A variable light transmission device comprising microcells

Abstract

A variable light transmission device is disclosed, which mitigates negative aperture diffraction and exhibits good switching speed between open and closed optical states. The device includes a microcell layer disposed between two light transmission electrode layers, the microcell layer having a plurality of microcells, each microcell including an electrophoretic medium, and each microcell including a channel and a protrusion structure having one or more recesses.

Description

Technical Field

[0001] Related application: This application claims priority to U.S. Provisional Patent Application No. 63 / 640,380, filed April 30, 2024, which is incorporated by reference, along with all other patents and patent applications disclosed therein. Prior Technology

[0002] This invention relates to a variable light transmission device. Specifically, it relates to an electro-optic device comprising an electrophoretic medium containing a plurality of charged pigment particles, a charge control agent, and a nonpolar liquid. The electrophoretic medium can be switched between a plurality of optical states using an electric field. The variable light transmission device modulates the total amount of light and other electromagnetic radiation passing through it. Such variable light transmission devices can be used in mirrors, windows, skylights, and similar products. For example, the device of this invention can be applied to windows that modulate infrared radiation to control the temperature inside buildings and vehicles. Examples of electrophoretic media that can be incorporated into various embodiments of the present invention include, for example, 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 Publication No. 2014 / 00558. 41. Electrophoretic media described in U.S. Patent Application Nos. 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, are all incorporated herein by reference in their entirety.

[0003] The movement of multiple charged pigment particles through a suspended fluid under the influence of an electric field in a particle-based electrophoretic display has been a focus of intensive research and development for many years. Compared to liquid crystal displays, such displays can offer advantages such as good brightness and contrast, wide viewing angles, dual stability, and low power consumption.

[0004] The terms "bistable" and "bistable" are used herein in their conventional sense in the art to refer to a display comprising a plurality of display elements having first and second display states that differ in at least one optical characteristic, such that after any given element has been driven to present its first or second display state by an address pulse of a finite duration, when the address pulse has terminated, the state will remain at least several times, for example at least four times, the minimum duration of the address pulse required to change the state of the display element. U.S. Patent Application No. 2002 / 0180687 illustrates some particle-based electrophoretic displays with grayscale capability that are stable not only in their extreme black and white states but also in their intermediate gray states, and the same applies to some other types of electro-optic displays. This type of display is appropriately called "multistable" rather than bistable, although for convenience the term "bistable" is used herein to encompass both bistable and multistable displays.

[0005] As indicated above, the electrophoretic medium requires the presence of a suspension fluid. In most prior art electrophoretic media, this suspension is a liquid, but the electrophoretic medium can be generated using a gaseous suspension fluid. Such gas-based electrophoretic media will experience particle sedimentation as in liquid-based electrophoretic media, and appear to be susceptible to the same type of problem when these media are used in a location that allows such sedimentation, for example, when the medium is placed in a trace in a vertical plane. Indeed, because the lower viscosity of the gaseous suspension fluid compared to the liquid allows for more rapid sedimentation of the charged pigment particles, particle sedimentation appears to be a more serious problem in gas-based electrophoretic media than in liquid-based media.

[0006] This patent and application, attributed to MIT, E Ink, E Ink California LLC, and related companies, describes various techniques for encapsulation and microcell electrophoresis, as well as other electro-optic media. Encapsulated electrophoretic media comprise numerous microcapsules, each containing an inner phase and a capsule wall surrounding that inner phase, which contains a plurality of electrophoretically mobile particles in a liquid medium. Typically, these capsules are held in a polymeric binder to form a coherent layer positioned between two electrodes. In a microcell electrophoretic display, charged pigment particles and liquid are not encapsulated within microcapsules, but rather retained within a plurality of cavities formed in a carrier medium, typically a polymeric film. The techniques described in these patents and applications include: (a) Electrophoretic microparticles, 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, 6,92 7,892, 6,956,690, 6,958,849, 7,002,728, 7,038,655, 7,052,766, 7,110,162, 7,113,323, 7,141,688, 7,142,351, 7,170,670, 7,226,550, 7,230,750, 7,230,751, 7,236,290, 7,277,218, 7,286,279, 7,312,916, 7,382,514, 7,390,901, 7,473,782, 7,561,324, 7,583,2 51, 7,572,394, 7,576,904, 7,580,180, 7,679,814, 7,848,006, 7,903,319, 8,018,640, 8,115,729, 8,257,614, 8,270,064, 8,363,306, 8,390,918, 8,582,196, 8,654,436, 8,902,491, 8,961,831, 9,052,564, 9,341,915, 9,348,193, 9,361,836, 9,366,935, 9,372,380, 9,382,427, 9,423,666, 9,428,649, 9,557,623, 9,670,367, 9,671,667, 9,688,859, 9,726,957, 9,752,034, 9,765,015, 9,778,535, 9,778,537, 9,835,926, 9,953,588, 9,995,987, 10,025,157, 10,031,394, 10,040,954, 10,061,123, 10,062,337, 10,147,366, and 10,514,Patent Application Publication No. 583, and U.S. Patent Application Publication Nos. 2003 / 0048522, 2003 / 0151029, 2003 / 0164480, 2004 / 0030125, 2004 / 0105036, 2005 / 0012980, 2009 / 0009852, 2011 / 0217639, 2012 / 0049125, 2013 / 0161565, 2013 / 0 Numbers 193385, 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. Patent Nos. 5,930,026, 6,067,185, 6,130,774, 6,262,706, 6,327,072, 6,392,786, 6,459,418, 6,727,881, 6,839,158, 6,866,760, 6,922,276, 6,958,848, 6,987,603, 7,110,164, 7,1 Patent applications Nos. 48,128, 7,184,197, 7,304,634, 7,327,511, 7,339,715, 7,411,719, 7,477,444, 7,561,324, 7,910,175, 7,952,790, 8,129,655, 8,446,664, and U.S. Patent Application Publications Nos. 2005 / 0156340, 2007 / 0091417, and 2009 / 0122389; (c) Microcell structures, wall materials, and methods for forming microcells; see, for example, U.S. Patent Nos. 6,672,921, 6,751,007, 6,753,067, 6,781,745, 6,788,452, 6,795,229, 6,806,995, 6,829,078, 6,850,355, 6,865,012, and 6,870. 0,662, 6,885,495, 6,930,818, 6,933,098, 6,947,202, 7,046,228, 7,072,095, 7,079,303, 7,141,279, 7,156,945, 7,205,355, 7,233,429, 7,261,920, 7,271,947, 7,304 780, 7,307,778, 7,327,346, 7,347,957, 7,470,386, 7,504,050, 7,580,180, 7,715,087, 7,767,126, 7,880,958, 8,002,948, 8,154,790, 8,169,690, 8,441,432, 8,891 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, and 7,560,004. Patent applications Nos. 7,564,614, 7,572,491, 7,616,374, 7,715,087, 7,715,088, 8,361,356, 8,625,188, 8,830,561, 9,346,987, and 9,759,978, and U.S. Patent Application 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. Patent Nos. 6,825,829, 6,982,178, 7,110,164, 7,158,282, 7,554,712, 7,561,324, 7,649,666, 7,728,811, 7,826,129, 7,839,564, and 7,843,6 21, 7,843,624, 7,952,790, 8,034,209, 8,177,942, 8,390,301, 9,238,340, 9,470,950, 9,835,925, and U.S. Patent Application Publication Nos. 2005 / 0122563, 2007 / 0237962, and 2011 / 0164301; (f) Methods used in back panels, adhesive layers and other auxiliary layers, and displays; see, for example, U.S. Patent Nos. D485,294, 5,930,026, 6,120,588, 6,124,851, 6,177,921, 6,232,950, 6,252,564, 6,312,304, 6,312,971, 6,376,828, 6,392,786, 6,413,790, 6,480,182, 6,498,114, 6,506,438, 6,518,949, 6,545,291, 6,639,578, 6,657,772, 6,664,944, 6,683,333, 6,7 10,540, 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, 7,012,60 0, 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, 7,2 23,672, 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, 7,492,49 7、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、7,8 80,958, 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, 8,362,48 8、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、9,6 32,373, 9,666,142, 9,671,635, 9,715,155, 9,777,201, 9,897,891, 10,037,735, 10,190,743, 10,324,577, 10,365,533, 10,372,008, 10,446,585, 10,466,565, 10,495,941 10,503,041, 10,509,294, 10,613,407, and U.S. Patent Application Publication Nos. 2002 / 0060321, 2004 / 0085619, 2004 / 0105036, 2005 / 0122306, 2005 / 0122563, 2006 / 0255322, 2009 / 0122389, 2010 / 0 Patent applications Nos. 177396, 2011 / 0164301, 2011 / 0292319, 2014 / 0192000, 2014 / 0210701, 2014 / 0368753, and 2016 / 0077375, and international patent applications Nos. WO2000 / 038000, WO2000 / 005704, and WO1999 / 067678; (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 6,017,584, 6,545,797, 6,664,944, 6,788,452, 6,864,875, 6,914,714, 6,972,893, 7,038,656, 7,038,670, 7,046,228, 7,052,571, 7,075,502, 7,167,155, 7,385,751, 7,492,505, and 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,Patent Application Publication No. 666, and U.S. Patent Application Publication Nos. 2008 / 0043318, 2008 / 0048970, 2009 / 0225398, 2010 / 0156780, 2011 / 0043543, 2012 / 0326957, 2013 / 0242378, 2013 / 0278995, 2014 / 0055840, 2014 / 0078576, 2014 / 0340430, 2014 / 0340736, 2014 / 0 Numbers 362213, 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, and 7,304,787. 7,312,794、7,327,511、7,408,699、7,453,445、7,492,339、7,528,822、7,545,358、7,583,251、7,602,374、7,612,760、7,679,599、7,679,813、7,6 83,606, 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, 8,462,10 2, 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、9,21 8,773, 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 9,412Patent Application Publication No. 314, and U.S. Patent Application Publication 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, and 2009 / 01955. 68, 2009 / 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 2013 / 0063333, 2013 / 0194250, 2013 / 0249782, 2013 / 0321278, 2014 / 0009817, 2014 / 0085355, 2014 / 0204012, 2014 / 0218277, 2014 / 0240210, 2014 / 0240373, 2014 / 0253425, 2014 / 0292830, 2014 / 0293398, 2014 / 0333685, 2 Numbers 014 / 0340734, 2015 / 0070744, 2015 / 0097877, 2015 / 0109283, 2015 / 0213749, 2015 / 0213765, 2015 / 0221257, 2015 / 0262255, 2015 / 0262551, 2016 / 0071465, 2016 / 0078820, 2016 / 0093253, 2016 / 0140910, and 2016 / 0180777; (i) Applications of displays; see, for example, U.S. Patent Nos. 6,118,426, 6,473,072, 6,704,133, 6,710,540, 6,738,050, 6,825,829, 7,030,854, 7,119,759, 7,312,784, 7,705,824, 8,009,348, 8,011,592, 8,064,962, 8,162,212, 8,553,012, 8,973,837, and 9,188. 829, and 9,197,704, and U.S. Patent Application Publications Nos. 2002 / 0090980, 2004 / 0119681, 2007 / 0285385, 2013 / 0176288, 2013 / 0221112, 2013 / 0233930, 2013 / 0235536, 2014 / 0049808, 2014 / 0062391, 2014 / 0206292, and 2016 / 0035291, and International Patent Application Publication No. WO 00 / 36560; and (j) Non-electrophoretic displays, such as 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 8,994,7 For the descriptions in U.S. Patent Application Publications Nos. 05, 2005 / 0099575, 2006 / 0262249, 2007 / 0042135, 2007 / 0153360, 2008 / 0020007, 2012 / 0293858, and 2015 / 0277160; and for applications of encapsulation and microcell technology beyond displays, see, for example, U.S. Patent No. 7,615,325, and U.S. Patent Application Publications Nos. 2015 / 0005720 and 2016 / 0012710.

[0007] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thereby producing a so-called polymer-dispersion electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete microdroplets of a nonpolar liquid and a continuous phase of a polymeric material, and recognize that such discrete microdroplets of the electrophoretic medium in such a polymer-dispersion electrophoretic display can be considered as capsules or microcapsules, even without a discrete capsule membrane associated with each individual microdroplet; see, for example, No. 2002 / 0131147 above. Accordingly, for the purposes of this application, such polymer-dispersion electrophoretic media are considered a subtype of encapsulated electrophoretic media.

[0008] One related type of electrophoretic display is a so-called "microcell electrophoretic display." In a microcell electrophoretic display, charged pigment particles and suspended liquid are not encapsulated within microcapsules, but rather retained within a plurality of cavities formed within a carrier medium, typically a polymeric thin film. See, for example, International Patent Application Publication No. WO 02 / 01281 and U.S. Patent Application Publication No. 2002 / 0075556, both assigned to Sipix Imaging.

[0009] Although the electrophoretic medium is often opaque (because, for example, in many electrophoretic media, these particles substantially block visible light from passing through the display) and operates in a reflective mode, many electrophoretic displays can be configured to operate in a so-called "light shutter mode," where one display state is substantially opaque and the other is translucent. See, for example, U.S. Patent Nos. 6,130,774 and 6,172,798, and U.S. Patent Nos. 5,872,552, 6,144,361, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, similar to electrophoretic displays but relying on variations in electric field strength, can operate in a similar mode; see U.S. Patent No. 4,418,346. Other types of electro-optic displays may also operate in a light shutter mode.

