MX2014008471A - Reversible thermochromic and photochromic ink pens and markers. - Google Patents

Abstract

Reversible thermochromic and photochromic ink compositions and markers, pens or writing instruments that use them are herein disclosed.

Description

FEATHERS AND MARKERS OF TEBMOCRÓMICA AND PHOTOCRÓMICA INK REVERSIBLE BACKGROUND Ink is a liquid or paste that contains pigments or dyes and is used to color a surface to produce an image, text or design. The ink is used to draw or write with a quill, brush or feather. The thicker inks, in the form of paste, are used extensively in letterpress and lithographic printing. Conventional inks contain solvents, pigments, dyes, resins, lubricants, solubilizers, surfactants, particulate materials, fluorescents and other materials. These materials control the flow and thickness of the ink and the appearance of the ink when it dries.

Ink dyes include pigments and dyes. Pigment inks are used more frequently than dyes because they are more color fixers. Even so, pigments are often more expensive, less consistent in color and have less of a color range than dyes. The pigments are opaque, solid particles suspended in the ink to provide color. The pigment molecules typically bind together in crystalline structures that are 0.1-2 mm in size and usually comprise 5-30 percent of the volume of the ink. The qualities such as hue, saturation and clarity They vary depending on the source and type of pigment.

Dye-based inks can have better color development than pigment-based inks, since they can produce more color density per unit mass. However, because the dyes dissolve in the liquid phase, they have a tendency to soak into the paper, rendering the ink less efficient and potentially allowing the ink to run on the edges of an image. To avoid this problem, dye-based inks are made with solvents that dry quickly or are used with fast-drying printing methods, such as blowing hot air over fresh printing.

Chemicals that change color over a range of temperatures are known as thermochromic systems. Thermochromic chemicals can be manufactured to have a color change that is reversible or irreversible. U.S. Patent No. 5,591,255, entitled "Thermochromic Ink Formulations, Nail Lacquer and Methods of Use", issued January 7, 1997 to Small et al., Describes methods for producing thermochromic coating formulations without known ingredients that are harmful to thermochromic inks. The use of distilled water as a source solution for off-set printing using thermochromic ink is also described.

Thermochromic systems use dyes that are either liquid crystals or leuco dyes. Liquid crystals are used less frequently than leuco dyes because they are very difficult to work with and require highly specialized printing and handling techniques. Thermochromic pigments are a system of interacting parts. Leuco dyes act as dyes, while weak organic acids act as color developers. Solvents or waxes interact with the leuco dyes variably according to the temperature of the system. As is known in the art, thermochromic systems are microencapsulated in a protective coating to protect the contents from the undesired effects of the environment. Each microcapsule is self-contained, having all of the components of the complete system that are required for the color change. The components of the system interact with each other differently at different temperatures. Generally, the system is ordered and colored below a temperature corresponding to the full color point. The system becomes increasingly disordered and begins to lose its color at a temperature corresponding to an activation temperature.

Below the activation temperature, the system is usually colored. Above the activation temperature the system is usually clear or slightly colored. The activation temperature corresponds to a temperature range in which the transition takes place between the full color point and the rinsing point. Generally, the activation temperature is the temperature at which the human eye can perceive that the system is beginning to lose color, or alternatively, beginning to gain color. Currently, thermochromic systems are designed to have activation temperatures over a wide range, from about -20 ° C to about 80 ° C or more. With heating, the system becomes more and more disordered and continues to lose color until reaching a level of disorder at a temperature corresponding to a rinse point. At the rinsing point, the system lacks any recognizable color.

In this way, the thermochromic pigments change from a specific to a clear color in the application of thermal energy or heat in a thermally induced cycle exhibiting well-known hysteresis behavior. Thermochromic pigments come in a variety of colors. When applied to a substrate, such as paper, the pigment exhibits the color of the dye in the core of the microcapsules. In one example, when heat is generally applied in the range of 30 to 32 ° C, the ink changes color from pigment to light. When the substrate is allowed to return to a temperature below about 30 ° C, the ink returns to the original color of the pigment.

U.S. Patent No. 5,785,746, entitled "Preparation Method for Shear-Thinning Water-Based Ball-Point Pen in Compositions and Ball-Point Pens Employing the Same", issued July 28, 1998 to Kito et al. describes the reversible thermochromic microcapsular pigment mixed in an ink composition. The microcapsules have concavities to moderate the stress that results from an external force during use in a ball point pen.

U.S. Patent No. 5,805,245, entitled "Multilayered Dispersed Thermochromic Liquid Crystal", issued September 8, 1998 to Davis, discloses a thermochromic substance, applied to inert films in layers stacked with a non-invasive barrier between each thermochromic substance . The thermochromic substance in each layer responds in a different temperature range so that as the temperature changes, each layer repeats a similar sequence of colors. The substrate is a formulation of water-based acrylic copolymer coated or pearled with a black pigment. A transparent inert film or non-invasive barrier serves as a protective coating for the thermochromic film and as a support for the next layer of the thermochromic substance.

Thermochromic specific coating formulations are known in the art. See, for example, U.S. Patent Nos. 4,720,301, 5,219,625 5,558,700, 5,591,255, 5,997,849, 6,139,779, 6,494,950 and 7,494,537, all of which are expressly incorporated herein by reference. These thermochromic coatings are known to use components in their formulations and are generally reversible in their color change. Thermochromic pigments for use in these coatings are commercially available in various colors, with various activation temperatures, rinsing points and full color dots. Thermochromic coatings can be printed by processes of offset lithography, dry offset, letterpress, gravure, flexography and serigraphy, among others.

Ink pens having thermochromic inks that can be activated by frictional heat in a colorless state have been previously developed. The colored form of the thermochromic ink can not be recovered without considerable difficulty. For example, the reversal of the colorless to colorless thermochromic transition has previously required difficult and burdensome conditions, such as the cooling of the thermochromic ink at a temperature of approximately below the freezing point of the water. In addition to being very difficult to recover or reverse the transition In contrast, the colorless transitions to previous colorings do not allow a transition from color to color and / or black to color.

SHORT DESCRIPTION Presently improved and novel reversible thermochromic and photochromic ink compositions useful in pens and markers are presented herein. The gel ink and ball ink pens described herein use thermochromic and photochromic ink compositions, such as thermochromic ink that is subject to transition from one color to another color, and / or from color to colorless.

In one modality,. The thermochromic ink compositions described herein are activated at about body temperature.

In one embodiment, the thermochromic ink compositions described herein are activated at about room temperature or higher than room temperature.

In one embodiment, the present disclosure relates to compositions for reversible thermochromic and photochromic inks useful in ball point pens for shear thinning, and a ball tip pen or gel ink making use of the ink composition. The markers and pens using the described ink compositions have eliminated the difficulties involved in the thermochromic and photochromic inks of the conventional ball point pen by providing thermochromic ink compositions that allow reversible thermochromic and photochromic transitions from color to color, color to black and novel colorless to colorless transitions. The feathers described here can give a touch of smooth writing.

A reversible thermochromic composition may contain, by way of example, a reversible thermochromic pigment in an amount of 1% to 50% by weight of the ink. The reversible thermochromic pigment is susceptible to a temperature-modulated color change between a first state and a second state along a thermally activated hysteresis loop. A non-thermochromic pigment is also provided. This can be, for example, a dye or photochromic material. The non-thermochromic pigment is of a different color from the reversible thermochromic pigment when the reversible thermochromic pigment is in a colored state, such that the non-thermochromic pigment and the reversible thermochromic pigment together exhibit a first color when the reversible thermochromic pigment is in the first state and together they present a second color when the reversible thermochromic pigment is in the second state. These pigments are mixed for substantially homogeneous distribution in a vehicle like the rest of the composition. This vehicle can be formulated to present an ink for use in a ball tip pen, a gel pen or a marker.

In one aspect, a thermochromic ink formulation displaces the color, either reversibly or irreversibly, from one color to another color in the application of heat to the ink or to the substrate in which the ink resides. The thermochromic ink formulation preferably includes one or more thermochromic pigments in combination with a non-thermochromic pigment.

The ink can be formulated as a gel ink, a pen ink having less viscosity than the gel ink or as a marker ink.

The ink can be formulated such that the thermochromic microcapsules are mixed with a microencapsulated photochromic dye as the non-thermochromic dye.

DETAILED DESCRIPTION A thermochromic ink formulation moves from one color to another color in the application of heat, either to the ink or to the substrate in which the ink has been applied. The thermochromic ink formulation preferably includes at least one thermochromic pigment in combination with a non-thermochromic dye, such as conventional pigment or dye. The non-thermochromic dye can be any type of conventional dye known for the technique.

In some modalities, the ink is formulated as a gel ink, replacing the dyes described herein with the dyes of a conventional gel ink. In other embodiments, the ink is formulated as a pen ink, substituting the dyes described herein with the dyes of a conventional pen ink. In other embodiments, the formulation is used in a marker, substituting the dyes described herein for the dyes of a conventional label.

The thermochromic ink formulation includes at least two components, such that after creating an image on a substrate, for example, paper, and in the application of a certain amount of thermal energy, the image changes from one color to another color. The thermochromic ink formulation may include, for example, thermochromic microcapsules and a conventional pigment which differs in color from the developed color of the thermochromic pigment. The color of the thermochromic ink formulation can be the dominant or visible color, as the ink is applied to the substrate. However, in the application of thermal energy to the ink image, the thermochromic ink is displaced or changed from colored to clear, in order to allow the non-dominant color of the non-thermochromic component to reach be visible In another example, a thermochromic pigment and a non-thermochromic pigment can be combined in relative proportions so that the combined color pigments create a different color together when the thermochromic color develops and a second color when the thermochromic color does not develop. For example, the developed color of the thermochromic pigment may be blue, while the color of the non-thermochromic pigment may be yellow so that, when mixed, they create a green color. Then, in the application of thermal energy, the color of the thermochromic pigment becomes clear, thus allowing the yellow of the non-thermochromic pigment to dominate as the only visible color. The result is that the color of the image changes from green to yellow when it is heated. The image returns to the "mixed" green color when the image is allowed to cool beyond the color development temperature. The mixing of a color changing thermochromic ink with a static color ink provides essentially unlimited potential for the image.

