WO2013150314A2 - Procédé d'impression - Google Patents

Procédé d'impression Download PDF

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Publication number
WO2013150314A2
WO2013150314A2 PCT/GB2013/050893 GB2013050893W WO2013150314A2 WO 2013150314 A2 WO2013150314 A2 WO 2013150314A2 GB 2013050893 W GB2013050893 W GB 2013050893W WO 2013150314 A2 WO2013150314 A2 WO 2013150314A2
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WO
WIPO (PCT)
Prior art keywords
ink
meth
multifunctional
oligomer
inkjet
Prior art date
Application number
PCT/GB2013/050893
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English (en)
Other versions
WO2013150314A3 (fr
Inventor
Nigel Gould
Jeremy Ward
Original Assignee
Sericol Limited
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.)
Filing date
Publication date
Application filed by Sericol Limited filed Critical Sericol Limited
Priority to GB1419344.5A priority Critical patent/GB2515708A/en
Publication of WO2013150314A2 publication Critical patent/WO2013150314A2/fr
Publication of WO2013150314A3 publication Critical patent/WO2013150314A3/fr

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Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M7/00—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock
    • B41M7/0081—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock using electromagnetic radiation or waves, e.g. ultraviolet radiation, electron beams
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
    • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
    • B41J11/002—Curing or drying the ink on the copy materials, e.g. by heating or irradiating
    • B41J11/0021—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
    • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
    • B41J11/002—Curing or drying the ink on the copy materials, e.g. by heating or irradiating
    • B41J11/0021—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation
    • B41J11/00214—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation using UV radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M7/00—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock
    • 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

Definitions

  • the present invention relates to a printing method and in particular to an inkjet printing method using a low-intensity radiation source.
  • Inkjet printers comprise one or more printheads that include a series of nozzles through which ink is ejected onto a substrate.
  • the printheads are typically provided on a printer carriage that traverses the print width (moves back and forth across the substrate) during the printing process.
  • solvent-based inkjet printers are an economic route into the industry as they are a relatively low cost option compared to the more complex machines employed for UV curing.
  • Solvent-based inkjet printing also has other advantages. As well as the lower cost, the ink films produced are thinner (and therefore flexible) and yield a good quality natural looking image with a gloss finish. Furthermore, it is difficult to achieve very high pigment loadings in UV curable inks owing to the high viscosity of the ink: if too much pigment is added, the ink becomes too viscous on account of particle-particle interactions between the fine pigment particles and cannot be jetted.
  • solvent-based inks include a high proportion of solvent and therefore have a lower viscosity, which means that higher pigment loadings can be tolerated.
  • the printed film produced from solvent-based inkjet inks is formed predominantly of pigment along with comparatively few other solids that are included in the ink. The pigment is therefore largely unobscured, resulting in intense, vivid and vibrant colours and a large colour gamut.
  • solvent-based inkjet technology there are some limitations to solvent-based inkjet technology.
  • solvent-based inks may not adhere to certain types of substrate, particularly non-porous substrates such as plastics, and the cured films have poor resistance to solvents.
  • UV curable ink systems have largely replaced solvent ink printers in the higher productivity range, wide format graphics market.
  • the ink deposited on the surface does not appreciably evaporate upon heating. Instead, the material is transformed into a solid through exposure to an energy source.
  • the energy source is an intense UV light, which causes photo-crosslinking of curable molecules in the presence of a photoinitiator to form a solid.
  • the energy source is typically any source of actinic radiation that is suitable for curing radiation curable inks but is preferably a UV source. Suitable UV sources include light emitting diodes (LEDs), flash lamps, fluorescent tubes, mercury discharge lamps, and combinations thereof.
  • LED sources that are currently available are relatively expensive and a printing apparatus comprising a LED source of UV radiation is unlikely to be suitable for use an entry level printer.
  • development of UV LED sources for curing inks is on-going and it is envisaged that the cost of LED sources will decrease significantly in the future.
