GB2461147A

GB2461147A - Inkjet printing ink composition and method

Info

Publication number: GB2461147A
Application number: GB0908687A
Authority: GB
Inventors: Christine Russell
Original assignee: Sericol Ltd
Current assignee: Sericol Ltd
Priority date: 2008-05-20
Filing date: 2009-05-20
Publication date: 2009-12-30
Anticipated expiration: 2029-05-20
Also published as: GB0908687D0; GB2461147B

Abstract

An inkjet ink comprising a solvent blend containing a bio-solvent and a dibasic ester, a carrier resin, a colouring agent, and an organornodified polysiloxane. The bio-solvent may be a solvent from a biological source and may comprise soy methyl ester, lactate esters such as ethyl lactate, polyhydroxyalkanoates, terpenes, non-linear alcohols, and D-limonene. The dibasic ester may be a di(C1-C4 alkyl) ester of a dicarboxylic acid having 3 to 8 carbon atoms such as esters of succinic acid, glutaric acid, and adipic acid. The organomodified polysiloxane may be a polyether modified polysiloxane.

Description

INTELLECTUAL

. .... PROPERTY OFFICE Application No. GB0908687.7 RTM Date:20 October 2009 The following terms are registered trademarks and should be read as such wherever they occur in this document:

CINQUASIA

CONTROL TAC

DYSPERBYK

ELVACITE

EUROMEDIA

GLANOL

HOSTAPERM

IRGALITE

JETFLEX

MICROLITH

ORAJET

PALIOTOL

SOLSPERSE

TEGO

VIVAK

Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk A printing ink This invention relates to a printing ink and in particular to a solvent-based ink for ink-jet printing.

In 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 F; forms an image on the substrate. For high-speed printing, the inks must flow rapidly from the printing heads, and, to ensure that this happens, they must have in use a low viscosity, typically at or below 50 mPas at 25Â°C, or using an HSS head, at or below mPas when measured at 25Â°C (although when ejected through the nozzles, the jetting temperature is often elevated to about 40Â°C).

Ink-jet inks 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 Henry R. Kang Journal of Imaging Science 1991, 35(3), 179-188). Tn another common type the liquid is a low-boiling solvent or mixture of solvents. For example, EP 0 314 403 discloses an ink employing a lower alcohol and a lower ketone, e.g. methanol with acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone or cyclohexanone and EP 0 424 714 discloses a combination of a non-volatile non-aqueous solvent such as a ketone or alcohol with a volatile non-aqueous solvent such as a monohydric aliphatic alcohol.

However, while these so-called "full" solvents work well on a variety of solvents, the market for more environmentally friendly inks is growing as users and regulatory authorities raise ever stricter health and environmental concerns. The requirements are for inks displaying dramatic reductions in the levels of VOCs (volatile organic compounds) and HAPs (hazardous afr pollutants).

H

One approach is to use aqueous inks (see H.R. Kang, Journal of Imaging Science 1991, 35(3), 179-188) although these inks are limited in their application since they tend to be less durable and can only be used on a narrow range of substrates.

I

An alternative has been to use "mild" or "light" solvent inks which have similar formulations to the full solvent inks but contain reduced levels of VOCs and HAPs.

An example of a full and a mild ink might be: Table I, Full-and mild-solvent inks.

Component Full Mild Pigment 5% 5% Vinyl resin 3% 3% Butyl glycol acetate 70% 87% Cyclohexanone 22% 5% A further alternative has been to use biologically derived-solvent inks which have similar formulations to the full solvent inks but contain a solvent which is derived from a biological source. Further, these biologically derived solvents tend to exhibit reduced levels of VOCs and HAPs compared to conventional full solvent ink formulations. Unlike most solvents which are based on crude oil feedstocks, making them unsustainable or non eco-friendly, bio-solvents are derived from biological sources.

Bio-solvents, or solvent replacements from biological sources, have the potential to reduce dramatically the amount of environmentally-polluting VOCs released in to the atmosphere and have the further advantage that they are sustainable. Moreover, new methods of production of bio-solvents derived from biological feedstoeks are being discovered, which allow bio-solvent production at lower cost and higher purity.

