THERMOCHROMIC INK COMPOSITION FOR INK JET PRINTING

Abstract

Thermochromic ink composition for ink jet printing, liquid at room temperature, comprising: a) a solvent; b) a binder; c) a heat resistant, and water or steam resistant pigment; d) a heat sensitive, and water or steam sensitive, dye;
wherein the pigment and the dye are selected to be complementary in the colour spectrum, and wherein said dye is capable of undergoing decomposition upon exposure to both heat and water or steam so that the colour of the ink composition or of a marking printed using said ink composition changes to the colour of the pigment upon exposure to both heat and water or steam.

Method for marking a substrate by spraying said ink composition onto this substrate, and substrate provided with a marking obtained by drying and/or absorption of said ink composition.

Method of indicating sterilization or pasteurization or autoclaving of a substrate using said ink.

Claims

1. A thermochromic ink composition for ink jet printing, liquid at room temperature, comprising: a) a solvent comprising one or several organic solvent compound(s); b) a binder, comprising at least one binding resin; c) a heat resistant, and water or steam resistant pigment; d) a heat sensitive, and water or steam sensitive, dye; wherein the pigment and the dye are selected so that the colour of the pigment and the colour of the dye are complementary in the colour spectrum, and wherein said heat sensitive, and water or steam sensitive dye is capable of undergoing decomposition upon exposure to both heat and water or steam so that the colour of the ink composition or of a marking printed using said ink composition changes to the colour of the heat resistant, and water or steam resistant pigment upon exposure to both heat and water or steam.

2. The ink composition according to claim 1, wherein the heat resistant, and water or steam resistant pigment is chosen from among Colour Index (C.I.) pigments.

3. The ink composition according to claim 1, wherein the heat sensitive, and water or steam sensitive dye is chosen from among Colour Index (C.I.) solvent dyes, such as metal complex dyes.

4. The ink composition according to claim 1, wherein the colour of the heat resistant, and water or steam resistant pigment is blue or green or red and the colour of the heat sensitive, and water or steam sensitive, dye is red or blue.

5. The ink composition according to claim 4, wherein the heat resistant, and water or steam resistant pigment is chosen from among Pigment Blue 60 and Pigment Blue 15:3.

6. The ink composition according to claim 4, wherein the heat sensitive, and water or steam sensitive, dye is Solvent red 160.

7. The ink composition according to claim 1, comprising from 0.5 to 15%, preferably from 1 to 10%, still preferably from 1 to 5% by weight of the heat resistant, and water or steam resistant pigment.

8. The ink composition according to claim 1, comprising from 0.5 to 15%, preferably from 1 to 10%, still preferably from 1 to 5% by weight of the heat sensitive, and water or steam sensitive, dye.

9. The 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 and combinations of two or more of the latter.

10. The 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. The 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. The 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. The 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, of one or several solvent compound(s) selected from among ketones with 3 to 10 carbon atoms, such as acetone, butanone (methyl-ethyl-ketone or “MEK”), pentanone-2 (methyl-propyl-ketone or “MPK”), pentanone-3 (diethyl ketone), methyl-3 butanone-2 (methyl-isopropyl-ketone or “MiPK”) and methyl-4 pentanone-2 (methyl isobutyl ketone or “MIBK”).

14. The ink composition according claim 1, in which the solvent consists of one or several solvent compound(s) selected from among ketones with 3 to 10 carbon atoms, such as acetone, butanone (methyl-ethyl-ketone or “MEK”), pentanone-2 (methyl-propyl-ketone or “MPK”), pentanone-3 (diethyl ketone), methyl-3 butanone-2 (methyl-isopropyl-ketone or “MiPK”) and methyl-4 pentanone-2 (methyl isobutyl ketone or “MIBK”)

15. The ink composition according to claim 13, in which the solvent comprises a majority amount by weight relative to the total weight of the solvent of MEK, preferably, the solvent consists of MEK.

16. The ink composition according to claim 1, also 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 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, formates, acetates, sulphates, propionates, trifluoroacetates, triflates (trifluoromethane sulphonates), hexafluorophosphates, hexafluoroantimonates, tetrafluoroborates, picrates, carboxylates or sulphonates.

17. The ink composition according to claim 1, that has a conductivity in the liquid state greater than or equal to 5 μS/cm at 20° C., preferably greater than or equal to 300 μS/cm à 20° C., even more preferably greater than or equal to 500 μS/cm at 20° C.

18. A method for marking a substrate, support or object, article, by spraying an ink onto this substrate, support or object, article, using an ink jet printing technique, characterised in that the sprayed ink is an ink composition according to claim 1.