  • Flash lamps operate by discharge breakdown of an inert gas, such as xenon or krypton, between two tungsten electrodes. Flash lamps have the advantage of switching on instantaneously, with no thermal stabilisation time.
  • the envelope material can also be doped, to prevent the transmission of wavelengths that would generate harmful ozone. Flash lamps are therefore economical to operate and therefore suitable for use in entry level printers.
  • UV fluorescent lamps find wide application.
  • High- and medium-pressure mercury discharge lamps can be relatively expensive to operate.
  • the lamp units themselves can be heavy and expensive and often additional shielding is required to prevent unintentional UV exposure to the operator. Extraction is also required to remove ozone that is produced by the lamps.
  • electronic ballast is required because the resistance of the gas used in the lamp changes during use. High- and medium-pressure mercury discharge lamps are not therefore preferred UV sources.
  • Low-pressure mercury discharge lamps would be highly desirable as they are inexpensive, do not generate ozone and do not heat the substrate.
  • the inkjet inks must contain (meth)acrylate monomers and/or oligomers having a high acrylate functionality in order to achieve sufficient reactivity to give well-cured coatings.
  • high functionality acrylates generally have a high viscosity and in order to achieve an ink jettable viscosity it is necessary to add organic solvents (or water) to reduce the viscosity.
  • organic solvents or water
  • the present invention provides method of inkjet printing comprising the following steps:
  • an inkjet ink comprising a multifunctional (meth)acrylate monomer and/or oligomer, an N-vinyl amide and/or N-(meth)acryloyl amide, a free radical photoinitiator and a tertiary amine which may be present as a separate component or covalently bonded to the multifunctional (meth)acrylate monomer and/or oligomer, wherein the ink contains less than 5 wt% of water and volatile organic solvents based on the total weight of the ink;
  • FIG. 1 shows a section view of a low-pressure mercury lamp provided with a reflective coating.
  • the ink-jet ink of the present invention dries by curing, i.e. by the polymerisation of the monomers and/or oligomers present, as discussed hereinabove, and hence is a radiation- 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 small amounts of such components may be tolerated, e.g. by absorption of atmospheric moisture or the presence of residual solvent in commercially available ink components.
  • the ink-jet ink of the present invention contains less than 5% by weight of water and volatile organic solvents, wherein the wt% represents the combination of water and volatile organic solvents and is based on the total weight of the ink.
  • the ink of the present invention may contain monofunctional (meth)acrylate monomers.
  • onofunctional (meth)acrylate monomers are well known in the art and are preferably the esters of acrylic acid.
  • Preferred examples include phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), isobornyl acrylate (IBOA), tetrahydrofurfuryl acrylate (THFA), 2-(2- ethoxyethoxy)ethyl acrylate, octadecyl acrylate (ODA), tridecyl acrylate (TDA), isodecyl acrylate (IDA) and lauryl acrylate.
  • PEA is particularly preferred.
  • the total amount of the monofunctional (meth)acrylate monomer is from 10 to 50 wt% based on the total weight of the ink
  • the ink of the present invention also comprises a multifunctional (meth)acrylate monomer and/or oligomer.
  • a multifunctional (meth)acrylate monomer and/or oligomer are well known in the art and have a functionality of two or higher.
  • Multifunctional (meth)acrylate monomers typically have a viscosity of less than 2 Pas at 25°C and a molecular weight of less than 450. Functionalities of two, three or four are preferred and preferably this monomer is a difunctional monomer.
  • Examples of the multifunctional acrylate monomers that may be included in the ink-jet inks include hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethyleneglycol diacrylate (for example tetraethyleneglycol diacrylate), dipropyleneglycol diacrylate, tri(propylene glycol) diiacrylate, neopentylglycol diacrylate, bis(pentaerythritol) hexaacrylate, and the acrylate esters of ethoxylated or propoxylated glycols and polyols, for example, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, and mixtures thereof.
