OPAQUE GREY INK JET INK COMPOSITION

Abstract

Opaque grey ink jet ink composition, comprising: a solvent comprising one or more organic solvent compound(s); b) a binder, comprising one or more binding resin(s); wherein the ink jet ink composition further comprises: one or more black pigment(s) and/or one or more black dye(s); one or more white pigment(s); wherein the one or more black pigment(s) and/or the one or more black dye(s) is(are) present in a total amount from 0.01% to 9% by weight, of the total weight of the ink jet ink composition; wherein the one or more white pigment(s) is(are) present in a total amount from 0.5% to 30% by weight, of the total weight of the ink jet ink composition; and wherein the ratio:amount by weight of the one or more black pigment(s) and/or the one or more black dye(s)/amount by weight of the one or more white pigment(s) is from 0.001 to 1.

Claims

1. Opaque grey ink jet ink composition, liquid at room temperature, comprising: a) a solvent comprising one or more organic solvent compound(s); b) a binder, comprising one or more binding resin(s); wherein the ink jet ink composition further comprises: c) one or more black pigment(s) and/or one or more black dye(s); d) one or more white pigment(s); wherein the one or more black pigment(s) and/or the one or more black dye(s) c) is(are) present in a total amount from 0.01% to 9% by weight, preferably from 0.01% to 8.5% by weight, more preferably from 0.01% to 5% by weight, even more preferably from 0.05% to 4.5% by weight, better from 0.08% to 4.5% by weight, still better from 0.1% to 2.55% by weight of the total weight of the ink jet ink composition; wherein the one or more white pigment(s) is(are) present in a total amount from 0.5% to 30% by weight, preferably from 1% to 15% by weight, more preferably from 2% to 10% by weight, better from 3% to 9% by weight of the total weight of the ink jet ink composition; and wherein the ratio:amount by weight of the one or more black pigment(s) and/or the one or more black dye(s)/amount by weight of the one or more white pigment(s) is from 0.001 to 1, preferably from 0.001 to 0.5, more preferably from 0.001 to 0.3, better from 0.005 to 0.3, still better from 0.01 to 0.3, especially from 0.01 to 0.1, more especially from 0.01 to 0.05, even more especially from 0.02 to 0.05.

2. Opaque grey ink jet ink composition according to claim 1 comprising one or more black pigments and no black dyes, wherein said black pigment(s) is(are)present in a total amount from 0.01% to 5% by weight, preferably from 0.08% to 4.5% by weight, more preferably from 0.1% to 2.55% by weight of the total weight of the ink jet ink composition; and wherein the ratio:amount by weight of the one or more black pigment(s)/amount by weight of the one or more white pigment(s) is from 0.001 to 0.3, preferably from 0.01 to 0.3, more preferably from 0.01 to 0.1, better from 0.01 to 0.05, still better from 0.02 to 0.05.

3. Opaque grey ink jet ink composition according to claim 1 comprising one or more black dye(s) and no black pigments, wherein said black dye(s) is(are)present in a total amount from 0.01% to 9% by weight, preferably from 0.01% to 8.5% by weight, more preferably from 0.01% to 5% by weight, even more preferably from 0.05% to 4.5% by weight, of the total weight of the ink jet ink composition; and wherein the ratio:amount by weight of the one or more black dye(s)/amount by weight of the one or more white pigment(s) is from 0.001 to 1, preferably from 0.001 to 0.5, more preferably from 0.001 to 0.3, better from 0.005 to 0.3, still better from 0.01 to 0.3, especially from 0.01 to 0.1, more especially from 0.01 to 0.05, even more especially from 0.02 to 0.05.

4. Opaque grey ink jet ink composition according to claim 1, wherein the black pigment(s) is (are) selected from C.I. (Colour Index) Pigment Blacks, such as C.I. Pigment Black 6 (carbon black), and C.I. Pigment Black 7 (carbon black), and the black dye(s) are selected among C.I. (Colour Index) Solvent Blacks, such as C.I. Solvent Black 27, C.I. Solvent Black 29, C.I. Solvent Black 35, and C.I. Solvent Black 45.

