Colored polymer particles for electrophoretic displays

Abstract

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

Claims

1. Coloured polymer particles consisting of monomer units of at least one polymerisable dye having at least two polymerizable groups, at least one co-monomer, at least one polymerisable steric stabiliser selected from poly(dimethylsiloxanes) having one polymerisable group, wherein the percentage of polymerisable steric stabiliser is at least 20% by weight based on the weight of the polymer particle.

2. The coloured polymer particles according to claim 1, wherein the polymerisable steric stabiliser is a methacryloyloxypropyl terminated polydimethylsiloxane.

3. The coloured polymer particles according to claim 1, wherein the polymerisable steric stabiliser is a poly(dimethylsiloxane) macromonomer with a molecular weight in the range of 1000-50000.

4. The coloured polymer particles according to claim 1, wherein the polymerisable dye is selected from the group consisting of azo dyes, metallised dyes, anthraquinone dyes, phthalocyanine dyes, benzodifuranones dyes, Brilliant Blue derivatives, pyrroline dyes, squarilium dyes, triphendioxazine dyes, and mixtures of these dyes.

5. The coloured polymer particles according to claim 1, wherein at least one dye of Formula (VII) is used ##STR00024## 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 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 may be replaced by O, S and/or N, preferably O; 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.

6. The coloured polymer particles according to claim 1, wherein the coloured polymer particles have a diameter of 400-1000 nm.

7. The coloured polymer particles according to claim 1, wherein the coloured polymer particles have a diameter of 400-700 nm.

8. The coloured polymer particles according to claim 1, wherein the at least one polymerisable dye is a dye of Formula (I), (II) or (VII), ##STR00025## wherein R is H; R1 and R2 are independently of one another alkyl; L1 and L2 are independently of one another a single bond; Y1 and Y2 are methyl acrylate or methyl methacrylate; ##STR00026## 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 is H or OR with R=a linear, branched or cyclic alkyl group; R2 is a linear, branched or cyclic alkyl group; R3 and R4 are independently of one another groups of the structure L3-Y3, L4-Y4; L3, and L4 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; Y3, and Y4 are identical and are a polymerisable group; wherein at least one of X1, X2, and X3 is an electron-withdrawing group.

9. A process for the preparation of coloured polymer particles according to claim 1, comprising a) polymerising at least one polymerisable dye having at least two polymerizable groups, at least one co-monomer, at least one polymerisable steric stabiliser selected from poly(dimethylsiloxanes) having one polymerisable group, at least one initiator, optionally a chain transfer agent, optionally a charged co-monomer, and optionally a crosslinking co-monomer by dispersion or emulsion polymerisation in a non-aqueous, non-polar solvent, and optionally b) washing and drying the coloured polymer particles.

10. A method comprising utilizing particles prepared by a process according to claim 9 in optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting and electrophoretic displays and/or devices, and in security, cosmetic, decorative, and diagnostic applications.

11. An electrophoretic fluid comprising coloured polymer particles prepared by a process according to claim 9.

12. A method comprising utilizing the coloured polymer particles according to claim 1 in optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting and electrophoretic displays and/or devices, and in security, cosmetic, decorative, and diagnostic applications.

13. An electrophoretic fluid comprising coloured polymer particles according to claim 1.

14. An electrophoretic display device comprising an electrophoretic fluid according to claim 13.

15. An electrophoretic display device according to claim 14, wherein the electrophoretic fluid is applied by a technique selected from inkjet printing, slot die spraying, nozzle spraying, and flexographic printing, or any other contact or contactless printing or deposition technique.

Description

EXAMPLES

(1) PDMS macromonomers are purchased from Gelest Inc. 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. The water used is de-ionised. Magenta and Yellow dyes used to make particles are previously reported in WO 2012/019704 Particle size is measured by SEM.

(2) 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.

