Electrophoretic particles containing organic pigments and graphene oxide

Abstract

The electrophoretic medium comprises a plurality of first-type charged particles in a nonpolar liquid. Each of the plurality of first-type charged particles has a core and a shell. The core comprises an organic pigment and a graphene oxide layer. The shell comprises an organosilane layer and a polymer layer. The electrophoretic medium may be incorporated into a color electrophoresis device to improve its electro-optical performance. The present invention relates to an electrophoretic medium for electro-optical displays, comprising a nonpolar liquid and charged particles. Each particle has a core and a shell, the core comprises an organic pigment and graphene oxide, and the shell comprises an organosilane layer and a polymer layer.

Description

Technical Field

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 579,431, filed Aug. 29, 2023, which is hereby incorporated by reference in its entirety, together with all other patents and patent applications disclosed herein.

[0002] Field of the Invention The present invention relates to an electrophoretic medium for electro-optical displays, the electrophoretic medium including a nonpolar liquid and charged particles. Each particle has a core and a shell, the core including an organic pigment and graphene oxide, and the shell including an organosilane layer and a polymer layer.

Background Art

[0003] Background of the Invention The term “electro-optical” as applied to a material or display is used herein in its conventional sense in imaging technology to refer to a material having first and second display states with at least one different optical property, the material changing from its first display state to its second display state by the application of an electric field to the material. The optical property is typically a color perceptible to the human eye, but may also be another optical property such as a pseudo-color in the sense of a change in reflectivity of an electromagnetic wavelength outside the visible range for a display intended for light transmission, reflectivity, luminescence, or machine-readable purposes.

[0004] Some electro-optical materials are solid in the sense that the material has a solid outer surface, but the material may and often does have an internal liquid or gas-filled space. Displays using such solid electro-optical materials may hereinafter be referred to for convenience as “solid electro-optical displays.” Thus, the term “solid electro-optical display” includes rotatory dichroic member displays, encapsulated electrophoretic displays, microcell electrophoretic displays, and encapsulated liquid crystal displays.

[0005] The terms “bistable” and “bistable” are used herein in their conventional sense to refer to a display including a display element having a first and second display state having at least one different optical property, wherein any given element is driven by a finite-duration address pulse to take either its first or second display state, and then, upon termination of the address pulse, the state persists for at least several times, e.g., at least four times, the minimum duration of the address pulse required to change the state of the display element. U.S. Patent No. 7,170,670 shows that several particle-based electrophoretic displays capable of grayscale are stable not only in their extreme black and white states but also in their intermediate gray state, and the same is true for several other types of electro-optic displays. While these types of displays are properly called “multistable” rather than bistable, the term “bistable” may be used herein for convenience to encompass both bistable and multistable displays.

[0006] One type of electro-optical display that has been the subject of intensive research and development for many years is the particle-based electrophoretic display, in which multiple charged particles move through a fluid under the influence of an electric field. Compared to liquid crystal displays, electrophoretic displays may have characteristics such as good brightness and contrast, a wide viewing angle, state bistability, and low power consumption. Nevertheless, problems with the long-term image quality of these displays have hindered their widespread adoption. For example, the particles that make up electrophoretic displays tend to settle, resulting in insufficient lifespan for these displays.

[0007] As mentioned above, electrophoretic media require the presence of a fluid. In most conventional electrophoretic media, this fluid is a liquid, but electrophoretic media may also be produced using a gaseous fluid. (See, for example, Kitamura, T., et al., "Electrical toner movement for electronic paper-like display", IDW Japan, 2001, Paper HCS1-1 and Yamaguchi, Y., et al., "Toner display using insulative particles charged triboelectrically", IDW Japan, 2001, Paper AMD4-4). See also U.S. Patents 7,321,459 and 7,236,291. Such gaseous electrophoretic media are susceptible to the same types of particle sedimentation problems as liquid-based electrophoretic media when used in orientations that allow such sedimentation, for example, in signs where the media is positioned vertically. In fact, particle sedimentation appears to be a more serious problem with gas-based electrophoretic media than with liquid-based electrophoretic media, because the lower the viscosity of the gaseous suspension compared to the liquid suspension, the faster the electrophoretic particles can sediment.

[0008] Numerous patents and applications, assigned to or filed in the names of the Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC, and their affiliates, describe various techniques used in encapsulation and microcell electrophoresis media and other electro-optical media. Encapsulated electrophoresis media contain numerous small capsules, each containing an inner phase that itself contains particles movable by electrophoresis in a fluid medium, and a capsule wall surrounding the inner phase. Typically, the capsules are held within a polymer binder to form a coherent layer positioned between two electrodes. In microcell electrophoresis displays, charged particles and fluids are not encapsulated within microcapsules, but instead held within a carrier medium, typically multiple cavities formed within a polymer film. The techniques described in these patents and applications include: (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 6,822,782; 7,002,728; 7,679,814; 8,018,640; 8,199,395; 9,372,380; 10,825,586; and 11,099,452; and U.S. Patent Application Publication Nos. 2018 / 0210312; and 2021 / 0247658. (b) Capsules, binders, and encapsulation processes; see, for example, U.S. Patent No. 6,922,276 and No. 7,411,719. (c) Microcell structures, wall materials, and methods for forming microcells; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906. (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088. (e) Films and subassemblies containing electro-optical materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564. (f) Backplanes, adhesive layers, and other auxiliary layers and methods used in displays; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624. (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564. (h) Methods for driving a display; see, for example, U.S. Patent Nos. 7,012,600 and 7,453,445. (i) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348. (j) Non-electrophoretic displays as described in U.S. Patent Nos. 6,241,921 and 2015 / 0277160; as well as applications of encapsulation and microcell technologies other than displays; see, for example, U.S. Patent Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0009] Many of the aforementioned patents and applications recognize that the walls surrounding individual microcapsules in an encapsulated electrophoretic medium may be replaced by a continuous phase, thereby producing a so-called polymer-dispersed electrophoretic display in which the electrophoretic medium comprises multiple individual droplets of electrophoretic fluid and a continuous phase of polymer material, and that individual droplets of electrophoretic fluid within such a polymer-dispersed electrophoretic display may be considered capsules or microcapsules even if each individual droplet is not associated with an individual capsule membrane. See, for example, U.S. Patent No. 6,866,760. Therefore, for the purposes of this application, such polymer-dispersed electrophoretic media can be considered a variant of encapsulated electrophoretic media.

[0010] Electrophoretic media are often opaque (for example, many electrophoretic media operate in reflective mode because the particles substantially block the transmission of visible light through the display), but many electrophoretic displays can operate in a so-called "shutter mode," where one display state is substantially opaque and the other is light-transmitting. See, for example, U.S. Patents 5,872,552, 6,130,774, 6,144,361, 6,172,798, 6,271,823, 6,225,971, and 6,184,856. Dielectric displays, which are similar to electrophoretic displays but depend on changes in electric field strength, can operate in a similar mode. See U.S. Patent 4,418,346. Other types of electro-optic displays may also be able to operate in shutter mode. Electro-optic media operating in shutter mode may be useful for multilayer structures for full-color displays. In such a structure, at least one layer adjacent to the observation surface of the display operates in shutter mode to expose or conceal a second layer further away from the observation surface. Encapsulated electrophoretic displays typically do not suffer from the clustering and sedimentation failure modes of conventional electrophoretic devices and offer further advantages such as the ability to print or coat displays on a wide variety of flexible and rigid substrates. (The use of the term "printing" is intended to include, but is not limited to, all forms of printing and coating, including pre-metering coating, e.g., patch die coating, slot or extrusion coating, slide or cascade coating, curtain coating, roll coating, e.g., knife-over roll coating, forward and reverse roll coating, gravure coating, immersion coating, spray coating, meniscus coating, spin coating, brush coating, air knife coating, silkscreen printing processes, electrostatic printing processes, thermal printing processes, inkjet printing processes, electrophoretic deposition (see U.S. Patent No. 7,339,715), and other similar techniques.) Thus, the resulting displays may be flexible. Furthermore, because the display medium can be printed (using various methods), the displays themselves can be manufactured inexpensively. Image quality in electrophoretic devices containing electrophoretic media with charged pigment particles in a nonpolar liquid can be reduced, especially if the charged particles contain organic pigments, due to the possibility of aggregation of the charged particles in the electrophoretic media. This aggregation can occur between charged particles of the same color or between charged pigment particles of different types, i.e., between charged particles of different colors. For example, an electrophoretic medium may contain charged particles containing pigments of four different colors, such as blue, red, yellow, and white. In such an electrophoretic medium, aggregation between blue-red and blue-yellow particles prevents complete separation between electrophoretic particles during device operation, reducing the saturation of the device's color state. If the blue pigment used is an inorganic pigment, aggregation between organic pigment particles may be somewhat mitigated. However, blue inorganic pigments do not provide images with saturated color. Therefore, the charged particles used in the electrophoretic medium need to be improved. The inventors of the present invention have surprisingly found that when using charged particles having a core and a shell, wherein the charged particles comprise (1) a core containing an organic pigment and a graphene oxide layer, and (2) a shell containing an organosilane layer and a polymer layer, the color saturation of the color state that can be achieved by the device is significantly improved. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] U.S. Patent No. 7,170,670 [Patent Document 2] U.S. Patent No. 7,321,459 [Patent Document 3] U.S. Patent No. 7,236,291 [Patent Document 4] U.S. Patent No. 6,822,782 [Patent Document 5] U.S. Patent No. 7,002,728 [Patent Document 6] U.S. Patent No. 7,679,814 [Patent Document 7] U.S. Patent No. 8,018,640 [Patent Document 8] U.S. Patent No. 8,199,395 [Patent Document 9] U.S. Patent No. 9,372,380 [Patent Document 10] U.S. Patent No. 10,825,586 [Patent Document 21] U.S. Patent No. 11,099,452 [Patent Document 22] U.S. Patent Application Publication No. 2018 / 0210312 [Patent Document 23] U.S. Patent Application Publication No. 2021 / 0247658 [Patent Document 24] U.S. Patent No. 6,922,276 [Patent Document 25] U.S. Patent No. 7,411,719 [Patent Document 26] U.S. Patent No. 7,072,095 [Patent Document 27] U.S. Patent No. 9,279,906 [Patent Document 28] U.S. Patent No. 7,144,942 [Patent Document 29] U.S. Patent No. 7,715,088 [Patent Document 30] U.S. Patent No. 6,982,178 [Patent Document 31] U.S. Patent No. 7,839,564 [Patent Document 32] U.S. Patent No. 7,116,318 [Patent Document 33] U.S. Patent No. 7,535,624 [Patent Document 34] U.S. Patent No. 7,075,502 [Patent Document 35] U.S. Patent No. 7,012,600 [Patent Document 36] U.S. Patent No. 7,453,445 [Patent Document 37] U.S. Patent No. 7,312,784 [Patent Document 38] U.S. Patent No. 8,009,348 [Patent Document 39] U.S. Patent No. 6,241,921 [Patent Document 40] U.S. Patent Application Publication No. 2015 / 0277160 [Patent Document 41] U.S. Patent Application Publication No. 2015 / 0005720 [Patent Document 42] U.S. Patent Application Publication No. 2016 / 0012710 [Patent Document 43] U.S. Patent No. 5,872,552 [Patent Document 44] U.S. Patent No. 6,130,774 [Patent Document 45] U.S. Patent No. 6,144,361 [Patent Document 46] U.S. Patent No. 6,172,798 [Patent Document 47] U.S. Patent No. 6,271,823 [Patent Document 48] U.S. Patent No. 6,225,971 [Patent Document 49] U.S. Patent No. 6,184,856 [Patent Document 50] U.S. Patent No. 4,418,346 [Non-patent literature]

[0012] [Non-Patent Document 1] Kitamura, T., et al., "Electrical toner movement for electronic paper-like display", IDW Japan, 2001, Paper HCS1-1 [Non-Patent Document 2] Yamaguchi, Y., et al., "Toner display using insulative particles charged triboelectrically", IDW Japan, 2001, Paper AMD4-4 [Overview of the Initiative] [Means for solving the problem]

[0013] Summary of the Invention According to one aspect of the present invention, the electrophoretic medium comprises a plurality of first type charged particles and a nonpolar liquid. Each of the plurality of first type charged particles has a core and a shell. The core comprises a first type organic pigment having a surface and a graphene oxide layer comprising graphene oxide. The graphene oxide in the graphene oxide layer is in contact with the surface of the first type organic pigment. The shell comprises an organosilane layer comprising organosilane and a polymer layer comprising a polymer. The organosilane in the organosilane layer is covalently bonded to the polymer in the polymer layer.

