COLOURED OR BLACK PARTICLES

Abstract

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

Claims

1. A dispersion consisting of; 1) at least one non-polar perfluorinated solvent, colored or black particles consisting of at least one dye, optionally at least one light stabilizer, and at least one fluorinated surfactant, and optionally at least one polymer selected from poly(vinyl pyrrolidone), poly(acrylamide), poly(acrylic acid), and poly(methacrylic acid), or 2) at least one non-polar non-fluorinated hydrocarbon solvent, and colored or black particles consisting of at least one dye selected from Direct Black 22, Acid Black 52, Acid Black 132, Acid Black 107, Acid Black 172, Solvent Black 27, and Solvent Black 29, optionally at least one light stabiliser, and at least one surfactant, wherein the dispersion 1) and 2) optionally includes at least one dye which is soluble in a non-polar solvent.

2. The dispersion according to claim 1, wherein the colored or black particles consist of at least one dye, optionally at least one light stabiliser, at least one poly(hexafluoropropylene oxide) polymeric surfactant with a monofunctional carboxylic acid end group and a weight-average molecular weight Mw between 5000 and 8000, and optionally poly(vinyl pyrrolidone) and/or poly(acrylic acid).

3. An electronic device comprising a dispersion of claim 1, 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.

4. The device according to claim 3, 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.

5. The device according to claim 3, wherein the dispersion is applied to the device by a technique selected from inkjet printing, slot die spraying, nozzle spraying, and flexographic printing.

6. The dispersion according to claim 1, wherein the colored or black particles consist of at least one dye, optionally at least light stabiliser, and at least one fluorinated surfactant, and the at least one dye is selected from the group consisting of Solvent Blacks: 1, 8, 18, 25, 27, 29, 33, 36, 37, 38, 40, 45, 48, 51; Disperse Blacks: 10 Acetate, 12 Acetate, 13, 28 Acetate, 28 Polyester, 29 Acetate, 29 Polyester, 30; Direct Blacks: 22, 52, 53, 54, 58, 59, 60, 61, 62, 63, 64, 69, 71, 88, 89, 91, 92, 94, 95, 97, 98, 101, 102, 104, 107, 108, 109, 112, 113, 114, 116, 117, 118, 121, 122, 124, 125, 127, 128, 129, 130, 132, 133, 134, 137, 140, 142, 143, 144, 145, 146, 147; Acid Blacks: 1, 24, 84, 52, 107, 132, 172; Acid Reds: 1, 106, 114, 129, 249, 315, 336; Acid Greens: 27, 16; Acid Blues: 25, 80, 83, 113, 185, 324; Acid Violets: 17, 48; and Acid Yellows: 17, 29, 79, 127, 151, 220.

7. The dispersion according to claim 1, wherein the colored or black particles consist of at least one dye, optionally at least light stabiliser, and at least one fluorinated surfactant, and the at least one dye is selected from the group consisting of Acid Red 37, Acid Fuchsine, 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.

8. The dispersion according to claim 1, wherein the colored or black particles consist of at least one dye, optionally at least light stabiliser, and at least one fluorinated surfactant, and the at least one dye is selected from the group consisting of Direct Black 22, Acid Black 52, Acid Black 132, Acid Black 107, Acid Black 172, Solvent Black 27, Solvent Black 29, Acid Red 37, and Acid Fuchsine.

9. The dispersion according to claim 1, wherein the colored or black particles consist of at least one dye, optionally at least light stabiliser, and at least one fluorinated surfactant, and the at least one dye is selected from the group consisting of Direct Black 22, Acid Black 52, Acid Black 132, Acid Black 107, Acid Black 172, Solvent Black 27, and Solvent Black 29.

