TW201107430A - Electrophoretic particles - Google Patents

Abstract

In electrophoretic media, it is advantageous to use pigment particles having polymer shells comprising from 0.1 to 5 mole per cent of repeating units derived from a fluorinated acrylate or fluorinated methacrylate monomer. The polymer desirably has a branched chain structure with side chains extending from a main chain.

Description

201107430 VI. Description of the Invention: [Technical Field] The present invention relates to an electrophoretic particle (i.e., a particle used for an electrophoretic medium) and a method of producing the electrophoretic particle. The invention also relates to electrophoretic media and displays incorporating such particles. More specifically, the present invention relates to electrophoretic particles whose surface has been modified by a polymer. In the present application, the applicant's international application No. WO 02/093 246, the reader may refer to as background information. [Prior Art] Electrophoretic displays have become the subject of intensive development in recent years. Compared to liquid crystal displays, this display has good brightness and contrast, wide viewing angle, state bistability, and low power consumption. (The terms "bistable" and "bistable" are used herein to refer to a display having display elements having first and second display states (at least one optical property is different), as used in the conventional sense of the art, and Equivalently, after the specified pulse is driven by the address pulse for a limited period of time, it is assumed that the first or second display state is required to change the state of the display element at least several times (eg, at least four times) after terminating the address pulse. The minimum period of address pulse.) Nevertheless, the long-term image quality problems of these displays make them unusable for use. For example, particles that make up an electrophoretic display tend to settle, causing improper display of these displays. A number of patents and applications owned by MIT or MIT and E Ink Corporation have recently been published to describe various techniques for encapsulating electrophoresis and media. The encapsulating medium comprises a plurality of sachets, each of which comprises a type. 201107430 In the fluid medium, the inner phase of the particles is moved electrophoretically, and the wall surrounding the inner phase. Generally, the bladder itself is held within the polymeric binder to form an inner cohesive layer between the two electrodes. The techniques described in these patents and applications include: (a) Electrophoretic particles, fluids and fluid additives; see, for example, U.S. Patent Nos. 5,961,804; 6,017,584; 6,120,588; 6,120,839: 6,262,706; 6,2 62,8 3 3; 6,3 00,93 2; 6,3 23,989; 6,3 77,3 87 ;6,515,649 ; 6,538,801 ; 6,580,545 ; 6,652,075 ; 6,693,620 ; 6,72 1,083 ; 6,727,88 1 ; 6,822,782 ; 6,870,66 1 ; 7,002,728; 7,038,655; 7,170,670; 7,180,649; 7,230,750; 7,230,751; 7,236,290; 7,247,379: 7,312,916; 7,375,875; 7,411,720; 7,532,388; and 7,679,814; and U.S. Patent Application Publication No. 2005/00 1 2980; 2006/0202949; /0013155 ; 2008/0013156 ; 2008/0266245 ; 2008/0266246 ; 2009/0009852 ; 2009/0027762 ; 2009/0206499 ; 2009/0225398 ; and 2010/0045592 ; (b) capsules, adhesives and packaging methods; see for example U.S. Patent Nos. 6,922,276 and 7,411,719; (c) Films and sub-assemblies containing electro-optic materials; see, for example, U.S. Patent No. 6,982,178; and U.S. Patent Application Publication No. 2007/0 1 092 1 9 (d) Backsheets, adhesive layers and other auxiliary layers, and methods for use in displays; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624; (e) Color formation and color adjustment; see, e.g., U.S. Patent No. 4-201107430 7,075, 5 02; and U.S. Patent Application Publication No. 2007/0 1 092 1 9» (f) methods of driving a display; see, for example, U.S. Patent Nos. 7,012,600 and 7,453,445; and (g) display applications; see, for example, U.S. Patent No. 7, 312, 784; and U.S. Patent Application Publication No. 2006/0279527. As known, for example, in U.S. Patent No. 6,870,661, known electrophoretic media (packaged and unencapsulated) can be divided into two main types, for convenience. The following are called "single particle" and "double particle". Single-particle media have only single-type electrophoretic particles suspended in a colored suspending medium whose at least one optical characteristic is different from the particles. Two-part media have two different types (at least one optical feature is different) of particles, and a suspending fluid (which may be uncolored or colored, but generally uncolored). The electrophoretic mobility of the two types of particles is different: the difference in mobility can be polar (this type can be referred to below as the "charge opposite two-particle" medium) and/or size. Both single and dual particle electrophoretic displays can be optically characterized by an intermediate gray state intermediate the two extreme optical states already described. - The above patents and published applications disclose encapsulated electrophoretic media having three or more different types of particles within each capsule. For the purposes of the present invention, this multiparticulate medium is considered to be a sub-species of a two-particle medium. Many of the above patents and applications recognize that the walls surrounding the discontinuous microcapsules in the encapsulated electrophoretic medium can be replaced by a continuous phase, thus producing a so-called polymer dispersed electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete electrophoretic fluid droplets, and a continuous phase of polymeric material, and the discrete electrophoretic fluid droplets in the polymer dispersed electrophoretic display can be considered as capsules or microcapsules, even if individual

