Note: Descriptions are shown in the official language in which they were submitted.
21 5254 4
COLOR CHANGING COMPOSITIONS FOR HIGHLIGHTERS
FIELD OF THE INVENTION
This invention relates generally to the field of
coloring compositions and more particularly to a pair of
coloring compositions which are especially useful for
highlighting and may be used in conjunction with each other
to enable laying down an initial mark using a first coloring
composition yielding a first color and then using an
overcolor coloring composition to enable a change of color
of a portion or the entirety of the initial mark while still
enabling the text or other indicia marked over to be easily
perceived and read where appropriate.
BACKGROUND OF THE INVENTION
Children enjoy various drawing and coloring activities
using a variety of mediums. Useful in such activities are
markers containing inks, crayons and pencils of various
colors. However, children would often like to change the
color of a mark after they have made the mark. One instance
21 5254 4
2
would be the desire to add yellow daisies in a previously
colored field of grass and pink flowers. Other consumers
including students and various types of workers also require
differential marking capability as, for instance, those who
routinely highlight clauses of written material of
particular relevance. These consumers, as do the children,
may change their mind after making a mark, and desire to
change the color to set apart certain material.
Changing the color of a mark is not readily done with
the typical coloring instruments previously used by
consumers, such as those instruments described. In the
past, marks were changed by placing the mark of one color
over the mark of another color. When performing this using
traditional marking pens, the marks produced are often not
the desired colors and the tips of the markers get soiled
with the other inks, rendering the marker useless. Also,
with traditional highlighter inks, the colors tend to bleed
together, resulting in undesirable color smears and
combinations. Furthermore, oftentimes the use of a second
color over the first renders the text illegible.
Therefore, there has been a long felt need for coloring
compositions, for use as inks for highlighting, and markers
containing such compositions, which produce marks of a first
color that can be readily changed into a wide variety of
second colors while leaving the highlighted indicia easily
visible (i.e., have "read-through" capability). Especially
needed is such a group of compositions which may be used in
markers without soiling the nib of the second used marking
instrument. Optimally, such compositions can be used on
different types of paper without fading. In general,
coloring compositions are mixtures of a coloring matter
dispersed or dissolved in a carrier fluid. If the coloring
matter is readily soluble in the carrier fluid it is termed
a dye.
In one available marker application, a consumer is able
to change a specific initial mark laid down to a second
21 5254 4
3
specific color by applying a reducing agent to the first
mark yielding a change in color. The marker inks used in
these markers are typically prepared by blending a reducing
agent (sometimes termed a bleaching agent) or pH-sensitive
dye with a dye that is stable in the presence of reducing
agent or high pH. For example, German Patent Specification
No. 2724820, (hereinafter "the German Patent"), concerns the
combining of a chemically stable dye and a chemically
unstable dye in an ink formulation. Once a mark using this
combination of stable and unstable dyes is laid down, the
mark may be overwritten with a clear reducing agent
solution, eliminating the color contribution of the unstable
dye. The resulting mark of the stable dye, with its
characteristic color, remains.
There are several drawbacks to such a marking system.
First, there are strict limitations on the number of color
changes which may be produced. Specifically, in
formulations made according to the German Patent, the
particular ink composition may only be changed from a first
color to a fixed second color. For example, a green mark
may only be changed to a violet color as the inks are
described in the practice of the German Patent. In
addition, since one of the required pair of markers contains
only the reducing agent, that reducing agent marker cannot
render a visible mark and may only be used in combination
with the base color marker. Once the base color marker is
used up, the reducing agent marker is of no use. Or, once
the reducing agent marker is used up, the base color marker
may only be used for the color which it initially marks
with. A further disadvantage of the marking process of the
German Patent is that the nib of the reducing agent marker
tends to get soiled by picking up the colors of the stable
dye in the base coloring composition, thus tainting the
color of subsequent marks.
The coloring composition may also optionally include
such ingredients as humectants, preservatives, and drying
21 5254 4
4
agents. Humectants function to improve freeze/thaw
stability and to control drying out of the tip when the
coloring composition is used as a marker ink. Preservatives
serve the obvious function of preventing spoilage of the
coloring composition during the expected shelf life of the
product derived therefrom (e. g., marker, ink or dyej.
Drying agents speed drying of a mark laid down by a marker.
Therefore, an object of the present invention is to
provide a coloring composition system which is capable of
enhanced multiple color changing abilities, and is
especially suitable for highlighting.
An additional object of the present invention is to
produce a coloring composition system for use in
highlighting which includes at least two different coloring
compositions each of which may be used independently or
which may be used in combination to provide color changing
ability, and each of which preferably leave the highlighted
indicia easily visible, either when used alone, or in
combination.
A further object of the present invention is to provide
a coloring composition system in the form of inks which
prevent a nib of a color changing marker from becoming
visibly soiled from contacting a base color composition.
These and other objects will become apparent to those
skilled in the art to which the invention pertains.
SOMMARY OF TH$ IldOENTION
The present invention overcomes the drawbacks
associated with prior overwriting ink compositions in that a
particular undercolor coloring composition made according to
the invention may be changed to a different second color,
and perhaps even multiple second colors, depending upon the
dye present in the overcolor coloring composition.
An advantage of an undercolor coloring composition of
the present invention are that it produces marks of a first
color that can be used on different types of paper (e. g.,
~ 1~ ~.~ 44
copy paper) without fading, and while leaving the
highlighted indicia easily visible.
