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`citnal of the
`SOCIETY FOR
`INFORMATION
`DISPLAY
`
`SEK_
`
`
`
`Combined Special Issues on
`Selected Papers from the 9th International
`Display Workshops (IDW ’02)
`and
`Selected Papers from the 22ndInternational
`Display Research Conference (EuroDisplay ’02)
`
`,
`
`
`
`»
`
`Previously published as
`"?roceedings of the Society for Information Display
`L
`
`
`
`SOCIETY FOR INFORMATION DISPLAY
`
`SAMSUNG, EXH. 1021, P. 2
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`SAMSUNG, EXH. 1021, P. 2
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`G « -
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`
`Journal of the SID
`The quarterly Journal of the SID publishes original work dealing with the
`theory and practice of information display. Coverage includes hard and soft
`copy; the underlying chemistry, physics, physiology, and psychology;
`measurement techniques; and all aspects of the interaction between
`equipment andi its users.
`The Society also publishes Symposium Digests, containing extended
`abstracts of papers presented al the annual International Symposia, and the
`monthly magazine Information Display. We cooperate in publishing the
`digests of technical papers presented at the annual International Display
`Research Conferences. Information about all of these publications and
`meetings is available from the Society's headquarters (see below) and on
`our web page (www.sid.org).
`Information on membership can be found with the Table of Contents.
`Detailed information for contributors is at the back of this issue. Full-length
`papers, brief communications, and letters are welcomed; they may be
`submitted to any of the Associate Editors orto the Editor.
`
`Vision Science/Human Factors
`Haruo Isono, Human Science Research Division, NHK Science and Technic,
`Japan
`Research Labs, 1-10-11, Kinuta, Setagaya-ku, Tokwer 157-4510,J
`+81-3-5404-2340,fax: +61-3-5404-2971, isono@strl.nhk.or.jp
`Alan R. Jacohsen, Boeing Commercial Airplane Group, P.O, Box 3707,
`MC 02-]H, Seattle, WA 98124-2207 USA
`425/294-0562, fax -0515, alan.r.jacobsen@boeing.com
`
`al
`
`Light-Emitting Displays (LEDs, OLEDs, ELDs, Phosphors, etc.)
`GhassanE. Jabbour, Optical Science Center, The Universily of Arizona,
`1630 E. University Blvcl., Tucson, AZ 85721 USA
`520/626-8324, fax 520/621 4442, gej@optics,Arizona.edu
`Webster C.
`I loward, Consultant, 4 Lee Lane, Lagrangeville, NY 12540-6332 USA
`845/223-7716, whoward494@aol.com
`Peter Seats, Display Technology Consultant, 300 Indian Springs Rd.,
`Williamsburg, VA 23185 USA
`757/220-3183, fax: -3263, peterseats@cox.net
`
`Published as Proceedings of the SID from 1963 through 1991 (Volumes 1-32)
`
`Editor
`Andras |. Lakatos
`4681 S. Golden Arrow Drive, Green Valley, AZ 85614-5474 USA
`520/625-1457, fax -9855, e-mail: editor@sid.org
`
`Associate Editors
`
`LCDs
`Allan R, Kmetz, 50 EdgewoodRoad, Chatham, NJ 07928-2002 USA
`akmetz@aya,yale.ecdu
`Shunsuke Kobayashi, Science University of Tokyo in Yamaguchi,
`1-1-1 Daigaku-dori, Onada, Yamaguchi, 757 Japan
`+81-836-88-4540, fax -3844; kobayasi@ed.yama,sut.ac.jp
`Ernst Lueder, University of Stultgart, Germany, ancl Clectro-Optical
`Consultancy, LLC, 9471 E. Yucca St., Scottsdale, AZ 85260 USA
