U.S. patent application number 16/984019 was filed with the patent office on 2020-11-19 for thermosensitive recording material.
The applicant listed for this patent is OMNOVA Solutions Inc.. Invention is credited to James L. VAUGHN.
Application Number | 20200361227 16/984019 |
Document ID | / |
Family ID | 1000004993638 |
Filed Date | 2020-11-19 |
United States Patent
Application |
20200361227 |
Kind Code |
A1 |
VAUGHN; James L. |
November 19, 2020 |
THERMOSENSITIVE RECORDING MATERIAL
Abstract
A thermosensitive recording material comprising a support; an
insulating layer that includes a porous polymeric pigment; and an
image-forming layer.
Inventors: |
VAUGHN; James L.; (Hudson,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OMNOVA Solutions Inc. |
Beachwood |
OH |
US |
|
|
Family ID: |
1000004993638 |
Appl. No.: |
16/984019 |
Filed: |
August 3, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15960148 |
Apr 23, 2018 |
10730334 |
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16984019 |
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62488295 |
Apr 21, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 2207/53 20130101;
C08F 2800/20 20130101; B41M 5/5254 20130101; C08F 220/18 20130101;
Y10T 428/2998 20150115; D21H 19/22 20130101; B41M 5/0052 20130101;
C08L 25/14 20130101 |
International
Class: |
B41M 5/52 20060101
B41M005/52; B41M 5/00 20060101 B41M005/00; C08F 220/18 20060101
C08F220/18; C08L 25/14 20060101 C08L025/14 |
Claims
1. A thermosensitive recording material comprising: (i) a first
layer, where said first layer is adapted to provide imaging when
exposed to heat; and (ii) a second layer including porous hollow
particles and a binder, where the porous hollow particles have a
void volume fraction of at least 40%.
2. The thermosensitive recording material of claim 1, where the
porous hollow particles have a void volume fraction of from about
45% to about 83%.
3. The thermosensitive recording material of claim 2, where the
porous hollow particles have a void volume fraction of from about
55% to about 77%
4. The thermosensitive recording material of claim 2, where the
porous hollow particles have a pore surface area of at least
1%.
5. The thermosensitive recording material of claim 4, where the
porous hollow particles have a pore surface area of at least
3%.
6. The thermosensitive recording material of claim 5, where porous
hollow particles have a pore surface area of at least 5%.
7. The thermosensitive recording material of claim 4, where the
porous hollow particles have a pore surface area of from about 3%
to about 45%.
8. The thermosensitive recording material of claim 1, where the
second layer includes from about 20 to about 90 percent by weight
porous hollow particles, on a dry weight basis, relative to the
weight of the layer.
9. The thermosensitive recording material of claim 8, where the
second layer includes from about 5 to about 50 percent by weight
binder, on a dry weight basis, relative to the weight of the
layer.
10. The thermosensitive recording material of claim 1, where the
binder is selected from the group consisting of synthetic latexes,
starch, soy, casein, albumin, polyvinyl alcohol, carboxymethyl
cellulose, hydroxymethyl cellulose, polyacrylate salt, and mixtures
thereof.
11. The thermosensitive recording material of claim 1, where the
second layer further includes a pigment selected from the group
consisting of kaolin, talc, calcined clay, structured clay, ground
calcium carbonate, precipitated calcium carbonate, titanium
dioxide, aluminum trihydrate, satin white, silica, zinc oxide,
barium sulfate, and mixtures thereof.
12. The thermosensitive recording material of claim 1, where the
porous hollow particles are prepared by treating a core-shell
polymeric particle under conditions sufficient to form the porous
hollow particles, where the core-shell polymeric particles have
acrylate units in the shell and acrylate units in the core.
13. The thermosensitive recording material of claim 12, where the
core includes at least 10 wt % acrylate units.
14. The thermosensitive recording material of claim 12, where the
shell includes at least 5 wt % acrylate units.
15. The thermosensitive recording material of claim 12, where the
acrylate units derive from monomer selected from the group
consisting of methyl acrylate, ethyl acrylate, butyl acrylate,
hexyl acrylate, 2-ethyl hexyl acrylate, octyl acrylate, iso-octyl
acrylate, n-decyl acrylate, iso-decyl acrylate, tertbutyl acrylate,
and 2-hydroxyethyl acrylate.
16. The thermosensitive recording material of claim 15, where the
acrylate units derive from monomer selected from the group
consisting of ethyl acrylate, butyl acrylate, and hexa acrylate.
Description
[0001] This application is a continuation application of U.S.
Non-Provisional application Ser. No. 15/960,148 filed on Apr. 23,
2018, which claims the benefit of U.S. Provisional Application Ser.
No. 62/488,295 filed on Apr. 21, 2017, which are incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] Embodiments of the invention are directed toward
thermosensitive recording materials, also known as thermal papers,
that include a hollow polymeric pigment with a porous shell.
BACKGROUND OF THE INVENTION
[0003] Thermosensitive recording materials generally include an
image forming layer situated on a substrate. The image forming
layer includes a thermoresponsive dye, which upon heating changes
color to produce a visible image or marking on the thermosensitive
recording material. An image or a marking may be formed on a
thermosensitive recording material using a printer with a thermal
head, a thermal pen, laser light, or in some instances, friction
across the material will generate enough heat to produce a mark or
an image.
[0004] Some thermosensitive recording materials include an
insulating layer, which may employ voided particles to provide
insulating properties to the thermosensitive recording material.
Insulating layers may provide a thermosensitive recording paper
with improved print density and clearer printed images. Voided
particles typically have a single void entirely encapsulated by a
polymer shell.
