Liquid Crystal Display

Transcription

1 University of Centra Forida UCF Patents Patent Liquid Crysta Dispay Xinyu Zhu University of Centra Forida Zhibing Ge University of Centra Forida Wang-Yang Li Harvard University Chung-Kuang Wei Harvard University Shin-Tson Wu University of Centra Forida Find simiar works at: University of Centra Forida Libraries Recommended Citation Zhu, Xinyu; Ge, Zhibing; Li, Wang-Yang; Wei, Chung-Kuang; and Wu, Shin-Tson, "Liquid Crysta Dispay" (212). UCF Patents. Paper This Patent is brought to you for free and open access by the Technoogy Transfer at STARS. It has been accepted for incusion in UCF Patents by an authorized administrator of STARS. For more information, pease contact

2 I I US8288B2 c12) United States Patent Zhu et a. (1) Patent o.: US 8,28,8 B2 (45) Date of Patent: Jun.26,212 (54) LIQUID CRYSTAL DISPLAY (75) Inventors: Xinyu Zhu, Orando, FL (US); Zhibing Ge, Orando, FL (US); Shin-Tson Wu, Orando, FL (US); Wang-Yang Li, Tainan County (TW); Chung-Kuang Wei, Taipei (TW) (73) Assignees: Chimei Innoux Corporation, Miao-Li County (TW); University of Centra Forida Research Foundation, Inc., Orando, FL (US) 6,424,396 B 6,661,488 B 6,71,825 B2 6,768,53 B2 * 6,85,31 B2 * 7,88,413 B2 * 7,274,348 B2 * 7,295,272 B2 * 7,355,664 B2 * 7,586,559 B2 * 8,45,115 B2 * 8,17,25 B2 * 7122 Kim et a. 12/23 Takeda et a. 3/24 Kubo et a. 7/24 Matsuyama et a / Shimoshikiryo. 349/129 8/26 Martinot-Lagarde et a.. 349/129 9/27 Izumi et a.. 345/ Hegee et a.. 349/123 4/28 Ogishima et a.. 349/ Minoura et a. 349/62 1/211 Lee et a / Shimizu et a.. 349/33 (Continued) ( *) otice: Subject to any discaimer, the term ofthis patent is extended or adjusted under 35 U.S.C. 154(b) by 594 days. C FOREIG PATET DOCUMETS A 3/22 (Continued) (21) App. o.: 11/683,26 (22) Fied: Mar. 7, 27 (65) Prior Pubication Data US 28/ A Sep. 11, 28 (51) Int. C. G2F (26.1) G2F (26.1) (52) U.S. C /33; 349/143 (58) Fied of Cassification Search 349/33, 349/34, 114, 139, 141, 143, 38, 39, 115, 349/123 See appication fie for compete search history. (56) References Cited U.S. PATET DOCUMETS 4,257,682 A * 3/1981 Suzuki et a.. 349/13 6,151,93 A * 1112 Takiguchi et a. 349/172 6,327,13 B* 12/21 Tombing et a.. 349/139 OTHER PUBLICATIOS Office Action, Taiwanese Patent Appication , 13 pages, ov. 25, 211. (Continued) Primary Examiner - Akm Uah (74) Attorney, Agent, or Firm - ThomasKayden (57) ABSTRACT A dispay incudes pixe circuits, each pixe circuit incuding a first eectrode, a second eectrode, a third eectrode, and a iquid crysta ayer doped with a chira materia. The first eectric is eectricay couped to a first reference votage. The second eectrode receives a pixe votage corresponding to a gray scae eve, the second eectrode incuding a conducting ayer having openings. The third eectrode is eectricay couped to a second reference votage. The second eectrode is between the first and third eectrodes, and the iquid crysta ayer is between the first and second eectrodes. 22 Caims, 14 Drawing Sheets (iu Hb 12b =::' 18 I OG m: J2a 11 "CJ j (Ja 11 ihi

3 US 8,28,8 B2 Page A * 23/2626 A * 24/21816 A 24/ A * 25/2132 A* 26/ A JP TW TW U.S. PATET DOCUMETS 12/21 umano et a / Kobayashi et a /115 1/24 Chen et a. 349/ Yoshida et a / Wen et a.. 349/ Shih FOREIG PATET DOCUMETS A / OTHER PUBLICATIOS K. H. Kim, et a. "Domain divided vertica aignment mode with optimized fringe fied effect" Proceeding of the 18th Internationa Dispay Research Conference (Asia Dispay'98), pp , Y. Ishii, et a. "High Performance TFT-LCDs for AVC Appications" SID'O, Digest, 41.1 (21). Y. Kume, et a. "Advanced ASM Mode (Axiay Symmetric Aigned Microce Mode): Improvement of Dispay Performances by Using egative Dieectric Liquid Crysta'' SID'98, 41.4 (1998). * cited by examiner

4 U.S. Patent Jun.26,212 Sheet 1of14 US 8,28,8 B2,..,c;... co G'.1,.,...,. -,_-<,..,... o::i ::d CV ce m...,.;; OC 'Xi "'1' ':D "'..;,..,,.--<,...-;,...-<,...; ;,.--,..;,...-i,., G'.1 \ / _;\ r---- \ \ f, ' \ }

