U.S. patent application number 17/417644 was filed with the patent office on 2022-02-24 for pre-treatments for publishing print media.
This patent application is currently assigned to Hewlett-Packard Development Company, L.P.. The applicant listed for this patent is Hewlett-Packard Development Company, L.P.. Invention is credited to Mark Drake, Jason Swei, Rajasekar Vaidyanathan.
Application Number | 20220056302 17/417644 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-24 |
United States Patent
Application |
20220056302 |
Kind Code |
A1 |
Vaidyanathan; Rajasekar ; et
al. |
February 24, 2022 |
PRE-TREATMENTS FOR PUBLISHING PRINT MEDIA
Abstract
A pre-treatment coating composition can include an evaporable
liquid vehicle and a pre-treatment coating matrix carried by the
evaporable liquid vehicle. The pre-treatment coating matrix in this
example can include from 30 wt % to 70 wt % multivalent organic
salt including a multivalent metal acetate or a multivalent metal
propionate, from 5 wt % to 30 wt % dispersed polymeric binder
having a weight average molecular weight from 20,000 Mw to
1,000,000 Mw, from 0.5 wt % to 8 wt % of a high molecular weight
polyvinyl alcohol binder, and from 10 wt % to 30 wt % of a low
molecular weight polyvinyl alcohol binder. The low molecular weight
polyvinyl alcohol binder and the high molecular weight polyvinyl
alcohol binder in this example can be present in the pre-treatment
coating matrix at a 3:1 to 15:1 weight ratio. Weight percentages in
this example are based on dry weight of the pre-treatment coating
matrix.
Inventors: |
Vaidyanathan; Rajasekar;
(San Diego, CA) ; Drake; Mark; (San Diego, CA)
; Swei; Jason; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hewlett-Packard Development Company, L.P. |
Spring |
TX |
US |
|
|
Assignee: |
Hewlett-Packard Development
Company, L.P.
Spring
TX
|
Appl. No.: |
17/417644 |
Filed: |
March 9, 2020 |
PCT Filed: |
March 9, 2020 |
PCT NO: |
PCT/US2020/021673 |
371 Date: |
June 23, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2019/050798 |
Sep 12, 2019 |
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17417644 |
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International
Class: |
C09D 129/04 20060101
C09D129/04; B41M 5/52 20060101 B41M005/52; C09D 175/04 20060101
C09D175/04 |
Claims
1. A pre-treatment coating composition, comprising: an evaporable
liquid vehicle; and a pre-treatment coating matrix carried by the
evaporable liquid vehicle, the pre-treatment coating matrix,
comprising: from 30 wt % to 70 wt % multivalent organic salt
including a multivalent metal acetate or a multivalent metal
propionate, from 5 wt % to 30 wt % dispersed polymeric binder
having a weight average molecular weight from 20,000 Mw to
1,000,000 Mw, from 0.5 wt % to 8 wt % of a high molecular weight
polyvinyl alcohol binder, and from 10 wt % to 30 wt % of a low
molecular weight polyvinyl alcohol binder, wherein the low
molecular weight polyvinyl alcohol binder and the high molecular
weight polyvinyl alcohol binder are present in the pre-treatment
coating matrix at a 3:1 to 15:1 weight ratio, and wherein weight
percentages are based on dry weight of the pre-treatment coating
matrix.
2. The pre-treatment coating composition of claim 1, wherein the
multivalent salt includes a divalent metal selected from calcium,
magnesium, iron, aluminum, zinc, or a combination thereof.
3. The pre-treatment coating composition of claim 1, wherein the
dispersed polymeric binder includes a dispersed polyurethane
binder.
4. The pre-treatment coating composition of claim 4, wherein the
dispersed polyurethane binder has a weight average molecular weight
from 30,000 Mw to 100,000 Mw.
5. The pre-treatment coating composition of claim 1, further
comprising a block copolymer surfactant that stabilizes components
of the pre-treatment coating matrix by steric hindrance, and having
a weight average molecular weight from 4,000 Mw to 12,000 Mw with
an acid value from 5 mg KOH/g to 30 mg KOH/g.
6. A publishing print medium, comprising: a media substrate having
a basis weight of 50 gsm to 350 gsm; and a first pre-treatment
matrix layer on a first side of the media substrate and a second
pre-treatment matrix layer on a second side of the media substrate,
the first pre-treatment matrix layer and the second pre-treatment
matrix layer independently comprising: from 30 wt % to 70 wt %
multivalent organic salt, from 5 wt % to 30 wt % dispersed
polymeric binder having a weight average molecular weight from
20,000 Mw to 1,000,000 Mw, from 0.5 wt % to 8 wt % of a high
molecular weight polyvinyl alcohol binder, and from 10 wt % to 30
wt % of a low molecular weight polyvinyl alcohol binder, wherein
the low molecular weight polyvinyl alcohol binder and the high
molecular weight polyvinyl alcohol binder are present in the
pre-treatment matrix layer at a 3:1 to 15:1 weight ratio, and
wherein weight percentages are based on dry weight of the
pre-treatment matrix layer.
7. The publishing print medium of claim 6, wherein the multivalent
organic salt includes a divalent metal cation selected from
calcium, magnesium, iron, aluminum, zinc, or a combination thereof,
and an anion selected from acetate, propionate, or a combination
thereof.
8. The publishing print medium of claim 6, wherein the dispersed
polymeric binder includes a dispersed polyurethane binder.
9. The publishing print medium of claim 6, wherein the dispersed
polymeric binder includes a polymer or a copolymer including
polyurethane, acrylic, vinyl acetate, polyester, vinylidene
chloride, butadiene, styrene-butadiene, acrylonitrile-butadiene, or
sulfonated styrene-butadiene.
10. A method of preparing a publishing print medium, comprising:
coating a first side of media substrate with a first pre-treatment
coating composition and a second side of media substrate with a
second pre-treatment coating composition, the first and second
pre-treatment coating compositions comprising an evaporable liquid
vehicle and a pre-treatment coating matrix carried by the
evaporable liquid vehicle, the pre-treatment coating matrix,
comprising: from 30 wt % to 70 wt % multivalent organic salt, from
5 wt % to 30 wt % dispersed polymeric binder having a weight
average molecular weight from 20,000 Mw to 1,000,000 Mw, from 0.5
wt % to 8 wt % of a high molecular weight polyvinyl alcohol binder,
and from 10 wt % to 30 wt % of a low molecular weight polyvinyl
alcohol binder, wherein the low molecular weight polyvinyl alcohol
binder and the high molecular weight polyvinyl alcohol binder are
present in the pre-treatment coating matrix at a 3:1 to 15:1 weight
ratio, and wherein weight percentages are based on dry weight of
the pre-treatment coating matrix; drying the first pre-treatment
coating composition to remove evaporable liquid vehicle therefrom
to form a first pre-treatment matrix layer; and drying the second
pre-treatment coating composition to remove evaporable liquid
vehicle therefrom to form a second pre-treatment matrix layer.
11. The method of claim 10, wherein the media substrate has a basis
weight from 50 gsm to 350 gsm.
12. The method of claim 10, wherein the first pre-treatment coating
composition is applied to the first side at a basis weight from 0.1
gsm to 10 gsm, and the second pre-treatment coating composition is
applied to the second side at a basis weight from 0.1 gsm to 10
gsm.
13. The method of claim 10, further comprising printing on both
sides of the publishing print medium.
14. The method of claim 10, wherein coating the first side and the
second side is carried out in-line with the printing.
15. The method of claim 10, wherein the multivalent organic salt
includes a divalent metal cation selected from calcium, magnesium,
iron, aluminum, zinc, or a combination thereof, and an anion
selected from acetate, propionate, or a combination thereof.
Description
BACKGROUND
[0001] Inkjet technology has expanded its application to
high-speed, commercial and industrial printing, in addition to home
and office usage. This technology is a non-impact printing method
in which an electronic signal controls and directs droplets or a
stream of ink that can be deposited on a wide variety of
substrates. Current inkjet printing technology involves forcing the
ink drops through small nozzles by thermal ejection or
piezoelectric pressure or oscillation onto the surface of a media.
