Ceramic inkjet ink for red decoration

Disclosed are compositions, such as inkjet inks, for jetting onto a ceramic substrate, and associated methods and systems. The compositions comprise a pigment compound that is configured to be jetted on a ceramic substrate during a ceramic inkjet process to impart a color effect to the ceramic substrate, and a reduction agent which, when exposed to a firing temperature, reacts with the pigment compound to cause a reduction reaction. In some embodiments, the pigment compound comprises jettable copper particles, which can cause the fired composition to take on a red or oxblood color, which can be used for decoration.

FIELD OF THE INVENTION

At least one embodiment of the present invention pertains to compositions that produce a reduction reaction, which impart a color effect to a ceramic substrate when exposed to a firing temperature.

BACKGROUND

In ceramic inkjet printing processes, traditional inorganic ceramic glazes and/or stains can produce stable red shades at higher temperatures, from zircon-encapsulated cadmium selenide (CdSe) pigments, which are commonly referred to as cadmium red.

However, inkjet ink pigments require smaller particle sizes than traditional ceramic stains and therefore usually include a pigment milling step in the manufacturing process. This milling step compromises the protective encapsulation layer used with CdSe pigments, and leaves the pigment vulnerable to degradation and color loss. CdSe pigments are not useable in ceramic inkjet inks at this time.

In the field of inkjet ceramics, options for red shade colors at porcelain firing conditions are not known to exist at this time.

DETAILED DESCRIPTION

Introduced here is a technique that enhances or extends an available color gamut for inkjet ceramics to provide, for example, red shade color options at porcelain firing conditions.

In certain embodiments, the technique introduced here involves the following sequence of actions, as described more fully below. Initially, an enhanced composition is jetted onto a ceramic substrate (also called a “workpiece”), e.g., a ceramic tile. The composition comprises a pigment compound, and a corresponding reduction agent, which are configured to be jetted, either together or separately, onto a ceramic workpiece. In some embodiments, the pigment compound comprises particles of a copper component, wherein the pigments are sized, e.g., by milling, to be jetted through an inkjet system. The reduction agent is configured to react with the pigment compound during the firing of the ceramic workpiece.

In some embodiments, the enhanced composition can expand the available color gamut, as compared to prior jettable compositions, such as to produce a red component, e.g., oxblood red, either alone or combined with other color components.

FIG. 1illustrates an embodiment100of an enhanced composition106, e.g., an inkjet ink, on a ceramic substrate104, wherein the enhanced composition106comprises a pigment compound108and a reduction agent110. The composition106can be jetted314(FIG. 3),502(FIG. 5) onto the ceramic substrate104, such as by one or more print heads306. The composition106shown inFIG. 1can comprise one or more jetted layers106,602,604(FIG. 6,FIG. 7). The ceramic workpiece102is subsequently fired (e.g., in a kiln), causing a reduction reaction204between the pigment compound108and the reduction agent110.

While the workpiece104is generally described herein as a ceramic substrate104, it should be understood that the technique introduced here can be suitably adapted for a wide variety of workpieces that can be fired, e.g., tiles, such as ceramics, which can be manufactured from clay, minerals and water, or porcelain, which can be manufactured from finely ground sand.

In some embodiments, the pigment component108includes particles of a copper component, such as comprising any of CuO, CuCO3, or CuS04. The size of the particles is configured to be jetted314(FIG. 3), such as within a carrier902(FIG. 9). For example, in an embodiment, the pigment particles are milled to an average particle size of 1 micron or less. In some embodiments, the copper particles cause the enhanced composition106to take on a red color, e.g., having a characteristic wavelength of 620-740 nm, upon firing504(FIG. 5). In some embodiments, the copper particles cause the enhanced composition106to take on a violet, burgundy, or oxblood color, e.g., having a characteristic wavelength of 380-440 nm, upon firing504.

In an embodiment of the composition106, the reduction agent110is configured to produce a reduction reaction with the pigment component108, when fired on the ceramic substrate104. For instance, for a pigment component108comprising a copper component, as discussed above, the reduction agent110may preferably comprise any of SiO, SiC, SiN, or BN.

