WO2015036812A1 - Formulations d'encre et constructions de films les utilisant - Google Patents

Formulations d'encre et constructions de films les utilisant Download PDF

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Publication number
WO2015036812A1
WO2015036812A1 PCT/IB2013/002571 IB2013002571W WO2015036812A1 WO 2015036812 A1 WO2015036812 A1 WO 2015036812A1 IB 2013002571 W IB2013002571 W IB 2013002571W WO 2015036812 A1 WO2015036812 A1 WO 2015036812A1
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WO
WIPO (PCT)
Prior art keywords
ink
formulation
inkjet ink
ink formulation
water
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Application number
PCT/IB2013/002571
Other languages
English (en)
Inventor
Benzion Landa
Gregory Nakhmanovich
Galia Golodetz
Sagi Abramovich
Gal AVIDOR
Dan AVITAL
Jose Kuperwasser
Original Assignee
Landa Corporation Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Landa Corporation Ltd. filed Critical Landa Corporation Ltd.
Priority to PCT/IB2013/002571 priority Critical patent/WO2015036812A1/fr
Publication of WO2015036812A1 publication Critical patent/WO2015036812A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/10—Printing inks based on artificial resins
    • C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/10—Printing inks based on artificial resins
    • C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C09D11/107—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from unsaturated acids or derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks

Definitions

  • the presently claimed invention relates to ink formulations suitable for ink jet printing systems, and more particularly for indirect printing systems.
  • a process that is better suited for short run high quality digital printing is used in the HP -Indigo printer.
  • an electrostatic image is produced on an electrically charged image bearing cylinder by exposure to laser light.
  • the electrostatic charge attracts oil-based inks to form a color ink image on the image bearing cylinder.
  • the ink image is then transferred by way of a blanket cylinder onto paper or any other substrate.
  • Inkjet and bubble jet processes are commonly used in home and office printers. In these processes droplets of ink are sprayed onto a final substrate in an image pattern. In general, the resolution of such processes is limited due to wicking by the inks into paper substrates. Fibrous substrates, such as paper, generally require specific coatings engineered to absorb the liquid ink in a controlled fashion or to prevent its penetration below the surface of the substrate. Using specially coated substrates is, however, a costly option that is unsuitable for certain printing applications, especially for commercial printing.
  • coated substrates creates its own problems in that the surface of the substrate remains wet and additional costly and time consuming steps are needed to dry the ink, so that it is not later smeared as the substrate is being handled, for example stacked or wound into a roll. Furthermore, excessive wetting of the substrate by the ink causes cockling and makes printing on both sides of the substrate (also termed perfecting or duplex printing) difficult, if not impossible.
  • Using an indirect or offset printing technique overcomes many problems associated with inkjet printing directly onto the substrate. It allows the distance between the surface of the intermediate image transfer member and the inkjet print head to be maintained constant and reduces wetting of the substrate, as the ink can be dried on the intermediate image member before being applied to the substrate. Consequently, the final image quality on the substrate is less affected by the physical properties of the substrate.
  • transfer members which receive ink droplets from an ink or bubble jet apparatus to form an ink image and transfer the image to a final substrate have been reported in the patent literature.
  • Various ones of these systems utilize inks having aqueous carriers, non-aqueous carrier liquids or inks that have no carrier liquid at all (solid inks).
  • aqueous based inks has a number of distinct advantages. Compared to non-aqueous based liquid inks, the carrier liquid is not toxic and there is no problem in dealing with the liquid that is evaporated as the image dries. As compared with solid inks, the amount of material that remains on the printed image can be controlled, allowing for thinner printed images and more vivid colors.
  • silicone coated transfer members are preferred, since this facilitates transfer of the dried image to the final substrate.
  • silicone is hydrophobic which causes the ink droplets to bead on the transfer member. This makes it more difficult to remove the water in the ink and also results in a small contact area between the droplet and the blanket that renders the ink image unstable during rapid movement of the transfer member.
  • the presently claimed invention pertains to a particular aspect of a novel printing process and system for indirect digital inkjet printing using aqueous inks, other aspects of which are described and claimed in other applications of the same Applicant which have been filed or will be filed at approximately the same time as the present application. Further details on examples of such printing systems are provided in co-pending PCT application Nos. PCT/IB2013/051716, PCT/IB2013/051717 and PCT/IB2013/051718. A non-limitative description of such printing systems will be provided below.
  • the printing process shared in particular, but not exclusively, by the above- mentioned systems, comprises directing droplets of an aqueous inkjet ink onto an intermediate transfer member having a hydrophobic release layer to form an ink image on the release layer, the ink including an organic polymeric resin and a colorant in an aqueous carrier, and the transfer member having a hydrophobic outer surface.
  • each ink droplet in the ink image spreads to form an ink film.
  • the ink is then dried while the ink image is being transported by the intermediate transfer member, by evaporating the aqueous carrier from the ink image to leave a residue film of resin and coloring agent.
  • the residue film is then transferred to a substrate.
  • a water- based inkjet ink formulation comprising: (a) a solvent containing water and, optionally, a co-solvent, said water constituting at least 8 wt.% of the formulation; (b) at least one colorant dispersed or at least partly dissolved within the solvent, the colorant constituting at least 1 wt.% of the formulation; and (c) an organic polymeric resin, which is dispersed or at least partially dissolved within the solvent, the resin constituting 6 to 40 wt.% of the formulation, wherein the average molecular weight of the resin is at least 8,000, the ink formulation having at least one of (i) a viscosity of 2 to 25 centipoise (cP) at at least one temperature in the range of 20-60°C and (ii) a surface tension of not more than 50 milliNewton/m (mN/m) at at least one temperature in the range of 20-60°C; and wherein at least
  • the ink is such that, when substantially dried, (a) at at least one temperature in the range of 90°C to 195°C, the dried ink has a first dynamic viscosity in the range of 1,000,000 (1 x 10 6 ) cP to 300,000,000 (3 x 10 8 ) cP, and (b) at at least one temperature in the range of 50°C to 85°C, the dried ink has a second dynamic viscosity of at least 80,000,000 (8 x 10 7 ) cP, wherein the second dynamic viscosity exceeds the first dynamic viscosity.
  • the first dynamic viscosity is at most 25 » 10 7 cP, at most 20 » 10 7 cP, at most 15 » 10 7 cP, at most 12 » 10 7 cP, at most 10 » 10 7 cP, at most 9 » 10 7 cP, at most 8 » 10 7 cP, or at most 7 » 10 7 cP.
  • the first dynamic viscosity is at least 2 x 10 6 cP, at least 4 x 10 6 cP, at least 5 x 10 6 cP, at least 6 x 10 6 cP, at least 7 x 10 6 cP, at least 8 x 10 6 cP, at least 9 x 10 6 cP, at least 1 x 10 7 cP, at least 1.1 x 10 7 cP, at least 1.2 x 10 7 cP, at least 1.3 x 10 7 cP, at least 1.4 x 10 7 cP, at least 1.5 x 10 7 cP, at least 1.6 x 10 7 cP, at least 2.5 x 10 7 cP, or at least 4 x 10 7 cP.
  • the first dynamic viscosity is within a range of 10 6 cP to 2.5 » 10 8 cP, 10 6 cP to 2.0 » 10 8 cP, 10 6 cP to 10 8 cP, 3 » 10 6 cP to 10 8 cP, 5 » 10 6 cP to 3 » 10 8 cP, 5 » 10 6 cP to 3 » 10 8 cP, 8 » 10 6 cP to 3 » 10 8 cP, 8 » 10 6 cP to 3 » 10 8 cP, 8 » 10 6 cP to 10 8 cP, 10 7 cP to 3 » 10 8 cP, 10 7 cP to 2 » 10 8 cP, 10 7 cP to 10 8 cP, 2 » 10 7 cP to 3 » 10 8 cP, 2 » 10 7 cP to 2 » 10 8 cP, or 2 » 10 7 cP to 10 8 cP.
  • the first dynamic viscosity of the substantially dried ink is in the range of 10 7 cP to 3 xlO 8 cP.
  • the first dynamic viscosity is at least 1.1 x 10 7 cP, at least 1.2 x 10 7 cP, at least 1.3 x 10 7 cP, or at least 1.4 x 10 7 cP; in some of these embodiments the first dynamic viscosity is at most 25 » 10 7 cP, at most 20 » 10 7 cP, at most 15 » 10 7 cP, at most 12 » 10 7 cP, at most 10 » 10 7 cP, at most 9 » 10 7 cP, at most 8 » 10 7 cP, or at most 7 » 10 7 cP; in some of these embodiments, the first dynamic viscosity is within a range of 10 7 cP to 3 » 10 8 cP, 10 7 cP to 2 » 10 8 cP, 10 7 cP to 10 8 cP, 2 » 10 7 cP to 3 » 10 8 cP, 2 » 10 7 cP to 2 » 10 8 cP, or 2 » 10
  • the formulation further comprises a dispersant.
  • the dispersant constitutes not more than 3.5 wt.%, not more than 3 wt.%, not more than 2.5 wt.%, not more than 2 wt.%, not more than 1.5 wt.%, not more than 1 wt.% or not more than 0.5 wt.% of the formulation.
  • the formulation comprises a dispersant and, when substantially dried, has a first dynamic viscosity as mentioned above, at at least one temperature in the range of 90°C to 125°C the first dynamic viscosity of the substantially dried ink is in the range of 4 x 10 7 cP to 2 x 10 8 cP.
  • the first dynamic viscosity is at least 5 x 10 7 cP or 6 x 10 7 cP; in some of these embodiments the first dynamic viscosity is at most 5 x 10 7 cP or 6 x 10 7 cP; in some of these embodiments the dispersant is selected from the group consisting of a high molecular weight aminourethane (Disperbyk ® 198), a modified polyacrylate polymer (EFKA ® 4560, EFKA ® 4580), or acrylic block copolymer made by controlled free radical polymerisation (EFKA ® 4585, EFKA ® 7702), or an ethoxylated non-ionic fatty alcohol (Lumiten ® N-OC 30).
  • a high molecular weight aminourethane Dispersant
  • EFKA ® 4560, EFKA ® 4580 modified polyacrylate polymer
  • EFKA ® 4585, EFKA ® 7702 acrylic block copolymer made by controlled free radical polymer
  • the second dynamic viscosity is at least 9 ⁇ 10 7 cP, at least 10 8 cP, at least 1.1-10 8 cP, at least 1.2-10 8 cP, at least 1.3 ⁇ 0 8 cP, at least 1.4 ⁇ 10 8 cP, at least 1.5 ⁇ 0 8 cP, at least 2.0 ⁇ 0 8 cP, at least 2.5 ⁇ 0 8 cP, at least 3.0 ⁇ 0 8 cP, at least 3.5 ⁇ 0 8 cP, at least 4.0 ⁇ 0 8 cP, at least 5.0 ⁇ 0 8 cP, at least 6 ⁇ 10 8 cP, at least 7.5 ⁇ 0 8 cP, at least 10 9 cP, at least 2 ⁇ 10 9 cP, at least 4 ⁇ 10 9 cP, or at least 6 ⁇ 10 9 cP.
  • the ratio of the second dynamic viscosity to the first dynamic viscosity is at least 1.2: 1, at least 1.3:1, at least 1.5:1, at least 1.7:1, at least 2: 1, at least 2.5: 1, at least 3:1, at least 3.5:1, at least 4: 1, at least 4.5: 1, at least 5: 1, at least 6: 1, at least 7: 1, at least 8: 1, at least 10:1, at least 15: 1, at least 20: 1, at least 25:1, at least 50: 1, at least 100: 1, at least 500: 1, or at least 1000: 1.
  • a ratio of said second dynamic viscosity, at 90°C, to said first dynamic viscosity, at 60°C, is at least 1.2: 1, at least 1.3: 1, at least 1.5:1, at least 1.7: 1, at least 2:1, at least 2.5: 1, at least 3:1, at least 4: 1, at least 4.5 :1, at least 5: 1, at least 6: 1, at least 7: 1, or at least 8: 1.
  • the ratio of the first dynamic viscosity to the second dynamic viscosity is at most 30: 1, at most 25: 1, at most 20: 1, at most 15: 1, at most 12: 1, or at most 10: 1.
  • the weight ratio of the polymeric resin to the colorant is at least 1 : 1. In some embodiments, the weight ratio of the polymeric resin to the colorant is at least 1.25: 1, at least 1.5: 1, at least 1.75: 1, at least 2: 1, at least 2.5: 1, at least 3: 1, at least 3.5:1, at least 4: 1, at least 5: 1, at least 7: 1, or at least 10: 1. In some embodiments, the weight ratio of the polymeric resin to the colorant is at most 15: 1, at most 12: 1, at most 10: 1, at most 7: 1, at most 5: 1, at most 4: 1, at most 3: 1, at most 2.5: 1, at most 2: 1, or at most 1.7: 1.
  • the inkjet ink formulation when substantially dried, has a glass transition temperature (T g ) of at most 50°C, at most 47°C, at most 45°C, at most 44°C, at most 43°C, at most 42°C, at most 40°C, at most 39°C, at most 37°C, at most 35°C, at most 32°C, at most 30°C or at most 28°C.
  • T g glass transition temperature
  • the polymeric resin is an acrylic-based polymer selected from an acrylic polymer and an acrylic-styrene copolymer.
  • the inkjet ink formulation comprises a co-solvent.
  • the co-solvent is miscible with the water.
  • the co- solvent is miscible with water at the at least one particular temperature in the range of 20°C to 60°C, whereby the solvent is a single-phase solvent.
  • the co- solvent is selected to provide the single-phase solvent with a reduced vapor pressure relative to water at the at least one particular temperature in the range of 20°C to 60°C.
  • the co-solvent is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, glycerol, PEG 400, N-methyl pyrrolidone, and mixtures thereof.
  • the co-solvent is not a water-soluble polymer.
  • the co-solvent is not a water-soluble polymer having an average molecular weight greater than 1000, greater than 750, or greater than 500.
  • the co-solvent constitutes at least 5 wt.%, at least 10 wt.%, at least 15 wt.%>, at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, at least 35 wt.%, or at least 40 wt.% of the formulation. In some embodiments, the co-solvent constitutes not more than 40 wt.%, not more than 35 wt.%, not more than 30 wt.%, not more than 25 wt.%, not more than 20 wt.%, not more than 15 wt.%, not more than 10 wt.%, or not more than 5 wt.% of the formulation. In some embodiments, the ratio of co-solvent to water, on a weight-weight basis, is within the range of 0.2: 1 to 1.5 : 1.
  • the inkjet ink formulation further comprises a surfactant, in addition to the polymeric resin, colorant, water and optional co-solvent.
  • the surfactant is present in an amount of not more than 2 wt.%, not more than 1.5 wt.%, not more than 1 wt.%, or not more than 0.5 wt.%.
  • the surfactant is a non-ionic surfactant.
  • the surfactant is an anionic surfactant.
  • the surfactant is a cationic surfactant.
  • the polymeric resin has a T g below 50°C. In various embodiments, the polymeric resin has a T g that is at most 48°C, at most 47°C, at most 45°C, at most 40°C, at most 35°C, or at most 30°C.
  • the average molecular weight of the polymeric resin is not more than 70,000, not more than 65,000, not more than 60,000, not more than 55,000, not more than 50,000, not more than 45,000 or not more than 40,000. In some embodiments, the average molecular weight of the polymeric resin is at least 10,000, at least 15,000, at least 20,000, at least 25,000 or at least 30,000.
  • the average molecular weight of the polymeric resin is at least 70,000, at least 80,000, at least 100,000, at least 120,000, at least 140,000, at least 160,000, at least 180,000, or at least 200,000.
  • the colorant comprises a pigment or a mixture of pigments.
  • the average particle size (D 50 ) of the at least one pigment is not more than 120 nm, not more than 110 nm, not more than 100 nm, not more than 90 nm, not more than 80 nm, not more than 70 nm, not more than 65 nm, or not more than 60 nm.
  • the average particle size (D 50 ) of the pigment is at least 20 nm, at least 25 nm, at least 30 nm, at least 35 nm, at least 40 nm, at least 45 nm, at least 50 nm, at least 55 nm, at least 60 nm, at least 65 nm, or at least 70 nm.
  • the average particle size (D 50 ) of the pigment is in the range of 20-120 nm, in the range of 20- 110 nm, in the range of 20-100 nm, in the range of 20-90 nm, in the range of 20-80 nm, in the range of 20-70 nm, in the range of 30-120 nm, in the range of 30-110 nm, in the range of 30-100 nm, in the range of 30-90 nm, in the range of 30-80 nm, in the range of 30-70 nm, in the range of 35-120 nm, in the range of 35-110 nm, in the range of 35-100 nm, in the range of 35-90 nm, in the range of 35-80 nm, in the range of 35-70 nm, in the range of 40-120 nm, in the range of 40-110 nm, in the range of 40-100 nm, in the range of 40-90 nm, in the range of 40
  • water constitutes at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, at least 35 wt.%, at least 40 wt.%, at least 45 wt.%, at least 50 wt.%, at least 55 wt.%, at least 60 wt.%, at least 65 wt.%, at least 70 wt.%, at least 75 wt.%, or at least 80 wt.% of the formulation.
  • water constitutes not more than 85 wt.%, not more than 80 wt.%, not more than 75 wt.%, not more than 70 wt.%, not more than 65 wt.%, not more than 60 wt.%, not more than 55 wt.%, not more than 50 wt.%, not more than 45 wt.%, or not more than 40 wt.% of the formulation.
  • the polymeric resin is a negatively chargeable resin. In some embodiments, the polymer resin is negatively charged.
  • the ink when substantially dried contains at least 1.2 wt.%, at least 1.5 wt.%, at least 2 wt.%, at least 3 wt.%, at least 4 wt.%, at least 6 wt.%, at least 8 wt.%, or at least 10 wt.% of the colorant.
  • the ink when substantially dried contains at least 5 wt.%, at least 7 wt.%, at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, at least 30 wt.%, at least 40 wt.%), at least 50 wt.%, at least 60 wt.%, or at least 70 wt.% of the polymeric resin.
  • a solubility of the resin in water, at a temperature within a temperature range of 20°C to 60°C, and at a pH within a pH range of 8.5 to 10, is at least 3%), at least 5%, at least 8%, at least 12%, at least 18%, or at least 25%, by weight of dissolved resin to weight of solution.
  • the inkjet ink formulation comprises a pH-raising compound.
  • the pH-raising compound constitutes not more than 2 wt.%, not more than 1.5 wt.%, or not more than 1 wt.% of the formulation.
  • an inkjet ink concentrate comprising: (a) a solvent containing water and, optionally, a co- solvent; at least one colorant dispersed or at least partly dissolved within said solvent; and an organic polymeric resin, which is dispersed or at least partially dissolved within said solvent, wherein the average molecular weight of said resin is at least 8,000, and (d) optionally, at least one of a surfactant, a dispersant, and a pH raising compound; wherein the concentrate, when diluted with a solvent comprising water and a co-solvent, yields an aqueous inkjet formulation as described herein.
  • the concentrate must be diluted with at least 50%, at least 100%), at least 150%, at least 200%), at least 250%), at least 300%), least 350%> or at least 400%) solvent on a weight/weight basis relative to the concentrate to yield the aqueous inkjet ink formulation.
  • the co-solvent is selected from the group consisting of glycerol, propylene glycol, ethylene glycol, diethylene glycol, N-methyl pyrrolidone, PEG 400, and mixtures thereof.
  • the inkjet ink formulation has both a viscosity of 2 to 25 cP at at least one temperature in the range of 20-60°C and a surface tension of not more than 50 (mN/m) at at least one temperature in the range of 20-60°C.