Advantageously, the overcolor coloring compositions of
the present invention make a visible mark, thus they may be
used alone or in combination with undercolor coloring
compositions. This differential marking capacity is of
particular benefit in highlighting applications.
An additional advantage of the overcolor compositions
of the present invention is that, unlike currently used
color change markers and highlighters, the nib of the tip of
the marker containing a particular overcolor coloring
composition does not become visibly soiled with the
undercolor coloring composition color because the undercolor
is immediately destroyed upon contact with the overcolor
composition.
In general, the present invention is a multiple
coloring composition system wherein the coloring effect of
an undercolor coloring composition may be changed upon
treatment with an overcolor coloring composition, once the
overcolor coloring composition has been deposited over the
undercolor coloring composition. In one embodiment, the
multiple coloring composition system comprises:
(a) an aqueous undercolor coloring composition
comprising an undercolor dye whose coloring ability is
destroyed in the presence of a reducing agent and/or a pH of
about 10 or greater, and a compatible surfactant in an
amount sufficient to increase the stability of the coloring
composition; and
(b) an aqueous overcolor coloring composition
comprising an overcolor dye capable of maintaining its
characteristic color in the presence of a reducing agent
and/or a pH of about 10 or greater, a reducing agent and/or
an effective amount of a base sufficient to yield a pH of
the aqueous overcolor coloring composition of about 10 or
greater, and a compatible surfactant in an amount sufficient
6
to increase the capillary flow of the aqueous overcolor
coloring composition.
Also disclosed is a multiple coloring composition
system comprising:
(a) an aqueous undercolor coloring composition
comprising an undercolor dye whose coloring ability is
destroyed in the presence of a reducing agent and/or a pH of
about 10 or greater, and a compatible surfactant in an
amount sufficient to increase the stability of the coloring
composition; and
(b) an aqueous overcolor coloring composition
comprising an overcolor dye capable of maintaining its
characteristic color in the presence of a reducing agent
and/or a pH of about 10 or greater, from about 1% to about
20% by weight of a reducing agent, an effective amount of a
base sufficient to yield a pH of the aqueous overcolor
coloring composition of about 10 or greater, and a
compatible surfactant in an amount sufficient to increase
the capillary flow of the aqueous overcolor coloring
composition.
A color changing marking system is also disclosed which
comprises at least two marking instruments, an undercolor
marking instrument and an overcolor marking instrument. The
undercolor marking instrument contains an undercolor
coloring composition comprising: (a) an effective amount of
an acid sufficient to maintain the pH of the undercolor
coloring composition at from about 3 to about 6; (b) from
about 0.05% to about 15% by weight of an undercolor dye; and
(c) from about 20% to about 60% by weight of a surfactant.
The overcolor marking instrument contains an overcolor
coloring composition comprising: (a) from about 0.1% to
about 12% by weight of a base; (b) from about 1% to about
20% by weight of a reducing agent; (c) from about 0.05% to
about 15% by weight of an overcolor dye which maintains its
characteristic color in the presence of a reducing agent and
~1 5254 4
base in an amount from about 10% to about 12% by weight; and
from about 0.5% to about 20% by weight of a surfactant.
The coloring compositions of the present invention may
also optionally comprise a humectant, a drying agent, and a
preservative.
DBTAIL$D D$BCRIPTIO~T 08 THB I~1V8NTION
The present invention imparts the desirable ease of
application and convenience of use of traditional color
changer systems while avoiding the strict limitations of
current color change markers. The composition of the
present invention therefore imparts improved and convenient
coloring properties.
In general, the present invention is a multiple
coloring composition system wherein the color of a mark laid
down by an undercolor coloring composition, for example
using a marker to dispense the composition, may be
overwritten by a variety of second colors upon the
application of an overcolor coloring composition over the
undercolor coloring composition. These coloring
compositions are especially useful for highlighting indicia
on substrates such as paper. Moreover, these coloring
compositions are particularly advantageous in that the
undercolor and overcolor coloring compositions each have
"read-through" capability, or, leave the highlighted indicia
easily legible, either when used alone, or when used in
combination. Optimally, the read-through capability of the
undercolor and overcolor coloring compositions should be
such that xeroxed copies made of the highlighted material
should also preferably leave the highlighted indicia easily
visible. An embodiment of this marking system comprises:
(a) an aqueous undercolor coloring composition
comprising an undercolor dye whose coloring ability is
destroyed in the presence of a reducing agent and/or a pH of
about 10 or greater, and a compatible surfactant in an
r
21 5254 4
8
amount sufficient to increase the stability of the coloring
composition; and
(b) an aqueous overcolor coloring composition
comprising an overcolor dye capable of maintaining its
characteristic color in the presence of a reducing agent
and/or a pH of about 10 or greater, a reducing agent and/or
an effective amount of a base sufficient to yield a pH of
the aqueous overcolor coloring composition of about l0 or
greater, and a compatible surfactant in an amount sufficient
to increase the capillary flow of the aqueous overcolor
coloring composition.
To increase the pH of the aqueous overcolor coloring
composition, a base in an amount sufficient to elevate the
pH of the aqueous coloring composition to a level of about
or greater, and preferably from about 10 to about 12, is
preferably used.