5. Opaque grey ink jet ink composition according to claim 1, wherein the white pigment(s) is (are) selected from C.I. (Colour Index) Pigment Whites, such as C.I. Pigment White 5 (Lithopone, mixture of barium sulphate and zinc sulphide), 6 (TiO.sub.2), 12 (ZrO.sub.2), and 21 (BaSO.sub.4).

6. Opaque grey ink jet ink composition according to claim 1, further comprising one or more dye(s) and/or one or more pigment(s) having a colour other than white and other than black.

7. Opaque grey ink jet ink composition according to claim 6, wherein the one or more dye(s) and/or the one or more pigment(s) having a colour other than white and other than black is(are) present in a total amount from 0.01 to 1.5%, preferably from 0.01 to 0.9%, still preferably from 0.05 to 0.2% by weight of the total weight of the ink jet ink composition.

8. Opaque grey ink jet ink composition according to claim 6, wherein the one or more dye(s) having a colour other than white and other than black is (are) selected from among Colour Index (C.I.) solvent dyes, and the one or more pigment(s) having a colour other than white and other than black is (are) selected from among Colour Index (C.I.) pigments.

9. Opaque grey ink jet ink composition according to claim 1, wherein the binding resin(s) is(are) selected from (meth)acrylic, vinylic, ketonic, hydroxyaromatic, for example phenolic, cellulosic, styrenic, epoxy, polyurethane, styrene-acrylate, alkoxysilane, ester resins, and combinations thereof; preferably the binding resin(s) is(are) selected from vinyl acetate/vinyl chloride copolymers, phenolic resins, cellulosic resins, (meth)acrylic resins and combinations thereof.

10. Opaque grey ink jet ink composition according to claim 1, wherein the binder represents from 0.1 to 50% by weight, preferably from 1 to 45% by weight, still preferably from 5 to 30% by weight, better from 10 to 20% by weight, of the total weight of the ink composition.

11. Opaque grey ink jet ink composition according to claim 1, in which the solvent represents from 20 to 99% by weight, preferably from 30 to 95% by weight, more preferably from 30 to 90% by weight, even more preferably from 60 to 80% by weight of the total weight of the ink composition.

12. Opaque grey ink jet ink composition according to claim 1, in which said organic solvent compound(s) of the solvent is (are) selected from among alcohols, particularly low molecular weight alcohols, for example aliphatic alcohols such as ethanol; ketones preferably with a low molecular weight; alkylene glycols ethers; alkylene glycols esters and esters of alkylene glycols ethers such as acetates; dimethyl formamide; N-methyl pyrrolidone; acetals; esters; linear or cyclic ethers; aliphatic, cyclic or linear hydrocarbons; aromatic hydrocarbons; and carbonates such as propylene carbonate, ethylene carbonate and dimethyl and diethylcarbonates; and mixtures thereof.

13. Opaque grey ink jet ink composition according to claim 1, in which the solvent comprises a majority amount by weight (50% or more by weight) relative to the total weight of the solvent, preferably consists of, one or several solvent compound(s) selected from ketones with 3 to 10 carbon atoms, such as acetone, butanone (methylethylketone or “MEK”), pentanone-2 (methyl propyl ketone or “MPK”), methyl-3 butanone-2 (methyl-isopropyl ketone or “MiPK”) and methyl-4 pentanone-2 (methyl isobutyl ketone or “MiBK”); preferably, the vehicle comprises a majority amount by weight relative to the total weight of the vehicle of MEK, preferably, consists of MEK.

14. Opaque grey ink jet ink composition according to claim 1, further comprising at least one conductivity salt, preferably with a content of 0.1 to 20% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.1 to 5% by weight of the total weight of the ink composition; preferably, said conductivity salt is chosen from among salts of alkaline metals such as lithium, sodium, potassium salts, salts of alkaline earth metals such as magnesium and calcium salts, and single or quaternary ammonium salts; these salts being in the form of halides, perchlorates, nitrates, thiocyanates, formiates, acetates, sulphates, propionates, trifluoroacetates, triflates (trifluoromethane sulphonates), hexafluorophosphates, hexafluoroantimonates, tetrafluoroborates, picrates, carboxylates or sulphonates.