  • polyethyleneglycol diacrylate for example tetraethyleneglycol diacrylate
  • dipropyleneglycol diacrylate tri(propylene glycol)
  • Suitable multifunctional methacrylate monomers also include esters of methacrylic acid (i.e. methacrylates), such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate, 1 ,4-butanediol dimethacrylate. Mixtures of (meth)acrylates may also be used.
  • methacrylates esters of methacrylic acid
  • methacrylates such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate, 1 ,4-butanediol dimethacrylate.
  • the total amount of the multifunctional (meth)acrylate monomer is from 10 to 70 wt% based on the total weight of the ink
  • the ink also contains a polymerisable (i.e. curable) (meth)acrylate oligomer.
  • polymerisable oligomer has its standard meaning in the art, namely that the component is partially reacted to form a pre-polymer having a plurality of repeating monomer units which is capable of further polymerisation.
  • the oligomer is a curable, e.g. UV-curable, (meth)acrylate.
  • the oligomer preferably has a molecular weight of at least 450.
  • the molecular weight is preferably 4,000 or less, more preferably from 2,000 or less and most preferably 1500 or less.
  • the degree of functionality of the oligomer determines the degree of crosslinking and hence the properties of the cured ink.
  • the oligomer is multifunctional meaning that it contains on average more than one reactive functional group per molecule.
  • the average degree of functionality is preferably from 2 to 6, more preferably 2 to 4 and most preferably 3.
  • UV-curable oligomers of this type are well known in the art.
  • the oligomer is preferably based on bisphenol A, a polyester, a polyether or a urethane.
  • the total amount of the polymerisable (meth)acrylate oligomer is preferably from 3 to 30 wt%, based on the total weight of the ink.
  • (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.
  • Monomers may be distinguished from the oligomers on account of the lack of repeat units.
  • the monomers typically have a molecular weight of less than 450 and more often less than 300.
  • the ink of the present invention also contains tertiary amine. It has surprisingly been found that the presence of a tertiary amine allows the ink to be cured using a low intensity radiation source.
  • the amine may be covalently bound to the (meth)acrylate monomer or oligomer (termed herein an "amine-modified (meth)acrylate monomer or oligomer"), or it may be present as a separate component (i.e. one which is not covalently bound to the (meth)acrylate monomer or oligomer).
  • Suitable amine-modified (meth)acrylate monomers or oligomers may be prepared by a pseudo-Michael addition reaction between a multifunctional (meth)acrylate monomer or oligomer (i.e. those with two or more (meth)acrylate groups) and a primary or secondary amine.
  • a reaction may be represented as follows:
  • R 1 represents the remainder of the multifunctional (meth)acrylate monomer or oligomer (which may be a C 1-8 -alkyl, C 1-8 -alkanol, C 3 . 8 -cycloalkyl Cs-e-cycloalkyl-C s-alkyl, phenyl, polyester oligomer or polyether oligomer, substituted with a further 1 -6 (meth)acrylate groups), and
  • R 2 and R 3 may be the same or different and represent C ⁇ -alkyl, C,. 8 -alkanol, C 3 . 8 -cycloalkyl C 3 8 -cycloalkyl-C 1 8 -alkyl or phenyl (the alkyl groups may be straight chain or branched).
  • All of the multifunctional (meth)acrylate monomers and/or oligomers may be amine modified, or the ink may contain a mixture of multifunctional (meth)acrylate monomers and/or oligomers and amine-modified multifunctional (meth)acrylate monomers and/or oligomers.
  • a tertiary amine may be added as a separate component to the multifunctional (meth)acrylate monomer or oligomer.
  • the nature of the tertiary amine is not limited.
  • An example is a benzoate containing an -N(Ci -6 -alkyl) 2 group.
  • the amino group may be directly attached to the benzene ring, preferably at the 4-positon, and the alcohol moiety of the benzoate is based on a C 1-8 -alcohol, wherein the alkyl chain of the alcohol is optionally interrupted by 1-3 oxygen atoms.
