DE102017005949A1 - Process for the preparation of an ink and ink - Google Patents

Abstract

The invention relates to a method for producing an ink,
with the steps:
a) choice of a volatile, surface-active substance,
b) choice of the remaining components of the ink,
c) mixing the volatile surface-active substance after step a) with the components after step b).
An ink of the invention is disclosed.

Description

The invention relates to a method for producing an ink and to an ink as such.

State of the art

Surface phenomena are of critical importance in inkjet printing. They must be viewed to ensure controllable and efficient printing of an ink from an inkjet nozzle, that is, a thin capillary. For this, the nozzle must be wetted as well as possible and sufficiently with the ink. If the ink only wets the material of the nozzle very little, a so-called capillary depression is encountered in the nozzle, and an additional pressure against capillary pressure must be exerted by a piezo drive in order to eject the drops from the nozzle.

In the prior art, the wettability of the nozzle with an aqueous ink is adjusted by the addition of a surfactant (amphiphilic molecules). The surfactant forms an adsorption layer at the interface between the ink and the inkjet nozzle, as well as at the air-ink droplet surface, thus reducing the surface and interfacial tension of the ink. This allows efficient jetting of the drops. Normally, the ink has a very low viscosity of about 2-30 mPas and a surface tension in the range of about 25-40 mN / m.

Disadvantageously, the conventional surfactants have a low biodegradability, in particular in the case of perfluorinated surfactants. Also disadvantageously, the conventional surfactants constitute an additional component of the ink formulation that does not contribute to the functionality of the printed structures.

Object of the invention

The object of the invention is to provide a method for producing an ink, which is inexpensive and with which a higher resolution of the printed structures can be achieved, as with inks of the prior art. Further, it is an object of the invention to provide a related ink.

Solution of the task

The object is achieved with the method according to claim 1 and the ink according to the independent claim. Advantageous embodiments of this result in each case from the back-related claims.

Description of the invention

1. a) Wahl einer flüchtigen oberflächenaktiven Substanz,
2. b) Wahl der übrigen Komponenten der Tinte,
3. c) Mischen der oberflächenaktiven Substanz nach Schritt a) mit den Komponenten nach Schritt b).

The method according to the invention for producing an ink provides the following steps.

1. a) choosing a volatile surface-active substance,
2. b) choice of the remaining components of the ink,
3. c) mixing the surface-active substance after step a) with the components after step b).

• d) Messung der dynamischen und
• e) der statischen Oberflächenspannung der Tinte.

It is advantageously a

• d) Measurement of the dynamic and
• e) the static surface tension of the ink.

The steps d) and e) do not represent a time sequence.

A volatile surfactant completely or at least partially replaces the prior art surfactant. The volatile surfactant (FOS) is added to the ink formulation for this purpose.

• - Durch die Messung der dynamischen Oberflächenspannung wird die ausreichende Menge der flüchtigen, oberflächenaktiven Substanz in der Tintenformulierung überprüft. Hierzu kann ein Blasendrucktensiometer verwendet werden. Eine ausreichende Menge an flüchtiger, oberflächenaktiver Substanz ist erzielt, wenn die dynamische Oberflächenspannung etwa 50±10 mN/m bei einem Oberflächenalter von etwa 10-50 ms beträgt. Hierzu wird die flüchtige, oberflächenaktive Substanz in der Mischung aufgelöst und die dynamische Oberflächenspannung z. B. durch das Blasendrucktensiometer gemessen.
• - Durch die Messung der statischen Oberflächenspannung der Tinte wird die Flüchtigkeit der oberflächenaktiven Substanz überprüft. Flüchtigkeit der flüchtigen, oberflächenaktiven Substanz im Sinne der Erfindung liegt dann vor, wenn die statische Oberflächenspannung der Tinte nach der Mischung der Komponenten innerhalb einer Zeit von 3 Minuten um mindestens 3 mN*m^-1 ansteigt.

