# Patent

## Title
Method of highlighting with a reversible highlighting mixture, highlighting kit, and highlighted complex

## Abstract

A highlightable mixture, such as an ink, including a colored pigment, an eradicable colorant, and a non-eradicable colorant; a kit including the highlightable mixture and an eradicator fluid; an colorant complex including a colorless or substantially colorless eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, and methine dyes, and a colored pigment; and methods of applying an eradicator to at least a portion of a marking made with a highlightable mixture, are described herein.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of application Ser. No. 10/956,584 filed on Oct. 1, 2004, which is a continuation-in-part of application Ser. No. 10/680,362 filed Oct. 7, 2003 now U.S. Pat. No. 7,083,665, the disclosures of which are hereby incorporated by reference.


BACKGROUND
1. Technical Field
The invention relates generally to color changing compositions.
2. Brief Description of Related Technology
Eradicable mixture systems, such as inks, generally include two components. One component is an aqueous mixture that includes a dye—typically a triarylmethane—that can be rendered substantially colorless when contacted with a substance such as a sulfite reducing agent, an amine, or other basic compounds such as hydroxides. The second component is an aqueous eradicator fluid that includes a complementary substance that can cause the dye to convert to a substantially colorless form. For example, a user writes with an eradicable ink and, if correction is necessary, applies the eradicator fluid to the ink marking to decolorize the dye.
Highlighting a marking is typically performed using a fluorescent ink applied over a regular marking made by an ink on a substrate (e.g., paper). A typical fluorescent highlighting ink has a translucent quality to allow for a user to apply the highlight ink and yet still see the regular ink marking under the fluorescent ink marking made by the marker. While this process serves to highlight a regular ink marking, it also has the undesirable effects, such as highlighting areas of the substrate that do not include a regular ink marking.
SUMMARY
One aspect of the disclosure is a method of reversibly highlighting including the steps of applying a mixture including water, a pigment, and an eradicable dye to a substrate to make a mark, applying an eradicator fluid to at least a portion of said mark, and applying an oxidizing agent to at least a portion of said mark. Any of such marks are optionally free of volatile solvents.
Another aspect of the disclosure includes a method of highlighting including the step of applying an oxidizing agent to an eradicated dye to produce a visible dye.
Another aspect of the disclosure is a kit including a highlightable mixture described herein, an eradicator fluid, and an oxidizing agent.
Yet another aspect of the disclosure is a complex, including a mixture of a colored pigment, an eradicable dye, an eradicator fluid, and an oxidizing agent, and optionally the complex is free of volatile solvents.
Further aspects and advantages of the invention will be apparent to those skilled in the art from a review of the following detailed description, taken in conjunction with the appended claims. While the mixture, method of using the mixture, the kit, and the complex are susceptible of embodiments in various forms, the description hereinafter includes specific embodiments with the understanding that the disclosure is illustrative, and is not intended to limit the claims to the specific embodiments described herein.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a theoretical mechanism for the conversion of Acid Violet 17 from a violet colored compound to a substantially colorless (eradicated) compound.
FIG. 2 illustrates a theoretical mechanism for the conversion from Acid Violet 17 that has been rendered colorless by a reducing agent to a colored state.



DETAILED DESCRIPTION
The process of ink marking and eradication can proceed in two steps: the first is the marking of a substrate (e.g., paper) with an eradicable ink, and the second is the application of an eradication solution to the marking. A typical formulation for an eradicable ink includes a solvent (e.g., water) to dissolve a dye that is capable of being eradicated (e.g., a triarylmethane dye). The eradication solution includes an eradicator that, by a chemical process, converts a complementary colored dye into a substantially colorless compound or a color that matches that of the substrate (e.g., white for white paper). Such compounds include oxidizing agents, reducing agents, acid-base reactants, and chemicals that can sublime under the influence of heat. Without intending to be limited to any particular method of eradication, it is believed that for triarylmethane dyes, for example, the active colored dye is able to reflect color in the visible range (between 380 nm to 780 nm) because of the conjugation of the aromatic rings in the molecule; however, once a reducing agent (e.g., sodium sulfite) is applied to the triarylmethane dye, it destroys the conjugation by converting the sp2 carbon center (shown in FIG. 1 with a *) to an sp3 carbon by oxidizing that carbon center. Once this change in the hybridization takes place, the conjugation between the various rings of the dye molecule is lost and the dye molecule becomes colorless. This proposed process is shown in FIG. 1 for Acid Violet 17.
The highlightable nature of the ink is derived from the ability to convert the dye (chromophore) from a colored compound to at least substantially colorless, while not substantially affecting the substantially insoluble, colored pigment. As discussed above, this can be achieved with the combination of a colored pigment and a dye that is sensitive to an eradicator (e.g., a reducing agent, a base, heat, etc.). Dyes which are capable of becoming at least substantially colorless upon the application of an eradicator include diarylmethane derivative dyes, triarylmethane derivative dyes, and methine derivative dyes. Diaryl dyes suitable for use with the inks described herein include Auramine O (Chemical Index No. 41000), and Basic Yellow 2 (Chemical Index No. 41000). In the colored state, the bi- and triarylmethane, and methine dyes often contain one or more cationic imine groups. The generic structure of a triarylmethane dye is shown below in formula (II):




wherein each R group is the same or different and preferably is selected from C1 to C10 alkyl groups. A non-exhaustive list of triarylmethane dyes for use in inks described herein are listed below in Table I.