In one example, an oxblood red color results from the reduction of Cu2+to Cu+/Cu0. Since SiO2is a primary component in glaze formulations, the SiO2produced during the reduction of the copper pigment component108is incorporated into the resultant glaze206(FIG. 2), upon the application of sufficient heat. An example is shown in Equation (1)
4CuO(Black)+Si→2Cu2O(Red)+SiO2.  (1)

FIG. 2is a schematic block diagram200of an enhanced composition104(FIG. 1) on a ceramic substrate102, wherein the workpiece102is exposed to a firing temperature202, and wherein the reduction agent110reacts with the pigment compound108to cause a reduction reaction204. The substrate104may comprise a variety of ceramics104that can be fired in any temperature range that corresponds to the reduction reaction204. In some embodiments of the enhanced composition106wherein the pigment component108includes copper, the firing temperature202, when controlled within a kiln404(FIG. 4) has a range of 1050 degrees C. to 1300 degrees C. The jetted composition106on the workpiece102forms a glaze206as a result of the firing504(FIG. 5), whereby the color of the resultant glaze206takes on a color due to the reduction reaction204between the pigment compound108and the reduction agent110. The specific resultant color can also depend on specific operational parameters, e.g., specific temperatures, firing schedules, temperature ramping, down-firing, etc., and/or the use of one or more additional constituents in the composition106, such as other pigments906(FIG. 9), dyes908(FIG. 9), and/or other additives, dispersions, or particles910(FIG. 9).

FIG. 3is a schematic diagram300of an illustrative printing system302for jetting314a composition106onto a ceramic workpiece104, wherein the composition106comprises a pigment compound108and a reduction agent110. The printing system302seen inFIG. 3includes a print head assembly304, comprising one or more print heads306having corresponding jets312. A supply module308is connected to the print heads306, whereby the composition is transferred to the print heads306, for jetting314onto a ceramic substrate104, as controlled by a print controller310.

FIG. 4is a schematic diagram400of a firing system402for heating a ceramic workpiece102having a jetted composition104(FIG. 3), wherein when exposed to sufficient heat, the reduction agent110and the pigment compound108react to cause a reduction reaction204. The firing system402seen inFIG. 4includes a kiln404having an interior406defined therein, and a heating system410, under the control of, e.g., a firing controller408, wherein the heating system410comprises a heat source and can additionally comprise a mechanism for air circulation, e.g., a fan. The firing system402is operable to heat the jetted substrate102to a firing temperature202in a temperature range from 1050 degrees C. to 1300 degrees C., to cause a reduction reaction204between the pigment compound108and the reduction agent110. The jetted composition106on the workpiece102forms a glaze206as a result of the firing, while the color of the resultant glaze206takes on a color due to the reduction reaction204between the pigment compound108and the reduction agent110.

FIG. 5is a flowchart of a method500for producing an enhanced ceramic, which comprises jetting502a composition106onto a ceramic substrate, i.e., a workpiece104, wherein the composition106comprises a pigment compound108and a reduction agent110, and heating504the composition to a temperature at which a reduction reaction204occurs between the reduction agent110and the pigment compound108, causing a color effect to be produced on the ceramic substrate104.

In some embodiments of the technique introduced here, the pigment compound108and the reduction agent110can be supplied in a single composition106, such as within an appropriate jettable carrier902(FIG. 9), e.g., water, whereby the pigment compound108and the reduction agent110are jetted502concurrently onto the ceramic substrate104. However, other embodiments of the technique allow separate jetting of the pigment compound108and the reduction agent110, as long as the pigment compound108and the reduction agent110come into contact with each other during the heating504, to initiate the reduction reaction204between the reduction agent110and the pigment compound108.

For example,FIG. 6illustrates an embodiment600of an enhanced composition106on a ceramic substrate104, wherein the enhanced composition106comprises a layer602of reduction agent110that is jetted502onto the ceramic substrate104, and a layer604of pigment compound108that is jetted502onto the layer602of reduction agent110.

As another example,FIG. 7shows an embodiment700of an enhanced composition106on a ceramic substrate104, wherein the enhanced composition106comprises a layer604of pigment compound108that is jetted502onto the ceramic substrate104, and a layer602of reduction agent110that is jetted502onto the jetted layer604of pigment compound108.