In a preferred embodiment, the aqueous overcolor
coloring composition comprises both a reducing agent and a
base in an amount sufficient to elevate the pH of the
aqueous overcolor coloring composition to about 10 or
greater, and preferably from about 10 to about 12. In this
preferred embodiment, the marking system comprises:
(a) an aqueous undercolor coloring composition
comprising an undercolor dye whose coloring ability is
destroyed in the presence of a reducing agent and/or a pH of
about 10 or greater, and a compatible surfactant in an
amount sufficient to increase the stability of the coloring
composition; and
(b) an aqueous overcolor coloring composition
comprising an overcolor dye capable of maintaining its
characteristic color in the presence of a reducing agent
and/or a pH of about 10 or greater, from about 1% to about
20% by weight of a reducing agent, an effective amount of a
base sufficient to yield a pH of the aqueous overcolor
coloring composition of about 10 or greater, and a
compatible surfactant in an amount sufficient to increase
~ ~.~2~ 44
9
the capillary flow of the aqueous overcolor coloring
composition.
The base is included in the aqueous overcolor coloring
composition to elevate the pH of the aqueous overcolor
coloring composition to a level of about 10 or greater, and
preferably from about 10 to about 12. In a preferred
embodiment, the aqueous overcolor coloring composition
comprises both a reducing agent and a base in an amount
sufficient to elevate the pH of the aqueous overcolor
coloring composition to about l0 or greater and preferably
from about 10 to about 12.
Appropriate undercolor dyes are generally selected to
be used in conjunction with the selection of appropriate
overcolor dyes. Where an undercolor dye is incapable of
maintaining its characteristic color when exposed to a pH of
about 10 or greater, an overcolor dye is selected which is
capable of maintaining its characteristic color at such a
pH, and a base is added to the overcolor coloring
composition to yield a pH of about 10 or greater. Where an
undercolor dye is incapable of maintaining its
characteristic color when exposed to a reducing agent, an
overcolor dye is selected which is capable of maintaining
its characteristic color in the presence of a reducing agent
and a reducing agent is added to the overcolor coloring
composition.
Certain undercolor dyes may be selected which are
incapable of maintaining their characteristic color when
exposed to a combination of a pH of about 10 or greater and
a reducing agent. In such a case, an overcolor dye is
selected which is capable of maintaining its characteristic
color in the presence of a pH of about 10 or greater and a
reducing agent and both a base and a reducing agent are
added to the overcolor coloring composition.
Most suitable for use as dyes in the undercolor
coloring compositions are dyes that are easily destroyed by
reducing agent. Such coloring compositions are commonly
~~.5~54-4-
known in the field and are occasionally used as chemically
"erasable" inks. Also suitable for use as dyes in the
undercolor coloring compositions are dyes which are easily
destroyed in the presence of a pH of about 10 or greater.
Dyes must also be compatible with the surfactant employed in
the undercolor and overcolor coloring compositions.
Especially suitable for use as dyes in the undercolor
coloring compositions of the invention are triphenylmethane
dyes and azo dyes which are unstable in the presence of a
reducing agent and/or a pH of about 10 or greater. Other
suitable dyes for use in the undercolor coloring composition
of the present invention are polymethine dyes, cyanine dyes
and methine dyes. Such dyes include the dyes marketed under
the tradenames BASACRYL X-RL YELLOW"' (Basic Yellow 49),
marketed by the BASF Corporation, ASTRAZON BLUE FRR"' (Basic
Blue 69), ASTRAZON BRILLIANT RED 4G"' (Basic Red 14), and
ASTRAZON PINK FBB" (Basic Red 49) by Miles (Mobay); and the
dyes marketed under the tradenames Acid Green 3 by
International Dyestuffs Corporation, Acid Blue 93 and Acid
Violet 19 marketed by Spectra Color Corporation as well as
mixtures thereof. Preferred dyes for use in the undercolor
coloring composition of the present invention are Basic Red
14, Acid Green 3, Acid Violet 19, Acid Blue 93, and mixtures
thereof.
The listed ASTRAZON dyes are classified as polymethine
dyes. Polymethine dyes are colored substances in which a
series of -CH= (methine) groups connect to terminal groups
of a chromophore. Polymethine and cyanine are often used
interchangeably as generic terms for all polymethine dyes.
The previous primary usage for polymethine dyes are dying
acetate rayon as well as polyacrylnitrile and
polyacrylamide. Acid Green 3, Acid Blue 93 and Acid Violet
19 are triphenylmethane dyes. Acid Green 3 is commonly used
in making pulp colors or lakes. Acid Violet dyes are
primarily fashion colors.
__~~~~~'254 4
To achieve good coloring of the undercolor coloring
composition, the minimum concentration of dye which will
produce a workable ink is governed by the color intensity
desired, though as little as 0.05% by weight of dye may be
sufficient for certain applications. The maximum workable
concentration of dye is determined largely by the ability to
maintain a stable composition and the depth of color
desired, and can vary widely depending upon the
concentration of other components. It is also a function of
the characteristics of the desired end product. In this
case, the desired undercolor coloring composition is
suitable for use as a highlighter and should preferably
leave the highlighted indicia easily visible (i.e.,
legible), either when used alone, or when used in
combination with an overcolor coloring composition.
