WO1996017894A1 - Composition d'encre pour imprimante a jet d'encre - Google Patents

Composition d'encre pour imprimante a jet d'encre Download PDF

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Publication number
WO1996017894A1
WO1996017894A1 PCT/GB1995/002907 GB9502907W WO9617894A1 WO 1996017894 A1 WO1996017894 A1 WO 1996017894A1 GB 9502907 W GB9502907 W GB 9502907W WO 9617894 A1 WO9617894 A1 WO 9617894A1
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WO
WIPO (PCT)
Prior art keywords
composition
diluent
disperse phase
ink
pigment
Prior art date
Application number
PCT/GB1995/002907
Other languages
English (en)
Inventor
John Philip Tatum
Leslie George Howarth
Clare Conboy
Original Assignee
Xaar 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 Xaar Limited filed Critical Xaar Limited
Publication of WO1996017894A1 publication Critical patent/WO1996017894A1/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
    • C09D11/30—Inkjet printing inks
    • C09D11/36—Inkjet printing inks based on non-aqueous solvents

Definitions

  • This invention relates to pigment ink compositions and more particularly to ink compositions for printing on plain paper using an ink jet printer, and a method of ink jet
  • the invention is especially concerned with compositions suitable for use as inks in so-called “drop-on-demand” ink jet printers; however it is anticipated that the inks may also be suitable for use in other applications.
  • a fluid ink is forced under pressure, and sometimes at elevated temperature, through a very small nozzle in a printing head.
  • Drop-on-demand printer In another kind of printer, known as a "drop-on-demand” (DOD) printer, the ink droplets are expelled from the nozzle of a print head only when required during the printing process.
  • DOD printers can use an electrostatically accelerated ink jet or
  • each drop of ink is individually ejected from a nozzle by means of pressure pulses induced e.g. by use of a piezo-electric actuator acting on the ink in the channel supplying the nozzle or by generation of a vapour bubble in response to a thermal pulse.
  • the ink For use in a DOD ink jet printer, it is important that the ink be stable on standing or storage. In particular, on standing it should not become concentrated through loss of diluent. Nor should it form aggregates in the nozzle or at the orifice of the nozzle, because this could lead to clogging of the nozzle itself or of the channel supplying the nozzle. It should also not form deposits around the periphery of the nozzle orifice during
  • ink jet printer inks should be capable of producing print on plain, ie. uncoated, paper substrates which are at ambient temperatures. Moreover, the resultant print is expected to be well-defined and of good colour density despite the fibrous nature of the substrate.
  • Good print definition quality requires inter alia (a) rapid formation of a solid coloured dot from the ejected droplet of ink composition, (b) concentration of the ink colorants on the
  • the print should not deteriorate as a result of the action of water or light.
  • the colorant is generally associated with a liquid diluent sometimes
  • a solvent referred to as a solvent and it has been assumed that to achieve the desired rapid formation of the solid dot requires either rapid solidification of the diluent, e.g. by cooling, or rapid removal of the diluent from the colour dot on the paper, e.g. by evaporation or rapid sorption of the diluent into the paper. At the same time, however, it is desirable to control the sideways spread of the droplet after it has landed on the paper. It will be understood that these requirements are to some extent conflicting because
  • the ink is a dispersion of finely divided colorant in a liquid diluent.
  • the formulation of such inks presents inherently conflicting requirements.
  • the diluent it is desirable for the diluent to have a low volatility so as to minimise the risk of evaporation in the printhead nozzle, the rate at which the print dries can be enhanced by increasing the volatility of the diluent.
  • the particles of colorant are too small, their tendency to pass through the interstices between the fibres forming the surface of the paper will increase, thereby reducing one or both of colour density and print definition.
  • a further problem is that of the viscosity of the ink because while a low viscosity is required to assist ink flow in the passages in the print head and ejection of the droplets from the print head, lowering the viscosity will generally increase the rate at which the droplet will spread over the paper surface and into the pores of the paper, thus adversely affecting both the colour density and definition of the print dot.
  • an ink jet printer ink composition which at ambient temperatures is in the form of a dispersion having a disperse phase of finely divided solids in a liquid diluent and wherein the colorant is in the disperse phase and the maximum volume packing fraction of the disperse phase is not greater than 0.25 at 30°C.
  • ambient temperatures means temperatures in the range 15 to 30° C.