S 201107430 Microdrops does not carry a discontinuous capsule; see, for example, the aforementioned U.S. Patent No. 6,866,760. Thus, for the purposes of the present invention, the polymer dispersed electrophoretic medium is considered to be a sub-species of the encapsulated electrophoretic medium. As indicated above, the electrophoretic medium requires the presence of a fluid. In most prior art electrophoretic media, the fluid is a liquid, but the electrophoretic medium can be made using a gaseous fluid; see, for example, Kitamura, T. et al. "Electrical toner movement for electronic paper-like display 55, IDW Japan, 2001, Paper. HCS1-1, and Yamaguchi, Y. et al. "Toner display using insulative particles charged triboelectrically'', IDW Japan, 2001, Paper AMD 4-4). See also U.S. Patents 7,321,459 and 7,236,291. When the medium is used in such an orientation that it can be so settled, the gas as the main electrophoretic medium tends to have the same type of problem as the liquid-based electrophoretic medium is caused by particle sedimentation, such as the indication that the medium is disposed in a vertical plane. In fact, due to the lower viscosity of the gaseous suspension fluid compared to the liquid, the electrophoretic particles settle more quickly, and the sedimentation of the particles appears to be a more serious problem in liquid-based electrophoretic media. A related type of electrophoretic display is a so-called "micro-cell electrophoretic display". In a microelectrophoresis display, both charged particles and fluid are not encapsulated within the microcapsules, but remain in a plurality of pockets formed within the carrier medium (typically a polymeric film). See, for example, U.S. Patent Nos. 6,672,92 1 and 6,788,449, each assigned to Sipix Imaging, Inc. It has long been known that the physical and surface characteristics of electrophoretic particles can be modified by adsorbing various materials on the surface of the particles or by chemically bonding the materials to these surfaces. It was later discovered that due to changes in operating conditions, some or all of the 201107430 modified materials may leave the surface of the particles, causing undesirable changes in the electrophoretic properties of the particles; modifying the material may deposit on other surfaces within the electrophoretic display, which may cause further problems. Simply coating the electrophoretic particles with modified materials is not entirely satisfactory. Thus, techniques have been developed to fix modified materials to the surface of the particles. The above-mentioned WO 02/093246 patent describes a plurality of coated polymer electrophoretic particles β teaching that a plurality of monomers which can be used for coating the polymer particles are specific fluorinated monomers, and this patent application contains Working Example 20, which will be approximately 10 mole % of fluorinated monomer combines about 90 mole % of non-fluorinated monomer to form a polymer coating. SUMMARY OF THE INVENTION It has now been found that a relatively small molar ratio (not more than about 5 mole %) of fluorinated acrylate or fluorinated methacrylate monomer (especially methyl) is used in the polymer shell of the electrophoretic particles. 2,2,2-trifluoroethyl acrylate, hereinafter abbreviated as "TFEM", yields significant advantages not mentioned in the above-mentioned WO 02/093246. In particular, the use of this fluorinated monomer adjusts the charge on the pigment particles. In one aspect, the invention provides an electrophoretic medium comprising a plurality of pigment particles in a fluid, the pigment particles having a polymer chemically bonded to the pigment particles, wherein the polymer comprises from about 〇_1 to about 5 mol% Repetitive units derived from fluorinated acrylate or fluorinated methacrylate monomers. The electrophoretic medium of the present invention can be incorporated into any of the optional features of the polymer shell described in the above-mentioned WO 02/093246. The preferred proportion of polymer in the coated particles is generally substantially as described in the above-mentioned WO 02/093246 patent 201107430, i.e., particles having from about 4 to about 15, desirably from about 8 to about 12 weight percent polymer particles. Bond particles. The particles may comprise a metal oxide or hydroxide, such as titanium white. The polymer may comprise a charged or chargeable group, such as an amine or carboxylic acid group. The polymer may comprise a backbone and a plurality of side chains of autonomous chain extension, each side chain comprising at least about 4 carbon atoms. In general, the polymer is formed from two or more acrylate and/or methacrylate monomers. In general, a fluorinated single system is used in combination with a non-fluorinated acrylate or methacrylate monomer (ie, the polymer may comprise residues derived from fluorinated and non-fluorinated acrylate or methacrylate monomers). The preferred monomer for this purpose is lauryl methacrylate. The molar ratio of fluorinated monomers to non-fluorinated monomers can vary, but fluorinated monomers generally comprise from about 1 to about 5 mole percent of all monomers in the polymer. It is preferably a highly fluorinated monomer having at least three fluorine atoms. The preferred fluorinated monomer is 2,2,2-trifluoroethyl methacrylate, but other fluorinated monomers such as 2,2,3,4,4,4-hexafluorobutyl acrylate may also be used. 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate. The invention extends to an electrophoretic display comprising the electronic medium of the invention and at least one electrode arranged to apply an electric field to the electrophoretic medium, and an e-book reader, portable computer, desktop computer, mobile phone including the display , smart card, logo, watch, shelf label, or flash drive. [Embodiment] Before discussing the electrophoretic medium and method of the present invention in detail, it is believed that it is desirable to briefly describe some types of electrophoretic displays in which these media are intended to be used.