Example 1: (E)-4,4-(4-((2,6-dicyano-4-nitrophenyl)diazenyl)-2-methoxy-5-(3,5,5-trimethylhexanamido)phenylazanediyl)bis(butane-4,1-diyl) diacrylate (Dye 3)

(3) ##STR00023##

Step 1: 4,4-(5-acetamido-2-methoxyphenylazanediyl)bis(butane-4,1-diyl) diacetate

(4) A stirred mixture of 3-amino-4-methoxyacetanilide (18.0 g, 0.1 mol), 4-bromobutyl acetate (48.8 g, 0.25 mol), 1-methyl-2-pyrrolidinone (50 ml) and sodium bicarbonate (55.2 g, 0.66 mol) is heated in an oil bath at 105 C. overnight, allowed to cool and then poured into water (500 ml). After stirring for 30 minutes, the oil that separates is extracted with dichloromethane (150 ml), the organic layer is dried (MgSO.sub.4) and evaporated to give a thick brown oil (57.0 g). The oil is used directly without further purification (95% purity).

Step 2: 4,4-(5-amino-2-methoxyphenylazanediyl)dibutan-1-ol

(5) Crude 4,4-(5-acetamido-2-methoxyphenylazanediyl)bis(butane-4,1-diyl) diacetate (0.1 mol) is dissolved in dioxane (200 ml) and 1M LiOH (300 ml) is added. After 15 minutes, the reaction is neutralised with 35% HCl (5 ml) then evaporated to give a brown oil. The oil is dissolved in a mixture of water (200 ml) and 35% HCl (100 ml) and heated for 4 h at 90 C., allowed to cool to RT, basified to pH 11.0 and the resultant oil is extracted with DCM (2150 ml), dried (MgSO.sub.4) and evaporated to give a dark brown viscous oil. (28.3 g, 100%). The crude product is used directly without purification.

Step 3: N-(3-(Bis(4-hydroxybutyl)amino)-4-methoxyphenyl)-3,5,5-trimethylhexanamide

(6) 4,4-(5-Amino-2-methoxyphenylazanediyl)dibutan-1-ol (50 mmol) is dissolved in dichloromethane (200 ml) and to this is added triethylamine (7.6 g, 75 mmol). 3,5,5-Trimethylhexanoyl chloride (8 ml) is added dropwise, Methanol (100 ml) is added and the reaction is stirred overnight and is used directly without further purification.

Step 4: (E)-N-(5-(Bis(4-hydroxybutyl)amino)-2-((2-bromo-6-cyano-4-nitrophenyl)diazenyl)-4-methoxyphenyl)-3,5,5-trimethylhexanamide

(7) Sulfuric acid (80% w/w, 75 ml) is cooled to 5 C. and 6-bromo-2-cyano-4-nitroaniline (9.7 g, 40 mmol) is added and stirred for 10 minutes at <5 C. until fully dispersed. Nitrosyl sulfuric acid 40% (w/w) in sulfuric acid (15.3 g, 0.048 mol) is added in portions at 3-5 C. over 30 minutes, then stirred for a further hour at <5 C. N-(3-(Bis(4-hydroxybutyl)amino)-4-methoxyphenyl)-3,5,5-trimethylhexanamide (assume 41 mmol) is diluted with methanol (100 ml), cooled externally in an ice bath to 5 C. and solid ice (50 g) and water (50 ml) are added. Sulfamic acid (10 ml) is added. The above diazonium salt solution is added dropwise over 1 hour. The reaction is stirred overnight, then the solid filtered-off and dried overnight at 40 C. (13.4 g, 50%). The crude product is recrystallised from hot IMS to give the required dye as a green crystalline solid (8.9 g, 32%).

Step 5: (E)-N-(5-(bis(4-hydroxybutyl)amino)-2-((2,6-dicyano-4-nitrophenyl)diazenyl)-4-methoxyphenyl)-3,5,5-trimethylhexanamide

(8) N-(5-(Bis(4-hydroxybutyl)amino)-2-((2-bromo-6-cyano-4-nitrophenyl)diazenyl)-4-methoxyphenyl)-3,5,5-trimethylhexanamide (8.8 g, 13.0 mmol) is suspended in 1-methyl-2-pyrrolidinone (15 ml) and warmed to 55 C. to dissolve. Zinc cyanide (0.82 g, 7 mmol) followed by copper(I) cyanide (0.4 mg, 0.45 mmol) are added and the reaction heated to 105 C. (bath temp). After 3 h, external heating is removed and methanol (45 ml) is added. The resultant crystalline solid is filtered off. The solid is recrystallised from IMS (6.1 g, 75%).