Thermochromic pigments for use in formulations of the present disclosure are commercially available from a number of different manufacturers or suppliers. Manufacturers of thermochromic inks include, but are not limited to, Color Change Corporation (Streamwood, Illinois, US), LCR Hallcrest (Glenview, Illinois, US), Gem'innov (Gemenos, France), ISCA Limited (Newport, Wales, UK), B &H Color Change (London, England, UK), Thermographics Measurements Limited (Flintshire, UK), Fujian Mecode Chemical Industry Company (Quanzhou, Fujian, China) and Matsui Color (Gardena, California, US). Distributors of thermochromic suspensions include, but are not limited to, QCR Solutions Corporation (Port St. Lucie, Florida, US), Woo Jeong Ind. Inc. (Seoul, South Korea), HW Sands Corp. (Jupiter, Florida, US ), Devine Chemicals (Consett, England, UK), Chemical Plus (Bangkok, Thailand) and PMC Chemicals Limited (Altrincham, England, UK).

In a preferred embodiment, a thermochromic ink formulation includes thermochromic microcapsules in the thermochromic suspension that are spherical or substantially spherical in shape and exhibit a narrow particle size distribution to achieve a homogeneous dispersion in the thermochromic ink formulation. The thermochromic microcapsules are preferably all small or substantially all small and more preferably all or substantially all below three micrometers in diameter. The thermochromic suspension preferably does not include flat or hemispherical microcapsules or microcapsules with surface concavities or other irregularities.

In a method for preparing a thermochromic ink formulation, a thermochromic ink formulation is used as the pigment in a conventional gel ink or a pen ink. The viscosity of the combination can be adjusted by adding compatible solvent to or removing the solvent from the combination to achieve the thermochromic ink formulation. The viscosity of the thermochromic ink formulation is preferably adjusted to a predetermined value dependent on the application for which the thermochromic ink formulation is to be used.

In some embodiments, the thermochromic ink formulation includes one or more additives, which may include, but is not limited to, one or more of a fluorescent additive, an optical brightener and an infrared (IR) additive. In a non-limiting embodiment, the additive is used to provide a cover or a safety benefit to a substrate to which the thermochromic ink formulation is applied.

A non-thermochromic dye is preferably mixed with a thermochromic pigment in a ratio in the range of 1: 1 to 3: 1 by weight. The non-thermochromic dye is more preferably mixed with the thermochromic pigment in a ratio in the range of 1.5: 1 to 2.5: 1 by weight. In some embodiments, the non-thermochromic dye is mixed with the thermochromic pigment in a ratio in the range from 1.9: 1 to 2.1: 1 in weight. In one embodiment of the present invention, a non-thermochromic dye is mixed with a thermochromic pigment in a 2: 1 weight ratio.

In some embodiments, the ink is a fluorescent gel ink. In some embodiments, the color of the thermochromic pigment and the color of the non-thermochromic dye are contrasting -or complementary- and create a mixing color in the thermochromic ink formulation below the critical temperature, although any combination of colors can be used within the spirit of the present invention.

In other embodiments, a thermochromic ink formulation includes more than one thermochromic pigment such that at least two temperature-dependent color changes of the thermochromic ink formulation occur. The thermochromic pigments preferably have different critical temperatures such that, in the case of a thermochromic ink formulation with two thermochromic pigments, at a first temperature below the critical temperatures of both thermochromic pigments, the formulation has a first color, which is the sum of the colors of the first thermochromic pigment, the second thermochromic pigment and the non-thermochromic dye. At a temperature above the critical temperature of the first thermochromic pigment but below the critical temperature of the second pigment Thermochromic, the formulation has a second color different from the first color, which is the sum of the colors of the second thermochromic pigment and the non-thermochromic dye. At a temperature above the critical temperatures of the first thermochromic pigment and the second thermochromic pigment, the formulation has a third color different from the first and second colors, which is the color of the non-thermochromic dye. Any number of thermochromic pigments can be combined in this way.

In a non-limiting example, the thermochromic ink is blue, the non-thermochromic pigment is fluorescent ink, the thermochromic pigment is purple below a critical temperature and the thermochromic ink formulation is pink above the critical temperature. In some embodiments, the process is reversible, with the thermochromic pigment returning to a purple color in cooling below the critical temperature. In other modalities, the change of color is irreversible. The reversibility of the color change depends on the hysteresis of the color change. The reversibility of the color change is preferably selected based on the specific application for the thermochromic ink.

In the case of a thermochromic ink formulation where the color changes are reversible, the thermochromic ink formulation can be used as an indicator of visual temperature range, especially when multiple thermochromic pigments are used in the formulation to indicate multiple temperature thresholds. In the case of such a thermochromic ink formulation where the color changes are irreversible, the thermochromic ink formulation can be used as a visual indicator of the maximum temperature range at which the thermochromic ink formulation has been exposed.

The critical temperature is also preferably selected based on the specific application for the thermochromic ink. In some modes, the critical temperature is below the ambient temperature. In other embodiments, the critical temperature is above ambient temperature but below the human body temperature such that the color change is activated by human touch. In some modes, the critical temperature is between 25 and 37 ° C. In some embodiments, the critical temperature is approximately 31 ° C. In still other embodiments, the critical temperature is above the human body temperature such that another source of heat is required to bring the ink to the critical temperature.

In a non-limiting example, a thermochromic pen ink formulation or a thermochromic gel ink formulation of the present invention is converted to a thermochromic marker ink formulation of the present invention by adding about 10% water by volume to the thermochromic pen ink formulation or thermochromic gel ink formulation.

In some embodiments, a gel pen of the present invention includes a thermochromic gel ink formulation of the invention. In some embodiments, the gel pen includes a ball tip of approximately 8-mm. In some embodiments, the ball tip is at least 8 mm in diameter. An 8-mm ball point in diameter allows passage of the thermochromic particles without damaging the particles for some thermochromic gel ink formulations of the present invention.

In some embodiments, a marker of the present invention includes a marker ink composition of the present invention. In some embodiments, the marker is a mechanical valve type marker, also known as a paint marker, with a porous felt tip tip.

Accordingly, it will be understood that the embodiments of the invention described herein are only illustrative of the application of the principles of the invention. Reference herein to the details of the illustrated modes is not proposed to limit the scope of the claims, which by themselves cite those characteristics considered essential for the invention.

Review of Thermochromic Pigments The reversible thermochromic and photochromic ink pens described herein contain thermochromic systems that are prepared by combining a molecule or color-forming molecules such as leuco dyes that are capable of extended conjugation by proton gain or electron donation; a developer or developer or color developers who donate a proton or accept an electron; and a single solvent or a mixture of co-solvents. The solvent or mixture of co-solvents are chosen based on the melting point and establish the thermochromic temperature range of the system. These formulations are then microencapsulated within a polymeric shell.

These microcapsules encapsulate a thermochromic system mixed with a solvent. The thermochromic system has a material property of a thermally conditional hysteresis window that has a thermal separation. The thermochromic encapsulated dyes undergo a color change over a specific temperature range. By way of example, a dye can change from a particular color at low temperature to colorless at a high temperature, such as red at 21 ° C and colorless at above 33 ° C. The color change temperature is controllable, such that the color change can take place at different temperatures. In one example, the color change may occur at a temperature only below an external body temperature of the person so that a color change occurs in response to a human touch or may transition to approximately room temperature. For example, the ideal temperature of the color change can vary from 12 ° C to 15 ° C, 21 ° C to 27 ° C, 23 ° C to 27 ° C, 27 ° C to 33 ° C. Traditional pigments and thermochromic inks with specified color and transition temperature ranges can be formulated and produced in commercial order from such companies as Chromatic Technologies, Inc. of Colorado Springs, Colorado.

Various types of ingredients are traditionally added to ink formulations. The combination of all the ingredients in an ink, different from the pigment, is called the vehicle. The vehicle takes the pigment to the substrate and bonds the pigment to the substrate. The correct combination of the vehicle ingredients will result in the wetting of an ink. This wetting means that the vehicle forms a film absorbed around the pigment particles. The main ingredient in an ink is the binder. This can be a resin, lacquer or varnish or some other polymer. The characteristics of the binder vary depending on the type of printing that is being made and the final product wanted. The second main ingredient is the dye itself, for example, as described above. The remaining ingredients are added to increase the color and printing characteristics of the binder and colorant. These remaining ingredients may include reductants (solvents), waxes, surfactant, thickeners, dryers and / or UV inhibitors.

Definitions Activation temperature - The temperature above which the ink has almost reached its final light or light end point. The color begins to disappear at approximately 4 ° C below the activation temperature and will be between the colors within the activation temperature range.

Ball tip pen - As referred to herein, ball tip pens and gel ink pens are interchangeable embodiments of pen media utilizing reversible thermochromic and photochromic ink compositions of the present disclosure. A ball point pen can also be referred to as a marker. A ball point pen can also be referred to as a writing instrument.

Rinse Point - The temperature at which the color of a thermochromic system decreases to a minimum amount and does not appear to lose the additional color density in the additional heating.

Full Color Point - The temperature at which a thermochromic system has reached the maximum color density on cooling and appears to gain additional color density if cooled at a lower temperature.

A gel ink, as used herein, refers to a fluid composition that includes a pigment suspended in a gel based. Gel inks typically have a higher viscosity than pen inks and may have a higher concentration of pigment. Gel inks are available in a wide variety of colors, including, but not limited to, pastel colors, bright colors, metallic colors, glossy colors, and opalescent colors. The pigments in a gel ink are generally not in a dissolved state.

Gel ink pen - As referred to herein, ball tip pens and gel ink pens are interchangeable embodiments of pen media utilizing reversible thermochromic and photochromic ink compositions of the present disclosure. A gel ink pen can also be referred to as a marker. A gel ink pen can also be referred to as a writing instrument.

Hysteresis - The difference in the temperature profile of a thermochromic system when heated from system when it is cooled.

Hysteresis Window - The temperature difference in terms of degrees that a thermochromic system moves as measured between the graph of the chroma derivative of a spectrophotometer reading between the cooling curve and the heating curve.

A marker, as used herein, refers to any writing instrument with a porous tip or felt tip made of a fibrous material to supply ink.

A pen, as used herein, refers to any ink-based, non-marking writing instrument that includes, but is not limited to, ball point pens, rolling ball pens and fountain pens.

