PARTICLES FOR ELECTROPHORETIC DISPLAYS

Abstract

This invention relates to polymer particles preferably with surface functionality for charge retention, 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.-18. (canceled)

19. A coloured polymer particle for use in electrophoretic devices comprising at least one A-B diblock copolymer comprising a hydrophobic polymer block A and a hydrophilic polymer block B containing a charge or being chargeable, and monomer units of at least one monomer, of at least one polymerisable dye, optionally of at least one charged co-monomer, and optionally of at least one crosslinking co-monomer.

20. The coloured polymer particle according to claim 19, wherein block A is a polymethylmethacrylate block.

21. The coloured polymer particle according to claim 19, wherein block B comprises amino groups or carboxylic acid groups.

22. The coloured polymer particle according to claim 19, wherein block B is charged with 0.2% to 100% permanent charge based on partially or completely quaternised nitrogen groups or partially or completely neutralised acid groups.

23. The coloured polymer particle according to claim 19, wherein a polymerisable dye comprises a chromophore, at least one polymerisable group, optionally at least one linker group, and optionally at least one charged group is used.

24. The coloured polymer particle according to claim 19, wherein the polymer particles have a diameter of 50-1000 nm.

25. The coloured polymer particle according to claim 19, wherein a water-soluble polymerisable dye is used.

26. The coloured polymer particle according to claim 19, wherein a water-soluble polymerisable dye is used selected from Disperse Red 1 methacrylate or acrylate, a dye of Formula 1, especially methacrylate or acrylate ester derivative of CI Basic Blue 41, a dye of Formula 2, especially with Hal=Cl and R5 and R6=CH.sub.3, a dye of formula 3, especially with R7=C.sub.2H.sub.5 and R8=CH.sub.3, a dye of formula 4, especially with R10=C.sub.2H.sub.5, and R9 and R11=CH.sub.3, a dye of formula 5a/b, especially with R13=C.sub.2H.sub.5 and R12, R14=CH.sub.3, or a dye of formula 6a/b, especially with R15=C.sub.2H.sub.5 and R16=CH.sub.3, and a dye of Formula 7 ##STR00063## ##STR00064## wherein R9, R10, R12, R13, R15, and R17 to R19=H and alkyl, preferably C1-C4 alkyl, especially CH.sub.3 and C.sub.2H.sub.5, R11, R14, R16, and R20=H or CH.sub.3, preferably CH.sub.3, L is a single bond, optionally substituted cycloalkyl or aromatic ring, linear or branched, optionally substituted, alkylene, where one or more non-adjacent C atoms may be replaced by O, S and/or N, and/or one or more double and/or triple bonds may be present in the chain and/or side chain or a combination thereof, preferably phenylene or C1-C6 alkyl or a polyether alkyl chain or a combination thereof, and A.sup.=halogen, monobasic acid (oxo) anions, preferably acetate, propionate, lactate, methane sulphonate, p-toluenesulphonate, hydroxide, or nitrate.

27. A process for the preparation of coloured polymer particles for use in electrophoretic devices, comprising a) the reaction of at least one monomer, at least one A-B diblock copolymer comprising a hydrophobic polymer block A and a hydrophilic polymer block B containing a charge or being chargeable, at least one initiator, optionally at least one polymerisable dye, optionally of at least one charged co-monomer, and optionally of at least one crosslinking co-monomer, b) optionally colouring the polymer particles by incorporation of at least one dye and/or at least one pre-polymerised dye and/or at least one polymerisable dye, and optionally c) washing the polymer particles.

28. The process according to claim 27, wherein block A is polymethylmethacrylate and block B comprises amino groups or carboxylic acid groups.

29. The process according to claim 27, wherein block B is charged with 0.2% to 100% permanent charge based on partially or completely quaternised nitrogen groups or partially or completely neutralised acid groups.

