A variable light transmission device comprising microcells

Abstract

A variable light transmission device is disclosed, which can mitigate negative aperture diffraction effects and exhibit good switching speed between open and closed optical states. The device includes a micro-unit layer disposed between two light-transmitting electrode layers. The micro-unit layer has a plurality of micro-units, each micro-unit including an electrophoretic medium, and each micro-unit including a channel and a protrusion structure, the protrusion structure including a conical geometry.

Description

Technical Field

[0001] [Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 664,321, filed June 26, 2024, the entire contents of which are incorporated herein by reference, together with all other patents and patent applications disclosed herein.

[0002] This invention relates to a variable light transmission device. Specifically, it relates to a micro-unit electro-optic device comprising an electrophoretic medium having charged pigment particles and a non-polar liquid. The electrophoretic medium can be switched between optical states using an electric field. The variable light transmission device can adjust the amount of light passing through it and other electromagnetic radiation. It can be used in mirrors, windows, skylights, and similar items. For example, this invention can be applied to windows that can regulate the amount of light entering buildings and vehicles. Examples of electrophoretic media that can be incorporated into various embodiments of the present invention include, for example, those described in U.S. Patent Nos. 7,116,466, 7,327,511, 8,576,476, 10,319,314, 10,809,590, 10,067,398, 10,067,398 and 11,143,930, and U.S. Patent Application Publications Nos. 2014 / 0055841, 2017 / 0351155, 2017 / 0235206, 2011 / 0199671, 2020 / 0355979, 2020 / 0272017, 2021 / 0096439, and U.S. Patent Application No. 17 / 953,386, filed September 27, 2022, the entire contents of which are incorporated herein by reference. Prior Technology

[0003] Particle-based electrophoretic displays have been a subject of intensive research for years, in which multiple charged pigment particles move through a suspended fluid under the influence of an electric field. Compared to liquid crystal displays, such displays offer superior brightness and contrast, wider viewing angles, dual stability, and lower power consumption.

[0004] The terms "bistable" and "bistability" are used herein in their conventional sense to refer to a display comprising display elements having first and second display states that are different in at least one optical property, and to present either the first or second display state after any given element is driven by an addressing pulse of finite duration, and that state persists at least several times, for example, at least four times, after the addressing pulse terminates; the addressing pulse requires a minimum duration to change the state of the display element. Published U.S. Patent Application No. 2002 / 0180687 shows that some particle-based electrophoretic displays with grayscale capabilities are stable not only in their extreme black and white states but also in their intermediate gray states, and the same is true for some other types of electro-optical displays. This type of display may be appropriately called multi-stable rather than bistable, but for convenience, the term "bistable" may be used herein to encompass both bistable and multi-stable displays.

[0005] As mentioned above, electrophoretic media require the presence of a suspending fluid. In most conventional electrophoretic media, this suspending system is liquid, but gaseous suspending fluids can be used to produce electrophoretic media. When the medium is used in a configuration that allows particle settling (e.g., in the case of media arranged in a vertical plane), such gas-based electrophoretic media appear to be susceptible to the same type of problems caused by particle settling as liquid-based electrophoretic media. More precisely, particle settling appears to be a more severe problem in gas-based electrophoretic media than in liquid-based electrophoretic media because the lower viscosity of gaseous suspending fluids allows charged pigment particles to settling more rapidly than in liquid suspending fluids.

[0006] Numerous patents and applications, assigned 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 microcell electrophoresis and other electro-optic media. Encapsulated electrophoretic media comprise a plurality of small capsules, each capsule including an internal phase containing electrophoretically moving particles in a liquid medium and a capsule wall surrounding the internal phase. Typically, these capsules are held in a polymer binder to form a coherent layer between two electrodes. In microcell electrophoretic displays, charged pigment particles and liquid are not encapsulated within microcapsules but are retained within a plurality of cavities formed in a carrier medium (typically a polymer film). The techniques described in these patents and applications include: (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 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; 7,0 02,728;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;7,277,21 8;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;7,9 03,319;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;9,341,9 15;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;10,147,366; and 10,514,583; and U.S. Patent Application Publications 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; (b) Capsules, binders, and encapsulation processes; see, for example, U.S. Patents 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; 7,14 U.S. Patent Application Publications Nos. 8,128; 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 Publications Nos. 2005 / 0156340; 2007 / 0091417; and 2009 / 0122389; (c) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patents 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; 6,870,66 2;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;7,304,7 80;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, U.S. Patent Application Publications Nos. 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 Publications Nos. 2003 / 0203101, 2014 / 0050814, and 2016 / 0059442; (d) Methods 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 U.S. Patent Application Publications Nos. 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 Publications Nos. 2002 / 0188053; 2004 / 0120024; 2004 / 0219306; and 2015 / 0098124; (e) Thin films and subassemblies containing electro-optic materials; see, for example, U.S. Patents 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 U.S. Patent Application Publications Nos. 843,621, 7,843,624, 7,952,790, 8,034,209, 8,177,942, 8,390,301, 9,238,340, 9,470,950, and 9,835,925; and U.S. Patent Application Publications Nos. 2005 / 0122563, 2007 / 0237962, and 2011 / 0164301; (f) Backplates, adhesive layers, and other auxiliary layers used in displays, and methods thereof; 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;10,495,9 41;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;201 Applications Nos. 0 / 0177396, 2011 / 0164301, 2011 / 0292319, 2014 / 0192000, 2014 / 0210701, 2014 / 0368753, and 2016 / 0077375; and International Application Publications Nos. WO2000 / 038000, WO2000 / 005704, and WO1999 / 067678; (g) Color formation and color adjustment; see, for example, U.S. Patents 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;8,830 ,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 / 004331 8;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; (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; 7,3 12,794;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;7,683, 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;8,125,501 ;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;8,681 ,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;9,218,77 3;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; and 9,412,314;And U.S. Patent Application Publications Nos. 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;20 13 / 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;20 14 / 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; (i) Applications of displays; see, for example, U.S. Patents 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 Publications 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 WO 00 / 36560; and (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 8,99 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 packaging and microcell technologies other than displays; see, for example, U.S. Patent No. 7,615,325; and U.S. Patent Application Publications 2015 / 0005720 and 2016 / 0012710.

[0007] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in a capsule-type electrophoretic medium can be replaced by a continuous phase, thereby producing a so-called polymer dispersion electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete droplets of a nonpolar liquid and a continuous phase of polymeric material, and even without discrete capsule membranes associated with each individual droplet, the electrophoretic medium of the discrete droplets within such a polymer dispersion electrophoretic display can be considered as capsules or microcapsules; see, for example, the aforementioned U.S. Patent Application Publication No. 2002 / 0131147. Thus, for the purposes of this application, such polymer dispersion electrophoretic media are considered a subtype of capsule-type electrophoretic media.

[0008] One related type of electrophoretic display is the so-called "microcell electrophoretic display." In a microcell electrophoretic display, instead of encapsulating charged pigment particles and a suspension of liquid in microcapsules, they are held in multiple cavities formed within a carrier medium (e.g., a polymer film). See, for example, International Application Publication No. WO 02 / 01281 and published U.S. Application No. 2002 / 0075556, both of which have been assigned to Sipix Imaging, Inc.

[0009] Although electrophoretic media are typically opaque (because, for example, in many electrophoretic media, particles substantially block the transmission of visible light through the display) and operate in a light-reflective mode, many electrophoretic displays can also operate in a so-called "shutter mode," in which one display state is substantially opaque and another display state is transparent. See, for example, the aforementioned U.S. Patents 6,130,774 and 6,172,798 and U.S. Patents 5,872,552; 6,144,361; 6,271,823; 6,225,971; and 6,184,856. Dielectrophoretic displays (which are similar to electrophoretic displays but depend on changes in electric field strength) can operate in a similar mode; see U.S. Patent 4,418,346. Other types of electro-optic displays can also operate in a shutter mode.

[0010] A capsule-shaped or micro-unit electrophoretic display typically does not suffer from the clustering and settling failure modes of conventional electrophoresis devices and offers additional advantages, such as the ability to print or coat the display on a variety of flexible and rigid substrates. The term "printing" is intended to encompass all forms of printing and coating, including but not limited to: pre-metered coatings (e.g., patch die coating, slot or extrusion coating, slide or cascade coating, and curtain coating); roll coating (e.g., knife over roll coating and forward and reverse roll coating); gravel coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; silk screen printing processes; electrostatic printing processes; thermal printing processes; and inkjet printing processes. Processes); electrophoretic deposition; and other similar techniques. Therefore, the resulting display can be flexible. Furthermore, because the display medium can be printed (using various methods), the display itself can be manufactured inexpensively.

[0011] One potentially important market for electrophoretic media is windows with variable transmittance. As energy efficiency in buildings and transportation becomes increasingly important, electrophoretic media can be used as a coating on windows to electrically control the proportion of incident radiation transmitted through the window by changing the optical state of the electrophoretic media. The effective implementation of this "variable transmittance" ("VT") technology in buildings is expected to (1) reduce unnecessary heating effects during hot weather, thereby reducing the energy required for cooling, the size of air conditioning equipment, and peak power demand; (2) increase the utilization of natural light, thereby reducing lighting energy and peak power demand; and (3) improve occupant comfort by increasing thermal and visual comfort. Greater benefits can be obtained in automobiles, where the ratio of glass surface area to enclosed volume is significantly greater than in typical buildings. Specifically, the effective implementation of VT technology in automobiles is expected to not only provide the above benefits, but also (1) improve driving safety, (2) reduce glare, (3) enhance mirror performance (by using electro-optic coatings on mirrors), and (4) enhance the ability to use head-up displays. Other potential applications of VT technology include privacy glass in electronic devices and anti-glare screen protectors.

[0012] This technology provides an example of an apparatus comprising an electrophoretic medium sandwiched between electrode layers, the electrophoretic medium being capable of achieving a closed optical state (opaque optical state) and an open optical state (transparent optical state) and switching between these states by applying an electric field throughout the electrophoretic medium. Furthermore, light from luminescent objects (e.g., light sources) in dark environments or specularly reflected sunlight in bright environments can easily diffract when passing through the apparatus. This phenomenon is visible to the viewer and can even be disturbing, making the apparatus less desirable. The inventors of this invention have unexpectedly discovered that a device comprising micro-unit layers with a specific architecture can achieve efficient switching between open and closed optical states and improve the optical performance in the open optical state. Summary of the Invention

[0013] In one embodiment, the present invention provides a variable light transmission device (200), comprising a first light-transmitting electrode layer (202), a second light-transmitting electrode layer (207), and a micro-unit layer (203). The micro-unit layer (203) is disposed between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207). The micro-unit layer (203) includes a plurality of micro-units (204) and a sealing layer (206). Each of the plurality of micro-units (204) includes an electrophoretic medium (209) comprising charged pigment particles (223), a charge control agent, and a nonpolar liquid. Each of the plurality of micro-units (204) has a micro-unit opening (205). The sealing layer (206) spans the micro-unit openings (205) of the plurality of micro-units (204). Each microcell's sealing layer (206) has an upper surface and a lower surface, the lower surface being in contact with the electrophoretic medium (209), and the upper surface being in contact with (i) the first light-transmitting electrode layer (202) or (ii) an adhesive layer. The adhesive layer is disposed between the first light-transmitting electrode layer (202) and the upper surface of the sealing layer (206). Each of the plurality of microcells (204) includes a microcell bottom layer (210), a protrusion structure (217), a microcell wall (212), and a channel (215). The microcell bottom layer (210) has a microcell bottom inner surface (211), which is composed of an exposed microcell bottom inner surface (211a) and an unexposed microcell bottom inner surface (211b). The protrusion structure (217) has a protruding bottom surface (218), a protruding surface (221), a protruding top surface (219), a protruding height (220), and a protruding volume. The protruding top surface (219) is a point on the protrusion structure that is shorter than all other points on the protrusion structure (217) from the microcell opening (205). The protruding height (220) is the distance between the protruding bottom surface (218) and the protruding top surface (219). The protruding surface (221) is the surface of the protrusion structure (217) that contacts the electrophoretic medium (209). The unexposed inner surface (211b) of the microcell bottom surface contacts the protruding bottom surface (218). The exposed inner surface (211a) of the microcell bottom surface contacts the electrophoretic medium (209). The micro-unit wall (212) has an inner surface (213) and an upper surface (214). The inner surface (213) is the surface in contact between the micro-unit wall (212) and the electrophoretic medium (209). The upper surface (214) is the surface in contact between the micro-unit wall (212) and the sealing layer (206). The channel (215) has a channel height (216h), a channel bottom surface, a channel bottom surface width, an inner bottom surface perimeter, and an outer bottom surface perimeter.The channel height (216h) is 50% of the protrusion height (220). The inner bottom perimeter is the intersection of the micro-unit wall (212) and the exposed micro-unit bottom inner surface (211). The outer bottom perimeter is the intersection of the protrusion bottom surface and the exposed micro-unit bottom inner surface. The channel bottom width is the smaller distance between a point on the inner bottom perimeter and a point on the outer bottom perimeter. The channel (215) has a three-dimensional shape defined by the space between the exposed micro-unit bottom inner surface (211a), the protrusion surface (221), a plane parallel to the micro-unit bottom inner surface (211), and the micro-unit wall inner surface (213), wherein the distance between the plane and the micro-unit bottom inner surface (211) is equal to the channel height (216h). The protrusion structure has a three-dimensional shape composed of one geometric shape or two or more geometric shapes. The geometric shape, or at least one of the two or more geometric shapes, is a cone-shaped body, wherein the protruding bottom surface is selected from the group consisting of: a teardrop shape, a teardrop shape with a rounded end, an ellipse with two apexes, a lemon shape, a lemon shape with a rounded end, a curved polygon, and a curved polygon with a rounded vertex, the curved polygon having 3 to 6 sides. A first electric field is applied between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207) with a first waveform, causing the charged pigment particles (223) to move toward the channel (215), thereby causing the variable light transmission device (200) to switch to an on optical state. A second electric field with a second waveform is applied between the first transparent electrode layer (202) and the second transparent electrode layer (207), causing the charged pigment particles (223) to move toward the first transparent electrode layer (202), wherein the closed optical state has a lower percentage of transparency than the open optical state. The second electric field causes the charged pigment particles (223) to move toward the first transparent electrode layer (202) at a velocity, which may have a lateral component. The second waveform may include at least one positive voltage and at least one negative voltage, and the second waveform has a net positive pulse or a net negative pulse. The second waveform may include an AC waveform having a duty cycle of 5% to 45%, or wherein the second waveform includes a DC bias waveform formed by the superposition of a DC voltage component and an AC waveform.

