WO2012092906A1

WO2012092906A1 - Electrophoretic display solution and method of preparing particles thereof

Info

Publication number: WO2012092906A1
Application number: PCT/CN2012/071583
Authority: WO
Inventors: 吴笑雨; 张磊; 曾晞
Original assignee: 广州奥熠电子科技有限公司
Priority date: 2011-01-04
Filing date: 2012-02-24
Publication date: 2012-07-12
Also published as: CN102591086B; CN102591086A; WO2012092906A9

Abstract

Disclosed are an electrophoretic display solution and a method of preparing particles thereof. The electrophoretic display solution comprises a suspension and multiple display particles dispersed in the suspension, said display particles comprise a first particle and a second article of different optical states. Said first particle and second particle exhibit different movements in the suspension under the influence of an electric field. The electrophoretic display solution also comprises: a third particle that does not participate in electrophoretic display, having 0.01 to 5 parts by weight, said third particle having a functional group on the surface and a particle diameter of 0.1 to 5 microns. By adding the third particle to the electrophoretic display solution, the display effects and image stability are improved without affecting the switching time of a display device or the actuating voltage.

Description

Electrophoretic display liquid and preparation method thereof

Technical field

The invention relates to the technical field of electrophoretic display, in particular to an electrophoretic display liquid and a preparation method thereof for a third type of particles.

Background technique

Electrophoretic displays prepared by electrophoretic media have received much attention in the display industry in recent years. Compared with liquid crystal displays, electrophoretic displays have good contrast, close viewing angle of 180°, low power consumption and state stability.

However, most of the black and white electrophoresis displays now have two major defects. One is that the contrast between black and white is not ideal, and the other is that the stability of the image caused by sedimentation of the electrophoretic particles is not good.

Bi-stable refers to a characteristic of a display comprising display elements having at least one first and second display states different in optical properties; the electrophoretic display has such bistableness that the displayed image can be retained after the image is rendered . In fact, in some particle-based electrophoretic displays, not only in the extreme state, the display is stable, but also stable in the middle state, more appropriate should be called 'Multi-stable'.

However, the bistable state of the electrophoretic display of the present invention is not absolute. Those skilled in the art of electrophoretic media and electrophoretic display know that electrophoresis shows that the particle size of the particles is large, and it is prone to coagulation and stability. Poor. The displayed image fades slowly over time, and the chromaticity and brightness values decrease, so the image must be refreshed periodically if the image needs to be held for a long time.

Chinese Patent Application No. 200480036461.9 It is disclosed that the polymer shell coated with the surface of the charged particles is a repeating unit of at least one monomer, which is relatively high, so that the coagulation of the particles can be effectively prevented. However, this method has an obvious disadvantage, the process is too complicated and completely unsuitable for mass production.

Chinese Patent Application No. 02807863.2 Disclosed is a method for preparing an electrophoretic medium which can improve image stability by adding a polymer to increase the viscosity of a suspension fluid to overcome image fading caused by sedimentation of electrophoretic toner particles under the action of gravity. As explained in the patent, the time during which the toner particles pass through the fluid medium is proportional to the viscosity of the fluid medium. Increasing the viscosity tends to increase the switching time. The method disclosed in this patent is only a compromise method that selects a more appropriate balance between switching time and image stability. It is impossible to improve the stability of the image without affecting the switching time of the electrophoretic display.

Summary of the invention

The technical problem to be solved by the present invention is to provide an electrophoretic display liquid and a preparation method thereof, which can improve the black-and-white contrast and stability of an electrophoretic display image, thereby effectively improving the photoelectric performance of the electrophoretic display liquid.

In order to solve the above problems, the present invention provides an electrophoretic display liquid comprising a suspension and a plurality of display particles dispersed in a suspension, the display particles including first particles and second particles having different optical states, A particle and a second particle are capable of exhibiting different motion behaviors in the suspension under the action of an electric field; the suspension is further dispersed in parts by weight A third particle of 0.01-5 that does not participate in electrophoretic display. In one embodiment, the electrophoretic display liquid comprises: 20-70 parts by weight of the suspension, 2-50 parts by weight of the first particles, 2-50 Parts by weight of the second particles, and 0.01 to 5 parts by weight of the third particles. In one embodiment, the electrophoretic display liquid comprises: 40-70 parts by weight of the suspension, 3-30 parts by weight of the first particles, 3 to 30 parts by weight of the second particles, and 0.05 to 5 parts by weight of the third particles. In one embodiment, the electrophoretic display liquid comprises: 40-60 parts by weight of a suspension, 10-20 Parts by weight of the first particles, 10-20 parts by weight of the second particles, and 0.05-5 parts by weight of the third particles.

