INK BASED ON SILVER NANOPARTICLES

Abstract

The present invention relates to thermoformable and/or stretchable ink formulations based on silver nanoparticles. In particular, the present invention relates to ink formulations based on silver nanoparticles, polyurethane and metal microparticles of silver, copper and/or nickel.

Claims

1. Thermoformable and/or stretchable ink adapted to the production of stretchable and/or deformable conductive tracks, said ink comprising at least 90% by weight of the following compounds: 1. silver nanoparticles in a content of at least 15% by weight of the ink, 2. metal microparticles of silver, copper and/or nickel in a content of at least 15% by weight of the ink, 3. monohydric alcohol of boiling point greater than 150° C. in a content of at least 20% by weight of the ink, 4. film-forming polymer in a content of at least 0.5% by weight of the ink, 5. polyol and/or polyol ether in a content of at least 1.5% by weight of the ink, and 6. a cellulose compound in a content of at least 0.4% by weight of the ink.

2. Ink according to claim 1, characterised in that it comprises: 1. the silver nanoparticles in a content of at least 20% by weight of the ink and less than 45% by weight of the ink, 2. the metal microparticles of silver, copper and/or nickel in a content of at least 20% by weight of the ink and less than 45% by weight of the ink, 3. the monohydric alcohol in a content of at least 25% by weight of the ink and less than 50% by weight of the ink, 4. the film-forming polymer in a content of at least 0.75% by weight of the ink and less than 2% by weight of the ink, 5. the polyol and/or polyol ether in a content of at least 2% by weight of the ink and less than 4% by weight of the ink, and 6. the cellulose compound in a content of at least 0.75% by weight of the ink and less than 2% by weight of the ink.

3. Ink according to claim 1, characterised in that it comprises: 1. the silver nanoparticles in a content of less than 40% by weight of the ink, 2. the metal microparticles of silver, copper and/or nickel in a content of less than 40% by weight of the ink, 3. the monohydric alcohol in a content of less than 45% by weight of the ink, 4. the film-forming polymer in a content of less than 1.25% by weight of the ink, 5. the polyol and/or polyol ether in a content of less than 3.5% by weight of the ink, and 6. the cellulose compound in a content of less than 1.5% by weight of the ink.

4. Ink according to claim 1, characterised in that the silver nanoparticles are spheroidal, for example spherical.

5. Ink according to claim 1, characterised in that the silver nanoparticles have a mean diameter of between 20 and 200 nm, preferably between 30 and 150 nm.

6. Ink according to claim 1, characterised in that the silver nanoparticles have D50 values of between 30 and 150 nm.

7. Ink according to claim 1, characterised in that the microparticles have a mean area of between 1 and 25 μm.sup.2, preferably between 5 and 15 μm.sup.2, and/or a mean perimeter of between 3 and 20 μm, preferably between 5 and 15 μm, and/or a mean diameter of between 1 and 7 μm, preferably between 1 and 5 μm.

8. Ink according to claim 1, characterised in that the film-forming polymer is a synthetic polymer selected from polyacrylics, polyvinyls, polyesters, polysiloxanes and/or polyurethanes.

9. Ink according to claim 8, characterised in that the film-forming polymer is an aliphatic polyurethane, for example a semi-aliphatic polyurethane, for example a functional or non-functional, saturated or unsaturated semi-aliphatic polyurethane.

10. Ink according to claim 1, characterised in that the monohydric alcohol of boiling point greater than 150° C. is 2,6-dimethyl-4-heptanol and/or terpene alcohol.

11. Ink according to claim 10, characterised in that the terpene alcohol is terpineol.

12. Ink according to claim 1, characterised in that the polyol and/or polyol ether is selected from glycols and/or glycol ethers.

13. Ink according to claim 1, characterised in that the polyol and/or polyol ether is selected from ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 2,3-butylene glycol, pentamethylene glycol, hexylene glycol, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, propylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether (butyl carbitol), propylene glycol methyl ether, propylene glycol butyl ether, propylene glycol propyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, glymes, diethylene glycol diethyl ether, dibutylene glycol diethyl ether, diglymes, ethyl diglyme, butyl diglyme.

14. Ink according to claim 1, characterised in that the ink viscosity measured at a shear rate of 40 s.sup.−1 and at 20° C. is between 1000 and 100 000 mPa.Math.s, preferably between 3000 and 30 000 mPa.Math.s, for example between 5000 and 20 000 mPa.Math.s.

15. Use of an ink according to claim 1 for its printing/adhesion on glass, ITO (indium tin oxide) or PVDF (polyvinylidene fluoride) substrates.

Description

[0094] The present invention and its advantages are also illustrated using the following example which shows the combined effect of the film-forming polymer and the metal microparticles on the properties of the ink after thermoforming.

TABLE-US-00004 TABLE 4 Ink % silver % metal % other No. % polyurethane nanoparticles microspheres compounds 303 0 55 0 45 315 1 55 0 44 338 1 30 30 39

TABLE-US-00005 TABLE 5 Resistance before Resistance after Surface condition Ink thermoforming thermoforming after No. (ohm) (ohm) thermoforming 303 8 Ø Crackled 315 90 Ø Partially crackled 338 58 47 Smooth

[0095] FIG. 1 is graphical representation of the thermoformed ink 338. The comparison between the surface conditions of 303 and 315 illustrates the positive effect of the presence of polyurethane in the ink, changing from a crackled to partially crackled surface condition. Nevertheless, to obtain a smooth surface condition and preserve good electrical properties after thermoforming, the effect of the polyurethane must be combined with that of the microparticles, as demonstrated by the results obtained on ink 338.

[0096] FIG. 2 is a graphical representation of the surface condition of the thermoformed inks, respectively from left to right on the figure, inks 303, 315 and 338. The present invention and its advantages are also illustrated using the following example which shows the effect of a mixture of polymorphous particles (wires, spheres of different sizes) on the properties of the ink after stretching:

[0097]

TABLE-US-00006 TABLE 6 % silver % metal % poly- % other Ink % poly- nano- micro- morphous com- No. urethane particles spheres particles pounds 21-1 1 30 30 0 39 21-2 1 30 0 30 39 21-4 1 30 15 15 39

TABLE-US-00007 TABLE 7 Resistance Resistance Resistance Resistance Resistance (ohm) (ohm) (ohm) (ohm) (ohm) Ink at 0% at 10% at 20% at 30% at 40% No. elongation elongation elongation elongation elongation 21-1 800 / / / / 21-2 11 44 99 195 340 21-4 88 600 1700 1500000 /

[0098] These results show the effect of the presence of polymorphous particles which make the deposit stretchable. The presence of these particles at up to 30% preserves good electrical properties even under 40% stretching.

[0099] The following tables show the change in the electrical performance of the ink deposit 21-2 and 21-11 depending on the number of times it has been subjected to 30 elongation for conductive line widths of 2 mm in [Table 8] and line widths of 250 μm for [Table 9]:

TABLE-US-00008 TABLE 8 Number of 30% elongations R (ohm) ink deposit 21-2 0 11 10 24 25 24 50 35

TABLE-US-00009 TABLE 9 Number of ΔR (ohm)/Initial R ΔR (ohm)/Initial R 30% elongations (Ohm) ink deposit 21-2 (Ohm) ink deposit 21-11 0 0 0 10 1.6 0.4 20 2.5 0.6 30 4.0 0.6 40 4.8 0.8 50 5.5 1.0

[0100] These results indicate satisfactory electrical performance even after fifty 30 elongations. We observe a slight increase in the resistance with the number of elongations.