects and advantages of the invention will now be
further described in conjunction with the accompanying drawings in which:
Fig. 1 is a graph of Ink Transfer (%) versus HST of the Base Paper;
Fig. 2 is a graph of Ink Transfer (%) versus calcium chloride salt coverage
(gsm);
Fig. 3 is a graph of black density (OW versus HST of the Base Paper;
Fig. 4 is a graph of black density (OW versus calcium chloride salt
15. coverage (gsm);
Fig. 5 is a graph of edge acuity (EA) versus HST of the Base Paper; and
Fig. 6 is a graph of edge acuity (EA) versus calcium chloride salt coverage
(gsm).
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a recording sheet for use in printing comprising a
substrate formed from ligno cellulosic fibers and having in contact with at
least
one surface thereof a water soluble divalent metal salt. Applicants have
surprisingly discovered that sizing level of the substrate, as measured by the
HST
of the substrate, and the amount of divalent metal salts on the surface of the
substrate impact on image dry time of the recording sheet. The recording sheet
of
this invention exhibits enhanced image dry time as determined by the amount of
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ink transferred from a printed to an unprinted portion of the recording sheet
after
rolling with a roller of fixed weight. The "ink transfer", that is defined as
the
amount of optical density transferred after rolling with a roller; it is
expressed as a
percentage of the optical density transferred to the unprinted portion of the
recording sheet after rolling with a roller. The method involves printing
solid
colored blocks on paper, waiting for a fixed amount of time, 5 seconds after
printing, and then folding in half so that the printed portion contacts an
unprinted
portion of the recording sheet, and rolling with a 4.5 lb hand roller as for
example
roller item number HR-100 from Chem Instruments, Inc., Mentor, OH, USA. .
The optical density is read on the transferred (ODT), the non-transferred
(0D0)
portions of the block, and an un-imaged area (ODB) by a reflectance
densitometer
(X-Rite, Macbeth. Etc.). The percent transferred ("IT%") is defined as IT% =
RODT ¨ ODB)/(0Do ¨ ODB)]X 100.
The Hercules Sizing Test Value ("HST") of the substrate and the amount of
divalent salt are selected such that the recording sheet has a percent ink
transferred
("IT%") equal to or less than about 60. Preferably, the IT% is from 0% to
about
50%. More preferably, the IT% is from 0% to about 40%. Most preferably, the
IT% is from 0% to about 30%.
In addition to improved image dry time, some recording sheets of this
invention preferably exhibit good print quality. As used herein, print quality
(PQ)
is measured by two important parameters: print density and edge acuity. Print
density is measured using a reflectance densitometer (X-Rite, Macbeth. Etc.)
in
units of optical density ("OD"). The method involves printing a solid block of
color on the sheet, and measuring the optical density. There is some variation
in
OD depending on the particular printer used and the print mode chosen, as well
as
the densitometer mode and color setting. The printer used in this patent is an
HP
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,
Deskjet 6122, manufactured by Hewlett-Packard, which uses a #45 (HP product
number 51645A) black ink jet cartridge. The print mode is determined by the
type
of paper and the print quality selected. For the data in this patent, the
default
setting of Plain Paper type and Fast Normal print quality print mode was
selected.
The densitometer used was an X-Rite model 528 spectrodensitometer with a 6 min
aperature. The density measurement settings were Visual color, status T, and
absolute density mode. An increase in print density is usually seen when
sufficient amounts of divalent water soluble metal salts are on the paper
surface.
In general, the target optical density for pigment black ("OD0") is equal to
or
greater than 1.30 in the standard (plain paper, normal) print mode for the HP
desktop ink jet printers that use the most common black pigment ink
(equivalent to
the #45 ink jet cartridge). Preferably, the 0130 is equal to or greater than
about
1.40. More preferably, the 0D0 is equal to or greater than about 1.50. Most
preferably, the OD is equal to or greater than about 1.60.