19. A substrate, support or object, article, characterised in that it is provided with a marking obtained by drying and/or absorption of the ink composition according to claim 1; preferably, the substrate, support or object, article is made of metal, for example of iron, aluminium; of an alloy, for example of 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 PVDC, PVC, polyesters, PET, polyolefins, such as polyethylenes (PE), polypropylenes (PP); made 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.

20. A method of indicating sterilization or pasteurization or autoclaving of a substrate, support or object, article, which comprises the following successive steps: a) marking said substrate, support or object, article, by the method according to claim 18, namely by spraying an ink on said substrate, support or object, article, using an ink jet printing technique, the sprayed ink being an ink composition according claim 1, whereby a marked substrate, support or object, article, having a marking on at least one surface is obtained; b) exposing the marked substrate, support or object, article to both an elevated, high temperature and steam or water during a period of time so that the colour of the marking printed using said ink composition changes to the colour of the heat resistant, and water or steam resistant pigment; said elevated temperature being the temperature used in sterilization or pasteurization or autoclaving processes to complete the sterilization or pasteurization or autoclaving processes, and said period of time being the period of time used in sterilization or pasteurization or autoclaving process to complete the sterilization or pasteurization or autoclaving processes.

Description

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0225] The invention will be better understood upon reading the following description of embodiments of the invention, given as illustrative and non-limiting examples.

Examples

[0226] In all these examples, thermochromic ink compositions according to the invention are prepared.

[0227] These ink compositions comprise, the ingredients, constituents, mentioned in Table 1, in the proportions mentioned in Table 1.

[0228] These compositions are generally prepared by simply mixing the ingredients.

[0229] The binder percentages are given as wt. % solid, and the pigment percentages are given as wt. % solid.

[0230] The Viscosity at 20° C. (mPa.Math.s/cPs), the conductivity at 20° C. (μS/cm), the colour of the ink compositions (before sterilization), the L*a*b*, the Colour change after sterilization, and the Delta E (ΔE) have also been specified in Table 1.

TABLE-US-00001 TABLE I INK COMPOSITIONS Constituents (% by weight) Example 1 Example 2 Methyl-Ethyl- Ketone (MEK) 82.85 82.85 Copolymer of vinyl chloride 9.5 9.5 and vinyl acetate (Vinnol ® H14/36TF Tetrabutyl ammonium 1.2 1.2 hexafluorophosphate Polyether modified 0.1 0.1 polysiloxane Pigment blue 60 (50% 4.5 dispersion in vinyl resin) Pigment blue 15:3 (50% 4.5 dispersion vinyl resin) Solvent red 160 1.85 1.85 Viscosity at 20° C. (mPa .Math. s/ 5.1 5.1 cPs) Conductivity at 20° C. 850 850 (μS/cm) Colour black black L*a*b* See below See below Colour change after from black to from black to sterilization blue blue Delta E >15 >15

[0231] Let us specify that the weight percentage of the dispersion of pigment(s) is expressed as a weight percentage of solid pigment based on the total weight of the ink composition and not on the percentage of liquid dispersion, the concentration of which may vary.

[0232] The dynamic viscosities have been measured by means of a viscometer with coaxial cylinders namely a Brookfield LVT viscometer, at a shearing rate of the order of 60 s.sup.−1 or a viscometer of the “Couette” type of the Contraves® Company.

[0233] The electric conductivities have been measured with a commercially available conductimeter of the Radiometer® Company.

[0234] The ink compositions according to the invention of examples 1 and 2, were sprayed, using Markem-Imaje® printers 9450 and 9040, which use the continuous deflected ink jet printing technique (but other printers may be used) on PET, aluminium, steel, stainless steel, iron or other metals, and Polypropylene substrates shaped as foils, cans, or bottles.

[0235] L*, a*, and b* were measured by means of an eXact® spectrophotometer of the Xrite® company with a M3 filter, i.e. reflectance being measured with an illuminent A having a crossed polarization excluding UV component (previously polarized filter).

[0236] ΔE was calculated according to CIE-1976.

[0237] On the same PET, aluminium, steel, stainless steel, iron or other metals, and Polypropylene substrates, a Markem-Imaje® thermochromic Ink referenced 5595 (MI 5595) available on the market, was also sprayed using the same Markem-Imaje® printers, i.e. 9450 and 9040, and the same printing parameters, but other printers may be used. Said ink is used as a control ink or comparative ink because it is currently commonly used as a thermochromic ink for marking substrates to be sterilized.

[0238] Comparative ink MI 5595 is not an ink according to the invention.

[0239] One hour after having been marked the marked substrates are then steam sterilized at 121° C. for 30 minutes.