Optimally, the depth of color of the desired end product
should be such that xeroxed copies made of the highlighted
material should preferably leave the highlighted indicia
easily visible. A practical upper limit in the formulation
of, for example, a marker ink comprised of the undercolor
coloring composition, is about 15% by weight of dye. The
preferred concentration range for most applications is from
about 0.05% to about 5% by weight of dye, preferably from
about 0.05% to about 1% dye, and even more preferably from
about 0.1% to about 0.5% dye.
A surfactant is also included in the undercolor
coloring compositions of the multiple coloring composition
system. Examples of suitable surfactants include anionic
surfactants such as disulfonated surfactants. The
disulfonated surfactant manufactured by Dow Chemical Co. and
sold under the trademark Dowfax 8390 is preferred for use in
the undercolor coloring compositions of the present
invention.
The surfactant is preferably included in the undercolor
coloring composition such that the undercolor coloring
composition comprises from about l0% to about 60%,
21 5254 4
12
preferably from about 20% to about 40%, and even more
preferably from about 25% to about 35% by weight of
surfactant. This relatively high amount of surfactant
increases the stability of the coloring composition, by
helping to maintain the color of the composition. In the
context of the present invention, any compatible surfactant
which increases the stability of the coloring composition by
helping to maintain the color of the composition is suitable
provided such surfactant does not negate the read-through
capability of the resultant undercolor coloring composition.
For example, DOWFAX 3B2 may be used.
The undercolor coloring compositions of the present
invention are preferably formulated using an acid such as
citric acid, or other antioxidant. Inclusion of an acid
such as citric acid, or another antioxidant in the
undercolor coloring composition such that the acid or other
antioxidant is present at levels from about 0.1% to about
3.0% by weight of the undercolor coloring composition
maintains a low pH of the composition (i.e., from about 3 to
about 6) and, in combination with a surfactant, increases
the resistance to fading of a mark produced by the
undercolor coloring compositions of the present invention on
different types of paper, and in particular, on copy paper
such as is routinely used in copier machines, and on coated
paper having a "waxy-appearing" surface. Acids and other
antioxidants other than citric acid can also be employed in
the context of the present invention. Generally the
antioxidant is employed in an effective amount sufficient to
maintain the pH of the undercolor coloring composition at
about 3 to about 6. Thus, generally, for instance, when
citric acid is used, it is present in an amount from about
0.1% to about 3.0% by weight of the undercolor coloring
composition. Preferably the acid such as the citric acid or
other antioxidant is contained in the undercolor coloring
composition in an amount of from about 0.1 to about 1.0%,
and more preferably from about 0.4 to about 0.8% by weight.
21 5254 4
13
The water used in the undercolor coloring compositions
of the present invention is preferably deionized water. The
amount of water present in the undercolor coloring
compositions is typically from about 10% to about 90% by
weight, and this amount is in large part determined by the
desired end use of the undercolor coloring composition, for
instance, as an ink, and the amount of other components
included in the undercolor color composition. To achieve a
desirable viscosity when the undercolor coloring composition
is used in the form of, for example, an ink, water is
preferably present in the undercolor coloring composition in
an amount of from about 20% to about 80%, and most
preferably from about 45% to about 60% by weight.
Accordingly, the present invention provides an
undercolor coloring composition comprising (a) an effective
amount of an acid sufficient to maintain the pH of the
undercolor coloring composition at from about 3 to about 6;
(b) from about 0.05% to about 1% by weight of an undercolor
dye; and (c) from about 10% to about 60% by weight of a
surfactant.
The present invention also provides overcolor coloring
compositions. The overcolor coloring compositions of the
present invention are preferably formulated by combining a
surfactant, a reducing agent, and a base with an overcolor
dye which maintains its characteristic color in the presence
of reducing agent and in high pH conditions. Preferably,
the overcolor dye should maintain its characteristic color
in the presence of an acid such as citric acid in an amount
from about 0.1% to about 3.0% by weight, which may be
included in the undercolor coloring composition. Of course,
where dyes used in the undercolor composition are only
affected by a reducing agent, the base may be deleted.
Also, where dyes used in the undercolor composition are only
affected by an elevated pH, the reducing agent may be
eliminated. However, for maximum commercial application and
for maximum effect upon a wider variety of undercolor
21 5254 4
14
compositions, the overcolor composition is preferably
formulated with a reducing agent and base in combination.
The dye must also be compatible with the surfactant employed
in the undercolor coloring composition and the overcolor
coloring composition.
A limited number of dyes meet this criteria. Dyes to
be used in the overcolor coloring composition must be highly
resistant to chemical attack such as from a reducing agent
or high pH conditions. Overcolor dyes meeting this criteria
include xanthene dyes, pthalocyanine dyes, and azo dyes
which are stable in the presence of a pH of about 10 or
greater and/or are stable in the presence of a reducing
agent and in the presence of an acid such as citric acid in
an amount from about 0.1% to about 3.0% by weight.
One overcolor dye which has been found to meet these
criteria is PYRANINE 120"' marketed by Miles (Mobay).
Accordingly, a preferred overcolor dye for use in the
overcolor coloring composition of the present invention is
Pyranine 120. Other dyes which also meet these criteria
include Acid Red 52 marketed by Carolina Color, Food Red 14
marketed by Hilton-Davis, BASANTOL GREEN 910"' marketed by
BASF, Acid Red 87 marketed by Hilton-Davis, Acid Red 92
marketed by International Dyestuffs Corporation, Acid Red
388 and Direct Blue 199 marketed by Crompton & Knowles, and
mixtures thereof.