15. Opaque grey ink jet ink composition according to claim 1, that has a conductivity in the liquid state greater than or equal to μS/cm at 20° C., preferably greater than or equal to 300 μS/cm at 20° C., even more preferably greater than or equal to 500 μS/cm at 20° C.

16. Method for marking a substrate, support or object by spraying an ink composition onto this substrate, support or object using an ink jet printing technique, wherein the sprayed ink composition is an opaque grey ink jet ink composition according to any one of claim 1.

17. Substrate, support or object wherein it is provided with a marking obtained by drying and/or absorption of the opaque grey ink jet ink composition according to claim 1; preferably, the substrate, support or object is made of metal, for example of iron, aluminium, or steel; of glass; of ceramic; of a material containing cellulose such as cellophane, paper, possibly coated or glazed, cardboard or wood; of an organic polymer, particularly of a thermoplastic polymer (plastic), for example chosen from among PVDCs, PVCs, polyesters, PETs, polyolefins, such as polyethylenes (PE) or polypropylenes (PP); of polymethyl methacrylate PMMA (“Plexiglas”); of fabric; of natural or synthetic rubber; or of any other non-porous or porous substance; or of a composite of several of the above materials.

18. Substrate, support or object according to claim 17, which is an extruded, moulded, blow-moulded, injection-moulded, or rotation-moulded part made of one or more organic polymer(s), in particular made of one or more thermoplastic polymer(s), preferably selected from polyvinylchlorides (PVCs), and polyolefins, such as polyethylenes (PEs) or polypropylenes (PPs); or made of rubber.

19. Substrate, support or object according to claim 18, wherein said part is selected from wires, cables, hoses, pipes, cable ducts, cable trays, and boxes, coatings and housings such as electrical boxes and cable boxes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0211] FIG. 1 is a photograph of a printed message obtained by jetting Ink composition 3 according to the invention, using a Markem-Imaje® printer 9040C (which uses the continuous deflected ink jet printing technique), on a white PE cable and on a black PE cable.

[0212] FIG. 2 is a photograph of a printed message obtained by jetting Ink composition 5 according to the invention, using a Markem-Imaje® printer 9040C (which uses the continuous deflected ink jet printing technique), on a black PE cable and on a white PE cable.

[0213] FIG. 3 is a photograph of a printed message obtained by jetting Ink composition 6 according to the invention, using a Markem-Imaje® printer 9040C (which uses the continuous deflected ink jet printing technique), on a black PE cable and on a white PE cable.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Examples (Part I)

[0214] In examples 1 to 7, opaque, grey, ink jet ink compositions according to the invention are prepared. These ink jet ink compositions according to the invention contain a black pigment

[0215] In comparative examples 1 and 2, opaque, grey, ink compositions not according to the inventions are prepared.

[0216] These ink compositions comprise, the ingredients, constituents, mentioned in Table I below, in the proportions mentioned in Table I below.

[0217] These compositions are generally prepared by simply mixing the ingredients.

[0218] The binder percentages are given as wt. % solid.

[0219] The Viscosity at 20° C. (mPa.Math.s/cPs), the conductivity at 20° C. (μS/cm), and ΔL*n and ΔL*b have also been specified in Table I.

[0220] ΔL*n is the colour difference between L*n, i.e. L* of the dried ink coated on a black strip of an opacity chart, and L*ref, i.e. L* (average) of the black strip (i.e. black background) of the opacity chart.

[0221] ΔL*b is the colour difference between L*b, i.e. L* of the dried ink coated on a white strip of an opacity chart, and L*ref, i.e. L* (average) of the white strip (i.e. white background) of the opacity chart.