Examples of bio-solvents include soy methyl ester, lactate esters, polyhydroxyalkanoates, terpenes and non-linear alcohols, and D-limonene,. Soy methyl ester is prepared from soy. Soy is an oil extracted from soybeans and typically contains 7% linolenic acid (Cl8:3), 51% linoleic acid (C-l8:2) and 23% oleie acid (C- 18:1), 4%stearic acid and 10% palmitie acid. The fatty acid ester is produced by esterifleation of the soy oil with methanol. Lactate esters preferably use fermentation-derived lactic acid which is reacted with methanol and/or ethanol to produce the ester.

An example is ethyl lactate which is derived from corn (a renewable source) and is approved by the FDA for use as a food additive. Polyhydroxyalkanoates are linear polyesters which are derived from fermentation of sugars or lipids. Terpenes and non linear ificohol may be derived from corn cobs/rice hulls. An example is D-limonene which may be extracted from citrus rinds.

These bio-solvent-containing inks have been introduced onto the market and have had some commercial success. An example is an ink containing ethyl lactate as a solvent and a nittocellulose renewable resin. While these inks have appropriate environmental credentials, they tend to lack adhesion to key substrates, can have a poor colour gamut due to viscosity constraints and may show poor stability. There remains, therefore, a need in the art for environmentally friendly ink with components derived from renewable sources, but which have improved end-user properties.

Accordingly, the present invention provides an ink-jet ink comprising a bio-solvent, such as ethyl lactate, a carrier resin, a colouring agent and an organomodificd polysiloxane.

This ink composition has been found to have excellent printing properties despite the constraints imposed upon it by the environmental requirements.

Ethyl lactate (ethyl 2-hydroxypropionate) is a known bio-solvent in that it is derived from renewable sources. It also has low volatility and is not classed as an HAP. The drawback of ethyl lactate is, however, that it is a soft solvent in that it is poor at softening the substrate on to which the ink is printed. As a consequence, it has a tendency to provide poor adhesion.

The present invention provides a formulation which gives good printing properties despite using a soft solvent such as ethyl lactate. By "soft solvent" is meant a solvent which is poor at softening the substrate onto which the ink is printed.

The softening may be determined by the "PVC etch test" according to ASTM Dl308- 02(2007), "Spot Test, Open" as modified by Sericol Ltd. The test is as follows. The test is conducted at 23 Â� 2Â°C and 50 Â� 5% relative humidity. A self-adhesive PVC substrate is provided (e.g. Euromedia Power Gloss which has the following characteristics: molecular weight: Mw 123,744, Mn 28,831 and Mz 255,754; thickness (mm) 0.12; width (cm) 100, (36 inches); dimensional stability <0.20% measured at 65Â°C, 48 hours; tensile strength (kg/inch) 10 KS A 1107 C.R.E, 1" cut strip; and elongation (%) 204 KS A 1107 C.R.E). Place one or more drops (each of 0.05 mL) of the chosen solvent onto the PVC substrate. Remove solvent drop-by-drop from substrate with a lint-free absorbent cellulose/rayon wipe (e.g. E-TorkÂ�) and note the time of wiping each drop. Determine visually the etching of the substrate. By taking a number of measurements determine the time taken to etch into the substrate.

The time is the PVC etch time. The PVC preferably has a weight average molecular weight of 50,000 to 500,000, and more preferably from 100,000 to 250,000; a number average molecular weight of 5,000 to 100,000, more preferably 10,000 to 50,000; and a z-average molecular weight of 100,000 to 750,000, more preferably 200,000 to 500,000.

The results for a number of solvents using this test are listed below.

Table 2. Etch times for various solvents.

Solvent PVC etch time Duty! glycol acetate 30 sees Cyclohexanone 5 sees PMA 7 sees Ethyihexyl acetate 1 mm Butyrolactone 5 sees Ethyl lactate >5 mins Dibasie ester 15 sees Dipropylene glyeol methyl ether >5 mins (Dowanol DPM) The soft solvent of the present invention typically has a PVC etch time of 30 seconds or above, more preferably 1 mm or above and most preferably 3 mm or above.