Acid Red dyes, classified as xanthene dyes, are
generally used as colorants for foods, drugs and cosmetics.
Specifically, Acid Red 87, is the disodium salt of 2,4,5,7 -
tetrabromo-9-o-carboxyphenyl-6-hydroxy-3-isoxanthone. Acid
Red 87 is also called D & C Red No. 22 by the Food and Drug
Administration ("FDA"), and sold under the tradenames Eosine
YS'~ and Eosine G"'. In addition, Acid Red 92, the disodium
salt of 2,4,5,7-tetrabromo-9-3,4,5,6 tetrachloro-o-
carboxylphenyl-6-hydroxy-3-isoxanthone, is called D & C Red
No. 28 by the FDA, and sold under the tradename Phloxine B"'.
Acid Red 52 is a colorant for plastics. Further, Food Red
21 5254 4
14 or FD&C Red No. 3, commercially available under the
tradenames Erythrosine"' and Erythrosine Bluish"', is the
disodium salt of 9(o-carboxyphenyl)-6-hydroxy-2,4,5,7-
tetraiodo-3H-xanthen-3-one, which contains smaller amounts
of lower iodinated fluoresceins.
To achieve good coloring of the overcolor coloring
composition, the minimum concentration of dye which will
produce a workable ink is governed by the color intensity
desired, though as little as 0.05% by weight of dye may be
sufficient for certain applications. The maximum workable
concentration of dye is determined largely by the ability to
maintain a stable composition and the depth of color
desired, and can vary widely depending upon the
concentration of other components. It is also a function of
the characteristics of the desired end product. In this
case, the desired end product should preferably be capable,
on making a mark through text leaving the highlighted
indicia easily visible (i.e., legible), either when used
alone, or when used in combination with the undercolor
coloring composition. Optimally, the depth of color of the
desired end product should be such that xeroxed copies made
of the highlighted material should preferably leave the
highlighted indicia easily visible. A practical upper limit
in the formulation of, for example, a marker ink comprised
of the overcolor coloring composition, is about 15% by
weight. The preferred concentration range for most
applications is from about 0.05% to about 10% by weight of
dye, preferably from about 1% to about 5% dye, and even more
preferably from about 1% to about 3% dye.
A surfactant is also included in the overcolor coloring
compositions of the multiple coloring composition system.
Examples of suitable surfactants include anionic surfactants
such as disulfonated surfactant. The disulfonated
surfactant manufactured by Dow Chemical Co. and sold under
the trademark Dowfax 3B2'~ is preferred for use in the
overcolor coloring compositions of the present invention.
2 ~.'S ~ 5 ~-4
16
Other suitable surfactants include Dowfax 8390 and Polyterge
382, available from Olin Chemical Co.
The surfactant is preferably included in the overcolor
coloring composition such that the overcolor coloring
composition comprises from about 0.5% to about 20%,
preferably from about 1.0% to about 5.0%, and even more
preferably from about 2.5% to about 3.5% by weight of
surfactant. This relatively low amount of surfactant
increases flow rate and cap off of the compositions, and for
instance, aids in capillary flow of the composition through
the nib of a writing or marking instrument when the
compositions are used in the form of an ink. In the context
of the present invention, any compatible surfactant which
increases the flow rate and cap off of the compositions is
suitable provided such surfactant does not negate the read-
through capability of the resultant overcolor coloring
composition. Such a surfactant must also be stable in high
pH compositions, and in compositions containing reducing
agents and bleaches.
Typical reducing agents for use in the overcolor
coloring composition of the invention include hydrogen
sulfide, sodium sulfite, sodium bisulfite, and stannous
chloride. Certain limited bleaches which act as weak
oxidizing agents such as sodium hypochlorite and hydrogen
peroxide may also operate to effect a color change.
Hydrogen peroxide is also known to sometimes operate as a
weak reducing agent. The preferred reducing agent for use
in the overcolor coloring composition of the invention is
Na2S03 (sodium sulfite). Reducing agent is generally present
in the overcolor coloring composition of the invention in an
amount from about 1% to about 20% by weight with a minimal
amount required to allow for the elimination of the
undercolor coloring composition of the invention and the
maximum amount determined by the stability of the
composition and the safety of the composition for use by
children. Preferably, the reducing agent is contained in
~~.~~~4.4-
17
the overcolor coloring composition in an amount of from
about 5% to about 15%, and most preferably in an amount of
from about 8% to about 12% by weight of the overcolor
coloring coaposition.
Overcolor coloring compositions of the invention may be
formulated using only a reducing agent. However, the
reducing agents used in overcolor coloring compositions of
the invention perform most effectively in the presence of an
elevated pH. To elevate the pH of the overcolor coloring
composition, a base is added. Bases which may be used in
the overcolor coloring composition of the invention are
typically strong bases, usually having a pH of from about 10
to about 12. Typical bases which may be employed in the
overcolor coloring composition of the invention include
ammonium hydroxide, sodium hydroxide, and sodium carbonate.
The preferred base is sodium hydroxide.