The present invention also provides an electrophoretic display liquid comprising: 20-70 parts by weight of a suspension, 2-50 parts by weight of the first particles, 2-50 parts by weight of the second particles, and 0.01-5 a third particle by weight; the first particle, the second particle, and the third particle are dispersed in the suspension, the first particle and the second particle have different optical states and are capable of being under the action of an electric field The suspension exhibits different motor behaviors, and the third particles do not participate in electrophoretic display. In one embodiment, the electrophoretic display liquid comprises: 40-70 parts by weight of the suspension, 3-30 parts by weight of the first particles, 3-30 parts by weight of the second particles, and 0.05-5 Part by weight of the third particles. In one embodiment, the electrophoretic display liquid comprises: 40-60 parts by weight of the suspension, 10-20 parts by weight of the first particles, 10-20 parts by weight of the second particles, and 0.05-5 parts by weight of the third particles.

In the present invention, the display particles which can be used as the present invention may be various types of pigments including, but not limited to, titanium white, zinc antimony white, zinc oxide, silicon dioxide, iron black, carbon black, and chromia. Acid salt, chromate, silicate, chrome oxide green, lead chrome green, copper oxide, titanium yellow, chrome yellow, iron yellow, lead chrome green, manganese violet, iron blue, cobalt blue, zinc white, cadmium yellow, Cadmium red, barium sulfate, molybdenum orange, ultramarine blue, azure blue, emerald green, emerald green, etc., the particle size should be lower than 10 microns, preferably 0.01 - 5 microns, the best choice is 0.1 - 1 micron.

As an embodiment of the present invention, the first particle of the present invention is a positively charged or only negatively charged charged pigment particle, and the second particle of the present invention is a neutral pigment different from the color of the charged pigment particle. particle.

Neutral pigment particles are used as a highly effective coloring agent to produce the background color of the electrophoresis liquid, but do not participate in the particle electrophoresis behavior under the electric field. Under the action of the electric field, only the charged pigment particles move, and the charged pigment particles are in the microcapsules. The up and down movement, combined with the background color produced by the neutral pigment particles, allows the viewer to produce a visual color change for display purposes.

As another embodiment of the present invention, the first and second particles of the present invention are positively-charged pigment particles and negatively-charged pigment particles each having a different color.

As still another embodiment of the present invention, the first and second particles of the present invention are first pigment particles and second pigment particles having the same polarity charge but different colors, and the first pigment particles and the second pigment Particles have different electrophoretic mobility.

The pigment of the charged pigment particles of the present invention needs to be micronized, and the particle size is preferably 0.01-5. Micron. The pigment of the neutral pigment particles of the present invention also needs to be micronized, and the particle size is preferably 0.1 - 1 Micron. The micronization method includes grinding and pulverization, ultrasonication, solvent dispersion, etc., and the related equipment may include a colloid mill, a ball mill, a freeze pulverizer, an ultrasonic machine, and the like.

In addition, the neutral pigment particles and the pigments of the charged pigment particles of the present invention may be surface-treated by physical or chemical methods to increase their stability in a solvent, and the physical methods mainly include high physical adsorption of pigment particles on the surface. Polymers, surfactants, etc., chemical methods mainly include silane modification of the surface of the pigment particles, grafting of the polymer, and the like.

The invention adds a plurality of third particles to the electrophoretic display liquid, and the steric hindrance and surface charge generated by the surface groups thereof have a certain repulsive effect on the display particles, that is, the first and second particles, thereby effectively preventing the first particle. The coagulation of a particle and a second particle.

The third particles of the present invention may preferably be blue pigment particles, and the material of the blue pigment particles may be ultramarine, and the surface of the blue pigment particles may be coated with a layer of high molecular polymer, and the weight of the blue pigment particles. The number of parts may preferably be 0.05-2.5. When the added third particle is a blue pigment particle, since it can reflect blue light, the contrast of the black-and-white display can be improved, and the optical effect of the image display can be further improved.

The invention also provides a particle preparation method for improving the stability of the electrophoretic display liquid according to the invention, the preparation method of the third particle comprises: coupling inorganic particles or organic particles with a polymer monomer in a suspension Mixture with polymer reaction chain initiator Reaction in the temperature range of 30-120 ° C for 4-48 hours.

The polymer monomer is a low-polarity or non-polar small molecule capable of undergoing polymer polymerization, including but not limited to methacrylates, olefins or diolefins such as styrene, butadiene, and halogen. Preferred mixtures of olefins such as vinyl chloride and the like are acrylates, methacrylates such as lauryl methacrylate, styrene, and mixtures and derivatives thereof.