[0014] In one example, the variable light transmission device of the present invention includes a micro-unit having a protruding structure having a three-dimensional shape composed of a geometric body, the geometric body being a cone shape.

[0015] The micro-unit opening (205) of each of the plurality of micro-units (204) in the micro-unit layer (203) is geometrically shaped, and the geometry of the micro-unit opening (205) can be the same as the geometry of the protruding bottom surface of the micro-unit.

[0016] Each of the plurality of micro-units (204) may have a length of 400 micrometers to 800 micrometers and a height of 20 micrometers to 100 micrometers, and the width of the channel of each of the plurality of micro-units (204) is 10 micrometers to 30 micrometers.

[0017] Each micro-unit in the plurality of micro-units of the variable light transmission device of the present invention may have a micro-unit length of 400 micrometers to 850 micrometers, 450 micrometers to 800 micrometers, 500 micrometers to 750 micrometers, or 600 micrometers to 740 micrometers. Each micro-unit in the plurality of micro-units of the variable light transmission device of the present invention may have a micro-unit height of 20 micrometers to 100 micrometers, 20 micrometers to 90 micrometers, 20 micrometers to 80 micrometers, 20 micrometers to 60 micrometers, 20 micrometers to 40 micrometers, 30 micrometers to 90 micrometers, 30 micrometers to 80 micrometers, 30 micrometers to 60 micrometers, 40 micrometers to 50 micrometers, 25 micrometers to 40 micrometers, 50 micrometers to 100 micrometers, or 50 micrometers to 80 micrometers.

[0018] The height of the protrusion (220) can be 15 micrometers to 90 micrometers, 20 micrometers to 90 micrometers, 20 micrometers to 80 micrometers, 20 micrometers to 70 micrometers, 20 micrometers to 50 micrometers, 20 micrometers to 30 micrometers, 30 micrometers to 80 micrometers, 30 micrometers to 70 micrometers, 30 micrometers to 50 micrometers, 30 micrometers to 40 micrometers, 40 micrometers to 90 micrometers, 40 micrometers to 50 micrometers, 30 micrometers to 50 micrometers, 25 micrometers to 35 micrometers, 50 micrometers to 90 micrometers, or 50 micrometers to 70 micrometers.

[0019] The micro-unit layer may include a set of two adjacent micro-units, namely a first micro-unit and a second micro-unit. The first micro-unit may include a first protrusion structure having a first protruding bottom surface, the geometry of which is (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end, the geometry of which has an axis and a direction; the second micro-unit may include a second protrusion structure having a second protruding bottom surface, the geometry of which is (iii) a symmetrical curved triangle or (iv) a symmetrical curved triangle with a rounded vertex, the geometry of which has three axes, each of which has a direction. One of the three axes of the geometry of the second protruding bottom surface may be parallel to the axis of the geometry of the first protruding bottom surface and have the same direction as the axis of the geometry of the first protruding bottom surface.

[0020] The micro-unit layer may include a set of two adjacent micro-units, namely a third micro-unit and a fourth micro-unit; the third micro-unit may include a third protrusion structure having a third protruding bottom surface, the geometry of which is (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end, and the geometry of which has an axis; the fourth micro-unit may include a fourth protrusion structure having a fourth protruding bottom surface, the geometry of which is (iii) a symmetrical curved triangle or (iv) a symmetrical curved triangle with a rounded vertex, and the geometry of which has three axes. One of the three axes of the geometry of the fourth protruding bottom surface may form an angle of 30 to 60 degrees with the axis of the third protruding bottom surface.

[0021] The micro-unit layer may include a set of four micro-units, namely a first, second, third, and fourth micro-unit; the first micro-unit may include a first protrusion structure having a first protruding bottom surface; the second micro-unit may include a second protruding structure having a second protruding bottom surface; the third micro-unit may include a third protruding structure having a third protruding bottom surface; the fourth micro-unit may include a fourth protruding structure having a fourth protruding bottom surface; the first micro-unit is adjacent to the second micro-unit and the third micro-unit, the second micro-unit is adjacent to the first micro-unit, the third micro-unit, and the fourth micro-unit, the third micro-unit is adjacent to the first micro-unit, the second micro-unit, and the fourth micro-unit, and the fourth micro-unit is adjacent to the second micro-unit and the third micro-unit; the geometry of the first protruding bottom surface may be (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end, the geometry of the first protruding bottom surface has a first axis, the first axis has a first direction; the geometry of the second protruding bottom surface may be (iii) a symmetrical teardrop shape or (i) a symmetrical teardrop shape. v) A symmetrical teardrop shape with a rounded end, the geometry of the second protruding bottom surface having a second axis, the second axis having a second direction; the geometry of the third protruding bottom surface can be (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the third protruding bottom surface having three axes, each of the three axes having a direction; the geometry of the fourth protruding bottom surface can be (vii) a symmetrical curved triangle or (viii) a symmetrical curved triangle with a rounded vertex, the geometry of the fourth protruding bottom surface having three axes, each of the three axes having a direction; the first axis can be parallel to the second axis, the direction of the first axis being opposite to the direction of the second axis; one of the axes of the geometry of the third protruding bottom surface can be parallel to the first axis and the second axis and have the same direction as the first direction; one of the axes of the geometry of the fourth protruding bottom surface can be parallel to the first axis and the second axis and have the same direction as the second direction. The micro-unit layer may include two or more groups of micro-units, each group having four micro-units, and each group consisting of the first, second, third and fourth micro-units.

[0022] The micro-unit layer may include a set of four micro-units, namely the fifth, sixth, seventh, and eighth micro-units; the fifth micro-unit may include a fifth protrusion structure having a fifth protrusion bottom surface; the sixth micro-unit may include a sixth protrusion structure having a sixth protrusion bottom surface; the seventh micro-unit may include a seventh protrusion structure having a seventh protrusion bottom surface; the eighth micro-unit may include an eighth protrusion structure having an eighth protrusion bottom surface; the fifth micro-unit may be adjacent to the sixth and seventh micro-units; the sixth micro-unit may be adjacent to the fifth, seventh, and eighth micro-units; the seventh micro-unit may be adjacent to the fifth, sixth, and eighth micro-units; the eighth micro-unit may be adjacent to the sixth and seventh micro-units; the geometry of the fifth protrusion bottom surface may be (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end; the geometry of the fifth protrusion bottom surface may have a fifth axis, the fifth axis having a fifth direction; the geometry of the sixth protrusion bottom surface may be (iii) a symmetrical teardrop. The geometry of the sixth protrusion's base can be (iv) a symmetrical teardrop shape with a rounded end; the geometry of the seventh protrusion's base can be (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex; the geometry of the seventh protrusion's base can have three axes, each of which has a direction; the geometry of the eighth protrusion's base can be (vii) a symmetrical curved triangle or (viii) a symmetrical curved triangle with a rounded vertex; the geometry of the eighth protrusion's base can have three axes, each of which has a direction; the fifth axis can be parallel to the sixth axis, and the direction of the fifth axis is opposite to the direction of the sixth axis; one of the axes of the seventh protrusion's base can be parallel to the fifth axis and the sixth axis and have a direction opposite to the fifth direction; one of the axes of the eighth protrusion's base can be parallel to the fifth axis and the sixth axis and have the same direction as the fifth direction. The micro-unit layer may include two or more groups of micro-units, each group having four micro-units, and each group consisting of the fifth, sixth, seventh and eighth micro-units.In addition to the fifth, sixth, seventh, and eighth microunits, this group of microunits also includes the ninth, tenth, eleventh, and twelfth microunits; the ninth microunit may include a ninth protrusion structure having a ninth protruding bottom surface; the tenth microunit may include a tenth protrusion structure having a tenth protruding bottom surface; the eleventh microunit may include an eleventh protrusion structure having an eleventh protruding bottom surface; the twelfth microunit may include a twelfth protrusion structure having a twelfth protruding bottom surface; the seventh microunit may be adjacent to the fifth, sixth, eighth, and ninth microunits; the eighth microunit may be adjacent to... The sixth, seventh, ninth, and tenth micro-units; the ninth micro-unit may be adjacent to the seventh, eighth, tenth, and eleventh micro-units; the tenth micro-unit may be adjacent to the eighth, ninth, eleventh, and twelfth micro-units; the eleventh micro-unit may be adjacent to the ninth, tenth, and twelfth micro-units; the twelfth micro-unit may be adjacent to the tenth and eleventh micro-units; the geometry of the bottom surface of the ninth protrusion may be (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end, the geometry of the bottom surface of the ninth protrusion having a ninth axis, the ninth axis having a ninth direction; the tenth protrusion bottom The geometry of the surface can be (iii) a symmetrical teardrop shape or (iv) a symmetrical teardrop shape with a rounded end, the geometry of the bottom surface of the tenth protrusion having a tenth axis, the tenth axis having a tenth direction; the geometry of the bottom surface of the eleventh protrusion can be (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the bottom surface of the eleventh protrusion having three axes, each of the three axes having a direction; the geometry of the bottom surface of the twelfth protrusion can be (vii) a symmetrical curved triangle or (viii) a symmetrical curved triangle with a rounded vertex. The triangle-shaped bottom surface of the twelfth protrusion has three axes, each with a direction. The ninth axis can be parallel to the tenth axis, and its direction can be opposite to that of the tenth axis. One of the axes of the bottom surface of the eleventh protrusion can be parallel to both the ninth and tenth axes and have the same direction as the ninth direction. The fifth axis can form an angle of 30 to 60 degrees with the ninth axis. The micro-unit layer can include two or more groups of micro-units, each group having eight micro-units, each group consisting of the fifth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth micro-units.

[0023] The variable light transmission device of the present invention may include a micro-unit having a micro-unit inner wall surface (213) and a micro-unit bottom inner surface (211), wherein the micro-unit inner wall surface (213) and the micro-unit bottom inner surface (211) form an angle (φ) of 90 degrees to 120 degrees.

[0024] The variable light transmission device of the present invention may include (i) an adhesive layer disposed between the first light-transmitting electrode layer (202) and the sealing layer (206); (ii) a second adhesive layer disposed between the micro-unit layer (203) and the second light-transmitting electrode layer (207); or (iii) the adhesive layer and the second adhesive layer.

[0025] The variable light transmission device may include a light blocking layer (230) disposed between the upper surface (214) of the micro unit wall and the sealing layer (206); the light blocking layer (230) may contain light-absorbing pigment; the light-absorbing pigment of the light blocking layer (230) may be black.

[0026] The variable light transmission device (200) has a first outer surface (250) and a second outer surface (251). The first outer surface (250) is located on the side of the variable light transmission device closer to the first light-transmitting electrode layer (202), while the second outer surface (251) is located on the side of the variable light transmission device closer to the second light-transmitting electrode layer (207).

[0027] The electrophoretic medium may contain a charge control agent. The content of the charge control agent in the electrophoretic medium of the variable light transmission device may be from 0.1 wt% to 8 wt% by weight of the electrophoretic medium. The molecular structure of the charge control agent may contain a quaternary ammonium functional group and a nonpolar tail. The nonpolar liquid of the electrophoretic medium may include materials selected from the group consisting of: aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, polydimethylsiloxane, or mixtures thereof. Simple Explanation of the Diagram

[0028] Figure 1A illustrates the planar shape of a teardrop;

[0029] Figure 1B illustrates a planar shape with a teardrop shape at one rounded end;

[0030] Figure 1C illustrates a planar shape with an ellipse at two apex;

[0031] Figure 1D illustrates the lemon-shaped planar shape;

[0032] Figure 1E illustrates the planar shape of the curved triangle;

[0033] Figure 1F illustrates a curve segment composed of three curve segments;

[0034] Figure 2 illustrates cylindrical particles in a liquid under the influence of an applied electric field and the resultant force acting on the particles;

[0035] Figures 3A, 3B, 3C, and 3D are side views illustrating an example of a portion of the variable light transmission device of the present invention;

[0036] Figures 4A and 4B illustrate side views of the microunit in the open optical state and the microunit in the closed optical state, respectively; the electrophoretic medium contains one type of charged pigment particles;

[0037] Figure 5A shows an example of a DC unbalanced waveform that can be applied to a variable light transmission device to achieve a closed optical state; this waveform includes an AC waveform with a duty cycle higher than 50%.

[0038] Figure 5B shows an example of a DC unbalanced waveform that can be applied to a variable light transmission device to achieve a closed optical state; this waveform is a superposition of a DC voltage component and an AC waveform.