`phone/fax 480/451-8074, e.lueder@att.net
`Matin Schadt, ROLIC, Ltd,, Gewerbestrasse 18,
`CH-4123 Allschwil, Switzerlancl
`+41-61-487-2222, fax -2288, Martin.Schadi@rolic.ch
`
`Plasma Displays
`Munisamy Anandan, Organic Lighting Technologies, LLC,
`13009 ThomeValley Dr., Del Valle, TX 78617-3489 USA
`phoneffax 512/247-6863, manandan@o-lite.com
`Heiju Uchiike, Saga University, Dept. of Electranics,
`1, Honjo-machi, Saga 840-8502 Japan;
`+61-952-28-8640,fax -8651, uchiike@cc.saga-u.ac.jp
`
`Display Manufacturing
`Jin Jang, Head, TFT-LCD National Lab, Kyung Hee University,
`Dongdaemoon-ku, Scoul, 130-701, Korea
`+82-2-961-0270,fax +82-2-968-6924,jjang@khu.ac.ki
`
`Display Systems and Driver Electronics
`Hideaki Kawakami, Hitachi, Ltd., 3300, Hayano, Mobara-shi,
`Chiba-ken, 297-8622 Japan
`+81-475-25-9074, fax: +81-475-24-2463,
`kawakami-hideaki@mobara.hitachi.co.jp
`
`Projection Displays
`Shinji Morozumi, Crystage, Inc., 1-19-4, Hipashi-Nakajima,
`Higashi-Yocdagawa-ku, Osaka, 533 0033 Japan
`+81-6-4809-41 25, fax: -4127, s.morozumi@crystage.com
`
`CRTs
`ManagingEditor
`A. A. Seyno Sluyterman, LG.Philips Displays, Bldg, RAF-1, P.Q, Box 807,
`Jay Morreale, Palisades Convention Management
`5600 AV, Eindhoven, The Netherlands
`411 Lafayette Street, 2ncl Floor, New York, NY 10003, USA
`+31-40-2782817, fax -2786185, seyno.sluyterman@lyphilips-cisplays.com
`212/460-8090 x212, fax -5460, jmorreale@pcm411.com
`
`
`The Society for Information Display
`
`Executive Officers
`»
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`Treasurer .
`wR. Seery
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`ALR. Kimetz
`President .........
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`San Di@go cecceccesesesessseceesscacvecsseepesseeeneerees T. Iki
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`Singaporc/Malaysia.
`. B.A. Ghani
`Canada voccccccccecccsscsccscssesseceenseeneere T. Schmidt
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`LOS AMBeleS oo.
`ssaeeteereeeetetseneseeneene P, Baron
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`Southwest
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`soon D, Hopper
`Dayton wvisserccsieees
`Mid-Atlantic... GS... A. Ghosh
`Taipei cece.
`HP, Shieh
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`SAMSUNG, EXH. 1021, P. 3
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`

`Journalof the Society for Information Display
`Published as Proceedings of the SID from 1963 through 1991 (Volumes 1-32)
`Table of Contents
`
`Volume 11. Number3
`
`2003
`
`429
`
`Announcement: W. E. Howard, S. Morozumi, and P. Seats Become Associate Editors
`
`SELECTED PAPERS FROM THE 9TH INTERNATIONAL DISPLAY WORKSHOPS
`
`431
`433
`
`Introduction
`Electro-optic properties of an intrinsic half-V-mode FLCD andits application to field-sequential
`full-color LCDs using a poly-Si matrix TFT array
`H. Furata et a/., Tokyo University of Science, Japan
`
`437—Electrically commanded surfaces: A new LCD concept
`L. Komitov, Chalmers University of Technology & Géteborg University, Sweden
`
`443
`
`449
`
`457.
`
`461
`
`467
`
`
`Domain walls in photoaligned double-domain twisted-nematic LCD
`D. K. G. de Boer et al., Philips Research Labs, The Netherlands
`
`F. A. Fernandéz et al., University College of London, U.K.