The coupling agent is selected to be a coupling agent having an unsaturated functional group and capable of performing a polymer reaction. These include, but are not limited to, titanate coupling agents, zirconate coupling agents, aluminate coupling agents, and the like. The preferred coupling agent is a titanate coupling agent, and the unsaturated functional group includes a functional group such as a double bond, a triple bond, and a conjugated double bond.

The polymeric reaction chain initiator selection includes, but is not limited to, an azo chain initiator such as azobisisobutyronitrile (AIBN) And azobisisoheptanenitrile, etc., organic peroxygen initiators such as dibenzoyl peroxide (BPO) ), dodecyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, peroxidation Dicyclohexyl dicarbonate, cumene hydroperoxide, tert-butyl hydroperoxide, and various oil-soluble oxidation-reduction chain initiators, etc., the most preferred choice is azobisisobutyronitrile, azobisisoheptane Nitrile, dibenzoyl peroxide ( BPO), dicumyl peroxide.

Further, the electrophoretic display liquid of the present invention may further comprise 0.1-10 parts by weight. a thickening stabilizer; selected from the group consisting of polymethyl methacrylate, polyethylene, polypropylene, polystyrene, rubbers such as polyisoprene, polyisobutylene or mixtures thereof, preferably polymethyl methacrylate, poly Ethylene, polypropylene. Further, in one embodiment of the electrophoretic display liquid of the present invention, the weight fraction of the suspension of the present invention is 40-60; the charged pigment particles are 10-20 parts by weight; the neutral pigment particles are 10-20 parts by weight; and the thickening stabilizer is preferably 0.5-5 parts by weight.

Specifically, the suspension of the present invention may be an aromatic hydrocarbon or a halogenated hydrocarbon; it may also be a linear, branched and cyclic aliphatic hydrocarbon or a halogenated hydrocarbon.

The electrophoretic display solution of the present invention may further comprise a charge control agent or / and a surface tension controlling agent or / and a dispersing wetting agent.

The listed composition ranges described in the present invention are merely examples for convenience in explaining the composition of the electrophoretic display liquid. These numbers do not imply that the composition of each component is limited to the range of compositions listed, and the composition of each component in the actual electrophoretic display liquid can also be in a larger range. At the same time, the components in the electrophoretic display liquid are not limited to the above-listed components, and may include other components required for preparing the electrophoretic display liquid and the display device, such as but not limited to a charge control agent such as OLOA11000, surface tension control agent such as Span80 Wetting dispersing agents such as silicone surfactants such as polyether modified trisiloxane, and the like, and combinations thereof. The various arrangements set forth elsewhere in this patent or others apply equally to the situations set forth herein.

The invention also discloses an electrophoretic display material, which is an electrophoretic display material obtained by encapsulating the electrophoretic display liquid of the invention in a microcapsule. The synthesis method of the microcapsules includes, but is not limited to, in-situ polymerization, interfacial polymerization, single, complex coacervation, phase separation, surface deposition and the like, and the preferred synthesis method is an in-situ polymerization method. These synthetic methods are Japanese patents. The method disclosed in U.S. Patent No. 5,057,363. Electrophoretic display solutions can also be filled in microcups, microcells, or other tiny units for electrophoretic display.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of coordinates of a Lab color space;
2 is a schematic view showing the principle of display of an electrophoretic display liquid according to an embodiment of the present invention;
3 is a schematic view showing the principle of display of an electrophoretic display liquid according to another embodiment of the present invention;
4 is a flow chart of an electrophoretic display liquid preparation method in an embodiment of the present invention;
Figure 5 is a graph showing the relationship between the amount of blue pigment particles added and the intrinsic viscosity of the electrophoretic medium;
Figure 6 is a diagram showing the correspondence between the amount of blue pigment particles added and the b* value of the electrophoretic medium;
Figure 7 is a schematic diagram showing the stability of the black and white state of the electrophoretic display liquid before and after the addition of the third particle.

detailed description

In order to better illustrate the invention, the following definitions of some of the terms to be mentioned in the present invention are explained below:

The Lab color space was developed by the International Commission on Illumination (CIE) in 1976, see Figure 1, which uses L*, a*, b* Three mutually perpendicular axes represent a color space, the L* axis represents lightness, black is at the bottom, and white is at the top. +a* means magenta, -a* means green, +b* means yellow, -b* means blue, a* axis is red ---- green axis, b* axis is yellow ---- blue axis; hue and feature of any color can be represented by a*, b* values.

L* reflects the reflected light intensity, and the higher the L*, the higher the reflectance. For black and white dual particle electrophoretic displays, L* The higher the value, the better the whiteness is in the white state, and the lower the L*, the better the blackness in the black state. Reflectance R= (( L*+16 ) /116 ) ^3*100 , and contrast =R white /R black.

Switching time refers to the time required to switch display between two extreme optical states at a given operating voltage, or any given pixel.