S 201107430 The electrophoretic medium of the present invention may be of the type described in the above-mentioned E Ink and MIT patents and applications, and a preferred embodiment of the medium will now be described with reference to Figures 1 to 4 of the accompanying drawings. Figs. 1A and 1B The first electrophoretic display (commonly referred to as 1 〇〇) comprises a packet of electrophoretic medium (commonly referred to as 102) comprising a plurality of capsules 104 (only panels 1A and 1B are shown), each containing a suspension ι 〇6 and a plurality of single-type particles 108 dispersed therein (assumed to be black for purposes of description). The particles 108 are electrophoretically moved and may be formed of carbon black. In the following description it is assumed that the particles 108 are positively charged, although of course negatively charged particles can be used if desired. (The triangles of particles 1〇8, and the squares and circles of the other particles discussed below are used purely for the purpose of easily distinguishing the various types of particles in the drawings, and are in no way corresponding to the physical form of the actual particles. It is generally substantially spherical. However, the present display does not preclude the use of non-spherical particles.) The display 1 further includes a conventional transparent front electrode 110 that forms a viewing surface through which the viewer views the display 100, and a plurality of defined displays A discontinuous rear electrode 112 of one pixel of 100 (only the one rear electrode 112 is shown in FIGS. 1A and 1B). For ease of description and understanding, Figures 1A and 1B show only a single microcapsule that forms the pixels defined by the back electrode 112, although in practice each pixel typically uses a large number (20 or more) of microcapsules. The rear electrode 112 is mounted on the substrate 114. The suspension 106 is colored such that the viewer sees through the front electrode 110 that the display 108 does not see the particles 108 located adjacent the adjacent back electrode 112 shown in Figure 1A. The necessary color of the suspension 106 can be provided by dissolving the dye in a liquid. Since the electrophoretic medium 102 201107430 is rendered opaque by the colored suspension 106 and particles 108, the back electrode Π 2 and the substrate 114 may be transparent or opaque because it is not visible through the opaque electrophoretic medium 102. The bladder 104 and the particles 108 can be made to a wide range of sizes. Preferably, however, the thickness of the bladder is measured in the range of from about 15 to 500 microns perpendicular to the electrode, while the particles 108 generally have a diameter of from about 0.25 to about 2 microns. Figure 1 shows a display 100 with the back electrode 112 negatively charged and the front electrode 110 positively charged. Under this condition, the positively charged particles 108 are attracted by the negative back electrode 1 1 2, so that they are located adjacent to the rear electrode .1 1 2, where they are viewed by the viewer through the front electrode 1 1 0 The coloring liquid 106 is hidden. Thus the pixel shown in Figure 1 shows the color of the liquid 106 to the viewer, which is assumed to be white for purposes of description. (Although display 100 is depicted in Figures 1 and 1 as rear electrode 112 at the bottom, in practice for the maximum visibility of display 100, the front and rear electrodes are generally vertically disposed. Generally, the media and display of the present invention are not described herein. Depending on gravity, the movement of the particles is controlled; this movement under gravity is actually too slow to control the movement of the particles.) Figure 1 shows a display 1 前 with the front electrode 11 〇 opposite the back electrode 112. Since the particles 108 are positively charged, they are attracted by the negatively charged front electrode 110, such that the particles 108 move to the adjacent front electrode 110, and the pixels display the black color of the particles 108. In Figures 1 and 1 , the capsule 104 is depicted as a substantially prismatic form having a width (parallel electrode faces) that is significantly greater than its height (vertical to these faces). This prismatic shaped capsule 104 is deliberate. If the capsule 104 is substantially spherical, then in the black state shown in Figure 18, the particles tend to accumulate in the highest part of the capsule, centered in the center of the capsule, in the limited -10- 201107430 region. The color seen by the viewer is the essentially average color of the central black zone and the white annulus surrounding the central zone, where the white liquid 106 is visible. Thus, even if the black state is assumed here, the viewer sees gray instead of pure black, and the contrast between the two extreme optical states is limited. Conversely, with the microcapsules in the form of mirrors shown in Figures 1A and 1B, the particles 108 cover the entire cross-section of the capsule such that no or at least very few white liquids are visible, and the contrast between the extreme optical states of the capsule is enhanced. Further discussion of this and the need to complete the tight filling of the capsules in the electrophoretic layer is described in the above-referenced U.S. Patent No. 6,067,185, the disclosure of which is incorporated herein by reference. As also described in the above-mentioned E Ink and MIT patents and applications, in order to provide mechanical integrity to the electrophoretic medium, the microcapsules are usually embedded in a solid binder, but the binders are omitted in Figures 1 to 3 for ease of description. The second electrophoretic display (generally referred to as 200) shown in Figures 2A and 2B comprises a packet electrophoretic medium (commonly referred to as 202) comprising a plurality of capsules 204 each containing a suspension 206 and a plurality of positively charged black particles 108 Dispersed therein is the same as discussed above for the first display 100 discussed above. The display 200 further includes a front electrode 110, a rear electrode 112, and a substrate 114, both of which are identical to the corresponding numbers of the first display 100. However, in addition to the black particles 108, a plurality of negatively charged particles 218 are suspended in the liquid 206, which is assumed to be white for the purposes of the present invention. In general, liquid 206 is uncolored (i.e., substantially transparent), although some color may be present to adjust the optical properties of the various states of the display. Figure 2A shows that electrode 112 is positively charged after having a relatively described pixel