Another parameter of recording sheets that is important to the determination
of good print quality is the edge acuity ("EA"). Some recording sheets of this
invention exhibit good edge acuity. Edge acuity is measured by an instrument
such
as the QEA Personal Image Analysis System (Quality Engineering Associates,
Burlington, MA), the QEA ScannerIAS, or the ImageXpert KDY camera-based
system. All of these instruments collect a magnified digital image of the
sample
and calculate an edge acuity value by image analysis. This value is also
called
edge raggedness, and is defined in ISO method 13660. The method involves
printing a solid line 1.27 millimeters or more in length, sampling at a
resolution of
at least 600 dpi. The instrument calculates the location of the edge based on
the
darkness of each pixel near the line edges. The edge threshold is defined as
the
point of 60% transition from the substrate reflectance factor (light area,
Rmax) to
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the image reflectance factor (dark area, Rmax) using the equation R60 = Rmax ¨
60%
(Rmax - Rmin). The edge raggedness is then defined as the standard deviation
of the
residuals from a line fitted to the edge threshold of the line, calculated
perpendicular to the fitted line. The value of edge acuity is preferably less
than
about 15. Preferably, the EA is less than about 12. More preferably, the EA is
less than about 10. Most preferably, the EA is less than about 8.
One essential component of the recording sheet of this invention is a
substrate comprised of ligno cellulosic fibers. The type of fiber is not
critical and
any such fiber known for use in paper making can be used. For example, the
substrate can made from pulp fibers derived from hardwood trees, softwood
trees,
or a combination of hardwood and softwood trees prepared for use in a
papermaking furnish by any known suitable digestion, refining, and bleaching
operations as for example known mechanical, thermomechanical, chemical and
semichemical, etc., pulping and other well known pulping processes. The term
"hardwood pulps" as used herein refers to fibrous pulp derived from the woody
substance of deciduous trees (angiosperms) such as birch, oak, beech, maple,
and
eucalyptus, whereas "softwood pulps" are fibrous pulps derived from the woody
substance of coniferous trees (gymnosperms) such as varieties of fir, spruce,
and
pine, as for example loblolly pine, slash pine, Colorado spruce, balsam fir
and
Douglas fir. In certain embodiments, at least a portion of the pulp fibers may
be
provided from non-woody herbaceous plants including, but not limited to,
kenaf,
hemp, jute, flax, sisal, or abaca although legal restrictions and other
considerations
may make the utilization of hemp and other fiber sources impractical or
impossible. Either bleached or unbleached pulp fiber may be utilized in the
process of this invention. Recycled pulp fibers are also suitable for use. In
a
preferred embodiment, the cellulosic fibers in the paper include from about
30% to
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% by weight dry basis softwood fibers and from about 70% to about 0%
by weight dry basis hardwood fibers.
In addition to the ligno cellulosic fibers, the substrate may also include
other conventional additives such as, for example, fillers, retention aids,
wet
strength resins and dry strength resins that may be incorporated into ligno
cellulosic fiber based substrates. Among the fillers that may be used are
inorganic
and organic pigments such as, by way of example, minerals such as calcium
carbonate, barium sulfate, titanium dioxide, calcium silicates, mica, kaolin
and
talc, and polymeric particles such as polystyrene latexes and
polymethylmethacrylate. Other conventional additives include, but are not
restricted to, alum, fillers, pigments and dyes.
The paper substrate may also include dispersed within the lingo cellulose
fibers from expanded or unexpanded microspheres. Expanded and expandable
microspheres are well known in the art. For example, suitable expandable
is microspheres are described in USP Nos. 6,802,938, 6,866,906, 3,556,934,
5,514,429, 5,125,996,
3,533,908, 3,293,114, 4,483,889, and 4,133,688; and UK Patent Application
23074887.
All conventional microspheres can be used in the practice of this
25 chloride and combinations of two or more of the foregoing. Preferred
resinous
particles comprise a polymer containing from about 65 to about 90 percent by
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" weight vinylidene chloride, preferably from about 65 to about 75
percent by
weight vinylidene chloride, and from about 35 to about 10 percent by weight
acrylonitrile, preferably from about 25 to about 35 percent by weight
acrylonitrile.
Suitable expandable microspheres are available from Akzo Nobel of Marietta,
Georgia under the trade name EXPANCEL. Expandable microspheres and their
usage in paper materials are described in more detail USP Nos. 6;802,938 and
6,866,906.
The Hercules Sizing Test Value ("HST") of the substrate may vary widely
and is selected to provide the desired dry time characteristics. The HST value
is
measured following the conventions described in TAPPI Standard Method number
T-530, using 1% foilnic acid ink and 80% reflectance endpoint. This test is
commonly used for alkaline papers containing calcium carbonate filler, as
noted in
the TAPPI Journal article by S.R. Boone, Feb, 1996, pg 122. The HST of the
substrate can be adjusted by the addition of a sizing agent to the substrate.