[0010] Encapsulated or microcell electrophoretic displays typically avoid the clustering and deposition failure modes of conventional electrophoretic devices and offer further advantages, such as the ability to print or coat displays on various flexible and rigid substrates. The term "printing" is intended to encompass all forms of printing and coating, including, but not limited to: pre-quantitative coatings such as sheet substrate coating, slot or extrusion coating, slide or tandem coating, and curtain coating; roller coatings such as blade coating on rollers, forward and reverse roller coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; pneumatic blade coating; screen printing; electrostatic printing; thermal printing; inkjet printing; electrophoretic deposition; and other similar techniques. Thus, the final 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 light transmittance. As the energy performance of buildings and vehicles becomes increasingly important, electrophoretic media can be used in windows to electrically control the proportion of incident radiation transmitted through them by varying the optical state of the media. The effective implementation of such "variable transmittance" ("VT") technology in buildings is expected to provide (1) reduced undesirable heating effects during hot weather, thereby reducing the total energy required for cooling, the size of air conditioners, and peak power demand; (2) increased use of natural daylight, thereby reducing energy used for lighting and peak power demand; and (3) increased occupant comfort by increasing both thermal and visual comfort. Significant benefits are even expected in automobiles, where the ratio of glossy surfaces to enclosed volume is significantly greater than in a typical building. Specifically, the effective implementation of VT technology in automobiles is expected to provide not only the aforementioned benefits, but also (1) increased driving safety, (2) reduced glare, (3) enhanced mirror performance (by using an electro-optic coating on the mirror), and (4) increased capability for using head-up displays. Other potential applications of VT technology include privacy glass and glare protection in electronic devices.

[0012] This technology provides an example of a device comprising an electrophoretic medium sandwiched by a plurality of electrode layers, capable of achieving a closed optical state (opaque state) and an open optical state (transparent state), switching between these states by applying an electric field across the electrophoretic medium. However, conventional electrophoretic devices using known structures and waveforms require long switching times. Furthermore, light from a bright object in a dark environment, such as a light source, or specular reflection of sunlight in a bright environment, may be affected by visible or even distracting diffraction phenomena when passing through the device, making such devices less than ideal. The inventors of this invention have unexpectedly discovered a device comprising a microcell layer having a plurality of microcells, each of the plurality of microcells having a protruding structure with one or more recesses, achieving efficient switching between the open and closed optical states and improved optical performance of the open optical state. Summary of the Invention

[0013] In one embodiment, the present invention provides a variable light transmission device comprising a first light transmission electrode layer, a second light transmission electrode layer, and a microcell layer. The microcell layer comprises a plurality of microcells and a sealing layer. The microcell layer is disposed between the first light transmission layer and the second light transmission layer.

[0014] Each of the plurality of microcells includes an electrophoretic medium comprising a plurality of charged pigment particles, a charge control agent, and a nonpolar liquid. Each of the plurality of microcells has a microcell opening, and the sealing layer extends across the microcell openings of the plurality of microcells.

[0015] Each of the plurality of microcells includes a microcell bottom layer, a protruding structure, a plurality of microcell walls, and a channel. The microcell bottom layer has an inner surface of the microcell bottom, which includes an exposed inner surface of the microcell bottom and an unexposed inner surface of the microcell bottom.

[0016] Each microcell has a sealing layer with an upper surface and a lower surface. The upper surface is in contact with the first light-transmitting electrode layer, and the lower surface is in contact with the electrophoretic medium.

[0017] The protruding structure has a protruding base, a total protruding surface, an exposed protruding surface, a protruding apex, a protruding height, a protruding volume, and one or more recesses. The protruding base has a surface. The protruding apex is a point or set of points of the protruding structure, which has a shorter distance from the opening of the microcell than all other points of the protruding structure. There is a distance between the protruding apex (219) and the protruding base (218). The protruding height is the distance between the protruding base and the protruding apex. If the protruding apex is a set of points, then the protruding apex has a surface. If the protruding apex is a point, then the surface of the protruding apex is zero. The exposed protruding surface is the total protruding surface, (i) excluding the surface of the protruding base, and (ii) excluding any portion of the surface of the protruding apex. The exposed protruding surface is in contact with the electrophoretic medium. The inner surface of the bottom of the unexposed microcell is in contact with the protruding base. The inner surface of the bottom of the exposed microcell is in contact with the electrophoretic medium.

[0018] The microcell walls have an inner wall surface and an upper wall surface. The inner wall surface is one surface of the microcell wall that is in contact with the electrophoretic medium. The upper wall surface is one surface of the microcell wall that is in contact with the sealing layer.

[0019] The channel has a channel height, an inner base perimeter, and an outer base perimeter. The channel height is 50% of the protruding height. The inner base perimeter is the intersection of the wall of the microcell and the inner surface of the exposed microcell bottom. The outer base perimeter is the intersection of the protruding base and the inner surface of the exposed microcell bottom. The channel is a volume defined by the inner surface of the exposed microcell bottom, the exposed protruding surface, the inner wall surface of the microcell, and a plane parallel to the inner surface of the microcell bottom. The distance between this plane and the inner surface of the microcell bottom is equal to the channel height.

[0020] The variable light transmission device has a first outer surface and a second outer surface. The first outer surface is located on the side of the light transmission device closest to the first light transmission electrode layer. The second outer surface is located on the side of the light transmission device closest to the second light transmission electrode layer. The second outer surface of the variable light transmission device is closer to the protruding base than the first outer surface of the variable light transmission device.

[0021] Each of the one or more recesses in the protruding structure is a geometric shape, having a volume, a height, a depth, and a width. Each recess has an upper base, a lower base, and a surrounding surface. The lower base of each recess is in contact with the inner surface of the exposed microcell bottom. The lower base of each recess has a shape selected from a flattened circle, a flattened circle segment, a flattened circle sector, an elliptical segment, an elliptical sector, a circular segment, a circular sector, a triangle, a square, a rectangle, or a group of polygons (a circular segment) having 5 to 20 sides. Each recess is occupied by the electrophoretic medium of the variable light transmission device.

[0022] The protruding volume is a geometric shape. This geometric shape of the protruding volume is selected from a group consisting of the following: (a) A polygonal pyramid having a vertex and a polygonal base having 3 to 20 sides, the polygonal base being the protruding base (218) of the protruding structure (217) and the lower base (222a) of the one or more recesses (222) of the protruding structure (217), the vertex of the polygonal pyramid being the protruding vertex (219). (b) A truncated polygonal pyramid having a first polygonal base and a second polygonal base, the first polygonal base being the protruding vertex (219), the second polygonal base being the protruding base (218) and the lower base (222a) of one or more recesses (222) of the protruding structure (217), the first and second polygonal bases of the truncated polygonal pyramid having 3 to 20 sides. (c) A polygonal pyramid on a polygonal prism, the polygonal pyramid having a polygonal base, the polygonal base of the polygonal pyramid having a surface area, the polygonal prism having a first polygonal base and a second polygonal base, the first polygonal base having a surface area, the second polygonal base having a surface area, the polygonal base of the polygonal pyramid being in contact with the first polygonal base of the polygonal prism, the surface area of ​​the polygonal base of the polygonal pyramid being the same as the surface area of ​​the first polygonal base of the polygonal prism, the polygonal base of the polygonal pyramid and the first and second polygonal bases of the polygonal prism having 3 to 20 sides, the second polygonal base of the polygonal prism being the protruding base (218) of the protruding structure (217). (d) A polygonal pyramid on a truncated polygonal pyramid, the polygonal pyramid having a polygonal base, the polygonal base having a surface area, the polygonal truncated pyramid having a first polygonal base and a second polygonal base, the first polygonal base of the polygonal truncated pyramid having a first surface area, the second polygonal base of the polygonal truncated pyramid having a second surface area, the polygonal vertex of the polygonal pyramid being the protruding vertex (219), the polygonal base of the polygonal pyramid being in contact with the first polygonal base of the polygonal truncated pyramid, the surface area of ​​the polygonal base of the polygonal pyramid being the same as the first surface area of ​​the first polygonal base of the polygonal truncated pyramid, the second polygonal base of the polygonal truncated pyramid being the protruding base (218), the polygonal base of the polygonal pyramid, and the first and second polygonal bases of the polygonal truncated pyramid having 3 to 20 sides. e) A first polygonal pyramid truncated stage on a second polygonal pyramid truncated stage, the first polygonal pyramid truncated stage having a first polygonal base and a second polygonal base, the first polygonal base of the first polygonal pyramid truncated stage having a first surface area, the second polygonal base of the first polygonal pyramid truncated stage having a second surface area, the first polygonal base of the second polygonal pyramid truncated stage having a first surface area, the second polygonal base of the second polygonal pyramid truncated stage having a second surface area, the first polygonal pyramid truncated stage... The first polygonal base is the protruding vertex (219), the second polygonal base of the first polygonal truncated pyramid is in contact with the first polygonal base of the second polygonal truncated pyramid, the second surface area of ​​the second polygonal base of the first polygonal truncated pyramid is the same as the first surface area of ​​the first polygonal base of the second polygonal truncated pyramid, the second polygonal base of the second polygonal truncated pyramid is the protruding base (218), the first and second polygonal bases of the first polygonal truncated pyramid and the first and second polygonal bases of the second polygonal truncated pyramid have 3 to 20 sides. (f) A cone having a vertex and a base, the vertex being the projecting vertex (219) and the base being the projecting base (218). (g) A truncated cone having a first base and a second base, the first base being the protruding apex (219) and the second base being the protruding base (218). (h) A cone on a cylinder, the cone having a vertex and a base, the vertex of the cone being the protruding vertex (219), the base of the cone having a surface area, the cylinder having a first base and a second base, the first base of the cylinder having a first surface area and the second base of the cylinder having a second surface area, the base of the cone being in contact with the first base of the cylinder, the surface area of ​​the base of the cone being the same as the first surface area of ​​the first base of the cylinder, and the second base of the cylinder being the protruding base (218). (i) A cone on a truncated cone having a vertex and a base, the vertex being the protruding vertex (219), the base having a surface area, the truncated cone having a first base and a second base, the first base having a surface area, the second base having a surface area, the base of the cone contacting the first base of the truncated cone, the surface area of ​​the base of the cone being the same as the surface area of ​​the first base of the truncated cone, and the second base of the truncated cone being the protruding base (218). (j) A first conical truncated column on a second conical truncated column, the first conical truncated column having a first base and a second base, the first base of the first conical truncated column having a first surface area, the second base of the first conical truncated column having a second surface area, the first base of the first conical truncated column being the protruding apex (219), the second conical truncated column having a first base and a second base, the first base of the second conical truncated column having a first surface area, the second base of the second conical truncated column having a second surface area, the second base of the first conical truncated column being in contact with the first base of the second conical truncated column, the second surface area of ​​the first conical truncated column being the same as the first surface area of ​​the first base of the second conical truncated column, the second base of the second conical truncated column being the protruding base (218).

[0023] The protruding structure of an ultramicro battery may have fewer than six recesses. The protruding structure of an ultramicro battery may have 1 to 20 recesses, 1 to 16 recesses, 1 to 12 recesses, 1 to 10 recesses, 1 to 8 recesses, 1 to 6 recesses, 1 to 4 recesses, 2 to 12 recesses, 2 to 8 recesses, 2 to 6 recesses, 2 to 5 recesses, 3 to 10 recesses, 3 to 8 recesses, 3 to 6 recesses, 4 to 10 recesses, 4 to 8 recesses, 5 to 10 recesses, or 5 to 8 recesses.

[0024] A first electric field is applied between the first and second light-transmitting electrode layers via a first waveform, causing the charged pigment particles to move toward the channel, resulting in the variable light transmission device switching to an open optical state. A second electric field is applied between the first and second light-transmitting electrode layers via a second waveform, causing the charged pigment particles to move toward one of the first light-transmitting electrode layers, wherein the closed optical state has a lower percentage of transparency than the open optical state. The second waveform may include at least one positive voltage and at least one negative voltage, and the second waveform has a net positive or net negative pulse. The second waveform may include an AC waveform with a duty cycle from 5% to 45%. The second waveform may include a DC bias waveform, which is formed by superimposing a DC voltage component with one of the AC waveforms. The second electric field causes the charged pigment particles to move toward one of the first light-transmitting electrode layers at a velocity, wherein the velocity may have a lateral component.

[0025] Each microcell of the variable light transmission device of the present invention has a microcell opening with a shape selected from a group consisting of a circle, a square, a rectangle, and a polygon, the polygon having 5 to 12 sides. The shape of the microcell opening can be pentagonal, hexagonal, heptagonal, or octagonal. The shape of the microcell opening can also be a polygon with 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 sides.

[0026] Each of the plurality of microcells in the variable light transmission device of the present invention has a microcell length, which is from 400 micrometers to 850 micrometers, from 450 micrometers to 800 micrometers, from 500 micrometers to 750 micrometers, or from 600 micrometers to 740 micrometers. A length of one of the microcells is defined as the longest distance between any two points of the opening of that microcell. Each of the plurality of microcells in the variable light transmission device of the present invention has a microcell height, which is ranging from 20 micrometers to 100 micrometers, from 20 micrometers to 90 micrometers, from 20 micrometers to 80 micrometers, from 20 micrometers to 60 micrometers, from 20 micrometers to 40 micrometers, from 30 micrometers to 90 micrometers, from 30 micrometers to 80 micrometers, from 30 micrometers to 60 micrometers, from 30 micrometers to 40 micrometers, from 40 micrometers to 80 micrometers, from 40 micrometers to 60 micrometers, from 40 micrometers to 50 micrometers, from 25 micrometers to 40 micrometers, from 50 micrometers to 100 micrometers, or from 50 micrometers to 80 micrometers. The microcell height is the distance between the opening of the microcell and the inner surface of the bottom of the microcell.