S -11- .201107430 Display 200 of front electrode 110. The positively charged particles 108 electrostatically hold adjacent rear electrodes 112, while the negatively charged particles 218 are electrostatically held close to the front electrode 110. Thus, as the white particles 218 are visible and the black particles 108 are hidden, the viewer viewing the display 200 through the front electrode 110 sees the white pixels. Figure 2B shows display 200 with electrode 112 as negatively charged electrode 110 with respect to the described pixel. » A corresponding optical state as shown in Figure 1B, positively charged particles 108 are now electrostatically attracted by negative front electrode 110, and The negatively charged particles 218 are electrostatically attracted by the positive rear electrode 112. Thus, the particles 108 move to the adjacent front electrode 110, and the pixels display the black color of the particles 108, which hide the white particles 218. The third electrophoretic display (commonly referred to as 300) of the present invention shown in Figures 3A and 3B comprises a packet electrophoretic medium (commonly referred to as 302) comprising a plurality of pockets 304. The display 300 further includes a front electrode 110, a rear electrode 112, and a substrate 114, both of which are identical to the corresponding numbers of the aforementioned displays 100 and 200. Display 300 is similar to display 200 described above, with liquid 306 uncolored and white negatively charged particles 218 suspended therein. However, display 300 differs from display 200 in the presence of red negatively charged particles 320, which have substantially lower electrophoretic mobility than white particles 218. Figure 3A shows display 300 with electrode 112 being positively charged front electrode 110 with respect to the described pixel. Both the negatively charged white particles 218 and the negatively charged red particles 320 are attracted by the front electrode 110, but since the white particles 218 have a substantially higher electrophoretic moving force, they first reach the front electrode 110 (note that the optical state shown in Fig. 3A) Usually by showing Figure 3B