Though inkjet printing is versatile, with certain types of printing
and processing applications, there can be challenges related to
inkjet or digital printing technology.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] FIG. 1 is a schematic view of an example pre-treatment
coating composition in accordance with the present disclosure;
[0003] FIG. 2 is a cross-sectional schematic view of the
pre-treatment matrix layer applied to a print media substrate and
having an ink composition printed thereon in accordance with the
present disclosure;
[0004] FIG. 3 depicts a flow chart of an example method in
accordance with the present disclosure;
[0005] FIG. 4 is a graphical representation of an example that
illustrates gloss provided by print media having a pre-treatment
matrix layer prepared in accordance with the present disclosure
applied thereto in accordance with the present disclosure;
[0006] FIG. 5 is a graphical representation of a comparative
example that provides coefficient of friction (COF) provided by
print media having a comparative pre-treatment matrix layer applied
thereto relative to pre-treatment matrix layers prepared in
accordance with the present disclosure;
[0007] FIG. 6 is a graphical representation of a comparative
example that illustrates the effect of the ratio of low molecular
weight PVA to high molecular weight PVA on dot gain on a
pre-treatment matrix layer in accordance with the present
disclosure; and
[0008] FIG. 7 is a graphical representation of an example that
compares mean cyan ink inefficiency provided by print media having
comparative pre-treatment matrix layers applied thereto relative to
pre-treatment matrix layers prepared in accordance with the present
disclosure.
DETAILED DESCRIPTION
[0009] A pre-treatment coating composition, and the pre-treatment
matrix layer that is formed therefrom (after drying, e.g., solvent
evaporation), can be used in the publishing area for providing
publishing media suitable for high-speed printing, for example.
These coatings can likewise be applied to both sides of the print
media substrate to provide a glossy paper appearance both at
printed and unprinted areas of the publishing print media.
Furthermore, these pre-treatment matrix layers can be prepared so
that they essentially match the gloss of the underlying paper media
substrate, e.g., glossy substrates may relatively closely retain
their gloss and matte paper substrates may relatively closely
retain their matte appearance. In addition to providing and/or
retaining gloss levels, these pre-treatment coating compositions
(applied as pre-treatment matrix layers) can also provide more ink
saturation due to enhanced (ink) dot gain compared to other coating
layers. Higher dot gain provides greater ink density on a media
substrate due to more dot spreading upon printing. This can lead to
either enhanced saturation or the same saturation with less ink use
compared to other coatings. Furthermore, these pre-treatment matrix
layers can also provide durability at an acceptable level for
publishing applications, even high speed publishing applications,
e.g., from 50 feet per minute (fpm) to 1200 fpm.
[0010] In accordance with an example of the present disclosure, a
pre-treatment coating composition includes an evaporable liquid
vehicle and a pre-treatment coating matrix carried by the
evaporable liquid vehicle. The pre-treatment coating matrix in this
example includes from 30 wt % to 70 wt % multivalent organic salt
including a multivalent metal acetate or a multivalent metal
propionate, from 5 wt % to 30 wt % dispersed polymeric binder
having a weight average molecular weight from 20,000 Mw to
1,000,000 Mw, from 0.5 wt % to 8 wt % of a high molecular weight
polyvinyl alcohol binder, and from 10 wt % to 30 wt % of a low
molecular weight polyvinyl alcohol binder. The low molecular weight
polyvinyl alcohol binder and the high molecular weight polyvinyl
alcohol binder in this example are present in the pre-treatment
coating matrix at a 3:1 to 15:1 weight ratio. Weight percentages in
this example are based on dry weight of the pre-treatment coating
matrix. In further detail, the multivalent salt can include a
divalent metal selected from calcium, magnesium, iron, aluminum,
zinc, or a combination thereof. The dispersed polymeric binder can
be, for example, a polyurethane binder, e.g., a polyurethane binder
having a weight average molecular weight from 30,000 Mw to 100,000
Mw. In still further detail, the pre-treatment coating composition
can include a block copolymer surfactant that stabilizes components
of the pre-treatment coating matrix by steric hindrance, and can
have a weight average molecular weight from 4,000 Mw to 12,000 Mw
with an acid value from 5 mg KOH/g to 30 mg KOH/g.
[0011] In another example, a publishing print medium includes a
media substrate having a basis weight of 50 gsm to 350 gsm, a first
pre-treatment matrix layer on a first side of the media substrate,
and a second pre-treatment matrix layer on a second side of the
media substrate. The first pre-treatment matrix layer and the
second pre-treatment matrix layer in this example independently
include from 30 wt % to 70 wt % multivalent organic salt, from 5 wt
% to 30 wt % dispersed polymeric binder having a weight average
molecular weight from 20,000 Mw to 1,000,000 Mw, from 0.5 wt % to 8
wt % of a high molecular weight polyvinyl alcohol binder, and from
10 wt % to 30 wt % of a low molecular weight polyvinyl alcohol
binder. The low molecular weight polyvinyl alcohol binder and the
high molecular weight polyvinyl alcohol binder in this example are
present in the pre-treatment coating matrix at a 3:1 to 15:1 weight
ratio. Weight percentages in this example are based on dry weight
of the pre-treatment coating matrix. In one example, the
multivalent organic salt includes a divalent metal cation selected
from calcium, magnesium, iron, aluminum, zinc, or a combination
thereof. The pre-treatment coating matrix can include an anion
selected from acetate, propionate, or a combination thereof. The
dispersed polymeric binder can be a dispersed polyurethane binder,
for example. Alternatively or additionally, the dispersed polymeric
binder includes a polymer or a copolymer including polyurethane,
acrylic, vinyl acetate, polyester, vinylidene chloride, butadiene,
styrene-butadiene, acrylonitrile-butadiene, or sulfonated
styrene-butadiene.
[0012] In another example, a method of preparing a publishing print
medium includes coating a first side of media substrate with a
first pre-treatment coating composition and a second side of media
substrate with a second pre-treatment coating composition, the
first and second pre-treatment coating composition in this example
including an evaporable liquid vehicle and a pre-treatment coating
matrix carried by the evaporable liquid vehicle. The pre-treatment
coating matrix includes from 30 wt % to 70 wt % multivalent organic
salt, from 5 wt % to 30 wt % dispersed polymeric binder having a
weight average molecular weight from 20,000 Mw to 1,000,000 Mw,
from 0.5 wt % to 8 wt % of a high molecular weight polyvinyl
alcohol binder, and from 10 wt % to 30 wt % of a low molecular
weight polyvinyl alcohol binder. The low molecular weight polyvinyl
alcohol binder and the high molecular weight polyvinyl alcohol
binder in this example are present in the pre-treatment coating
matrix at a 3:1 to 15:1 weight ratio. Weight percentages in this
example are based on dry weight of the pre-treatment coating
matrix. Furthermore, the method includes drying the first
pre-treatment coating composition to remove evaporable liquid
vehicle therefrom to form a first pre-treatment matrix layer, and
drying the second pre-treatment coating composition to remove
evaporable liquid vehicle therefrom to form a second pre-treatment
matrix layer. In one more specific example, the media substrate can
have a basis weight from 50 gsm to 350 gsm. The first pre-treatment
coating composition can be applied to the first side at a basis
weight from 0.1 gsm to 10 gsm, and the second pre-treatment coating
composition is applied to the second side at a basis weight from
0.1 gsm to 10 gsm. The method can include, for example, printing on
both sides of the publishing print medium. Coating the first side
and the second side can be carried out in-line with printing, for
example. The multivalent organic salt can include a divalent metal
cation selected from calcium, magnesium, iron, aluminum, zinc, or a
combination thereof. Furthermore, the multivalent organic salt can
include anion selected from acetate, propionate, or a combination
thereof.
[0013] When discussing the pre-treatment coating compositions, the
print media, and the methods herein, these various discussions can
be considered applicable to each of these examples, whether or not
they are explicitly discussed in the context of that example. Thus,
for example, in discussing a dispersed polymeric binder in a
pre-treatment coating composition, such a polyurethane can also be
used for the publishing print media examples, the method examples,
etc., and vice versa.
[0014] It is noted that the term "pre-treatment coating
composition" refers to the composition used to form a
"pre-treatment matrix layer." Furthermore, to avoid confusion, the
pre-treatment coating composition includes an aqueous liquid
vehicle, e.g., water or a mixture of water and other volatile
liquids that are evaporable therefrom, that carries a
"pre-treatment coating matrix," which is the solids or "dry"
formulation carried by the liquid vehicle that when dried on a
media substrate, forms a "pre-treatment matrix layer." Thus, the
term "pre-treatment" can be used to describe the pre-treatment
coating composition, the pre-treatment coating matrix (the solids
present in the coating composition), or the matrix layer (solids
that remain as a dried layer on the print media substrate). The
solids content of the pre-treatment coating composition (referred
to as the "pre-treatment coating matrix") and the solids content of
the pre-treatment matrix layer should be about the same, as both
exclude the aqueous liquid vehicle in their calculation. For
example, a pre-treatment coating composition includes an evaporable
liquid vehicle and a pre-treatment coating matrix (solids of the
coating) such that the evaporable liquid vehicle (when evaporated)
from the solids, leaves the pre-treatment matrix layer coated on
the media substrate. In accordance with this, the evaporable liquid
vehicle is not included in weight percent (wt %) calculations for
either the coating matrix components or the matrix layer
components, e.g., dry weight is provided unless the context
dictates otherwise.