30. The process according to claim 27, wherein a water-soluble polymerisable dye is used in step a) or b), preferably Disperse Red 1 methacrylate or acrylate, a dye of Formula 1, especially methacrylate or acrylate ester derivative of CI Basic Blue 41, a dye of Formula 2, especially with Hal=Cl and R5 and R6=CH.sub.3, a dye of formula 3, especially with R7=C.sub.2H.sub.5 and R8=CH.sub.3, a dye of formula 4, especially with R10=C.sub.2H.sub.5, and R9 and R11=CH.sub.3, a dye of formula 5a/b, especially with R13=C.sub.2H.sub.5 and R12, R14=CH.sub.3, or a dye of formula 6a/b, especially with R15=C.sub.2H.sub.5 and R16=CH.sub.3, and/or a dye of Formula 7 ##STR00065## ##STR00066## wherein R1, R2, R3, R5, R7=alkyl, preferably C1-C4 alkyl, R4, R6, R8=H or CH.sub.3, Hal=halogen, R9, R10, R12, R13, R15, and R17 to R19=H and alkyl, preferably C1-C4 alkyl, especially CH.sub.3 and C.sub.2H.sub.5, R11, R14, R16, and R20=H or CH.sub.3, preferably CH.sub.3, L is a single bond, optionally substituted cycloalkyl or aromatic ring, linear or branched, optionally substituted, alkylene, where one or more non-adjacent C atoms may be replaced by O, S and/or N, and/or one or more double and/or triple bonds may be present in the chain and/or side chain or a combination thereof, preferably phenylene or C1-C6 alkyl or a polyether alkyl chain or a combination thereof, and A.sup.=halogen, monobasic acid (oxo) anions, preferably acetate, propionate, lactate, methane sulphonate, p-toluenesulphonate, hydroxide, or nitrate.

31. The process according to claim 27, wherein the polymer particles are prepared from a composition comprising a monomer, a A-B block copolymer, a crosslinker, polymerisable dye, an ionic co-monomer, and an initiator in a batch emulsion process.

32. A method comprising utilizing the polymer particles according to claim 19 in optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting and electrophoretic displays and/or devices, and in security, cosmetic, decorative, and diagnostic applications.

33. An electrophoretic fluid comprising polymer particles according to claim 19.

34. An electrophoretic display device comprising electrophoretic fluid according to claim 33.

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.

36. A compounds according to Formulas 4, 5a, 5b, 6a, 6b, and 7 ##STR00067## ##STR00068## wherein R9, R10, R12, R13, R15, and R17 to R19=H and alkyl, preferably C1-C4 alkyl, especially CH.sub.3 and C.sub.2H.sub.5, R11, R14, R16, and R20=H or CH.sub.3, preferably CH.sub.3, L is a single bond, optionally substituted cycloalkyl or aromatic ring, linear or branched, optionally substituted, alkylene, where one or more non-adjacent C atoms may be replaced by O, S and/or N, and/or one or more double and/or triple bonds may be present in the chain and/or side chain or a combination thereof, preferably phenylene or C1-C6 alkyl or a polyether alkyl chain or a combination thereof, and A.sup.=halogen, monobasic acid (oxo) anions, preferably acetate, propionate, lactate, methane sulphonate, p-toluenesulphonate, hydroxide, or nitrate.

Description

EXAMPLES

Abbreviations

[0116] AIBN: 2,2-azobis(2-methylpropionitrile) or 2, 2 azoisobutyronitrile

[0117] CPDB: 4-cyanopentanoic dithiobenzoate

[0118] DMAEMA: N,N-dimethylaminoethyl methacrylate

[0119] MMA: Methyl methacrylate

[0120] RAFT: Reversible-Addition Fragmentation Chain-Transfer

[0121] DMSO Dimethyl sulfoxide

[0122] THF Tetrahydrofuran

[0123] PTFE Polytetrafluoroethylene

[0124] PMMA Poly(methyl methacrylate)

[0125] PDMAEMA Poly(N,N-dimethylaminoethyl methacrylate)

[0126] A-B diblock copolymers PMMA-b-PDMAEMA are prepared by RAFT polymerisation according to J. Chiefari et al, Macromolecules, 1998, 31, 5559 using CPDB, MMA, DMAEMA, and AIBN.

[0127] Description of Analytical Techniques

[0128] Particle Analysis

[0129] 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. Particle size is also calculated using SEM and image analysis in some cases. The SEM used is a Leo 1455 VP SEM and the image analysis software used is ImageJ. At least 500 particles are counted in each case and the particle size polydispersity is calculated as the percentage standard deviation of the mean size.