[0240] The properties of the markings are summarized in Table II below.

TABLE-US-00002 TABLE II Comparative Example: Example 1 Example 2 Ink 5595 Dry Rubbing with a OK (Marking OK (Marking OK (Marking finger, 10 back and unchanged, not unchanged, not unchanged, not forth movements. damaged or erased) damaged or erased) damaged or erased) Before sterilization. Color before and Black to blue Black to blue black to red after Sterilization Dry Rubbing with a OK (Marking OK (Marking OK but sometimes finger, 10 back and unchanged, not unchanged, not premature colour forth movements. damaged or erased) damaged or erased) change After sterilization. Printing quality after OK (visually: round OK (visually: round Spread marking: poor sterilization. dots, well separated) dots, well separated) definition of the dots - dots are merging making the message hardly readable

[0241] The colour changes observed with the inventive inks of Examples 1 and 2 are quite similar. L*, a*, b* of the black marking (marking before sterilization): L*<8//−1<a*<−0.5//−10<b*<0.6.

[0242] L*, a*, b* of the blue marking (marking after sterilization): L*<8//−15<a*<−10//−16<b*<−10.

[0243] Delta E (ΔE)>15.

[0244] Other tests were carried out using the following procedure.

[0245] The ink composition according to the invention, of example 1, was sprayed, using a Markem-Imaje® printer 9450 or 9040 on the same white part of a PET substrate (pouch).

[0246] Using the same procedure, a comparative ink composition was sprayed, using Markem-Imaje® printers 9450 and 9040 on the same white part of a PET substrate.

[0247] Said comparative ink is a Markem-Imaje® thermochromic Ink referenced 5595 (MI 5595) available on the market.

[0248] Said ink is used as control ink or comparative ink because it is currently commonly used as a thermochromic ink for marking substrates to be sterilized.

[0249] Comparative ink MI 5595 is not an ink according to the invention.

[0250] One hour after having been marked the marked substrates are then steam sterilized at 121° C. for 30 minutes.

[0251] The properties of the markings (L*, a*, b*) before and after sterilization are summarized in Table III below.

[0252] L*, a*, and b* were measured by means of an eXact® spectrophotometer of the Xrite® company with a M3 filter, i.e. reflectance being measured with an illuminent A having a crossed polarization excluding UV component (previously polarized filter).

[0253] ΔE was calculated according to CIE-1976.

TABLE-US-00003 TABLE III ΔE (Before and after L* a* b* Sterilization) Example 1 according to the invention Before Sterilization CIE L*a*b* Measurement 1 5.1244 19.2506 −35.7718 CIE L*a*b* Measurement 2 5.1876 19.3692 −35.7667 CIE L*a*b* Measurement 3 4.7651 18.7451 −35.2848 CIE L*a*b* Average of the above 5.0257 19.1216333 −35.6077667 measurements After Sterilization CIE L*a*b* Measurement 1 18.2399 12.6445 −49.6324 20.33 CIE L*a*b* Measurement 2 18.1788 12.2379 −48.931 19.95 CIE L*a*b* Measurement 3 16.8458 15.5115 −50.624 19.45 Average of the above 17.7548 13.4646 −49.7291 19.91 measurements Comparative example (MI 5595) Before Sterilization CIE L*a*b* Measurement 1 13.3518 38.314 19.374 CIE L*a*b* Measurement 2 13.9121 38.4673 19.5809 CIE L*a*b* Measurement 3 10.9368 36.1164 16.6288 CIE L*a*b* Average of the above 12.7335 37.6325 18.5279 measurements After Sterilization CIE L*a*b* Measurement 1 22.0826 40.7532 16.1508 10.14 CIE L*a*b* Measurement 2 20.5899 40.1068 16.4116 8.5 CIE L*a*b* Measurement 3 21.3666 40.449 16.4649 9.31 Average of the above 21.34637 40.43633 16.34243 9.32 measurements
The ink from example 1 according to the invention shows ΔE>15 corresponding to no questionable colour change.

[0254] Still other tests were carried out using the following procedure.

[0255] The ink composition according to the invention, of example 1, was sprayed, using a Markem-Imaje® printer 9450 or 9040 on PET and aluminium substrates.

[0256] The PET substrates are shiny white or orange pouches. The PET and the aluminium substrates have or have not a punching oil residue on their surfaces.

[0257] Using the same procedure comparative ink compositions were sprayed, using a Markem-Imaje® printer 9450 or 9040 on the white part of a PET substrate.