[0027] Each of the plurality of microcells in the variable light transmission device of the present invention has a protrusion height, which is ranging from 15 micrometers to 90 micrometers, from 20 micrometers to 90 micrometers, from 20 micrometers to 80 micrometers, from 20 micrometers to 70 micrometers, from 20 micrometers to 50 micrometers, from 20 micrometers to 30 micrometers, from 30 micrometers to 80 micrometers, from 30 micrometers to 70 micrometers, from 30 micrometers to 50 micrometers, from 30 micrometers to 40 micrometers, from 40 micrometers to 90 micrometers, from 40 micrometers to 50 micrometers, from 30 micrometers to 50 micrometers, from 25 micrometers to 35 micrometers, from 50 micrometers to 90 micrometers, or from 50 micrometers to 70 micrometers. The protrusion height of one protruding structure of a microcell is the distance between the protruding base and the protruding apex of the protruding structure.

[0028] In the variable light transmission device of the present invention, each recess in one or more protruding structures of one of the plurality of microcells of a microcell may have a height ranging from 15 micrometers to 90 micrometers, from 20 micrometers to 90 micrometers, from 20 micrometers to 80 micrometers, from 20 micrometers to 70 micrometers, from 20 micrometers to 50 micrometers, from 20 micrometers to 30 micrometers, from 30 micrometers to 80 micrometers, from 30 micrometers to 70 micrometers, from 30 micrometers to 50 micrometers, from 30 micrometers to 40 micrometers, from 40 micrometers to 90 micrometers, from 40 micrometers to 50 micrometers, from 30 micrometers to 50 micrometers, from 25 micrometers to 35 micrometers, from 50 micrometers to 90 micrometers, or from 50 micrometers to 70 micrometers. The height of a recess in one of the protruding structures is the longest distance between any point in the recess and the lower base of the recess.

[0029] In the variable light transmission device of the present invention, each of the more than one recesses of one of the plurality of microcells of the microcell may have a depth ranging from 5 micrometers to 50 micrometers, from 5 micrometers to 40 micrometers, from 5 micrometers to 30 micrometers, from 5 micrometers to 20 micrometers, from 5 micrometers to 10 micrometers, from 10 micrometers to 40 micrometers, from 10 micrometers to 30 micrometers, from 10 micrometers to 20 micrometers, from 15 micrometers to 40 micrometers, from 15 micrometers to 30 micrometers, from 15 micrometers to 25 micrometers, from 20 micrometers to 40 micrometers, and from 20 micrometers to 30 micrometers. In the variable light transmission device of the present invention, each of the recesses in one or more protruding structures of one of the plurality of microcells of the microcell may have a width ranging from 5 micrometers to 50 micrometers, from 5 micrometers to 40 micrometers, from 5 micrometers to 30 micrometers, from 5 micrometers to 20 micrometers, from 5 micrometers to 10 micrometers, from 10 micrometers to 40 micrometers, from 10 micrometers to 30 micrometers, from 10 micrometers to 20 micrometers, from 15 micrometers to 40 micrometers, from 15 micrometers to 30 micrometers, from 15 micrometers to 25 micrometers, from 20 micrometers to 40 micrometers, and from 20 micrometers to 30 micrometers.

[0030] One of the plurality of microcells in the variable light transmission device of the present invention may include a microcell having a protruding structure with 2, 3, 4, 5, or 6 recesses. The combination of the protruding base of the microcell and the base beneath the recesses forms a first geometric shape having a center. The protruding base may be symmetrical about an axis of symmetry Cn, the axis of symmetry being perpendicular to the plane of the protruding base and passing through the center of the first geometric shape, where n is the number of recesses in the protruding structure. Cn symmetry means that a rotation about the axis of rotation through an angle of 360° / n will make the protruding base indistinguishable from the protruding base before the rotation. The center of a geometric shape is also called the "centroid" of the geometric shape and is defined as the point at which the geometric shape is balanced when the geometric shape is a uniform thin plate. The protruding base of one or more microcells of the device is symmetrical about an axis of symmetry Cn, as described above.

[0031] One of the plurality of microcells in the variable light transmission device of the present invention may include a microcell having a protruding structure with 2, 3, 4, 5, or 6 recesses. The combination of the protruding base of the microcell and the base beneath the recesses forms a first geometry having a center. The protruding base may lack symmetry about an axis of symmetry Cn, which is perpendicular to the plane of the protruding base and passes through the center of the first geometry, where n is the number of recesses in the protruding structure. Cn symmetry means that a rotation about the axis of rotation by an angle of 360° / n will make the protruding base indistinguishable from the protruding base before the rotation. The protruding base of one or more microcells in the device lacks symmetry about an axis of symmetry Cn, as described above.

[0032] The variable light transmission device may include a first microcell and a second microcell. The first microcell includes a first protruding structure having a first protruding base and 1, 2, 3, 4, 5, or 6 recesses, each recess having a lower base. The combination of the first protruding base of the first microcell and the lower bases of the recesses forms a first geometric shape, which has a first center. The second microcell may include a second protruding structure having a second protruding base and 1, 2, 3, 4, 5, or 6 recesses, each recess having a lower base. The combination of the second protruding base of the second microcell and the lower bases of the recesses forms a second geometric shape, which has a second center. The first protruding base may not be symmetrical about an axis of symmetry relative to the second protruding base (C2), the axis of symmetry being perpendicular to the plane of the first protruding base and passing through a point at the midpoint between the first center and the second center. The symmetry of the first protruding base with respect to the second protruding base at C2 means that a rotation of 180° around the axis of symmetry will render the first and second protruding bases indistinguishable from their original state before the rotation. The variable light transmission device may include a third microcell in addition to the first and second microcells. The third microcell may include a third protruding structure having a third protruding base and 1, 2, 3, 4, 5, or 6 recesses, each recess having a lower base. The combination of the third protruding base of the third microcell and the lower bases of the recesses forms a third geometry having a third center. The third protruding base may not be symmetrical about an axis of symmetry with respect to the first protruding base at C2, the axis of symmetry being perpendicular to the plane of the first protruding base and passing through a point at the midpoint between the first center and the third center. The third protruding base may not be symmetrical about an axis of symmetry relative to the second protruding base C2, the axis of symmetry being perpendicular to the plane of the second protruding base, the axis of symmetry passing through a point at the midpoint between the second center and the third center.

[0033] The variable light transmission device of the present invention may include a micro battery, wherein the geometry of the protruding volume may be a polygonal pyramid on a truncated polygonal pyramid. The polygonal pyramid has a first slope (θ1), and the truncated pyramid has a second slope (θ2). The second slope (θ2) may be greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) may be from 1 to 25 degrees, from 1 to 30 degrees, from 2 to 20 degrees, from 2 to 15 degrees, from 2 to 12 degrees, from 2 to 9 degrees, from 2 to 8 degrees, from 3 to 8 degrees, or from 4 to 8 degrees. The geometry of the protruding volume of the protruding structure of a micro battery may be a first polygonal pyramid on a truncated second polygonal pyramid. The first polygonal pyramid has a first slope (θ1), and the second pyramid has a second slope (θ2). The second slope (θ2) may be greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) may be from 1 to 25 degrees, from 1 to 30 degrees, from 2 to 20 degrees, from 2 to 15 degrees, from 2 to 12 degrees, from 2 to 9 degrees, from 2 to 8 degrees, from 3 to 8 degrees, or from 4 to 8 degrees. The geometry of the protruding volume of the protruding structure of an ultramicro battery may be a cone on a truncated cone having a first slope (θ1) and a second slope (θ2). The second slope (θ2) may be greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) may be from 1 to 25 degrees, from 1 to 30 degrees, from 2 to 20 degrees, from 2 to 15 degrees, from 2 to 12 degrees, from 2 to 9 degrees, from 2 to 8 degrees, from 3 to 8 degrees, or from 4 to 8 degrees. The geometry of the protruding volume of the protruding structure of an ultramicro battery may be a first truncated cone on a second truncated cone, the first truncated cone having a first slope (θ1) and the second truncated cone having a second slope (θ2). The second slope (θ2) may be greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) may be from 1 to 25 degrees, from 1 to 30 degrees, from 2 to 20 degrees, from 2 to 15 degrees, from 2 to 12 degrees, from 2 to 9 degrees, from 2 to 8 degrees, from 3 to 8 degrees, or from 4 to 8 degrees.

[0034] The variable light transmission device of the present invention includes a microcell having an inner sidewall surface and a bottom surface. The inner sidewall surface and the bottom surface of the microcell form an angle (φ). The angle (φ) can be from 90 to 120 degrees, 90 to 110 degrees, 90 to 100 degrees, 92 to 120 degrees, 92 to 110 degrees, 92 to 100 degrees, 95 to 120 degrees, 95 to 110 degrees, or 95 to 110 degrees.

[0035] The variable light transmission device of the present invention may include a first adhesive layer disposed between the sealing layer and the first light transmission electrode layer. The variable light transmission device of the present invention may also include a second adhesive layer disposed between the microcell layer and the second light transmission electrode layer. The variable light transmission device of the present invention may include a first adhesive layer and a second adhesive layer. The first adhesive layer is disposed between the sealing layer and the first light transmission electrode layer, and the second adhesive layer is disposed between the microcell layer and the second light transmission electrode layer.

[0036] The variable light transmission device of the present invention may include a light-blocking layer disposed between the upper surface of the microcell and the sealing layer. The light-blocking layer may include a light-absorbing pigment. The light-absorbing pigment of the light-blocking layer may be black. The light-blocking layer may also include a light-reflecting pigment. The light-absorbing pigment of the light-blocking layer may be white.

[0037] The electrophoretic medium contains a charge control agent. The content of the charge control agent in the electrophoretic medium of the variable light transmission device can range from 0.1% to 8% by weight of the charge control agent. The molecular structure of the charge control agent may include a quaternary ammonium functional group and a nonpolar tail. The nonpolar liquid in the electrophoretic medium may contain a material selected from the group consisting of an aliphatic hydrocarbon, a cyclic aliphatic hydrocarbon, an aromatic hydrocarbon, a halogenated aliphatic hydrocarbon, a polydimethylsiloxane, or mixtures thereof. Simple Explanation of the Diagram

[0038] Figure 1 is an illustration of a cylindrical particle in a liquid, which is affected by an applied electric field and the resultant force on the particle.

[0039] Figures 2A, 2B, 2C and 2D show a side view of an example of a variable light transmission device according to the present invention.

[0040] Figure 3(a) shows a side view of an ultramicrocell in the open optical state of one of the variable light transmission devices of the present invention; Figure 3(b) shows a side view of the ultramicrocell in the closed optical state. The electrophoretic medium comprises a type of charged pigment particles.

[0041] Figure 4A is an example of a DC unbalanced waveform that can be applied to a variable light transmission device to achieve a closed state; the waveform includes an AC waveform with a duty cycle of more than 50%.

[0042] Figure 4B is an example of a DC unbalanced waveform that can be applied to a variable light transmission device to achieve a closed state; the waveform is an overlap of a DC voltage component and an AC waveform.

[0043] Figure 5 illustrates the force applied to the surface of a conical protrusion of the variable light transmission device of the present invention by means of a charged pigment particle.

[0044] Figure 6 shows a comparison of one of the Fraunhofer diffraction patterns formed by apertures of the following shapes: (a) triangle, (b) square, (c) pentagon, and (d) hexagon.

[0045] Figure 7 shows a comparison of one Fraunhofer diffraction pattern formed by a circular aperture.

[0046] Figure 8 shows a comparison of one of the Fraunhofer diffraction patterns formed by a circular aperture with a sawtooth notch.

[0047] Figure 9 shows a microcell base of a microcell in a variable light transmission device of the present invention. The microcell has a hexagonal shape and a conical protrusion structure with a recess.

[0048] Figure 10 illustrates the base beneath the recess of the protruding structure of the microcell of the variable light transmission device of the present invention shown in Figure 9; the recess has a depth of 222d and a width of 222w.

[0049] Figure 11 shows a microcell base of a microcell in a variable light transmission device of the present invention. The microcell has a hexagonal shape and a conical protrusion structure with two recesses.

[0050] Figure 12 shows a microcell base of a microcell in a variable light transmission device of the present invention. The microcell has a hexagonal shape and a conical protrusion structure with three recesses.

[0051] Figure 13 is a top view of the microcell shown in Figure 12, which illustrates the microcell channel (215); the channel has an inner base periphery (224), an outer base periphery (225), and a channel width 216w.

[0052] Figure 14 is a side view of an ultramicro battery of a variable light transmission device according to the present invention. The ultramicro battery includes a protruding structure (217) with a recess (222) having a recess height (222h).

[0053] Figure 15 is a side view of an ultramicro battery of a variable light transmission device according to the present invention. The ultramicro battery includes a protruding structure (217) with a recess (222) having a recess height (222h). The ultramicro battery also includes a light blocking layer (230).

[0054] Figure 16 is a side view of an ultramicro battery of a variable light transmission device according to the present invention. The ultramicro battery includes a protruding structure (217) and a plurality of ultramicro battery walls (212). The ultramicro battery wall has an inner sidewall surface 213 and an ultramicro battery bottom surface (211). The inner sidewall surface (213) and the ultramicro battery bottom surface (211) form an angle (φ) greater than 90 degrees.

[0055] Figure 17 is a side view of an ultramicro battery of a variable light transmission device according to the present invention. The ultramicro battery includes a protruding structure (217), which is a cone on a truncated cone. The slope θ2 of the truncated cone is greater than the slope θ1 of the cone.

[0056] Figure 18 is a side view of an ultramicro battery of a variable light transmission device according to the present invention. The ultramicro battery includes a protruding structure (217), which is a cone on a truncated cone. The slope θ2 of the truncated cone is greater than the slope θ1 of the cone. In the ultramicro battery, the inner wall surface (213) and the bottom surface (211) of the ultramicro battery form an angle (φ) greater than 90 degrees.

[0057] Figure 19(a) shows a top view of a variable light transmission device according to one of the present invention, the device comprising a plurality of microcells, each of the plurality of microcells having a protruding structure having three recesses.

[0058] Figure 19(b) shows a Fraunhofer diffraction pattern formed by the variable light transmission device illustrated in Figure 19(a).