The base is generally present in the overcolor coloring
composition of the invention in an amount from about 0.1% to
about 20% by weight. Preferably, the base is added in an
amount sufficient to raise the pH of the composition to a pH
of from about 10 to about 12. Preferably, the base is
contained in the overcolor coloring composition in an amount
of from about 5% to about 15%, and most preferably from
about 10% to about 12% by weight of the overcolor coloring
composition.
The water used in the overcolor coloring compositions
of the present invention is preferably deionized water. The
amount of water present in the overcolor coloring
composition is also governed in large part by the desired
end use of the composition, for instance, as an ink, and the
amount of other components included in the overcolor
coloring composition. The amount of water present in the
overcolor coloring compositions is typically from about 10%
to about 90% by weight. To achieve a desirable viscosity
when the overcolor coloring composition is used in the form
of, for example, an ink, water is preferably present in an
N
18
amount of from about 20% to about 80%, and most preferably
from about 45% to about 60% by weight.
Accordingly, the present invention provides an
overcolor coloring composition comprising (a) from about
0.1% to about 12% by weight of a base; (b) from about 1% to
about 20% by weight of a reducing agent; (c) from about
0.05% to about 15% by weight of an overcolor dye which
maintains its characteristic color in the presence of a
reducing agent and base in an amount from about 10% to about
12% by weight; and from about 0.5% to about 20% by weight of
a surfactant.
Optionally, both the undercolor coloring compositions
and the overcolor coloring compositions according to the
invention may further comprise such additives as humectants,
drying agents and preservatives such as biocides and
fungicides.
Addition of a humectant ensures that coloring
compositions of the invention, when in the form of an ink,
do not prematurely dry in a capillary marking system, such
as a bonded fiber marking nib. Typical humectants which may
be employed in the coloring compositions of the present
invention include polyhydric alcohols such as ethylene
glycol, propylene glycol, hexylene glycol and polyethylene
glycol), and hydroxylated starches. The humectant is
preferably glycerin.
The humectant is generally used in the composition in
an amount of from about 0% to about 30% by weight, though
this range is by no means critical. The amount of humectant
to be added is determined by the type of nib used in the
writing or marking instrument to be employed and the
protection time period desired. In one preferred
composition, the humectant, glycerin, is added to the
coloring composition in an amount of from about 10% to about
20% by weight.
To achieve a more rapid drying rate and to improve
marking characteristics upon nonporous materials, a drying
19
agent may be added to increase the overall volatility and
therefore the evaporation rate of the water and the pH
regulant. Any compatible material which performs this
function may be used.
The drying agent preferably should be a volatile polar
material so as to ensure compatibility with the primary
components of the marker ink. Straight chain C2-C4 alcohols
are good, highly volatile drying agents, and of these,
ethanol is preferred because of its relatively low cost and
because it does not contribute any unpleasant odor to the
composition. Alcohols can also provide added benefits, such
as reducing surface tension, increasing adherence of the ink
to porous surfaces, and providing bactericidal activity when
added to the ink composition.
To discourage improper usage of the marker ink, such as
ingesting the ink, the alcohol may contain a bittering agent
or a conventional denaturant. An alcohol utilizing a
bittering agent will discourage such improper usage of the
ink by simply imparting a disagreeable taste, while not
requiring the use of toxic denaturants as methanol or
benzene, and is therefore preferred. A conventional
denatured alcohol may, of course, also be utilized. The
most preferred drying agent is an ethyl alcohol which
contains a bittering agent and which is sold under the trade
name SDA 40B, manufactured by Aaper Alcohol.
When utilized, the drying agent preferably is added
from about 5% up to about 30% by weight, with the most
preferred concentration being about 8-10% by weight, though
these amounts are not critical to the practice of the
invention. About 8% per weight of drying agent is
ordinarily required to ensure rapid drying of the ink on a
nonporous surface, while amounts in excess of about 30% by
weight may adversely affect stability of the ink unless
other stabilizing additives are employed.
To maintain the shelf life of the composition, a
preservative may be added. The preservative preferably
20
serves as both a bactericide and a fungicide, and is added
in any effective amount, though a typical concentration
range is from about 0.1% up to about 5.0% by weight. The
use of preservatives in levels greater than about 5% by
weight may cause the ink to become toxic or unstable and
may, in any event, be unnecessary. Should alcohol be added
to the composition as a drying agent, that alcohol will
function as a preservative to some extent also.
Any conventional preservative may be utilized in the
invention as long as there is compatibility with the
remaining ink components. For example, preservatives
manufactured by Dow Chemical Co. and sold under the
trademarks Dowicil 75 (1-(3-chloroallyl)-3,5,7-triaza-1-
azoniaadamantane chloride) and Dowicil 200 (3-chlorovinyl-
hexamethylene tetrammonium chloride) or a preservative
manufactured by Rohm and Haas and sold under the trademark
Kathon PFM (isothiazolinones), or a preservative
manufactured by Sutton Labs and sold under the trademark
Germall II (imazolidinyl urea), or a preservative
manufactured by Merck and sold under the trademark Tektamer
38 (1,2 dibromo-2,4-dicyanobutane), will work in the
composition of the invention.