5 U.S. Patent Jun.26,212 Sheet 2of14 US 8,28,8 B2 I \ / /.,..-/ / C-..:,.

6 U.S. Patent Jun.26,212 Sheet 3of14 US 8,28,8 B2 \ \

7 U.S. Patent Jun.26,212 Sheet 4of14 US 8,28,8 B2 u OO! <=:;\,...,i

8 14b Ob = 2' := 1J1 ('D = ('D. U..i;... d rj ' _,.oo = =,Z x )--;,. y u!,, b 1.: "-/ --..., 18 Oa,...'f'"'",..."'"Y.1,...,.. 1 i. f.,.,.r,..,-r"r r1"'.'i--r-1 i-r-.-:'" , )-...--,-1-,,,--,...,"".'i r"...,...., r,.. '1'.. -.,...,.. 1 '> "I'...,.,., f) ; 1 f t 1,,,f, J,', 1 tij,, 1, 1) 1!i{ 1;, t 4 j;,! 1 1 ; 1 1,; 11;; ;1 ;(; i 1 1,.,, <:11 ), 'c(, ;) 1(1t 1»(c cc,),1 c< 11 ;',,;) 1, < 1 ",), t \ t 1 1), ;),,,:1 ', ),f', }, '. 1!, 1,i,1;i1, t{t,>,:; 1..!.-4t -- J ' t 1..:..,J..!J..!J: 1 1 J! I.>.'...t!J:.(,!J:!J'J.f..L;JJ:.'J_'.{t!!J'.-!-!.C..:.!)'.(:.,,!J_.:.,..C.:JJ. 1,.t:,:!.), (.:;}:.i...:i.J!.),.:S,!i!J!;.,.'..!J.!;!CJ.!,.(.A.!;.!..t.."!.J,J: --."'. - t. J, /. I,, ,,_.._...-. w '... \ ',,.. 14a I I I.,,... _y , -"""", -_ ! \ \,_ '(' L "'-- : 134 FIG. 3 "' f a

9 U.S. Patent Jun.26,212 Sheet 6of14 US 8,28,8 B2 I \ \\ \ \ \ \ \ / ( I,.. i C::>! LO-'\ \ 1! i i! \ (" c ro I I u.\ 1 i.!.f,...,, f,.... "tj"<' "". <I"'"",,..,... I \... ;_,--j o : it, _!.,,.., /I I I t. : f If\., I \!! f

10 = 2' := 1J1 ('D = ('D. :i..i;... d r.r;_ ' = JHJ (!) t:: 15a & 15b, == , T _,,,..,,_,_.,,,.,..,, 4/ '----,,,,,.,.,.,,_r-----,,,, ' 1 6 <J ' \f /_, t.j f,.).25- ro :=: *"'.2.. E t.i) c e v--v ' , r- "T"'" , Transverse position within one pixe (rnicrometer).:'j("' AB r_.j LJ:)

11 U.S. Patent Jun.26,212 Sheet 8of14 US 8,28,8 B2 ' i f! I! " I i! : i ; ' I I I i 1 J i I :

12 = 2' := 1J1 ('D = ('D. "..i;... d rj. ' = 18 1 ''C'j,. )Lt) "!"2. ) ;a r-..a --y-.a....,,4 "T"" '..wm..wt.. '" ' ----m r- M.-.,.,,),,.,,.,,,,,,'f""_'_,,,,..,;.,.....,,""... (L35-182,,., 3- (1) c u.25.. E.2 t,fj c I- "15..i.1.5..:J,- ' I!;..,_, I Transverse position within one pixe (micrometer) FIG 5B

13 U.S. Patent Jun.26,212 Sheet 1 of 14 US 8,28,8 B2 < \ \ '\.. ':-1 t -A 1 1 i '!, / } } " i i i!.f _J j f f ' - - \ 9 ;; \ 1 t i ' ' t! J J ' ' J i t/......, ' J J.. " * - t 1 f! ' J i J.;,.;, t ;. 1 i \',,-'-- ' t <I'..,, i j ; i J J i >I' ff" ' r., ' ' "\., ' 1 t \ t, ' ' \...,.,.,. - _..,. i J J i J! J J I.,,-"" -t.:! J,.,,, :'. i \ i 1 \ \!, ' ::,., ' '\,.. ' ' J i - i i J j.,... Ii..... ' " t! t t,., '11t1\'.,, \ '' \' ;:4,.,,.ck..,J,ii,,"tJ.. J--,-:-.,.

14 U.S. Patent Jun.26,212 Sheet 11of14 US 8,28,8 B2 51 r-r -&;.. (j ro -! s... u { \ ri f -! -E 'O rw -4> x i - j }.. \i <1> r c: i 1 io e :- :: J::. I } 1 1 ' r n': r -.. c..o -?: , c: i r U) r Q. r (1) w \.. s» ' > fh! '! i:; i.n t() U) m ' M (>") C\I r- ci d. ci """" d ci au::>e:;!wsu\:u

15 ... _. 11 Ga = 2' := 1J1 ('D = ('D...i;... d r.r;_ ' = 21 1./ ::====:::== ,,.-. '"',, >J.> --- ) ,,,- 1 J 6 "J D Jtr' // , r b J_/ / Q9-) t.1l mmmmmmmgmemm o 4 b 22: '! b u (\ u \j u u u -} 2 11a " --*' "' ',.,/ J C)C), ,!f!;!;:; ;:; ::f!: ; : fi::;: ;;i'i!!; :: :!;:: :::!::;:::!;;!;!i '.; I 17.._ --,-... ;,,.i..; \: '"" m _ - - \ ',\\, ,,,,.,....,.,..,...,....,, : ' () 212 1t.,a 4) 1..4a FIG 7

16 ' = 2' := 1J1 ('D = ('D. (.H..i;... d rj. ' = 21, v/,,--..,p _._,,...,..--.,..,.,,.,..,,, b /;.. 114b --- : : : ;:: ;J.. -J 2 t,,,,,,,..,,,,,,,,,,,,,,, " - - j' ' ) ' " ' : - -, ' J(1.. t.) ' J JOb 12 - J ( T " "f? ] 2 't'"'f""(' 'T"("J"')"'"C ;> ry.-c-" "Y'"! "T"T'.'-YT'"...,..'"'\"'?",.,..1"T ',, 1 ',' '''f' J 1 c'1 1 '/i)1 1 c '1t 1 1'1.',1,.'. 1 f 1 1' "'t1 ),t,... f;:.. 4'. ' ' ' I I ' I I I ' -"'--- \... f,,,,j.}.,,-!,!u1 -r-- J '"'. 12,,. -,,/ Oa !. - :.. _L ""- -- ' s - ---=-214 :::: ti. t ---t.,.'\ \ -==-=t; ::== =-==--=--=-== = ==\;; \ 13 4 ' ,, ,,_,,., 12a 14a 116a FIG. 8

