Electro-optic device

Abstract

An electro-optic device is disclosed, comprising a first transparent electrode layer, an electro-optic material layer, a durable conductive adhesive layer, and a second electrode layer. The adhesive layer comprises acrylic resin, conductive filler, and polymer dispersant.

Description

Technical Field

[0001] Related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 618,497, filed January 8, 2024, the entire contents of which, together with all other patents and patent applications disclosed herein, are incorporated herein by reference.

[0002] Invention Field This invention relates to an electro-optic device comprising a durable conductive adhesive layer. The adhesive layer is formed from a solvent-based adhesive composition comprising an acrylic resin, conductive filler particles, and a dispersant. Prior Technology

[0003] When applied to materials or displays, the term "electro-optic" is used here in its conventional sense in imaging technology, referring to a material having different first and second display states in at least one optical property, which is altered from its first to its second display state by applying an electric field to the material. While this optical property is typically color that can be distinguished by the human eye, it can be another optical property, such as light transmittance, reflectivity, luminescence; or, in the case of a display intended for machine reading, false color in the sense of a change in reflectivity at electromagnetic wavelengths outside the visible light range.

[0004] The term "gray state" is used here in its conventional sense in imaging technology, referring to a state between two extreme optical states of a pixel, and does not necessarily imply a black-to-white transition between these two extreme states. For example, several E Ink patents and published applications described below describe electrophoretic displays where the extreme states are white and dark blue, such that the intermediate "gray state" would actually be light blue. More precisely, as already mentioned, this change in optical state may not be a color change at all. The terms "black" and "white" may be used below to indicate two extreme optical states of a display, and it should be understood that this normally includes extreme optical states that are not strictly black and white, such as the aforementioned white and dark blue states. The term "monochrome" may be used hereafter to indicate a driving scheme that drives pixels only to their two extreme optical states without a gray state occurring in between.

[0005] Some electro-optic materials are solid in the sense that they have a solid outer surface, although the material may and often does indeed have internal spaces filled with liquid or gas. For convenience, displays using solid-state electro-optic materials will henceforth be referred to as "solid-state electro-optic displays." Therefore, the term "solid-state electro-optic display" includes rotating dual-color component displays, encapsulated electrophoretic displays, microcellular electrophoretic displays, and encapsulated liquid crystal displays.

[0006] The terms "bistable" and "bistable" are used herein in their art-known sense, referring to a display comprising display elements having at least one optically distinct first and second display states, such that after any provided element has been driven to its assumed first or second display state by an addressing pulse of a finite duration, the state remains for a period of time after the addressing pulse has terminated, which is at least several times, for example, at least four times, the minimum period of the addressing pulse required to change the state of the display element. It has been shown in U.S. Patent No. 7,170,670 that some particle-based electrophoretic displays with grayscale capability are stable not only in their extreme black and white states but also in their intermediate gray states, and that some other types of electro-optic displays have the same property. Although for convenience the term "bistable" may be used herein to encompass both bistable and multistable displays, this type of display is properly referred to as "multistable" rather than bistable.

[0007] One type of electro-optic display that has been the subject of intensive research and development for several years is the particle-based electrophoretic display, in which multiple charged particles move through a fluid under the influence of an electric field. Compared with liquid crystal displays (LCDs), electrophoretic displays offer advantages such as good brightness and contrast, wide viewing angles, state bistableness, and low power consumption. However, long-term image quality issues have hindered their widespread use. For example, the particles constituting an electrophoretic display tend to settle, leading to a shorter lifespan for these displays.

[0008] As mentioned above, the electrophoretic medium requires the presence of a fluid. In most prior art electrophoretic media, this fluid system is liquid, but a gaseous fluid can be used to manufacture the electrophoretic medium; 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. Patent Nos. 7,321,459 and 7,236,291. When the medium is used in an orientation that allows for this sedimentation, for example, in a sign where the medium is positioned in a vertical plane, this gas-based electrophoretic medium appears to be susceptible to the same type of problems due to particle sedimentation as liquid-based electrophoretic media. More precisely, particle sedimentation in gas-based electrophoretic media exhibits more severe problems than in liquid-based media because the lower viscosity of gaseous suspensions allows for faster electrophoretic particle sedimentation compared to liquids.

[0009] Numerous patents and applications belonging to or in the name of the Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC, and related companies describe various techniques used in encapsulated and microcellular electrophoresis and other electro-optic media. This encapsulated electrophoresis medium comprises a plurality of microcapsules, each containing an inner phase of electrophoretically moving particles in a fluid medium, and a capsule wall surrounding the inner phase. Typically, these capsules are themselves housed within a polymer binder to form a coherent layer between two electrodes. In microcellular electrophoresis displays, the charged particles and the fluid are not encapsulated within microcapsules, but rather retained within a plurality of cavities formed in a carrier medium, typically a polymer membrane. [[Hereinafter, the term "microcavity electrophoresis display" may be used to encompass both encapsulated and microcellular electrophoresis displays]]. The techniques described in these patents and applications include:

[0010] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 5,961,804; 6,017,584; 6,120,588; 6,120,839; 6,262,706; 6,262,833; 6,300,932; 6,323,989; 6,377,387; 6,515,649; 6,538,801; 6,580,545; 6,652,075; 6,693,620; 6,721,083; 6,727,881; 6,822,782; 6,831,771; 6,870,661; 6,927,892; 6,956,690; 6,958,849; 7 ,002,728;7,038,655;7,052,766;7,110,162;7,113,323;7,141,688;7,142,351;7,170,670;7,226,550;7,230,750;7,230,751;7,236,290;7,277, 218;7,286,279;7,312,916;7,382,514;7,390,901;7,473,782;7,561,324;7,583,251;7,572,394;7,576,904;7,580,180;7,679,814;7,848,006;7 ,903,319;8,018,640;8,115,729;8,257,614;8,270,064;8,363,306;8,390,918;8,582,196;8,654,436;8,902,491;8,961,831;9,052,564;9,341, 915;9,348,193;9,361,836;9,366,935;9,372,380;9,382,427;9,423,666;9,428,649;9,557,623;9,670,367;9,671,667;9,688,859;9,726,957;9 ,752,034;9,765,015;9,778,535;9,778,537;9,835,926;9,953,588;9,995,987;10,025,157;10,031,394;10,040,954;10,061,123;10,062,337;1 0,147,366; and 10,514,583; and U.S. Patent Application Publication Nos. 2003 / 0048522; 2003 / 0151029; 2003 / 0164480; 2004 / 0030125; 2004 / 0105036; 2005 / 0012980; 2009 / 0009852;2011 / 0217639; 2012 / 0049125; 2013 / 0161565; 2013 / 0193385; 2013 / 0244149; 2013 / 0063333; 2014 / 0011913; 2014 / 0078576; 2014 / 0104674; 2014 / 0231728; 2015 / 0177590; 2015 / 0185509; 2015 / 0241754; 2015 / 0301425; and 2016 / 0170106;

[0011] (b) Capsules, adhesives, and encapsulation methods; see, for example, U.S. Patent Nos. 5,930,026; 6,067,185; 6,130,774; 6,262,706; 6,327,072; 6,392,786; 6,459,418; 6,727,881; 6,839,158; 6,866,760; 6,922,276; 6,958,848; 6,987,603; 7,110,164; 7,1 48,128;7,184,197;7,304,634;7,327,511;7,339,715;7,411,719;7,477,444;7,561,324;7,910,175;7,952,790;8,129,655;8,446,664; and U.S. Patent Application Publication Nos. 2005 / 0156340; 2007 / 0091417; and 2009 / 0122389;

[0012] (c) Microcellular structures, wall materials, and methods for forming microcells; see, for example, U.S. Patent Nos. 6,672,921; 6,751,007; 6,753,067; 6,781,745; 6,788,452; 6,795,229; 6,806,995; 6,829,078; 6,850,355; 6,865,012; 6,870,6 62;6,885,495;6,930,818;6,933,098;6,947,202;7,046,228;7,072,095;7,079,303;7,141,279;7,156,945;7,205,355;7,233,429;7,261,920;7,271,947;7,304, 780;7,307,778;7,327,346;7,347,957;7,470,386;7,504,050;7,580,180;7,715,087;7,767,126;7,880,958;8,002,948;8,154,790;8,169,690;8,441,432;8,891 ,156;9,279,906;9,291,872;9,388,307;9,436,057;9,436,058;9,470,917;9,919,553; and 10,401,668; and U.S. Patent Application Publication Nos. 2003 / 0203101; 2014 / 0050814; and 2016 / 0059442;

[0013] (d) A method for filling and sealing microcells; see, for example, U.S. Patent Nos. 6,545,797; 6,788,449; 6,831,770; 6,833,943; 6,930,818; 7,046,228; 7,052,571; 7,166,182; 7,347,957; 7,374,634; 7,385,751; 7,408,696; 7,557,981; 7,560,004 ;7,564,614;7,572,491;7,616,374;7,715,087;7,715,088;8,361,356;8,625,188;8,830,561;9,346,987; and 9,759,978; and U.S. Patent Application Publication Nos. 2002 / 0188053; 2004 / 0120024; 2004 / 0219306; and 2015 / 0098124;

[0014] (e) Films and sub-components containing electro-optic materials; see, for example, U.S. Patent Nos. 6,825,829; 6,982,178; 7,110,164; 7,158,282; 7,554,712; 7,561,324; 7,649,666; 7,728,811; 7,826,129; 7,839,564; 7,843,6 21; 7,843,624; 7,952,790; 8,034,209; 8,177,942; 8,390,301; 9,238,340; 9,470,950; 9,835,925; and U.S. Patent Application Publication Nos. 2005 / 0122563; 2007 / 0237962; and 2011 / 0164301;