  • the colorant in the disperse phase is hereinafter referred to as pigment.
  • the pigment may form the disperse phase.
  • the disperse phase may also include other components, in particular extenders, that are insoluble in the diluent at
  • the pigment should form more than 7% by weight, based on the weight of the ink. In general, however, it should not form more than 25% by weight.
  • the inks according to the invention exhibit a high rate of increase of viscosity with increase in concentration of the disperse phase, e.g. as the diluent volatilises or separates from the droplet after the droplet has been deposited on the substrate on which the print is to be formed (by, for example, absorption into the substrate), thereby leading to more rapid solidification of the dot formed from the droplet,
  • MVPF volume fraction
  • ⁇ m volume fraction of the disperse phase where the viscosity tends to infinity; i.e. solid-like rather than liquid-like behaviour is observed due to the close packing and interaction of the solid particles forming the disperse phase. This can be determined by measuring the theological properties, including viscosity, of formulations having a range of concentrations of the disperse phase. A useful theoretical model which may be used to model the change in
  • ⁇ 0 is the viscosity of the diluent
  • ⁇ is the solid colloidal particle volume fraction
  • ⁇ m is the maximum volume packing fraction
  • [ ⁇ ] is a dimensionless parameter referred to as the intrinsic viscosity.
  • the intrinsic viscosity [ ⁇ ] and the MVPF can be determined by preparing a range of dispersions having different diluent contents. These dispersions should ideally range from pure diluent through to solid-like systems. This will eliminate the need to perform extrapolations with the data.
  • the rheological properties of each dispersion sample can be measured with a rheometer such as a "Bohlin CS" [Bohlin Instruments Division, Metric Group Ltd., Love Lane, Cirencester. Gloucestershire GL7 1YG. UK] with a "CP 4/40" cone and plate measuring system at a temperature of 30° C. It is convenient to measure the viscosity of the dispersion samples under conditions of constant stress. For
  • the MVPF value of the solids content of the ink is reduced, the print quality is improved at a given concentration of the pigment, all other things being equal.
  • the MVPF is not greater than 0.20 and more preferably not
  • the MVPF of the disperse phase is not less than about 0.05 to 0.06, preferably not less than 0.10, more preferably
  • the maximum concentration should not exceed 25% by weight. It has also been found that the viscosity of an ink containing a given concentration of pigment tends to increase with decrease in the value of MVPF of the disperse phase. Thus, on the whole, the maximum acceptable concentration of pigment in the ink tends to decrease
  • the concentration is preferably no greater than 25% by weight at an MVPF of 0.25 and the preferred maximum is about 11% at an
  • the optimum concentration of pigment in the ink will depend inter alia on its MVPF and
  • the concentration need not be more than 7%. Nevertheless amounts less than 7%, e.g. down to 5%, or even as low as 2 or 3% for coated papers, may be acceptable, especially where the disperse phase includes other insoluble solids in addition to the pigment. However, it should not exceed 25%, preferably 20%, by weight of the ink. In many cases the concentration need not be more than 7%. Nevertheless amounts less than 7%, e.g. down to 5%, or even as low as 2 or 3% for coated papers, may be acceptable, especially where the disperse phase includes other insoluble solids in addition to the pigment. However, it should not exceed 25%, preferably 20%, by weight of the ink. In many cases the concentration need not be more than 7%. Nevertheless amounts less than 7%, e.g. down to 5%, or even as low as 2 or 3% for coated papers, may be acceptable, especially where the disperse phase includes other insoluble solids in addition to the pigment. However, it should not exceed 25%, preferably 20%, by weight of the ink
  • intrinsic viscosity may also have some bearing on the performance of the ink in an ink jet printer. It seems that the intrinsic viscosity should desirably be at least 17
  • the ink may become difficult to use.
  • the pigment is selected to be insoluble in the chosen diluent at ambient temperatures and also at the chosen o ⁇ erating temperature if that is above ambient temperature. Where it is the only component of the disperse phase it should have an MVPF of not greater than
  • the disperse phase contains other components, in addition tc the pigment, then it is the MVPF of the entire disperse phase including these additional components which is relevant.
  • additional components include extenders, e.g. clays, organo-clays and silicas.
  • pigments are found amongst those characterised as “pigment dyes” in the Colour Index. Mixtures of pigments may be used, if desired.
  • the pigment will be black or of a primary subtractive hue. It should also be
  • the pigment should be water insoluble to prevent smearing of the print upon contact with water-containing substances.