[0039] Figure 6 illustrates the force exerted by a charged pigment particle on the surface of a conical protrusion of the variable light transmission device of the present invention;

[0040] Figure 7 is a side view of a portion of a variable light transmission device having a micro-unit, which includes a light blocking layer (230);

[0041] Figure 8 is a side view of a portion of a variable light transmission device having a micro-unit, which includes a protruding structure (217), a micro-unit wall (212) (having an inner surface (213) of the micro-unit wall), and an inner surface (211) of the bottom of the micro-unit. The inner surface (213) of the micro-unit wall and the inner surface (211) of the bottom of the micro-unit form an angle (φ) greater than 90 degrees.

[0042] Figures 9A, 9B, 9C, and 9D are top views illustrating examples of micro-units of the variable light transmission device of the present invention;

[0043] Figures 10A and 10B illustrate a top view of a set of two micro-units of the variable light transmission device of the present invention;

[0044] Figures 11A, 11B, 11C, 11D, 11E and 11F illustrate top views of various micro-unit groups of the variable light transmission device of the present invention;

[0045] Figure 12A illustrates a top view of a portion of a variable light transmission device having a plurality of micro-units, each of which has a hexagonal inner base perimeter and an outer base perimeter;

[0046] Figure 12B shows the Fraunhofer diffraction pattern formed by the hexagonal aperture of the device; a portion of the device is shown in Figure 12A.

[0047] Figure 13 shows the Fraunhofer diffraction pattern formed by the variable light transmission device, and a top view of a portion of the variable light transmission device is shown in Figure 11F. Implementation

[0048] As used herein, a "variable light transmission device" is a device that includes an electrophoretic medium, wherein the amount of light transmitted through the device can be controlled by applying an electric field over the entire electrophoretic medium.

[0049] "The first outer surface of the variable light transmission device" and "the second outer surface of the variable light transmission device" are the outer surfaces of the devices that are parallel to the first and second light-transmitting electrode layers, respectively. As used herein, the term "outer surface" refers only to the main surface on the viewing side of the variable light transmission device, and not to the smaller surfaces surrounding the device.

[0050] "Exposed microcell bottom inner surface" refers to the portion of the microcell bottom inner layer that is in contact with the electrophoresis medium. Conversely, "unexposed microcell bottom inner surface" refers to the portion of the microcell bottom inner layer that is not in contact with the electrophoresis medium.

[0051] The "transparency percentage of the variable light transmission device" (%T) at a certain location of the device is given by Formula 1. Therefore, the "transparency percentage of the variable light transmission device" (%T) at a certain location of the device is the ratio of the intensity (I) of light transmitted through the variable light transmission device and emitted from a certain location on the second outer surface of the variable light transmission device to the intensity (Io) of light entering the variable light transmission device from a certain location on the first outer surface of the variable light transmission device, multiplied by 100; the location of the second outer surface is symmetrical to the location of the first outer surface with respect to a plane system, which is located at equal distances between the first and second light-transmitting electrode layers. %T = (I / Io) × 100 (Formula 1)

[0052] The distance between a point and a plane is the shortest perpendicular distance from that point to that plane.

[0053] The distance between two planes in three-dimensional space is the shortest distance between those two planes. It is the shortest distance between any point on one plane and any point on the other plane.

[0054] As used herein, the term "cone" refers to a three-dimensional shape having a base, a curved surface, and a apex (point A). The base of the cone is a planar shape; the base has a surface and a perimeter, and the surface of the base is part of plane P. The perimeter of the base of the cone is the boundary of the base shape; that is, the perimeter encloses the shape of the base. The curved surface connects the perimeter of the base of the cone to the apex of the cone. The apex is the pointed tip of the cone opposite the base. All points of the cone lie within the space defined by plane P and plane R, plane R being parallel to plane P and containing point A (apex). The apex is a point on the cone whose distance to the base is greater than any other point on the cone. The plane of the cone is not circular (as with a typical cone). The protruding structure of the micro-unit of the variable light transmission device of the present invention has a three-dimensional shape composed of one or more geometric shapes, wherein the one or at least one of the two or more geometric shapes is a cone as defined above. The base of the cone is a planar shape selected from the group consisting of: teardrop shape, teardrop shape with one rounded end, ellipse with two pointed ends, lemon shape, lemon shape with rounded end, curved polygon, and curved polygon with rounded vertices. The variable light transmission device of the present invention may include various types of micro-units with different protrusion structures and protrusion bases.

[0055] A "curve segment" is a part of a curve defined by two points (the start point and the end point).

[0056] The “teardrop shape” used in this paper (an example of which is shown in Figure 1A) is a planar shape containing various radii of curvature. The teardrop shape comprises two ends: a first end and a second end. The first end is a point on the perimeter of the teardrop shape with the smallest radius of curvature. The second end is located on the side of the perimeter of the teardrop shape opposite to the first end, and has a large radius of curvature. In the following text, the first end is referred to as the “teardrop tip” (101), and the second end as the “teardrop head” (102). In one type of teardrop shape, the teardrop tip is a point on the perimeter of the teardrop shape where the two curved segments of the perimeter intersect; at the teardrop tip, an abrupt change in the curvature of the teardrop shape's perimeter can be observed, as shown in the shape of Figure 1A. In this type of teardrop shape, the teardrop tip is called the “point,” and the teardrop shape is called a teardrop shape with a point. In another teardrop shape example, the curvature change at the apex of the teardrop is gentler than that of a teardrop with a pointed tip, and the portion of the circumference at the apex is rounded. In this case, the apex is called a "rounded end," and the teardrop shape is called a teardrop with a rounded end. An example of this type of teardrop shape is illustrated in Figure 1B. The line passing through the apex (101) and head (102) of the teardrop is called the teardrop axis (103). The teardrop axis has a direction that runs from the apex to the head. In some examples, the teardrop axis is an axis of symmetry, meaning that the axis divides the teardrop shape into two identical halves that are mirror images of each other. In this case, the teardrop shape is called a "symmetrical teardrop shape," or synonymously, a "teardrop shape with an axis of symmetry." The teardrop shapes shown in Figures 1A and 1B are symmetrical teardrop shapes. In the following text, unless specifically referred to as "teardrop shape with a rounded end", the term "teardrop shape" is considered to mean a teardrop shape with a pointed end.

[0057] The term "ellipse with two apexes" as used herein refers to a geometry resembling an ellipse that tapers to a point at both ends, rather than a typical ellipse with smoothly rounded ends. An example of an ellipse with two apexes is illustrated in Figure 1C. The line containing the two apexes (111) is called the axis of the ellipse with two apexes. In one type of ellipse with two apexes, the axis of ellipse is an axis of symmetry, meaning that this axis divides the ellipse with two apexes (111) into two identical halves that are mirror images of each other. Therefore, in this type of shape, the ellipse with two apexes has an axis of symmetry (113), and this type of ellipse with two apexes is called a "symmetric ellipse with two apexes."

[0058] The “lemon shape” used in this paper is a planar shape with a perimeter consisting of a first end, a second end, a first curved segment, and a second curved segment. Figure 1D illustrates a top view of the planar shape of a lemon shape with a first end (121) and a second end (122). The line passing through the first end and the second end is the axis (123) of the lemon shape. The curve above the axis in the figure is the first curved segment; the curve below the axis in the figure is the second curved segment. In one type of lemon shape, the axis of the lemon shape is an axis of symmetry, which means that this axis divides the lemon shape into two identical halves that are mirror images of each other. The axis 123 of the lemon shape example in Figure 1D is an axis of symmetry. Therefore, in this type of lemon shape, the lemon shape has an axis of symmetry and is called a “symmetrical lemon shape.” The lemon shape example in Figure 1D is a symmetrical lemon shape. The first curved segment connects the first end to the second end, and the second curved segment also connects the first end to the second end. The first curve segment consists of three curve segments A, B, and C. Each of these segments has a start point and an end point. The start point of curve segment A contacts the first end, the end point of curve segment A contacts the start point of curve segment B, the end point of curve segment B contacts the start point of curve segment C, and the end point of curve segment C contacts the second end. Curve segments A and C are concave, while curve segment B is convex. The second curve segment consists of three curve segments D, E, and F. Each of these segments has a start point and an end point. The start point of curve segment D contacts the first end, the end point of curve segment D contacts the start point of curve segment E, the end point of curve segment E contacts the start point of curve segment F, and the end point of curve segment F contacts the second end. Curve segments D and F are concave, while curve segment F is convex. An example of a lemon shape is illustrated in Figure 1D. In one type of lemon shape, the first and second ends are the points where the first and second curve segments intersect on the perimeter, and a sudden change in the curvature of the lemon shape's perimeter can be observed at the teardrop apex, as shown in Figure 1D. In this case, the first and second ends of the shape are called "points," and the lemon shape is called a lemon shape with points or a pointed lemon shape. In another type of lemon shape, the change in curvature of the perimeter at the teardrop apex is gentler than that of a pointed lemon shape, and the perimeter portions containing the first and second ends are rounded. In this case, the first and second ends of the lemon shape are called rounded ends, and this type of lemon shape is called a lemon shape with rounded ends or a rounded-end lemon shape. A rounded-end lemon shape can also be described as follows.

[0059] A rounded-end lemon shape is a planar shape with a perimeter composed of a first end, a second end, a first curved segment, and a second curved segment. The lines passing through the first and second ends form the axis of the rounded-end lemon shape. In one type of rounded-end lemon shape, the axis is an axis of symmetry, meaning that this axis divides the rounded-end lemon shape into two identical half-parts that are mirror images of each other. Therefore, in this type of lemon shape, the rounded-end lemon shape has an axis of symmetry, and this type of lemon shape is called a "symmetrical lemon shape." The first curved segment connects the first end to the second end, and the second curved segment also connects the first end to the second end. The first curved segment consists of five curved segments G, H, I, J, and K, each of which has a starting point and an ending point. The starting point of curve segment G contacts the first end; the ending point of curve segment G contacts the starting point of curve segment H; the ending point of curve segment H contacts the starting point of curve segment I; the ending point of curve segment I contacts the starting point of curve segment J; the ending point of curve segment J contacts the starting point of curve segment K; and the ending point of curve segment K contacts the second end. Curve segments G, I, and K are convex, while curve segments H and J are concave. The second curve segment consists of five curve segments L, M, N, O, and P. Each of curve segments L, M, N, O, and P has a starting point and an ending point. The starting point of curve segment L contacts the first end; the ending point of curve segment L contacts the starting point of curve segment M; the ending point of curve segment M contacts the starting point of curve segment N; the ending point of curve segment N contacts the starting point of curve segment O; the ending point of curve segment O contacts the starting point of curve segment O; and the ending point of curve segment O contacts the second end. Curve segments L, N, and P are convex, while curve segments M and O are concave. The difference between a lemon shape and a rounded-end lemon shape lies in the presence of convex curve segments G, K, L, and P; these convex curve segments provide the rounding of the first and second ends of the rounded-end lemon shape. In the following text, the term "lemon" is considered to refer to a lemon shape without rounded ends, unless specifically referred to as a "rounded-end lemon shape." Furthermore, a lemon shape (not a rounded-end lemon shape) must contain two curve segments (connecting the two ends), each of which consists of two concave curve segments and one convex curve segment, in the order of concave-convex-concave. A rounded-end lemon shape must also contain two curve segments (connecting the two ends), each of which consists of two concave curve segments and three convex curve segments, in the order of convex-concave-convex-concave-convex.

[0060] The "curved polygon" used herein is a polygon in which each side is a curved segment; the curved polygon disclosed in this application has 3 to 6 vertices; furthermore, the curved polygon disclosed in this application has 3 to 6 sides. Each side of the curved polygon has a first vertex and a second vertex; each curved segment comprises three smaller curved segments: curve segments Q, R, and S. Each curved segment has a start point and an end point. The following description relates to a curved triangle, but the description relating to other curved polygons can be readily understood. An example of a curved triangle is illustrated in Figure 1E. The curved triangle has three sides and three vertices (i.e., a first vertex, a second vertex, and a third vertex). The start point of curve segment Q contacts the first vertex of the curved triangle, the end point of curve segment Q contacts the start point of curve segment R, the end point of curve segment R contacts the start point of curve segment S, and the end point of curve segment S contacts the second vertex of the curved triangle. Curve segments Q and R are concave, while curve segment R is convex. An example of a curved segment consists of two concave segments (Q and S) and one convex segment R. The other two sides of a curved triangle are composed of similar curve segments, thus forming a "curved triangle". Similarly, all four sides of a curved square, all five sides of a curved pentagon, etc., are composed of similar curve segments. Figure 1F is an example of a curve segment composed of three curve segments QRS as described above.

[0061] The aforementioned curved polygons contain vertices where the radius of curvature changes abruptly. In another type of curved polygon, the radius of curvature changes gradually at the vertices. That is, in this type of curved polygon, the vertices are rounded. The "curved polygon with rounded vertices" used herein refers to a polygon where each edge is a curve segment; the curved polygons disclosed in this application have 3 to 6 vertices; furthermore, the curved polygons disclosed in this application have 3 to 6 edges. Each edge of the curved polygon has a first vertex and a second vertex; each curve segment contains five smaller curve segments T, U, V, X, and Y. Each curve segment has a start point and an end point. The following description relates to curved triangles with rounded vertices, but this description can be easily extended to other curved polygons with rounded vertices. A curved triangle with rounded vertices has three edges and three vertices (a first vertex, a second vertex, and a third vertex). The starting point of curve segment T contacts the first vertex of the curved triangle with rounded vertices; the ending point of curve segment T contacts the starting point of curve segment U; the ending point of curve segment U contacts the starting point of curve segment V; the ending point of curve segment V contacts the starting point of curve segment X; and the ending point of line segment Y contacts the second vertex of the curved triangle with rounded vertices. Curve segments T, V, and Y are convex, while curve segments U and X are concave. The other two sides of the curved triangle with rounded vertices are composed of similar curve segments, thus forming a "curved triangle with rounded vertices". Similarly, all four sides of a curved square, all five sides of a curved pentagon, etc., are composed of similar curve segments. The difference between a curved triangle and a curved triangle with rounded vertices lies in the presence of convex curve segments (e.g., convex curve segments T and U) that contact the vertices; these convex curve segments provide the rounding of the vertices of the curved triangle.

