Printing paste containg graphite

Abstract

A printing paste, in particular for producing three-dimensional screen-printed workpieces, comprising at least one solid, at least one solvent, and at least one rheology additive, the solid comprising at least one graphite material and the percentage by weight of the solid being at least 25%.

Description

[0001] PRINTING PASTE WITH GRAPHITE

[0002] The present invention relates to a printing paste, in particular for the production of three-dimensional screen-printed workpieces.

[0003] In the screen printing process, a printing ink or printing paste can be printed in the conventional way with a squeegee through a printing screen or through a stencil onto the material to be printed or onto the existing substrate.

[0004] The printing inks or pastes used for simple screen printing are often unsuitable, or only marginally suitable, for the layer-by-layer construction of a three-dimensional workpiece using the three-dimensional screen printing process. Such inks or pastes can lead to smearing or significant printing inaccuracies after just two or three layers, and these problems can worsen with an increasing number of layers. Therefore, inks or pastes developed and used for two-dimensional screen printing are generally too fluid and thus unsuitable for three-dimensional screen printing.

[0005] For the production of a three-dimensional screen-printed workpiece, namely one with numerous superimposed layers, suitable printability of the printing paste must be ensured. This is intended to enable the creation of a precise printed layer through a printing screen using a squeegee with sufficiently high repeatability. Simultaneously, good dimensional stability after the printing of a layer is required to allow for the precise printing of a subsequently applied layer.

[0006] This requires, among other things, good drying properties of the printing paste after printing. Drying can be achieved, for example, by heating in separate drying ovens. Such thermal drying can be accompanied by shrinkage. This must be taken into account when determining the precise composition of the printing paste to be used and may lead to further restrictions.

[0007] Against the background set out above, the object of the invention was to provide a printing paste that can be printed layer by layer with high precision and enables or facilitates the production of three-dimensional screen-printed workpieces while ensuring good drying ability.

[0008] This problem has been solved by the subject matter of claim 1. Advantageous embodiments are the subject matter of the dependent claims and are discussed below.

[0009] A printing paste according to the invention is particularly designed and / or configured for the production of three-dimensional screen-printed workpieces. A printing paste according to the invention comprises at least one solid, at least one solvent, and at least one rheology additive, wherein the solid comprises at least one graphite material and wherein the mass fraction of the solid is at least 25%.

[0010] The rheology additive provided according to the invention allows the rheological properties of the printing paste to be specifically influenced. In particular, the addition of a rheology additive prevents undesirable flow of the printing paste after printing, thus ensuring sufficiently high printing precision. At the same time, despite the addition of a rheology additive, adequate wetting of a printing screen can be achieved without clumping or excessive thickening.

[0011] Finally, a relatively high solids content of at least 25% by weight can ensure particularly good mechanical properties in the printed workpieces. At the same time, a high solids content can promote high printing precision. Finally, such a high solids content can result in relatively simple and efficient deposition, and unwanted shrinkage before, during, and / or after curing and / or sintering can be avoided.

[0012] Overall, this method ensures high workpiece quality while simultaneously providing good printability and efficient process control.

[0013] According to a preferred embodiment, the solid can be produced and / or mixed in as a powder. Likewise, the solid can consist of powdered material and / or be produced or consist of graphite in powdered form. Such a solid can be provided with relatively little effort and distributed uniformly within the printing paste, resulting in high print quality.

[0014] According to a further preferred embodiment, the mass fraction of the solid can be more than 27%, preferably more than 28%, more preferably more than 30%, even more preferably more than 32%, even more preferably more than 35%, even more preferably more than 45%, even more preferably more than 50%, even more preferably more than 55%, even more preferably more than 65%, and even more preferably more than 75%. In this way, the mechanical properties of the printed workpieces and / or the printing precision can be further improved. Furthermore, this ensures a simplified unwinding process and avoids undesirable shrinkage before, during, and / or after curing and / or sintering in a further improved manner.