[0130] .sup.1H NMR

[0131] .sup.1H NMR spectra are recorded on a Bruker AC-500 (500 MHz) spectrometer using 5 mm diameter tubes. The NMR solvents used are CDCl.sub.3 or in DMSO. The chemical shift scale is calibrated to the NMR solvent peak. The analyses of the spectra are carried out using Bruker 1D WinNMR software. The polymer conversions are determined by using the peak integral value corresponding to the vinyl protons of the monomer, and the integral value corresponding to the broad CH.sub.2 polymer peak plus the equivalent monomer CH.sub.2 group. The following equation is used:

[00001]$\mathrm{Conversion}.Math..Math.\mathrm{in}.Math..Math.\%=\frac{\mathrm{moles}.Math..Math.\mathrm{of}.Math..Math.\mathrm{reacted}.Math..Math.\mathrm{monomer}}{\mathrm{moles}.Math..Math.\mathrm{of}.Math..Math.\mathrm{monomer}.Math..Math.\mathrm{added}}*100=\frac{H_p}{H_P+H_M}*100$

[0132] Size Exclusion Chromatography (SEC)

[0133] SEC is used to determine the number average molar mass (M.sub.n) and the polydispersity index (PDI=M.sub.w/M.sub.n with M.sub.w the weight average molar mass) of the polymers. The polymer samples are dissolved in THF and filtered through a 0.2 m PTFE membrane filter. The samples are injected into two PLgel mixed C columns in series (bead diameter 5 m), thermostated at 30 C. The flow rate of the THF eluent is 1 mL/minute. Detection is made with a RI detector. Data analysis is performed using the Cirrus software from Polymer Laboratories, and the calculation made using a calibration curve based on poly(methyl methacrylate) PMMA standards from Polymer Laboratories. The following Mark-Houwink parameters are used for PMMA, K=10.4 and =0.697.

[0134] Proof of Incorporation of AB Polymers

[0135] The AB block polymers are quaternised using methyl iodide to calculate how much polymer has been included in these particles. An argentometric titration using a Metrohm 798 MPT Titrino apparatus with TiST and a silver ring electrode is used. A surface charge titration with silver nitrate solution 0.1 mol/L (slow) is used to determine the quantity of AB diblock polymer incorporated in the particles. About 10.0000 g latex is weighed into a 150 mL beaker, deionised water (100 ml) and nitric acid (5 ml, 25%) are added and mixed. A potentiometric titration is performed with silver nitrate solution (0.1 mol/L) while strongly stirring. The calculation takes place automatically after the end of titration by means of the instrument software acc. to the following formula:

[00002]$c\left[\mathrm{mmol}.Math.\text{/}.Math.100.Math..Math.\mathrm{mL}\right]=\frac{V_{\left({\mathrm{AgNO}}_3\right)}\left[\mathrm{mL}\right].Math.t_{\left({\mathrm{AgNO}}_3\right)}.Math.100}{\mathrm{sample}.Math..Math.\mathrm{weight}.Math..Math.\mathrm{substance}.Math.\left[g\right]}$

V(AgNO.sub.3)=consumption of volumetric AgNO.sub.3 solution 0.1 mol/L
t(AgNO.sub.3)=titre of volumetric AgNO.sub.3 solution 0.1 mol/L
sample weight substance=weighed-in mass of substance

Example 1

[3-{4-Ethyl-2[-(2-methylacrylolyloxy)-ethyl]amino}-phenylazo)phenyl] trimethylammonium Chloride (Yellow 4)

[0136] ##STR00057##

[0137] Preparation of Coupling Component

##STR00058##

Stage 1. Preparation of 3-Amino-N,N,N-trimethylanilinium Sulphate

[0138] Dimethyl sulphate (50.45 g., 0.4 mol) is added dropwise to a stirred solution of 3-aminoacetanilide (15 g, 0.1 mol) in water (100 ml) at 50 C. at 50-60 C. pH is maintained at 7.5-8.5 with sodium hydroxide solution. The mixture is stirred for 16 hours at 50 C. after which a solution is formed. The solution is cooled to 5 C., sulphuric acid (specific gravity 1.83, 15 ml) is added and the mixture is heated to 100 C. and kept at this temperature for 3 hours. After cooling, the solution is made up to 150 ml and used as such, that is 0.01 m/15 ml.