[0059] Figure 20(a) illustrates a variable light transmission device having one of a plurality of microcells, each of which has a conical protrusion structure and a channel with a circular inner and outer base around its perimeter.

[0060] Figure 20(b) shows a Fraunhofer diffraction pattern formed by the variable light transmission device illustrated in Figure 20(a).

[0061] Figure 21(a) illustrates a variable light transmission device having one of a plurality of microcells, each of which has a hexagonal inner and outer base perimeter.

[0062] Figure 21(b) shows a Fraunhofer diffraction pattern formed by the variable light transmission device illustrated in Figure 21(a). Implementation

[0063] For example, in this context, a "variable light transmission device" is a device that includes an electrophoretic medium, wherein the amount of transmitted light through the device can be controlled by applying an electric field across the electrophoretic medium.

[0064] "A first outer surface of a variable light transmission device" and "a second outer surface of a variable light transmission device" are the outer surfaces of the device that are parallel to the first light transmission electrode layer and the second light transmission electrode layer, 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.

[0065] "One location of a variable light transmission device" refers to a point on either the first outer surface or the second outer surface of the device.

[0066] The percentage transparency (%T) of a variable light transmission device at one location of the device is given by Equation 1. Thus, the percentage transparency (%T) of a variable light transmission device at one location of the device is the ratio of the intensity (I) of light transmitted through the variable light transmission device and exiting from a 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 location on the first outer surface of the variable light transmission device, multiplied by 100; the location on the second outer surface is symmetrical to the location on the first outer surface with respect to a plane, which is located at an equal distance between the first light transmission electrode layer and the second light transmission electrode layer. %T=(I / Io)x100 (Equation 1)

[0067] Similarly, the "transparency or transmission" of a variable light transmission device at one location of the device is the ratio of the intensity (I) of light transmitted through the variable light transmission device and exiting from a 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 location on the first outer surface of the variable light transmission device.

[0068] The optical density (OD) of a variable light transmission device at one location of the device is given by Equation 2. Therefore, the percentage of optical density (OD) of a variable light transmission device at one location of the device is calculated as the ratio of the intensity (IO) of light entering the device at a location on the first outer surface of the variable light transmission device to the intensity (I) of light transmitted through the variable light transmission device and exiting at a location on the second outer surface of the variable light transmission device; the location on the second outer surface is symmetrical to the location on the first outer surface relative to a plane at an equal distance between the first and second light transmission electrode layers. OD = log(Io / I) (Equation 2)

[0069] "A location of a device adjacent to a channel" means that if a line is drawn perpendicularly from that location to one of the outer surfaces of the device, the line will cross the channel of the microcell.

[0070] The distance from a point to a plane is the shortest orthogonal distance from that point to the plane. The shortest distance from a point to a plane is the length of an orthogonal line parallel to the normal vector from the given point to the given plane.

[0071] In three-dimensional space, the distance between two planes is the shortest distance between those planes. This is the shortest distance between any point on one plane and any point on the other plane.

[0072] "The average particle size of a type of particle" is the average length of the largest dimension of such particles.

[0073] A "flat-topped truncated pyramid" is a base portion of a cone or a polygonal pyramid obtained by cutting the vertex portion with a plane parallel to the base. Because it does not have a vertex but has two parallel bases, it is also called a flat-topped cone or pyramid.

[0074] The slope of a cone is defined as an angle, having (a) a vertex (A) on the circumference of the base of the cone, (b) a first arm, a line connecting point A (vertex) to the center C of the base of the cone, and (c) a second arm, a line connecting point A (vertex) to the vertex of the cone.

[0075] The slope of a truncated cone is defined as an angle, having (a) a vertex (A) on the circumference of the base (large) of the cone, (b) a first arm connecting point A (vertex) to the center C of the base of the truncated cone, and (c) a second arm, the line connecting the transverse surface of the truncated cone to a plane including a linear segment AC, the plane being perpendicular to the base of the truncated cone.

[0076] The slope of a polygonal pyramid is defined as an angle, having (a) a vertex (A) at a point on the periphery of the base of the polygonal pyramid, (b) a first arm, a line connecting point A (vertex) to the center C of the base of the polygonal pyramid, and (c) a second arm, a line connecting point A (vertex) to the vertex of the pyramid. The slope of a truncated polygonal pyramid is defined as an angle, having (a) a vertex (A) at a point on the periphery of the base (large) of the polygonal pyramid, (b) a first arm, a line connecting point A (vertex) to the center C of the base of the truncated polygonal pyramid, and (c) a second arm, a line connecting the transverse surface of the truncated polygonal pyramid to a plane including a linear segment AC, the plane being perpendicular to the base of the truncated polygonal pyramid.

[0077] The term "charged pigment microparticles" refers to charged pigment microparticles that may or may not have a polymeric material on their surface.

[0078] The term "protruding volume" refers to the volume of a protruding structure and includes the volume of all recesses of one or more recesses. To clarify the term "protruding volume," the protruding structure can be considered as a combination of a solid component of the protruding structure and one or more recesses. The protruding volume consists of the volume of the protruding solid component and the volumes of all the recesses. The protruding volume is a geometric shape.

[0079] The term "total protruding surface" refers to the total surface of the protruding structure excluding the one or more recesses within the protruding structure. That is, the total protruding surface comprises the surface of the protruding base and the surface of the protruding structure in contact with the electrophoretic medium. The term "exposed protruding surface" refers to the total protruding surface excluding the surface of the protruding base and any portion of the surface of the protruding apex. If the protruding apex is a single point, then the surface of that protruding apex is zero. If the protruding apex is a set of points, then the set of points has a surface higher than zero.

[0080] The "inner wall surface of the microcell" refers to the surface of the microcell wall that is in contact with the electrophoretic medium of the microcell.

[0081] The "upper surface of the microcell wall" refers to the surface of the microcell wall that is in contact with the sealing layer of the microcell. In the case where there is a light blocking layer on the upper surface of the microcell wall, the light blocking layer is disposed between the upper surface of the microcell wall and the sealing layer.

[0082] The term "channel width" is defined as the minimum distance between the perimeter of the inner base and the perimeter of the outer base within a channel.

[0083] The term "DC-balanced waveform" or "DC-balanced drive waveform" applied to a pixel refers to a drive waveform in which the drive voltage applied to the pixel is approximately zero when integrated over the entire application period of the waveform. DC balance is achieved by balancing each phase of the waveform, i.e., by selecting a first positive voltage such that its integral over subsequent negative voltages is zero or approximately zero. If the waveform is not DC-balanced, it is referred to as a "DC-unbalanced waveform" or "DC-unbalanced drive waveform." The drive waveform applied to a pixel may have a DC unbalanced portion and an additional pulse with at least one opposite pulse to ensure that the overall 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) a square or sinusoidal AC waveform with a duty cycle of less than (or more than) 50%, and (b) a square or sinusoidal AC waveform with a DC bias.

[0084] The term "pulse" refers to the integral of voltage with respect to time. That is, for a waveform pulse with a voltage V applied for a time t, the pulse is V×t. If the polarity of voltage V is positive, the pulse is positive; if the polarity of voltage V is negative, the pulse is negative.

[0085] The term "net positive pulse" in waveform refers to the phenomenon during which negatively charged pigment particles are attracted to and move toward the first light-transmitting electrode layer when the waveform is applied.

[0086] The term "lateral component of velocity," as opposed to the movement of charged pigment particles in a microcell of the variable light transmission device of the present invention, refers to the velocity in the horizontal direction. For this definition, it is assumed that the velocity of the charged particles is a vector resulting from the addition of the horizontal velocity (Vh) and the vertical velocity (Vv), and that the vertical direction, assuming the movement of charged pigment particles inside an electrophoretic microcell, is either from the first light-transmitting electrode layer to the second light-transmitting electrode layer, or from the second light-transmitting electrode layer to the first light-transmitting electrode layer. In the same system, the horizontal direction of movement of charged pigment particles inside an electrophoretic microcell is from one side of the microcell wall to the other side of the microcell wall, parallel to the first light-transmitting electrode layer. Therefore, "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.

[0087] The "vertical plane" of one channel of an ultramicro battery is defined herein as a plane that is perpendicular to the plane of the exposed inner surface of the bottom of the ultramicro battery and contains points A and B, where point A is a point on the periphery of an outer base of one channel of an ultramicro battery, and point B is a point on the periphery of an inner base of the same ultramicro battery. A and B are portions of a line segment that corresponds to the minimum distance between the periphery of the outer base and the periphery of the inner base of the channel.

[0088] The phenomenon of induced charge electroosmosis (ICEO) can be utilized to cause polarizable particles, such as pigment particles, existing in an electrophoretic medium to move laterally. That is, these polarizable particles can move parallel to the electrode layers surrounding the electrophoretic medium. In the presence of an electric field, a particle can experience a force caused by the polarization of the particle (or by the polarization of an adsorbed conductive coating on the particle surface, or by the polarization of the electrical double layer surrounding the particle). This force can cause a slight perturbation in the flow of mobile charges, such as ions or charged microcells, in the electrophoretic medium, as illustrated in Figure 1 for a cylindrical particle 101 surrounded by the liquid of the electrophoretic medium in an applied electric field. This diagram is by Bazant and Squires, J. Fluid Mech.

[2004] Articles 509, 217-252 are reprinted.

[0089] An ideally symmetrical, spherical particle will experience no net force, but less symmetrical particles will experience forces, which have a component orthogonal to the direction of the applied field. The cooperative flow established by a large group of particles experiencing such forces can induce a "vortex" in an electrophoretic medium containing multiple particles. Based on the theory proposed in the paper by Bazant and Squires, the maximum velocity u of this vortex for a specific particle will be approximately given by Equation 1. In Equation 1, E represents the electric 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 accumulate a shielding charge layer by carrying charge around the charge in the solvent. The time scale τ is given by Equation 3.

[0090] In Equation 3, λ represents the Debye screening length of the D system, the particle radius of the R system, and the diffusion constant of the charge carrier in the D system fluid.

[0091] 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 appears in the same direction and can therefore be driven by an alternating field.

[0092] When the electrophoretic medium, such as in an electrophoretic display, is contained within a microcell, the geometry of the induced flow is influenced by the shape of the specific microcell used. For example, in the simplest case of two parallel electrodes, when using an appropriate electric field strength and alternating frequency, the flow can employ a rolling structure with periodic intervals corresponding to the width of the gap between the electrodes.

[0093] The inventors of this invention utilize a complex microcell structure, which can be formed by an embossing method, to fabricate a variable light transmission device. In one example, the embossed structure includes a protruding structure on the bottom of each microcell. Figures 2A, 2B, and 2C illustrate a side view of a microcell of a variable light transmission device according to the present invention, wherein the protruding structure of the variable light transmission device is a cone on a cylinder. The protruding structure includes one or more recesses (222). In the examples of Figures 2A, 2B, and 2C, the protruding structure has one recess. The recess 222 of the protruding structure 217 includes an electrophoretic medium. The protruding structure can guide the electrophoretic flow of particles into a channel, as shown in Figures 2A, 2B, and 2C. If the electric field applied across the electrophoretic medium has the 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 applied voltage through the light-transmitting electrodes causes a negative polarity on the second light-transmitting electrode, the charged pigment particles will move toward the channel. The same movement will occur if the charged pigment particles are negatively charged and the applied voltage through the light-transmitting electrodes causes a positive polarity on the second light-transmitting electrode. Figures 2A, 2B, and 2C show a cross-section (not to scale) of a portion of a variable light-transmitting device, showing only one of the plurality of microcells in the device. All three figures, 2A, 2B, and 2C, are identical in terms of the device structure shown, but different components of the device are identified in each of the figures.

[0094] The variable light transmission device 200 shown in Figures 2A, 2B, and 2C comprises a microcell containing a microcell layer 204 and a sealing layer 206. Although only one microcell is shown in Figures 2A, 2B, and 2C, it is conceivable that an overall variable light transmission device includes a microcell layer 203 containing a plurality of microcells 204. The variable light transmission device 200 may include a first light transmission substrate 201, a first light transmission electrode layer 202, a microcell layer 203 containing a plurality of microcells 204 and a sealing layer 206, a second light transmission electrode layer 207, and a second light transmission substrate 208. Each of the plurality of microcells 204 includes an electrophoretic medium 209, which includes a plurality of charged pigment particles, a charge control agent, and a nonpolar liquid. The composition of the electrophoretic medium 209 (charged microparticles, charge control agent, nonpolar liquid) is not shown in Figures 2A, 2B, and 2C. Each of the plurality of microcells 204 has a microcell opening 205, and a sealing layer 206 spans the microcell openings 205 of the plurality of microcells 204. Each of the plurality of microcells 204 includes a microcell bottom layer 210, a protruding structure 217, a plurality of microcell walls 212, and a channel 215. The microcell bottom layer 210 has an inner surface 211 of the microcell bottom. The inner surface 211 of the microcell bottom includes an exposed inner surface 211a and an unexposed inner surface 211b. The unexposed inner surface 211b is in contact with the protruding base 218.

[0095] In this example of a microcell, the protruding structure 217 is a cone located on a cylinder and also includes a protruding structure 222 comprising an electrophoretic medium 209. The protruding structure 217 has a protruding base, an exposed protruding surface 221, a protruding apex 219, a protruding height 220, and a recess (222). Generally, one of the microcells in the variable light transmission device of the present invention may have a protruding structure comprising one or more recesses. The plurality of microcells in the variable light transmission device of the present invention may have a protruding structure, each having no more than six recesses. In the examples of Figures 2A to 2C, the protruding volume of the protruding structure is a geometric shape located on a cone on a cylinder. The protruding apex 219 is a point (or a group of points) of the protruding structure 217, having a shorter distance from the microcell opening 205 than all other points of the protruding structure 217. In the examples of the variable light transmission device in Figures 2A, 2B, and 2C, the protruding vertex 219 is a point. This protruding vertex is the apex of the cone. The protrusion height 220 is the distance between the protruding base 218 and the protruding vertex 219. If the protruding structure 217 has a protruding vertex 219 and the protruding vertex comprises more than one point, then the protruding vertex is a flat surface. In this case, the protrusion height 220 is the distance between the flat surface of the protruding vertex of the protruding structure 217 and the protruding base 218. A microcell layer comprising a plurality of microcells 204, and having a protruding structure 217, can be manufactured by embossing a thermoplastic or thermosetting primer layer using a pre-patterned mold and then releasing the mold. The primer layer can be hardened during or after the embossing step by radiation, cooling, solvent vaporization, or other means.