[0015] According to a further preferred embodiment, the mass fraction of the solid can be less than 90%, preferably less than 85%, more preferably less than 80%, more preferably less than 70%, more preferably less than 60%, more preferably less than 50%, and more preferably less than 45%. This ensures good printability, in particular sufficiently fluid properties of the printing paste, which allows printing through a printing screen.

[0016] According to a further preferred embodiment, the solvent can be or comprise an organic solvent and / or glycol ether, in particular dipropylene glycol methyl ether and / or dipropylene glycol monomethyl ether. Such a solvent has proven particularly advantageous as a component of a printing paste for use in three-dimensional screen printing. It ensures suitable dilution of the respective solid without impairing the mechanical properties of the solid after curing.

[0017] According to a further preferred embodiment, the mass fraction of solvent can be at least 25%, preferably more than 30%, more preferably more than 35%, more preferably more than 40%, and more preferably more than 42%. A solvent in such a quantity can be removed after printing with relatively little effort by debinding and simultaneously ensures sufficient dilution.

[0018] According to a further preferred embodiment, the mass fraction of separate solvent can be less than 70%, preferably less than 60%, more preferably less than 50%, and more preferably less than 45%. This can particularly favorably improve the flow properties, especially avoiding excessive flowability.

[0019] According to a further preferred embodiment, the printing paste can contain at least one dispersing additive. The use of such a dispersing additive allows for a particularly high solids content in the printing paste. This ensures a particularly uniform mixing of the respective solids in the printing paste and thus guarantees high print quality.

[0020] According to a further preferred embodiment, the dispersing additive can be a wetting and dispersing additive or act exclusively as a dispersing additive. A wetting and dispersing additive can particularly preferably ensure good utilization of the printing paste, especially without the formation or remaining of unwetted areas or dry spots in a printing screen or after printing. An embodiment as an exclusive dispersing additive can be provided with minimal effort and at reduced costs.

[0021] According to a further preferred embodiment, the dispersing additive can comprise and / or be a polyglycol ester. Furthermore, the addition of a dispersing additive, or a dispersing and / or wetting additive in the form of a polyglycol ester, can produce a particularly fine and uniform distribution of solid particles in a printing paste, ensuring long-term stability of the printing paste. This results in improved processability and more efficient manufacturing.

[0022] According to a further preferred embodiment, the dispersing additive can have a mass fraction of the active substance of at least 20% and / or less than 40%, in particular 30% or about 30%. Likewise, the dispersing additive can have a mass fraction of the active substance of at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or 100% or about 100%. Such a dispersing additive can therefore have a low concentration and thus be dosed precisely. Likewise, a high concentration can be provided, so that adding the dispersing additive results in only a slight dilution of the printing paste.

[0023] According to a further preferred embodiment, the mass fraction of the dispersing additive can be at least 0.5%, preferably more than 0.5%, more preferably more than 0.6%, more preferably more than 0.7%, more preferably more than 0.8%, more preferably more than 0.9%, more preferably about 1%, more preferably more than 2%, more preferably more than 3%, more preferably more than 4%, and more preferably more than 5%. Such a mass fraction can ensure sufficient mixing and wetting while minimally affecting the overall composition of the printing paste.

[0024] According to a further preferred embodiment, the mass fraction of the dispersing additive can be less than 10%, preferably less than 8%, preferably less than 7%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 1.5%, and more preferably less than 1.2%. By limiting the dispersing additive in this way, other components of the printing paste can be provided in relatively high mass fractions, in particular a high mass fraction of the solid.

[0025] According to a further preferred embodiment, the printing paste can contain a plurality of different rheological additives. The rheological properties can thus be particularly advantageously tailored, especially with regard to the other components of the printing paste and their mass fractions. According to a further preferred embodiment, the at least one rheological additive can be a liquid substance and / or be mixed in liquid form. In this way, the printing paste can be produced with minimal effort and, for example, made available for a three-dimensional screen printing process.

[0026] According to a further preferred embodiment, the at least one rheology additive can be a powdered substance and / or mixed in powder form. Likewise, the at least one rheology additive can contain cellulose and / or consist of cellulose. This can be achieved cost-effectively and allows for simple storage for the subsequent production of the printing paste.