  • Carbon blacks having maximum volume packing fractions not greater than 0.25 and which are suitable for use in the invention are generally found amongst furnace blacks and other blacks formed by thermal-oxidative processes. Examples of suitable blacks are
  • diluent refers to all components of the ink composition which, individually, are normally liquid at ambient temperatures.
  • the diluent may be a single component or a mixture of such components.
  • the diluent is preferably organic, it is believed that the invention is also applicable to aqueous inks.
  • the diluent should be selected to form a low viscosity dispersion with the selected pigment, and other non- diluent components where employed. It is therefore desirable for the diluent itself to have a low viscosity.
  • the diluent viscosity at the operating temperature of the printer should not be more than 10 mPas, preferably not more than 6 mPas.
  • the viscosity of the ink is less than 60 mPas and for ease of use in DOD printers, it is preferred that the viscosity of the ink be not more than 20 mPas, more preferably not more than 15 mPas.
  • the viscosities referred to here are those measured at 30°C using a Bohlin CS rheometer with a CP 4/40 cone and plate geometry at a shear stress of at least
  • the diluent prefferably has a low volatility.
  • the boiling point of the diluent be at least 100°C, more preferably more than 180°C, at atmospheric pressure.
  • the reference to boiling point is to the temperature at which the mixture starts to boil.
  • the surface tension should not be too low because otherwise the separation of the drop ligament from the nozzle is impeded during drop ejection.
  • the surface tension should be in the range 20 to 40 mNm' 1 at
  • Organic diluents especially polar organic diluents, are particularly preferred because they are also readily absorbable into cellulosic fibres, and therefore do not have to rely on volatility for removal from a dot printed on a paper substrate.
  • polar organic diluents especially polar organic diluents, are particularly preferred because they are also readily absorbable into cellulosic fibres, and therefore do not have to rely on volatility for removal from a dot printed on a paper substrate.
  • solvents which are preferred are ethers of alkylene glycols and ethers of polyalkylene glycols.
  • Specific examples include polypropylene glycol ethers and n-butyl ethers of ethylene glycol and polyethylene glycols, especially the ethers of di- and tri- propylene glycol and the n-butyl ethers of diethylene glycol and triethylene glycol.
  • Particularly preferred are the monomethyl ethers of di- and tripropylene glycol and the mono-n-butyl ethers of diethylene glycol and triethylene giycol.
  • the diluent consists primarily or essentially of such a glycol ether or a mixture of such glycol ethers. However mixtures of these ethers with other diluents, especially organic diluents, are also contemplated.
  • diluents that may be employed include, for example, hydrocarbons, especially
  • the diluents are preferably selected from hydrocarbons, organic polar diluents and
  • the diluent is preferred to be substantially non-aqueous, by which is meant that the diluent contains no more than about 5% by weight of water, including moisture absorbed from the atmosphere.
  • the diluent is preferably free of any added water and the amount of water it is capable of absorbing from the atmosphere under normal operating conditions (that is to say at ambient temperature and at the printing temperature, if other than ambient temperature) is no more than 2% and more preferably no more than 1%, by weight.
  • An aqueous diluent is thus one which contains at least 5%, and preferably more than 50%, by weight of water.
  • a preferred embodiment of the ink of the invention includes a resinous dispersant for the pigment.
  • the resinous dispersant which may comprise a single component or a mixture of two or more components, should be selected to be capable in the absence of the pigment of dissolving in the chosen diluent at ambient temperature (and at the operating temperature of the print head if that is higher than ambient) and in the concentration in which it is employed in the ink, and to disperse the chosen pigment in the diluent so as to form a substantially stable dispersion.
  • dissolve ' ' we mean that the dispersant is in solution in the diluent or is so highly solvat ⁇ d by it that the product is substantially
  • the dispersant preferably will also adhere well to a paper substrate since then it can also contribute to binding the pigment to the paper substrate.
  • the resinous dispersant is preferably insoluble in water.
  • the combination of the dispersant and the chosen pigment will separate from the diluent when a droplet of the ink comes into contact with plain paper, e.g. due to action of the water in the paper and/or some other property or component of the paper, or because of the concentration effect caused by absorption of