Existing black and white electrophoretic display papers are generally displayed by two different colored particles dispersed in an electrophoretic suspension, one being a black pigment particle and the other being a white pigment particle, which appears to be white when displayed. Yellow, and the stability of the image display is also poor (reference picture) The middle two lines in 7 indicate the holding time of an existing black and white electrophoresis display paper. Trend of change). Therefore, the present invention adds a third type of particles (third particles) to the existing electrophoretic medium, and the surface structure of such particles itself has many functional groups, and the polymer polymerization can be grown on the surface after the polymer reaction. So that the surface has more groups and the particle size is Between 0.1 and 5 microns, it is generally larger than the particle size (0.1 - 1 μm) of the first and second particles originally present in the electrophoretic display solution. . . . The third particle added in the present invention has excellent dispersibility, a large number of surface groups, and a charge on the surface, and when the three types of particles in the suspension are close to each other, the space generated by the surface group of the third particle The steric hindrance and surface charge have a certain repulsive effect on it, thereby effectively preventing the coagulation of the first and second particles. Thereby, the stability of the electrophoretic display is improved without affecting the switching time of the image display at all. As shown As shown in Figure 7, the uppermost line indicates the brightness value of the electrophoretic display liquid after adding the third particle in the white state (0-400s). The change of the bottom line indicates the change of the brightness value with time (0-400s) in the black state after the addition of the third particle in the electrophoretic display liquid; It can be seen that the stability of the electrophoretic display liquid after adding the third particles is significantly better than that when the third particles are not added.

The third particles of the present invention may be inorganic particles, including inorganic pigment particles, such as various metal oxides. , aluminum magnesium silicate, kaolin, organic bentonite, silica, chromate, carbonate, sulfate and sulfide, such as aluminum powder, copper powder, carbon black, zinc white, titanium white, chrome yellow, Iron blue, cadmium red, cadmium yellow, lithopone, carbon black, iron oxide red, iron oxide yellow, etc. The third particles may also be organic particles, including organic pigment particles such as azo pigments, phthalocyanine pigments.

For some color pigment particles, adding to the electrophoretic medium can not only improve the stability of the image, but also improve the visual effect of the displayed image. In the Lab color space, due to b* The yellow and blue colors on the shaft are complementary colors. When blue is added to the yellow color, the yellow chromaticity is neutralized and becomes white. Therefore, for a black and white two-color electrophoretic display, when a small amount of blue pigment particles are added, the brightness of the display can be significantly improved, so that the displayed image appears to have a higher resolution without affecting the saturation value of the electrophoretic display particles. The added blue pigment particles can reflect blue light, which can improve the black-and-white contrast of the electrophoretic display, thereby effectively improving the optical effect of the image display. Adding this type of pigment particles eliminates the yellow hue in the white state, making the white look whiter and the black look softer.

From the viewpoint of improving the visual effect of displaying an image, any particle made of a substance capable of reflecting blue light may be added, including but not limited to: ultramarine blue, Organic blue pigment, blue dye and blue fluorescent material.

The third type of particles added in the present invention is preferably a particle of a blue pigment, and the selected blue pigment may be an inorganic blue pigment (such as Prussian blue, ultramarine blue, cobalt blue) or an organic blue pigment ( For example, indigo pigment, indanthrone pigment); in the present invention, the best choice of blue pigment is brightly colored ultramarine ( Ultramarine), an inorganic pigment, is a special crystalline aluminosilicate containing sodium sulfide. Ultramarine reflects blue light (wavelength at 420~470nm) Between the two, this blue light is exactly complementary to the yellowish white reflected by the white/black particles, so people see the electronic paper as 'white/black' and more 'bright' with the naked eye. Therefore, the display visual effect of the image is effectively improved. Ultramarine is a bright blue color powder. It can eliminate the yellow color of white matter. It is resistant to alkali, heat and light. It is decomposed and discolored by acid and insoluble in water. Therefore, in the present invention, ultramarine blue is preferred as a raw material for such added blue pigment particles.

The following is an example of a specific design example. The examples given are only intended to help illustrate this patent and are not meant to be limited to the examples listed.

The electrophoretic display liquid generally includes at least the following components: 20-70% dispersion solvent, 0.1-10% The thickening stabilizer may further include a charge control agent, a surface tension controlling agent, and a dispersing wetting agent.

The dispersing solvent of the present invention includes various non-polar and / Or low-polarity organic solvents and mixtures thereof, and low-level dispersion solvents include, but are not limited to, various aromatic hydrocarbons such as toluene, benzene, xylene, and halogenated hydrocarbons such as, but not limited to, chloroform, tetrachloroethylene, and the like; Non-polar dispersing solvents include, but are not limited to, various linear, branched, and cyclic aliphatic hydrocarbons such as, but not limited to, n-hexane, decane, sunflower, synthetic isoparaffin ( Isopar), synthetic paraffin (Norpar), synthetic naphthenes (Nappar), synthetic alkanes (Varsol/Naphtha ), cyclohexane, and halogenated hydrocarbons such as, but not limited to, carbon tetrachloride.

