Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/28—Treatment by wave energy or particle radiation
• • 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
  • C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing
• • 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
  • C09D11/32—Inkjet printing inks characterised by colouring agents
  • C09D11/322—Pigment inks
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Definitions

• This invention concerns inks for use in ink-jet printers.
• this invention concerns inks for use in ink-jet printers that are cured using ultraviolet radiation.
• ink-jet printing minute droplets of black, white or coloured ink are ejected in a controlled manner from one or more reservoirs or printing heads through narrow nozzles on to a substrate which is moving relative to the reservoirs.
• the ejected ink forms an image on the substrate.
• the inks must flow rapidly from the printing heads, and, to ensure that this happens, they must have in use a low viscosity, typically below 100 mPas at 25 0 C although in most applications the viscosity should be below 50 mPas, and often below 25 mPas.
• the ink when ejected through the nozzles, the ink has a viscosity of less than 25 mPas, preferably 5- 15 mPas and ideally 10.5 mPas at the jetting temperature which is often elevated to about 4O 0 C (the ink might have a much higher viscosity at ambient temperature).
• the inks must also be resistant to drying or crusting in the reservoirs or nozzles.
• ink-jet inks for application at or near ambient temperatures are commonly formulated to contain a large proportion of a mobile liquid vehicle or solvent. In one common type of ink-jet ink this liquid is water - see for example the paper by Henry R. Kang in the Journal of Imaging Science, 35(3), pp.
• ink-jet inks that include a large proportion of water or solvent cannot be handled after printing until the inks have dried, either by evaporation of the solvent or its absorption into the substrate. This drying process is often slow and in many cases (for example, when printing on to a heat-sensitive substrate such as paper) cannot be accelerated.
• ink-jet ink contains unsaturated organic compounds, termed monomers, which polymerise by irradiation, commonly with ultraviolet light, in the presence of a photoinitiator.
• monomers unsaturated organic compounds
• This type of ink has the advantage that it is not necessary to evaporate the liquid phase to dry the print; instead the print is exposed to radiation to cure or harden it, a process which is more rapid than evaporation of solvent at moderate temperatures.
• monomers possessing a low viscosity.
• ink-jet inks largely based on monomers suffer from significant draw-backs compared to ink-jet inks containing solvent or more traditional inks such as screen or flexographic systems, where the higher viscosities allowed give greater formulation latitude.
• These types of ink can have significant amounts of the monomer content replaced with acrylate oligomers or inert thermoplastic resins whose higher molecular weight leads to a reduction in the number of bonds that must be formed during the curing process.
• the bond length between the repeat units reduces leading to shrinkage of the cured film and unless this is controlled stress is imparted to the substrate. With plastic substrates this film shrinkage can lead to severe embrittlement of the printed article and post print finishing, such as guillotining, becomes problematic.
• UV ink-jet inks are formulated with difunctional acrylate monomers in order to achieve adequate cure speeds. Inks produced from these types of materials suffer badly from film shrinkage and consequent substrate embrittlement. Theoretically it should be possible to reduce shrinkage by use of wholly monofunctional acrylate or vinyl monomer based systems, however this approach has generally been avoided due to very low cure speeds associated with monofunctional monomers.
• the present invention provides an ink-jet ink comprising at least one monofunctional (meth)acrylate monomer; at least one monofunctional N-vinyl amide monomer; at least one radical photoinitiator; and at least one colouring agent; wherein the ink has a viscosity of less than 100 mPas at 25 0 C, and wherein the molar ratio of the at least one monofunctional (meth)acrylate monomer to the at least one monofunctional N-vinyl amide monomer is from 1.0 to 6.0.
• Fig. 1 shows a graph of cure response against composition for three ink-jet inks of the present invention
• Fig. 2 shows a graph of cure response against composition for an ink-jet ink of the present invention containing IsTVP and IBOA.
• the ink-jet ink of the present invention dries primarily by curing, i.e. by the polymerisation of the monomers present, as discussed hereinabove, and hence is a curable ink.
• the ink does not, therefore, require the presence of water or a volatile organic solvent to effect drying of the ink, although the presence of such components may be tolerated.
• the ink-jet ink of the present invention is substantially free of water and volatile organic solvents.
• N- Vinyl amides are well-known monomers in the art and a detailed description is therefore not required.
• N- Vinyl amides have a vinyl group attached to the nitrogen atom of an amide which may be further substituted in an analogous manner to the (meth)acrylate monomers.
• NVC N-vinyl caprolactam
• NDP N-vinyl pyrrolidone
• the monofunctional (meth)acrylate monomers are also well known in the art and are preferably the esters of acrylic acid. Preferred examples include:
• IBOA Isobornyl acrylate
• THFA Tetrahydrofurfuryl acrylate
• ODA Octadecyl acrylate
• TDA Tridecyl acrylate
• the substituents of the monofunctional monomers are not limited other than by the constraints imposed by the use in an ink-jet ink, such as viscosity, stability, toxicity etc.