[0005] Multi-voided particles have also been employed in the art
for use in insulating layers. U.S. Pat. Pub. No. 2002/0123425
discloses a thermosensitive recording material with a first layer
that includes multi-voided particles. Suitable multi-voided
particles are described as being prepared from a core-shell
emulsion polymerization process in which the core polymer contains
a copolymerized ester functional group-monomer, such as methyl
acrylate, methyl methacrylate, and vinyl acetate, which may be
hydrolyzed to form multiple voids within the particle when
dried.
[0006] Presently there is a need in the art to prepare
thermosensitive recording materials with improved insulating
properties.
SUMMARY OF THE INVENTION
[0007] One or more embodiments provides a thermosensitive recording
material comprising: a support; an insulating layer that includes a
porous polymeric pigment; and an image-forming layer.
[0008] Another embodiment provides a thermosensitive recording
material comprising of a support; an insulating layer; an
absorption layer that includes a porous polymeric pigment; and an
image-forming layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The FIGURE provides a partial sectional view of a
thermosensitive recording of one or more embodiments of the
invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0010] Embodiments of the invention are based, at least in part, on
the discovery that highly porous hollow polymeric pigments may
advantageously be used in thermosensitive recording materials.
While the prior art contemplates the use of porous hollow polymeric
pigments in thermosensitive recording materials, the porous hollow
polymeric pigments employed in the present invention have higher
porosity than those porous hollow polymeric pigments previously
used in thermosensitive recording materials. By employing porous
hollow polymeric pigments with higher porosity, unexpected results,
relative to their use in thermosensitive recording materials, are
contemplated. According to embodiments of the present invention,
the highly porous hollow polymeric pigments may be used in an
insulating layer of a thermosensitive recording material. In these
or other embodiments, the highly porous hollow polymeric pigments
may be used in an absorption layer of a thermosensitive recording
material. In other embodiments, the highly porous hollow polymeric
pigments may be used in a hybrid layer that provides both
insulation and absorption in a thermosensitive recording
material.
Thermosensitive Recording Material
[0011] With reference to the FIGURE, thermosensitive recording
material 10 is shown and includes a substrate 12 situated on an
insulating layer 14. Between substrate 12 and insulating layer 14
may optionally be a primer layer or coat (not shown). Situated on
insulating layer 14 is an image-forming layer 16. A primer layer or
coat (not shown) may optionally be disposed between insulating
layer 14 and image-forming layer 16. Other layers, such as coating
layers or multiple successive repeating insulating layers, optional
absorption layers, optional primer layers, and multiple
image-forming layers may be included. Embodiments may also include
dual-sided thermosensitive recording materials, where the
thermosensitive recording material has at least one image-forming
layer on each side of the substrate.
Porous Polymeric Pigment
[0012] In one or more embodiments, porous hollow polymeric
pigments, which may be referred to as porous hollow particles,
suitable for use in a thermosensitive recording material according
to the present invention include particles with multiple pores that
extend from the surface of the particle to the hollow interior of
the particle. In one or more embodiments, the porous hollow
particles may be prepared from a core-shell polymeric particle. As
those skilled in the art will appreciate, a core-shell polymeric
particle includes a polymeric core surrounded by a shell that
includes a different polymer composition than the core. The
core-shell particle may optionally include one or more intermediate
shells on layers between the core and the shell. For example, in
one or more embodiments, the core-shell polymeric particle may
include a shell formed from a polymer with units derived from
styrene and acrylate monomers and a core formed from a polymer with
units derived from hydrolyzable monomer such as acrylate monomers.
In these or other embodiments, a porous hollow particle may be
prepared by subjecting the core-shell polymeric particle to
conditions that will hydrolyze the polymer or polymeric units
deriving from the polymerization of acrylate monomer to thereby
provide the resulting hollow, porous structure.
[0013] The core-shell polymeric particle may be prepared by a
multistage polymerization. For example, the core-shell polymeric
particle may be prepared by an emulsion polymerization process
using discrete charges of one or more monomers or using a
continuously-varied charge of two or more monomers. The core may be
prepared first and the shell or shells are subsequently
polymerized. An example of porous polymeric pigments produced with
the inclusion of acrylate monomers in the shell formation is
described in WO 2010/120344, which is incorporated herein by
reference in its entirety.
Core
[0014] In one or more embodiments, the core of the core-shell
polymer particle may comprise a homopolymer or copolymer that is
swellable upon neutralization or hydrolysis. In these or other
embodiments, at least one of the monomers polymerized to form the
core bears or results in a unit that upon contact with a base can
be hydrolyzed, neutralized, or a combination thereof. In one or
more embodiments, the core may optionally include crosslinking.
[0015] In one or more embodiments, the core may be characterized by
the quantity of neutralizable units, which can be described with
reference to the weight percent monomer feed giving rise to these
units. In one or more embodiments, the core is prepared by
including (i.e. polymerizing) at least 5 wt %, in other embodiments
at least 10 wt %, in other embodiments at least 25 wt %, in other
embodiments at least 40 wt %, and in other embodiments at least 50
wt %, monomers that result in a neutralizable unit relative to the
total weight of monomer used to polymerize the core. In these or
other embodiments, the core is prepared by including at most 100 wt
%, in other embodiments at most 99 wt %, in other embodiments at
most 95 wt %, and in other embodiments at most 90 wt %, and in
other embodiments at most 70 wt %, monomers that result in a
neutralizable unit relative to the total weight of monomer used to
polymerize the core. In one or more embodiments, the core is
prepared by including from about 5 wt % to about 100 wt %, in other
embodiments about 10 wt % to about 99 wt %, in other embodiments
about 25 wt % to about 95 wt %, in other embodiments about 40 wt %
to about 90 wt %, and in other embodiments about 50 wt % to about
70 wt %, monomers that result in a neutralizable unit relative to
the total weight of monomer used to polymerize the core.