A pen ink, as used herein, refers to a fluid or gel composition that includes a pigment and a carrier or vehicle in which the pigment is suspended. In some modalities, the vehicle is water. In other embodiments, the solvent is a non-aqueous solvent, such as an organic solvent such as alcohol. Photochromic ink - A mixture of dyes, solvents and additives (encapsulated or unencapsulated) that can be subjected to reversible color change in response to exposure to light of various wavelengths.

Thermochromic system - A mixture of dyes, developers, solvents and additives (encapsulated or non-encapsulated) that can be subjected to reversible color change in response to temperature changes.

Thermochromic ink - An ink containing a pigment formed from a mixture of dyes, developers, solvents and additives that are encapsulated and can undergo reversible color change in response to temperature changes. The color change is based on the action of microencapsulated and revealing leuco dyes, which are referred to herein as thermochromic pigments. The thermochromic pigments can be sold as dry powders or in suspensions based on encapsulated dye water.

Leuco dye - A leuco dye is a dye whose molecules can acquire two forms, one of which is colorless.

Thermochromic inks The thermochromic inks useful in ball point pens and gel ink pens contain microcapsules, which encapsulate a thermochromic system mixed with a solvent. The thermochromic system has a material property of a thermally conditional hysteresis advantage that has a thermal separation. These inks can be improved according to the instrumentalities described herein by using a co-solvent that is combined with the thermochromic system and selected from the group consisting of myristic acid derivatives, behenylic acid derivatives, palmitic acid derivatives and combinations thereof. This material can be provided in an amount effective to reduce the thermal separation in the complete ink to a level less than eighty percent separation that would otherwise occur if the material was not added. This effective amount may vary, for example from 12% to 15% by weight of the composition.

The thermochromic system may contain, for example, at least one organic chromatic compound and solvents.

An example of a thermochromic system includes a leuco dye having a lactone ring structure and a phenolic developer or developer. Within encapsulated thermochromic systems, complexes are formed between the dye and the weak acid developer or developer that allows the lactone ring structure of the leuco dye to be opened. The nature of the complex is such that the hydroxyl groups of the phenolic developer or developer interact with the open lactone ring structure forming a supra-molecular structure that orders dyes and developers such that a color is formed. Color is formed from this supra-molecular structure because the dye molecule in the open ring structure is cationic in nature and the molecule has conjugation extended that allows absorption in the visible spectrum in this way producing a colored species. The color perceived by the eye is that visible light is not absorbed by the complex. The nature of the dye / developer or developer complex depends on the molar ratio of the dye and developer or developer. The stability of the colored complex is determined by the affinity of the solvent itself, the developer or developer or the dye / developer or developer complex. In a solid state, below the full color point, the dye / developer or developer complex is stable. In the molten state, the solvent destabilizes the dye / developer or developer complex and equilibrium is more favorably displaced to a developer or developer / solvent complex. This happens at temperatures above the full color point because the dye / developer or developer complex is interrupted and the extended conjugation of the p-cloud electrons that allow the absorption of visible light is destroyed.

The melting and crystallization profile of the solvent system determines the nature of the thermochromic system. The full color point of the system occurs when the maximum amount of dye develops. In a state of crystallized solvent, the dye / developer or developer complex is favored where the dye and the developer or developer they exist in a single crystallized structure, often interspersed with each other to create an extended conjugate system. In the molten state, the solvent (s), in excess, has enough kinetic energy to disrupt the stability of the dye / developer or developer complex and the thermochromic system becomes discolored.

The addition of a co-solvent with a significantly higher melting point than the other dramatically changes the fusion properties of both of the solvents. By mixing two solvents that have certain properties, a mixture can be achieved that possesses a eutectic melting point. The melting point of a eutectic mixture is lower than the melting point of any of the cosolvents alone and the melting point is more acute, which occurs over a smaller temperature range. The degree of destabilization of the dye / developer or developer complex can be determined by the choice of solvents. By creating unique eutectic mixtures, both the rinsing point and the full color point can be altered simultaneously. The degree of hysteresis then shifts in both directions simultaneously as the acuity of the melting point increases.

Temperature changes in thermochromic systems are associated with color changes. If this change is plotted on a graph that has temperature axes and color, the curves do not align and are misaligned between the heating cycle and the cooling cycle. The full color against the temperature curve has the shape of a loop. This result shows that the color of a thermochromic system does not only depend on the temperature, but also on the thermal history, that is, whether the particular color was reached during heating or during cooling. This phenomenon is generally referred to as a hysteresis cycle and specifically referred to herein as color hysteresis or the hysteresis window. Decreasing the width of this hysteresis window to approximately zero would allow a single value for the full color point and a single value for the rinsing point. This would allow a reliable color transition that is observed with respect to whether the system is being heated or cooled. However, the concept of decreasing the separation through the hysteresis window is difficult to achieve in practice. Thus, it is an object of the present disclosure to provide thermochromic systems with a reduced hysteresis window achieved by moving both the full color point and the rinsed point such as in memory inks, for example.

It is also an objective of this disclosure to provide extended hysteresis window formulations in the ink formulations.

Leuco Dyes Leuco dyes much more commonly used as color formers in thermochromic systems of the present disclosure include, but are not limited to, generally; spirolactones, fluoranos, spiropyrans and fulgida; and more specifically; diphenylmethane phthalide derivatives, phenylindolylphthalide derivatives, indolylphthalide derivatives, diphenylmethane azaphthalide derivatives, phenyl indolylazaphthalide derivatives, fluoran derivatives, styrynoquinoline derivatives and diaza-rhodamine lactone derivatives which may include: 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide; 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide; 3,3-bis (l-n-butyl-2-methylindol-3-yl) phthalide; 3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide; 3- [2-ethoxy-4- (N-ethylanilino) phenyl] -3- (l-ethyl-2-methylindol-3-yl) -4-azaphthalide; 3,6-dimethoxyfluoran; 3,6-di-n-butoxifluoran; 2-methyl-6- (N-ethyl-N-p-tolylamino) fluoran; 3-chloro-6-cyclohexylaminofluoran; 2-methyl-6-cyclohexylamino-fluoran; 2- (2-chloroanilino) -6-di-n-butylamino fluoran; 2- (3-trifluoromethylanilino) -6-diethylaminofluoran; 2- (N-methyl-anilino) -6- (N-ethyl-N-p-tolylamino) fluoran, 1,3-dimethyl-6-diethylaminofluoran; 2-chloro-3-methyl-6-diethylamino fluoran; 2-anilino-3-methyl-6-diethylaminofluoran; 2-anilino-3-methyl-6-di-n-butylamino fluoran; 2-xylidino-3-methyl-6-diethylamino-fluoran; 1,2-benzo-6-diethylaminofluoran; 1,2-benzo-6- (N- ethyl-N-isobutylamino) fluoran, 1,2-benzo-6- (N-ethyl-N-isoamylamino) fluoran; 2- (3-methoxy-4-dodecoxystyryl) quinoline; spiro [5 H- (1) benzopyran (2,3-d) pyrimidin-5,1 '(3'H) isobenzofuran] -3'-one; 2- (diethylamino) -8- (diethylamino) -4-methyl-spiro [5H- (1) benzopyran (2,3-d) pyrimidin-5,1 '(3'H) isobenzofuran] -3'- ona; 2- (di-n-butylamino) -8- (di-n-butylamino) -4-methyl-spiro [5H- (1) benzopyran (2,3-d) pyrimidin-5,1 '(3'H) iso-benzofuran] -3'-one; 2- (di-n-butylamino) -8- (diethylamino) -4-methyl-spiro [5H- (1) enzopyran (2,3-d) pyrimidin-5, r (3'H) iso-benzofuran] - 3 '-one; 2- (di-n-butylamino) -8 (N-ethyl-N-isoamyl-amino) -4-methyl-spiro [5H- (1) 5,1 '(3'II) isobenzofuran] -3'-one; and 2- (di-n-butylamino) -8- (di-n-butylamino) -4-phenyl and trisubstituted pyridines.

Developers The weak acids that can be used as color developers act as proton donors, changing the dye molecule between its leuco form and its protonated colored form; stronger acids make the change irreversible. Examples of developers used in the present disclosure include but are not limited to: bisphenol A; bisphenol F; tetrabromobisphenol A; 1'-methylenedi-2-naphthol; 1,1,1-tris (4-hydroxyphenyl) ethane; 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane; 1,1-bis (4-hydroxy-3-methylphenyl) cyclohexane; 1,1-bis (4-hydroxyphenyl) -cyclohexane; 1,3-bis [2- (4-hydroxyphenyl) -2-propyl] benzene; 1-naphthol; 2- naphthol; 2,2 bis (2-hydroxy-5-biphenylyl) propane; 2,2-bis (3-cyclohexyl-4-hydroxy) propane; 2,2-bis (3-sec-butyl-4-hydroxyphenyl) propane; 2,2-bis (4-hydroxy-3-isopropylphenyl) -propane; 2,2-bis (4-hydroxy-3-methylphenyl) ropano; 2,2-bis (4-hydroxyphenyl) propane; 2,3,4-trihydroxydiphenylmethane; 4,4'- (1,3-Dimethylbutylidene) diphenol; 4,4 '- (2-Ethylidene) diphenol; 4,4 '- (2-hydroxybenzylidene) bis (2,3,6-trimethylphenol); 4,4'-biphenol; 4,4'-dihydroxydiphenyl ester; 4,4'-dihydroxy-diphenylmethane; 4,4'-methylidenebis (2-methylphenol); 4- (1,1,3,3-tetramethylbutyl) phenol; 4-phenylphenol; 4-tert-butylphenol; 9,9-bis (4-hydroxyphenyl) fluorine; 4,4 '- (ethane-1,1-diyl) diphenol; alpha, alpha'-bis (4-hydroxyphenyl) -1,4-diisopropylbenzene; alpha, alpha, alpha'-tris (4-hydroxyphenyl) -1-ethyl-4-isopropylbenzene; Benzyl 4-hydroxybenzoate; bis (4-hydroxyphenyl) sulfide; bis (4-hydroxyphenyl) sulfone; Propyl 4-hydroxybenzoate; Methyl 4-hydroxybenzoate; resorcinol; 4-tert-butyl catechol; 4-tert-butyl-benzoic acid; 1,1'-methylenedi-2-naphthol-l, 1,1-tris (4-hydroxyphenyl) ethane; 1,1-bis (3-cyclohexyl-4-hydroxy-phenyl) cyclohexane; 1,1-bis (4-hydroxy-3-ethylphenyl) cyclohexane; 1,1-bis (4-hydroxyphenyl) cyclohexane; 1,3-bis [2- (4-hydroxyphenyl) -2-propyl] benzene; 1-naphthol 2,2'-biphenol; 2,2-bis (2-hydroxy-5-biphenylyl) propane; 2,2-bis (3-cyclohexyl-4-hydroxyphenyl) propane; 2,2-bis (3-sec-butyl-4-hydroxyphenyl) -propane; 2,2-bis (4-hydroxy-3-isopropylphenyl) propane; 2,2-bis (4-hydroxy-3-methylphenyl) propane; 2,2-bis (4-hydroxyphenyl) - propane; 2,3,4-trihydroxydiphenylmethane; 2-naphthol; 4,4 '- (1,3-dimethylbutylidene) diphenol; 4,4 '- (2-ethylhexylidene) diphenol 4,4 '- (2-hydroxybenzylidene) bis (2,3,6-trimethylphenol); 4,4'-biphenol; ether, 4'-dihydroxydiphenyl; 4,4'-dihydroxy-diphenylmethane; 4,4'-ethylidenebisphenol; 4, '-methylenebis (2-methylphenol); 4- (1,1,3,3-tetramethylbutyl) phenol; 4-phenylphenol; 4-tert-butylphenol; 9,9-bis (4-hydroxyphenyl) fluorine; alpha, alpha'-bis (4-hydroxyphenyl) -1,4-diisopropylbenzene; a, a, a-tris (4-hydroxyphenyl) -1-ethyl-4-isopropylbenzene; Benzyl 4-hydroxybenzoate; bis (4-hydroxyphenyl) sulfide; Methyl 4-hydroxybenzoate of bis (4-hydroxyphenyl) sulfone; resorcinol; tetrabromo-bisphenol A; 3,5-di-tert-butyl-salicylic acid; Zinc 3,5-di-tert-butylsalicylate; 3-phenyl salicylic acid; acid 5-tert-butyl salicylic; 5-n-octyl salicylic acid; 2,2'-biphenol; 4,4'-di-tert-butyl-2,2'-biphenol; 4,4'-di-n-alkyl-2,2'-biphenol; and 4,4'-di-halo-2,2'-biphenol, wherein halo is chloro, fluoro, bromo or iodo.