The volatile surface-active substance is selected from substances which, after mixing with the other components of the ink, have the following properties in the course of surface tension measurements:

• - By measuring the dynamic surface tension, the sufficient amount of the volatile surfactant in the ink formulation is checked. For this purpose, a bubble pressure tensiometer can be used. A sufficient amount of volatile surfactant is achieved when the dynamic surface tension is about 50 ± 10 mN / m with a surface age of about 10-50 ms. For this purpose, the volatile, surface-active substance is dissolved in the mixture and the dynamic surface tension z. B. measured by the bubble pressure tensiometer.
• - By measuring the static surface tension of the ink, the volatility of the surfactant is checked. Volatility of the volatile surfactant according to the invention is present when the static surface tension of the ink increases by at least 3 mN * m ^-1 within a period of 3 minutes after the components have been mixed.

Thus, a surfactant is chosen which will produce in the ink within 3 minutes an increase in surface tension of at least 3mN * m ^-1 at room temperature.

Surfactants used in the art for inks do not volatilize to that extent. Rather, the inks in the prior art show a lowering of the surface tension within several minutes.

In the context of the invention, it has been recognized that conventional surfactants previously used in inks have a negative influence on the dissolution of the final properties of the printed material. It has been found that the surfactant concentration added for the optimum surface tension values in the ink formulation simultaneously acts on the wetting of the substrate by the drops, which disadvantageously leads to larger end structures. This will prevent the printing of z. B. prevents thin lines. As a result, the overall geometry of the printed structures is difficult to control.

It has been recognized that an important additional surface phenomenon responsible for the quality of inkjet printing concerns the wetting and adhesion of the printed drops on the substrate. The production method according to the invention and the ink according to the invention achieve a much higher resolution of the printed structures. The more dots and the finer they are on the substrate, the more accurate and sharper the print becomes. It has been recognized that high resolution is significantly penalized by the use of prior art surfactants in ink formulations. The reason for this is that the surfactants provide a strong wetting of the substrate surface by the ink droplet. Due to wetting, the printed drops on the substrate become larger.

The process and thus prepared ink counteract these disadvantages by selecting a volatile surfactant which has the necessary surface property of the ink during jetting (nozzle wetting and nozzle exit) but after pressure from the nozzle of the surface the drop leaves the prior art because of high volatility of the selected surfactant as compared to prior art surfactants.

It has also been recognized that the volatile surfactant ink after drying has better adhesion of the printed structures to the substrate than conventional surfactant ink. The explanation for this is that the adsorption layer of the conventional surfactants on the substrate surface reduces the adhesion of the structures, so that usually a primer in the ink formulation must be used to combat the poor adhesion. The choice of a volatile surfactant avoids the problem of poor adhesion.

Therefore, it is advantageous with volatile, surface-active substances to sufficiently wet the nozzle without influencing the wetting of the substrate. After printing on the substrate or even during the printing process, the volatile, surface-active substance evaporates.

At the same time, the volatility causes a rapid evaporation of the surface-active substance. This advantageously causes a possible undesired interaction of the volatile surface-active substance with other components of the ink, such. As functional (nano) particles, dispersants, binders, rheology additives, and so on is prevented.

The choice of a volatile surfactant also advantageously has the effect of no longer adversely affecting the conductivity of printed metallic lines, as opposed to prior art surfactant adsorption layers.

The volatile surfactant also sufficiently wets the inkjet nozzle so that the ink is printable.

Unlike conventional surfactants as part of ink-jet inks, the volatile surfactant does not remain in the print image on the surface of the printed substrate.

On the one hand, the volatile, surface-active substance advantageously brings about an improvement in the wetting of the inkjet nozzle with the ink and, on the other hand, a greater resolution of the printed structures. This is accomplished by evaporating the volatile surfactant of the ink on the way from the nozzle to the substrate due to their high volatility, thus contributing to less wetting of the polymer substrate by printed drops. This advantageously has the effect of achieving a higher resolution, which contributes, for example, to thinner lines and smaller dots in the printed image.