  • the second dynamic viscosity is not more than 6 x 10 9 cP, not more than 5 x 10 9 cP, not more than 4 x 10 9 cP, not more than 3 x 10 9 cP, not more than 2 x 10 9 cP, not more than 1 x 10 9 cP, not more than 9 x 10 8 cP, not more than 8 x 10 8 cP, not more than 7 x 10 cP, not more than 6 x 10 cP, not more than 5 x 10 cP, not more than 4 x 10 8 cP, not more than 3 x 10 8 cP, or not more than 2 x 10 8 cP.
  • the polymeric resin comprises primarily or exclusively one or more negatively chargeable polymers, such as polyanionic polymers.
  • a negatively chargeable polymer or “negatively chargeable polymer resin” is meant a polymer or polymeric resin which has at least one proton which can easily be removed to yield a negative charge; as used herein, the term refers to an inherent property of the polymer, and thus may encompass polymers which are in an environment in which such protons are removed, as well as polymers in an environment in which such protons are not removed.
  • a negatively charged polymer resin refers to a resin in an environment in which one or more such protons have been removed.
  • Such groups can be covalently bound to polymeric backbones; for example styrene-acrylic copolymer resins have carboxylic acid functional groups which readily lose protons to yield negatively-charged moieties.
  • Many polymers suitable for use in embodiments of the invention when dissolved in water, will be negatively charged; others may require the presence of a pH raising compound to be negatively charged.
  • polymers will have many such negatively chargeable groups on a single polymer molecule, and thus are referred to as polyanionic polymers.
  • polyanionic polymers include, for instance, polysulfonates such as polyvinylsulfonates, poly(styrenesulfonates) such as poly(sodium styrenesulfonate) (PSS), sulfonated poly(tetrafluoroethylene), polysulfates such as polyvinylsulfates, polycarboxylates such as acrylic acid polymers and salts thereof (e.g., ammonium, potassium, sodium, etc.), for instance, those available from BASF and DSM Resins, methacrylic acid polymers and salts thereof (e.g., EUDRAGIT ® , a methacrylic acid and ethyl acrylate copolymer), carboxymethylcellulose, carboxymethylamylose and carboxylic acid derivatives of various other polymers, polyanionic peptide
  • the polymeric resin comprises an acrylic-based polymer, viz. a polymer or copolymer made from acrylic acid or an acrylic acid derivative (e.g. methacrylic acid or an acrylic acid ester), such as polyacrylic acid or an acrylic acid- styrene copolymer.
  • the polymeric resin may be, or include, an acrylic styrene co-polymer.
  • the polymeric resin comprises primarily or exclusively an acrylic-based polymer selected from an acrylic polymer and an acrylic-styrene copolymer.
  • the polymeric resin comprises an aliphatic polyurethane.
  • the polymeric resin is at least partly water soluble; in some instances, the polymeric resin is water dispersible, and may be provided as an emulsion or a colloid.
  • examples of such materials that are available commercially that have been found suitable for use in embodiments of the present invention include Joncryl 142-E, Joncryl 637, Joncryl 638, Joncryl 8004, Joncryl HPD 296, Neocryl BT-26, Neocryl BT-100, Neocryl BT-102, and Neocryl BT-9. (Joncryl® and Neocryl® are registered trademarks of BASF Corporation and DSM, respectively.)
  • the water, co-solvent if present, colorant, and polymeric resin constitute at least 65 wt.%, at least 70 wt.%, at least 75 wt.%, at least 80 wt.%, at least 85 wt.%, at least 90 wt.% or at least 95 wt.% of the formulation.
  • the colorant contains less than 5% dye. In some embodiments, the colorant is substantially free of a dye.
  • the colorant comprises a dye. In some embodiments, the colorant contains less than 5% pigment. In some embodiments, the colorant comprises a dye and is substantially free of pigment.
  • the polymeric resin constitutes not more than 20 wt.%, not more than 19 wt.%, not more than 18 wt.%, not more than 17 wt.%, not more than 16 wt.%, not more than 15 wt.%, not more than 14 wt.%, not more than 13 wt.%, not more than 12 wt.%, not more than 1 1 wt.%, not more than 10 wt.%, not more than 9 wt.%, or not more than 8 wt.% of the formulation.
  • the polymeric resin is at least partially soluble in the solvent. In some embodiments, the polymeric resin is partially soluble in the solvent at a pH of 8.5-10. In various embodiments, at at least one temperature in the range of 20- 60 ° C, the solubility of the polymeric resin in water is at least 2%, at least 3%, at least 5%, at least 7.5%, or at least 10% on a resin-to-water weight- weight basis.
  • the polymeric resin has a viscosity of less than 10 11 cP, of 5 x 10 10 cP or less, of 10 10 cP or less, of 5 x 10 9 cP or less, of 10 9 cP or less, or of 5 x 10 8 cP or less.
  • the polymeric resin has a viscosity of 5 x 10 8 cP or less, of 10 8 cP or less, or of 5 x 10 7 cP or less.
  • the polymeric resin consists predominantly of acrylic styrene copolymer. In some embodiments, the polymeric resin consists essentially of acrylic styrene copolymer. In various embodiments, the weight ratio of the acrylic styrene copolymer to the total amount of polymeric resin is at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 0.95, or substantially 1.
  • the viscosity of the formulation is within a range of 2-25 cP. In some embodiments, the viscosity in this temperature range is at least 2 cP, at least 3 cP, at least 4 cP, at least 5 cP, or at least 6 cP. In some embodiments, the viscosity in this temperature range is not more than 25 cP, not more than 22 cP, not more than 20 cP, not more than 18 cP, or not more than 15 cP.
  • the surface tension of the formulation at at least one particular temperature within a temperature range of 20°C to 60°C is not more than 50 milliNewton/m, not more than 45 mN/m, or not more than 40 mN/m. In various embodiments, the surface tension of the formulation at this temperature is at least 18 mN/m, at least 20 mN/m, or at least 22 mN/m.
  • the formulation is substantially free of water soluble polymer. In some embodiments, the formulation is substantially free of saccharide. In some embodiments, the formulation is substantially free of wax. In some embodiments, other than a pH-controlling agent, the formulation is substantially free of salt. In some embodiments, other than salts having the polymeric resin and/or the dispersant, if present, as one of the ions in the salt, the formulation is substantially free of salt. In some embodiments, the formulation is substantially free of precipitant. In some embodiments, the formulation is substantially free of a dye insolubilizing agent. In some embodiments, the formulation is substantially free of a coagulating agent.
  • the formulation contains less than 5 wt.% inorganic filler particles (such as silica particulates, titania particulates and alumina particulates), less than 3 wt.% inorganic filler particles, less than 2 wt.% inorganic filler particles, less than 1 wt.% inorganic filler particles, less than 0.5 wt.% inorganic filler particles, or less than 0.1 wt.% filler particles. In some embodiments, the formulation is substantially free of inorganic filler particles.
  • inorganic filler particles such as silica particulates, titania particulates and alumina particulates
  • the formulation is substantially free of inorganic filler particles.
  • the formulation is substantially free of a co-solvent having a molecular weight of 1000 or higher, having a molecular weight of 750 or higher, or having a molecular weight of 500 or higher.
  • the co-solvent of which the formulation is substantially free is a polymer having a plurality of hydroxyl groups.
  • the polymer having a plurality of hydroxyl groups is selected from a polyethylene glycol and a polypropylene glycol.
  • the formulation is devoid or substantially devoid of oils such as mineral oils and vegetable oils (e.g., linseed oil and soybean oil), or other oils used in offset ink formulations, and thus contains at most 1%, at most 0.5%, at most 0.1%, or at most 0%), by weight, of one or more oils, cross-linked fatty acids, or fatty acid derivatives produced upon air-drying.
  • oils such as mineral oils and vegetable oils (e.g., linseed oil and soybean oil), or other oils used in offset ink formulations, and thus contains at most 1%, at most 0.5%, at most 0.1%, or at most 0%), by weight, of one or more oils, cross-linked fatty acids, or fatty acid derivatives produced upon air-drying.
  • the total amount of material in the formulation which remains as solids when the formulation is substantially dried constitutes less than 20 wt.%, less than 19 wt.%, less than 18 wt.%, less than 17 wt.%, less than 16 wt.%, less than 15 wt.%), less than 14 wt.%, less than 13 wt.%, or less than 12 wt.% of the formulation.
  • the colorant and the polymeric resin together constitute at least 50 wt.%, at least 55 wt.%, at least 60 wt.%, at least 65 wt.%, at least 70 wt.%, at least 75 wt.%, at least 80 wt.%, at least 85 wt.%, at least 90 wt.%, at least 95 wt.% or at least 97 wt.% of the material in the formulation which remains as solids when the formulation is substantially dried.
  • the chemical agent used in the pre -treatment of the release layer prior to ink jetting may be referred to as a conditioning agent.
  • the chemical agent has at least one of (1) a positive charge density of at least 3 meq/g of chemical agent and an average molecular weight of at least 250, and (2) a nitrogen content of at least 1% and a molecular weight of at least 10,000.
  • the chemical agent has a positive charge density of at least 3 meq/g and an average molecular weight of at least 5,000; or a positive charge density of at least 6 meq/g and an average molecular weight of at least 1 ,000; or a nitrogen content of at least 1 wt.% and an average molecular weight of at least 50,000; or a nitrogen content of at least 18 wt.% and an average molecular weight of at least 10,000.
  • the chemical agent comprises nitrogen atoms in functional groups selected from primary amines and linear, branched and cyclic secondary and tertiary amines, as well as quaternized ammonium groups and combinations of such groups.
  • the chemical agent is selected from the group consisting of linear polyethylene imine, branched polyethylene imine, modified polyethylene imine, poly(diallyldimethylammonium chloride), poly(4-vinylpyridine), polyallylamine, a vinyl pyrrolidone-dimethylaminopropyl methacrylamide co-polymer (e.g., Viviprint 131), a vinyl caprolactam-dimethylaminopropyl methacryamide hydroxy- ethyl methacrylate copolymer (e.g., Viviprint 200), a quaternized copolymer of vinyl pyrrolidone and dimethylaminoethyl methacrylate with diethyl sulfate (e.g., Viviprint 650), a guar hydroxypropyltrimonium chloride, and a hydroxypropyl guar hydroxypropyl- trimonium
  • the chemical agent is applied as a dilute solution, resulting in a very thin layer of chemical agent on the release layer and a low concentration of the chemical agent on the release layer after evaporation of the solvent.
  • an ink film construction including: (a) a printing substrate; and (b) a plurality of continuous ink films, fixedly adhered to a surface of the printing substrate, the ink films containing at least one colorant dispersed in an organic polymeric resin; the ink films having a first dynamic viscosity within a range of 10 6 cP to 5 » 10 7 cP for at least a first temperature within a first range of 60°C to 87.5°C, the ink films having a second dynamic viscosity of at least 6 » 10 7 cP, for at least a second temperature within a second range of 50°C to 55°C.
  • an ink film construction including: (a) a printing substrate; and (b) a plurality of continuous ink films, fixedly adhered to a surface of the printing substrate, the ink films containing at least one colorant dispersed in an organic polymeric resin, and a softening agent selected to improve a flowability of the polymeric resin; the ink films having a first dynamic viscosity within a range of 10 6 cP to 5 » 10 7 cP for at least a first temperature within a first range of 60°C to 100°C, the ink films having a second dynamic viscosity of at least 6 » 10 7 cP, for at least a second temperature within a second range of 50°C to 55°C, the softening agent having a vapor pressure of at most 0.40 kPa at 150°C.
  • a water- based inkjet ink formulation including: (a) a solvent containing water; (b) at least one colorant dispersed or at least partly dissolved within the solvent; and (c) at least one organic polymeric resin, dispersed within the solvent; the ink formulation forming, when dried, a dried ink residue having: (i) a first dynamic viscosity within a range of 10 6 cP to 5 » 10 7 cP at at least a first temperature within a first range of 60°C to 87.5°C; and (ii) a second dynamic viscosity of at least 6 » 10 7 cP, for at least a second temperature within a second range of 50°C to 55°C.
  • the first dynamic viscosity is at most 4 » 10 7 cP, at most 3 » 10 7 cP, at most 2.5 » 10 7 cP, at most 2 » 10 7 cP, at most 1.5 » 10 7 cP, or at most M0 7 cP.
  • the first dynamic viscosity is at least 2 » 10 6 cP, at least 4 » 10 6 cP, at least 6 » 10 6 cP, at least 7 » 10 6 cP, at least 8 » 10 6 cP, at least 9 » 10 6 cP, or at least M0 7 cP.
  • the first dynamic viscosity is within a range of 10 6 cP to 4 » 10 7 cP, 10 6 cP to 3 » 10 7 cP, 10 6 cP to 2 » 10 7 cP, 3 » 10 6 cP to 4 » 10 7 cP, 3 « 10 6 cP to 3 « 10 7 cP, 5 « 10 6 cP to 3 « 10 7 cP, 7 « 10 6 cP to 3 « 10 7 cP, 8 » 10 6 cP to 3 » 10 7 cP, 9 » 10 6 cP to 3 » 10 7 cP, 10 7 cP to 5 » 10 7 cP, 10 7 cP to 5 » 10 7 cP, 10 7 cP to 4 » 10 7 cP, 10 7 cP to 3 » 10 7 cP, 1.5 » 10 7 cP to 3 » 10 7 cP, or 10 7 cP to 3 » 10 7 cP.
  • the second dynamic viscosity is at least 8 » 10 7 cP, at least 9 » 10 7 cP, at least 10 8 cP, at least 1.2 » 10 8 cP, at least 1.5 » 10 8 cP, at least 2.0 » 10 8 cP, at least 2.5 » 10 8 cP, at least 3.0 » 10 8 cP, at least 3.5'10 8 cP, at least 4.0 » 10 8 cP, at least 5.0 » 10 8 cP, or at least 7.5 » 10 8 cP.
  • the second dynamic viscosity is at most 6 » 10 9 cP, at most 4 » 10 9 cP, at most 3 » 10 9 cP, at most 2 » 10 9 cP, at most 1.5 » 10 9 cP, or at most 10 9 cP.
  • the second dynamic viscosity is within a range of 7 » 10 7 cP to 5 » 10 9 cP, 7 » 10 7 cP to 3 » 10 9 cP, 7'10 7 cP to 2 » 10 9 cP, 7 » 10 7 cP to M0 9 cP, 8 » 10 7 cP to 5 » 10 9 cP, 9 » 10 7 cP to 5 » 10 9 cP, 9 » 10 7 cP to 3 » 10 9 cP, 9 » 10 7 cP to 2 » 10 9 cP, 9 » 10 7 cP to 1.5 » 10 9 cP, M0 8 cP to 5 » 10 9 cP, M0 8 cP to 3 » 10 9 cP, M0 8 cP to 2'10 9 cP, or 1.5 » 10 8 cP to 1.5 » 10 9 cP.
  • the upper temperature limit of the first range is 87°C, 86°C, 85°C, 84°C, 82°C, 80°C, 78°C, 76°C, 74°C, 72°C, 70°C, or 68°C.
  • the lower temperature limit of the first range is 61°C, 62°C, 63°C, 64°C, or 65°C.
  • the average single ink-film thickness or height of the films is at most 2,000nm, at most l,800nm, at most l,600nm, at most l,400nm, at most l,200nm, at most ⁇ , ⁇ , or at most ⁇ , ⁇ .
  • the average single ink-film thickness or height of the films is at most 900nm, at most 800nm, at most 700nm, at most 650nm, at most 600nm, or at most 550nm.
  • the ink films or dried ink residue have a glass transition temperature (T g ) of at least 52°C, at least 54°C, at least 56°C, or at least 58°C.
  • the ink films or dried ink residue have a glass transition temperature (T g ) of at least 60°C, at least 65°C, at least 70°C, or at least 75°C.
  • the plurality of ink films or dried ink residue contain at least one water-soluble material or at least one water-dispersible material.
  • the at least one water-soluble material includes an aqueous dispersant.
  • the ink films or dried ink residue contain at least 2%, at least 3%, at least 5%, or at least 8%, by weight, of the water-soluble material.
  • the ink films or dried ink residue contain at least 30%, at least 40%, at least 50%>, at least 60%>, or at least 70%>, by weight, of the water dispersible material.
  • the ink films or dried ink residue contain at most 10%, at most 7%, at most 5%, at most 3%, at most 2%>, at most 1%, or at most 0.5%> inorganic filler particles, by weight.
  • the ink films are laminated onto the surface of the printing substrate.
  • the ink films or dried ink residue contain at least 1.2%, at least 1.5%, at least 2%, at least 3%, at least 4%, at least 6%, at least 8%, at least 10%, at least 12%, at least 15%, or at least 20% of the colorant, by weight.
  • the ink films or dried ink residue contain at least 20%, at least 30%, at least 40%, at least 50%, at least 60%), or at least 70%> of the resin, by weight.
  • the colorant includes at least one pigment.
  • the weight ratio of the resin to the colorant within the plurality of ink films or dried ink residue is at least 1 : 1, at least 1.25: 1, at least 1.5: 1, at least 1.75: 1, at least 2: 1, at least 2.5: 1, at least 3: 1, at least 3.5: 1, at least 4: 1, at least 5: 1, at least 7: 1, or at least 10:1.
  • ⁇ defines a temperature differential between a temperature (T F ) at which the ink films or dried ink residue begin to exhibit a particular degree of flowability, and a baseline temperature (T B ):
  • the degree of flowability being defined by a critical viscosity ( ⁇ at which the degree of flowability is achieved, and wherein, when the baseline temperature equals 50°C, and the critical viscosity equals 10 8 cP, the temperature differential is at least 3°C, at least 4°C, at least 5°C, at least 7°C, at least 12°C, at least 15°C, at least 18°C, at least 20°C, or at least 25°C.
  • the printing substrate is a fibrous printing substrate.
  • the fibrous printing substrate is a commodity coated printing substrate.
  • the fibrous printing substrate is an uncoated printing substrate.
  • the continuous ink film of the continuous ink films is defined as an ink dot
  • a dimensionless aspect ratio (R asp ect) is defined by:
  • D do t is an average diameter of the dot
  • H do t is an average thickness of the dot
  • the dimensionless aspect ratio being at least 15, at least 20, at least 25, or at least 30, at least 40, at least 50, at least 60, at least 75, at least 85, at least 95, at least 110, or at least 120.
  • the dimensionless aspect ratio is at most 200 or at most 175.
  • the plurality of continuous ink films are fixedly adhered directly on the surface of the printing substrate.
  • the colorant constitutes at least 0.3%, at least 0.5%, at least 0.7%>, at least 0.85%>, at least 1%, at least 1.2%, at least 1.4%, at least 1.6%, at least 1.8%, or at least 2%, by weight, of the formulation.
  • the formulation further includes a softening agent.
  • the softening agent has a vapor pressure of at most 0.40 kPa, at most 0.35 kPa, at most 0.25 kPa, at most 0.20 kPa, at most 0.15 kPa, at most 0.12 kPa, at most 0.10 kPa, at most 0.08 kPa, at most 0.06 kPa, or at most 0.05 kPa, at 150°C.
  • the softening agent is stable up to a temperature of at least 170°C, at least 185°C, at least 200°C, or at least 220°C.
  • the formulation contains at most 10%, at most 8%, at most 6%, at most 4%, at most 2%, at most 1%), or at most 0.2% glycerol, by weight.
  • the formulation or the at least one organic polymeric resin further includes an aqueous dispersant.
  • the dispersant constitutes at most 5%, at most 4.5%, at most 4%, at most 3.5 wt.%, at most 3 wt.%, at most 2.5 wt.%, at most 2 wt.%, at most 1.5 wt.%, at most 1 wt.% or at most 0.5 wt.% of the formulation.