[0015] (f) Backplanes, adhesive layers, and other auxiliary layers and methods used in displays; see, for example, U.S. Patent Nos. D485,294;5,930,026;6,120,588;6,124,851;6,177,921;6,232,950;6,252,564;6,312,304;6,312,971;6,376,828;6,392,786;6,413,790;6,480,182;6,498,114;6,506,438;6,518,949;6,545,291;6,639,578;6,657,772;6,664,944;6,683,333;6 710,540;6,724,519;6,816,147;6,819,471;6,825,068;6,831,769;6,842,279;6,842,657;6,865,010;6,873,452;6,909,532;6,967,640;7,012,6 00;7,012,735;7,030,412;7,075,703;7,106,296;7,110,163;7,116,318;7,148,128;7,167,155;7,173,752;7,176,880;7,190,008;7,206,119;7, 223,672;7,230,751;7,256,766;7,259,744;7,301,693;7,304,780;7,327,346;7,327,511;7,347,957;7,365,733;7,388,572;7,401,758;7,492,4 97;7,535,624;7,551,346;7,554,712;7,560,004;7,583,427;7,649,674;7,667,886;7,672,040;7,688,497;7,826,129;7,830,592;7,839,564;7, 880,958;7,893,435;7,905,977;7,952,790;7,986,450;8,034,209;8,049,947;8,072,675;8,120,836;8,159,636;8,177,942;8,237,892;8,362,4 88;8,395,836;8,437,069;8,441,414;8,456,589;8,514,168;8,547,628;8,576,162;8,610,988;8,714,780;8,743,077;8,754,85​​9;8,797,258;8,797,633;8,797,636;9,147,364;9,025,234;9,025,238;9,030,374;9,140,​​952;9,201,279;9,223,164;9,238,340;9,285,648;9,454,057;9,529,240;9,620,066; 9,632,373;9,666,142;9,671,635;9,715,155;9,777,201;9,897,891;10,037,735;10,190,743;10,324,577;10,365,533;10,372,008;10,446,585;10,466,565;10,495 ,941;10,503,041;10,509,294;10,613,407; and U.S. Patent Application Publication Nos. 2002 / 0060321;2004 / 0085619;2004 / 0105036;2005 / 0122306;2005 / 0122563;2006 / 0255322;2009 / 0122389;20 10 / 0177396; 2011 / 0164301; 2011 / 0292319; 2014 / 0192000; 2014 / 0210701; 2014 / 0368753; and 2016 / 0077375; and international application publication numbers WO2000 / 038000; WO2000 / 005704; and WO1999 / 067678;

[0016] (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 6,017,584; 6,545,797; 6,664,944; 6,788,452; 6,864,875; 6,914,714; 6,972,893; 7,038,656; 7,038,670; 7,046,228; 7,052,571; 7,075,502; 7,167,155; 7,385,751; 7,492,505; 7,667,684; 7,684,108; 7,791,789; 7,800,813; 7,821,702; 7,839,564; 7,910,175; 7,952 ,790;7,956,841;7,982,941;8,040,594;8,054,526;8,098,418;8,159,636;8,213,076;8,363,299;8,422,116;8,441,714;8,441,716;8,466,852 ;8,503,063;8,576,470;8,576,475;8,593,721;8,605,354;8,649,084;8,670,174;8,704,756;8,717,664;8,786,935;8,797,634;8,810,899;8,83 0,559;8,873,129;8,902,153;8,902,491;8,917,439;8,964,282;9,013,783;9,116,412;9,146,439;9,164,207;9,170,467;9,170,468;9,182,646;9,195,111;9,199,441;9,268,191;9,285,649;9,293,511;9,341,916;9,360,733;9,361,836;9,383,623; and 9,423,666; and U.S. Patent Application Publication No. 2008 / 00433 18;2008 / 0048970;2009 / 0225398;2010 / 0156780;2011 / 0043543;2012 / 0326957;2013 / 0242378;2013 / 0278995;2014 / 0055840;2014 / 0078576;2014 / 0340430;2014 / 0340736;2014 / 0362213;2015 / 0103394;2015 / 0118390;2015 / 0124345;2015 / 0198858;2015 / 0234250;2015 / 0268531;2015 / 0301246;2016 / 0011484; 2016 / 0026062; 2016 / 0048054; 2016 / 0116816; 2016 / 0116818; and 2016 / 0140909;

[0017] (h) A method for driving a display; see, for example, U.S. Patent Nos. 5,930,026; 6,445,489; 6,504,524; 6,512,354; 6,531,997; 6,753,999; 6,825,970; 6,900,851; 6,995,550; 7,012,600; 7,023,420; 7,034,783; 7,061,166; 7,061,662; 7,116,466; 7,119,772; 7,177,066; 7,193,625; 7,202,847; 7,242,514; 7,259,744; 7,304,787; 7 ,312,794;7,327,511;7,408,699;7,453,445;7,492,339;7,528,822;7,545,358;7,583,251;7,602,374;7,612,760;7,679,599;7,679,813;7,68 3,606;7,688,297;7,729,039;7,733,311;7,733,335;7,787,169;7,859,742;7,952,557;7,956,841;7,982,479;7,999,787;8,077,141;8,125,50 1;8,139,050;8,174,490;8,243,013;8,274,472;8,289,250;8,300,006;8,305,341;8,314,784;8,373,649;8,384,658;8,456,414;8,462,102;8 ,514,168;8,537,105;8,558,783;8,558,785;8,558,786;8,558,855;8,576,164;8,576,259;8,593,396;8,605,032;8,643,595;8,665,206;8,68 1,191;8,730,153;8,810,525;8,928,562;8,928,641;8,976,444;9,013,394;9,019,197;9,019,198;9,019,318;9,082,352;9,171,508;9,218,7 73;9,224,338;9,224,342;9,224,344;9,230,492;9,251,736;9,262,973;9,269,311;9,299,294;9,373,289;9,390,066;9,390,661;and9,412,314;and U.S. patent application publication numbers 2003 / 0102858; 2004 / 0246562; 2005 / 0253777; 2007 / 0091418; 2007 / 0103427; 2007 / 0176912; 2008 / 0024429; 2008 / 0024482; 2008 / 0136774; 2008 / 0291129; 2008 / 0303780; 2009 / 0174651; 2009 / 0195568;2 009 / 0322721;2010 / 0194733;2010 / 0194789;2010 / 0220121;2010 / 0265561;2010 / 0283804;2011 / 0063314;2011 / 0175875;2011 / 0193840;2011 / 0193841;2011 / 0199671;2011 / 0221740;2012 / 0001957;2012 / 0098740;2 013 / 0063333;2013 / 0194250;2013 / 0249782;2013 / 0321278;2014 / 0009817;2014 / 0085355;2014 / 0204012;2014 / 0218277;2014 / 0240210;2014 / 0240373;2014 / 0253425;2014 / 0292830;2014 / 0293398;2014 / 0333685;2 014 / 0340734; 2015 / 0070744; 2015 / 0097877; 2015 / 0109283; 2015 / 0213749; 2015 / 0213765; 2015 / 0221257; 2015 / 0262255; 2015 / 0262551; 2016 / 0071465; 2016 / 0078820; 2016 / 0093253; 2016 / 0140910; and 2016 / 0180777;

[0018] (i) Applications of displays; see, for example, U.S. Patent Nos. 6,118,426; 6,473,072; 6,704,133; 6,710,540; 6,738,050; 6,825,829; 7,030,854; 7,119,759; 7,312,784; 7,705,824; 8,009,348; 8,011,592; 8,064,962; 8,162,212; 8,553,012; 8,973,837; 9,188,829 ; and 9,197,704; and U.S. Patent Application Publication Nos. 2002 / 0090980; 2004 / 0119681; 2007 / 0285385; 2013 / 0176288; 2013 / 0221112; 2013 / 0233930; 2013 / 0235536; 2014 / 0049808; 2014 / 0062391; 2014 / 0206292; and 2016 / 0035291; and International Application Publication No. WO00 / 36560; and

[0019] (j) Non-electrophoretic displays, such as those described in U.S. Patent Nos. 6,241,921; 6,784,953; 6,795,138; 6,914,713; 6,950,220; 7,095,477; 7,182,830; 7,245,414; 7,420,549; 7,471,369; 7,576,904; 7,580,180; 7,850,867; 8,018,643; 8,023,071; 8,282,762; 8,319,759; and 8, See, for example, U.S. Patent Application Publications 2005 / 0099575; 2006 / 0262249; 2007 / 0042135; 2007 / 0153360; 2008 / 0020007; 2012 / 0293858; and 2015 / 0277160; and applications of encapsulation and microcell technology other than displays, see, for example, U.S. Patent No. 7,615,325; and U.S. Patent Application Publications 2015 / 0005720 and 2016 / 0012710.

[0020] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thus producing a so-called polymer dispersion electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete electrophoretic fluid droplets and a continuous polymeric material phase, and the discrete electrophoretic fluid droplets within this polymer dispersion electrophoretic display can be considered as capsules or microcapsules even without discrete capsule films associated with each individual droplet; see, for example, the aforementioned U.S. Patent No. 6,866,760. Therefore, for the purposes of this application, this polymer dispersion electrophoretic medium is considered a subtype of encapsulated electrophoretic media.

[0021] Although electrophoretic media are often opaque (because, for example, in many electrophoretic media, these particles substantially impede visible light from passing through the display) and operate in reflective mode, many electrophoretic displays can operate in so-called "shutter mode," in which one display state is substantially opaque and another is translucent. See, for example, U.S. Patent Nos. 5,872,552, 6,130,774, 6,144,361, 6,172,798, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, which are similar to electrophoretic displays but rely on changes in electric field strength, can operate in a similar mode; see U.S. Patent No. 4,418,346. Other types of electro-optic displays may also operate in shutter mode. In the multi-layer structure of a full-color display, an electro-optic medium operating in shutter mode can be useful; in such a structure, at least one layer adjacent to the viewing surface of the display operates in shutter mode to expose or hide a second layer further away from the viewing surface.

[0022] Encapsulated electrophoretic displays typically do not suffer from the clustering and settling failure modes of conventional electrophoresis apparatus and offer further advantages, such as the ability to print or coat displays on a wide variety of flexible and rigid substrates. Therefore, the resulting display is flexible. Furthermore, because the display medium can be printed (using various methods), the display itself can be manufactured inexpensively.

[0023] An electrophoretic display typically comprises a layer of electrophoretic material and at least two other layers disposed on opposite sides of the electrophoretic material, one of which is an electrode layer. In most of these displays, both layers are electrode layers, and one or both of these electrode layers are patterned to define pixels of the display. For example, one electrode layer may be patterned as an elongated column electrode, and the others may be patterned as elongated row electrodes arranged at right angles to the column electrode, the pixels being defined by the intersections of the column and row electrodes. Alternatively and more commonly, one electrode layer has a single continuous electrode configuration, and the other electrode layers are designed as a pixel electrode matrix, each defining a pixel of the display. In another type of electrophoretic display intended to use a stylus, printhead, or similar movable electrode separate from the display, only one of the layers adjacent to the electrophoretic layer contains an electrode, and the layer on the opposite side of the electrophoretic layer is typically a protective layer intended to prevent the movable electrode from damaging the electrophoretic layer.