As volatile, surface-active substance in particular fragrances such. As perfumes, aromatic or amphiphilic substances selected. The volatile surface-active substance is referred to hereinafter as a component with the abbreviation A.

The volatile surfactant acts on the dynamic surface tension of water and water-based mixtures. Inks according to the invention should have water as solvent.

The prior art conventional surfactants in prior inkjet inks are either completely or partially replaced by the volatile surfactant. This advantageously causes the dynamic surface tension, one of the most important parameters of inks, to be lowered.

The static surface tension or interfacial tension is the time-independent value of the surface tension in the thermodynamic equilibrium, in contrast to the dynamic surface tension, which is related to a certain surface age. Due to their adsorption on the surface or interface, surfactants cause a lowering of the surface tension or interfacial tension. After a certain time dependent on the system, a thermodynamic equilibrium is established between the surface concentration as the so-called excess concentration of the surfactant and the concentration in the volume phase. The static surface tension is the value measured in this state.

There is a difference between the dynamic surface tension or interfacial tension and the equilibrium value on the one hand and dynamic and static methods on the other hand. In a dynamic Tensiometer, z. B. a drop volume or bubble pressure tensiometer, the size of the interface changes during the measurement. Nevertheless, with a sufficiently slow change, an equilibrium value can often be measured in addition to the time-dependent values. In turn, even static methods in which the interface size does not change (eg in the case of the Wilhelmy plate method), the time course of the adjustment of the equilibrium can be followed.

According to the invention, the dynamic surface tension of the volatile, surface-active substance can be checked with a bubble-pressure tensiometer. This requires knowledge of the solubility of the volatile surface-active substance in water. Many additives of the invention are soluble in water in very small amounts.

To this end, the volatile surfactant is added in an amount in the aqueous solution which should be higher than its solubility in water, that is, a concentration higher than a saturated solution is set. The solubility of the selected volatile surface-active substance in water can be determined by the person skilled in the art. B. using relevant tables as a guide to determine.

A person skilled in the art can determine by means of the measurement of the dynamic surface tension, which concentration of the volatile surface-active substance selected by him achieves a lowering of the surface tension of the ink to the desired extent.

• • Plattenmethode nach Wilhelmy: Gemessen wird die auf eine optimal benetzbare, senkrecht in die Flüssigkeit eingetauchte Platte wirkende Kraft, siehe z. B. https://www.kruss.de/de/service/schulung-theorie/glossar/plattenmethodenach-wilhelmy
• • Stabmethode: Wie Plattenmethode, wobei für die Messung mit kleinerem Flüssigkeitsvolumen ein zylindrischer Stab mit kleinerer benetzter Länge verwendet wird.
• • Ringmethode nach Du Noüy: Gemessen wird die an einem optimal benetzbaren Ring wirkende Kraft, die beim Herausziehen des Ringes durch die Spannung der herausgezogenen Flüssigkeitslamelle wirkt. Die Methode ist nur quasi-statisch, da nur bei genügend langsamer Dehnung der Lamelle ein Gleichgewichtswert gemessen wird.
• • Spinning-Drop-Methode: Eine waagerechte Kapillare, gefüllt mit einer umgebenden Phase und einer Tropfenphase, wird in Rotation versetzt. Der Durchmesser des durch die Fliehkraft in die Länge gezogenen Tropfens korreliert mit der Grenzflächenspannung.
• • Methode des hängenden Tropfens (Pendant Drop): Die Form eines an einer Kanüle hängenden Tropfens wird durch die Oberflächenspannung und das Eigengewicht des Tropfens bestimmt. Aus dem Bild des Tropfens kann per Tropfenkonturanalyse die Oberflächenspannung ermittelt werden. Für die Ausführung von Schritt b) werden die anderen Komponenten der Tinte ausgewählt. Viele chemisch verschiedene Komponenten machen aus einem Tropfen Tinte ein hochkomplexes, technisches Gebilde. Die erfindungsgemäße Inkjet Tinte basiert auf Wasser.