• the substituents are typically alkyl, cycloalkyl, aryl and combinations thereof, any of which may be interrupted by heteroatoms.
• Non-limiting examples of substituents commonly used in the art include C 1-18 alkyl, C 3-1 S cycloalkyl, C 6-10 aryl and combinations thereof, such as C 6-10 aryl- or C 3-18 cycloalkyl-substituted CM S alkyl, any of which may be interrupted by 1-10 heteroatoms, such as oxygen or nitrogen, with nitrogen further substituted by any of the above described substituents.
• the substituents may together also form a cyclic structure.
• the monofunctional (meth)acrylate is a cyclic monofunctional (meth)acrylate. That is, the radical covalently bonded to the (meth)acrylate unit is cyclic.
• the cyclic radical may be saturated or unsaturated, including aromatic.
• Preferred cyclic monofunctional (meth)acrylates are phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), isobornyl acrylate (IBOA), tetrahydrofurfuryl acrylate (THFA) or mixtures thereof.
• PDA phenoxyethyl acrylate
• CTFA cyclic TMP formal acrylate
• IBOA isobornyl acrylate
• THFA tetrahydrofurfuryl acrylate
• the monofunctional (meth)acrylates present are exclusively cyclic, i.e. they are the sole monofunctional (meth)acrylate(s) present.
• the total amount of the at least one monofunctional (meth)acrylate monomer and the at least one monofunctional N-vinyl amide monomer in combination is preferably at least 60 wt%, more preferably at least 70 wt% and most preferably at least 80 wt%, based on the total weight of the ink.
• the molar ratio of the at least one monofunctional (meth)acrylate monomer to the at least one monofunctional N-vinyl amide monomer is from 1.0 to 6.0.
• the upper limit to this ratio is preferably 4.0 or less, more preferably 3.5 or less, more preferably 2.0 or less and most preferably 1.6 or less.
• the lower limit to this ratio is preferably 1.1 or more, more preferably 1.2 or more, more preferably 1.3 or more and most preferably 1.5 or more.
• a particularly preferred range is 1.25 to 1.53.
• Monofunctional acrylates and monofunctional N-vinyl amide when combined, offer significant improvements in cure response over the non-combined monomers.
• AU of the combinations tested exhibited a minimum in the dose of UV light required for cure when cure response was plotted against monomer blend composition (further details are given in the examples hereinbelow). The depth of these minima are dependent on the individual cure speeds of the component monomers: the faster curing the acrylate monomers when taken alone, the deeper the minimum in UV dose required.
• Examples of the multifunctional acrylate monomers which may be included in the ink-jet ink formulation include hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethyleneglycol diacrylate, for example, tetraethyleneglycol diacrylate), dipropyleneglycol diacrylate, tri(propylene glycol) triacrylate, neopentylglycol diacrylate, bis(pentaerythritol) hexa-acrylate, and the acrylate esters of ethoxylated or propoxylated glycols and polyols, for example, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, and mixtures thereof.
• suitable multifunctional acrylate monomers include esters of methacrylic acid (i.e. methacrylates), such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate; 1,4-butanediol dimethacrylate.
• methacrylates esters of methacrylic acid
• methacrylates such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate; 1,4-butanediol dimethacrylate.
• the ink is substantially free of multifunctional monomer, meaning that only trace amounts will be present, for example as impurities in the monofunctional material or as a component in a commercially available pigment dispersion.
• the multifunctional monomer is present in an amount of no more than 30 wt%, preferably no more than 25 wt%, more preferably no more than 20 wt% and most preferably no more than 15 wt% based on the total weight of the ink.
• the multifunctional monomer which is limited in amount may be any multifunctional monomer which could be involved in the curing reaction, such as a multifunctional (meth)acrylate monomer or a multifunctional vinyl ether.
• the ink is substantially free of oligomeric and polymeric material meaning that only trace amounts will be present.
• oligomeric or polymeric material is included, the oligomeric and polymeric material is present in an amount of no more than 20 wt%, more preferably no more than 10 wt%, most preferably no more than 5 wt% based on the total weight of the ink.
• Oligomeric and polymeric materials e.g. acrylate oligomers and inert thermoplastic resins, respectively
• Oligomeric and polymeric materials are known in the art and typically have a molecular weight above 500, more preferably above 1000.
• the compositions include a photoinitiator, which, under irradiation by, for example, ultraviolet light, initiates the polymerisation of the monomers.
• a photoinitiator which, under irradiation by, for example, ultraviolet light, initiates the polymerisation of the monomers.