[0027] According to a further preferred embodiment, at least one rheology additive can be designed to generate thixotropic flow behavior. This can promote the flow behavior during printing and simultaneously prevent undesirable flowing before or after printing. Three-dimensional screen printing with such a printing paste can thus be facilitated, and high printing precision can be achieved.

[0028] According to a further preferred embodiment, at least one rheology additive can be designed for medium-polar solvent-containing and / or solvent-free systems. The rheology additive can therefore be used particularly for medium-polar solvent-containing and / or solvent-free systems, thereby ensuring particularly high functionality for such a system.

[0029] According to a further preferred embodiment, at least one rheology additive can be designed for highly polar or low-polar solvent-containing and / or solvent-free systems. The rheology additive can therefore be used particularly for highly polar or low-polar solvent-containing and / or solvent-free systems, thereby ensuring particularly high functionality for such a system.

[0030] According to a further preferred embodiment, at least one rheology additive can be formulated as a solution of modified urea. Such a rheology additive can be provided particularly cost-effectively, thus ensuring economical production. After being stirred into the printing paste, this additive forms a three-dimensional network structure. The resulting thixotropic flow behavior is particularly advantageous for preventing sediment formation and increasing stability. The flow characteristics of the printing paste are not, or only minimally, impaired.

[0031] According to a further preferred embodiment, at least one rheology additive can have dimethyl sulfoxide as a solvent. Such a solvent ensures suitable dilution of the additive without negatively affecting its efficacy in influencing flow behavior.

[0032] According to a further preferred embodiment, at least one rheology additive can comprise an amide ether as a solvent. Such a solvent also ensures suitable dilution of the additive without negatively affecting its efficacy in influencing the flow behavior.

[0033] According to a further preferred embodiment, the rheology additive can have a mass fraction of the active substance of at least 20%, preferably more than 20%, more preferably more than 30%, more preferably more than 40%, or 40%, and more preferably more than 50%, 50%, or 52%. Such a minimum active substance fraction allows sufficient rheological effect to be achieved with a relatively small addition. According to a further preferred embodiment, the rheology additive can have a mass fraction of the active substance of less than 70%, in particular less than 60% or less than 55%. This allows for particularly precise dosing of the active substance and minimal overall impact on the mass fractions of the other components of the printing paste.

[0034] According to a further preferred embodiment, the printing paste can contain a minimum amount of a binder and / or polyvinyl butyral as a binder. The addition of a binder and / or polyvinyl butyral as a binder also results in even better processability of the printing paste for three-dimensional screen printing.

[0035] According to a further preferred embodiment, the mass fraction of binder and / or polyvinyl butyral can be at least 1%, preferably more than 2%, more than 3%, more than 4%, or more than 5%. The addition of a binder and / or polyvinyl butyral as a binder in such a minimum quantity results in particularly good processability of the printing paste for three-dimensional screen printing.

[0036] According to a further preferred embodiment, the mass fraction of binder and / or polyvinyl butyral can be less than 6%, preferably less than 5%, less than 4.5%, less than 4%, or less than 3%. The addition of a binder and / or polyvinyl butyral as a binder in such a maximum quantity results in particularly suitable overall processability of the printing paste for three-dimensional screen printing.

[0037] According to a further preferred embodiment, the printing paste can contain the following components in mass percent:

[0038] Graphite as a solid: 35% to 45%

[0039] Solvent: 40% to 45%

[0040] Binder: 4% to 6% Dispersing additive(s): 4% to 6% Rheological additive(s): 0.5% to 2% Remainder unavoidable impurities

[0041] Such a printing paste is particularly well-suited for the production of three-dimensional screen-printed workpieces. It allows for good printability using three-dimensional screen printing and enables curing with relatively little effort. With such a printing paste, workpieces with high-quality characteristics, especially high manufacturing accuracy and good mechanical properties, can be produced.