`
`
`Novelliquid-crystal materials for AMLCDs
`Cr, cove ne
`CPYRIGHT OF ES
`S. Kibe et al., Chisso Petrochemical Corp., Japan
`
`A broadbandcircularly polarized film
`L-S. Luh et al., Union Chemical Laboratories, Taiwan
`An Integrated poly-Si TFT current data driver with a data-line pre-charge function
`M. Shimoda et al., NEC Corp., Japan
`Tracking system ofthe Fast Intelligent Tracking (F!T) tube
`H. B. van den Brink and O. H. Willemsen, Philips Research Laboratories, The Netherlands
`
`473
`
`The oxide cathode revisited
`D. den Engelsen, LG.Philips Displays, The Netherlands
`481 Mechanical properties and fracture analysis of glass substrate for PDPs
`K. Maeda and Y. Nakao, Asahi Glass Co., Lid., Japan
`
`485
`
`493
`
`499
`
`New metacode coding conceptfor improving PDP gray-scale quality
`S. Weitbruch et al., Thomson Multimedia Research Laboratory, Germany
`Developmentof new high-luminance green EL devices based on Eu-doped calcium
`thioaluminate materials system
`A. M. Nakua et al, iFire Technology, Canada
`
`Properties and cathodoluminescence of Y,O0,S:Eu thin films
`M. M. Sychov, St. Petersburg State Institute of Technology, Russia
`bh»
`Y. Hatanaka, Aichi University, Japan
`Y. Nakanishi et al., Shizuoka University, Japan
`
`continued
`OO
`
`Membership in the Society for Information Display is open to
`qualified individuals active or interested in any area of information
`display technology or use. Membership includes subscriptions to the
`Journal of the SID, Information Display, and member's chapter
`publications and newsletters; members are admitted to Society functions
`at reduced rates. Individual membership costs $75/year. For further
`information, including reduced fees for student members and the
`benefits of Sustaining Membership, contact $ID Headquarters.
`Subscriptions for non-members are $100/year ($110/year outside
`North America). Single copies are $25; consult $ID Headquarters for
`availability of back issues. Copies of the Symposium Digests are
`available from SID Headquarters; price varies with the year.
`Subscriptions to Information Display are available gratis to qualified
`individuals; contact SID Headquartersfor information.
`Editorial content of Society publications is the responsibility of the
`
`individual authors; the Society does not endorse any opinions or
`products presented in its publications unless such endorsementis
`explicitly stated.
`Copyright © 2003 The Society for Information Display. Copying of
`material in this Journal for internal or personal use, beyond the fair-use
`provisions granted by US Copyright Law,is subject to the paymentof
`copying fees to the Copyright Clearance Center (CCC), 27 Congress St.,
`Salem, MA 01970. The fee and article code numberarelisted at the
`bottom ofthe first page of each paper. All other copying of any material
`in this Journal without the specific permission of the Society is prohibited.
`Journalof SID (ISSN 1071-0922) is published four times a year by the
`Society for Information Display. See above for subscription prices.
`POSTMASTER: Send address changesto Journalof the SID, 610 S. 2nd
`Street, San Jose, CA 95112.
`
`SAMSUNG, EXH. 1021, P. 4
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`Volume 11 Number 3
`Journalof the Society for Information Display
`Published as Proceedings of the SID trom 1963 through 1991 (Volumes 1-32)
`
`2003
`
`°
`
`Table of Contents (Continued)
`
`505
`
`511.
`
`Characteristics of aluminum oxinitride film grown by plasma-enhanced atomic layer deposition
`as the insulator of an electroluminescent device
`). W. Lim et al., ETRI, Korea
`
`A retinal scanning display with a wavefront curvature modulator
`M. Watanabeet al/., Brother Industries, Ltd., Japan
`
`SELECTED PAPERS FROM THE 22nd INTERNATIONAL DISPLAY RESEARCH CONFERENCE
`517—Introduction
`
`>
`
`a “
`
`a
`
`=
`
`519
`
`Novel photo-aligned LC-polymer compensation film for wide-view TN displays
`T. Bachels et al., ROLIC Research, Ltd., Switzerland
`G. Gomez and E. Criton, Thales Avionics LCD, France
`
`525 Multi-layered flat-surface micro-optical components directly molded on an LCD panel
`F, Yamada etal., Tokyo Research Laboratory, Japan
`
`533.
`
`539
`
`543
`
`551.
`
`559
`
`571
`
`579
`
`585
`
`BiNem® manufacturing process for mass production
`J. Angelé et al., Nemoptic, France
`J. W. Lin and J. Tung, Picvue Electronics, Taiwan
`
`Threshold-voltage drift of amorphous-silicon TFTs in integrated drivers for active-matrix LCDs
`H. Lebrun et al., Thales Avionics LCD, France
`
`Organic-polymer thin-film transistors for active-matrix flat-panel displays
`5. Martin et al., The University of Michigan, U.S.A.