[0024] The manufacture of a three-layer electrophoretic display typically involves at least one lamination operation. For example, several of the aforementioned MIT and E Ink patents and applications describe a method for manufacturing an encapsulated electrophoretic display in which an encapsulated electrophoretic medium containing capsules in an adhesive is coated onto a flexible substrate, wherein the flexible substrate comprises an indium tin oxide (ITO) or similar conductive coating on a plastic film (which acts as an electrode of the final display); the capsule / adhesive coating is dried to form a coherent layer of electrophoretic medium firmly bonded to the substrate. Separately, a backplate containing an array of pixel electrodes and appropriately arranged conductors is prepared to connect the pixel electrodes to a drive circuit system. To form the final display, the substrate with the capsule / adhesive layer is laminated to the backplate using a lamination adhesive. (A very similar method can be used to prepare an electrophoretic display that can use a stylus or similar movable electrodes, replacing the backplate with a simple protective layer such as a plastic film on which a stylus or other movable electrodes can slide). In a preferred embodiment of this method, the backplane itself is flexible and is fabricated by printing the pixel electrodes and conductors onto a plastic film or other flexible substrate. A significant lamination technique used in the mass production of displays via this method is roll lamination with a laminating adhesive.

[0025] An electro-optic display typically comprises a layer of electro-optic material and at least two other layers disposed on opposite sides of the electro-optic material, one of which is an electrode layer. In most of these displays, both layers are electrode layers, and one or both of these electrode layers are patterned to define pixels of the display. For example, one electrode layer may be patterned as an elongated column electrode, and the others may be patterned as elongated row electrodes arranged at right angles to the column electrode, the pixels being defined by the intersections of the column and row electrodes. Alternatively and more commonly, one electrode layer has a single continuous electrode configuration, and the other electrode layers are designed as a pixel electrode matrix, each defining a pixel of the display. In another type of electrophoretic display intended to use a stylus, printhead, or similar movable electrode separate from the display, only one of these layers adjacent to the electrophoretic layer contains an electrode, and the layer on the opposite side of the electro-optic layer is typically a protective layer intended to prevent the movable electrode from damaging the electrophoretic layer.

[0026] The manufacture of three-layer electro-optic displays typically involves at least one lamination operation. For example, several of the aforementioned MIT and E Ink patents and applications describe a method for manufacturing encapsulated electrophoretic displays, which involves coating an encapsulated electrophoretic medium containing capsules in an adhesive onto a flexible substrate, wherein the flexible substrate is a plastic film containing an indium tin oxide (ITO) or similar conductive coating (which acts as an electrode of the final display); drying the capsule / adhesive coating to form a coherent layer of electrophoretic medium firmly bonded to the substrate.

[0027] The aforementioned U.S. Patent No. 6,982,178 describes a method well-suited for mass production of assembling solid-state electro-optic displays (including encapsulated electrophoretic displays). Essentially, this patent describes a so-called "front planar laminate" ("FPL") which sequentially comprises a light-transmitting conductive layer; a solid electro-optic dielectric layer electrically in contact with the conductive layer; an adhesive layer; and a release liner. Typically, the light-transmitting conductive layer is supported on a preferably flexible light-transmitting substrate, wherein, in a sense, the substrate can be manually wound around a drum with a diameter (approximately) 10 inches (254 mm) without permanent deformation. In this patent and herein, the use of the term "transmittance" means that the indicated layer transmits light sufficient to allow an observer to see through the layer in order to observe changes in the display state of the electro-optic medium, wherein such changes are normally visible through the conductive layer and the adjacent substrate (if present); in cases where the electro-optic medium shows changes in reflectivity at non-visible wavelengths, the term "transmittance" should of course be interpreted as transmission at the associated non-visible wavelengths. The substrate is typically a polymer film and typically has a thickness ranging from about 1 to about 25 mils (25 to 634 µm), preferably from about 2 to about 10 mils (51 to 254 µm). The conductive layer is suitably a thin metal or metal oxide layer, such as aluminum or ITO, or may be a conductive polymer. Poly(ethylene terephthalate) (PET) films coated with aluminum or ITO are commercially available, for example, "Aluminized Mylar" ("Mylar" is a registered trademark) from EI du Pont de Nemours & Company, Wilmington DE, and this commercial material can be used in front-plane laminates with good results.

[0028] An assembly of an electro-optic display using a previously planar laminate can be secured to the backplate by removing the release liner from the front planar laminate and allowing the adhesive layer to contact the backplate while effectively adhering it to the backplate. This ensures that the adhesive layer, electro-optic dielectric layer, and conductive layer are fixed to the backplate. This method is well-suited for mass production because the front planar laminate can typically be mass-produced using roll-to-roll coating technology and then cut into segments of any size required for use with a specific backplate.

[0029] U.S. Patent No. 7,561,324 describes a so-called "dual release sheet," which is essentially a simplified version of the planar laminate mentioned earlier in U.S. Patent No. 6,982,178. One form of dual release sheet includes a solid electro-optic dielectric layer sandwiched between two adhesive layers, one or both of which are covered by the release sheet. Another form of dual release sheet includes a solid electro-optic dielectric layer sandwiched between two release sheets. Both forms of dual release films are intended for use in methods substantially similar to those used in assembling electro-optic displays from a previously described front planar laminate, but involve two separate laminations; typically, in the first lamination, the dual release sheet is laminated to a front electrode to form a first component; then in the second lamination, the first component is laminated to a backplate to form the final display; however, the order of these two laminations can be reversed if necessary.

[0030] U.S. Patent No. 7,839,564 describes a so-called "inverted front planar laminate," which is a variation of the previous planar laminate described in the aforementioned U.S. Patent No. 6,982,178. This inverted front planar laminate sequentially comprises at least one of a light-transmitting protective layer and a light-transmitting conductive layer; an adhesive layer; a solid electro-optic dielectric layer; and a release liner. This inverted front planar laminate is used to form an electro-optic display having a single adhesive layer between the electro-optic layer and the front electrode or front substrate; a second, typically thin adhesive layer may or may not be present between the electro-optic layer and the backplate. This electro-optic display combines good resolution with good low-temperature performance.

[0031] The aforementioned 2007 / 0109219 also describes various methods designed to manufacture electro-optic displays in high-volume production using inverted front-plane laminates; a preferred form of these methods is the "multi-up" method, which is designed to allow the lamination of multiple electro-optic display components at a time.

[0032] When compared to liquid crystal displays (LCDs), which typically require transparent substrates on both sides of the liquid crystal medium, such as glass, the electrophoretic medium and the display tend to be mechanically robust. Several of the aforementioned E Ink patents and applications describe methods for manufacturing electrophoretic displays, which involve coating an electrophoretic medium onto a flexible plastic substrate having a conductive layer, and laminating the resulting electrophoretic medium / substrate sub-assemblies onto a backplate including an electrode matrix to form the final display. Furthermore, the aforementioned U.S. Patent No. 6,825,068 describes a backplate useful in electrophoretic displays, primarily composed of stainless steel foil coated with polyimide. This technology can produce flexible electrophoretic displays that are less susceptible to breakage than glass-based LCDs.

[0033] However, although electrophoretic displays are mechanically robust, they can be damaged under extreme stress, such as when a portable electrophoretic display is dropped or comes into contact with heavy objects, for example, in a travel bag. Typically, this failure occurs due to mechanical fracture of the capsule wall in the case of capsule-based displays, or due to fracture of the continuous phase in polymer dispersion displays. Either type of failure allows the internal phase of the electrophoretic medium (electrophoretic particles and surrounding fluid) to migrate within the display. Typically, the laminated adhesive layer is adjacent to the electrophoretic medium, and fluid dissolves in this adhesive layer, leaving electrophoretic particles as non-switching regions with no optical activity, causing visual defects in any image subsequently written onto the display. Therefore, there is a need to improve the mechanical robustness of the electrophoretic medium and the display to reduce the occurrence of this visual defect.

[0034] Electro-optic displays manufactured using the aforementioned front-plane laminates or double release films typically have a lamination layer between the electro-optic layer and the backplane, and the presence of this lamination layer affects the electro-optic characteristics of the display. In particular, the conductivity of this lamination layer affects both the display's low-temperature performance and resolution. The display's low-temperature performance can (empirically) be improved by increasing the conductivity of the lamination layer, for example, by doping the layer with tetrabutylammonium hexafluorophosphate or other materials, as described in the aforementioned U.S. Patent Nos. 7,012,735 and 7,173,752. However, increasing the conductivity of the lamination layer in this way tends to increase pixel diffusion (the phenomenon where the area of ​​the electro-optic layer that changes its optical state in response to voltage changes at the pixel electrode is larger than the pixel electrode itself), and this diffusion tends to reduce the display's resolution. Therefore, this type of display inherently requires a compromise between low-temperature performance and display resolution, and in practice, low-temperature performance is usually sacrificed.

[0035] In the method described above, vacuum lamination can advantageously be used to laminate the substrate carrying the electro-optic layer to the backing plate. Vacuum lamination effectively removes air between the two materials to be laminated, thus avoiding unwanted air bubbles in the final display, which can introduce undesirable artifacts into the image produced by the display. However, vacuum laminating the two parts of the electro-optic display in this manner imposes some stringent requirements on the laminating adhesive used, especially in the case of displays using encapsulated electrophoretic media. The laminating adhesive should have sufficient adhesive strength to bond the electro-optic layer to the layer to be laminated (typically the electrode layer), and in the case of encapsulated electrophoretic media, the adhesive should also have sufficient adhesive strength to mechanically hold these capsules together. If the electro-optic display is flexible (and one of the important advantages of rotating dual-color components and encapsulated electrophoretic displays is that they can be made flexible), the adhesive should have sufficient flexibility so as not to introduce defects into the display when the display flexes. The laminating adhesive should possess suitable flow properties at the lamination temperature to ensure high-quality lamination. In this respect, the requirements for laminating encapsulated electrophoresis and certain other types of electro-optic media are particularly challenging. The lamination is performed at a temperature not exceeding approximately 130°C, as the medium cannot be exposed to substantially higher temperatures without damage. However, the adhesive flow must cope with the rather uneven surface of the encapsulated layer, the irregularity provided by the underlying capsules. More precisely, the lamination temperature should be kept as low as possible, ideally room temperature lamination, but no commercially available adhesives have been found that allow for this room temperature lamination. The laminating adhesive should be chemically compatible with all other materials in the display.

[0036] As discussed in detail in the aforementioned U.S. Patent No. 6,831,769, the laminating adhesives used in electro-optic displays must meet certain electrical criteria, which introduces considerable problems in the selection of laminating adhesives. Commercial manufacturers of laminating adhesives naturally expend considerable effort to ensure that the properties of these adhesives, such as adhesive strength, and lamination temperatures are adjusted so that the adhesive performs well in its primary applications, which typically include laminated polymers and similar films. However, in these applications, the electrical properties of these laminating adhesives are irrelevant, and therefore commercial manufacturers disregard these electrical properties. More precisely, in some electrical properties, substantial variations (up to several times) can occur between different batches of the same commercial laminating adhesive, presumably because the manufacturer attempts to optimize the non-electrical properties of the laminating adhesive (e.g., resistance to bacterial growth) and is completely unconcerned about the resulting variations in electrical properties.

