COLOURED OR BLACK PARTICLES

Abstract

This invention relates to a process for the preparation of a dispersion comprising coloured or black particles, such coloured or black particles prepared by the process, the use of the dispersion and the coloured or black particles in electrophoretic fluids, and electrophoretic display devices comprising such fluids.

Claims

1. A process for the preparation of coloured or black particles dispersed in a non-polar solvent, the process comprising the following steps: a) forming a reverse emulsion comprising at least one dye, at least one polymer, at least one polar solvent, at least one non-polar, fluorinated solvent, and at least one surfactant, or a′) forming a reverse emulsion comprising at least one dye, at least one polar solvent, at least one non-polar, fluorinated solvent, and at least one surfactant, a″) forming a reverse emulsion comprising at least one dye, at least one polar solvent, at least one non-polar, non-fluorinated solvent, and at least one surfactant, and b) removing the polar solvent or polar solvents by evaporative methods, wherein the non-polar fluorinated or non-polar non-fluorinated solvent or solvents are not removed.

2. Process according to claim 1, wherein the forming of the reverse emulsion of step a) is prepared by: a1) forming a polar phase by mixing at least one dye, at least one polymer, and at least one polar solvent, a2) forming a non-polar phase by mixing at least one non-polar, fluorinated solvent and at least one surfactant, a3) combining the polar phase and the non-polar phase, and a4) homogenizing the combined phases to form the reverse emulsion; or the forming of the reverse emulsion of step a′) is prepared by: a′1) forming a polar phase by mixing at least one dye and at least one polar solvent, a′2) forming a non-polar phase by mixing at least one non-polar, fluorinated solvent and at least one surfactant, a′3) combining the polar phase and the non-polar phase, and a′4) homogenizing the combined phases to form the reverse emulsion; or the forming of the reverse emulsion of step a″) is prepared by: a″1) forming a polar phase by mixing at least one dye and at least one polar solvent, a″2) forming a non-polar phase by mixing at least one non-polar, non-fluorinated solvent and at least one surfactant, a″3) combining the polar phase and the non-polar phase, and a″4) homogenizing the combined phases to form the reverse emulsion.

3. Process according to claim 1, wherein the polymer of step a) is produced from at least monomer which is insoluble in the non-polar fluorinated solvent or that the monomer is soluble but the polymer is insoluble in the non-polar fluorinated solvent.

4. Process according to claim 1, wherein the at least one polymer of step a) is selected from poly(vinyl pyrrolidone), poly(acrylamide), poly-(acrylic acid) or poly-(methacrylic acid).

5. Process according to claim 1, wherein the non-polar, fluorinated solvent used in step a) has a refractive index and a density similar to that of the at least one polymer.

6. Process according to claim 1, wherein the non-polar fluorinated solvent used in step a) or step a′) is a perfluorinated hydrocarbon having a refractive index of ≦1.3, a dielectric constant≦10, a viscosity≦5 cst, and a boiling point≧80° C.

7. Process according to claim 1, wherein the polar solvent used in step a) or step a′) is selected from water, low molecular weight alcohols, acetonitrile, DMSO, DMF or mixtures thereof.

8. Process according to claim 1, wherein the reverse emulsion comprises perfluoro(tributylamine) or dodecane as non-polar phase, and a polar phase comprising water, ethanol, methanol, industrial methylated spirits or mixtures thereof.

9. Process according to claim 1, further comprising as step c) concentrating the non-polar solvent or solvents.

10. Process according to claim 1, further comprising as step c′) removing the non-polar solvent or solvents.

11. A dispersion prepared by a process according to claim 1.

12.-20. (canceled)

21. A dispersion prepared by a process according to claim 10, and comprising colored or black particles.

22. A dispersion comprising; 1) at least one non-polar, fluorinated solvent, and colored, or black particles, comprising at least one dye, optionally at least one light stabilizer, and at least one fluorinated surfactant, and optionally at least one polymer, or 2) at least one non-polar, non-fluorinated solvent, and colored, or black particles, comprising at least one dye, optionally at least one light stabilizer, and at least one surfactant, wherein the dispersion 1) and 2) optionally includes at least one dye which is soluble in a non-polar solvent.

23. The dispersion according to claim 22, wherein the non-polar, fluorinated solvent, and the colored or black particles consist of at least one dye, optionally at least one light stabilizer, at least one poly(hexafluoropropylene oxide) polymeric surfactant with a monofunctional carboxylic acid end group and a weight-average molecular weight Mw between 5000 and 8000, and optionally polyvinyl pyrrolidone) and/or poly(acrylic acid).