[0014] The core of the first type of charged particle may include a metal oxide layer containing a metal oxide. The metal oxide layer is located between the graphene oxide layer of the core and the organosilane layer of the shell. The metal oxide layer may contain aluminum oxide, silica, titanium dioxide, zirconium oxide, zinc oxide, or a mixture thereof.

[0015] The metal oxide layer of the first type of charged particles may be formed on the graphene oxide core by a reaction between a metal oxide precursor and a reagent. The reagent reacts with the metal oxide precursor to form the metal oxide. The metal oxide precursors include trimethylaluminum, triethylaluminum, dimethylaluminum chloride, diethylaluminum chloride, trimethoxyaluminum, triethoxyaluminum, dimethylaluminum propoxide, aluminum triisopropoxide, tributoxyaluminum, tris(dimethylamino)aluminum, tris(diethylamino)aluminum, tris(propylamino)aluminum, aluminum trichloride, trichlorosilane, hexachlorodisilane, silicon tetrachloride, tetramethoxysilane, tetraethoxysilane, tris(tert-pentoxy)silanol, tetraisocyanatesilane, and tetrachlorosilane (silicon The organosilane layer may be selected from the group consisting of tertrachoride, tris(methylamino)silane, tris(ethylamino)silane, titanium tetrachloride, titanium tetraiodide, tetramethoxytitanium, tetraethoxytitanium, titanium isopropoxide, tetrakis(methylamino)titanium, tetrakis(ethylamino)titanium, dimethylzinc, diethylzinc, methylzinc isopropoxide, zirconium tetrachloride, zirconium tetraiodide, tetramethoxyzirconium, tetraethoxyzirconium, tetraisopropoxyzirconium, tetrabutoxyzirconium, tetrakis(methylamino)zirconium, tetrakis(ethylamino)zirconium, and mixtures thereof. The reagent may be selected from the group consisting of water, oxygen, ozone, ammonia, and mixtures thereof. The organosilane layer is covalently bonded to the metal oxide layer.

[0016] The organosilane layer may be formed from an organosilane reagent. The organosilane reagent may contain a first functional group. If the first type of charged particle contains a metal oxide, the first functional group of the organosilane reagent can react with the metal oxide in the metal oxide layer to form a covalent bond between the organosilane in the organosilane layer and the metal oxide in the metal oxide layer of the first type of charged particle. The first functional group of the organosilane reagent may be selected from the group consisting of alkoxy, alkylamino, halide, hydrogen, and hydroxy. The molecular structure of the organosilane reagent may contain one or more alkoxy, alkylamino, halide, hydrogen, or hydroxyl functional groups. The molecular structure of the organosilane reagent may contain one, two, or three alkoxy functional groups. The molecular structure of the organosilane reagent may contain one, two, or three halide functional groups. The molecular structure of the organosilane reagent may contain one, two, or three hydroxyl functional groups.

[0017] The polymer in the polymer layer may be formed from macromonomers or from polymerization of monomers. The polymer in the polymer layer may be covalently bonded to the organosilane in the organosilane layer. The organosilane reagent may contain a second functional group. The macromonomer or monomer may contain a third functional group. The second functional group of the organosilane reagent can react with the third functional group of the macromonomer or monomer to form a covalent bond between the organosilane in the organosilane layer and the polymer in the polymer layer of the first type of charged particles. The second functional group of the organosilane reagent may be selected from the group consisting of epoxy, vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, amino, hydroxy, carboxy, alkoxy groups, and chlorides. The third functional group of the monomer or macromonomer may be selected from the group consisting of vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, epoxy, amino, hydroxy, carboxy, and chloride. The second functional group of the organosilane may be vinyl, and the third functional group of the macromonomer or monomer may be vinylbenzyl.

[0018] The electrophoretic medium may contain, in addition to, a plurality of first type charged particles, a plurality of second type charged particles, a plurality of third type charged particles, and a plurality of fourth type charged particles. Each of the plurality of second type charged particles may contain a second type organic pigment. Each of the plurality of third type charged particles may contain a third type organic pigment. Each of the plurality of fourth type charged particles may contain an inorganic pigment.

[0019] The organic pigment of the first type of charged particles may be selected from the group consisting of azo pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, isoindoline pigments, anthranone pigments, indanthron pigments, carbon black pigments, rhodamine pigments, benzamine pigments, carbon black pigments, and mixtures thereof. The organic pigments of the first type of charged particles, the second type of charged particles, and the third type of charged particles may be independently CI pigment blue 15, 15:1, 15:2, 15:3, 15:4 15:6, 60, and 79; Pigment Red 2, 4, 5, 9, 12, 14, 38, 48:2, 48:3, 48:4, 52:2, 53:1, 57:1, 81, 112, 122, 144, 146, 147, 149, 168, 170, 176, 177, 179, 184, 185, 187, 188, 208, 209, 210, 214, 242, 254, 255, 257, 262, 264, 282, and 285; CI Pigment Violet 1, 19, 23, and 32; CI Pigment Yellow 1, 3, 12, 13, 14, 15, 16, 17, 7 3, 74, 81, 83, 97, 109, 110, 111, 120, 126, 127, 137, 138, 139, 150, 151, 154, 155, 174, 175, 176, 180, 181, 184, 191, 194, 213 and 214; CI Pigment Green 7 and 36; CI Pigment Black 1 and 7; CI Pigment Brown 25, 32, 41; Pigment Orange 5, 13, 34, 36, 38, 43, 61, 62, 64, 68, 67, 72, 73 and 74, and mixtures thereof may be selected from the group.

[0020] According to another aspect of the present invention, the electrophoretic device includes a first light-transmitting electrode layer, an electro-optic material layer containing an electrophoretic medium, and a second electrode layer. The electrophoretic medium includes a plurality of first-type charged particles and a non-polar liquid. Each of the plurality of first-type charged particles has a core and a shell. The core includes a first-type organic pigment having a surface and a graphene oxide layer containing graphene oxide. The graphene oxide in the graphene oxide layer is in contact with the surface of the first-type organic pigment. The shell includes an organosilane layer containing organosilane and a polymer layer containing a polymer. The organosilane in the organosilane layer may be covalently bonded to the polymer in the polymer layer. Alternatively, the core of the first-type charged particle may include a metal oxide layer containing a metal oxide. The metal oxide layer may be placed between the graphene oxide layer and the organosilane layer. The organosilane in the organosilane layer of the shell may be covalently bonded to the metal oxide in the metal oxide layer. The metal oxide layer may contain aluminum oxide, silica, titanium dioxide, zirconium oxide, zinc oxide, or a mixture thereof. The polymer in the polymer layer may be formed from macromonomers or from polymerization of monomers. The polymer in the polymer layer may be covalently bonded to the organosilane in the organosilane layer. The organosilane reagent may contain a second functional group. The macromonomer or monomer may contain a third functional group. The second functional group of the organosilane reagent can react with the third functional group of the macromonomer or monomer to form a covalent bond between the organosilane in the organosilane layer and the polymer in the polymer layer of the first type of charged particles. The second functional group of the organosilane reagent may be selected from the group consisting of epoxy, vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, amino, hydroxy, carboxy, alkoxy groups, and chlorides. The third functional group of the monomer or macromonomer may be selected from the group consisting of vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, epoxy, amino, hydroxy, carboxy, and chloride.The second functional group of the organosilane may be vinyl, and the third functional group of the macromonomer or monomer may be vinylbenzyl. The electrophoretic medium may contain, in addition to, a plurality of first type charged particles, a plurality of second type charged particles, a plurality of third type charged particles, and a plurality of fourth type charged particles. Each of the plurality of second type charged particles may contain a second type organic pigment. Each of the plurality of third type charged particles may contain a third type organic pigment. Each of the plurality of fourth type charged particles may contain an inorganic pigment.

[0021] According to another aspect of the present invention, the electrophoretic assembly comprises, in order, a first light-transmitting electrode layer, an electro-optic material layer containing an encapsulated electrophoretic medium, an adhesive layer, and a release sheet. The electrophoretic medium comprises a non-polar liquid and a plurality of first-type charged particles, the first-type charged particles having the structure described above.

[0022] According to another aspect of the present invention, an electrophoresis assembly comprising, in order, a first release sheet, a first adhesive layer, an electro-optic material layer containing an encapsulated electrophoretic medium, an adhesive layer, a second adhesive layer, and a second release sheet. The electrophoretic medium comprises a non-polar liquid and a plurality of first type charged particles, the first type charged particles having the structure described above.

[0023] According to yet another aspect of the present invention, a method for producing an electrophoretic medium. The electrophoretic medium comprises a nonpolar liquid and a plurality of first-kind charged particles having a core and a shell. A manufacturing method comprising the following steps: (a) preparing graphene oxide; (b) dispersing graphene oxide in a polar organic solvent to prepare a graphene oxide dispersion; (c) adding an organic pigment to the graphene oxide dispersion to prepare an organic pigment-graphene oxide dispersion; (d) mixing the organic pigment-graphene oxide dispersion to prepare an organic pigment-graphene oxide complex in a polar organic solvent; (e) adding a metal oxide precursor and a reagent to the organic pigment-graphene oxide complex in a polar organic solvent to prepare a dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer, wherein the metal oxide layer contains a metal oxide; (f) adding an organosilane reagent to the dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer to prepare a dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer, wherein the organosilane layer contains organosilane and the organosilane is covalently bonded to the metal oxide. (g) separating particles containing an organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer from a polar organic solvent; (h) washing the particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer with a solvent; (i) transferring the washed particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer to a nonpolar liquid to prepare a dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer in a nonpolar liquid; (j) adding a monomer or macromonomer to the dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer in a nonpolar liquid; and (k) polymerizing the monomer or reacting the organosilane of the organosilane layer of the particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer with a macromonomer to prepare a dispersion of a first type of charged particles in a nonpolar liquid.Each of the first type of charged particles comprises an organic pigment-graphene oxide composite having a metal oxide layer, an organosilane layer, and a polymer layer, wherein the polymer layer contains a polymer, and the polymer is covalently bonded to the organosilane in the organosilane layer. The process may also include (k) adding a charge control agent to a dispersion containing the third type of charged particles in a nonpolar liquid.

[0024] Various aspects and embodiments of this application will be described with reference to the following figures. Please note that the figures are not necessarily drawn to scale. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a side cross-sectional view of an example of a first type of charged particle of the electrophoretic medium of the present invention, the charged particle having a core and a shell.

[0026] [Figure 2] Figure 2 is a top cross-sectional view of an example of a first type of charged particle of the electrophoretic medium of the present invention, the charged particle having a core and a shell.

[0027] [Figure 3] Figure 3 is a side cross-sectional view of an example of a first type of charged particle of the electrophoretic medium of the present invention, the charged particle having a core and a shell, the core comprising a metal oxide layer.

[0028] [Figure 4] Figure 4 is a top cross-sectional view of an example of a first type of charged particle of the electrophoretic medium of the present invention, the charged particle having a core and a shell, the core containing a metal oxide layer.

[0029] [Figure 5] Figure 5 shows the reaction scheme for the formation of the organic pigment-graphene oxide complex.