S -12- 201107430 The polarity of the electrode of the optical state is sharply reversed, thus forcing the white particles 218 and the red particles 320 to traverse the thickness of the capsule 404, and thus the white particles 218 may be caused by the large moving force thereof. It reaches the position of its adjacent front electrode 1 1 0 before the red particles 320). The white particles 2 1 8 thus form a continuous layer in close proximity to the front electrode 110, thus hiding the red particles 320. Thus, as the white particles 218 are visible and the red particles 320 are hidden, the viewer viewing the display 300 through the front electrode 看见 sees the white pixels. Figure 3B shows display 300 with electrode 112 being negatively charged front electrode 110 with respect to the described pixel. Both the negatively charged white particles 218 and the negatively charged red particles 3 20 are attracted by the rear electrode 112, but since the white particles 218 have a higher electrophoretic moving force, the optical state shown in Fig. 3B is by the optical shown in Fig. 3A. When the polarity of the electrode of the state is sharply reversed, the white particles 218 reach the rear electrode 112 earlier than the red particles 3 20 such that the white particles 218 form a continuous layer adjacent to the back electrode 112, leaving a continuous layer of red particles 320. Pair the front electrode 110. Thus, since the red particles 320 are visible and the white particles 218 are hidden, the viewer viewing the display 300 through the front electrode 110 sees the red pixels. Figures 4A and 4B depict a polymer dispersed electrophoretic medium of the present invention and a method for making the medium. The polymer dispersion medium contains non-spherical droplets and is prepared using a film forming material which produces a film which is substantially shrinkable after it is formed. The preferred discontinuous phase for this purpose is gelatin, although other proteinaceous materials may be used, possibly with crosslinkable polymers. A mixture of liquid material (which ultimately forms a continuous phase) and droplets is formed and coated on a substrate to form a structure as depicted in Figure 4A. Figure 4A shows a layer 410 comprising droplets 412 dispersed in a liquid medium 414 in a method of forming a film, which layer 410 has been coated with a layer 418 previously having a transparent conductive material (e.g., indium tin oxide). The substrate 416 (preferably a flexible polymeric film such as a polyester film). The liquid material forms a relatively thick layer 4 1 0 containing essentially spherical droplets 4 1 2; as shown in Figure 4A. After the layer 410 has formed a solid continuous layer, the layer is preferably dried at about room temperature (although the layer can be heated if desired) to be sufficient to dehydrate the gelatin, thereby causing substantial reduction in layer thickness and fabrication of the fourth layer. The figure depicts a pattern in which the dried and contracted layer is referred to as 410' in Figure 4B. The vertical shrinkage of the layer (i.e., the contraction perpendicular to the surface of the substrate 416) actually compresses the original spherical droplet into a flat ellipsoid having a thickness perpendicular to the surface that is substantially smaller than its transverse dimension parallel to the surface. In practice, the droplets are typically sufficiently tightly packed so that the lateral edges of adjacent droplets contact each other such that the final form of the droplets more closely resembles an irregular ridge rather than a oblate ellipsoid. As also shown in Figure 4B, more than one layer of droplets may be present in the final medium. In the case where the medium is shown in Fig. 4B in which the droplets are polydisperse (i.e., droplets having a large size range), the presence of the plurality of layers is advantageous because it reduces the chance that the small area of the substrate is not covered by any droplets; The multilayer thus helps to ensure that the electrophoretic medium is completely opaque, and that no part of the substrate is visible in the display formed by the medium. However, when using a medium that is essentially monodisperse droplets (ie, droplets that are substantially the same size), it is generally recommended to apply the medium to a layer that is tightly packed to form a single layer of droplets after shrinking, with reference to US patents. No. 6,839,158. Because of the absence of relatively hard microcapsule walls in the microencapsulated electrophoretic medium, the droplets in the polymeric dispersion medium of the present invention tend to be more densely packed into a tighter monolayer than the microcapsules.