TABLE-US-00001 TABLE 1 Not according to the invention According to the invention Constituents Comparative Comparative Example Example Example Example Example Example Example (wt. %) Example 1 Example 2 1 (limit) 2 (limit) 3 4 5 6 7 MEK 72.854 58.4 72.708 65.7 72.416 72.27 72.124 71.686 71.8 Vinnol ® E15/40A 5.988 4.8 5.976 5.4 5.952 5.94 5.928 5.892 5.9 Elvacite ® 2008 4.99 4 4.98 4.5 4.96 4.95 4.94 4.91 4.9 White pigment 14.97 12 14.94 13.5 14.88 14.85 14.82 14.73 14.8 dispersion KPF.sub.6 Potassium 0.7984 0.64 0.7968 0.72 0.7936 0.792 0.7904 0.7856 0.8 Hexafluoro- phosphate BYK-UV 3500 ® 0.1996 0.16 0.1992 0.18 0.1984 0.198 0.1976 0.1964 0.1968 Black pigment 0.2 20 0.4 10 0.8 1 1.2 1.8 1.2 dispersion Yellow pigment 0 0 0 0 0 0 0 0 0.4 dispersion Total wt. % 100 100 100 100 100 100 100 100 100 ΔL * n 51 4 47.5 12 44 42 38 34 38 ΔL * b 12 88 20 79 32 35.5 42 47 42 Conductivity 1142 1175 1145 1161 1147 1149 1151 1155 1130.00 (MS/cm at 20° C.) Viscosity 4.7 4.95 4.71 4.86 4.75 4.76 4.79 4.8 4.8 (mPa .Math. s − 1/ 20° C.) Wt. % white 9.7305 7.8 9.711 8.775 9.672 9.6525 9.633 9.5745 9.594 pigment Wt. % black 0.051 5.1 0.102 2.55 0.204 0.255 0.306 0.459 0.306 pigment Wt. % yellow 0 0 0 0 0 0 0 0 0.1 pigment

[0222] The white pigment dispersion is a dispersion in MEK, containing 65 wt. % Pigment White 6 (TiO.sub.2, Rutile form) available from the Kronos® Company under the denomination “Kronos® 2064”.

[0223] The black pigment dispersion is a dispersion in MEK, containing 25.5 wt. % Carbon Black.

[0224] The yellow pigment dispersion is a dispersion in MEK, containing 25 wt. % Pigment Yellow 83.

[0225] ELVACITE® 2008 is an acrylic resin available from Lucite International.

[0226] More exactly, ELVACITE® 2008 is a low molecular weight methylmethacrylate copolymer.

[0227] ELVACITE® 2008 has methacrylic acid incorporated for pigment dispersions.

[0228] VINNOL® E15/40A is a hydroxyl-containing copolymer of approx. 84 wt % vinyl chloride (VC) and approx. 16 wt. % of acrylic acid esters, available from Wacker Chemie AG.

[0229] BYK-UV 3500® is a crosslinking, silicone-containing surface additive, namely a Polyether-modified, acryl-functional polydimethylsiloxane, available from the BYK company.

[0230] Let us specify that the weight percentages of the pigment dispersions specified in the above Table I, are expressed as a weight percentage of the liquid dispersions on the total weight of the ink composition.

[0231] The dynamic viscosities were measured at 20° C., by means of a viscometer with coaxial cylinders, namely the “low shear 30” from the Contraves® Company at a shearing rate of 60 s.sup.−1.

[0232] The electric conductivities were measured at 20° C. with a commercially available conductimeter of the Radiometer® Company.

[0233] The ink compositions recited in Table I above were coated on opacity charts and allowed to dry in air at room temperature.

[0234] Said opacity charts were opacity charts Leneta Form 2A from Labomat®.

[0235] Leneta Form 2A are black and white sealed opacity charts. The top is black and the bottom is white with overall dimensions of 5-½×10 inches (140×254 mm).

[0236] The handcoater is a K Control Coater from RK Printcoat Instruments.

[0237] The coating conditions were as follows: [0238] N° 2 Bar. [0239] Speed 6.
The coated thickness is very precisely defined by the specific bar used for coating, namely the N° 2 bar.

