FR2899593A1 - Aqueous jet ink comprises coloring agents, preferably dyes, organic solvents, surfactants, optionally additives and wetting agents - Google Patents

Abstract

Aqueous jet ink (I) comprises a coloring agent (1-7 wt.%), preferably dyes, and further comprises an organic solvent (solvent (A) (up to 7 wt.%) and/or solvent (B) (up to 10 wt.%)), surfactant (0.05-2 (preferably 0.05-1) wt.%), optionally additives, wetting agents (5-20 wt.%), and (I) exhibits a static surface tension of 23-40 mN/m at 25[deg]C. Aqueous jet ink (I) comprises a coloring agent (1-7 wt.%), preferably black, yellow, cyan or magenta colored coloring agents or dyes, where (I) further comprises an organic solvent (solvent (A) (up to 7 wt.%) having a boiling point of more than 205[deg]C; and/or solvent (B) (up to 10 wt.%) having a boiling point of less than 205[deg]C); surfactants (0.05-2 (preferably 0.05-1) wt.%), optionally additives, wetting agents (5-20 wt.%) in the form of glycerin, urea and/or urea derivatives; where the quantity of (A), (B) or the sum of (A) and (B) amounts to at least 2 wt.% (preferably at least 5 wt.%) and (I) exhibits a static surface tension of 23-40 mN/m at 25[deg]C.

Description

The invention relates to an ink jet printing ink containing a

  dye, in particular a dye of black, yellow, cyan or magenta color, the ink also containing an organic solvent, surfactants, moisture-retaining agents, as well as, where appropriate, conventional additives. Inkjet printing or "Ink Jet printing" is a method of immediate direct contactless printing, without physical print form, which is based on thermal or electrophysical principles. The information to be printed is transferred to a print medium, usually paper, in the form of individual ink droplets. With the continuous jet process, the droplets are generated from a continuous ink jet coming out of a nozzle with a static overpressure. Excited by a piezoelectric converter, for example, the ink jet is then broken down into droplets of a defined size which, depending on the nature of the ink, are placed in the desired manner on the printing medium under the effect of a magnetic or electrostatic field. Unnecessary droplets are deflected by field effect to an ink return device. With respect to this, the droplet generation is performed "on demand" with the "Drop on Demand" method, namely by a targeted electrical pulse control of a droplet generator, which then delivers a droplet on demand. ink droplet from a nozzle. Piezoelectric, electromagnetic or electrostrictive converters are generally used as droplet generators. A particular position is occupied by said bubble jet method. The generation of droplets is in this case carried out thermally by means of the temporary overheating of a heating element arranged in the ink. The vapor bubble generated in this case discharges the ink above the heating element in the form of pulses, and leads to the output of a droplet of the associated nozzle, which is again placed on the support of 'impression. Compared to the aforementioned methods, mechanically moved components are removed with the bubble jet process. Since printheads with electrothermal converters can generally be of a smaller size and manufactured at a higher cost than heads with electromechanical conversion elements, bubble jet printers have nowadays a wide spread in the market. The inks used in inkjet printing are generally fluid inks based on water and / or solvents with a viscosity of the order of 1 to 30 mPa.s. In addition to the water component, essential for the steam generation in the bubble jet process, they generally contain a mixture of different organic solvents (in part up to eight components for controlling the drying time), and especially ketones (essentially methyl ethyl ketone), acetates, ether glycol, pyrrolidones, glycols, glycerin and alcohols (eg ethanol). The proportion of solvents for droplet technology on demand is generally in the range of 15 to 60% by weight. For the continuous inkjet process, the proportion of solvents can be up to 98% by weight. The dyes, which generally constitute an amount in the range of 2 to 6% by weight of the inkjet ink, are essentially soluble dyestuffs of high light fastness and high thermal stability. but in part also insoluble pigments with a particle size of less than about 3 μm, especially less than 1 μm.