Solvents The best solvents to use within the thermochromic system are those that have low reactivity, have a relatively large molecular weight (ie above 100) and are relatively non-polar. Aldehydes of very low molecular weight, ketones, diols and aromatics should not be used as solvents within the thermochromic system.

The thermochromic inks described herein use a co-solvent which is combined with the thermochromic system and are selected from the group consisting of myristic acid derivatives, behenylic acid derivatives, palmitic acid derivatives and combinations thereof. This material can be provided in an amount effective to reduce the thermal separation in the total ink to a level less than eighty percent separation that would otherwise occur if the material was not added. This effective amount may vary, for example from 12% to 15% by weight of the composition.

The addition of a co-solvent with a significantly higher melting point than the other dramatically changes the fusion properties of both of the solvents. By mixing two solvents having certain properties, a mixture having a eutectic melting point can be achieved. The melting point of a eutectic mixture is less than the melting point of any of the cosolvents alone and the melting point is more acute, occurring over a smaller temperature range. The degree of destabilization of the dye / developer or developer complex can be determined by the choice of solvents. By creating unique eutectic mixtures, both the rinsing point and the full color point can be altered simultaneously. The degree of hysteresis then shifts in both directions simultaneously as the sharpness of the melting point increases. The copending application no. 13 / 363,070 filed January 31, 2012 describes thermochromic systems with controlled hysteresis, and is incorporated herein by reference to the same degree as if it were fully replicated herein. In accordance with the instrumentalities described herein, the icroencapsulated pigments can be formulated to have color transition temperatures through a hysteresis window of less than five degrees centigrade or more than 60 or 80 degrees centigrade.

The properties of at least one of the co-solvents used in the present disclosure include having a long fatty end of between 12 and 24 carbons and having a melting point that is about 70 ° C to about 200 ° C higher than the associated with the co-solvent. The co-solvents are preferably also completely miscible in any ratio.

Solvents and / or co-solvents used in thermochromic generally can include, but are not limited to, sulfur, ethers, ketones, esters, alcohols and acid amides. These solvents can be used alone or in mixtures of 2 or more. Examples of the sulfides include: di-n-octyl sulfide; di-n-nonyl sulfide; di-n-decyl sulfide; di-n-dodecyl sulfide; sulfur di-n- tetradecyl; sulfide .di-n-hexadecyl; di-n-octadecyl sulfide; octyl dodecyl sulfide; diphenyl sulfide; dibenzyl sulfide; ditolyl sulfide; sulfur diethylphenyl; dinaphthyl sulfide; 4,4'-dichlorodiphenyl sulfide; and 2, 4,5,4'-tetrachlorodiphenyl sulfide. Examples of the ethers include: aliphatic esters having 10 or more carbon atoms, such as dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, ditridecyl ether, ditetradecyl ether, ether dipentadecyl, dihexadecyl ether, dioctadecyl ether, diethylene diol dimethyl ether, dimethyldiol dimethyl ether, dodecanediol dimethyl ether, tridecanediol dimethyl ether, diethylene diol ether and diethylene dicanediol ether; alicyclic ethers such as s-trioxane; and aromatic ethers such as phenyl ether, benzyl phenyl ether, dibenzyl ether, di-p-tolyl ether, 1-methoxynaphthalene and 3,4,5-trimethoxytoluene.

Examples of ketone solvents include: aliphatic ketones having 10 or more carbon atoms, such as 2-decanone, 3-decanone, 4-decanone, 2-undecanone, 3-undecanone, 4-undecanone, 5-undecanone, 6- undecanone, 2-dodecanone, 3-dodecanone, 4-dodecanone, 5-dodecanone, 2-tridecanone, 3-tridecanone, 2-tetradecanone, 2-pentadecanone, 8-pentadecanone, 2-hexadecanone, 3-hexadecanone, 9-heptadecanone, 2-pentadecanone, 2-octadecanone, 2- nonadecanone, 10-nonadecanone, 2-eicosanone, 11-eicosanone, 2-heneicosanone, 2-docosanone, laurone and stearone; aryl alkyl ketones having 12 to 24 carbon atoms, such as n-octadecatophenone, n-heptadecatophenone, n-hexadecatophenone, n-pentadecatophenone, n-tetradecatophenone, 4-n-dodeca-acetophenone, n-tridetophenone, 4-n- undecanoacetophenone, n-laurophenone, 4-n-decanoacetophenone, n-undecanophenone, 4-n-nonylacetophenone, n-decanophenone, 4-n-octylacetophenone, n-nonanophenone, 4-n-heptylacetophenone, n-octanophenone, 4-n- Hexylacetophenone, 4-n-cyclohexyl acetophenone, 4-tert-butylpropiophenone, n-heptafenone, 4-n-pentylacetophenone, cyclohexyl phenyl ketone, benzyl n-butyl ketone, 4-n-butylacetophenone, n-hexanophenone, 4-isobutylacetophenone, 1- acetonaphthone, 2-acetonaphthone and lopentyl phenyl ketone; aryl aryl ketones such as benzophenone, benzyl phenyl ketone and dibenzyl ketone; and alicyclic ketones such as cyclooctanone, cyclododecanone, cyclopentadecanone and 4-tert-butylcyclohexanone, ethyl caprylate, octyl caprylate, stearyl caprylate, myristyl caprate, stearyl caprate, docosyl caprate, 2-ethylhexyl laurate, n-laurate -decyl, 3-methylbutyl myristate, cetyl myristate, isopropyl palmitate, neopentyl palmitate, nonyl palmitate, cyclohexyl palmitate, n-butyl stearate, 2-methylbutyl stearate, stearyl stearyl behenate 3,5,5- trimethylhexyl, n-undecyl stearate pentadecyl stearate, stearyl stearate, cyclohexylmethyl stearate, isopropyl behenate, hexyl behenate, lauryl behenate, behenyl behenate, cetyl benzoate, stearyl p-tert-butylbenzoate, dimyristyl phthalate, distearyl phthalate, dimyristyl oxalate , dicetyl oxalate, dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyl adipate, dilauryl azelate, di-n-nonyl sebacate, 1,18-dineopentyloctadecylmethylenedicarboxylate, ethylene glycol dimyristate, propylene glycol dilaurate, propylene glycol distearate , hexylene glycol dipalmitate, 1,5-pentanediol dimyristate, 1,2,6-hexanetriol trimiristate, 1,4-cyclohexanediol didecanoate, 1,4-cyclohexanedimethanol dimyristate, xylene glycol dicaprate and xylene glycol distearate.

The ester solvents can be selected from fatty acid esters saturated with a branched aliphatic alcohol, unsaturated fatty acid esters or a saturated fatty acid having one or more branches or substituents with an aliphatic alcohol having one or more branches or or more carbon atoms, cetyl butyrate, stearyl butyrate and behenyl butyrate which includes 2-ethylhexyl butyrate, 2-ethylhexyl behenate, 2-ethylhexyl myristate, 2-ethylhexyl caprate, 3.5.5 laurate -trimethylhexyl, 3,5,5-trimethylhexyl palmitate, 3,5,5-trimethylhexyl stearate, 2-methylbutyl caproate, 2-methylbutyl caprylate, 2-methylbutyl caprate, 1-ethylpropyl palmitate, 1-ethylpropyl stearate, 1-ethylpropyl behenate, laurate 1- ethylhexyl, 1-ethylhexyl myristate, 1-ethylhexyl palmitate, 2-methylpentyl caproate, 2-methylpentyl caprylate, 2-methylpentyl caprate, 2-methylpentyl laurate, 2-methylbutyl stearate, 2-methylbutyl stearate, 3-methylbutyl stearate, 2-methylheptyl stearate, 2-methylbutyl behenate, 3-methylbutyl behenate, 1-methylheptyl stearate, 1-methylheptyl behenate, 1-ethylpentyl caproate, 1-ethylpentyl palmitate, stearate 1-methylpropyl, 1-methyloctyl stearate, 1-methylhexyl stearate, 1,1-dimethylpropyl laurate, 1-methylpentyl caprate, 2-methylhexyl palmitate, 2-methylhexyl stearate, 2-methylhexyl behenate, laurate 3,7-dimethyloctyl, 3,7-dimethyloctyl myristate, 3,7-dimethyloctyl palmitate, stearate 3,7-dimethyloctyl, 3,7-dimethyloctyl behenate, stearyl oleate, behenyl oleate, stearyl linoleate, behenyl linoleate, 3,7-dimethyloctyl erucate, stearyl erucate, isostearyl erucate, cetyl isostearate, stearyl isostearate, 2-methylpentyl 12-hydroxystearate, isostearyl 2-ethylhexyl 2-ethylhexyl 2-ketomyristate 2-ethylhexyl-2-fluoromyristate butyrate cetyl, stearyl butyrate and behenyl butyrate.