It is
preferred that the desired HST is obtained by internally sizing the substrate;
that is,
that sizing agents be added to the pulp suspension before it is converted to a
paper
web or substrate. Internal sizing helps prevent the surface size from soaking
into
the sheet, thus allowing it to remain on the surface where it has maximum
effectiveness. The internal sizing agents for use in the practice of this
invention
encompass any of those commonly used at the wet end of a paper machine. These
include rosin sizes, ketene dimers and multimers, and alkenylsuccinic
anhydrides.
The internal sizes are generally used at concentration levels known to art as
for
examples at levels of from about 0 wt. % to about 1.0 wt. % based on the
weight of
the dry paper sheet. More preferably, the internal size is used at levels of
about
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" "0161.% TO -about 0.5 wt. %. Most preferably, the internal size is used
at levels of
about 0.025% to about 0.25 wt. %. Methods and materials utilized for internal
sizing with rosin are discussed by E. Strazdins in The Sizing of Paper, Second
Edition, edited by W. F. Reynolds, TAPPI Press, 1989, pages 1-33. Suitable
ketene
dimers for internal sizing are disclosed in U.S. Pat. No. 4,279,794,
and in United Kingdom Patent Nos.
786,543; 903,416; 1,373,788 and 1,533, 434, and in European Patent Application
Publication No. 0666368 A3. Ketene dimers are commercially available, as
Aquapel® and Precis® sizing agents from Hercules Incorporated,
Wilmington, Del. Ketene multimers for use in internal sizes are described in
European Patent Application Publication No. 0629741A1, filed June 6, 1994;
European Patent
Application Publication No. 0666368A3, and USP No. 5,846,663. Alkenyl succinic
anhydrides
for internal sizing are disclosed in U.S. Pat. No. 4,040,900 and by C.E.
Farley and R.B. Wasser in
The Sizing of Paper, Second Edition, edited by W.F. Reynolds, TAPPI Press,
1989, pages 51-62.
A variety of alkenylsuccinic anhydrides are commercially available from
Albemarle Corporation,
Baton Rouge, LA.
As it is well known to those of ordinary skill in the art, the HST will vary
directly with the basic weight of the substrate and other factors known to
those of
ordinary skill in the art as for example the amount and type of internal
sizing agent
as well as the type, amount, and surface area of filler, the ink used and the
reflectance end point as specified in TAPPI T 530 Based upon the foregoing
information, one of ordinary skill in the art can use conventional techniques
and
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procedures to calculate, determine and/or estimate a particular HST for the
substrate used to provide the desired image dry time characteristics. In the
preferred embodiments of this invention, the HST value is preferably from
about 1
second to about 400 seconds with 1% formic acid ink and 80% reflectance. The
HST is more preferably from about 3 seconds to about 300 seconds and most
preferably from about 5 seconds to about 200 seconds. In the embodiments of
choice, the HST is from about 20 seconds to about 100 seconds.
The Gurley porosity of the base substrate is selected to provide the desired
dry time characteristics. The Gurley porosity is measured by the procedure of
TAPPI T460 om-88. In the preferred embodiments of this invention, the
substrate
has a Gurley porosity preferably from about 5 sec/100 ml to about 75 sec/100
ml.
The Gurley porosity is more preferably from about 5 sec/100 ml to about 70
sec/100 ml and most preferably from about 5 sec/100 ml to about 50 sec/100 ml.
In
the embodiments of choice, the Gurley porosity is from about 10 sec/100 ml to
about 35 sec/100 ml.
The pore diameter of the substrate is selected to provide the desired dry time
characteristics. The pore diameter is measured by mercury intrusion
porosimetry.
In the preferred embodiments of this invention, the substrate has a pore
diameter is
preferably from about 2.0 to about 3.5. The pore diameter is more preferably
from
about 2.2 to about 3.3 and most preferably from about 2.4 to about 3.1. In the
embodiments of choice, the pore diameter is from about 2.6 to about 3Ø
The substrate can be of any basis weight. Preferably, the substrate basis
weight is from about 20 to about 500 g/m2, although substrate basis weight can
be
outside of this range if desired. The basis weight is more preferably from
about 20
to about 300 g/m2 and most preferably from about 50 to about 200 g/m2. In the
embodiments of choice, the basis weight is from about 60 to about 120 g/m2.