The thickening stabilizer of the present invention may be a non-polar polymer, including but not limited to polymethyl methacrylate, polyethylene, polypropylene, rubbers such as polyisoprene, polyisobutylene, etc. Polymethyl methacrylate, polyethylene, and polypropylene are the best choices.

Referring to FIG. 2, the electrophoretic display liquid of the present invention comprises:
Charged pigment particles 101 of 2-50 parts by weight, the charged pigment particles 101 are only positively charged or only negatively charged;
The neutral pigment particles 102 having a difference in optical characteristics from the charged pigment particles 101 of 2 to 50 parts by weight, one of the charged pigment particles 101 and the neutral pigment particles 102 are white;
Blue pigment particles 103 in a part by weight of 0.01 to 5; the blue pigment particles 103 are preferably ultramarine pigment particles;
The low-polarity and/or non-polar dispersion solvent having a weight fraction of 20-70, wherein the three particles of the present invention are uniformly dispersed therein; specifically, the low-polarity dispersion solvent is an aromatic hydrocarbon or a halogenated hydrocarbon; The nonpolar dispersion solvent is a linear, branched and cyclic aliphatic hydrocarbon or a halogenated hydrocarbon.

The electrophoretic display liquid of the present invention may also be added in a weight fraction of 0.1-10 a thickening stabilizer; preferably, the dispersing solvent of the present invention may have a weight fraction of 40-60; the charged pigment particles may have a weight fraction of 10-20; and the neutral pigment particles may have a weight fraction of 10 -20 The thickening stabilizer is 0.5-5 parts by weight; the blue pigment particles 103 may be 0.05-2.5 parts by weight.

The following uses experimental data for comparison to illustrate the beneficial effects of the present invention:

1. Effect of adding ultramarine pigment particles before and after 'contrast' and black and white 'L* value'

Using 15V The driving voltage is respectively driven by the electrophoretic display layer to which the ultramarine blue and the ungrouped ultragreen are added, and when the black state and the white state are respectively displayed, the black reflected light in two cases is measured by the spectrophotometer (X-Rite I-1). Strong L* Black and white reflected light intensity L* white; then calculate reflectance and contrast using the following formula: reflectance R= (( L*+16 ) /116 ) ^3*100 , contrast =R white /R Black.

The measured data is shown in Table 1:
Table 1

Photoelectric performance	L* white	L* black	Contrast
After adding ultramarine	72.78	16.58	20.23
No ultramarine	68.37	24.81	8.84

From the data in Table 1 above, the black-and-white contrast of the electrophoretic display liquid is greatly improved after the addition of the ultramarine pigment particles.

2, the effect of the amount of ultramarine pigment particles on the intrinsic viscosity of the electrophoretic medium

Referring to Fig. 5, the intrinsic viscosity in the figure is that the viscosity of the electrophoretic medium to which the ultramarine is not added is 1, and the intrinsic viscosity of the electrophoretic medium to which the ultramarine is added is: the actual viscosity of the electrophoretic medium / the actual viscosity of the electrophoretic medium to which the ultramarine is not added .
It can be seen from Fig. 5 that the intrinsic viscosity of the electrophoretic medium is slightly agitated near 1 and the addition of the ultramarine pigment particles has little effect on the intrinsic viscosity of the electrophoretic medium, and does not affect the surface charge of the electrophoretic display particles, so it does not affect the electrophoresis. It does not cause any adverse effects on the switching time.
Since the viscosity of the electrophoretic medium is not changed, the droplets are more easily dispersed during the capsule reaction, the particle size is relatively easy to control in a small and suitable range, the conversion rate is high, and the cost can be saved in mass production.

3. The effect of adding ultramarine pigment particles on the b* value in black and white.
Referring to Fig. 6, it can be seen that the addition of ultramarine pigment particles can effectively improve the b* value. The more the amount of the ultramarine pigment particles added, the smaller the b* value, the bluer the color of the electrophoretic display; when the addition amount reaches 5%, b* The value is approximately -5 and the display state is clearly blue.

4. The influence of the optimal addition amount on the image stability is shown in Fig. 7. The abscissa indicates time, the unit is second, and the ordinate is L* value. The figure is for the electrophoretic display liquid with the addition of 0.05% by weight of ultramarine particles. Take measurements. As can be seen from the figure, after the ultramarine pigment particles are added, the L* value of the black-and-white state of the electrophoretic display image does not change substantially with time, which indicates that the stability of the image display is better.

