Use of a component in a composition, composition for laser transfer printing, and laser transfer printing method

Abstract

The invention relates to the use of a component in a composition and / or the use of a composition comprising a component. The invention is characterized in that the component is a laser-activatable component which is activated by laser irradiation during use such that the viscosity and / or the elasticity and / or the tack of the composition is increased on the basis of the temperature increase of the composition.

Description

[0001] USE OF A COMPONENT IN A

[0002] COMPOSITION

[0003] COMPOSITION FOR LASER TRANSFER PRINTING AND LASER TRANSFER PRINTING PROCESS

[0004] The invention relates to the use of a component in a

[0005] Composition, a composition for laser transfer printing, and a laser transfer printing process.

[0006] The state of the art provides the foundations for the so-called

[0007] Laser transfer printing known, wherein a laser beam-transparent carrier, arranged opposite a substrate to be printed, is equipped with a

[0008] The printing substance is coated, wherein by irradiating the coating with laser beam energy at a defined position on the substrate a part of the printing substance evaporates, wherein the non-evaporated printing substance at the defined position on the substrate is accelerated by the evaporated printing substance from the laser beam-transparent substrate towards the substrate, wherein the non-evaporated portion of the printing substance partially deposits at a specific target location on the substrate to form a coating.Regarding the individual and precise details concerning the fundamental procedural principles of the laser transfer printing process, full reference is made to the disclosures in patent specifications US 6,805,918 B2, EP 2474 004 Bl, EP 2 155 499 Bl, EP 1 268 211 Bl and EP 1 485 255 Bl, so that the disclosures therein also constitute part of the disclosure of the current patent application and can therefore be fully relied upon.

[0009] Disadvantage of those known from the prior art

[0010] One of the drawbacks of laser transfer printing (LTP) is that this process often exhibits a certain tendency to spatter and / or spray mist when printing onto the substrate. Another is that the distance between the carrier and the substrate is typically limited to 0.1–0.2 mm, as the impulse required to detach a droplet at larger distances leads to the droplet bursting and a very irregular print image. Larger distances, however, are crucial for the industrial implementation of this process.

[0011] It is therefore the object of the present invention to provide uses,

[0012] to provide compositions and related laser transfer printing processes that at least partially minimize the aforementioned disadvantages, resulting in a very clean print image at significantly larger sizes

[0013] Distances between the carrier and the substrate are made possible.

[0014] This problem is solved according to the invention by a use according to claim 1, a composition according to claim 12, and a

[0015] Laser transfer printing method according to claim 14.

[0016] The rheology (viscosity, elasticity, slurring) of inks and pastes is a crucial factor influencing their properties. The interplay of viscosity, elasticity, and slurring is generally considered in relation to the printing process used.

[0017] optimized. However, the optimal theological properties of the printing process usually do not coincide with the optimal theological properties observed during storage, pumping, or, for example, after the

[0018] The printing process on the substrate demands specific requirements. Therefore, inks and pastes are usually a compromise that attempts to balance these different demands.

[0019] This tension between different optimal rheological properties also applies to laser transfer printing (LTP).

[0020] to balance. The invention takes advantage of the fact that the laser action causes local heating, which in turn triggers a temporally and spatially limited change in the rheology of the components contained in the printing substance (also referred to as the composition in this context). In the simplest case, this involves, for example, the melting of contained

[0021] Polymer particles. Melting increases, among other things, the

[0022] Viscosity of the printing substance, which results in, for example, lower viscosity during the printing process.

[0023] exhibits a tendency to splash and / or due to stabilization of the

[0024] A larger pressure difference is possible during the transfer of the pressurized substance. This could, in principle, also be achieved through a generally higher viscosity, but with the disadvantage that, for example, the pumping and application processes would be made more difficult.

[0025] The term transfer refers to the entire process, beginning with the effect of the laser radiation on the printing substance and ending as soon as the movement of the portion of the printing substance transferred to the substrate has ceased due to kinetics and surface tension, and only changes due to the evaporation of solvents in the

[0026] ambient atmosphere. According to the invention, a component in a composition and / or a composition with a component is used, wherein the component is a laser-activated component which is used by

[0027] Laser irradiation is activated in such a way that the viscosity and / or elasticity and / or tensile strength of the composition increases due to a temperature increase of the composition.