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Suitable substrates can be purchased from commercial sources as for
example International Paper Company of prepared by conventional techniques.
Methods and apparatuses for preparing a substrate formed of ligno cellulosic
fibers are well known in the paper and paperboard art. See for example
"Handbook For Pulp & Paper Technologies", 2nd Edition, G.A. Smook, Angus
Wilde Publications (1992) and references cited therein. Any conventional
method
and apparatus can be used. Preferably the process comprises: a) providing an
aqueous suspension of ligno cellulosic fibers; b) sheeting and drying the
aqueous
ligno cellulosic fiber suspension to obtain dried paper web; c) drying the
paper
web to obtain dried paper web and d) calendering the dried paper web. In
addition
to these process steps, additional process steps known to those of ordinary
skill in
the art may be employed as for example a coating step to coat one or more
surfaces of the web with a coating comprising a binder containing dispersant
pigment.
The substrate contains an "effective amount" of the divalent water soluble
metal salt preferably in contact with at least one surface of the substrate.
As used
herein, an "effective amount" is an amount which is sufficient to enhance the
dry
time of the substrate to any extent. This total amount of divalent water
soluble
metal salt in the substrate can vary widely, provided that the desired result
is
achieved. Usually, this amount is at least 0.02 g/m2' although lower or higher
amounts can be used. The amount of divalent water soluble metal salt is
preferably
from about 0.1g/m2 to about 3 g/m2 and most preferably from about 0.2 g/m2 to
about 2.0 g/m2.In the embodiments of choice, The amount of divalent water
soluble
metal salt is preferably from about 0.4g/m2 to about 1.5 g/m2
Any divalent metal salt can be used in the practice of this invention.
Suitable divalent water soluble metal salts include but are not limited to
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.obpoiiiid.S.containing calcium or magnesium. The counter ions may vary widely
and include chloride, sulfate, nitrate, hydroxide and the like. Illustrative
of such
materials are calcium chloride, magnesium chloride, and calcium hydroxide.
Preferred divalent water soluble metal salts for use in the practice of this
invention
are water soluble calcium salts, especially calcium chloride.
In the most preferred embodiments of this invention, a mixture comprising
calcium chloride and one or more starches is in contact with at least one
surface of
the substrate. Illustrative of useful starches for the practice of this
preferred
embodiment of the invention are naturally occurring carbohydrates synthesized
in
corn, tapioca, potato and other plants by polymerization of dextrose units.
All such
starches and modified forms thereof such as starch acetates, starch esters,
starch
ethers, starch phosphates, starch xanthates, anionic starches, cationic
starches,
oxidized starches, and the like which can be derived by reacting the starch
with a
suitable chemical or enzymatic reagent can be used in the practice of this
invention. Useful starches may be prepared by known techniques or obtained
from
commercial sources. For example, the suitable starches include Ethylex 2035
from
A.E. Staley, PG-280 from Penford Products, oxidized corn starches from ADM,
Cargill, and Raisio, and enzyme converted starches such as Amyzet 150 from
Amylum.
Preferred starches for use in the practice of this invention are modified
starches. More preferred starches are cationic modified chemically modified
starches such as ethylated starches, oxidized starches, and AP and enzyme
converted Pearl starches. Most preferred are chemically modified starches such
as
ethylated starches, oxidized starches, and AP and enzyme converted Pearl
starches.
When the preferred divalent water soluble metal salt, calcium chloride, and
the preferred Ethylex 2035 starch are used, the desired dry time of the sheet
is
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obtained when the weight ratio of the calcium chloride to the starch is equal
to or
greater than about 5% to about 200%. In these embodiments, the weight ratio of
the calcium chloride to the starch is preferably from about 5% to about 100%,
more
preferably from about 7% to about 70%, and most preferably from about 10% to
about 40%.
In these preferred embodiments of the invention, the amount of the mixture
of divalent water soluble metal salt and one or more starches on the surface
of a
substrate may vary widely and any conventional amount can be used. In general,
the amount of the mixture in the substrate is at least about 0.02 g/m2 of
recording
sheet, although higher and lower amounts can be used. The amount is preferably
at
least about 0.05 g/m2, more preferably at least about 1.0 g/m2 and most
preferably
from about 1.0 g/m2 to about 4.0 g/m2.