[0015] In accordance with FIG. 1, a pre-treatment coating
composition 100A is shown schematically by example. The structures
shown are not to scale, and are merely examples that individually
and graphically represent a wider class of structures. As shown,
the pre-treatment coating composition includes an aqueous liquid
vehicle 110 which includes solids either dispersed or solvated
therein. Those solids include, for example, multivalent organic
salt 120, low molecular weight polyvinyl alcohol binder 130, high
molecular weight polyvinyl alcohol binder 140, and dispersed
polymeric binder 150, such as polymers and copolymers including
acrylic polymers, vinyl acetate polymers, polyester polymers,
vinylidene chloride polymers, butadiene polymers, styrene-butadiene
polymers, acrylonitrile-butadiene polymers, polyurethane, acrylic
polymers, sulfonated styrene butadiene, or the like.
[0016] Regarding the various iterations of the formulations
described herein as "pre-treatment" coating composition(s) or
matrices, the ingredients that are selected for use can provide a
benefit to the pre-treatment coating composition 100A, e.g.,
formulation stability, etc., and/or can provide a benefit to the
pre-treatment matrix layer 100B (not shown in this FIG., but shown
in FIG. 2) that is dried and formed on the media substrate using
the pre-treatment coating composition. For example, in the
pre-treatment coating composition or the pre-treatment matrix layer
formed therefrom, the multivalent organic salt 120 acts in part as
an ink fixer to contribute to the high image quality by preventing
color bleed and other visual artifacts when an aqueous ink is
printed thereon. It may also increase image quality by keeping the
image close to the surface of the pre-treatment coating.
Furthermore, the use of a multivalent organic salt (rather than an
inorganic salt, such as chloride, bromide, etc.), and in some
examples, multivalent acetates and/or propionates, tends to be less
corrosive to some metals, which can be present in various equipment
that may come into contact with the pre-treatment coating
composition. In further detail, inclusion of the multivalent
organic salts described herein can act to stabilize the
pre-treatment coating compositions, which in accordance with the
present disclosure, can include greater than a 3:1 weight ratio of
low molecular weight polyvinyl alcohol binder 130 to high molecular
weight polyvinyl alcohol binder 140, and can further include the
dispersed polymeric particles 150.
[0017] Example multivalent metal salts 120 that can be used include
a salt of a multivalent metal and a carboxylate ion such as those
present in various organic acids, for example. Examples of
multivalent metal cations include divalent metal ions, such as
Ca.sup.2+, Cu.sup.2+, Ni.sup.2+, Mg.sup.2+, Zn.sup.2+, and/or
Ba.sup.2+; and trivalent metal ions, such as Al.sup.3+, Fe.sup.3+,
and/or Cr.sup.3+. In one example, the multivalent metal ion can be
Ca.sup.2+, Mg.sup.2+ or Zn.sup.2+. In one aspect, the multivalent
metal ion(s) can be Ca.sup.2+, Mg.sup.2+, and/or Al.sup.3+.
Examples of organic anions that can be used include carboxylate
having the formula RCOO.sup.-, where R is hydrogen or a low
molecular weight hydrocarbon chain, e.g., C1 to C12. When R is H,
the organic salt is a multivalent formate, when R is C1 the organic
salt is a multivalent acetate, when R is C2, the multivalent salt
is a propionate, and so forth. In a more specific example, the
multivalent organic salt can include carboxylated anion derived
from saturated aliphatic monocarboxylic acid having 1 to 6 carbon
atoms (C1 to C6), or in a still more specific example, the
carboxylated anion can be derived from a saturated aliphatic
monocarboxylic acid having 1 or 2 carbon atoms, e.g., acetate (C1)
or propionate (C2). Examples of saturated aliphatic monocarboxylic
acid having 1 to 6 carbon atoms may include formic acid, acetic
acid, propionic acid, butyric acid, isobutyric acid, valeric acid,
isovaleric acid, pivalic acid, and/or hexanoic acid. In other
examples, the carboxy or a carbocyclic monocarboxylic acid has 7 to
11 carbon atoms. In certain more specific examples, the multivalent
organic salt can include calcium acetate, calcium propionate,
magnesium acetate, magnesium propionate, aluminum acetate, aluminum
propionate, zinc acetate, zinc propionate, or a combination
thereof.
[0018] Regardless of the multivalent organic salt 120 used, whether
used singly or as a combination of multivalent organic salts, a
total amount of multivalent cationic salt in the pre-coating
composition (by dry weight) and in the pre-coating matrix can be
from 25 wt % to 75 wt %, from 30 wt % to 70 wt %, or from 35 wt %
to 65 wt %, for example. In further detail in examples herein, the
multivalent organic salt can be selected that has a solubility (on
the basis of anhydrous salt) in water from 15 g multivalent organic
salt per 100 mL water (15 g/100 mL solubility) or more, e.g., from
15 g/100 mL to 100 g/100 mL, or from 20 g/100 mL to 75 g/100 mL, or
from 25 g/100 mL to 60 g/100 mL). The solubility of the multivalent
ion in solution can provide a good mechanism to crash the pigment
when an ink composition is applied to the pre-treatment matrix
layer, and the multivalence nature of the multivalent metal cation
can provide more effective crashing and/or pigment fixation
compared to monovalent metal ions.
[0019] Thus, with these formulations, images printed on the
pre-treatment matrix layer (see 100B of FIG. 2), formed from a
pre-treatment coating composition 110A, can be enhanced with
respect to both durability and print quality by the presence of the
multivalent organic salt 120, as it provides a stable composition
including the multiple polyvinyl alcohol binders 130, 140 and a
dispersed polymeric binder 150. As one example, this combination
provides good image quality, including relatively even image and
media gloss and/or enhanced or increased dot gain which can relate
to image saturation. These coatings can also provide good rub
durability for publishing applications. For example, with respect
to image quality, ink compositions printed on the pre-treatment
coating matrices of the present disclosure can exhibit enhanced or
increased dot gain, meaning the ink dots printed thereon are
slightly larger (with more spreading) so that upon digitally
printing, a higher ink density can be achieved compared to print
media without the coating or even with some other state of the art
coatings. Thus, less ink may be used to achieve an acceptable
amount of color when printed on the pre-coating matrix, or
alternatively, richer color saturation may be achievable with the
same amount of ink compared to uncoated media or media coated with
some other state of the art coatings.
[0020] In further detail regarding the multiple polyvinyl alcohol
(PVA) binders, one binder is the low molecular weight polyvinyl
alcohol binder 130 and the other binder is the high molecular
weight polyvinyl alcohol binder 140. In accordance with examples of
the present disclosure, "low molecular weight" polyvinyl alcohol
can have a viscosity of a 4 wt % solution from 2.5 mPas to 7 mPas,
from 3 mPas to 6 mPas, or from 3.5 mPas to 4.5 mPas. The "high
molecular weight" polyvinyl alcohol can have a viscosity from 9
mPas to 110 mPas, from 10 mPas to 60 mPas, or from 11.5 mPas to
14.5 mPas. These molecular weights (e.g., low and high Mw PVA) are
thus relative to one another, and can be quantified by viscosity,
and in some examples, may further be quantified by weight average
molecular weight.
[0021] With respect to the use of viscosity to quantify the
molecular weight of the polyvinyl alcohols used herein, the
viscosities are measured at 20.degree. C. as a 4 wt % polyvinyl
alcohol solution in water, as per ISO standard 12058-1:2018(E),
which is a dynamic viscosity standard testing protocol. The
viscosity value is expressed in millipascal seconds (mPas) using a
falling ball viscometer. With this methodology, the apparatus
includes an inclined measurement tube (falling-ball tube of
thermally aged, calibrated, precision borosilicate glass tubing
with a coefficient of linear expansion of 3.3.times.10.sup.-6)
filled with liquid to be tested, e.g., polyvinyl alcohol solution
(4 wt % in water at 20.degree. C.). One of six balls is selected,
depending on the expected viscosity range (No. 1 and No. 2 balls
are appropriate, as the viscosity values collected will range from
0.6 mPas to 10 mPas (Ball No. 1; 15.81 mm diameter) or from 7 mPas
to 130 mPas (Ball No. 2; 15.60 mm diameter). If both balls return
results, the value of the slower moving ball will be used.