[0240] L*, a*, and b* of the dried coated ink compositions were measured in CIELAB coordinates, CIELAB color space (also known as CIE L*a*b*) by means of an eXact® spectrophotometer of the X-rite Pantone® company using the following measurement conditions: [0241] Illuminent D65; [0242] Viewing angle: 10°; [0243] Polarizing filter: M3; [0244] Measurements: [0245] Three L*, a*, and b* measurements on the white area of the opacity chart (left-middle-right); [0246] Three L*, a*, and b* measurements on the black area of the opacity chart (left-middle-right).
L* is the lightness from black (0) to white (100).
L*b is the averaged value of the three L*, a*, and b* measurements on the white area of the opacity chart.
L*n is the averaged value of the three L*, a*, and b* measurements on the black area of the opacity chart.

[0247] L*ref, i.e. L* (average) of the black strip (i.e. black background) of the opacity chart, and L*ref, i.e. L* (average) of the white strip (i.e. white background) of the opacity chart, were also measured.

[0248] L*ref, i.e. L* (average) of the black strip (i.e. black background) of the opacity chart was 1.71 with a standard deviation of 0.39, and L*ref, i.e. L* (average) of the white strip (i.e. white background) of the opacity chart was 93.24 with a standard deviation of 0.08.

[0249] ΔL_*n and ΔL_*b were then calculated.

[0250] ΔL*n=L*n−L*ref, i.e. L* (average) of the black strip of the opacity chart.

[0251] ΔL*b=L*b−L*ref, i.e. L* (average) of the white strip of the opacity chart.

[0252] ΔL_*n and ΔL_*b of the dried coated ink compositions according to the invention of examples 1 to 7 clearly show that all said inventive ink compositions give grey marking having high contrast both on white surfaces and black surfaces and are therefore easily legible, visible, on both substrates.

[0253] ΔL_*n and ΔL_*b are corresponding to contrast (i.e. contrast between the marking consisting of the dried coated ink composition and the support, background) measurements. The higher the values of ΔL_*n and ΔL*b the more the marking is visible.

When ΔL_*n and ΔL_*b are close to each other, visibility of the marking is optimal both on the white background and on the black background.
The optimal values of ΔL_*n and ΔL_*b (examples wherein visibility, legibility of the marking is the best) are both close to 40.

[0254] Contrast, legibility, visibility, of the dried coated ink compositions prepared as above on opacity charts, were assessed with the naked eyes by several observers, namely a panel of four observers.

[0255] Contrast, legibility, visibility, of the ink compositions according to the invention (Examples 1 to 7) proved to be good: See Table II below.

TABLE-US-00002 TABLE 11 Comparative Comparative Example Example Example Example Example Example Example Example 1 Example 2 1 (limit) 2 (limit) 3 4 5 6 7 Visibility on black good hardly good visible good good good good good background- visible Observer 1 Visibility on black good not good visible good good good good good background- visible Observer 2 Visibility on black good not good visible good good good good good background- visible Observer 3 Visibility on black good not good visible good good good good good background- visible Observer 4 Visibility on white hardly good visible good good good good good good background- visible Observer 1 Visibility on white not good visible good good good good good good background- visible Observer 2 Visibility on white not good visible good good good good good good background- visible Observer 3 Visibility on white hardly good hardly good good good good good good background- visible visible Observer 4

[0256] Accordingly, the ink compositions according to the invention which give printed messages, markings having good contrast, good legibility, both on black surfaces and on white surfaces, i.e. the two extremes on the colorimetric scale, will also obviously have good contrast, good legibility on all surfaces having colours intermediate between these two extremes such as dark coloured surfaces and light coloured surfaces. [0257] Ink compositions 3, 5 and 6 according to the invention were also jetted, using a Markem-Imaje® printer 9040C, which uses the continuous deflected ink jet printing technique (but other printers may be used), on black PE cables, and on white PE cables.