  If it is necessary to adjust an electrical conductivity, a conductive salt is generally used to obtain electrical conductivity if possible greater than 104 52-1 cm-1. In the state of rest, the ink contained in the nozzles must not in the long run either dry out or become encrusted. Biocides are generally added to inkjet inks to develop sufficient storage so that they can not, for example, be infested with bacteria or mold. Ink-jet inks must be compatible with the materials of the ink tank, the ink supply and the print head; they must not be corrosive and therefore contain, for example, corrosion inhibitors. Other important parameters of the inks for the ink jet process are viscosity, surface tension and pH value. Depending on the system, the stated physical values of the inkjet ink should be tailored to the requirements of the individual case. It has been found that known inks do not desirably meet the requirements mentioned above when used in ink tanks or cartridges. Thus, it is desirable to increase the stability of the inkjet ink in the ink tank or the cartridge, and to improve the flow rate of the inkjet printing inks. from refilled ink tanks or cartridges to prevent the formation of streaks. Of course, there are proposals aimed at achieving an improvement by increasing the proportion of surfactants in inkjet printing inks to such an extent that they come out easily from the cartridges. Too high a proportion of surfactants has the drawback of generally leading to an undesirable high formation of foam. So-called "fish eyes" are formed further, which is the sign of the presence of troublesome insoluble proportions. In particular, the problems are not solved if the cartridge or the ink tank contains a sponge that can cause bubbles, which lead to an impaired impression. Other problems were related to the ink jet printing inks known hitherto, as they frequently led to streaking prints due to adhesion of the ink being printed on the nozzle plate and clogging of the nozzles. This problem occurs with many inks for inkjet printing and manifests itself particularly notably and unfavorably with high resolution printers and the printing of more and more common photos on normal papers. Expressed in an abstract manner, it was therefore necessary to improve the print quality, and also the print reliability, of such faster drying time inks. The solution of the problem mentioned above has certainly been the subject of various technical proposals in the state of the art. Thus, the publication EP 1 203 798 proposes to provide a low concentration of surfactants in the inkjet ink, but to choose a very large proportion of solvents. Ink-jet inks which, as a solvent, contain ethylene glycol in concentrations that are too high (eg more than 20%) are classified as harmful to health (hazard class Xn). Too high a concentration of solvents can lead to a degradation of their printing reliability. The ink-jet ink then has good wetting properties, but it stains the nozzle plate and causes nozzle deflections. Unwanted streaks are detectable in a fast print mode. Another proposal for solving the above-mentioned problems is given in EP 1,167,474 A1. This publication is strictly limited to defined surfactants, such as, for example, silicone-based surfactants. From a certain concentration, such surfactants can lead to smearing of the nozzle plate by the inkjet ink, which means degradation of the print quality of the ink for printing inkjet. The object of the invention is therefore to eliminate the above-mentioned problems inherent in the print quality and print reliability of inkjet printing inks, including the smudging of the printing plate. nozzles, and to prevent deviated nozzles. According to the invention, this object is achieved by an ink jet ink of the type mentioned in the introduction, in that it contains about 5 to 20% by weight of moisture-retaining agents in the form of glycerol, urea and / or a urea derivative, up to 7% by weight of a solvent A with a boiling point of more than 205 ° C and / or up to 10% by weight a solvent B with a boiling point of less than 205 ° C., about 0.05 to 2% by weight, in particular about 0.05 to 1% by weight of surfactants, and about 1 to 7% by weight of dye, in particular of dyestuff, the amount of solvent A, solvent B or the sum of the amount of solvent A and solvent B being at least about 2% by weight, in particular at least of the order of 5% by weight, and the inkjet ink having 25 C static surface tension of 23 to 40 mN / m.

  With regard to the ink jet ink according to the invention, it is generally appropriate to mention the following which contains a sufficient quantity of moisture-holding agents not to dry in the nozzles and not cause deflection of nozzles. The amount of organic solvents, which will still be explained in detail below, is limited for both solvent A and solvent B. This applies in a similar way also to their common use. However, a minimum limit must be respected, which will also be explained in detail below. If the concentrations are increased beyond the indicated values, this adversely affects the wetting properties of the inkjet ink and leads to smearing of the nozzle plate therewith. Because of the proportion of ink adhering to the nozzles, the droplets can not dissociate in a timely manner from the nozzles and are thus deviated. This leads to unwanted prints. The low evoked static surface tension leads to sufficiently fast drying of the inks on the printing medium (normal paper as well as photo paper). Examples of the solvent A indicated above are in particular solvents with a boiling point greater than 230 ° C., of which diethylene glycol (246 ° C.), triethylene glycol (287.6 ° C.) and butyltriglycol (260 ° C.) are part; , butyldiglycol (230.4 ° C.) and 2-pyrrolydone (245 ° C.), while examples for solvent B include solvents with a boiling point below 200 ° C., namely ethylene glycol ( 197 C), butyl glycol (171 C), isopropyl glycol (143 0C) and propylene glycol (187 C). When choosing the preferred solvent A and solvent B, the solvent A has a boiling point of less than 200 ° C., and the solvent B has a boiling point of greater than 230 ° C. The inkjet printing ink according to the invention contains about 0.05 to 2% by weight, especially about 0.05 to 1% by weight of surfactants. It is in this case preferred that the surfactant is contained in an amount of about 0.1 to 0.7% by weight. For the choice of surfactants, the invention is not significantly limited. The following surfactants are particularly relevant: silicone-based surfactants (polydimethyl siloxanes with modified polyether) and / or N-alkylpyrrolidones (especially 1-octyl-2-pyrrolidone or 1-dodecylcyclohexyl). 2-pyrrolidone), a surfactant in the form of an acetylene glycol surfactant being particularly advantageous in certain individual cases. This can be represented by the following general formula (III):