Equipment used for this test can be a Hoepler viscometer (described
in DIN 53015:1978), or equivalent. The measurement tube is marked
defining distances of 100 mm, and the tube is jacketed to provide
temperature control (at 20.degree. C.) and to provide a 10 degree
incline. The ends are plugged, with one end including a capillary
joined to a hollow space to avoid pressure fluctuations. The
polyvinyl alcohol solution is kept completely within the tube and
between the plugs. The travel time of the ball between the two
marks is used to determine the viscosity of the fluid, based on
formulations and calculations published in ISO standard
12058-1:2018(E).
[0022] Regarding weight average molecular weight of the polyvinyl
alcohol binders, the "low molecular weight" polyvinyl alcohol
binder, in some examples, can be further defined, or alternatively
defined, to include polyvinyl alcohol binders with a weight average
molecular weight from 15,000 Mw to 60,000 Mw, from 15,000 Mw to
50,000 Mw, from 15,000 Mw to 45,000 Mw, from 20,000 Mw to 60,000
Mw, from 20,000 Mw to 50,000 Mw, from 20,000 Mw to 45,000 Mw, or
from 25,000 Mw to 50,000 Mw, for example. The "high molecular
weight" polyvinyl alcohol binder can be further defined, or
alternatively defined herein, to include polyvinyl alcohol binders
with a weight average molecular weight from 50,000 Mw to 300,000
Mw, from 60,000 Mw to 300,000 Mw, from 75,000 Mw to 300,000 Mw,
from 100,000 Mw to 300,000 Mw, from 50,000 Mw to 200,000 Mw, from
75,000 Mw to 200,000 Mw, or from 100,000 Mw to 250,000 Mw, for
example. Notably, as the range of low molecular weight and high
molecular weight ranges may overlap in some instances (though the
viscosity ranges defining high and low molecular weight above do
not overlap), it is noted that these two terms are likewise
intended to be relative to one another (low molecular weight is
considered to be determined relative to high molecular weight
polyvinyl alcohol). Thus, in practice, the ranges for the low and
high molecular weight polyvinyl alcohol are not intended to overlap
in most instances. Thus, in some examples, irrespective of
overlapping overall weight ranges, the low molecular weight
polyvinyl alcohol may have a weight average molecular weight from
10,000 Mw to 285,000 Mw lower than the high molecular weight
polyvinyl alcohol binder. In a more detailed example, the
difference in molecular weight ranges between the low to high
molecular weight polyvinyl alcohol can be from 20,000 Mw to 200,000
Mw, or from 30,000 Mw to 150,000 Mw.
[0023] The low molecular weight polyvinyl alcohol binder 130 and
the high molecular weight polyvinyl alcohol binder 140 can be
present in the pre-coating composition or in the pre-coating matrix
at a weight ratio from 3:1 to 15:1, from 4:1 to 15:1, from 5:1 to
15:1, from 3:1 to 10:1, from 4:1 to 10:1, or from 5:1 to 10:1, for
example. In one example, the weight ratio of low molecular
polyvinyl alcohol to high molecular weight polyvinyl alcohol can be
from 6:1 to 8:1.
[0024] Examples of polyvinyl alcohol binders 130, 140 that can be
used include partially hydrolyzed polyvinyl alcohol, fully
hydrolyzed polyvinyl alcohol, or copolymers including polyvinyl
alcohol, provided they are water-soluble. When describing polyvinyl
alcohol herein, this can refer to either the low molecular weight
polyvinyl alcohol or the high molecular weight polyvinyl alcohol,
or to both in a common formulation. Furthermore, for definitional
purposes, 98% hydrolyzed polyvinyl alcohol (or greater, based on
percentage of alcohol groups present relative to total side groups
of both alcohol and acetate groups) is considered to be fully
hydrolyzed polyvinyl alcohol. Polyvinyl alcohol that is less than
98% hydrolyzed polyvinyl alcohol is considered to be partially
hydrolyzed. In one specific example, the polyvinyl alcohol used can
be partially hydrolyzed, and in more specific examples, the
polyvinyl alcohol can be partially hydrolyzed at from 80% to 94%.
In other examples, the polyvinyl alcohol binders that can be used
include water-soluble copolymers of polyvinyl alcohol and other
polymeric groups copolymerized therewith, e.g., copolymers of
polyvinyl alcohol and poly(ethylene oxide), polyvinyl alcohol and
polyvinylamine, cationic polyvinyl alcohol, acetoacetylated
polyvinyl alcohol, silyl-modified polyvinyl alcohol, etc. In one
example, the polyvinyl alcohol (which includes water-soluble
copolymers thereof) can be included at a concentration where it is
fully solubilized in the pre-treatment coating compositions, for
example.
[0025] In further detail regarding the dispersed polymeric binder
150 in the pre-treatment coating composition, or the polymeric
binder in the pre-treatment coating matrix (or that remains with
the pre-treatment matrix layer), these dispersed polymeric binder
particulates may enhance durability by binding the ingredients of
the matrix to each other and to the underlying media. In some
examples, the polymeric binder particles can be included to allow
ink components to penetrate the matrix, providing a surface
morphology for receiving aqueous inkjet ink. Thus, the combination
of the high molecular weight polyvinyl alcohol, the low molecular
weight polyvinyl alcohol, and the dispersed polymeric binder can
provide good durability. The dispersed polymeric binder can be, for
example, polymer or copolymer particles including a polyurethane,
acrylic, vinyl acetate, polyester, vinylidene chloride, butadiene,
styrene-butadiene, acrylonitrile-butadiene, sulfonated styrene
butadiene, etc. The weight average molecular weight of the
dispersed polymeric binder can be, for example, from 20,000 Mw to
1,000,000 Mw, from 30,000 Mw to 500,000 Mw, from 30,000 Mw to
250,000 Mw, or from 30,000 Mw to 100,000 Mw, for example.
[0026] The particle size of the dispersed polymeric binder can be
from 10 nm to 1 .mu.m, from 10 nm to 500 nm, from 50 nm to 250 nm,
from 50 nm to 200 nm, or from 60 nm to 160 nm, for example. The
particle size distribution of the dispersed polymeric binder is not
particularly limited. However, it is also possible to use two or
more distribution sizes of dispersed polymeric binder particles
with their own mono-dispersed particle size distribution can be
used in combination.
[0027] As used herein, particle size can refer to a value of the
diameter of spherical particles, or in the case of particles that
are not spherical, can refer to the equivalent spherical diameter
of the volume of that particular particle if reshaped at the same
density as a spherical particle. The particle size distribution can
be in a Gaussian distribution or a Gaussian-like distribution (or
normal or normal-like distribution). Gaussian-like distributions
are distribution curves that can appear Gaussian in distribution
curve shape, but which can be slightly skewed in one direction or
the other (toward the smaller end or toward the larger end of the
particle size distribution range). In these or other types of
particle distributions, the particle size can be characterized in
one way using the 50.sup.th percentile of the particle size,
sometimes referred to as the "D50" particle size. For example, a
D50 value of about 25 .mu.m means that about 50% of the particles
(by number) have a particle size greater than about 25 .mu.m and
about 50% of the particles have a particle size less than about 25
.mu.m. Whether the particle size distribution is Gaussian,
Gaussian-like, or otherwise, the particle size distribution can be
expressed in terms of D50 particle size, which may approximate
average particle size, but may not be the same. In examples herein,
the particle size ranges disclosed herein can be modified to
"average particle size," providing sometimes slightly different
size distribution ranges.
[0028] In one example, the dispersed polymeric binder 150 can be in
the form of polyurethane binder particles. In more specific detail,
in addition to the molecular weight ranges cited previously for the
dispersed polymeric binder, the polyurethane binder particles may
have a weight average molecular weight (Mw) from 30,000 Mw to
100,000 Mw, from 30,000 Mw to 80,000 Mw, from 30,000 Mw to 70,000
Mw, or from 40,000 Mw to 70,000 Mw, for example. In one specific
example, the polyurethane binder particles having a weight average
molecular weight from 40,000 Mw to 70,000 Mw can be further
characterized to have a number average molecular weight (Mn) from
20,000 Mn to 30,000 Mn and/or a polydispersity from 2.1 to 2.5. In
some examples, the glass transition temperature (Tg) of the
polyurethane binder particles can be from 40.degree. C. to
140.degree. C., from 50.degree. C. to 100.degree. C., or from
60.degree. C. to 90.degree. C., for example. Glass transition
temperature (Tg) parameters can be measured by Differential
Scanning calorimetry (DSC), for example.
