PARTICLES FOR ELECTROPHORETIC DISPLAYS

Abstract

This invention relates to polymer particles, a process for their preparation, the use of these particles for the preparation of an electrophoretic device, electrophoretic displays comprising such particle, and new polymerisable dyes.

Claims

1.-17. (canceled)

18. Coloured polymer particles for use in electrophoretic devices comprising monomer units of at least one polymerisable dye and at least one co-monomer, wherein the polymerisable dyes are selected of Formula (1) ##STR00020## wherein A is a chromophoric residue comprising at least one polymerisable group; R.sup.1 and R.sup.2 are independently of each other linear or branched, substituted or unsubstituted alkyl, where one or more non-adjacent carbon atoms may be replaced by O, S and/or N, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl; R.sup.3 and R.sup.4 are independently of each other H or linear or branched, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or R.sup.3 and R.sup.4 forming a cycloaliphatic ring.

19. The coloured polymer particles according to claim 18, wherein at least one co-monomer comprises at least one amino group.

20. The coloured polymer particles according to claim 18, wherein at least one co-monomer is selected from 2-Aminoethyl methacrylate hydrochloride, 2-(tert-Butylamino)ethyl methacrylate, 2-(Diethylamino)ethyl methacrylate, 2-(Dimethylamnino)ethyl methacrylate, [2-methacryloxyethyl] trimethyl ammonium chloride, [3-(Methacryloylamino)propyl]trimethylammonium chloride, and [2-(Methacryloyloxy)ethyl]trimethylammonium methyl sulfate.

21. The coloured polymer particles according to claim 18, wherein the polymerisable dyes are selected of Formula (2) ##STR00021## wherein Y is a polymerisable group, L and L are a linker group, A and A independently of each other are an aromatic residue y1, l and l=0 or 1, m1, n0, and a=1.

22. The coloured polymer particles according to claim 22, wherein Y is a polymerisable group, L and L are a linker group, A and A independently of each other are a naphthyl or phenyl ring, y1, l and l=0 or 1, m1, n0, and a=1.

23. The coloured polymer particles according to claim 18, wherein the polymerisable dyes are selected of Formula (3) ##STR00022## wherein R.sup.1 and R.sup.2=independently linear or branched, substituted or unsubstituted alkyl, where one or more non-adjacent carbon atoms may be replaced by 0, S and/or N, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, R.sup.3 and R.sup.4=independently H or linear or branched, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or R.sup.3 and R.sup.4 forming a cycloaliphatic ring; L.sup.j and L.sup.2 are 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.sup.1 and Y.sup.2 are independently of one another linear or branched alkyl groups or polymerisable groups; and wherein at least one of Y.sup.1 and Y.sup.2 is a polymerisable group.

24. The coloured polymer particles according to claim 22, wherein Y.sup.1-L.sup.1 and Y.sup.2-L.sup.2 are unsaturated alkyl groups comprising acrylate and methacrylate groups.

25. The coloured polymer particles according to claim 18, wherein R.sup.1 and R.sup.2 are independently of each other aryl or C1-C15 alkyl, especially C2-C12 alkyl.

26. The coloured polymer particles according to claim 18, wherein R.sup.3 and R.sup.4 are independently of each other aryl or C1-C20 alkyl, especially C1-C15 alkyl.

27. The coloured polymer particles according to claim 18, wherein at least one black polymerisable dye is used.

28. The coloured polymer particles according to claim 18, wherein the polymer particles have a diameter of 100-1000 nm.

29. A process for the preparation of the coloured polymer particles according to claim 18 comprising a) polymerizing at least one polymerisable dye, at least one co-monomer, and at least one initiator, by dispersion polymerisation in at least one non-aqueous, non-polar solvent, and optionally b) washing and drying the polymer particles wherein dyes of Formula (1) are used ##STR00023## wherein A is a chromophoric residue comprising at least one polymerisable group; R.sup.1 and R.sup.2 are independently of each other linear or branched, substituted or unsubstituted alkyl, where one or more non-adjacent carbon atoms may be replaced by O, S and/or N, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl; R.sup.3 and R.sup.4 are independently of each other 1-1 or linear or branched, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, or R.sup.3 and R.sup.4 forming a cycloaliphatic ring.

30. A device comprising the polymer particles according to claim 18, wherein the device is an optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting and electrophoretic displays and/or devices, and in security, cosmetic, decorative, and diagnostic applications.