Description

EXAMPLES

[0080] FC-43 and Novec® 7500 are purchased from Acota Ltd, UK. Krytox® 157 FS(H) (=Krytox® 157 FSH, weight-average molecular weight Mw 7000-7500) is purchased from GBR Technologies, UK. Methanol is purchased from VWR. Direct Black 22, Acid Black 52 and Acid Black 132 are acquired from Simpsons UK and Colour Synthesis Solutions Limited, UK. Acid Black 107 and Acid Black 172 are acquired from Town End (Leeds) plc, UK. Solvent Black 27 and Solvent Black 29 are acquired from Keystone Europe Ltd, UK. Polyvinyl pyrrolidone (weight-average average molecular weight Mw=29 000), poly(acrylic acid) (weight-average average molecular weight Mw 100,000), Solvent Blue 35, Acid Red 37, Acid Fuchsine, and 1,2,2,6,6-pentamethyl-4-piperidinol are purchased from Sigma-Aldrich, UK. MCR-C22 (monocarbinol terminated PDMS) is purchased from Gelest.

[0081] 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.

[0082] The colour coordinates of this dispersion are measured using an X-rite Color i5 spectrophotometer in a 50 micron thickness glass cell in reflective mode unless stated otherwise.

Example 1

Preparation of a Dispersion of Black Dyed PVP Particles

[0083] Solvent Black 27 (0.70 g), polyvinyl pyrrolidone (0.70 g, Mw=29000) and methanol (10 ml) are combined in a first flask, vortex mixed and then stirred on a roller-mixer for 3 hours.

[0084] Krytox® 157-FS (H) (0.70 g) and FC-43 (10 ml) are added to a second flask and are homogenised using shear-mixing for five minutes.

[0085] The mixture in the first flask is dripped into the fluorinated mixture in the second flask, continuing to mix on the shear mixer for two minutes. The combined mixture is sonicated for 5 minutes at 40% strength on a Branson Sonifier to form an emulsion (whilst being cooled in an ice bath).

[0086] The emulsion is added to a 100 ml florentine flask and evaporated on a rotary evaporator. The temperature of the water bath is 60° C. and the pressure is set to 350 mbar. The pressure is reduced in 50 mbar steps to 50 mbar to remove the methanol. The dispersion is filtered through 50 micron cloth, solid content is calculated. Particle size is 124 nm.

[0087] An electrophoretic ink is prepared by vortex mixing 0.066 g of the black particles (3.0 wt % particles), 0.011 g of Krytox® 157-FS(H) (0.5 wt % in FC43) and 2.123 g of FC-43. The dispersion is then roller mixed for a minimum of 30 minutes. Drops of this dispersion are added to 1.0 ml of FC-43 until the solution is slightly turbid and roller mixed for a minimum of 30 minutes. NanoZS particle analyser shows zP: −110.0 mV mobility: −3.92×10.sup.−10 m.sup.2/Vs

[0088] and Xrite spectrophotometer shows L* measurement is 0.5 and Y is 4.1. Similarly prepared particles are made and measured using different dye, polymer and surfactant combinations as shown in Table 2 and Table 3.

TABLE-US-00002 TABLE 2 Zeta Mobility FC-43 Krytox ® MeOH PVP Dye Y- Size Potential (×10.sup.−10 Example (ml) (g) (ml) (g) Dye (g) Value L* (nm) (mV) m.sup.2/Vs) 1 10 0.7 10 0.7 Solvent Black 27 0.7 0.5 4.1 124 −110.0 −3.92 2 10 1.2 10 0.7 Solvent Black 27 0.7 0.3 3.1 99 42.40 1.52 3 10 1.0 10 0.7 Solvent Black 27 0.7 0.3 3.1 107 16.10 0.58 4 30 1.2 10 2.4 Acid Black 52 0.1 28.3 60.1 106 145.00 5.20 5 30 1.2 10 2.4 Acid Black 132 0.1 37.7 67.8 95 −301.00 −10.76 6 30 1.2 10 2.4 Acid Black 107 0.1 33.0 64.1 113 189.00 6.77 7 30 1.2 10 2.4 Acid Black 172 0.1 40.7 70.0 103 8 30 1.2 10 2.4 Solvent Black 27 0.1 25.3 57.4 111 9 30 1.2 10 2.4 Direct Black 22 0.1 25.6 57.7 108 −26.20 −0.94

