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  Latex-based overcoat for ink-jet printing applicationsUSPTO Application #: 20070296784Title: Latex-based overcoat for ink-jet printing applications Abstract: Compositions, systems, and methods for protecting an ink-jet produced image printed on a substrate are provided. The composition can comprise a liquid vehicle and latex particulates dispersed in the liquid vehicle, wherein the latex particulates have a surface dielectric constant from 2.0 to 3.0 at room temperature, and a bulk density from 0.90 g/cm3 to 1.10 g/cm3. An alternative composition can comprise a liquid vehicle and latex particulates dispersed in the liquid vehicle, wherein the latex particulates have a reactive surfactant covalently attached thereto. (end of abstract) Agent: Hewlett Packard Company - Fort Collins, CO, US Inventors: Kent Vincent, Sivapackia Ganapathiappan USPTO Applicaton #: 20070296784 - Class: 347098000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070296784. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present application is a divisional of U.S. patent application Ser. No. 10/404,260, filed on Mar. 31, 2003, which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention relates generally to the ink-jet printing of durable images. More particularly, the present invention relates to a latex coating composition that can be used to overcoat ink-jet printed images. BACKGROUND OF THE INVENTION [0003] Computer printer technology has evolved to a point where very high-resolution images can be transferred to various types of media, including paper. One particular type of printing involves the placement of small drops of a fluid ink onto a media surface in response to a digital signal. Typically, the fluid ink is placed or jetted onto the surface without physical contact between the printing device and the surface. Within this general technique, the specific method that the ink-jet ink is deposited onto the printing surface varies from system to system, and can include continuous ink deposit and drop-on-demand. [0004] With regard to continuous printing systems, inks used are typically based on solvents such as methyl ethyl ketone and ethanol. Essentially, continuous printing systems function as a stream of ink droplets that are ejected and directed by a printer nozzle. The ink droplets are directed additionally with the assistance of an electrostatic charging device in close proximity to the nozzle. If the ink is not used on the desired printing surface, the ink is recycled for later use. With regard to drop-on-demand printing systems, the ink-jet inks are typically based upon water and solvents such as glycols. Essentially, with these systems, ink droplets are propelled from a nozzle by heat or by a pressure wave such that all of the ink droplets ejected are used to form the printed image. [0005] There are several reasons that ink-jet printing has become a popular way of recording images on various media surfaces, particularly paper. Some of these reasons include low printer noise, capability of high-speed recording, and capability of multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. [0006] Though there has been great improvement in ink-jet printing technology, as described previously, there is still improvement that can be made in many areas. With respect to ink-jet ink chemistry, the majority of commercial ink-jet inks are water-based. Thus, their constituents are generally water-soluble, as in the case with many dyes, or water dispersible, as in the case with pigments. Furthermore, ink-jet inks have low viscosity (typically 5 cps or less) to accommodate high frequency jetting and firing chamber refill processes common to ink-jet pens. [0007] Ink-jet prints are often known for poor durability when exposed to water or high humidity. This results from the use of water-soluble and water dispersible colorants within the water-based ink. There has been great improvement in the area of water durability of ink-jet inks through incorporation of certain ink-jet compatible latex polymers. When printed as part of an ink-jet ink, a latex component of the ink can form a film on a media surface, entrapping and protecting at least some of the colorant within the hydrophobic print film. However, not all colorant will necessarily be protected upon printing, as would be optimal. [0008] Polymers that form durable films are typically made from copolymers having bulk densities on the order of 1.15 g/cm.sup.3 or greater, which is appreciably greater than water, the primary component of thermal ink-jet ink. As such, conventional latex particles are normally designed to flocculate so that latex precipitate may be easily shaken or stirred back into dispersion without agglomeration. Such flocculation behavior is well known with latex paints. Unfortunately, these conventional teachings do not address the unique needs of ink-jet printing applications. For example, the micro-channel ink feeds in ink-jet pens are easily clogged with precipitant, particularly when a pen is stored or otherwise unused for prolonged periods of time. Such precipitation is not easily redispersed by pen shaking, as flow constriction prohibits adequate mixing within micro-channels of pen architecture. Additionally, micro-channels used for jetting can house some of the ink over prolonged periods in