[0028] Surprisingly, temperature-dependent viscosity measurements revealed that the viscosity of the investigated printing substances initially decreased with increasing temperature up to a certain point, and then, contrary to the typical behavior of fluids, increased abruptly. This surprising effect occurs around the melting point of added polymers or other additives. Further analysis showed that in these specific compositions, the solubility of the added components was sometimes exceeded, and therefore the component was partially undissolved at room temperature.

[0029] In practice, it has proven advantageous that the activation of the component leads to an increase in viscosity of at least 100 mPa-s, preferably by 500 mPa-s, particularly preferably by 1000 mPa-s.

[0030] Furthermore, it is advantageous if the activation of the component involves a phase transition, for example and especially from solid to liquid, in its composition.

[0031] Furthermore, it is advantageous if the activation of the component includes an increase in its solubility within the composition. It is particularly advantageous if this component is a meltable polymer.

[0032] The aforementioned advantages lead to an improvement in the ratio of the composition's storage modulus to its loss modulus through laser activation of the component – ​​ultimately resulting in the gel-like character of the

[0033] Composition - increases.

[0034] In practice, it has proven advantageous if the laser-activated component is a polymer from the groups

[0035] Polyethylene glycol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyacrylate, polyester or copolymers of these polymers or blends.

[0036] In this context, it is advantageous if the molecular weight of the polymer is chosen such that the polymer composition is optimal at the

[0037] The operating temperature of the printing process is not fully resolved.

[0038] In this context, it is particularly advantageous, as it has proven effective, if it concerns

[0039] a) Polyethylene glycol with a molar mass > 600 g / mol; and / or

[0040] b) Polyvinylpyrrolidone with a molar mass of, for example, 10,000 g / mol; and / or

[0041] c) Polyvinyl acetate with a molar mass of, for example, 55,000–70,000 g / mol; and / or

[0042] d) Polyvinyl alcohol with a molar mass of, for example, 31,000 g / mol; and / or

[0043] e) Polyacrylate, for example the sodium salt of polyacrylic acid with a molar mass of 5,100 g / mol; and / or f) polyester, for example poly(D,L)-lactide with a molar mass of 10,000-18,000 g / mol.

[0044] This list is exemplary and not exhaustive. For example, epoxides, polysaccharides, polyurethanes, poly(organo)siloxanes,

[0045] Formaldehyde condensates, (modified) natural resins, (modified) natural substances, waxes, and polyethers function as laser-activated components.

[0046] Finally, in the overall inventive context, it is particularly advantageous if the application involves laser transfer printing.

[0047] Furthermore, a composition for laser transfer printing, comprising a laser-activatable component as previously described according to the invention, is claimed.

[0048] It is particularly advantageous if the following substances are present in the specified weights:

[0049] Fillers (e.g. Shepherd Black 30C941, Sigma-Aldrich silver powder 2-3.5 prn)

[0050] 10 - 90 wt.%

[0051] Solvents (e.g. water, dipropylene glycol methyl ether)

[0052] 1 - 90 wt% laser-activated component 0.01 - 80 wt%

[0053] Glass frit (e.g. Schott G018-255, G018-249) 0 - 60 wt.%

[0054] Organometallic compounds (e.g., silver oxalate) 0–10 wt%

[0055] Absorption agents for laser radiation (e.g. Kremer Pigments flame soot)

[0056] 0 - 5 wt%

[0057] Additives (e.g. BYK-7420 ES) 0 - 5 wt% Binder (e.g. Kremer Pigments Gum arabic, Casein)

[0058] 0 - 90 wt.%

[0059] Finally, a laser transfer printing method is also claimed, wherein a laser-activatable component and / or a related composition according to the invention is used as the printing substance, and in this context printing distances of > 300 pm are possible.

[0060] In the inventive method, a corresponding laser pulse causes local heating of the inventive composition, such that a corresponding component of the inventive melts locally and selectively and / or its solubility in the composition is increased, wherein, in addition, a portion of a solvent, for example and in particular water, alcohols, aliphatic and aromatic solvents, evaporates, resulting in a change in viscosity and / or elasticity and / or tensile strength, and this leads to a stabilization and / or a stronger cohesion of the material of the inventive method.