TABLE-US-00003 TABLE 3 FC-43 Krytox ® Solvent Polymer Dye Particle Example (ml) (g) Solvent (ml) Polymer (g) Dye (g) Size (mm) 10 30 1.2 Methanol 10 PAA 2.4 Solvent Black 29 0.12 182 11 30 1.2 Water 10 PAA 2.4 Acid Red 37 0.12 213 12 30 1.2 Water 10 PAA 2.4 Acid Fuschia 0.12 210 13 30 1.2 Water 10 PVP 2.4 Acid Red 37 0.12 173 14 30 1.2 Water 10 PVP 2.4 Acid Fuschia 0.12 190 15 30 1.2 Water 10 PVP 2.4 Acid Fuschia 0.24 180

Example 16

Preparation of a Dispersion of Black Particles

[0089] Solvent Black 29 (2.00 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0090] Krytox® 157-FS(H) (0.20 g) and FC-43 (10 ml) are added to a flask and are homogenised for five minutes.

[0091] The dyed methanol solution is dripped into the fluorinated phase, continuing to mix on the shear mixer for two minutes. The solution is then sonicated for 5 minutes at 40% strength on a Branson Sonifier to form an emulsion (whilst being cooled in an ice bath).

[0092] The emulsion is added to a 100 ml florentine flask and evaporated on a rotary evaporator. The temperature of the water bath is 60° C. and the pressure is set to 350 mbar. The pressure is reduced in 50 mbar steps to 50 mbar to complete removal of methanol.

[0093] Particle size is 222 nm, PDI=0.09.

[0094] Particles are formulated (3% particles and 0.5% Krytox® in FC-43): 0.072 g of the black particles, 0.012 g of Krytox® 157-FS(H) and 2.314 g of FC-43 are combined and measured as described in example 1. zP: −40.3 mV, Mobility: −1.44×10.sup.−10 m.sup.2/Vs

[0095] L* 4.7 and Y is 0.52.

[0096] Similarly prepared particles are made, formulated and measured using the following amounts of reagents as shown in Table 4.

TABLE-US-00004 TABLE 4 Zeta Mobility FC-43/ Krytox ® Methanol/ Dye/ Y- Size/ Potential/ (×10.sup.−10 Example ml g ml Dye Type g Value L* nm PDI mV m.sup.2/Vs) 16 10.0 0.2 10.0 Solvent Black 29 2.9 0.3 4.7 222 0.00 −40.30 −1.44 17 15.0 0.8 10.0 Solvent Black 27 1.5 0.4 3.8 200 0.42 −134.00 −4.80 18 15.0 0.8 10.0 Solvent Black 29 1.5 0.4 4.0 142 0.16 253.00 9.06 19 15.0 0.8 10.0 Acid Black 52 1.5 0.3 2.5 115 0.07 20 15.0 0.8 10.0 Acid Black 107 1.5 0.4 3.9 129 0.16 20.20 0.72  21* 10 0.2 10 Solvent Black 27 2.0 0.3 2.6 357 0.36 42.2 1.51 “Reaction” carried out using 20 mL dodecane and 15 mL methanol.

Example 22

Preparation of a Dispersion of Black Particles Using 2 Dyes

[0097] Solvent Black 29 (1.00 g), Solvent Black 27 (1.01 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0098] Krytox® 157-FS(H) (0.20 g) and FC-43 (10 ml) are added to a flask and are homogenised for five minutes.

[0099] The experiment is repeated as described for example 16.

[0100] Particle size is 111 nm

[0101] Particles are formulated and measured (3% particles and 0.5% Krytox® in FC-43):

[0102] zP: 54.30 mV, Mobility: 1.94×10.sup.−10 m.sup.2/Vs

[0103] L*3.22 and Y is 0.36.

