Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-09-27
2004-08-10
Brooke, Michael S (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C523S161000, C347S102000
Reexamination Certificate
active
06773102
ABSTRACT:
FIELD OF THE INVENTION
This invention related to ink jet printing method using an ink jet ink and ink receiver combination wherein the ink is an aqueous inkjet ink comprises a pigment and a polymer binder, and the receiver comprises a non-absorbing substrate, e.g. an untreated vinyl.
BACKGROUND OF THE INVENTION
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets on a substrate (paper, transparent film, fabric, etc.) in response to digital signals. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging and large format printing for outdoor applications such as banners, signage, displays, posters, billboard and bus wraps.
This technique of printing is well suited for printing on a variety of surfaces (receivers) including porous and non-porous surfaces. Porous inkjet receivers have the advantage of large fluid intake and this provides fast printing speed. However, in some applications, such as banners, signage, displays, posters, billboard and bus wraps, these porous receivers suffer from durability issues such as lightfastness, waterfastness, abrasion resistance and weather resistance. In order to overcome these problems, the prints are usually post treated by methods such as lamination, which adds to the cost considerably. Historically, in order to overcome these problems, solvent based inks or UV curable inks were developed for printing on non-absorbing substrates such as vinyl to achieve the desired durability. U.S. Pat. No. 4,106,027 describes such a solvent-based ink that is suitable for printing images on non-absorbing receivers with improved adhesion and durability. EP 0 882 104 B1 describes a UV curable inkjet ink composition for better durability of the print on non-absorbing substrate. A significant environmental, health and safety concern with both of these types of ink is the evaporation of solvent or UV monomer during printing.
U.S. Pat. No. 6,087,416 describes the use of an aqueous based pigment ink for printing on non-absorbing vinyl substrate. That ink contains a grafted copolymer binder that is soluble in the aqueous vehicle but insoluble in water. However, the problem with the ink is that, due to the soluble nature of the binder in the ink vehicle, the ink viscosity is high and the printing reliability is poor. In addition, the printed images are not durable to solvents.
U.S. Pat. No. 4,762,875 described a printing ink containing pigment and polymer additives for plastics and metal surfaces. However, there is a problem with this invention that the solid content for this ink is high, therefore the viscosity of the ink is too high for inkjet ink applications; in addition, the additives used in this invention is hydrophilic in nature therefore the resulted coatings has poor water resistance.
Therefore, there is a need for an ink jet printing method that uses an aqueous based inkjet ink to provide good waterfastness, lightfastness, abrasion resistance, good adhesion to non-absorbing substrates including untreated vinyl, and that can be printed reliably through a piezo or thermal printhead.
SUMMARY OF THE INVENTION
The present invention discloses an ink jet printing method that uses an aqueous based inkjet ink to provide good waterfastness, lightfastness, abrasion resistance, good adhesion to non-absorbing substrates including untreated vinyl, and that can be printed reliably through a piezo or thermal printhead. The invention discloses an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading said printer with an ink jet recording element comprising a non-absorbing substrate;
C) loading said printer with an ink jet ink composition comprising an aqueous ink jet ink composition comprising:
a pigment;
a polymer binder containing less than 25% of hydrophilic monomer by weight of the total polymer, which is dispersible but insoluble in aqueous media;
at least one surfactant; and
a humectant; and
D) printing on said ink jet recording element accompanied by a heating step using said ink jet ink composition in response to said digital data signals.
DETAILED DESCRIPTION OF THE INVENTION
The method used in the present invention is suited for printing on a variety of non-absorbing substrates. The receivers that may be used in the present invention include any substrate that is essentially non-porous and has very low or no fluid absorbing capacity. Usually, these substrates are hydrophobic. Examples of such non-absorbing substrates are metal such as aluminum, copper, stainless steel and alloy etc.; plastics such as vinyl, polycarbonate, polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polystyrene, cellulose; and other substrates such as ceramics, glass.
In order to achieve good image durability when printing aqueous based inks onto a non-absorbing substrate, the polymeric binder in the ink composition needs to be essentially hydrophobic, capable of providing good adhesion strength to the non-absorbing substrate, and also not be easily re-dispersible in water after drying. In addition, in order to provide good ink storage stability and prevent potential nozzle clogging, the hydrophobic polymer binder also needs to be sufficiently stable as a dispersion and compatible with other ink components, such as surfactant, colorants and humectants. Therefore, the polymer binders need to be dispersible in aqueous ink environment but not soluble to achieve low ink viscosity and print durability to both water and solvents. Furthermore, the ink should have sufficiently low surface tension to have good wettability to the non-absorbing substrate.
The pigment used in the current invention can be either self-dispersible pigment such as those described in U.S. Pat. No. 5,630,868, encapsulated pigments as those described in the pending U.S. patent application Ser. No. 09/822,723, filed Mar. 30, 2001, or can be stabilized by a dispersant. The process of preparing inks from pigments commonly involves two steps: (a) a dispersing or milling step to break up the pigment to the primary particle, and (b) dilution step in which the dispersed pigment concentrate is diluted with a carrier and other addenda to a working strength ink. In the milling step, the pigment is usually suspended in a carrier (typically the same carrier as that in the finished ink) along with rigid, inert milling media. Mechanical energy is supplied to this pigment dispersion, and the collisions between the milling media and the pigment cause the pigment to deaggregate into its primary particles. A dispersant or stabilizer, or both, is commonly added to the pigment dispersion to facilitate the deaggregation of the raw pigment, to maintain colloidal particle stability, and to retard particle reagglomeration and settling.
There are many different types of materials which may be used as milling media, such as glasses, ceramics, metals, and plastics. In a preferred embodiment, the grinding media can comprise particles, preferably substantially spherical in shape, e.g., beads, consisting essentially of a polymeric resin. In general, polymeric resins suitable for use as milling media are chemically and physically inert, substantially free of metals, solvent and monomers, and of sufficient hardness and firability to enable them to avoid being chipped or crushed during milling. Suitable polymeric resins include crosslinked polystyrenes, such as polystyrene crosslinked with divinylbenzene, styrene copolymers, polyacrylates such as poly(methyl methylacrylate), olycarbonates, polyacetals, such as Derlin™, vinyl chloride polymers and copolymers, polyurethanes, polyamides, poly(tetrafluoroethylenes), e.g., Teflon™, and other fluoropolymers, high density polyethylenes, polypropylenes, cellulose ethers and esters such as cellulose acetate, poly(hydroxyethylmethacrylate), poly(hydroxyethylacrylate), silicone containing polymers such as polysiloxanes and the like. The polymer can be biodegradable. Exemplary biode
Chen Huijuan D.
Frazier Ricky G.
Wang Xiaoru
Brooke Michael S
Eastman Kodak Company
Wells Doreen M.
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