[0016] In one or more embodiments, the core may be characterized by
the quantity of hydrolyzable units, which can be described with
reference to the weight percent monomer feed giving rise to these
units. In one or more embodiments, the core is prepared by
including at least 5 wt %, in other embodiments at least 10 wt %,
in other embodiments at least 25 wt %, in other embodiments at
least 40 wt %, and in other embodiments at least 50 wt %, monomers
that result in a hydrolyzable unit relative to the total weight of
monomer used to polymerize the core. In these or other embodiments,
the core is prepared by including at most 100 wt %, in other
embodiments at most 99 wt %, in other embodiments at most 95 wt %,
and in other embodiments at most 90 wt %, and in other embodiments
at most 70 wt %, monomers that result in a hydrolyzable unit
relative to the total weight of monomer used to polymerize the
core. In one or more embodiments, the core is prepared by including
from about 5 wt % to about 100 wt %, in other embodiments about 10
wt % to about 99 wt %, in other embodiments about 25 wt % to about
95 wt %, in other embodiments about 40 wt % to about 90 wt %, and
in other embodiments about 50 wt % to about 70 wt %, monomers that
result in a hydrolyzable unit relative to the total weight of
monomer used to polymerize the core.
[0017] Suitable monomers that can be used to give rise to a
polymeric unit that may be hydrolyzed include acrylate monomers
(which do not include methacrylates, e.g. methyl methacrylate).
Specific examples of acrylate monomers include methyl acrylate,
ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethyl hexyl
acrylate, octyl acrylate, iso-octyl acrylate, n-decyl acrylate,
iso-decyl acrylate, tertbutyl acrylate, 2-hydroxyethyl acrylate,
and acrylamide.
[0018] Suitable monomers that can be used to give rise to a
polymeric unit that may be neutralized include acid monomers.
Specific examples of acid monomers include acrylic acid,
methacrylic acid (i.e. methacrylates), (meth)acryloxypropionic
acid, itaconic acid, aconitic acid, maleic acid or anhydride,
fumaric acid, crotonic acid, monomethyl maleate, monomethyl
fumarate, and monomethyl itaconate.
[0019] Other suitable monomers that may make up the balance of the
core include acrylates of methacrylic acid. Exemplarily acrylates
of methacrylic acid include methyl methacrylate, butyl
methacrylate, hexyl methacrylate, isobutyl methacrylate, isopropyl
methacrylate and allyl methacrylate.
[0020] In one or more embodiments, the core of the core-shell
polymeric particle may include, but is not limited to, an acid core
and/or an ester core. Examples of core-shell polymeric particles
that include an acid core are described in U.S. Pat. No. 4,468,498
to Kowalski, which is incorporated herein by reference in its
entirety. Examples of core-shell polymeric particles that include
an ester core are described in U.S. Pat. Nos. 5,157,084 and
5,521,253 to Lee, and U.S. Patent Publication 2010/0317753, all of
which are incorporated herein by reference in their entirety.
Shell
[0021] In one or more embodiments, the shell of the core-shell
polymer particle may comprise a copolymer that includes a unit or
units that are hydrolyzable and a unit or units that are
non-hydrolyzable. As suggested above, the core-shell polymer
particle may be subjected to conditions that hydrolyze that
hydrolyzable unit to produce the pores of the porous polymeric
pigment. The non-hydrolyzable units remain to produce or form the
porous shell. As noted above, suitable hydrolyzable units include
those derived from acrylates.
[0022] In one or more embodiments, the shell may be characterized
by the quantity of hydrolyzable units, which can be described with
reference to the weight percent monomer feed giving rise to these
units. In one or more embodiments, the shell is prepared by using
at least 2 wt %, in other embodiments at least 5 wt %, and in other
embodiments at least 10 wt %, monomers that result in a
hydrolyzable unit relative to the total weight of monomer used to
polymerize the shell. In these or other embodiments, the shell is
prepared by using at most 35 wt %, in other embodiments at most 30
wt %, and in other embodiments at most 25 wt %, monomers that
result in a hydrolyzable unit relative to the total weight of
monomer used to polymerize the shell. In one or more embodiments,
the shell is prepared by using about 2 wt % to about 35 wt %, in
other embodiments about 5 wt % to about 30 wt %, and in other
embodiments about 10 wt % to about 25 wt %, monomers that result in
a hydrolyzable unit relative to the total weight of monomer used to
polymerize the shell.
[0023] Suitable monomers that can be used to give rise to a
polymeric unit that is non-hydrolyzable include styrene,
vinyltoluene, ethylene, vinyl acetate, vinyl chloride, vinylidene
chloride, acrylonitrile, methacrylamide, and esters of methacrylic
acid.
[0024] In one or more embodiments, acrylic acid monomer may be
included during the formation of the shell. In one or more
embodiments, the amount of acrylic acid may be less than 5 wt %, in
other embodiments less than 4 wt %, in other embodiments less than
3 wt % in other embodiments less than 2 wt %, and in other
embodiments less than 1 wt % relative to the total weight of
monomer used to polymerize the shell. In one or more embodiments,
the amount of acrylic acid may be from about 0.1 wt % to about 5 wt
%, in other embodiments from about 0.3 wt % to about 4 wt %, in
other embodiments from about 0.7 wt % to about 3 wt %, and in other
embodiments about 1 wt % to about 2 wt % relative to the total
weight of monomer used to polymerize the shell.