• photoinitiators which produce free radicals on irradiation (free radical photoinitiators) such as, for example, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-(4- morpholinophenyl)butan-l-one, benzil dimethylketal, bis(2,6-dimethylbenzoyl)-2,4,4- trimethylpentylphosphine oxide or mixtures thereof.
• photoinitiators are known and commercially available such as, for example, under the trade names Irgacure, Darocur (from Ciba) and Lucerin (from BASF).
• the photoinitiator is present from 1 to 20% by weight, preferably from 4 to 10% by weight, of the ink.
• the ink-jet ink of the present invention also includes a colouring agent, which maybe either dissolved or dispersed in the liquid medium of the ink.
• a colouring agent is a dispersible pigment, of the types known in the art and commercially available such as, for example, under the trade-names Paliotol (available from BASF pic), Cinquasia, Irgalite (both available from Ciba Speciality Chemicals) and Hostaperm (available from Clariant UK).
• the pigment may be of any desired colour such as, for example, Pigment Yellow 13, Pigment Yellow 83, Pigment Red 9, Pigment Red 184, Pigment Blue 15:3, Pigment Green 7, Pigment Violet 19, Pigment Black 7.
• black and the colours required for trichromatic process printing may be used.
• the total proportion of pigment present is preferably from 0.5 to 15% by weight, more preferably from 1 to 5% by weight.
• the ink of the present invention cures by a free radical mechanism
• the ink of the present invention may also be a so-called "hybrid" ink which cures by a radical and cationic mechanism.
• the ink-jet ink of the present invention in one embodiment, therefore further comprises at least one cationically curable monomer, such as a vinyl ether, and at least one cationic photoinitiator, such as an iodonium or sulfonium salt, e.g. diphenyliodonium fluoride and triphenylsulfonium hexafluophosphate.
• Suitable cationic photoinitiators include the Union Carbide UVl-69-series, Deuteron UV 1240 and IJY2257, Ciba Irgacure 250 and CGI 552, IGM-C440, Rhodia 2047 and UV9380C.
• components of types known in the art may be present in the ink to improve the properties or performance.
• these components may be, for example, surfactants, defoamers, dispersants, synergists for the photoinitiator, stabilisers against deterioration by heat or light, reodorants, flow or slip aids, biocides and identifying tracers.
• the present invention also provides a method of ink-jet printing using the above- described ink and a substrate having the cured ink thereon.
• Suitable substrates include styrene, PolyCarb (a polycarbonate), BannerPVC (a PVC) and VIVAK (a polyethylene terephthalate glycol modified).
• the ink of the present invention is preferably cured by ultraviolet irradiation and is suitable for application by ink-jet printing.
• the present invention further provides an ink-jet ink cartridge containing the ink-jet ink as defined herein.
• the cartridge comprises an ink container and an ink delivery port which is suitable for connection with an ink-jet printer.
• the ink-jet ink exhibits a desirable low viscosity (less than 100 mPas, preferably less than 50 mPas and most preferably less than 25 mPas at 25°C).
• (Meth)acrylate is intended herein to have its standard meaning, i.e. acrylate and/or methacrylate.
• Mono and multifunctional are also intended to have their standard meanings, i.e. one and two or more groups, respectively, which take part in the polymerisation reaction on curing.
• the inks of the invention may be prepared by known methods such as, for example, stirring with a high-speed water-cooled stirrer, or milling on a horizontal bead-mill.
• Ink-jet ink formulations were prepared by varying the monomer composition whilst holding all the other components constant, as set out in Table 1. Table 1. Cyan formulation used for all cure response testing.
• Table 4 Minimum UV dose for individual acrylates and corresponding NVC/acrylate blends.
• Fig. 1 also shows a graphical representation of UV dose minima against the amount of NVC present.
• the doses for cure are as set out in Reference Example 1.
• the dose required for cure decreases showing that the addition of NVC advantageously increases cure speed.
• the increase in cure speed provides an improved ink with the maximum improvement in the cure speed being identified by the minima in Fig. 1.
• the doses required for the cure of the di- and trifunctional acrylates DPGDA and TMPTA when taken alone are also shown in Fig. 1.
• a cyan ink-jet ink formulation of the present invention was prepared by combining the following components:

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Medicinal Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Polymers & Plastics (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)
• Ink Jet Recording Methods And Recording Media Thereof (AREA)
• Ink Jet (AREA)
• Pens And Brushes (AREA)
• Luminescent Compositions (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)

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• 2006
  • 2006-04-27 GB GBGB0608463.6A patent/GB0608463D0/en not_active Ceased
• 2007
  • 2007-04-19 WO PCT/GB2007/001416 patent/WO2007125273A1/en not_active Ceased
  • 2007-04-19 US US12/298,754 patent/US8133936B2/en active Active
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• 2009
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