preparation for firing, and settled latex particulates can cause further constricting of the micro-channels. This can result in ink-jet pen failure due to clogging of the micro-channels. Further, the micron-order settling distances found in the fluid channels of thermal inkjet pens exacerbate the problem. SUMMARY OF THE INVENTION [0009] It has been recognized that it would be advantageous to develop a latex-based overcoat for ink-jet printing applications. Such latex-based overcoats can be applied as a protective coating to dye-based and/or pigment-based ink-jet ink produced images. [0010] Specifically, a composition for protecting an ink-jet produced image printed on a substrate can comprise a liquid vehicle void of colorant and having latex particulates dispersed in the liquid vehicle. The latex particulates can have a surface dielectric constant from 2.0 to 3.0 at room temperature, and a bulk density from 0.90 g/cm.sup.3 to 1.10 g/cm.sup.3. Additionally, in one embodiment, non-reactive surfactant can be adsorbed on the surface of the latex particulates. [0011] Alternatively, a composition for protecting an ink-jet produced image printed on a substrate can comprise a liquid vehicle void of colorant and having latex particulates dispersed in the liquid vehicle, wherein the latex particulates have a reactive surfactant covalently attached thereto. [0012] Additionally, a system for producing waterfast and humidfast images can comprise a media substrate, an ink-jet ink including a colorant, and a coating composition. The ink-jet ink can be configured for being printed on the media substrate. Further, the coating composition can include latex particulates dispersed in a liquid vehicle. The coating composition can also be configured for overcoating the ink-jet ink on the media substrate. Further, the latex particulates can have surfactant associated with the surface of the latex particulates. [0013] A method for producing waterfast and humidfast images is also disclosed which can comprise steps of jetting an ink-jet ink including a colorant onto a media substrate and jetting a coating composition including latex particulates dispersed in a liquid vehicle over the ink-jet ink previously jetted on the media substrate. The latex particulates can have surfactant associated the surface of the latex particulates. [0014] Additional features and advantages of the invention will be apparent from the detailed description that follows which illustrates, by way of example, features of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) [0015] Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular process steps and materials disclosed herein because such process steps and materials may vary somewhat. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only. The terms are not intended to be limiting because the scope of the present invention is intended to be limited only by the appended claims and equivalents thereof. [0016] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. [0017] As used herein, "liquid vehicle" or "ink vehicle" refers to the fluid in which colorants and/or latex particulates are added to form solutions and/or solutions. Many liquid vehicles, as well as specific vehicle components that can be used to formulate the liquid vehicles, are known in the art. Typical ink vehicles can include a mixture of a variety of different agents, such as co-solvents, surfactants, buffers, biocides, sequestering agents, viscosity modifiers, and water. [0018] "Colorant" can include dyes and/or pigments that may be used to impart color to an ink vehicle in accordance with embodiments of the present invention. In accordance with the present invention, colorant is typically used in ink-jet inks to be overcoated by the latex particulate-containing coating compositions of the present invention. This in not to say that the latex can not be present in the colorant-containing ink-jet ink as well. [0019] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of "0.1 wt % to 5 wt %" should be interpreted to include not only the explicitly recited concentration of 0.1 wt % to 5 wt %, but also include individual concentrations and the sub-ranges within the indicated range. Thus, included in this numerical range are individual concentrations, such as 1 wt %, 2 wt %, 3 wt %, and 4 wt %, and sub-ranges, such as from 0.1 wt % to 1.5 wt %, 1 wt % to 3 wt %, from 2 wt % to 4 wt %, from 3 wt % to 5 wt %, etc. This same principle applies to ranges reciting only one numerical value. For example, a range recited as "less than 5 wt %" should be interpreted to include all values and sub-ranges between 0 wt % and 5 wt %. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described. [0020] As used herein, "effective amount" refers to at least the minimal amount of a substance or agent, which is sufficient to achieve a desire effect. For example, an effective amount of a "liquid vehicle" is at least the minimum amount required in order to create an ink composition, while maintaining properties necessary for effective ink-jetting. Continue reading... Full patent description for Latex-based overcoat for ink-jet printing applications Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Latex-based overcoat for ink-jet printing applications patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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