TABLE I1






Color



Color Index Name
Index No.
Common/Commercial Name

















Acid Blue 22
42755
Water Blue I


Acid Blue 93
42780
Methyl Blue


Acid Fuchsin
42685
Acid Fuchsin


Acid Green
42095
Light Green Sf Yellowish


Acid Green 5
42095
Light Green Sf Yellowish


Acid Magenta
42685
Acid Fuchsin


Acid Roseine
42685
Acid Fuchsin


Acid Rubin
42685
Acid Fuchsin


Acid Violet 17
42650
Acid Violet 4BN


Acid Violet 19
42685
Acid Fuchsin


Alizarol Cyanin R
43820
Eriochrome Cyanin R


Aluminon
43810
Triphenylmethane Chrome




Violet Cg


Aniline Blue Ws

Aniline Blue Ws


Basic Blue 8
42563
Victoria Blue 4r


Basic Blue 15
44085
Night Blue


Basic Blue 20
42585
Methyl Green


Basic Blue 26
44045
Victoria Blue B


Basic Fuchsin

Basic Fuchsin


Basic Green 4
42000
Malachite Green


Basic Red 9
42500
Pararosanilin


Basic Red 14
48016
Cationic Brilliant Red 5GN


Basic Violet 2
42520
New Fuchsin


Basic Violet 3
42555
Crystal Violet


Basic Violet 4
42600
Ethyl Violet


Basic Violet 14
42510
Rosanilin


Chrome Violet Cg
43810
Triphenylmethane Chrome




Violet Cg


Chromoxane Cyanin R
4382
Eriochrome Cyanin R


Cotton Blue
42780
Methyl Blue


Crystal Violet
42555
Crystal Violet


Dahlia
42530
Hoffman's Violet


Diamond Green B
42000
Malachite Green


Eriochrome Cyanin R
43820
Eriochrome Cyanin R


Ethyl Green
42590
Ethyl Green


Ethyl Violet
42600
Ethyl Violet


Fast Green Fcf
42053
Fast Green Fcf


Food 3
42053
Fast Green Fcf


Gentian Violet

Methyl Violet 2b


Helvetia Blue
42780
Methyl Blue


Hoffman's Violet
42530
Hoffman's Violet


Light Green
42095
Light Green Sf Yellowish


Lissamine Green Sf
42095
Light Green Sf Yellowish


Magenta 0
42500
Pararosanilin


Magenta I
42510
Rosanilin


Magenta II

Magenta II


Magenta III
42520
New Fuchsin


Malachite Green
42000
Malachite Green


Methyl Blue
42780
Methyl Blue


Methyl Green
42585
Methyl Green


Methyl Violet
42535
Methyl Violet 2b


Methyl Violet 2b
42535
Methyl Violet 2b


Methyl Violet 10b
42555
Crystal Violet


Mordant Blue 3
43820
Eriochrome Cyanin R


Mordant Violet 39
43810
Triphenylmethane Chrome




Violet Cg


New Fuchsin
4252
New Fuchsin


Night Blue
44085
Night Blue


Pararosanilin
42500
Pararosanilin


Primula
42530
Hoffman's Violet


Rosanilin
42510
Rosanilin


Solochrome Cyanin R
43820
Eriochrome Cyanin R


Victoria Blue 4r
42563
Victoria Blue 4r


Victoria Blue B
44045
Victoria Blue B


Victoria Green B
42000
Malachite Green


Water Blue I
42755
Water Blue I





1See, R. D. Lillie, Conn's Biological Stains (8th ed., 1969), Williams and Wilkins Company, Baltimore, Maryland; Susan Budavari (Ed.), The Merck Index, (12th ed., 1996), Merck & Co., Whitehouse Station, N.J; see also, P. A. Lewis (Ed.), Pigment Handbook Vol. I, Properties and Economics, sections I(D)f(1) and I(D)g, John Wiley & Sons, (2nd ed., 1988); H. Zollinger, Color Chemistry: Syntheses, Properties, and Applications of OrganicDyes And Pigments, Chapter 4, VCH Publishers (1987); D. R. Waring and G. Hallas (Eds.), The Chemistry and Application of Dyes, Chapter 2, Section IX, Plenum Press (1990); and M. Okawara, T. Kitao, T. Hirashima, and M. Matsuoka, Organic Colorants: A Handbook of Data of Selected Dyes for Electro-Optical Applications, Section VI, Elsevier (1988), the disclosures of which are hereby incorporated by reference.






Another type of dye that can be used in an ink are the methine class of dyes. The methine dyes generally contain one or more methine group chromophores (—CH═), also called methylidyne or methine group. When the methine dye only contains one methine group the dye is sometimes referred to as a cyanine dye, with three methine groups the dye is sometime referred to as a carbocyanine dye, and with more than three methine groups the dye is often referred to as a polymethine dye. An example of a methine dye is Thiazole Orange:




wherein the bonds that make up the methine group are shown above as broken lines. Other examples of methine dyes include Basic Red 15, Basic Yellow 11, and Basic Yellow 13. For a comprehensive listing of methine dyes, see F. M. Hamer, The Chemistry of Heterocyclic Compounds, A. Weissberger (Ed.), The Cyanine Dyes and Related Compounds, Wiley Interscience, New York (1964).

When formulating a highlightable ink of a particular color, whether by the addition of one eradicable dye or a mixture of eradicable dyes and a pigment, the rate of eradication of a dye is a consideration when selecting an eradicable dye. Without intending to be limited to a particular mechanism, it is believed that the rate of eradication of diarylmethane, triarylmethane, and methine dyes is proportional to the concentration of the dye in the mixture (e.g., ink or marking made with a mixture). The highlightable ink described herein includes one or more eradicable dyes selected from the group consisting of diarylmethane dyes, triarylmethane dye, methine dyes, and combinations thereof. In a marking composition, the dye preferably is present in an amount at least about 0.01% and up to about 40% by weight of the total weight of the mixture, more preferably about 0.1% to about 10% by weight, for example up to about 1% by weight or about 1.5% by weight.
In selecting particular dyes and colored pigments for use in the ink, there are a number of dyes and pigments to choose from and, as a result, dyes and pigments of different colors can be mixed to create an ink of almost any color. A highlightable ink described herein can include one or more dyes and one or more pigments that, when combined, provide an ink from of a variety of colors. In one embodiment, the dye and pigment are combined to provide an ink that is black in color in the non-eradicated state and is red in color in the eradicated (highlighted) state. There are at least two competing considerations when formulating an ink that includes at least one eradicable dye—the rate of eradication and the intensity of the color. An increase in the concentration of the eradicable dye used to create the a particular color will increase the intensity of the color, however, as discussed above, an increase in the dye concentration also increases the amount of time needed to eradicate the dye. It has been found that for the ink described herein a dye concentration in an amount at least about 0.1% and up to about 40% by weight based on the total weight of the mixture is a preferred concentration to balance these considerations.
The ink disclosed herein is can be used on porous or non-porous substrates. Nonlimiting examples of non-porous substrates include glass, ceramics, porcelain, plastics, metal, glossy paper and other non-porous paper such as cardboard or other hardboard material. It has been found that the use of a substantially non-soluble pigment in combination with an eradicable dye prevents smearing of the ink upon eradication. Without intending to be limited to a particular mechanism for smear reduction, it is believed that when the substantially insoluble pigment is applied to a porous substrate such as paper, the pigment is not re-dissolved by the eradicator (e.g., aqueous eradicator) and is further prevented from smearing by being disposed in the pores of the substrate and thereby less influenced by the eradicator solution. Alternatively, a similar effect can be achieved with the use of a binder that binds a colorant (e.g., a pigment) to the substrate and, thereby, allows the colorant to be less influenced by the eradication solution. A preferred ink includes one or more colored pigments, and one or more eradicable dyes.
The eradication solution preferably includes water or an organic solvent as the primary solvent, an eradicator such as a sulfite (e.g., sodium sulfite), bisulfite, or an amine (e.g., sodium glycinate) that can cause susceptible dyes to lose their colors (e.g., triarylmethane dyes) or to change color, and a film-forming polymer. A suitable eradicator solution for the inks described herein is a commercially available eradicator solution that includes both a sulfite and an amine as active eradicating agents (available from Sanford Reynolds of Valence, France).
It has been found, quite surprisingly, that the eradication process can be made reversible upon the application of an oxidizing agent to the eradicated mixture (or at least a portion of a marking made with the mixture and then eradicated). The reversible nature of the eradication process allows for a substantially colorless eradicated dye to substantially revert back to its original color. It is expected that the reversal system can be used as a mechanism to correct a highlighting or eradication error such as an unintended eradication of a marking made with a highlightable and/or eradicable mixture. Without intending to be limited to any particular method of reversing the eradication, it is believed that for triarylmethane dyes, for example, the active colored dye is able to reflect color in the visible range (between 380 nm to 780 nm) because of the conjugation of the aromatic rings in the molecule; however, once a reducing agent (e.g., sodium sulfite) is applied to the triarylmethane dye, it destroys the conjugation by converting the sp2 carbon center (shown in FIG. 2 with a *) to an sp3 carbon by oxidizing that carbon center. Once this change in the hybridization takes place, the conjugation between the various rings of the dye is lost and the dye becomes at least substantially colorless. It is believed that the reverse of this process occurs when the oxidizing agent accepts electrons from the sp3 carbon of a substantially colorless dye back to a sp2 carbon center which is now conjugated with the aromatic rings of the dye and is able to reflect color in the visible range. This proposed process is shown in FIG. 2 for Acid Violet 17. For complete reversal of the eradication, the oxidizing agent must be able to neutralize any remaining eradicator left in the mixture (or marking make with the mixture).
It has been found that the selection of the eradicator solution for use in a reversible eradication system described herein is selected from compounds that can effect this theoretical change from an sp2 carbon center to an sp3 carbon center, and upon the application of an oxidizing agent, revert back to an sp2 carbon center. Preferably, the eradicator fluid includes a reducing agent and is selected from the group consisting of a sulfur-containing reducing agent, a basic reducing agent, and combinations thereof. It has also been found that when a sulfur-based reducing agent eradicator (e.g., sodium sulfite) is used, the reversibility of the eradication process is particularly facile. Thus, a reducing agent eradicator is preferably used to eradicate an eradicable mixture, more preferably a sulfur-based reducing agent (e.g., sodium sulfite). Still more preferably, a sulfur-based eradicator is selected from the group consisting of a sulfite reducing agent (e.g., sodium sulfite), a bisulfite reducing agent, a metasulfite reducing agent, a thiosulfite reducing agent, and combinations thereof.
The reversion of the eradicable dye from its substantially colorless state back to its substantially colored state can be performed by the application of an oxidizing agent to the mixture that has been eradicated or to a marking made with a mixture described herein and then eradicated. Oxidizing agents are substances that cause some other species to be oxidized or to lose electrons. For an oxidation process to occur, the oxidizing agent must undergo reduction and the relative oxidizing and reducing strengths of the oxidizing agent and the colorless dye can be used to predict whether or not the oxidation is likely to occur on an given species. For an eradicable dye used herein the agent to be reduced (i.e., lose electrons) is an sp3 carbocation. A example of one such carbocation is the eradicated Acid Violet 17 shown below (the sp3 carbocation is labeled with a “*”):