[0042] According to a further preferred embodiment, the printing paste can contain the following components in mass percent:

[0043] Graphite as a solid: 35% to 45%

[0044] Dipropylene glycol methyl ether: 40% to 45% Polyvinyl butyral: 4% to 6% Polyglycol esters: 4% to 6% Rheological additive(s): 0.5% to 2% Remainder unavoidable impurities

[0045] Such a printing paste is also advantageously suited for the production of three-dimensional screen-printed workpieces. Particularly good printability can be achieved using three-dimensional screen printing, and curing can be accomplished with relatively little effort. With such a printing paste, workpieces with high quality characteristics, especially high manufacturing accuracy and good mechanical properties, can be produced. A further aspect of the present invention relates to a method for producing a three-dimensional screen-printed workpiece using a printing paste as described above.

[0046] A further aspect of the present invention relates to a method for producing a three-dimensional screen-printed workpiece with a printing paste comprising a rheology additive as an ingredient and preferably also a graphite material.

[0047] The details described above relating to the printing paste also apply equally to the method for producing a three-dimensional screen-printed workpiece according to the further aspects of the present invention.

[0048] The invention is explained in more detail below with reference to exemplary embodiments in conjunction with the associated drawings.

[0049] It shows:

[0050] Fig. 1 shows a schematic representation of the composition of a printing paste according to an embodiment of the present invention before hardening.

[0051] Figure 1 shows a schematic representation of the composition of a printing paste 10 according to an embodiment of the present invention before possible hardening.

[0052] The printing paste 10 is particularly suitable for the production of three-dimensional screen-printed workpieces and comprises at least one solid 12, at least one solvent 14, and at least one rheology additive 16, wherein the solid 12 comprises at least one graphite material and wherein the mass fraction of the solid 12 is at least 25%. The solid 12 can be produced and / or mixed in as a powder. Likewise, the solid 12 can consist of powdered material. The solid can be produced from or consist of graphite in powdered form.

[0053] The mass fraction of solid 12 can be more than 27%, preferably more than 28%, more preferably more than 30%, even more preferably more than 32%, even more preferably more than 35%, even more preferably more than 45%, even more preferably more than 50%, even more preferably more than 55%, even more preferably more than 65%, even more preferably more than 75%. Furthermore, the mass fraction of solid 12 can be less than 90%, preferably less than 85%, more preferably less than 80%, more preferably less than 70%, more preferably less than 60%, more preferably less than 50%, or more preferably less than 45%.

[0054] The solvent 14 can be an organic solvent and / or glycol ether, in particular dipropylene glycol methyl ether and / or dipropylene glycol monomethyl ether. The mass fraction of solvent 14 can be at least 25%, preferably more than 30%, more preferably more than 35%, more preferably more than 40%, and more preferably more than 42%. Furthermore, the mass fraction of separate solvent 14 can be less than 70%, preferably less than 60%, more preferably less than 50%, and more preferably less than 45%.

[0055] The printing paste 10 may further comprise at least one dispersing additive 18. The dispersing additive 18 may be a wetting and dispersing additive or act exclusively as a dispersing additive. The dispersing additive 18 may comprise and / or be polyglycol esters.

[0056] The dispersing additive 18 can have a mass fraction of the active substance of at least 20% and / or less than 40%, in particular 30% or about 30%. Likewise, the dispersing additive 18 can have a mass fraction of the active substance of at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or 100% or about 100%. The mass fraction of the dispersing additive 18 in the printing paste 10 can be at least 0.5%, preferably more than 0.5%, more preferably more than 0.6%, more preferably more than 0.7%, more preferably more than 0.8%, more preferably more than 0.9%, more preferably about 1%, more preferably more than 2%, more preferably more than 3%, more preferably more than 4%, and more preferably more than 5%.

[0057] Furthermore, the mass fraction of the dispersing additive 18 in the printing paste 10 can be less than 10%, preferably less than 8%, preferably less than 7%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 1.5%, more preferably less than 1.2%, more preferably less than 1.1%.