[0037] The lamination process used to manufacture electro-optic displays imposes stringent requirements on the mechanical and electrical properties of the laminating adhesive. A typical electro-optic display includes an adhesive layer disposed between the electro-optic material layer and one or two electrode layers. For robust devices, this adhesive layer must be durable and resistant to the formation of voids (i.e., delamination) over time. Voids create visible defects in the image on the display and reduce the device's lifespan. The problem of void formation can be exacerbated when the device is used outdoors in extreme temperature and humidity conditions. The inventors of this invention have surprisingly discovered that an extremely durable conductive adhesive layer can be formed by a composition comprising an acrylic resin, a conductive filler such as carbon black, and a polymeric dispersant having a molecular structure, wherein the polymeric dispersant has a molecular structure containing a polyalkylimide polymer backbone or a styrene-maleic anhydride copolymer backbone and two or more side chains, at least one of which contains a functional group selected from the group consisting of: aromatics, esters, amides, aminos, quaternary ammonium groups, hydroxyl groups, carboxylic acids, and polyepoxides.

[0038] As mentioned above, the adhesive layer is disposed between the electrodes of the device, wherein the electrodes apply an electric field necessary to change the electrical state of the electro-optic medium. Therefore, the electrical properties of the adhesive are crucial. If the resistivity of the adhesive layer is too high, a substantial voltage drop will occur within the adhesive layer, requiring an increase in the voltage across the electrodes, and consequently increasing power consumption. If the resistivity of the adhesive layer adjacent to the pixel electrode is too low (that is, if the conductivity is too high), crosstalk will occur between the adjacent pixel electrodes, reducing the display resolution and resulting in poor image quality.

[0039] This phenomenon, known as halosing, refers to the tendency of applying a voltage to a pixel electrode to alter the optical state of the electro-optic medium over an area larger than the physical size of the pixel electrode. Because the conductivity of most materials increases rapidly with temperature, halosing becomes more pronounced at higher temperatures. Conversely, at low temperatures, the resulting reduced conductivity can decrease the speed of image switching or increase voltage drop and energy consumption. The inventors of this invention have surprisingly discovered that, compared to similar adhesive layers containing uncrosslinked resins, adhesive layers containing crosslinked acrylic resins, conductive fillers such as carbon black, and polymer dispersants exhibit a significantly smaller difference in resistivity at low and high temperatures. Therefore, using the adhesive layer of this invention reduces halosing at high temperatures, improving the optical performance of the device without significantly affecting switching speed and energy consumption at low temperatures. Summary of the Invention

[0040] In one embodiment, the present invention provides an electro-optic device comprising, sequentially, a first light-transmitting electrode layer, an electro-optic material layer, an adhesive layer, and a second electrode layer. The second electrode layer comprises a plurality of pixel electrodes. The electro-optic material layer comprises a microcell layer or a microcapsule layer.

[0041] The microcellular layer comprises a plurality of microcells and a sealing layer. Each microcell includes a base, a partition wall, and an opening. The sealing layer spans the opening of each microcell. Each microcell contains an electrophoretic medium comprising charged pigment particles in a nonpolar liquid. The adhesive layer is disposed between the sealing layer and the second electrode layer of the microcellular layer.

[0042] The microcapsule layer comprises a plurality of microcapsules and an adhesive. Each microcapsule contains an electrophoretic medium. The electrophoretic medium comprises charged pigment particles in a nonpolar liquid. The adhesive layer is disposed between the microcapsule layer and the second electrode layer.

[0043] The adhesive layer comprises: an acrylic resin in an amount of 30% to 90% by weight, based on the weight of the adhesive layer excluding volatile solvents; a conductive filler in an amount of 5% to 35% by weight, based on the weight of the adhesive layer excluding volatile solvents; and a polymer dispersant in an amount of 1% to 20% by weight, based on the weight of the adhesive layer excluding volatile solvents.

[0044] The acrylic resin of the adhesive layer can be crosslinked. The acrylic resin can be crosslinked with a metal acetopyruvate crosslinking agent. The metal acetopyruvate crosslinking agent can be titanium acetopyruvate or aluminum acetopyruvate. The acrylic resin can be crosslinked with a melamine derivative. The melamine derivative can contain functional groups selected from the group consisting of methoxymethyl and hydroxymethyl functional groups.

[0045] The conductive filler in the adhesive layer may be carbon black. The adhesive layer may also contain a rheology modifier, which may be a cellulose polymer.

[0046] The polymer dispersant of the adhesive layer has a molecular structure containing a polymer or copolymer backbone and two or more side chains. The polymer or copolymer backbone may be a styrene-maleic anhydride copolymer or a polyalkylimide polymer. At least one of the two or more side chains may contain a functional group selected from the group consisting of: aromatics, esters, amides, aminos, quaternary ammonium groups, hydroxyl groups, carboxylic acids, and polyepoxides. The average molecular weight of the polymer dispersant may be between 800 and 4000 g / mol.

[0047] In one specific example, the polymeric dispersant has a molecular structure containing a styrene-maleic anhydride copolymer backbone, and at least one of the two or more side chains may contain an amino functional group or a quaternary ammonium functional group. At least one of the two or more side chains may contain a quaternary ammonium group and a polyester side chain. At least one of the two or more side chains may contain polyethylene oxide, polypropylene oxide, or both polyethylene oxide and polypropylene oxide. At least one of the two side chains may contain an aromatic ring. The polymeric dispersant may have an amine value of 12 to 50 mg KOH / g or 15 to 30 mg KOH / g.

[0048] In another specific example, the polymeric dispersant has a molecular structure containing a polyalkylimide polymer backbone, and at least one of the two or more side chains contains an amino group or a quaternary ammonium functional group. The polyalkylimide polymer backbone may be a polyethylimide polymer backbone. At least one of the two or more side chains may contain an ester functional group and a polyethylene oxide functional group. At least one of the two or more side chains may contain polyethylene oxide, polypropylene oxide, or both polyethylene oxide and polypropylene oxide. At least one of the two side chains may contain an aromatic ring. The polymeric dispersant may have an amine value of 15 to 60 mg KOH / g, or an amine value of 35 to 50 mg KOH / g.

[0049] The adhesive layer can be formed by curing the adhesive composition, which includes acrylic resin, conductive filler, polymer dispersant and volatile solvent. The curing can be achieved by solvent evaporation.

[0050] The electrophoretic medium of the electro-optic device may contain first-type and second-type charged pigment particles. The first-type charged pigment particles may have a first charge polarity, and the second-type charged pigment particles may have a second charge polarity, which is opposite to the first charge polarity.

[0051] The electrophoretic medium of the electro-optic device may contain first, second, third, and fourth types of charged pigment particles. The first and third types of charged pigment particles may have a first charge polarity, and the second and fourth types of charged pigment particles may have a second charge polarity opposite to the first charge polarity. The first, second, and third types of charged pigment particles may contain organic pigments, and the fourth type of charged pigment particles may contain inorganic pigments.

[0052] The electrophoretic medium of the electro-optic device may contain first, second, third, and fourth types of charged pigment particles. The first, second, and third types of charged pigment particles may have a first charge polarity, and the fourth type of charged pigment particles may have a second charge polarity opposite to the first charge polarity. The first, second, and third types of charged pigment particles may contain organic pigments, and the fourth type of charged pigment particles may contain inorganic pigments. The first and second types of charged pigment particles may contain organic pigments, and the third and fourth types of charged pigment particles may contain inorganic pigments.

[0053] Various forms and specific examples of this application will be described with reference to the following figures. It should be understood that these figures are not necessarily drawn to scale. Simple Explanation of the Diagram

[0054] Figure 1 is a side view of a portion of an electro-optic device, which includes an electrophoretic medium encapsulated in a plurality of microcells. The device includes a first transparent electrode layer, a microcell layer, an adhesive layer, and a second electrode layer.

[0055] Figure 2 is a side view of a portion of an electro-optic device, which includes an electrophoretic medium encapsulated in a plurality of microcells. The device includes a first transparent electrode layer, an electrophoretic material layer, a first adhesive layer, and a second electrode layer.

[0056] Figure 3 is a side view of a portion of an electro-optic device, which includes an electrophoretic medium encapsulated in a plurality of microcells. The device includes a first transparent electrode layer, a second adhesive layer, an electrophoretic material layer, the first adhesive layer, and the second electrode layer.

[0057] Figure 4 shows a method for producing microcells for use in this invention using a roll-to-roll method.

[0058] Figures 5A and 5B detail the production of microcells for electro-optical display devices using photolithography exposure through a photomask coated with a thermosetting precursor.

[0059] Figures 5C and 5D detail alternative specific examples of using photolithography to fabricate microcells for electro-optical display devices. In Figures 5C and 5D, a combination of top and bottom exposure is used, such that the partition wall in one lateral direction is cured by exposure of the top photomask; and the partition wall in another lateral direction is cured by bottom exposure through the opaque substrate conductor film.

[0060] Figures 6A-6D illustrate the steps of filling and sealing the microcell array to be used in an electro-optical display device.

[0061] Figure 7 shows the skeletal structure of the styrene-maleic anhydride copolymer.

[0062] Figure 8 shows a schematic diagram of the reaction between the styrene maleic anhydride precursor polymer and the diamine.

[0063] Figure 9 shows the skeletal structure of the poly(ethylene ethylene imine) polymer.

[0064] Figure 10 is a graph showing the number of defects observed in the adhesive layers of Comparative Example 1 and Examples 2 and 3 after exposure to 85°C and 85% relative humidity for different numbers of days.

[0065] Figure 11 is a graph showing the number of defects observed in the adhesive layers of Comparative Example 4 and Example 5 after being exposed to 85°C and 85% relative humidity for different number of days.

[0066] Figure 12 shows photographic images of the adhesive layers of Comparative Examples 1 and 4, and Examples 2, 3 and 5 after exposure to 85°C and 85% relative humidity for 5 days and 10 days, respectively. Implementation

[0067] Detailed description of the invention The "quaternary ammonium functional group" is a functional group containing a positively charged nitrogen atom. The nitrogen atom of the quaternary ammonium is directly connected to four organic substituents; that is, the nitrogen of the quaternary ammonium functional group is not directly connected to a hydrogen atom.

[0068] The term "amino functional group" can refer to a primary amino functional group, a secondary amino functional group, or a tertiary amino functional group.

[0069] The polymer dispersant of the adhesive layer of the present invention has a molecular structure comprising a polymer or copolymer backbone and two or more side chains. The polymer or copolymer backbone may be a linear polymer or a branched polymer. The side chains of the molecular structure have functional groups that are different from the functional groups of the backbone.