17 / 12 / = = := 1J1 ('D =- ('D..i;.....i;... d r.r;_ ' = r - n.. ; / 1..I -; 1--; Pi xe i data v,, :oiierf r ;:is -- - r- :s- ---! /rs I J!t[" 1-/1 r 15fiifi./1 1-D;;{c;i.1! 1 : ut L2Tii! '- - r I L-1 Driver I Driver i 1 Driver I I Driver I J Jr """ "'< n-i "-L ;;,., ,. Gate! -BO /// 32 r-- -:/ Dr1' Vf rf-----1i I' /(':::. :::.:-:;:.-;.,. 4 ::: : GI=!..:::: ,\ 1, ; CLc C:, 1 :..-16 c)..! ) \_, 92 -->!. - ',( _, {I J ' I I () I --- t... I f ("' _._ L j\ 1 D: =r r-=; I L- 16 I, - 1 I C1ate HI [ -,. -! '- " I I ' ' \ 94 / ' L / !.. Dr i Vf'r ----, I 1 I L_ Array of Pixe Circuits FIG. 9 I --.., j

18 1 LIQUID CRYSTAL DISPLAY PARTIES TO A JOIT RESEARCH AGREEMET The subject matter discosed in this patent appication was deveoped under a joint research agreement between Chi Mei Optoeectronics and the University of Centra Forida. BACKGROUD OF THE IVETIO This description reates to iquid crysta dispays. Liquid crysta dispays (LCDs) can be used in many eectronic devices, such as ce phones, persona digita assistants, aptop computers, desktop monitors, and fat pane teevisions. For exampe, a iquid crysta dispay has a iquid crysta ayer positioned between two crossed inear poarizers for moduating ight using an eectro-optic effect. A votage appied to the iquid crysta ayer changes the orientations of the iquid crysta moecues and the optica phase retardation of the iquid crysta ayer, thereby changing the amount of ight that passes the crossed inear poarizers. The iquid crysta dispay has an array of pixe circuits that can be individuay addressed. The pixe circuits moduate ight according to pixe data (pixe votages), thereby generating images. Each pixe of the dispay can show a range of gray scae eves depending on the votage appied to the iquid crysta ayer. Use of coor fiters aows the dispay to show coor images. SUMMARY In one aspect, in genera, a dispay incudes pixe circuits, each pixe circuit incuding a first eectrode to be eectricay couped to a first reference votage, a second eectrode to receive a pixe votage corresponding to a gray scae eve, the second eectrode incudes a conducting ayer having openings, a third eectrode to be eectricay couped to a second reference votage, the second eectrode being between the first and third eectrodes, and a iquid crysta ayer between the first and second eectrodes, the iquid crysta ayer being doped with a chira materia. Impementations of the dispay may incude one or more of the foowing features. The first reference votage is equa to the second reference votage. The first and second reference votages are equa to a ground votage of the pixes. The chira materia is seected to cause the iquid crysta ayer to form twisted structures each having a free pitch of at east ten times a thickness of the iquid crysta ayer. The first, second, and third eectrodes and the chira dopant are configured such that when the pixe votage is appied to the second eectrode, an eectric fied generated by the first, second, and third eectrodes cause iquid crysta moecues above the openings to US 8,28,8 B2 tit by amounts that are more than haf of those of the iquid crysta moecues above the conducting ayer away from the openings, the amount of tit being measured from initia positions of the moecues when the pixe votage is beow a 55 threshod. In some exampes, when the pixe circuit is in a bright state, the transmissivity of portions of the pixe corresponding to the openings is at east haf the transmissivity of portions of the pixe corresponding to the conducting ayer away from the openings. In some exampes, when the pixe circuit is in a bright state, the transmissivity of portions of the pixe corresponding to the openings is at east 9% the transmissivity of portions of the pixe corresponding to the conducting ayer away from the openings. The first, second, and third eectrodes and the chira dopant are configured such that azimuth anges ofiquid crysta directors vary continuousy across the 2 pixe when the pixe votage is appied to the second eectrode. The iquid crysta ayer incudes iquid crysta moecues that are aigned aong a direction substantiay norma to the surfaces of the first and second eectrodes when the pixe votage is beow a threshod. In some exampes, the openings incude circes having diameters in a range between.1 µm to 8 µm. In some exampes, the openings incude eongated sits each having a width in a range between.1 µm to 8 µm. The eongated sits 1 have at east one of straight, curved, and piecewise inear shapes. In some exampes, the third eectrode incudes a continuous conducting ayer without openings. In some exampes, the third eectrode incudes a conducting ayer having openings. The conducting ayer incudes portions hav- 15 ing shapes that correspond to the shapes of the openings of the second eectrode. The second and third eectrodes are configured such that iquid crysta moecues adjacent to the openings are subject to eectric fieds having directions from the iquid crysta ayer to the third eectrode. The first, second, 2 and third eectrodes are configured such that iquid crysta moecues farther away from the openings are subject to eectric fieds having directions from the second eectrode to the first eectrode. The dispay incudes an aignment fim between the iquid 25 crysta ayer and the second eectrode. The dispay incudes an aignment fim between the iquid crysta ayer and the first eectrode. Each pixe incudes a storage capacitor having terminas that incude portions of the second eectrode and the third eectrode. The first eectrodes of different pixes are 3 eectricay connected. The third eectrodes of different pixes are eectricay connected. The dispay incudes a first circuar poarizer and a second circuar poarizer, the iquid crysta ayer being between the first and second circuar poarizers. The dispay incudes a first inear poarizer and a second 35 inear poarizer, the iquid crysta ayer being between the first and second inear poarizers. In another aspect, in genera, a dispay incudes a first substrate, a second substrate, and pixe circuits between the first and second substrates. Each pixe circuit incudes a first 4 eectrode to be eectricay couped to a ground reference votage, a second eectrode to receive a pixe votage corresponding to a gray scae eve, the second eectrode incudes a conducting ayer having openings, a third eectrode to be eectricay couped to the ground reference votage, the sec- 45 ond eectrode being between the first and third eectrodes, and a iquid crysta ayer between the first and second eectrodes. The dispay incudes a first aigrnnent ayer between the iquid crysta ayer and the first eectrode of each pixe circuit, and a second aignment ayer between the iquid crysta ayer 5 and the second eectrode of each pixe circuit. Impementations of the dispay may incude one or more of the foowing features. The iquid crysta ayer incudes a chira materia. In another aspect, in genera, a method incudes generating an eectric fied in a iquid crysta ayer of a pixe circuit of a dispay, the eectric fied causing iquid crysta moecues in the iquid crysta ayer to tit from initia positions, the eectric fied having a distribution such that the iquid crysta ayer forms a continuous domain in which the iquid crysta mo- 6 ecues at different ocations tit in different directions, and the tit directions of the iquid crysta moecues vary continuousy across the pixe circuit. The method incudes providing a twisting force to the iquid crysta moecues to cause the iquid crysta moecues to tit at aong different azimuth 65 anges across the pixe. Impementations of the method may incude one or more of the foowing features. Providing a twisting force incudes