According to the invention, the volatility of the volatile surface-active substance can be checked by a pendant drop method or by another static tensiometric method:

• • Plate method according to Wilhelmy: The force acting on an optimally wettable plate, immersed vertically in the liquid, is measured. B. https://www.kruss.de/de/service/schulung-theorie/glossar/plattenmethodenach-wilhelmy
• • Bar method: Same as plate method, using a cylindrical rod of smaller wetted length to measure with a smaller volume of liquid.
• • Ring method according to Du Noüy: Measures the force acting on an optimally wettable ring, which acts when the ring is pulled out by the tension of the liquid lamella pulled out. The method is only quasi-static, since an equilibrium value is only measured if the slat has stretched sufficiently slowly.
• • Spinning Drop Method: A horizontal capillary filled with a surrounding phase and a drop phase is rotated. The diameter of the drag drawn by the centrifugal force correlates with the interfacial tension.
• • Pendant drop method: The shape of a drop hanging from a cannula is determined by the surface tension and the weight of the drop. From the image of the drop, the surface tension can be determined by drop contour analysis. For the execution of step b), the other components of the ink are selected. Many chemically different components turn a drop of ink into a highly complex, technical entity. The inkjet ink according to the invention is based on water.

Some further components which are selected according to the invention according to step b) are, for. As color pigments, surfactants, adhesion promoters, functional (nano) particles, dispersants, binders, rheology additives and other additives.

The steps a ) and b ) also do not specify a time sequence, but can be performed in any order. The remaining components of the ink are hereinafter referred to as component with the abbreviation B.

The volatile surfactant preferably consists of a polar moiety, such as a functional group, and a non-polar moiety, such as a hydrocarbon backbone, which may advantageously result in amphiphilic compounds. But this is not a mandatory requirement.

• - Verbindungen mit einer Summenformel, die zwischen 4 und 13 Kohlenstoffatome enthalten; und/oder
• - die einen Verteilungskoeffizienten zwischen Oktanol und Wasser logP (auf der Basis von 10) zwischen 1,5 bis 4 aufweisen; und/oder
• - die einen Sättigungsdampfdruck von mindestens 3 µm Hg bei 25°C haben; und/oder
• - die eine der folgenden chemischen Funktionalitäten aufweisen:
  1. i. Ether mit der Summenformel R₁OR₂;
  2. ii. Aldehyd oder Nitril mit der Summenformel R₁X, mit X=CHO (Formyl-) oder X=CN (Nitrilgruppe);
  3. iii. Alkohol oder Phenol mit der Summenformel R₁OH; oder
  4. iv. Keton mit der Summenformel R₁COR₂
  5. v. Ester mit der Summenformel R₁CO₂R₂
  6. vi. oder die zu einer chemischen Stoffklasse von zyklischen oder linearen Terpenen bzw. Aromaten gehören;

Wobei R₁ und R₂ jeweils beliebig substituierte, verzweigte, zyklische oder lineare, auch untereinander verbundene Alkyl- Aryl- Aralkyl- und Alkarylreste darstellen können.Volatile surfactants in the context of the invention are, for. B. defined as:

• - compounds with a molecular formula containing between 4 and 13 carbon atoms; and or
• - have a partition coefficient between octanol and water logP (based on 10) between 1.5 to 4; and or
• - Have a saturation vapor pressure of at least 3 microns Hg at 25 ° C; and or
• - having one of the following chemical functionalities:
  1. i. Ethers with the empirical formula R ₁ OR ₂ ;
  2. ii. Aldehyde or nitrile with the empirical formula R ₁ X, with X = CHO (formyl) or X = CN (nitrile group);
  3. iii. Alcohol or phenol with the empirical formula R ₁ OH; or
  4. iv. Ketone with the molecular formula R ₁ COR ₂
  5. v. Esters with the empirical formula R ₁ CO ₂ R ₂
  6. vi. or belonging to a chemical class of cyclic or linear terpenes or aromatics;

Wherein R ₁ and R _{2 may} each represent any desired substituted, branched, cyclic or linear, also interconnected alkyl aryl aralkyl and alkaryl radicals.