Step 6: (E)-4,4-(4-((2,6-dicyano-4-nitrophenyl)diazenyl)-2-methoxy-5-(3,5,5-trimethylhexanamido)phenylazanediyl)bis(butane-4,1-diyl) bis(3-chloropropanoate)

(9) (E)-N-(5-(Bis(4-hydroxybutyl)amino)-2-((2,6-dicyano-4-nitrophenyl)diazenyl)-4-methoxyphenyl)-3,5,5-trimethylhexanamide (6.0 g, 9.7 mmol) and sodium bicarbonate (8.1 g, 97 mol) are suspended in dichloromethane (120 ml) and 3-chloropropionyl chloride (3.7 g, 29.1 mmol) added. The mixture is heated at 40 C. overnight. Methanol (300 ml) is added and the mixture is concentrated in vacuo to half volume. The precipitated tarry solid is filtered off. The solid is added to dichloromethane (100 ml) and stirred for 5 minutes to dissolve, before inorganics are removed by filtration. The dichloromethane solution is evaporated to give the crude product as a black tarry solid (7.7 g, 90%). The material was purified over silica gel, eluting with 2-5% ethyl acetate in dichloromethane. Combination and evaporation of the pure fractions afford the required compound as a black tarry solid (6.8 g, 80%), which is >99% pure by HPLC.

Step 7: (E)-4,4-(4-((2,6-dicyano-4-nitrophenyl)diazenyl)-2-methoxy-5-(3,5,5-trimethylhexanamido)phenylazanediyl)bis(butane-4,1-diyl) bis(acrylate)

(10) (E)-4,4-(4-((2,6-dicyano-4-nitrophenyl)diazenyl)-2-methoxy-5-(3,5,5-trimethylhexanamido)phenyl-azanediyl)bis(butane-4,1-diyl) bis(3-chloropropanoate) (6.8 g, 8.5 mmol) is dissolved in dichloromethane (68 ml) and triethylamine (6.0 ml, 43 mmol) is added. The reaction is warmed for 3 h at 35 C. The solution is washed with 0.2 N HCl, then with water, dried (Na.sub.2SO.sub.4) and filtered. The solution is evaporated and the resultant tarry solid redissolved in dichloromethane (200 ml), diluted with methanol (400 ml) and stirred overnight allowing solvent to slowly evaporate. The resultant solid is filtered-off, washed with methanol on the filter and dried under high vacuum until a constant weight was obtained. The required dye was obtained as a dark blue solid (5.4 g, 87%). Mp: 120-121 C., .sub.max (EtOAc) 642 nm (98,000), band width=70 nm. .sup.1H NMR (CDCl.sub.3, 300 MHz) 0.92 (9H, s), 1.03 (3H, d, J 6.6), 1.17 (1H, dd, J 14.0, J 6.6), 1.34 (1H, dd, J 14.0, J 3.7), 1.81 (8H, m), 2.16 (1H, m), 2.42 (1H, dd, J 14.0, J 8.0) 2.52 (1H, dd, J 14.0, J 6.5), 3.71 (4H, m), 3.88 (3H, s), 4.23 (4H, t, J 6.0), 5.84 (2H, dd, J 10.5, J 1.5), 6.13 (2H, dd, J 17.3, J 10.5), 6.42 (2H, J 17.3, J 1.5), 7.54 (1H, s), 8.32 (1H, s), 8.63 (2H, s), 9.27 (1H, br. s).