  • the amino group may alternatively be attached to the afore-defined alcohol moiety.
  • N(Ci -g -alkyl) 3 Another example is N(Ci -g -alkyl) 3 , wherein one or more of the alkyl groups is optionally substituted with hydroxy groups. Preferably one or two of the alkyl groups is a methyl group.
  • An example is methyl diethanol amine. Where the amine is added as a separate component, it is preferably present in an amount from 1 to 15 wt%, based on the total weight of the ink.
  • N-vinyl amides and N-(meth)acryloyl amides may also be used in the inks of the invention.
  • N- vinyl amides are well-known monomers in the art.
  • 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.
  • Preferred examples are N-vinyl caprolactam (NVC) and N- vinyl pyrrolidone (NVP):
  • N-acryloyl amides are also well-known in the art. N-acryloyl amides also have a vinyl group attached to an amide but via the carbonyl carbon atom and again may be further substituted in an analogous manner to the (meth)acrylate monomers. Regarding the nomenclature, since this compound incorporates a carbonyl group adjacent to the nitrogen atom, it is referred to as an amide rather than an amine. A preferred example is N- acryloylmorpholine (ACMO):
  • the monomer selected from an N-vinyl amide, an N-acryloyl amide or a mixture thereof is preferably selected from N-vinyl caprolactam (NVC), N-vinyl pyrrolidone (NVP), N- acryloylmorpholine (ACMO) and mixtures thereof.
  • NVC N-vinyl caprolactam
  • NNP N-vinyl pyrrolidone
  • ACMO N- acryloylmorpholine
  • the monomer selected from an N-vinyl amide, an N-acryloyl amide or a mixture thereof is preferably present in the ink at a total amount of from 10 to 40 wt% based on the total weight of the ink.
  • the ink used in the present invention preferably contains a combination of a monofunctional (meth)acrylate monomer, a multifunctional (meth)acrylate monomer, an N-vinyl amide and an amine-modified multifunctional (meth)acrylate oligomer.
  • a particularly preferred ink contains PEA as the monofunctional (meth)acrylate monomer and NVC as the N-vinyl amide.
  • compositions include a photoinitiator which, under irradiation, for example by ultraviolet light, initiates the polymerisation of the monomers.
  • the photoinitiators produce free radicals on irradiation (free radical photoinitiators).
  • Examples include benzophenone, 1 -hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-(4-morpholinophenyl)butan-1 -one, benzil dimethylketal, bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzoyl- diphenyl phosphine oxide, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, isopropyl thioxanthone or mixtures thereof.
  • photoinitiators are known and commercially available such as, for example, under the trade names Irgacure, Darocur (from Ciba) and Lucirin (from BASF).
  • the photoinitiator is present from 1 to 20% by weight, more preferably from 5 to 15% by weight, based on the total weight of the ink.
  • the wavelength of the radiation and the nature of the photoinitiator system used must of course coincide.
  • the ink is cured by irradiation with actinic radiation, such as UV, x-ray, electron beam etc, although UV curing is preferred.
  • the ink of the present invention can be a coloured ink or a colourless ink.
  • colourless is meant that the ink is substantially free of colourant such that no colour can be detected by the naked eye. Minor amounts of colourant that do not produce colour that can be detected by the eye can be tolerated, however.
  • the amount of colourant present will be less than 0.3 % by weight based on the total weight of the ink, preferably less than 0.1 %, more preferably less than 0.03 %.
  • Colourless inks may also be described as “clear” or "water white”.
  • the ink-jet ink of the present invention may include a colouring agent, which may be either dissolved or dispersed in the liquid medium of the ink.
  • the colouring agent is a dispersed pigment, of the types known in the art and commercially available such as 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.
  • Especially useful are black and the colours required for trichromatic process printing. Mixtures of pigments may be used.
  • Cyan phthalocyanine pigments such as Phthalocyanine blue 15.4.
  • Yellow azo pigments such as Pigment yellow 120, Pigment yellow 151 and Pigment yellow 155.