To completely effect the reversal of the eradication, any remaining eradicator in the mixture (or marking make with the mixture) should be neutralized by the oxidizing agent. Thus, the oxidizing agent used in the reversible eradication described herein has a reduction potential that, when compared to the reduction potential for the eradicator, yields a net negative Gibb's free energy (ΔG). The acid oxidizing agent can be a strong acid or weak acid, or a combination thereof. The acid oxidizing agent can also be selected from the group consisting of monobasic acids, di-basic acids, tri-basic acids, tetra-basic acids, and combinations thereof. Preferably, the oxidizing agent used is an acid and is selected from the group consisting of mineral acids, organic acids, and combinations thereof. Preferably, the mineral acids are selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, nitric acid, sulfuric acid, carbonic acid, chromic acid, phosphoric acid, phosphorous acid, phosphonic acid, and combinations thereof. Preferably, the organic acids are selected from the group consisting of benzoic acid, lactic acid, acetic acid, propanoic acid, acetoacetic acid, crotonic acid, formic acid, glycolic acid, glyoxylic acid, lactic acid, pyruvic acid, trans-aconitic acid, fumaric acid, maleic acid, malic acid, tartaric acid, acetylenedicarboxylic acid, tetrahydrophthalic acid, mesaconic acid, phthalic acid, isophthalic acid, terephthalic acid, itaconic acid, transethyleneoxidedicarboxylic acid, succinic acid, adipic acid, pimellic acid, suberic acid, azelic acid, substituted phosphoric acid, substituted phosphorous, citric acid, hemimellitic acid, trimellitic, trimesic acid, 2-carboxyethyliminodiacetic acid, nitrilotriacetic acid, phosphonic acid, substituted phosphonic acid, mellophanic acid, prehnitic acid, pyromellitic acid, 2-phosphonoethyliminodiacetic acid, diethylenetetraacetic acids, and combinations thereof. The oxidizing agent is preferably miscible or soluble in water, and the oxidizing agent is preferably an aqueous mixture.

It has also been found that the eradication can be reversed with the addition of a strongly nucleophilic species. Without intending to be limited to a particular mechanism, it is believed that a strongly nucleophilic species is attracted to the carbocation of the eradicated dye, and this attraction leads to the attack by the nucleophilic species on the carbocation and the formation of a re-conjugated colored eradicable dye. Thus, an eradicable reaction described herein is preferably reversed by the application of a nucleophile to the eradicable mixture or a marking made with the eradicable mixture, more preferably the nucleophile is an alkoxide.
The process of reversibly highlighting with an ink begins with the eradication of the eradicable dye(s) in the ink mixture with an eradicator. The colored pigment, however, is substantially unaffected by the eradicator and continues to contribute to the color of the ink. A highlightable ink described herein can have three different colored states. The first state can be described as the non-eradicated state, wherein the ink (or at least a portion of a marking made with the ink) has not come in contact with an eradicator. A second state of color can be described as the eradicated (highlighted) state, wherein the ink (or at least a portion of a marking made with the ink) has come in contact with the an eradicator and the ink has made a change in color, preferably sufficient to be perceptible to the human eye. A third state of color can be described as the reversed state of color, wherein the color of the mixture (or mark) includes contributions from a pigment and the eradicable dye that has been converted from substantially colorless to substantially back to its original non-eradicated color. Upon complete reversal, the third state of color is the same as or visually indistinguishable from the first state. Once the dye is eradicated (the eradicable dye is in the eradicated state), the color of the ink preferably is primarily determined by the color contributed by the colored pigments in the ink mixture. It is preferred that the color contributed by the color pigments is different from the color of the ink in its non-eradicated state, to achieve drastic highlighting and reversal effects that are at least noticeable to human eye. Preferably, the color of the ink in its non-eradicated state is black, and the color of the ink in the eradicated state is either red, green, or blue.
Pigments for use in the ink described herein cover a wide variety of colors and types, including organic, inorganic, natural, and synthetic pigments. Preferred pigments are substantially insoluble in an aqueous medium and are particulate material that is dispersed in the ink solution. Typically, pigments are chemically inert, non-toxic, and stable to heat and light. A non-exhaustive list of pigment for use in inks described herein are listed below in Table II.