`
`Improvement of PDP discharge efficiency based on macro-cell studies
`L. Tessier et af., Thomson Plasma, France
`]. Ouyang et al., Université P. Sabatier, France
`
`The FastIntelligent Tracking (F!T) tube: Electronic aspects of a CRT without a shadow mask
`P. J. Engelaar and P. J. G. Lieshout, Philips Research Laboratories, The Netherlands
`
`MISCELLANEOUS PAPERS
`
`Anew solution for splay-to-bend transition in OCB mode with a twisted area
`|. Inoue et al., Tohoku University, Japan
`Y. Yamada and Y.Ishii, Sharp Corp., Japan
`
`»
`
` Azo-dye aligning layers for liquid-crystal cells
`V. Chigrinov et al., The Hong Kong University of Science and Technology
`H. Akiyama et al., Dai Nippon Ink & Chemicals, Inc., Japan
`
`Novel screen technology for high-contrast front-projection display by controlling ambient-light reflection
`B. Katagiri et al., Tohoku University, Japan
`
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`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`Anintegrated poly-Si TFT current data driver with a data-line pre-charge function
`
`M. Shimoda
`K. Abe
`H. Haga
`H. Asada
`H. Hayama
`K. Iguchi
`D. Iga
`H. Imura
`S. Miyano
`
`Abstract — We have developed an integrated poly-Si TFT current data driver with a data-line pre-
`charge function for active-matrix organic light-emitting diode (AMOLED)displays. The current data
`driver is capable of outputting highly accurate (£0.8%) current determined by6-bit digital input data.
`A novel current-programming approach employing a data-line pre-charge function heips achieve
`accurate current programming at low brightness. A 1.9-in. 120 x 136-pixel AMOLEDdisplay using
`these circuits was demonstrated.
`
`Keywords —- OLED, currentdata driver, current program, pre-charge.
`
`gramming time. To deal with this we need a data-line pre-
`charge function.
`In this paper, we propose for AMOLEDdisplays an
`integrated poly-Si TFT 6-bit current data driver and a novel
`current-programming approach that employs a data-line
`pre-charge function, The proposed design reduces current-
`programmingtimesat low brightness and achieves accurate
`current programming, We also demonstratea 1.9-in. poly-Si
`TFT OLEDdisplay which employsthese circuits.
`
` 1
`
`Introduction
`Poly-Si thin-film-transistor (TFT) OLEDdisplays hold
`great promise for use in mobile phones, PDAs, PCs, and
`TVs, offering wide viewing angles, fast response, low power
`consumption, and panel thinness.
`To obtain uniform images on poly-Si TFT AMOLED
`displays, it is necessary to ensure uniformity in the bright-
`ness ofeachpixel. This brightness is dependent on the cur-
`rent in the OLEDthatis driven by each pixelcircuit, and an
`important issue for poly-Si TFT OLED displays has been
`the pixel-driving technology needed to achieve uniformity
`in OLED currents. The main difficulty is non-uniformity in
`Driver configuration
`2.1.
`the current-voltage characteristics of the poly-Si TFTs that
`Figure 1 is a block diagram of the poly-Si TFT 6-bit current
`form part of the pixel circuit. A number of pixel-driving
`data driver, which contains 60-bit shift-register 1, 6-bit data
`schemes have been proposed to overcomethis disadvan-
`registers, 6-bit data latches, 60-bit shift register 2, 60 6-bit
`tage. 17 Amongthem,those that employa current-program-
`digital-to-current converters (DCCs), a standard current
`ming approach,45 which works to compensate for variations
`source circuit, pre-charge circuits, and 1-to-2 selectors.
`in both V; and mobility in poly-Si TFTs, are effective in
`These last five componentsform the design’s “currentsignal
`achieving good uniformity. Unfortunately, however, this
`block.”
`approach suffers from a serious drawback. Specifically, the
`Each 6-bit data register receives 6-bit digital gray-
`lowness ofits current for a dark gray scale meansthat (1)
`scale data when scanning signals are output from 60-bit shift
`programmingtimewill be relatively long and (2) a highly
`register 1, and it outputs this data to each 6-bit data latch.