Although the ink can include ethyl lactate as the sole solvent present, the solvent is preferably a blend of ethyl lactate and a second solvent. The second solvent can be any solvent other than ethyl lactate which is suitable for use in solvent based ink-jet inks, although clearly it ought not to be an HAP and should allow the ink to maintain a low overall VOC. The second solvent is preferably a dibasic ester. The dibasic ester is also a known solvent in the art. It can be described as a di(Ci-C4 alkyl) ester of a saturated aliphatic dicarboxylic acid having 3 to 8 carbon atoms and has the following general formula: R1 OAOR2 in which A represents (CH2)1.o, and R1 and R2 may be the same or different and represents C1-C4 alkyl which may be a linear or branched alkyl radical having 1 to 4 carbon atoms, preferably methyl or ethyl, and most preferably methyl.

The dibasic ester comprises at least one di(C1-C4 alkyl) ester of a saturated aliphatie dicarboxylic acid having 4 to 6 carbon atoms. In other words, the ink of the present invention preferably comprises a di(Ci-C4 alkyl) ester of butanedioic acid (succinic acid), a di(C 1-C4 alkyl) ester of pentanedioic acid (glutaric acid) a di(C 1-C4 alkyl) ester of hexanedioic acid (adipic acid), or a mixture thereof More preferably the ink of the present invention comprises the dimethyl ester of butanedioic acid (dimethyl succinate), the dimethyl ester of pentanedioic acid (dimethyl glutarate) or the dimethyl ester of hexanedioic acid (dimethyl adipate), or a mixture thereof Most preferably the ink of the invention comprises a mixture of the dimethyl esters of butanedioic acid, pentanedioic acid and hexanedioic acid. Mixtures of the dimethyl esters of butanedioic acid, pentanedioic acid and hexanedioic acid are generally lcnown as "dibasie esters" or "DBE" and arc commercially available from Invista Speciality Intermediates, for example.

A typical DBE product comprises 5 5-65% by weight of the dimethyl ester of pentanedioic acid, 10-25% by weight of the dimethyl ester of hexanedioic acid and 15-25% by weight of the dimethyl ester of butanedioic acid, for example 59% by weight of the dimethyl ester of pentanedioic acid, 21% by weight of the dimethyl ester of hexanedioic acid and 20% by weight of the dimethyl ester of butanedioic acid together with trace amounts of methanol and water. The dibasic ester may be a compound of the above formula or a mixture of two or more compounds of the above formula The ink of the present invention preferably comprises 5 0-95% by weight, more preferably 60-90% by weight and most preferably 70-90% by weight of solvent based on the total weight of the ink. In this regard, the majority of the solvent present is a soft solvent. The ink is preferably a blend of a soft solvent such as ethyl lactate and a dibasic ester. The ink preferably contains 50-95% by weight, mote preferably 60-P 90% by weight and most preferably 70-90% by weight of the soft solvent such as ethyl lactate. The ink may also contain 1-20% by weight, and more preferably 5-15% by weight of the second solvent, e.g. the dibasic ester.

The ink of the present invention is preferably substantially free of water, e.g. it comprises less than 5% by weight of water, more preferably less than 2% by weight of water and most preferably less than 1% by weight of water, based on the total weight of the ink.

The ink of the present invention also seeks to minimise the VOC content. There are a number of different definitions of VOCs; however, the European Solvent Directive (Council Directive 1999/1 3/PC) defines a VOC as "any organic compound having at 293.15 K a vapour pressure of 0.01 KPa or more, or having a corresponding volatility under the particular conditions of use". In order to minimise the VOC content, solvents with high vapour pressures are avoided. In this regard, at the afore-mentioned temperature, ethyl lactate has a vapour pressure of 2 hPa (1 hPa = 0.1 KPa) and the components of DBE have vapour pressures of: dimethyl adipate 0.03 hPa, dimethyl glutarate 0.08 hEat and dimethyl succinate 0.27 hPa. Cyclohexanone, in contrast, has a vapour pressure of 5 hPa. In a preferred embodiment, the ink of the present invention is substantially free of any solvents having a vapour pressure of 4 hPa or higher, is preferably substantially free of any solvents having a vapour pressure of 3 hPa or higher, and most preferably is substantially free of any solvents having a vapour pressure greater than 2 hPa.