TABLE II







Color Index


Pigment Common/Commercial Name
Manufacturer
Hue







Permanent Yellow DHG
Hoechst
Yellow 12



(Frankfurt, Germany)


Permanent Yellow GR
Hoechst
Yellow 13



(Frankfurt, Germany)


Permanent Yellow G
Hoechst
Yellow 14



(Frankfurt, Germany)


Permanent Yellow NCG-71
Hoechst
Yellow 16



(Frankfurt, Germany)


Permanent Yellow GG
Hoechst
Yellow 17



(Frankfurt, Germany)


Hansa Yellow RA
Hoechst
Yellow 73



(Frankfurt, Germany)


Hansa Brilliant Yellow 5GX-02
Hoechst
Yellow 74



(Frankfurt, Germany)


DALAMAR Yellow YT-858-D
Heubach
Yellow 74



(Langelsheim, Germany)


Hansa Yellow X
Hoechst
Yellow 75



(Frankfurt, Germany)


NOVOPERM Yellow HR
Hoechst
Yellow 83



(Frankfurt, Germany)


CHROMOPHTAL Yellow 3G
Ciba-Geigy
Yellow 93



(Basle, Switzerland)


CHROMOPHTAL Yellow GR
Ciba-Geigy
Yellow 95



(Basle, Switzerland)


NOVOPERM Yellow FGL
Hoechst
Yellow 97



(Frankfurt, Germany)


Hansa Brilliant Yellow 10GX
Hoechst
Yellow 98



(Frankfurt, Germany)


Permanent Yellow G3R-01
Hoechst
Yellow 114



(Frankfurt, Germany)


CHROMOPHTAL Yellow 8G
Ciba-Geigy
Yellow 128



(Basle, Switzerland)


IRGAZIN Yellow 5GT
Ciba-Geigy
Yellow 129



(Basle, Switzerland)


HOSTAPERM Yellow H4G
Hoechst
Yellow 151



(Frankfurt, Germany)


HOSTAPERM Yellow H3G
Hoechst
Yellow 154



(Frankfurt, Germany)


L74-1357 Yellow
Sun Chemical



(Cincinnati, Ohio)


L75-1331 Yellow
Sun Chemical



(Cincinnati, Ohio)


L75-2377 Yellow
Sun Chemical



(Cincinnati, Ohio)


HOSTAPERM Orange GR
Hoechst
Orange 43



(Frankfurt, Germany)


PALIOGEN Orange
BASF
Orange 51



(Mount Olive, New Jersey)


IRGALITE Rubine 4BL
Ciba-Geigy
Red 57:1



(Basle, Switzerland)


QUINDO Magenta
Mobay Chemical
Red 122



(Haledon, New Jersey)


INDOFAST Brilliant Scarlet
Mobay Chemical
Red 123



(Haledon, New Jersey)


HOSTAPERM Scarlet GO
Hoechst
Red 168



(Frankfurt, Germany)


Permanent Rubine F6B
Hoechst
Red 184



(Frankfurt, Germany)


MONASTRAL Magenta
Ciba-Geigy
Red 202



(Basle, Switzerland)


MONASTRAL Scarlet
Ciba-Geigy
Red 207



(Basle, Switzerland)


HELIOGEN Blue L 6901F
BASF
Blue 15:2



(Mount Olive, New Jersey)


HELIOGEN Blue NBD 7010
BASF



(Mount Olive, New Jersey)


HELIOGEN Blue K 7090
BASF
Blue 15:3



(Mount Olive, New Jersey)


HELIOGEN Blue L 7101F
BASF
Blue 15:4



(Mount Olive, New Jersey)


PALIOGEN Blue L 6470
BASF
Blue 60



(Mount Olive, New Jersey)


HEUCOPHTHAL Blue G, XBT-583D
Heubach
Blue 15:3



(Langelsheim, Germany)


HELIOGEN Green K 8683
BASF
Green 7



(Mount Olive, New Jersey)


HELIOGEN Green L 9140
BASF
Green 36



(Mount Olive, New Jersey)


MONASTRAL Violet R
Ciba-Geigy
Violet 19



(Basle, Switzerland)


MONASTRAL Red B
Ciba-Geigy
Violet 19



(Basle, Switzerland)


QUINDO Red R6700
Mobay Chemical



(Haledon, New Jersey)


QUINDO Red R6713
Mobay Chemical



(Haledon, New Jersey)


INDOFAST Violet
Mobay Chemical
Violet 23



(Haledon, New Jersey)


MONASTRAL Violet Maroon B
Ciba-Geigy
Violet 42



(Basle, Switzerland)


RAVEN 1170
Columbian Chemicals
Black 7



(Marietta, Georgia)


Special Black 4A
Degussa
Black 7



(Parsippany, New Jersey)


STERLING NS Black
Eastech Chemical, Inc.
Black 7



(Philadelphia, Pennsylvania)


STERLING NSX 76
Eastech Chemical, Inc.
Black 7



(Philadelphia, Pennsylvania)


TIPURE R-101
Du Pont,



(Wilmington, Delaware)


Mogul L
Eastech Chemical, Inc.
Black 7



(Philadelphia, Pennsylvania)