`accurate current data driver will be required. While such
`The 6-bit data latches send 6-bit digital data to the 6-bit
`driving accuracy might be externally supplied, as with, for
`DCCs, The 6-bit DCCs carry out two different operations.
`example, drivers composed of crystal-Si MOSFETsthat
`Oneig to memorize values of the six standard currents (Is,
`offer high uniformity in current-voltage characteristics, the
`Is x 2, Is x 4, Is x 8, Is x 16, Is x 32) generated by the inte-
`use of such drivers would increase programming time fur-
`grated standard current sourcecircuit in the driver. The
`ther because of the increase in high parasitic capacitance
`other is to output the gray-scale currents (Is, Is x 2,..., Is x
`inducedby the connection between the datadrivers and the
`62, or Is x 63) determinedbythedigital data from the 6-bit
`data latch. Each 6-bit DCC is composed of 6 1-bit DCCs
`display panel. What is needed,then, is to integrate high-
`accuracy current data drivers into the AMOLEDdisplay
`connectedin parallel. Each 6-bit DCC sendsan analog cur-
`substrateitself.
`rent signal to the pre-chargecircuit. A 1-to-2 selector out-
`puts the signals to each of two outputs of the driver, one
`Further, there is also high parasitic capacitance in the
`after the other. This is accomplished overa single horizontal
`data-line capacitors, and the need at low current levels to
`period. 60-bit shift register 2 outputs scanning signals to
`charge these data-line capacitors would also increase pro-
`ee
`Revised version of a paper presented at the 9th International Display Workshops (IDW ‘02) held December 4-6, 2002, in Hiroshima, Japan.
`The authors are with SOG Research Laboratories, NEC Corp., 1120 Shimokuzawa, Sagamihara, Kanagawa 229-1198 Japan;
`telephone +81-42-771-0689, fax -0780, e-mail: m-shimoda@ct.jp.nec.com.
`K. Abe is with the 5th System LS! Division, 2nd Business Development Operations Unit, NEC Electronics Corp., Japan
`© Copyright 2003 Society for Information Display 1071-0922/03/1103-0461$1.00
`
`2
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`Current data driver
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`Data shift signals
`
`
`
`
`
`
`
`
`
`U Voltage signal
`60- bit shift-—— 1
`R Current signal
`
`6- bit data registers
`
` 6-bit digital data
`Do 5-*
`6- bit data latches
`(": 1» 60)
`
`
`
`6- bit digital signals
`» RGB
`
`Latch signals
`
`Memorization signals,
`
`G- bit standard current
`source circuit * AGB
`
`Standard current
`control vqltages
`
`|i
`
`
`
`
`
`i 60- bit shift-— 2
`
`60 6- bit Digital-to-C urrent C onverters
`(60 6-bitDCC)* RGB
`
`
`
`
`
`
`
`
`
`pre-charge circuits
`
`
`
`1-to-2 selectors
`
`
`120 Outputs * RGB
`
`Pre-charge signal
`
`Selector signals
`
`FIGURE 1 — Block diagram of current data driver, which contains shift
`register 1, 6-bit data registers, 6-bit data latches, shift-register 2, 6-bit
`digital-to-current converters (DCCs), a standard current source circuit,
`pre-chargecircuits, and 1-to-2 selectors.
`
`6-bit DCCs. The output timing of the scanning signals is
`synchronouswith the 6-bit DCC’s operation of memorizing
`the values of current supplied by the standard current
`source circuit.
`
`
`
` =1-bit digital-to-current converter
`2.2
`The current-copier-type 1-bit DCCs of which the 6-bit
`DCCis composedare able to output a highly accurate cur-
`
`Signal for memorization
`MS
`
`1- bit digital data
`DO 5
`
`(1- to- 60)
`
`(1-to- 60)
`
`
`
`
`
`Driving TFT
`
`SW2TFT2
`
`SWIFT!
`
`Standard current line
`
`''I1
`
`lout
`
`FIGURE 2 — Basic 1-bit current-copier-type DCC, composed of a
`current-copier circuit and a switching TFT (SW3) controlled by 1-bit
`digital data signals sent ‘from a 6-bit data latch.