[0030] [Figure 6]Figure 6 shows the reaction scheme for the formation of an organic pigment-graphene oxide composite having a metal oxide layer.

[0031] [Figure 7] Figure 7 shows the reaction scheme for the formation of an organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer.

[0032] [Figure 8] Figure 8 shows the reaction scheme for the formation of electrophoretic particles from an organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer.

[0033] [Figure 9] Figure 9 shows the reaction scheme for the preparation of a first type of charged particle comprising an organic pigment, a graphene oxide layer, a silica layer, an organosilane layer, and a polymer layer containing polylauryl methacrylate.

[0034] [Figure 10A] Figure 10A shows a side cross-section of an example of an electrophoretic device including an electro-optic material layer containing an electrophoretic medium in a microcapsule.

[0035] [Figure 10B] Figure 10B shows a side cross-section of an example of an electrophoretic device including an electro-optic material layer containing an electrophoretic medium in a microcell.

[0036] [Figure 11] Figure 11 shows a side cross-section of an example of a front laminate including a first light-transmitting layer, an electro-optic material layer containing an encapsulated electrophoretic medium, an adhesive layer, and a release sheet.

[0037] [Figure 12] Figure 12 shows a side cross-section of an example of a double release sheet, which includes a first release sheet, a first adhesive layer, an electro-optic material layer containing an encapsulated electrophoretic medium, a second adhesive layer, and a second release sheet.

[0038] [Figure 13] Figure 13 shows graphs of reflectance versus wavelength for copper phthalocyanine pigment in the visible spectrum, and graphs of reflectance versus wavelength for inorganic ultramarine blue pigment in the visible spectrum. [Modes for carrying out the invention]

[0039] Detailed description of the invention The present invention provides an electrophoretic medium comprising a nonpolar liquid and a plurality of first type charged particles. Each of the plurality of first type charged particles has a core and a shell. The core of the first type charged particle comprises a first type organic pigment having a surface and a graphene oxide layer comprising graphene oxide. The graphene oxide layer is in contact with the surface of the first type organic pigment. The shell comprises an organosilane layer comprising organosilane and a polymer layer comprising polymer. The organosilane in the organosilane layer of the shell is bonded to the polymer in the polymer layer. The organosilane in the organosilane layer of the shell may be covalently bonded to the polymer in the polymer layer. The organosilane in the organosilane layer of the shell may be bonded to the polymer in the polymer layer via electrostatic bonding. The polymer layer is located on the outer surface of the shell of the first type charged particle and contributes to the dispersion stability of the first type charged particle in the electrophoretic medium.

[0040] The core of the first type of charged particle may further include a metal oxide layer positioned between the graphene oxide layer and the organosilane layer. The organosilane in the organosilane layer may be covalently bonded to the metal oxide in the metal oxide layer.

[0041] Figure 1 shows a cross-sectional side view of an example of a first type of charged particle of the electrophoretic medium of the present invention. The first type of charged particle 100 comprises a first type of organic pigment 101, a graphene oxide layer L1 containing graphene oxide 102, an organosilane layer L2 containing organosilane 103, and a polymer layer L3 containing polymer 104.

[0042] Figure 2 is a top cross-sectional view of an example of a first type of charged particle of the electrophoretic medium of the present invention. The first type of charged particle 100 comprises a first type of organic pigment 101, a graphene oxide layer L1 containing graphene oxide 102, an organosilane layer L2 containing organosilane 103, and a polymer layer L3 containing polymer 104. The thicknesses of the various layers of the first type of charged particle 100 are not depicted at the same scale. The thicknesses of the various layers may differ from each other. In fact, the thickness of the layers of one charged particle may differ from the thickness of the same type of layer of another particle.

[0043] Figure 3 shows a side cross-section of an example of a first type of charged particle of the electrophoretic medium of the present invention, the core of the first type of charged particle further comprising a metal oxide layer. The first type of charged particle 200 comprises a first type of organic pigment 101, a graphene oxide layer L1 containing graphene oxide 102, a metal oxide layer L4 containing metal oxide 105, an organosilane layer L2 containing organosilane 103, and a polymer layer L3 containing polymer 104.

[0044] Figure 4 is a top cross-sectional view of an example of a first type of charged particle of the electrophoretic medium of the present invention. The first type of charged particle 100 comprises a first type of organic pigment 101, a graphene oxide layer L1 containing graphene oxide 102, a metal oxide layer L4 containing metal oxide 105, an organosilane layer L2 containing organosilane 103, and a polymer layer L3 containing polymer 104. The thicknesses of the various layers of the first type of charged particle 200 are not depicted at the same scale. The thicknesses of the various layers may differ from each other. In fact, the thickness of the layers of one charged particle may differ from the thickness of the same type of layer of another particle.

[0045] The first type of charged particles of the present invention may be manufactured using a multi-step process. Examples of such processes are summarized in Figures 5-8. The first type of charged particles 200 manufactured by the processes of Figures 5-8 include layers L1-L5.

[0046] The process involves treating a first type of organic pigment with graphene oxide. This step is shown in Figure 5. The graphene oxide particles are first dispersed in a polar organic solvent such as ethanol. Dispersion can be achieved by grinding the graphene oxide particles in the solvent using standard dispersion equipment such as a media mill, sonicator, or other instruments. Then, particles of the organic pigment 101 are slowly added to the graphene oxide dispersion under stirring conditions, and the dispersion is heated at a high temperature (e.g., 50°C) with stirring to prepare particles 112 containing organic pigment-graphene oxide complexes in a polar organic solvent. Each pigment-graphene oxide complex particle 112 contains the first type of organic pigment 101 and a graphene oxide layer L1, where the graphene oxide layer L1 contains graphene oxide 102. The graphene oxide layer L1 is in contact with the surface of the first type of organic pigment 101. The first type of organic pigment can be added to the graphene oxide dispersion as a dispersion prepared by grinding the organic pigment in a polar organic solvent using standard dispersion equipment such as a media mill, sonicator, or other instruments. The polar organic solvent used for dispersing the organic pigment may be the same as or different from the polar organic solvent used for the graphene oxide dispersion. Non-limiting examples of polar organic solvents used for preparing the organic pigment dispersion and the graphene oxide dispersion are methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dimethylformamide, ethyl ether, dimethyl sulfoxide, methanol, ethanol, isopropanol, and other solvents. The weight ratio of graphene oxide to organic pigment used for preparing particle 112 may be 0.01-0.2, 0.015-0.15, 0.02-0.10, 0.022-0.9, or 0.025-0.8. The weight ratio of graphene oxide to organic pigment used for preparing particle 112 may be higher than 0.001, or higher than 0.01, or higher than 0.02, or higher than 0.03, or higher than 0.05, or higher than 0.07. The weight ratio of graphene oxide to the organic pigment used in the preparation of particles 112 may be less than 0.15, less than 0.1, or less than 0.7.The first type of organic pigment 101 is shown as a single particle in Figures 1-8, but aggregates of organic pigment particles may be present in the core.

[0047] The next steps in the production of the first type of charged pigment particles 200 are summarized in Figure 6. This involves treating the organic pigment-graphene oxide complex 112 with a metal oxide precursor to form a metal oxide layer L4 containing metal oxide 105. In this step, the organic pigment-graphene oxide complex 112 is treated with a metal oxide precursor and a reagent to form a metal oxide layer L4 containing metal oxide 105. This is achieved by starting with a dispersion of the organic pigment-graphene oxide complex in a polar organic solvent, adding the metal oxide precursor under mixed conditions, and then adding the reagent to the dispersion to form the metal oxide 105 on the surface of the organic pigment-graphene oxide complex particles 112. That is, the reagent reacts with the metal oxide precursor to form a metal oxide, which precipitates on the surface of the organic pigment-graphene oxide complex particles 112 to form a dispersion of particles 113 containing the organic pigment-graphene oxide complex having a metal oxide layer (L4). The weight ratio of the metal oxide in the metal oxide layer to the organic pigment in the particle 113 may be 0.1 to 1, 0.2 to 0.9, 0.3 to 0.8, or 0.4 to 0.7. The weight ratio of the metal oxide in the metal oxide layer to the organic pigment in the particle 113 may be higher than 0.05, higher than 0.07, higher than 0.1, higher than 0.15, higher than 0.30, or higher than 0.5. The weight ratio of the metal oxide in the metal oxide layer to the organic pigment in the particle 113 may be lower than 0.5, lower than 0.4, lower than 0.3, or lower than 0.2.

[0048] The next steps for producing the first type of charged pigment particles are summarized in Figure 7. This involves treating particles 113 of an organic pigment-graphene oxide complex having a metal oxide layer with an organosilane reagent 314 to form particles 114 containing an organic pigment-graphene oxide complex having a metal oxide layer (L3) and an organosilane layer (L2). The organosilane reagent 314 has a first functional group F1 and a second functional group F2. As shown in Figure 7, the first functional group F1 of the organosilane reagent 314 reacts with the metal oxide in the metal oxide layer of the particle 113. The organosilane reagent 314 may have multiple functional groups that react with the metal oxide. That is, the organosilane reagent may have two or more functional groups (the same as or different from F1) that react with the metal oxide. The weight ratio of organosilane in the organosilane layer to the organic pigment in particle 114 may be 0.005 to 0.3, 0.01 to 0.2, or 0.015 to 0.18. The weight ratio of organosilane in the organosilane layer to the organic pigment in particle 114 may be higher than 0.005, higher than 0.01, higher than 0.012, higher than 0.015, or higher than 0.02. The weight ratio of organosilane in the organosilane layer to the organic pigment in particle 114 may be lower than 0.3, lower than 0.2, or lower than 0.1.

[0049] The next steps for the production of the first type of charged pigment particles 100 are summarized in Figure 8. First, the polar organic solvent in the dispersion formed in the previous step of the process is replaced with a non-polar liquid. This is achieved by first separating the particles (114) of the organic pigment-graphene oxide complex having a metal oxide layer with an organosilane reagent from the polar organic solvent by filtration, centrifugation, or other methods. The particles 114 are washed once or multiple times with the solvent. After each wash, the particles are separated from the solvent by filtration, centrifugation, or other methods. The washed and separated particles 114 are then transferred to a non-polar liquid to prepare a dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer in the non-polar liquid. The dispersion is treated with macromonomers or monomers M1-F3 to form the first type of charged particles 200. The polymer can be prepared in situ from the polymerization of monomers M1-F3 to form a polymer layer L3. The molecular structures of monomers M1-F3 include functional groups involved in the polymerization of monomers. This functional group may be the same as or different from the third functional group. In other words, the third functional group F3 of monomers M1-F3 may be a functional group used in the polymerization reaction of the monomer. Alternatively, the third functional group F3 may be involved in a reaction that forms a covalent bond between the polymer of the polymer layer and the organosilane of the organosilane layer via the reaction of functional group F3 with the second functional group F2. In another example, a polymer layer is formed using a prepolymerized macromonomer instead of a monomer. In this case, the molecular structure of the macromonomer may also include a third functional group F3 that reacts with the second functional group F2 of the organosilane reagent. Thus, the materials of the polymer layer L3 and the organosilane layer L2 may be covalently bonded. If there is no functional group in the monomer or macromonomer that can react with any of the functional groups of the organosilane reagent to form a covalent bond, the polymer of the polymer layer L3 is physically adsorbed to layer L2. However, if the organosilane has a positive charge (or partial positive charge) and the polymer has a negative charge (or partial negative charge), there is a possibility of electrostatic bonding (or ionic bonding) between the organosilane in the organosilane layer and the polymer in the polymer layer.Similarly, if the organosilane has a negative charge (or partial negative charge) and the polymer has a positive charge (or partial positive charge), an electrostatic bond may be formed between the organosilane in the organosilane layer and the polymer in the polymer layer. The resulting dispersion of the third type of charged particles in a nonpolar liquid is the electrophoretic medium of the present invention. In another step, a charge control agent may be added to the dispersion of the third type of charged particles in a nonpolar liquid.