To prepare an ink of a particular color, the amount of colored pigment used in an ink can be balanced with the amount of dye present in the ink to produce the desired color of the ink in its non-eradicated state. Also, when a large amount of colored pigment is used, depending on the substrate, the pigment may over saturate the substrate once the solvent (e.g., water) has evaporated. If over-saturation occurs, the application of the eradicator fluid to the marking can cause smearing of the pigment on the surface of the substrate. Thus, the ink preferably contains an effective amount to prevent smearing upon application of the eradicator solution, when the smearing effect is not desired. The colored pigment preferably is present in an amount at least about 0.01% and up to about 50% by weight of the total weight of the mixture, more preferably at least about 0.1% and up to about 20% by weight, for example up to about 3.5%, 7%, or 10% by weight.
The color of the ink will primarily be determined by the combination of an eradicable dye and a colored pigment which causes the ink to reflect a particular wavelength of visible light. The mixture of a dye and pigment of different colors can form an ink mixture in a wide variety of colors. The color selection can be done with the use varying amounts of two or more complementary colors, or combinations that contain all three primary colors (red, yellow, and blue). When two complementary colors are mixed, the resultant mixture is gray, with black being the completely saturated form of gray. The complement color of red is green, the complement color of orange is blue, and the complement color of yellow is violet. When using complementary colors, these pairs of complementary colors actually reflect all three primary colors. For example, when red and green dyes are mixed as complementary colors, it is the equivalent of mixing red with yellow and blue, because green is composed of a mixture of the two primary colors yellow and blue. In another example, the mixture of the two complementary colors yellow and violet is the equivalent of mixing yellow with red and blue, because violet is composed of two primary colors, red and blue.
An ink described herein can optionally include a binder resin to impart smear resistance and water resistance to the ink. Binder resins for use in the ink preferably include glycols such as polyethylene glycol, polyvinylpyrrolidone and copolymers and salts thereof, polyvinylacetate and copolymers and salts thereof, and polyacrylic acids and copolymers and salts thereof, other film-forming, water-soluble resins, and combinations of the foregoing. The binder resin preferably is selected from PVP and copolymers thereof, PVA and copolymers thereof, and combinations of the foregoing. More preferably, the binder resin is selected from PVP, copolymers thereof, and combinations of the foregoing.
The binder resin can also be used to control the viscosity of the ink. When a highly viscous ink is desired (e.g., cP>10,000), the use of a larger amount a binder resin will achieve a highly viscous ink. When the binder resin used is a polymer (e.g., PVP), the resin can be selected with a wide range of viscosities and molecular weights. For example, PVP is commercially available at various viscosities, and in a molecular weight range of 10,000 daltons to 1,300,000 daltons (Aldrich Chemical Co., Inc., Milwaukee, Wis.) for example. Thus, depending on the molecular weight of the polymer resin, there can be a great deal of variation in the amount of resin utilized in the ink, and the overall viscosity of the ink. When, for example, a low molecular weight PVP is used, the ink can achieve smear and water resistance while still maintaining a low viscosity (e.g., about 2 cP to about 5 cP). A binder resin used herein preferably is present in an amount in a range of about 1 wt. % to about 80 wt. % based on the total weight of the mixture, more preferably about 5 wt. % to about 20 wt. %.
The ink preferably is an aqueous mixutre. Water preferably is present in an amount in a range of about 50% to about 95% by weight of the total weight of the mixture, more preferably about 60% to about 80% by weight. The water acts to dissolve the dye component and as a medium in which to suspend the colored pigment and also provides an improved washability of the ink from various materials (e.g., clothes) as compared to oil-based inks.
When an aqueous ink is used in a delivery system such as a writing instrument or an ink-jet cartridge, is it preferred to use one or more organic solvents to control the amount of time it takes for the ink to dry once it is applied to a substrate (drying time). Preferred delivery systems include a writing instrument and an ink-jet cartridge. As compared to water, organic solvents will typically evaporate faster than water, and when an aqueous ink includes an organic solvent, the drying time will decrease. In order to optimize and exercise control over the drying time of an ink, it may be necessary to include more than one organic solvent. An organic solvent preferably is substantially soluble in water. Preferably, the organic solvent is selected from the group consisting of glycols, ureas, fatty alcohols, dimethylformamide, formamide, dimethylsulfoxide, high molecular weight hydrocarbons (i.e., a hydrocarbon with twelve or more carbon atoms), low molecular weight hydrocarbons (i.e., a hydrocarbon with eleven or fewer carbon atoms), and combinations thereof. More preferably, the organic solvent is polyethylene glycol. The organic solvent, when used, preferably is present in the ink at least about 5% and up to about 30% by weight based on the total weight of the mixture, more preferably at least about 10% and up to about 20% by weight, to achieve a drying time suitable for typical writing instruments and marking applications.
Glycols for use as an organic solvent include, but are not limited to, three broad categories of glycols: (a) glycol ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether); (b) glycol ether acetates (e.g., ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monoisopropyl ether acetate, ethylene glycol dimethyl ether acetate, ethylene glycol diethyl ether acetate, diethylene glycol dimethyl ether acetate, propylene glycol monomethyl ether acetate, and the like); and (c) glycol acetates (e.g., ethylene glycol monoacetate, ethylene glycol diacetate, and diethylene glycol diacetate). In other embodiments, the ink can include other glycols not within one of these three categories, including glycols such as ethylene glycol, and ethoxylated glycols. A glycol can be used in the ink composition preferably in an amount in the range of about 10% to about 20% by weight based on the total weight of the mixture.
Fatty alcohols for use as an organic solvent include, but are not limited to, alcohols having eight through twenty carbon atoms, and fatty alcohols that are ethoxylated with one to three molar equivalents of ethylene oxide. Examples of fatty alcohols and ethoxylated fatty alcohols include, but are not limited to, behenyl alcohol, caprylic alcohol, cetyl alcohol, cetaryl alcohol, decyl alcohol, lauryl alcohol, isocetyl alcohol, myristyl alcohol, oleyl alcohol, stearyl alcohol, tallow alcohol, steareth-2, ceteth-1, cetearth-3, and laureth-2. Additional suitable fatty alcohols are listed in CTFA Cosmetic Ingredient Handbook, First ed., J. Nikotakis (Ed.), The Cosmetic, Toiletry and Fragrance Association, pages 28 and 45 (1988), incorporated herein by reference.
A mixture described herein can include one or more humectants to decrease or increase the drying time or cap-off time of an ink described herein (e.g., when the mixture is disposed in a writing instrument or ink-jet application). Without intending to be limited to a particular mechanism of altering the drying time, it is believed that a humectant, which is typically an organic solvent, added to the ink contributes to the volatility of the ink mixture such that the humectant either increases or decreases the volatility of the ink, and thereby decreases the drying time (i.e., when the mixture is applied to a substrate) and/or increase the cap-off time (i.e., when the mixture is disposed in a delivery device such as a writing instrument). Preferably, for an aqueous mixture described herein a humectant is selected such that it is miscible with water, and more preferably is an organic solvent that is miscible with water. Preferably, a volatile organic solvent is selected from the group consisting of polyethylene glycol, ethylene glycol, propylene glycol, diethylene glycols, glycerine, dipropylene glycols, polypropylene glycols, amides, urea, substituted ureas, ethers, carboxylic acids, esters, alcohols, organosulfides, organosulfoxides, sulfones, alcohol derivatives, carbitol, butyl carbitol, ether derivatives, amino alcohols, ketones, N-methylpyrrolidinone, 2-pyrrolidinone, cyclohexylpyrrolidone, hydroxyethers, amides, sulfoxides, lactones, and combinations thereof.
Preferably, the ratio of water in a mixture to organic in the mixture (e.g., organic solvent and/or humectant) is in a range of about 100:0 to about 30:70 by weight based on the total weight of the mixture, more preferably from about 97:3 to about 50:50.
For a liquid to effectively wet and spread out on a surface (e.g., paper), the surface tension of the liquid must be less than the surface tension of the surface. An organic solvent can also be selected to alter the surface tension of the mixture to create a mixture that has enough surface tension to wet a variety of surfaces. The mixture preferably includes a glycol to alter the surface tension of the mixture, more preferably polyethylene glycol.
In the ink described herein, the color green can be achieved by the mixing of the combination of dyes and pigments of either two complementary colors (e.g., green-red, or yellow-magenta) or by dyes/pigments with the combination of all three primary colors (red, yellow, and blue). A dark green ink is preferably formed from the combination of a green dye with a pigment selected from the group consisting of a red pigment, a violet pigment, and combinations thereof. A preferred combination is a green dye and red pigment, and the preferred combination is Basic Green 4 and a red pigment or a combination of pigments that combine to form a red pigment dispersion. The preferred red pigment dispersion is LUCONYL 3855 available from BASF of Charlotte, N.C.