19 US 8,28,8 B2 3 using chira dopants in the iquid crysta ayer to provide the twisting force. Generating the eectric fied incudes providing a first reference votage to a first eectrode, providing a pixe votage to a second eectrode, and providing a second reference votage to a third eectrode, the iquid crysta ayer 5 being between the first and second eectrodes, the second eectrode being between the first and third eectrodes, the second eectrode incudes a conducting ayer having openings. The method incudes titing the iquid crysta moecues above the openings by amounts that are more than haf of 1 those of the iquid crysta moecues above the conducting ayer away from the openings. The method incudes providing a substantiay uniform transmittance across the pixe upon appication of the pixe votage, the transmittance of portions of the pixe corresponding to the openings being more than haf of the transmittance of portions of the pixe 15 corresponding to the conducting ayer away from the openings. The method incudes aigning iquid crysta moecues of the iquid crysta ayer aong directions substantiay norma to substrates at two sides of the iquid crysta ayer prior to generating the eectric fied. In another aspect, in genera, a method incudes forming a first eectrode on a first substrate, forming a third eectrode on a second substrate, forming an insuation ayer on the third eectrode, forming a second eectrode on the insuation ayer, the second eectrode incudes a conducting ayer having 25 openings, positioning the first substrate parae to and at a distance to the second substrate, and providing a iquid crysta ayer between the first and second eectrodes. Impementations of the method may incude one or more of the foowing features. The method incudes adding a chira 3 materia to the iquid crysta materia of the iquid crysta ayer. Adding the chira materia incudes adding a chira materia having a concentration seected to cause the iquid crysta ayer to form a twisted structure having a free pitch of at east ten times a thickness of the iquid crysta ayer. Advantages of the iquid crysta dispays can incude one or 35 more of the foowing. The dispay can have a high ight efficiency. The dispay can have wide viewing ange in which there is ow coor shift when viewing from obique viewing directions. DESCRIPTIO OF DRAWIGS FIG. 1 is a cross-sectiona diagram of a pixe. FIGS. 2A-2C are diagrams of patterned ITO ayers. FIG. 3 is a cross-sectiona diagram of a pixe, showing an eectric fied distribution at the pixe. FIG. 4A is a diagram showing simuated orientations of iquid crysta moecues. FIG. 4B is a graph showing the transmittance profie of a pixe. FIG. SA is a diagram showing simuated orientations of iquid crysta moecues. FIG. SB is a graph showing the transmittance profie of a pixe. FIG. 6A is a diagram that shows simuated orientations of iquid crysta moecues. FIG. 6B is a graph showing the transmittance profie of a pixe. FIG. 7 is a cross-sectiona diagram of a pixe. FIG. 8 is a cross-sectiona diagram of a pixe, showing an eectric fied distribution at the pixe. FIG. 9 is a schematic diagram of a iquid crysta dispay, showing driving circuits of the dispay. DETAILED DESCRIPTIO FIG. 1 is a cross-sectiona diagram of an exampe of a pixe 9 of a vertica aignment mode iquid crysta dispay 1 that 4 incudes a first transparent substrate 12a coated with an indium tin oxide (ITO) ayer 14a, a non-conductive panar ayer 16, a patterned ITO ayer 18, and a first vertica aignment fim 11 Oa. The patterned ITO ayer 18 has a shape that extends over ony a portion of the pixe 9. The dispay 1 incudes a second transparent substrate 12b coated with an ITO ayer 14b and a second vertica aignment fim Ob. A negative dieectric anisotropic nematic iquid crysta ayer 112, doped with a chira materia, is positioned between the first vertica aignment fim Oa and the second vertica aignment fim Ob. When no votage is appied across the iquid crysta ayer 112, iquid crysta moecues 113 in the ayer 112 are aigned substantiay norma to the surfaces of the substrates 12a and 12b. A first phase retardation fim 114a and a first inear poarizer 6a are aminated on an outer surface of the first substrate 12a. The phase retardation fim 114a can be, e.g., a chromatic quarter-wave fim or a broadband quarter-wave fim, so that the combination of the phase retardation fim 2 4a and the inear poarizer 6a forms a circuar poarizer. A second phase retardation fim 114b and a second inear poarizer 116b are aminated on an outer surface of the second substrate 12b. Simiary, the phase retardation fim 114b can be, e.g., a chromatic quarter-wave fim or a broadband quarter-wave fim so that the combination of the phase retardation fim 114b and the inear poarizer 6b forms a circuar poarizer. The dispay 1 can incude a coor fiter ayer (not shown) that is paced between the second substrate 12b and the second aignment fim Ob, aowing the dispay 1 to show coor images. The coor fiter can aso be paced between the first substrate 12a and the first aignment fim Oa. The patterned ITO ayer 18 functions as a pixe eectrode and is connected to a thin-fim-transistor (TFT) switch 2 and a storage capacitorcsr22 (FIG. 9). The ITO ayer 14a on the first substrate 12a functions as a first common eectrode. The ITO ayer 14a of different pixes can be eectricay connected. For exampe, the ITO ayer 14a can be a continuous ayer on the first substrate 12a that extends across a of the 4 pixes. The ITO ayer 14b on the second substrate 12b functions as a second common eectrode. For exampe, the ITO ayer 14b can be a continuous ayer on the second substrate 12b that extends across a of the pixes. The first common eectrode (ITO ayer 14a) and the second common 45 eectrode (ITO ayer 14b) can both be connected to a ground votage. The ITO ayer 18, ITO ayer 14a, and ITO ayer 14b wi aso be referred to as the pixe eectrode 18, the first common eectrode 14a, and the second common eectrode 5 14b, respectivey. The pixe eectrode 18, the common eectrodes 14a, 14b, the iquid crysta ayer 112, the thin fim transistor 2, and the storage capacitor Csr 22 of a pixe are coectivey referred to as a pixe circuit. As described beow, the pixe eectrode 18, the first com- 55 mon eectrode 14a, and the second common eectrode 14b are configured to generated eectric fieds having a distribution that, in combination with a twisting effect caused by the chira dopants, faciitates the formation of a continuous domain in the iquid crysta ayer 112 of the pixe 9. The 6 iquid crysta moecues 113 at different ocations in the iquid crysta ayer 112 tit in different directions that vary continuousy across the pixe 9. This increases the viewing ange of the dispay 1 because ight traveing at different anges through the iquid crysta ayer 112 wi experience simiar 65 phase retardation. The substrates 12a and 12b can be made of, e.g., gass. The non-conductive panar ayer 16 can be made of, e.g.,