  • Magenta quinacridone pigments, such as Pigment violet 19 or mixed crystal quinacridones such as Cromophtal Jet magenta 2BC and Cinquasia RT-355D.
  • Black carbon black pigments such as Pigment black 7.
  • Pigment particles dispersed in the ink should be sufficiently small to allow the ink to pass through an inkjet nozzle, typically having a particle size less than 8 pm, preferably less than 5 ⁇ , more preferably less than 1 ⁇ and particularly preferably less than 0.5 pm.
  • the colorant is preferably present in an amount of 20 weight % or less, preferably 10 weight % or less, more preferably 8 weight % or less and most preferably 2 to 5 % by weight, based on the total weight of the ink.
  • a higher concentration of pigment may be required for white inks, however, for example up to and including 30 weight %, or 25 weight % based on the total weight of the ink.
  • 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 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 UVI-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.
  • Suitable substrates include polyolefin substrates, such as polyethylene and polypropylene, e.g. PE85 Trans T/C, PE85 White or PP Top White, polyethylene terephthalate (PET) and paper.
  • Polyolefin substrates represent the most difficult of these substrates on which to gain adhesion.
  • the ink-jet ink exhibits a desirable low viscosity, i.e. 50 mPas or less, preferably 30 mPas or less and most preferably 28 mPas or less at 25°C. Viscosity may be determined using a Brookfield DV-I + running at 20 rpm.
  • the inks used in the present 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.
  • the ink of the present invention is cured using a low intensity radiation source. That radiation source which emits all of its peak intensities within a wavelength of 230-460 nm, more preferably 250-445 nm. Moreover, within those ranges, the radiation source emits a total power output of 10-100 mW/cm 2 preferably 15-50 mW/cm 2 , more preferably 20-40 mW/cm 2 , most preferably 25-35 mW/cm 2 .
  • the peak intensities are preferably found at 250-260, 280-320, 320-390 and 395-445 nm.
  • the power output at these ranges is preferably 10-20 mW/cm 2 at 250-260 nm, 3-5 mW/cm 2 at 280-320 nm, 3.2-5.2 mW/cm 2 at 320-390 nm and 5-15 mW/cm 2 at 395-445 nm.
  • the radiation source is preferably a low-pressure mercury lamp.
  • Low-pressure mercury lamps are much more efficient than medium-pressure mercury lamps. Approximately 35% of the energy input is converted to UV radiation, 85% of which has a wavelength of 254 nm (UVC). These lamps therefore generate less heat in use than medium- pressure mercury lamps, which means that they are more economical to run and less likely to damage sensitive substrates. Furthermore, low-pressure mercury lamps can be manufactured in such a way as not to generate ozone in use and are therefore safer to use than medium-pressure mercury lamps. Typical medium-pressure mercury lamps have an output in the range of 80 to 240 W/cm, which is significantly higher than the maximum output for low-pressure mercury lamps.
  • the Wood lamp is a low-pressure mercury arc with an added fluorescent layer that emits in the UV-A spectral region (315-400 nm)."
  • Low-pressure mercury lamps are used extensively in the water purification industry and are therefore widely available.
  • low-pressure mercury lamps predominantly emit UV radiation with a peak wavelength of around 254 nm but the wavelength of the radiation can be varied by coating the internal surface of the lamp with a phosphor. In a preferred embodiment of the lamp, there is no such phosphor coating.
  • the lamp preferably emits radiation with a peak wavelength of around 254 nm, or put another way, the natural or unaltered wavelength of radiation emitted by mercury vapour in a low pressure lamp environment.
  • the use of a phosphor coating can lead to a reduction in lamp luminous efficiency.
  • the preferred phosphor-free lamps used according to the invention have an efficiency exceeding 45% for UVC generation, however. This high efficiency helps to minimise the cure unit running costs.
  • the UV output varies with temperature.
  • the vapour pressure of the mercury reaches an optimum level and the output of UVC radiation reaches a maximum.