When combining two or more colors to form an ink of a desired color, it is understood that the desired color (e.g., black), may be reached even though an undertone of another color (e.g., a redish color) might be perceptible. For example, it is understood that an ink that is colored black can have a red or a green undertone, and yet still be considered a black ink.
It has been found that the combination of a green eradicable dye and a violet and/or a red dye is able to mix to form a green highlightable ink. One embodiment of an ink described herein is a green highlightable ink, including a mixture of one or more of a colored pigment and one or more dyes selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, methine dyes, and combinations thereof, wherein the mixture of dye and pigment appears green in color.
A green eradicable dye preferably is selected from the group consisting of Acid Green, Acid Green 5, Basic Green 4, Diamond Green B, Ethyl Green, Fast Green Fcf, Food Green 3, Light Green, Lissamine Green Sf, Malachite Green, Methyl Green, Victoria Green B, and combinations thereof, more preferably, the green dye is selected from Basic Green 3, Basic Green 4, and combinations thereof. Preferably, a red dye is selected from the group consisting of Basic Red 9, Basic Red 14, Basic Red 15, Basic Red 29, Basic Red 46, and combinations thereof. Preferably, a violet dye is selected from the group consisting of Acid Violet 17, Acid Violet 19, Basic Violet 2, Basic Violet 3, Basic Violet 4, Basic Violet 14, Chrome Violet Cg, Crystal Violet, Ethyl Violet, Gentian Violet, Hoffman's Violet, Methyl Violet, Methyl Violet 2b, Methyl Violet 10b, Mordant Violet 39, and combinations thereof. To form a yellow ink, a yellow dye is preferably selected from the group consisting of Basic Yellow 11, Basic Yellow 13, Basic Yellow 21, Basic Yellow 28, Basic Yellow 29, Basic Yellow 40, Basic Yellow 49, Basic Yellow 291, and combinations thereof.
Preferably a mixture described herein is black in color. It has been found, quite surprisingly, that the addition of one or more non-eradicable dyes to the mixture including a pigment and an eradicable dye improves the richness of the black color in a black highlightable composition and improves the contrast between the non-highlighted mixture and the highlighted mixture. Accordingly, a mixture described herein preferably includes a non-eradicable dye.
It has been found that the addition of a blue, red, violet, yellow, and/or orange non-eradicable dye improves the richness of the black color in a black mixture described herein. Thus, in one embodiment a non-eradicable dye is present in a mixture described herein and is preferably selected from blue non-eradicable dyes, red non-eradicable dyes, violet non-eradicable dyes, yellow non-eradicable dyes, orange non-eradicable dyes, and combinations of the foregoing. Preferably, a blue non-eradicable dye is selected from the group consisting of Acid Blue 1, Acid Blue 104, Acid Blue 182, Acid Blue 204, Acid Blue 74, Acid Blue 9, Acid Blue 90, Basic Blue 1, Basic Blue 7, Basic Blue 9, Basic Blue 33, Direct Blue 199, Direct Blue 281, Disperse Blue 73, Reactive Blue 19, Reactive Blue 21, and combinations thereof. Preferably, a red non-eradicable dye is selected from the group consisting of Acid Red 18, Acid Red 249, Acid Red 52, Acid Red 87, Acid Red 92, Basic Red 22, Basic Red 28, Basic Red 46, Direct Red 236, Direct Red 252, and combinations thereof. Preferably, a violet non-eradicable dye is selected from the group consisting of Acid Violet 12, Acid Violet 126, Acid Violet 17, Acid Violet 49, Basic Violet 1, Basic Violet 10, Basic Violet 3, and combinations thereof. Preferably, a yellow non-eradicable dye is selected from the group consisting of Acid Yellow 17, Acid Yellow 118, Acid Yellow 23, Acid Yellow 3, Acid Yellow 32, Acid Yellow 36, Basic Yellow 21, Basic Yellow 28, Basic Yellow 37, Basic Yellow 40, Basic Yellow 49, Basic Yellow 291, and combinations thereof. Preferably, an orange non-eradicable dye is selected from the group consisting of Acid Orange 10, Reactive Orange 16, and combinations thereof.
One embodiment of the mixtures, methods, and kits described herein is a method of reversibly highlighting, including the steps of applying a mixture comprising water, a colored pigment, and an eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, methine dyes, and combinations thereof to a substrate to make a mark, applying an eradicator fluid to the mark, and applying an oxidizing agent to the mark.
Also contemplated is a kit including a mixture including water, a colored pigment, and an eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, methine dyes, and combinations thereof, an eradicator solution, and an oxidizing agent. Each of the mixture, eradicator fluid, and oxidizing agent can be disposed in a writing instrument (e.g., a pen) for ease of use or it may be supplied in another applicator form such as a dauber, a bottled free ink solution, a stamp pad, and the like. Preferably, a mixture described herein is disposed in a writing instrument and the writing instrument is, for example, a ball-point pen, an extruded plastic porous tip pen, or a marker.
In one application, after a highlightable ink mixture described herein is applied to a substrate, the volatile solvent(s) present in the mixture (e.g., water) will at least substantially evaporate. Upon eradication, the volatile solvent(s) present in the eradicator fluid (e.g., water) will at least substantially evaporate after the eradicator has been applied to the mixture. Likewise, when an oxidizing agent present in a solvent is applied to the mixture or marking made therewith, the volatile solvent(s) present in the oxidizing agent will evaporate, thus, leaving the eradication agent (e.g., sulfite, bisulfite) along with the mixture components (e.g., colored eradicable dye and colored pigment), and the oxidizing agent. Thus, another aspect of the invention is a colored complex of the mixture described herein with an eradicator fluid and oxidizing agent after the volatile solvent(s) have substantially or completely evaporated. The highlighted complex includes a colored (i.e., substantially non-eradicated) eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, methine dyes, and combinations thereof, a colored pigment, an eradicator (e.g., a reducing agent), an oxidizing agent (e.g., a mineral and/or organic acid), and any optional additives described herein. In other useful embodiments, the agents and/or mixtures described herein may be combined in the presence of a reaction medium (e.g., a solvent) under conditions in which the medium (e.g., a solvent) is not fugative (e.g., does not evaporate).
The highlighting or color-changing effect of a mixture described herein in best achieved when the color of the pigment present in the mixture is substantially unaffected by an eradication solution. Where the color of the pigment is substantially unaffected by the eradication solution, the color of the pigment contributes to the overall color of the complex created by the mixture of eradicated dye, pigment, and eradication solution that is created when the eradication solution is applied to the mixture. Thus, preferably the color of the colored pigment present in a mixture described herein is substantially unaffected by one or more of a reducing agent, an oxidizing agent, and a change in pH of the mixture.
A mixture described herein can be used as an ink to make markings on a variety of substrates (e.g., paper). In an ink, a surfactant can be used to improve the absorption of an ink by a substrate (e.g., paper), and a film-forming agent can be used to improve the adhesion of the resulting mark to the substrate. Thus, the mixture described herein can include one or more additives selected from the group consisting of pH buffers, surfactants, biocides, anti-corrosive agents, sequestering agents, anti-crusting agents, rehology control agents, binder resins, film-forming agents, and combinations thereof, in the amounts and proportions conventionally used in inks for various applications.
A mixture described herein can be used in a delivery system such as in an ink-jet application. The mixture can be used in a home-office ink-jet system (e.g., a HEWLETT-PACKARD ink-jet printer cartridge), and in commercial and industrial ink-jet applications. Ink-jet printers for use with a mixture described herein include those that use the continuous inkjet printer technology, which deflects and controls a continuous inkjet droplet stream direction onto the printed media or into a gutter for recirculation by applying an electric field to previously charged inkjet droplets, and those that use the drop-on-demand inkjet technology (e.g., piezoelectric and thermal ink-jet printhead), which ejects ink droplets only when they are needed to print on the media. Preferred delivery systems include the piezoelectric ink-jet printheads and thermal ink-jet printheads.
A mixture described herein can be used in a number of applications, including those that do not involve the application of the mixture onto a substrate (e.g., as an ink). Thus, a mixture described herein can be used with or without a substrate serving as a situs of the highlighting or color-changing effect. For example, the mixture described herein could be used in an application wherein the mixture and an eradication solution mix in the liquid phase to create a color change to the mixture when the eradication solution contacts the mixture. In another example, the aqueous mixture described herein can be combined in the liquid phase with an non-aqueous eradicator solution that creates a biphasic mixture wherein the highlighting or color-changing effect of the mixture occurs at the biphasic interface of the two solutions.
EXAMPLES
The following examples are provided to illustrate the invention but is not intended to limit the scope of the invention.
Example 1
A highlightable ink was prepared with the ingredients identified below in the amounts shown in Table III:











TABLE III







Component
Function
Amount (wt. %)




















Water
Solvent
76.48



Propylene Glycol
Organic Solvent
19.12



Basic Green 4
Dye
0.96



LUCONYL 3855
Pigment
3.44










The propylene glycol (available from EM Science of Gibbstown, N.J.), was added at room temperature to the water and mixed until a homogenous, particulate-free solution was formed. The Basic Green 4 dye was then added to this solution and the solution was mixed until the dye were fully dissolved. The pigment was then added and the solution was mixed for an hour until a homogenous solution was formed.
The resulting ink was then put into a SHARPIE marker and applied to a sheet of white paper to determine the color of the ink once applied to the substrate. The ink was observed to be a dark green color.
As described above, it is believed that the major contributing factor to the length of time it takes to highlight an ink described herein is proportional to the weight percent of eradicable dye present in the ink. Thus, after the ink was applied to a white sheet of paper, the eradication time was tested with a commercially available eradicator solution available from Sanford Reynolds of Valence, France. Upon the application of the eradication solution to the marking, the marking changed in color from a dark green to a red, and this conversion took approximately five seconds.
Example 2
Two highlightable ink mixtures were prepared with the ingredients identified below in the amounts shown in Table IV:










TABLE IV







Amount (wt. %)
Amount (wt. %)


Component
Function
Formulation 1
Formulation 2


















Deionized Water
Solvent
66.15
64.1


Propylene Glycol
Organic
20.00
20.00



Solvent


SPECTRAZINE
Non-
0.35
0.50


Yellow GRL 200%
Eradicable



Dye


SPECTRAZINE
Non-

3.00


Brilliant Blue
Eradicable



Dye


SPECTRA Soluble
Eradicable

1.50


Blue 2B EX
Dye


SPECTRACID Black
Eradicable
6.00



Dye


HOSTAFINE RED
Pigment
7.50


HF3S


HOSTAFINE
Pigment

10.00


GREEN GN


Sodium Acetate
Salt

0.90









The propylene glycol (available from EM Science of Gibbstown, N.J.), was added at room temperature to the water and mixed until a homogenous, particulate-free solution was formed. The eradicable dyes (SPECTRACID Black (available from Spectra Colors Corporation, Kearny, N.J.) to Formulation 1 and SPECTRA Soluble Blue 2B EX (available from Spectra Colors Corporation, Kearny, N.J.) to Formulation 2) and non-eradicable dyes (SPECTRAZINE Yellow GRL 200%, Colour Index No. Basic Yellow 291 (available from Spectra Colors Corporation, Kearny, N.J.) to Formulations 1 and 2, and SPECTRAZINE Bril. Blue, Colour Index No. Basic Blue 1 (available from Spectra Colors Corporation, Kearny, N.J.) to Formulation 2) were then added to this solution and the solution was mixed until the dyes were fully dissolved. The pigments (HOSTAFINE RED HF3S, Colour Index No. Pigment Red 188 (available from Clariant Corporation, Coventry, R.I.) to Formulation 1 and HOSTAFINE GREEN GN, Colour Index No. Pigment Green 7 (available from Clariant Corporation, Coventry, R.I.) to Formulation 2) were then added and the solution was mixed for an hour until a homogenous solution was formed.
The resulting inks were then put into SHARPIE markers and applied to a sheet of white paper to determine the color of the ink once applied to the substrate. The markings resulting from the application of formulations 1 and 2 were observed as a rich black in color. The resulting markings on white paper where then treated with a commercially available eradicator solution available from Sanford Reynolds of Valence, France. The markings made with Formulation 1 changed color from black to red, and the marking made with Formulation 2 changed color from black to green. The eradication of the markings made with both formulations 1 and 2 did not result in smearing of the marking and only the marking made with the ink (e.g., words written on paper) changed color (i.e., showed a highlighting effect).
Example 3
Mixtures that include an acid oxidizing agent were prepared by mixing the materials listed in Table V until a homogenous mixture was formed:











TABLE V







Component
Function
Amount (wt. %)




















Water
Solvent
95



Phosphoric acids
Acid/Oxidizing Agent
5



(75%)










The resulting aqueous mixture was placed in a POCKET ACCENT marker and applied to a marking made and eradicated as described in Example 1. The application of this aqueous acid mixture to the eradicated marking converted the red eradicated marking back to a dark green color that appears to the human eye to be identical to the color of the non-eradicated mixture prepared in Example 1. The reversal of color from red to dark green (apparently black) took approximately five seconds.
Example 4
Mixtures that include an acid oxidizing agent were prepared by mixing the materials listed in Table VI until a homogenous mixture was formed:











TABLE VI







Component
Function
Amount (wt. %)




















Water
Solvent
95



Citric Acid
Acid/Oxidizing Agent
5










The resulting aqueous mixture was placed in a POCKET ACCENT marker and applied to a marking made and eradicated as described in Example 1. The application of this aqueous acid mixture to the eradicated marking converted the red eradicated marking back to a dark green color that appears to the human eye to be identical to the color of the non-eradicated mixture prepared in Example 1. The reversal of color from red to dark green (apparently black) took approximately five seconds.
Example 5
Mixtures that include an acid oxidizing agent were prepared by mixing the materials listed in Table VII until a homogenous mixture was formed:











TABLE VII







Component
Function
Amount (wt. %)




















Water
Solvent
85



Citric Acid
Acid/Oxidizing Agent
10



Phosphoric acids
Acid/Oxidizing Agent
5



(75%)










The resulting aqueous mixture was placed in a POCKET ACCENT marker and applied to a marking made and eradicated as described in Example 1. The application of this aqueous acid mixture to the eradicated marking converted the red eradicated marking back to a dark green color that appears to the human eye to be identical to the color of the non-eradicated mixture prepared in Example 1. The reversal of color from red to dark green (apparently black) took approximately five seconds.
The foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the invention may be apparent to those having ordinary skill in the art. Throughout the specification, where compositions are described as including components or materials, it is contemplated that the compositions can also consist essentially of, or consist of, any combination of the recited components or materials, unless stated otherwise.

## Claims

1. A method of reversibly highlighting, comprising the steps of applying a mixture comprising water, a colored pigment, and an eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, methine dyes, and combinations thereof to a substrate to make a mark, applying an eradicator fluid to said mark, and applying an oxidizing agent to said mark.

2. The method of claim 1, wherein said eradicator fluid comprises a reducing agent.

3. The method of claim 2, wherein said reducing agent is selected from the group consisting of a sulfur-containing reducing agent, a basic reducing agent, and combinations thereof.

4. The method of claim 3, wherein said sulfur-containing reducing agent is selected from the group consisting of a sulfite reducing agent, a bisulfite reducing agent, a metasulfite reducing agent, a thiosulfite reducing agent, and combinations thereof.

5. The method of claim 1, wherein said oxidizing agent comprises an acid.

6. The method of claim 5, wherein said acid is selected from the group consisting of mineral acids, organic acids, and combinations thereof.

7. The method of claim 6, wherein said mineral acids are selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, nitric acid, sulfuric acid, carbonic acid, chromic acid, phosphoric acid, phosphorous acid, phosphonic acid, and combinations thereof.