FIG. 8illustrates an alternative embodiment800of an enhanced composition106on a ceramic substrate104, which can include one or more jetted layers below802and/or above804the composition106. For example, a jetted lower layer802can comprise any of a primer, a basecoat, and/or one or more jetted colors. Similarly, a jetted upper layer804may comprise one or more jetted clear, translucent or opaque color layers over at least a portion of the jetted composition106.

FIG. 9is a schematic block diagram900of components that can be included in some embodiments of the enhanced composition106. As discussed above, the pigment compound108and the reduction agent110can be supplied as a single composition106with, e.g., an appropriate carrier902. The combined composition106can further comprise, for example, any of additional colorants904, e.g., other pigments906and/or dyes908, or other constituents910, such as additives, dispersions, and/or jettable particles.

As also discussed above, some embodiments of the technique allow for separate jetting of the pigment compound108and the reduction agent110, whereby each of the pigment compound108and the reduction agent110are supplied as jettable compositions, e.g., each within a corresponding carrier902. One or both of the pigment compound108and the reduction agent110can further comprise any of additional colorants904, e.g., other pigments906and/or dyes908, or other constituents910, such as additives, dispersions, and/or jettable particles.

FIG. 10is a flowchart of a method1000for manufacturing an enhanced composition106for jetting502onto a ceramic substrate104. As shown inFIG. 10, the manufacturing1002can comprise adding1004a jettable pigment compound108to a carrier902, such as water. As discussed above, the pigment compound108can comprise particles, e.g., copper, having an average particle size of, for example, less than 1 micron (to allow jetting), whereby the particles can be milled or polished to achieve a desired size. The manufacturing method1000seen inFIG. 10also comprises adding1006a jettable reduction agent110to a carrier902, which can be a separate carrier902, such as for independent jetting502of layers602,604(FIG. 6,FIG. 7). In some embodiments, the jettable reduction agent110is added to the same carrier902as that used for the jettable pigment compound108, such as for concurrent jetting502. Once prepared, the enhanced composition106, comprising either a single composition106, or separate jettable components108,110, is typically provided for use by the printing system302(FIG. 3).

FIG. 11is a high-level block diagram showing an example of a processing device1100that can be a part of any of the systems described above, such as the print controller310, the firing controller408, or a system for manufacturing the enhanced compound106. Any of these systems may be or include two or more processing devices such as represented inFIG. 11, which may be coupled to each other via a network or multiple networks.

In the illustrated embodiment, the processing system1100includes one or more processors1102, memory1104, a communication device1106, and one or more input/output (I/O) devices1108, all coupled to each other through an interconnect1110. The interconnect1110may be or include one or more conductive traces, buses, point-to-point connections, controllers, adapters and/or other conventional connection devices. The processor(s)1102may be or include, for example, one or more general-purpose programmable microprocessors, microcontrollers, application specific integrated circuits (ASICs), programmable gate arrays, or the like, or a combination of such devices. The processor(s)1102control the overall operation of the processing device1100. Memory1104may be or include one or more physical storage devices, which may be in the form of random access memory (RAM), read-only memory (ROM) (which may be erasable and programmable), flash memory, miniature hard disk drive, or other suitable type of storage device, or a combination of such devices. Memory1104may store data and instructions that configure the processor(s)1102to execute operations in accordance with the techniques described above. The communication device1106may be or include, for example, an Ethernet adapter, cable modem, Wi-Fi adapter, cellular transceiver, Bluetooth transceiver, or the like, or a combination thereof. Depending on the specific nature and purpose of the processing device1100, the I/O devices1108can include devices such as a display (which may be a touch screen display), audio speaker, keyboard, mouse or other pointing device, microphone, camera, etc.

Unless contrary to physical possibility, it is envisioned that (i) the methods/steps described above may be performed in any sequence and/or in any combination, and that (ii) the components of respective embodiments may be combined in any manner.

The jetting and/or firing techniques introduced above can be implemented by programmable circuitry programmed/configured by software and/or firmware, or entirely by special-purpose circuitry, or by a combination of such forms. Such special-purpose circuitry (if any) can be in the form of, for example, one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc.

Note that any and all of the embodiments described above can be combined with each other, except to the extent that it may be stated otherwise above or to the extent that any such embodiments might be mutually exclusive in function and/or structure.