[0061] The composition is transferred, i.e., during detachment from the carrier or movement towards the substrate, resulting in a better, more reproducible and cleaner print image with fewer splashes and fewer so-called satellite droplets, less overspray formation and a larger possible print distance (up to 5 mm according to the invention!).

[0062] During the transfer of the printing substance from the carrier to the substrate, shearing of the printing substance occurs due to the acting mechanical forces. This shearing, just like the temperature increase caused by the

[0063] Laser radiation can alter the theological properties of the printing material. This alteration can counteract the effects of the temperature increase.

[0064] The temperature of the carrier can be used for further control of the

[0065] Composition properties are adjusted, for example by lowering the temperature of the carrier to increase the difference to the temperature and composition after the laser pulse, which results in the solubility of the component according to the invention becoming even lower.

[0066] The dipole moment and polarizability properties of the individual components in relation to each other with respect to the composition according to the invention lead to hydrogen bonds and other associative bonds.

[0067] Interactions as a further means of adapting the

[0068] Composition properties serve, wherein the components according to the invention actively and / or passively participate in such a

[0069] hydrogen bonding network, whereby in general the composition according to the invention has a gel-like character at least during the transfer (that is, that the storage module of the

[0070] (the composition is greater than the loss modulus of the composition).

[0071] The invention is explained in more detail by the following exemplary embodiments in a non-limiting manner.

[0072] Examples of implementation:

[0073] Composition 1:

[0074] 50 g of polyethylene glycol 2000 (Carl Roth GmbH + Co. KG, molar mass: 1800-2200 g / mol) are heated together with 400 g of polyethylene glycol 400 (Carl Roth GmbH + Co. KG, molar mass: 380-420 g / mol) to approximately 70 °C and stirred to a clear solution. At this temperature, 550 g of black pigment (The Shepherd Color Company, Black IG) are slowly stirred in. The still-warm mixture is homogenized stepwise using a three-roll mill (EXAKT Advanced Technologies GmbH, EXAKT 80E, AI203 roller material) heated to 20 °C, with progressively smaller gaps (starting at 120 pm down to 5 pm). The resulting paste can be used directly for the LTP process or stored for several weeks in a dry environment.

[0075] Composition 2:

[0076] 50 g of polyethylene glycol 2000 (Carl Roth GmbH + Co. KG, molar mass: 1800-2200 g / mol) are heated to approximately 70 °C together with 300 g of polyethylene glycol 400 (Carl Roth GmbH + Co. KG, molar mass: 380-420 g / mol) and 100 g of ethylene glycol (Carl Roth GmbH + Co. KG) and stirred to a clear solution. At this temperature, 550 g of black pigment (The Shepherd Color Company, Black IG) are slowly stirred in. The still-warm mixture is homogenized stepwise using a three-roll mill (EXAKT Advanced Technologies GmbH, EXAKT 80E, AI203 roller material) heated to 20 °C, with progressively smaller gaps (starting at 120 pm down to 5 pm). The resulting paste can be used directly for the LTP process.

[0077] Can be used or stored in a dry place for several weeks. Composition 3:

[0078] 11.3 g of polyethylene glycol 2000 (Carl Roth GmbH + Co. KG, molar mass: 1800-2200 g / mol) are heated together with 25 g of polyethylene glycol 400 (Carl Roth GmbH + Co. KG, molar mass: 380-420 g / mol) to approximately 70 °C and stirred to a clear solution. To this solution, 0.14 g of BYK 378 (BYK-Chemie GmbH) and 2.10 g of BYK 7420 ES (BYK-Chemie GmbH) are added while stirring. At this temperature, 93.5 g of silver particles (Sigma-Aldrich, particle size: 2-3.5 nm) and 19.3 g of silver particles (Sigma-Aldrich, particle size: < 100 nm, PVP coated), 1.55 g of carbon (Kremer Pigmente GmbH & Co. KG) and 1.5 g of Bi203 (Carl Roth GmbH + Co. KG) are then slowly added.