  • the dispersant is selected from the group consisting of high molecular weight polyurethanes or aminourethanes, styrene-acrylic copolymers, modified polyacrylate polymers, acrylic block copolymer made by controlled free radical polymerization, sulfosuccinates, acetylenic diols, ammonium salts of carboxylic acid, alkylol ammonium salts of carboxylic acid, aliphatic polyethers with acidic groups, and ethoxylated non-ionic fatty alcohols.
  • the polymeric resin includes, mainly includes, or consists essentially of an acrylic-based polymer selected from the group consisting of an acrylic polymer and an acrylic-styrene copolymer; or includes, mainly includes, or consists essentially of linear or branched resins of polyester or co-polyester.
  • the formulation is adapted such that when diluted by at least 50%, at least 100%, at least 150%, at least 200%, at least 250%, at least 300%, at least 350%, or at least 400%, on a weight/weight basis by a diluting solvent or water, a resultant mixture is an aqueous inkjet ink having: (i) a viscosity of 2 to 25 cP at at least one particular temperature in a range of 20-60°C; and (ii) a surface tension of at most 50 milliNewton/m at at least one particular temperature within the range.
  • the presently claimed invention pertains to aqueous inkjet ink formulations. These formulations may be used in indirect printing systems having an intermediate transfer member.
  • the present formulations may be used as part of and in conjunction with, respectively, a novel printing process and system for indirect digital inkjet printing, other novel aspects of which are described and claimed in other applications of the same applicant being filing at the same time as the present patent application.
  • the printing process comprises directing droplets of an aqueous inkjet ink onto an intermediate transfer member having a hydrophobic release layer to form an ink image on the release layer, the ink including an organic polymeric resin and a colorant in an aqueous carrier.
  • release layer is used herein to denote the hydrophobic outer surface of the intermediate transfer member, and while in some instances that outer surface may be part of a layer that is readily distinguishable from the rest of the intermediate transfer member, in theory it is possible that the intermediate transfer member has a uniform construction, in which case the outer surface will not, strictly speaking, be part of a separate layer.
  • the release layer may be pretreated with a conditioning agent. Upon impinging upon the intermediate transfer member, each ink droplet in the ink image spreads to form an ink film having a pancake-like structure.
  • the ink is then dried while the ink image is on the intermediate transfer member, generally while being transported by the intermediate transfer member, by evaporating the aqueous carrier from the ink image to leave a residue film of resin and coloring agent.
  • the residue film is then transferred to a substrate.
  • each ink droplet tends to spread out into a pancake-like structure due to the kinetic energy of the droplet itself.
  • the ink used in the process described above is aqueous, but the release layer of the intermediate transfer member is hydrophobic, the ink droplets tend to bead on the transfer member.
  • the term "to bead” is used herein to describe the action of surface tension to cause a pancake or disk-like film to contract radially and increase in thickness so as to form a bead, that is to say a near-spherical globule.
  • the chemical compositions of the ink and of the release layer or of the chemical agent which is applied to the surface of the intermediate transfer member are selected, inter alia, so as to counteract the tendency of the ink film produced by each droplet to bead under the action of the surface tension of the aqueous carrier, without causing each droplet to spread by wetting the surface of the intermediate transfer member.
  • this is due to mutually attractive intermolecular forces between molecules in the region of each droplet nearest the surface of the intermediate transfer member and molecules on the surface of the intermediate transfer member itself.
  • a hydrophobic outer surface on the intermediate transfer member is desirable as it assists in the eventual transfer of the residue film to the substrate.
  • Such a hydrophobic outer surface or release layer is however undesirable during ink image formation, among other reasons because bead-like ink droplets cannot be stably transported by a fast moving intermediate transfer member and because they result in a thicker film with less coverage of the surface of the substrate.
  • the hydrophobic release layer may comprise positively chargeable molecules or moieties, such as amino silicones as further detailed in a co-pending PCT application No. PCT/IB2013/051751.
  • the contacting of the release layer with a positively chargeable polymeric chemical agent prior to the jetting of the aqueous ink facilitates the preservation, or freezing, of the thin pancake shape of each ink droplet, that is caused by the flattening of the ink droplet on impacting the surface of the intermediate transfer member, despite the hydrophobicity of the surface of the intermediate transfer member.
  • a “positively chargeable polymer” or “positively chargeable group” is meant a polymer or chemical moiety which either can readily add a proton (e.g., -NH 2 ) or has a permanent positive charge (e.g., -N(CH 3 ) 3 + ); as used herein, the term refers to an inherent property of the polymer or moiety, and thus may encompass polymers or moieties which are in an environment in which such protons are added, as well as polymers in an environment in which such protons are not added.
  • the term "a positively charged” polymer or group refers to a polymer or group in an environment in which one or more such protons have been added or which has a permanent positive charge.
  • the invention described and claimed in PCT/IB2013/000757 facilitates printing using an aqueous ink and an intermediate transfer member having a hydrophobic surface, by applying to the surface of the transfer member to which the ink is applied - i.e. by applying to the hydrophobic release layer - a small amount, preferably in the form of a thin layer, of chemical agent that reduces the tendency of the aqueous inkjet ink droplet that has been printed onto the release layer to contract.
  • Measurements show that the contact angle of water on a hydrophobic release layer so treated remains high, indicating that, in contrast to wetting agents, treatment with the chemical agent does not result in a loss of surface tension.
  • the chemical agent advantageously reduces droplet contraction, without causing an undesired spreading of the droplet much beyond its initial impact pancake shape.
  • Electron micrographs of aqueous inkjet inks in accordance with embodiments of the present invention, printed onto a release layer so treated, then dried while still on the release layer and then transferred to a paper substrate show that the edges of such ink droplets are sharper than the edges of ink droplets transferred to paper by other means.
  • the chemical agent thus fixes the ink film to the release layer, although it will be appreciated that such fixation is weaker than the subsequent adhesion of the resin in the ink film to the substrate.
  • the positively chargeable functional groups of the molecules on the release layer are part of the release layer itself (e.g., if the release layer has protonatable elastomers such as amino silicones) or whether they are part of the chemical agent applied on the electrically neutral hydrophobic release layer (e.g., silanol terminated silicones), such positive groups may interact with negatively charged functional groups of molecules of the ink.
  • Such groups can be covalently bound to polymeric backbones; for example styrene-acrylic copolymer resins have carboxylic acid functional groups which readily lose protons to yield negatively- charged moieties.
  • the hydrophobic release layer of the intermediate transfer member may be silicone-based.
  • the release layer can be the product of cross-linking a silanol-terminated polydialkylsiloxane, such as a polymer of formula (I):
  • Rl to R6 are each independently a Ci to C 6 hydrocarbon group (linear or branched, saturated or unsaturated)
  • R7 is selected from the group consisting of OH, H or a Ci to C 6 hydrocarbon group (linear or branched, saturated or unsaturated)
  • n is an integer from 50 to 400. In some cases, n is an integer between 200 and 350.
  • the silicone has a molecular weight of between 15,000 to 26,000 g/mole, e.g., 16,000 to 23,000 g/mol, prior to crosslinking. In one example of such a material, the silicone is a silanol- terminated polydimethylsiloxane, i.e.
  • the crosslinker which may be present in an amount between e.g., 5 to 20 wt.%, such as 9 to 12 wt.%, relative to the polymer prior to crosslinking, may be a oligomeric condensate of a polyethylsilicate monomer, such as Silopren E 0.7 (Momentive), PSI023 (Gelest) and Ethylsilicate 48 (Colcoat).
  • the silicon polymer may be made by condensation curing.
  • Release layers so prepared are amenable to pre-treatment with a conditioning agent as afore mentioned.
  • a conditioning agent as afore mentioned.
  • the chemical agent generally be dry prior to the jetting of the ink, and in practice this is the the conditioning agent may be immediately removed following application ⁇ e.g., by air flow) and release layer will generally be heated, resulting in drying of the chemical agent solution before jetting of the ink occurs, so that the ink droplets are directed onto a substantially dry surface.
  • Aqueous inkjet inks in accordance with embodiments of the present invention which are suitable for use in the process and with the system described above and hereinbelow, contain water-soluble or water-dispersible colorants, e.g., nano pigments, and a water-dispersible or water-soluble polymeric resin.
  • water-soluble or water-dispersible colorants e.g., nano pigments
  • a water-dispersible or water-soluble polymeric resin e.g
  • the inks should also be formulated so as to transfer well from the intermediate transfer member to the substrate under the conditions of use, and preferably should be susceptible to having most or substantially all of the solvent and, if present, other volatiles removed therefrom prior to the transfer.
  • the ratio of charges in the ink droplet to the charges in the region of the release layer upon which the ink droplet rests may be small, but this need not be the case, and often there will be a significantly larger number of negative charges in an ink droplet relatively the area of the release layer upon which the ink is jetted.
  • the intermediate transfer member is a flexible blanket of which the outer surface is the hydrophobic outer surface upon which the ink image is formed.
  • the blanket may be looped to form a continuous belt when mounted in suitable printing systems. It is however alternatively possible for the intermediate transfer member to be constructed as a drum.
  • the ink image prior to transferring the residue film onto the substrate, is heated to a temperature at which the residue film of resin and coloring agent that remains after evaporation of the aqueous carrier is rendered tacky (e.g. , by softening of the resin).
  • the temperature of the tacky residue film on the intermediate transfer member may be higher than the temperature of the substrate, whereby the residue film cools during adhesion to the substrate.
  • the effect of the cooling may be to increase the cohesion of the residue film, whereby its cohesion exceeds its adhesion to the transfer member so that, when brought into contact with the substrate e.g., at an impression station (see below), for which it has greater affinity than for the release layer, substantially all of the residue film is separated from the intermediate transfer member and impressed as a film onto the substrate. In this way, it is possible to ensure that the residue film is impressed on the substrate without significant modification to the area covered by the film nor to its thickness.
  • inks in accordance with embodiments of the invention which may be used if desired in conjunction with a chemical agent on the release layer, preferably utilize an aqueous carrier, which reduces safety concerns and pollution issues that occur with inks that utilize volatile hydrocarbon carrier.
  • the ink must have the physical properties that are needed to apply very small droplets close together on the transfer member.
  • ink jet printers require a trade-off between purity of the color, the ability to produce complete coverage of a surface and the density of the ink-jet nozzles. If the droplets (after beading) are small, then, in order to achieve complete coverage, it is necessary to have the droplets close together. However, it is very problematic (and expensive) to have the droplets closer than the distance between pixels. By forming relatively flat droplet films that are held in place in the manner described above, the coverage caused by the droplets can be close to complete.
  • the carrier liquid in the image is evaporated from the image after it is formed on the transfer member. Since the colorant in the droplets is distributed within the droplet, either as a solution (e.g., in the case of a dye) or as a dispersion (e.g., in the case of a pigment), a preferred method for removal of the liquid is by heating the image, either by heating the transfer member or by external heating of the image after it is formed on the transfer member, or by a combination of both. In some instances, the carrier is evaporated by blowing a heated gas (e.g. air) over the surface of the transfer member.
  • a heated gas e.g. air
  • different ink colors are applied sequentially to the surface of the intermediate transfer member and a heated gas is blown onto the droplets of each ink color after their deposition but before deposition on the intermediate transfer member of the next ink color. In this way, merging of ink droplets of different colors with one another is reduced.
  • the polymer resin used in the ink is a polymer that enables the ink to form a residue film when it is heated (the term residue film is used herein to refer to the ink droplets after evaporation of the liquid carrier therefrom).
  • residue film is used herein to refer to the ink droplets after evaporation of the liquid carrier therefrom.
  • Acrylic-styrene copolymers with an average molecular weight around 60,000, for example, have been found to be suitable.
  • Preferably all of the liquid in the ink is evaporated, however, a small amount of liquid, that does not interfere with the forming of a residue film may be present.
  • the formation of a residue film has a number of advantages. The first of these is that when the image is transferred to the final substrate all, or nearly all, of the image can be transferred.
  • the residue film is very thin, preferably between 10 nm and 800 nm and more preferably between 50 nm and 500 nm. Such thin films are transferred intact to the substrate and, because they are so thin, replicate the surface of the substrate by closely following its contours. This results in a much smaller difference in the gloss of the substrate between printed and non-printed areas.
  • the residue film When the residue film reaches a transfer or impression station at which it is transferred from the intermediate transfer member to the final substrate, it is pressed against the substrate, having preferably previously been heated to a temperature at which it becomes tacky in order to attach itself to the substrate.
  • the substrate which is generally not heated, cools the image so that it solidifies and transfers to the substrate without leaving any of residue film on the surface of the intermediate transfer member.
  • additional constraints are placed on the polymer in the ink.
  • the carrier is termed an aqueous carrier is not intended to preclude the presence of certain organic materials in the ink, in particular, certain innocuous water miscible organic material and/or co-solvents, such as ethylene glycol or propylene glycol.
  • the outer surface of the intermediate transfer member is hydrophobic, there may be little or substantially no swelling (e.g., less than 1.5%) of the transfer member due to absorption of water from the ink; such swelling is known to distort the surface of transfer members in commercially available products utilizing silicone coated transfer members and hydrocarbon carrier liquids. Consequently, the process described above and hereinbelow may achieve a highly smooth release surface, as compared to intermediate transfer member surfaces of the prior art.
  • the image transfer surface is hydrophobic, and therefore not water absorbent, substantially all the water in the ink should be evaporated away if wetting of the substrate is to be avoided.
  • certain co-solvents such as ethylene glycol or propylene glycol, which have higher boiling points than water, may reduce the rate at which the solvent evaporates relative to the situation in which water is the only solvent.
  • the ink droplets on the transfer member are of sufficiently small thickness relative to their surface area, and are usually heated at a temperature for a time, sufficient to allow for evaporation of substantially all of the solvent prior to transfer to the substrate.
  • FIG. 1 is an exploded schematic perspective view of a printing system in accordance with which an embodiment of the invention may be used;
  • Figure 2 is a schematic vertical section through the printing system of Fig.1, in which the various components of the printing system are not drawn to scale;
  • Figure 3 is a schematic representation of a printing system of the invention in accordance with which an embodiment of the invention may be used;
  • Figures 4 and 5 are scans of paper onto which ink was transferred from a hydrophobic release layer, illustrating the effects of contacting the release layer with different (or no) chemical agents prior to jetting of the ink onto the release layer;
  • Figure 6 is a ramped-down temperature sweep plot of dynamic viscosity as a function of temperature, for several ink formulations of the present invention.
  • Figure 7 is a ramped-down temperature sweep plot of dynamic viscosity as a function of temperature, for several ink formulations of the present invention, vs. several commercially available inkjet inks;
  • Figure 8 is a magnified view of the plot of Figure 8, for lower viscosities
  • Figure 9A provides temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of various ink formulations, including ink formulations according to the present invention
  • Figure 9B provides temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of inventive ink formulations containing various polyester resins;
  • Figure 10 provides temperature sweep plots of dynamic viscosity as a function of temperature, for representative dried ink dried residues of various ink formulations provided in Figures 9 A and 9B;
  • Figure 11 provides temperature sweep plots of dynamic viscosity as a function of temperature, for representative dried ink residues of ink formulations of the present invention, vs. dried ink residues of several commercially available inkjet inks;
  • Figure 12A provides a first plurality of temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of five ink formulations having identical components, and a varying ratio of softening agent, using a first thermoplastic resin and a first softening agent;
  • Figure 12B provides a second plurality of temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of five ink formulations having identical components, and a varying ratio of softening agent, using a different thermoplastic resin and a different softening agent with respect to those used in Figure 17 A;
  • Figures 18A-18D are temperature sweep plots of dynamic viscosity as a function of temperature, for residue films of ink formulations having different softening agents, and varying concentrations of those agents;
  • Figure 14 provides temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of four ink formulations having different colorants (C, M, Y, K) but otherwise identical formulation components;
  • Figures 15A-F display two-dimensional ( Figures 15A-C) and three- dimensional ( Figures 15D-F) laser-microscope acquired magnified images of ink films on coated paper substrates, obtained using various printing technologies, wherein: Figures 15A and 15D are magnified images of a liquid electro-photography film (LEP); Figures 15B and 15E are magnified images of an offset splotch; and Figures 15C and 15F are magnified images of an inkjet ink film construction according to the present invention;
  • LEP liquid electro-photography film
  • Figures 15B and 15E are magnified images of an offset splotch
  • Figures 15C and 15F are magnified images of an inkjet ink film construction according to the present invention
  • Figures 16A-F display two-dimensional ( Figures 16A-C) and three- dimensional ( Figures 16D-F) laser-microscope acquired magnified images of ink films on uncoated paper substrates, obtained using various printing technologies, wherein: Figures 16A and 16D are magnified images of a liquid electro-photography film (LEP); Figures 16B and 16E are magnified images of an offset splotch; and Figures 16C and 16F are magnified images of an inkjet ink film construction according to the present invention;
  • LEP liquid electro-photography film
  • Figures 16B and 16E are magnified images of an offset splotch
  • Figures 16C and 16F are magnified images of an inkjet ink film construction according to the present invention
  • Figures 17A-1 to 17E-1 provide a magnified view of a field of ink dots or films on commodity-coated fibrous substrates ( Figures 17A-1 to 17C-1) and uncoated fibrous substrates ( Figures 17D-1 and 17E-1), produced using an ink formulation of the present invention;
  • Figures 17A-2 to 17E-2 provide further magnified views of a portion of the frames of Figures 17A-1 to 17E-1, in which the ink films disposed on commodity-coated paper are provided in Figures 17A-2 to 17C-2, and in which the ink films disposed on uncoated paper are provided in Figures 17D-2 and 17E-2; corresponding optical uniformity profiles are provided in Figures 17A-3 to 17E-3; [00145] Figures 17A-4 to 17E-4 provide magnified views of ink films disposed on coated paper ( Figures 17A-4 to 17C-4) and un coated paper ( Figures 17D-4 and 17E-4), along with corresponding image-processor computed contours and convexity projections thereof, the ink films produced using an ink formulation of the present invention;
  • Figure 18A provides a magnified view of a field of ink dots on a commodity-coated fibrous substrate, produced using a commercially available, aqueous, direct inkjet printer;
  • Figure 18B provides a magnified view of a field of ink dots on an uncoated fibrous substrate, produced using the identical, commercially available, aqueous, direct inkjet printer;
  • Figures 19A-2 to 19F-2 provide images of ink splotches or films obtained using various prior-art printing technologies on uncoated ( Figures 19A-2 to 19C-2) and coated ( Figures 19D-2 to 19F-2) paper, and optical uniformity profiles (19A-1 to 19F-1) therefor;
  • Figure 20A shows a two-dimensional shape having the mathematical property of a convex set
  • Figure 20B shows a two-dimensional shape having the mathematical property of a non-convex set
  • Figure 20C is a schematic top projection of an ink film having a rivulet and an inlet, the schematic projection showing a smoothed projection of the ink image;
  • Figures 21 A and 2 IB provide respective schematic cross-sectional views of an inventive ink film construction and an inkjet ink dot construction of the prior art, wherein the substrate is a fibrous paper substrate;
  • Figures 22A and 22C each show an image of the surface of the outer layer of an intermediate transfer member;
  • Figures 22B and 22D are corresponding images of the surface of the ink films produced using those outer layers, in accordance with the present invention.
  • the printing system shown in Figs. 1 and 2 essentially comprises three separate and mutually interacting systems, namely a blanket system 100, an image forming system 300 above the blanket system 100 and a substrate transport system 500 below the blanket system 100.
  • the blanket system 100 comprises an endless belt or blanket 102 that acts as an intermediate transfer member and is guided over two rollers 104, 106.
  • An image made up of dots of an aqueous ink is applied by image forming system 300 to an upper run of blanket 102 at a location referred herein as the image forming station.
  • a lower run selectively interacts at two impression stations with two impression cylinders 502 and 504 of the substrate transport system 500 to impress an image onto a substrate compressed between the blanket 102 and the respective impression cylinder 502, 504.