8. The method of claim 6, wherein said organic acids are selected from the group consisting of benzoic acid, lactic acid, acetic acid, propanoic acid, acetoacetic acid, crotonic acid, formic acid, glycolic acid, glyoxylic acid, pyruvic acid, trans-aconitic acid, fumaric acid, maleic acid, malic acid, tartaric acid, acetylenedicarboxylic acid, tetrahydrophthalic acid, mesaconic acid, phthalic acid, isophthalic acid, terephthalic acid, itaconic acid, trans-ethyleneoxidedicarboxylic acid, succinic acid, adipic acid, pimellic acid, suberic acid, azelic acid, substituted phosphoric acid, substituted phosphorous, citric acid, hemimellitic acid, trimellitic, trimesic acid, 2carboxyethyliminodiacetic acid, nitrilotriacetic acid, phosphonic acid, substituted phosphonic acid, mellophanic acid, prehnitic acid, pyromellitic acid, 2-phosphonoethyliminodiacetic acid, diethylenetetraacetic acid, and combinations thereof.

9. The method of claim 1, wherein said oxidizing agent is a strong nucleophile.

10. The method of claim 9, wherein said strong nucleophile is an alkoxide.

11. The method of claim 1, wherein said mixture is black.

12. The method of claim 1, wherein said substrate is paper.

13. The method of claim 12, wherein said paper is non-porous paper.

14. The method of claim 1, wherein said eradicable dye is a triarylmethane derivative.

15. The method of claim 1, wherein said eradicable dye is present in said mixture in an amount at least about 0.01% and up to about 40% by weight of the total weight of the mixture.

16. The method of claim 15, wherein said eradicable dye is present in said mixture in an amount at least about 0.1% and up to about 10% by weight of the total weight of the mixture.

17. The method of claim 1, wherein said colored pigment is present in said mixture in an amount at least about 0.01% and up to about 50% by weight of the total weight of the mixture.

18. The method of claim 17, wherein said colored pigment is present in said mixture in an amount at least about 0.1% and up to about 20% by weight of the total weight of the mixture.

19. The method of claim 1, wherein said mixture further comprises a non-eradicable dye.

20. The method of claim 19, wherein said non-eradicable dye is selected from the group consisting of non-eradicable blue dyes, non-eradicable red dyes, non-eradicable violet dyes, non-eradicable yellow dyes, non-eradicable orange dyes, and combinations of the foregoing.

21. The method of claim 1, wherein said applying said mixture comprises dispensing said mixture from a writing instrument.

22. The method of claim 1, wherein said applying said mixture comprises dispensing said mixture from a printer cartridge.

23. The method of claim 22, said applying said mixture comprises dispensing said mixture from a continuous ink-jet printhead.

24. The method of claim 22, said applying said mixture comprises dispensing said mixture from a drop-on-demand ink-jet printhead.

25. The method of claim 24, wherein said drop-on-demand ink-jet printhead comprises a printhead selected from the group consisting of a piezoelectric ink-jet printhead, and a thermal ink-jet printhead.

26. A kit, comprising a first solution comprising a mixture comprising water, a colored pigment, and an eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, methine dyes, and combinations thereof; a second solution comprising an eradicator fluid; and a third solution comprising an oxidizing agent.

27. The kit of claim 26, wherein said eradicator comprises a reducing agent.

28. The kit of claim 27, wherein said reducing agent is selected from the group consisting of a sulfur-containing reducing agent, a basic reducing agent, and combinations thereof.

29. The kit of claim 28, wherein said sulfur-containing reducing agent is selected from the group consisting of a sulfite reducing agent, a bisulfite reducing agent, a metasulfite reducing agent, a thiosulfite reducing agent, and combinations thereof.

30. The kit of claim 26, wherein said oxidizing agent comprises an acid.

31. The kit of claim 30, wherein said acid is selected from the group consisting of mineral acids, organic acids, and combinations thereof.

32. The kit of claim 31, wherein said mineral acids are selected from the group consisting of hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, nitric acid, sulfuric acid, carbonic acid, chromic acid, phosphoric acid, phosphorous acid, phosphonic acid, and combinations thereof.

33. The kit of claim 31, wherein said organic acids are selected from the group consisting of benzoic acid, lactic acid, acetic acid, propanoic acid, acetoacetic acid, crotonic acid, formic acid, glycolic acid, glyoxylic acid, pyruvic acid, trans-aconitic acid, fumaric acid, maleic acid, malic acid, tartaric acid, acetylenedicarboxylic acid, tetrahydrophthalic acid, mesaconic acid, phthalic acid, isophthalic acid, terephthalic acid, itaconic acid, trans-ethyleneoxidedicarboxylic acid, succinic acid, adipic acid, pimellic acid, suberic acid, azelic acid, substituted phosphoric acid, substituted phosphorous, citric acid, hemimellitic acid, trimellitic, trimesic acid, 2-carboxyethyliminodiacetic acid, nitrilotriacetic acid, phosphonic acid, substituted phosphonic acid, mellophanic acid, prehnitic acid, pyromellitic acid, 2-phosphonoethyliminodiacetic acid, diethylenetetraacetic acid, and combinations thereof.

34. The kit of claim 26, wherein said mixture is black.

35. The kit of claim 26, wherein said eradicable dye is a triarylmethane derivative.

36. The kit of claim 26, wherein said eradicable dye is present in said mixture in an amount at least about 0.01% and up to about 40% by weight of the total weight of the mixture.

37. The kit of claim 36, wherein said eradicable dye is present in said mixture in an amount at least about 0.1% and up to about 10% by weight of the total weight of the mixture.

38. The kit of claim 26, wherein said colored pigment is present in said mixture in an amount at least about 0.01% and up to about 50% by weight of the total weight of the mixture.

39. The kit of claim 38, wherein said colored pigment is present in said mixture in an amount at least about 0.1% and up to about 20% by weight of the total weight of the mixture.

40. The kit of claim 26, wherein said mixture further comprises a non-eradicable dye.

41. The kit of claim 40, wherein said non-eradicable dye is selected from the group consisting of non-eradicable blue dyes, non-eradicable red dyes, non-eradicable violet dyes, non-eradicable yellow dyes, non-eradicable orange dyes, and combinations of the foregoing.

42. The kit of claim 26, wherein said mixture further comprises a binder resin.

43. The kit of claim 26, wherein said mixture further comprises an organic solvent.

44. The kit of claim 26, wherein said mixture further comprises an additive selected from the group consisting of pH buffers, surfactants, biocides, anti-corrosive agents, sequestering agents, anti-crusting agents, rehology control agents, binder resins, film-forming agents, and combinations thereof.

45. The kit of claim 26, wherein said mixture is disposed in a writing instrument.

46. The kit of claim 26, wherein said mixture is disposed in a printer cartridge.

47. The kit of claim 46, wherein said mixture is disposed in a continuous ink-jet printhead.

48. The kit of claim 46, wherein said mixture is disposed in a drop-on-demand ink-jet printhead.

49. The kit of claim 48, wherein said drop-on-demand ink-jet printhead comprises a printhead selected from the group consisting of a piezoelectric ink-jet printhead, and a thermal ink-jet printhead.