`
`462
`
`Shimoda et al. /An integrated poly-Si TFT current data driver
`
` {
`
`Digital data “H”.-----T- Mose at
`(ting
`state
`for
`digilal-
`data
`
`“H”
`
`Digital data “L” -----E----..-- “
`
`Sa
`
`|
`
`FIGURE 3 — Operation states of the current-copier-type 1-bit
`digital-to-current converter: the memorizing state, the outputting state
`for 1-bit data “H,” and the outputting state for 1-bit data “L.”
`
`rent. In this section, in order to clarify what makes this
`accuracypossible, we give a detailed explanation ofthe 1-bit
`DCC’s design and operations.
`Figure 2 showsthebasic circuit of a 1-bit DCC. Itis
`composedof a current-copiercircuit and a switching TFT
`(SW3) controlled by 1-bit digital data signals sent from a
`6-bit data latch. The current-copier circuit is composed of a
`driving TFT, two memorizing-switches TFT (SW1, SW2)
`controlled by a signal [MS (1-to-60)] sent from 60-bit shift
`register 2, and a hold capacitor.
`Figure 3 showsthe three operationstates of the 1-bit
`DCC: the memorizing state, the outputting state for 1-bit
`data “H,” and the outputtingstate for 1-bit data “L.” In the
`memorizingstate, SW1 and SW2 are ON, SW3 is OFF, and
`the hold capacitor and the gate capacitorof the driving TFT
`have been chargedin order to send a standard current(Is,
`Is x 2, Is x 4, Is x 8, Is x 16, or Is x 32) into the driving TFT
`(in Fig. 3, this currentis “Is”). In the outputting states, SW1
`and|SW2 are OFF, SW3 is ON or OFF, andthe driving TFT
`outputs “Is” or zero so that the hold capacitor and the driv-
`ing TFT’s gate capacitor can retain their charge so as to send
`“Ts.” Note that of the four TFTsin this 1-bit DCC, three are
`switches; the fourth is the “driving TFT’ used for memoriz-
`ing and outputting.
`
`
`Experiments
`2.3
`Wehaveexperimentally fabricated the 6-bit DCC described
`above. Its measured output characteristics are shown in
`Fig. 4. Here, the output current value of the driver
`increases as the value of the gray scale increases, which
`indicates 6-bit monotony for the current output. Figure 5
`shows deviations among the MSB (63 gray-scale) output
`currents for four outputs in each frame, as measuredforfive
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`1200
`
`1000
`
`(nA) 200
`Averageoutputcurrent
`
`
`
`800
`
`600
`
`400
`
`0
`
`io
`
`20
`
`30
`
`40
`
`50
`
`60
`
`Digital gray- scale
`
`FIGURE 4 — Current driver output characteristics.
`
`6-bit Accuracy
`
`
`
` DeviationoftheMSBoutputcurrents(%)
`
`
`
`lout-1
`
`Jout-2
`
`Tout-3
`
`lout-4
`
`
`
`Novel current-programming approach
`3
`with data-line pre-charge function
`Aspreviously noted, the 6-bit DCCsare able to output cur-
`rent accurately, with 6-bit resolution. The problem oflong
`current-programming time remains, however, and in this
`section we explain our novel current-programming approach,
`which employs a data-line pre-charge function in order to
`reduce current-programming times and to achieve accurate
`current-programming at low gray-scale levels, This
`approach has becomepossible because the current data
`driver has been integrated into the display substrate itself.
`
`Circuit design
`3.1
`Figure 6 is a diagram of both the pixel circuit and theinte-
`grated current data driver containing a pre-charge circuit.
`The pre-charge circuit is composed of one TFT (T1) and a
`voltage-follower amplifier. TFTs (T2 ~ T4) are switching
`TFTs. The current source indicated in the diagram repre-
`sents a 6-bit DCC which generates an analog current on the
`basis of 6-bit digital data that has been input to it, as was
`previously noted in Section 2. The output of the data driver
`is connected to a data line via a selector, which is used to
`select an appropriate data line for connection.
`Thepixel circuit contains five TFTs: one driving TFT
`(T5) and four switching TFTs (T6 ~ T9). The gate length
`and width of the driving TFT (T5) are designed to be the
`same as thoseof the driving TFT in the pre-chargecircuit.
