Black polymer particles

Abstract

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

Claims

1. A process for the preparation of black polymer particles dispersed in at least one non-polar fluorinated solvent for use in electrophoretic devices, the process comprising the steps of a) forming a reverse emulsion comprising at least one polymer selected from poly(vinyl pyrrolidone) or poly(acrylic acid), at least one carbon black pigment, at least one polar solvent, at least one non-polar fluorinated solvent, at least one fluorinated surfactant, and a blue and/or black dye, wherein the reverse emulsion comprises perfluoro(tributlylamine) as a non-polar phase, and b) removing the polar solvent or solvents by evaporative methods, wherein the non-polar, fluorinated solvent or solvents are not removed.

2. The process according to claim 1, wherein the reverse emulsion of step a) is prepared by a process comprising; a1) forming a polar phase by mixing at least one polymer, at least one carbon black pigment, 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.

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

4. The process according to claim 1, wherein the non-polar fluorinated solvent used in step a) is a perfluorinated hydrocarbon having a refractive index of ≦1.3, a dielectric constant ≦10, and a boiling point ≧80 ° C., and has a refractive index and a density similar to that of the polymer used in step a).

5. The process according to claim 1, wherein the polar solvent used in step a) is selected from water, low molecular weight alcohols, methyl ethyl ketone, acetonitrile, DMSO, DMF or mixtures thereof.

6. The process according to claim 1, wherein a polar phase comprises one or more of water, ethanol, methanol, methyl ethyl ketone, or industrial methylated spirits.

7. The process according to claim 1, further comprising step c) concentrating the non-polar fluorinated solvent or solvents.

8. The process according to claim 1, further comprising step c′) removing the non-polar fluorinated solvent or solvents.

9. A dispersion comprising black particles prepared according to claim 8.

10. A mono, bi or polychromal electrophoretic device comprising the dispersion according to claim 9.

11. A Total Internal Reflection (TIR) device comprising the dispersion according to claim 9.

12. An electrophoretic display device comprising the dispersion according to claim 9.

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

14. The process according to claim 1, wherein the blue and/or black dye is selected from the group consisting of Solvent Blue 35, Solvent Black 27, Solvent Black 29, Solvent Black 34, Acid Black 52, Acid Black 107, Acid Black 132, Acid Black 172, Acid Black 194, Acid Black 211, Acid Black 222, Direct Black 19, Direct Black 22, Direct Black 51, Direct Black 80, and Direct Black 112.

15. The process according to claim 1, wherein the blue and/or black dye comprises a stabilizer selected from the group consisting of 1,2,2,6,6-pentamethylpiperidine, 1,2,2,6,6-pentamethyl-4-piperidinol, and bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[(3,5-bis(1 ,1 -di methyl)-4-hydroxyphenyl]methylbutylmalonate.

16. A dispersion comprising a non-polar, fluorinated solvent, and black particles, wherein the black particles comprise carbon black, a polymer selected from poly(vinyl pyrrolidone) or poly(acrylic acid), a fluorinated surfactant, and a blue and/or black dye, and wherein the dispersion comprises perfluoro(tributylamine) as a non-polar phase.

17. The dispersion according to claim 16, comprising perfluoro(tributylamine), and the black particles consist of the carbon black, poly(vinyl pyrrolidone) and/or poly(acrylic acid), and a poly(hexafluoropropylene oxide) polymeric surfactant with a monofunctional carboxylic acid end group, and a weight-average molecular weight Mw between 5000 and 8000.

18. An electronic device comprising a dispersion of claim 16, 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.

19. The device according to claim 18, 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.

20. The device according to claim 18, 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

(1) FC-43 and Novec® 7500 are purchased from Acota Ltd, UK. Krytox® 157 FS(H) (weight-average molecular weight Mw 7000-7500) is purchased from GBR Technologies, UK. Methanol is purchased from VWR. Polyvinyl pyrrolidone (PVP; weight-average average molecular weight Mw=29 000) and polyacrylic acid (PAA, weight-average average molecular weight Mw 100,000), Solvent Blue 35 are purchased from Sigma-Aldrich, UK. Carbon Black FW200 or XPB229 is obtained from Orion Engineered Carbons. Solvent Black 27 is obtained from BASF.