[0050] Figure 9 shows an example of a process for preparing an electrophoretic medium containing a first type of charged particles, the first type of charged particles comprising an organic pigment 101, the organic pigment may be a copper phthalocyanine pigment, specifically pigment blue in a 15:3 ratio. This pigment is well known and widely used in the coatings industry due to its photostability, high saturation, and good color intensity.

[0051] The first step of the scheme in Figure 9 involves preparing particles containing a copper phthalocyanine-graphene oxide complex in a polar organic solvent. As described above, the particles containing the organic pigment-graphene oxide complex contain an organic pigment having a graphene oxide layer on its surface. In this example, the graphene oxide layer has a thickness of 300-800 nm.

[0052] The second step of the scheme in Figure 9 involves preparing particles comprising an organic pigment, a graphene oxide layer, and a metal oxide layer containing a metal oxide. The metal oxide is formed on the surface of the graphene oxide layer by an in-situ reaction between a metal oxide precursor and a reagent. In this example, the metal oxide precursor is tetraethyl orthosilicate (TEOS), and the reagent is an aqueous solution of ammonium hydroxide. The reaction of tetraethyl orthosilicate with water produces silica particles, which precipitate on the graphene oxide layer.

[0053] The third step of the scheme in Figure 9 involves the formation of an organosilane layer. This step can be carried out in the same reaction vessel as the second step and involves the preparation of particles containing an organic pigment-graphene oxide complex, a metal oxide layer (containing silica), and an organosilane layer containing organosilane. The organosilane layer is formed from an organosilane reagent, which reacts with the metal oxide in the metal oxide layer. In this example, the organosilane reagent is 3-(trimethoxysilyl)propyl methacrylate. This organosilane reagent is supplied by Dow as a methanol solution under product code Z-6032 Silane. The molecular structure of Z-6032 Silane contains three methoxy functional groups attached to the silicon atoms of the reagent. The methoxy groups of the organosilane reagent react with the silica in the metal oxide layer to form an organosilane layer containing organosilane. Thus, the organosilane in the organosilane layer is covalently bonded to the silica in the metal oxide layer.

[0054] Finally, the fourth step of the scheme in Figure 9 involves the formation of a polymer layer that contributes to the dispersion stability of the first type of charged particles in the electrophoretic medium. Before the formation of the polymer layer, the particles are separated from most of the polar organic solvent, washed with the solvent as described above, and the polar organic solvent from which the previous step was performed is replaced with a nonpolar liquid by adding a nonpolar liquid to the particles, which contain a copper phthalocyanine pigment, a graphene oxide layer, a metal oxide layer (containing silica), and an organosilane layer. The formation of the polymer layer is achieved by adding a monomer and a polymer initiator to the dispersion. In this case, the monomer is lauryl methacrylate and the polymer initiator is 2,2'-azobis(2-methylpropionitrile) (AIBN). The lauryl methacrylate is polymerized under conditions that provide a poly(lauryl methacrylate) polymer. The vinyl functional groups of the organosilane in the organosilane layer are also involved and react with the carbon-carbon bond of lauryl methacrylate (LMA). Therefore, as shown in step 4 (graft polymerization) of Figure 9, a polymer layer is formed in which poly(lauryl methacrylate) of the first type of charged particles is covalently bonded to the organosilane of the organosilane layer.

[0055] The electrophoretic medium of the present invention, comprising a first type of charged particles in a nonpolar liquid, can be used to form an electrophoretic device. The electrophoretic device may be an electrophoretic display comprising an electro-optic material layer. The electro-optic material layer may have a plurality of microcapsules. Each microcapsule or microcell of the plurality of microcapsules contains the electrophoretic medium. That is, the electrophoretic medium is encapsulated in microcapsules. The electrophoretic display also comprises a first light-transmitting electrode layer, which may also be called a front electrode, and a second electrode layer, which may also be called a back electrode. The second electrode may or may not be light-transmitting. The electro-optic material layer is placed between the first light-transmitting electrode layer and the second electrode layer. The electrophoretic medium comprises a first type of charged particles in a nonpolar liquid. A side view of an example of electrophoretic device 1000 is shown in Figure 10A. The electrophoretic device comprises an electro-optic material layer 1025. The electro-optic material layer 1025 contains a plurality of microcapsules, each containing an electrophoretic medium 1020 encapsulated within a microcapsule 1050. The electrophoretic device also includes a first light-transmitting electrode layer 1010 and a second electrode layer 1040. The second electrode layer 1040 is bonded to the electro-optic material layer by an adhesive layer 1030. The electrophoretic device may also include a second adhesive layer (not shown in Figure 10A) used to bond the first light-transmitting layer 1010 to the electro-optic material layer 1025. In addition to the microcapsules 1050, the electro-optic material layer 1025 may also contain a binder 1022. In the example in Figure 10A, the electrophoretic medium 1020 contains two types of particles in a non-polar liquid. One or more types of particles may have a core and a shell (as the first type of charged particle). The particles can be moved by applying an electric field through electrodes 1010 and 1040.

[0056] Another example of the electrophoresis device 1055 shown in Figure 10B includes multiple microcells instead of microcapsules. The electrophoresis device 1055 includes an electro-optic material layer 1026. The electro-optic material layer 1026 includes multiple microcells 1056 and a sealing layer 1028. Each microcell contains electrophoretic medium 1020 encapsulated within the multiple microcells 1056. Each microcell 1056 of the multiple microcells has an opening. The sealing layer 2028 spans the openings of each microcell. The electrophoresis device 1055 also includes a first light-transmitting electrode layer 1010 and a second electrode layer 1040. The second electrode layer 1040 may be bonded to the electro-optic material layer by an adhesive layer 1030. The electrophoresis device may include a second adhesive layer, which is not shown in Figure 10B. A second adhesive layer may be used to bond the sealing layer 1028 onto the first light-transmitting layer 1010. In the example of Figure 10B, the electrophoretic medium 1020 contains two types of particles in a nonpolar liquid. One or more types of particles may have a core and a shell (as the first type of charged particle). These particles can be moved when an electric field is applied through electrodes 1010 and 1040.

[0057] The electrophoretic media of the present invention may be used to manufacture electrophoretic assemblies such as a front laminate and a double release sheet. As shown in Figure 11, the front laminate 1100 includes a light-transmitting electrode layer 1010, an electro-optic material layer 1025, and a release sheet 1160. The release sheet 1160 is bonded to the electro-optic material layer 1025 by an adhesive layer 1030. The electro-optic material layer 1025 may include a binder 1022 in addition to microcapsules 1050. In the example of Figure 11, the electrophoretic media 1020 includes two types of particles in a non-polar liquid. One or more types of particles may have a core and a shell (as the first type of charged particle). An electrophoretic device is formed by removing the release sheet 1160 and connecting a backplane containing the electrode layer to the exposed surface of the electro-optic material layer 1025 via the adhesive layer 1030.

[0058] The electrophoretic medium of the present invention can be used to manufacture electrophoretic assemblies such as the double release sheet 1200 shown in Figure 12. The double release sheet 1200 comprises two adhesive layers (1275 and 1030) and two release sheets (1270 and 1030). Specifically, in this example, the first release sheet 1270 is attached to the electro-optic material layer 1025 using the first adhesive layer 1275. The second release sheet 1160 is attached to the electro-optic material layer 1025 using the second adhesive layer 1030. In the example of Figure 12, the electrophoretic medium 1020 comprises two types of particles in a non-polar liquid. One or more types of particles may have a core and a shell, the core comprising an organic pigment core and the shell comprising a metal oxide layer and an organosilane layer. The electrophoretic device is formed by removing the release sheet 1270, connecting the first light-transmitting electrode layer to the exposed surface of the electro-optic material layer 1025 via the adhesive layer 1275, and then removing the release sheet 1160 and connecting a backplane containing the second electrode to the exposed surface on the opposite side of the electro-optic material layer 1025.

[0059] The electrophoretic medium of the present invention can be used to manufacture electrophoretic assemblies such as inverted front laminates. The inverted front laminate comprises, in order: (i) a first electrode layer, (ii) a first adhesive layer, (iii) an electro-optic material layer containing an encapsulated electrophoretic medium, and (iv) a release sheet. The inverted front laminate may also include a second adhesive layer between the electro-optic material layers. The inverted front laminate can be converted into an electro-optical device by removing the release sheet and connecting a second electrode layer onto the exposed electro-optic material layer (or second adhesive layer).

[0060] The electrophoretic medium of the present invention may contain more than one type of particles that may have different colors, charge polarities, and charge values. For example, an electrophoretic display may contain an electrophoretic medium having oppositely charged white and black particles. An electrophoretic display may contain four different types of particles in the electrophoretic medium, three of which are organic pigments and one is an inorganic pigment. The use of organic pigments is generally preferred for a variety of colors because they provide brighter and more saturated colors compared to inorganic pigments. Typical organic pigments used in electrophoretic displays may include cyan, magenta, yellow, red, green, blue, and black. Non-limiting examples of types of organic pigments include azo, phthalocyanine, quinacridone, perylene, diketopyrrolopyrrole, benzimidazolone, isoindoline, anthranone, indanthron, rhodamine, benzamine, and carbon black. Some people skilled in the art consider carbon black pigment to be an inorganic pigment, but for the purposes of this patent application, this type of pigment is considered an organic pigment because some of its physical properties, such as hydrophobicity and specific surface area, are similar to those of organic pigments.Non-limiting examples of specific organic pigments that can be used as electrophoretic media include CI Pigment Blue 15, 15:1, 15:2, 15:3, and 15:4. 15:6, 60 and 79; Pigment Red 2, 4, 5, 9, 12, 14, 38, 48:2, 48:3, 48:4, 52:2, 53:1, 57:1, 81, 112, 122, 144, 146, 147, 149, 168, 170, 176, 177, 179, 184, 185, 187, 188, 208, 209, 210, 214, 242, 254, 255, 257, 262, 264, 282 and 285; CI Pigment Violet 1, 19, 23 and 32; CI Pigment Yellow 1, 3, 12, 13, 14, Examples include 15, 16, 17, 73, 74, 81, 83, 97, 109, 110, 111, 120, 126, 127, 137, 138, 139, 150, 151, 154, 155, 174, 175, 176, 180, 181, 184, 191, 194, 213 and 214; CI Pigment Green 7 and 36; CI Pigment Black 1 and 7; CI Pigment Brown 25, 32, 41; Pigment Orange 5, 13, 34, 36, 38, 43, 61, 62, 64, 68, 67, 72, 73 and 74.

[0061] The organic pigment of the core of the first type of charged particle of the present invention may have an average diameter of 10 nm to about 100 μm, or 50 nm to 1 μm, or 100 nm to 800 nm.

[0062] Organic pigments provide color by absorbing specific wavelengths of incident light corresponding to visible light. Generally, their color saturation and intensity increase as the particle size decreases; that is, their color saturation increases as the specific surface area increases. Therefore, they are often used as particles with a relatively large specific surface area, which makes them difficult to disperse and stabilize in liquids.

[0063] The electrophoretic medium of the present invention may contain a plurality of first-type charged particles in a nonpolar liquid. Each particle comprises a core and a shell. The core comprises a first-type organic pigment having a surface and a graphene oxide layer containing graphene oxide, and the shell comprises an organosilane layer containing organosilane and a polymer layer containing a polymer. The polymer in the polymer layer can be formed by polymerization of monomers. The polymer in the polymer layer can be physically bonded to the organosilane in the organosilane layer. Alternatively, the polymer in the polymer layer can be bonded to the organosilane in the organosilane layer via ionic bonds, that is, one of the bonded species has a positive charge or a partially positive charge, and the other has a negative charge or a partially negative charge. The electrophoretic medium of this embodiment may further contain first-type charged particles, the core of which comprises a metal oxide layer containing a metal oxide. The metal oxide layer may be placed between the graphene oxide layer and the organosilane layer. The metal oxide in the metal oxide layer may be covalently bonded to the organosilane in the organosilane layer. That is, the organosilane reagent used to form the organosilane layer contains a first functional group that reacts with the metal oxide in the metal oxide layer to form a covalent bond.