The ink of the present invention also includes a film-forming thermoplastic carrier resin. Carrier resins suitable for use in solvent-based ink-jet inks are known in the art.

The resin and solvents need to be chosen such that the carrier resin is soluble in the solvents. Examples of suitable resins include acrylic resins, epoxy resins, ketone resins, nitrocellulose resins, phenoxy resins, polyester resins, or mixtures or copolymers thereof Preferably the resin is an acrylic resin. The weight average molecular weight of the resin is preferably from 5,000 to 100,000, more preferably from 20,000 to 80,000. Tn a preferred embodiment, the resin is a methyl methacrylate/n-butyl methacrylate copolymer, which aids with the low viscosity requirement of the ink, such as Elvacite 2614 from Lucite Solutions which has a molecular weight of 56,000, a T5 of 79Â°C, an acid number of 14 and a Tukon Hardness Knoop No of 13.

The ink of the present invention preferably comprises 1 to 20% by weight of carrier resin, more preferably 3 to 15% by weight and most preferably 5 to 10% by weight based on the total weight of the ink.

The ink of the present invention also includes a colouring agent, which may be either dissolved or dispersed in the liquid medium of the ink. Preferably the colouring agent is a dispersible pigment which is dispersed in the ink. Colouring agents are known in the art and are commercially available, e.g. Microlith, Cinquasia, and Irgalite (all from Ciba Speciality Chemicals), Paliotol (available from BASF plc), Hostaperm (available from Clariant UK) and Sun Yellow 271-9151 and Yellow 4G0 (available from Sun Chemical Performance Pigments). 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 (i.e. CMYK), although other colour sets may be used such. as Hexaehrome (CMYKOG). Mixtures of pigments may be used in the same ink if required.

The colorant is preferably present in the ink of the invention in an amount of from I to 10% by weight, preferably 3 to 8% by weight based on the total weight of the ink.

The ink of the present invention also contains an organomodified polysiloxane as a slip aid, which has been found to increase the adhesion of the ink to the substrate providing a usable ink despite the relatively poor solvating power of the soft solvent of the present invention compared to conventional solvents, such as cyclohexanone.

The organomodified polysiloxane has a structural unit represented by Si(R3R4)O-wherein R3 and R4 are the same or different and represent an alkyl group (e.g. C14, an aryl group (e.g. phenyl), an aralkyl group (e.g. benzyl), a group including a polyether moiety (e.g. polyoxyethylene and/or polyoxypropylene), or a group including a polyester moiety.

Specific examples of the organomodified polysiloxane include dimethyl silicone, alkyl-modified silicones, aryl-modified silicones, aralkyl-modified silicones, polyether-modified silicones, polyester-modified silicones, alkyl-polyether-modified silicones and polyether-polyester modified silicones, among which dimethyl silicone, alkyl-modified silicones and polyether-modified silicones are preferred. Such materials are commercially available and are exemplified by from Tego Glide 100, Tego Aglide A-I 15, Tego Glide B-1484, Tego Glide 200, Tego Glide ZG-400, Tego Glide 410, Tego Glide 420, Tego Glide 440 and Tego Glide 450 from Tego Chemie Service GmbH; Glanol 110, Glanol 115, Glanol B-1484, Glanol 200, Glanol 400, Glanol 410, Glanol 420, Glanol 440 and Glanol 450 from Kyoei Chemical Co Ltd; T5F4452 and T5F4460 from Toshiba Silicone Co Ltd; and KF352A, KF615A, KF6008 and KF6012 from Shinetsu Chemical Industry Co Ltd. Preferably, the organomodified polysiloxane is a polyether-modified polysiloxane, typically including polyoxyethylene and/or polyoxypropylene moieties as the polyether unit. The hydrophilic property of the polyether-modified polysiloxane is enhanced with an increase in the proportion of polyoxyethylene in the polyether, while the hydrophobic property of the polyether-mo.dified silicone is enhanced with an increase in the proportion of polyoxypropylene in the polyether. That is, the affinity of the polyether-modified silicone for organic polar solvents is reduced with an increase in the proportion of polyoxypropylene in the polyether. Thus, when an organomodified polysiloxane including polyoxypropylene in a greater proportion is added to an ink composition containing an organic polar solvent, the modified silicone migrates to the surface of an ink film of the resulting ink composition as the organic polar solvent in the ink composition evaporates.