[0025] In one or more embodiments, the core-shell particle may
include one or more optional intermediate stage or layers. An
intermediate stage may be situated between the core and the shell
of the core-shell polymer particle. Suitable intermediate stage may
be prepared from a polymer blend that is compatible with the core
and/or the shell.
Hydrolyzation
[0026] As noted above, the porous polymeric particles employed in
the present invention may be prepared by subjecting the core-shell
polymeric particle to conditions that will hydrolyze the units
deriving from the polymerization of acrylate monomer to thereby
produce the hollow, porous structure. In these or other
embodiments, the hydrolyzation reaction may be performed by adding
a base to the core-shell polymeric particles. In one or more
embodiments, the base may be added to the emulsion polymerization
mixture after the preparation of the core-shell polymeric
particles. In other embodiments, core-shell polymeric particles
that are pre-prepared may be hydrolyzed in the presence of a base.
Suitable bases include ammonia, sodium hydroxide, potassium
hydroxide and/or amines.
[0027] The hydrolysis conditions, such as time, temperature, and
pressure, required to prepare a porous polymeric particle from a
core-shell polymeric particle may depend on the specific types and
amounts of hydrolyzable monomers used prepare the core-shell
polymeric particle as well as the specific temperature, pressure
used, and the amount and type of base employed. Accordingly,
specific hydrolyzable conditions cannot be definitively set forth
except to say that hydrolyzation may occur under hydrolyzable
conditions, and those skilled in the art can readily ascertain the
appropriate conditions in view of the teachings herein.
[0028] In one or more embodiments, the porous hollow particles may
be prepared at a temperature of at least 100.degree. C., in other
embodiments at least 140.degree. C., and in other embodiments at
least 155.degree. C. In these or other embodiments, the porous
hollow particles may be prepared at a temperature of at most
200.degree. C., in other embodiments at most 190.degree. C., and in
other embodiments at most 180.degree. C. In one or other
embodiments, the porous hollow particles may be prepared at a
temperature from about 100.degree. C. to about 200.degree. C., in
other embodiments from about 140.degree. C. to about 190.degree.
C., and in other embodiments at least from about 155.degree. C. to
about 180.degree. C.
[0029] In one or other embodiments, the hydrolysis reaction to
prepare the porous hollow particles may take at least 60 min, in
other embodiments at least 90 min, and in other embodiments at
least 120 min. In these or other embodiments, the hydrolysis
reaction to prepare the porous hollow particles of at most 1440
min, in other embodiments at most 720 min, and in other embodiments
at most 480 min. In one or other embodiments, the hydrolysis
reaction to prepare the porous hollow particle may take from about
60 min to about 1440 min, in other embodiments from about 90 min to
about 720 min, and in other embodiments at least from about 120 min
to about 480 min.
Porous Polymeric Pigment Properties
[0030] As noted above, the porous hollow particles may be a hollow
polymeric pigment with a porous outer shell. The porous hollow
particles may be characterized by a pore surface area. In one or
more embodiments, the pore surface area can be determined
analytically using SEM images in conjunction with the following
calculations. As the skilled person understands, reference can be
made to the difference between a total theoretical exterior surface
area (e.g., total theoretical exterior surface area=4 .pi. r.sup.2
for an assumed spherical particle) and an actual exterior surface
area. To determine pore surface area, some inferences from the data
are used. First, the only pore areas reliably illustrated and
measurable are located on the top surface of the hollow porous
structure of the organic polymeric particle, which is likely only
the middle third of the projected diameter that is seen in the
images. This is due to the fact that the pores that are further
toward the side of the organic polymeric particle are at an angle,
so that the projected cross-section of the pore is less than the
true cross-section of the pore. Second, the SEM shows a
straight-down projection of the sphere, so the "area" of the hollow
porous structure of the organic polymeric particle that is measured
is off by a factor of two. The weighted average of the largest 10
percent of the pores is used as the pore size.
[0031] To estimate the pore area as a fraction of a sphere surface,
it is estimated that the SEM images provide an image of only a
portion of the organic polymeric particle, termed a "cap." The cap
is created by cutting the sphere with a plane:
S=2.pi.rh
where S is the surface area of the cap; r is the radius of the
spherical organic polymeric particle; and h is the height of the
cap above the intersecting plane.
[0032] If c is defined as the fractional radius of the base of the
cap compared to the radius of the sphere, then:
S=2.pi.r.sup.2(1- {square root over ((1-c.sup.2))})
[0033] In one or more embodiments, the porous hollow particles may
have a pore surface area of at least 1%, in other embodiments at
least 3%, in other embodiments at least 5%, in other embodiments at
least 7%, and in other embodiments at least 10%. In these or other
embodiments, the porous hollow particles may have a pore surface
area of at most 50%, in other embodiments at most 45%, in other
embodiments at most 40%, in other embodiments at most 35%, and in
other embodiments at most 30%. In one or more embodiments, the
porous hollow particles may have a pore surface area from about 1%
to about 50%, in other embodiments from about 3% to about 45%, in
other embodiments from about 5% to about 40%, in other embodiments
from about 7% to about 35% and in other embodiments from about 10%
to about 30%.