20 US 8,28,8 B2 5 siicon dioxide (Si 2 ) or siicon nitride (Six). The first and second aignment fims Oa and Ob can be made of, e.g., poyimide materias. The first and second phase retardation fims 114a and 114b can be made of, e.g., poycarbonate or poyviny acoho (PVA). The first and second inear poariz- 5 ers 116a and 116b can be, e.g., ineary oriented poyviny acoho (PVA) fim with iodine soution imbibitions. FIG. 2A is a diagram of a first exampe of the patterned ITO ayer 18. The patterned ITO ayer 18 has a conductive portion 12 made ofindium-tin-oxide, and openings 122. The 1 openings 122 can be formed by etching away a portion of the IDIUM TI OXIDE in the ayer 18. In this exampe, the openings 122 have circuar shapes each having a diameter W in a range between.1 µm to 8 µm. FIG. 2B is a diagram of a second exampe of the patterned 15 ITO ayer 18, which incudes a conductive portion 12 made of indium tin oxide, and openings 122. In this exampe, the openings 122 have piecewise inear, chevron-ike shapes. The gap width W of each opening 122 can be in a range between.1 µm to 8 µm. FIG. 2C is a diagram of a third exampe of the patterned ITO ayer 18, which incudes a conductive portion 12 made of indium tin oxide, and openings 122. In this exampe, the openings 122 have ong rectanguar shapes. The gap width W of the opening 122 can be in a range between.1 µm to 8 µm. 25 FIG. 3 is a cross-sectiona diagram of the pixe 9, showing eectric fied ines at a votage-on state. The votage-on state refers to a condition in which a pixe votage is appied to the pixe eectrode 18, such that eectric fieds are generated in the regions between the pixe eectrode 18 and the first 3 common eectrode 14a, and in the regions between the pixe eectrode 18 and the second common eectrode 14b. As described beow, the pixe eectrode 18, the first common eectrode 14a, and the second common eectrode 14b are configured to generated eectric fieds having a distribu- 35 ti on that faciitates rotation ofiquid crysta moecues 113 so that that the amount of tit of the iquid crysta moecues 113 above the openings 122 are comparabe to the amount of tit of the iquid crysta moecues 113 above the conductive portion 12. The transmissivities of the portion of the iquid 4 crysta ayer 112 above the openings 122 are comparabe to those above the conductive portion 12. This increases the overa ight efficiency of the pixe 9, resuting in a brighter pixe for a given amount ofbackight. The eectric fied in the iquid crysta ayer is a function of 45 position within the iquid crysta ayer 112. A Cartesian coordinate system having x, y, and z axes is used as a reference for describing the orientations of the components of the dispay 1. In this exampe, the z-axis is seected to be perpendicuar to the surfaces of the substrates 12a and 12b. The x-axis 5 and the y-axis are parae to the surfaces of the substrates 12a and 12b. The eectric fied in the iquid crysta ayer 112 incudes a "ongitudina eectric fied" 13 at a region 136 above the conductive portion 12 of the pixe eectrode 18, and "fringe eectric fieds" 132and134 at a region 138 above the opening 122 of the pixe eectrode 18. In the ongitudina eectric fied 13, the eectric fied ines are substantiay parae to the z-axis. In the fringe eectric fied 132, the eectric fied ines generay extend from the pixe eectrode 18 toward the second common eectrode 14b aong directions that are not parae to the z-axis (except near the eectrodes 18 and 14b ). In the fringe eectric fied 134, the eectric fied ines generay extend from the pixe eectrode 18 partiay into the iquid crysta ayer 112, then turn toward the opening 122, pass the opening 122, and end at the first common eectrode 14a. 6 FIG. 4A is a diagram 146 showing an exampe of simuated orientations of iquid crysta moecues 113 in the iquid crysta ayer 112 of a portion of the pixe 9 when the pixe 9 is operating in a bright state. The average orientations of iquid crysta moecues 113 in sma ocaized regions are represented by unit vectors caed iquid crysta directors 14. In FIG. 4A, each iquid crysta director 14 is represented by a head 142 and a tai 144. In this exampe, a negative dieectric anisotropy iquid crysta materia (MLC-6882 with ne =1.582 and n =1.484, avaiabe from Merck, Germany) doped with a chira materia (CB15, avaiabe from Merck, Germany) is used in the iquid crysta ayer 112. The first common eectrode 14a and the second common eectrode 14b are connected to ground votage ( V), and the patterned pixe eectrode 18 is connected to a pixe votage V DArA=6V. The thickness of the iquid crysta ayer 112 is 3.4 µm. FIG. 4A shows a cross section of the pixe 9 aong the Y-Z 2 pane, with the positive x direction extending outwards out of the paper of FIG. 4A. The substrates 12a and 12b are parae to the X-Y pane. The pixe eectrode 18 has openings 122 each having a ong rectanguar shape, simiar to those shown in FIG. 2C. The ong sides of the rectanguar openings 122 are parae to the x-axis. The gap width W of the openings 122 is 2 µm. The eectric fied causes the iquid crysta moecues 113 to form a continuous domain that has mutipe regions, e.g., SOa and SOb, within the pixe 9. The iquid crysta directors 14 tit in different directions in which the tit ange (e.g., 81or82) vary continuousy from one ocation to another. For exampe, the iquid crysta directors 14 coser to the top and bottom boundaries S and 1S3 of the iquid crysta ayer 112 are tited down ess (e.g., ange 81or82 is smaer) reative to initia vertica aignment positions (parae to the z-axis ). The iquid crysta directors 14 coser to the midde portion SS of the iquid crysta ayer 112 are tited down more (e.g., ange 81 or 82 is arger) reative to the initia vertica aignment positions. The azimutha anges of the iquid crysta directors 14 aso vary continuousy aong a direction parae to the X-Y pane, graduay rotating either cockwise or counter cockwise. Here, a director 14 having a head 142 that is darker than a tai 144 indicates that the head 142 is coser to the -x direction, and vice versa. To iustrate the rotation of the iquid crysta moecues 113 within each pixe 9, a director (e.g., 148a) more parae to the Y-Z pane is shown to be onger than a director (e.g., 148b) that is more perpendicuar to the Y-Zpane. For exampe, moving from a ocation P to ocations P2, P3, P4, and PS (which are a ocated on the same X-Y pane) in sequence, the iquid crysta directors 14 rotate continuousy from pointing approximatey in the -x direction to the -y, +x, +y, and +x directions, respectivey. The azimuth 55 anges of the iquid crysta moecues vary continuousy from one ocation to another within the pixe 9. The transition from one region (e.g., SOa) to another region (e.g., SOb) in the iquid crysta ayer 112 is continuous. The twist forces imparted by the chira dopant assist in 6 titing down the iquid crysta moecues 113 from their initia vertica aignment positions (parae to the z-axis) when a pixe votage is appied to the pixe eectrode 18. The iquid crysta moecues 113 at ocations (e.g., P and PS) directy above the openings 122 are tited reative to initia positions 65 by amounts comparabe to (or greater than haf of) those at ocations (e.g., P2, P3, and P4) above the conducting portions 12.