Stage 2. N-Ethyl-N-(2-methacryloyloxyethyl)aniline

[0139] Methacryloyl anhydride (18.5 g, 0.12 mol) is added dropwise to a stirred solution of N-ethyl-N-(2-hydroxyethyl)-aniline (16.5 g, 0.1 mol) in pyridine. The mixture is stirred at 55 C. for 2 hours, poured onto ice/water and extracted with hexane. The organic layer is passed through silica gel eluted with hexane, followed by removal of solvent to yield N-ethyl-N-(2-methacryloyloxyethyl)aniline (17.4 g, 70%), as a pale yellow oil.

Stage 3. [3-{4-Ethyl-2[-(2-methylacrylolyloxy)-ethyl]amino}-phenylazo)phenyl] trimethylammonium Chloride (Yellow 4)

[0140] 3-Amino trimethylanilinium sulphate solution (0.01 mol) is diazotised at 0-5 C.; a solution of 2-methacrylic acid-(2-ethylphenylamino)-ethyl ester (1.2 g, 0.005 m) in acetic acid (5 ml) is added. The pH of the cold solution is raised to 3 by dropwise addition of 2N aqueous ammonia. The mixture is stirred for 16 hours at room temperature to yield a sticky tar which is dissolved in methylene chloride and purified by passing through silica gel. Collection of the appropriate fractions followed by evaporation of the solvent affords a reddish yellow tar (0.19 g, 9%). max 432, max 30,000.

Example 2

2-Methacrylic Acid-2-[ethyl-(5-phenylimino-5H-benzo[a]phenoxazin-9-yl)-amino]-ethyl Ester (Magenta 4)

[0141] ##STR00059##

Stage 1. 2-[Ethyl(4-nitrosophenyl)amino]ethanol

[0142] 2N Sodium nitrite is added dropwise to a stirred solution of N-ethyl-N--hydroxyethyl (16.5 g, 0.1 mol) in dilute hydrochloric acid, keeping the temperature below 5 C. and the pH at 1.5 to 2.0, until all of the starting material is consumed. Ammonia solution is added until the pH 9 is reached and the resulting oil is extracted with methylene chloride. Removal of solvent affords a greenish oil. Yield 16 g, 82%.

Stage 2. 9-[Ethyl-(2-hydroxyethyl)-amino]benzo[a]phenoxazin-7-ylium Nitrate

[0143] 2-[Ethyl(4-nitrosophenyl)amino]ethanol hydrochloride (4.6 g, 0.02 mol) is made by adding gaseous HCl to a solution of 2-[ethyl(4-nitrosophenyl)amino]ethanol (0.02 mol) in diethyl ether. The solvent is decanted off and the freshly prepared compound is added portionwise, over 2 hours to a mixture of 2-naphthol (2.88 g, 0.02 mol) and zinc chloride (1.54 g, 0.0113 mol) in refluxing methylated spirit (20 ml); refluxing is continued for a further 2 hours. On cooling, solid is collected and washed with a small volume of methylated spirit (4.5 g, 46%). This solid is stirred in boiling water (400 ml) and, on cooling, this is treated with conc. nitric acid (12 ml). The resulting tarry solid is washed by decantation with dilute nitric acid (0.2 N) and dried. Yield 2.3 g, 29%.

Stage 3. 9-[Ethyl-(2-hydroxyethyl)-amino]-5-phenylamino-benzo[a]phenoxazine

[0144] 9-[Ethyl-(2-hydroxyethyl)amino]benzo[a]phenoxazin-7-ylium nitrate (2.3 g, 0.006 mol) and aniline (2.0 g, 0.0215 mol) are stirred in methanol (25 ml) at room temperature for 16 hours. Solvent is removed by decantation and the remaining tarry solid is washed repeatedly by decantation with toluene. After standing the tar became solid. Yield 2.4 g., 85%.

[0145] .sub.max (MeOH+1 drop 2N HCl) 652 nm; .sub.max 60,000.

[0146] .sub.max (acetone) 522 nm, .sub.max 35,000;

[0147] .sub.max (acetone+1 drop 2N HCl), .sub.max 658 nm; .sub.max 70,000.