E -14- 201107430 Contrary to expectations, it has been experimentally found that the droplets do not aggregate during drying of the medium. However, it does not exclude that some wall ruptures between adjacent capsules may occur in a particular embodiment of the invention, thus providing the possibility of partial connection between droplets" the extent of droplet deformation that occurs during the drying step, and thus The final form of the drop can be varied by controlling the proportion of water in the gelatin and the ratio of the solution to the droplets. For example, an experiment is carried out using 2 to 15% by weight of a gelatin solution, and using 200 g of each gelatin solution and 50 g of a non-aqueous internal phase (which forms droplets). In order to produce a final layer of electrophoretic medium having a thickness of 30 microns, it must be coated with a 2% thick gelatin solution/internal phase mixture layer of 139 microns; this layer is made to produce a 30 micron thick electrophoretic medium containing 92.6% by volume of droplets upon drying. . On the other hand, in order to manufacture an electrophoretic medium of the same thickness, it was coated with a 15 μm gelatin solution/internal phase mixture having a thickness of 93 μm, and an electrophoretic medium containing 62.5 vol% of droplets was produced upon drying. Media made from 2% gelatin solution are less fragile when subjected to rude treatment; media made from gelatin solution containing 5 to 15% by weight of gelatin have satisfactory mechanical properties. The degree of deformation of the droplets in the final electrophoretic medium is also affected by the initial size of the droplets and the relationship between the initial size and the final layer thickness of the electrophoretic medium. Experiments have shown that the larger the average size of the droplets at the beginning and/or the greater the ratio of the average size to the thickness of the final layer, the more the droplets are deformed by the spheres in the final layer. It is generally preferred that the average initial size of the droplets is from about 25 % to about 400% of the thickness of the final layer. For example, in the foregoing experiment in which the final layer thickness was 30 μm, a good result was obtained with an initial average droplet size of 10 to 100 μm. 3 -15- 201107430 Gelatin forms a film by sol/gel conversion, but the sol/gel transition forms a film forming material of its film. Polymerization of the precursor or oligomer, by radiation hardening of the monomer or oligomer 'or by any other known film forming means in which the film is first formed and then caused to shrink in thickness, the shrinkage does not have to shrink by gelatin film The same type, but can be accomplished by removing the aqueous or non-aqueous solvent from the membrane, and by other conventional steps. In the polymer dispersed electrophoretic medium of the present invention, the electrophoretic medium is at least 40%, and preferably about 50 to see U.S. Patent No. 6,866,760. It should be emphasized that the droplets used in the bulk medium may have any combination of the particles described in Figures 1 to 3. The present invention can be applied to any of the swimming media shown in Figures 1 to 4. However, the invention is not limited to packets and polymers and can also be applied to micelles and unencapsulated media. It is apparent from the following examples that the use of a controlled amount of fluorinated monomer in the electrophoretic ampoule shell, increasing the band position, and as is often the case here, the negative particles are white), the resulting increase in the negative zeta potential itself is revealed Improved (compared to: potential with the proportion of fluorinated monomer in the polymer shell. However, higher than about 5 mol% of fluorinated monomer is a specific state of image loss (measured not to drive the display after a period of time after the dark state of the display The change) begins to increase, and the dark state invention is not limited thereto, as the film formation can be accomplished by means of a single polymer, by means of a polymer. Similarly, the dehydration mechanism of the preferred variant of the invention completes the polymerization film, or any desired droplet Containing about 80% by volume; in the form of a polymer-dispersed electrophoretic medium of the polymer molecule and the suspension fluid of the present invention, the white state of the electro-negative particles of the particles of the indicator (such as titanium white: reflective) The increase and the more negative defects become obvious. The dark space (such as 2 minutes) itself becomes less dark-16-.201107430, thus negatively affecting the dynamic range of the display (the dark and white state of the display measured in L* units) The difference, (where L* has the general CIE definition: L* = 116(R/R〇) 1/3-16, where R is the reflectance and R〇 is the standard reflection 値)). Therefore, it is generally preferred to use fluorine. The molar ratio of the monomer in the polymer shell is maintained in the range of from about 0.1 to about 5, desirably in the range of from about 1 to 5 mole %. It is understood that the optimum ratio of fluorinated monomer can be specified with the use of the specified fluorinated single The body (especially its degree of fluorination), other monomers used, and other factors, including other particles present in the electrophoretic medium, vary slightly. Typically, the optimum ratio of fluorinated monomers appears to be about 1 mol% because This fluorinated monomer content produces a substantially substantial increase in the zeta potential while avoiding the disadvantages associated with the higher fluorinated monomers described above. The coated polymer particles useful in the electrophoretic media of the present invention can be borrowed from any of the above WO 02/09 3 246 Made by the method described in the patent. In one such method, the particles on which the polymer is to be formed are formed, and the functional groups which are reactive and bonded to the particles are polymerizable with the functional group (for example, vinyl or The other difunctional reagent of the ethylenically unsaturated group is reacted. The following examples by way of illustration only show the range of particularly preferred reagents, conditions and techniques for use in the present invention. Example 1: 2,2,2-trifluoroethyl methacrylate and methacrylic acid in a polymer shell Preparation of a white titanium white pigment of lauryl ester A DuPont R-794 titanium white functionalized on the surface of 3-(trimethoxydecyl) propyl methacrylate was prepared essentially as described in the above PCEP application. In the bottle, 500 grams of this pigment was dispersed in 426 grams (500 ml) of toluene by ultrasonic. A 1 liter glass reactor was placed.