In addition to the required divalent metal salt, the mixture used to treat the
substrate may include other ingredients in addition to the starch used in the
preferred embodiments of the invention, including a pigment typically applied
to
the surface of a recording sheet in conventional amounts. Such optional
components also include dispersants, surface sizing agents, optical
brighteners,
fluorescent dyes, surfactants, deforming agents, preservatives, pigments,
binders,
pH control agents, coating releasing agents, and the like.
Other optional components are nitrogen containing compounds. Suitable
nitrogen containing organic species are compounds, oligomers and polymers are
those containing one or more quaternary ammonium functional groups. Such
functional groups may vary widely and include substituted and unsubstituted
amines, imines, amides, urethanes, quaternary ammonium groups, dicyandiamides,
guanides, and the like. Illustrative of such materials are polyamines,
polyethyleneimines, copolymers of diallyldimethyl ammonium chloride
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MAD1V1AO, copolymers of vinyl pyrrolidone (VP) with quaternized
diethylaminoethylmethacrylate (DEAMEMA), polyamides, cationic polyurethane
latex, cationic polyvinyl alcohol, polyalkylamines dicyandiamid copolymers,
amine
glycigyl addition polymers, poly[oxyethylene (dimethyliminio) ethylene
(dimethyliminio) ethylene] dichlorides, guanidine polymers, and polymeric
biguanides. These types of compounds are well known, and are described in, for
example, US Pat. No. 4,554,181, US Pat. No. 6,485,139, US Pat. No. 6,686,054,
US Pat. No. 6,761,977, and US Pat. No. 6,764,726.
Preferred nitrogen containing organic species for use in the practice of this
invention are low to medium molecular weight cationic polymers and oligomers
having a molecular equal to or less than 100,000, preferably equal to or less
than
about 50,000 and more preferably from about 10,000 to about 50,000.
Illustrative
of such materials are polyalkylamine dicyandiamide copolymers, poly
[oxyethylene
(dimethyliminio ethylene (dimethyliminioethylene] dichlorides and polyamines
having molecular weights within the desired range. More preferred nitrogen
containing organic species for use in the practice of this invention are low
molecular weight cationic polymers such as polyalkylamine dicyandiamid
copolymer, poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio)
ethylene] dichloride, guanidine polymers, and polymeric biguanides. Most
preferred nitrogen containing organic species for use in the practice of this
invention are low molecular weight polyalkylamine dicyandiamid copolymers,
guanidine polymers, and polymeric biguanides such as
polyhexamethylenebiguanide.
The recording sheet of this invention can be prepared using known
conventional techniques. For example, the essential one or more divalent water
soluble metal salt preferably admixed with one or more starches, and one or
more
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opiionil Components can be dissolved or dispersed in an appropriate liquid
medium, preferably water, and can be applied to the substrate by any suitable
technique, such as a size press treatment, dip coating, reverse roll coating,
extrusion coating or the like. Such coating techniques are well known in the
art
and will not be described in any great detail.
For example, the coating can be applied with conventional size press
equipment having vertical, horizontal or inclined size press configurations
conventional used in paper preparation as for example the Symsizer (Valmet)
type
equipment, a KRK size press (Kumagai Riki Kogyo Co., Ltd., Nerima, Tokyo,
Japan) by dip coating. The KRK size press is a lab size press that simulates a
commercial size press. This size press is normally sheet fed, whereas a
commercial size press typically employs a continuous web.
In dip treating, a web of the material to be treated is transported below the
surface of the liquid coating composition by a single roll in such a manner
that the
exposed site is saturated, followed by removal of any excess treating mixture
by
the squeeze rolls an drying at 1000 C in an air dryer. The liquid treating
composition generally comprises the desired treating composition dissolved in
a
solvent such as water, methanol, or the like. The method of surface treating
the
substrate using a coater results in a continuous sheet of substrate with the
treating
material applied first to one side and then to the second side of this
substrate. The
substrate can also be treated by a slot extrusion process, wherein a flat die
is
situated with the die lips in close proximity to the web of substrate to be
treated,
resulting in a continuous film of the treating solution evenly distributed
across one
surface of the sheet, followed by drying in an air dryer at a suitable drying
temperature as for example 100 C.