24. An electronic device comprising a dispersion of claim 22, wherein the electronic device is selected from the group consisting of an electrooptical device, electrochemical device, electrophotographic device, electrowetting device, electro-osmotic device, electrohydrodynamic device, and electrophoretic device.

25. A mono, bi or polychromal electrophoretic device comprising the dispersion according to claim 21.

26. A Total Internal Reflection (TIR) type device comprising the dispersion according to claim 21.

27. The device according to claim 24, the device selected from the group consisting of a dynamic keypad, e-paper watch, dynamic pricing and advertising device, e-reader, rollable display, smart card media, product packaging, mobile phone, lab top, display card, digital signage and shelf edge label.

28. The device according to claim 24, wherein the dispersion is applied to the device by a technique selected from inkjet printing, slot die spraying, nozzle spraying, and flexographic printing.

Description

EXAMPLES

[0079] FC-43 and Novec® 7500 are purchased from Acota Ltd, UK. Krytox® 157 FS(H) (=Krytox® 157 FSH, weight-average molecular weight Mw 7000-7500) is purchased from GBR Technologies, UK. Methanol is purchased from VWR. Direct Black 22, Acid Black 52 and Acid Black 132 are acquired from Simpsons UK and Colour Synthesis Solutions Limited, UK. Acid Black 107 and Acid Black 172 are acquired from Town End (Leeds) plc, UK. Solvent Black 27 and Solvent Black 29 are acquired from Keystone Europe Ltd, UK. Polyvinyl pyrrolidone (weight-average average molecular weight Mw=29 000), poly(acrylic acid) (weight-average average molecular weight Mw 100,00), Solvent Blue 35, Acid Red 37, Acid Fuchsine, and 1,2,2,6,6-pentamethyl-4-piperidinol are purchased from Sigma-Aldrich, UK. MCR-C22 (monocarbinol terminated PDMS) is purchased from Gelest.

[0080] The characterisation of the formulations is performed using a Malvern NanoZS particle analyser. This instrument measures the size of particles in dispersion and the zeta potential of an electrophoretic fluid. The Zeta potential (ZP) is derived from the real-time measurement of the electrophoretic mobility and thus is an indicator of the suitability of the fluid for use in electrophoretic applications.

[0081] The colour coordinates of this dispersion are measured using an X-rite Color i5 spectrophotometer in a 50 micron thickness glass cell in reflective mode unless stated otherwise.

Example 1

Preparation of a Dispersion of Black Dyed PVP Particles

[0082] Solvent Black 27 (0.70 g), polyvinyl pyrrolidone (0.70 g, Mw=29000) and methanol (10 ml) are combined in a first flask, vortex mixed and then stirred on a roller-mixer for 3 hours.

[0083] Krytox® 157-FS (H) (0.70 g) and FC-43 (10 ml) are added to a second flask and are homogenised using shear-mixing for five minutes.

[0084] The mixture in the first flask is dripped into the fluorinated mixture in the second flask, continuing to mix on the shear mixer for two minutes. The combined mixture is sonicated for 5 minutes at 40% strength on a Branson Sonifier to form an emulsion (whilst being cooled in an ice bath).

[0085] The emulsion is added to a 100 ml florentine flask and evaporated on a rotary evaporator. The temperature of the water bath is 60° C. and the pressure is set to 350 mbar. The pressure is reduced in 50 mbar steps to 50 mbar to remove the methanol. The dispersion is filtered through 50 micron cloth, solid content is calculated. Particle size is 124 nm.

[0086] An electrophoretic ink is prepared by vortex mixing 0.066 g of the black particles (3.0 wt % particles), 0.011 g of Krytox® 157-FS(H) (0.5 wt % in FC43) and 2.123 g of FC-43 The dispersion is then roller mixed for a minimum of 30 minutes. Drops of this dispersion are added to 1.0 ml of FC-43 until the solution is slightly turbid and roller mixed for a minimum of 30 minutes. NanoZS particle analyser shows zP: −110.0 mV mobility: −3.92×10.sup.−10m.sup.2/Vs

[0087] and Xrite spectrophotometer shows L* measurement is 0.5 and Y is 4.1. Similarly prepared particles are made and measured using different dye, polymer and surfactant combinations as shown in Table 2 and Table 3.