Stage 4. 2-Methacrylic acid-2-[ethyl-(5-phenylimino-5H-benzo[a]phenoxazin-9-yl)-amino]-ethyl Ester (Magenta 4)

[0148] Methacryloyl chloride (0.58 g, 0.0057 mol) is added dropwise to a stirred solution of 9-[ethyl-(2-hydroxyethyl)-amino]-5-phenylamino-benzo[a]phenoxazine base (1.8 g, 0.0038 mol) in pyridine (15 ml) and the stirred mixture is maintained at 70 C. for 18 hours. On cooling the solution is poured into water (150 ml); the resulting solid is collected, washed thoroughly with water and dried. Yield 1.3 g, 62%.

Example 3

3/4-Methyl-2-[4-{N-ethyl-N-(-acryloyloxyethyl)phenylamino}phenylazo]-[1,2,4]-thiadiazolium Methosulphate (Magenta 3)

[0149] ##STR00060##

Stage 1. N-Ethyl-N--acryloyloxyethyl Aniline

[0150] N-Hydroxyethyl-N-ethyl aniline is acylated in quantitative yield by stirring with methacrylic anhydride in pyridine, for 18 hours at ambient temperature. A small quantity of water is added to destroy excess anhydride and the reaction mixture is poured into water. The product is extracted into hexane and the organic layer passed through silica gel. On removal of solvent, product is obtained as a pale yellow oil which is used direct.

Stage 2. 2-[4-{N-ethyl-N-(-acryloyloxyethyl)phenylamino}phenylazo]-[1,2,4]-thiadiazole

[0151] 2-Amino-1,2,4-thiadiazole (2.02 g, 0.02 mol) is diazotised by stirring in a mixture of acetic acid and water and adding conc. sulphuric acid (2 g) followed by sodium nitrite (1.4 g, 0.021 mol). The mixture is stirred at 0 to 5 C. for 3 hours and excess nitrous acid is destroyed by adding a small quantity of sulphamic acid. The above coupling component N-ethyl-N--acryloyloxyethyl aniline (4.66 g, 0.02 mol), dissolved a small volume of acetic acid is added, with stirring. The product precipitates as a mobile tar and is extracted with methylene chloride. This is washed with 2N sodium carbonate solution and passed through silica gel to remove baseline impurities. The fractions containing product are collected and solvent removed to leave a tarry oil which, although essentially homogeneous by thin layer chromatography, could not be induced to crystallize.

3/4-Methyl-2-[4-{N-ethyl-N-(-acryloyloxyethyl)phenylamino}phenylazo]-[1,2,4]-thiadiazolium Methosulphate (Magenta 3)

[0152] The above disperse dye is dissolved in a mixture of ethyl acetate and dimethyl sulphoxide. Dimethyl sulphate (1.5 m equiv.) is added and the stirred mixture is immersed in an oil bath heated to 80 C. The reaction cannot be induced to go to completion so the reaction mixture is allowed to cool. The precipitated tarry residue is collected and passed through silica gel. Elution with ethyl acetate removes starting disperse dye; further elution with acetone yielded the desired product as a mixture of isomers. Yield 0.2 g, 2%.

[0153] .sub.max (methanol) 568 nm

Example 4

[0154] Preparation of Methacrylate Ester Derivative of CI Basic Blue 41 (Blue 1)

##STR00061##

Stage 1

[0155] 2-Amino-6-methoxybenzothiazole (18.0 g) is stirred in a mixture of acetic acid (70 ml) and propionic acid (50 ml) at 50 C. The resulting solution is cooled to 10 C. Nitrosylsulphuric acid solution (40 weight-% in sulphuric acid) (32.0 g) is added dropwise. This mixture is added to a stirred solution of N-ethyl-N-(2-hydroxyethyl) aniline and sulphamic acid (1.0 g) in acetic acid (25 ml) and ice/water (100 ml). After 20 minutes, the pH is raised to 4 by the dropwise addition of potassium hydroxide solution. A tarry residue is formed; the mixture is stirred for a further 2 hours until the tar solidifies. This solid is collected, washed with water and then dissolved in alcohol and acetone to give a deep red solution. Hot water is added to precipitate a solid which is removed by filtration. The solid is washed with cold alcohol and dried (29.5 g, 83% yield) Mp 178-179 C.

