Particles for electrophoretic displays

Abstract

This invention relates to polymer particles, a process for their preparation, electrophoretic fluids comprising such particles, and electrophoretic display devices comprising such fluids.

Claims

1. Polymer particles for use in electrophoretic devices comprising monomer units of a) at least one ethylenically unsaturated monomer; b) at least one polymerisable ionic liquid (PIL) selected from A to S listed below: TABLE-US-00008 PIL Cation Anion A B C D E F G H I J K L M N O P Q R S c) optionally at least one polymerisable dye, and d) optionally at least one polymerisable steric stabilizer and wherein the particles are spherical and have a diameter particle size in the range of 50-1200 nm.

2. Polymer particles according to claim 1, wherein the polymerisable dye is present and is a dye of the formula (I)-(VI), or (VII) ##STR00110## wherein R is H; R1 and R2 are independently of one another alkyl, OR, SR, C(O)R, C(O)OR, NHCOR, NO.sub.2, CN, with R equal to H or alkyl; L.sup.1 and L.sup.2 are independently of one another a single bond, C1-C6 alkyl, a polyether alkyl chain, or a combination thereof; and Y.sup.1 and Y.sup.2 are methyl acrylate or methylmethacrylate; X.sub.1, X.sub.2, and X.sub.3 are independently of one another H or an electron-withdrawing group; R.sub.1 is H or OR with R=a linear, branched or cyclic alkyl group; R.sub.2 is a linear, branched or cyclic alkyl group; R.sub.3 and R.sub.4 are independently of one another groups of the structure L.sub.3-Y.sub.3, L.sub.4-Y.sub.4; L.sub.3, and L.sub.4 are linker groups and independently of one another linear or branched, substituted or unsubstituted alkylene groups where one or more non-adjacent carbon atoms is optionally replaced by O, S and/or N; Y.sub.3, and Y.sub.4 are independently of one another polymerisable groups; wherein at least one of R.sub.3 and R.sub.4 comprises a polymerisable group and at least one of X.sub.1, X.sub.2, and X.sub.3 is an electron-withdrawing group.

3. Polymer particles according to claim 2, wherein wherein R is H; R1 and R2 are independently of one another CH.sub.3, NO.sub.2, OH, CN, COCH.sub.3, CO.sub.2CH.sub.2CH.sub.3, NHCOR; L.sup.1 and L.sup.2 are, identical, C2-C4 alkyl, and Y.sup.1 and Y.sup.2 are, identical, methyl acrylate or methyl methacrylate, X.sub.1, X.sub.2, and X.sub.3 are independently of one another, an electron-withdrawing group selected from the group consisting of NO.sub.2, CN, halogen, acyl, trifluoromethoxy, trifluoromethyl, SO.sub.2F, and CO.sub.2R, SO.sub.2R, SO.sub.2NRR and SO.sub.2NHR, with R being independently linear or branched C1-C4 alkyl, with at least one of X.sub.1, X.sub.2, and X.sub.3 is NO.sub.2, CN, Br, Cl, SO.sub.2NRR or SO.sub.2NHR and Y.sub.3 and Y.sub.4 are identical and are methacrylate or acrylate.

4. Polymer particles according to claim 1, wherein the polymerisable dye is present and is a dye of the Dye 1 to Dye 19: TABLE-US-00009 Dye 1 Dye 2 Dye 3 Dye 4 Dye 5 Dye 6 Dye 7 Dye 8 Dye 9 Dye 10 Dye 11 Dye 12 Dye 13 Dye 14 Dye 15 Dye 16 Dye 17 Dye 18 Dye 19

5. Polymer particles according to claim 1, wherein the at least one polymerisable dye is present and the polymerisable dye is selected from the group consisting of monoazo dyes, disazo dyes, metallised dyes, anthraquinone dyes, phthalocyanine dyes, benzodifuranones dyes, Brilliant Blue derivatives, pyrroline dyes, squarilium dyes, triphendioxazine dyes and mixtures of these dyes.

6. Polymer particles according to claim 1, wherein said at least one polymerisable ionic liquid is selected from the A, B, C, D, E, F, G, H, I, J, K, O, P, Q, or R.

7. Polymer particles according to claim 1, wherein said at least one polymerisable dye is present, and said at least one polymerisable steric stabilizer is present.