[0029] In additional detail, the pre-treatment coating compositions
(and pre-treatment coating matrices and layers) prepared in
accordance with the present disclosure can be further modified in
some examples by the inclusion of a surfactant.
[0030] In one specific example, however, it has been found that
some surfactants provide better performance with respect to image
quality and/or durability. As an example, certain surfactants sold
under the trade name Disperbyk.RTM., including Disperbyk.RTM. 190
as an example, provided better performance than other comparative
surfactants, such as Tego.RTM. Wet surfactants. That said, either
or both may be used in the formulations of the present disclosure.
Some surfactants, such as Disperbyk.RTM. 190 and the like, may be
beneficial for use due to it being sterically stabilizing for some
of the dispersed pre-treatment coating matrix components within the
pre-treatment coating composition, e.g., by steric hindrance with
its long chain size. These polymers may have a molecular weight
from 4,000 Mw to 12,000 Mw (or from 5,500 Mw to 8,500 Mw), for
example. In further detail, certain surfactants may likewise have
some acid groups that form anionic moieties in the pre-treatment
coating compositions (in the presence of the aqueous liquid vehicle
or water). Even more specifically, these and other similar
surfactants may be beneficial as they include a block copolymer
that stabilizes components of the pre-treatment coating matrix by
steric hindrance, and may have a weight average molecular weight
from 4,000 Mw to 12,000 Mw with an acid value (or acid number) from
5 mg KOH/g to 30 mg KOH/g. This combination may provide additional
benefits, even though other surfactants may alternatively or
additionally be used.
[0031] Non-limiting examples of other suitable surfactants include
anionic surfactant, nonionic surfactant, cationic surfactant, and
combinations thereof. In one example, the surfactant can be a
nonionic surfactant. Several commercially available nonionic
surfactants that can be used in the formulation of the
pre-treatment coating composition include ethoxylated alcohols such
as those from the Tergitol.RTM. series (e.g., Tergitol.RTM. 15S30,
Tergitol.RTM. 15S9), manufactured by Dow Chemical; surfactants from
the Surfynol.RTM. series (e.g. Surfynol.RTM. 440 and Surfynol.RTM.
465), and Dynol.TM. series (e.g. Dynol.TM. 607 and Dynol.TM. 604)
manufactured by Air Products and Chemicals, Inc.; fluorinated
surfactants, such as those from the Zonyl.RTM. family (e.g.,
Zonyl.RTM. FSO and Zonyl.RTM. FSN surfactants), manufactured by
E.I. DuPont de Nemours and Company; Alkoxylated surfactant such as
Tego.RTM. Wet 510 manufactured from Evonik; fluorinated
PolyFox.RTM. nonionic surfactants (e.g., PF159 nonionic
surfactants), manufactured by Omnova; or combinations thereof.
Suitable cationic surfactants that may be used in the pre-treatment
coating composition include long chain amines and/or their salts,
acrylated diamines, polyamines and/or their salts, quaternary
ammonium salts, polyoxyethylenated long-chain amines, quaternized
polyoxyethylenated long-chain amines, and/or combinations
thereof.
[0032] The surfactant, if present, can be included in the
pre-treatment coating composition at from 0.05 wt % to 1.5 wt %. In
one example, the surfactant can be present in an amount ranging
from 0.1 wt % to 1 wt %. In one aspect, the surfactant can be
present in an amount ranging from 0.2 wt % to 0.6 wt %.
[0033] Other additives can be added to the pre-treatment coating
composition including cross-linkers, defoamers, plasticizers,
fillers, stabilizers, dispersants, biocides, optical brighteners,
viscosity modifiers, leveling agents, UV absorbers, anti-ozonants,
wax, etc. Such additives can be present in the pre-treatment
coating compositions in amounts from 0.01 wt % to 20 wt %. However,
it is noted that in one specific example, the pre-treatment coating
composition (and the pre-treatment matrix layer applied to the
media substrate) can be devoid of wax. The term "wax" is defined
herein to include both natural waxes and synthetic waxes. Example
waxes include petroleum wax, vegetable or plant wax, animal wax,
modified plant or animal wax, mineral wax, ceresin wax, montan wax,
ozocerite wax, peat wax, paraffin wax, microcrystalline wax,
polyethylene wax or polypropylene wax, PTFE wax,
polytetrafluoroethylene wax, carnauba wax, bee's wax, paraffin wax,
polyamide wax, etc. Furthermore, the binders described herein, such
as the polyurethane binder particles, are not considered to be a
wax consistent with the present disclosure, as the pre-treatment
coating compositions are defined herein to include a polyurethane
binder in the form of dispersed particles in the composition or as
dispersed particles within the matrix applied and dried on the
media substrate.
[0034] The pre-treatment coating composition can include these, and
in some cases other, solids suspended in an aqueous liquid vehicle,
which may be simply water, or may be a combination of water and
other evaporable solvents or liquids. That stated, in one example,
the aqueous liquid vehicle can be water (or water and any other
evaporable liquid component that may be present in the individual
components used to formulate the pre-treatment coating
composition). Regardless of whether or not there are other
evaporable components present or not, the water can be included in
the pre-treatment coating composition at from 35 wt % to 90 wt %,
from 50 wt %, to 85 wt %, or from 60 wt % to 80 wt %, for
example.
[0035] Referring more specifically to FIG. 2, a publishing print
medium 200A is shown that includes a pre-treatment coating
composition (shown at 100A of FIG. 1) that is applied to a media
substrate 210 and dried to form pre-treatment matrix layers 100B,
which is shown in this example as a layer on both sides of the
media substrate where the aqueous liquid vehicle has been
evaporated or dried therefrom. It is understood that not 100 wt %
of water and/or evaporable solvent is typically removed during
drying, as coating layers applied to media tend to retain some
moisture, but for purposes of the present disclosure, the
pre-treatment matrix layer is considered to be a "dried" coating in
a manner suitable for receiving an ink composition when printed
thereon.
[0036] The media substrate 210 that can be coated with the
pre-treatment coating composition and resulting pre-treatment
matrix layer 100B can be any substrate that is suitable for
receiving the pre-treatment coating composition and which is
suitable for use with publishing. The pre-treatment coating
composition can include a weight ratio of aqueous liquid vehicle
from 1:3 to 10:1, from 1:2 to 9:1, or from 1:1 to 9:1, for example.
The aqueous liquid vehicle may be water or may include water and
other volatile liquids that evaporate from the media substrate
after applying as a coating thereon, e.g., mostly such as less than
10 wt % or less than 7 wt % or less than 5 wt % of the weight of
the pre-treatment coating matrix, which is applied as part of the
pre-treatment matrix layer on the media substrate after drying.
Methods that can be used to apply the coating compositions
generally include flexo coating, roll coating, slot-die coating,
rod coating such as Mayer rod coating, blade coating, gravure
coating, knife-over-roll coating, cascade coating, curtain coating,
and the like. Generally, the pre-treatment coating composition can
be applied to leave a pre-treatment matrix layer with a basis
weight of 0.1 gsm to 10 gsm. In one example, the basis weight can
be from 0.3 gsm to 5 gsm, and in another aspect, from 0.3 gsm to 4
gsm. The printed image can be applied, for example, at from 0.1 gsm
to 5 gsm or from 0.1 gsm to 3 gsm, for example.
[0037] The publishing print medium 200A can be further modified
with a printed image 60 by applying an ink composition on one or
both sides, for example, and the ink composition can interact with
the pre-treatment matrix layer, and the image can be applied with
good durability, saturation, dot gain, image gloss, and/or the
like. In one specific example, the media substrate 210, such as an
offset coated media substrate, may be coated with the pre-treatment
coating composition, which is dried to essentially remove
evaporable liquid vehicle (usually including evaporable solvent,
water, or both) to leave the pre-treatment matrix layer 100B. The
image may then be printed thereon using ink printing technologies,
such as digital printing/inkjet printing, and dried. Thus, for
definitional purposes, the evaporable aqueous liquid vehicle (or
some cases water) is not part of the matrix, as it is removed (or
mostly removed within tolerances for printing on the "dried"
pre-treatment matrix layer) from the pre-treatment coating
composition after application to the media substrate.