  • a convenient test for a suitable dispersant is to determine whether it is precipitated from a solution thereof in the desired concentration in the chosen diluent, when the solution is contacted with plain paper or with water.
  • the dispersant should be soluble in the chosen diluent and should also be soluble in
  • mixtures of the diluent and small quantities of water such as may be absorbed from the atmosphere on standing, in one embodiment of the invention it is chosen such that it separates from the diluent on addition of a larger concentration of water.
  • Such water sensitivity reduces the risk of undesired spread of the dot.
  • Suitable dispersants for non-aqueous systems are those sold by BYK Chemie GmbH of Germany under the trade names “ANTI-TERRA”, “DISPERBYK” and “BYK” , dispersants sold by Efka Chemicals BV of Holland under the tradename "EFKA” and
  • Preferred polymeric dispersants give a solution in the chosen diluent which, at the concentration of the dispersant employed in the ink, has a viscosity not very much greater
  • the viscosity of the solution of the dispersant in the diluent is not greater than 20 mPas, and more preferably not greater than
  • dispersant is neither part of the diluent nor part of the disperse phase as defined herein.
  • the ink may also contain other additives known to be employable in ink jet printer inks and which are capable of dissolving in the chosen diluent at ambient temperatures e.g. dispersion stabilisers, electrolytes, binders, surfactants, drag reducers and the like. Dissolved components, as well as dispersed solid particles, will have an effect upon rheological properties, and thus where the ink contains dissolved components such as a dispersant, it is preferred that the MVPF of the totality of non-diluent components of the ink, i.e. the dissolved components and the undissolved components, is not greater than 0.45 and preferably not greater than 0.4 when measured at 30° C.
  • This MVPF may be determined in the manner described above for the disperse phase but
  • volume fraction is now judged to be the sum of the non-diluent components of the
  • the concentrations of the various components in the ink may be varied to suit particular
  • the amount of dispersant required will depend upon the choice of the diluent and the
  • the disperse phase and also the particle size of the disperse phase. If too little is used, the dispersion will be unstable. However, we have observed that there is a
  • the amount of dispersant that gives the minimum viscosity for a particular ink composition may be determined by measuring the viscosities of a number of compositions containing the dispersant in varying concentrations and plotting a graph of measured viscosity against concentration of
  • the amount of dispersant required will depend upon the nature of the pigment and any other solids to be dispersed, the nature of the diluent and the nature of the dispersant itself but will generally be in the range of 0.1 to 1 part per part of disperse phase by weight although larger or smaller amounts may also be used.
  • the weaker dispersants will be used to determine the amount of dispersant required.
  • the diluent forms at least 60% of the ink composition, more preferably 75% to 95% by weight. For most formulations, the diluent will form 80% to 90% by weight
  • inks according to the invention may be formulated for operation at ambient
  • inks are intended for use at such elevated temperatures, it will be understood that somewhat higher concentrations of disperse phase and/or dispersant may be employed than in inks to be used at ambient temperature or alternatively the viscosity of the ink at the operating temperature may be lower, thereby reducing energy requirements and permitting the use of lower actuation voltages and less expensive drive circuits.
  • Print with very good definition and colour density is obtainable from the use in ink jet printers of ink compositions according to the invention containing simply the diluent, dispersant and pigment.
  • the dot spread is lower and the colour density is higher, and in many cases, the strike-through is less than that normally obtainable with the same concentration of a pigment having a MVPF above 0.25.
  • Inks according to the invention may be prepared by any suitable process. In one method. dispersant and pigment are dispersed in a small amount of diluent, e.g. by milling, and the resultant concentrated dispersion is then let down to the required concentration by
  • TPM tripropylene glycol monomethyl ether
  • EFKA 47EA is a resinous dispersant sold by EFKA Chemicals BV of Holland.
  • A is Regal 250R of Cabot
  • MVPF of the pigment in the ink is less than 0.25 is readily seen. While the MVPF of a pigment is an intrinsic property thereof, it is possible that the
  • MVPF values referred to therein are those obtained from measurements of pigment dispersions wherein the diluent is TPM, the dispersant is EFKA 47EA and the dispersant
  • a number of ink samples were prepared using the diluent, dispersant, pigment and ratio of dispersant to pigment employed in Examples 1, 2, 4 and 5 but in all cases using a pigment concentration of 10% by weight.