8. Polymer particles according to claim 1, wherein the polymerisable dye is present and is a dye of the formula (VIII) ##STR00130## wherein X.sub.1, X.sub.2, and X.sub.3 are independently of one another H or an electron-withdrawing group; R.sub.1 and R.sub.2 are independently of one another groups of the structure L.sub.1-Y.sub.1, L.sub.2-Y.sub.2 or linear, branched or cyclic alkyl groups; R.sub.3 and R.sub.4 are independently of one another groups of the structure L.sub.3-Y.sub.3, L.sub.4-Y.sub.4 or linear, branched or cyclic, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N; L.sub.1, L.sub.2, L.sub.3, and L.sub.4 are linker groups and independently of one another linear or branched, substituted or unsubstituted alkylene groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N; Y.sub.1, Y.sub.2, Y.sub.3, and Y.sub.4 are independently of one another polymerisable groups; R is a linear or branched alkyl group, OR.sub.5, H, NHCOR.sub.6 or NHSO.sub.2R.sub.7; R is OR.sub.5, H or NHCOR.sub.6, R.sub.5, R.sub.6, and R.sub.7 are independently of one another linear or branched alkyl groups; and wherein at least one of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a polymerisable group and at least one of X.sub.1, X.sub.2, and X.sub.3 is an electron-withdrawing group.

9. Polymer particles according to claim 1, wherein the ethyleneically unsaturated monomer is methacrylates and/or acrylates.

10. Polymer particles according to claim 1, wherein the at least one polymerisable dye is present and the polymerisable dye is selected from azo dyes.

11. Polymer particles according to claim 1, wherein the at least one polymerisable steric stabilizer is present and the polymerisable steric stabilizer is a poly(dimethylsiloxane) macromonomer with at least one polymerisable group and a molecular weight in the range of 1000-50000.

12. Polymer particles according to claim 1, wherein the at least one polymerisable steric stabilizer is present and the polymerisable steric stabilizer is a mono-methacrylate terminated poly-dimethylsiloxane.

13. Polymer particles according to claim 1, wherein the particles are spherical and have a diameter particle size in the range of 400-1000 nm.

14. Polymer particles according to claim 1, wherein the particles are spherical and have a diameter particle size in the range 400-700 nm.

15. Polymer particles according to claim 10, wherein the particles are spherical and have a diameter particle size in the range 400-700 nm, and with a monodisperse size distribution.

16. A process for the preparation of polymer particles according claim 1, comprising a) polymerizing said at least one ethylenically unsaturated monomer, said at least one polymerisable ionic liquid, at least one initiator, said at least one polymerisable dye, and said at least one polymerisable steric stabiliser by dispersion or emulsion polymerisation in a non-aqueous, non-polar solvent, and b) optionally washing and drying the polymer particles.

17. An electrophoretic fluid comprising polymer particles prepared by the process according to claim 16.

18. An optical display, electrooptical display, electronic display, electrochemical display, electrophotographic display, electrowetting display, electrophoretic display, optical device, electrooptical device, electronic device, electrochemical device, electrophotographic device, electrowetting device, electrophoretic device, in security applications, cosmetic applications, decorative applications or diagnostic applications comprising polymer particles according to claim 1.

19. A mono, bi or polychromal electrophoretic devices which comprises polymer particles according to claim 1.

20. An electrophoretic fluid comprising polymer particles according to claim 1.

21. An electrophoretic display device comprising an electrophoretic fluid according to claim 20.

22. The electrophoretic display device according to claim 21, wherein the electrophoretic fluid is applied by a technique selected from inkjet printing, slot die spraying, nozzle spraying, flexographic printing, contact printing, contactless printing or deposition technique.

Description

EXAMPLES

(1) PDMS monomers are purchased from Fluorochem, UK. Reagents and dodecane are purchased from Sigma-Aldrich Company and used without further purification. AIBN initiator is purchased from VWR. V59 initiator is purchased from Wako. Polymerisable ionic liquids are prepared before use from the corresponding bromide salt.

(2) Magenta dye (Dye 1) dye synthesis is previously disclosed in WO 2012/019704/example 11.

(3) Yellow dye (Dye 2) synthesis is previously disclosed in WO 2012/019704/example 24.

(4) Black dye (Dye 3) synthesis is previously disclosed in WO 2013/079146019704/example 3.

(5) Particle size is measured by SEM and image analysis. One drop of a particle dispersion is added to 2.5 ml heptane. One drop of this solution is deposited onto a silica wafer attached to the SEM stub. Samples are sputtered by gold for 120 seconds at 18 mA before being assessed in the SEM chamber.