Examples of the alcohol solvents include monohydric aliphatic saturated alcohols such as decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol, behenyl alcohol and docosyl alcohol; unsaturated aliphatic alcohols such as allyl alcohol and oleyl alcohol, alicyclic alcohols such as cyclopentanol, cyclohexanol, cyclooctanol, cyclododecanol and 4-tert-butylcyclohexanol; aromatic alcohols such as 4-methylbenzyl alcohol and benzhydrol; and polyhydric alcohols such as polyethylene glycol. Examples of acidic amides include acetamide, propionamide, butyramide, capronamide, caprylamide, capric amide, lauramide, myristamide, palmitamide, stearamide, behenamide, oleamide, erucamide, benzamide, capronanilide, caprylanilide, capric anilide, lauranylide, myristanilide, palmitanilide, stearanilide, behenanilide, oleanilide, erucanilide, N-methylcapronamide, N-methylcaprylamide, N-methyl (capric amide), N-methyl-lauramide, N-methylmiristamide, N-methylpalmitamide, N-methyl-stearamide, N-methylbehenamide, N-methylol amide, N- metilerucamide, N-ethyl-lauramide, N-etilmiristamida, N-etilpalmitamida, N-etilestearamida, N-etiloleamida, N-butil-lauramida, N-butilmiristamida, N- butylpalmitamide, N-butyltearamide, N-butylleamide, N-octyl lauramide, N-octylmiristamide, N-octylpalmitamide, N-octyltearamide, N-octyllelamide, N-dodecyl lauramide, N-dodecylmistamide, N-dodecylpalmitamide, N-dodecyl- stearamide, N-dodecylolamide, dilauroylamine, dimiris-toylamine, dipalmitoylamine, distearoylamine, dioleoylamine, trilauroylamine, trimyristoylamine, tripalmitoylamine, tristearoylamine, trioleonylamine, succinamide, adipamide, glutaramide, malonamide, azelamide, maleamide, N-methylsuccin ida, N-methyladipamide, N-methylglutaramide, N-methylmalonamide, N-methylazelamide, N-ethylsuccinamide, N-ethyladipamide, N-ethylglutaramide, N-ethylmalonamide, N-ethylaceulide, N-butylsuccinamide, N-butyladipamide, N-butylglutaramide, N-butylmalonamide, N- octyladipamide and N-dodecyldipamide.

Among these solvents, it has been found that certain solvents have the effect of reducing the hysteresis window. The solvent can be material combined with the thermochromic system, for example, to reduce the thermal separation through the hysteresis window to a level of 80%, 70%, 50%, 40%, 30% or less of the thermal separation that would exist if the co-solvent was not present. The co-solvent is selected from the group consisting of misric acid derivatives, behenyl acid derivatives, palmitic acid derivatives and combinations thereof. Generally, these materials include myristates, palmitates, behenates, together with myristyl, stearyl and behenyl materials and certain alcohols. In one aspect, these materials are preferably solvents and co-solvents from the group including isopropyl myristate, isopropyl palmitate, methyl palmitate, methyl stearate, myristyl myristate, cetyl alcohol, stearyl alcohol, behenyl alcohol, stearyl behenate. and stearamide. These co-solvents are added to the encapsulated thermochromic system in an amount which, for example, varies from 9% to 18% by weight of the thermochromic system as encapsulated, i.e., excluding the weight of the capsule. This range is more preferably from about 12% to about 15% by weight.

Light stabilizers Thermochromic inks containing leuco dyes are available for all major ink types such as ultraviolet, water based and epoxy curing. The properties of these inks differ from the process inks. For example, most thermochromic inks contain thermochromic systems such as microcapsules, which are not inert and insoluble since they are ordinary process pigments. The size of the microcapsules that contain the thermochromic systems typically vary between 3-5 mm which is more than 10 times larger than the pigment particles regular found in most inks. The post-printing functionality of thermochromic inks can be adversely affected by ultraviolet light, temperatures in excess of 140 ° C and aggressive solvents. The life time of these inks is sometimes very limited due to the degradation caused by exposure to ultraviolet light from sunlight.

In other examples, the additives used to fortify encapsulated thermochromic systems by imparting a resistance to ultraviolet light degradation by having a double functionality also reduce the separation width on the hysteresis window. Light stabilizers are additives that prevent the degradation of a product due to exposure to ultraviolet radiation. Examples of light stabilizers used in thermochromic systems of the present disclosure and which may also influence the hysteresis window include but are not limited to: avobenzone, disodium bisdisulizol, diethylaminohydroxybenzoyl hexyl benzoate, Ecamsul, ethyl anthranilate, 4-aminobenzoic acid, Cinoxate, ethylhexyl triazone, homosalate, 4-methylbenzylidene camphor, octyl methoxycinnamate, octyl salicylate, Padimate O, phenylbenzimidazole sulfonic acid, polysilicone-15, trolamine salicylate, bemotrizinol, benzophenones 1-12, dioxybenzone, drometrizol trisiloxane iscotrizinol, octocrylene, oxybenzone, sulisobenzone, bisoctrixol, titanium dioxide and zinc oxide.

Careful preparation of encapsulated reversible thermochromic material increases coating stability in the presence of low molecular weight polar solvents that are known to adversely affect thermochromic performance. An expert in the microencapsulation technique can use well-known processes to increase the stability of the microcapsule. For example, it is understood that increasing the crosslink density will reduce the permeability of the capsule wall, and thus also reduce the deleterious effects of the low molecular weight solvents. It is also commonly understood that, under certain conditions, weak acids with a pKa greater than about 2 can catalyze the polymerization of the microcapsule wall and increase the resulting crosslink density. It is currently the case that using formic acid as a catalyst increases the stability of the solvent of blue thermochromic microcapsules in the presence of low molecular weight ketones, diols and aldehydes at room temperature. Furthermore, it is well understood that increasing the diameter of the thermochromic microcapsule can result in increased solvent stability.

The selection of material for use as the Non-polar solvent for the thermochromic dye and developer or developer of color that is encapsulated within the thermochromic pigment determines the temperature at which the color change is observed. For example, changing the solvent from a single component to a two-component solvent system can change the temperature at which the full color is perceived to be nearly 7 ° C from just below 19 ° C to 12 ° C. The present disclosure shows how to apply this knowledge in preparing resin-based vehicle coatings for use in can and roll coatings with full color temperatures, i.e. the temperature at which the maximum color intensity is observed, so low as -5 ° C and as high as 65 ° C. None of the adverse effects on the physical properties of the resulting coating were observed since the full color temperature was changed over the previous range by the use of different straight chain alkyl esters, alcohols, ketones or amides.

Thermochromic materials that include encapsulated thermochromic systems with a variety of color properties can be purchased in commercial order from such companies as Chromatic Technologies, Inc., of Colorado Springs, Colorado.

Control over observed color intensity is demonstrated in various ways, generally by providing increased amounts of pigment. For a coating Typically, the material thickness varies from 1 mg / in2 to 6 mg / in2. Very intense color is observed for coatings with thicknesses greater than approximately 3 mg / in2. Increasing the thermochromic pigment solids can also result in a more intense observed color even when the coating thickness is decreased. However, dry film properties such as flexibility and hardness can be compromised if too much thermochromic pigment is incorporated. The optimum range of thermochromic pigment solids is within 5 to 40% by weight of the coating.

Vehicle The physical properties of the finished coating can be significantly affected by the selection of the resin that is used. When no resin is used in the formulation of a reversible thermochromic coating, a matte finish is achieved which is capable of being formed into ends of cans, flanges, lids and / or other closures. While this result may be desired, the inclusion of a monomer, oligomer, monomer, relatively low molecular weight resin, low viscosity or combination thereof, may increase the gloss and affect other physical film properties such as hardness, flexibility and chemical resistance. The resin is designed to supplement the total solids deposited on the substrate, from this way to impact the physical properties of the dry film. Any resin material, monomer, oligomer, polymer or combination thereof that can be polymerized in the commercially available can and roll coating material is suitable for inclusion in the current reversible thermochromic tins and roll coating formulation. Acceptable classes of resins include, but are not limited to polyester, urethane, acrylic acid and acrylate, or other types of resin systems with suitably high solids content.

Encapsulation Process Almost all thermochromic systems require encapsulation for protection. As is known in the art, the much more common process for encapsulation is interfacial polymerization. During interfacial polymerization the internal phase (material inside the capsule), external phase (capsule wall material) and water are combined through high speed mixing. By controlling all the temperature, pH, concentrations and velocity precisely mixed, the external phase will surround the droplet of the internal phase while crosslinking by itself. Usually the capsules are between 3-5 mm or smaller. Such small capsule sizes are referred to as microcapsules and the thermochromic system within the microcapsules are microencapsulated. Microencapsulation allows systems Thermochromic materials that are used in a wide variety of materials and products. The size of the microcapsules requires some adjustments to adapt the particular printing and manufacturing processes.

The size distribution of the microcapsules can vary from as much as 0.2pm to 100pm. Additional example techniques of physical microencapsulation include but are not limited to tray coating, air suspension coating, centrifugal extrusion, vibration nozzle and spray drying. Examples of chemical microencapsulation techniques include but are not limited to interfacial polymerization, in-situ polymerization and matrix polymerization. Exemplary polymers used in the preferred chemical microencapsulation include but are not limited to polyester, polyurethane, polyureas, urea-for-aldehyde, epoxy, melamine-formaldehyde, polyethylene, polyisocyanates, polystyrene, polyamides, and polysilanes.