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The recording sheet of this invention can be printed by generating images
on a surface of the recording sheet using conventional printing processes and
apparatus as for example laser, Ink jet, offset and flexo printing processes
and
apparatus. In this method, the recording sheet of this invention is
incorporated into
a printing apparatus; and an image is fatined on a surface of the sheet. The
recording sheet of this invention is preferably printed with ink jet printing
processes and apparatus as for example desk top ink jet printing and high
speed
commercial ink jet printing. One preferred embodiment of the present invention
is
directed to ink jet printing process which comprises applying an aqueous
recording liquid to a recording sheet of the present invention in an image
wise
pattern. Another embodiment of the present invention is directed to ink jet
printing process which comprises (1) incorporating into an ink jet printing
apparatus containing an aqueous ink a recording sheet of the present
invention,
and (2) causing droplets of the ink to be ejected in an image wise pattern
onto the
recording sheet, thereby generating images on the recording sheet. Ink jet
printing
processes are well known, and are described in, for example, US Pat. No.
4,601,777, US Pat. No. 4,251,824, US Pat. No. 4,410,899, US Pat. No.
4,412,224,
and US Pat. No. 4,532,530. In a particularly preferred embodiment, the ink jet
printing apparatus employs a theimal ink jet process wherein the ink in the
nozzles
is selectively heated in an imagewise pattern, thereby causing droplets of the
ink to
be ejected in imagewise pattern. The recording sheets of the present invention
can
also be used in any other printing or imaging process, such as printing with
pen
plotters, imaging with color laser printers or copiers, handwriting with ink
pens,
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..=
offset printing processes, or the like, provided that the toner or ink
employed to
form the image is compatible with the ink receiving layer of the recording
sheet.
The present invention will be described with references to the following
examples.
The examples are intended to be illustrative and the invention is not limited
to the
materials, conditions, or process parameters set forth in the example. All
parts and
percentages are by unit weight unless otherwise indicated.
Example 1
(A) Preparation of Lab Drawdown Compositions
A series of coating composition were prepared using the following
procedure. The coating is prepared in the lab using a low shear mixer. A
certain
amount of water is added to the coating container, and then anhydrous calcium
chloride (94-97%, Mini pellets from the Dow Chemical Co., Midland, MI, and
USA.) is added under proper shear actions until dissolved. The coating
compositions and specifications are set for the in the following Table 1.
Table 1
Compositions
Composition Calcium Chloride, Parts Water, Parts
1 2.5 97.5
2 5 95
3 10 90
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B. Preparation of Treated Substrates
Several commercially available base papers a basis weight of about 75 g/m2
and HST values ranging from about 20 seconds to about 220 seconds were coated
with the coating compositions of Table 1. The base sheets and there
specifications
are set forth in the following Table 2.
Table 2
Base paper
Base Paper Commercial Name Sizing Level
(HST, s)
A Office Max MaxBrite 20
Xerox Premium Multipurpose 61
Hewlett Packard MultiPurpose 157
Hewlett Packard Everday Ink Jet 218
To apply the coating formulation, both ends of a 9" x 12" sheet of base paper
are
taped to a backing sheet, the coating composition is applied in a thin line
above
the paper substrate, and a Meyer rod is drawn down the sheet in a uniform
manner.
By controlling the compositions solids and rod size, a pickup weight of 0.25
to 1.0
g/m2 per side is achieved. The coated substrates and their specifications are
set
forth in the following Table 3.