Stage 2

[0156] The above hydroxyethyl disperse dye (10.7 g) dye is stirred in methylene chloride (100 ml) and pyridine (20 ml). Methacrylic anhydride (10 ml) is added and the mixture is heated under reflux for 24 hours. On cooling to room temperature, water (5 ml) is added and the mixture is stirred for 2 hours. A volatile material is removed under reduced pressure, to leave a tarry residue which is stirred in 5 weight-% aqueous sodium bicarbonate solution for 16 hours. The resulting crude product is dissolved in methylene chloride/hexane (60/40) and passed through silica gel. After removal of solvent the solid residue (9.7 g) is crystallised from propan-2-ol to yield a rubine crystalline solid.

[0157] Yield 7.0 g, 55%. mp 123-125 C.

Stage 3

[0158] Dimethyl sulphate (1 ml) is added dropwise to a stirred solution of the methacrylate ester (1.06 g) in toluene (25 ml) at 100 C. After 10 minutes a tar begins to deposit on the walls of the flask and the mixture is allowed to cool to room temperature. The tar is washed with cold toluene and is stirred overnight in ethyl acetate (25 ml). The resulting semi-solid residue is collected, added to propan-2-ol and the mixture is heated to boiling. On cooling a solid is deposited which is washed with cold propan-2-ol and dried. Yield 1.22 g, 89%. Mp 140-142 C. (97.3% main component by hplc) C23H27N4OS gives a mass ion of 439.

[0159] A mass spectrum of the sample gave a spectrum in positive ion mode. (EI+) The spectra show ions at m/z 439 which corresponds with the cation for the proposed structure.

Example 5 N-[5-Diethylamino-2-(5-ethylthio-[1,3,4]-thiadiazol-2-ylazo)-phenyl]-acrylamide (Magenta 14)

[0160] Prepared by a 4 step procedure as detailed below:

##STR00062##

Step 1: N,N-Diethyl-m-phenylene Diamine

[0161] 3-Diethylaminoacetanilide (10.8 g, 0.05 mol) is stirred under reflux for 4 hours in 10% HCl (45 ml). The solution is evaporated to dryness and the tarry residue washed with several portions of cold acetone until it solidifies. The hydrochloride is dissolved in water (100 ml) and stirred at 15 C. while caustic liquor is added dropwise until the pH is 9-10 and the product separates as a syrup. This product is extracted into methylene chloride, dried (MgSO.sub.4), poured through silica gel and evaporated to dryness, yielding N,N-Diethyl-m-phenylene diamine as a mobile, light-brown oil (9.0 g, approx. 100%).

Step 2: 3-Chloro-N-(3-diethylaminophenyl)-propionamide

[0162] N,N-Diethyl-m-phenylene diamine (8.2 g, 0.05 mol) and sodium hydrogen carbonate (10 g, 0.119 mol) are stirred at room temperature in methylene chloride (80 ml) while -chloropropionyl chloride (7.61 g, 0.06 mol) is added dropwise over 30 minutes. The reaction mixture is stirred overnight at room temperature. Water (5 ml) is added and stirred a further 2 hours at ambient temperature. The methylene chloride fraction is dried (MgSO.sub.4), poured through silica gel and evaporated to dryness yielding 3-chloro-N-(3-diethylaminophenyl)-propionamide as a grey-brown solid (12.2 g, 95%). The material is recrystallised from methanol, isolating the material at 0 C. as almost colourless needles, mp=88-90 C.

Step 3: 3-Chloro-N-[5-diethylamino-2-(5-ethylthio-[1,2,4]-thiadiazolyl-2-ylazo)-phenyl]-propionamide

[0163] 2-Amino-5-ethylthio-[1,3,4]-thiadiazole (2.32 g, 0.02 mol) is added in portions to a mixture of propionic acid (10 ml) and acetic acid (20 ml) and stirred at room temperature. The resultant solution is cooled and stirred at 0-5 C. while nitrosyl sulphuric acid (6.34 g, 0.02 mol) is added dropwise. After a further hour at 0-5 C., the diazonium salt solution is added dropwise to a suspension prepared by adding a solution of 3-chloro-N-(3-diethylaminophenyl)-propionamide (5.5 g, 0.016 mol) in acetone to a stirred mixture of ice and water containing a little sulphamic acid. The reaction mixture is stirred overnight, allowing to warm up to room temperature and the product is collected by filtration, washed with cold water. After drying, the crude product is purified by silica flash chromatography and recrystallisation from methylene chloride/methylated spirits yields 3-chloro-N-[5-diethylamino-2-(5-ethylthio-[1,2,4]-thiadiazolyl-2-ylazo)-phenyl]-propionamide as crimson needles (2.5 g, 29%), .sub.max (EtOAc) 516 nm, .sub.max 60,000, band width 79 nm. The preparation is repeated on 0.015M scale, yielding 2.7 g (42%) of product.