R 'R2 R3 ù C ù C C ù C ù R4 o o

  In which R 1, R 2, R 3 and R 4, which are respectively independent of one another, represent a weak alkyl radical, and the sum of n + m is between 0 and 30, in particular between 5 and 15. When using such a surfactant, it is particularly preferred that the mentioned alkyl radical contains 1 to 10 carbon atoms, in particular 1 to 4 carbons, with a particularly optimal adaptation of the different parameters of the ink. for inkjet printing according to the invention, the static surface tension at 25 C can advantageously be controlled, in particular in the range of 23 to 40 mN / m important according to the invention, the respect of this condition framework for the voltage The static surface leads to an optimum output flow of the ink-jet ink from the nozzles of the ink jet cartridge, and furthermore to the absence of streaks in the ink-jet image. It is particularly Advantageously, the stated static surface tension of the aqueous inkjet ink according to the invention is between about 26 and 36 mN / m. The nature of the dyes respectively contained in the ink according to the invention is not limited. It can be, both dyes and pigments, black dyes or pigments also relevant. The dyes are yellow dyes, magenta dyes, and cyan dyes commonly used in inkjet printing inks. For the yellow dyes, the direct yellow 143 and the acid yellow 23 are preferred, for the magenta dyes the acid red 52, the reactive red 23 and the acid red 27, for the cyan dyes the acid blue 9 and the direct blue 199, and for the black dyes, the direct black 168 and the reactive black 31. Instead of the dyes, it is also possible to use pigments, in particular pigments with a particle size of less than 500 nm, such as the blue pigment. 15: 3, red pigment 122, yellow pigment 74, yellow pigment 155 and black pigment 7.

  The coloring agents are contained in the ink jet ink according to the invention in the context of the order of 1 to 7% by weight defined according to the invention, especially in the range of about 2 at 5% by weight. In order to achieve the objective according to the invention in a particularly optimal way, it is advantageous to adjust the pH value appropriately. This is preferably between 5 and 10, especially between 6 and 9. Corrosion problems in the equipment are thereby eliminated. The addition of corrosion inhibitors is no longer necessary. Primary, secondary and / or tertiary amines are especially used for adjusting the pH value, alkanolamine, especially triethanolamine, being preferred. For the adjustment of the pH value, it is for example also possible to use caustic soda, any acids, buffers, such as ammonium acetate, and the like. The person skilled in the art has the possibility of improving the inkjet ink according to the invention by adding, according to the requirements profile, other usual additives. It may in this case be, for example stabilizers, wetting agents and / or preservatives, including biocides. For example, ethylene diamine acetic acid (EDTA) is one of the stabilizers. Particularly advantageous preservative agents are those associated with the following groups: thiazole and isothiazole compounds. In some individual cases, it may also be wise for the desired success that the aqueous ink jet ink contains a volatilization additive. it is an easily evaporable liquid which can preferably be mixed with water and which falls under the optional feature "other additives". It may for example be weak alcohols, especially alcohols containing about 1 to 4 carbon atoms. Preferred are methanol, ethanol, propanol, isopropanol, butanol, pentanol and their isomers. Isopropanol is particularly advantageous. The properties associated with this are reflected in particular faster drying ink for inkjet printing on paper and an improvement in staining resistance. The use of the volatilizing agent allows those skilled in the art to adjust the appropriate concentration without problems. Exceeding an upper limit of the order of 10 to 12% by weight, however, is not generally advisable. As the ink leaves the nozzles, this can lead to the formation of unwanted satellite droplets, and thus to a reduction in print quality, including edge sharpness and print contrast. For the applications of the invention, it has proved advantageous to adjust a kinematic viscosity [mm 2 / s] of the order of 1.3 to 3.0, which favors the achievement of the fixed objective. This applies in particular to the range of the order of 1.4 to 2.6. It has also been found that the inkjet printing inks according to the invention have a desirable stability of the surface tension. This is also the case with regard to the viscosity of the ink. The advantages that can be obtained with the ink according to the invention also reside in the fact that they lead to an improved flow rate of refilled cartridges and prevent the formation of streaks during printing. It has also been found that when the cartridges are recharged again after use, the ink introduced has optimum compatibility with the residual ink. The invention is further explained below in more detail using different formulations, which illustrate the qualitative and quantitative composition. These formulations also illustrate qualitative assessments.