The capsule isolates the thermochromic system from the environment, but the barrier that the capsule provides is soluble by itself to certain solvents. Therefore, the microcapsule constituents interact with the environment to the same degree. The solubility parameter describes how at most one material will swell in the presence of different solvents. This swelling will directly impact the characteristics of the reaction potential within the capsule, as well as potentially make the capsule more permeable, both of which will probably adversely affect the thermochromic system. The solvents in which the microcapsules are exposed are chosen so as not to destroy, or affect, the thermochromic system within.

The capsule is hard, thermally stable and relatively impermeable. The infiltration of compounds through the capsule is stopped or decelerated to the point that the characteristics of the dye are not affected. The contamination of the thermochromic system inside the capsule by the environmental solvents affects the shelf life of the thermochromic system. Therefore, the formulation of the applied thermochromic system, as an ink for example, must be carefully considered.

In one embodiment of the present disclosure, the capsules are made of urea formaldehyde. A technique used to produce thermochromic encapsulated systems is to combine water, dye, oil and urea formaldehyde and mix to create a very fine emulsification. Due to the properties of the compounds, the oil and dye end up inside the capsule and the water ends up outside, with urea formaldehyde constituting the capsule itself. The capsule can then be thermo-stable, similar to other resins, such as formica. The thermo-stable substance is very hard and will not break, even at higher temperatures than the encapsulated thermochromic system is designed to be exposed. The formaldehyde urea capsule is almost completely insoluble in most solvents, but it is permeable to certain solvents that could destroy the thermochromic color system's ability and discolor over a whole range of temperatures.

The degree to which the capsules will react with their environment is influenced by the pH of the surrounding medium, the permeability of the capsule, the polarity and reactivity of the compounds in the medium and the solubility of the capsule. The preferred medium used in forming encapsulated thermochromic systems are designed to reduce the reactivity between the medium and the capsules at a rather low level that the reactivity will not influence the characteristics of the dye over a prolonged period of time.

Highly polar solvent molecules, with the exception of water, frequently interact more with the leuco dye than with the capsule shell and other non-polar molecules of the thermochromic system. Therefore, polar solvents that are capable of traversing the capsule barrier must, in general, be removed from the medium within which the encapsulated thermochromic system is formulated.

The aqueous medium that thermochromic systems encapsulates placed inside should have a narrow pH range of about 6.5 to about 7.5. When an encapsulated thermochromic system is added to a formulation having a pH outside this range, often the thermochromic properties of the system are destroyed. This is an irreversible effect.

One aspect of the present disclosure is for a method to improve the thermochromic system formulations by removing any of the aldehydes, ketones and diols and replacing them with solvents that do not adversely affect the thermochromic system. Solvents that have a large molecular weight (ie, greater than 100) are generally compatible with thermochromic systems. The acid content of the system is preferably adjusted to an acid number below 20 or preferably adjusted to be neutral, approximately 6.5-7.5. Implementing these solvent parameters for use in the thermochromic system will preserve the reversible coloring ability of leuco dyes.

The formulations for thermochromic systems are designed with all the previously mentioned considerations. The examples immediately describe a thermochromic system with excellent color density, low residual color, narrow temperature ranges between full color and rinsing point and a hysteresis window narrow. The full color point and the rinsing point are determined by visual inspection of the thermochromic system in a temperature range. The difference in temperature between the maximum of the color change during the cooling cycle and the heating cycle is used to calculate the hysteresis.

Acid Content Adjustment Water-based inks are pH adjusted before the addition of the thermochromic pigment. As mentioned in the above, the pH must be neutral unless the observation indicates that a different pH is required. To achieve the correct pH, use a good donor or proton acceptor, depending on whether the pH is going to be adjusted up or down. To lower the pH, sulfuric acid is used, to elevate it, the best proton acceptor until now is KOH. These two chemicals are very effective and do not seem to impart undesirable characteristics to the environment. The much more effective pH is about 7.0, however, some tolerance has been observed between 6.0 and 8.0. A pH below 6.0 and above 8.0 has almost always destroyed the pigment immediately.

The acid value is defined as the number of milligrams of a 0.1 N KOH solution required to neutralize the alkali reactive groups in 1 gram of material under the conditions of the ASTM D Test Method. 1639-70. It is not yet fully understood how non-aqueous substances containing acid affect the thermochromic, but high-acid substances have inactivated thermochromic pigments. Generally, the lower the number of acid is, the better. To date ink formulations with an acid value below 20 and which do not include the deleterious solvents described above have worked well. Some formulations of higher acid value may be possible but it is generally better to use vehicle ingredients with low acid numbers or to adjust the acid value when adding an alkaline substance. The greater benefit of a vehicle of neutral or low acid value will increase the shelf life. Buffer solutions have historically been used in misalignment ink formulations to minimize the effects of the source solution on pigment particles. This is a possible solution to the problem of potential acidity of varnishes. An ingredient frequently used as a buffer is cream tartar. A dispersion of cream of tartar and linseed oil can be incorporated into the ink. The pure effect is that the pigments in the ink are protected from the acidic source solution.

Ink Formulations Encapsulated thermochromic systems of the. present description can be referred to as pigments. To add normal pigment to the ink, dye or lacquer, the pigment itself is milled at the base. This disperses the pigment throughout the base. The addition of more pigment intensifies the color. Since the pigment often has a very intense color, only about 10% of the final ink that is made up of normal pigments is sometimes acceptable.

A base for an ink formulation using encapsulated thermochromic systems of the present disclosure can be developed using the shelf ingredients. The ink will be incorporated, where possible, and will be compatible with different types of ink and solvents with molecular weights larger than 100 while avoiding aldehydes, diols, ketones and, in general, aromatic compounds. Important considerations regarding the ingredients within the ink vehicle are the reactivity of the ingredients with the encapsulated thermochromic system.

Undesired interactions between the medium and encapsulated thermochromic systems can occur between compounds found in the ink formulations. The long alkyl chains of many of the compounds found in the ink vehicles may have reactive portions that can pass through the pores of the capsule and interact with the inert phase and denaturalize it through this interaction. Since the functioning of the thermochromic system is related to the shape and location of its molecules at given temperatures, interrupting these structures could have a great impact on the characteristics of the thermochromic system. Even molecules that can not pass through the pores of the capsule can have reactive portions that could protrude into the capsule and thereby influence the color transition of the thermochromic system within the capsule. Therefore, mineral essences, ketones, diols and aldehydes are preferably minimized in any medium in which the encapsulates are also preferably avoided. If these compounds are substantially reduced or eliminated from the thermochromic systems they will be made better and will have a longer shelf life.

Another important step in using the encapsulated thermochromic systems of the present disclosure in ink formulations is to adjust the pH or decrease the acid value of the ink base before the thermochromic system is added. This can be done by ensuring that each individual component of the base is at the correct pH or acid value or by simply adding a proton donor or proton acceptor to the base itself before adding the thermochromic system. The appropriate specific pH it is generally neutral, or 7.0. The pH will vary between 6.0 and 8.0 depending on the type of ink and the color and batch of the thermochromic system.

Once the suspension and base have been properly prepared, they are combined. The method for stirring should be at low speed with blades to stir not metal. Other additives can be incorporated to keep the thermochromic system suspended. The ink should be stored at room temperature.

Most thermochromic pigments undergo a color change from a specific color to colorless. Therefore, layers of background colors can be provided under thermochromic layers that will only be observed when the thermochromic pigment changes to colorless. If a lower layer of yellow is applied to the substrate and then a layer containing blue thermochromic pigment is applied the color will appear to change from green to yellow, when what is really happening is that the blue is changed to colorless.

The substrates in which the thermochromic inks are printed are preferably neutral in pH, and should not impart any chemical to the capsule which will have a detrimental effect thereon.

Thermochromic inks or coatings contain, in combination, a vehicle and a pigment that they include thermochromic microcapsules. The thermochromic microcapsules are preferably present in an amount varying from 1% to 50% of the ink by weight on a variable scale relative to other pigments. The vehicle contains a solvent that is preferably present in an amount ranging from 25% to 75% by weight of the coating.

Aqueous pigment suspensions have particle sizes less than 5 microns and when drawn on the ink proof paper and dried, the pigment coating exhibits reversible thermochromic properties when cooled to the solidification point of the fatty ester, alcohol, amide or a mixture designed to obtain a specific temperature for the formation of complete color. Such pigments can be designed to have a temperature range for complete absorption temperature transition (full absorption color or UVA absorption point) at no color or no UVA absorption temperature (rinsing point) of 2-7 ° C. The pigments are very useful for the manufacture of ink, coating and injection molded plastic products by spray-drying prior to formulation in inks or coating or extrusion compositions in the thermoplastic polymers to produce pellet concentrates for the manufacture of products of injection molded thermochromic plastic such as cups, cup lids, jars, straws, stirrers, hoses of containers, shrink wrap labels. For example, thermochromic compositions were identified that allow the generation of high quality saturated photo quality yellow color that is very useful for formulating new colors orange, red and green when mixed with thermochromic magenta and / or cyan pigments or by co- Initial encapsulation of yellow leuco dye with leuco magenta and / or cyan dyes and appropriate color developers during pigment manufacture. Alternatively the leuco pigments were identified that can change absorption mainly in the region from 280 to 350 nm to the absorption mainly from 350 to 400 nm. In one embodiment, this leuco dye can be used in a photochromic gel ink pen as described above.

Ball Point Pens The ball tip pens employing the thermochromic inks described herein may be used in a conventional ball tip pen or marker mechanism.

The thermochromic inks described herein are endowed with thixotropic properties. The thermochromic inks described herein have a high viscosity when allowed to stand without application of shear and are stably held in the ball tip pen mechanism and only the ink around the ball it becomes of low viscosity at the time of writing due to the high shear force attributable to the ball rotating at a high speed, so that the ink gently passes through a space between the ball and a ball holder by action capillary and transferred to the surface of the paper. The ink transferred to the surface of the paper or the like is freed of the shear stress and consequently is again carried in a highly viscous state, not causing the plumeado in the writing.