(2) The characterisation of the formulations was 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. The colour coordinates of this dispersion are measured using an X-rite Color i5 spectrophotometer in a 50 micron thickness glass cell in transmissive mode unless stated otherwise and formulated at 3 wt % dispersion of particles with 0.5 wt % Krytox®,

Example 1

Preparation of Carbon Black PVP Particles

(3) Krytox® 157-FS(H) (1.8 g) is dissolved in FC-43 (30 ml) to make the oil phase.

(4) Separately, methanol (10 ml), FW200 (0.5 g) and PVP (3.6 g) are combined and stirred until homogeneous and homogenised by high shear mixing for 5 minutes (whilst being cooled in an ice bath).

(5) The two phases are then combined and mixed by shear mixer.

(6) The dispersion is then sonicated for 5 minutes at 40% strength on the Branson Sonifer to form an emulsion (whilst being cooled in an ice bath). The emulsion is added into a 500 ml florentine flask and methanol is removed on a rotary evaporator where the temperature of the bath is 60° C. and the pressure is set to 300 mbar. Pressure is reduced in 50 mbar steps to 50 mbar pressure and left there for 1 hour to ensure complete removal of solvents.

(7) Reaction mixture is filtered through 50 micron cloth. Solids content is 11.4 weight %, particle size is 211 nm.

(8) Zp: +6.4 (3% particles, 0.5% Krytox® 157-FS(H) in FC-43) Mobility: 0.03 ×10.sup.−10 m.sup.2/Vs

(9) L* 33, Y 7.53, x 0.41, y 0.39

Example 2

Preparation of Carbon Black PVP Particles

(10) Krytox® 157-FS(H) (10.8 g) is dissolved in FC-43 (120 ml) to make the oil phase.

(11) Separately, methanol (60 ml), carbon black FW200 (3.0 g) and PUP (21.6 g) are combined and stirred until homogeneous using a high shear mixer for 10 minutes whilst being cooled in an ice bath.

(12) The two phases are then combined and mixed by shear mixer for 10 minutes whilst being cooled in an ice bath.

(13) The dispersion is then sonicated for 5 minutes at 40% strength on the Branson Sonifer to form an emulsion (whilst being cooled in an ice bath).

(14) The emulsion is added into a 500 ml florentine flask and methanol is removed on a rotary evaporator where the temperature of the bath is 60° C. and the pressure is set to 300 mbar. Pressure is reduced in 50 mbar'steps to 50 mbar pressure and left there for 1 hour. The flask is raised out of the water bath and left at 50 mbar for a further 1 hour to ensure complete removal of solvents.

(15) Reaction mixture is filtered through 50 micron cloth into an amber bottle.

(16) Solids: 13.4%

(17) Yield: 88%

(18) The product mixture is concentrated using a stirred filtration using the 100 nm membrane and is filtered at 10 psi for 18 hrs.

(19) Solids: 22.8%

(20) The concentrated mixture is then refiltered to increase the solid content under the same conditions as before.

(21) Solids: 27.6%

(22) Size: 243 nm

(23) Zp: +40.2 (3% particles, 0.5% Krytox® 157-FS(H) in FC-43) Mobility: 0.009 ×10.sup.−10 m.sup.2/Vs

Example 3

Preparation of Carbon Black PVP Particles with Solvent Exchange

(24) Krytox® 157-FS(H) (10.8 g) is dissolved in FC-43 (120 ml) to make the oil phase and submitted to high shear mixing for 10 minutes.

(25) Separately, methanol (60 ml), carbon black FW200 (3.0 g) and PVP (21.6 g) are combined and stirred until homogeneous using high shear mixing for 10 minutes (whilst being cooled in an ice bath).

(26) The two phases are then combined and mixed by shear mixer for 10 minutes.

(27) The dispersion is then sonicated for 5 minutes at 40% strength on the Branson Sonifer to form an emulsion (whilst being cooled in an ice bath). The emulsion is added into a 500 ml florentine flask and methanol is removed on a rotary evaporator where the temperature of the bath is 60° C. and the pressure is set to 300 mbar. Pressure is reduced in 50 mbar steps to 50 mbar pressure and left there for 1 hour to ensure complete removal of solvents.

(28) Reaction mixture is filtered through 50 micron cloth into an amber bottle.