[0038] In addition to offset media, the pre-treatment coating
compositions and matrices of the present disclosure can be suitable
for use on many types of other substrates of print media, including
but not limited to, paper media, nonporous media, swellable media,
microporous media, photobase media, coated media, uncoated media,
and other types of media including plastics, vinyl media, fabrics,
woven substrate, etc. In certain examples, the substrate can be
swellable media or microporous media. As mentioned, offset media
can likewise be used.
[0039] Returning again to FIG. 2, the printed image 260 can be
referred to as printed ink, printed indicia, printed matter, or the
like. In this example, the printed image can be applied to portions
of the pre-treatment matrix layers 100B, which may be the case
where some areas are imaged and other areas remain unprinted with
ink or coated with a colorless ink, for example. In one example,
the printed image can be a pigment-based printed image, and in
other examples, the printed image can be a dye-based printed image.
These printed images can be applied by inkjet ink or other digital
printing technologies, or may be applied by analog printing
technologies, for example.
[0040] Inkjet inks generally can include a colorant dispersed or
dissolved in an ink vehicle. As used herein, "ink vehicle" refers
to the liquid fluid in which a colorant is placed to form an ink.
Many different types of ink vehicles are available, and a wide
variety of ink vehicles may be used with the systems and methods of
the present disclosure (for inks to print on the pre-treatment
matrix layer). Such ink vehicles may include a mixture of a variety
of different agents, including, surfactants, solvents, co-solvents,
anti-kogation agents, buffers, biocides, sequestering agents,
viscosity modifiers, surface-active agents, water, etc. Though not
part of the ink vehicle per se, in addition to the colorants, the
ink vehicle can carry solid additives such as polymers, latexes, UV
curable materials, plasticizers, etc.
[0041] Generally the colorant discussed herein can include a
pigment and/or dye. As used herein, "dye" refers to compounds or
molecules that impart color to an ink vehicle. As such, dye
includes molecules and compounds that absorb electromagnetic
radiation or certain wavelengths thereof. For example, dyes include
those that fluoresce and those that absorb certain wavelengths of
visible light. Generally, dyes are water soluble. Furthermore, as
used herein, "pigment" generally includes pigment colorants,
magnetic particles, aluminas, silicas, and/or other ceramics,
organo-metallics or other opaque particles. In one example, the
colorant can be a pigment.
[0042] Typical ink vehicle formulations can include water, and can
further include co-solvents present in total at from 0.1 wt % to 40
wt %, depending on the jetting architecture, though amounts outside
of this range can also be used. Further, additional non-ionic,
cationic, and/or anionic surfactants can be present, ranging from
0.01 wt % to 10 wt %. In addition to the colorant, the balance of
the formulation can be purified water with other small amounts of
other ingredients. In some examples, the inkjet ink may include
latex for added durability.
[0043] Consistent with the formulation of this disclosure, various
other additives may be employed to enhance the properties of the
ink composition for specific applications. Examples of these
additives are those added to inhibit the growth of harmful
microorganisms. These additives may be biocides, fungicides, and
other microbial agents, which are routinely used in ink
formulations. Examples of suitable microbial agents include, but
are not limited to, NUOSEPT.RTM. (Nudex, Inc.), UCARCIDE.TM. (Union
carbide Corp.), VANCIDE.RTM. (R.T. Vanderbilt Co.), PROXEL.RTM.
(ICI America), and combinations thereof.
[0044] Sequestering agents, such as EDTA (ethylene diamine tetra
acetic acid), may be included to eliminate the deleterious effects
of heavy metal impurities, and buffer solutions may be used to
control the pH of the ink. From 0 wt % to 2 wt %, for example, can
be used. Viscosity modifiers and buffers may also be present, as
well as other additives known to those skilled in the art to modify
properties of the ink as desired. Such additives can be present at
from 0 wt % to 20 wt %.
[0045] In another example, as shown in FIG. 3 by way of example, a
method 300 of preparing a publishing print medium includes coating
310 a first side of media substrate with a first pre-treatment
coating composition and a second side of media substrate with a
second pre-treatment coating composition, the first and second
pre-treatment coating compositions including an evaporable liquid
vehicle and a pre-treatment coating matrix carried by the
evaporable liquid vehicle. The pre-treatment coating matrix can
include from 30 wt % to 70 wt % multivalent organic salt, from 5 wt
% to 30 wt % dispersed polymeric binder having a weight average
molecular weight from 30,000 Mw to 100,000 Mw, from 0.5 wt % to 8
wt % of a high molecular weight polyvinyl alcohol binder, and from
10 wt % to 30 wt % of a low molecular weight polyvinyl alcohol
binder. The low molecular weight polyvinyl alcohol binder and the
high molecular weight polyvinyl alcohol binder can be present in
the pre-treatment coating matrix at a 3:1 to 15:1 weight ratio
(weight percentages based on dry weight of the pre-treatment
coating matrix). The method can further include drying 320 the
first pre-treatment coating composition to remove evaporable liquid
vehicle therefrom to form a first pre-treatment matrix layer, and
drying 330 the second pre-treatment coating composition to remove
evaporable liquid vehicle therefrom to form a second pre-treatment
matrix layer. The media substrate in this example can have a basis
weight from 50 gsm to 350 gsm, from 60 gsm to 300 gsm, or from 60
gsm to 250 gsm, for example.
[0046] It is to be understood that this disclosure is not limited
to the particular process steps and materials disclosed herein
because such process steps and materials may vary somewhat. It is
also to be understood that the terminology used herein is used for
the purpose of describing particular examples only. The terms are
not intended to be limiting because the scope of the present
disclosure is intended to be limited only by the appended claims
and equivalents thereof.
[0047] It is be noted that, as used in this specification and the
appended claims, the singular forms "a," "an," and "the" include
plural referents unless the context clearly dictates otherwise.
[0048] The term "acid value" or "acid number" refers to the mass of
potassium hydroxide (KOH) in milligrams that can be used to
neutralize one gram of substance (mg KOH/g), such as the
polyurethane binders disclosed herein. This value can be
determined, in one example, by dissolving or dispersing a known
quantity of a material in organic solvent and then titrating with a
solution of potassium hydroxide (KOH) of known concentration for
measurement.
[0049] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0050] Concentrations, amounts, and other numerical data may be
expressed or presented herein in a range format. It is to be
understood that such a range format is used merely for convenience
and brevity and thus should be interpreted flexibly to include not
only the numerical values explicitly recited as the limits of the
range, but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. As an illustration, a
numerical range of "about 1 to about 5" should be interpreted to
include not only the explicitly recited values of about 1 to about
5, but also include individual values and sub-ranges within the
indicated range. Thus, included in this numerical range are
individual values such as 2, 3, and 4 and sub-ranges such as from
1-3, from 2-4, and from 3-5, etc. Additionally, a numerical range
with a lower end of "0" can include a sub-range using "0.1" as the
lower end point.
EXAMPLES
[0051] The following examples illustrate the pre-treatment coating
compositions and matrices, and data associated therewith. However,
it is to be understood that the following are only exemplary or
illustrative of the application of the principles of the present
compositions print media, and methods. Numerous modifications and
alternative pre-treatment coating compositions or matrices may be
devised without departing from the spirit and scope of the present
compositions, media sheets, and methods. The appended claims are
intended to cover such modifications and arrangements. Thus, while
the above has been described with some particularity, the following
provides further example details.
Example 1
Selection of Fixative Salts and Dispersed Polymeric Binder for
Pre-Treatment Coating Compositions
[0052] The present evaluation was conducted to determine if there
were certain fixative multivalent salts and/or dispersed polymeric
binders (or combinations thereof) that provided better gloss than
others with respect to the gloss commonly present on publishing
print media. If the gloss of the pre-treatment coating composition
provides a noticeably different gloss at coated locations compared
to printed locations or uncoated locations, then the printed
publishing media tends to be not as appealing to end users or
consumers of the printed media. To conduct this evaluation, several
different publishing pre-treatment coating compositions, or
primers, were prepared. Notably, four different Dispersed Polymeric
Binders and four different Fixative Salts were prepared using water
as a solvent carrier leaving 25 wt % solids content, totaling 16
different pre-treatment coating compositions as set forth in Table
1 below:
TABLE-US-00001 TABLE 1 Pre-treatment Coating Compositions Dry Parts
by Ingredient Category Weight (wt %) .sup.1 Latex Polymer Dispersed
Polymeric Binder 22.06 .sup.2 Salt Multivalent Metal Salt 55.15
Poval .TM. 13-88 High Mw PVA (110,000 Mw) in 22.06 in Solution
solution with Latex Stabilizer Tego .RTM. Wet 510 Surfactant 0.74
Water Solvent Carrier -- .sup.1 One of four Dispersed Polymeric
Binders selected, See Table 2 for specific binder. .sup.2 One of
four Multivalent Metal Salts selected, See Table 2 for specific
salt.