S -17- 201107430 Packed with 1.7158 moles of monomer, lauryl methacrylate and TFEM are added to produce the desired molar concentration of each monomer. The molar ratio of TFEM is 0.1, 1, 5, 10, 25 and 50 mol%, and the rest is lauryl methacrylate. The pigment dispersion is added to the reactor, and the reactor is flushed with nitrogen and heated to 65 °C. . A free radical initiator (5.0 g of 2,2'-arsenazo (2-methylpropionitrile), AIBN) previously dissolved in 110 ml of toluene was added dropwise over 60 minutes. The vessel was heated under continuous agitation at 65 ° C under nitrogen and then exposed to the atmosphere. The mixture was then dispensed into four 1 liter plastic bottles and approximately 500 milliliters of other toluene was added to each bottle. The bottle was stirred vigorously. The pigment was isolated by centrifugation at 3 5 00 rpm for 20 minutes. The supernatant was discarded, and about 70 ml of toluene was added to each vial to wash the pigment twice, vigorously stirred to disperse the pigment, and centrifuged at 3 500 rpm for 20 minutes. The pigment was air dried and then dried under vacuum at 65 °C overnight. Thermogravimetric analysis (TGA) was carried out and a polymer concentration of between 6.7% and 9.7% by weight was produced. Zeta potential measurements were performed on samples of Isopar E dispersed with a surfactant (Solsperse 17K) using Colloidal Dynamics ZetaProbe. The zeta potential number is shown in Fig. 5. From the data in Fig. 5, the degree of zeta potential increases as the TFEM in the polymer shell increases. Example 2: Preparation of display using electrophoretic particles of the present invention The coated polymer titanium white particles prepared in the above Example 1 were converted into an electrophoretic display in the following manner. Part A: Preparation of the capsules The pigments prepared in Example 1 and the following procedure were used to prepare gelatin-Arabic

S -18- 201107430 Adhesive microcapsules. The following ingredients were combined in a 25 ml plastic bottle to prepare a 55% internal BK-444 main black pigment (see application number No. 61/150,827, filed on February 9, 2009) / Isopar E 25.88 grams of 60 military halo ° / 〇 white pigment / Isopar E 106.77 grams of 13 military halo ° /. Polyisobutylene/Isopar E 7.73 g 10 wt ° / 〇 Solsperse 17K / Isopar E 23.49 g Isopar E 10.12 g and then substantially converted into gelatin gum arabic as described in the above-mentioned U.S. Patent No. 6,822,782, 27-29 Micropart B: Preparation of the display The microcapsules prepared in the above section A were allowed to stand and the excess water was poured to mix the capsules in a weight ratio of 8 parts to 1 part of the adhesive to form a slurry. The target coating thickness of the slurry was applied to the coated indium tin oxide (I TO) polymeric film using a 4 mil (101 micron) gap and dried in a 60 ° C conveyor oven for approximately 2 minutes, and the resulting pellets were obtained. The release sheet is separately coated with a 25 micron layer custom polyurethane laminate adhesive (doped with 180 tetrabutylammonium hexafluorophosphate) as in U.S. Patent No. 7,0 1 2, 7 3 5 , and cut into The microcapsule/polymer membrane is slightly smaller. The two sheets were laminated by a hot roll laminator layer set to 120 ° C by means of upper and lower rolls, and the resulting combined film was cut into a desired size. Remove release, instance. Then, the mixture is applied to the smear at a size of 18 microliters, and the size of the tablet is cut into the number of ppm, and -19-.201107430 is again layered by using a laminator at a temperature of 93 ° C. A 2 吋 (51 mm) square polymer film with a graphite layer. A single-pixel display was cut from the resulting laminate, an electrical connection was applied, and the experimental single-pixel display thus fabricated was adjusted to 5 Torr at a relative humidity of 50%. Example 3: Electro-optic test Electro-optical measurements were made on a single-pixel display prepared in Example 2 using a PR-650 SpectraScan Colorimeter. In these tests, the display was repeatedly driven to its black and white extreme optical state using a 250 volt 15 volt pulse and then driven to its black or white extreme optical state. About 3 seconds after the final drive pulse (to eliminate specific transient effects), then 2 minutes after the final drive pulse, measure the reflectance of the optical state, and compare the two measurements to detect any image instability (ie lack of image) Bistability). The results are shown in Fig. 6 (where "DS" refers to the dark state and "WS" refers to the white state - due to the image instability of the white state, the reflectance is low, and the white image is unstable and negative), which is known to follow the TFEM. The content in the polymer shell exceeds 1 mol%, and the image instability is significantly increased. At TFEM of 0.1 to 1 mol%, the image instability is equal to or slightly better than the control. Figure 7 (where "DR" refers to the dynamic range) shows the maximum white state, the minimum dark state, and the full dynamic range of each display after considering the image instability shown in Figure 6. An improvement trend in the control of the optical state is seen as the TFEM content increases, but does not include 10 mol%. The reduction in optical state improvement at higher TFEM levels can be attributed to the reduced image stability shown in Figure 6. It can be seen from Figures 6 and 7 that the addition of TFEM to the polymer shell improves the optical state, especially the final dynamic range, and has a TFEM window that provides improved optical state without image bistability loss, which is a major advantage of electrophoretic displays. .