(29) Solids: 13.4%

(30) Yield: 85%

(31) The product mixture is then submitted to stirred filtration using a 100 nm membrane and is filtered at 10 psi for 2 days.

(32) Solids: 33.6%

(33) mass product: 15.98 g (31.53 g FC-43)

(34) 47.29 g of Novec® 7500 is added at this stage

(35) The concentrated mixture is then refiltered to increase the solid content under the same conditions as before.

(36) Solids: 41.5%

(37) Zp: +93.7 (3% particles, 0.5% Krytox® 157-FS(H) in FC-43) Mobility: 0.02 ×10.sup.−10 m.sup.2/Vs

(38) Size: 282 nm

Example 4

Preparation of Carbon Black PAA Particles

(39) Krytox® 157-FS(H) (0.8 g) is dissolved in FC-43 (30 ml) to make the oil phase.

(40) Separately, methanol (10 ml), XPB229 (0.35 g) and PAA (1.6 g) are combined and stirred until homogeneous and high shear mixed for 5 minutes whilst being cooled in an ice bath.

(41) The two phases are then combined and mixed by a Turrax high shear mixer whilst being cooled in an ice bath.

(42) The dispersion is sonicated for 5 minutes at 40% strength on the Branson Sonifier to form an emulsion whilst being cooled in an ice bath.

(43) The emulsion is added into a 500 ml florentine flask and methanol is removed on a rotary evaporator where the temperature of the bath is 60° C. and the pressure is set to 300 mbar. Pressure is reduced in 50 mbar steps to 50 mbar pressure and left there for 1 hour to ensure complete removal of solvents.

(44) Reaction mixture is filtered through 50 micron cloth.

(45) Size: 382 nm,

(46) Zp: +23.7 (3% particles, 0.5% Krytox® 157-FS(H) in FC-43) Mobility: 0.005 ×10.sup.−10 m.sup.2 Vs.

Example 5

Prepartion of Particles of Carbon Black and PAA with Additional Blue Dye

(47) Krytox® 157-FS(H) (1.8 g) is dissolved in FC-43 (30 ml) to make the oil phase.

(48) Separately, methanol (10 ml), XPB229 (0.5 g), Solvent Blue 35 (0.1 g) and FAA (3.6 g) are combined and stirred until homogeneous and high shear mixed for 5 minutes whilst being cooled in an ice bath.

(49) The two phases are then combined and mixed by a Turrax high shear mixer whilst being cooled in an ice bath.

(50) The solution is then sonicated for 5 minutes at 40% strength on the Branson Sonifier to form an emulsion whilst being cooled in an ice bath.

(51) The emulsion is added into a 500 ml florentine flask methanol is removed on a rotary evaporator where the temperature of the bath is 60° C. and the pressure is set to 300 mbar. Pressure is reduced in 50 mbar steps to 50 mbar pressure and left there for 1 hour to ensure complete removal of solvents.

(52) Reaction mixture is filtered through 50 micron cloth.

(53) Size: 356 nm, L* 5.41, Y 0.5999, x 0.47, y 0.42

Example 6

Preparation of Particles of Carbon Black and PVP with added Black Dye

(54) Krytox® 157-FS(H) (0.72 g) is dissolved in FC-43 (20 ml) to make the oil phase.

(55) Separately, methanol (10 ml), FW200 (0.4 g), Solvent Black 27 (0.1 g) and PVP (3.6 g) are combined and stirred until homogeneous and subjected to high shear mixing for 5 minutes whilst being cooled in an ice bath.

(56) The two phases are combined and high shear mixed whilst being cooled in an ice bath.

(57) The solution is sonicated for 5 minutes at 40% strength on the Branson Sonifier to form an emulsion whilst being cooled in an ice bath.

(58) The emulsion is added to a 500 ml florentine flask and methanol is removed on a rotary evaporator where the temperature of the bath is 60° C. and the pressure is set to 300 mbar. Pressure is reduced in 50 mbar steps to 50 mbar pressure and left there for 1 hour to ensure complete removal of solvents.

(59) Reaction mixture is filtered through 50 micron, Size: 252 nm

(60) Yield: 78%

(61) L* 12.23, Y 1.44, x 0.44, y 0.40