21 US 8,28,8 B2 7 The type of materia and concentration of the chira dopant are seected such that the iquid crysta mixture (incuding the iquid crysta materia and the chira dopant) has a free pitch greater than 1 times the ce gap (thickness of the iquid crysta ayer 112). For exampe, ifthe ce gap is 4.5 µm, the 5 chira dopant is seected such that the iquid crysta mixture has a free pitch of more than 4.5 µmx1=45 µm. In the exampe of FIG. 4A, the ce gap is 3.4 µm and the free pitch of the iquid crysta mixture is 1 µm. The term "free pitch" refers to the pitch ength of the twisted structures in the iquid 1 crysta ayer doped with the chira materia when no externa force (or votage) is appied to the iquid crysta ayer, and ony one substrate surface is coated with a rubbed homogeneous aignment ayer whie the other substrate surface is coated with an unrubbed homogeneous aignment ayer. The 15 free pitch decreases as the concentration of the chira dopant mcreases. FIG. 4B is a graph 16 showing the transmittance profie 162 of the pixe 9 based on the iquid crysta director profie of FIG. 4A. The transmittance is between about 3% to 35% across the pixe 9. The transmittance above the conducting area 12 is about 35%, and the transmittance above the openings 122 is about 3%. The transmittance vaues shown in FIG. 4B take into account the reduction in ight caused by the phase retardation fims 114a, 4b and inear poarizers 6a, 25 6b. When the transmittance vaues shown in FIG. 4B are normaized to the transmittance of two parae inear poarizers, the overa ight efficiency of the pixe 9 is about 97.5% (assuming that the substrates 12a, 12b, eectrodes 14a, 14b, 18, aignment fims Oa, Ob, and the panar ayer 16 are competey transparent). The graph 16 shows that the transmittance drops sighty in the regions above the openings 122. This is because the iquid crysta moecues 113 in regions above the openings 122 have tit anges (the ange between the iquid crysta 35 director direction and the z-axis) sighty smaer than those in regions above the conducting portions 12. The overa accumuated phase retardation by the iquid crysta ayer 112 in the region above the opening 122 is sighty smaer than that in the region above the conducting portion 12. Thus, when 4 circuar poarizers are aminated on both sides of the dispay 1, the transmittances in the regions above the openings 122 are sighty ower than those in the regions above the conducting portion 12. For comparison, FIG. SA is a diagram 17 showing an 45 exampe of simuated orientations ofiquid crysta moecues in a iquid crysta ayer 22 of a portion of a pixe in which the iquid crysta ayer 22 does not incude chira dopants. The eectric fied causes mutipe domains (e.g., 1S2a and 1S2b) to be formed in the iquid crysta ayer 22. Because there is no 5 chira dopant, the iquid crysta moecues do not rotate significanty about the z-axis when moving from, e.g., ocation P to ocations P2, P3, P4, and PS. Some of the iquid crysta moecues at the domain boundaries (e.g., 1S4a, 1S4b, and 1S4c) are not tited and remain at their initia positions 55 (aigned parae to the z-axis). One possibe reason for the iquid crysta moecues not titing at the domain boundaries is that the eectric fied is symmetricay distributed at the domain boundaries, so the forces inducing the iquid crysta moecues to tit in one direction (e.g., cockwise) is as strong 6 as the forces inducing the moecues to tit in an opposite direction (e.g., counter cockwise). The different forces acting on the iquid crysta moecues cance each other, so the moecues do not tit and remain at their initia positions. FIG. SB is a graph 18 showing the transmittance profie of the pixe based on the iquid crysta director profie of FIG. SA (in which the iquid crysta ayer 22 does not 8 incude chira dopants). The graph 18 shows the transmittance profie of the entire pixe in which the pixe width is 8 µm. At the domain boundaries above the openings 122, the iquid crysta moecues are not tited, so the accumuated phase retardation is sma. Therefore, the transmittances at the domain boundaries (e.g., 1S4a, 1S4b, 1S4c) are ow, and the domain boundaries appear as dark ines. The transmittance profie 182 is obtained using circuar poarizers on both sides of the iquid crysta pane. The overa ight efficiency of the pixe in the exampe of FIG. SB is around 88.7% when normaized to the transmittance of two parae inear poarizers. This is ower than the ight efficiency (97.5%) of the pixe 9 the exampe of FIG. 4B in which the iquid crysta ayer 122 incudes chira dopants. FIG. 6A is a diagram 19 that shows an exampe of simuated orientations ofiquid crysta moecues 113 in the iquid crysta ayer 112 of a pixe 194 operating in a bright state. The pixe 194 used in the simuation of FIG. 6A is simiar to the pixe 9 used in the simuation of FIG. 4A, except that the 2 widths W of the openings 122 in the pixe 194 is smaer than the widths W of the openings 122 in the pixe 9. In the exampe of FIG. 6A, the width Wis.5 µm (as compared to W=2 µmin FIG. 4A), the ce gap is 3.4 µm, and the free pitch of the iquid crysta mixture is 1 µm. When the widths of the openings 122 is reduced, the fringe fieds (132 and 134 in FIG. 3) are stronger, causing the iquid crysta moecues 113 to tit more at regions above the openings 122, increasing overa ight efficiency of the pixe 194. In the diagram 19, in the buk region 192 of the iquid crysta 3 ayer 122, amost a ofiquid crysta moecues 113 are tited and aigned aong directions substantiay parae to the substrates 12a and 12b. FIG. 6B is a graph 2 showing the transmittance profie 22 of the pixe 194 based on the iquid crysta director profie of FIG. 6A. A substantiay fat transmittance profie is achieved across the whoe pixe 194. In this exampe, the ight efficiency of the pixe 194 is more than 99.2% when normaized to the transmittance of two parae inear poarizers. FIG. 7 is a cross-sectiona diagram of an exampe of a pixe 218 of a vertica aignment mode iquid crysta dispay 21 that incudes a pixe eectrode 18 having openings 122 and a iquid crysta ayer 112 doped with a chira materia. The dispay 21 is simiar to the dispay 1 offig.1, except that the dispay 21 incudes a patterned first common eectrode 212 that has conductive portions 214 and openings 216. The conductive portions 214 have shapes that correspond to the shapes of the openings 122 of the pixe eectrode 18. The widths of the conductive portions 214 are sighty arger than the widths of the openings 122. FIG. 8 is a cross-sectiona diagram of the pixe 218, showing eectric fied ines at a votage-on state. The eectric fied generated by the pixe eectrode 18, the first common eectrode 212, and the second common eectrode 14b in FIG. 8 is simiar to those shown in FIG. 3. This indicates that the openings 216 in the first common eectrode 212 do not affect the titing of the iquid crysta moecues 113 in the iquid crysta ayer 112. The optica performance of the dispay 21 in FIG. 8 is simiar to that of the dispay 1 in FIG. 1. FIG. 9 is a schematic diagram of an exampe of the iquid crysta dispay 1, which incudes an array 12 of pixes 9 that are controed by one or more gate drivers 16 and one or more data drivers 18. Each pixe 9 incudes one or more thin fim transistors (TFT) 2, a storage capacitor Csr 22, and a iquid crysta ce 112 that has an effective capacitance represented by a capacitor CLc 24. The storage capacitor Csr22 can be formed by the pixe eectrode 18 and the first common eectrode 4a. The capacitors Csr22 andclc24 can be, e.g.,