Abstract

Composition d'encre pour imprimante à jet d'encre contenant une dispersion de pigment dans un diluant et dans laquelle la fraction volumique à tassement maximal des particules de la phase dispersée ne dépasse pas 0,25 à 30 °C. Si d'autres solides sont présents dans la phase dispersée en plus du pigment, la valeur de la fraction volumique à tassement maximal des particules s'applique à la teneur en matière sèche totale de la phase dispersée. Si le pigment est le seul constituant de la phase dispersée, celle-ci devrait constituer plus de 7 %, mais pas plus de 25 %, en poids, de l'encre. Si l'encre renferme un constituant dissous dans le diluant, la fraction volumique à tassement maximal des particules des constituants de la compositon autres que le diluant ne devrait pas dépasser 0.45.
PCT/GB1995/002907 1994-12-09 1995-12-08 Composition d'encre pour imprimante a jet d'encre WO1996017894A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9424917.4 1994-12-09
GBGB9424917.4A GB9424917D0 (en) 1994-12-09 1994-12-09 Ink jet printer ink composition

Publications (1)

Publication Number Publication Date
WO1996017894A1 true WO1996017894A1 (fr) 1996-06-13

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PCT/GB1995/002907 WO1996017894A1 (fr) 1994-12-09 1995-12-08 Composition d'encre pour imprimante a jet d'encre

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GB (1) GB9424917D0 (fr)
WO (1) WO1996017894A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0408333A1 (fr) * 1989-07-14 1991-01-16 Xaar Limited Encre d'impression par jet utilisable à la température ambiante
EP0454872A1 (fr) * 1989-11-21 1991-11-06 Seiko Epson Corporation Encre pour impression a jet d'encre
WO1992012209A1 (fr) * 1991-01-11 1992-07-23 Xaar Limited Composition pour encre

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0408333A1 (fr) * 1989-07-14 1991-01-16 Xaar Limited Encre d'impression par jet utilisable à la température ambiante
EP0454872A1 (fr) * 1989-11-21 1991-11-06 Seiko Epson Corporation Encre pour impression a jet d'encre
WO1992012209A1 (fr) * 1991-01-11 1992-07-23 Xaar Limited Composition pour encre

Also Published As

Publication number Publication date
GB9424917D0 (en) 1995-02-08

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