[0064] The electrophoretic medium of the present invention may comprise a plurality of first-type charged particles in a nonpolar liquid. Each particle comprises a core and a shell. The core comprises a first-type organic pigment having a surface and a graphene oxide layer comprising graphene oxide. The shell comprises an organosilane layer comprising organosilane and a polymer layer comprising a polymer. The polymer in the polymer layer may be formed using macromonomers. The polymer in the polymer layer can be covalently bonded to the organosilane in the organosilane layer. That is, a third functional group of the macromonomer can react with a second functional group of the organosilane in the organosilane layer to form a covalent bond. The third-type particle of the electrophoretic medium may further comprise a metal oxide layer comprising a metal oxide. The metal oxide layer may be positioned between the graphene oxide layer of the core and the organosilane layer of the shell. The metal oxide in the metal oxide layer may be covalently bonded to the organosilane in the organosilane layer. In other words, the organosilane reagent used to form the organosilane layer contains a first functional group that reacts with the metal oxide in the metal oxide layer to form a covalent bond.

[0065] If the first type of charged particles in the electrophoretic medium of the present invention includes a metal oxide layer, the metal oxide may include aluminum oxide, silica, titanium dioxide, zirconium oxide, zinc oxide, or mixtures thereof. The metal oxide may be formed by the reaction of a metal oxide precursor with a reagent. Non-limiting examples of metal oxide precursors include trimethylaluminum, triethylaluminum, dimethylaluminum chloride, diethylaluminum chloride, trimethoxyaluminum, triethoxyaluminum, dimethylaluminum propoxide, aluminum triisopropoxide, tributoxyaluminum, tris(dimethylamino)aluminum, tris(diethylamino)aluminum, tris(propylamino)aluminum, aluminum trichloride, trichlorosilane, hexachlorodisilane, silicon tetrachloride, tetramethoxysilane, tetraethoxysilane, tris(tert-pentoxy)silanol, tetraisocyanatesilane, and tetrachlorosilane (silicon These include tertrachoride, tris(methylamino)silane, tris(ethylamino)silane, titanium tetrachloride, titanium tetraiodide, tetramethoxytitanium, tetraethoxytitanium, titanium isopropoxide, tetrakis(methylamino)titanium, tetrakis(ethylamino)titanium, dimethylzinc, diethylzinc, methylzinc isopropoxide, zirconium tetrachloride, zirconium tetraiodide, tetramethoxyzirconium, tetraethoxyzirconium, tetraisopropoxyzirconium, tetrabutoxyzirconium, tetrakis(methylamino)zirconium, tetrakis(ethylamino)zirconium, and mixtures thereof. Non-limiting examples of reagents include water, oxygen, ozone, ammonia, and mixtures thereof. The metal oxide layer may have a thickness of about 1 nm to about 2 μm, or about 30 nm to about 2 μm, or about 30 nm to about 0.8 μm.

[0066] Non-limiting examples of the first functional group of an organosilane reagent that can react with a metal oxide layer include alkoxy, alkylamino, halide, hydrogen, and hydroxy. That is, the silicon atom of the organosilane may be bonded to an alkoxy group, alkylamino group, halide group, hydrogen group (Si-H), and hydroxyl group, respectively. The molecular structure of the organosilane reagent may contain one, two, or more of the first functional groups. Non-limiting examples of the second functional group of an organosilane reagent include epoxy, vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, amino, hydroxy, carboxy, alkoxy, and chloride. An example of a certain class of organosilane reagents for bonding to the metal oxide layer is a trialkoxysilane coupling group, e.g., 3-(trimethoxysilyl)propyl methacrylate, which is commercially available from Dow Chemical Company, Wilmington, DE under the trade name Z-6032. The first functional group of this reagent is methoxy, and the second functional group is methacrylate. A corresponding acrylate may be used. Another example of a silane reagent of this class is vinylbenzylaminoethylaminopropyltrimethoxysilane, which is available from Dow Chemical Company under the trade name Dowsil(trademark) Z-6032. In this reagent, the first functional group is methoxy, and the second functional group is vinyl. Other organosilane reagents that can be used to form the first type of charged particles are described in U.S. Patent Application No. 2018 / 0210312, the contents of which are incorporated herein by reference in their entirety.

[0067] The organosilane reagent forming the organosilane layer may contain a fourth functional group that does not participate in the reaction between the organosilane reagent and the metal oxide of the metal oxide layer, or between the organosilane reagent and the monomer or macromonomer. The fourth functional group of the organosilane reagent that may be present in the organosilane of the organosilane layer may be useful for modifying the surface of the electrophoretic medium and / or for imparting charge to the first type of charged particles of the electrophoretic medium. Non-limiting examples of the fourth functional group of the organosilane layer are alkyl groups, alkyl halides, alkenyl groups, aryl groups, hydroxyl groups, carboxyl groups, sulfate groups, sulfonate groups, phosphate groups, phosphonic acid groups, amine groups, quaternary ammonium groups, dimethylsiloxane groups, ester groups, amide groups, and ethyleneimine groups.

[0068] As described above, the first type of charged particles in the electrophoretic medium includes a polymer layer formed by polymerization of monomers or macromonomers. Various polymerization techniques known to those skilled in the art can be used. For example, the polymer layer can be obtained by random graft polymerization (RGP), ion random graft polymerization (IRGP), and atom transfer radical polymerization (ATRP), as described in U.S. Patent No. 6,822,782 (the contents of which are incorporated herein by reference in their entirety). As used herein and throughout the claims, “macromonomer” means a polymer having one terminal group that enables it to act as a monomer. Suitable monomers for forming polymer layers include styrene, α-methylstyrene, methyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, vinylpyridine, n-vinylpyrrolidone, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hexyl acrylate, hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, n-octadecyl acrylate, n-octadecyl methacrylate, 2-perfluorobutylethyl acrylate, 2,2,2 Examples include, but are not limited to, trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate. Macromonomers may contain terminal functional groups selected from the group consisting of acrylate groups, vinyl groups, or combinations thereof.

[0069] The polymer in the polymer layer may be physically adsorbed to the organosilane layer, covalently bonded to the organosilane in the organosilane layer, or electrostatically bonded to the organosilane in the organosilane layer. In the case of covalent bonding, the molecular structure of the macromonomer or polymerizable monomer contains a third functional group, the organosilane reagent contains a second functional group, and the third functional group is reactive with respect to the second functional group. Therefore, covalent bonding may be formed as a result of the reaction between the second functional group and the third functional group of the organosilane reagent. The second functional group may be epoxy, vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, amino, hydroxy, carboxy, alkoxy groups, and chlorides.

[0070] Other macromonomer reagents that may be used to form the first type of charged particles are described in U.S. Patent Application No. 2018 / 0210312, the contents of which are incorporated herein by reference in their entirety.

[0071] One type of macromonomer that can be used to form the polymer layer may be an acrylate-terminated polysiloxane, such as Gelest, MCR-M11, MCR-M17, or MCR-M22. Another type of macromonomer suitable for the above process is the PE-PEO macromonomer shown below: R m O-[CH2CH2O] n -CH2-phenyl-CH=CH2, or R m O-[CH2CH2O] n -C(=O)-C(CH3)=CH2. The substituent R may be a polyethylene chain, n may be 1 to 60, and m may be 1 to 500. The synthesis of these compounds can be found in Dongri Chao et al., Polymer Journal, Vol. 23, no. 9, 1045 (1991) and Koichi Ito et al, Macromolecules, 1991, 24, 2348. Further types of preferred macromonomers are the PE macromonomers shown below: CH3-[CH2] n -CH2O--C(=O)-C(CH3)=CH2. In this case, n may be between 30 and 100. The synthesis of this type of macromonomer can be found in Seigou Kawaguchi et al, Designed Monomers and Polymers, 2000, 3, 263.

[0072] When selecting a bifunctional or polyfunctional compound, such as an organosilane reagent containing a first, second, and fourth functional group, to provide polymerizability or initiating functionality on particles, attention should be paid to the relative positions of the two groups in the reagent. As should be apparent to those skilled in polymer production, the reaction rate of a polymerizability or initiating group bound to a particle can vary greatly depending on whether the group is firmly held near the particle surface or whether the group is separated from its surface (on an atomic scale) and thus can extend into the reaction medium surrounding the particle. The latter is a more favorable environment for the chemical reaction of the functional group. In general, it is preferable that there are at least three atoms in the linear chain between two functional groups of the same molecule. For example, the aforementioned 3-(trimethoxysilyl)propyl methacrylate provides a chain of four carbon atoms and one oxygen atom between the silyl group and the ethylenically unsaturated group, while the aforementioned 4-vinylaniline separates the amino group (or diazonium group in actual reaction forms) from the vinyl group by the entire width of the benzene ring, which corresponds to approximately the length of a three-carbon chain.

[0073] In any of the above processes, the amounts of reagents used (e.g., organic core pigment particles, graphene oxide in the graphene oxide layer, metal oxide in the metal oxide layer, organosilane in the organosilane layer if present, and monomers or macromonomers forming the polymer layer) can be adjusted and controlled to achieve the desired content of the resulting particles. Furthermore, the process of the present invention may include one or more steps and / or one or more types of polymerization.

[0074] As described above, the third type of charged particles of the electrophoretic medium of the present invention are dispersed in a nonpolar liquid. It is desirable that the polymer layer has high compatibility with the nonpolar liquid. The suspended nonpolar liquid of the electrophoretic medium may be hydrocarbon-based, but the nonpolar liquid may also contain a certain proportion of halocarbons, which are used to increase the density of the nonpolar liquid and thus reduce the difference between the density of the nonpolar liquid and the density of the particles. Accordingly, it is important that the polymer layer of the first type of charged particles is compatible with the nonpolar liquid, and therefore the polymer layer itself contains a major proportion of hydrocarbon chains. As will be discussed below, a large number of strong ionic groups are undesirable, as they reduce the solubility of the polymer layer material in the hydrocarbon suspended nonpolar liquid and thus adversely affect the stability of the particle dispersion, except for the groups provided for charging purposes. Also, as already discussed, at least when the medium in which the particles are used contains an aliphatic hydrocarbon suspended nonpolar liquid, as is the case in general, it is advantageous that the polymer of the polymer layer has a branched or "comb-like" structure having a main chain and a plurality of side chains extending away from the main chain. Each of these side chains should have at least about four, preferably at least about six, carbon atoms. Substantially longer side chains may be advantageous. For example, some preferred materials for polymer layers are lauryl(C) 12) may have side chains. The side chains may be branched themselves. For example, each side chain may be a branched alkyl group such as a 2-ethylhexyl group. The present invention is by no means limited by this idea, but because hydrocarbon chains have a high affinity for hydrocarbon suspensions in nonpolar liquids, it is thought that the branches of the polymer layer material spread out from each other in a brush- or dendritic structure through a large volume of liquid, thus increasing the affinity of the particles to the suspension in nonpolar liquids and increasing the stability of the particle dispersion.

[0075] There are two basic methods for forming such comb-like polymers. The first method uses monomers that essentially provide the necessary side chains. Typically, such monomers have a single polymerizable group at one end of a long chain, and the long chain has at least four, preferably at least six, carbon atoms. Examples of this type of monomer include hexyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, isobutyl methacrylate, and 2,2,3,4,4,4-hexafluorobutyl acrylate. It may be desirable to limit the number of side chains formed in such a process, which can be achieved by using a mixture of monomers, for example, a mixture of lauryl methacrylate and methyl methacrylate, to form a random copolymer in which only a portion of the repeating units have long side chains. Another method, exemplified by the RGP-ATRP process, uses a mixture of monomers to carry out a first polymerization reaction in which at least one of these monomers has an initiator group, and thus a first polymer containing such an initiator group is produced. Next, the product of this first polymerization reaction is subjected to a second polymerization, typically under different conditions than the first polymerization, so that the initiator groups in the polymer induce further polymerization of monomers in the original polymer, thereby forming the desired side chains. As with the bifunctional reagents discussed above, the possibility of some chemical modification of the initiator groups occurring between the two polymerizations is not ruled out. In such a process, the side chains themselves do not need to be highly branched and can be formed from small monomers, such as methyl methacrylate.