In particular, volatile surfactants can be selected from the wide range of commercially available fragrances.

A list of potentially suitable alcohols, ketones, aldehydes, esters, ethers, nitrites, and alkenes such as. B. Terpenes may be the subject of the publication "Perfume and Flavor Chemicals", Vols. I and II; Steffen Arctander Allured Pub. Co. (1994) and "Perfumes: Art, Science and Technology"; Muller, PM and Lamparsky, D., Blaclde Academic and Professional (1994) , remove.

The possible volatile surface-active substances also include so-called hydrotrophic amphiphiles and Solvo surfactants (Solvo surfactants) with volatile properties, such as. B. off Lunkenheimer et al. (Dowanol DPnB in water as an example of a solvov surfactant system: adsorption and foam properties, 2004. Progr. Colloid Polym Sci 126: 14-20 ).

Other volatile surface-active substances are those in the publication US 2009/0137450 A1 counted chemical substances, see tables 1 and 2 there.

The volatile surface-active substances mentioned in the three abovementioned citations are incorporated by incorporation into the present patent application.

The surface-active substance can be selected to a first approximation from substances having a molecular weight Mn between 70 and 300. Butanol is then a volatile, surface-active substance in the context of the invention. In principle, however, all substances which are volatile and thus evaporate again from the mixture during the flight or after the pressure are suitable as the surface-active substance.

With an aqueous solvent as one of the components after step b), water is first included without further constituents. Water is then part of component B.

However, step b) may also provide for the choice of a substantially water-based solvent. Essentially means that the aqueous solvent further additives for an inkjet ink, such. As pigments, or other coloring or the conductivity of the printed structures influencing impact substances may be attached, as indicated above. For example, gold particles, silver particles or soot particles or graphene particles or graphite particles can then be suspended in the water. On this the selection of step b) is not yet limited. It can in the water z. B. other metal nanoparticles, ceramic nanoparticles, sols, gels, polymers, biomolecules, pigments, inorganic and organic substances and thickeners are suspended.

The thickening agents in the context of the invention basically include all substances which are miscible with water and have a higher viscosity than the aqueous solvent and thus increase the viscosity of the ink after mixing with water compared to the aqueous solvent alone.

The mixing of the two substances A and B takes place in the laboratory z. B. by the skilled person available measures and standard devices, eg. B. with a vortex, ultrasonic device, magnetic or KPG stirrer or other mixing methods according to the prior art.

Care should be taken that by mixing the two substances a ) and b ) and according to the step c ) a viscosity of about 10 to 15 cP at 25 ° C is achieved. Then, the ink advantageously has a viscosity in which it can be well printed well from the nozzle of an ink jet print head in drop form.

One skilled in the art knows the viscosity of prior art water, it is about 0.9 cP at 25 ° C. As a rule, the person skilled in the art also knows the viscosity of conventional thickeners for inks. The skilled person can then estimate on the basis of his expertise, taking into account the volumes and degrees of purity, for example, which viscosity the ink after the step c ). The skilled person can also look up using relevant tables, which viscosity at certain volumes and degrees of purity of the ingredients by the mixture after c ) can be achieved approximately.

According to the step c ), the mixture is made for the inkjet ink.

The volatile surfactant may be used in a weight ratio of 10 ^-2 - 5 wt% in the ink.

Prior to the addition of the volatile surfactant, the viscosity and / or surface tension of the ink can be measured with a bubble pressure tensiometer. This gives the skilled person an indication of the amount of volatile surface-active substance to be added to the ink.

In the ink according to the invention, it is advantageous to allow a lower concentration of a surfactant than in the prior art in the printed material with the same dynamic effect, where appropriate the ink does not contain a surfactant.

The process according to the invention proposes to replace a proportion of about 50% to 100% of the surfactant according to the prior art by the volatile, surface-active substance.

In one embodiment of the invention, a volatile amphiphile is chosen as the surface-active substance.