[0034] In one or more embodiments, relative degree of porosity of
the porous hollow particles can be determined with reference to the
void volume fraction. The void volume fraction is the volume
fraction of the organic polymeric particle that is not occupied by
the polymer forming the organic polymeric particle. The void volume
fraction may be determined by centrifugation. The latex may be
placed in a centrifuge and spun. After sufficient centrifugation,
the supernatant is decanted and weighed. From the latex mass,
percent solids, and supernatant mass the void volume fraction
(f.sub.void) is determined using the following equations:
f.sub.void=((VT-S.sub.H.sub.2.sub.O)*(F.sub.R-V.sub.P))/((V.sub.T-S.sub.-
H.sub.2.sub.O)*F.sub.R)
where: Vp=Polymer volume (polymer mass/polymer density) where the
density of copolymers is calculated using literature values for the
density of the homopolymer of each monomer, and assuming that the
density of the copolymer is a linear function of the composition of
the copolymer. See Peter A. Lovell and Mohamed S. El-Aasser,
"Emulsion Polymerization and Emulsion Polymers"; p. 624, John Wiley
and Sons: New York (1997), which is incorporated herein by
reference in its entirety. V.sub.T=total volume in the tube (mass
latex/density of latex) S.sub.H.sub.2.sub.O=volume of
supernatant=weight of supernatant F.sub.R=packing factor equals
0.64 for random packing of essentially monodisperse spheres. The
packing factor is a correction corresponding to the volume fraction
of solids in the hard pack.
[0035] The skilled person will appreciate that void volume accounts
for interior void volume and shell void volume of a particle. Thus,
where two particle populations having similar interior void volume
are compared, the particle population with a higher void volume
will have greater shell void volume (i.e. greater porosity).
[0036] In one or more embodiments, the porous polymeric pigment may
have a void volume fraction of at least 40%, in other embodiments
at least 45%, in other embodiments at least 50%, in other
embodiments at least 55%, and in other embodiments at least 60%. In
these or other embodiments, the porous polymeric pigment may have a
void volume fraction of at most 85%, in other embodiments at most
83%, in other embodiments at most 80%, in other embodiments at most
78%, and in other embodiments at most 75%. In one or more
embodiments, the porous polymeric pigment may have a void volume
fraction from about 40% to about 85%, in other embodiments from
about 45% to about 83%, in other embodiments from about 50% to
about 80%, in other embodiments from about 55% to about 77% and in
other embodiments from about 60% to about 75%.
[0037] In one or more embodiments, the porous hollow particles may
be characterized by an average particle size, which may be measured
by hydrodynamic chromatography. In one or more embodiments, the
porous hollow particles may have an average particle size (i.e.
particle diameter) of at least 0.5 .mu.m, in other embodiments at
least 0.6 .mu.m, in other embodiments at least 0.7 .mu.m, in other
embodiments at least 0.9 .mu.m, in other embodiments at least 1.0
.mu.m, in other embodiments at least 1.1 .mu.m, in other
embodiments at least 1.3 .mu.m, and, in other embodiments at least
1.4 .mu.m. In these or other embodiments, the porous hollow
particles may have an average particle size of at most 3.0 .mu.m,
in other embodiments at most 2.5 .mu.m, in other embodiments at
most 2.2 .mu.m, in other embodiments at most 2.0 .mu.m, in other
embodiments at most 1.9 .mu.m, in other embodiments at most 1.8
.mu.m, in other embodiments at most 1.7 .mu.m, and in other
embodiments at most 1.5 .mu.m. In one or more embodiments, the
porous hollow particles may have an average particle size of from
about 0.5 to about 3.0 .mu.m, in other embodiments about 0.6 to
about 2.5 .mu.m, in other embodiments from about 0.7 to about 2.2
.mu.m, in other embodiments from about 0.9 to about 2.0 .mu.m, in
other embodiments from about 1.0 to about 1.9 .mu.m, in other
embodiments from about 1.1 to about 1.8 .mu.m, in other embodiments
from about 1.3 to about 1.7 .mu.m, in other embodiments from about
1.4 to about 1.5 .mu.m, in other embodiments from about 1.1 to
about 3.0 .mu.m, in other embodiments from about 1.2 to about 2.9
.mu.m, in other embodiments from about 1.3 to about 2.8 .mu.m, in
other embodiments from about 0.2 to about 1.0 .mu.m, in other
embodiments from about 0.3 to about 0.9 .mu.m, in other embodiments
from about 0.4 to about 0.8 .mu.m, and in other embodiments from
about 0.5 to about 0.7 .mu.m.
Substrate
[0038] As noted above, the thermosensitive recording material
includes a substrate. The substrate may serve as a support for the
various layers of the thermosensitive recording material. In one or
more embodiments, suitable substrate for use in the thermosensitive
recording material may be a sheet or a plate. The substrate may be
made of metal, plastic, paper, or paper board. In one or more
embodiments, the substrate may include an adhesive backing.
Insulating Layer
[0039] As noted above, the insulating layer of the thermosensitive
recording material includes hollow particles as described herein.
For example, the porous hollow particles may be included in the
binder of a paper coating.
[0040] In one or more embodiments, the binders may also include
synthetic latexes, a starch or other natural binder such as a
protein (e.g. soy, casein, albumin), polyvinyl alcohol,
carboxymethyl cellulose, hydroxymethyl cellulose, polyacrylate
salt, and mixtures thereof.
[0041] Specific latexes include those selected from the group of a
polymerized form of styrene, butadiene, acrylonitrile, butyl
acrylate, methyl methacrylate, styrene-butadiene,
styrene-butadiene-acrylonitrile, styrene-acrylic,
styrene-butadiene-acrylic, vinyl acetate, and mixtures thereof.