  • the purpose of there being two impression cylinders 502, 504 is to permit duplex printing. In the case of a simplex printer, only one impression station would be needed.
  • the printer shown in Figs. 1 and 2 can print single sided prints at twice the speed of printing double sided prints. In addition, mixed lots of single and double sided prints can also be printed.
  • ink images are printed by the image forming system 300 onto an upper run of blanket 102.
  • run is used to mean a length or segment of the blanket between any two given rollers over which the blanket is guided.
  • the ink While being transported by the blanket 102, the ink is heated to dry it by evaporation of most, if not all, of the liquid carrier.
  • the ink image is furthermore heated to render tacky the film of ink solids remaining after evaporation of the liquid carrier, this film being referred to as a residue film, to distinguish it from the liquid film formed by flattening of each ink droplet.
  • the image is impressed onto individual sheets 501 of a substrate which are conveyed by the substrate transport system 500 from an input stack 506 to an output stack 508 via the impression cylinders 502, 504.
  • the substrate may be a continuous web, in which case the input ant output stacks are replaced by a supply roller and a delivery roller.
  • the substrate transport system needs to be adapted accordingly, for instance by using guide rollers and dancers taking slacks of web to properly align it with the impression station.
  • the image forming system 300 comprises print bars 302 which may each be slidably mounted on a frame positioned at a fixed height above the surface of the blanket 102.
  • Each print bar 302 may comprise a strip of print heads as wide as the printing area on the blanket 102 and comprises individually controllable print nozzles.
  • the image forming system can have any number of bars 302, each of which may contain an aqueous ink of a different color.
  • the heads can be moved between an operative position (at which the bar remains stationary), in which they overlie blanket 102 and an inoperative position (at which the bar can be accessed for maintenance).
  • the ink may be constantly recirculated, filtered, degassed and maintained at a desired temperature and pressure, as known to the person skilled in the art without the need for more detailed description.
  • each print bar 302 it is possible to provide a blower following each print bar 302 to blow a slow stream of a hot gas, preferably air, over the intermediate transfer member to commence the drying of the ink droplets deposited by the print bar 302.
  • a blower following each print bar 302 to blow a slow stream of a hot gas, preferably air, over the intermediate transfer member to commence the drying of the ink droplets deposited by the print bar 302.
  • the blanket 102 in one variation, is seamed.
  • the blanket is formed of an initially flat strip of which the ends are fastened to one another, releasably or permanently, to form a continuous loop often referred to as a belt.
  • a releasable fastening may be a zip fastener or a hook and loop fastener that lies substantially parallel to the axes of rollers 104 and 106 over which the blanket is guided.
  • a permanent fastening may be achieved by the use of an adhesive or a tape.
  • the belt may be seamless.
  • the primary purpose of the blanket is to receive an ink image from the image forming system and to transfer that image dried but undisturbed to the impression stations.
  • the blanket has a thin upper release layer that is hydrophobic, suitable examples of which have been above described.
  • the strength of the blanket can be derived from a support or reinforcement layer.
  • the reinforcement layer is formed of a fabric. If the fabric is woven, the warp and weft threads of the fabric may have a different composition or physical structure so that the blanket should have, for reasons to be discussed below, greater elasticity in its widthways direction (parallel to the axes of the rollers 104 and 106) than in its lengthways direction.
  • the blanket may comprise additional layers between the reinforcement layer and the release layer, for example to provide conformability and compressibility of the release layer to the surface of the substrate.
  • Other layers provided on the blanket may act as a thermal reservoir or a thermal partial barrier and/or to allow an electrostatic charge to the applied to the release layer.
  • An inner layer may further be provided to control the frictional drag on the blanket as it is rotated over its support structure.
  • Other layers may be included to adhere or connect the aforementioned layers one with another or to prevent migration of molecules therebetween.
  • the blanket support system may comprise thermally conductive support plates 130 forming a continuous flat support surface both on the top side and bottom side of the support frame. Electrical heating elements can be inserted into transverse holes of the plates to apply heat to the plates 130 and through plates 130 to the blanket 102. Other means for heating the blanket will occur to the person of skill in the art and may include heating from below, above, or within the blanket itself.
  • the pressure rollers 140, 142 are mounted on the blanket support frame in gaps between the support plates 130 covering the underside of the frame.
  • the pressure rollers 140, 142 are aligned respectively with the impression cylinders 502, 504 of the substrate transport system. Each impression roller and corresponding pressure roller, when both are engaged with the blanket passing therebetween, form an impression station.
  • the blanket support system further comprises a continuous track which can engage formations on the side edges of the blanket to maintain the blanket taut in its width ways direction.
  • the formations may be spaced projections, such as the teeth of one half of a zip fastener sewn or otherwise attached to the side edge of the blanket.
  • the formations may be a continuous flexible bead of greater thickness than the blanket.
  • the lateral track guide channel may have any cross-section suitable to receive and retain the blanket lateral formations and maintain it taut. To reduce friction, the guide channel may have rolling bearing elements to retain the projections or the beads within the channel.
  • the position and speed of the blanket must be both known and controlled.
  • the blanket can be marked at or near its edge with one or more markings spaced in the direction of motion of the blanket.
  • One or more sensors 107 sense the timing of these markings as they pass the sensor.
  • the speed of the blanket and the speed of the surface of the impression rollers should be the same, for proper transfer of the images to the substrate from the transfer blanket.
  • Signals from the sensor(s) 107 are sent to a controller 109 which also receives an indication of the speed of rotation and angular position of the impression rollers, for example from encoders on the axis of one or both of the impression rollers (not shown).
  • Sensor 107, or another sensor (not shown) also determines the time at which the seam of the blanket passes the sensor. For maximum utility of the usable length of the blanket, it is desirable that the images on the blanket start as close to the seam as feasible.
  • Fig.l shows schematically a roller 190 positioned on the external side of the blanket immediately before roller 106.
  • a roller 190 may be used optionally to apply a thin film of pre-treatment solution containing a conditioning chemical agent, as above described.
  • the pre-treatment or conditioning material can alternatively be sprayed onto the surface of the blanket and optionally spread more evenly, for example by the application of a jet from an air knife.
  • the location at which such pre-print treatment can be performed may be referred herein as the conditioning station.
  • the alternative printing system illustrated in Figure 3 may also include a conditioning station.
  • the shape of the ink droplet is "frozen" such that at least some and preferably a major part of the flattening and horizontal extension of the droplet present on impact is preserved. It should be understood that since the recovery of the droplet shape after impact is very fast, the methods of the prior art would not effect phase change by agglomeration and/or coagulation and /or migration.
  • the concentration and distribution of the charged resin particles in the drop is not substantially changed as a result of contact with the chemical agent on the release layer. Furthermore, since the ink is aqueous, the effects of the positive charge are very local, especially in the very short time span needed for freezing the shape of the droplets.
  • conditioning solution was applied to the transfer member, immediately removed and evaporated, leaving no more than few layers of the suitable chemical agent.
  • Ink droplets were jetted on such pre -treated blanket, dried and transferred to the printing substrate.
  • the ink film image so printed could be identified by the presence on their outer surface of the conditioning agent.
  • the dried ink droplet upon transfer ripped the underlayer of conditioning agent and was impressed on the final substrate in inversed orientation.
  • the inventors have found that low-temperature operation of the image forming station may appreciably complicate or increase the difficulty of the conditioning duty. Without wishing to be limited by theory, the inventors believe that at higher temperatures, the evaporation of the carrier of the ink formulation proceeds at a relatively high rate, which reduces the requisite duty of the conditioning agents with respect to the retardation of droplet beading. However, at lower operating temperatures, the evaporation kinetics may be significantly slower, as are the kinetics for the attraction process between the positively-charged conditioning agents and the negatively-charged functional groups in the ink (typically in the resin).
  • the aqueous conditioning formulation may be sufficiently active, at low temperatures (Image Forming Station temperatures within a range of 40°C to 95°C, 60°C to 95°C, 75°C to 95°C, 60°C to 90°C, or 60°C to 85°C) to efficaciously interact with various negatively charged molecules in the ink, within the requisite time frame (at most a few seconds), such that beading of the droplet is sufficiently retarded.
  • Image Forming Station temperatures within a range of 40°C to 95°C, 60°C to 95°C, 75°C to 95°C, 60°C to 90°C, or 60°C to 85°C
  • the inventive aqueous conditioning formulation may include: a positively chargeable polymeric conditioning agent, typically having an amine functional group, such as a polyethylene imine (PEI), and a resolubilizing agent selected to improve resolubilization of the conditioning agent, both disposed within an aqueous carrier liquid.
  • a positively chargeable polymeric conditioning agent typically having an amine functional group, such as a polyethylene imine (PEI)
  • PEI polyethylene imine
  • a resolubilizing agent selected to improve resolubilization of the conditioning agent both disposed within an aqueous carrier liquid.
  • the PEI has an average molecular weight of at least 5,000 and a positive charge density of at least 10 meq/g.
  • the resolubilizing agent may advantageously have, in a pure state, a vapor pressure of less than 0.025, less than 0.020, less than 0.015, less than 0.012, less than 0.010, or less than 0.008 bar at 90°C.
  • the weight ratio of the resolubilizing agent to the PEI, within the conditioning formulation is typically within a range of 1 : 10 to 20: 1, within a range of 1 :5 to 20: 1, within a range of 1 :5 to 15: 1, and more typically, within a range of 1 :3 to 10: 1, within a range of 1 :3 to 7: 1, within a range of 1 :3 to 5: 1, within a range of 1 :2 to 5: 1, or within a range of 1 : 1 to 5 : 1.
  • the resolubilizing agent may have a solubility in water of at least 1%, at least 3%, at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50% at 25°C and a pH of 7.
  • the PEI, resolubilizing agent, and carrier liquid may make up at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, or at least 99% of the formulation, by weight.
  • the PEI may be a linear polyethylene imine, a branched polyethylene imine, a modified (e.g., ethoxylated) polyethylene imine, or combinations thereof.
  • the average molecular weight of the PEI may be at least 25,000, at least 50,000, at least 100,000, at least 150,000, at least 200,000, at least 250,000, at least 500,000, at least 750,000, at least 1,000,000, or at least 2,000,000.
  • the charge density of the PEI may be at least 11 meq/g, at least 12 meq/g, at least 13 meq/g, at least 14 meq/g, at least 15 meq/g, at least 16 meq/g, at least 17 meq/g, at least 18 meq/g, at least 19 meq/g, or at least 20 meq/g.
  • the concentration of PEI within the formulation may be not more than 5 wt.%, not more than 4 wt.%, not more than 3 wt.%, not more than 2 wt.%, not more than 1 wt.%, not more than 0.5 wt.%, not more than 0.4 wt.%, not more than 0.3 wt.%, not more than 0.2 wt.%, not more than 0.1 wt.%, not more than 0.05 wt.%, or not more than 0.01 wt.%.
  • the resolubilizing agent may be stable at a temperature of up to at least 100°C, at least 125°C, at least 150°C, at least 175°C, at least 200°C, or at least 225°C.
  • the resolubilizing agent may include, mainly include, or consist essentially of at least one sugar, at least one alcohol, at least one amine, or combinations thereof.
  • conditioning solutions that can be used to treat an ITM upon which ink formulations of the present invention can be deposited are provided hereinbelow the amount of the respective ingredients being provided in weight percent (wt.%) of the complete conditioning formulation:
  • Such conditioning solutions were typically prepared by mixing the conditioning agent with most of the water, subsequently adding the resolubilizing agent and further stirring the mixture. Water was then added to complete the conditioning formulation up to 100 weight parts and the resulting formulation was optionally filtered through a 0.5 ⁇ filter.
  • conditioning solutions can be prepared as concentrated stock to be diluted to the final concentration desired in operation of a relevant printing system.
  • Exemplary concentrated stock of conditioning solutions that can be diluted used to treat an ITM upon which ink formulations of the present invention can be deposited are provided hereinbelow, the amount of the respective ingredients being provided in weight percent (wt.%) of the stock:
  • PEI Lupasol® PS (BASF) 1 %
  • Inks in accordance with embodiments of the presently claimed invention which are suitable for use in the process and in conjunction with the system described herein are, for example, aqueous inkjet inks that contain (i) a solvent comprising water and optionally a co-solvent, (ii) a negatively chargeable polymeric resin (the ink may include a small amount of a pH-raising substance to ensure that the polymer is negatively charged), and (iii) at least one colorant.
  • aqueous inkjet inks that contain (i) a solvent comprising water and optionally a co-solvent, (ii) a negatively chargeable polymeric resin (the ink may include a small amount of a pH-raising substance to ensure that the polymer is negatively charged), and (iii) at least one colorant.
  • water constitutes at least 8 wt.% of the ink; the at least one colorant is dispersed or at least partly dissolved within the solvent and constitutes at least 1 wt.% of the ink; the polymeric resin is dispersed or at least partially dissolved within the solvent and constitutes 6 to 40 wt.% of the ink; the average molecular weight of the polymeric resin is at least 8,000 and in some cases not more than 70,000; and prior to jetting the ink has at least one of (i) a viscosity of 2 to 25 cP at at least one temperature in the range of 20-60°C and (ii) a surface tension of not more than 50 milliNewton/m at at least one temperature in the range of 20-60°C.
  • the colorant may contain a pigment, preferably a nanopigment, for example having an average particle size (D 50 ) of not more than 120 nm.
  • the ink is such that, when substantially dried, (a) at at least one temperature in the range of 90°C to 195°C, the dried ink has a first dynamic viscosity in the range of 1,000,000 (1 x 10 6 ) cP to 300,000,000 (3 x 10 8 ) cP, and (b) at at least one temperature in the range of 50°C to 85°C, the dried ink has a second dynamic viscosity of at least 80,000,000 (8 x 10 7 ) cP, wherein the second dynamic viscosity exceeds the first dynamic viscosity; or (2) the weight ratio of the resin to the colorant is at least 1 : 1.
  • substantially dried refers to ink that has no more solvent and other volatile compounds than does a layer of the ink of 1 mm initial thickness after such a layer is dried in an oven for 12 hours at 100°C.
  • the polymer resins such as acrylic-based polymers
  • the polymeric resin may be negatively charged at alkaline pH. Consequently, in some embodiments, the polymeric resin has a negative charge at pH 8 or higher; in some embodiments the polymeric resin has a negative charge at pH 9 or higher.
  • the solubility or the dispersability of the polymeric resin in water may be affected by pH.
  • the formulation comprises a pH-raising compound. Examples of such are diethyl amine, monoethanol amine, and 2-amino-2-methyl propanol.
  • pH-raising compounds when included in the ink, are generally included in small amounts, e.g., about 1 wt.% of the formulation and usually not more than about 2 wt.% of the formulation.
  • acrylic-based polymers having free carboxyl groups may be characterized in terms of their charge density or, equivalently, the acid number, viz. the number of mg of KOH needed to neutralize one g of dry polymer.
  • the polymeric resin has an acid number in the range of 70-144.
  • the ink formulation contains at least one colorant.
  • colorant refers to a substance that is considered, or would be considered to be, a colorant in the art of printing.
  • the concentration of the at least one colorant within the ink formulation when substantially dry may be at least 2%, at least 3%, at least 4%, at least 6%, at least 8%, at least 10%, at least 15%, at least 20%, or at least 22%, by weight.
  • the concentration of the at least one colorant within the ink film is at most 40%, at most 35%, at most 30%, or at most 25%.
  • the ink formulation when substantially dry may contain 2-30%, 3- 25%, or 4-25% of the at least one colorant.
  • the colorant may include at least one pigment. Alternatively or additionally, the colorant may include at least one dye.
  • pigment refers to a finely divided solid colorant.
  • the pigment may have an organic and/or inorganic composition. Typically, pigments are insoluble in, and essentially physically and chemically unaffected by, the vehicle or medium in which they are incorporated. Pigments may be colored, fluorescent, or pearlescent. Pigments may alter appearance by selective absorption, interference and/or scattering of light. They are usually incorporated by dispersion in a variety of systems and may retain their crystal or particulate nature throughout the pigmentation process.
  • die refers to at least one colored substance that is soluble or goes into solution during the application process and imparts color by selective absorption of light.
  • average particle size refers to an average particle size, by weight, as determined by a laser diffraction particle size analyzer (e.g., MastersizerTM 2000 of Malvern Instruments, England), using standard practice.
  • a laser diffraction particle size analyzer e.g., MastersizerTM 2000 of Malvern Instruments, England
  • a variety of pigments are suitable for use in the inks in accordance with embodiments of the invention, although it has been found that results are best when the average particle size (D 50 ) of the pigment is from 10 nm to 300 nm, such as 120 nm or less, for example on the order of 70-80 nm.
  • the pigments may thus be nanopigments; the particle size of the nanopigments may depend on the type of pigment and on the size reduction methods used in the preparation of the pigments.
  • the particle size for magenta and yellow pigments may be in the range of 10 nm to 100 nm, while blue or green pigments may be in the range of 75 nm to 200 nm.
  • the D50 of the pigment particles may be within a range of 10 nm to 270 nm.
  • Pigments of various particle sizes, utilized to give different colors, may be used for the same print. Some pigments having such particle sizes are commercially available, and may be employed as-is in embodiments of the invention; in other cases, the pigments may be milled to the appropriate size. It will be appreciated that in general, the pigments are dispersed (or at least partly dissolved) within the solvent along with the polymeric resin, or are first dispersed within the polymeric resin (e.g., by kneading) to obtain colored resin particles which are then mixed with the solvent.
  • the weight ratio of the polymeric resin to the colorant may be at most 7: 1, at most 5: 1, at most 3: 1, at most 2.5: 1, at most 2: 1 , or at most 1.7:1.
  • Another example is polyethylene glycol 400 (PEG 400), although in some embodiments, the ink formulation is substantially free of water soluble polymers. In some embodiments the ink formulation is substantially free of saccharides.
  • the co-solvent may be present as a mixture of co-solvents.
  • a surfactant e.g., 0.5- 1.5 wt.% of the ink.
  • the surfactant is a non-ionic surfactant.
  • the ink formulation is devoid or substantially devoid of wax.
  • the ink formulation contains less than 30 wt.% wax, less than 20 wt.% wax, less than 15 wt.%> wax, less than 10 wt.%> wax, less than 7 wt.%> wax, less than 5 wt.%) wax, less than 3 wt.%> wax, less than 2 wt.%> wax, or less than 1 wt.%> wax.
  • wax is included in the ink formulation in order to impart greater abrasion resistance in the printed ink.
  • Such waxes may be natural or synthetic, e.g.
  • the formulation may comprise for example 0.1-10 wt.% wax, e.g., up to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7. 0.8, 0.9, 1.0, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9 or 10 wt.% wax.
  • the wax may be incorporated into the formulation as an aqueous dispersion of small wax particles, e.g., having average size of 10 micron or smaller, preferably having average size of 1 micron or smaller.
  • the ink formulation is devoid or substantially devoid of oils such as mineral oils and vegetable oils (e.g., linseed oil and soybean oil).
  • oils such as mineral oils and vegetable oils (e.g., linseed oil and soybean oil).
  • the ink formulation contains at most 20 wt.%, at most 12 wt.%, at most 8 wt.%, at most 5 wt.%), at most 3 wt.%, at most 1 wt.%, at most 0.5 wt.%, or at most 0.1 wt.%, by weight, of one or more oils, cross-linked fatty acids, or fatty acid derivatives produced upon air- drying.
  • the formulation is substantially free of a plasticizer.
  • the ink formulation is devoid or substantially devoid of one or more salts, including salts used to coagulate or precipitate ink on a transfer member or on a substrate (e.g., calcium chloride).
  • the ink formulation contains at most 8 wt.%), at most 5 wt.%, at most 3 wt.%, at most 1 wt.%, at most 0.5 wt.%, at most 0.1 wt.%, or substantially 0 wt.% of one or more salts.