[0070] The acrylic resin of the adhesive layer of this inventive electro-optic device can be crosslinked with a melamine derivative. Non-limiting examples of such melamine derivative crosslinking agents can be represented by Formula I, wherein R1 to R6 are selected from the group consisting of hydroxymethyl (-CH2OH) and methoxyalkyl (-CH2OR) groups, wherein R is an alkyl group. Commercial crosslinking agents of this type include Cymel® 303, which is a methoxymethyl-substituted melamine; and Cymel® 370, which is a methoxymethyl and hydroxymethyl-substituted melamine. Formula I

[0071] The acrylic resin of the adhesive layer of this inventive electro-optic device can be crosslinked with a metal acetylacetate crosslinking agent. Non-limiting examples of such crosslinking agents include titanium acetylacetate (Formula II) and aluminum acetylacetate (Formula III). Formula II Formula III

[0072] The adhesive composition used to form the adhesive layer may contain 0.5 to 9 weight percent of a crosslinking agent, based on the weight of the adhesive composition excluding volatile solvents. The adhesive composition may contain 0.7 to 8, 0.8 to 7, 0.9 to 6, or 1.0 to 5 weight percent of a crosslinking agent, based on the weight of the adhesive composition excluding volatile solvents.

[0073] An example of an inventive electro-optic device comprising microcells is illustrated in FIG1. ​​The electro-optic device of FIG1 sequentially comprises a first electrode layer 101, an electro-optic material layer 102, an adhesive layer 104, and a second electrode layer 103 comprising a plurality of pixel electrodes. The adhesive layer 104 connects the sealing layer 132 of the electro-optic material layer 102 to the second electrode layer 103. The electro-optic material layer 102 of the electro-optic display 100 comprises a plurality of microcells 112 and a sealing layer 132. Each of the plurality of microcells 112 has a bottom 142, a partition wall 152, and an opening, and the sealing layer 132 spans the opening of each microcell. Each of the plurality of microcells 112 comprises an electrophoretic medium 122. The electrophoretic medium 122 comprises a plurality of first-type particles 172 and a plurality of second-type particles 162 in a non-polar liquid. A viewer can view the image of the display 300 from the viewing side 150.

[0074] The micro-cell electro-optic device of Figure 3 may further include a light-transmitting front substrate (not shown in Figure 1) adjacent to the first electrode layer 101, wherein the electrode layer is disposed between the front substrate and the electro-optic material layer. The light-transmitting front substrate may be a plastic film, such as a polyethylene terephthalate (PET) sheet having a thickness of 25 to 200 µm. The light-transmitting front substrate may further include one or more additional layers, such as a protective layer for absorbing ultraviolet radiation, a barrier layer to prevent oxygen or moisture from entering the display, and an anti-reflective coating to improve the optical properties of the display.

[0075] Another example of this electro-optic device includes an electro-optic material layer comprising an electrophoretic medium encapsulated in microcapsules or microcells, as described in U.S. Patent No. 6,982,178. Figure 2 shows a side view of an example of the structure of a portion of an electro-optic display comprising microcapsules. The electro-optic display 200 includes: a first electrode layer 101 comprising light-transmitting electrodes, an electro-optic material layer 202, a first adhesive layer 104, and a second electrode layer 103, the second electrode layer comprising a plurality of pixel electrodes. The first adhesive layer 104 connects the electro-optic material layer 102 to the second electrode layer. The electro-optic material layer 202 comprises a plurality of microcapsules 212. Each microcapsule has a microcapsule wall and includes an electrophoretic medium 122 having particles in a nonpolar liquid. Typically, the plurality of microcapsules are retained within a polymeric adhesive 232. A viewer can view an image of the device 200 from a viewing side 250. The electro-optic material layer 100 can be constructed from a front plane laminate, as described in the background of the invention.

[0076] Another example of an electro-optic display is shown in Figure 3. Figure 3 illustrates a side view of an example of the basic structure of a portion of an electro-optic display having microcapsules. The electro-optic display 300 has a viewing side 350. It sequentially includes: a first electrode layer 101 containing light-transmitting electrodes, a second adhesive layer 105, an electro-optic material layer 202, a first adhesive layer 104, and a second electrode layer 103 containing a plurality of pixel electrodes. The second adhesive layer 105 connects the first electrode layer 101 to the electro-optic material layer 202. The first adhesive layer 104 connects the electro-optic material layer 202 to the second electrode layer. The electro-optic material layer 202 contains a plurality of microcapsules 212. Each microcapsule has a microcapsule wall and includes an electrophoretic medium 122 containing particles in a nonpolar liquid. Typically, the plurality of microcapsules are retained within a polymer adhesive 232. The electro-optic material layer 300 can be constructed from a dual release sheet as described above.

[0077] The microcapsule electro-optic displays of Figures 2 and 3 may further include a light-transmitting front substrate (not shown in Figures 2 and 3) adjacent to the first electrode layer 101, wherein the electrode layer is disposed between the front substrate and the electro-optic material layer (for the display of Figure 2) or between the front substrate and the second adhesive layer (for the display of Figure 3). The front substrate may be a plastic film, such as a polyethylene terephthalate (PET) sheet having a thickness of 25 to 200 µm. The front substrate may further include one or more additional layers, such as a protective layer for absorbing ultraviolet radiation, a barrier layer for preventing oxygen or moisture from entering the display, and an anti-reflective coating for improving the optical properties of the display.

[0078] In the electro-optic displays of Figures 1, 2 and 3, the first electrode layer may be a conductive layer with a thin, continuous coating of conductive material that has minimal intrinsic electromagnetic radiation absorption in the visible spectrum, such as indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS), graphene or similar materials.

[0079] The electrophoretic medium 122 of the electro-optic device illustrated in Figures 1, 2, and 3 comprises a plurality of first-type pigment particles and a plurality of second-type pigment particles. Each of the plurality of first-type particles comprises a core and a shell, the core comprising an organic pigment. Each of the plurality of second-type particles may also comprise an organic pigment. The electrophoretic medium 122 may further comprise a plurality of third-type particles and a plurality of fourth-type particles. The electrophoretic medium 122 may further comprise a plurality of fifth-type particles. That is, the electrophoretic medium 122 may comprise a plurality of first, second, third, and fourth-type particles. The electrophoretic medium 122 may comprise a plurality of first, second, third, fourth, and fifth-type particles. The second-type particles may also comprise an organic pigment. The content of electrophoretic particles in the nonpolar liquid can vary. For example, one type of particle may account for 0.1% to 50%, preferably 0.5% to 15%, based on the volume of the nonpolar liquid.

[0080] The electrophoretic medium of the present invention may contain a charge control agent (CCA). The CCA controls the charge on the electrophoretic particles. The CCA is a surfactant-like molecule having ionic or other polar groups, hereinafter referred to as head groups; and a nonpolar chain (typically a hydrocarbon chain), hereinafter referred to as tail. The CCA can recombine with or adsorb onto the charged particles. It is believed that the CCA forms invert cells in the electrophoretic medium. These are small groups of charged invert cells that contribute to conductivity in the medium. The invert cells contain a polar core, the size of which can vary from 1 nm to tens of nanometers, and can have spherical, cylindrical, or other geometric shapes surrounded by the nonpolar tail groups of the CCA molecules. Typically, three phases can be distinguished in the electrophoretic medium: solid particles with surfaces, a highly polar phase distributed in the form of tiny droplets (invert cells), and a continuous phase containing the nonpolar fluid. Both the electrophoretic particles and the charged invert cells can move through the fluid after an electric field is applied. Therefore, there are two parallel pathways for electrical conduction via the fluid (which typically has imperceptibly low conductivity). The charge control agent in the electrophoretic medium can be 0.1 to 8 wt%, 0.3 to 7 wt%, 0.5 to 5 wt%, 0.6 to 4 wt%, 0.7 to 3 wt%, or 0.8 to 2 wt% of the charge control agent, based on the weight of the electrophoretic medium.

[0081] The electrophoretic medium of this invention comprises particles suspended in a nonpolar liquid. This nonpolar liquid may be transparent and colorless. For high particle mobility, it preferably has a dielectric constant in the range of about 2 to about 30, more preferably about 2 to about 15. Examples of suitable dielectric solvents include hydrocarbons such as isoparaffins, decaline, 5-ethylidene-2-norbornene, fatty oils, and paraffin oils; silicone fluids; aromatic hydrocarbons such as toluene, xylene, phenylxylene ethane, dodecylbenzene, or alkylnaphthalene; halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorotrifluorotoluene, 3,4,5-trichlorotrifluorotoluene, chloropentafluorobenzene, dichlorononane, or pentachlorobenzene; and perfluorinated solvents such as FC-43, FC-70, or FC-5060 from 3M, St. Paul MN; low molecular weight halogenated polymers such as poly(perfluoropropylene oxide) from TCI America, Portland, Oregon; and poly(chlorotrifluoroethylene), such as Halocarbon from Halocarbon Product Corp., River Edge, NJ. Oils; perfluoropolyalkyl ethers, such as Galden from Ausimont or Krytox Oils and Greases K-Fluid series from DuPont, Delaware; polydimethylsiloxane polysiloxane oil (DC-200) from Dow-corning.

[0082] Microcells can be formed in batch processes or in a continuous roll-to-roll process, as disclosed in U.S. Patent No. 6,933,098. The latter provides a continuous, low-cost, high-volume manufacturing technique for producing compartments used in a variety of applications, including electro-optical display devices. Microcell arrays suitable for use in this invention can be produced using microimprinting, as illustrated in Figure 4. A male mold 402 can be placed on a web 404, as shown in Figure 4, or under the web 404 (not shown); however, alternative arrangements are possible. See U.S. Patent No. 7,715,088, the entire contents of which are incorporated herein by reference. A conductive substrate can be constructed by forming a conductive film 401 (first electrode) on a polymer substrate, wherein the polymer substrate will become a support for a device. Then, a composition 400 comprising a thermoplastic, thermosetting, or precursor thereof is coated on the conductive film. The thermoplastic or thermosetting precursor layer is imprinted using a mold in the form of a roller, plate, or conveyor belt at a temperature higher than the glass transition temperature of the thermoplastic or thermosetting precursor layer.