31. The device as claimed in claim 30, wherein the device is in mono, bi or polychromal electrophoretic device.

32. An electrophoretic fluid comprising the polymer particles according to claim 18.

33. An electrophoretic fluid comprising polymer particles prepared by the process according to claim 29.

34. An electrophoretic display device comprising an electrophoretic fluid according to claim 32.

35. The electrophoretic display device according to claim 34, 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

[0088] All materials and solvents used are sourced from Sigma-Aldrich and used without further purification unless otherwise stated. Polydimethylsiloxane-methacrylate (PDMS-MA) with a molecular weight of 10,000 is obtained from Fluorochem. V-59 is obtained from VWR. Sizing of particles on SEM is done using ImageJ which is a public domain, Java-based image processing program.

Example 1: Preparation of Black Dye

[0089] ##STR00019##

Step 1: 2-Methyl-2-propyl-2,3-dihydro-1H-perimidine

[0090] 1,8-Diaminonaphthalene (31.6 g, 0.20 mol) is dissolved in 2-pentanone (344.5 g, 4.0 mol) and 35% HCl (2 ml) added and is heated to 50 C. After 1 h at this temp., the solution is allowed to cool then washed with saturated NaHCO.sub.3 solution. Evaporation of excess 2-pentanone in vacuo affords a brown oil. The oily solid is triturated with hexane and the resultant solid is filtered off. After drying at 40 C., the title compound is obtained as a beige solid (37.8 g, 83%).

Step 2: 2-Methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidine

[0091] A stirred mixture of 2-methyl-2-propyl-2,3-dihydro-1H-perimidine (11.3 g, 0.05 mol), 1-bromooctane (24.1 g, 0.125 mol), 1-methyl-2-pyrrolidone and sodium hydrogen carbonate (21.0 g, 0.250 mol) is heated for 24 h at 100 C. then allowed to cool to room temp. The mixture is poured into water and extracted with hexane. The organic extracts are combined, dried (Na.sub.2SO.sub.4) and evaporated in vacuo to afford a brown oil. The crude oil is purified by flash column chromatography eluted with an increasing gradient of dichloromethane (0-10%) in hexane. Appropriate fractions are combined and evaporated to give the title compound as a straw coloured oil (10.1 g, 45%).

Step 3: 4-((4-Aminonaphthalen-1-yl)diazenyl)-N,N-bis(2-hydroxyethyl)benzenesulfonamide

[0092] N-(4-(N,N-Bis(2-hydroxyethyl)sulfamoyl)phenyl)acetamide (12.0 g, 39.7 mmol) is suspended in water (120 ml) and sodium hydroxide (9.5 g, 238 mmol) is added. The solution is heated for 1 h at 90 C. then allowed to cool to room temp. The solution is cooled further in an ice bath to 3 C. and 35% HCl (ca 40 ml) added dropwise at <10 C., until pH 1. A solution of sodium nitrite (3.0 g, 43.7 mmol) in water (20 ml) is then added at <5 C. 1-Napthylamine (5.7 g, 39.7 mmol) is charged to a separate vessel and suspended in water (100 ml). 5M HCl (10 ml, 50 mmol) is added and the mixture heated to 80 C. to dissolve all solid. The 1-napthylamine solution is then allowed to cool to room temp. producing a fine solid suspension. This suspension is added to the above diazonium salt solution concurrently with a solution of sodium acetate trihydrate (26 g, 190 mmol) in water (100 ml). After stirring overnight, the solid is filtered off then re-suspended in water (500 ml). The solid is collected again by filtration, then re-slurried in 2-propanol (300 ml). After stirring for 30 minutes, the solid is filtered off and dried, to give the title compound as a brown solid (11.8 g, 72%).

Step 4: N,N-Bis(2-hydroxyethyl)-4-(-(4-(-2-methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidin-6-yl)naphthalen-1-yl)diazenyl)benzenesulfonamide

[0093] 4-((4-Aminonaphthalen-1-yl)diazenyl)-N, N-bis(2-hydroxyethyl)benzenesulfonamide (7.8 g, 18.9 mmol) is dissolved in 1-methyl-2-pyrrolidone (30 ml) and cooled in an ice bath to 3 C. 40% (w/w) Nitrosyl sulfuric acid (7.2 g, 22.6 mmol) is added dropwise at <5 C. This diazonium salt solution is then added to a solution of 2-methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidine (8.5 g, 18.9 mmol) in THF (100 ml) containing 10% sulfamic acid solution (20 ml). Ice/water (100 g) is added and the reaction mixture is stirred overnight. The supernatant is decanted off to leave a black gum. The residue is dissolved in dichloromethane, dried (MgSO.sub.4) and evaporated in vacuo. The residue is purified over silica gel eluting with dichloromethane. Pure product fractions are combined and evaporated in vacuo to afford the pure title compound as a black foam (6.4 g, 39%).