22 US 8,28,8 B2 9 connected in parae to a first node 26 and a second node 28. The TFT 2 incudes a gate 3 that is connected to a gate ine 32, which is connected to the gate driver 16. When the gate driver 16 drives the gate ine 32 to turn on the TFT 2, the data driver 18 drives a data ine 34 with a votage signa (e.g., V DATA) that is passed to the capacitors CsT 22 and CLc 24. In some exampes, the first node 26 is connected to the pixe eectrode 18 (FIG. 1), and the second node 28 is connected to the first and second common eectrodes 14a, 14b. The votage (e.g., V DATA) across the capacitor CsT 22 deter- 1 mines the votage appied to the iquid crysta ce 112. The votage on the data ine 34 is sometimes referred to as a "pixe votage" or "gray scae votage" because it determines the gray scae eve shown by the pixe 9. A number of embodiments of the invention have been 15 described. Other impementations are aso within the scope of the foowing caims. For exampe, the first common eectrode 14a can be connected to a first reference votage, and the second common eectrode 14b can be connected to a second reference votage. The first and second reference vot- 2 ages do not necessariy have to be equa to the ground votage. The first and second reference votages can be the same or different. Additiona passivation ayers, aignnient ayers, and compensation fims can be used in the dispays described above. The components of the dispays, such as the iquid crysta ayer and the poarization fims can use materias and have parameters different from those described above. The retardation vaues of the fims can be different from those described above. The orientations of the iquid crysta moecues described above refer to the directions of directors of the iquid crysta moecues. The moecues may tend to point more in one direction (represented by the director) over time than other directions. For exampe, the phrase "the iquid crysta moecues are substantiay aigned aong a direction norma to 35 the substrates" means that the average direction of the directors of the iquid crysta moecues are generay aigned aong the norma direction, but the individua moecues may point to different directions. What is caimed is: 1. A dispay comprising: pixe circuits each comprising: a first eectrode to be eectricay couped to a reference votage; a second eectrode to receive a pixe votage corresponding to a gray scae eve, the second eectrode comprising a conducting ayer having openings; a third eectrode to be eectricay couped to the reference votage, the second eectrode being between the first and third eectrodes, wherein the votage eve of 5 the first eectrode and the votage eve of the third eectrode are the same; and a iquid crysta ayer between the first and second eectrodes, the iquid crysta ayer comprising a negative dieectric type vertica aignment iquid crysta doped 55 with a chira materia, wherein the chira materia is seected to cause the iquid crysta ayer to form twisted structures each having a free pitch of at east ten times a thickness of the iquid crysta ayer. 2. The dispay of caim 1 wherein the first and second 6 reference votages are equa to a ground votage of the pixes. 3. The dispay of caim 1 wherein the first, second, and third eectrodes and the chira dopant are configured such that when the pixe votage is appied to the second eectrode, an eectric fied generated by the first, second, and third eec- 65 trodes cause iquid crysta moecues above the openings to tit by amounts that are more than haf of those of the iquid 1 crysta moecues above the conducting ayer away from the openings, the amount of tit being measured from initia positions of the moecues when the pixe votage is beow a threshod. 4. The dispay of caim 1 wherein when the pixe circuit is in a bright state, the transmissivity of portions of the pixe corresponding to the openings is at east haf the transmissivity of portions of the pixe corresponding to the conducting ayer away from the openings. 5. The dispay of caim 1 wherein when the pixe circuit is in a bright state, the transmissivity of portions of the pixe corresponding to the openings is at east 9% the transmissivity of portions of the pixe corresponding to the conducting ayer away from the openings. 6. The dispay of caim 1 wherein the first, second, and third eectrodes and the chira dopant are configured such that azimuth anges of iquid crysta directors vary continuousy across the pixe when the pixe votage is appied to the second eectrode. 7. The dispay of caim 1 wherein the iquid crysta ayer comprises iquid crysta moecues that are aigned aong a direction substantiay norma to the surfaces of the first and second eectrodes when the pixe votage is beow a threshod. 8. The dispay of caim 1 wherein the openings comprise 25 circes having diameters in a range between.1 m to 8 m. 9. The dispay of caim 1 wherein the openings comprise eongated sits each having a width in arange between.1 µm to 8 µm. 1. The dispay of caim 9 wherein the eongated sits have 3 at east one of straight, curved, and piecewise inear shapes. 11. The dispay of caim 1 wherein the third eectrode comprises a continuous conducting ayer without openings. 12. The dispay of caim 1 wherein the third eectrode comprises a conducting ayer having openings. 13. The dispay of caim 1 wherein the second and third eectrodes are configured such that iquid crysta moecues adjacent to the openings are subject to eectric fieds having directions from the iquid crysta ayer to the third eectrode. 14. The dispay of caim 13 wherein the first, second, and 4 third eectrodes are configured such that iquid crysta moecues farther away from the openings are subject to eectric fieds having directions from the second eectrode to the first eectrode. 15. The dispay of caim 1 wherein each pixe comprises a 45 storage capacitor having terminas comprising the second eectrode and the third eectrode. 16. The dispay of caim 1 wherein the first eectrodes of different pixes are eectricay connected. 17. The dispay of caim 1 wherein the third eectrodes of different pixes are eectricay connected. 18. The dispay of caim 1, further comprising a first circuar poarizer and a second circuar poarizer, the iquid crysta ayer being between the first and second circuar poarizers. 19. The dispay of caim 1, further comprising a first inear poarizer and a second inear poarizer, the iquid crysta ayer being between the first and second inear poarizers. 2. A dispay comprising: a first substrate; a second substrate; pixe circuits between the first and second substrates, each pixe circuit comprising: a first eectrode to be eectricay couped to a ground reference votage; a second eectrode to receive a pixe votage corresponding to a gray scae eve, the second eectrode comprising a conducting ayer having openings;