In a further particularly advantageous embodiment of the invention, butoxybenzene and / or linalool and / or benzyl acetate and / or (3Z) -3-hexenyl acetate is selected as the volatile surface-active substance.

These substances are non-toxic in the case of linalool and benzyl acetate, and they have sufficient volatility in the above sense. These substances also have the necessary value of dynamic surface tension in aqueous solution (see 5 ).

The ink prepared in this way achieves the object of the invention and leads to improved resolution in the printed image.

An ink of the invention contains the volatile surfactant.

The ink advantageously has a viscosity of about 10-15 cp.

Immediately after step c), the ink has a static surface tension between 20-40 mN * m ^-1 . The ink then exhibits a measurable increase in static surface tension over a period of 3 minutes of at least 3 mN * m ^-1 .

The ink has a dynamic surface tension of about 50 ± 10 mN / m with a surface age of about 10-50 ms.

An ink according to the invention is packaged after its preparation and filled gas-tight.

embodiments

In addition, the invention will be explained in more detail with reference to embodiments and the accompanying figures, without this being intended to limit the invention.

Static surface tension measurements were made by the Pendant Drop method or the Wilhelmi plate method.

The pendant drop is the drop hanging from a cannula in a surrounding, liquid or gaseous phase, the shape of which results from the relationship between surface tension or surface tension and gravity. In the pendant-drop method, the surface tension or interfacial tension is calculated from the shadow image of a hanging drop by drop contour analysis. From the interfacial tension between inner and outer phase results in an increased pressure inside the drop. The relationship between the pressure difference Δp, the radii of curvature of the surface r ₁ and r ₂ and the interfacial tension is described by the Young-Laplace equation: $$\Delta p=\sigma \cdot \left(\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="DE102017005949A1\_0005.png,DE102017005949A1\_0007.png"\; state="\{\{state\}\}">r</figure-callout>}}_1}+\frac{1}{r_2}\right)$$

Under the influence of gravity, the hanging drop is deformed because, due to the weight force, a hydrostatic pressure is generated inside the drop, which influences the main curvature radii r ₁ and r ₂ takes ( 1 , State of the art).

Since the hydrostatic pressure is height-dependent, the curvature of the droplet boundary surface also changes in the vertical direction. This creates the characteristic "pear shape" of a hanging drop.

The degree of deviation from the spherical shape reflects the relationship between the weight of the drop and its surface tension. If the density difference between the phases is known, the surface tension can be calculated from the drop shape. The shape is not freely scalable; rather, the real dimensions of the drop are included in the calculation.
During a measurement, the image scale of the video image is first acquired in order to make the real drop dimensions accessible. The drop contour is then determined from the video image of the dosed drop by gray scale analysis. Subsequently, in a numerical method, a shape parameter designated B is varied until the calculated drop contour coincides with the actual one. From the density difference Δp and the adjusted B parameter, the interfacial tension is calculated.

• 1: Pendant Drop-Verfahren nach dem Stand der Technik.
• 2: Wirkungsprinzip des flüchtigen, amphiphilen Additivs als oberflächenaktiver Substanz.
• 3: Optische Mikroskopiebilder der gedruckten Inkjet Tropfen auf einem PEN Substrat für eine Tinte, bestehend aus Wasser und Ethylenglykol ohne oberflächenaktive Additive (oben), mit einem konventionellen Tensid Perfluoroctansäure (mittig) und mit einem flüchtigen erfindungsgemäßen oberflächenaktiven Additiv (Hier Linalool unten).
• 4: Pendant Drop Messung der Zunahme der statischen Oberflächenspannung der Tinte als Nachweis für die Flüchtigkeit der flüchtigen oberflächenaktiven Substanz.
• 5: Blasendruck Messungen der dynamischen Oberflächenspannung.