[0258] Said comparative inks are a Markem-Imaje® thermochromic Ink referenced 5590 (MI 5590), a Markem-Imaje® thermochromic Ink referenced 5595 (MI 5595) available on the market, a Markem-Imaje® thermochromic Ink referenced 9560 (MI 9560) available on the market, a Videojet® thermochromic ink referenced V4274L available on the market, and a Videojet® thermochromic ink referenced V4275L available on the market.

[0259] Said inks are used as control inks or comparative inks because they are currently commonly used as a thermochromic ink for marking substrates to be sterilized.

[0260] Said comparative inks are not inks according to the invention.

[0261] One hour after having been marked, the marked substrates are then steam sterilized at 121° C. for 30 minutes.

[0262] The properties of the markings before and after sterilization are summarized in Table IV below.

[0263] It is shown from Tables III and IV that the ink from example 1 shows: [0264] Superior black colour strength before sterilization [0265] Very clear colour change after sterilization [0266] Higher printing quality [0267] Higher reliability (100%) in colour change with sterilization process [0268] No transfer.

TABLE-US-00004 TABLE IV Dry Rubbing Rubbing with a with a finger, 10 finger on oil, back and 10 back and forth forth movements. movements. Drying Before Before Sterilization Inks Substrates time Printing quality sterilization. sterilization Colour 121° C./30 min Example 1 Coloured 1 sec Good, even on Good Good Bluish black yes according PET oily substrates to the White PET 1 sec Good, even on Good Good Bluish black yes invention oily substrates Aluminium 1 sec Good, even on Good Good Bluish black yes oily substrates V4274L Coloured 5 sec Good but Good Good black yes (black to PET spread a lot on blue) oily substrates White PET 5 sec Good but Good Good black yes spread a lot on oily substrates Aluminium 5 sec Good but Good Good Greenish black yes spread a lot on oily substrates V4275L Coloured 4 sec Good but Good Good Greenish grey yes (black to PET spread a lot blue) with or without oiiy substrates White PET 4sec Good but Good Good Greenish grey yes spread a lot with or without oily substrates Aluminium 4 sec Good but Good Good Greenish blue yes spread a lot with or without oily substrates 5590 Coloured 5 sec Good but Good Good Greenish grey yes (black to PET spread a lot on blue) oily substrates White PET 5 sec Good but Good Good Greenish grey yes spread a lot on oily substrates Aluminium 5 sec Good but Good Bonne Greenish blue yes spread a lot on oily substrates 5595 Coloured 5 sec Good but Good Partial Red from the yes (black to PET spread a lot on disappearance start red) oily substrates White PET 5 sec Good but Good Partial Red from the yes spread a lot on disappearance start oily substrates Aluminium 5 sec Good but Good Partial Red from the yes spread a lot on disappearance start oily substrates 9560 Coloured 5 sec Good but Good Partial black yes (black to PET spread a bit on disappearance blue) oily substrates White PET 5 sec Good but Good Partial black yes spread a bit on disappearance oily substrates Aluminium 5 sec Good but Good Partial black yes spread a bit on disappearance oily substrates Dry Rubbing with a finger, 10 back and forth movements. After Inks Colour Change sterilization Printing quality Transfer Example 1 Yes- to blue Good Good No transfer according Yes- to blue Good Good to the Yes-to blue Good Good Not tested invention V4274L Not clear Good Good but spread a lot transfer (black to on oil blue) Not clear Good Good but spread a lot on oil Not clear Good Good but spread a lot Not tested on oil V4275L Not clear Good Spread a lot transfer (black to Not clear Good Spread a lot blue) Not clear-just more intense blue Good Spread a lot Not tested 5590 Yes- to blue Good Good but spread a lot transfer (black to on oil blue) Yes- to blue Good Good but spread a lot on oil Yes-to blue Good Good but spread a lot Not tested on oil 5595 No - Colour change before Good Good but spread a lot transfer (black to sterilization on oil red) No - Colour change before Good Good but spread a lot sterilization on oil No - Colour change before Good Good but spread a lot Not tested sterilization on oil 9560 No clear colour change Good Good transfer (black to No clear colour change Good Good blue) No clear colour change Good Good Not tested

[0269] Transfer was assessed as follows: Substrates were stacked and in contact during sterilization process. Transfer occurred if ink was transferred from the in contact surface of one substrate to the in contact surface of the other(s) substrate(s).

[0270] Table IV shows that the performances of the inventive ink of Example 1 are superior to the performances of comparative inks.

[0271] The ink according to the invention of Example 1: [0272] Exhibits 100% reliability in color change with sterilization process. [0273] Gives High Impression quality. [0274] Shows no transfer from one substrate to the other. [0275] Exhibits Oil fastness(less smudging on oily substrates), [0276] Clear color change always occurs after sterilization.