The present invention is capable of increasing the image stability of an electrophoretic medium by several orders of magnitude, but does not increase the switching time at all. The electrophoretic display liquid of the invention can achieve at least about 400s Image stability, and the electrophoretic display solution without the ultramarine can only obtain image stability of about several seconds; (The image stability time mentioned here refers to the optical state change by L* 2 The time required for each unit to determine).

Example 1: Synthesis of Neutral Black Pigment Particles In a 1000 ml three-necked flask, 50 g of iron black Fe3O4 (Guangzhou Guocai Pigment Chemical Co., Ltd.) was added, and 5 g of isopropyl trioleate with a double bond was added. Acyloxy titanate (Nanjing Shuguang Chemical Group Co., Ltd.), 50 g of lauryl methacrylate, 150 g of toluene, 0.5 g of AIBN. Mix in an inert atmosphere with nitrogen-filled system for 20 minutes at a stirring speed of 350 rpm. The temperature of the reaction mixture was slowly raised to 85 degrees under a nitrogen atmosphere and a condensing reflux device for 16 hours. Referring to Figure 2, the reaction product was centrifuged at 3,500 RPM to collect the precipitate, and the product was washed twice with toluene. Through the chemical reaction process provided by the present invention, the titanate can graft a layer of titanate hydrolyzate film 22 on the surface of the pigment particle 21 by a coupling reaction; and the polymer chain 23 produced in the solution passes through the titanate molecule. The double bond in the reaction reacts to graft on the surface of the pigment particles.

Example 2: Synthesis of neutral white pigment particles In a 1000 ml three-necked flask, 50 g of titanium dioxide R101 (DuPont, USA) was added, and 3 g of titanate KR7 (Kenrich Petrochemicals Inc.), 50 g of lauryl methyl group was added. Acrylate, 150 grams of toluene, 0.3 grams of AIBN. Mix in an inert atmosphere with nitrogen-filled system for 20 minutes at a stirring speed of 350 rpm. The temperature of the reaction mixture was slowly raised to 85 degrees under a nitrogen atmosphere and a condensing reflux device for 16 hours. Referring to Figure 2, the reaction product was centrifuged at 3,500 RPM to collect the precipitate, and the product was washed twice with toluene. Through the chemical reaction process provided by the present invention, the titanate can graft a layer of titanate hydrolyzate film 22 on the surface of the pigment particle 21 by a coupling reaction; and the polymer chain 23 produced in the solution passes through the titanate molecule. The double bond reacts to graft onto the surface of the pigment particles

Example 3: Synthesis of white negatively charged pigment particles In a 1000 ml three-necked flask, 50 g of titanium dioxide R706 (DuPont, USA), 2.0 g of silane Z6030 with methacrylic functional groups (Dow Corning, USA), 50 K-lauric methacrylate (Aldrich, USA), 100 g of toluene, 0.5 g of AIBN. Mix in an inert atmosphere with nitrogen-filled system for 20 minutes at a stirring speed of 350 rpm. The temperature of the reaction mixture was slowly raised to 85 degrees under a nitrogen atmosphere and a condensing reflux device for 16 hours, see Figure 3. The reaction product was centrifuged at 3,500 RPM to collect the precipitate, and the product was washed twice with toluene. Through the chemical reaction process provided by the present invention, silane is formed on the surface 31 of the pigment particles by a coupling reaction to form a silane hydrolyzate film 32 (organic silane and its crosslinked product produced after hydrolysis); and simultaneously produced in the solution. The polymer chain 33 is grafted on the surface of the pigment particles by reacting with a double bond in the coupling agent molecule.

Example 4: Synthesis of black positively charged pigment particles In a 1000 ml three-necked flask, 50 g of iron black Fe3O4 (Guangzhou Guocai Pigment Chemical Co., Ltd.), 2.0 g of silane Z6020 with amino functional groups were added. Dow Corning), 50 grams of lauryl methacrylate (Aldrich, USA), 100 grams of toluene, 0.5 grams of AIBN. Mix in an inert atmosphere with nitrogen-filled system for 20 minutes at a stirring rate of 350 rpm. The temperature of the reaction mixture was slowly raised to 85 degrees under a nitrogen atmosphere and a condensing reflux device for 16 hours, see Figure 3. The reaction product was centrifuged at 3,500 RPM to collect the precipitate, and the product was washed twice with toluene. Through the chemical reaction process provided by the present invention, silane is formed on the surface 31 of the pigment particles by a coupling reaction to form a silane hydrolyzate film 32 (organic silane and its crosslinked product produced after hydrolysis); and simultaneously produced in the solution. The polymer chain 33 is grafted on the surface of the pigment particles by reacting with a double bond in the coupling agent molecule.