Usable as the polyether-modified polysiloxane in the present invention are polyether-modified silicones including polyoxypropylene as the polyether in a high proportion, for example, those including polyoxypropylene in a proportion of 50% by weight or greater, more preferably 70% by weight or greater, and most preferably 90% by weight or greater of the polyoxypropylene portion relative to the overall polyether portion. Particularly preferred is a polyoxypropylene-modified silicone.

Examples of commercially available polyoxypropylene-modified polysiloxanes include TSF4460 and Tego Glide A-us.

The number average molecular weight of the organomodified polysiloxane is not particularly limited, but may be from 1,000 to 60,000. More specifically, in the case of the polyoxypropylene-modified polysiloxane, the molecular weight thereof is preferably from 1,000 to 30,000, more preferably from 2,000 to 20,000, and most preferably from 5,000 to 20,000. If the organomodifled polysiloxane has an excessively low molecular weight, the resulting ink has a reduced water resistance; if the organomodified polysiloxane has an excessively high molecular weight, the surface adherence suppressing effect and the ink film fixability are reduced because it is difficult for the organomodified polysiloxane to migrate to the surface of the ink film.

The organomodified polysiloxane may be suitably present at 0.005 to 10% by weight, preferably 0.01 to 5% by weight and most preferably from 0.05 wt to 1% by weight based on the total weight of the ink. If the proportion of the organomodified polysiloxane is higher than this amount, the organomodified polysiloxane may migrate not only to the surface of an ink film of the resulting ink composition but also to a portion of the ink film closer to the surface of an article on which the ink composition is applied, so that the ink composition is prevented from firmly adhering onto the surface of the article and suffers like side effects. If the proportion of the organomodified polysiloxane is lower, the surface adherence suppressing property and the ink film fixability are reduced.

Other 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, dispersants (e.g. Dysperbyk, Tego Dispers, Soisperse etc.), synergist, other surface tension modifiers, defoamers, stabilisers against deterioration by heat or light, reodorants, flow or slip aids, biocides and identifying tracers. Inks of the present invention may, for example, comprise 0.50 to 3% by weight of a dispersant. Suitable dispersants include SolsperseÂ� 32000, optionally together with the synergist SolspcrseÂ� 5000, (available from Lubrizol) and BYK-168 (available from BTK Chemie).

The ink-jet inks exhibit a desirable low viscosity (200 mPas or less, preferably 100 mPas or less, more preferably 50 mPas or less and most preferably 25 mPas or less at 2 5Â°C). Viscosity may be measured using a Brookfield viscometer fitted with a thermostatically controlled cup and spindle arrangement, such as model LDV 1 + with the ULA spindle and cup arrangement at 25Â°C or a DV 1 low-viscosity viseometer running at 20 rpm at 25Â°C with spindle 00.

The inks of the present invention may he prepared by known methods such as, for example, stirring with a high-speed water-cooled stirrer, or milling on a horizontal bead-mill.

The present invention also provides a method of ink-jet printing using the above-described ink, and a substrate having the printed ink thereon. The ink of the present invention is particularly suited to piezoelectrie drop-on-demand ink-jet printing. The inks of the invention can be used on a wide range of substrates such as styrene, PolyCarb (a polyearbonate), and VIVAK (a polyethylene terephthalate glycol modified) but are particularly suitable for printing on vinyl film substrates, for example polyvinyl chloride film. Suitable vinyl substrates are known in the art and examples include those available under the trade-names Orajet (from Oracal), Control Tae (from 3M), BannerPVC (a PVC), JetElex (from Ritrama) and MPT 1005 EZ, from Avery.

The present invention further provides an ink-jet ink cartridge containing an ink-jet ink as defined herein. The cartridges comprise an ink container and an ink deliveiy port which is suitable for connection with an ink-jet printer.

The advantages of the inks of the present invention are demonstrated in the following

examples

Examples

The invention vi1l now be described, by way of example, with reference to the following example (parts given are by weight).