[0258] FIGS. 1, 2 and 3, clearly show that all the printed messages, markings, have a good contrast, a high printing quality, are legible, and visible, both on black PE cables, and on white PE cables.

[0259] More precisely, the printing quality is high and the markings visually appear as distinct, well separated, round dots (or droplets), which do not merge with each other and the printed message is clear, easily legible, visible and has a good contrast

[0260] In other words, the marking dots exhibit a high definition and do not smear or smudge. [0261] Ink compositions 3, 4, 5 and 6 according to the invention were also jetted using a Markem-Imaje® printer 9040C, which uses the continuous deflected ink jet printing technique (but other printers may be used), on colored substrates.

[0262] Said colored substrates are blue, red, yellow, orange, and green PE cables.

[0263] Colour photographs of the printed messages, markings were taken. All printed messages, markings, have a good contrast, a high printing quality, are legible, and visible, whatever the colour of the substrate.

[0264] More precisely, the printing quality is high and the markings visually appear as distinct, well separated, round dots (or droplets), which do not merge with each other and the printed message is clear, easily legible, visible and has a good contrast, whatever the colour of the substrate.

[0265] In other words, the marking dots exhibit a high definition and do not smear or smudge, whatever the colour of the substrate. [0266] Moreover, various tests were carried out, and clearly demonstrate that the ink compositions according to the invention (when jetted using a Markem-Imaje® printer 9040C, which uses the continuous deflected ink jet printing technique), such as the ink compositions of Table I, provide, especially on PE and PVC cables, markings that resist to friction, rubbing with a finger and with a gum, and are not damaged or erased.

[0267] Tests have also shown that markings obtained with the ink compositions according to the invention (when jetted using a Markem-Imaje® printer 9040C, which uses the continuous deflected ink jet printing technique) do not transfer (cables against cables with pressure and temperature being applied).

[0268] The markings obtained with the ink composition according to the invention also give good results when subjected to the “Scotch Tape” test.

[0269] Tests were also carried out clearly showing that the markings obtained with the opaque grey ink jet ink compositions according to the invention are also highly resistant to water, ethanol, isopropanol, and gasoline and to rubbing with said substances.

[0270] Other tests have been carried out and have actually demonstrated that the opaque grey ink jet ink compositions according to the invention have a high lightfastness.

[0271] Finally, tests have been carried out, and have actually demonstrated that all the above properties (resistance to friction, rubbing, non-transfer, resistance to solvents, lightfastness . . . ) of the ink compositions according to the invention such as the inks of examples 1 to 7 of Table I, containing only pigments as coloring agents and no dye, are far better than the properties of ink compositions containing a white pigment and a black dye. In particular, non-transfer and lightfastness of the ink compositions according to the invention are significantly improved when compared to non-transfer and lightfastness of ink compositions containing a white pigment and a black dye.

Examples (Part II)

[0272] In examples 1′ to 5′, opaque, grey, ink jet ink compositions according to the invention are prepared. These ink jet ink compositions according to the invention contain a black dye.

[0273] In Reference Example 1, a reference ink composition is prepared. This reference ink composition does not comprise any black pigment or dye and only comprise a white pigment.

[0274] In comparative examples 1′ and 2′, opaque, grey, ink compositions not according to the inventions are prepared.

[0275] These ink compositions comprise, the ingredients, constituents, mentioned in Table III below, in the proportions mentioned in Table III below.

[0276] These compositions are generally prepared by simply mixing the ingredients.

[0277] The binder percentages are given as wt. % solid.

[0278] The Viscosity at 20° C. (mPa.Math.s/cPs), the conductivity at 20° C. (μS/cm), and ΔL*n and ΔL_*b have also been specified in Table I.

[0279] ΔL*n is the colour difference between L*n, i.e. L* of the dried ink coated on a black strip of an opacity chart, and L*ref, i.e. L* (average) of the black strip (i.e. black background) of the opacity chart.

[0280] ΔL*b is the colour difference between L*b, i.e. L* of the dried ink coated on a white strip of an opacity chart, and L*ref, i.e. L* (average) of the white strip (i.e. white background) of the opacity chart.