[0058] The printing paste 10 can further comprise a plurality of different rheology additives 16. The at least one rheology additive 16 can be a liquid substance and / or be mixed into the printing paste 10 in liquid form. Likewise, the at least one rheology additive 16 can be a powdered substance and / or be mixed into the printing paste 10 in powder form. The at least one rheology additive 16 can comprise cellulose and / or consist of cellulose. The rheology additive 16 can furthermore be designed to generate thixotropic flow behavior.

[0059] Rheology additive 16 can be formulated for medium-polar solvent-containing and / or solvent-free systems. Likewise, rheology additive 16 can be formulated for high-polarity or low-polarity solvent-containing and / or solvent-free systems. At least one of the rheology additives can be a solution of a modified urea.

[0060] Furthermore, at least one rheology additive 16 can comprise dimethyl sulfoxide as a solvent. Likewise, at least one rheology additive 16 can comprise amide ethers as a solvent. The rheology additive can have a mass fraction of the active substance of at least 20%, preferably more than 20%, more preferably more than 30%, more preferably more than 40%, or 40%, and more preferably more than 50%, or 50%, or 52%. The rheology additive can also have a mass fraction of the active substance of less than 70%, in particular less than 60% or less than 55%.

[0061] The printing paste 10 may further comprise a minimum proportion of a binder and / or polyvinyl butyral as a binder, which is not described in detail here. The mass fraction of binder and / or polyvinyl butyral may be at least 1%, preferably more than 2%, more than 3%, more than 4%, or more than 5%. Likewise, the mass fraction of binder and / or polyvinyl butyral may be less than 6%, preferably less than 5%, less than 4.5%, less than 4%, or less than 3%.

[0062] The printing paste 10 according to the embodiment in Figure 1 can contain the following components in mass percent before hardening:

[0063] - Graphite as a solid: 35% to 45%

[0064] - Solvent: 40% to 45%

[0065] - Binder: 4% to 6%

[0066] - Dispersing additive(s): 4% to 6%

[0067] - rheological additive(s): 0.5% to 2%

[0068] - Remaining unavoidable impurities

[0069] Preferably, the printing paste 10 according to the embodiment in Figure 1 may contain the following components in mass percent before hardening:

[0070] Graphite as a solid: 35% to 45%

[0071] Dipropylene glycol methyl ether: 40% to 45%

[0072] Polyvinyl butyral: 4% to 6% - Polyglycol ester: 4% to 6%

[0073] - rheological additive(s): 0.5% to 2%

[0074] - Residual unavoidable impurities In a process for producing a three-dimensional screen-printed workpiece, a layer-by-layer workpiece build-up can be carried out by repeated printing with a printing paste 10 according to the preceding description.

[0075] For this purpose, the printing paste 10 can be pressed through a printing screen (also not shown) using a squeegee (not shown in detail here) and applied to a printing substrate or to a partially constructed screen-printed workpiece. Following printing, the respective printed layer can be cured using this method.

Claims

PATENT CLAIMS 1. Printing paste, in particular for the production of three-dimensional screen-printed workpieces, comprising at least one solid, at least one solvent and at least one rheology additive, wherein the solid comprises at least one graphite material and wherein the mass fraction of the solid is at least 25%.

2. Printing paste according to claim 1, characterized in that the solid is produced and / or mixed in powder form and / or that the solid consists of powder material and / or that the solid is produced or consists of graphite in powder form.

3. Printing paste according to one of the preceding claims, characterized in that the mass fraction of the solid is more than 27%, preferably more than 28%, further preferably more than 30%, even more preferably more than 32%, even more preferably more than 35%, even more preferably more than 45%, even more preferably more than 50%, even more preferably more than 55%, even more preferably more than 65%, even more preferably more than 75%.

4. Printing paste according to one of the preceding claims, characterized in that the mass fraction of the solid is less than 90%, preferably less than 85%, further preferably less than 80%, further preferably less than 70%, further preferably less than 60%, further preferably less than 50%, further preferably less than 45%.

5. Printing paste according to one of the preceding claims, characterized in that the solvent is an organic solvent and / or Glycol ether is, in particular, dipropylene glycol methyl ether and / or dipropylene glycol monomethyl ether.