[0096] The microcell wall 212 has an inner wall surface 213 and an upper wall surface 214. The inner wall surface 213 is in contact with the electrophoretic medium 209. The upper wall surface 214 is the surface of the microcell wall 212 of the microcell that is in contact with the sealing layer 206. Furthermore, Figure 2B shows a first outer surface 250 located on the side of the variable light transmission device near the first light transmission electrode layer (202), and a second outer surface (251) located on the side of the variable light transmission device near the second light transmission electrode layer (207).

[0097] Channel 215 is defined as the volume between the exposed inner surface 211a of the bottom of the microcell, the inner wall surface 213 of the microcell, the exposed protruding surface 221, the inner wall surface (213) of the microcell, and a plane parallel to the inner surface (211) of the bottom of the microcell. This plane has a distance equal to the channel height (216h) between it and the inner surface (211) of the bottom of the microcell. This definition shows that a portion of the recessed volume 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 periphery of the inner base and the periphery of the outer base within the channel.

[0098] Figure 2D shows a side view of a portion of an example of a variable light transmission device according to the present invention, wherein the protruding volume is a cone located on a cylinder. The recess or recesses of the protruding structure are not shown in Figure 2D. The variable light transmission device shown in Figure 2D is similar to those illustrated in Figures 2A, 2B, and 2C, but shows that the device includes a larger portion of four microcells. The variable light transmission device 200 includes a first light transmission substrate 201, a first light transmission electrode layer 202, a microcell layer 203 comprising a plurality of microcells 204 and a sealing layer 206, a second light transmission electrode layer 207, and a second light transmission substrate 208. Each of the plurality of microcells includes an electrophoretic medium comprising a plurality of charged pigment particles 223, a charge control agent, and a nonpolar liquid. Each of the plurality of microcells 204 has a microcell opening, and a sealing layer 206 spans the microcell openings of the plurality of microcells. Each of the plurality of microcells includes a microcell bottom layer 210, a protruding structure 217, a microcell wall 212, and a channel 215. The variable light transmission device shown in Figure 2D is in a closed optical state.

[0099] When a first electric field is applied between the first light-transmitting electrode layer 202 and the second light-transmitting electrode layer 207 through a first waveform, the charged pigment particles 223 will move toward the channel when the polarity of the charged pigment particles 223 is opposite to the voltage polarity of the second light-transmitting electrode layer. If the polarity of the charged pigment particles 223 is opposite to the voltage polarity of the second light-transmitting electrode layer, the charged pigment particles 223 will be attracted by the second light-transmitting electrode layer, and the variable light transmission device will switch to an open optical state, which has a higher percentage of transparency than the closed optical state. Figure 3(a) illustrates the open optical state, where the charged pigment particles 223 are represented by filled black circles. In this example, the electrophoretic medium contains one type of charged pigment particles 223. In this open optical state, the charged pigment particles 223 are present in the channel of the microcell. Thus, in this open optical state, light passing through the variable light transmission device from one of the locations adjacent to the channel will be blocked, and the variable light transmission device will appear opaque in the location adjacent to the channel, while the variable light transmission device will be transparent at other locations.

[0100] A second electric field is applied between the first light-transmitting electrode layer 202 and the second light-transmitting electrode layer 207 via a second waveform, causing charged pigment particles 223 to move toward the first light-transmitting electrode layer 202 at a certain velocity. This results in a closed optical state, as shown in Figure 3(b). This velocity has a lateral component. Without this lateral component of velocity, the charged pigment particles 223 would move toward the first light-transmitting electrode layer 202 from the open channel, but these charged pigment particles 223 would occupy a region near the sealing layer 206, close to the periphery of a microcell, so the closed optical state would not occur. That is, the charged pigment particles 223 would not spread across the surface of the first light-transmitting electrode layer 202. Thus, since the closed optical state would have a relatively high light transmittance, the closed optical state would not be effectively formed.

[0101] Because of the angle of the protruding structures such as the cones in Figures 3(a) and 3(b), when the charged pigment particles impact the exposed protruding surface of the protruding structure during their movement toward the second light-transmitting electrode layer, a lateral component of their velocity will be transmitted, thus indicating above that it is slightly easier to achieve a transition from the closed optical state to the open optical state.

[0102] The electric field within the variable light transmission device can be shaped by making the conductivity of the electrophoretic medium and the cone substantially different. For example, if the cone is much less conductive than the electrophoretic medium, the field lines will tend to guide the charged pigment particles into the channel. However, even in such cases, a larger horizontal force component may still be necessary to redistribute the charged pigment particles from the channel throughout the entire microcell volume. Furthermore, when the resistivity of the cone material and the electrophoretic medium are approximately equal at about 10¹⁰ ohms per centimeter, it may be easier to assemble and operate the device, in which case the electric field lines will be approximately oriented perpendicularly through the microcell. Therefore, it is preferable to use a waveform with lateral motion transmitted to the charged pigment particles.

[0103] A first electric field can be applied through a first waveform between the first and second light-transmitting electrode layers to cause the charged pigment particles to move toward the channel, resulting in a switch of the variable light transmission device to an open optical state. In this open optical state, the charged pigment particles are located inside the channel. A second electric field can be applied through a second waveform between the first and second light-transmitting electrode layers to cause the charged pigment particles to move toward one of the first light-transmitting electrode layers at a velocity, thus switching the variable light transmission device to an open optical state. This velocity has a transverse component and causes a closed optical state. The second waveform includes a series of at least two positive and negative pulses, having a net positive or net negative pulse. The closed optical state has a lower percentage of transparency than the open optical state. The charged pigment particles can be light-absorbing or light-reflecting particles. The electrophoretic medium can contain two types of charged pigment particles, a first type and a second type. The first type of charged pigment particles may be light-absorbing, and the second type of charged pigment particles may be light-reflective. The first type of charged pigment particles may be black. The second type of charged pigment particles may be white. The first and second types of charged pigment particles may have the same charge polarity. The first and second types of charged pigment particles may have the same charge polarity but different charge values. The first and second types of charged pigment particles may have a positive charge. One of the first type of charged pigment particles may have a larger positive charge than one of the second type of charged pigment particles. The first and second types of charged pigment particles may have a negative charge. One of the first type of charged pigment particles may have a larger negative charge than one of the second type of charged pigment particles.

[0104] The second waveform can be DC unbalanced. The second waveform can include at least one positive voltage and at least one negative voltage, and the second waveform has a net positive or a net negative pulse. The selection of a net positive or net negative pulse depends on the polarity of the charged pigment particles to be moved to a position near the sealing layer of the electrophoretic medium. Specifically, if the closed state involves the movement of negatively charged pigment particles, a net positive pulse is required to move these particles from the channel toward the first light-transmitting electrode layer. In other words, this movement requires the net result of an applied voltage, whereby the first light-transmitting electrode layer becomes an attraction for the negatively charged particles due to a positive voltage relative to the second light-transmitting electrode layer. Conversely, if the closed state involves the movement of positively charged pigment particles, a net negative pulse is required to move these charged pigment particles from the channel near the second light-transmitting electrode layer 207 toward the first light-transmitting electrode layer.

[0105] A closed optical state is achieved by applying a second electric field with a second waveform between the two light-transmitting electrode layers.

[0106] The second waveform may include an AC waveform with a duty cycle different from 50%. Figure 4A illustrates one example of this second waveform.

[0107] The AC waveform can have a positive or negative DC bias. The DC bias can be achieved by controlling the duty cycle of the waveform. The duty cycle for a positive DC bias waveform is higher than 50%. The duty cycle for a positive DC bias waveform can be higher than 55%, higher than 60%, or higher than 65%. The duty cycle for a positive DC bias waveform can range from 55% to 95%, from 58% to 90%, from 60% to 88%, from 65% to 85%, or from 70% to 80%. Similarly, the duty cycle for a negative DC bias waveform is lower than 50%. The duty cycle for a negative DC bias waveform can be lower than 45%, lower than 40%, or lower than 35%. The duty cycle for a negative DC bias waveform can range from 5% to 45%, from 8% to 40%, from 10% to 38%, from 15% to 35%, or from 20% to 30%.

[0108] The waveform illustrated in the example of Figure 4A comprises an AC square waveform with two or more cycles. Each cycle may include a first pulse with amplitude V1 applied for a time period t1 and a second pulse with amplitude V2 applied for a time period t2, where V1 is positive and V2 is negative, and t1 is greater than t2. When the amplitude of V1 equals the amplitude of V2 (|V1|=|V2|), the DC bias is achieved by the difference in time periods. In the example of Figure 4A, since the positive voltage V1 is applied for a longer time period (t1) than the negative voltage V2 (t2), there is a positive DC bias. A positive DC bias means that if the charged pigment particles of the variable light transmission device are negatively charged, the charged pigment particles will move towards the first light transmission electrode layer of the device. The duty cycle of this waveform can be calculated using Equation 4. Working period = 100 x (V1.t1) / [(V1.t2) + (V2.t2)] Equation 4

[0109] In the waveform example in Figure 4A, the amplitude of V1 can be equal to the amplitude of V2 (|V1|=|V2|), but in general, the amplitudes V1 and V2 can be different from each other.

[0110] The example drive waveform in Figure 4A is DC unbalanced. However, more than one additional pulse can be included in the waveform of Figure 4A as an opposite pulse, ensuring that the overall waveform applied to a pixel is DC unbalanced. This additional pulse (or multiple additional pulses) can be applied before the DC unbalanced waveform (pre-pulse). Also, the example waveform in Figure 4A is a square AC waveform. Other examples of AC waveforms that can be used include sine waves, triangular waves, and sawtooth waves.

[0111] The alternating current waveform can have an amplitude from 10 volts to 200 volts and a frequency from 0.1 Hz to 6000 Hz. The alternating current waveform can have an amplitude from 15 volts to 180 volts, from 20 volts to 160 volts, from 25 volts to 150 volts, or from 30 volts to 140 volts. The alternating current waveform can have a frequency from 0.5 Hz to 5000 Hz, from 1 Hz to 4000 Hz, from 5 Hz to 3000 Hz, from 10 Hz to 2000 Hz, from 15 Hz to 1000 Hz, from 20 Hz to 800 Hz, or from 25 Hz to 600 Hz. The frequency of the alternating current waveform can range from 400 Hz to 2000 Hz according to the weight percentage of the charge control agent in the electrophoretic medium.

[0112] The second waveform may comprise a waveform formed by superimposing a DC voltage component with an AC waveform. An example of such a second waveform is illustrated in Figure 4B.

[0113] The waveform in Figure 4B has a net negative pulse due to the DC bias (Vd). Although the duration of the applied positive pulse (t3) is equal to the duration of the applied negative pulse (t4), the DC bias is achieved by the difference in the amplitudes of these pulses. 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 4B has a DC bias.

[0114] The example drive waveform in Figure 4B is DC unbalanced. However, more than one additional pulse can be included in the waveform of Figure 4B as an opposite pulse, ensuring that the overall waveform applied to a pixel is DC unbalanced. This additional pulse (or multiple additional pulses) can be applied before the DC unbalanced waveform (pre-pulse). Also, the example waveform in Figure 4B is a square AC waveform. Other examples of AC waveforms that can be used include sine waves, triangular waves, and sawtooth waves.

[0115] The alternating current waveform can have an amplitude from 10 volts to 200 volts and a frequency from 0.1 Hz to 6000 Hz. The alternating current waveform can have an amplitude from 15 volts to 180 volts, from 20 volts to 160 volts, from 25 volts to 150 volts, or from 30 volts to 140 volts. The alternating current waveform can have a frequency from 0.5 Hz to 5000 Hz, from 1 Hz to 4000 Hz, from 5 Hz to 3000 Hz, from 10 Hz to 2000 Hz, from 15 Hz to 1000 Hz, from 20 Hz to 800 Hz, and from 25 Hz to 600 Hz. The frequency of the alternating current waveform can range from 400 Hz to 2000 Hz according to the weight percentage of the charge control agent in the electrophoretic medium.

[0116] In cases where the ICEO induced motion of these charged pigment particles is relatively low, the protruding structure of the microcell contributes to the effective operation of the variable light transmission device, even if the device is driven by a DC-balanced AC waveform. In an example where the protruding structure is a cone, any charged pigment particles located on the surface of the cone will experience a net force that moves these charged pigment particles toward the apex of the cone, as shown in Figure 5. Figure 5 shows charged pigment particles 223 in contact with the protruding structure 517 (cone) in an electric field 502. In this case, the ICEO flow system, illustrated by the curved arrow, is more restricted on the "uphill" side of the cone than on the "downhill" side. This transmits a force to the particle, illustrated by the dotted horizontal arrow. There will be an opposing force orthogonal to the cone, forcing the particle toward the apex of the cone. With proper selection of the AC field and frequency, these particles can move out of the channel region and thus climb onto the side of the cone.