Step 4: N-[5-Diethylamino-2-(5-ethylthio-[1,3,4]-thiadiazol-2-ylazo)-phenyl]-acrylamide (Magenta 14)

[0164] 3-Chloro-N-[5-diethylamino-2-(5-ethylthio-[1,2,4]-thiadiazolyl-2-ylazo)-phenyl]-propionamide (6.1 g, 0.0143 mol) is stirred in dichloromethane (60 ml) at ambient temperature and triethylamine (3.1 g, 0.308 mol) are added drop wise. The solution is stirred overnight, extracted with water (75 ml), dried (MgSO.sub.4) and evaporated to dryness. Recrystallisation from methylene chloride/methylated spirit yields N-[5-diethylamino-2-(5-ethylthio-[1,3,4]-thiadiazol-2-ylazo)-phenyl]-acrylamide (Magenta 14) as crimson needles (5.1 g, 91%), .sub.max (EtOAc) 518 nm, .sub.max 59,000, band width 78 nm.

Example 6

[0165] Synthesis of PMMA Particles

[0166] A-B diblock copolymer (PMMA.sub.14-PDMAEMA.sub.21) (0.14 g) is added to water (85 g) in a 250 ml 3 neck flask equipped with a condenser, an overhead stirrer and a nitrogen inlet. Methyl methacrylate (7.13 g), ethylene glycol dimethacrylate (0.60 g) and [3-(methacryloylamino)propyl]trimethylammonium chloride solution (75 weight % in water) (0.30 g) are added. The reaction mixture is heated to 70 C. under a nitrogen atmosphere. Initiator 2,2-azobis (2-methylpropionamidine) dihydrochloride (0.08 g) is added to water (10 g), stirred until dissolved and added to the reaction mixture. After 20 hours the latex is allowed to cool to room temperature, and is filtered through a 5 micron cloth. After washing with water, zeta-size analysis is 216 nm, zeta-potential is 63 mV in water. The suspension is freeze dried to give a fine white powder.

[0167] PMMA particles are prepared using PMMA-b-PDMAEMA A-B diblock copolymers 1-9 of Table 5. Details are given in Table 6.

TABLE-US-00005 TABLE 5 Description of diblock copolymers PMMA-b-PDMAEMA Degree of quaternisa- Mn Sample Polymer tion.sup.a (g/mol) PDI 1 PMMA.sub.14-PDMAEMA.sub.21 0% 5720.sup.b; 1.14 4770.sup.c 2 PMMA.sub.14-q.sub.20PDMAEMA.sub.21 20% 4830.sup.c 3 PMMA.sub.14-q.sub.100PDMAEMA.sub.21 100% 5070.sup.c 4 PMMA.sub.14-PDMAEMA.sub.54 0% 10735.sup.b; 1.2 10110.sup.c 5 PMMA.sub.14-q.sub.20PDMAEMA.sub.54 20% 10280.sup.c 6 PMMA.sub.14-q.sub.100PDMAEMA.sub.54 100% 10920.sup.c 7 PMMA.sub.14-PDMAEMA.sub.108 0% 18200.sup.b; 1.2 18600.sup.c 8 PMMA.sub.14-q.sub.20PDMAEMA.sub.108 20% 18930.sup.c 9 PMMA.sub.14-q.sub.100PDMAEMA.sub.108 100% 20220.sup.c .sup.athe degree of quaternisation is calculated from the .sup.1H NMR analyses in DMSO. .sup.bthe molecular weight Mn and the polydispersity PDI of sample 1, 4 and 7 are determined by size exclusion cnromatography (SEC) in tetrahydrofuran using PMMA as standard. .sup.cMolecular weight are calculated based on results from .sup.1H NMR analyses.