  • salts may be referred to herein as "precipitants", and it will be appreciated that when it is stated that a formulation does not include a salt or contains salt in an amount less than a certain weight percentage, this does not refer to salts that may form between the polymer(s) of the polymeric resin and pH modifiers, such as alcohol amines, or that may be present in the polymeric resin itself if the polymeric resin is provided as a salt. As discussed above, it is presently believed that the presence of negative charges in the polymeric resin is beneficial to the print process.
  • the ink formulation is devoid or substantially devoid of inorganic particulates, e.g., silica particulates, titania particulate or alumina particulates, containing less than 2 wt.%, less than 1 wt.%, less than 0.1 wt.% or substantially no inorganic particulates.
  • silica particulates is meant fumed silica, silica chips, silica colloids, and the like.
  • silica particulates include those available from DuPont Company under the names: Ludox AM-30, Ludox CL, Ludox HS-30; and those available from Nyacol Nanotechnologies Company under the names: NexSil 12, NexSil 20, NexSil 8, Nexsil 20, Nexsil 85.
  • the term "silica particulates" does not include colorants.
  • the heaters are used to heat the blanket to a temperature that is appropriate for the rapid evaporation of the ink carrier and compatible with the composition of the blanket.
  • a temperature that is appropriate for the rapid evaporation of the ink carrier and compatible with the composition of the blanket.
  • heating is typically of the order of 150°C, though this temperature may vary within a range from 70°C to 180°C, depending on various factors such as the composition of the inks and/or of the conditioning solutions if needed.
  • Blankets comprising amino silicones may generally be heated to temperatures between 70°C and 130°C.
  • the blanket When using beneath heating of the transfer member, it is desirable for the blanket to have relatively high thermal capacity and low thermal conductivity, so that the temperature of the body of the blanket 102 will not change significantly as it moves between the optional pre -treatment or conditioning station, the image forming station and the impression station(s).
  • the blanket When using top heating of the transfer member, the blanket would preferably include a thermally insulating layer to prevent undue dissipation of the applied heat.
  • additional external heaters or energy sources may be used to apply energy locally, for example prior to reaching the impression stations to render the ink residue tacky (see 231 in Figure 3), prior to the image forming station to dry the conditioning agent if necessary and at the printing station to start evaporating the carrier from the ink droplets as soon as possible after they impact the surface of the blanket.
  • the external heaters may be, for example, hot gas or air blowers 306 (as represented schematically in Figure 1) or radiant heaters focusing, for example, infrared radiation onto the surface of the blanket, which may attain temperatures in excess of 175°C, 190°C, 200°C, 210°C, or even 220°C.
  • the residue film left behind may have an average thickness below 1500 nm, below 1200 nm, below 1000 nm, below 800 nm, below 600 nm, below 500 nm, below 400 nm, or below 300 nm.
  • Cooling may be effected by passing the belt 210 over a roller of which the lower half is immersed in a coolant, which may be water or a cleaning/treatment solution, by spraying a coolant onto the belt of by passing the belt 210 over a coolant fountain.
  • a coolant which may be water or a cleaning/treatment solution
  • Printing systems as described herein may be produced by modification to existing lithographic printing presses.
  • the modification of a tower would involve replacement of the plate cylinder by a set of print bars and replacement of the blanket cylinder by an image transfer drum having a hydrophobic outer surface or carrying a suitable blanket.
  • the plate cylinder would be replaced by a set of print bars and a belt passing between the existing plate and blanket cylinders.
  • the substrate handling system would require little modification, if any.
  • Color printing presses are usually formed of several towers and it is possible to convert all or only some of the towers to digital printing towers.
  • Various configurations are possible offering different advantages.
  • each of two consecutive towers may be configured as a multicolor digital printer to allow duplex printing if a perfecting cylinder is disposed between them.
  • multiple print bars of the same color may be provided on one tower to allow an increased speed of the entire press.
  • a general procedure for preparing inks in accordance with embodiments of the invention is as follows: first, a pigment concentrate is prepared by mixing distilled water, at least a portion of the polymeric resin or dispersant, if used, and colorant, and milling until a suitable particle size is reached; if a pH-raising compound is used it may be included in this step. Thereafter, the remaining ingredients, including additional polymeric resin, are mixed in, and then the ink is filtered.
  • Joncryl HPD 296 (BASF) polymeric resin (acrylic styrene co10.6** (solid resin polymer solution, ave. MW content)
  • the polymeric resin was provided in a 35.5 wt.% water solution; 30 wt.% of the final formulation consisted of this solution, i.e. 10.6 wt.% in the final ink formulation consisted of the polymeric resin itself.
  • An inkjet ink formulation was prepared containing:
  • BT-9 resin was provided in a 40 wt.% water dispersion
  • HPD 296 was provided in a 35.5 wt.% water solution. 16.5% and 9%, respectively, of the final formulation consisted of these two components, i.e. 6.6 wt.% of the final ink formulation consisted of BT-9 itself and 3.2 wt.% consisted of HPD 296 itself.
  • pigment concentrates containing pigment (14%), water (79%) and Joncryl HPD 296 296 (7%) was prepared by mixing these ingredients and milling them until the particle size (D 50 ) reached 70 nm, as described in Example 1. Then the remaining materials were added to the pigment concentrate and mixed. After mixing the inks were filtered through 0.5 micron filter. At 25°C, the viscosity of the inks thus obtained was about 13 cP, the surface tension about 27 mN/m, and the pH 9-10.
  • Neocryl BT-26 50% water polymeric resin (acrylic 17.25 (6.9 solid resin)** dispersion) (DSM resins) polymer, ave. MW 25,000)
  • the polymeric resin was provided in a 40 wt.% water dispersion; the final ink formulation consisted of 17.25 wt.% of this dispersion, i.e. 6.9 wt.% in the final ink formulation consisted of the polymeric resin itself
  • the polymeric resin was provided in a 40 wt.% water dispersion; the final ink formulation consisted of 17.5 wt.% of this dispersion, i.e. 7 wt.% in the final ink formulation consisted of the polymeric resin itself
  • Example 4A To prepare these ink formulations, first a pigment concentrate was made by mixing the pigment (10%), water (69%), Neocryl BT-26 (20%) and monoethanolamine (1%) and milling as described in Example 1 until the particle size (D 50 ) reached 70 nm. Then the rest of materials were added to the pigment concentrate and mixed. After mixing the ink was filtered through a 0.5 micron filter. At 25°C, the viscosity of the ink thus obtained was about 8 cP, and the surface tension was approximately 24 mN/m, and the pH 9-10.
  • Example 4A To prepare these ink formulations, first a pigment concentrate was made by mixing the pigment (10%), water (69%), Neocryl BT-26 (20%) and monoethanolamine (1%) and milling as described in Example 1 until the particle size (D 50 ) reached 70 nm. Then the rest of materials were added to the pigment concentrate and mixed. After mixing the ink was filtered through a 0.5 micron filter. At 25°C, the viscosity of
  • the polymeric resin was provided in a 40 wt.% water dispersion; the final ink formulation consisted of 25 wt.% of this dispersion, i.e. 10 wt.% of the final ink formulation was polymeric resin itself
  • a pigment concentrate was formed by mixing the pigment (12.3%), water (84.4%o) and Joncryl 683 fully neutralized with KOH (3.3%) and milling as described in Example 1 until the particle size (D 50 ) reached 70 nm. Then the rest of materials were added to the pigment concentrate and mixed. After mixing the ink was filtered through a 0.5 micron filter. At 25°C, the viscosity of the ink thus obtained was about 7 cP, and the surface tension was approximately 24 mN/m, and the pH 7-8.
  • An inkjet ink formulation was prepared containing:
  • NeoRad R-440 50% water polymeric resin (aliphatic 30 (12 solid resin)** emulsion) (DSM resins) polyurethane, MW 25,000)
  • the polymeric resin was provided in a 40 wt.% water emulsion; the final ink formulation consisted of 30 wt.% of this emulsion, i.e. 12 wt.% in the final ink formulation was polymeric resin itself
  • a pigment concentrate was formed by mixing the pigment (14.6%), water (81.5%)) and Joncryl 671 fully neutralized with KOH (3.9%>) and milling as described in Example 1A until the particle size (D 50 ) reached 70 nm. Then the rest of materials were added to the pigment concentrate and mixed. After mixing the ink was filtered through a 0.5 micron filter. At 25°C, the viscosity of the ink thus obtained was about 10 cP, the surface tension was approximately 26 mN/m, and the pH 9-10.
  • the polymeric resin was provided in a 40 wt.% water dispersion; this dispersion constitute 18% of the final product, so that the 7.2 wt.% in the final ink formulation refers to the concentration of the polymeric resin itself, without water
  • the polymeric resin was provided in a 35.5 wt.% water solution; this solution constitutes 20% of the final product, so that the 7.1 wt.% in the final ink formulation refers to the concentration of the polymeric resin itself
  • An inkjet ink formulation was prepared containing:
  • the polymeric resin was provided in a 35.5 wt.% water solution; the 12.5 wt.% in the final ink formulation refers to the concentration of the polymeric resin itself
  • a pigment concentrate was formed by mixing the pigment (14 wt.%), Joncryl HPD 296 (7 wt.%) solids), and water (79 wt.%, triple distilled) and milling until the particle size (D 50 ) reached 70 nm. Then the rest of materials were then added to the pigment concentrate and mixed. After mixing the ink was filtered through a 0.5 micron filter. At 25°C, the viscosity of the ink thus obtained was about 9 cP and the surface tension was approximately 24 mN/m.
  • An inkjet ink formulation may be prepared containing:
  • a pigment concentrate is formed by mixing the pigment (10 wt.%), water (83.6 wt.%) and Disperbyk-198 (6.4 wt.%) and milling. The progress of milling is controlled on the basis of particle size measurement (Malvern, Nanosizer). The milling is stopped when the particle size (D 50 ) reaches 70 nm. Then the rest of materials are added to the pigment concentrate and mixed. After mixing the ink is filtered through a 0.5 micron filter. At 25°C, the viscosity of the ink thus obtained is about 15 cP, the surface tension is approximately 26 mN/m, and the pH 9-10.
  • An inkjet ink formulation may be prepared containing:
  • the polymeric resin was provided in a 40 wt.% water emulsion; this constitutes 17.5 wt.% of the final ink formulation, i.e. 7 wt.% in the final ink formulation is BT-9 resin itself.
  • a pigment concentrate is formed by mixing the pigment (10 wt.%), water (87.6 wt.%) and EFKA 4580 (5.5 wt.%) and milling. The progress of milling is controlled on the basis of particle size measurement (Malvern, Nanosizer). The milling is stopped when the particle size (D 50 ) reaches 70 nm. Then the rest of materials are added to the pigment concentrate and mixed. After mixing the ink is filtered through a 0.5 micron filter. At 25°C, the viscosity of the ink thus obtained is about 9 cP, the surface tension is approximately 24 mN/m, and the pH 9-10. [00241] Formulations similar to those of Examples 9 A and 10A may be prepared using EFKA ® 4560, EFKA ® 4585, EFKA ® 7702 or Lumiten ® N-OC 30 as the dispersant.
  • the polymeric resin was provided in a 40 wt.% water emulsion; this constituted 20 wt.% of the final ink formulation, i.e. 8 wt.% in the final ink formulation was BT-102 resin itself.
  • a pigment concentrate was formed by mixing pigment (14 wt.%), water (72 wt.%) and Disperbyk 198 (14 wt.%) and milling. The progress of milling was controlled on the basis of particle size measurements (Malvern, Nanosizer). The milling was stopped when the average particle size (D 50 ) reached 70 nm. The remaining materials were then added to the pigment concentrate and mixed. After mixing, the ink was filtered through a 0.5 ⁇ filter. At 25°C, the viscosity of the ink thus obtained was about 5.5 cP, the surface tension about 25 mN/m, and the pH 6.5.
  • BYK 348 (BYK) surfactant sicone
  • the polymeric resin was provided in a 40 wt.% water dispersion; this dispersion constituted 10% of the final product, i.e. 4 wt.% of the final ink formulation was Joncryl 142E resin per se
  • the polymeric resin was provided in a 46.5 wt.% water dispersion; this dispersion constituted 15% of the final product, i.e. 7 wt.% of the final ink formulation was Joncryl 537E resin per se
  • a pigment concentrate was prepared by mixing pigment (10%), water (72.5%) and Disperbyk 198 (17.5%) and milling until the average particle size (d 50 ) reached 70 nm. The remaining materials were then added to the pigment concentrate and mixed. After mixing, the ink was filtered through a 0.5 ⁇ filter. At 25°C, the viscosity of the ink thus obtained was about 7.5 cP, the surface tension about 27 mN/m, and the pH 8-9. [00247] With respect to the foregoing examples, various milling procedures and apparati will be apparent to those of ordinary skill in the art. Various commercially available nano- pigments may be used in the inventive ink formulations.
  • pigment preparations such as Hostajet Magenta E5B-PT and Hostajet Black O-PT, both from Clariant, as well as pigments demanding post-dispersion processes, such as Cromophtal Jet Magenta DMQ and Irgalite Blue GLO, both from BASF.
  • pigments and pigment formulations may include, or consist essentially of, inkjet colorants and inkjet colorant formulations.
  • the colorant may be a dye.
  • dyes suitable for use in the ink formulations of the present invention include: Duasyn Yellow 3GF-SF liquid, Duasyn Acid Yellow XX-SF, Duasyn Red 3B-SF liquid, Duasynjet Cyan FRL-SF liquid (all manufactured by Clariant); Basovit Yellow 133, Fastusol Yellow 30 L, Basacid Red 495, Basacid Red 510 Liquid, Basacid Blue 762 Liquid, Basacid Black X34 Liquid, Basacid Black X38 Liquid, Basacid Black X40 Liquid, Basonyl Red 485, Basonyl Blue 636 (all manufactured by BASF).
  • an ink concentrate it is possible to formulate. This is similar to the procedure described above, differing in that, after forming the pigment (or dye) concentrate, the remaining ingredients are added and mixed, except that most or all of the additional solvent (water and co-solvent) is not added.
  • the additional solvent may be mixed into such a concentrate at a later time, for example after the concentrate has been shipped to an end-user, to yield an inkjet ink formulation in accordance with embodiments of the invention.
  • the concentrate may be diluted by addition of, for example, at least 50%, at least 100%, at least 150%), at least 200%), at least 250%o, at least 300%>, least 350%> or at least 400%> solvent on a weight/weight basis relative to the concentrate to yield the aqueous inkjet ink formulation
  • Each conditioning solution was manually applied to a release layer surface of a blanket of approximately 20 cm x 30 cm size, the release layer comprising a silanol-terminated polydimethylsiloxane silicone and being at a temperature of 150°C.
  • the conditioning solution was applied by moistening a Statitech 100% polyester cleanroom wiper with the solution and wiping the release layer surface. The conditioning solution was then allowed to dry spontaneously on the heated blanket.
  • a black ink as per Example 8 above (containing Carbon Black Mogul L (Cabot), 1.3 wt.%, Joncryl HPD 296 35.5% water solution (BASF), 35% (12% solids), glycerol 15%, Zonyl FSO-100 (DuPont) 0.2% and balance water) was jetted at a resolution of 600 dpi x 600 dpi onto the conditioned release layer while still at 150°C, using conventional Kyocera inkjet print heads. It will be appreciated that during printing the heated release layer was moved relative to the print heads at a rate of 75 cm/s. The test file printed for the experiment printed a gradient of ink coverage, from a less to more dense population of ink dots.
  • the drop size was set to 3 or 4, which corresponds to 13 pi or 18 pi respectively of ink.
  • the ink film formed was allowed to dry for at least 5 seconds and then while still hot was transferred to Condat Gloss ® 135 gsm paper using manual pressure, using one of two methods, either by the Paper On Blanket (POB) method, or the Roll method.
  • POB Paper On Blanket
  • Roll the paper was tightly fixed with tape to a metal cylinder and the ink image was transferred to the paper by manually rolling this paper (with pressure) over the inked blanket. Representative printouts obtained by the POB method are shown in Fig.
  • Tack (or tackiness) may be defined as the property of a material that enables it to bond with a surface on immediate contact under light pressure. Tack performance may be highly related to various viscoelastic properties of the material (polymeric resin, or ink solids). Both the viscous and the elastic properties would appear to be of importance: the viscous properties at least partially characterize the ability of a material to spread over a surface and form intimate contact, while the elastic properties at least partially characterize the bond strength of the material. These and other thermo-rheological properties are rate and temperature dependent.
  • the effect of cooling may be to increase the cohesion of the residue film, whereby its cohesion exceeds its adhesion to the release layer of the intermediate transfer member so that all or substantially all of the residue film is separated from the image transfer member and impressed as a film onto a substrate. In this way, it is possible to ensure that the residue film is impressed on the substrate without significant modification to the area covered by the film nor to its thickness.
  • Viscosity temperature sweeps — ramp and step — were performed using a Thermo Scientific HAAKE RheoStress® 6000 rheometer having a TM-PE-P Peltier plate temperature module and a P20 Ti L measuring geometry (spindle).
  • Samples of dried ink residue having a 1mm depth in a 2cm diameter module were tested. The samples were dried overnight in an oven at an operating temperature of 100°C. A volume of sample (pellet) was inserted into the 2cm diameter module and softened by gentle heating. The sample volume was then reduced to the desired size by lowering the spindle to reduce the sample volume to the desired depth of 1mm.
  • the sample temperature was allowed to stabilize at low temperature (typically 25°C to 40°C) before being ramped up to a high temperature (typically 160°C to 190°C) at a rate of approximately 0.33°C per second. Viscosity measurements were taken at intervals of approximately 10 seconds. The sample temperature was then allowed to stabilize at high temperature for 120 seconds before being ramped down to low temperature, at a rate of approximately 0.33°C per second. Again, viscosity measurements were taken at intervals of approximately 10 seconds. Oscillation temperature sweeps were performed at a gamma of 0.001 and at a frequency of 0.1 Hz.
  • Figure 6 provides ramped-down temperature sweep plots of dynamic viscosity as a function of temperature, for several dried ink formulations suitable for the ink film construction of the present invention. After reaching a maximum temperature of approximately 160°C, and waiting 120 seconds, the temperature was ramped down as described.
  • the lowest viscosity curve is that of a dried residue of an inventive yellow ink formulation, containing about 2% pigment solids, and produced according to the procedure described hereinabove.
  • the rheometer measured a viscosity of about 6.7 ⁇ 10 6 cP.
  • the viscosity steadily and monotonically increased to about 6 ⁇ 10 7 cP at 95°C, and to about 48 ⁇ 10 7 cP at 58°C.
  • the intermediate viscosity curve is that of a dried residue of an inventive cyan ink formulation, containing about 2% pigment solids, and produced according to the procedure described hereinabove.
  • the rheometer measured a viscosity of about 86 ⁇ 10 6 cP.
  • the viscosity increased to about 187 ⁇ 0 6 cP at 94°C, and to about 8 ⁇ 10 8 cP at 57°C.
  • the highest viscosity curve is that of a dried residue of an inventive black ink formulation, containing about 2% pigment solids, and produced according to the procedure described hereinabove.
  • the rheometer measured a viscosity of about 196 ⁇ 10 6 cP.
  • the viscosity steadily and monotonically increased to about 763 ⁇ 10 6 cP at 95°C, and to about 302 ⁇ 10 7 cP at 59°C.
  • Figure 7 is a ramped-down temperature sweep plot of dynamic viscosity as a function of temperature, for several dried ink formulations of the present invention, vs. several ink residues of prior art ink formulations.
  • the viscosity curves of the prior art formulations are labeled 1 to 5, and are represented by dashed lines; the viscosity curves of the inventive formulations are labeled A to E, and are represented by solid lines.