[0076] Free radical polymerization of ethylenic groups or similar radical polymerizable groups attached to particles can be carried out at high reaction temperatures, preferably 60-70°C, using conventional free radical initiators such as azobis(isobutylnitrile) (AIBN). On the other hand, ATRP polymerization can be carried out using conventional metal complexes, as described in Wang, JS, et al., Macromolecules 1995, 23, 7901, and J. Am. Chem. Soc. 1995, 117, 5614, and Beers, K. et al., Macromolecules 1999, 32, 5772-5776. See also U.S. Patents No. 5,763,548, No. 5,789,487, No. 5,807,937, No. 5,945,491, No. 4,986,015, No. 6,069,205, No. 6,071,980, No. 6,111,022, No. 6,121,371, No. 6,124,411, No. 6,137,012, No. 6,153,705, No. 6,162,882, No. 6,191,225, and No. 6,197,883. The full disclosures of these papers and patents are incorporated herein by reference. The currently preferred catalyst for carrying out ATRP is cuprous chloride in the presence of bipyridyl (Bpy).

[0077] The RGP process of the present invention, which reacts polymerizable particles with monomers in the presence of an initiator, may result in the formation of some "free" polymer that is not attached to the particles as the monomers in the reaction mixture polymerize. The unattached polymer can be removed by repeatedly washing the particles with a solvent such as a hydrocarbon to which the unattached polymer is soluble, or by removing the treated particles from the reaction mixture by centrifugation (with or without prior addition of solvent or diluent), redispersing the particles in a fresh solvent, and repeating these steps until the proportion of unattached polymer is reduced to an acceptable level. The reduction in the proportion of unattached polymer can be tracked by thermogravimetric analysis of the polymer sample. Empirically, the presence of small proportions of unattached polymer on the order of 1 weight percent does not appear to have a significant adverse effect on the electrophoretic properties of the treated particles. In fact, in some cases, depending on the chemical properties of the unattached polymer and the suspension of nonpolar liquid, it may not be necessary to separate the polymer-attached particles from the unattached polymer before using the particles in an electrophoretic display.

[0078] There is an optimal range for the amount of polymer layer that should be formed on electrophoretic particles; forming an excess of polymer on the particles can degrade their electrophoretic properties. The optimal range varies depending on several factors, including the density and size of the particles being coated, the properties of the suspension medium in which the particles are intended to be used, and the properties of the polymer formed on the particles. For specific particles, polymers, and suspension mediums, the optimal range is best determined empirically. However, as a general guideline, it should be noted that the denser the particles, the lower the optimal polymer ratio relative to the particle's weight; conversely, the finer the particles, the higher the optimal polymer ratio. Generally, particles should be coated with at least about 2 weight percent, preferably at least about 4 weight percent, of the particle's weight. Often, the optimal polymer ratio is in the range of about 4 to 15 weight percent of the particle's weight.

[0079] Comonomers can be added to the polymerization reaction medium to incorporate functional groups for charge generation of pigment particles. The comonomers can either directly charge the first type of charged particles or interact with charge control agents in the nonpolar liquid of the electrophoretic medium to bring about desired charge polarity and charge density in the first type of charged particles. Suitable comonomers include vinylbenzylaminoethylaminopropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, acrylic acid, methacrylic acid, vinyl phosphoric acid, 2-acrylamino-2-methylpropanesulfonic acid, 2-(dimethylamino)ethyl methacrylate, and N-[3-(dimethylamino)propyl]methacrylamide. Suitable comonomers may include fluorinated acrylates or methacrylates, such as 2-perfluorobutylethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, or 2,2,3,3,4,4,4-heptafluorobutyl methacrylate. Alternatively, charged or charged groups may be incorporated into the polymer.

[0080] Functional groups, such as acidic or basic groups, may be provided in a "blocked" form during polymerization and subsequently deblocked after the polymer is formed. For example, since ATRP cannot be initiated in the presence of acid, if it is desired to provide acidic groups within the polymer, esters such as t-butyl acrylate or isobornyl methacrylate can be used, and residues of these monomers in the final polymer can be hydrolyzed to provide acrylic or methacrylic acid residues.

[0081] When it is desired to generate charged or charged groups on electrophoretic particles and further to generate a polymer layer separately attached to the particles, it can be very convenient to treat the particles (after metal oxide coating) with a mixture of two reagents, one of which supports the charged or charged groups (or the groups ultimately treated to generate the desired charged or charged groups), and the other supports the polymerizable or polymerization initiator groups. Preferably, the two reagents have the same or essentially the same functional groups that react with the particle surface, so that even slight variations in reaction conditions will similarly change the relative rate at which the reagents react with the particles, and the ratio of the number of charged or charged groups to the number of polymerizable or polymerization initiator groups will remain substantially constant. It is understood that this ratio can be changed and controlled by changing the relative molar amounts of the two or more types of reagents used in the mixture. Examples of reagents that provide a charged site but not a polymerizable group or polymerization initiator include 3-(trimethoxysilyl)propylamine, N-[3-(trimethoxysilyl)propyl]diethylenetriamine, N-[3-(trimethoxysilyl)propyl]ethylene, and 1-[3-(trimethoxysilyl)propyl]urea, all of which can be purchased from United Chemical Technologies, Inc., Bristol, Pa., 19007. As already mentioned, an example of a reagent that provides a polymerizable group but not a charged group or a polymerizable group is 3-(trimethoxysilyl)propyl methacrylate.

[0082] The first type of charged particles according to the present invention is useful for electrophoretic devices. Firstly, the particle shell allows for modification and control of the surface properties and charge of the organic pigment. Therefore, different types of electrophoretic particles in a medium may be surface-modified using different silane treatments, which may contribute to effective separation and consequently to improved electro-optical performance. The metal oxide layer allows for covalent bonding of the organosilane layer to the particle surface. By depositing a layer of metal oxide on the surface of the organic pigment-graphene oxide complex, the subsequent organosilane layer adheres strongly to the surface of the complex. The likelihood of desorption of organosilane from the surface of the organic pigment-graphene oxide complex is low, and the effect of the surface treatment is enhanced. Surface treatments including a polymer layer are similar. The polymer layer prevents particle aggregation, and therefore contributes to the stability of the particle dispersion. The steric effect caused by polymer adhesion to the pigment particle surface prevents particle aggregation. It has been observed that the stronger the adhesion, the less polymer is desorbed from the particle surface, so the stronger the adhesion, the more effective the stabilization. Therefore, in the case of covalent bonding of polymers to the particle surface, more effective particle stabilization and improved electro-optical performance are observed.

[0083] The amount of polymer layer on the first type of charged particles can be controlled. Forming an excess amount of polymer on the particles can degrade their electrophoretic properties. The optimal range varies depending on several factors, including the density and size of the organic pigment, the density and thickness of the metal oxide layer, the properties of the nonpolar liquid electrophoresis medium, and the properties of the polymer in the polymer layer. It has been previously found that the higher the particle density, the lower the optimal ratio of the polymer layer to the weight of the charged particles. Furthermore, the finer the organic pigment core is divided, the higher the optimal ratio of the polymer layer. The polymer layer may be 1–50 weight percent, 2–30 weight percent, 3–20 weight percent, or 4–15 weight percent relative to the weight of the first type of charged particles.

[0084] The nonpolar liquid in which the electrophoretic particles are dispersed may be colorless and transparent. It preferably has a dielectric constant in the range of about 2 to about 30, preferably about 2 to about 15, for high particle mobility. Examples of suitable dielectric solvents include hydrocarbons, e.g., isoper, decahydronaphthalene (DECALIN), 5-ethylidene-2-norbornene, fatty oils, paraffin oils, silicon fluids, aromatic hydrocarbons, e.g., toluene, xylene, phenylxylethane, dodecylbenzene, or alkylnaphthalene, halogenated solvents, e.g., perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5-trichlorobenzotrifluoride, chloropentafluorobenzene, dichlorononane, or pentachlorobenzene, and perfluorinated solvents, e.g., FC-43, FC-70, or FC-5060 from 3M Company (St. Paul MN), low molecular weight halogen-containing polymers, e.g., poly(perfluoropropylene oxide) from TCI America (Portland, Oregon), poly(chlorotrifluoroethylene), e.g., Halocarbon Product Corp. (River Edge, NJ) Examples include oils, perfluoropolyalkyl ethers, such as Ausimont's Galden, or DuPont (Delaware)'s Krytox Oil and Greases K-Fluid Series, and Dow Corning's polydimethylsiloxane-based silicone oil (DC-200).

[0085] The content of electrophoretic particles in the nonpolar liquid may vary. For example, one type of particle may account for 0.1% to 50% by volume, preferably 0.5% to 15% by volume, of the nonpolar liquid. [Examples]

[0086] Examples of the present invention are described below. The present invention is not limited to these examples.

[0087] Example 1

[0088] Preparation of Blue 15:3-Graphene Oxide Composite Particles: A commercially available sample of graphene oxide was mixed with ethanol, and the mixture was sonicated to disperse the graphene oxide. A commercially available sample of Pigment Blue 15:3 powder was slowly added to the graphene oxide dispersion, and the mixture was heated to 50°C while mixing for 5 hours to produce a dispersion containing the Pigment Blue 15:3-Graphene Oxide Composite.

[0089] Example 2

[0090] Preparation of particles containing Blue 15:3-graphene oxide complex and silica layer: Tetraethyl orthosilicate (TEOS) and ammonium hydroxide were added to the dispersion prepared in Example 1 and mixed for 1 hour.

[0091] Example 3

[0092] Preparation of particles containing pigment blue 15:3-graphene oxide complex, silica layer, and organosilane layer: 3-(trimethoxysilyl)propyl methacrylate was added to the dispersion prepared in Example 2 and stirred to prepare an ethanol dispersion of particles containing pigment blue 15:3-graphene oxide complex, silica layer, and organosilane layer.

[0093] Example 4

[0094] Solvent transfer: The dispersion from Example 3 was washed three times with ethanol, centrifuged, and the ethanol in the supernatant was removed. The resulting paste was washed three times with toluene, centrifuged, and the ethanol in the supernatant was removed. The paste was further diluted with toluene.

[0095] Example 5

[0096] Preparation of the first type of charged particles: Lauryl methacrylate monomer and the radical initiator 2,2'-azobis(2-methylpropionitrile) were added to the dispersion prepared in Example 4. The mixture was placed under nitrogen and then stirred at 70°C for 20 hours. The dispersion was then washed three times with Isopar E (hydrocarbon solvent), centrifuged after each wash, diluted with Isopar E, sonicated, and then oven-dried at 50°C.

[0097] Various experiments in Examples 1-5 were conducted using different amounts of pigment blue 15:3, graphene oxide, TEOS, 3-(trimethoxysilyl)propyl methacrylate, and lauryl methacrylate. Table 1 summarizes the relative amounts of materials in the final particles, as determined by thermogravimetric analysis.

[0098] [Table 1]

[0099] Example 6

[0100] Performance evaluation of particles from Example 5

[0101] To observe the performance of the blue particles from Example 5, three pigment dispersions were prepared using the following compositions: 5 wt% blue pigment, 30% white pigment, 12% yellow pigment, and 0.25% charge control agent (Solsperse® 19,000). Furthermore, a control dispersion was prepared using the same composition, but the blue particles of the present invention were replaced with control pigment particles. The control pigment particles were prepared from pigment blue 15:3 and lauryl methacrylate using dispersion polymerization. All dispersions were sonicated and vortexed before further evaluation. (a) Electrophoretic devices were prepared using dispersions containing blue particles from Example 5D, blue particles from Comparative Example 5E, and control blue particles from dispersion polymerization. The corresponding electrophoretic devices were driven to the blue, white, yellow, and green states, and the L*a*b* color values ​​for each state were measured by a colorimeter (reflection). Tables 2, 3, and 4 summarize the color evaluation of the three dispersions.