  • the temperature of the lamp increases further the vapour pressure continues to rise, reducing the UVC output.
  • Low-pressure mercury lamps are therefore operated at an optimum temperature at which maximum UVC output can be achieved and this temperature is typically around 25-40°C for standard low pressure lamps. This limit on the operating temperature limits the energy input, however, because the lamp temperature can be raised above the optimum temperature if the energy input is too high. Limiting the energy input limits the maximum UV output achievable.
  • Standard low-pressure mercury lamps have linear power densities of less than 380 mW/cm in their normal configuration.
  • U-shaped lamps can have effective total power densities of up to twice this, for example 650 mW/cm.
  • the low-pressure mercury lamp is an amalgam lamp.
  • amalgam lamps an amalgam of mercury, typically with bismuth and/or indium, is used instead of liquid mercury.
  • Other suitable materials that are compatible with, or are capable of forming an amalgam with mercury could be used instead of bismuth or indium, however.
  • Amalgam lamps have the same spectral output as conventional low-pressure mercury lamps. In operation, the amalgam gradually releases mercury vapour as the temperature increases, but vapour is reabsorbed if the pressure becomes too high. This self- regulation means that the optimum mercury vapour pressure is achieved at a higher temperature, approximately 80-160°C, for example 83°C, depending on the type of lamp and manufacturer. Amalgam lamps therefore operate at a higher optimum temperature than standard low-pressure mercury lamps, which means that higher energy inputs can be tolerated. A higher energy input leads to an accompanying increase in UVC output, which remains stable during extended operation of the lamp.
  • amalgam lamps can run at temperatures up to 140°C with linear power densities exceeding 380 mW/cm and such lamps can achieve outputs that equate to approximately five times the output of a conventional low-pressure mercury lamp.
  • the combination of the increased radiation and heat generated by the amalgam lamp offers a useful advantage in drying and curing the inks used in the present invention when compared to regular low- pressure mercury lamps.
  • Standard low-pressure mercury lamps have current densities not exceeding 0.45 Amps/cm whereas amalgam lamps have current densities above this level.
  • the temperature of the amalgam lamp may be controlled in order to allow the optimal UV light output to be maintained. Temperature control can be achieved by immersing the lamp in water within a quartz sleeve. As well as providing electrical insulation against the water, the air gap around the lamp prevents overcooling by the water. By controlling the water flow past the lamps, the optimal lamp temperature can be maintained for maximum UV output. While convenient, this method is not preferred as it incurs the additional cost of a chiller. In a preferred embodiment air is blown across the low-pressure mercury lamp(s) to control the lamp temperature.
  • the low-pressure mercury lamp is preferably used together with auxiliary ballast electronics in order to regulate the current through the lamp.
  • auxiliary ballast electronics are available.
  • Preferred for use in this invention are electronic ballasts that convert input mains frequency to frequencies greater than the relaxation time of the ionised plasma in the lamp, thereby maintaining optimal light output.
  • an electronic ballast operating in rapid or instant start mode wherein electrodes of the low-pressure mercury lamp may be pre-warmed before ignition in order to reduce electrode damage caused by frequent switching.
  • pre-heating is preferred because the preferred amalgam lamp of the present invention is high power, operates at high temperature and in use is likely to be frequently switched.
  • Low-pressure mercury lamps emit light in all directions.
  • the lamp is therefore preferably used in conjunction with at least one reflector to ensure that the majority of emitted UV light is efficiently directed to the printed surface.
  • the reflector is preferably made of a material that efficiently reflects the UV light with minimal loss, for example aluminium, which has a reflective efficiency of greater than 80%.
  • pre-anodised aluminium is preferred, such as 320G available from Alanod. This material is easily formed into curved or faceted shapes by rolling or bending to provide efficient reflectors.
  • the reflector preferably has en elliptical shape such that the radiation directed at the printed substrate is focussed to a narrow line, thereby increasing the peak irradiance at the printed substrate.