[0053] A total of 16 pre-treatment coating compositions that were
prepared were hand coated at a 1.5 gsm to 2 gsm dry coating weight
basis to Metsaboard Kemi Prime WKL offset coated paper (185 gsm).
The coated publishing print media substrates were then dried using
a heat gun and printed with colored images using an HP CM8060 Color
MFP Edgeline Technology printer with HP A50 inks, which included a
total of seven colored inks (CMYKRGB) and unprinted areas remaining
white. The unprinted pre-treatment matrix layers and the printed
areas on the pre-treatment matrix layers were evaluated for gloss
at 75 degrees (no units) using a BYK Gardner 75.degree.
Micro-TRI-Glossmeter. The printed areas were evaluated for gloss by
averaging all of the printed colors and the unprinted white areas
using the following Gloss Scoring metrics: 1=75-90 Gloss; 2=65-75
Gloss; 3=55-65 Gloss; and 4=40-55 Gloss. The data collected is
provided in Table 2, as follows:
TABLE-US-00002 TABLE 2 Gloss of Unprinted and Printed Pre-treatment
Matrix Layers Dispersed Multivalent Metal Salt ID Latex Unprinted
Calcium Calcium Calcium Calcium Polymer ID or Printed Chloride
Acetate Propionate Nitrate Polyurethane Unprinted 2 1 1 4
Polyurethane Printed 3 2 2 4 Vinyl Acetate Unprinted 2 2 2 2 Vinyl
Acetate Printed 3 2 3 3 Acrylic Unprinted 1 1 1 1 Acrylic Printed 3
1 2 3 Sulfonated Unprinted 1 1 1 2 Styrene Butadiene Sulfonated
Printed 3 1 2 3 Styrene Butadiene Polyurethane used is available
under the trade name PrintRite DP388 from Lubrizol (USA). Vinyl
Acetate used is available under the trade name Neocar .RTM. Latex
2300 from Arkema (France). Acrylic available used is under the
trade name Raycat .RTM. 78 from Specialty Polymers (USA).
Sulfonated Styrene Butadiene used is available under the trade name
Novajet .RTM. 3800 from Omnova (Canada).
[0054] As can be seen in Table 2, the gloss for both the unprinted
sheet portions and the printed portions was better and more uniform
with the multivalent organic salts, namely in this example, calcium
acetate and the calcium propionate, compared to the multivalent
inorganic salts, namely calcium chloride and calcium nitrate.
Example 2
Preparation of Pre-Treatment Coating Compositions for
Comparison
[0055] Three different pre-treatment coating compositions were
prepared for comparison purposes, namely an example pre-treatment
coating composition (P-1) prepared in accordance with the present
disclosure, a first comparative pre-treatment coating composition
that is similar to a commercially available pre-treatment coating
composition (P-Comp), and a second comparative pre-treatment
composition (P-Comp2) that includes a polyamide wax. The coating
compositions were prepared with water as the solvent carrier with a
total of about 25 wt % solids content. The formulations prepared
are shown in Table 3, as follows:
TABLE-US-00003 TABLE 3 Pre-treatment Coating Compositions for
Comparison Coating ID P-1 P-Comp P-Comp2 Ingredient Category (dry
wt %) (dry wt %) (dry wt %) PrintRite .RTM. DP-388 Polyurethane 23
-- 15.5 Latex Polymer Raycat .RTM. 78 Acrylic Latex -- 40.9 --
Polymer Neocar .RTM. 2300 Vinyl Acetate -- 6 -- Latex Polymer Poval
.TM. 4-88 Low Mw PVA 15.4 8 10.4 (31,000 Mw) Poval .TM. 13-88 High
Mw PVA 1.9 4 15.5 (110,000 Mw) Orgasol .RTM. 2002 Polyamide-12 --
-- 15.5 EXD Nat 1 Wax Wax Ultralube .RTM. D806 Polyethylene -- 6 --
Wax Gasil .RTM. 23F Silica Matting -- 3 -- Agent Tego .RTM. Wet 510
Surfactant -- 0.3 0.78 Disperbyk .RTM. 190 Surfactant 0.77 -- --
BYK .RTM. 018 Defoamer 1.15 2.7 3.2 Calcium Chloride Multivalent --
29 38.8 Inorganic Salt Calcium Acetate Multivalent 57.6 -- --
Organic Salt Acticide .RTM. M20 Biocide 0.05 0.04 0.05 Acticide
.RTM. B20 Biocide 0.14 0.11 0.16 PrintRite .RTM. DP-388 is
available from available from Lubrizol (USA). Raycat .RTM. 78 is
available from Specialty Polymers (USA). Neocar .RTM. 2300 is
available from Arkema (France). Poval .TM. 4-88 and 13-88 are both
available from Kuraray (USA). Orgasol .RTM. 2002 is available from
Arkema (France). Ultralube .RTM. D806 is available from Keim
Additec (Germany). Gasil .RTM. 23F is available from PQ Corporation
(USA). Tego .RTM. Wet 510 is available from Evonik Industries AG
(Germany). Disperbyk .RTM. 190 and BYK .RTM. 018 are available from
BYK-Chemie GmbH (Germany). Acticide .RTM. M20 and B20 are available
from Thor (USA).
Example 3
Gloss, Coefficient of Friction, and Color Gamut Evaluation
[0056] Two of the pre-treatment coating compositions from Table 3
(P-1 and P-Comp) were prepared and hand coated on matte offset
coated paper (rolled 45# Verso New Era Matte) at a speed of 300
feet per minute (fpm), as well as on glossy offset coated paper
(rolled 60# Verso Sterling Ultra Gloss) at a speed of 200 fpm. The
application of the pre-treatment composition (or priming) occurred
on both sides of the paper substrates from an anilox roll,
transferring the primer first onto a rubber roller and then onto
the paper. The applied coat weight ranged from about 0.33-0.36 gsm
dry per side. The primer was applied in-line with duplex printing
using a T240 HP Pagewide Web Press equipped with HP A50 inks.
[0057] A gloss comparison is shown in FIG. 4, which graphically
shows the relative gloss levels for unprinted and printed portions
using both P-1 and P-Comp pre-treatment coating compositions on
both matte and glossy offset coated paper substrates. On the 60#
Sterling Ultra Gloss paper, the pre-treatment matrix layer coated
using the P-1 pre-treatment coating composition maintained nearly
the same level of gloss as the uncoated or unprimed media
substrate, whereas the pre-treatment matrix layer formed from the
P-Comp pretreatment coating composition lost a significant amount
of gloss, leading to a noticeably distracting gloss difference. The
same was true for the printed images, though the difference was
less significant than in the unprinted areas. Regarding the 45#
matte offset paper substrate, the gloss values in both instances
were kept about the same, though P-1 exhibited just a small
increase in gloss at both the unprinted and printed areas. Thus,
though the pre-treatment coating compositions (e.g., the
pre-treatment matrix layers formed therefrom) can provide
acceptable gloss on glossy paper substrates, as shown by the matte
paper substrate example, they can likewise retain the level of
gloss of the underlying paper substrate, thus also providing a good
pre-treatment coating option for matte media substrates.
[0058] An analysis of coefficient of friction (COF) for paper
substrates coated with the P-1 and P-Comp pre-treatment coating
compositions was carried out to evaluate the amount of paper slip
provided by both resulting pre-treatment matrix layers. The data
collected is shown in FIG. 5. COF is an attribute considered for
printing paper, particularly in high-speed finishing operations,
such as during web turns, folding, cutting, stacking etc. COF, and
particularly kinetic COF should be high enough so that the
publishing print media does not slip during printing and/for
finishing. FIG. 5 shows the results of the COF evaluation for
various print media which are uncoated (by the pre-treatment
coating compositions, but are still offset coated), inkjet printed,
coated with the P-1 pre-treatment coating composition, and coated
with the P-Comp pre-treatment coating composition. In the case of
both the glossy and matte paper substrates, the P-1 pre-treatment
coating composition (and resultant pre-treatment matrix layer)
showed higher kinetic COF than the paper coated with the P-Comp
coating composition.