[0062] Suppose a curved triangle (or a curved triangle with rounded vertices) has vertices A, B, and C. A line passing through (i) vertex A of the curved triangle (or a curved triangle with rounded vertices) and (ii) point D (point D lies on the line segment connecting vertex B and vertex C, where line segment BD is equal to line segment DC) is called the axis of the curved triangle (or a curved triangle with rounded vertices). That is, the axis of the curved triangle (or a curved triangle with rounded vertices) is a line passing through vertex A and the midpoint of the line segment connecting the other two vertices. A curved triangle (or a curved triangle with rounded vertices) has three axes. Each of these three axes can be an axis of symmetry of the curved triangle (or a curved triangle with rounded vertices), meaning that this axis divides the teardrop shape into two identical halves that are mirror images of each other. When these three axes are axes of symmetry, the curved triangle (or a curved triangle with rounded vertices) is a "symmetric curved triangle" (or a "symmetric curved triangle with rounded vertices"). Each axis of a curved triangle (or a curved triangle with rounded vertices) has a direction. The direction of each axis is from one vertex of the curved triangle (or a curved triangle with rounded vertices) toward the midpoint of the line segment that connects the other two vertices.

[0063] Suppose a curved square (or a curved square with rounded vertices) has vertices A, B, C, and D, where vertices A, B, C, and D form sides AB, BC, CD, and DA. A line passing through (i) point E (which lies on line segment AB connecting vertex A and vertex B, where line segment AE equals line segment EB) and (ii) point F (which lies on line segment CD connecting vertex C and vertex D, where line segment CF equals line segment FD) is called the axis of the curved square (or the curved square with rounded vertices). The curved square (or the curved square with rounded vertices) has two such axes. Each of these axes can be the axis of symmetry of the curved square (or the curved square with rounded vertices), meaning that this axis divides the curved square (or the curved square with rounded vertices) into two identical halves that are mirror images of each other.

[0064] Suppose a curved pentagon (or a curved pentagon with rounded vertices) has vertices A, B, C, D, and E, where vertices A, B, C, D, and E form sides AB, BC, CD, DE, and DA, respectively. A line passing through (i) vertex A of the curved pentagon (or a curved pentagon with rounded vertices) and (ii) point F (point F lies on line segment CD connecting vertex C and vertex D, where line segment CF is equal to line segment FD) is called an axis of the curved pentagon (or a curved pentagon with rounded vertices). The curved pentagon (or a curved pentagon with rounded vertices) has 5 such axes. Each of these 5 axes can be an axis of symmetry of the curved pentagon (or a curved pentagon with rounded vertices), meaning that this axis divides the curved pentagon (or a curved pentagon with rounded vertices) into two identical halves that are mirror images of each other. Each axis of the curved pentagon (or a curved pentagon with rounded vertices) has a direction. The direction of each axis is from the vertex (A) of the curved pentagon (or a curved pentagon with rounded vertices) toward the midpoint (F) of the line segment that connects the two vertices CD.

[0065] Suppose a curved hexagon (or a curved hexagon with rounded vertices) has vertices A, B, C, D, E, and F, where vertices A, B, C, D, E, and F form sides AB, BC, CD, DE, DF, and FA, respectively. A line passing through (i) point G (located on line segment AB connecting vertex A and vertex B, where line segment AG equals line segment GB) and (ii) point H (located on line segment DE connecting vertex D and vertex E, where line segment CD equals line segment DE) is called an axis of the curved hexagon (or a curved hexagon with rounded vertices). A curved hexagon (or a curved hexagon with rounded vertices) has three such axes. Each of these three axes can be an axis of symmetry of the curved hexagon (or a curved hexagon with rounded vertices), meaning that this axis divides the curved hexagon (or a curved hexagon with rounded vertices) into two identical halves that are mirror images of each other.

[0066] The term "charged pigment particle" (223) can refer to a charged pigment particle on which there is no polymer material on its surface. The term "charged pigment particle" can also refer to a charged pigment particle on which there is polymer material on its surface. The synonym is "electrophoretic particle".

[0067] "Inner surface of micro-unit wall" (213) is the surface of the micro-unit wall that is in contact with the electrophoretic medium of the micro-unit.

[0068] "Micro-unit wall upper surface" (214) is the surface of the micro-unit wall that is in contact with the sealing layer of the micro-unit. In the case where there is a light blocking layer on the micro-unit wall upper surface, the light blocking layer is disposed between the micro-unit wall upper surface and the sealing layer.

[0069] The "length of a micro-unit" is the longest distance between any point of the micro-unit opening and any other point of the micro-unit opening.

[0070] "Channel bottom width" is the minimum distance between the inner bottom perimeter and the outer bottom perimeter of the micro-unit's channel.

[0071] Two micro-units (micro-unit A and micro-unit B) are "adjacent micro-units", wherein at least a portion of the micro-unit wall of micro-unit A is a portion of the micro-unit wall of micro-unit B.

[0072] The term "DC-balanced waveform" or "DC-balanced drive waveform" applied to a pixel is a drive waveform in which the drive voltage applied to the pixel is substantially zero when integrated over the entire application period of the waveform. DC balancing can be achieved by balancing each stage of the waveform, that is, selecting a first positive voltage such that integration over the subsequent negative voltage results in zero or substantially zero. If the waveform is not DC-balanced, it is called a "DC-unbalanced waveform" or "DC-unbalanced drive waveform." The drive waveform applied to a pixel may have a DC-unbalanced portion and at least one additional pulse with opposite pulses to ensure that the entire waveform applied to the pixel is DC-balanced. This additional pulse may be applied before the DC-unbalanced portion of the waveform (pre-pulse). Typical examples of DC-unbalanced waveforms include (a) an AC square wave or sine wave with a duty cycle of less than (or greater than) 50%, and (b) an AC square wave or sine wave with DC bias.

[0073] The term "pulse" refers to the integral of voltage with respect to time. That is, for a waveform pulse of voltage V with an applied time t, the pulse is V × t. If the polarity of voltage V is positive, the pulse will be positive; if the polarity of voltage V is negative, the pulse will be negative.

[0074] The term "net positive pulse" in waveform refers to the phenomenon where negatively charged pigment particles are attracted to and move toward the first light-transmitting electrode layer during the application of the waveform.

[0075] The term "lateral component of velocity" related to the motion of charged pigment particles in the microcells of the variable light transmission device of the present invention refers to the velocity in the horizontal direction. For this definition, we assume that the velocity of a charged particle is the vector obtained by adding the vectors of the horizontal velocity (Vh) and the vertical velocity (Vv), and that, in the case of the charged pigment particles moving within the electrophoretic microcell, the vertical direction is the direction from the first phototransmitting electrode layer to the second phototransmitting electrode layer or from the second phototransmitting electrode layer to the first phototransmitting electrode layer. In the same system, the horizontal direction of the movement of charged pigment particles within the electrophoretic microcell is the direction from one side of the microcell wall to the other side of the microcell wall, parallel to the first phototransmitting electrode layer. Therefore, the statement regarding the velocities of a plurality of charged pigment particles that "the velocity of the charged pigment particles has a lateral component" means that the magnitude of the velocity in the horizontal direction is greater than zero.

[0076] The phenomenon of induced charge electroosmosis (ICEO) can be used to laterally move polarizable particles, such as pigment particles, present in an electrophoretic medium. That is, polarizable particles can move parallel to the electrode layer sandwiching the electrophoretic medium. In the presence of an electric field, the particles may experience a force caused by the polarization of the particles (or by the polarization of a conductive coating adsorbed on the particle surface or the electric double layer surrounding the particles). As shown in Figure 2, where cylindrical particles 101 are surrounded by the liquid of the electrophoretic medium in an applied electric field, this force may cause disturbances in the flow of mobile charges (e.g., ions or charged microparticles) within the electrophoretic medium. This figure is reproduced from the article by Bazant and Squires, J. Fluid Mech., 2004, 509, 217-252.

[0077] Perfectly symmetrical spherical particles experience no net force, but less symmetrical particles experience a force with a component perpendicular to the applied field. The coordinated flow of a group of particles, each experiencing such a force, causes a "vortex" to form in the electrophoretic medium containing multiple particles. According to the theory proposed in the Bazant and Squires paper, the maximum velocity u of the vortex for a given particle can be approximately represented by equation (1): In Equation 1, E represents the field strength, ε represents the dielectric constant of the solvent, η represents the viscosity of the electrophoretic fluid, ω represents the applied sinusoidal alternating frequency, and τ represents the time scale used to establish the screening charge layer by transmitting the movement of solvent-borne charges around the charge. The time scale τ is represented by Equation (3):

[0078] In Equation 3, λ is the Debye shielding length of the D system, R is the particle radius, and D is the diffusion constant of the charge carrier in the fluid.

[0079] According to Equation 1, as the frequency increases, the value of ω²τ² increases and the maximum velocity of the induced charge flow decreases. Furthermore, for ω²τ² values ​​significantly greater than 1, the maximum vortex velocity is proportional to the square of the ratio E / ω. Regardless of the polarity of the applied electric field, the induced charge flow occurs in the same direction, and therefore can be driven by an alternating field.

[0080] When the electrophoretic medium is contained within microcells (which is preferred in electrophoretic displays), the resulting flow geometry is influenced by the shape of the specific microcells used. For example, in the simplest case with two parallel electrodes, it has been shown that, using appropriate electric field strength and alternating frequency, the flow can employ a roll structure with periodic intervals corresponding to the gap width between the electrodes.

[0081] The inventors of this invention use a complex micro-unit structure formed by an embossing method to manufacture a variable light transmission device. In one example, the embossed structure includes a protrusion structure on the bottom of each micro-unit. Figures 3A, 3B, and 3C illustrate an example of a variable light transmission device according to the present invention, wherein the protrusion structure of the variable light transmission device is conical. A cone is a geometric shape similar to a cone. The protrusion structure can guide the electrophoretic flow of particles into the channel (215) to achieve the opening of the optical state. If the electric field applied across the entire electrophoretic medium has appropriate polarity relative to the polarity of the charged pigment particles, the charged pigment particles will move toward the channel. For example, if the charged pigment particles are positively charged and the voltage applied through the light-transmitting electrode causes the second light-transmitting electrode to be negatively polarized, the charged pigment particles will move toward the channel. If the charged pigment particles are negatively charged and the voltage applied through the light-transmitting electrode causes the second light-transmitting electrode to be positively polarized, the same movement will occur. Figures 3A, 3B, and 3C show partial cross-sectional views (not drawn to scale) of a variable light transmission device, showing only one of the multiple micro-units of the device. Figures 3A, 3B, and 3C are identical in terms of the device structure, but different components of the device are identified in each figure. That is, the figures in Figure 3B and 3C are repeated from Figure 3A to facilitate identification of the various parts and components of the device. These figures illustrate only a portion of the display (not drawn to scale), showing only one micro-unit. Furthermore, in Figures 3A, 3B, and 3C, the protruding tip is shown as a point, and when a vertical line is drawn from this tip to the inner surface of the bottom of the micro-unit, the vertical line is located at or near the center of the inner surface of the bottom of the micro-unit. However, this may not usually be the case.

[0082] The variable light transmission device 200 in Figures 3A, 3B, and 3C includes a micro-unit layer having a plurality of micro-units and a sealing layer (206). The variable light transmission device may include a first light-transmitting substrate 201, a first light-transmitting electrode layer 202, a micro-unit layer 203 containing a plurality of micro-units 204 and a sealing layer 206, a second light-transmitting electrode layer 207, and a second light-transmitting substrate 208. Each micro-unit in the plurality of micro-units 204 includes an electrophoretic medium 209, which contains charged pigment particles and a non-polar liquid. The composition of the electrophoretic medium (charged pigment particles and non-polar liquid) is not shown in Figures 3A, 3B, and 3C. Each micro-unit in the plurality of micro-units 204 has a micro-unit opening 205, and the sealing layer 206 spans the micro-unit openings 205 of the plurality of micro-units 204. Each of the plurality of micro-units 204 includes a micro-unit bottom layer 210, a protrusion structure 217, a micro-unit wall 212, and a channel 215. The micro-unit bottom layer 210 has a micro-unit bottom inner surface 211, which includes an exposed micro-unit bottom inner surface 211a and an unexposed micro-unit bottom inner surface 211b. The unexposed micro-unit bottom inner surface 211b contacts the protrusion bottom surface 218.

[0083] In the examples of Figures 3A, 3B, and 3C, the protrusion structure 217 is conical. The surface of the cone in this example is complex because the slope of the protrusion structure surface near the bottom is different from the slope of the protrusion surface near the top. The protrusion structure includes an electrophoretic medium 209. The protrusion structure 217 has a protrusion bottom surface 218, a protrusion surface 221, a protrusion top surface 219, and a protrusion height 220. The protrusion top surface 219 is the point on the protrusion structure 217 whose distance from the micro-unit opening 205 is shorter than all other points on the protrusion structure 217. The protrusion height 220 is the distance between the protrusion bottom surface 218 and the protrusion top surface 219. A micro-unit layer comprising a plurality of micro-units 204 having the protrusion structure 217 can be manufactured by embossing a thermoplastic or thermosetting precursor layer using a pre-patterned male mold and then demolding. The precursor layer can be hardened during or after the embossing step by radiation, cooling, solvent evaporation or other means.