TABLE-US-00002 TABLE 2 Zeta Mobility FC-43 Krytox ® MeOH PVP Dye Y- Size Potential (×10.sup.−10 Example (ml) (g) (ml) (g) Dye (g) Value L* (nm) (mV) m.sup.2/Vs) 1 10 0.7 10 0.7 Solvent Black 0.7 0.5 4.1 124 −110.0 −3.92 27 2 10 1.2 10 0.7 Solvent Black 0.7 0.3 3.1 99 42.40 1.52 27 3 10 1.0 10 0.7 Solvent Black 0.7 0.3 3.1 107 16.10 0.58 27 4 30 1.2 10 2.4 Acid Black 52 0.1 28.3 60.1 106 145.00 5.20 5 30 1.2 10 2.4 Acid Black 132 0.1 37.7 67.8 95 −301.00 −10.76 6 30 1.2 10 2.4 Acid Black 107 0.1 33.0 64.1 113 189.00 6.77 7 30 1.2 10 2.4 Acid Black 172 0.1 40.7 70.0 103 8 30 1.2 10 2.4 Solvent Black 0.1 25.3 57.4 111 27 9 30 1.2 10 2.4 Direct Black 22 0.1 25.6 57.7 108 −26.20 −0.94

TABLE-US-00003 TABLE 3 FC-43 Krytox ® Solvent Polymer Dye Particle Example (ml) (g) Solvent (ml) Polymer (g) Dye (g) Size (nm) 10 30 1.2 Methanol 10 PAA 2.4 Solvent Black 0.12 182 29 11 30 1.2 Water 10 PAA 2.4 Acid Red 37 0.12 213 12 30 1.2 Water 10 PAA 2.4 Acid Fuchsin 0.12 210 13 30 1.2 Water 10 PVP 2.4 Acid Red 37 0.12 173 14 30 1.2 Water 10 PVP 2.4 Acid Fuchsin 0.12 190 15 30 1.2 Water 10 PVP 2.4 Acid Fuchsin 0.24 180

Example 16

Preparation of a Dispersion of Black Particles

[0088] Solvent Black 29 (2.00 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0089] Krytox® 157-FS(H) (0.20 g) and FC-43 (10 ml) are added to a flask and are homogenised for five minutes.

[0090] The dyed methanol solution is dripped into the fluorinated phase, continuing to mix on the shear mixer for two minutes. The solution is then sonicated for 5 minutes at 40% strength on a Branson Sonifier to form an emulsion (whilst being cooled in an ice bath).

[0091] The emulsion is added to a 100 ml florentine flask and evaporated on a rotary evaporator. The temperature of the water bath is 60° C. and the pressure is set to 350 mbar. The pressure is reduced in 50 mbar steps to 50 mbar to complete removal of methanol.

[0092] Particle size is 222 nm, PDI=0.09.

[0093] Particles are formulated (3% particles and 0.5% Krytox® in FC-43): 0.072 g of the black particles, 0.012 g of Krytox® 157-FS(H) and 2.314 g of FC-43 are combined and measured as described in example 1. zP: -40.3 mV, Mobility:-1.44×10.sup.−10m.sup.2/Vs

[0094] L* 4.7 and Y is 0.52.

[0095] Similarly prepared particles are made, formulated and measured using the following amounts of reagents as shown in Table 4.

TABLE-US-00004 TABLE 4 Zeta Mobility FC-43/ Krytox ®/ Methanol/ Dye/ Y- Size/ Potential/ (×10.sup.−10 Example ml g ml Dye Type g Value L* nm PDI mV m.sup.2/Vs) 16 10.0 0.2 10.0 Solvent Black 2.0 0.5 4.7 222 0.09 −40.30 −1.44 29 17 15.0 0.8 10.0 Solvent Black 1.5 0.4 3.8 200 0.42 −134.00 −4.80 27 18 15.0 0.8 10.0 Solvent Black 1.5 0.4 4.0 142 0.16 253.00 9.06 29 19 15.0 0.8 10.0 Acid Black 52 1.5 0.3 2.5 115 0.07 20 15.0 0.8 10.0 Acid Black 107 1.5 0.4 3.9 129 0.16 20.20 0.72  21* 10 0.2 10 Solvent Black 2.0 0.3 2.6 357 0.36 42.2 1.51 27 *Reaction* carried out using 20 mL dodecane and 15 mL methanol.