  • the residues of the prior art inks were prepared from various commercially available inkjet inks, of different colors.
  • a magnified view of the plot of Figure 7, for viscosities of less than 36 ⁇ 10 is provided in Figure 8. Only the viscosity curves of the inventive formulations A to E, and that of prior-art formulation 5, may be seen in Figure 8.
  • organic polymeric resins exist and many recognized to serve for the preparation of ink compositions are commercially available and known to persons skilled in this industry. Generally such polymers, whether well established ink resins or less typical to this field, serve to entrap (e.g., encapsulate) or otherwise immobilize or associate with the coloring agent of relevance through physical, covalent or ionic interactions, ultimately also enabling the ink image to attach to the printed substrate. Such polymeric resins are therefore often referred to as binders. Some polymers may alternatively or additionally serve as dispersants, maintaining the ink formulations in desired suspension or emulsion form. Though the exact function of an organic polymeric resin may vary in the context of a specific formulation or may include more than one function, it is used herein to refer to the predominant binder function which typically account for most of such polymers presence in a final ink composition.
  • Water dispersible thermoplastic resins include, but are not limited to linear and branched acrylic polymers, acrylic styrene copolymers, styrene polymers, polyesters, co-polyesters, polyethers, polyamides or polyester amides, polyurethanes and polyamines.
  • Such polymers are typically supplied with basic data on their average molecular weight (MW), their glass transition (T g ) or softening temperature, their minimal film forming temperature (MFFT), their hardness, their ability to contribute to the gloss of the final printed inks, or to their adherence to the printed substrate, or to their resistance to abrasion.
  • Some polymers may be defined by their reactivity or by the density of their functional groups, the acid number or the hydroxyl number being but examples of such qualifications.
  • Ink formulators are familiar with such parameters and will readily appreciate that the selection of a suitable organic polymeric resin may depend on the intended purpose. For instance, binders need not provide high gloss if the printed image is intended to be matte or if the ink image is to be further laminated or coated with a varnish that would independently provide the desired optical effect.
  • Such gloss-related information is generally provided by the supplier, but can be independently measured, for example by using a gloss meter at a fixed angle of incidence. Using a Micro-gloss (BYK-Gardner, Germany) single-angle gloss meter at 75°, prints displaying a gloss above 65-70 are regarded as glossy, whereas prints having a gloss below 65 are regarded as matte.
  • the presence of a laminate or varnish may reduce the need to select polymers providing good to excellent abrasion resistance.
  • Each supplier may use variations of the standard resistance test ASTM D5264 to assess this property.
  • ASTM D5264 In absence of coating protection and if the printed product is intended or may be subjected to scrub, then polymers having higher abrasion resistance should be preferred.
  • the hardness of the polymer can correlate with its ability to form ink film images that may have the desired resistance to abrasion, if needed. Therefore, for certain purposes, resins having a good to high hardness are preferred.
  • Such a coating may also improve the adhesion of the ink image to certain substrates. Understandingly, the degree of adherence a polymer would need to have would depend on the intended substrate.
  • Some organic resins provide good adherence to coated or synthetic substrates typically having a relatively low surface roughness. Other resins have superior abilities and can additionally or alternatively adhere to substrates having a higher surface roughness, such as most of the uncoated printing substrates.
  • the resins may also be selected to suit cellulose-based, cellulose-free, plastic-based or metal-based printing substrates, as commonly used in the field of commercial printing.
  • a suitable organic polymeric resin shall be appropriate for a broad range of possible substrates. This capability to adhere to the substrate of choice, if not provided by the resin manufacturer, can be readily assessed using a tape adherence test on the intended printing substrate.
  • the acid number also termed the acid value or neutralization number, relates to the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of a chemical substance.
  • KOH potassium hydroxide
  • the acid number is usually provided by the manufacturer, but readily measurable as per its definition.
  • Resins having a high acid number are expected to yield ink films less stable when exposed to water (water fastness) and should therefore be avoided when the intended use of the printed matter may expose it to conditions that would be deleterious to films comprising such resins.
  • Resins suitable for the present invention generally have an acid number below 100, or below 90.
  • the organic polymeric resins have an acid number between 60 and 100, and in particular, between 70 and 90.
  • the acid number may be below 15, below 12, below 10, below 7, below 5, or below 2.5.
  • Such polymeric resins may have an acid number between 0 and 15, between 0 and 10, and in particular, between 0 and 5 or between 1 and 5.
  • the polymer resins such as acrylic-based polymers, may be negatively charged at alkaline pH. Consequently, in some embodiments, the polymeric resin has a negative charge at a pH above 7.5, above 8 or above 9. Furthermore, the solubility or the dispersability of the polymeric resin in water may be affected by pH.
  • the formulation comprises a pH-raising compound. Examples of such are diethyl amine, monoethanol amine, and 2-amino-2-methyl propanol.
  • pH-raising compounds when included in the ink, are generally included in small amounts, e.g., about 1 wt.% of the formulation and usually not more than about 2 wt.% of the formulation.
  • Some resins are characterized by a hydroxyl number, also termed the hydroxyl value, which is a measure of the content of free hydroxyl groups in a compound, hence typically used in connection with esters. This value, if not provided, can be determined by acetylation of the free hydroxyl groups of the compound of interest and standard titrations and calculations known in the art. As other functional groups, such as primary or secondary amines, may take part in the chemical reactions used to assess this number, they can also be reported as hydroxyl. Hence the hydroxyl number may serve to assess the more general reactivity / functionality of the resin.
  • KOH potassium hydroxide
  • suitable resins e.g., polyester or polyester-based resins, including co-polyester resins, linear and branched polyester or co- polyester resins, can have a hydroxyl value between 15 and 60, between 25 and 55, or between 35 and 50.
  • a suitable resin needs to satisfy the thermo-rheological conditions to be described in more detail in the following sections.
  • rheological patterns can be adapted to the intended purpose.
  • the viscosity of the dried ink film at a high temperature may be higher than the viscosity of the dried ink film intended to adhere on a substrate having a higher surface roughness.
  • the ink composition to be suited for uncoated substrates would require a relatively lower viscosity of the dried film that would allow the image to better follow the contour of the surface topography, hence increasing area of contact for better adherence.
  • the selection of the organic polymeric (binder) resin to be included in the ink formulations of the present disclosure may further take into account the temperature at which the ink is jetted at the image forming station, the type of inkjet head (such as continuous ink jet (CD) or drop-on-demand (DOD)), the temperature at which it contacts the intermediate transfer member, the temperature at which it is dried upon the transfer member and the temperature at which it is transferred from the transfer member to the intended printing substrate at the impression station.
  • the type of inkjet head such as continuous ink jet (CD) or drop-on-demand (DOD)
  • CD continuous ink jet
  • DOD drop-on-demand
  • suitable organic polymeric resins include acrylic polymers, acrylic styrene copolymers, styrene polymers, polyesters.
  • the resins are one or more polymers selected from the group comprising Joncryl® 90, Joncryl® 530, Joncryl® 537E, Joncryl® 538, Joncryl® 631, Joncryl® 1158, Joncryl® 1180, Joncryl® 1680E, Joncryl® 1908, Joncryl® 1925, Joncryl® 2038, Joncryl® 2157, Joncryl® Eco 2189, Joncryl® LMV 7051, Joncryl® 8055, Joncryl® 8060, Joncryl® 8064, Joncryl® 8067, all acrylic-based polymers available from BASF; Dynacoll® 7150, Desmophen® XP2607 and Hoopol® F-37070, all polyester-based polymers respectively available from Evonik, Bayer and Synthesia International,
  • Joncryl® 90 >200,000 1 10 °C >85 °C 76
  • Joncryl® 631 >200,000 107 °C >85 °C 70
  • Joncryl® 1180 >200,000 107 °C >85 °C
  • the molecular weight of the resin need not be limited.
  • the resin has an average molecular weight of at least 1 ,200, at least 1 ,500, at least 2,000, or at least 5,000, at least 25,000, at least 50,000, at least 100,000, at least 150,000, or at least 200,000.
  • suitable organic polymeric resins, and particularly polyester or polyester-based resins, including co-polyester resins, linear and branched polyester or co-polyester resins may have an average molecular weight of at most 12,000, at most 10,000, at most 8,000, at most 6,000, at most 5,000, at most 4,000, at most 3,500, or at most 3,000.
  • the below formulations are presented using Carbon Black as pigment to serve for black (K) color inks.
  • Some of the below formulations were prepared with cyan pigments (e.g., PV Fast Blue BG), magenta pigments (e.g., Cromophtal® Jet Magenta DMQ) or yellow pigments (e.g., Hansa Brilliant Yellow 5GX03) at the same concentrations as indicated for the black pigment, to yield respectively cyan (C), magenta (M) and yellow (Y) inks.
  • C cyan
  • M magenta
  • Y yellow
  • Results obtained with black inks will be referred to by their appropriate example number. If such results are displayed or discussed with reference to colors other than black, the one letter code of the specific color is indicated. For instance, 'Ex.
  • Polymeric binder resins are commercially available in many forms, including various solid forms, such as amorphous or crystalline structures.
  • the resins may be available as free-flowing powders, and pellets.
  • the resins may be available in liquid form, as emulsions or dispersions, typically blended with suitable additives. Additionally, each such commercially available resins may have a particular, characteristic particle size distribution.
  • the viscosity of a composition can be affected by the type of ingredients it contains, their respective inherent rheological properties and their concentration.
  • the particle size may also affect the viscosity, to some degree, since the same amount of a material having a lower particle size, provides a higher surface area available for interactions capable of modifying some of its original physico-chemical properties.
  • the particle size is, however, but one parameter, and need therefore not be limited.
  • the resins have an average particle size d 5 o of 3 micrometer ( ⁇ ) or less, or of less than 1 ⁇ , or of less than 0.5 ⁇ , or of less than 400 nm, or of less than 300 nm, or of less than 200 nm, or of less than 100 nm.
  • a general procedure for preparing inks in accordance with embodiments of the invention for resins available in liquid form is as follows: first, a pigment or dye concentrate is prepared by mixing distilled water, at least a portion (typically about 20%) of the polymeric resin or dispersant, if used, and colorant, and milling by procedure known in the art using any appropriate apparatus until a suitable particle size is reached. If a dispersant was used in this step, it was typically at a 1 : 1 ratio with the colorant.
  • nano-pigments e.g., having a d 5 o below 1 ⁇
  • sub-micron to low micronic range resins e.g., having a d 5 o below 5 ⁇
  • a pH-raising compound it may be included in this step.
  • the milling process was monitored on the basis of particle size measurements using a dynamic light scattering particle size analyzer (e.g., ZETASIZERTM Nano-S, ZEN 1600 of Malvern Instruments, England), using standard practice. Unless otherwise stated, the process was stopped when the average particle size (d 5 o) reached about 70 nm.
  • the remaining materials were then added to the pigment concentrate and mixed. After mixing, the ink was filtered through a 0.5 ⁇ filter.
  • the viscosity of the inks thus obtained was measured at 25°C using viscometer (DV II + Pro by Brookfield) and was typically in the range of about 2 cP to 25 cP.
  • the surface tension was measured using a standard liquid tensiometer (EasyDyne by Kruss) and was generally in the range of approximately 20 to 30 mN/m.
  • the resulting pH was usually in the range of 6.5 to 10.5 range, and more typically, in the range of 7.0 to 9.0.
  • the polymeric resin when available in solid form, an alternative procedure can be used.
  • the resin is thoroughly milled with a dispersant, before being admixed with the coloring agent and any other ingredient of the ink formulation.
  • a dispersant for the preparation of some formulations herein-disclosed, a slurry consisting of 37.5g Dynacoll® 7150 (Evonik, flakes), 93.75g Dispex Ultra PX 4575 (BASF) and 131.25 ml of distilled water was milled at 5°C for 48 hours in a ball mill (Atrittor OS, Union Process, USA), having a ceramic inner surface and 0.8 mm Zirconia beads.
  • the ground slurry was then mixed at desired ratio with a concentrate of coloring agent (e.g., a black pigment dispersed in a standard milling apparatus with a dispersant).
  • a concentrate of coloring agent e.g., a black pigment dispersed in a standard milling apparatus with a dispersant.
  • the pigment was dispersed with the same Dispex Ultra PX 4575 so that the final ratio of resin to dispersant was 1 :0.35.
  • a softening agent was added to the resin - pigment mix, and water was added if needed to achieve the final formulation.
  • the fully formulated ink was then mixed and filtered through a 0.5 ⁇ filter. Viscosity, surface tension and pH were measured as mentioned hereinabove.
  • a partial list of the ink formulations prepared by these exemplary methods is presented below, the content of each ingredient being indicated in weight percent (wt. %) of the stock material, whether a liquid or solid chemical or a diluted solution, dispersion or emulsion comprising the material of interest, the weight percent being relative to the total weight of the final formulation.
  • Concentrated versions having a solid content of at least 45% (see Example 42) and of about 80% are also provided (see Examples 40 and 41). Persons skilled in the art to which this invention pertains will readily appreciate that other methods of preparation may be equally suitable.
  • Resin Joncryl® ECO 2189 (48% nvs) as is 27.0
  • Resin Joncryl® ECO 2189 (48% nvs) as is 26.2
  • nano-pigments may be used in the inventive ink formulations. These include pigment preparations such as CAB-O-JET® 352K by Cabot, Hostajet Magenta E5B-PT and Hostajet Black O-PT, both by Clariant as well as pigments demanding post-dispersion processes, such as Cromophtal Jet Magenta DMQ and Irgalite Blue GLO, both by BASF.
  • pigment preparations such as CAB-O-JET® 352K by Cabot, Hostajet Magenta E5B-PT and Hostajet Black O-PT, both by Clariant as well as pigments demanding post-dispersion processes, such as Cromophtal Jet Magenta DMQ and Irgalite Blue GLO, both by BASF.
  • pigments and pigment formulations may include, or consist essentially of, inkjet colorants and inkjet colorant formulations.
  • the colorant may be a dye.
  • dyes suitable for use in the ink formulations of the present invention include: Duasyn Yellow 3GF-SF liquid, Duasyn Acid Yellow XX-SF, Duasyn Red 3B-SF liquid, Duasynjet Cyan FRL-SF liquid (all manufactured by Clariant International Ltd.); Basovit Yellow 133, Fastusol Yellow 30 L, Basacid Red 495, Basacid Red 510 Liquid, Basacid Blue 762 Liquid, Basacid Black X34 Liquid, Basacid Black X38 Liquid, Basacid Black X40 Liquid (all manufactured by BASF).
  • dispersants may include high molecular weight polyurethane or aminourethane (e.g., Disperbyk® 198), a styrene-acrylic copolymer (e.g., Joncryl® HPD 296), a modified polyacrylate polymer (e.g., EFKA® 4560, EFKA® 4580), an acrylic block copolymer made by controlled free radical polymerization (e.g., EFKA® 4585, EFKA® 7702), a sulfosuccinate (e.g., Triton GR, Empimin OT ), an acetylenic diol (e.g., Surfynol CT), an ammonium salt of carboxylic acid (e.g., EFKA 7571), an alkylol ammonium salt of carboxylic acid (e.g., EFKA 5071), an alipha-N-acrylate polymer (e.g., EFKA 4571), an alky
  • a surfactant e.g., 0.5-1.5 wt.% of the ink.
  • a surfactant may serve as wetting agents and/or as leveling agents.
  • the surfactant is a non-ionic surfactant.
  • wetting agents and/or leveling agents include silicones, modified organic polysiloxanes and polyether modified siloxanes (e.g., BYK ® 307, BYK ® 333, BYK ® 345, BYK ® 346, BYK ® 347, BYK ® -348, or BYK ® -349, from BYK, or Hydropalat WE 3240 from BASF).
  • Fluorosurfactants such as Capstone FS-10, Capstone FS-22, Capstone FS-31 , Capstone FS- 65 (DuPont), Hydropalat WE 3370, and Hydropalat WE 3500, may also be suitable.
  • Hydrocarbon surfactants such as block copolymers (e.g., Hydropalat WE 31 10, WE 3130), sulfosuccinates (e.g., Hydropalat WE 3475), and acetylene diol derivatives (e.g., Hydropalat WE 3240) can be used as wetting and/or leveling agents.
  • block copolymers e.g., Hydropalat WE 31 10, WE 3130
  • sulfosuccinates e.g., Hydropalat WE 3475
  • acetylene diol derivatives e.g., Hydropalat WE 3240
  • humectants that are miscible with water are ethylene glycol, diethylene glycol, propylene glycol, glycerol, N-methyl pyrrolidone, and polyethylene glycol 400 (PEG 400).
  • the inventive process in which the ink formulations can be used may include the heating of the ink film or image, during transport on the surface of the image transfer member, to evaporate the aqueous carrier from the ink image.
  • the heating may also facilitate the reduction of the ink viscosity to enable the transfer conditions from the ITM to the substrate.
  • the ink image may be heated to a temperature at which the residue film of organic polymeric resin and colorant that remains after evaporation of the aqueous carrier is rendered tacky (e.g., by softening of the resin).
  • the residue ink film on the surface of the image transfer member may be dry or substantially dry.
  • the film includes the resin and the colorant from the ink formulation.
  • the residue film may further include small amounts of one or more surfactants or dispersants, which are typically water soluble at the pH of the ink (i.e., prior to jetting).
  • the ink residue film may be rendered tacky before it reaches the impression cylinder.
  • the film may cool at the impression station, by its contact with the substrate and exposure to the environment.
  • the already tacky ink film may adhere immediately to the substrate onto which it is impressed under pressure, and the cooling of the film may be sufficient to reduce film adhesion to the image transfer surface to the point that the film peels away neatly from the image transfer member, without compromising adhesion to the substrate.
  • Tack (or tackiness) may be defined as the property of a material that enables it to bond with a surface on immediate contact under light pressure. Tack performance may be highly related to various viscoelastic properties of the material (polymeric resin, or ink solids). Both the viscous and the elastic properties would appear to be of importance: the viscous properties at least partially characterize the ability of a material to spread over a surface and form intimate contact, while the elastic properties at least partially characterize the bond strength of the material. These and other thermo-rheological properties are rate and temperature dependent.
  • Such ink droplets need to be able to form instantaneously, once on the ITM surface, a skin preventing disturbance of droplet position and shape on the blanket, as long as the ink carrier is not fully evaporated. If the adhesion needs to be facilitated by the treatment of the blanket with a conditioning solution prior to ink jetting and image formation, the type of interaction with the optional conditioning agents may also be affected by temperature.
  • residue films which are obtained from the ink formulations of the present invention, and may be processed substantially as described herein, may have several salient features, including:
  • ultra-thin film thickness typically about 0.5 ⁇ for a single-layer film
  • the process may require the inventive residue films to have sufficient fiowability to readily transfer from the ITM to the printing substrate at low temperatures (e.g., below 140°C, below 120°C, below 100°C or below 90°C).
  • the process may also require the inventive residue films to have sufficiently low fiowability at lower temperatures (e.g., below 55°C) such that the residue films "permanently" adhere to the printing substrate at such temperatures, without developing a tendency to adhere to other surfaces.
  • the effect of the cooling may be to increase the cohesion of the residue film, whereby its cohesion exceeds its adhesion to the transfer member so that all or substantially all of the residue film is separated from the image transfer member and impressed as a film onto the substrate. In this way, it is possible to ensure that the residue film is impressed on the substrate without significant modification to the area covered by the film nor to its thickness.
  • the dried or substantially dried ink residue or ink residue film may advantageously have a first dynamic viscosity within a range of 10 6 cP to 5 » 10 7 cP for at least a first temperature within a first range of 60°C to 87.5°C.