TABLE-US-00003 TABLE III Not according to the invention According to the invention Constituents Reference Comparative Comparative Example Example Example Example Example (wt. %) Example Example 1′ Example 2′ 1′ (limit) 2′ (limit) 3′ 4′ 5′ MEK 73.0 72.982 65.700 72.964 66.795 72.927 71.175 69.715 Vinnol ® E15/40A 6.0 5.999 5.400 5.997 5.490 5.994 5.850 5.730 ELVACITE ® 2008 5.0 4.999 4.500 4.998 4.575 4.995 4.875 4.775 White pigment 15.0 14.996 13.500 14.993 13.725 14.985 14.625 14.325 dispersion (Salt) KPF.sub.6 0.8 0.800 0.720 0.800 0.732 0.799 0.780 0.764 Potassium Hexafluoro- phosphate BYK-UV 3500 ® 0.2 0.200 0.180 0.200 0.183 0.200 0.195 0.191 Black Dye 0.0 0.025 10.0 0.05 8.5 0.1 2.5 4.5 Yellow pigment 0.0 0 0 0 0 0.0 0.0 0.0 dispersion Total wt.% 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 ΔL * n 55 51 1 50.5 2 47 17 6.5 ΔL * b 0 4 91 7 92 12 72 84 Conductivity (μS/cm 1139 1138 1653 1140 1601 1154 1365 1463 at 20° C.) Viscosity (mPa .Math. s.sup.−1/ 4.66 4.68 8.02 4.71 7.52 4.76 5.78 6.37 20° C.) Wt. % white 9.75 9.747 8.775 9.745 8.921 9.74 9.506 9.311 pigment Wt. % black dye 0 0.025 10.0 0.05 8.5 0.1 2.5 4.5 Wt. % yellow 0 0 0 0 0 0 0 0 pigment Ratio Black Dye/ 0 0.002565 1.1396 0.00513 0.9528 0.0102 0.263 0.483 White pigment

[0281] The white pigment dispersion is a dispersion in MEK, containing 65 wt. % Pigment White 6 (TiO.sub.2, Rutile form) available from the Kronos® Company under the denomination “Kronos® 2064”.

[0282] The black dye is Solvent Black 27. This black dye is in the form of a powder (100% solid) available from Orient Chemical Industries Co. Ltd under the denomination VALIFAST® Black 3830.

[0283] The yellow pigment dispersion is a dispersion in MEK, containing 25 wt. % Pigment Yellow 83.

[0284] ELVACITE® 2008 is an acrylic resin available from Lucite International.

[0285] More exactly, ELVACITE® 2008 is a low molecular weight methylmethacrylate copolymer.

[0286] ELVACITE® 2008 has methacrylic acid incorporated for pigment dispersions.

[0287] VINNOL® E15/40A is a hydroxyl-containing copolymer of approx. 84 wt. % vinyl chloride (VC) and approx. 16 wt. % of acrylic acid esters, available from Wacker Chemie AG.

[0288] BYK-UV 3500® is a crosslinking, silicone-containing surface additive, namely a Polyether-modified, acryl-functional polydimethylsiloxane, available from the BYK company.

[0289] Let us specify that the weight percentages of the pigment dispersions specified in the above Table III, are expressed as a weight percentage of the liquid dispersions on the total weight of the ink composition.

[0290] The dynamic viscosities were measured at 20° C., by means of a viscometer with coaxial cylinders, namely the “low shear 30” from the Contraves® Company at a shearing rate of 60 s.sup.−1.

[0291] The electric conductivities were measured at 20° C. with a commercially available conductimeter of the Radiometer® Company.

[0292] The ink compositions recited in Table III above were coated on opacity charts and allowed to dry in air at room temperature.

[0293] Said opacity charts were opacity charts Leneta Form 2A from Labomat®.

[0294] Leneta Form 2A are black and white sealed opacity charts. The top is black and the bottom is white with overall dimensions of 5-½×10 inches (140×254 mm).