Show it:

• 1 : Pendant drop method according to the prior art.
• 2 : Principle of action of the volatile, amphiphilic additive as a surface-active substance.
• 3 : Optical microscopy images of the printed inkjet drops on a PEN substrate for an ink consisting of water and ethylene glycol without surface-active additives (top), with a conventional surfactant perfluorooctanoic acid (in the middle) and with a volatile surface-active additive according to the invention (here linalool below).
• 4 : Pendant Drop Measurement of the increase in the static surface tension of the ink as evidence of the volatility of the volatile surfactant.
• 5 : Bubble pressure measurements of the dynamic surface tension.

The mode of action of the volatile, surface-active substance during the printing process is in the 2 shown. There is sufficient wetting of the nozzle without affecting the wetting of the substrate. After printing on the substrate or even during the printing process, the volatile surface-active substance evaporates.

After preparing an ink by adding water to the thickener ethylene glycol (molar ratio of ethylene glycol x _EG = 0.54) and carbon black as the active component at room temperature, the viscosity (η) and the static and dynamic surface tension (γ) of the ink were measured.

The viscosity was determined using a Brookfield LVDV3T viscometer, the surface tension being measured by the Wilhelmy plate method using a Kino Surface Tensiometer Model A3. In this method, the surface tension of a monomolecular film at the interface between a liquid and the air was measured by means of an analytical balance. This determines the force necessary to hold the plate in the same position.

The surface tension of an ink is determined here before linalool is added to reduce the surface tension. The static surface tension of the ink without additives is 57.7 mN * m ^-1 . The surface tension in the ink needed for printing was determined empirically for the given ink and after addition of the additives is between 20 and 40 mN * m ^-1 . The desired static surface tension was adjusted by addition of a surfactant and then re-controlled by the Wilhelmy plate method.

By the addition of 5.5 μl (to wt% of 4.72 x 10 ^-2 %) of the volatile, surface-active substance linalool to beyond saturation, according to IUPAC 3,7-dimethyl-1,6-octadiene-3 ol, purchased from Sigma Aldrich at 10.0 g to the ink at 20 ° C, the static surface tension is lowered from 57.7 to 26.2 mN * m ^-1 , whereby jetting of the ink, in advance no or only limited jetting was possible, is now possible. The time-dependent static surface tension of the ink increases by about 10 mN * m ^-1 in three minutes. The dynamic surface tension is in the range of 55 ± 5 mN / m with a surface age of 50 ms shown here by the example of 6.9 g * l ^-1 benzyl acetate or saturated benzyl acetate solution in water. For Linalool corresponding values are achieved.

The same experiment was conducted with a commercially available perfluorinated surfactant-based additive by measuring the surface tension of the ink after the addition of 300 μl (to wt% of 2.9 x 10 ^-4 %) of an aqueous DX4000 (purchased from Dynax ) 0.1 wt% solution is measured. The surface tension is lowered from 57.7 to 33.1 mN * m ^-1 . Microscopy images of 10 by 10 inkjet drops were taken on a flexible polyethylene naphthalate (PEN) substrate. The structures were made with a Unijet OJ300 inkjet printer, which is operated with the "OmniJet300 DMCDPN" software. When printing the drops, the same waveform was used with a voltage of 20 V, dwell-time of 10 μs, rising and falling time for all inks.

The optical images were examined directly after printing with a Carl Zeiss Ag microscope and recorded using an AxioCamMR5 camera. By measuring the mean droplet size ( x After printing, it can be determined whether the surface-active volatile additives evaporate or remain in the ink after the drops have landed on the substrate, by adding a volatile, surface-active additive ( 3 , bottom, γ = 26.2 mN / m), with a conventional surfactant ( 3 , center, γ = 33.1 mN / m) and without surface-active additives ( 3 , above, γ = 57.7 mN / m).

Since the conventional surfactant remains at the interface between the ink drop and the substrate, the wetting between the two phases becomes stronger, and accordingly the mean drop size is significantly larger ( x = 69 μm) than in the case of the ink without any surface-active additives ( x = 37 μm). If you take the printed image of the ink with the linalool, you notice that the average drop size at x = 45 μm, which is closer to the value without additive. This indicates that the wetting between the ink and the substrate is not strong, proving that the surface tension of the ink has increased due to the evaporation of the surface-active, volatile additives.