[0117] One problem encountered by variable light transmission devices in the open optical state of a microcell containing light-absorbing charged pigment particles is the observable diffraction pattern. This type of diffraction pattern, known as Fraunhofer diffraction, can interfere with a viewer when light from a small object in a dark environment (such as a light source) or when sunlight is specularly reflected from a bright environment passes through the variable light transmission device in the open optical state. This diffraction occurs because the microcell channel contains multiple straight edges with abrupt transitions from light absorption to light transmission. These straight edges are formed by the arrangement of the absorbing particles within the microcell channel. The well-known end result is that the diffraction pattern is directly related to the light transmission shape (aperture) of the microcell in the open state. The image on the right side of Figure 6 shows various Fraunhofer diffraction patterns formed by various aperture shapes, which are shown on the left side of Figure 6. Specifically, the triangular aperture forms the diffraction pattern shown in Figure 6(a), the square aperture forms the diffraction pattern shown in Figure 6(b), the pentagonal aperture forms the diffraction pattern shown in Figure 6(c), and the hexagonal aperture forms the diffraction pattern shown in Figure 6(d). In all these examples, the resulting diffraction patterns include highly visible linear components. Thus, the diffraction pattern shown in Figure 6(a) has six linear components, the diffraction pattern shown in Figure 6(b) has four linear components, the diffraction pattern shown in Figure 6(c) has ten linear components, and the diffraction pattern shown in Figure 6(d) has six linear components.

[0118] Several methods can be used to mitigate diffraction patterns with highly visible linear characteristics. First, a diffraction pattern is formed using a circular aperture, where the intensity of diffraction is uniformly distributed across all diffraction angles. Thus, in the case of a circular aperture, the highly visible linear diffraction patterns shown in Figures 6(a) to 6(d) are transformed into less visible diffraction rings with lower intensity, as shown in Figure 7. Figure 7 shows a diffraction pattern comprising a plurality of concentric rings with decreasing light intensity as the diameter of the ring increases. Second, a previously proposed method (U.S. Patent Application Publication No. 2023 / 0100320A1) uses apodization, replacing the straight edges of hexagonal and circular apertures with irregular or regular shapes to soften the abrupt transition from light absorption to light transmission, thereby mitigating highly visible linear diffraction patterns. Regular shapes, including those described by sine waves and triangular zigzags or sawtooth features, are called sawtooth notches. However, theoretical calculations show that using a sawtooth notch in a circular aperture provides only limited suppression of diffraction rings. The results of the calculations are shown in Figure 8, which provides a diffraction pattern for a circular aperture with a sawtooth notch. For the calculations, the diameter of the aperture was set to 275 micrometers, and the viewing distance was set to 25 meters. To improve the visibility of the printed diffraction pattern, the contrast was enhanced by a factor of 2.5. In addition, experiments with circular apertures with sawtooth notches showed that circular apertures without sawtooth notches do not exhibit additional high-frequency color image diffraction patterns. Furthermore, it has been observed that when multiple charged pigment particles that absorb light are used in a variable light transmission device having a channel with a sawtooth notch edge, these particles penetrate into the sawtooth notch in the open optical state. Thus, the sawtooth notch reduces the severity of the diffraction pattern by being masked by these particles.

[0119] The inventors of this invention have discovered that undesired diffraction patterns observed in an open optical state can be mitigated using a variable light transmission device. This device has a microcell layer comprising a plurality of microcells, each microcell including an electrophoretic medium, and each microcell having a channel and one or more protruding structures with recesses. An example of such a microcell in a variable light transmission device is illustrated in Figures 2A to 2C. Specifically, the mitigation of the undesired diffraction pattern is achieved by a non-repetitive shift in optical density or visible spectrum at the channel. This shift in optical density can be achieved by a specific architecture of the microcell, where the channel has a complex shape.

[0120] In one example, the charged particles of the electrophoretic medium in the variable light transmission device are light-absorbing. The variable light transmission device includes a plurality of microcells, each microcell including a channel and a protruding structure having one or more recesses. The microcells include an electrophoretic medium having a plurality of light-absorbing charged particles. The protruding volume of the protruding structure is a geometric shape, which is a cone or other geometric shape located on a cylinder. The protruding volume can also be another geometric shape, such as a polygonal pyramid, a truncated polygonal pyramid, a polygonal prism on a polygonal pyramid, a polygonal pyramid on a truncated polygonal pyramid, a first truncated polygonal pyramid on a second truncated polygonal pyramid, a cone, a truncated cone, a cone on a truncated cone, or a first truncated cone on a second truncated cone. In the open optical state of the device, the charged electrophoretic pigment particles are present in the ultramicro battery channel, which includes the recesses of the protruding structure.

[0121] The various geometric systems of this protruding volume are described below. (a) A polygonal pyramid having a vertex and a polygonal base having 3 to 20 sides, the polygonal base being the protruding base of the protruding structure and the lower base of the protruding structure having one or more recesses, the vertex of the polygonal pyramid being the protruding vertex. (b) A truncated polygonal pyramid having a first polygonal base and a second polygonal base, the first polygonal base being the protruding vertex, the second polygonal base being the protruding base and the lower base of the protruding structure having one or more recesses, the first and second polygonal bases of the truncated polygonal pyramid having 3 to 20 sides. (c) A polygonal pyramid on a polygonal prism, the polygonal pyramid having a polygonal base, the polygonal base of the polygonal pyramid having a surface area, the polygonal prism having a first polygonal base and a second polygonal base, the first polygonal base having a surface area, the second polygonal base having a surface area, the polygonal base of the polygonal pyramid being in contact with the first polygonal base of the polygonal prism, the surface area of ​​the polygonal base of the polygonal pyramid being the same as the surface area of ​​the first polygonal base of the polygonal prism, the polygonal base of the polygonal pyramid and the first and second polygonal bases of the polygonal prism having 3 to 20 sides, the second polygonal base of the polygonal prism being the protruding base of the protruding structure. (d) A polygonal pyramid on a truncated polygonal pyramid, the polygonal pyramid having a polygonal base, the polygonal base having a surface area, the polygonal truncated pyramid having a first polygonal base and a second polygonal base, the first polygonal base of the polygonal pyramid having a first surface area, the second polygonal base of the polygonal pyramid having a second surface area, the polygonal vertex of the polygonal pyramid being the protruding vertex, the polygonal base of the polygonal pyramid being in contact with the first polygonal base of the polygonal pyramid, the surface area of ​​the polygonal base of the polygonal pyramid being the same as the first surface area of ​​the first polygonal base of the polygonal pyramid, the second polygonal base of the polygonal pyramid being the protruding base, the polygonal base of the polygonal pyramid and the first and second polygonal bases of the polygonal pyramid having 3 to 20 sides. e) A first polygonal pyramid truncated stage on a second polygonal pyramid truncated stage, the first polygonal pyramid truncated stage having a first polygonal base and a second polygonal base, the first polygonal base of the first polygonal pyramid truncated stage having a first surface area, the second polygonal base of the first polygonal pyramid truncated stage having a second surface area, the first polygonal base of the second polygonal pyramid truncated stage having a first surface area, the second polygonal base of the second polygonal pyramid truncated stage having a second surface area, the first polygonal pyramid truncated stage having a first surface area, the second polygonal base of the second polygonal pyramid truncated stage having a second surface area, the first polygonal pyramid truncated stage having a first polygonal base and a second polygonal base, the first polygonal base of the second ... surface area, the second polygonal base of the second polygonal pyramid truncated stage having a second surface area, the first polygonal base having a first surface area, the second polygonal base of the second polygonal pyramid truncated stage having a second surface area, the first polygonal base having a first surface area, the second polygonal base of the second polygonal pyramid truncated stage having a first surface area, the second polygonal base of the second polygonal pyramid truncated stage having a second surface area, the first polygonal base having a first surface area, The first polygonal base of the truncated pyramid is the protruding vertex, the second polygonal base of the first polygonal truncated pyramid is in contact with the first polygonal base of the second polygonal truncated pyramid, the second surface area of ​​the second polygonal base of the first polygonal truncated pyramid is the same as the first surface area of ​​the first polygonal base of the second polygonal truncated pyramid, the second polygonal base of the second polygonal truncated pyramid is the protruding base, the first and second polygonal bases of the first polygonal truncated pyramid and the first and second polygonal bases of the second polygonal truncated pyramid have 3 to 20 sides. (f) A cone having a vertex and a base, the vertex being a projecting vertex and the base being a projecting base. (g) A conical frustum having a first base and a second base, wherein the first base of the conical frustum is the protruding apex and the second base of the conical frustum is the protruding base. (h) A cone on a cylinder, the cone having a vertex and a base, the vertex of the cone being the protruding vertex, the base of the cone having a surface area, the cylinder having a first base and a second base, the first base of the cylinder having a first surface area and the second base of the cylinder having a second surface area, the base of the cone being in contact with the first base of the cylinder, the surface area of ​​the base of the cone being the same as the first surface area of ​​the first base of the cylinder, and the second base of the cylinder being the protruding base. (i) A cone on a truncated cone, the cone having a vertex and a base, the vertex being the protruding vertex, the base having a surface area, the truncated cone having a first base and a second base, the first base of the truncated cone having a surface area, the second base of the truncated cone having a surface area, the base of the cone contacting the first base of the truncated cone, the surface area of ​​the base of the cone being the same as the surface area of ​​the first base of the truncated cone, and the second base of the truncated cone being the protruding base. (j) A first conical truncated column on a second conical truncated column, the first conical truncated column having a first base and a second base, the first base of the first conical truncated column having a first surface area, the second base of the first conical truncated column having a second surface area, the first base of the first conical truncated column being the protruding apex, the second conical truncated column having a first base and a second base, the first base of the second conical truncated column having a first surface area, the second base of the second conical truncated column having a second surface area, the second base of the first conical truncated column being in contact with the first base of the second conical truncated column, the second surface area of ​​the first conical truncated column being the same as the first surface area of ​​the first base of the second conical truncated column, the second base of the second conical truncated column being the protruding base.

[0122] Each recess of a protruding structure has a lower base and an upper base. The lower base of the recess is in contact with the inner surface of the exposed microcell bottom. The lower base of the recess and the protruding base of the protruding structure are located in the same plane. The upper base of the protruding structure (218) is the intersection of the recess and the exposed protruding surface. Figure 9 is an illustration of one example of a protruding base of a microcell having a hexagonal shape and a length L. The protruding structure of this example has only one recess. The protruding volume is a cone. Figure 9 also shows the lower base 222a of the recess, the microcell wall 212, and the channel 215. The channel is depicted in black and includes the recess. Figure 10 illustrates the lower base of the recess (222a), such as the depth 222d and the width 222a of the recess.

[0123] Figure 11 illustrates one example of a protruding base of an ultramicro battery, which has a hexagonal shape and a length L. The protruding structure of this example has two recesses. The protruding volume of the protruding structure (including the recesses) is a cone. Figure 11 shows the base 222a below the two recesses, the ultramicro battery wall 212, and the channel 215. The channel in which the electrophoretic particles are present in an open optical state is depicted in black and includes the two recesses. In this example, the bases of the two recesses are arranged at a 180-degree angle to each other along the bases of the recesses. Thus, in this example, the bases (222a) below all the recesses of the protruding structure are symmetrical about an axis of symmetry C2, which is perpendicular to the plane of the protruding base (218) and passes through the center of the protruding base. C2 symmetry means that a rotation around the axis of symmetry by an angle of 180 degrees (360 / 2) will make the recessed lower base (222a) of the protruding structure indistinguishable from the recessed lower base before the rotation.

[0124] Figure 12 is an illustration of an example of a protruding base of a microcell, which has a hexagonal shape and a length L. The protruding structure of this example has three recesses. The protruding volume is a cone. Figure 12 shows the lower bases of the three recesses 222a, the microcell wall 212, and the channel 215. The channel is depicted in black. In this example, the lower bases of the three recesses are arranged at a 120-degree angle to each other along the bases of the recesses. Thus, in this example, all the lower bases (222a) of the protruding structure are symmetrical about an axis of symmetry C3, which is perpendicular to the plane of the protruding base (218) and passes through the center of the protruding base. C3 symmetry means that a rotation of 120 degrees (360 / 3) around this axis of symmetry will make the lower bases (222a) of the protruding structure indistinguishable from the lower bases of the recesses before the rotation. Generally, if the protruding structure has n recesses, and these recesses are symmetrically arranged around the protruding structure, then it can be said that the base (222a) under all the recesses of the protruding structure is symmetrical about an axis of symmetry Cn, which is perpendicular to the plane of the protruding base (218) and passes through the center of the protruding base. Cn symmetry means that a rotation about the axis of symmetry by an angle of 360 / n degrees will make the base (222a) under the recesses of the protruding structure indistinguishable from the base under the recesses.

[0125] The variable light transmission device may include a microcell, the base (222a) beneath all the recesses of the protruding structure (217) of the microcell lacking symmetry about one of the axes of symmetry Cn, which is perpendicular to the plane of the protruding base (218) and passes through the center of the protruding base. The variable light transmission device may include more than one such microcell. All such microcells in the variable light transmission device may also exhibit a lack of such symmetry.

[0126] The diffraction pattern observed in the open state of the variable light transmission device is mitigated by the complex shape forming the microcell channel, as shown in Figures 9 to 12. This mitigation can also be achieved by a variable light transmission device comprising a layer of microcells, each microcell having 1 to 6 recesses. The variable light transmission device can have two types of microcells: a first type and a second type. The first type has a protruding structure with m recesses, and the second type has a protruding structure with p recesses, where m and p are integers and m is different from p. For example, m can be 1, and p can be 2 or 3. The variable light transmission device can also have three types of microcells: a first type, a second type, and a third type. The first type of ultramicro battery has a protruding structure with m recesses, the second type of ultramicro battery has a protruding structure with p recesses, and the third type of ultramicro battery has a protruding structure with q recesses, where m, p, and q are integers, m is different from p and q, and p is different from q. For example, m can be 1, p can be 2, and q can be 3. The parameters m, p, and q represent the number of recesses in the protruding structure of the first, second, and third type of ultramicro battery. The integers m, p, and q can range from 1 to 10, or from 1 to 8, or from 1 to 6, or from 1 to 4, or from 1 to 3.