  • "Elliptical reflector” is a term known in the art.
  • the finite diameter of the low-pressure mercury lamp prevents all of the emitted light from originating at the focus of the ellipse.
  • low-pressure mercury lamps with diameter below 30 mm, preferably below 20 mm and more preferably below 10 mm are therefore used in combination with an elliptical reflector, in order to increase the peak irradiance at the substrate even further.
  • the bulb of the low-pressure mercury lamp is partially coated with a reflective coating such that the radiation produced by the bulb is directed towards the print surface.
  • Fig. 1 is a section view of a low-pressure mercury lamp that is provided with a reflective coating.
  • the lamp (1) comprises a bulb (3) that produces the UV radiation.
  • the bulb is mounted within a reflector (5).
  • the bulb surface that is orientated away from the print surface (7) is coated with a reflective coating (9), which directs radiation (10) emitted from the bulb towards the print surface (7) and therefore improves lamp efficiency. Furthermore, the presence of the reflective coating allows gaps (1 1) in the reflector (5) to be provided, allowing cooling of the lamp.
  • the reflective material can be any material that reflects UVC radiation, and the coating can be can be applied by painting or vacuum deposition, for example.
  • the total UV dose received by the ink printed on the substrate is inversely proportional to the speed that the substrate moves past the lamp.
  • the low-pressure mercury lamps used according to the preferred embodiment of the present invention have a relatively low power output when compared to medium pressure mercury lamps, the use of a static lamp allows the printed ink to be exposed to the radiation from the lamp for longer periods than are achieved with traditional scanning type large format printers. Hence, the total dose provided by the low pressure lamps can exceed that provided by scanning type cure units using higher output lamps.
  • the envelope of a low-pressure mercury lamp is typically made from fused quartz, which allows production of lamps with lengths exceeding one meter. To ensure even curing across the full print width using a static in-line cure unit, it is preferable to provide a lamp with an arc length exceeding the print width by several centimetres to counter the emission variance near the electrodes.
  • the final lamp length could approach 3 m in some cases. This length of lamp is achievable for envelopes with a wide diameter. However, narrower lamps would be more fragile and require additional support along their length, which could interfere with the irradiance profile. In this case, it may be preferable to use several smaller lamps in a castellated or staggered arrangement to achieve full width curing.
  • the present invention provides an inkjet printer comprising a radiation source which emits all of its peak intensities within a wavelength of 230-460 nm and with a total power output of 10-100 mW/cm 2 within the wavelength of 230-460 nm, as the sole means for drying and curing the ink to a solid film.
  • a radiation source which emits all of its peak intensities within a wavelength of 230-460 nm and with a total power output of 10-100 mW/cm 2 within the wavelength of 230-460 nm, as the sole means for drying and curing the ink to a solid film.
  • Other preferred features of this radiation source are as described hereinabove.
  • Inks were prepared by mixing the components in the given amounts. Amounts are given as weight percentages based on the total weight of the ink. Table 1. Acrylate functionality (f) vs reactivity for acrylate esters and amine-modified acrylate esters.
  • the output of the lamp is shown in Table 2.
  • the inks were formulated to achieve a viscosity of about 25 mPas at 25°C which is a typical viscosity for an inkjet ink used in heated print heads.
  • Example 2
  • Inks were prepared by mixing the components in the given amounts. Amounts are given as weight percentages based on the total weight of the ink.
  • Inks 1 -4 are inks of the invention and contain an amine-modified acrylate.
  • Inks 5-9 are comparative inks which do not contain an amine-modified acrylate.
  • the inks were formulated to achieve a viscosity of about 25 mPas at 25°C. Full cure is defined as being tack free to touch (surface cure) and resistant to 100 IPA double rubs (through cure). It is apparent that:
  • the amine may be either chemically attached to the acrylate (inks 1 ,2,3) or separate (chemically not attached) (ink 4).