Example 2: Preparation of Cyan Polymeric Particles Using a Mono-Terminated PDMS Methacrylate Stabiliser

(11) Polydimethylsiloxane monomethacrylate terminated, mw. 10,000 (1.70 g) is dissolved in dodecane (42 g) in a 100 ml 3-neck round bottom flask. Methyl methacrylate (5.4 ml), cyan dye (Dye 3) (0.25 g) and octane thiol (0.13 ml) are added. The flask was heated with stirring at 300 rpm to 80 C. under nitrogen. AIBN (0.11 g) is added. The mixture is stirred for 2 hours and then is cooled to room temperature and the contents are filtered though a 50 micron cloth. The cyan dispersion is cleaned by centrifugation and replacing the supernatant with clean dodecane. Average particle size is 449 nm.

Example 3: Preparation of Magenta Polymeric Particles Using a Mono-Terminated PDMS Methacrylate Stabiliser

Example 3A

(12) Polydimethylsiloxane monomethacrylate terminated, mw. 10,000 (170 g) is dissolved in dodecane (42 g) in a 100 ml 3-neck round bottom flask. Methyl methacrylate (5.4 ml), magenta dye (Dye 2; acrylic acid 2-[[3-butyrylylamino-4-(4-cyano-3-methylisothiazol-5-ylazo)-phenyl]-(2-acryloyloxyethyl)-amino]-ethyl ester) (0.25 g), and octane thiol (0.13 ml) are added. The flask is heated with stirring to 80 C. under nitrogen. AIBN (0.11 g) is added. The mixture is stirred for 2 hours and then is cooled to room temperature and the contents are filtered though a 50 micron cloth. The magenta dispersion is cleaned by centrifugation and replacing the supernatant with clean dodecane. Average particle size is 655 nm.

Example 3B

(13) Magenta particles are similarly prepared from the following combination: methyl methacrylate (10.3 g), PDMS (2.06 g), Dye 2 (0.1 g), AIBN (0.09 g) in dodecane (75 ml) giving 345 nm particles.

Example 3C

(14) Magenta particles are similarly prepared from the following combination: methyl methacrylate (5.1 g), PDMS (1.70 g), Dye 2 (0.05 g), AIBN (0.11 g) in dodecane (42 ml) giving 283 nm particles.

Example 3D

(15) Polydimethylsiloxane monomethacrylate terminated, mw. 10,000 (2.50 g), methyl methacrylate (12.3 ml), magenta dye (Dye 2; acrylic acid 2-[[3-butyrylylamino-4-(4-cyano-3-methylisothiazol-5-ylazo)-phenyl]-(2-acryloyloxyethyl)-amino]-ethyl ester) (0.63 g), and methacrylic acid (0.25 ml) are weighed out into a 100 ml 3-neck round bottom flask, which is stirred at 300 rpm. Dodecane (29 g) is added to the stirring solution, followed by octane thiol (0.07 ml). The flask is heated with stirring to 80 C. under nitrogen. V-59 (0.2 g) is added. The mixture is stirred for 2 hours and is then cooled to room temperature and the contents are filtered though a 50 micron cloth. The magenta dispersion is cleaned by centrifugation and replacing the supernatant with clean dodecane. Average particle size is 815 nm.

Example 4: Preparation of Yellow Polymeric Particles Using a Mono-Terminated PDMS Methacrylate Stabiliser

(16) Similarly prepared are yellow particles using yellow dye (Dye 1; 2,2-(4-((5-cyano-1-(2-ethylhexyl)-2-hydroxy-4-methyl-6-oxo-1,6-dihydropyridin-3-yl)diazenyl)phenylsulfonylazanediyl)bis(ethane-2,1-diyl) diacrylate). Average particle size is 478 nm.

Example 5: Preparation of Cyan Polymeric Particles Using a Di-Terminated PDMS Methacrylate Stabiliser

(17) Polydimethylsiloxane dimethacrylate terminated, mw. 20,000-30,000 (1.70 g) is dissolved in dodecane (42.0 g) in a 100 ml 3-neck round bottom flask. Methyl methacrylate (5.4 ml), cyan dye (Dye 3) (0.25 g) and octane thiol (0.13 ml) are added. The flask is heated with stirring to 80 C. under nitrogen. V-59 initiator (0.2 g) is added. The mixture is stirred for 2 hours and then is cooled to room temperature and the contents are filtered though a 50 micron cloth. The cyan dispersion is cleaned by centrifugation and replacing the supernatant with clean dodecane. Average particle size is 509 nm.