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Table 3
Treated Substrates
Treated Composition Base Paper Salt
Coverage,
Substrate (gsm)
lA 1 A 0.25
1B 1 B 0.25
1C 1 C 0.25
1D 1 D 0.25
2A 2 A 0.5
2B 2 B 0.5
2C 2 C 0.5
2D 2 D 0.5
3A 3 A 1.0
3B 3 B 1.0
3C 3 C 1.0
4D 3 D 1.0
Example 2
A series of experiments were carried out to evaluate the suitability of the
substrates of Table 3 for use in ink printing. The properties selected for
evaluation
were drying time, print density and edge acuity. For comparison purposes, the
same properties were evaluate for Base Papers A, B, C and D. The procedures
used are as follows:
A. Dry Time ("IT%"):
In this evaluation, paper samples were imaged with a Hewlett-Packard
Deskjet 6122, manufactured by Hewlett-Packard, using a (HP product number
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51.643 black ink jet cartridge under TAPPI room condition (23 C and 50%
RH). The print mode is determined by the type of paper and the print quality
selected. The printer default setting of Plain Paper type and Fast Normal
print
quality print mode was selected. The densitometer used was an X-Rite model 528
spectrodensitometer with a 6 mm aperature. The density measurement settings
were Visual color, status T, and absolute density mode. After waiting 5
seconds
after printing, the samples were folded in half and rolled with a 4.5 kg
rubber hand
roller, item number HR-100 from ChemInstruments, Inc., Mentor, OH, USA. The
samples were then unfolded and allowed to air dry. The densities of the
samples
were measured with an X-Rite 500 series densitometer to indicate the density
before (OW and after (ODT) rolling. An unprinted area was also measured to
obtain a value for the paper background (ODB). The percent transferred ("IT%")
for the various papers is then calculated using the following equation:
IT% --- [(ODT ODB)/(0D0 ¨ ODB)JX 100.
B. Print Density ("0D0")
In this evaluation, paper samples were imaged with a Hewlett-Packard
Deskjet 6122, manufactured by Hewlett-Packard, using a (HP product number
51645A) black ink jet cartridge under TAPPI room condition (23 C and 50%
RH). The print mode is determined by the type of paper and the print quality
selected. The printer default setting of Plain Paper type and Fast Normal
print
quality print mode was selected. The samples were then allowed to air dry. The
densities of the samples were measured with an X-Rite model 528
spectrodensitometer with a 6 mm aperature. The density measurement settings
were Visual color, status T, and absolute density mode. .
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' C. 'Edge Acuity ("EA"):
In this evaluation, paper samples were imaged with a Hewlett-Packard
Deskjet 6122, manufactured by Hewlett-Packard, using a (HP product number
51645A) black ink jet cartridge under TAPPI room condition (23 C and 50%
RH). The print mode is determined by the type of paper and the print quality
selected. The printer default setting of Plain Paper type and Fast Normal
print
quality print mode was selected. The samples were then allowed to air dry. The
. edge acuity of the samples were measured with a QEA Personal Image Analysis
System (Quality Engineering Associates, Burlington, MA),.
The results of these evaluations are set forth in the following Table 4 and
Figures 1 to 6.
Table 4
Treated Substrate IT% 0D0 EA HST Salt
(s) Coverage
(gsm)
1A 4 1.62 13.8 20
0.25
1B 20 1.68 8.7 61
0.25
1C 59 1.63 6.8 157
0.25
1D 58 1.63 6.3 218
0.25
2A 3 1.61 9.1 20
0.5
2B 18 1.65 8.1 61
0.5
2C 43 1.64 7.0 157
0.5
2D 71 1.62 5.9 218
0.5
3A 4 1.61 8.5 20
1.0
3B 27 1.64 6.8 61
1.0
3C 49 1.62 6.4 157
1.0
3D 68 1.59 5.9 218
1.0
Base Paper A 1 _ 1.06 29.7 20 0
Base Paper B 46 1.31 18.6 61 0
Base Paper C 76 1.43 23.8 157 0
Base Paper D 87 1.51 6.3 218 0
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Example 3
(A) Preparation of Size Press Compositions
A series of coating compositions were prepared using the following
procedure. The coating is prepared in the lab using a low shear mixer. A
certain
amount of pre-cooked starch is added to the coating container, then the water
and
then the water soluble divalent metal salt under proper shear actions. Then
0.6
parts of a styrene-based surface sizing agent was added to the coating under
shear.
The desired coating solids for this application is in a range of 11 to 16%
depending on the tolerance of the system to coating or size press treatment
viscosity, and the desired pickup. The coating compositions and specifications
are
set for the in the following Table 5.
Table 5
Size Press Compositions
Size Press Ethylated Starch , Calcium Chloride, Water,
Parts
Composition Parts Parts
1 11 0 89
2 11 1 88
3 11 2 87
4 12 3 85
5 12 4 84
(B) Preparation of Size Press Treated Ink Jet Paper
1. Substrate Preparation
The substrates used in this experiment were made on a paper machine from
a fiber furnish consisting of 60% softwood and 40% eucalyptus fibers and 15%
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p-ieclpitited calcium carbonate with alkenyl succinic anhydride (ASA) internal
size. The basis weight of the substrate paper was about 75 g/m2 and HST value
of
about 20 seconds.