Examples Description Example Example Example Example Example Example Raw 1 2 3 4 Comparative 1 Reason 2 Demineralized 78.15 77.95 71.23 80.55 65.05 69.85 Preservative 0.10 0.10 0.1 0.1 0.1 0.10 (Preventol D2 VP0C3058) (Biocide) Triethylene Glycol 12 Ethylene Glycol 10 5 Diethylene Glycol 5.00 5 10 15.00 Glycerin 15.00 10.00 10 10 6.00 Butyldiglycol 3.5 2.00 Urea 5 Triethanolamine 1.20 1.50 0.1 2.00 EDTA Tetrasodium salt 0.05 0.05 0.1 0.15 0.05 0.05 Surfynol 465 (surfactant 0, 50 0.40 0.5 0.4 acetylene glycol) Surfynol 440 (surfactant 0.15 0.15 0.15 0.1 0.15 acetylene glycol) Silwet L7607 (surfactant 0.02 0.5 silicone base) Acid red 52 (dye) 0.80 0.80 0.80 Red reagent 180 (dye) 4.05 4.05 4.05 Direct blue 199 (dye) 3.4 3.6 3 , 3 Total 100.00 100.00 100.00 100.00 100.00 100.00 Surface tension 29.4 30, 30 29.6 29.1 26.1 33.4 dyne / cm Viscosity [mm2 / s] 1.6 1.7 1.95 1.5 2.55 2.2 Print quality on very very very very much contrails normal paper good good good good Print quality on very very very very streaks good photo paper good good good good 11 35 Note: Quantity in parts by weight

Claims (11)

  An aqueous inkjet ink containing a dye, especially a dye of black, yellow, cyan or magenta color, the ink jet ink further containing an organic solvent, surfactants and the if appropriate, conventional additives, characterized in that the ink contains about 5 to 20% by weight of moisture-retaining agents in the form of glycerine, urea and / or a urea derivative, up to at 7% by weight of a solvent A with a boiling point of more than 205 ° C. and / or up to 10% by weight of a solvent B with a boiling point below 205 ° C., approximately 0.05 to 2% by weight, especially about 0.05 to 1% by weight of surfactants, as well as 1 to 7% by weight of dye, in particular of dyestuff, the amount of solvent A, solvent B or the sum the amount of solvent A and solvent B, being at least of the order of 2% by weight, in particular at least about 5% by weight, and the ink for jet printing ink having at 25 0C a static surface tension of 23 to 40 mN / m.   2. Ink for inkjet printing according to claim 1, characterized in that it contains the moisture maintaining agent in an amount of the order of 7 to 18% by weight, especially of the order of 9 to 16% by weight.   3. Ink jet ink according to claim 1 or 2, characterized in that it contains the surfactant in an amount of the order of 0.1 to 0.7% by weight.   Ink jet ink according to at least one of claims 1 to 3, characterized in that it contains a surfactant in the form of an acetylene glycol surfactant.   5. ink jet printing ink according to one of claims 1 to 4, characterized in that it has a static surface tension of the order of 26 to 36 mN / m.   6. Ink jet ink according to one of the preceding claims, characterized in that it has a pH value of 5 to 10, in particular 6 to 9.   Ink jet printing ink according to one of the preceding claims, characterized in that, for the adjustment of the desired pH value, it contains a primary, secondary and / or tertiary amine, in particular an alkanolamine.   Ink jet ink according to Claim 7, characterized in that the alkanolamine is present in the form of triethanolamine.   Ink jet ink according to one of the preceding claims, characterized in that it contains additives in the form of a stabilizer, a wetting agent and / or an agent. conservation, including biocides.   Ink jet ink according to one of the preceding claims, characterized in that the solvent A has a boiling point of less than 200 ° C, and that the solvent B has a boiling point. greater than 230 C.   Ink jet ink according to one of the preceding claims, characterized in that it has a kinematic viscosity [mm 2 / s] of the order of 1.3 to 3.0, especially from 1.4 to 2.6.