  • the inventors have found that such a first dynamic viscosity may be correlated with efficacious low- temperature transfer of the dried ink film from the ITM to various fibrous (e.g. , coated and uncoated papers and cardboards) and non- fibrous (e.g., various types of plastic) substrates.
  • the ink residue film may advantageously have a second dynamic viscosity of at least 7 » 10 7 cP, for at least a second temperature within a second temperature range of 50°C to 55°C. At such viscosities and temperatures, the residue films may display good adhesion to the printing substrate, while surface tack is sufficiently low to discourage adhesion to other surfaces.
  • Viscosity temperature step sweeps were performed using a Thermo Scientific HAAKE Mars III rheometer having a TM-PE-P Peltier plate temperature module and a P20 Ti L measuring geometry or PP20 disposable (spindle).
  • Samples of dried ink residue having a 1mm depth in a 2cm diameter module were tested.
  • the samples were dried in an oven at an operating temperature of 110°C until the weight of the sample did not further change (and typically reached the weight expected on the basis of the non-volatile materials). Typically, the samples were dried for one hour or more and up to overnight (i.e., up to 18 hours).
  • a volume of sample (pellet) was inserted into the 2cm diameter module and softened by gentle heating (typically at 80°C for less than one minute) to ensure adequate contact between the surface of the sample and the spindle. The sample volume was then reduced to the desired size by lowering the spindle to reduce the sample volume to the desired depth of 1mm.
  • the sample temperature was allowed to stabilize for 120 seconds at low temperature (typically 45°C to 55°C, in particular circa 50°C) before being ramped up to a high temperature (typically 150°C to 190°C, in particular circa 180°C).
  • the measurements were performed under two regimens, termed, respectively, the "long method” and "short method".
  • the temperature was set to increase at a rate of approximately 0.08°C per second up to about 110°C and at a rate of approximately 0.04°C per second at higher temperature (above 110°C).
  • Viscosity measurements were taken at intervals of approximately 10°C, 20 repeat measurements being carried out at each time point.
  • the sample temperature was then allowed to stabilize at high temperature for 120 seconds before being ramped down to low temperature, at the same rates.
  • the temperature was set to increase at a rate of approximately 0.11°C per second up to about 110°C and at a rate of approximately 0.07°C per second at higher temperature.
  • viscosity measurements were taken at intervals of approximately 90 seconds, ten repeat measurements being carried out at each time point.
  • the sample temperature was then allowed to increase to the target high temperature during 940 seconds, at which time the viscosity was last measured without ramping down back to lower temperature.
  • the spindle was set to oscillate at a frequency of 1 Hz.
  • the rheometer used in the present experimental setup provided up to ten repeat measurements for a given temperature and for temperatures of up to 100°C, the rheometer ranked the quality of each of the measurements, allowing trained operators to manually select, if needed, the most representative values in the linear viscous elastic range (typically at least the last three measurements in a series performed at a given temperature). Above 110°C, the samples were generally viscous and generally had a sufficient linear viscous elastic range to permit automatic measurement.
  • Figure 9A provides a temperature sweep plot of dynamic viscosity as a function of temperature, for residue films of various ink formulations, including ink formulations of the present invention.
  • the twenty plots provided correspond to dried ink residues of the ink formulations of Example Nos. 1-4, 7-15, 18, 20, 23, 24, 28, 31 and 33, and the viscosity axis spans from l » 10 6 cP to l » 10 9 cP.
  • the dried ink residues were obtained using the drying procedure provided hereinabove.
  • the dried ink residues may be advantageous for the dried ink residues to exhibit a dynamic viscosity of at least 7 » 10 7 cP, within a temperature range of 50°C to 55°C.
  • the dried ink residues may advantageously exhibit a dynamic viscosity of at least 8 » 10 7 cP, at least 9 » 10 7 cP, at least l » 10 8 cP, or at least 1.5 » 10 8 cP.
  • the residue films may display good adhesion to the printing substrate, while surface tack is sufficiently low to discourage adhesion to other surfaces.
  • a first rectangular window (Wl), plotted in Figure 9A, shows suitable viscosities for dried ink residues at 60°C to about 87.5°C, within the temperature sweep.
  • the inventors have found that residue films exhibiting good transfer properties at low temperature generally display temperature sweep viscosity curves that fall within this window.
  • a rectangular window (W2) also plotted in Figure 9A, shows suitable viscosities for dried ink residues at 50°C to 55°C, within the temperature sweep.
  • the dried ink residues may advantageously have a viscosity in excess of the upper bound of the plot, i.e., M0 9 cP.
  • the temperature sweep plot of dynamic viscosity as a function of temperature, for residue films may fall within both windows (Wl, W2).
  • Figure 9B provides temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of inventive ink formulations containing various polyester resins.
  • the plots provided correspond to dried ink residues of the ink formulations of Example Nos. 34-39 and the viscosity axis spans from l » 10 7 cP to l » 10 8 cP to magnify the area of interest.
  • the dried ink residues were obtained using the drying procedure provided hereinabove.
  • the temperature sweep plot of dynamic viscosity as a function of temperature, for residue films containing polyester based resins may fall within both windows (Wl, W2), both shown in truncated form in Figure 9B.
  • Figure 10 provides temperature sweep plots of dynamic viscosity as a function of temperature, for representative dried ink residues of various ink formulations, some of which were provided in Figure 9A and 9B.
  • the temperature sweep of residue #16 (of formulation #16 from Example 16) passes through W2 at a viscosity of approximately l » 10 9 cP.
  • the viscosity of residue #16 drops monotonically.
  • the slope (or negative slope) is far from sufficient for the thermo-rheological plot of residue #16 to pass through Wl.
  • the temperature sweep of residue #2 passes through W2 at a viscosity of close to l » 10 9 cP, and at temperatures above 55°C, the viscosity drops monotonically.
  • the slope is easily sufficient for the thermo-rheo logical plot of residue #2 to pass through Wl.
  • the temperature sweep of residue #34 passes through W2 at a viscosity of about 7 » 10 7 cP, and at temperatures above 55°C, the viscosity drops monotonically. However, the slope is low with respect to residue #2 and residue #19.
  • the temperature sweep passes through W2 at a viscosity approaching 2 » 10 8 cP. At temperatures above 55°C, the viscosity drops monotonically, the slope being comparable to that of residue #2.
  • the temperature sweep passes through a central area of W2.
  • the temperature sweep of residue #7 passes through W2 at a viscosity of around 2 » 10 8 cP.
  • the viscosity drops sharply, such that the sweep passes through Wl near the bottom, left-hand corner, attaining a viscosity of l » 10 6 cP at around 70°C.
  • the temperature sweep of residue #15 (from the ink formulation provided in Example 15) has a slope that is similar to that of residue #7, however, the residue has sufficiently-high flowability at low temperatures such that the temperature sweep falls outside the bounds of both Wl and W2.
  • the temperature sweep of residue #14 passes through Wl, but at lower temperatures of 50°C to 55°C, fails to develop the requisite viscosity for dry ink residues according to the present invention.
  • Figure 11 provides temperature sweep plots of dynamic viscosity as a function of temperature, for representative dried ink residues of ink formulations of the present invention, vs. dried ink residues of several commercially available inkjet inks.
  • the dried ink residues of inventive ink formulations 2, 7 and 8 are those described hereinabove with reference to Figure 12; residue #35 was obtained by drying the inventive ink formulation provided in Example 35.
  • the commercially available inkjet inks are black inks of Canon, Epson, HP, and Toyo, and are labeled accordingly.
  • the inventors of the present invention successfully transferred all of the inventive ink residues to a printing substrate, but failed to transfer any of the prior-art ink films to a printing substrate, even after heating to over 160°C.
  • the transferability to printing substrates of ink formulations prepared as described in previous examples was assessed as follows: the formulations being tested were applied to the outer surface of a printing blanket of approximately 20 cm x 30 cm size pre -heated to a desired temperature, typically between 70 and 90°C. Unless otherwise stated, this surface comprised a silanol-terminated polydimethyl-siloxane silicone release layer.
  • a conditioning solution generally comprising 0.3wt.% of polyethylenimine (PEI) (e.g., Lupasol® PS) in water, was manually applied to the release layer surface by moistening a Statitech 100% polyester cleanroom wiper with the solution and wiping the release layer surface. The conditioning solution was then allowed to dry spontaneously on the heated blanket and the temperature of the release layer was monitored using an IR Thermometer Dual Laser by Extech Instruments.
  • PEI polyethylenimine
  • the ink formulation was applied and evened on the surface of the heated and optionally pre-conditioned blanket using a coating rod (e.g. , Mayer rod) yielding a wet layer having a characteristic thickness of approximately 12 micrometers.
  • a coating rod e.g. , Mayer rod
  • the ink film so formed was allowed to dry for at least 5 seconds and then, while still hot, was transferred to the desired printing substrate, such as Condat Gloss® 135 gsm coated paper.
  • the paper was placed on the surface of the dried ink and the transfer was performed using a metal roller by applying manual pressure. The quality of the transferred image was visually assessed. The surface of the release layer was observed in the event of partial transfer.
  • the transferability test was performed at least three times for each temperature of transfer and/or printing substrate.
  • softening agents may be introduced to the ink formulations according to the present invention.
  • the addition of such softening agents may enable the use of various resins exhibiting characteristically poor flowability at low temperatures.
  • Figure 12A displays a first plurality of temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of five ink formulations having identical components, and a varying ratio of softening agent, using a first thermoplastic resin (Joncryl® 1680E), and a first softening agent (polyethylene glycol (PEG) 20,000).
  • the dried residues were obtained from the ink formulations corresponding to Examples 5, 6, 7, 25 and 26.
  • Figure 12B provides a second plurality of temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of five ink formulations having identical components, and a varying ratio of softening agent, using a second thermoplastic resin, namely, Joncryl® 8060, and a second softening agent, namely, PEG 8,000.
  • the dried residues were obtained from the ink formulations corresponding to Examples 16, 17, 21, 22 and 23.
  • Figures 13A-13D are temperature sweep plots of dynamic viscosity as a function of temperature, for residue films of ink formulations having different softening agents, and varying concentrations of those agents.
  • the pigment and the polymeric resin were the same black pigment and Joncryl® 2038, and were kept at a 1 :4 ratio for all samples.
  • Figure 13A provides the thermo-rheological behavior of dried residues of ink formulations comprising Tween® 20 (Examples 27-28);
  • Figure 13B displays sweep plots observed for formulations comprising Tween® 40 (Examples 29-31);
  • Figure 13C for formulations comprising Tween® 60 (Examples 9-10);
  • Figure 13D for formulations comprising Tween® 80 (Examples 32-33).
  • the softening agent may have a vapor pressure of at most 0.40 kPa, at most 0.35 kPa, at most 0.25 kPa, at most 0.20 kPa, at most 0.15 kPa, at most 0.12 kPa, at most 0.10 kPa, at most 0.08 kPa, at most 0.06 kPa, or at most 0.05 kPa, at 150°C.
  • the softening agent may be stable up to a temperature of at least 170°C, at least 185°C, at least 200°C, or at least 220°C.
  • the weight ratio of the softening agent to the resin within the formulation may be at least 0.05: 1, at least 0.10: 1, at least 0.15: 1, at least 0.2: 1, at least 0.25:1, at least 0.35: 1, at least 0.4: 1, at least 0.5: 1, at least 0.6: 1, at least 0.75: 1, at least 1 :1, at least 1.25: 1, at least 1.5: 1, at least 1.75: 1, at least 2: 1, at least 2.5: 1, at least 3:1 , at least 3.5:1, at least 4: 1, at least 5: 1, at least 6: 1, or at least 7: 1.
  • this weight ratio may be at most 15: 1, at most 12: 1, at most 10: 1, at most 9: 1, at most 8: 1, or at most 7.5: 1.
  • colorant or “coloring agent”, as used herein in the specification and in the claims section that follows, refers to a substance that is considered, or would be considered to be, a colorant in the art of printing.
  • the colorant may include at least one pigment.
  • the colorant may include at least one dye.
  • pigment refers to a solid colorant, typically finely divided.
  • the pigment may have an organic and/or inorganic composition.
  • pigments are insoluble in, and essentially physically and chemically unaffected by, the vehicle or medium in which they are incorporated.
  • Pigments may be colored, fluorescent, metallic, magnetic, transparent or opaque. Pigments may alter appearance by selective absorption, interference and/or scattering of light. They are usually incorporated by dispersion in a variety of systems and may retain their crystal or particulate nature throughout the pigmentation process.
  • die refers to at least one colored substance that is soluble or goes into solution during the application process and imparts color by selective absorption of light.
  • d 5 o average particle sizes
  • PSDs particle size distributions
  • the pigments may thus be nanopigments; the particle size of the nanopigments may depend on the type of pigment and on the size reduction methods used in the preparation of the pigments. Pigments of various particle sizes, utilized to give different colors, may be used for the same print.
  • pigments having such particle sizes are commercially available, and may be employed as-is in embodiments of the invention; in other cases, the pigments may be milled to the appropriate size. It will be appreciated that in general, the pigments are dispersed (or at least partly dissolved) within the solvent along with the polymeric resin, or can be first dispersed within the polymeric resin (e.g., by kneading) to obtain colored resin particles that are then mixed with the solvent.
  • the concentration of the at least one colorant within the ink formulation, when the formulation is substantially dry, may be at least 2%, at least 3%, at least 4%, at least 6%, at least 8%, at least 10%, at least 15%, at least 20%>, or at least 22%, by weight.
  • the concentration of the at least one colorant within the ink film is at most 40%, at most 35%, at most 30%, or at most 25%. More typically, the dry ink residue may contain 2-30%, 3- 25%, or 4-25% of the at least one colorant.
  • the weight ratio of the polymeric resin to the colorant may be at most 10: 1 , at most 7: 1 , at most 5 : 1 , at most 3 : 1 , at most 2.5 : 1 , at most 2: 1 , or at most 1.7: 1.
  • Figure 19 provides temperature sweep plots of dynamic viscosity as a function of temperature, for dried ink residues of four ink formulations having different colorants (C, M, Y, K) but otherwise identical formulation components.
  • the black formulation is as disclosed in Example 4.
  • inventive formulations may be modified in a fairly predictable manner to achieve desired formulation properties, and in particular, thermo-rheological properties.
  • exemplary formulations, and thermo-rheological plots thereof have been provided.
  • the plots have been arranged within the Figures to provide guidance on the effect of resin to pigment ratio on the thermo-rheological behavior.
  • Figure 12A and Figure 12B demonstrate the effect of the softening agent to resin ratio on thermo-rheological behavior, for 2 different thermoplastic resins and 2 different softening agents. Higher softening agent to resin ratios are generally associated with lower viscosities.
  • Relatively hard resins may be made suitable for low-temperature transfer by the softening agents.
  • Figures 13A-13D demonstrate the effect of different softening agents on thermo-rheological performance, combined with varying softening agent to resin ratio, while keeping other formulation parameters constant. From the similarity of the curves in Figure 19 it is evident that the colorants play a thermo-rheological role, but that that role is generally of secondary importance.
  • the first, "high-temperature” viscosity (associated with Wl) provides a general indication of film transfer properties, which is important in the transfer of the film from the release layer of the ITM.
  • the maximum viscosity value associated with that physical property may be represented by the top line or area of Wl .
  • the second, "low-temperature" viscosity (associated with W2 at 50-55°C) provides a general indication of how the film will behave on the printing substrate.
  • the minimum viscosity value associated with that physical property may be represented by the bottom of W2.
  • the terms “substantially dried” or “substantially dry”, with regard to an ink-containing sample refer to a sample dried according to the following conditions (or substantially identical conditions): samples of ink formulations (5 g) are placed on an aluminum crucible and dried in a vacuum oven (VT 6025, Thermo Scientific) at a temperature of 110°C and under a pressure of 1 mbar (absolute). The level of dryness is gravimetrically checked every hour, and the drying procedure is stopped when the difference in weight loss between immediately adjacent weighings (1 hour apart) of the sample is less than 2%. For low vapor pressure materials such as glycerol, the weight loss between immediately adjacent weighings (1 hour apart) of the sample is less than 0.5%.
  • the target stable weight can be estimated on the basis of the amount of solids or other non-volatile materials in the formulation.
  • the ink formulation is devoid or substantially devoid of wax.
  • the ink formulation contains less than 30 wt.% wax, less than 20 wt.% wax, less than 15 wt.% wax, less than 10 wt.% wax, less than 7 wt.% wax, less than 5 wt.% wax, less than 3 wt.% wax, less than 2 wt.% wax, or less than 1 wt.% wax.
  • wax is included in the ink formulation in order to impart greater abrasion resistance in the printed ink.
  • Such waxes may be natural or synthetic, e.g.
  • the formulation may comprise, for example, 0.1-10 wt.% wax, e.g., up to 0.1, 0.3, 0.5, 0.7, 1.0, 1.5, 2, 3, 4, 6, 8, or 10 wt.%> wax.
  • the wax may be incorporated into the formulation as an aqueous dispersion of small wax particles, e.g., having an average size of 10 micrometers or smaller, preferably having average size of 1 ⁇ or smaller.
  • the ink formulation is devoid or substantially devoid of oils such as mineral oils and vegetable oils (e.g., linseed oil and soybean oil).
  • oils such as mineral oils and vegetable oils (e.g., linseed oil and soybean oil).
  • the ink formulation contains at most 20 wt.%, at most 12 wt.%, at most 8 wt.%, at most 5 wt.%, at most 3 wt.%), at most 1 wt.%>, at most 0.5 wt.%>, or at most 0.1 wt.%>, by weight, of one or more oils, cross-linked fatty acids, or fatty acid derivatives produced upon air-drying.
  • the ink formulation is devoid or substantially devoid of glycerol.
  • the ink formulation contains at most 10%, at most 8%, at most 6%, at most 4%), at most 2%>, at most 1%>, at most 0.5%>, or at most 0.2%> glycerol, by weight.
  • the ink formulation is devoid or substantially devoid of one or more salts, including salts used to coagulate or precipitate ink on a transfer member or on a substrate (e.g., calcium chloride).
  • the ink formulation contains at most 8 wt.%, at most 5 wt.%>, at most 3 wt.%>, at most 1 wt.%>, at most 0.5 wt.%>, at most 0.1 wt.%>, or substantially 0 wt.% of one or more salts.
  • salts may be referred to herein as "precipitants", and it will be appreciated that when it is stated that a formulation does not include a salt or contains salt in an amount less than a certain weight percentage, this does not refer to salts that may form between the polymer(s) of the polymeric resin and pH modifiers, such as alcohol amines, or that may be present in the polymeric resin itself if the polymeric resin is provided as a salt. As discussed above, it is presently believed that the presence of negative charges in the polymeric resin is beneficial to the print process.
  • the ink formulation is devoid or substantially devoid of inorganic particulates, e.g., silica particulates, titania particulate or alumina particulates, containing less than 2 wt.%>, less than 1 wt.%>, less than 0.1 wt.%> or substantially no inorganic particulates.
  • silica particulates is meant fumed silica, silica chips, silica colloids, and the like.
  • silica particulates include those available from DuPont Company under the names: Ludox® AM-30, Ludox® CL, Ludox® HS-30; and those available from Nyacol Nanotechnologies Company under the names: NexSilTM 12, NexSilTM 20, NexSilTM 8, NexSilTM 85.
  • the term "silica particulates" does not include colorants.
  • the ink dot may essentially be laminated onto a top surface of the printing substrate.
  • the form of the dot may be determined or largely determined prior to the transfer operation, and the dot is transferred as an integral unit to the substrate.
  • This integral unit may be substantially devoid of solvent, such that there may be no penetration of any kind of material from the blanket transfer member into, or between, substrate fibers.
  • the continuous dot which may largely contain organic polymeric resin and colorant, adheres to, or forms a laminated layer on, the top surface of the fibrous printing substrate.