S -20- 201107430 Other experiments have shown other fluorinated monomers (ie 2,2,3,4,4,4-hexafluorobutyl acrylate and acrylic acid 3,3,4,4,5,5,6,6 , 7,7,8,8,8-tridecafluorooctyl ester) Adjusts the zeta potential of the white pigment in a manner similar to TFEM, and provides the same optical state improvement. The exact mechanism by which these fluorinated monomers produce changes in zeta potential and optical state is currently unknown. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A and 1B are schematic cross-sectional views of a first electrophoretic display according to the present invention, wherein an electrophoretic medium contains monotype particles in a colored suspension fluid. Figures 2A and 2B are schematic cross-sectional views of a second electrophoretic display according to the present invention, substantially similar to Figures 1A and 1B, wherein the electrophoretic medium comprises two different types of particles (with opposite polarity charges) in the uncolored suspension fluid. 3A and 3B are schematic cross-sectional views of the third electrophoretic display according to the present invention, wherein the electrophoretic medium contains two different types (charges of the same polarity but electrophoretic mobility) in the uncolored suspension fluid. Different) particles. Figures 4A and 4B depict a polymer dispersed electrophoretic medium of the present invention, and a method for making the medium. Figure 5 is a bar graph showing the variation of the (zeta) potential with the proportion of fluorinated monomer in the polymer shell in the experiment reported in Example 1 above. Figure 6 is a graph showing the experiment reported in Example 3 above. Bar graph of dark state and white state instability as a function of the proportion of fluorinated monomer in the polymer shell. Figure 7 is a graph showing the maximum white state, minimum dark state and total dynamic range in the experiment reported in Example 3 above. A bar graph showing the variation in the proportion of fluorinated monomers in the polymer shell.

S -21 - 201107430 [Description of main components] 100 Electrophoretic display 102 Electrophoretic medium 104 Capsule 106 Suspension 1 08 Particle 110 Front electrode 112 Rear electrode 114 Substrate 200 Electrophoretic display 202 Electrophoretic medium 204 Capsule 206 Suspension 2 18 Particle 3 00 Electrophoresis Display 302 Electrophoretic Medium 304 Capsule 306 Liquid 320 Particle 4 10 Layer 4 1 0 5 Layer 4 12 Droplet 4 14 Liquid Medium 4 16 Substrate 4 18 Layer-22-

Claims (1)

.201107430 VII. Patent application scope · · ι_ an electrophoretic medium containing a plurality of pigment particles suspended in a fluid, the pigment particles having a polymer chemically bonding pigment particles, wherein 0.1 to 5 mol% of the polymer comprises a derivative Repeating unit of self-fluorinated acrylate or fluorinated methacrylate monomer. 2. The electrophoretic medium of claim 2, wherein 1 to 5 mol% of the monomers in the polymer comprise fluorinated monomers. The electrophoretic medium according to claim 1, wherein the particles have a polymer of 4 to 15% by weight of the chemically bonded pigment particles. 4. The electrophoretic medium according to claim 3, wherein the particles have a polymer of 8 to 12% by weight of the chemically bonded pigment particles. 5. The electrophoretic medium according to claim 1, wherein the polymer comprises a main chain and a plurality of side chains extending from the autonomous chain, each side chain comprising at least 4 carbon atoms. 6. The electrophoretic medium of claim 1, wherein the polymer further comprises a residue derived from a non-fluorinated acrylate and/or methacrylate monomer. 7. The electrophoretic medium of claim 1, wherein the unfluorinated methacrylate monomer comprises lauryl methacrylate. 8. The electrophoretic medium according to claim 2, wherein the fluorinated monomer comprises 2,2,2-trifluoroethyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate and acrylic acid At least one of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl ester. 9. The electrophoretic medium of claim 1, which has two types of at least one particle having different optical characteristics and different electrophoretic mobility. S -23-201107430 i. The electrophoretic medium of claim 9, wherein the two types of particles have opposite polarity charges. An electrophoretic medium according to claim 1, wherein the pigment particles and the flow system are encapsulated in a plurality of capsules or micelles. 12. The electrophoretic medium of claim U, wherein the capsule is held within the polymeric binder. 13. The electrophoretic medium of claim 1, wherein the pigment particles and the flow system are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material. 14. The electrophoretic medium of claim 1, wherein the fluid is in a gaseous state. 15. An electrophoretic display' comprising an electrophoretic medium as in claim 1 of the patent application and at least one electrode arranged to apply an electric field to the electrophoretic medium. 16. An e-book reader, portable computer, desktop computer, mobile phone, smart card, logo, watch, shelf label, or flash drive' Display II of Article 15 of the patent scope. -twenty four-