TABLE-US-00006 TABLE 6 Details of PMMA particles Quantity Dye PMMA (wt % cf Zeta (wt % cf Particles Additive MMA) MOTAC (g) Potential Size MMA) PDI 1 Sample 1 2 0.3 62 204 0 2 Sample 1 5 0.3 63 401 0 3 Sample 2 5 0.3 57 187 0 4 Sample 3 5 0.3 64 108 0 5 Sample 4 2 0.3 65 177 0 6 Sample 4 2 0.3 55 206 Blue 1 0.06 example 4 0.5 7 Sample 4 5 0.3 57 115 0 8 Sample 4 5 0 46 84 0 9 Sample 5 0.5 0.3 62 387 0 10 Sample 5 1 0.3 61 262 0 11 Sample 5 2 0.3 56 195 0 12 Sample 5 4 0.3 57 125 0 13 Sample 5 5 0.3 58 138 0 14 Sample 6 2 0.3 62 184 0 15 Sample 6 2 0.3 59 133 Blue 1 0.13 example 4 0.5 16 Sample 6 2 0.3 54 147 Yellow 4 0.09 example 1 0.5 17 Sample 6 5 0.3 60 102 0 18 Sample 6 5 0 54 74 0 19 Sample 6 2 0.3 Magenta 4 example 2 0.5 20 Sample 6 2 0.3 Magenta 3 example 3 0.5 21 Sample 6 2 0 Magenta 3 example 3 0.5 22 Sample 7 2 0.3 61 258 0 23 Sample 7 5 0.3 57 187 0 24 Sample 8 5 0.3 54 111.7 0 25 Sample 9 5 0.3 63 109 0

[0168] Proof of Incorporation of AB Polymers:

[0169] PMMA Particles 4:

[0170] 0.71 mmol/100 g Iodide, 2.21 mmol/100 g Chloride (sample weight 13.7 g, 9.4 wt %)

[0171] Analysis shows iodide content to be 0.71 mmol per 100 g, compared to 1.08 mmol per 100 g theory added to reaction mixture, thus showing 66% incorporation.

[0172] PMMA Particles 24:

[0173] 0.35 mmol/100 g Iodide 1.97 mmol/100 g Chloride (sample weight 11.3 g, 8.3 wt %)

[0174] Analysis showed iodide content to be 0.35 mmol per 100 g solution, compared to 0.357 mmol per 100 g theory showing 98% incorporation assuming no halide exchange.

Example 7

[0175] Electrophoretic Fluid Containing PMMA Particles 22

[0176] 0.19950 g of PMMA particles 22 is added to 0.0199 g of OLOA 11000 (Chevron Chemicals) and 0.0600 g of Solsperse 3000 (Lubrizol) in 2.002 g of dodecane (Sigma Aldrich) and vortex mixed. The resultant dispersion is then homogenised using an ultra-turrax T25 homogeniser for 30 minutes and sonicated for a further 30 minutes in an Ultrawave ultrasonic bath. The dispersion is then roller mixed overnight to yield an electrophoretic fluid. Size (142 nm), Electrophoretic Mobility (0.05643 mcm/Vs), ZP (+60.8 mV)

Example 8

[0177] Electrophoretic Fluid Containing PMMA Particles 22

[0178] 0.0602 g of PMMA particles 22 is added to 0.111 g of Solsperse 3000 (Lubrizol) in 2.08 g of dodecane (Sigma Aldrich) and vortex mixed. The resultant dispersion is then homogenised using an ultra-turrax T25 homogeniser for 30 minutes and sonicated for a further 30 minutes in an Ultrawave ultrasonic bath. 0.09 g of Aerosol-OT (Aldrich) is added as a charge control agent. The dispersion is then roller mixed overnight to yield an electrophoretic fluid.

[0179] Size (172 nm), Electrophoretic Mobility (0.02103 mcm/Vs), ZP (22.7 mV).

Example 9

[0180] Electrophoretic Fluid Containing PMMA Particles 1

[0181] 0.035 g of PMMA particles 1 is added to 0.0102 g of Solsperse 13940 (Lubrizol) in 0.963 g of dodecane (Sigma Aldrich) and vortex mixed. The resultant dispersion is then homogenised using an ultra-turrax T25 homogeniser for 30 minutes and sonicated for a further 30 minutes in an Ultrawave ultrasonic bath. The dispersion is then roller mixed overnight to yield an electrophoretic fluid.)

[0182] Size (215 nm), Electrophoretic Mobility (0.01515 mcm/Vs), ZP (+16.3 mV)