[0295] The handcoater is a K Control Coater from RK Printcoat Instruments.

[0296] The coating conditions were as follows: [0297] N° 2 Bar. [0298] Speed 6.
The coated thickness is very precisely defined by the specific bar used for coating, namely the N° 2 bar.

[0299] L*, a*, and b* of the dried coated ink compositions were measured in CIELAB coordinates, CIELAB color space (also known as CIE L*a*b*) by means of an eXact® spectrophotometer of the X-rite Pantone® company using the following measurement conditions: [0300] Illuminent D65; [0301] Viewing angle: 10°; [0302] Polarizing filter: M3; [0303] Measurements: [0304] Three L*, a*, and b* measurements on the white area of the opacity chart (left-middle-right); [0305] Three L*, a*, and b* measurements on the black area of the opacity chart (left-middle-right).
L* is the lightness from black (0) to white (100).
L*b is the averaged value of the three L*, a*, and b* measurements on the white area of the opacity chart.
L*n is the averaged value of the three L*, a*, and b* measurements on the black area of the opacity chart.

[0306] L*ref, i.e. L* (average) of the black strip (i.e. black background) of the opacity chart, and L*ref, i.e. L* (average) of the white strip (i.e. white background) of the opacity chart, were also measured.

[0307] L*ref, i.e. L* (average) of the black strip (i.e. black background) of the opacity chart was 1.71 with a standard deviation of 0.39, and L*ref, i.e. L* (average) of the white strip (i.e. white background) of the opacity chart was 93.24 with a standard deviation of 0.08.

[0308] ΔL_*n and ΔL_*b were then calculated.

[0309] ΔL*n=L*n−L*ref, i.e. L* (average) of the black strip of the opacity chart.

[0310] ΔL*b=L*b−L*ref, i.e. L* (average) of the white strip of the opacity chart.

[0311] ΔL_*n and ΔL_*b of the dried coated ink compositions according to the invention of examples 1′ to 5′ clearly show that all said inventive ink compositions give grey marking having high contrast both on white surfaces and black surfaces and are therefore easily legible, visible, on both substrates.

[0312] ΔL*n and ΔL*b are corresponding to contrast (i.e. contrast between the marking consisting of the dried coated ink composition and the support, background) measurements. The higher the values of ΔL*n and ΔL*b the more the marking is visible.

When ΔL*n and ΔL*b are close to each other, visibility of the marking is optimal both on the white background and on the black background.
The optimal values of ΔL*n and ΔL*b (examples wherein visibility, legibility of the marking is the best) are both close to 40.

[0313] Contrast, legibility, visibility, of the dried coated ink compositions prepared as above on opacity charts, were assessed with the naked eyes by several observers, namely a panel of four observers.

[0314] Contrast, legibility, visibility, of the ink compositions according to the invention (Examples 1′ to 5′) proved to be good: See Table IV below.

TABLE-US-00004 Comparative Comparative Example Example Example Example Example 1′ Example 2′ 1′ (limit) 2′ (limit) 3′ 5′ Colour of the ink dot Black Anthracite Grey on Black grey Background Visibility on black Not visible Visible Visible background- Observer 1 Visibility on black Not visible Visible Visible background- Observer 2 Visibility on black Not visible Visible Visible background- Observer 3 Visibility on black Not visible Visible Visible background- Observer 4 Colour of the ink dot White Grey Grey on white background Visibility on white Not visible visible visible background- Observer 1 Visibility on white Not visible visible visible background- Observer 2 Visibility on white Not visible visible visible background- Observer 3 Visibility on white Not visible Not visible background- visible Observer 4 Visibility on white Not visible Not visible background- visible Observer 5

[0315] Accordingly, the ink compositions according to the invention, containing a black pigment or a black dye as well, which give printed messages, markings having good contrast, good legibility, both on black surfaces and on white surfaces, i.e. the two extremes on the colorimetric scale, will also obviously have good contrast, good legibility on all surfaces having colours intermediate between these two extremes such as dark coloured surfaces and light coloured surfaces.