Example I

Inks 1-3 were prepared by combining the following components, with a high speed mixer: Table 3. Formulations of inks 1-3 Component Wt% Function Special black 250 5.00 Pigment 2-Ethylhexyl acetate 4.00 Solvent Solsperse 32,000 0.90 Dispersing Polymer Solsperse 5,000 0.09 Synergist Ethyl lactate 73.31 Solvent Dibasie ester 10 Solvent Resinlsolvent* 6.6 See below Total 100.00 * The additional resinlsolvent is: Ink I: No resin, replaced with 6.6 wt% ethyl lactate Ink 2: Elvaeite 2614 (an acrylic resin from Lucite Solutions), 6.6 wt% Ink 3: VMCC (vinyl chloride-vinyl acetate resin from Union Carbide), 3.6% resin added, remainder replaced with ethyl lactate

Example 2

The viscosity of the inks 1-3 prepared in Example I was measured and the inks were subsequently applied to a substrate and analysed. Viscosity was measured on a Brookfield DY-I + running at 30 rpm. The inks were drawn down onto two substrates, Euromedia Power Gloss Self adhesive Vinyl and Euromedia Back lit banner substrate using a K bar applicator to give a wet film weight of approximately 10-12.tm. The films were dried in an oven at 60Â°C for 3 mins, they were then left for 1 hour after drying before the film properties were assessed. The results are shown in

Table 4.

Table 4. Viscosity of inks 1-3.

Ink 2 3 Resin None Elvacite 2614 VMCC Viscosity 3,2 11.6 10.9 (mPas Â� 25Â°C) The base formulation without resin (ink 1) would be unsuitable for printing within an ink system.

The adhesion of the inks 1-3 prepared in Example 1 was measured. The inks were cured under the conditions set out in Example 2. The adhesion to these two different substrates was assessed via a finger-nail scratch test. The degree of ink removal was then assessed. The results are shown in Table 5 in which l" represents 100% removal of the dried ink and "5" represents 0% removal.

Table 5. Scratch test results for inks 1-3.

Ink Substrate SA PVC Backlit banner 2 1 1 3 -3 3

Example 4

The adhesion of the inks 1-3 prepared in Example 1 was measured. The inks were cured under the conditions set out in Example 2. The adhesion to these two different substrates was assessed via a dry rub test using a crockmeter 20 rubs. The degree of ink removal was then assessed. The results arc shown in Table 6 in which "1" represents 100% removal of the dried ink and "5" represents 0% removal.

Table 6. Scratch test results for inks 1-3.

Ink Substrate SA PVC Backlit banner 1 1 El 3 2 2

Example 5

To inks 2 and 3, 0.1% of Tego Al 15 was added and subjected to high-speed stirring to prepare inks 4 and 5. The adhesion of these new inks was then measured. The inks were cured under the conditions set out in Example 2. The adhesion to these two different substrates was assessed via a finger nail scratch and a dry rub test using a crockmeter 20 rubs. The degree of ink removal was then assessed. The results are shown in Table 7 with "1" and "5'> having the same meaning as in Example 4.

Table 7. Scratch test results for inks 4 and 5.

Ink Test Substrate SA PVC Baekjit banner 4 Scratch 4 4 Scratch 5 5 4 DryRub 5 5 DryRub 5 5

E

Example 6

The inks from Example 5 were then evaluated for their effect on offset. This is a key issue for ink jet inks used on roll-to-roll printers, as high pressures could be exerted onto prints on the collection roll. The inks were cured under the conditions set out in Example 2. The offset to these two different substrates was assessed by placing identical draw downs face-to-face and back-to-face, and then placing them under a 5 Kg weight for 24 hours. The degree of ink transfer was then assessed. The results are shown in Table 8 in which "1" represents 100% transfer of the dried ink and "5" represents 0% transfer.

Table 8. Offset test results for inks 4 and 5.

Ink Test Substrate SA PVC Backlit banner 4 Back-to-face 5 5 Back-to-face S S 4 Face-to-face 5 5 Face-to-face 3 3 The following inks of the present invention were formulated as a CYMK set.