[0102] [Table 2]

[0103] [Table 3]

[0104] [Table 4]

[0105] The data from Tables 2-4 shows that the blue state of the dispersion of the present invention in Table 4 has the highest saturation (lowest b* value). The yellow state of the dispersion of the present invention in Table 4 also has the highest saturation (highest b* value). The excellent yellow state observed in the present invention indicates that the blue particles are better separated from the yellow particles in the electrophoretic device, resulting in a more saturated blue and yellow state. Furthermore, the green state of the dispersion of the present invention in Table 4 also has the highest saturation (lowest a* value), resulting in a more desirable green color.

[0106] To further investigate the role of graphene oxide in the performance of blue particles, the dispersion of the present invention containing the blue particles of Example 5D was compared with a control dispersion containing blue particles prepared in the same manner as in Example 5D, but using poly(vinylpyrrolidone) instead of graphene oxide. PVP is often used as a polymer surfactant to form organic pigment dispersions with good color quality. The control (PVP-containing blue particles) and the particles of the present invention of Example 5D were used to prepare dispersions containing three pigments (blue, white, and yellow). That is, electrophoretic devices were prepared using these two dispersions and driven to the blue, white, yellow, and green states. The L*a*b* color values ​​for each state were measured by a colorimeter (reflectance). Tables 5 and 6 summarize the color evaluation of the two dispersions.

[0107] [Table 5]

[0108] [Table 6]

[0109] A dispersion containing control blue particles (containing PVP instead of graphene oxide) exhibits significant aggregation with the yellow pigment, as evidenced by the higher b* value in the blue state and the lower b* value in the yellow state (Table 5) compared to the dispersion containing the blue particles of the present invention (Table 6).

[0110] Therefore, a significant improvement in the color quality of electrophoretic devices is observed. This improvement is achieved using the blue particles of the present invention. Without wishing to be constrained by theory, the beneficial effect of graphene oxide in the graphene oxide layer may be a result of strong hydrophobic and / or π-π interactions between the extended aromatic system of copper phthalocyanine pigments (and other organic pigments) and graphene oxide. Thus, graphene oxide can effectively cover most of the surface of the pigment particles. At the same time, the hydrophilic polar groups of graphene oxide may be compatible with polar groups of other materials used for surface modification of electrophoretic particles, such as organosilanes and metal oxides. This promotes the quality of surface modification of the particles and results in excellent separation between particles of the same type and particles of different types.

[0111] The present invention enables the use of copper phthalocyanine blue in electrophoretic displays. The invention mitigates the aggregation between organic pigment particles of different colors (blue-red and blue-yellow) observed when using copper phthalocyanine blue pigments with surface treatments different from those of the present invention. Another method to mitigate the aggregation phenomenon is to use inorganic pigments such as ultramarine blue. However, due to the difference in surface properties between inorganic and organic pigment particles, the use of inorganic pigments such as ultramarine blue is undesirable, even though it is easy to separate inorganic blue pigment particles from organic pigment particles in the electrophoretic medium. Copper phthalocyanine blue offers a much better option as it achieves much higher saturation than ultramarine blue (and all other inorganic pigments), enabling better image quality. As shown in Figure 11, the visible reflectance spectrum of copper phthalocyanine (pigment blue 15:3) against wavelength shows high intensity in the blue wavelength region and almost no reflectance in the red region, where the red region corresponds to wavelengths higher than 680 nm. Conversely, the corresponding reflectance curve of ultramarine blue pigment shows strong reflectance in the red region. This means that Pigment Red 15:3 performs better in electrophoretic systems containing multiple pigment particles of different colors, such as four-pigment systems for full-color electrophoretic displays. For example, in a system where the black state is created by the reflection of multiple color particles (red, blue, and yellow), using Pigment Blue 15:3 allows for a superior black state without red shading. Furthermore, using Pigment Blue 15:3 in a multi-pigment electrophoretic medium allows for a superior green state by mixing yellow and blue.

[0112] To investigate the feasibility of using the technology of the present invention for pigments other than phthalocyanines, corresponding particles containing pyrrole pigments such as Pigment Red 254 (1,4-bis(4-chlorophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-3,6-dione) were prepared. The preparation involved the synthesis of particles containing the Pigment Red 254-graphene oxide complex, mixing the complex with organosilane (Z-6032), and graft polymerization using ethylhexyl acrylate monomer (EHA) in the presence of AIBN. Polymerization of the ethylhexyl acrylate monomer yields poly(ethylhexyl acrylate) or PEHA. The weight percentage content of the different layers of the prepared particles is shown in Table 7, with the particles of the present invention corresponding to Example 6. Control red particles (Comparative Examples 7 and 8) were also prepared using the same organic pigment for the core, organosilane reagent and monomer for the shell, but without the graphene oxide layer.

[0113] [Table 7]

[0114] While there was a significant difference in the amount of organosilane incorporated into the pigment surface between the particle content of Comparative Examples 7 and 8 and the particle content of Example 6 of the present invention, the ratio of pigment to organosilane used was similar in all three examples. The data in Table 7 demonstrate that graphene oxide enables a strong interaction between the hydrophobic pigment particle surface and the more hydrophilic organosilane reagent, resulting in effective organosilane incorporation into the particles.

[0115] In conclusion, the technology of the present invention enables good electrophoretic performance of charged particles containing organic pigments.

[0116] term

[0117] Item 1: An electrophoretic medium comprising a plurality of first type charged particles and a nonpolar liquid, wherein each of the plurality of first type charged particles has a core and a shell, the core comprising a first type organic pigment having a surface and a graphene oxide layer comprising graphene oxide, the graphene oxide layer being in contact with the surface of the first type organic pigment, the shell comprising an organosilane layer and a polymer layer, the organosilane layer comprising organosilane, the polymer layer comprising polymer, and the organosilane in the organosilane layer of the shell being covalently bonded to the polymer in the polymer layer.

[0118] Item 2: The electrophoretic medium according to Item 1, further comprising a metal oxide layer containing a metal oxide, wherein the metal oxide layer is disposed between the graphene oxide layer and the organosilane layer.

[0119] Item 3: The electrophoretic medium according to Item 2, wherein the metal oxide layer comprises aluminum oxide, silica, titanium dioxide, zirconium oxide, zinc oxide, or a mixture thereof.

[0120] Item 4: The metal oxide of the metal oxide layer of the first type of charged particles is formed on the graphene oxide layer by a reaction between a metal oxide precursor and a reagent, the reagent reacts with the metal oxide precursor to form the metal oxide of the metal oxide layer, the metal oxide of the metal oxide layer is in contact with the graphene oxide of the graphene oxide layer, and the metal oxide precursor is trimethylaluminum, triethylaluminum chloride, diethylaluminum chloride, trimethoxyaluminum, triethoxyaluminum, dimethylaluminum propoxide, aluminum triisopropoxide, tributoxyaluminum, tris(dimethylamino)aluminum, tris(diethylamino)aluminum, tris(propylamino)aluminum, aluminum trichloride, trichlorosilane, hexachlorodisilane, silicon tetrachloride, tetramethoxysilane, tetraethoxysilane, tris(tert-pentoxy)silanol, tetraisocyanatesilane, tetrachlorosilane (silicon An electrophoretic medium according to claim 2 or 3, wherein the reagent is selected from the group consisting of tertrachoride, tris(methylamino)silane, tris(ethylamino)silane, titanium tetrachloride, titanium tetraiodide, tetramethoxytitanium, tetraethoxytitanium, titanium isopropoxide, tetrakis(methylamino)titanium, tetrakis(ethylamino)titanium, dimethylzinc, diethylzinc, methylzinc isopropoxide, zirconium tetrachloride, zirconium tetraiodide, tetramethoxyzirconium, tetraethoxyzirconium, tetraisopropoxyzirconium, tetrabutoxyzirconium, tetrakis(methylamino)zirconium, tetrakis(ethylamino)zirconium, and mixtures thereof, wherein the reagent is selected from the group consisting of water, oxygen, ozone, ammonia, and mixtures thereof, and the organosilane in the organosilane layer is covalently bonded to the metal oxide in the metal oxide layer.

[0121] Item 5: The electrophoretic medium according to any one of items 2 to 4, wherein the organosilane layer is formed from an organosilane reagent, the organosilane reagent comprises a first functional group, and the first functional group of the organosilane reagent reacts with the metal oxide of the metal oxide layer to form a covalent bond between the organosilane of the organosilane layer and the metal oxide of the metal oxide layer of the first type of charged particle.

[0122] Item 6: The electrophoretic medium according to Item 5, wherein the first functional group of the organosilane reagent is selected from the group consisting of alkoxy, alkylamino, halide, hydrogen, and hydroxyl.

[0123] Item 7: The electrophoretic medium according to any one of items 1 to 6, wherein the polymer in the polymer layer is formed from macromonomers or from polymerization of monomers.

[0124] Item 8: The electrophoretic medium according to Item 7, wherein the organosilane reagent comprises a second functional group, and the macromonomer or monomer comprises a third functional group, wherein the second functional group reacts with the third functional group to form a covalent bond between the organosilane in the organosilane layer and the polymer in the polymer layer of the first type of charged particles.

[0125] Item 9: The electrophoretic medium according to Item 8, wherein the second functional group of the organosilane reagent is selected from the group consisting of epoxy, vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, amino, hydroxy, carboxy, alkoxy groups, and chlorides.

[0126] Item 10: The electrophoretic medium according to item 8 or 9, wherein the third functional group of the monomer or macromonomer is selected from the group consisting of vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, epoxy, amino, hydroxy, carboxy, and chloride.

[0127] Item 11: The electrophoretic medium according to item 8, wherein the second functional group of the organosilane is vinyl, and the third functional group of the macromonomer or monomer is vinylbenzyl.

[0128] Item 12: The electrophoretic medium according to any one of items 1 to 11, further comprising a plurality of second-type charged particles, a plurality of third-type charged particles, and a plurality of fourth-type charged particles.

[0129] Item 13: The electrophoretic medium according to Item 12, wherein each of the plurality of second types of charged particles comprises a second type of organic pigment, each of the plurality of third types of charged particles comprises a third type of organic pigment, and each of the plurality of fourth types of charged particles comprises an inorganic pigment.

[0130] Item 14: The electrophoretic medium according to any one of items 1 to 13, wherein the first type of organic pigment is selected from the group consisting of azo pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, isoindoline pigments, anthranone pigments, indanthron pigments, carbon black pigments, rhodamine pigments, benzamine pigments, carbon black pigments, and mixtures thereof.

[0131] Item 15: The first type of organic pigment, the second type of organic pigment, and the third type of organic pigment are independently CI Pigment Blue 15, 15:1, 15:2, 15:3, 15:4 15:6, 60 and 79; Pigment Red 2, 4, 5, 9, 12, 14, 38, 48:2, 48:3, 48:4, 52:2, 53:1, 57:1, 81, 112, 122, 144, 146, 147, 149, 168, 170, 176, 177, 179, 184, 185, 187, 188, 208, 209, 210, 214, 242, 254, 255, 257, 262, 264, 282 and 285; CI Pigment Violet 1, 19, 23 and 32; CI Pigment Yellow 1, 3, 12, 13, 14, 15, 16, 17, 73, 74, 81, 8 3, 97, 109, 110, 111, 120, 126, 127, 137, 138, 139, 150, 151, 154, 155, 174, 175, 176, 180, 181, 184, 191, 194, 213 and 214; CI Pigment Green 7 and 36; CI Pigment Black 1 and 7; CI Pigment Brown 25, 32, 41; Pigment Orange 5, 13, 34, 36, 38, 43, 61, 62, 64, 68, 67, 72, 73 and 74, and mixtures thereof, as described in item 13 or 14.