[0127] Alternatively, a variable light transmission device comprising two microcells can be used to mitigate the imbalance, where the two microcells lack C2 symmetry about a common axis. Specifically, a variable light transmission device may comprise a first microcell and a second microcell. The first microcell may include a first protruding structure having a first protruding base and 1, 2, 3, 4, 5, or 6 recesses, each recess having a lower base. The combination of the first protruding base of the first microcell and the lower bases of the recesses forms a first geometry having a first center. The second microcell may include a second protruding structure having a second protruding base and 1, 2, 3, 4, 5, or 6 recesses, each recess having a lower base. The combination of the second protruding base of the second microcell and the lower bases of the recesses forms a second geometry having a second center. The first protruding base may lack symmetry about an axis of symmetry relative to the second protruding base (C2), the axis of symmetry being perpendicular to the plane of the first protruding base and passing through a point at the midpoint between the first center and the second center. Symmetry of the first protruding base relative to the second protruding base (C2) means that a rotation about this axis of symmetry by a 180° angle will render the first and second protruding bases indistinguishable from their original state before the rotation. The variable light transmission device of the above example may further include a third microcell. The third microcell may include a third protruding structure having a third protruding base and 1, 2, 3, 4, 5, or 6 recesses, each recess having a lower base. The combination of the third protruding base of the third microcell and the lower bases of the recesses forms a third geometry having a third center. The third protruding base may lack symmetry about an axis of symmetry relative to the first protruding base (C2), the axis of symmetry being perpendicular to the plane of the first protruding base and passing through a point midway between the first center and the third center. The third protruding base may also lack symmetry about an axis of symmetry relative to the second protruding base (C2), the axis of symmetry being perpendicular to the plane of the second protruding base and passing through a point midway between the second center and the third center. The variable light transmission device may have multiple microcells, each having a plurality of protruding structures, wherein these protruding bases lack such symmetry with each other.

[0128] Figure 13 is a top view of the microcell shown in Figure 12. The prominent structure in Figure 12 has three recesses. Figure 13 clearly depicts the channel 215 of the microcell, in which a plurality of electrophoretic pigment particles reside in the open optical state. Channel 216 has an inner base periphery 224 and an outer base periphery 225. Channel 216 also has a channel width 216w, which is the minimum distance between the inner and outer base peripheries of the channel. As previously mentioned, the channel 215, including the volume of these recesses, represents the location where the plurality of electrophoretic particles exist in the open optical state of the variable light transmission device.

[0129] Figure 14 shows a side view of a microcell of a variable light transmission device 200 of the present invention, which includes a light transmission substrate 201, a first light transmission electrode layer 202, a microcell layer including a plurality of microcells and a sealing layer 206, a second light transmission layer 207, and a second light transmission substrate 208. The microcell includes a microcell wall 212, a channel 215, a protruding structure 217, a recess 222, and a microcell bottom 210. The height 222h of the recess is also shown in Figure 14. The microcells of the variable light transmission device 200 of the present invention may also include a light blocking layer 230, shown in Figure 15. The light blocking layer 230 is disposed between the upper surface of the microcell and the sealing layer 206. The light blocking layer 230 may include a light-absorbing pigment. The light-absorbing pigment of the light blocking layer may be black. The inventors of this invention have discovered that increasing the opacity of the device by partially using the light-transmitting wall material can improve the closed state of the light-blocking layer 230. The light-blocking layer 230 can be conductive, which can facilitate the switching of the device.

[0130] Figure 16 illustrates a microcell of a variable light transmission device 200 according to the present invention, comprising a light transmission substrate 201, a first light transmission electrode layer 202, a microcell layer comprising a plurality of microcells and a sealing layer 206, a second light transmission layer 207, and a second light transmission substrate 208. The microcell includes a microcell wall 212, a channel 215, a protruding structure 217, and a microcell bottom 210. The recess (or recesses) of the protruding structure are not shown in Figure 16. In the microcell of the variable light transmission device of Figure 16, the inner wall surface (213) of the microcell and the inner bottom surface (211) of the microcell form an angle (φ) greater than 90 degrees. The inventors of the present invention have discovered that such a structure significantly facilitates the embossing process used in the fabrication of microcells by enabling smooth removal of the embossing tool without damaging the microcell wall. The angle φ can range from 90 to 120 degrees, 93 to 117 degrees, 95 to 115 degrees, 98 to 118 degrees, or 100 to 115 degrees.

[0131] Another component contributing to the fabrication of the device is shown in Figure 17, illustrating a microcell of the variable light transmission device 200 of the present invention. The device includes a light-transmitting substrate 201, a first light-transmitting electrode layer 202, a microcell layer comprising a plurality of microcells and a sealing layer 206 (only one of the plurality of microcells is shown here), a second light-transmitting layer 207, and a second light-transmitting substrate 208. The microcell includes a microcell wall 212, a protruding structure 217, and a microcell bottom 210. The recess (or recesses) of the protruding structure are not shown in Figure 17. The protruding volume of the protruding structure is a geometric shape, which is a cone on a truncated cone. The cone has a first slope (θ1), and the truncated cone has a second slope (θ2). The second slope (θ2) is greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) is from 1 to 25 degrees, from 1 to 30 degrees, from 2 to 20 degrees, from 2 to 15 degrees, from 2 to 12 degrees, from 2 to 9 degrees, from 2 to 8 degrees, from 3 to 8 degrees, or from 4 to 8 degrees.

[0132] Figure 18 illustrates a microcell of a variable light transmission device 200 according to the present invention, which achieves a more convenient process for manufacturing the device. The variable light transmission device includes a light transmission substrate 201, a first light transmission electrode layer 202, a microcell layer comprising a plurality of microcells and a sealing layer 206 (only one of the plurality of microcells is shown here), a second light transmission layer 207, and a second light transmission substrate 208. The microcell includes a microcell wall 212, a protruding structure 217, and a microcell bottom 210. The protruding structure has a structure similar to that in Figure 17 (a cone on a truncated cone), with a slope θ2 (second slope) of the truncated cone that is larger than the slope θ1 (first slope) of the cone. The difference between the second slope (θ2) and the first slope (θ1) ranges from 1 to 25 degrees, from 1 to 30 degrees, from 2 to 20 degrees, from 2 to 15 degrees, from 2 to 12 degrees, from 2 to 9 degrees, from 2 to 8 degrees, from 3 to 8 degrees, or from 4 to 8 degrees. Furthermore, in the device of Figure 18, the inner wall surface (213) of the microcell and the inner bottom surface (211) of the microcell form an angle (φ) greater than 90 degrees, as shown in the structure of the device illustrated in Figure 16. The angle φ can range from 90 to 120 degrees, 93 to 117 degrees, 95 to 115 degrees, 98 to 118 degrees, or 100 to 115 degrees.

[0133] Figure 19(b) illustrates a Fraunhofer diffraction pattern formed by a variable light transmission device according to the present invention. The variable light transmission device, illustrated in Figure 19(b), comprises a plurality of microcells, each having a protruding structure and a channel, the protruding structure having three recesses. The protruding volume of the protruding structure is a cone on a cylinder. Figure 19(b) is a bottom view of the protruding bases of 10 microcells and the bases beneath the recesses. These recesses have a C3 symmetry within each microcell. However, the three-recess group of various microcells is oriented in different directions for different microcells. That is, the variable light transmission device of Figure 19(b) comprises a microcell layer containing a group of three or more microcells, each of which has a protruding base, wherein each of these protruding bases does not have any C2 symmetry about an axis of symmetry relative to a protruding base of any microcell in the group of three or more microcells. Here, C2 symmetry means that a rotation around this axis of symmetry by 180° will make the protruding bases of the group of three or more microcells indistinguishable from their original state before the rotation. For a group of two microcells with two protruding bases, the axis of symmetry is perpendicular to the plane of one of the protruding bases and passes through a point that is the midpoint of the distance between the centers of the geometry formed by the combination of the protruding base and the recessed base of each microcell. This microcell layer construction reduces the overall symmetry of the microcell layer, mitigating the effects of Fraunhofer diffraction patterns.

[0134] Figure 20(b) shows a Fraunhofer diffraction pattern formed by a variable light transmission device comprising a microcell layer containing a plurality of microcells. Each microcell includes a protruding structure (a cone on a cylinder) without any recesses. The channel has a circular outline. Figure 20(a) is a bottom view of a portion of the microcell layer, where the plurality of protruding bases are shown as circles.

[0135] Figure 21(b) shows a Fraunhofer diffraction pattern formed by a variable light transmission device comprising a layer of microcells, each microcell having a protruding structure. Each microcell and its channel have a hexagonal shape, as shown in Figure 21(b), which is a bottom view of a portion of the microcell layer.

[0136] The images in Figures 19(b), 20(b), and 21(b) show that the variable light transmission device of the present invention shown in Figure 19(a) effectively mitigates the Fraunhofer diffraction pattern caused by the device aperture.

[0137] Structural components in the diagram: 200 Variable light transmission device; 201 First light transmission substrate; 202 First light transmission electrode layer; 203 Microcell layer; 204 Multiple microcells; 205 Microcell opening; 206 Sealing layer; 207 Second light transmission electrode layer; 208 Second light transmission substrate; 209 Electrophoretic medium; 210 Microcell bottom layer; 211 Inner surface of microcell bottom; 211a Exposed inner surface of microcell bottom; 211b Unexposed inner surface of microcell bottom; 212 Microcell wall; 213 Inner wall surface of microcell; 214 Microcell Upper wall surface; 125 Channel; 216h Channel height; 216w Channel width; 217 Protruding structure; 218 Protruding base; 219 Protruding apex; 220 Protrusion height; 221 Exposed protruding surface; 222 Recess; 222a Base below the recess; 222h Height of the recess; 222d Depth of the recess pf; 222w Width of the recess; 223 Charged pigment particles; 224 Periphery of the base inside the channel; 225 Periphery of the base outside the channel; 230 Light blocking layer; 250 First outer surface of the variable light transmission device; 251 Second outer surface of the variable light transmission device.

[0138] 101: Cylindrical microparticles 200: Variable light transmission device 201: First light transmission substrate 202: First light transmission electrode layer 203: Ultra-micro battery layer 204: Multiple microcells 205: Microcell opening 206: Sealing layer 207: Second light-transmitting electrode layer, second light-transmitting layer 208: Second light transmission substrate 209: Electrophoretic medium 210: Substructure of an ultra-micro battery 211: Bottom inner surface of the micro battery 211a: Exposed inner surface of the bottom of the microcell 211b: The inner surface of the bottom of the microcell is not exposed. 212: Ultra-micro battery wall 213: Surface of the inner wall of the micro battery 214: Upper surface of the wall of the microcell, upper surface of the microcell 215: Channel 216h: Channel height 216w: Channel width 217: Emphasize Structure 218: Protruding base 219: Highlighting the Vertex 220: Highlighting Height 221: Exposed protruding surface 222: Depression 222a: Base with recess 222d: Depth of the depression 222h: Height of the depression 222w: Width of the depression 223: Charged pigment particles 224: The area around the base within the passageway 225: Outside the channel, around the base 230: Light blocking layer 250: First outer surface of the variable light transmission device 251: Second outer surface of the variable light transmission device 502: Electric Field 517: Emphasize Structure L: Length t1 to t4: Time period V1 to V4: Amplitude Vd: DC bias θ1: First slope θ2: Second slope φ: angle