Example 23

Preparation of Black Particles with Incorporation of Hindered Amine Light Stabiliser (HALS)

[0104] Solvent Black 29 (2.00 g), 1,2,2,6,6-pentamethyl-4-piperidinol (0.02 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0105] Krytox® 157-FS(H) (0.2 g) and FC-43 (10 ml) are added to a flask and homogenised on a Turax shear-mixer for five minutes.

[0106] The experiment is repeated as described for example 16.

[0107] Particle size is 109 nm

[0108] Particles are formulated and measured (3% particles and 0.5% Krytox® in FC-43):

[0109] zP: −43.6 mV, Mobility: −1.56×10.sup.−10 m.sup.2/Vs

[0110] L*2.85 and Y is 0.32.

Example 24

Preparation of Black Particles with Further Concentration of Fluid

[0111] Solvent Black 29 (12.0 g) and methanol (60 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0112] Krytox® 157-FS(H) (1.2 g) and FC-43 (60 ml) are added to a flask and are homogenised for ten minutes.

[0113] The dyed methanol solution is poured slowly onto the oil phase, continuing to mix on the shear mixer for ten minutes. The experiment is then followed as described in example 16.

[0114] Particle size is 221 nm.

[0115] Particles are formulated and measured (1.0% particles and 0.5% Krytox®& in FC-43) as described in Example 16.

[0116] zP: 55.50 mV, Mobility: 1.99×10.sup.−10 m.sup.2/Vs.

[0117] The colour coordinates of this dispersion are measured using an X-rite Color i5 spectrophotometer in transmissive mode, using a 50 micron thickness ITO cell and are: L*38.49 and Y is 10.36.

[0118] The sample is washed using a stirred filtration kit with a 0.1 micron filter under .sup.˜10 psi pressure over a weekend Solid content is increased from 10.51% to 19.78%. A 1:1 equivalent of Novec® 7500 to FC-43 is added to the solution and the sample re-concentrated overnight, with the solids content increasing to 28.19%. Screening results after each wash are as follows in Table

TABLE-US-00005 TABLE 5 Zeta Mobility Y- Size/ Potential/ (×10.sup.−10 Wash # Value L* nm PDI mV m.sup.2/Vs) 1 11.0 39.5 235 0.19 40.60 1.45 2 13.7 43.9 233 0.14 39.60 1.42

Example 25

Preparation of Black Particles in Dodecane

[0119] Direct Black 22 (0.50 g) and methanol (10 ml) are combined in a flask, vortex mixed and then stirred on the roller-mixer.

[0120] Monocarbinol terminated PDMS (MCR-C22, Gelest) (0.05 g) and dodecane (10 ml) are added to a flask and homogenised for five minutes.

[0121] The experiment is then repeated as described for example 16

[0122] Particles are formulated and measured (1% particles and 1% AOT in dodecane):

[0123] L*83.6 and Y is 63.2.

[0124] Similarly prepared particles are synthesised and formulated with the following parameters as shown in Table 6.

TABLE-US-00006 TABLE 6 Surfactant/ Dye/ Y Size/ Example Surfactant g Dye g Value L* nm PDI 26 Solsperse 17k 0.16 Acid Black 107 1.6 25.6 57.6 464 0.46 27 OLOA 0.16 Acid Black 107 1.6 26.4 58.4 886 0.82 28 Solsperse 17k 0.35 Solvent Black 27 3.500 65.5 84.8 29 Solsperse 17k 0.32 Acid Black 107 1.600 44.1 73.3 221 0.29 30 Solsperse 17k 0.48 Acid Black 107 1.600 51.1 76.8 182 0.25 31 Solsperse 17k 0.64 Acid Black 107 1.600 52.0 77.3 228 0.31 32 Solsperse 17k 0.80 Acid Black 107 1.600 45.3 73.1 386 0.59 33 Solsperse 17k 0.20 Acid Black 172 1.000 76.0 89.9