[0083] The thermoplastic or thermosetting precursors used for the preparation of microcells can be multifunctional acrylates or methacrylates, vinyl ethers, epoxides and their oligomers or polymers, and the like. Combinations of multifunctional epoxides and multifunctional acrylates are also very useful for achieving the desired physical-mechanical properties. Crosslinkable oligomers such as urethane acrylates or polyester acrylates can be added to improve the flexural resistance of the imprinted microcells. The composition may contain polymers, oligomers, monomers, and additives, or only oligomers, monomers, and additives. The glass transition temperature (or Tg) of this type of material is typically in the range of about -70°C to about 150°C, preferably about -20°C to about 50°C. The microimprinting method is typically carried out at temperatures above this Tg. The microimprinting temperature and pressure can be controlled using a heated die or a heated housing substrate (to which the die applies pressure).

[0084] As shown in Figure 4, the mold is released during or after the curing of the precursor layer to expose the array of microcells 403. Curing of the precursor layer can be achieved by cooling, solvent evaporation, or crosslinking by radiation, heat, or moisture. If the curing of the thermosetting precursor is achieved by UV radiation, UV light can radiate onto the transparent conductor film from the bottom or top of the mesh. Alternatively, the UV lamp can be placed inside the mold. In this case, the mold must be transparent to allow UV light to pass through the pre-patterned mold and irradiate the thermosetting precursor layer. The mold can be prepared by any suitable method, such as diamond turning or photoresist methods, followed by etching or electroplating. The master template for the mold can be manufactured by any suitable method, such as electroplating. In the case of electroplating, a thin layer of a submetal such as chromium ore (typically 3000 Å) is sputtered onto a glass substrate. Then, a photoresist layer is applied to the mold and it is exposed to UV light. A mask is placed between the UV and the photoresist layer. The exposed areas of the photoresist harden. The unexposed areas are then removed by cleaning with a suitable solvent. The remaining hardened photoresist is dried and a thin layer of a sub-metal is sputtered again. The master template is then ready for electroforming. A typical material used for electroforming is nickel-cobalt. Alternatively, the master template can be made from nickel by electroforming or electroless nickel deposition. The bottom layer of the template is typically between approximately 50 and 400 µm. The master template can also be made using other microengineering techniques, including electron beam writing, dry etching, chemical etching, laser writing, or laser interference, as described in "Replication techniques for micro-optics", SPIE Proc. Vol. 3099, pp.76-82 (1997). Alternatively, the template can be made using photomachining, using plastics, ceramics, or metals.

[0085] Before applying the UV-curable resin composition, the mold may be treated with a release agent to aid the demolding process. The UV-curable resin may be degassed before dispensing and may selectively contain a solvent. This solvent, if present, readily evaporates. The UV-curable resin is dispensed onto the mold by any suitable method such as coating, impregnation, or pouring. The dispenser may be mobile or stationary. A conductive film covers the UV-curable resin. If necessary, pressure may be applied to ensure proper adhesion between the resin and the plastic and to control the thickness of the underlying layer of the microcells. This pressure may be applied using laminating rollers, vacuum molding, pressurizing devices, or any other similar means. If the mold is metallic and opaque, the plastic substrate is typically transparent to the photochemical radiation used to cure the resin. Conversely, the mold may be transparent, and the plastic substrate may be opaque to this photochemical radiation. In order for the molded configuration to transfer well onto the transfer film, the conductor film needs to have good adhesion to the UV-curable resin, and the resin should have good release properties to the mold surface.

[0086] Photolithography. Photolithography can also be used to fabricate microcells. The photolithography process used to fabricate microcell arrays is illustrated in Figures 5A and 5B. As shown in Figures 5A and 5B, the microcell array 500 can be fabricated by exposing a radiation-curable material 501a coated onto a conductor film 502 by a known method to UV light (or alternatively, other forms of radiation, electron beams, and the like) through a mask 506 to form partition walls 501b corresponding to the image projected through the mask 506. The substrate conductor film 502 is preferably mounted on a support substrate mesh 503 that may contain plastic material.

[0087] In the photomask 506 of Figure 5A, the dark squares 504 represent the opaque areas, and the spaces between the dark squares represent the transparent areas 505 of the photomask 506. The UV irradiation reaches the radiation-curable material 502a via the transparent areas 505. Preferably, the exposure is performed directly on the radiation-curable material 502a, i.e., the UV radiation does not pass through the substrate 503 or the substrate conductor 502 (top exposure). For this reason, neither the substrate 503 nor the conductor 502 needs to be transparent to UV or other radiation wavelengths used.

[0088] As shown in Figure 5B, the exposed area 501b hardens, and then the unexposed area (protected by the opaque area 504 of the mask 506) is removed by a suitable solvent or developer to form microcells 507. The solvent or developer is selected from those commonly used to dissolve or reduce the viscosity of the radiation-curable material, such as methyl ethyl ketone (MEK), toluene, acetone, isopropanol, or the like. Similarly, the preparation of these microcells can be achieved by placing a photomask under the conductor film / substrate support mesh, in which case the UV light is irradiated from the bottom via the photomask, and the substrate needs to be radiation-transparent.

[0089] Imaging Exposure. Another alternative method for preparing the microcell array of the present invention by imaging exposure is illustrated in Figures 5C and 5D. When using opaque conductor lines, these conductor lines can be used as a photomask for bottom exposure. Additional exposure from the top through a second photomask having opaque lines perpendicular to the conductor lines forms durable microcell partitions. Figure 5C illustrates the fabrication of the microcell array 510 of the present invention using both top and bottom exposure principles. The substrate conductor film 512 is opaque and patterned with lines. The radiation-curable material 511a coated on the substrate conductor 512 and the substrate 513 is bottom exposed through the conductor line pattern 512 provided as a first photomask. A second exposure is performed from the "top" side through a second photomask 516 having a line pattern perpendicular to the conductor lines 512. The space 515 between these lines 514 is substantially transparent to UV light. In this process, the partition wall material 511b is cured from bottom to top in a transverse orientation and from top to bottom in a vertical orientation, thereby forming complete microcells 517. As shown in Figure 5D, the unexposed areas are then removed by a solvent or developer as described above to expose the microcells 517.

[0090] These microcells can be constructed from thermoplastic elastomers that have good compatibility with them and do not interact with the electrophoretic medium. Examples of useful thermoplastic elastomers include diblock, triblock, and multiblock copolymers of the ABA and (AB)n types, wherein A is styrene, α-methylstyrene, ethylene, propylene, or norbornene; B is butadiene, isoprene, ethylene, propylene, butene, dimethylsiloxane, or propylene sulfide; and A and B in the formula cannot be the same. The number n is ≥1, preferably 1-10. Diblock or triblock copolymers of styrene or ox-methylstyrene are particularly useful, such as SB (poly(styrene-b-butadiene)), SBS (poly(styrene-b-butadiene-b-styrene)), SIS (poly(styrene-b-isoprene-b-styrene)), SEBS (poly(styrene-b-ethylene / butene-b-styrene)), poly(styrene-b-dimethylsiloxane-b-styrene), poly((α-methylstyrene-b-isoprene), poly(α-methylstyrene-b-isoprene-b-α-methylstyrene), poly(α-methylstyrene-b-propenesulfide-b-α-methylstyrene), and poly(α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene). Commercially available styrene block copolymers are particularly useful, such as the Kraton D and G series (from Kraton). Polymer, Houston, Tex. Crystalline rubbers, such as poly(ethylene-co-propylene-co-5-methylene-2-norbornene); or EPDM (ethylene-propylene-diene terpolymer) rubbers, such as Vistalon 6505 (from Exxon Mobil, Houston, Tex.) and its graft copolymers, have also been found to be particularly useful.

[0091] The thermoplastic elastomer is soluble in a solvent or solvent mixture, wherein the solvent is immiscible with the display fluid in the microcell and has a lower specific gravity than the display fluid. For the overcoating composition, a low surface tension solvent is preferred because it has better wetting properties on the microcell septa and the electrophoretic fluid. A solvent or solvent mixture with a surface tension below 35 dynes / cm is preferred. A surface tension below 30 dynes / cm is even more preferred. Suitable solvents include alkanes (preferably C6-12 alkanes, such as heptane, octane, or Isopar solvent from Exxon Chemicals, nonane, decane, and their isomers), cycloalkanes (preferably C6-12 cycloalkanes, such as cyclohexane and naphthane, and their analogs), alkylbenzenes (preferably mono- or di-C1-6 alkylbenzenes, such as toluene, xylene, and their analogs), alkyl esters (preferably C2-5 alkyl esters, such as ethyl acetate, isobutyl acetate, and their analogs), and C3-5 alkyl alcohols (such as isopropanol, their analogs, and their isomers). Mixtures of alkylbenzenes and alkanes are particularly useful.

[0092] In addition to polymer additives, the polymer mixture may also include wetting agents (surfactants). Wetting agents (such as FC surfactants from 3M, Zonyl fluorinated surfactants from DuPont, fluoroacrylates, fluoromethyl acrylates, fluorinated long-chain alcohols, perfluorinated long-chain carboxylic acids and their derivatives, and Silwet polysiloxane surfactants from OSi, Greenwich, Conn.) may also be included in the composition to improve the adhesion of the sealant to the microcells and provide a more flexible coating method. Other components, including crosslinking agents (e.g., diazides, such as 4,4'-diazidodiphenylmethane and 2,6-di-(4'-azidobenzyl)-4-methylcyclohexanone), vulcanizing agents (e.g., 2-benzothiazole disulfide and tetramethylthiuram disulfide), multifunctional monomers or oligomers (e.g., hexanediol, diacrylate, trimethylolpropane, triacrylate, divinylbenzene, diallylphthalene), thermal initiators (e.g., dilauryl peroxide, benzyl peroxide), and photoinitiators (e.g., isopropyl thioxanthone (ITX), Irgacure 651 and Irgacure 369 from Ciba-Geigy), are also highly useful for improving the physical-mechanical properties of the sealant through crosslinking or polymerization reactions during or after the external coating process.

[0093] After fabrication of these microcells, they are filled with a suitable electrophoretic medium. The microcell array 640 can be prepared by any of the methods described above. As shown in cross-section in Figures 6A-6D, the microcell partition walls 661 extend upward from the substrate 663 to form the open cell. The microcells may include an undercoat 662 to passivate the mixture and prevent the microcell material from interacting with the mixture containing the electrophoretic medium 665.

[0094] Next, the microcells are filled with an electrophoretic medium 664 containing particles 665 in a nonpolar fluid. These microcells can be filled using various techniques. In some embodiments, a doctor blade coating method can be used to fill the microcells to the depth of the microcell septa 661. In other embodiments, inkjet microinjection can be used to fill the microcells. In still other embodiments, a microneedle array can be used to fill the microcell array.

[0095] As shown in Figure 6C, after filling, the microcells are sealed by applying polymer 1466, which forms the sealing layer. In some embodiments, the sealing method may include exposure to hot, dry air or UV radiation. The polymer 666 is compatible with the electrophoretic medium but is not fluidly dissolved by the electrophoretic medium 664. Therefore, the final microcell structure is largely unaffected by leakage and can withstand flexural deformation without delamination.