Claims

1. A variable light transmission device (200) comprising: a first light transmission electrode layer (202); a second light transmission electrode layer (207); and a microcell layer (203), the microcell layer (203) being disposed between the first light transmission electrode layer (202) and the second light transmission electrode layer (207), the microcell layer (203) comprising a plurality of microcells (204) and a sealing layer (206); each of the plurality of microcells (204) comprising an electrophoretic medium (209), the electrophoretic medium (209) comprising a plurality of charged pigment particles (223), a charge control agent, and a nonpolar liquid; each of the plurality of microcells (204) having a microcell opening (205), the sealing layer (206) spanning the microcell openings (205) of the plurality of microcells (204); Each microcell's sealing layer (206) has an upper surface and a lower surface. The upper surface is in contact with the first light-transmitting electrode layer (202), and the lower surface is in contact with the electrophoretic medium (209). Each of the plurality of microcells (204) includes a microcell bottom layer (210), a protruding structure (217), a plurality of microcell walls (212), and a channel (215). The microcell bottom layer (210) has a microcell bottom inner surface (211), which includes an exposed microcell bottom inner surface (211a) and an unexposed microcell bottom inner surface (211b). The protruding structure (217) has a protruding base (218), a total protruding surface, an exposed protruding surface (221), a protruding apex (219), a protruding height (220), a protruding volume, and one or more recesses (222). The protruding base has a surface. The protruding apex (219) is a point or a group of points of the protruding structure (217), which has a shorter distance from the microcell opening (205) than all other points of the protruding structure (217). There is a distance between the protruding apex (219) and the protruding base (218). If the protruding apex (219) If a set of points is defined, then the protruding vertex (219) has a surface, the protrusion height (220) is the distance between the protruding base (218) and the protruding vertex (219), the exposed protruding surface (221) is any part of the total protruding surface (i) the surface of the protruding base and (ii) the surface of the protruding vertex, the exposed protruding surface (221) is in contact with the electrophoretic medium (209), the unexposed inner surface of the bottom of the microcell (211b) is in contact with the protruding base (218), and the exposed inner surface of the bottom of the microcell (211a) is in contact with the electrophoretic medium (209); the microcell walls (212) have an inner wall surface (213) and an upper surface (214), the inner wall surface (213) is one surface of the microcell wall (212) of one of the microcells in contact with the electrophoretic medium (209),The upper surface (214) of the microcell wall is a surface of the microcell wall (212) that is in contact with the sealing layer (206); the channel (215) has a channel height (216h), an inner base periphery (224), and an outer base periphery (225), the channel height (216h) is 50% of the protrusion height (220), the inner base periphery (224) is the intersection of the microcell wall (212) and the inner surface (211) of the exposed microcell bottom, and the outer base periphery (225) is the intersection of the protruding base and the inner surface of the exposed microcell bottom; The channel (215) is a volume defined by the exposed inner surface of the bottom of the microcell (211a), the exposed protruding surface (221), the inner wall surface of the microcell (213), and a plane parallel to the inner surface of the bottom of the microcell (211). The distance between the plane and the inner surface of the bottom of the microcell (211) is equal to the height of the channel (216h). 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 light transmission device close to the first light transmission electrode layer (202), and the second outer surface (251) is located on the side of the light transmission device close to the second light transmission electrode layer (207). Each of the one or more recesses (222) of the protruding structure (217) is a geometric shape. The geometric shape of each of the one or more recesses (222) has a volume, a height (222h), a depth (222d), and a width (222w). The geometric shape of each of the one or more recesses (222) has an upper base (222b), a lower base (222a), and a surrounding surface. The lower base of each of the one or more recesses (222a) is in contact with the inner surface (211a) of the bottom of the exposed microcell. The lower base of each of the one or more recesses (222a) has a shape selected from a flat circle, a flat circle segment, a flat circle sector, a circular segment, a circular sector, or a triangle. The shape is a square, rectangle, or a group of polygons having 5 to 20 sides, each of the more than one recess (222) being occupied by the electrophoretic medium (209) of the variable light transmission device (200), the protruding volume of the protruding structure (217) being a geometric shape selected from the group of the following: (a) a polygonal pyramid having a vertex and a polygonal base having 3 to 20 sides, the polygonal base being the protruding base (218) of the protruding structure (217) and the lower base (222a) of the more than one recess (222) of the protruding structure (217), the vertex of the polygonal pyramid being the protruding vertex (219); (b) a polygonal pyramid truncated cone having a first polygonal base and a second polygonal base.The first polygonal base of the truncated polygonal pyramid is the protruding vertex (219), the second polygonal base of the truncated polygonal pyramid is the protruding base (218), and the lower base (222a) of one or more recesses (222) of the protruding structure (217). The first and second polygonal bases of the truncated polygonal pyramid have 3 to 20 sides. (c) A polygonal pyramid on a polygonal prism, the polygonal pyramid having a polygonal base, the polygonal base of the polygonal pyramid having a surface area, the polygonal prism having a first polygonal base and a second polygonal base, the first polygonal base having a surface area, the second polygonal base having a surface area, the polygonal base of the polygonal pyramid being in contact with the first polygonal base of the polygonal prism, the surface area of ​​the polygonal base of the polygonal pyramid being the same as the surface area of ​​the first polygonal base of the polygonal prism, the polygonal base of the polygonal pyramid and the first and second polygonal bases of the polygonal prism having 3 to 20 sides, the second polygonal base of the polygonal prism being the protruding base (218) of the protruding structure (217). (d) A polygonal pyramid on a truncated polygonal pyramid, the polygonal pyramid having a polygonal base, the polygonal base having a surface area, the polygonal truncated pyramid having a first polygonal base and a second polygonal base, the first polygonal base of the polygonal truncated pyramid having a first surface area, the second polygonal base of the polygonal truncated pyramid having a second surface area, the polygonal vertex of the polygonal pyramid being the protruding vertex (219), the polygonal base of the polygonal pyramid being in contact with the first polygonal base of the polygonal truncated pyramid, the surface area of ​​the polygonal base of the polygonal pyramid being the same as the first surface area of ​​the first polygonal base of the polygonal truncated pyramid, the second polygonal base of the polygonal truncated pyramid being the protruding base (218), the polygonal base of the polygonal pyramid, and the first and second polygonal bases of the polygonal truncated pyramid having 3 to 20 sides. e) A first polygonal pyramid truncated on a second polygonal pyramid truncated on top of a first polygonal pyramid truncated on top of a second polygonal pyramid truncated on top of a first polygonal base and a second polygonal base. The first polygonal base of the first polygonal pyramid truncated on top of the second polygonal pyramid truncated on top of the first polygonal base has a first surface area, and the second polygonal base of the second polygonal pyramid truncated on top of the second polygonal base truncated on top of the second polygonal pyramid truncated on top of the first polygonal base truncated on top of the second polygonal base truncated on top of the second polygonal base truncated on top of the first polygonal pyramid truncated on top of a second polygonal base ...The second polygonal base of the first polygonal truncated pyramid is in contact with the first polygonal base of the second polygonal truncated pyramid. The second surface area of ​​the second polygonal base of the first polygonal truncated pyramid is the same as the first surface area of ​​the first polygonal base of the second polygonal truncated pyramid. The second polygonal base of the second polygonal truncated pyramid is the protruding base (218). The first and second polygonal bases of the first polygonal truncated pyramid and the first and second polygonal bases of the second polygonal truncated pyramid have 3 to 20 sides. (f) A cone having a vertex and a base. The vertex of the cone is the protruding vertex (219), and the base of the cone is the protruding base (218). (g) A truncated cone having a first base and a second base, the first base being the protruding apex (219), and the second base being the protruding base (218); (h) A cone on a cylinder having a apex and a base, the apex being the protruding apex (219), the base having a surface area; the cylinder having a first base and a second base, the first base having a first surface area and the second base having a second surface area; the base of the cone contacting the first base of the cylinder; the surface area of ​​the base of the cone being the same as the first surface area of ​​the first base of the cylinder; and the second base being the protruding base (218). (i) A cone on a truncated cone, the cone having a vertex and a base, the vertex being the projecting vertex (219), the base having a surface area, the truncated cone having a first base and a second base, the first base of the truncated cone having a surface area, the second base of the truncated cone having a surface area, the base of the cone contacting the first base of the truncated cone, the surface area of ​​the base of the cone being the same as the surface area of ​​the first base of the truncated cone, and the second base of the truncated cone being the projecting base (218). (j) A first conical truncated cone on a second conical truncated cone, the first conical truncated cone having a first base and a second base, the first base of the first conical truncated cone having a first surface area, the second base of the first conical truncated cone having a second surface area, the first base of the first conical truncated cone being the protruding apex (219), the second conical truncated cone having a first base and a second base, the first base of the second conical truncated cone having a first surface area, the second base of the second conical truncated cone having a second surface area, the second base of the first conical truncated cone being in contact with the first base of the second conical truncated cone.The second surface area of ​​the first truncated cone is the same as the first surface area of ​​the first base of the second truncated cone, and the second base of the second truncated cone is the protruding base (218); wherein a first electric field is applied through a first waveform 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), resulting in the variable light transmission device (200) switching to an open optical state; wherein a second electric field is applied through a second waveform 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 one of the first light-transmitting electrode layers (202), wherein the closed optical state has a lower percentage of transparency than the open optical state.

2. The variable light transmission device of claim 1, wherein the protruding structure (217) of one of the microcells of the microcell layer has six or fewer recesses (222).

3. The variable light transmission device of claim 1, wherein the microcell opening (205) of each of the plurality of microcells (204) of the microcell layer (203) has a shape, the shape of the microcell opening (205) being selected from a group of a circle, a square, a rectangle and a polygon having 5 to 12 sides.

4. The variable light transmission device of claim 1, wherein each of the plurality of microcells (204) has a length ranging from 400 micrometers to 800 micrometers and a height ranging from 20 micrometers to 100 micrometers.

5. The variable light transmission device as claimed in claim 1, wherein the channel (215) has a width ranging from 10 micrometers to 30 micrometers.

6. The variable light transmission device of claim 1, wherein the protrusion height (220) is from 15 micrometers to 90 micrometers, and wherein the one or more recesses (222) of the protrusion structure (217) have a depth (222d) from 10 micrometers to 40 micrometers and a width (222w) from 10 micrometers to 40 micrometers.

7. A variable light transmission device as claimed in any of claims 1 to 6, wherein the variable light transmission device comprises a microcell having a protruding structure (217) with 2, 3, 4, 5 or 6 recesses (222), the combination of the protruding base of the microcell and the base under the recesses forming a first geometry having a center, wherein the protruding base (218) is symmetrical about an axis of symmetry Cn, the axis of symmetry being perpendicular to the plane of the protruding base (218) and passing through the center of the first geometry, n being the number of the recesses (222) of the protruding structure, and wherein symmetry Cn means that a rotation about the axis of rotation by an angle of 360° / n would make the protruding base (218) indistinguishable from the protruding base (218) before the rotation.

8. A variable light transmission device as claimed in any of claims 1 to 6, wherein the variable light transmission device comprises a microcell having a protruding structure (217) with 2, 3, 4, 5 or 6 recesses (222), the combination of the protruding base of the microcell and the base under the recesses forming a first geometry having a center, wherein the protruding base (218) is not symmetrical about an axis of symmetry Cn, the axis of symmetry being perpendicular to the plane of the protruding base (218) and passing through the center of the first geometry, n being the number of the recesses (222) of the protruding structure (217), and wherein symmetry Cn means that a rotation about the axis of rotation by an angle of 360° / n would make the protruding base (218) indistinguishable from the protruding base (218) before the rotation.

9. A variable light transmission device as claimed in any one of claims 1 to 6, wherein the variable light transmission device comprises a first microcell and a second microcell, the first microcell comprising a first protruding structure having a first protruding base and 1, 2, 3, 4, 5 or 6 recesses, each recess having a lower base, the combination of the first protruding base of the first microcell and the lower bases of the recesses forming a first geometry having a first center, the second microcell comprising a second protruding structure having a second protruding base and 1, 2, 3, 4, 5 or 6 recesses, each recess having a lower base. The combination of the second protruding base of the second microcell and the recessed bases forms a second geometry having a second center, wherein the first protruding base is not symmetrical about an axis of symmetry relative to the second protruding base at point C2, the axis of symmetry being perpendicular to the plane of the first protruding base and passing through a point at the midpoint of the distance between the first center and the second center, and wherein the symmetry of the first protruding base relative to the second protruding base at point C2 means that a rotation of 180° around the axis of symmetry would make the first and second protruding bases indistinguishable from the first and second protruding bases before the rotation.

10. The variable light transmission device of claim 9, wherein the variable light transmission device comprises a third microcell, the third microcell comprising a third protruding structure having a third protruding base and 1, 2, 3, 4, 5 or 6 recesses, each recess having a lower base, the combination of the third protruding base of the third microcell and the lower bases of the recesses forming a third geometry having a third center, wherein the third protruding base is not symmetrical about a symmetry axis relative to a first protruding base at point C2, the symmetry axis being perpendicular to the plane of the first protruding base and passing through a point at the midpoint of the distance between the first center and the third center, and wherein the third protruding base is not symmetrical about a symmetry axis relative to a second protruding base at point C2, the symmetry axis being perpendicular to the plane of the second protruding base and passing through a point at the midpoint of the distance between the second center and the third center.

11. A variable light transmission device as claimed in any of claims 1 to 6, wherein the geometric system of the protruding volume of the protruding structure (217) of a microcell is a polygonal pyramid on a truncated polygonal pyramid, the polygonal pyramid having a first slope (θ1) and the truncated pyramid having a second slope (θ2), the second slope (θ2) being greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) being from 1... The angle is up to 25 degrees, or the geometric system of the protruding volume of the protruding structure (217) is a first polygonal pyramid truncated table on a second polygonal pyramid truncated table, the first polygonal pyramid truncated table having a first slope (θ1), and the second pyramid truncated table having a second slope (θ2), the second slope (θ2) being greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) being from 1 to 25 degrees.

12. A variable light transmission device as claimed in any of claims 1 to 6, wherein the protruding volume of the protruding structure (217) of a microcell is a cone on a truncated cone of a geometric system, the cone having a first slope (θ1) and the truncated cone having a second slope (θ2), the second slope (θ2) being greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) being from 1 to 25 degrees; or wherein the first truncated cone on a second truncated cone of the geometric system has a first slope (θ1) and the second truncated cone having a second slope (θ2), the second slope (θ2) being greater than the first slope (θ1), and the difference between the second slope (θ2) and the first slope (θ1) being from 1 to 25 degrees.

13. A variable light transmission device as claimed in any one of claims 1 to 6, wherein the variable light transmission device comprises one or more microcells having an inner sidewall surface (213) and a microcell bottom surface (211), the inner sidewall surface (213) and the microcell bottom surface (211) forming an angle (φ) ranging from 90 to 120 degrees.

14. The variable light transmission device of any one of claims 1 to 6, wherein the variable light transmission device may include a first adhesive layer and a second adhesive layer, the first adhesive layer being disposed between the sealing layer (206) and the first light transmission electrode layer (202), and the second adhesive layer being disposed between the microcell layer (203) and the second light transmission electrode layer (207).

15. A variable light transmission device as claimed in any one of claims 1 to 6, wherein the variable light transmission device includes a light blocking layer (230) disposed between the upper surface (214) of the microcell and the sealing layer (206), the light blocking layer (230) including a light-absorbing pigment.

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

17. A variable light transmission device as claimed in any of claims 1 to 6, wherein the charged particles (223) of the electrophoretic medium (209) are light-absorbing.

18. A variable light transmission device as claimed in any of claims 1 to 6, wherein the second electric field causes the charged pigment particles (223) to move toward one of the first light transmission electrode layers (202) at a velocity having a lateral component.

19. A variable light transmission device as claimed in any of claims 1 to 6, wherein the second waveform includes at least one positive voltage and at least one negative voltage, and the second waveform has a net positive or a net negative pulse.

20. The variable light transmission device of claim 19, wherein the second waveform includes an AC waveform having a duty cycle from 5% to 45%, or wherein the second waveform may include a DC bias waveform formed by superimposing a DC voltage component onto an AC waveform.

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