Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2002-01-15
2004-08-10
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031650, C106S031670, C106S031860
Reexamination Certificate
active
06773496
ABSTRACT:
INTRODUCTION
1. Field of the Invention
The invention relates to inks for application to a heat resistant substrate such as glass, metal, or ceramic and subsequently firing to fuse the ink to the substrate.
2. Prior Art Discussion
U.S. Pat. No. 4,390,565 and U.S. Pat. No. 5,212,212 describe inks based on a UV curable ink system and are designed to be applied by a screen printing process. The ceramic ink formulations described are in liquid form and the solid constituents of the inks tend to sediment as a function of time in storage. Therefore the ink must be constantly mixed while not in use. This also applies to other types of liquid ink such as solvent or oil based ink.
EP0105994 (Corning Glass) describes a thermoplastic hot melt ink, the viscosity of which has a tacky paste consistency for application by elastomeric transfer printing to a substrate.
While such inks may adhere well to substrates such as ceramics, the printing methods involved suffer from the following disadvantages:
need for storage of screens or transfer members,
high cost for low volume printing and lack of versatility generally,
limitations in substrate surface printing coverage, in which edge-to-edge printing is often not possible, and
requirement for an even substrate surface.
The invention is therefore directed towards providing an ink for application to a heat resistant substrate to overcome at least some of the above problems.
SUMMARY OF THE INVENTION
According to the invention there is provided an ink suitable for application to a heat resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and comprising:
a carrier material;
a pigment;
a fusible vitreous agent comprising particles of less than 10 microns in size, and
the carrier having a melting point for phase change of the ink.
Preferably the pigment is in particulate form.
In one embodiment of the invention the pigment comprises ceramic pigment particles of less than 10 microns in size. Preferably the concentration of ceramic pigment in the ink is in the range of 10% to 60% by weight, preferably 20% to 50% by weight.
In another embodiment of the invention the pigment and fusible vitreous agent are combined in the form of ceramic pigment particles. Preferably the ceramic pigment particles are less than 5 microns in size.
In one embodiment of the invention the ink comprises a dispersant. Preferably the particles are coated with the dispersant.
Most preferably the dispersant is chemisorbed onto the particles.
The dispersant may be chemisorbed onto the particles by drying in an oven for up to 24 hours wherein the temperature of the oven is at least 120° C.
Preferably the dispersant is selected from a modified polyacrylate and fatty acid, most preferably the dispersant is selected from 12-hydroxystearic acid, stearic acid, tartaric acid, hydroxybenzoic acid and docosanoic acid. Ideally the dispersant comprises stearic acid.
In one embodiment of the invention the dispersant is present in a concentration by weight of the ceramic pigment from 2 to 5%, preferably approximately 4%.
Preferably the particles are coated with a dispersant in the presence of a solvent. Most preferably the dispersant is soluble in the solvent. The solvent may be toluene or butyl acetate.
The particles may be coated with a dispersant by ball milling or using a rotary dissolver.
Preferably the carrier material comprises a wax material. Most preferably the carrier material has a melting point of from 20 to 150° C., preferably 50 to 100° C.
In one embodiment of the invention, the pigment comprises a chemical dye.
In another embodiment of the invention the pigment comprises organometallic particles and metallic components.
The invention provides an ink suitable for application to a heat resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and comprising;
ceramic pigment particles of less than 10 microns in size;
fusible vitreous particles of less than 10 microns in size; and
a carrier having a melting point for phase change of the ink.
Preferably the particles are coated with a dispersant.
The invention also provides an ink suitable for application to a heat resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and comprising;
a carrier having a melting point for phase change of the ink;
ceramic pigment particles of less than 10 microns in size;
fusible vitreous particles of less then 10 microns in size; and
a dispersant which is chemisorbed onto the particles.
The invention further provides a method of producing an ink in a form for ink jet printing comprising the steps of:
milling a fusible vitreous agent to provide a powder having a particle size less than 10 &mgr;m;
providing a pigment for the ink;
heating a phase change carrier, and mixing the powder with the molten carrier; and
allowing the carrier to cool to provide solid ink.
Preferably the pigment is combined with the fusible vitreous agent as ceramic pigment particles.
The invention also provides a method of producing an ink comprising the steps of:
milling a fusible vitreous agent to provide a powder having a particle size less than 10 &mgr;m;
providing a pigment for the ink;
mixing the milled particles with a dispersant, and a solvent;
removing the solvent;
heating the mixture to a temperature in excess of 120° C. whereby the dispersant is chemisorbed onto the milled particles;
heating a phase change carrier, and mixing the powder mixture with the molten carrier; and
allowing the carrier to cool to provide solid ink.
Preferably the pigment is combined with the fusible vitreous agent as ceramic pigment particles.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to
FIG. 1
which is a graph showing dispersant adsorption.
The invention provides an improved phase change ink suitable for application to heat resistant substrates by ink jet printing.
The advantages of using an inkjet printing method over a screen printing method or elastomeric transfer printing include the following; 1). Images and patterns are produced and stored digitally, and therefore there is no requirement for storage of a large number of printing screens; 2) it is equally feasible to print images in small numbers as it is to print in large numbers; 3) the printer can change from printing one image to printing another without shutting down; 4) each image printed can be different from the previous one; 5) edge to edge printing is possible; 6) any size of image is possible; 7) process colours are possible; 8) it is possible to print onto uneven surfaces; 9) it is possible to print onto three dimensional shapes e.g. table ware and ornamental ware; 10) it offers greater flexibility in terms of the types of images that can be printed as well as the types of substrates that can be printed onto; 11) a smaller number of ink colours are required.
The ink of the invention in a form for ink jet printing comprises the following:
(a) a carrier material, preferably a wax having a melting point of from 20 to 150° C., preferably from 50 to 100° C., suitable for solid/liquid phase change of the ink,
(b) pigment particles of less than 10 microns in size;
(c) fusible vitreous particles of less than 10 microns in size; and
(d) a dispersant.
The ink is a phase change ink. In other words the ink remains in a solid form while in storage and when the temperature of the printer is lower than the melting point of the ink carrier material, for example when the printer is switched off. When the printer is operating the ink is heated to a temperature which is higher than the melting point of the carrier material, the carrier material melts, and the ink becomes liquid. In this way no sedimentation of the ceramic particles occurs while the ink is in storage thus effectively and significantly increasing the shelf life of the ink. The ink can be inkjet printed onto ceramic, glass, metal
Colrat Francois
Doyle Joseph
Genson Annaik
Hampshire Stuart
Meagher Patrick
Bell Mark L.
Carey Brothers Limited
Faison Veronica F.
Jacobson & Holman PLLC
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