2. Size Press Treatment
The base paper used in this procedure has a basis weight of about 75 g/m2
and an HST value of about 20 seconds. To apply the coating fotmulation, a 12"
wide roll of paper substrate is continuously fed between two rollers, and the
coating formulation is pumped into the nip reservoir, the paper being fed
through
the nip reservoir at a prefixed speed. By controlling the formulation solids,
nip
pressure, and size press running speed, a pickup weight of about 2.2 to 3.0
g/m2 is
achieved.
The size press treated substrates and their specifications are set forth in
the
following Table 6.
Table 6
Size Press Treated Substrates
Size Press Size Press Starch Coverage, (gsm)
Salt Coverage,
Treated Composition (gsm)
Substrate
1 1 2.2 0
2 2 2.2 0.2
3 3 2.2 0.4
4 4 2.2 0.6
5 5 2.2. 0.8
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Using the procedures of Example2, the IT%, 0D0 and EA of the size press
treated substrates of Table 6 were determined. The results of these
evaluations are
set forth in the following Table 7.
Table 7
Size Press Treated IT% 0D0 EA HST Salt
Substrate (s)
Coverage
(gsm)
1 70 1.24 9.1 57 0
2 42 1.56 7.7 47 0.2
3 28 1.57 8.1 47 0.4
4 31 1.60 7.4 58 0.6
5 30 1.51 6.9 47 0.8
Example 4
(A) Preparation of Size Press Treated Compositions
A series of coating compositions were prepared using the following
procedure. The coating ingredients such as pre-cooked starch, water soluble
divalent metal salt, water, various coating additives such as optical
brighteners,
defoamers, cationic polymers, sizing agents, and crosslinkers are continuously
fed
into the size press run tanks of the paper machine with mixing. The desired
coating solids for this application is in a range of 5 to 25% depending on the
tolerance of the system to coating or size press treatment viscosity. The size
press
compositions and specifications are set for the in the following Table 8.
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Table 8
Size Press Compositions
Size Press Ethylated Calcium Cationic
Water, Parts
Composition Starch , Parts Chloride, Parts Polymer, Parts
1 8 0 0 92
2 8 2.5 0
89.5
3 6 2.5 3.5 88
(B) Preparation of Size press Treated Ink Jet Paper
1. Substrate Preparation
The substrates used in this experiment were made on a paper machine from
a fiber furnish consisting of 60% softwood and 40% eucalyptus fibers and 15%
precipitated calcium carbonate with alkenyl succinic anhydride (ASA) internal
size. The basis weight of the substrate paper was about 75 g/m2 and HST values
ranging from about 30 seconds to about 150 seconds.
2. Machine trials
To apply the size press foimulation, the ingredients are pumped into a
stainless steel mixing tank at a predetermined rate, and metered onto the
paper
substrate using a rod-metered or puddle size press. By controlling the
formulation
solids and nip pressure, a pickup weight of about 3.0 g/m2 is achieved.
The size press treated substrates and their specifications are set forth in
the
following Table 9.
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Table 9
Size press Treated Substrates
Size Press Treated Size Press Composition Salt Coverage, (gsm)
Substrate
1 1 0
2 2 0.8
3 2 0.8
4 2 0.8
3 1.0
Using the procedures of Example2, the IT%, 0D0 and EA of the size press
5 treated substrates of Table 9 were determined. The results of these
evaluations are
set forth in the following Table 10.
Table 10
Coated Substrate IT% 0D0 EA HST Salt
(s)
Coverage
(gsm)
1 71 1.30 9.7 118 0
2 36 1.54 7.2 139 0.8
3 27 1.52 7.5 121 0.8
4 11 1.53 8.8 48 0.8
5 17 1.58 7.0 24 1.0
Finally, variations from the examples given herein are possible in view of
the above-disclosure.
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The foregoing
description of various and preferred embodiments of the present invention has
been provided for purposes of illustration only, and it is understood that
numerous
modifications, variations and alterations may be made.
27
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