Example 5: Synthesis of Blue Pigment Particles The surface of the ultramarine particles was preliminarily treated with a silane coupling agent or titanate, and the positively charged ultramarine particles 1 and the negatively charged ultramarine particles 2 were obtained using different coupling agents. Then, the polymer grafting reaction can be carried out to coat the surface with a layer of polymer to further improve the dispersibility. The ultramarine particles obtained at this time are positively charged ultramarine blue particles 3 and positively charged ultramarine blue particles 4; In the actual use, any one of the types of ultramarine blue described in the present invention may be separately added, or may be added in combination, for example, the ultramarine blue particles 3 and the ultramarine blue particles 4 may be simultaneously added according to the actual usage amount.

Example 6: Preparation of electrophoretic display liquid Referring to Fig. 4, 25 g of white negatively charged pigment particles prepared in the above Example 3 were placed in 65 g of tetrachloroethylene, and ultrasonically dispersed for 30 minutes to obtain a dispersion A. Then, 6 g of the neutral black pigment particles prepared in the above Example 1 was placed, and placed in the dispersion A under ultrasonic conditions, and ultrasonication was continued for 30 minutes to obtain a dispersion B; then the blue obtained in the above Example 5 was taken. Color pigment particles (cyanite particles 3 or / and ultramarine particles 4) 2.5 g was added to dispersion B for ultrasonic dispersion; 2.4 g of 10% polystyrene in cyclohexane solution was weighed, added to the above dispersion system, and uniformly mixed. An electrophoretic display solution was prepared.

Example 7: Preparation of electrophoretic display liquid Referring to Fig. 4, 6 g of black positively charged pigment particles prepared in the above Example 4 were placed in 62 g of tetrachloroethylene and ultrasonically dispersed for 30 minutes to prepare a dispersion. C; 28 g of the neutral white pigment particles prepared in the above Example 2 were further placed in the dispersion C under ultrasonic conditions, and ultrasonication was continued for 30 minutes to obtain a dispersion D; then, the obtained in the above Example 5 was obtained. Blue pigment particles (green particles 3 or / and ultramarine particles 4) 2.5 grams added to dispersion D for ultrasonic dispersion; weigh 4 grams of 5% polymethyl methacrylate in chloroform solution, 0.1 grams of polyether modified A solution of tris(ethylene oxide) and 1 g of 10% Span 80 in tetrachloroethylene was added to the above dispersion system, and the mixture was uniformly mixed to prepare an electrophoretic display liquid.

The pigments of the charged pigment particles, the neutral pigment particles and the blue pigment particles of the present invention are all subjected to micronization, and the particle size thereof is 0.01-5. Micron. At the same time, physical or chemical methods are used for surface treatment to increase its stability in the solvent. The electrophoretic display liquid of the present invention may further comprise a charge control agent or / and a surface tension controlling agent or And dispersing the wetting agent.

The electrophoretic display liquid of the present invention can be encapsulated in microcapsules 11 Or in the microcup, the microspheres are obtained by in-situ polymerization, interfacial polymerization, single, complex coacervation, phase separation, surface deposition, etc., and the optimal synthesis method is in situ polymerization. The display microspheres are dispersed in a water-soluble binder to prepare a display coating liquid, and a plurality of closely arranged, heat-cured display layers are precisely coated or printed by a coater. The display material layer of the present invention is then The ITO conductive layers are hot pressed together; an electric field is applied by applying a voltage to the ITO conductive layer 201 on both sides of the electrophoretic display liquid of the microcapsule 11 package, and the electrophoretic display shows the charged pigment particles inside the liquid 101 Electrophoresis is applied to one side of the ITO conductive layer under the force of an electric field, and the individual charged blue pigment particles 103 are also electrophoresed together to one side of the ITO conductive layer, and the neutral pigment particles 102. The uncharged blue pigment particles 103 remain in their original position and are unaffected by the electric field.

Example 8
When the third particle of the present invention is not added to the electrophoretic display liquid, the reflected light intensity L* value of the black state corresponding to the different time will gradually increase, and the reflected light intensity L* value of the white state will gradually decrease. Decrease, see the middle two lines in Figure 7. Take the two time points from the 0th and 400th seconds after the drive, the specific values are as follows:

	L* white	L* black
0s	68.95	25.46
400s	65.42	28.52

Example 9
When the third particle of the present invention is added to the electrophoretic display liquid, the reflected light intensity L* value of the black state corresponding to the black state at different times and the reflected light intensity L* value of the white state are compared with those of the above-described Embodiment 8 There is no significant change when no ultramarine is added, as shown in the top and bottom two lines in Figure 7. Take the two time points from the 0th and 400th seconds after the drive, the specific values are as follows:

	L* white	L* black
0s	72.78	16.58
400s	72.11	18.43

Example 10
Referring to FIG. 3, unlike the above examples, the electrophoretic display liquid in the present embodiment does not contain neutral pigment particles; instead, two oppositely charged pigment particles are used for display; specifically, it contains parts by weight. The number of positively charged pigment particles 104 of 2-50; the negatively charged pigment particles 101 having different optical characteristics from the positively charged pigment particles, the positively charged pigment particles 104 and the negatively charged pigment particles 101 At least one of them is white; further comprising blue pigment particles 103 in a weight fraction of from 0.01 to 5; and a low polarity and/or non-polar dispersion solvent in a weight fraction of from 20 to 70.

The positively charged pigment particles 104 and the negatively charged pigment particles 101 and the blue pigment particles thereof according to the present invention are 103 They were all prepared by the method used in the above examples.

There is another embodiment in which blue pigment particles are added to an electrophoretic display liquid containing two pigment particles having the same polar charge but different electrophoretic mobility; and the photoelectric properties of such an electrophoretic display liquid can also be improved. .

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope of the present invention. All should be covered by the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

An electrophoretic display liquid comprising a suspension and a plurality of display particles dispersed in a suspension, the display particles comprising at least first particles and second particles having different optical states, the first particles and the second particles being capable of Performing different motion behaviors in the suspension under the action of an electric field; characterized in that the suspension is further dispersed with a third particle having a weight fraction of 0.01-5 and not participating in electrophoretic display. .
The electrophoretic display solution according to claim 1, which comprises: 20 to 70 parts by weight of the suspension, 2 to 50 parts by weight of the first particles, 2 to 50 parts by weight of the second particles, and 0.01 to 5 parts by weight The third particle.
An electrophoretic display liquid according to claim 1 or 2, wherein the surface of said third particles has a functional group having a particle size of from 0.1 to 5 μm.
An electrophoretic display liquid according to claim 3, wherein said third particles are blue pigment particles; and at least one of said display particles is white.
An electrophoretic display liquid according to claim 4, wherein said blue pigment particles are ultramarine blue particles.
An electrophoretic display liquid according to claim 4, wherein the surface of the blue pigment particles is coated with a high molecular polymer by chemical or physical means.
An electrophoretic display liquid according to claim 5, wherein the blue pigment particles have a weight fraction of 0.05 to 2.5.
The electrophoretic display liquid according to claim 1 or 2, wherein the first particles are positively or only negatively charged charged pigment particles, and the second particles and the charged pigment particles are colored. Different neutral pigment particles.
An electrophoretic display liquid according to claim 8, wherein the suspension has a weight fraction of 40 to 60; and the charged pigment particles have a weight fraction of 10 to 20; the neutral pigment particles The parts by weight are 10-20.
The electrophoretic display liquid according to claim 1 or 2, wherein the first particles and the second particles are positively-charged pigment particles and negatively-charged pigment particles each having a different color.
The electrophoretic display liquid according to claim 1 or 2, wherein the first particles and the second particles are first pigment particles and second pigment particles having the same polarity charge but different colors, respectively. The first pigment particles have a different electrophoretic mobility than the second pigment particles.
An electrophoretic display liquid according to claim 8 or 10 or 11, which further comprises a thickening stabilizer in an amount of from 0.1 to 10 parts by weight.
An electrophoretic display liquid according to claim 1 or 2, wherein the suspension is an aromatic hydrocarbon or a halogenated hydrocarbon.
An electrophoretic display liquid according to claim 1 or 2, wherein the suspension is a linear, branched and cyclic aliphatic hydrocarbon or a halogenated hydrocarbon.
An electrophoretic display solution according to claim 8 or 10 or 11, further comprising a charge control agent or/and a surface tension controlling agent or/and a dispersing wetting agent.
A particle preparation method for improving stability of an electrophoretic display liquid, the electrophoretic display liquid comprising a suspension and a plurality of display particles dispersed in the suspension, the display particles comprising at least first particles and second particles having different optical states, The first particles and the second particles are capable of exhibiting different motion behaviors in the suspension under the action of an electric field; the suspension is further dispersed with a third particle having a weight fraction of 0.01-5 and not participating in electrophoretic display. The method for preparing the third particle comprises: mixing inorganic particles or organic particles with a polymer monomer, a coupling agent and a polymer reaction chain initiator in a suspension at 30-120 degrees. The reaction is carried out in the temperature range for 4 to 48 hours.
An electrophoretic display material comprising the electrophoretic display liquid according to any one of claims 1 to 15, wherein the electrophoretic display liquid is encapsulated in a microcapsule .