(6) The electrophoretic fluids are prepared by vortex mixing 3 wt % of particles, 3 wt % of AOT (sodium bis(2-ethylhexyl)sulfosuccinate); 5 wt % in dodecane, and 94 wt % of dodecane. The dispersion is then roller mixed for 30 minutes.

(7) The Zeta potentials of the formulations are performed using a Malvern NanoZS particle analyser unless otherwise stated. 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.

(8) Samples for analysis are prepared from PIL containing particle dispersions with known particle weight content. When using additives, surfactants are added at a concentration so that the ratio of particles to surfactant is 1:1 by weight.

(9) Preparation of Bromide Salts

(10) (Used for the Preparation of all Imidazolium and Pyrrolidinium Based Ionic Liquids)

(11) ##STR00070##

(12) Methyl imidazole (1 eq) and a bromoalkane (1.1 eq) are weighed into a round bottomed flask and acetonitrile is added. The flask is equipped with a magnetic stirrer bar, and a condenser. The mixture is stirred at 65 C. until consumption of methyl imidazole is evident by NMR analysis. The reaction mixture is then cooled and the mixture concentrated in vacuo. The resulting material is recrystallised using ethyl acetate.

(13) Anion Exchange

(14) (Used for the Preparation of all SPMA Ionic Liquids)

(15) ##STR00071##

(16) Amberlite IRA-400 (Cl) resin (100 ml) is loaded into a column and flushed with water until the solvent runs clear. A bromide salt (10 g) is dissolved in acetonitrile (100 ml) and is passed slowly through the resin. The resin is washed with further acetonitrile. The solvent is then concentrated in vacuo. The resulting chloride salt is then re-dissolved in acetonitrile (20 ml). In a separate flask the 3-sulfopropylmethyacylate potassium salt (1.1 eq) is dissolved in acetonitrile. This solution is added drop wise to the stirring chloride salt, once addition is complete allowed to stir at room temperature overnight. The resulting suspension is then filtered and concentrated in vacuo. The residue is re-dissolved in DCM, re-filtered and concentrated to yield the product ionic liquid.

Example 1: Synthesis of Undyed pMMA Particles with Positive Zeta Potential with AOT Surfactant in Dodecane (Larger Particles)

(17) Methyl methacrylate (20.58 g), N6666 SPMA (1.03 g) and PDMS-MA (10000 mw) stabiliser (1.05 g) are weighed out into a 100 ml 3-necked flask equipped with a condenser, nitrogen flow and an overhead stirrer.

(18) Dodecane (25.20 g) is added to the reaction flask. The mixture is heated with stirring at 300 rpm, and once the temperature in the flask is at 75 C., Vazo-59 (0.2 g) is added and the reaction stirred for 2 hours.

(19) The resulting solution is filtered through a 50 micron cloth to remove small lumps. The particles are cleaned using a centrifuge. Centrifugations are carried out at 10000 rpm for 20 minutes each, replacing the supernatant with dodecane three times. Average particle size is measured by SEM and image analysis: 1595 nm.

Examples

(20) TABLE-US-00003 Example PIL % PIL Size/nm zP in AOT/mV 1 N6666 5 1595 +44 SPMA 2 C8mim 5 1216 +2.5 SPMA

Example 3: Synthesis of Undyed pMMA Particles with Positive Zeta Potential with AOT Surfactant in Dodecane (Smaller Particles)

(21) Methyl methacrylate (5.08 g), N6666 SPMA (0.27 g) and PDMS-MA (10000 mw) stabiliser (1.7 g) are weighed out into a 100 ml 3-necked flask equipped with a condenser, nitrogen flow and an overhead stirrer.

(22) Dodecane (42.00 g) is added to the reaction flask. The mixture is heated with stirring at 300 rpm, and once the temperature in the flask is at 75 C., Vazo-59 (0.2 g) is added and the reaction stirred for 2 hours.

(23) The resulting solution is filtered through a 50 micron cloth to remove small lumps. The particles are cleaned using a centrifuge. Centrifugations are carried out at 10000 rpm for 20 minutes each, replacing the supernatant with dodecane three times. Average particle size is measured by SEM and image analysis: 358 nm.