[0059] Color gamut and black optical density (K-OD) of inkjet
images printed using HP A50 inks (CMYKRBG) was compared on both
types of paper media substrates (matte and glossy) as well as with
both pre-treatment coating compositions (P-1 and P-Comp). The data
collected is provided in Table 4, as follows:
TABLE-US-00004 TABLE 4 Color Gamut and K-OD Pre-treatment Coating
Composition ID 45# New Era 60# Sterling Ultra (Color Gamut or K-OD)
Matte (300 fpm) Gloss (200 fpm) P-1 (Color Gamut) 326,000 360,000
P-Comp (Color Gamut) 290,000 328,000 P-1 (K-OD) 1.45 1.56 P-Comp
(K-OD) 1.4 1.47
[0060] In this evaluation, color gamut was measured using a
GretagMacBeth Spectrolino Spectroscan Spectrophotometer based on
816 colors. Black optical density (K-OD) was measured using an
X-Rite Spectrodensitometer. As can be seen in Table 4, the color
gamut and K-OD that were measured on the various samples and the
color gamut for the pre-treatment matrix layer prepared with the
P-1 pre-treatment coating composition was about 10% greater, and
the K-OD was about 3-6% greater. Thus, better color gamut and/or
K-OD can be achieved, or the printer could use less ink with no
color penalty using the P-1 pre-treatment coating composition paper
coated with the P-1 pre-treatment matrix layer.
Example 4
Effect of Low molecular weight PVA to High molecular weight PVA on
Dot Gain
[0061] Multiple pre-treatment coating compositions similar to the
P-1 pre-treatment coating composition set forth in Table 3 were
prepared, except that the ratio of low molecular weight to high
molecular weight polyvinyl alcohol binder was varied. Dot gain was
evaluated and the data provided in FIG. 6. The cumulative dot area
and number of black dots (black ink drops on paper) were measured
in an area with a fixed, low ink density, in a region of interest
(ROI) under a Keyence VHX-6000 digital microscope using a
150.times.lens. The ROI was fixed at 4124972 .mu.m.sup.2 in all
cases, and all the large ink dots in this ROI, typically ca. 160,
were counted and sized, excluding small satellite drops. In this
instance, the T400S Packaging WebPress was operated at a variety of
speeds ranging from 400 fpm to 1000 fpm, and the data collected is
shown in this FIG. The trend line shows that dot gain can be
increased with a greater weight ratio of low molecular weight PVA
relative to high molecular weight PVA. At about 3:1 (shown as the
vertical dotted line) and greater, e.g., 3:1 to 15:1, 3:1 to 8:1
(as shown), etc., enough improvement can be shown to provide an
appreciably enhancement in dot gain relative to lower ratios.
Example 5
Dot Gain and Saturation Evaluation
[0062] As both calcium acetate and calcium propionate both
outperformed calcium chloride in terms of gloss, as shown in Table
2, the formulation including calcium acetate shown at P-1 of Table
3 was further studied relative to P-Comp and P-Comp2 as formulated
in accordance with Table 3. Differences between P-1 and the two
comparative pre-treatment compositions included (i) the use of
calcium chloride in the comparatives (instead of calcium acetate or
calcium propionate), (ii) different weight ratios of the low and
high molecular weight polyvinyl alcohols (e.g., P-1 had a low Mw
PVA to high Mw PVA weight ratio of about 8:1, whereas P-Comp had a
low Mw PVA to high Mw PVA weight ratio of about 2:1 and P-Comp2 had
a low Mw PVA to high Mw PVA weight ratio of about 2:3), and (iii)
surfactant choice was different for the comparative examples (e.g.,
Disperbyk.RTM. 190 was used in P-1 pre-treatment coating
composition and Tego.RTM. Wet 510 was used in the P-Comp and
P-Comp2 comparative examples). It has been found that
Disperbyk.RTM. 190 tends to provide better results than Tego.RTM.
Wet 510, so P-1 was prepared by Disperbyk.RTM. 190. P-Comp2, on the
other hand, included a polyamide wax additive for further
comparison to compare against no wax (of P-1) and polyethylene wax
(of P-Comp). Though wax can be used in pre-treatment coating
compositions of the present disclosure as well, with removal of wax
(e.g., polyethylene, polyamide, etc.) along with the presence of
the dispersed polymer or latex, the ratio of polyvinyl alcohol (low
to high Mw), and the multivalent organic salt can provide good dot
gain and durability. Thus, wax may or may not be present to provide
good durability, for example, with the formulations of the present
disclosure.
[0063] Dot gain or drop area refers to the area of ink that is
colored upon application of an ink composition to a media
substrate. If an ink tends to spread, then there can be more ink
coverage, leading to richer colors or the ability to apply less ink
to get acceptable ink coverage. Dot gain can be evaluated using
imagery from a digital microscope, such as a Keyence VHX-6000
digital microscope using a 150.times.lens. Measurements can be
based on the cumulative dot area and number of dots (ink drops on
paper) within that area, e.g., dots counted and/or measured in an
area with a fixed, low ink density, in a region of interest (ROI).
However, it was also found that ink saturation can be used as a
proxy for determining higher dot gain, as higher dot gain leads to
less white space between printed droplets, thus providing higher
saturation.
[0064] Regarding dot gain using a digital microscope, three sets of
images were generated to compare the printing performance on
pre-treatment matrix layers generated using pre-treatment coating
compositions P-1, P-Comp, and P-Comp2 as set forth in Table 3. The
image sets were printed on 45# Verso Liberty Gloss Paper with a
T240 HP Pagewide Web Press equipped with HP A50 inks and a printer
speed of 250 fpm. The cyan ink was used to evaluate dot gain using
a microscope. The first set of images was printed at 4% ink
saturation (causing the dots to be relatively far apart), and it
was determined that average area of the individual dots was about
30% larger in areas printed on the P-1 coated samples compared to
the P-Comp or the P-Comp2 coated samples.
[0065] The second set of images was printed at 52% ink saturation
(causing the dots to be closer together with some dot overlap), and
it was observed that average area of the individual dots was also
larger in areas printed on the P-1 coated samples compared to the
P-Comp or the P-Comp2 coated samples. Likewise, the third set of
images was also printed, but at 100% ink saturation (causing the
dots to be significantly overlapping with little white space
between dots), and it was also observed that average area of the
individual dots was also larger in areas printed on the P-1 coated
samples compared to the P-Comp or the P-Comp2 coated samples.
[0066] In part because of the dot overlap at 52% ink saturation and
the significant dot overlap at 100% ink saturation, rather than
calculating dot size for comparison, optical density (OD) can be
measured as a proxy for dot gain, as shown by Example in FIG. 7.
There, the higher OD is along a saturation curve from 0% to 100%.
At any given saturation percentage along the curve, by using the
P-1 pre-treatment coating composition data of FIG. 7 (e.g., cyan
ink printed on the pre-treatment matrix layer prepared from
composition P-1) as the baseline OD for a given saturation % level,
the inefficiency of the other two comparative compositions can be
calculated and expressed as a "mean cyan ink inefficiency" relative
to the P-1 data, such as by using the Formula I, as follows:
Mean .times. .times. Cyan .times. .times. Ink .times. .times.
Inefficiency = ( P .times. .times. 1 .times. .times. OD ) - (
Comparative .times. .times. Sample .times. .times. OD ) (
Comparative .times. .times. Sample .times. .times. OD ) * ( 100 )
Formula .times. .times. I ##EQU00001##
[0067] Using Formula I, for cyan samples printed using
pre-treatment coating composition P1, the values at any saturation
percentage would be 0, since it acts as the baseline. Calculating
the average mean cyan ink inefficiency within the mid-tone range
identified in FIG. 7, the P-Comp pre-treatment coating composition
can be calculated to have a mean cyan ink inefficiency of about 21
and the P-Comp2 mean cyan ink inefficiency can be calculated to be
about 18.6. The average mean cyan ink inefficiency was determined
using nine points in the cyan mid-tone range for the various
sample. In this analysis, the higher the number, the more different
(worse) the performance compared to the use of the P-1
pre-treatment coating composition. This data indicates that that
P-Comp and P-Comp2 comparatives do not provide as good of dot gain
as the P-1 compositions, using saturation relative to optical
density (OD) as a proxy for dot gain.
[0068] It was also determined that wax can provide some
enhancements with respect durability in some instances. That
stated, the P-1 pre-treatment coating composition tended to perform
the best compared to these comparative examples, even without the
use of wax.
* * * * *