Example 22

Preparation of a Dispersion of Black Particles using 2 Dyes

[0096] Solvent Black 29 (1.00 g), Solvent Black 27 (1.01 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0097] Krytox® 157-FS(H) (0.20 g) and FC-43 (10 ml) are added to a flask and are homogenised for five minutes.

[0098] The experiment is repeated as described for example 16.

[0099] Particle size is 111 nm

[0100] Particles are formulated and measured (3% particles and 0.5% Krytox® in FC-43):

[0101] zP: 54.30 mV, Mobility: 1.94×10.sup.−10 m.sup.2/Vs

[0102] L*3.22 and Y is 0.36.

Example 23

Preparation of Black Particles with Incorporation of Hindered Amine Light Stabiliser (HALS)

[0103] Solvent Black 29 (2.00 g), 1,2,2,6,6-pentamethyl-4-piperidinol (0.02 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0104] Krytox® 157-FS(H) (0.2 g) and FC-43 (10 ml) are added to a flask and homogenised on a Turax shear-mixer for five minutes.

[0105] The experiment is repeated as described for example 16.

[0106] Particle size is 109 nm

[0107] Particles are formulated and measured (3% particles and 0.5% Krytox® in FC-43):

[0108] zP: −43.6 mV, Mobility: −1.56×10.sup.−10 m.sup.2/Vs

[0109] L*2.85 and Y is 0.32.

Example 24

Preparation of Black Particles with Further Concentration of Fluid

[0110] Solvent Black 29 (12.0 g) and methanol (60 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0111] Krytox® 157-FS(H) (1.2 g) and FC-43 (60 ml) are added to a flask and are homogenised for ten minutes.

[0112] The dyed methanol solution is poured slowly onto the oil phase, continuing to mix on the shear mixer for ten minutes. The experiment is then followed as described in example 16.

[0113] Particle size is 221 nm.

[0114] Particles are formulated and measured (1.0% particles and 0.5% Krytox® in FC-43) as described in Example 16.

[0115] zP: 55.50 mV, Mobility: 1.99×10.sup.−10 m.sup.2/Vs.

[0116] The colour coordinates of this dispersion are measured using an X-rite Color i5 spectrophotometer in transmissive mode, using a 50 micron thickness ITO cell and are: L*38.49 and Y is 10.36.

[0117] The sample is washed using a stirred filtration kit with a 0.1 micron filter under ˜10 psi pressure over a weekend. Solid content is increased from 10.51% to 19.78%. A 1:1 equivalent of Novec® 7500 to FC-43 is added to the solution and the sample re-concentrated overnight, with the solids content increasing to 28.19%. Screening results after each wash are as follows in Table 5.

TABLE-US-00005 TABLE 5 Zeta Mobility Y- Size/ Potential/ (×10.sup.−10 Wash # Value L* nm PDI mV m.sup.2/Vs) 1 11.0 39.5 235 0.19 40.60 1.45 2 13.7 43.9 233 0.14 39.60 1.42

Example 25

Preparation of Black Particles in Dodecane

[0118] Direct Black 22 (0.50 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0119] Monocarbinol terminated PDMS (MCR-C22, Gelest) (0.05 g) and dodecane (10 ml) are added to a flask and homogenised for five minutes.

[0120] The experiment is then repeated as described for example 16

[0121] Particles are formulated and measured (1% particles and 1% AOT in dodecane):

[0122] L*83.6 and Y is 63.2.

[0123] Similarly prepared particles are synthesised and formulated with the following parameters as shown in Table 6.

TABLE-US-00006 TABLE 6 Example Surfactant Surfactant/g Dye Dye/g Y Value L* Size/nm PDI 26 Solsperse 17 k 0.16 Acid Black 107 1.6 25.6 57.6 464 0.46 27 OLOA 0.16 Acid Black 107 1.6 26.4 58.4 886 0.82 28 Solsperse 17 k 0.35 Solvent Black 27 3.500 65.5 84.8 29 Solsperse 17 k 0.32 Acid Black 107 1.600 44.1 72.3 221 0.29 30 Solsperse 17 k 0.48 Acid Black 107 1.600 51.1 76.8 182 0.25 31 Solsperse 17 k 0.64 Acid Black 107 1.600 52.0 77.3 228 0.31 32 Solsperse 17 k 0.80 Acid Black 107 1.600 45.3 73.1 386 0.59 33 Solsperse 17 k 0.20 Acid Black 172 1.000 76.0 89.9