23 US 8,28,8 B2 11 a third eectrode to be eectricay couped to the ground reference votage, the second eectrode being between the first and third eectrodes, wherein the votage eve of the first eectrode and the votage eve of the third eectrode are the same; and a iquid crysta ayer between the first and second eectrodes, the iquid crysta ayer comprising a negative dieectric type vertica aignment iquid crysta doped with a chira materia, wherein the chira materia is seected to cause the iquid crysta ayer to form 1 twisted structures each having a free pitch of at east ten times a thickness of the iquid crysta ayer; a first aignment ayer between the iquid crysta ayer and the first eectrode of each pixe circuit; and 15 a second aignment ayer between the iquid crysta ayer and the second eectrode of each pixe circuit. 21. A dispay comprising: pixe circuits each comprising: a first eectrode to be eectricay couped to a first ref- 2 erence votage; a second eectrode to receive a pixe votage corresponding to a gray scae eve, the second eectrode comprising a conducting ayer having openings; a third eectrode to be eectricay couped to a second 25 reference votage, the second eectrode being between the first and third eectrodes; and a iquid crysta ayer between the first and second eectrodes, the iquid crysta ayer comprising a chira materia; 12 wherein the first, second, and third eectrodes and the chira dopant are configured such that when the pixe votage is appied to the second eectrode, an eectric fied generated by the first, second, and third eectrodes cause iquid crysta moecues above the openings to tit by amounts that are more than haf of those of the iquid crysta moecues above the conducting ayer away from the openings, the amount of tit being measured from initia positions of the moecues when the pixe votage is beow a threshod. 22. A dispay comprising: pixe circuits each comprising: a first eectrode to be eectricay couped to a first reference votage; a second eectrode to receive a pixe votage corresponding to a gray scae eve, the second eectrode comprising a conducting ayer having openings; a third eectrode to be eectricay couped to a second reference votage, the second eectrode being between the first and third eectrodes; and a iquid crysta ayer between the first and second eectrodes, the iquid crysta ayer comprising a chira materia; wherein when the pixe circuit is in a bright state, the transmissivity of portions of the pixe corresponding to the openings is at east 9% the transmissivity of portions of the pixe corresponding to the conducting ayer away from the openings. * * * * *