Additional examples of monomers that can be used in the preparation
of synthetic latex include mixtures of ethylene and vinyl acetate,
and esters of acrylic acid and/or methacrylic acid. In certain
embodiments, the latex binder may be carboxylated. For example, the
synthetic latex binders provided herein can be carboxylated, i.e.
copolymerized with a carboxylic acid.
[0042] In one or more embodiment, the binder of the insulating
composition may be an aqueous dispersion of a polymer. As
appreciated, the aqueous portion of the binder is evaporated or
almost entirely evaporated during the manufacture of the
thermosensitive recording material, as discussed herein. In one
embodiment, the synthetic latex binder is an example of such an
aqueous dispersion of a polymer. In addition, the synthetic latex
can have a monomodal or polymodal, e.g., bimodal, particle size
distribution. Mixtures of binders can also be used in the paper
coating composition.
[0043] A wide variety of commercially available binders are
available. Examples of suitable latex binders include: CP 615NA, CP
638NA, DL 920, DL 966, PROSTAR 5401, and CP 692NA, manufactured by
The Dow Chemical Company; GenFlo 557 and GenFlo 576, manufactured
by Omnova Solutions Inc.; and Acronal S 504 and Acronal S 728,
manufactured by BASF Corporation. A suitable starch binder can
include Penford Gum PG290 (Penford Products Co., Cedar Rapids
Iowa).
[0044] In one or more embodiments, the insulating layer may be
characterized by the amount of porous hollow particles in the
layer, which may be defined, on dry weight basis, based on the
weight of porous hollow particles in the composition (i.e. the
insulating composition) used to prepare the layer. In one or more
embodiments, the insulating composition may include at least 20% in
other embodiments at least 50%, in other embodiments at least 60%,
and in other embodiments at least 70% porous polymeric pigment on
dry weight basis relative to the total weight of the composition.
In these or other embodiments, the insulating composition may
include at most 80% in other embodiments at most 90%, in other
embodiments at most 95%, and in other embodiments at most 99%
porous polymeric pigment on dry weight basis relative to the total
weight of the composition. In one or more embodiments, the
insulating composition may include from about 20% to about 99%
porous polymeric pigment, in other embodiments from about 50% to
about 95% porous polymeric pigment, in other embodiments from about
60% to about 90% porous polymeric pigment, and in other embodiments
from about 70% to about 80% porous polymeric pigment on dry weight
basis relative to the total weight of the composition.
[0045] In one or more embodiments, the insulating composition may
be characterized by the amount of binder in the insulating
composition based upon the dry weight of the insulating
composition. In one or more embodiments, the insulating composition
may include at least 1%, in other embodiments at least 5%, in other
embodiments at least 10%, and in other embodiments at least 20%
binder on dry weight basis. In these or other embodiments, the
insulating composition may include at most 30% binder, in other
embodiments at most 40% binder, in other embodiments at most 50%
binder, and in other embodiments at most 80% binder on dry weight
basis. In one or more embodiments, the insulating composition may
include from about 1% to about 80% binder, in other embodiments
from about 5% to about 50% binder, in other embodiments from about
10% to about 40% binder, and in other embodiments from about 20% to
about 30% binder on dry weight basis.
[0046] In one or more embodiments, the insulating layer may include
optional ingredients such as pigment or additives.
[0047] Examples of pigments include kaolin, talc, calcined clay,
structured clay, ground calcium carbonate, precipitated calcium
carbonate, titanium dioxide, aluminum trihydrate, satin white,
hollow polymeric pigment, solid polymeric pigment, silica, zinc
oxide, barium sulfate, and mixtures thereof.
[0048] In one or more embodiments, where the optional pigment is a
hollow polymeric pigment, the hollow polymeric pigment may be
prepared by an acid core process or an ester core process. Examples
of hollow polymeric pigments produced using an acid core process
can be found in U.S. Pat. No. 4,468,498 to Kowalski, which is
incorporated herein by reference in its entirety. Examples of
hollow polymeric pigments produced using an ester core process can
be found in U.S. Pat. No. 5,157,084 to Lee and U.S. Pat. No.
5,521,253 to Lee, both of which are incorporated herein by
reference in their entirety.
[0049] Examples of additives include conventional thickeners,
dispersants, dyes and/or colorants, preservatives, biocides,
anti-foaming agents, optical brighteners, wet strength agents,
lubricants, water retention agents, crosslinking agents,
surfactants, and pH control agents, and mixtures thereof.
[0050] The insulating layer may be applied to the substrate using a
number of different coating techniques. Examples of these
techniques include rod, grooved rod, curtain coating, stiff blade,
applicator roll, fountain, jet, short dwell, slotted die, bent
blade, bevel blade, air knife, bar, gravure, size press
(conventional or metering), spray application techniques, wet
stack, and/or application during the calendering process. Other
coating techniques are also possible. After the insulating layer is
applied to the substrate the insulating layer may then be dried.
Drying of the insulating layer can be accomplished by convection,
conduction, radiation, and/or combinations thereof.
[0051] In certain embodiment, where the image forming layer
includes a leuco dye and/or a developer, the leuco dye and/or a
developer may melt together when an image is formed on the
thermosensitive recording material. As noted above, the
thermosensitive recording material may include a hybrid layer that
provides both insulation and absorption. In these or other
embodiments, the porous hollow particles, and optionally other
pigments, may help to absorb the melted components from the
thermosensitive recording layer during imaging. In certain
embodiments, the optional absorption layer may include silica
and/or alumina pigments.
Optional Absorption Layer
[0052] In these or other embodiments, an optional absorption layer
may help to absorb the melted components from the thermosensitive
recording layer during imaging. The optional absorption layer may
include the porous particles. In certain embodiments, the optional
absorption layer may include silica and/or alumina pigments.