[0132] Item 16: An electrophoretic device comprising a first light-transmitting electrode layer, an electro-optic material layer containing an electrophoretic medium as described in any one of Items 1 to 15, and a second electrode layer.

[0133] Item 17: The electrophoretic device according to Item 16, wherein the electrophoretic medium of the electro-optical material layer is encapsulated in a plurality of microcapsules or a plurality of microcells.

[0134] Item 18: An electrophoretic assembly comprising, in order, a first light-transmitting electrode layer, an electro-optic material layer containing an electrophoretic medium as described in any one of items 1 to 15, an adhesive layer, and a release sheet.

[0135] Item 19: An electrophoretic assembly comprising, in order, a first release sheet, a first adhesive layer, an electro-optic material layer containing an electrophoretic medium as described in any one of items 1 to 15, a second adhesive layer, and a second release sheet.

[0136] Item 20: A method for producing an electrophoretic medium comprising a nonpolar liquid and a first type of charged particles, wherein the first type of charged particles has a core and a shell, and the method for producing the medium comprises: (a) preparing graphene oxide; (b) dispersing the graphene oxide in a polar organic solvent to prepare a graphene oxide dispersion; (c) adding an organic pigment to the graphene oxide dispersion to prepare an organic pigment-graphene oxide dispersion; (d) mixing the organic pigment-graphene oxide dispersion to prepare an organic pigment-graphene oxide complex in the polar organic solvent; (e) adding a metal oxide precursor and a reagent to the organic pigment-graphene oxide complex in the polar organic solvent to prepare a dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer, wherein the metal oxide layer contains a metal oxide; (f) adding an organosilane reagent to the dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer to prepare the organic pigment-graphene oxide complex having a metal oxide layer and an organosilane layer (g) a step of preparing a dispersion of particles containing a complex, wherein the organosilane layer has an organosilane and the organosilane is covalently bonded to the metal oxide; (h) a step of separating the particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer from the polar organic solvent; (i) a step of washing the particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer with a solvent; (j) a step of transferring the washed particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer to a nonpolar liquid to prepare a dispersion of the particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer in the nonpolar liquid; (k) a step of adding a monomer or macromonomer to the dispersion of particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer in the nonpolar liquid; and (k) polymerizing the monomer.A method comprising the step of reacting the organosilane in the organosilane layer of particles comprising the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer with the macromonomer to prepare a dispersion containing the first type of charged particles in a nonpolar liquid, wherein each of the first type of charged particles comprises the organic pigment-graphene oxide complex having the metal oxide layer, the organosilane layer and the polymer layer, the polymer layer comprising a polymer, and the polymer being covalently bonded to the organosilane in the organosilane layer.

Claims

1. An electrophoretic medium comprising a plurality of first type charged particles and a nonpolar liquid, wherein each of the plurality of first type charged particles has a core and a shell. The core comprises a first type of organic pigment having a surface and a graphene oxide layer containing graphene oxide, wherein the graphene oxide layer is in contact with the surface of the first type of organic pigment. An electrophoretic medium wherein the shell comprises an organosilane layer and a polymer layer, the organosilane layer comprises an organosilane, the polymer layer comprises a polymer, and the organosilane in the organosilane layer of the shell is covalently bonded to the polymer in the polymer layer.

2. An electrophoretic medium according to claim 1, further comprising a metal oxide layer containing a metal oxide, wherein the metal oxide layer is disposed between the graphene oxide layer and the organosilane layer.

3. The electrophoretic medium according to claim 2, wherein the metal oxide layer comprises aluminum oxide, silica, titanium dioxide, zirconium oxide, zinc oxide, or a mixture thereof.

4. The metal oxide of the first type of charged particles is formed on the graphene oxide layer by a reaction between a metal oxide precursor and a reagent, the reagent reacts with the metal oxide precursor to form the metal oxide of the metal oxide layer, the metal oxide of the metal oxide layer is in contact with the graphene oxide of the graphene oxide layer, and the metal oxide precursor is trimethylaluminum, triethylaluminum chloride, diethylaluminum chloride, trimethoxyaluminum, triethoxyaluminum, dimethylaluminum propoxide, aluminum triisopropoxide, tributoxyaluminum, tris(dimethylamino)aluminum, tris(diethylamino)aluminum, tris(propylamino)aluminum, aluminum trichloride, trichlorosilane, hexachlorodisilane, silicon tetrachloride, tetramethoxysilane, tetraethoxysilane, tris(tert-pentoxy)silanol, tetraisocyanatesilane, tetrachlorosilane (silicon The electrophoretic medium according to claim 2, wherein the reagent is selected from the group consisting of tertrachoride, tris(methylamino)silane, tris(ethylamino)silane, titanium tetrachloride, titanium tetraiodide, tetramethoxytitanium, tetraethoxytitanium, titanium isopropoxide, tetrakis(methylamino)titanium, tetrakis(ethylamino)titanium, dimethylzinc, diethylzinc, methylzinc isopropoxide, zirconium tetrachloride, zirconium tetraiodide, tetramethoxyzirconium, tetraethoxyzirconium, tetraisopropoxyzirconium, tetrabutoxyzirconium, tetrakis(methylamino)zirconium, tetrakis(ethylamino)zirconium, and mixtures thereof, and the reagent is selected from the group consisting of water, oxygen, ozone, ammonia, and mixtures thereof, and the organosilane in the organosilane layer is covalently bonded to the metal oxide in the metal oxide layer.

5. The electrophoretic medium according to claim 2, wherein the organosilane layer is formed from an organosilane reagent, the organosilane reagent contains a first functional group, and the first functional group of the organosilane reagent reacts with the metal oxide of the metal oxide layer to form a covalent bond between the organosilane of the organosilane layer and the metal oxide of the metal oxide layer of the first type of charged particle.

6. The electrophoretic medium according to claim 5, wherein the first functional group of the organosilane reagent is selected from the group consisting of alkoxy, alkylamino, halide, hydrogen, and hydroxyl.

7. The electrophoretic medium according to claim 1, wherein the polymer in the polymer layer is formed from macromonomers or from polymerization of monomers.

8. The electrophoretic medium according to claim 7, wherein the organosilane reagent comprises a second functional group, the macromonomer or monomer comprises a third functional group, and the second functional group reacts with the third functional group to form a covalent bond between the organosilane in the organosilane layer and the polymer in the polymer layer of the first type of charged particles.

9. The electrophoretic medium according to claim 8, wherein the second functional group of the organosilane reagent is selected from the group consisting of epoxy, vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, amino, hydroxy, carboxy, alkoxy groups, and chlorides.

10. The electrophoretic medium according to claim 8, wherein the third functional group of the monomer or macromonomer is selected from the group consisting of vinyl, vinylbenzyl, acryloyl, methacryloyl, methacryloxyalkyl, epoxy, amino, hydroxy, carboxy, and chloride.

11. The electrophoretic medium according to claim 8, wherein the second functional group of the organosilane is vinyl, and the third functional group of the macromonomer or monomer is vinylbenzyl.

12. The electrophoretic medium according to claim 1, further comprising a plurality of second type charged particles, a plurality of third type charged particles, and a plurality of fourth type charged particles.

13. The electrophoretic medium according to claim 12, wherein each of the plurality of second types of charged particles comprises a second type of organic pigment, each of the plurality of third types of charged particles comprises a third type of organic pigment, and each of the plurality of fourth types of charged particles comprises an inorganic pigment.

14. The electrophoretic medium according to claim 1, wherein the first type of organic pigment is selected from the group consisting of azo pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, isoindoline pigments, anthranone pigments, indanthron pigments, carbon black pigments, rhodamine pigments, benzamine pigments, carbon black pigments, and mixtures thereof.

15. The first type of organic pigment, the second type of organic pigment, and the third type of organic pigment are independently C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 60 and 79; Pigment Red 2, 4, 5, 9, 12, 14, 38, 48:2, 48:3, 48:4, 52:2, 53:1, 57:1, 81, 112, 122, 144, 146, 147, 149, 168, 170, 176, 177, 179, 184, 185, 187, 188, 208, 209, 210, 214, 242, 254, 255, 257, 262, 264, 282 and 285; C.I. Pigment Violet 1, 19, 23 and 32; C.I. Pigment Yellow 1, 3, 12, 13, 14, 15, 16, 17, 73, 74, 81, 83, 97, 109, 110, 111, 120, 126, 127, 137, 138, 139, 150, 151, 154, 155, 174, 175, 176, 180, 181, 184, 191, 194, 213 and 214; C.I. Pigment Green 7 and 36; C.I. Pigment Black 1 and 7; C.I. The electrophoretic medium according to claim 13, selected from the group consisting of pigment brown 25, 32, 41; pigment orange 5, 13, 34, 36, 38, 43, 61, 62, 64, 68, 67, 72, 73, and 74, and mixtures thereof.

16. A first light-transmitting electrode layer, An electro-optical material layer comprising the electrophoretic medium described in claim 1, The second electrode layer and Electrophoresis devices, including those mentioned above.

17. The electrophoretic device according to claim 16, wherein the electrophoretic medium of the electro-optic material layer is encapsulated in a plurality of microcapsules or a plurality of microcells.

18. A first light-transmitting electrode layer, An electro-optical material layer comprising the electrophoretic medium described in claim 1, Adhesive layer, Release sheet and An electrophoresis assembly containing the following in order.

19. The first release sheet, The first adhesive layer, An electro-optical material layer comprising the electrophoretic medium described in claim 1, A second adhesive layer, The second release sheet and An electrophoresis assembly containing the following in order.

20. A method for producing an electrophoretic medium comprising a nonpolar liquid and a first type of charged particles, wherein the first type of charged particles has a core and a shell, and the method for producing the medium is Steps to prepare graphene oxide, A step of preparing a graphene oxide dispersion by dispersing the aforementioned graphene oxide in a polar organic solvent, A step of preparing an organic pigment-graphene oxide dispersion by adding an organic pigment to the aforementioned graphene oxide dispersion, The steps include: mixing the organic pigment-graphene oxide dispersion to prepare an organic pigment-graphene oxide complex in the polar organic solvent; A step of preparing a dispersion of particles containing the organic pigment-graphene oxide complex having a metal oxide layer by adding a metal oxide precursor and a reagent to the organic pigment-graphene oxide complex in the polar organic solvent, wherein the metal oxide layer contains a metal oxide, A step of preparing a dispersion of particles containing the organic pigment-graphene oxide complex having the metal oxide layer, by adding an organosilane reagent to the dispersion of particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer, wherein the organosilane layer contains organosilane, and the organosilane is covalently bonded to the metal oxide. A step of separating the particles containing the organic pigment-graphene oxide composite having the metal oxide layer and the organosilane layer from the polar organic solvent, A step of washing the particles containing the organic pigment-graphene oxide composite having the metal oxide layer and the organosilane layer with a solvent, A step of transferring the washed particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer to a nonpolar liquid to prepare a dispersion of the particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer in the nonpolar liquid. The steps include adding monomers or macromonomers to the dispersion of particles containing the organic pigment-graphene oxide composite having the metal oxide layer and the organosilane layer in the nonpolar liquid, and A step of preparing a dispersion containing the first type of charged particles in a nonpolar liquid by polymerizing the monomer or reacting the organosilane in the organosilane layer of the particles containing the organic pigment-graphene oxide complex having the metal oxide layer and the organosilane layer with the macromonomer, wherein each of the first type of charged particles contains the organic pigment-graphene oxide complex having the metal oxide layer, the organosilane layer and the polymer layer, the polymer layer contains a polymer, and the polymer is covalently bonded to the organosilane in the organosilane layer. Methods that include...

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