  • An amine provides both a jettable viscosity (approximately 25 mPas (cP) at 25°C) and a full cure (inks 1 -4). Without the use of the amine, cure can be achieved but at a viscosity that is not practically ink-jettable (ink 9).
  • Inks were prepared as set out in Table 3. The inks were subjected to actinic radiation from a low-pressure amalgam lamp, 0.25 m/min and a medium-pressure Hg lamp, 1 x 80 W/cm lamp, belt speed 55 m/min.
  • the low-pressure lamp was used at the maximum printing speed of the printer and hence lowest dose achievable.
  • the medium-pressure lamp was used at the lowest intensity and dose achievable for this lamp corresponding to the lowest power setting and highest belt speed. The results are set out below.
  • the two lamps have very different outputs, both in terms of wavelength distribution and power.

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  • Chemical & Material Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Health & Medical Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Electromagnetism (AREA)
  • Physics & Mathematics (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)
  • Ink Jet Recording Methods And Recording Media Thereof (AREA)

Abstract

La présente invention a trait à un procédé d'impression à jet d'encre comportant les étapes suivantes : (i) fourniture d'une encre pour imprimante à jet d'encre comprenant un monomère et/ou oligomère (méth)acrylate multifonctionnel, un N-vinyl amide et/ou un N-(méth)acryloyl amide, un photoinitiateur radicalaire et une amine tertiaire qui peut être présente en tant que constituant séparé ou lié de manière covalente au monomère et/ou à l'oligomère (méth)acrylate multifonctionnel, l'encre contenant moins de 5 % en poids d'eau et de solvants organiques volatils en fonction du poids total de l'encre ; (ii) impression de l'encre sur un substrat au moyen d'une imprimante à jet d'encre ; et (iii) durcissement de l'encre avec une source de rayonnement qui émet toutes ses intensités de crête dans une longueur d'onde située dans la plage allant de 230 à 460 nm et avec une puissance de sortie totale située dans la plage allant de 10 à 100 mW/cm2 dans la longueur d'onde située dans la plage allant de 230 à 460 nm.
PCT/GB2013/050893 2012-04-05 2013-04-05 Procédé d'impression WO2013150314A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1419344.5A GB2515708A (en) 2012-04-05 2013-04-05 Printing Method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1206095.0 2012-04-05
GBGB1206095.0A GB201206095D0 (en) 2012-04-05 2012-04-05 Printing method

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WO2013150314A2 true WO2013150314A2 (fr) 2013-10-10
WO2013150314A3 WO2013150314A3 (fr) 2013-12-05

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GB (2) GB201206095D0 (fr)
WO (1) WO2013150314A2 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1674537A2 (fr) * 2004-12-21 2006-06-28 Seiko Epson Corporation Composition d'encre
US20060158493A1 (en) * 2004-09-30 2006-07-20 Seiko Epson Corporation Ink composition and image process using the same
US20080024577A1 (en) * 2006-02-28 2008-01-31 Seiko Epson Corporation Photo-curing ink composition, ink jet recording method, and ink jet recording apparatus
US20080213518A1 (en) * 2007-03-01 2008-09-04 Seiko Epson Corporation Ink set, ink-jet recording method, and recorded material

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060158493A1 (en) * 2004-09-30 2006-07-20 Seiko Epson Corporation Ink composition and image process using the same
EP1674537A2 (fr) * 2004-12-21 2006-06-28 Seiko Epson Corporation Composition d'encre
US20080024577A1 (en) * 2006-02-28 2008-01-31 Seiko Epson Corporation Photo-curing ink composition, ink jet recording method, and ink jet recording apparatus
US20080213518A1 (en) * 2007-03-01 2008-09-04 Seiko Epson Corporation Ink set, ink-jet recording method, and recorded material

Also Published As

Publication number Publication date
WO2013150314A3 (fr) 2013-12-05
GB2515708A (en) 2014-12-31
GB201419344D0 (en) 2014-12-17
GB201206095D0 (en) 2012-05-16

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