Examples

(24) TABLE-US-00004 Example PIL % PIL Size/nm zP in AOT/mV 3 N6666 5 358 +148 SPMA 4 C8mim 10 357 +78 SPMA 5 N6666 10 330 +110 SPMA 6 C12mpyrr 5 289 +81 SPMA 7 P66614 5 590 +112 SPMA 8 P66614 10 598 +93 SPMA 9 P66614 15 353 +83 SPMA 10 P66614 1 258 +91 SPMA 11 P66614 2.5 347 +111 SPMA 12 N6666 15 676 +118 SPMA 13 P4444 1 277 +115 SPMA 14 P4444 2.5 277 +80 SPMA 15 P4444 5 228 +76 SPMA

Example 16: Synthesis of Black pMMA Particles with Positive Zeta Potential with AOT Surfactant in Dodecane (Smaller Particles)

(25) Methyl methacrylate (5.08 g), N6666 SPMA (0.54 g), black dye (Dye 3; 0.23 g), yellow dye (Dye 2; 0.04 g) and PDMS-MA (10000 mw) stabiliser (1.7 g) are weighed out into a 100 ml 3-necked flask equipped with a condenser, nitrogen flow and an overhead stirrer. Stirring is initiated to facilitate dissolution of the dye. Dodecane (42.00 g) is added to the reaction flask.

(26) The mixture is heated with stirring at 300 rpm, and once the temperature in the flask is at 75 C., Vazo-59 (0.43 g) is added and the reaction stirred for 2 hours.

(27) The resulting solution is filtered through a 50 micron cloth to remove small lumps. The particles are cleaned using a centrifuge. Centrifugations are carried out at 10000 rpm for 20 minutes each, replacing the supernatant with dodecane until the supernatant is colourless. Average particle size is measured by SEM and image analysis: 539 nm.

Examples

(28) TABLE-US-00005 % % N6666 Black Example SPMA Dye Size/nm zP in AOT/mV 16 10 5 539 +172 17 1 5 450 +105 18 5 5 436 +184 19 2.5 5 272 +154 20 5 10 801 +114

Example 21: Synthesis of Magenta pMMA Particles with Positive Zeta Potential with AOT Surfactant in Dodecane

(29) Methyl methacrylate (5.08 g), N6666 SPMA (0.27 g), magenta dye (Dye 1; 0.27 g) and PDMS-MA (10000 mw) stabiliser (1.7 g) are weighed out into a 100 ml 3-necked flask equipped with a condenser, nitrogen flow and an overhead stirrer. Stirring is initiated to facilitate dissolution of the dye.

(30) Dodecane (42.00 g) is added to the reaction flask. The mixture is heated with stirring at 300 rpm, and once the temperature in the flask is at 75 C., Vazo-59 (0.43 g) is added and the reaction stirred for 2 hours.

(31) The resulting solution is filtered through a 50 micron cloth to remove small lumps. The particles are cleaned using a centrifuge. Centrifugations are carried out at 10000 rpm for 20 minutes each, replacing the supernatant with dodecane until the supernatant is colourless. Average particle size is measured by SEM and image analysis: 691 nm.

(32) TABLE-US-00006 % % N6666 Magenta Example SPMA Dye Size/nm zP in AOT/mV 21 5 5 691 +154

Example 22: Synthesis of Yellow pMMA Particles with Positive Zeta Potential with AOT Surfactant in Dodecane

(33) Methyl methacrylate (5.08 g), N6666 SPMA (0.27 g), yellow dye (Dye 2; 0.27 g) and PDMS-MA (10000 mw) stabiliser (1.7 g) are weighed out into a 100 ml 3-necked flask equipped with a condenser, nitrogen flow and an overhead stirrer. Stirring is initiated to facilitate dissolution of the dye.

(34) Dodecane (42.00 g) is added to the reaction flask. The mixture is heated with stirring at 300 rpm, and once the temperature in the flask is at 75 C., Vazo-59 (0.43 g) is added and the reaction stirred for 2 hours.

(35) The resulting solution is filtered through a 50 micron cloth to remove small lumps. The particles are cleaned using a centrifuge. Centrifugations are carried out at 10000 rpm for 20 minutes each, replacing the supernatant with dodecane until the supernatant is colourless. Average particle size is measured by SEM and image analysis: 680 nm.

(36) TABLE-US-00007 % % N6666 Yellow Example SPMA Dye Size/nm zP in AOT/mV 22 5 5 680 +83