  • Figures 15A-F display two-dimensional ( Figures 15A-C) and three-dimensional ( Figures 15D-F) laser-microscope acquired magnified images of ink films on commodity- coated paper substrates, obtained using various printing technologies, wherein: Figures 15A and 15D are magnified images of a liquid electro-photography film (LEP); Figures 15B and 15E are magnified images of an offset splotch; and Figures 15C and 15F are magnified images of an inkjet ink film construction according to the present invention.
  • the laser microscopy imaging was performed using an Olympus LEXT 3D measuring laser microscope, model OLS4000.
  • Figures 16A-F display two-dimensional ( Figures 16A-C) and three-dimensional ( Figures 16D-F) laser-microscope acquired magnified images of ink films on uncoated paper substrates, obtained using various printing technologies, wherein: Figures 16A and 16D are magnified images of a liquid electro-photography film (LEP); Figures 16B and 16E are magnified images of a lithographic offset splotch; and Figures 16C and 16F are magnified images of an inkjet ink film construction according to the present invention.
  • LEP liquid electro-photography film
  • Figures 16B and 16E are magnified images of a lithographic offset splotch
  • Figures 16C and 16F are magnified images of an inkjet ink film construction according to the present invention.
  • the ink dots in the ink dot constructions of the present invention may exhibit consistently good shape properties (e.g., roundness, edge raggedness, and the like), irrespective, to an appreciable degree, of the particular, local topographical features of the substrate, and irrespective, to an appreciable degree, of the type of printing substrate (coated or uncoated printing substrates, plastic printing substrates, etc.).
  • shape properties e.g., roundness, edge raggedness, and the like
  • the quality of ink dots in various known printing technologies, and in direct aqueous inkjetting technologies in particular may vary significantly with the type of printing substrate, and with the particular, local topographical features of the substrate.
  • the ink dot obtained may display significantly better shape properties, with respect to the other, or average ink dots disposed elsewhere on the substrate.
  • the inkjet ink drops have penetrated the surface of the paper, as may be best seen in Figures 16D-16F. Such penetration may be typical of various printing technologies using uncoated or commodity-coated paper, in which the paper may draw ink carrier solvent and pigment within the matrix of the paper fibers.
  • inventive inkjet ink film constructions may be characterized by well-defined individual ink films, disposed generally above, and adhering to, the fibrous substrates, both coated ( Figures IOC, 10F) and uncoated ( Figures 16C, 16F).
  • inventive inkjet single-drop ink film (or individual ink dot) construction was produced using the inventive system and method described herein, using an ink formulation Example 29 according to the present invention.
  • the perimeter of the offset ink splotch and the perimeter of the LEP ink splotch have a plurality of protrusions or rivulets, and a plurality of inlets or recesses. These ink forms may be irregular, and/or discontinuous.
  • the inkjet ink dot produced according to the present invention best seen in Figures IOC and 16C, has a manifestly rounded, convex, shape.
  • the perimeter of the ink film is relatively smooth, regular, continuous and well defined.
  • projections of the ink film of the invention against the substrate surface tend to be rounded, convex projections that form a convex set, i.e., for every pair of points within the projection, every point on the straight line segment that joins them is also within the projection.
  • a convex set is shown in Figure 20 A.
  • the rivulets and inlets in the projections of various prior-art define those projections as a non-convex sets, i.e., for at least one straight line segment within a particular projection, a portion of that straight line segment is disposed outside the projection, as illustrated in Figure 20B.
  • ink images may contain an extremely large plurality of individual or single ink films.
  • a 5mm by 5mm ink image, at 600 dpi may contain more than 10,000 of such single ink films. Therefore, it may be appropriate to statistically define the ink film constructions of the present invention: at least 10%, at least 20%), or at least 30%>, and more typically, at least 50%>, at least 70%>, or at least 90%>, of the single ink dots (selected at random), or projections thereof, may be convex sets.
  • ink images may not have crisp boundaries, particularly when those boundaries are viewed at high magnification. Therefore, it may be appropriate to relax the definition of the convex set whereby non-convexities (rivulets or inlets) having a radial length L r (as shown in Figure 20C) of up to 3,000nm, up to l,500nm, up to ⁇ , ⁇ , up to 700nm, up to 500nm, up to 300nm, or up to 200nm, are ignored, excluded, or are "smoothed", whereby the ink film or ink film projection is considered to be a convex set.
  • L r as shown in Figure 20C
  • the radial length L r is measured by drawing a radial line L from the center point C of the ink film image, through a particular rivulet or inlet.
  • the radial length L r is the distance between the actual edge of the rivulet or inlet, and a smoothed projection P s of the ink image, devoid of that rivulet or inlet, and matching the contour of the ink film image.
  • the perimeter of various ink dots or films of the prior art may characteristically have a plurality of protrusions or rivulets, and a plurality of inlets or recesses. These ink forms may be irregular, and/or discontinuous.
  • the inkjet ink dot produced according to the present invention characteristically has a manifestly rounded, convex, circular shape.
  • the perimeter of the ink dot of the invention may be relatively smooth, regular, continuous and well defined. Ink dot roundness, convexity, and edge raggedness are structural parameters used to evaluate or characterize shapes, or optical representations thereof.
  • the dot images were loaded to the image-processing software (ImageXpert). Each image was loaded in each of the Red, Green and Blue channels. The processing channel was selected based on a highest visibility criterion. For example, for cyan dots, the Red channel typically yielded the best dot feature visibility, and was thus selected for the image processing step; the Green channel was typically most suitable for a magenta dot.
  • the dot edge contour was detected (automatically computed), based on a single threshold. Using a "full screen view" mode on a 21.5" display, this threshold was chosen manually for each image, such that the computed edge contour would best match the real and visible dot edge. Since a single image-channel was processed, the threshold was a gray value (from 0 to 255, the gray value being a non color value).
  • a computed perimeter value was obtained from the image-processing software (e.g. , ImageXpert), the perimeter value being the sum of all distances between the adjacent, connected pixels at the edge of the dot or splotch. If, for example, the XY coordinates for adjacent pixels are (xl, yl) and (x2, y2), the distance is V[(x2-xl) 2 + (y2-yl) 2 ], while the perimeter + (yi+i-yi) 2 ] ⁇ -
  • an image comprising an ink dot is used as input for an algorithm that outputs perimeter length.
  • the pixel dimension MxN of the image may be stored in a two-element array or an ordered pair image _pixel_size.
  • the image magnification ratio or scale is obtained and stored in variable image jnagnification.
  • variable image jnagnification is 500.
  • image_pixel_size and image magnification of the two images are equal.
  • image_pixel_pitch the corresponding length of one square pixel - i.e. the side length in a real-world length units (e.g., micrometers) or a pixel.
  • This value is stored in a variable pixel _pitch.
  • variable pixel _pitch is 0.05 ⁇ .
  • the image is now converted to grayscale by methods known to the skilled artisan. One proposed method is converting the input image, the image typically in an sRGB color space, to the L*a*b* color space.
  • the preferred operator is a Canny edge detection operator.
  • any operator known in the art may be applied.
  • the operators are not limited to first order derivatives, such as the canny operator, but rather open to second derivatives as well.
  • a combination of operators may be used in order to obtain results that may be compared between operators and subsequently remove "unwanted" edges. It may be favorable to apply a smoothing operator such as a Gaussian blur prior to applying the edge detection operator.
  • the threshold level applied when applying the edge detection operator is such that an edge that forms an endless loop is first obtaining in the area between the formerly described minimal circumference Ink dot engulfing circle and the maximal circumference ink dot enclosed circle.
  • a thinning operator is now implemented to render the endless loop edge substantially one pixel wide. Any pixel that is not a part of the endless loop edge has its L* value change to zero, while any pixel that is part of the endless loop edge has its L* value change to 100.
  • the endless loop edge is defined as the perimeter of the ink dot.
  • a pixel link is defined as a straight line connecting to pixels. Each pixel along the perimeter incorporates two pixel links, a first pixel link and a second pixel link.
  • each pixel link may form a line from the center of the pixel to one of eight possible nodes.
  • the possible nodes being the corners of the pixel or a midpoint between two neighboring corners of the pixel.
  • Nodes at the corners of the pixels are of the type node_l one nodes at the midpoint between two corners are of type node_2.
  • there are six possibilities of pixel link paths within a pixel. can be categorized into three groups. Group A, B, and C. Each group has its own corresponding coefficient, namely, coefficient _A, coefficient _B, and coefficient _C.
  • coefficient_A is 1, the value of coefficient _B is the sqrt(2), and the value of coefficient _C is (l+sqrt(2))/2.
  • Group A contains pixels whose pixel link path coincides with nodes of type node_2.
  • Group B contains pixels whose pixel link path coincides with nodes of type node l .
  • Group C contains pixels whose pixel link path coincides with nodes of type node l and type node_2. It is now possible to calculate the pixel length of the perimeter.
  • the pixel length of the perimeter is calculated by summing all of the pixels in the perimeter multiplied by their corresponding coefficient. This value is stored in variable perimeter _pixel_length. It is now possible to calculate the actual length of the ink dot perimeter. This is done by multiplying perimeter _pixel_length by pixel _pitch. Roundness
  • a dimensionless roundness factor (ER), may be defined by:
  • P is the measured or calculated perimeter
  • A is the measured or computed area within the ink film, dot or splotch.
  • the deviation from a round, smooth shape may be represented by the expression (ER - 1). For a perfectly circular, idealized ink dot, this expression equals zero.
  • the R-square of the roundness factor may be computed for each of the 10 most representative dot images selected for each type of printing technology, and averaged into a single value.
  • the deviation from a round, smooth round shape [(ER - 1), henceforth, "deviation"] for the ink dots of the present invention is not ideal, and will exceed 0.
  • Figures 14A-2 to 14F2 exemplary magnified ink film images disposed on uncoated and coated substrates are provided for the following printers: direct inkjet: HP DeskJet 9000 (uncoated: Figure 14A-2; coated: Figure 14D-2); digital press: HP Indigo 7500 (uncoated: Figure 14B-2; coated: Figure 14E-2); and lithographic offset: Ryobi 755 (uncoated: Figure 14C-2; coated: Figure 14F-2).
  • Figures 12A-2 to 12E-2 provide magnified views of ink films disposed on coated paper (12A-2 to 12C-2) and uncoated paper (12D-2 and 12E-2), according to the present invention. These ink film images were obtained generally according to the image acquisition method detailed hereinabove.
  • the ink dots or films of the prior art may characteristically have a plurality of protrusions or rivulets, and a plurality of inlets or recesses. These ink forms may be irregular, and/or discontinuous.
  • the inkjet ink film produced according to the present invention characteristically has a manifestly rounded, convex, circular shape. Dot convexity, or deviation therefrom, is a structural parameter that may be used to evaluate or characterize shapes, or optical representations thereof.
  • the image acquisition method may be substantially identical to that described hereinabove.
  • the dot images were loaded to the image-processing software (ImageXpert). Each image was loaded in each of the Red, Green and Blue channels. The processing channel was selected based on a highest visibility criterion. For example, for cyan dots, the Red channel typically yielded the best dot feature visibility, and was thus selected for the image processing step; the Green channel was typically most suitable for a magenta dot.
  • the dot edge contour was detected (automatically computed), based on a single threshold. Using a "full screen view" mode on a 21.5" display, this threshold was chosen manually for each image, such that the computed edge contour would best match the real and visible dot edge. Since a single image-channel was processed, the threshold was a gray value (from 0 to 255, the gray value being a non color value).
  • a MATLAB script was created to compute the ratio between the area of the minimal convex shape that bounds the dot contour and the actual area of the dot. For each ink dot image, the (X,Y) set of points of the dot edge contour, created by ImageXpert, was loaded to MATLAB.
  • the dot edge was passed through a Savitzky-Golay filter (image-processing low-pass filter) to slightly smooth the edge contour, but without appreciably modifying the raggedness characteristic thereof.
  • a window frame size of 5 pixels was found to be generally suitable.
  • non-convexity The deviation from this convexity ratio, or “non-convexity", is represented by 1-CX, or DCdot-
  • the ink dots in the ink dot constructions of the present invention may exhibit consistently good shape properties (e.g., convexity, roundness, edge raggedness, and the like), irrespective, to a large degree, of the particular, local topographical features of the substrate, and irrespective, to some degree, of the type of printing substrate (coated or uncoated printing substrates, plastic printing substrates, etc.).
  • shape properties e.g., convexity, roundness, edge raggedness, and the like
  • the quality of ink dots in various known printing technologies, and in direct aqueous inkjetting technologies in particular may vary appreciably with the type of printing substrate, and with the particular, local topographical features of the substrate.
  • the ink dot constructions may be characterized as a plurality of ink dots disposed on the substrate, within a representative field of view. Assuming the characterization of the dot is obtained through image processing, a field of view contains a plurality of dot images, of which at least 10 dot images are suitable for image processing. Both the field of view and the dot images selected for analysis are preferably representative of the total population of ink dots on the substrate (e.g. , in terms of dot shape).
  • a printed sample preferably containing a high incidence of single ink dots, is scanned manually on the LEXT microscope, using a X20 magnification to obtain a field that includes at least 10 single dots in a single frame. Care should be taken to select a field whose ink dot quality is fairly representative of the overall ink dot quality of the printed sample.
  • Each dot within the selected frame is analyzed separately. Dots that are "cleaved" by the frame margins (which may be considered a square geometric projection) are considered to be part of the frame, and are analyzed. Any satellites and overlapping dots are excluded from the analysis.
  • a "satellite" is defined as an ink dot whose area is less than 25% of the average dot area of the dots within the frame, for frames having a generally homogeneous dot size, or as an ink dot whose area is less than 25% of the nearest adjacent dot, for non- homogeneous frames.
  • Each distinct ink dot is subsequently magnified with a XI 00 zoom, and image processing may be effected according to the procedure provided hereinabove with respect to the convexity and roundness procedures.
  • Figure 13A provides a magnified view of a field of ink dots on a commodity-coated fibrous substrate (Arjowiggins coated recycled gloss, 170gsm), produced using a commercially available, aqueous, direct inkjet printer.
  • Figure 13B provides a magnified view of a field of ink dots on an uncoated fibrous substrate (Hadar Top uncoated-offset 170gsm), produced using the identical, commercially available, aqueous, direct inkjet printer.
  • the frame of Figure 13A does not qualify as a "field" of ink dots, such fields requiring at least 10 single dots within a single frame, the frames are provided, and the dots are characterized, for illustrative purposes.
  • ink image A is a satellite, and is excluded from the analysis.
  • Dot B is cleaved by the frame margin, and is included in the analysis (i.e., the full ink dot is analyzed).
  • Tail or projection C is considered to be part of the ink dot disposed to its left.
  • the field contains only 6 ink dots for image processing.
  • dots E and F are distinct individual dots. While several splotches are reasonably round and well- formed, most of the splotches display poor roundness and convexity, have poorly-defined edges, and appear to contain multiple ink centers that are associated or weakly associated.
  • Figures 12A-1 to 12E-1 provide a magnified view of a field of ink dots or films on commodity-coated fibrous substrates ( Figures 12A-1 to 12C-1) and uncoated fibrous substrates ( Figures 12D-1 and 12E-1), produced in accordance with the present invention.
  • the printed image was prepared by jetting an ink, corresponding to Example 29, on a blanket having a release layer comprising a condensation cured silanol terminated polydimethylsiloxane.
  • the blanket was heated to about 70°C and was pre-treated with a conditioning solution comprising PEI subsequently removed and evaporated, as already described for the basic transferability test.
  • a black ink corresponding to Example 29 was jetted upon the treated release layer using a traditional ink jet head at a resolution of 600 x 1200 dpi (providing an average drop volume of 9pL) to form an ink image of varying ink coverage / dot density.
  • the relative speed of the blanket relative to the print bars was 0.5m/sec.
  • the ink image was dried at 200°C for up to 5 seconds and the dried image transferred to the substrates indicated in the table below and in Figures 12A-1 to 12E-3, by application of manual pressure.
  • Figures 12A-2 to 12E-2 provide further magnified views of a portion of the frames of Figures 12A-1 to 12E-1, in which the magnified views of the ink films disposed on commodity-coated paper are provided in Figures 12A-2 to 12C-2, and the magnified views of the ink films disposed on uncoated paper are provided in Figures 12D-2 and 12E-2.
  • That which is readily observed by the human eye may be quantified using the image- processing techniques and field-of-view processing procedures provided above.
  • fields of the ink dot construction according to the present invention exhibited a mean non-convexity of at most 0.05, at most 0.04, at most 0.03, at most 0.025, at most 0.020, at most 0.015, at most 0.012, at most 0.010, at most 0.009, or at most 0.008.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)
  • Ink Jet Recording Methods And Recording Media Thereof (AREA)

Abstract

L'invention porte sur des formulations aqueuses d'encre pour jet d'encre, comprenant un solvant comprenant de l'eau et un co-solvant, une résine polymère soluble dans l'eau ou dispersable dans l'eau, et une substance colorante. D'autres formes de réalisation sont aussi décrites.
PCT/IB2013/002571 2013-09-12 2013-09-12 Formulations d'encre et constructions de films les utilisant WO2015036812A1 (fr)

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WO2017208152A1 (fr) 2016-05-30 2017-12-07 Landa Corporation Ltd. Procédé et système d'impression numérique
DE112017002714T5 (de) 2016-05-30 2019-02-28 Landa Corporation Ltd. Digitales Druckverfahren
ES2707891A1 (es) * 2017-10-04 2019-04-05 Torrecid Sa Composicion de tinta en base agua
WO2020053709A1 (fr) 2018-09-13 2020-03-19 Landa Labs (2012) Ltd. Procédé et appareil d'impression sur des objets de forme cylindrique
WO2020202145A1 (fr) 2019-03-31 2020-10-08 Landa Corporation Ltd Systèmes et procédés pour empêcher ou minimiser les défauts d'impression dans les processus d'impression
US10907060B2 (en) 2017-10-18 2021-02-02 Hewlett-Packard Development Company, L.P. Printing on a textile
EP3409731B1 (fr) 2017-05-30 2021-08-11 Artech GmbH design + production in plastic Composition d'encres à base d'eau destinée à l'impression de surfaces plastiques

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WO2017208152A1 (fr) 2016-05-30 2017-12-07 Landa Corporation Ltd. Procédé et système d'impression numérique
DE112017002714T5 (de) 2016-05-30 2019-02-28 Landa Corporation Ltd. Digitales Druckverfahren
EP3875270A1 (fr) 2016-05-30 2021-09-08 Landa Corporation Ltd. Procédé d'impression numérique
EP3409731B1 (fr) 2017-05-30 2021-08-11 Artech GmbH design + production in plastic Composition d'encres à base d'eau destinée à l'impression de surfaces plastiques
ES2707891A1 (es) * 2017-10-04 2019-04-05 Torrecid Sa Composicion de tinta en base agua
WO2019068946A1 (fr) * 2017-10-04 2019-04-11 Torrecid, S.A. Composition d'encre à base d'eau
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US10907060B2 (en) 2017-10-18 2021-02-02 Hewlett-Packard Development Company, L.P. Printing on a textile
WO2020053709A1 (fr) 2018-09-13 2020-03-19 Landa Labs (2012) Ltd. Procédé et appareil d'impression sur des objets de forme cylindrique
US11541652B2 (en) 2018-09-13 2023-01-03 Landa Labs (2012) Ltd. Method and apparatus for printing on cylindrical objects
US11926144B2 (en) 2018-09-13 2024-03-12 Landa Labs (2012) Ltd. Method for printing on cylindrical objects
WO2020202145A1 (fr) 2019-03-31 2020-10-08 Landa Corporation Ltd Systèmes et procédés pour empêcher ou minimiser les défauts d'impression dans les processus d'impression

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