Cyan (ink 6): Component wt% Irgalite cyan GLVO blue 2.24 2-Ethyihexyl acetate 2.5 Solsperse 32,000 0.784 Soisperse 5,000 0.076 Ethyl lactate 77.3 Dibasic ester 10 Elvacite 2614 7.0 TegoAll5 0.1 Magenta (ink 7): Component Ciriquasia magenta RT35SD 3.93 2-Ethylhexyl acetate 5.745 Soisperse 32,000 1.575 Ethyl lactate 73.15 Dibasic ester 10 Elvacite 2614 5.5 TegoAllS 0.1 Yellow (ink 8): Component wt% Sym yellow 4G0 5.6 2-Ethylhexyl acetate 23.636 Solsperse 32,000 2.24 SolspersÃ� 22,000 0.224 Ethyl lactate 50 Dibasic ester 10 Elvacite 2614 5.8 TegoAll5 0.1 Black (ink 9): Component wt% Special black 250 5 2-Ethylhexyl acetate 4.1 Solsperse 32,000 0.9 Solsperse 5,000 0.09 Ethyl lactate 73.21 Dibasic ester 10 Elvacite 2614 6.6 TegoAll5 0.1 Inks having the same components as inks 6-9 may also be prepared in which the 2-ethylhexyl acetate is replaced with ethyl lactate.

Example S

Example 5 was repeated, but using 0.1% of Tego Glide 410 instead of Tego AilS in ink 4 to prepare ink 10 and the Backlit barmer substrate was changed to a Frontlit Perfect FR banner substrate. The adhesion of this new ink was then measured. The inks were cured under the conditions set out in Example 2. The adhesion to these two different substrates was assessed via a finger nail scratch and a dry rub test using a crockmeter 20 rubs. The degree of ink removal was then assessed. The results are

shown in Table 9

Table 9. Scratch test results for inks 10 and 11.

Ink Test Substrate SA PVC Frontlit Perfect _____________ _____________ _____________ FR banner 4 Scratch 4 4 ____________ Scratch 5 5 Scratch 4 4 4 DryRub -5 5 Dry Rub 5 5 DryRub 5 5 The results show that Tego Glide 410 is also suitable for use in the present invention.

However, it should be noted that inks 10 and II have a less than optimal dynamic surface tension profile, although still within tolerable limits for a number of ink-jet ink heads.

Claims

Claims I. An ink-jet ink comprising a solvent blend containing a bio-solvent and a dibasic ester, a carrier resin, a colouring agent and an organomodified polysiloxane.
2. An ink-jet ink as claimed in claim I, wherein the bio-solvent has a PVC etch time of 30 seconds or greater.
3. An ink-jet ink as claimed in claim 2, wherein the bio-solvent is ethyl lactate.
4. An ink-jet ink as claimed in any preceding claim, wherein the ink has a total solvent content of 50-95% by weight based on the total weight of the ink.
5. An ink-jet ink as claimed in any preceding claim, wherein the carrier resin is selected from an acrylic resin, an epoxy resin, a ketone resin, a nitrocellulose resin, a phenoxy resin, a polyester resin or a mixture or copolymer thereof
6. An ink-jet ink as claimed in claim 5, wherein the carrier resin is an acrylic resin.
7. An ink-jet ink as claimed in any preceding claim, wherein the organomodified polysiloxane is a polyether-modified polysiloxane.
8. An ink-jet ink as claimed in claim 7, wherein the polyether-modified polysiloxane is a polyoxyethylene-and/or polyoxypropylene-modified polysiloxane.
9. An ink-jet ink as claimed in any preceding claim, wherein the ink is substantially free of water.
10. An ink-jet ink as claimed in any preceding claim, wherein the ink is substantially free of any solvents having a vapour pressure of 4 hPa or higher.
11. An ink-jet ink as claimed in any preceding claim, comprising 50-95% by weight based on the total weight of the ink of a solvent blend containing a ethyl lactate and a dibasic ester, an acrylic carrier resin, a colouring agent and a polyoxyethylene-and/or polyoxypropylene-modified polysiloxane.
12. A method of ink-jet printing, comprising printing the ink-jet ink as claimed in any preceding claim on to a substrate and curing the ink.
13. A substrate having the ink-jet ink as claimed in any of claims I to 12 printed thereon.
14. An ink-jet ink cartridge containing the ink-jet ink as claimed in any of claims 1 to 12.