Image-Forming Layer
[0053] In one or more embodiments, the image forming layer includes
a dye or a dye and developing agent combination that changes color
to produce a visible marking on the thermosensitive recording
material upon when exposed to sufficient heat or pressure. In one
more embodiments, the dye may be a leuco dye or a combination of a
leuco dye and a developing agent.
[0054] Exemplary types of leuco dyes include triphenylmethane
phthalide compounds, triallyl methane compounds, fluoran compounds,
phenothiazine compounds, thiofluoran compounds, xanthen compounds,
indophthalyl compounds, spiropyran compounds, azaphthalide
compounds, chromenopyrazole compounds, methine compounds, rhodamine
aniline lactum compounds, rhodamine lactum compounds, quinazoline
compounds, diazaxanthen compounds, and bislactone compounds.
[0055] Specific examples of leuco dyes include,
2-anilino-3-methyl-6-diethylaminofluoran,
2-anilino-3-methyl-6-(di-n-butylamino)fluoran,
2-anilino-3-methyl-6-(di-n-pentylamino)fluoran,
2-anilino-3-methyl-6-(N-n-propyl-N-methylamino)fluoran,
2-anilino-3-methyl-6-(N-isopropyl-N-methylamino)fluoran,
2-anilino-3-methyl-6-(N-isobutyl-N-methylamino)fluoran,
2-anilino-3-methyl-6-(N-n-amyl-N-methyl amino)fluoran,
2-anilino-3-methyl-6-(N-sec-butyl-N-ethyl amino)fluoran,
2-anilino-3-methyl-6-(N-n-amyl-N-ethyl amino)fluoran,
2-anilino-3-methyl-6-(N-iso-amyl-N-ethyl amino)fluoran,
2-anilino-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran,
2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran,
2-anilino-3-methyl-6-(N-methyl-p-toluidino)fluoran,
2-(m-trichloromethylanilino)-3-methyl-6-diethylaminofluoran,
2-(m-trifluoromethylanilino)-3-methyl-6-diethylaminofluoran,
2-(m-trifluoromethylanilino)-3-methyl-6-(N-cyclohexyl-N-methyl
amino)fluoran,
2-(2,4-dimethylanilino)-3-methyl-6-diethylaminofluoran,
2-(N-ethyl-p-toluidino)-3-methyl-6-(N-ethylanilino)fluoran,
2-(N-methyl-p-toluidino)-3-methyl-6-(N-propyl-p-toluidino)fluoran,
2-anilino-6-(N-n-hexyl-N-ethyl amino)fluoran,
2-(o-chloranilino)-6-diethyl aminofluoran,
2-(o-bromoanilino)-6-diethyl aminofluoran,
2-(o-chloranilino)-6-dibutylaminofluoran,
2-(o-fluoroanilino)-6-dibutylaminofluoran, 2-(m-trifluoromethyl
anilino)-6-diethylaminofluoran,
2-(p-acetylanilino)-6-(N-n-amyl-N-n-butylamino)fluoran,
2-benzylamino-6-(N-ethyl-p-toluidino)fluoran,
2-benzylamino-6-(N-methyl-2,4-dimethyl anilino)fluoran,
2-benzylamino-6-(N-ethyl-2,4-dimethyl anilino)fluoran,
2-dibenzylamino-6-(N-methyl-p-toluidino)fluoran,
2-dibenzylamino-6-(N-ethyl-p-toluidino)fluoran, 2-(di-p-methyl
benzylamino)-6-(N-ethyl-p-toluidino)fluoran, 2-(.alpha.-phenylethyl
amino)-6-(N-ethyl-p-toluidino)fluoran, 2-methyl amino-6-(N-methyl
anilino)fluoran, 2-methyl amino-6-(N-ethyl anilino)fluoran,
2-methyl amino-6-(N-propylanilino)fluoran, 2-ethyl
amino-6-(N-methyl-p-toluidino)fluoran, 2-methyl
amino-6-(N-methyl-2,4-dimethyl anilino)fluoran, 2-ethyl
amino-6-(N-methyl-2,4-dimethyl anilino)fluoran, 2-dimethyl
amino-6-(N-methyl anilino)fluoran, 2-dimethyl amino-6-(N-ethyl
anilino)fluoran, 2-diethyl amino-6-(N-methyl-p-toluidino)fluoran,
benzo leuco methylene blue, 2-[3,6-bis(diethyl
amino)]-6-(o-chloranilino)xanthyl benzoic acid lactam,
2-[3,6-bis(diethyl amino)]-9-(o-chloranilino)xanthyl benzoic acid
lactam, 3,3-bis(p-dimethyl aminophenyl)phthalide,
3,3-bis(p-dimethyl aminophenyl)-6-dimethyl aminophthalide,
3,3-bis(p-dimethyl aminophenyl)-6-diethyl aminophthalide,
3,3-bis(p-dimethyl aminophenyl)-6-chlorphthalide,
3,3-bis(p-dibutylaminophenyl)phthalide, 3-(2-methoxy-4-dimethyl
aminophenyl)-3-(2-hydroxy-4,5-dichlorphenyl)phthalide,
3-(2-hydroxy-4-dimethyl
aminophenyl)-3-(2-methoxy-5-chlorphenyl)phthalide,
3-(2-hydroxy-4-dimethoxyaminophenyl)-3-(2-methoxy-5-chlorphenyl)phthalide-
, 3-(2-hydroxy-4-dimethyl a
nophenyl)-3-(2-methoxy-5-nitrophenyl)phthalide,
3-(2-hydroxy-4-diethyl aminophenyl)-3-(2 methoxy-5-methyl
phenyl)phthalide, 3,6-bis(dimethyl
amino)fluorenespiro(9,3')-6'-dimethyl aminophthalide,
6'-chloro-8'-methoxy-benzoindolino-spiropyran, and
6'-bromo-2'-methoxy-benzoindolino-spiropyran.