The thermochromic ink compositions described herein satisfy properties suitable for ball point pen inks, can be free of line splitting, smudging and smearing in writing, have stable viscosity characteristics over time and satisfy practical performances as Water-based ball point pen inks containing various colorants. Since dyes, pigments and dyes of various types can be used, and therefore ball point pens having a variety of color tones can be provided. Also, in the system where the thermochromic microcapsular pigment material is used as the dye, convenient ball point pens can be provided which can give written thermochromic images, promising the expansion of new uses. Such applicable uses and advantages attributable to them will be exemplified below.

In one embodiment, confidential images such as letters and films that cause metachromatism at a temperature lower than room temperature can be formed on postcards, Christmas cards, greeting cards and so on. In this way, images can be made to arrive at sight when they are cooled, to be applicable to magical use or images that can alternatively change color (A) to color (B) can be formed so that metachromatism can be cause by body temperature, temperature of the hand or other source of heat.

In another embodiment, the thermochromic inks described herein are capable of forming color only when cooled, for example, at a metachromatic temperature of 10 ° C, or a thermochromic pigment material having hysteresis characteristics over a wide temperature range , images that can not be read at room temperature can be recorded, using the ball tip pen of the present disclosure as a confidential pen. In this way, the pen can be used to write memos or similar ones that should be made confidential.

In another embodiment, pens using the thermochromic inks described herein for learning at school or the like can be used, for example, for questionnaires, tests, instructions, blank maps and translations in English, where answers or comments are necessary and written information is erased by heating again the problems or similar ones can be coupled in a completely readjusted state that does not they have no answer or memorandums.

In another embodiment, the pens using the thermochromic inks described herein may be used for temperature indication as if it functions as a thermometer. A set of thermochromic ink ball tip pens having different metachromatic temperatures can be provided so that several images are formed to make them function as temperature detectors. In this way, the ink composition of the present invention can be used not only in toys and stationery but also in a variety of industrial fields, for example, they can be conveniently used in temperature control of reaction tanks, temperature control of processing stages, indication for proper temperature control of low temperature circulation food, exhibit the prevention of overheating due to the short point of sale of electrical codes.

In another modality, thermochromic inks described herein may be used in articles of clothing, illustrations or photographs may be written on casual clothing such as T-shirts with a metachromatic thermochromic tita ball point pen of 30 ° C so that users themselves can design capable T-shirts of causing metachromatism using a temperature difference between the open air and the room in the summer temperate. This can also be applied for gloves, shoes, hats or caps, skiwear and swimsuits.

In another embodiment, pens using the thermochromic inks described herein can be used to prevent counterfeiting, genuine things and imitations can be discriminated upon cooling or heating. For example, some information may be handwritten with the ball point pen of the present description on tickets, merchandise bonuses, discount tickets and so on at a scale of private companies or small lots. This can effectively prevent counterfeiting.

In another embodiment, pens utilizing the thermochromic inks described herein can be used in combination with usual non-metachromatic ink-tip pens so that the state of change can be in more variety.

The present description provides inks thermochromic for use in a ball point pen for shear thinning. In one embodiment, the thermochromic ink compositions have a viscosity in the range of about 25 mPas to about 160 mPas and an index of shear thinning adjusted within the range of about 0.1 to about 0.6.

The non-limiting modalities that follow teach by way of example and should not be considered as unduly limiting the scope of this description.

In one aspect, a reversible thermochromic ink for use in pens contains a reversible thermochromic pigment in an amount of 1% to 40% by weight of the coating and a vehicle that forms the remainder of the coating. The vehicle including a resin is selected from the group consisting of polyester, urethane, acrylic acid and acrylate resins and combinations thereof.

Commercially available thermochromic pigments can be easily obtained in a variety of colors that demonstrate color transition temperature of about 5 ° C and up to about 65 ° C. A range of color formulations can be made by mixing the pigment that includes one or more of the following reversible thermochromic colors: yellow, magenta, cyan, and black. These can be mixed additionally to include other dyes or solid pigments that are not thermochromic in nature. The pigment can change from a colorless state to a colored state under cooling at the reactive temperature, or to a colored state under heating at the reactive temperature. It is preferred that the microcapsules are formed from urea formaldehyde or melamine formaldehyde which is acid catalyzed to increase the inherent stability in low molecular weight, polar solvents having a molecular weight of approximately less than 100 g / mol.

Thermochromic Inks Used in Pens In one embodiment, the thermochromic inks of the present disclosure contain micro-encapsulated leuco dyes, developer and solvent with the appropriate solvency and melting point to achieve color change activated with temperature. In one embodiment, the base dye is a permanently colored pigment or dye that is suspended in the ink formulation or soluble in the ink formulation.

In one embodiment, the shear thinning ink can be formulated using a film-forming compound such as ethylene maleic anhydride or an equivalent substitute completely hydrolyzed in water and adjusted to the desired thixotropic operation with xanthan gum. The film-forming properties of the ink could be achieved using many resins / vehicles such as ethylene maleic anhydride, styrene acrylonitrile polymers, acrylic emulsions or urethane emulsions for example. The rheology to achieve viscosity and shear thinning ability could be controlled by surfactants and agents such as xanthan gum and hydroxyl ethyl cellulose as well as a number of others.

In one embodiment, the temperature between full color development and rinse point activation can be designed with a mixture of alkyl esters such as methyl palmitate, methyl stearate, isopropyl palmitate, stearyl behenate and behenyl alcohol to produce the next color for color effects, for example: a full color development between 23 ° C and 27 ° C and a color rinse between 27 ° C and 33 ° C for easily reversible thermochromic color activated for color options.

In one embodiment, the ball tip pen and gel ink pens described herein use thermochromic inks that are subject to transition from one color to another color, or from color to colorless, when activated at approximately body temperature or approximately room temperature.

Examples of transition from strong color to color and color to colorless are as follows: Purple to pink Blue thermochromic + pink / red base color Green to yellow Thermochromic blue + yellow base color Orange to yellow Thermochromic red + base color Bordeaux yellow to blue Thermochromic red + blue base color Coffee to green Red thermochromic + green base color Green to blue Thermochromic yellow + blue base color Orange to pink Yellow thermochromic + base color pink / red Blue to colorless Thermochromic blue + white / clear Black to colorless Thermochromic black + white / light base color The above embodiments of color color options are achieved by mixing different ratios of thermochromic microcapsules with standard colored bases, as described herein. The base dyes may be pigments or dyes that are compatible in the ink formulation.

The color at color transitions sometimes lacks high contrast between the developed state of color and the base color. To increase the contrast, the transition inks from black to color are described herein.

In one embodiment, transitions from black to color use thermochromic blue / cyan, red / magenta, yellow and black with base dyes of red / magenta, blue / cyan, yellow and white. Examples of thermochromic inks that have transition from black to color are as follows: Black to blue magenta, black, yellow Thermochromic + blue base Black to yellow magenta, black, blue Thermochromic + base yellow Black to red / pink blue yellow, black Thermochromic + base pink / magenta Black to blue orange, black Thermochromic + pink and yellow base Black to magenta green, black Thermochromic + blue and yellow base Black to violet yellow, black Thermochromic + blue and pink base Black to blue coffee, black Thermochromic + pink base yellow blue By mixing different ratios of thermochromic pigments with standard colored bases, a neutral black to almost any colored base is possible. These transitions from black to color can be used to create black and white images that will change to colored states when heat is activated.

Photochromic Ink Pens In one embodiment, photochromic icrocapsules can also be formulated by encapsulating photochromic dyes in resins, monomers and polymers using standard encapsulation techniques to achieve a particle size between 300 nm and 5 microns. For example, in situ or interfacial polymerization using melamine resin, epoxy resin or urea-formaldehyde can be used to encapsulate hydrophobic internal phase materials, immiscible in water in which the dye dissolves. Antioxidants, hindered amine light stabilizers and UV absorbers can be used either alone or in combination with each other to increase the UV stability of the system. The internal phase solvent can be maintained as a liquid, or polymerized to a solid within the microcapsule.

The microencapsulated photochromic systems can then be formulated in a water-based shear thinning gel ink for use in rolling ball pens. Inks can be produced in that they are virtually invisible under normal fluorescent or incandescent lighting indoors, but they will develop vibrant colors under UV light such as natural sunlight. By mixing colored bases with photochromic inks, color development is also possible. The shear thinning properties and film-forming properties of the ink can be achieved using many resins / carriers such as ethylene maleic anhydride, styrene acrylonitrile polymers, acrylic emulsions or urethemulsions for example.

The rheological manipulations to achieve the viscosity and shear thinning of photochromic inks can be controlled by surfactants and agents such as xanthan gum, hydroxyl ethyl cellulose and various other agents well known in the art. The end result is a gel ink flowing from a rolling ball pen gently to form a uniform ink line without obstruction or blur.

The modalities of photochromic inks useful in pens include: Colorless to Blue Blue microencapsulated + Light gel base Yellow to Green Blue microencapsulated + Base color yellow + Light gel base Colorless to Red Red microencapsulated + Clear gel base Blue to Purple Red microencapsulated + Base color blue + Base gel clear EXAMPLES Temperature Memory Ink from Black to Green A thermochromic ink composition, commercially available from Chromatic Technologies Inc., with full color between 12 ° C and 15 ° C and color rinsing between 21 ° C and 27 ° C for a color color option was made so that the Color of the thermochromic portion of the ink was maintained up to room temperature, but easily activated by the body temperature to a rinsing point to reveal the base color.

The thermochromic ink was a composition consisting of a thermochromic blue dye with a leuco dye Magenta and a developer to achieve a reversible thermochromic system with a full color development around 12 ° C and a rinse temperature of 25 ° C. The thermochromic magenta capsules were incorporated in a water-based shear thinning gel ink with a neon blue pigmented gel ink and a neon yellow pigmented gel ink.

The thermochromic shear thinning ink was formulated using a film-forming compound such as ethylene maleic anhydride completely hydrolyzed in water and adjusted to the desired thixotropic operation with xanthan gum.

The result was a watery ink that appeared black when it cooled to a temperature below 12 ° C and remained black until it was heated to a temperature above 25 ° C when it changed to a bright green color.

The reversible thermochromic color changing ink was injected into a 0.7 mm to 1.0 mm standard gel tip pen for transfer to a paper substrate.

In one embodiment, a drawing or image written later could be made to appear black at room temperature. In one embodiment, the colored image can be easily activated to bright orange by gentle rubbing and the black color can only be recovered by cooling to a temperature around 12 ° C for a few minutes.