[0084] The micro-unit wall 212 has an inner surface 213 and an upper surface 214. The inner surface 213 is in contact with the electrophoretic medium 209. The upper surface 214 is the surface where the micro-unit wall 212 of the micro-unit contacts the sealing layer 206. Furthermore, Figure 3B shows that the first outer surface 250 is located on the side of the variable light transmission device closer to the first light-transmitting electrode layer (202), while the second outer surface (251) is located on the side of the variable light transmission device closer to the second light-transmitting electrode layer (207).

[0085] Channel 215 is defined as the volume between the exposed micro-unit bottom inner surface 211a, the micro-unit wall inner surface 213, the protruding surface 221, and a plane parallel to the micro-unit bottom inner surface (213), wherein the distance between this plane and the micro-unit bottom inner surface (211) is equal to the channel height (216h). This definition indicates that the volume of the concave surface is also part of the channel. The channel height 216h is 50% of the protrusion height 220. The channel width is the minimum distance between the perimeter of the inner bottom surface and the perimeter of the outer bottom surface of the channel. The perimeter of the inner bottom surface of the channel is the same as the perimeter of the protruding bottom surface. The perimeter of the outer bottom surface of the channel may have the same planar shape type as the perimeter of the protruding bottom surface.

[0086] The variable light transmission device in Figure 3D is similar to the variable light transmission devices shown in Figures 3A, 3B, and 3C, but shows a larger portion of the device comprising four micro-units. Each of the plurality of micro-units includes an electrophoretic medium containing charged pigment particles 223 and a nonpolar liquid. Each of the plurality of micro-units 204 has a micro-unit opening, and a sealing layer 206 spans the micro-unit openings of the plurality of micro-units. Each of the plurality of micro-units includes a micro-unit bottom layer 210, a protrusion structure 217, a micro-unit wall 212, and a channel 215. The variable light transmission device shown in Figure 3D is in a closed optical state.

[0087] When a first electric field of a first waveform is applied between the first transparent electrode layer 202 and the second transparent electrode layer 207, the charged pigment particles 223 move towards the channel if the polarity of the charged pigment particles 223 is opposite to the voltage polarity of the second transparent electrode layer. If the polarity of the charged pigment particles 223 is opposite to the voltage polarity of the second transparent electrode layer, the charged pigment particles 223 are attracted by the second transparent electrode, and the variable light transmission device switches to an open optical state, which has a higher percentage of transparency than the closed optical state. The open optical state is illustrated in Figure 4A, where the charged pigment particles 223 are represented by solid black circles. In this example, the electrophoretic medium contains one type of charged pigment particles 223. In the open optical state, the charged pigment particles 223 are present in the channels of the microcells. Therefore, in the open optical state, light passing through the variable light transmission device from a position adjacent to the channel is blocked, and the variable light transmission device is opaque at the position adjacent to the channel, while it is transparent at other positions.

[0088] A second electric field with a second waveform is applied between the first transparent electrode layer 202 and the second transparent electrode layer 207, causing charged pigment particles 223 to move towards the first transparent electrode layer 202 at a certain velocity. This results in a closed optical state as shown in FIG. 4B. The velocity may have a lateral component. Without the lateral component of the velocity, a closed optical state will not occur because the charged pigment particles 223 will move from the channel towards the first transparent electrode layer 202, but these charged pigment particles 223 will occupy the area near the microcells near the sealing layer 206. That is, the charged pigment particles 223 will not be completely dispersed across the entire surface of the first transparent electrode layer 202. Therefore, a closed optical state will not be effectively formed because a closed optical state would have relatively high transmittance.

[0089] The above facts suggest that the transition from the closed optical state to the open optical state is easier to achieve because when charged pigment particles collide with the protruding surface of the protruding structure as they move toward the second transparent electrode layer, the slope of the protruding structure (e.g., the cones in Figures 4A and 4B) will introduce a lateral component to the velocity of the charged pigment particles.

[0090] By applying a first electric field with a first waveform between the first and second light-transmitting electrode layers, causing charged pigment particles of the first type to move towards the channel, the variable light transmission device can be switched to an open optical state, wherein the charged pigment particles of the first type in the open optical state are located within the channel. By applying a second electric field with a second waveform between the first and second light-transmitting electrode layers, causing the charged pigment particles of the first type to move towards the first light-transmitting electrode layer at a certain velocity, the variable light transmission device can be switched to a closed optical state. This velocity has a transverse component and results in a closed optical state. The second waveform includes a series of at least two positive and negative pulses with net positive or net negative pulses, wherein the closed optical state has a lower percentage of transparency than the open optical state.

[0091] The second waveform can be DC unbalanced. The second waveform may include at least one positive voltage and at least one negative voltage, and the second waveform has a net positive pulse or a net negative pulse. The choice of net positive pulse or net negative pulse depends on the polarity of the charged pigment particles that are to move to a position near the sealing layer of the electrophoretic medium. Specifically, if the closed state involves the movement of negatively charged first-type charged pigment particles, a net positive pulse is needed to move those particles from the channel towards the first photosensitive electrode layer. In other words, this movement requires the net effect of the applied voltage to be the attraction of the positive voltage of the first photosensitive electrode layer relative to the second photosensitive electrode layer on the negatively charged particles. Conversely, if the closed state involves the movement of positively charged first-type charged pigment particles, a net negative pulse is needed to move the positively charged pigment particles from the channel near the second photosensitive electrode layer 207 towards the first photosensitive electrode layer.

[0092] A closed optical state is achieved by applying a second electric field with a second waveform between the two transparent electrode layers.

[0093] The second waveform may include an AC waveform with a duty cycle not equal to 50%. An example of a second waveform is illustrated in Figure 5A.

[0094] The AC waveform can have positive or negative DC bias. DC bias can be achieved by controlling the waveform's duty cycle. A positive DC bias waveform has a duty cycle greater than 50%. The duty cycle of a positive DC bias waveform may be greater than 55%, greater than 60%, or greater than 65%. The duty cycle of a positive DC bias waveform may be 55% to 95%, 58% to 90%, 60% to 88%, 65% to 85%, or 70% to 80%. Similarly, a negative DC bias waveform has a duty cycle less than 50%. The duty cycle of a negative DC bias waveform may be less than 45%, less than 40%, or less than 35%. The duty cycle of a negative DC bias waveform may be 5% to 45%, 8% to 40%, 10% to 38%, 15% to 35%, or 20% to 30%.

[0095] The waveform shown in the example of Figure 5A includes an AC square wave with two or more periods. Each period may include a first pulse with amplitude V1 applied to time period t1 and a second pulse with amplitude V2 applied to time period t2, where V1 is positive, V2 is negative, and t1 is greater than t2. DC bias is achieved through the difference in time periods when the amplitude of V1 equals the amplitude of V2 (|V1|=|V2|). In the example of Figure 5A, a positive DC bias exists because the application time (t1) of the positive voltage V1 is longer than the application time (t2) of the negative voltage V2. A positive DC bias means that if the charged pigment particles in the variable light transmission device are negatively charged, the charged pigment particles will move towards the first light-transmitting electrode layer of the device. The duty cycle of the waveform can be calculated using Equation 4. Working period = 100 × (V1·t1) / [(V1·t2) + (V2·t2)] Formula 4

[0096] In the waveform example in Figure 5A, the amplitude of V1 can be equal to the amplitude of V2 (|V1|=|V2|), but in general, the amplitudes of V1 and V2 can be different from each other.

[0097] The example drive waveform in Figure 5A is DC unbalanced. However, the waveform shown in Figure 5A can include one or more additional pulses with reverse pulses, which ensures that the overall waveform applied to the pixel is DC balanced. This additional pulse (or multiple additional pulses) can be applied before the DC unbalanced waveform (pre-pulse). Furthermore, the example waveform in Figure 5A is an AC square wave. Other examples of available AC waveforms include sine waves, triangle waves, and sawtooth waves.

[0098] The AC waveform can have an amplitude from 10V to 200V and a frequency from 0.1 to 6000Hz. The AC waveform can have an amplitude from 15V to 180V, from 20V to 160V, from 25V to 150V, or from 30V to 140V. The AC waveform can have a frequency from 0.5Hz to 5000Hz, from 1Hz to 4000Hz, from 5Hz to 3000Hz, from 10Hz to 2000Hz, from 15Hz to 1000Hz, from 20Hz to 800Hz, or from 25Hz to 600Hz. The ratio of the AC waveform frequency to the weight percentage of the charge control agent in the electrophoretic medium can be from 400Hz to 2000Hz.

[0099] The second waveform can include a waveform formed by superimposing a DC voltage component with an AC waveform. An example of a second waveform is illustrated in Figure 5B.

[0100] The waveform in Figure 5B has a net negative pulse due to the DC bias (Vd). Although the period for which the positive pulse is applied (t3) is equal to the period for which the negative pulse is applied (t4), the DC bias is achieved by the difference in pulse amplitude. Specifically, the amplitude V3 of the positive pulse is smaller than the amplitude V4 of the negative pulse. This is caused by the DC voltage component Vd of the waveform. That is, the waveform shown in Figure 5B has a DC bias.

[0101] The example of the drive waveform in Figure 5B is a DC unbalanced waveform. However, one or more additional pulses with opposite pulses can be included in the waveform of Figure 5B, which ensures that the overall waveform applied to the pixel is DC balanced. This additional pulse (or these additional pulses) can be applied before the DC unbalanced waveform (pre-pulse). Additionally, the waveform in Figure 5B is a real AC square wave. Other examples of AC waveforms that can be used include sine waves, triangular waves, and sawtooth waves.

[0102] The AC waveform can have an amplitude from 10V to 200V and a frequency from 0.1 to 6000Hz. The AC waveform can have an amplitude from 15V to 180V, from 20V to 160V, from 25V to 150V, or from 30V to 140V. The AC waveform can have a frequency from 0.5Hz to 5000Hz, from 1Hz to 4000Hz, from 5Hz to 3000Hz, from 10Hz to 2000Hz, from 15Hz to 1000Hz, from 20Hz to 800Hz, or from 25Hz to 600Hz. The ratio of the AC waveform frequency to the weight percentage of the charge control agent in the electrophoretic medium can be from 400Hz to 2000Hz.

[0103] Even when the kinematic coefficient caused by the ICEO of charged pigment particles is relatively low, the protruding structure of the microcells facilitates the efficient operation of the variable light transmission device, even when the device is driven using a DC-balanced AC waveform. As shown in Figure 6, in an example where the protruding structure is a cone, any charged pigment particle located on the surface of the cone experiences a net force that causes it to move towards the apex of the cone. Figure 6 shows charged pigment particles 223 in contact with the protruding structure 217 (cone) in the electric field 502. In this case, the ICEO flow is indicated by the curved arrows, and the ICEO flow is more constrained on the "upper slope" side of the cone compared to the "lower slope" side. This exerts a force on the particles as indicated by the dashed horizontal arrows. There is a counterforce perpendicular to the cone, forcing the particles towards the apex of the cone. By appropriately selecting the AC field and frequency, particles can be moved out of the channel region in this way and move upward along the side of the cone.

[0104] One problem encountered when the variable light transmission device is in the optically active state and the light-absorbing charged pigment particles are located only in a portion of each micro-unit (e.g., in the channel) is the observable diffraction pattern within the field of view. This diffraction pattern, called the Fraunhofer diffraction pattern, can be distracting to the viewer. It forms when light from a small object (e.g., a light source) in a dark environment or specularly reflected sunlight from a bright environment passes through the variable light transmission device in the optically active state.

[0105] As shown in Figure 7, the micro-unit of the variable light transmission device (200) of the present invention may also include a light-blocking layer 230. The light-blocking layer 230 is disposed between the upper surface of the micro-unit wall and the sealing layer 206. The light-blocking layer 230 may contain a light-absorbing pigment. The light-absorbing pigment of the light-blocking layer may be black. The inventors of the present invention have discovered that the light-blocking layer 230 helps improve the closed state by increasing the opacity of the device that may be caused by the partially translucent wall material. The light-blocking layer 230 may be conductive, which facilitates device switching.

[0106] Figure 8 also illustrates the variable light transmission device (560) of the present invention, which includes a first light-transmitting substrate 201, a first light-transmitting electrode layer 202, a micro-unit layer comprising a plurality of micro-units and a sealing layer 206 (only one micro-unit is shown here), a second light-transmitting electrode layer 207, and a second light-transmitting substrate 208. Each micro-unit includes a micro-unit wall 212, a channel 215, a protrusion structure 217, and a micro-unit bottom layer 210. In the micro-unit of the variable light transmission device in Figure 8, the inner surface (213) of the micro-unit wall and the inner surface (211) of the micro-unit bottom form an angle (φ) greater than 90 degrees. The inventors of the present invention have found that such a structure significantly facilitates the embossing process for manufacturing a plurality of micro-units because the embossing tool can be easily removed without damaging the micro-unit wall. The angle φ can be 90 to 120 degrees, 93 to 117 degrees, 95 to 115 degrees, 98 to 118 degrees, or 100 to 115 degrees.

[0107] As described above, the variable light transmission device of the present invention includes a micro-unit with a protruding structure. The protruding structure has a three-dimensional shape composed of one or more geometric shapes, at least one of which is a cone. The bottom surface of the protrusion is a geometric shape selected from the group consisting of: teardrop shape, teardrop shape with a rounded end, ellipse with two apexes, lemon shape, rounded-end lemon shape, curved polygon, and curved polygon with rounded vertices, wherein the polygon has 3 to 6 sides.