[0056] Specific examples of developing agents for use with a leuco
dye include, but are not limited to bisphenol A, tetrabromo
bisphenol A, gallic acid, salicylic acid, 3-isopropyl salicylate,
3-cyclohexyl salicylate, 3,5-di-tert-butyl salicylate,
3,5-di-.alpha.-methylbenzyl salicylate,
4,4'-isopropylidenediphenol,
1,1'-isopropylidenebis(2-chlorophenol),
4,4'-isopropylidenebis(2,6-dibromophenol),
4,4'-isopropylidenebis(2,6-dichlorophenol),
4,4'-isopropylidenebis(2-methyl phenol),
4,4'-isopropylidenebis(2,6-dimethyl phenol),
4,4'-isopropylidenebis(2-tert-butylphenol), 4,4'-sec-butylidene
diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene
bis(2-methyl phenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxy
diphenoxide, .alpha.-naphthol, .beta.-naphthol, 3,5-xylenol,
thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolak
phenol resin, 2,2'-thiobis(4,6-dichlorophenol), catechol, resorcin,
hydroquinone, pyrogallol, fluoroglycine, fluoroglycine carboxylic
acid, 4-tert-octylcatechol, 2,2'-methylenebis(4-chlorophenol),
2,2'-methylenebis(4-methyl-6-tert-butylphenol),
2,2'-dihydroxydiphenyl, ethyl p-hydroxy benzoate, propyl p-hydroxy
benzoate, butyl p-hydroxy benzoate, benzyl p-hydroxy benzoate,
p-chlorobenzyl-p-hydroxy benzoate, o-chlorobenzyl-p-hydroxy
benzoate, p-methyl benzyl-p-hydroxy benzoate, n-octyl-p-hydroxy
benzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic
acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoate,
4-hydroxydiphenyl sulfone, 4-hydroxy-4'-chlorodiphenyl sulfone,
bis(4-hydroxyphenyl)sulfide, 2-hydroxy-p-toluic acid, zinc
3,5-di-tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate,
tartaric acid, oxalic acid, maleic acid, citric acid, succinic
acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea
derivatives, 4-hydroxythiophenol derivatives, bis(4-hydroxyphenyl)
acetic acid, ethyl bis(4-hydroxyphenyl)acetate,
n-propyl-bis(4-hydroxyphenyl)acetate,
n-butyl-bis(4-hydroxyphenyl)acetate, phenyl
bis(4-hydroxyphenyl)acetate, benzyl bis(4-hydroxyphenyl)acetate,
phenethyl bis(4-hydroxyphenyl)acetate,
bis(3-methyl-4-hydroxyphenyl) acetic acid, methyl
bis(3-methyl-4-hydroxyphenyl)acetate,
n-propyl-bis(3-methyl-4-hydroxyphenyl)acetate,
1,7-bis(4-hydroxyphenylthio)-3,5-dioxaheptane,
1,5-bis(4-hydroxyphenylthio)-3-oxaheptane, dimethyl
4-hydroxyphthalate, 4-hydroxy-4'-methoxydiphenyl sulfone,
4-hydroxy-4'-ethoxydiphenyl sulfone, 4-hydroxy-4'-isopropxydiphenyl
sulfone, 4-hydroxy-4'-propxydiphenyl sulfone,
4-hydroxy-4'-butoxydiphenyl sulfone, 4-hydroxy-4'-isopropxydiphenyl
sulfone, 4-hydroxy-4'-sec-butoxydiphenyl sulfone,
4-hydroxy-4'-tert-butoxydiphenyl sulfone,
4-hydroxy-4'-benzyloxydiphenyl sulfone,
4-hydroxy-4'-phenoxydiphenyl sulfone, 4-hydroxy-4'-(m-methyl
benzyloxy)diphenyl sulfone, 4-hydroxy-4'-(p-methyl
benzyloxy)diphenyl sulfone, 4-hydroxy-4'-(o-methyl
benzyloxy)diphenyl sulfone,
4-hydroxy-4'-(p-chlorobenzyloxy)diphenyl sulfone, and
4-hydroxy-4'-oxyallyldiphenyl sulfone.
[0057] In one or more embodiments, the image forming layer may
include a sensitizer. A sensitizer may be employed to lower the
thermal threshold of the image forming layer. Suitable sensitizer
may melt at a temperature of about 80.degree. C. to about
120.degree. C., and in other embodiments about 90.degree. C. to
about 110.degree. C. An exemplary class of sensitizers include
organic either compounds. Examples of either compounds include
1,2-bis-(3-methylphenoxy)ethane and 2-benzyloxynapthalene.
[0058] In one or more embodiments, the image forming layer may
include a stabilizer. In certain embodiments, a leuco dye may be
unstable in its visible, colored, form. Stabilizers may be used to
inhibit the loss of color or return of the leuco dye to its
colorless form.
[0059] In one or more embodiments, the image forming layer may
include optional components such as pigments, additives or
binders.
[0060] Various modifications and alterations that do not depart
from the scope and spirit of this invention will become apparent to
those skilled in the art. This invention is not to be duly limited
to the illustrative embodiments set forth herein.
* * * * *