[0079] stirred in. The still-warm mixture is then heated to 20°C using a device that has cooled the mixture to 20°C.

[0080] tempered three-roll mill (EXAKT Advanced Technologies GmbH, EXAKT 80E, AI203 roll material) gradually with decreasing gap dimensions

[0081] (starting at 120 miti down to 10 miti) homogenized. The paste obtained in this way can be used directly for the LTP process or under

[0082] Store in a dry place for several weeks.

[0083] Transfer process 1:

[0084] For laser transfer printing, a fiber laser is used, which is located at a

[0085] The radiation emitted has a wavelength of 1070 nm. A polyimide film is used as the support, and glass as the substrate. A pressure distance of 500 µm between the support and substrate is chosen. The coating of the printing substance on the support has a thickness of 30 µm. The radiation source is operated in continuous wave mode at an average power of 150 W. Transmission process 2:

[0086] For laser transfer printing, a fiber laser emitting at a wavelength of 1070 nm is used. Glass serves as both the carrier and substrate. A printing distance of 1 mm is chosen between the carrier and substrate. The coating of the printing substance on the carrier has a thickness of 50 pm. The beam source operates in pulsed mode with a pulse duration of approximately 1 ps. The average power is 20 W at a pulse repetition rate of 100 kHz.

Claims

Patent claims 1. Use of a component in a composition and / or use of a composition containing a component, characterized by the fact that It is a laser-activated component which, in use, is activated by laser irradiation in such a way that the viscosity and / or elasticity and / or tensile strength of the composition increases due to a temperature increase of the composition.

2. Use according to claim 1, characterized in that the Activation of the component leads to an increase in viscosity of at least 100 mPa-s.

3. Use according to claim 2, characterized in that the increase in viscosity is up to approximately 500 mPa-s or up to approximately 1000 mPa-s.

4. Use according to one of claims 1 to 3, characterized in that the activation of the component involves a phase transition of this component in the composition.

5. Use according to any one of claims 1 to 4, characterized in that the activation of the component includes an increase in the solubility of the component in the composition.

6. Use according to any one of claims 1 to 5, characterized in that the component is a meltable polymer.

7. Use according to any one of claims 1 to 6, characterized in that the ratio of storage modulus of the composition to loss modulus is increased by laser activation of the component. The composition increases.

8. Use according to any one of claims 1 to 7, characterized in that the laser-activatable component is a polymer from the groups polyethylene glycol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyacrylate, polyester or copolymers thereof These are polymers or blends.

9. Use according to one of claims 6 to 8, characterized in that the molecular weight of the polymer is selected such that the polymer is not completely dissolved in the composition at the operating temperature of the printing process.

10. Use according to one of claims 8 to 9, characterized in that it is a a) Polyethylene glycol with a molar mass > 600 g / mol; and / or b) Polyvinylpyrrolidone with a molar mass of 10,000 g / mol; and / or c) Polyvinyl acetate with a molar mass of 55,000-70,000 g / mol; and / or d) Polyvinyl alcohol with a molar mass of 31,000 g / mol; and / or e) Polyacrylate as the sodium salt of polyacrylic acid with a molar mass of 5,100 g / mol; and / or f) Polyester, for example poly(D,L)-lactide with a molar mass of 10,000-18,000 g / mol.

11. Use according to any one of claims 1 to 10 for the Laser transfer printing.

12. Composition for laser transfer printing, with a laser-activatable component, as shown in any one of claims 1 to 11.

13. Composition according to claim 12, characterized in that it comprises the following substances in the manner shown. weight specifications are: Fillers 10 - 90 wt.% Solvent 1 - 90 wt% Laser-activated component 0.01 - 80 wt% Glass frit 0 - 60 wt.% Organometallic compounds 0 - 10 wt% Absorbing agent for laser radiation 0 - 5 wt.% Additives 0 - 5 wt.% Binder 0 - 90 wt.% 14. Laser transfer printing process, characterized in that a laser-activatable component, as shown in any one of claims 1 to 11, and / or a composition according to one of claims 12 to 13 is used as a printing substance.