[0108] Figure 9A shows a top view of a micro-unit with a protruding bottom surface (its geometry is teardrop-shaped). Figure 9B shows a top view of a micro-unit with a protruding bottom surface (its geometry is lemon-shaped). Figure 9C shows a top view of a micro-unit with a protruding bottom surface (its geometry is a curved triangle). Figure 9D shows a top view of a micro-unit with a protruding bottom surface (its geometry is a curved square). The bolded areas in Figures 9A, 9B, 9C, and 9D represent the micro-unit channels of the micro-units. As mentioned above, the perimeter of the inner bottom surface of the channel is also the perimeter of the protruding bottom surface. The bolded areas in Figures 10A, 10B, and 11A-11F also represent the micro-unit channels of the micro-units.

[0109] As shown in Figure 10A, the micro-unit layer of the variable light transmission device of the present invention may include a set of two adjacent micro-units, namely a first micro-unit and a second micro-unit. The first micro-unit includes a first protruding structure having a first protruding bottom surface, the first protruding bottom surface having a symmetrical teardrop-shaped geometry, the symmetrical teardrop-shaped geometry having an axis having a direction. The second micro-unit includes a second protruding structure having a second protruding bottom surface, the second protruding bottom surface having a symmetrical curved triangle geometry, the symmetrical curved triangle geometry having three axes, each of the three axes having a direction. In this example, one of the three axes of the curved triangle geometry is parallel to the axis of the teardrop shape and has the same direction as the axis of the teardrop shape.

[0110] Figure 10B illustrates another example of a set of two adjacent micro-units, namely the third micro-unit and the fourth micro-unit. The third micro-unit includes a third protrusion structure with a third protruding base surface, the third protrusion base surface having a symmetrical teardrop-shaped geometry, the symmetrical teardrop-shaped geometry having one axis; the fourth micro-unit includes a fourth protrusion structure with a fourth protruding base surface, the fourth protrusion base surface having a symmetrical curved triangle geometry, the symmetrical curved triangle geometry having three axes. In this example, one of the three axes of the symmetrical curved triangle forms an angle of 30 to 60 degrees with the axis of the teardrop shape.

[0111] Figure 11A illustrates another example of a group of four adjacent micro-units, designated as first, second, third, and fourth micro-units. The first micro-unit includes a first protrusion structure with a first protruding base; the second micro-unit includes a second protruding structure with a second protruding base; the third micro-unit includes a third protruding structure with a third protruding base; and the fourth micro-unit includes a fourth protruding structure with a fourth protruding base. The first micro-unit is adjacent to the second and third micro-units; the second micro-unit is adjacent to the first, third, and fourth micro-units; the third micro-unit is adjacent to the first, second, and fourth micro-units; and the fourth micro-unit is adjacent to the second and third micro-units. The first protruding base has a symmetrical teardrop-shaped geometry with a first axis and a first direction. The second protruding base has a symmetrical teardrop-shaped geometry with a second axis and a second direction. The third protruding base has a symmetrical curved triangular geometry with three axes, each of which has a direction. The fourth protrusion's base surface has a symmetrical curved triangle geometry with three axes, each having a direction. In this example, the first axis is parallel to the second axis, and the direction of the first axis is opposite to the direction of the second axis; one of the axes of the third protrusion's base surface geometry is parallel to both the first and second axes and has the same direction as the first direction; one of the axes of the fourth protrusion's base surface geometry is parallel to both the first and second axes and has the same direction as the second direction. The micro-unit layer can include multiple groups of micro-units, each group having a first, second, third, and fourth micro-unit. Figure 11B illustrates a top view of a portion of an example micro-unit layer, comprising six groups of micro-units, each group having a first, second, third, and fourth micro-unit.

[0112] Figure 11C illustrates another example of a group of four adjacent micro-units, designated as the fifth, sixth, seventh, and eighth micro-units. The fifth micro-unit includes a fifth protrusion structure with a fifth protruding base; the sixth micro-unit includes a sixth protrusion structure with a sixth protruding base; the seventh micro-unit includes a seventh protrusion structure with a seventh protruding base; and the eighth micro-unit includes an eighth protrusion structure with an eighth protruding base. The fifth micro-unit is adjacent to the sixth and seventh micro-units. The sixth micro-unit is adjacent to the fifth, seventh, and eighth micro-units. The seventh micro-unit is adjacent to the fifth, sixth, and eighth micro-units. The eighth micro-unit is adjacent to the sixth and seventh micro-units. The fifth protruding base has a symmetrical teardrop-shaped geometry with a fifth axis and a fifth direction. The sixth protruding base has a symmetrical teardrop-shaped geometry with a sixth axis and a sixth direction. The seventh protruding base has a symmetrical curved triangular geometry with three axes, each of which has a direction. The eighth protrusion's base surface has a symmetrical curved triangle geometry with three axes, each having a direction. In this example, the fifth axis is parallel to the sixth axis, and the direction of the fifth axis is opposite to the direction of the sixth axis; one of the axes of the seventh protrusion's base surface geometry is parallel to both the fifth and sixth axes and has a direction opposite to the fifth direction; one of the axes of the eighth protrusion's base surface geometry is parallel to both the fifth and sixth axes and has the same direction as the fifth direction. The micro-unit layer can include multiple groups of micro-units, each group having a fifth, sixth, seventh, and eighth micro-unit. Figure 11D illustrates a partial top view of one example of a micro-unit layer, comprising five groups of micro-units, each group having a fifth, sixth, seventh, and eighth micro-unit.

[0113] Figure 11E is a top view of a portion of the micro-unit layer of the variable light transmission device of the present invention. This portion of the micro-unit layer comprises a group of eight micro-units. These eight micro-units correspond to combinations of (i) the first, second, third, and fourth micro-units (Figure 11A) and (ii) the fifth, sixth, seventh, and eighth micro-units (Figure 11C). Figure 11F illustrates a top view of a portion of one example of the micro-unit layer, which comprises multiple groups of micro-units, each group as shown in Figure 11E.

[0114] Figure 12B shows a Fraunhofer diffraction pattern formed by a non-inventive variable light transmission device with a hexagonal aperture, a top view of a portion of which is shown in Figure 12A. The variable light transmission device of Figure 12A includes micro-units with conical protrusions and hexagonal channels. The diffraction pattern shown in Figure 12B contains a highly visible linear component, in which the light intensity gradually decreases as the linear component moves away from the center of the light pattern.

[0115] In contrast, Figure 13 shows the diffraction pattern formed by the variable light transmission device 200 shown in Figures 3A, 3B, and 3C. The unique micro-unit structure of the variable light transmission device of the present invention significantly improves the diffraction pattern of the generated light and reduces image blur. The micro-unit design of the device of the present invention improves the observed image. Aperture diffraction is reduced in the device of the present invention because (i) various types of micro-units with different shaped protruding bottom surfaces are used, and (ii) the curved features of the bottom surface shape of the channel (which is the intersection of the channel and the inner surface of the bottom of the micro-unit) and the variation replace the straight lines of the corresponding shape of the bottom surface of the channel in the design shown in Figure 12A.

[0116] The electrophoretic medium of the variable light transmission device of the present invention comprises charged pigment particles, a charge control agent, and a nonpolar liquid. The charge control agent is typically an oligomeric or polymeric material soluble in the nonpolar liquid of the electrophoretic medium. The charge control agent is a surfactant-type molecule having one or more polar functional groups (head end) and a nonpolar portion (tail end). The electrophoretic medium may contain a concentration of 0.1 wt% to 10 wt% of the charge control agent by weight. Alternatively, the electrophoretic medium may contain a concentration of 0.5 wt% to 9 wt%, 0.7 wt% to 8 wt%, 1 wt% to 7 wt%, or 1 wt% to 6 wt% of the charge control agent by weight.

[0117] The nonpolar liquid of the electrophoretic medium may include aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, polydimethylsiloxanes, or mixtures thereof.

[0118] Electrophoretic media can also contain flocculants, also known as depletors. Depletors create osmotic pressure differences between pigment particles and between pigment-particle depletor molecules. This, in turn, enhances the bistability of the device's optical states (on and off). Depletors are typically polymeric materials, such as polyisobutylene and polydimethylsiloxane.

[0119] [Terms and Conditions]

[0120] Clause 1: A variable light transmission device (200), comprising: First transparent electrode layer (202); A second light-transmitting electrode layer (207); and A micro-unit layer (203) is disposed between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207). The micro-unit layer (203) includes a plurality of micro-units (204) and a sealing layer (206). Each micro-unit in the plurality of micro-units (204) includes an electrophoretic medium (209), which includes charged pigment particles (223), a charge control agent, and a nonpolar liquid. Each micro-unit in the plurality of micro-units (204) has a micro-unit opening (205). The sealing layer (206) spans the micro-unit openings (205) of the plurality of micro-units (204). Each micro-unit's sealing layer (206) has an upper surface and a lower surface, the lower surface being in contact with the electrophoretic medium (209), and the upper surface being in contact with (i) the first light-transmitting electrode layer (202) or (ii) an adhesive layer, the adhesive layer being disposed between the first light-transmitting electrode layer (202) and the upper surface of the sealing layer (206); Each of the plurality of micro-units (204) includes a micro-unit bottom layer (210), a protrusion structure (217), a micro-unit wall (212), and a channel (215). The micro-unit bottom layer (210) has a micro-unit bottom inner surface (211), which is composed of an exposed micro-unit bottom inner surface (211a) and an unexposed micro-unit bottom inner surface (211b). The protrusion structure (217) has a protrusion bottom surface (218), a protrusion surface (221), a protrusion top surface (219), a protrusion height (220), and a protrusion volume. The protrusion top surface (219) is a point of the protrusion structure that is shorter than all other points of the protrusion structure (217) from the micro-unit opening (205). The protrusion height (220) is the distance between the protrusion bottom surface (218) and the protrusion top surface (219). The protrusion surface (221) is the surface of the protrusion structure (217) that contacts the electrophoretic medium (209). The unexposed inner surface of the micro-unit bottom surface (211b) contacts the protrusion bottom surface (218), and the exposed inner surface of the micro-unit bottom surface (211a) contacts the electrophoretic medium (209). The micro-unit wall (212) has an inner surface (213) and an upper surface (214). The inner surface (213) is the surface in contact between the micro-unit wall (212) and the electrophoretic medium (209), and the upper surface (214) is the surface in contact between the micro-unit wall (212) and the sealing layer (206). The channel (215) has a channel height (216h), a channel bottom surface, a channel bottom surface width, an inner bottom surface perimeter, and an outer bottom surface perimeter. The channel height (216h) is 50% of the protrusion height (220). The inner bottom surface perimeter is the intersection of the micro-unit wall (212) and the exposed micro-unit bottom inner surface (211). The outer bottom surface perimeter is the intersection of the protrusion bottom surface and the exposed micro-unit bottom inner surface. The channel bottom surface width is the smaller distance between a point on the inner bottom surface perimeter and a point on the outer bottom surface perimeter. The channel (215) has a three-dimensional shape defined by the space between the exposed micro-unit bottom inner surface (211a), the protruding surface (221), a plane parallel to the micro-unit bottom inner surface (211), and the micro-unit wall inner surface (213), wherein the distance between the plane and the micro-unit bottom inner surface (211) is equal to the channel height (216h); The protrusion structure has a three-dimensional shape composed of one or more geometric shapes, at least one of which is a cone shape, wherein the bottom surface of the protrusion is selected from the group consisting of: a teardrop shape, a teardrop shape with a rounded end, an ellipse with two apexes, a lemon shape, a lemon shape with a rounded end, a curved polygon, and a curved polygon with a rounded vertex, the curved polygon and the curved polygon with a rounded vertex having 3 to 6 sides; A first electric field with a first waveform is applied between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207), causing the charged pigment particles (223) to move toward the channel (215), thereby causing the variable light transmission device (200) to switch to an optically active state; A second electric field is applied between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207) with a second waveform, causing the charged pigment particles (223) to move toward the first light-transmitting electrode layer (202), wherein the closed optical state has a lower percentage of transparency than the open optical state.

[0121] Clause 2: The variable light transmission device as in Clause 1, wherein the micro-unit opening (205) of each of the plurality of micro-units (204) in the micro-unit layer (203) is geometrically shaped, and the geometry of the micro-unit opening (205) is the same as the geometry of the protruding bottom surface of the micro-unit.

[0122] Clause 3: The variable light transmission device as in Clause 1 or 2, wherein each of the plurality of micro-units (204) has a length of 400 micrometers to 800 micrometers and a height of 20 micrometers to 100 micrometers, and wherein the width of the channel of each of the plurality of micro-units (204) is 10 micrometers to 30 micrometers.

[0123] Clause 4: The variable light transmission device as described in any of Clauses 1 to 3, wherein the height (220) of the protrusion is between 15 micrometers and 90 micrometers.

[0124] Clause 5: A variable light transmission device as described in any of Clauses 1 to 4, wherein the micro-unit layer comprises a set of two adjacent micro-units, namely a first micro-unit and a second micro-unit, the first micro-unit comprising a first protrusion structure having a first protruding bottom surface, the geometry of the first protruding bottom surface being (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape having a rounded end, the geometry of the first protruding bottom surface having an axis having a direction, the second micro-unit comprising a second protruding bottom surface having a second protruding bottom surface, the geometry of the second protruding bottom surface being (iii) a symmetrical curved triangle or (iv) a symmetrical curved triangle having a rounded vertex, the geometry of the second protruding bottom surface having three axes, each of the three axes having a direction, wherein one of the three axes of the geometry of the second protruding bottom surface is parallel to the axis of the geometry of the first protruding bottom surface and has the same direction as the axis of the geometry of the first protruding bottom surface.