4 shows the measurement of the static surface tension after step e) of the method according to the invention with the pending drop method. The initial value of the above mentioned constituents increased rapidly from 40 mN * m ^-1 to more than 50 mN * m ^-1 after 5 min. This proves that linalool has a volatility as required for the purposes of the invention.

In principle, the static and / or dynamic surface tension and / or a viscosity determination can therefore be determined before and / or after the addition of the volatile surface-active substance to the other components of the ink.

Bibliography:

1. [1] https://www.kruss.de/de/service/schulung-theorie/glossar/plattenmethode-nachwilhelmy/, 30.01.2017
2. [2] Prasanthi, D., and P. K. Lakshmi. „Terpenes: effect of lipophilicity in enhancing transdermal delivery of alfuzosin hydrochloride.“ Journal of advanced pharmaceutical technology & research 3.4 (2012): 216.

1. [1] https://www.kruss.de/de/service/schulung-theorie/glossar/plattenmethode-nachwilhelmy/, 30.01.2017
2. [2] Prasanthi, D., and PK Lakshmi. "Terpenes: effect of lipophilicity in enhancing transdermal delivery of alfuzosin hydrochloride." Journal of advanced pharmaceutical technology & research 3.4 (2012): 216.

LIST OF REFERENCE NUMBERS

1

Piezoelectric signal generator

2

Perfume molecule with a) hydrophilic head group and b) hydrophobic group

3

Ink reservoir in the printhead

4

jet

5

ink drops

6

substratum

7

print image

8th

Volatile surfactant

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2009/0137450 A1 [0040]

Cited non-patent literature

• "Perfume and Flavor Chemicals", Vols. I and II; Steffen Arctander Allured Pub. Co. (1994) and "Perfumes: Art, Science and Technology"; Muller, P.M. and Lamparsky, D., Blaclde Academic and Professional (1994). [0038]
• Lunkenheimer et al. Dowanol DPnB in water as an example of a solvov surfactant system: adsorption and foam properties, 2004. Progr. Colloid Polym Sci 126: 14-20 [0039]

Claims (15)

Process for producing an ink, comprising the steps of: a) choice of a volatile, surface-active substance, b) choice of the remaining components of the ink, c) mixing the volatile surface-active substance after step a) with the components after step b). Method according to one of the preceding claims, characterized by d) measurement of the dynamic surface tension of the ink. Method according to Claim 2 , characterized in that the dynamic surface tension of the ink after step d) is adjusted to about 50 ± 10 mN / m with a surface age of about 10-50 ms. Method according to one of the preceding claims, characterized by e) measurement of the static surface tension of the ink. Method according to the preceding claim, characterized in that an ink is selected with which, during the measurement after step e), the static surface tension of the ink increases by at least 3 mN * m ^-1 within a time of 3 minutes. Method according to one of the preceding claims, characterized in that before the mixing of the volatile surface-active substance with the other constituents of the ink, the surface tension and / or the viscosity of the ink is measured. Method according to the preceding claim, characterized by the choice of a fragrance as volatile, surface-active substance. Process according to the preceding claim, characterized by the choice of an amphiphile as volatile, surface-active substance. Method according to one of the preceding claims, characterized in that the remaining components of the ink comprise water and optionally a thickening agent. Ink containing a volatile surfactant. An ink according to any preceding claim, wherein the ink has a static surface tension between 20-40 mN * m ^-1 . An ink according to the preceding claim, characterized in that the ink has a static surface tension increase of at least 3mN * m ^{-1 over} a period of 3 minutes. An ink according to any one of the preceding three claims, wherein the dynamic surface tension is about 50 ± 10 mN / m with a surface age of about 10-50 ms. Ink according to one of the preceding four claims, characterized in that the ink contains a fragrance as volatile, surface-active substance. Ink according to one of the preceding five claims, characterized by a viscosity of about 10-15 cp.

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