Step 5: 2,2-4-(-(4-(4-(2-methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidin-6-yl)diazenyl)naphthalen-1-yl)diazenyl)phenylsulfonylazanediyl)bis(ethane-2,1-diyl) bis(3-chloropropanoate)

[0094] N,N-Bis(2-hydroxyethyl)-4-(-(4-(-(2-methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidin-6-yl)diazenyl)naphthalen-1-yl)diazenyl)benzenesulfonamide (2.0 g, 2.3 mmol) is dissolved in dichloromethane (40 ml). Sodium bicarbonate (1.9 g, 23 mmol) is added, followed by 3-chloropropionyl chloride (0.9 g, 69 mmol). The mixture is heated at 35 C. for 16 h then a further portion of 3-chloropropionyl chloride (0.3 g, 23 mmol) is added. After a further 24 h at 35 C., the reaction is allowed to cool, filtered, and the filtrate concentrated in vacuo to a black gum. The crude material is purified over silica gel eluting with dichloromethane. Pure product fractions are combined and evaporated in vacuo to afford the pure title compound as a black tar (1.0 g, 41%), which is judged to be 97% pure by HPLC with 600 nm detection.

Step 6: 2,2-(4-(-(4-(-(2-methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidin-6-yl)diazenyl)naphthalen-1-yl)diazenyl)phenylsulfonylazanediyl)-bis(ethane-2,1-diyl)diacrylate

[0095] 2,2-(4-(-(4-(-(2-Methyl-1,3-dioctyl-2-propyl-2,3-dihydro-1H-perimidin-6-yl)diazenyl)naphthal-en-1-yl)diazenyl)phenylsulfonylazanediyl)bis(ethane-2,1-diyl) bis(3-chloropropanoate) (1.0 g, 1 mmol) is dissolved in dichloromethane (30 ml) and triethylamine (0.5 g, 5 mmol) is added. After 48 h, the solution is washed with 0.2 M HCl, dried (Na.sub.2SO.sub.4) and evaporated in vacuo to a black tar. The tar is dissolved in dichloromethane (50 ml) and methanol (100 ml) added. The solution is stirred in an open beaker overnight allowing solvent to slowly evaporate. The residual mother liquor (ca 20 ml) is decanted off and the residue is rinsed with methanol and dried under high vacuum to afford the title compound as a black gum (0.8 g, 84%); .sub.max (EtOAc) 636 nm (35,750), half bandwidth 162 nm.

Example 2 Preparation of Positive Black Polymer Particles

[0096] Black dye of example 1 (0.31 g), methyl methacrylate (2.7 ml) and dimethylaminoethyl methacrylate (2.7 ml) are added to a 250 ml round bottom flask and stirred to dissolve the dye. PDMS-MA mw 10000 (1.7 g) and dodecane (42.0 g) are added the flask and stirred at 300 rpm until homogenised. The flask is stirred under nitrogen, and heated to 85 C. V-59 is added. The reaction is stirred for 4 hours before being allowed to cool to room temperature. The dispersion is filtered through 50 micron cloth, then washed with dodecane and redispersed using a centrifuge (310000 rpm). Particles are viewed using SEM, average particle size is 320 nm.

Example 3: Formulation of Example 2

[0097] The electrophoretic ink is prepared by vortex mixing 0.099 g of particles comprising black dye of example 1, 0.0601 g of AOT (3 wt % solution in dodecane) and 1.8403 g of dodecane. The dispersion is then roller mixed for 30 minutes.

[0098] Two drops of this dispersion is then added to 1 ml of dodecane and roller mixed for 30 minutes. The zetapotential of the diluted sample is then measured using a Malvern NanoZS particle analyser.

[0099] zP: +204 mV

[0100] The colour coordinates of the dispersion are measured using an X-rite Color i5 spectrophotometer in a 50 micron Merck test cell.

TABLE-US-00002 L* a* b* X Y Z x y 69.92 2.59 1.07 37.723 40.634 42.667 0.3117 0.3358