[0125] Clause 6: A variable light transmission device as described in any of Clauses 1 to 5, wherein the micro-unit layer comprises a set of two adjacent micro-units, namely a third micro-unit and a fourth micro-unit, the third micro-unit comprising a third protrusion structure having a third protruding bottom surface, the geometry of the third protruding bottom surface being (i) a symmetrical teardrop shape, or (ii) a symmetrical teardrop shape having a rounded end, the geometry of the third protruding bottom surface having an axis, the fourth micro-unit comprising a fourth protruding structure having a fourth protruding bottom surface, the geometry of the fourth protruding bottom surface being (iii) a symmetrical curved triangle, or (iv) a symmetrical curved triangle having a rounded vertex, the geometry of the fourth protruding bottom surface having three axes, wherein one of the three axes of the geometry of the fourth protruding bottom surface forms an angle of 30 to 60 degrees with the axis of the third protruding bottom surface.

[0126] Clause 7: A variable light transmission device as described in any of Clauses 1 to 6, wherein the micro-unit layer comprises a set of four micro-units, namely a first, second, third, and fourth micro-unit; the first micro-unit comprises a first protrusion structure having a first protruding bottom surface; the second micro-unit comprises a second protruding structure having a second protruding bottom surface; the third micro-unit comprises a third protruding structure having a third protruding bottom surface; and the fourth micro-unit comprises a fourth protruding structure having a fourth protruding bottom surface. The first micro-unit is adjacent to the second micro-unit and the... The third micro-unit, the second micro-unit being adjacent to the first micro-unit, the third micro-unit, and the fourth micro-unit, the third micro-unit being adjacent to the first micro-unit, the second micro-unit, and the fourth micro-unit, the fourth micro-unit being adjacent to the second micro-unit and the third micro-unit, the geometry of the bottom surface of the first protrusion being (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end, the geometry of the bottom surface of the first protrusion having a first axis, the first axis having a first direction, the geometry of the bottom surface of the second protrusion being (ii) i) a symmetrical teardrop shape, or (iv) a symmetrical teardrop shape with a rounded end, the geometry of the second protrusion's base surface having a second axis, the second axis having a second direction, the geometry of the third protrusion's base surface being (v) a symmetrical curved triangle, or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the third protrusion's base surface having three axes, each of the three axes having a direction, the geometry of the fourth protrusion's base surface being (vii) a symmetrical curved triangle, or (viii) a symmetrical curved triangle with a rounded vertex, the geometry of the fourth protrusion's base surface having three axes, each of the three axes having a direction, the first axis being parallel to the second axis, the direction of the first axis being opposite to the direction of the second axis, one of the axes of the geometry of the third protrusion's base surface being parallel to the first axis and the second axis and having the same direction as the first direction, one of the axes of the geometry of the fourth protrusion's base surface being parallel to the first axis and the second axis and having the same direction as the second direction.

[0127] Clause 8: The variable light transmission device as described in Clause 7, wherein the micro-unit layer comprises two or more groups of micro-units, each group having four micro-units, each group consisting of the first, second, third and fourth micro-units.

[0128] Clause 9: A variable light transmission device as described in any of Clauses 1 to 8, wherein the micro-unit layer comprises a set of four micro-units, namely a fifth, sixth, seventh, and eighth micro-unit, wherein the fifth micro-unit comprises a fifth protrusion structure having a fifth protrusion bottom surface, the sixth micro-unit comprises a sixth protrusion structure having a sixth protrusion bottom surface, the seventh micro-unit comprises a seventh protrusion structure having a seventh protrusion bottom surface, and the eighth micro-unit comprises an eighth protrusion structure having an eighth protrusion bottom surface, wherein the fifth micro-unit is adjacent to the sixth micro-unit and the... The seventh micro-unit, the sixth micro-unit being adjacent to the fifth micro-unit, the seventh micro-unit, and the eighth micro-unit, the seventh micro-unit being adjacent to the fifth micro-unit, the sixth micro-unit, and the eighth micro-unit, the eighth micro-unit being adjacent to the sixth micro-unit and the seventh micro-unit, the geometry of the bottom surface of the fifth protrusion being (i) a symmetrical teardrop shape, or (ii) a symmetrical teardrop shape with a rounded end, the geometry of the bottom surface of the fifth protrusion having a fifth axis, the fifth axis having a fifth direction, the geometry of the bottom surface of the sixth protrusion being (i) ii) a symmetrical teardrop shape, or (iv) a symmetrical teardrop shape with a rounded end, the geometry of the bottom surface of the sixth protrusion having a sixth axis, the sixth axis having a sixth direction, the geometry of the bottom surface of the seventh protrusion being (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the bottom surface of the seventh protrusion having three axes, each of the three axes having a direction, the geometry of the bottom surface of the eighth protrusion being (vii) a symmetrical curved triangle, or (viii) a symmetrical curved triangle with a rounded vertex, the geometry of the bottom surface of the eighth protrusion having three axes, each of the three axes having a direction, the fifth axis being parallel to the sixth axis, the direction of the fifth axis being opposite to the direction of the sixth axis, one of the axes of the geometry of the bottom surface of the seventh protrusion being parallel to the fifth axis and the sixth axis and having a direction opposite to the fifth direction, one of the axes of the geometry of the bottom surface of the eighth protrusion being parallel to the fifth axis and the sixth axis and having a direction the same as the fifth direction.

[0129] Clause 10: The variable light transmission device as described in Clause 9, wherein the micro-unit layer comprises two or more groups of micro-units, each group having four micro-units, each group consisting of the fifth, sixth, seventh and eighth micro-units.

[0130] Clause 11: As in Clause 9, the variable light transmission device, wherein the group of micro-units includes, in addition to the fifth, sixth, seventh, and eighth micro-units, a ninth, tenth, eleventh, and twelfth micro-units, wherein the ninth micro-unit includes a ninth protrusion structure having a ninth protruding bottom surface, the tenth micro-unit includes a tenth protruding bottom surface, the eleventh micro-unit includes an eleventh protruding bottom surface, and the twelfth micro-unit includes a twelfth protruding bottom surface; the seventh micro-unit is adjacent to the fifth, sixth, eighth, and ninth micro-units. The eighth micro-unit is adjacent to the sixth, seventh, ninth, and tenth micro-units; the ninth micro-unit is adjacent to the seventh, eighth, tenth, and eleventh micro-units; the tenth micro-unit is adjacent to the eighth, ninth, eleventh, and twelfth micro-units; the eleventh micro-unit is adjacent to the ninth, tenth, and twelfth micro-units; and the twelfth micro-unit is adjacent to the tenth and eleventh micro-units. The geometry of the bottom surface of the ninth protrusion is (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end. The geometry of the bottom surface of the ninth protrusion has a ninth axis, and the ninth axis has a ninth direction. The geometry of the tenth protrusion's base is (iii) a symmetrical teardrop shape or (iv) a symmetrical teardrop shape with a rounded end, the geometry of the tenth protrusion's base having a tenth axis, the tenth axis having a tenth direction; the geometry of the eleventh protrusion's base is (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the eleventh protrusion's base having three axes, each of the three axes having a direction; the geometry of the twelfth protrusion's base is (vii) a symmetrical curved triangle or (viii) a triangle with a rounded vertex. The symmetrical curved triangle has a geometric shape with three axes on its bottom surface. Each of the three axes has a direction. The ninth axis is parallel to the tenth axis and its direction is opposite to that of the tenth axis. One of the axes of the geometric shape of the bottom surface of the eleventh protrusion is parallel to both the ninth and tenth axes and has the same direction as the ninth direction. One of the axes of the geometric shape of the bottom surface of the twelfth protrusion is parallel to both the ninth and tenth axes and has the same direction as the tenth direction. The fifth axis forms an angle of 30 to 60 degrees with the ninth axis.

[0131] Clause 12: The variable light transmission device as described in Clause 11, wherein the micro-unit layer comprises two or more groups of micro-units, each group having eight micro-units, each group consisting of the fifth, sixth, seventh, eighth, ninth, tenth, eleventh and twelfth micro-units.

[0132] Clause 13: A variable light transmission device as described in any of Clauses 1 to 12, wherein the variable light transmission device comprises a micro-unit having an inner wall surface (213) and a bottom inner surface (211) of a micro-unit, wherein the inner wall surface (213) of the micro-unit and the bottom inner surface (211) of the micro-unit form an angle (φ) of 90 degrees to 120 degrees.

[0133] Clause 14: A variable light transmission device as described in any of Clauses 1 to 13, wherein the variable light transmission device comprises (i) an adhesive layer disposed between the first light-transmitting electrode layer (202) and the sealing layer (206); (ii) a second adhesive layer disposed between the micro-unit layer (203) and the second light-transmitting electrode layer (207); or (iii) the adhesive layer and the second adhesive layer.

[0134] Clause 15: A variable light transmission device as described in any of Clauses 1 to 14, wherein the variable light transmission device includes a light blocking layer (230) disposed between the upper surface (214) of the micro-unit wall and the sealing layer (206).

[0135] Clause 16: The variable light transmission device as in Clause 15, wherein the light blocking layer (230) contains light-absorbing pigment.

[0136] Clause 17: The variable light transmission device as in Clause 16, wherein the light-absorbing pigment of the light-blocking layer (230) is black.

[0137] Clause 18: A variable light transmission device as described in any of Clauses 1 to 17, wherein the second electric field causes the charged pigment particles (223) to move toward the first light-transmitting electrode layer (202) at a velocity having a lateral component.

[0138] Clause 19: A variable light transmission device as described in any of Clauses 1 to 18, wherein the second waveform includes at least one positive voltage and at least one negative voltage, the second waveform having a net positive pulse or a net negative pulse.

[0139] Clause 20: The variable light transmission device as described in Clause 19, wherein the second waveform includes an AC waveform having a duty cycle of 5% to 45%, or wherein the second waveform includes a DC bias waveform formed by superimposing a DC voltage component with an AC waveform.

[0140] Components in the attached diagram: 101 Teardrop-shaped tip; 102 Teardrop-shaped head end; 103 Teardrop-shaped axis; 111 Elliptical tip with two points; 113 Elliptical axis of symmetry with two points; 121 Lemon-shaped first end; 122 Lemon-shaped second end; 123 Lemon-shaped axis; 200 Variable light transmission device; 201 First light-transmitting substrate; 202 First light-transmitting electrode layer; 203 Micro-unit layer; 204 Multiple micro-units; 205 Micro-unit opening; 206 Sealing layer; 207 Second light-transmitting electrode layer; 208 Second light-transmitting substrate; 209 Electrophoresis medium 210 Micro-unit bottom layer; 211 Micro-unit bottom inner surface; 211a Exposed micro-unit bottom inner surface; 211b Unexposed micro-unit bottom inner surface; 212 Micro-unit wall; 213 Micro-unit wall inner surface; 214 Micro-unit wall upper surface; 215 Channel; 216h Channel height; 217 Protrusion structure; 218 Protrusion bottom surface; 219 Protrusion top; 220 Protrusion height; 221 Protrusion surface; 223 Charged pigment particles; 230 Light blocking layer; 250 First outer surface of variable light transmission device; 251 Second outer surface of variable light transmission device; 502 Electric field.

[0141] 101: Teardrop-shaped tip 102: Teardrop-shaped tip 103: Teardrop-shaped axis 111: Tip 113: Axis of symmetry 121: First End 122: Second End 123: Axis 200: Variable light transmission device 201: First transparent substrate 202: First transparent electrode layer 203: Micro-unit layer 204: Microunit 205: Micro-unit opening 206: Sealing layer 207: Second transparent electrode layer 208: Second transparent substrate 209: Electrophoretic medium 210: Micro-unit bottom layer 211: Bottom inner surface of the micro-unit 211a: Exposed inner surface of the bottom of the micro-unit 211b: Unexposed inner surface of the bottom of the micro-unit 212: Micro-unit wall 213: Inner surface of micro-unit wall 214: Upper surface of micro-unit wall 215: Channel 216h: Channel height 217: Protruding structure 218: Protruding bottom surface 219: Top of the protrusion 220: Protrusion height 221: Protruding surface 223: Charged pigment particles 230: Light blocking layer 250: First outer surface 251: Second outer surface 502: Electric Field