Example 6: Preparation of Magenta Polymeric Particles Using a Di-Terminated PDMS Methacrylate Stabiliser

(18) Polydimethylsiloxane dimethacrylate terminated, mw. 20,000-30,000 (1.70 g) is dissolved in dodecane (42.0 g) in a 100 ml 3-neck round bottom flask. Methyl methacrylate (5.4 ml), magenta dye (Dye 2; acrylic acid 2-[[3-butyrylylamino-4-(4-cyano-3-methylisothiazol-5-ylazo)-phenyl]-(2-acryloyloxyethyl)-amino]-ethyl ester) (0.25 g), and octane thiol (0.13 ml) are added. The flask is heated with stirring to 80 C. under nitrogen. V-59 initiator (0.2 g) is added. The mixture is stirred for 2 hours and then is cooled to room temperature and the contents are filtered though a 50 micron cloth. The resultant magenta dispersion is cleaned by centrifugation and replacing the supernatant with clean dodecane. Average particle size is 443 nm.

Example 7: Preparation of Yellow Polymeric Particles Using a Di-Terminated PDMS Methacrylate Stabiliser

(19) Polydimethylsiloxane dimethacrylate terminated, mw. 20,000-30,000 (1.70 g) is dissolved in dodecane (42.0 g) in a 100 ml 3-neck round bottom flask. Methyl methacrylate (5.4 ml), yellow dye (Dye 1; 2,2-(4-((5-cyano-1-(2-ethylhexyl)-2-hydroxy-4-methyl-6-oxo-1,6-dihydropyridin-3-yl)diazenyl)phenylsulfonylazanediyl)bis(ethane-2,1-diyl) diacrylate) (0.25 g), and octane thiol (0.13 ml) are added. The flask is heated with stirring to 80 C. under nitrogen. AIBN initiator (0.12 g) is added. The mixture is stirred for 2 hours and then is cooled to room temperature and the contents are filtered though a 50 micron cloth. The resultant yellow dispersion is cleaned by centrifugation and replacing the supernatant with clean dodecane. Average particle size is 322 nm.

Example 8: Preparation of a Magenta Electrophoretic Ink from Fluid

Example 3

(20) The electrophoretic ink is prepared by vortex mixing 0.1412 g of particles of Example 3 (43.2% solids content), 1.2322 g of AOT (5 wt % in dodecane), and 0.6702 g of. The dispersion is then roller mixed for 30 minutes.

(21) Electrophoretic Mobility (0.03195 mcm/Vs), ZP (34.4 mV)

Example 9: Preparation of a Magenta Electrophoretic Ink from Fluid

Example 3

(22) The electrophoretic ink is prepared by vortex mixing 0.1431 g of particles of Example 3 (43.2% solids content), 1.2390 g of Span 85 (5 wt % Span 85 in dodecane), and 0.6896 g of dodecane. The dispersion is then roller mixed for 30 minutes.

(23) Electrophoretic Mobility (0.05827 mcm/Vs), ZP (62.8 mV)

Example 10: Preparation of a Yellow Electrophoretic Ink from Fluid

Example 4

(24) The electrophoretic ink is prepared by vortex mixing 0.2103 g of particles of Example 4 (30.2% solids content), 1.2827 g of AOT (5 wt % in dodecane), and 0.6441 g of dodecane. The dispersion is then roller mixed for 30 minutes.

(25) Electrophoretic Mobility (0.05342 mcm/Vs), ZP (57.6 mV)

Example 11: Preparation of a Yellow Electrophoretic Ink from Fluid

Example 4

(26) The electrophoretic ink is prepared by vortex mixing 0.1983 g of particles of Example 4 (30.2% solids content), 1.1976 g of Span 85 (5 wt % Span 85 in dodecane), and 0.6166 g of dodecane. The dispersion is then roller mixed for 30 minutes.

(27) Electrophoretic Mobility (0.03968 mcm/Vs), ZP (42.8 mV)