Color color options are achieved by mixing different ratios of thermochromic microcapsules with standard colored bases. The base dyes may be pigments or dyes that are compatible in the ink formulation. These color color options are artistically pleasing, but are sometimes limited in regard to the high contrast between the developed state of color and the color base. Thermochromic pigments are commercially available from Chromatic Technologies Inc. in Colorado Springs, CO.

To achieve a maximum effect of color for artistic reasons, neutral / black color charcoal options are proposed. In an example that shows the mixing of colors, these thermochromic pigments: blue / cyan, red / magenta, yellow and black can be mixed with the following coloring bases (pigments or dyes): red / magenta, blue / cyan, yellow and white.

On the other hand, any neutral black option or a is achievable.

This is achieved by mixing different thermochromic pigment ratios with standard colored bases. It is possible to achieve a neutral black to almost any colored base. This allows full dramatic effect to such an extent that the user can create a black and white image that will change to the colored state when the heat is activated. For example, imagine a natural scenario of a tree on a hillside. The trunk of the tree will be black to brown, the leaves of the tree will be black to green, the sun will be black to orange and black to yellow, the grass on the slope will be black to green and the clouds will be black to blue. By selectively choosing the color black option, any scene can be represented that is subjected to transition from the neutral black sketch to a fully colored sketch as it is heated.

The thermochromic component of the invention is a microencapsulated leuco dye, developer and solvent with the appropriate solvency and melting point to achieve the color change activated with temperature.

The base dye is a permanently colored pimento or dye that is suspended in the ink formulation or soluble in the ink formulation.

The temperature between full color development and rinse point activation can be easily designed with a variety of internal phase solvents as described in a number of patents to achieve microencapsulated pigments with color development between -10 C and 65 C.

Example of Black to Orange A microencapsulated pigment with an internal phase designed with a blue leuco dye and a phenolic developer to achieve a reversible thermochromic system with a complete color development between 23C and 27C and a rinse temperature between 28C and 31C (available from Chromatic Technologies, Inc.) The red thermochromic capsules are incorporated in a water-based shear dilution gel ink with a gel ink pigmented with neon pink and a gel ink pigmented with neon yellow.

The shear thinning ink can be formulated using a film-forming compound such as ethylene maleic anhydride completely hydrolyzed in water and adjusted to the desired thixotropic operation with xanthan gum. The film-forming properties of the ink could be achieved using many resins / vehicles such as ethylene maleic anhydride, styrene acrylonitrile polymers, acrylic emulsions or urethane emulsions for example. Rheology to achieve viscosity and shear thinning ability could be controlled by surfactants and agents such as xanthan gum and hydroxyl ethyl cellulose as well as a number of others.

A thermochromic ink composition, commercially available from Chromatic Technologies Inc., which It consists of a thermochromic blue with a blue leuco dye and a developer to achieve a reversible thermochromic system with a developed full color around 27 ° C and a rinse temperature of 32 ° C was produced. The blue thermochromic microcapsules 5 were incorporated in a water-based shear thinning gel ink with a neon pink pigmented gel ink and a neon yellow pigmented gel ink.

The resulting thermochromic ink appeared black when it was below 27C and gradually changed to a bright orange when it was heated to a temperature above 32C.

The reversible thermochromic reversible color ink was injected into a standard 0.7 m to 1.0 mm tip gel pen for transfer to a paper substrate.

COLUMN CHAMBER OF COLUMN BOOM / MARKER FORMULATION BLACK TO ORANGE: The result is an ink that will appear black when it was below 27 ° C and will gradually change to a bright orange when heated to a temperature above 31 ° C.

The reversible thermochromic color change ink is injected into a standard .7 mm to 1.0 mm tip gel pen for transfer to a paper substrate. As non-limiting examples, the formulated ink may be for a ball-tip pen writing instrument or a fibrous tip marker.

A non-limiting example of a Purple to Pink Temperature Memory Ink: Full color between 12 ° C and 15 ° C and color rinsing between 21 ° C and 27 ° C for a color color option so that the color of the thermochromic portion of the ink is maintained up to room temperature, but easily activated by body temperature to a rinse point to reveal the base color. A microencapsulated pigment designed to have a broad hysteresis effect using a magenta dye and a phenolic developer to achieve a reversible thermochromic system with a full color development between 12-13 ° C and a rinse temperature between 23-25 ° C.

The blue thermochromic capsules are incorporated in a water-based shear thinning gel ink with a neon pink pigmented gel ink.

The shear thinning ink is formulated using a film-forming compound such as ethylene maleic anhydride completely hydrolyzed in water and adjusted to the desired thixotropic operation with xanthan gum.

The result is an aqueous ink that will appear purple when it is cooled to a temperature below 12C and will remain purple until it is heated to a temperature above 23-25 ° C, where it will then change to a bright pink color.

The reversible thermochromic color change ink is injected into a tip gel ink pen of .7 m to 1.0 mm (or larger) standard for transfer to a paper substrate.

A picture or written image can be made so that it will appear purple at room temperature (20-23C). The colored image can easily be activated to bright pink when gently rubbing or heating. The purple color can be recovered only by cooling to a temperature of around 121 ° C for a few seconds that can be achieved by placing the printed image in a refrigerator set under normal conditions.

Photochromic Gel Ink Pen Photochromic microcapsules can also be formulated by encapsulating photochromic dyes in resins, monomers and polymers using standard encapsulation techniques to achieve microcapsules suitable for use as a pigment in a gel ink. For example, in situ or interfacial polymerization using melamine resin, epoxy resin or urea-formaldehyde can be used to encapsulate water-immiscible, hydrophobic internal phase materials in which the dye dissolves. Antioxidants, hindered amine light stabilizers and UV absorbers can be used either alone or in combination with each other to increase the UV stability of the system. The internal phase solvent can be maintained as a liquid, or polymerized to a solid within the microcapsule. The microencapsulated photochromic systems can then be formulated in a water-based shear thinning gel ink for use in rolling ball pens. Inks can be produced in which they are virtually invisible under normal fluorescents or incandescent lighting indoors, but which will develop vibrant colors under UV light such as natural sunlight. When mixing colored bases with photochromic inks, color development is also possible. The shear thinning properties and ink-forming properties of the ink could be achieved using many resins / vehicles such as ethylene maleic anhydride, styrene acrylonitrile polymers, acrylic emulsions or urethane emulsions for example. The rheology to achieve viscosity and shear thinning ability could be controlled by surfactants and agents such as xanthan gum and hydroxyl ethyl cellulose and a number of others. The end result would be a gel ink that would flow from a rolling ball pen smoothly to form a uniform ink line without obstruction or blur.

Clear Base Gel The non-limiting example that follows shows a modality for a clear base gel incorporating the instrumentalities described in the foregoing. The clear gel base can be formulated as follows: This can be mixed with pigment as follows. The amount of the pigment is added to suit the eye.

Colorless to Blue: Microencapsulated blue + Clear gel base Yellow to Green: Microencapsulated blue + Base color Yellow + Clear gel base Colorless to Red: Red microencapsulated + Clear gel base Blue to Purple: Red microencapsulated + Base color blue + Light gel base In general 50-98% of gel base is mixed with 1-50% photochromic dye or microencapsulated photochromic dye, and 1-50% of a colored dye. Preferably, 60-95% mixed with 5-40% of photochromic dye or 5 microencapsulated dye and 1-10% of a colored dye.

An example photochromic yellow-to-green pen / marker ink is: 90% gel base 5% photochromic microencapsulated pigment 5% tartrazine dye Additional temperature profiles with various degrees of color memory can be achieved with other internal phase materials such as tetradecanol, dodecyl decanoate and decanophenone, where the color can be fully developed at a lower temperature and maintain up to some point temperature of highest rinse.

The above description teaches by way of example, and not by way of limitation. Those skilled in the art will appreciate that what is claimed can be subject to non-substantial change if departing from the scope and spirit of the invention. Accordingly, the inventors hereby establish their intention to rely on the doctrine of Equivalents, to protect their rights in the invention.

Claims (16)

1. A reversible thermochromic composition, the reversible thermochromic ink composition characterized in that it comprises, a reversible thermochromic pigment in an amount of 1% to 50% by weight of the ink, the reversible thermochromic pigment that is susceptible to a temperature-modulated color change between a first state and a second state along a hysteresis loop; a non-thermochromic dye of a different color of the reversible thermochromic pigment when the reversible thermochromic dye is in a colored state, such that the non-thermochromic dye and the reversible thermochromic pigment together have a first color when the reversible thermochromic pigment is in the first state and together they present a second color when the reversible thermochromic pigment is in the second state; Y a vehicle that forms the rest of the composition.

2. The composition according to claim 1, characterized in that the first state is a colored state and the second state is substantially clear.

3. The composition according to claim 1, characterized in that the composition is formulated for use in a ball tip pen.

4. The composition according to claim 1, characterized in that the composition is formulated for use in a gel pen.

5. The composition according to claim 1, characterized in that the composition is formulated for use in a marker.

6. The composition according to claim 1, characterized in that the composition is formulated for use in a paint.

7. The composition according to claim 1, characterized in that the composition is formulated for use in a crayon.

8. The composition according to claim 1, characterized in that the thermochromic pigment is formulated to have a hysteresis window that extends through a range greater than 60 ° C.

9. The composition according to claim 1, characterized in that the thermochromic pigment is formulated to have a hysteresis window that extends through a range greater than 80 ° C.

10. The composition according to claim 1, characterized in that the ink is formulated to change the color as a result of heating from black to a color other than black.

11. The composition in accordance with the claim 1, characterized in that the ink is formulated to change the color as a result of heating from one color to a different color.

12. In a ball point pen or marker, 5 characterized in that the improvement comprises the composition of claim 1 used as an ink.

13. In a ball point pen or marker, characterized in that the improvement comprises the composition of claim 11 used as an ink.

14. The composition according to claim 1, characterized in that the non-thermochromic dye is a microencapsulated photochromic dye.

15. A method for using the composition of claim 1, characterized in that the composition is applied by a writing instrument to paper, clothing, cardboard or other surfaces and then subjected to a color change by the action of temperature change.

16. A reversibly visual enhancement method using the composition of claim 1, characterized in that it comprises applying the ink to a surface at a first temperature; Y changing the temperature of the surface to a second temperature whereby the ink becomes colorless.