[0096] Iterative photolithography can be used to fill a variety of individual microcells with a desired electrophoretic medium. This method typically involves coating an array of empty microcells with a positively reactive photoresist layer; exposing the photoresist by imaging; selectively opening a number of microcells by developing the photoresist; filling the opened microcells with a desired mixture; and sealing the filled microcells by a sealing method.

[0097] After filling the microcells 660, a trimming layer 668 can be laminated onto the sealed array, preferably by pre-coating the trimming layer 668 with an adhesive layer, wherein the adhesive layer may be a pressure-sensitive adhesive, a hot-melt adhesive, or a heat, moisture, or radiation-curable adhesive. If the top conductor film is transparent to radiation, the laminated adhesive can be post-cured by radiation such as UV passing through the top conductor film.

[0098] The electro-optic device of the present invention sequentially comprises a first light-transmitting electrode layer, an electro-optic material layer, an adhesive layer, and a second electrode layer. The second electrode layer comprises a plurality of pixel electrodes. The electro-optic material layer comprises a microcell layer or a microcapsule layer. The adhesive layer comprises: an acrylic resin, the content of which is 30% to 90% by weight, based on the weight of the adhesive layer excluding volatile solvents; a conductive filler, the content of which is 5% to 35% by weight, based on the weight of the adhesive layer excluding volatile solvents; and a polymer dispersant, the content of which is 1% to 20% by weight, based on the weight of the adhesive layer excluding volatile solvents.

[0099] In a first specific example, the electro-optic device of the present invention includes an adhesive layer comprising a polymeric dispersant having a molecular structure containing a styrene-maleic anhydride copolymer backbone and two or more side chains. At least one of the two or more side chains contains an amine functional group or a quaternary ammonium functional group. The polymeric dispersant can be formed from a precursor polymer after one or more reaction steps. The precursor polymer of the first specific example is a styrene-maleic anhydride copolymer. An example of this copolymer is shown in FIG. 7. The precursor styrene-maleic anhydride copolymer provides the polymeric backbone of the polymeric dispersant. The precursor copolymer contains reactive anhydride functional groups, which can react with one or more reagents in one or more steps to form the polymeric dispersant. In particular, the styrene-maleic anhydride copolymer can react with a nucleophilic reagent. This reaction causes the anhydride carbonyl group to open, forming a side chain on the styrene-maleic anhydride backbone. The nucleophilic reagent may contain, for example, an amine functional group, a hydroxyl functional group, or a thiol functional group. Because the precursor styrene-maleic anhydride copolymer can be designed as a random or block copolymer, the resulting polymer dispersant can also have a random polymer or block copolymer backbone.

[0100] The side chains of the polymer dispersant of the first specific example may contain polyester. The side chains of the polymer dispersant of the first specific example may contain polyethylene oxide, polypropylene oxide, or both polyethylene oxide functional groups and polypropylene oxide. The side chains of the polymer dispersant of the first specific example may contain aromatic rings. These aromatic groups in the side chains are separate from the styrene aromatic rings of the polymer backbone. The polymer dispersant may have an amine value of 12 to 50 mg KOH / g, 15 to 30 mg KOH / g, or 18 to 25 mg KOH / g. The number average molecular weight of the polymer dispersant may be 500 to 10,000 g / mol, 600 to 6,000 g / mol, 800 to 4,000 g / mol, or 1,000 to 3,000 g / mol.

[0101] One type of reagent that can be used to form the side chains of this polymeric dispersant is a diamine. For example, 3-dimethylaminopropylamine ((CH3)2-N-(CH2)3-NH2) is a diamine comprising both primary and tertiary amino functional groups. This primary amine can react with the carbonyl group of the anhydride group of the styrene anhydride polymer to open the anhydride ring and form an SMA copolymer containing side chains. According to the reaction diagram in Figure 12, the additional equivalent of the diamine reacts with the SMA precursor polymer precursor to form a polymer, where q is 2 or higher. Although the reaction product of the diagram in Figure 8 suggests that the polymer of the product is a block copolymer, or more precisely, a block terpolymer, the polymer product may be a random terpolymer. The molecular structure of the polymeric dispersant of this first specific example may contain two, three, four or more different side chains. It is possible that all the maleic anhydride units of the precursor polymer may react with the diamine reagent to provide the ring-opening structure. Other reagents that can be used to react with the precursor polymer include hydroxylamines, such as, for example, 3-dimethylamino-1-propanol ((CH3)2-N-(CH2)3-OH). In this case, the hydroxyl group of the reagent is attached to one of the carbonyl groups of the anhydride (similar to the primary amine in this reaction), as shown in Figure 8. The product of the reaction between the diamine or hydroxylamine and the SMA precursor polymer can be reacted with an alkylating agent in a subsequent step to provide a positively charged quaternary ammonium functional group. Depending on the molar equivalent number of the alkylating agent associated with the tertiary amino group, one, two, or more tertiary amino groups can be converted into quaternary ammonium groups.

[0102] Another type of reagent that can be used to form a polymeric dispersant from the SMA is a hydroxycarboxylic acid. This hydroxycarboxylic acid can form a polyester polymer via condensation polymerization. The anhydride of the SMA precursor polymer participates in this condensation polymerization, resulting in a block copolymer having an SMA backbone and one, two, or more polyester side chains. The reaction mixture may also contain other reagents, such as glycols or polyols. For example, the reaction mixture may contain ethylene oxide, propylene oxide, polyethylene oxide, and / or polypropylene oxide to introduce additional functional groups into the side chains. As mentioned above, multiple reaction steps can be used to form various side chains in the same polymeric dispersant.

[0103] Other reagents can be used to form polymeric dispersants from the SMA. For example, as an alternative to the hydroxycarboxylic acid described above, a dicarboxylic acid (or a dicarboxylic acid derivative) combined with a diol can be used. This combination also forms a polyester polymer via condensation polymerization. The anhydride of the SMA precursor polymer participates in this condensation polymerization, resulting in a block copolymer having an SMA backbone and one, two, or more polyester side chains. The diol reagent can be ethylene oxide (-(CH2CH2-O)-), propylene oxide (-(CH-(CH3)-CH2-O)-), polyethylene oxide (-(CH2CH2-O)r-), and / or polypropylene oxide (-(CH-(CH3)-CH2-O)t-), where r and t are integers, which introduce ethylene oxide, propylene oxide, polyethylene oxide, and / or polypropylene oxide into the side chains. Various side chains can be formed in the same polymeric dispersant using multiple reaction steps. For example, the reagent in the reaction described above can be an aromatic reagent such as aniline, benzylamine, or benzyl alcohol, to introduce aromatic rings into the side chain of the polymer dispersant. In the case where the conductive filler is carbon black, aromatic rings can be beneficial because these aromatic rings are carbon black analog groups (forming non-covalent interactions with carbon black particles), increasing the storage stability of the adhesive composition used to form the adhesive layer.

[0104] In a second specific example, the electro-optic device of the present invention includes an adhesive layer comprising a polymeric dispersant having a molecular structure containing a polyalkylimide polymer backbone and two or more side chains. At least one of the two or more side chains may contain a functional group selected from the group consisting of: aromatics, esters, amides, aminos, quaternary ammonium groups, hydroxyl groups, carboxylic acids, and polyepoxides. The precursor polymer may be a polyalkylene ethyleneimide containing primary, secondary, and tertiary functional groups. Examples of this precursor polymer are provided in FIG9.

[0105] Various reagents can be used to react with the primary, secondary, and tertiary functional groups of the precursor polymer. These reagents must contain functional groups that react with amines, such as carboxylic acids, carboxylic anhydrides, carboxylic halides, etc. Multiple reaction steps can be used to introduce different side chains into the molecular structure of the polymer dispersant, as explained in the examples of the first specific example. For example, benzyl chloride can be used to introduce side chains with aromatic rings. The polymer dispersant of the second specific example may have an amine value of 15 to 60 mg KOH / g, 20 to 55 mg KOH / g, or 35 to 50 mg KOH / g.

[0106] Example.

[0107] Prepare an adhesive composition having the components summarized in Table 1.

[0108] Table 1: Adhesion components. Comparative Example 1 Example 2 Example 3 Comparative Example 4 Example 5 Ingredients Solvent-based acrylic resin Locktite Duro-Tak 230A [1] 62 72 72 Solvent-based acrylic resin Aroset 1930-Z-47 [2] 62 72 Carbon black[3] 27 27 27 27 twenty three BykJet 9133 polymer dispersant [4] 11 11 Disperbyk 2013 polymer dispersant [5] 6 Disperbyk 2155TF polymer dispersant [6] 6 6 Rheological modifier E100 [7] 0 1 1 0 1.5 Peel force (N / inch) 1.8 7.9 7.4 2.1 6.8 The defect 5 days later many Defects after 10 days many many

[0109] [1] Solvent-based acrylic composition supplied by Henkel.

[0110] [2] Solvent-based acrylic composition supplied by Bostic.

[0111] [3] Nipex 150 carbon black, supplied by Orian Engineered Carbons.

[0112] [4] A polymer dispersant having a molecular structure containing an alkylammonium salt of a high molecular weight polymer, supplied by Byk Chemie.

[0113] [5] A polymeric dispersant having a molecular structure containing an SMA backbone and side chains with quaternary ammonium groups, supplied by Byk Chemie.

[0114] [6] A polymeric dispersant having a molecular structure containing a poly(ethylene ethylimide) backbone and a polyethylene glycol polyester, supplied by Byk Chemie.

[0115] [7] Ethocel 100 rheological modifier.

[0116] Adhesive compositions were prepared by mixing the components of each embodiment (Comparative Examples 1 and 4, and Examples 2, 3 and 5). These adhesive compositions were used to prepare an adhesive film that adheres a sealing layer of a microcellular electro-optic device to a second electrode layer comprising a plurality of pixel electrodes. This adhesive layer was thermally prepared by solvent evaporation.

[0117] After the adhesive composition cured, the peel force required to cause delamination of the prepared device was evaluated using an Instron® tester and a peel angle of 90°. This peel force is provided in Table 1. Table 1 shows that the peel force required for the comparative examples is significantly lower than that for the inventive embodiments.

[0118] The apparatus was prepared by aging the adhesive composition at 85°C and 85% relative humidity after curing. Defects in each adhesive layer were observed at various time points. Figure 9 shows the defects of Comparative Example 1 and Inventive Examples 2 and 3 over time. Figure 10 shows the defects of Comparative Example 4 and Inventive Example 5 over time. Figures 9 and 10 show that the defects in the comparative examples are significantly more than those in the corresponding inventive examples. Micrographs of the adhesive layers of all examples were collected after aging for 5 and 10 days.