Other acceptable preservatives include TROYSAN
POLYPHASE P100"', a 3-Iodo-2-Propynyl Butyl Carbamate sold by
Troy Chemical, PVP K-30"', solubilized in a 2-Pyrrolidinone,
1-Ethenyl-, Homopolymer solubilizer ((C6MgN0)x sold by ISP
Technologies Inc., and M-PYROL"' a 1-Methyl-Pyrrolidinone
solubilizer sold by GAF Chemicals Corporation. Addition of
preservatives to the undercolor and overcolor coloring
compositions inhibits the growth of bacteria and fungi in
water-based products.
Typically, a consumer may make marks or color a picture
using one or more markers containing various undercolor
coloring compositions on a suitable substrate, such as
paper. The consumer may then select one or more markers
containing various overcolor coloring compositions of the
21
invention. The consumer may then overwrite a portion or all
of the previously aade markings, eliminating the color of
the undercolor coloring composition as applied, and leaving
only the color of the overcolor coloring composition used to
overwrite the undercolor coloring composition. Because of
the surprisingly strong and immediate impact of the
overcolor coloring composition used to overwrite the
undercolor coloring composition, the overcolor marker
appears to paint a color over the undercolor on the portions
of the substrate on which it is applied.
A consumer may also apply the overcolor coloring
composition directly to the substrate. If an undercolor
coloring composition is then used to overwrite the mark laid
down by the overcolor coloring composition, the overcolor
coloring composition will eliminate the color contributed by
the undercolor coloring composition leaving only the color
of the overcolor coloring composition where that mark was
previously made. The undercolor color will be seen on other
locations on the substrate. This change has been observed
to occur more slowly than when the overcolor coloring
composition is applied over the undercolor coloring
composition. This slowed reaction is presumably caused by
the penetration of the overcolor coloring composition into
the paper substrate. A child consumer gains great play
benefit by viewing this slowly disappearing color.
Preferably, when the coloring compositions of the
invention are used in the form of inks, the inks are placed
in conventional markers. Various undercolor coloring
compositions are placed in an undercolor set of markers,
each containing an appropriate different color dye. Various
overcolor coloring compositions of the invention are placed
in a second group of markers, each of these compositions
containing an appropriate different color dye. For
convenience, it is also possible to construct a marker
containing one of a number of undercolor coloring
compositions in one half of the marker, and one of a number
2~~2~~4
22
of overcolor coloring compositions in the other half of the
marker, wherein the compositions are separated by a dam
within the marker, such that no intermixing of the
compositions can occur.
Preferably, the markers of the present invention
utilize reservoirs for storing the ink and nibs such as
bonded fiber or sintered plastic to dispense the ink.
Typically, an ink reservoir contains a sponge-like reservoir
which holds the ink. The preferred reservoirs for the
undercolor coloring compositions of the invention are made
of acetate, polyester or polypropylene. The preferred
reservoirs for the overcolor coloring compositions of the
invention are made of polypropylene, which more suitably
resists attack by any reducing agent contained in the
overcolor coloring composition, and is more resistant to
high pH conditions.
In general, any suitable nib may be used in conjunction
with the undercolor coloring compositions of the invention.
However, where nylon or polyamide fibers are used, they
should be checked for preferential dye absorption. Also,
any compatible nib may be used in conjunction with the
overcolor coloring compositions of the invention. Sintered
polyethylene nibs are preferred, and nylon and polyamide
nibs should be checked for preferential dye absorption. In
general, bonded polyester fiber nibs are not suitable for
use with the overcolor coloring compositions of the
invention.
A marking kit or system is also formed which comprises
both overcolor coloring compositions and undercolor coloring
compositions. The present invention provides a color
changing marking system comprising one or more undercolor
marking instruments and one or more overcolor marking
instruments. Preferably the undercolor marking instruments
contain an undercolor coloring composition comprising: (a)
an effective amount of an acid sufficient to maintain the pH
of the undercolor coloring composition at from about 3 to
21 5254 4
23
about 6; (b) from about 0.05% to about 15% by weight of an
undercolor dye; and (c) from about 20% to about 60% by
weight of a surfactant. Preferably the overcolor marking
instruments contain an overcolor coloring composition
comprising: (a) from about 0.1% to about 12% by weight of a
base; (b) from about 1% to about 20% by weight of a reducing
agent; (c) from about 0.05% to about 15% by weight of an
overcolor dye which maintains its characteristic color in
the presence of a reducing agent and base in an amount from
about 10% to about 12% by weight; and from about 0.5% to
about 20% by weight of a surfactant.
The following examples serve to illustrate further the
present invention and are not to be construed as in any way
limiting its scope.
ERAMPLES
Examples of marking systems of the present invention
formulated as an ink are as follows. Quantities presented
are in percent by weight of the total composition.
Ondercolor Color Ink Examples
Example 1 Example 2
Pink Ink Green Ink
Component
Deionized Water 51.5 51.4
Glycerin 15.0 15.0
Preservatives
Nuosept 95'~ 0.3 0.3
Premix
Troysan Polyphase
P-100 0.05 0.05
PVP-K30 0.05 0.05
M-Pyrol 2.4 2.4
Dowfax 8390 30.0 30.0
Citric Acid 0.5 0.5
Dye
Acid Green 3 ----- 0.3
Basic Red 14 0.2 -----
21 5254 4
24
Esaaple 3 mcaaple 4
Blue Ink Purple Ink
c~oneat
Deionized Water 51.4 51.4
Glycerin 15.0 15.0
Preservatives
Nuosept 95 0.3 0.3
Premix
Troysan Pol yphase
P-100 0.05 0.05
PVP-K30 0.05 0.05
M-Pyrol 2.4 2.4
Dowfax 8390 30.0 30.0
Citric Acid 0.5 0.5
--Dye
Acid Blue 93 0.3 ---
Acid Violet 19 --- 0.3
The inks of Examples 1-4 had acceptable working
properties. The pH ranged from 3.0 to 3.5, the specific
gravity ranged from 1.07 to 1.08, the viscosity ranged from
3.4 to 3.7 centipoise, and the surface tension ranged from
39 to 41 dynes/cm. The inclusion of the surfactant was
found to increase the stability of the inks in terms of
helping to maintain the color of the compositions.