Claims

1. A variable light transmission device (200), comprising: A first light-transmitting electrode layer (202); A second light-transmitting electrode layer (207); And a micro-unit layer (203) disposed between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207), the micro-unit layer (203) includes a plurality of micro-units (204) and a sealing layer (206), each of the plurality of micro-units (204) includes an electrophoretic medium (209), the electrophoretic medium (209) includes charged pigment particles (223), a charge control agent and a non-polar liquid, each of the plurality of micro-units (204) has a micro-unit opening (205), and the sealing layer (206) spans the micro-unit openings (205) of the plurality of micro-units (204); The sealing layer (206) of each micro-unit has an upper surface and a lower surface, the lower surface being in contact with the electrophoretic medium (209), and the upper surface being in contact with (i) the first light-transmitting electrode layer (202) or (ii) an adhesive layer disposed between the first light-transmitting electrode layer (202) and the upper surface of the sealing layer (206); Each of the plurality of micro-units (204) includes a micro-unit bottom layer (210), a protrusion structure (217), a micro-unit wall (212) and a channel (215), the micro-unit bottom layer (210) having a micro-unit bottom inner surface (211), the micro-unit bottom inner surface (211) being composed of an exposed micro-unit bottom inner surface (211a) and an unexposed micro-unit bottom inner surface (211b); The protrusion structure (217) has a protrusion bottom surface (218), a protrusion surface (221), a protrusion top surface (219), a protrusion height (220), and a protrusion volume. The protrusion top surface (219) is a point of the protrusion structure that is shorter than all other points of the protrusion structure (217) from the micro-unit opening (205). The protrusion height (220) is the distance between the protrusion bottom surface (218) and the protrusion top surface (219). The protrusion surface (221) is the surface of the protrusion structure (217) that contacts the electrophoretic medium (209). The unexposed micro-unit bottom inner surface (211b) contacts the protrusion bottom surface (218), and the exposed micro-unit bottom inner surface (211a) contacts the electrophoretic medium (209). The micro-unit wall (212) has an inner surface (213) and an upper surface (214) of the micro-unit wall. The inner surface (213) of the micro-unit wall is the surface in contact with the electrophoretic medium (209) of the micro-unit wall, and the upper surface (214) of the micro-unit wall is the surface in contact with the sealing layer (206).The channel (215) has a channel height (216h), a channel bottom surface, a channel bottom surface width, an inner bottom surface perimeter, and an outer bottom surface perimeter. The channel height (216h) is 50% of the protrusion height (220). The inner bottom surface perimeter is the intersection of the micro-unit wall (212) and the exposed micro-unit bottom inner surface (211). The outer bottom surface perimeter is the intersection of the protrusion bottom surface and the exposed micro-unit bottom inner surface. The channel bottom surface width is the smaller distance between a point in the inner bottom surface perimeter and a point in the outer bottom surface perimeter. The channel (215) has a three-dimensional shape defined by the space between the exposed micro-unit bottom inner surface (211a), the protrusion surface (221), a plane parallel to the micro-unit bottom inner surface (211), and the micro-unit wall inner surface (213). The distance between the plane and the micro-unit bottom inner surface (211) is equal to the channel height (216h). The protrusion structure has a three-dimensional shape composed of one or more geometric shapes, at least one of the one or two or more geometric shapes being a cone shape, wherein the bottom surface of the protrusion is a geometric shape selected from the group consisting of: a teardrop shape, a teardrop shape with a rounded end, an ellipse with two apexes, a lemon shape, a lemon shape with a rounded end, a curved polygon, and a curved polygon with a rounded vertex, the curved polygon and the curved polygon with a rounded vertex having 3 to 6 sides; wherein a first electric field is applied between the first light-transmitting electrode layer (202) and the second light-transmitting electrode layer (207) with a first waveform, causing the charged pigment particles (223) to move toward the channel (215), thereby causing the variable light transmission device (200) to switch to an on optical state; A second electric field with a second waveform is applied between the first transparent electrode layer (202) and the second transparent electrode layer (207) to cause the charged pigment particles (223) to move toward the first transparent electrode layer (202). The closed optical state has a lower percentage of transparency than the open optical state. The second waveform includes at least one positive voltage and at least one negative voltage, has a net positive pulse or a net negative pulse, and includes an AC waveform with a duty cycle of 5% to 45%. Alternatively, the second waveform includes a DC bias waveform formed by the superposition of a DC voltage component and an AC waveform.

2. The variable light transmission device of claim 1, wherein the micro-unit opening (205) of each of the plurality of micro-units (204) of the micro-unit layer (203) is geometrically shaped, and the geometry of the micro-unit opening (205) is the same as the geometry of the protruding bottom surface of the micro-unit.

3. The variable light transmission device of claim 1, wherein each of the plurality of micro-units (204) has a length of 400 micrometers to 800 micrometers and a height of 20 micrometers to 100 micrometers, and wherein the width of the channel of each of the plurality of micro-units (204) is 10 micrometers to 30 micrometers.

4. The variable light transmission device as claimed in claim 1, wherein the height (220) of the protrusion is from 15 micrometers to 90 micrometers.

5. The variable light transmission device of claim 1, wherein the micro-unit layer comprises a set of two adjacent micro-units, namely a first micro-unit and a second micro-unit, the first micro-unit comprising a first protrusion structure having a first protruding bottom surface, the geometry of the first protruding bottom surface being (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape having a rounded end, the geometry of the first protruding bottom surface having an axis having a direction, the second micro-unit comprising a second protruding bottom surface having a second protruding bottom surface, the geometry of the second protruding bottom surface being (iii) a symmetrical curved triangle or (iv) a symmetrical curved triangle having a rounded vertex, the geometry of the second protruding bottom surface having three axes, each of the three axes having a direction, wherein one of the three axes of the geometry of the second protruding bottom surface is parallel to the axis of the geometry of the first protruding bottom surface and has the same direction as the direction of the axis of the geometry of the first protruding bottom surface.

6. The variable light transmission device of claim 1, wherein the micro-unit layer comprises a set of two adjacent micro-units, namely a third micro-unit and a fourth micro-unit, the third micro-unit comprising a third protrusion structure having a third protruding bottom surface, the geometry of the third protruding bottom surface being (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape having a rounded end, the geometry of the third protruding bottom surface having an axis, the fourth micro-unit comprising a fourth protruding structure having a fourth protruding bottom surface, the geometry of the fourth protruding bottom surface being (iii) a symmetrical curved triangle or (iv) a symmetrical curved triangle having a rounded vertex, the geometry of the fourth protruding bottom surface having three axes, wherein one of the three axes of the geometry of the fourth protruding bottom surface forms an angle of 30 to 60 degrees with the axis of the third protruding bottom surface.

7. The variable light transmission device of claim 1, wherein the micro-unit layer comprises a set of four micro-units, namely a first, a second, a third, and a fourth micro-unit, the first micro-unit comprising a first protrusion structure having a first protruding bottom surface, the second micro-unit comprising a second protruding bottom surface having a second protruding bottom surface, the third micro-unit comprising a third protruding bottom surface having a third protruding bottom surface, and the fourth micro-unit comprising a fourth protruding bottom surface having a fourth protruding bottom surface, the first micro-unit being adjacent to the second micro-unit and the third micro-unit. The second micro-unit is adjacent to the first micro-unit, the third micro-unit, and the fourth micro-unit; the third micro-unit is adjacent to the first micro-unit, the second micro-unit, and the fourth micro-unit; the fourth micro-unit is adjacent to the second micro-unit and the third micro-unit; the geometry of the bottom surface of the first protrusion is (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end; the geometry of the bottom surface of the first protrusion has a first axis, the first axis has a first direction; the geometry of the bottom surface of the second protrusion is (iii) The geometry of the second protruding bottom surface is (iv) a symmetrical teardrop shape or (vi) a symmetrical teardrop shape with a rounded end, the geometry of the third protruding bottom surface is (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the third protruding bottom surface is three axes, each of the three axes having a direction, the geometry of the fourth protruding bottom surface is (vii) a symmetrical curved triangle or (viii) a symmetrical curved triangle with a rounded vertex, the geometry of the fourth protruding bottom surface is three axes, each of the three axes having a direction, the first axis being parallel to the second axis, the direction of the first axis being opposite to the direction of the second axis, one of the axes of the geometry of the third protruding bottom surface is parallel to the first axis and the second axis and has the same direction as the first direction, one of the axes of the geometry of the fourth protruding bottom surface is parallel to the first axis and the second axis and has the same direction as the second direction.

8. The variable light transmission device of claim 7, wherein the micro-unit layer comprises two or more groups of micro-units, each group having four micro-units, each group consisting of a first, second, third and fourth micro-units.

9. The variable light transmission device of claim 1, wherein the micro-unit layer comprises a set of four micro-units, namely a fifth, a sixth, a seventh, and an eighth micro-unit, the fifth micro-unit comprising a fifth protrusion structure having a fifth protrusion bottom surface, the sixth micro-unit comprising a sixth protrusion structure having a sixth protrusion bottom surface, the seventh micro-unit comprising a seventh protrusion structure having a seventh protrusion bottom surface, and the eighth micro-unit comprising an eighth protrusion structure having an eighth protrusion bottom surface, the fifth micro-unit being adjacent to the sixth micro-unit and the seventh micro-unit. The sixth micro-unit is adjacent to the fifth micro-unit, the seventh micro-unit, and the eighth micro-unit. The seventh micro-unit is adjacent to the fifth micro-unit, the sixth micro-unit, and the eighth micro-unit. The eighth micro-unit is adjacent to the sixth micro-unit and the seventh micro-unit. The geometry of the bottom surface of the fifth protrusion is (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end. The geometry of the bottom surface of the fifth protrusion has a fifth axis, and the fifth axis has a fifth direction. The geometry of the bottom surface of the sixth protrusion is (iii) The geometry of the sixth protrusion's base is (iv) a symmetrical teardrop shape or (vi) a symmetrical teardrop shape with a rounded end, the geometry of the seventh protrusion's base is (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the seventh protrusion's base has three axes, each of the three axes having a direction, the geometry of the eighth protrusion's base is (vii) a symmetrical curved triangle or (viii) a symmetrical curved triangle with a rounded vertex, the geometry of the eighth protrusion's base has three axes, each of the three axes having a direction, the fifth axis is parallel to the sixth axis, the direction of the fifth axis is opposite to the direction of the sixth axis, one of the axes of the seventh protrusion's base is parallel to the fifth axis and the sixth axis and has a direction opposite to the fifth direction, one of the axes of the eighth protrusion's base is parallel to the fifth axis and the sixth axis and has a direction the same as the fifth direction.

10. The variable light transmission device of claim 9, wherein the micro-unit layer comprises two or more groups of micro-units, each group having four micro-units, each group consisting of the fifth, sixth, seventh and eighth micro-units.

11. The variable light transmission device of claim 9, wherein the group of micro-units includes, in addition to the fifth, sixth, seventh, and eighth micro-units, a ninth, tenth, eleventh, and twelfth micro-units, wherein the ninth micro-unit includes a ninth protrusion structure having a ninth protruding bottom surface, the tenth micro-unit includes a tenth protruding structure having a tenth protruding bottom surface, the eleventh micro-unit includes an eleventh protruding structure having an eleventh protruding bottom surface, and the twelfth micro-unit includes a twelfth protruding structure having a twelfth protruding bottom surface, and the seventh micro-unit is adjacent to the fifth, sixth, eighth, and ninth micro-units. The eighth micro-unit is adjacent to the sixth, seventh, ninth, and tenth micro-units; the ninth micro-unit is adjacent to the seventh, eighth, tenth, and eleventh micro-units; the tenth micro-unit is adjacent to the eighth, ninth, eleventh, and twelfth micro-units; the eleventh micro-unit is adjacent to the ninth, tenth, and twelfth micro-units; and the twelfth micro-unit is adjacent to the tenth and eleventh micro-units. The geometry of the bottom surface of the ninth protrusion is (i) a symmetrical teardrop shape or (ii) a symmetrical teardrop shape with a rounded end. The geometry of the bottom surface of the ninth protrusion has a ninth axis, and the ninth axis has a ninth direction. The geometry of the tenth protrusion's base is (iii) a symmetrical teardrop shape or (iv) a symmetrical teardrop shape with a rounded end, the geometry of the tenth protrusion's base having a tenth axis, the tenth axis having a tenth direction; the geometry of the eleventh protrusion's base is (v) a symmetrical curved triangle or (vi) a symmetrical curved triangle with a rounded vertex, the geometry of the eleventh protrusion's base having three axes, each of the three axes having a direction; the geometry of the twelfth protrusion's base is (vii) a symmetrical curved triangle or (viii) a symmetrical curved triangle with a rounded vertex. The symmetrical curved triangle has a geometric shape with three axes on its bottom surface. Each of the three axes has a direction. The ninth axis is parallel to the tenth axis and its direction is opposite to that of the tenth axis. One of the axes of the geometric shape of the bottom surface of the eleventh protrusion is parallel to both the ninth and tenth axes and has the same direction as the ninth direction. One of the axes of the geometric shape of the bottom surface of the twelfth protrusion is parallel to both the ninth and tenth axes and has the same direction as the tenth direction. The fifth axis forms an angle of 30 to 60 degrees with the ninth axis.

12. The variable light transmission device of claim 11, wherein the micro-unit layer comprises two or more groups of micro-units, each group having eight micro-units, each group consisting of the fifth, sixth, seventh, eighth, ninth, tenth, eleventh and twelfth micro-units.

13. A variable light transmission device as claimed in any one of claims 1 to 12, wherein the variable light transmission device includes a micro-unit having a micro-unit inner wall surface (213) and a micro-unit bottom inner surface (211), wherein the micro-unit inner wall surface (213) and the micro-unit bottom inner surface (211) form an angle (φ) of 90 degrees to 120 degrees.

14. A variable light transmission device as claimed in any one of claims 1 to 12, wherein the variable light transmission device comprises (i) an adhesive layer disposed between the first light-transmitting electrode layer (202) and the sealing layer (206); (ii) a second adhesive layer disposed between the micro-unit layer (203) and the second light-transmitting electrode layer (207); or (iii) the adhesive layer and the second adhesive layer.

15. A variable light transmission device as claimed in any one of claims 1 to 12, wherein the variable light transmission device includes a light blocking layer (230) disposed between the upper surface (214) of the micro-unit wall and the sealing layer (206).

16. The variable light transmission device of claim 15, wherein the light blocking layer (230) comprises a light-absorbing pigment.

17. The variable light transmission device of claim 16, wherein the light-absorbing pigment of the light-blocking layer (230) is black.

18. A variable light transmission device as claimed in any of claims 1 to 12, wherein the second electric field causes the charged pigment particles (223) to move toward the first light-transmitting electrode layer (202) at a velocity having a lateral component.

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