[0119] These images demonstrate the improvements achieved by using an innovative polymeric dispersant in the adhesive layer. Similarly, the innovative polymeric dispersant provides (i) stabilization of the conductive filler toward agglomeration and (b) adhesion promotion for both.

[0120] Another set of adhesive components was prepared, as summarized in Table 2. The inventive components contain a crosslinking agent. That is, the acrylate resin in this adhesive layer is crosslinked.

[0121] Adhesive compositions were prepared by mixing the components of each embodiment (Comparative Example 6 and Examples 7, 8, 9, and 10). These adhesive compositions were used to prepare an adhesive film that adheres a sealing layer of a microcellular electro-optic device to a second electrode layer comprising a plurality of pixel electrodes. The adhesive layer was thermally prepared by solvent evaporation.

[0122] Table 2: Adhesive components containing crosslinking agents. Comparative Example 6 Example 7 Example 8 Ingredients Solvent-based acrylic resin Locktite Duro-Tak 154AHS [8] 71.3 70.8 70.8 Carbon black[3] 23.0 23.0 23.0 Disperbyk 2013 polymer dispersant [5] 5.7 5.7 5.7 Crosslinking agent: titanium acetylacetonate 0.5 Crosslinking agent: aluminum acetopyruvate 0.5 Highly methylated melamine as a crosslinking agent [9] Melamine with partially methylated crosslinking agent

[10] Volume resistivity at 0°C (ohms*cm) 2.43 x 10¹¹ 2.47 x 10¹¹ 2.24 x 10¹¹ Volume resistivity (ohms*cm) at 25℃ 7.37 x 1010 9.37 x 1010 6.44 x 1010 Volume resistivity (ohms*cm) at 50℃ 5.29 x 109 1.72 x 1010 1.23 x 1010 Example 9 Example 10 Ingredients Solvent-based acrylic resin Locktite Duro-Tak 154AHS [8] 66.3 66.3 Carbon black[3] 23.0 23.0 Disperbyk 2013 polymer dispersant [5] 5.7 5.7 Crosslinking agent: titanium acetylacetonate Crosslinking agent: aluminum acetopyruvate Highly methylated melamine as a crosslinking agent [9] 5.0 Melamine with partially methylated crosslinking agent

[10] 5.0 Volume resistivity at 0°C (ohms*cm) 2.58 x 1011 2.44 x 10¹¹ Volume resistivity (ohms*cm) at 25℃ 1.46 x 10¹¹ 1.07 x 1011 Volume resistivity (ohms*cm) at 50℃ 1.93 x 1010 1.54 x 1010

[0123] [3] Nipex 150 carbon black, supplied by Orian Engineered Carbons.

[0124] [5] A polymeric dispersant having a molecular structure containing an SMA backbone and side chains with quaternary ammonium groups, supplied by Byk Chemie.

[0125] [8] A solvent-based acrylic composition supplied by Henkel; the acrylic resin of this composition has the same structure as the acrylic resin of the Locktite Duro-Tak 230A composition.

[0126] [9] Cymel® 303, supplied by Allnex.

[0127]

[10] Cymel® 370, supplied by Allnex.

[0128] The components of each embodiment (Comparative Example 6 and Examples 7, 8, 9 and 10) were mixed to prepare an adhesive composition. Using these adhesive compositions, an adhesive film was prepared that adheres a sealing layer of a microcellular electro-optic device and a second electrode layer comprising a plurality of pixel electrodes together. The adhesive layer was thermally prepared by solvent evaporation.

[0129] The volume resistivity of these adhesive layers was measured using a Keithley Model 8009 resistivity fixture and a Model 6571 electrometer. This apparatus allows the user to determine the volume resistivity of an individual film by applying an alternating voltage to the substrate and measuring the output current. The resistance of the sample is then calculated from the voltage and current. The method includes coating the adhesive composition, curing the film, and conditioning the film at 25°C for 4 days. The thickness of the conditioned adhesive film was measured at desired temperatures (0°C, 25°C, and 50°C) and at 55% RH, and the film was placed on the substrate of the electrometer. This apparatus allows the user to determine the volume resistivity of an individual film by applying an alternating voltage to the substrate and measuring the output current. The resistance of the sample is then calculated from the voltage and current.

[0130] Table 3 shows the volume resistivity of all adhesive layers (Comparative Example 6 and Inventive Examples 7-10). However, the volume resistivity of Comparative Example 6 at 50°C (5.29 x 100⁹ ohms*cm) is significantly lower than that of all Inventive Examples 7, 8, 9, and 10 (1.72 x 10¹⁰ ohms*cm, 1.23 x 10¹⁰ ohms*cm, 1.93 x 10¹⁰ ohms*cm, and 1.54 x 10¹⁰ ohms*cm, respectively). This means that the inventive electro-optic device having an adhesive layer containing cross-linked acrylic resin exhibits better electro-optic performance (less dispersion).

[0131] 100: Electro-optical display 101: First electrode layer 102: Electro-optic material layer 103: Second electrode layer 104: Adhesive layer / First adhesive layer 105: Second adhesive layer 112: microcell 122: Electrophoretic medium 132: Sealing layer 142: Bottom 150: Viewing side 152: Partition wall 162: Second Type Particle 172: Type I Particles 200: Electro-optical display / device 202: Electro-optic material layer 212: Microcapsules 232: Polymer adhesives 250: Viewing side 300: Electro-optical display 350: Viewing side 400: Compositions comprising thermoplastics, thermosettings, or precursors thereof. 401: Conductive film 402:Male model 403: Microcell 404:net 500: Microcell Array 501a: Radiation-curable materials 501b: Partition wall 502: Conductor film / substrate conductor film / substrate conductor / conductor 503: Supported substrate mesh / substrate 504: Dark square / opaque area 505: Transparent Area 506: Mask / Light Mask 507: Microcell 510: Microcell Array 511a: Radiation-curable materials 511b: Partition wall material 512: Substrate conductor film / substrate conductor / conductor line pattern / conductor line 513: Substrate 514: Line 515: Space 516: Second Light Mask 517: Microcell 640: Microcell Array 660: Microcell 661: Microcellular septum 662: Primer Coating 663: Substrate 664: Electrophoretic medium 665: Particles 666: Polymer 668: Repair Layer

Claims

1. An electro-optic device, comprising, in sequence: a first light-transmitting electrode layer; an electro-optic material layer; an adhesive layer; and a second electrode layer, the second electrode layer comprising a plurality of pixel electrodes; wherein the electro-optic material layer comprises a microcell layer or a microcapsule layer; wherein the microcell layer comprises a plurality of microcells and a sealing layer, each of the plurality of microcells comprising a microcell bottom, a partition wall, and an opening, the sealing layer spanning the opening of each microcell, each of the plurality of microcells containing an electrophoretic medium comprising charged pigment particles in a non-polar liquid, the adhesive layer being disposed between the sealing layer of the microcell layer and the second electrode layer; wherein the microcapsule layer comprises a plurality of microcapsules and an adhesive, each of the plurality of microcapsules containing an electrophoretic medium comprising charged pigment particles in a non-polar liquid, the adhesive layer being disposed between the microcapsule layer and the second electrode layer; wherein the adhesive layer comprises: The adhesive layer comprises: an acrylic resin, in a content of 30% to 90% by weight, excluding the weight of the adhesive layer containing volatile solvents; a conductive filler, in a content of 5% to 35% by weight, excluding the weight of the adhesive layer containing volatile solvents; and a polymer dispersant, in a content of 1% to 20% by weight, excluding the weight of the adhesive layer containing volatile solvents, the polymer dispersant having a molecular structure containing a polymer or copolymer backbone and two or more side chains, the polymer backbone being a styrene-maleic anhydride copolymer or a polyalkylene imine polymer, and at least one of the two or more side chains containing a functional group selected from the group consisting of: aromatics, esters, amides, aminos, quaternary ammonium groups, hydroxyl groups, carboxylic acids, and polyepoxides.

2. The electro-optical device of claim 1, wherein the acrylic resin is cross-linked.

3. The electro-optical device as claimed in claim 2, wherein the acrylic resin is cross-linked with a metal acetylacetonate cross-linking agent.

4. The electro-optical device of claim 3, wherein the metal acetopyruvate crosslinking agent is titanium acetopyruvate or aluminum acetopyruvate.

5. The electro-optical device as claimed in claim 2, wherein the acrylic resin is cross-linked with a melamine derivative.

6. The electro-optical device of claim 5, wherein the melamine derivative contains a functional group selected from the group consisting of methoxymethyl and hydroxymethyl functional groups.

7. The electro-optical device of claim 1, wherein the conductive filler is carbon black.

8. The electro-optical device of claim 1, wherein the polymer dispersant has an average molecular weight of 800 to 4000 g / mol.

9. The electro-optic device of any one of claims 1 to 8, wherein the molecular structure of the polymer dispersant contains a styrene-maleic anhydride copolymer backbone, and at least one of the two or more side chains contains an amino functional group or a quaternary ammonium functional group.

10. The electro-optical device of claim 9, wherein at least one of the two or more side chains contains a quaternary ammonium group and a polyester side chain.

11. The electro-optical device of claim 9, wherein at least one of the two or more side chains contains polyethylene oxide, polypropylene oxide, or both polyethylene oxide and polypropylene oxide.

12. The electro-optical device of claim 9, wherein at least one of the two side chains contains an aromatic ring.

13. The electro-optical device of claim 9, wherein the polymeric dispersant has an amine value of 12 to 50 mg KOH / g.

14. The electro-optic device of any one of claims 1 to 8, wherein the molecular structure of the polymer dispersant contains a polyalkylimide polymer backbone, and at least one of the two or more side chains contains an amine group or a quaternary ammonium functional group.

15. The electro-optical device of claim 14, wherein the polyalkylimide polymer backbone has a polyethylimide polymer backbone.

16. The electro-optical device of claim 15, wherein at least one of the two or more side chains contains an ester functional group and a polyethylene oxide functional group.

17. The electro-optical device of claim 15, wherein at least one of the two or more side chains contains polyethylene oxide, polypropylene oxide, or both polyethylene oxide and polypropylene oxide.

18. The electro-optical device of claim 14, wherein at least one of the two side chains contains an aromatic ring.

19. The electro-optical device of claim 14, wherein the polymer dispersant has an amine value of 5 to 60 mg KOH / g for the crosslinking agent.

20. The electro-optical device of claim 1, wherein the adhesive layer is formed by curing an adhesive composition comprising the acrylic resin, the conductive filler, the polymer dispersant and the volatile solvent, the curing being achieved by solvent evaporation.

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