Furthermore, the inks of Examples 1-4 demonstrated
substantial read-through capability. Indicia highlighted
using these inks was easily visible (i.e., legible), and was
also easily visible on xeroxed copies made of the
highlighted material.
The inclusion of an acid (in this case, citric acid) in
the inks of Examples 1-4 was found to increase the
resistance to fading of these inks on paper. When citric
acid was not included in the inks, the stability of the inks
on certain types of paper, and in particular, on copy paper,
was found to be reduced. The inclusion of citric acid in
the compositions in an amount from at least about 0.1% by
weight (resulting in maintenance of a solution pH of about
3-6) was found to increase the resistance of the inks to
fading on different types of paper.
The inks of Examples 1-4 are especially suitable for
overcolor elimination by an overcolor coloring composition
21 5254 4
containing a reducing agent. Furthermore, the inks of
Examples 1-4 are especially suitable for overcolor
elimination by an overcolor coloring composition having a pH
of about 10 or greater whether or not a reducing agent is
present.
Inks that are especially appropriate for overcolor
elimination of the inks of Examples 1 and 2 is presented in
Examples 5-7.
Ov~roolor Coloring Inl~ S~caa~ples
Bxa~pl~ s
Yellow Ink
Component
Deionized Water 58.8
Glycerin 15.0
Na2S03 10 . 2
NaOH (5N Soln) 20%
Solution 11.0
Pyranine 120 2.0
Dowfax 3B2 3.0
8xample 6 Example 7
Green Ink Pink Ink
Deionized water 60.1 60.6
Glycerin 15.0 15.0
Na2S03 10 . 2 10 . 2
NaOH 5N (20% solution) 11.0 11.0
Dowfax 3B2 3.0 3.0
Direct Blue 199 0.3 ---
Pyranine 120 0.4 ---
Acid Red 388 --- 0.2
The inks of Examples 5-7 had acceptable working
properties. The pH of these inks ranged from 11.9 to 12.3,
the specific gravity ranged from 1.16 to 1.18, the viscosity
ranged from 3.9 to 4.2 centipoise, and the surface tension
ranged from 34 to 35 dynes/cm. The inclusion the surfactant
was found to increase the capillary flow of the ink, as
evidenced by an increase in the flow rate and cap off.
Furthermore, the inks of Examples 5-7 demonstrated
substantial read-through capability. Indicia highlighted
using these inks was easily visible (i.e., legible), and was
21 5254 4
26
also easily visible on xeroxed copies made of the
highlighted material. Read-through capability was retained
when the inks of Examples 1 and 2-4 were used in combination
with the ink of Examples 5-7.
Moreover, the inks of Examples 5-7 were found to be
stable in the presence of an acid such as citric acid.
Specifically, the inks of these examples were capable of
maintaining their characteristic color in the presence of
citric acid in an amount from about 0.1% up to about 3.0% by
weight of the overcolor coloring composition. Some
bleaching out of the overcolor coloring composition was
found to occur when citric acid was included in the
composition in an amount from about 3.0% by weight, but not
when citric acid was included in the composition in an
amount from about 0.5%.
In using the various above described overcolor coloring
composition and undercolor coloring compositions, a child
could place a mark of the undercolor green or pink coloring
composition on paper, perhaps to paint pink flowers in a
field of grass. If the child then wishes to add in yellow
daisies, the child may easily use the above-indicated
overcolor coloring ink composition, without tainting any of
the colors. Alternatively, if the child draws yellow
daisies using the yellow overcolor coloring composition, he
or she may draw in grass or pink flowers using the green and
pink undercolor inks right over the yellow without spoiling
the colors.
Similarly, the multiple coloring compositions may also
be used advantageously by other consumers. For example,
students or other types of workers needing differential
marking capability may employ the highlighters. Such
consumers may highlight clauses of written material of
particular relevance. If certain clauses within that clause
take on further significance, or if a clause has been
mismarked (as will often happen during highlighting), the
consumer may use the overwriter in addition to the
21 5254 4
27
underwriter to change the appearance of the highlighting.
This will make the person's task much easier, and will
prevent additional highlighted copies from having to be made
in the event of a highlighting error. Furthermore, the
read-through capability of the overcolor and undercolor
coloring compositions will optimally allow the highlighted
material to easily be read through the highlighter, and will
allow xeroxed copies of the highlighted material to be made
such that the previously highlighted material can easily be
read on the xeroxed copy.
From the foregoing description and examples, it is
apparent that the objects of the present invention have been
achieved. While only certain embodiments have been set
forth, alternative embodiments and various modifications
will be apparent to those skilled in the art. These and
other alternatives are considered equivalents and within the
spirit and scope of the present invention.