6. Printing paste according to one of the preceding claims, characterized in that the mass fraction of solvent is at least 25%, preferably more than 30%, further preferably more than 35%, further preferably more than 40%, further preferably more than 42%.

7. Printing paste according to one of the preceding claims, characterized in that the mass fraction of separate solvent is less than 70%, preferably less than 60%, more preferably less than 50%, more preferably less than 45%.

8. Printing paste according to one of the preceding claims, characterized by at least one dispersing additive.

9. Printing paste according to claim 8, characterized in that the dispersing additive is a wetting and dispersing additive or acts exclusively as a dispersing additive.

10. Printing paste according to one of claims 8 or 9, characterized in that the dispersing additive comprises and / or is a polyglycol ester.

11. Printing paste according to one of claims 8 to 10, characterized in that the dispersing additive has a mass fraction of the active substance of at least 20% and / or of less than 40%, in particular of 30% or about 30%, and / or that the dispersing additive has a mass fraction of the active substance of at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or 100% or about 100%.

12. Printing paste according to one of claims 8 to 11, characterized in that the mass fraction of the dispersing additive is at least 0.5%, preferably more than 0.5%, further preferably more than 0.6%, further preferably more than 0.7%, further preferably more than 0.8%, further preferably more than 0.9%, further preferably about 1%, further preferably more than 2%, further preferably more than 3%, further preferably more than 4%, further preferably more than 5%.

13. Printing paste according to one of claims 8 to 12, characterized in that the mass fraction of the dispersing additive is less than 10%, preferably less than 8%, preferably less than 7%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 1.5%, further preferably less than 1.2%, further preferably less than 1.1%.

14. Printing paste according to one of the preceding claims, characterized by a plurality of different rheology additives.

15. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive is a liquid substance and / or is mixed in liquid form.

16. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive is a powdered substance and / or is mixed in powder form and / or that the at least one rheology additive comprises cellulose and / or consists of cellulose.

17. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive is designed to produce thixotropic flow behavior.

18. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive is designed for medium-polar solvent-containing and / or solvent-free systems.

19. Printing paste according to one of claims 1 to 17, characterized in that the at least one rheology additive is designed for highly polar or low polar solvent-containing and / or solvent-free systems.

20. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive is formed as a solution of a modified urea.

21. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive comprises dimethyl sulfoxide as a solvent.

22. Printing paste according to one of the preceding claims, characterized in that the at least one rheology additive comprises an amide ether as a solvent.

23. Printing paste according to one of the preceding claims, characterized in that the rheology additive has a mass fraction of the active substance of at least 20%, preferably of more than 20%, more preferably of more than 30%, and more preferably of more than 40%. 40%, further preferably more than 50% or 50% or 52%.

24. Printing paste according to one of the preceding claims, characterized in that the rheology additive has a mass fraction of the active substance of less than 70%, in particular of less than 60% or of less than 55%.

25. Printing paste according to one of the preceding claims, characterized by a minimum component of a binder and / or polyvinyl butyral as a binder.

26. Printing paste according to claim 25, characterized in that the mass fraction of binder and / or polyvinyl butyral is at least 1%, preferably more than 2%, more than 3% or more than 4% or more than 5%.

27. Printing paste according to claim 25 or 26, characterized in that the mass fraction of binder and / or polyvinyl butyral is less than 6%, preferably less than 5%, less than 4.5% or less than 4% or less than 3%.

28. Printing paste according to one of the preceding claims, characterized by the following components in mass percent: - Graphite as a solid: 35% to 45% - Solvent: 40% to 45% - Binder: 4% to 6% - Dispersing additive(s): 4% to 6% - rheological additive(s): 0.5% to 2% - Remaining unavoidable impurities 29. Printing paste according to one of the preceding claims, characterized by the following components in mass percent: - Graphite as a solid: 35% to 45% - Dipropylene glycol methyl ether: 40% to 45% - Polyvinyl butyral: 4% to 6% - Polyglycol ester: 4% to 6% - rheological additive(s): 0.5% to 2% - Remaining unavoidable impurities

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