`The switching TFTs are controlled by signals that are output
`by an integrated gate driver to three pixel circuit inputs
`[Write scan] (WS1), Write scan 2A/B (WS2A/B), and Erase
`scan (ES)]. In order to control the emission period, the
`switching TFT (T8) is used to cut off the current to the
`OLED,andthe switching TFT (T9) is usedto initialize the
`OLED.
`
`FIGURE 5 — Deviation among four output currents for four outputs in
`each frame, as measured for five samples.
`
`samples. As may be seen, at MSB, where the output current
`is the highest, the current driver satisfies 6-bit accuracy
`(+0.8%) requirements.
`
`SE Precharge circuit
`Voltage follower
`amplifier
`
`
`Cparasitic
`i
`
`WS1
`WS2B
`
`
` Tl
`
`Pre-charge
`
`
`
`Current Data driver
`
`FIGURE 6 — The schematic diagram of both the pixel circuit and the current data driver with the pre-charge circuit.
`
`Journal of the SID 11/3, 2003
`
`463
`
`SAMSUNG, EXH. 1021, P. 8
`
`SAMSUNG, EXH. 1021, P. 8
`
`

`

`1 frame
`
`Pre-charge period Current-programmingperiod
`
`
`
`Horizontal period+
`|
`|
`|
`WS1
`WS2A
`for Odd Lineaaa
`WS2B
`|
`|
`for Even Line
`Emission periodoe
` ES
` |.- Current-programmingperiod
`|
`Pre-charge Period.Nl
`Pre-charge
`|
`
`Ve(T5) 10
`8
`(nA)
`80
`
`i(T5)
`
`40
`
`
`
`wv
`
`0.06
`0.04
`Time (msec)
`
`0.08
`
`0.10
`
`0.02
`
`00
`
`.00
`
`|
`
`ceo
`
`|
`
`|
`
`illustrating current data driver and pixel
`FIGURE 7 — Timing chart
`circuit operations. The signals Write scan1 (WS1), Write scan 2A/B
`(WS2A/B), and Erase scan (ES) are output by an integrated gate driver.
`
`
`(a) Pixel-driving with pre-charge
`
`Current-programming period
`
`
`
`Ve(T5)
`
`10
`8
`(nA)
`80
`
`i(T5)
`
`40
`
`Circuit operations
`3.2
`Figure 7 is a timing chart whichillustrates how the current
`data driver and pixel circuit work.
`A single horizontal period contains both the pre-
`charge and current-programming periods. In the pre-
`charge period, T2 and T3 are turned on,T4 is turned off,
`and current from the current source flows into T1. A volt-
`
`age-follower amplifier outputs the gate voltage of T1 into
`0 4 Ugaheni L ———_—L.
`
`
`
`the gate electrode of T5, with T6 and T7 turned on, This
`0.00
`0.02
`0.04
`0.06
`0.08
`0.10
`pre-charge function rapidly pre-charges the voltage in the
`gate electrode of T5 so that a current roughly equivalent to
`the value of the current source flows through T5.
`In the subsequent current-programming period, T4 is
`turned on, T2 and TS are turnedoff, the pre-chargecircuit
`is disconnected, and the current from the current sourceis
`directly supplied to the pixel circuit. While a pre-charge
`error may be generated if there exist variations in charac-
`teristics between T1 and T5,orif there is an offset voltage
`in the voltage-follower amplifier, this error can be compen-
`sated for during current-programmingperiods. Setting the
`current from the current source high makesit possible to
`compensate for the greater pre-charge error that occurs
`during current-programming periods. This improves the
`accuracyof current programmingsignificantly.
`After the horizontal period, T6 and T7 are turnedoff,
`T8 is turned on, and a current programmedby the data
`driver is supplied to the OLED.The emission periodis con-
`trolled by erase-scan signals which turn T8 and the reset
`TFT T9 onandoff. Setting the emission period short makes
`it possible to set the current of the current source high
`enoughto obtain the same average brightness over succes-
`sive frame periods.
`
`
`
`
`Time (msec)
`(b) Pixel-driving without pre-charge
`
`FIGURE 8 — Simulationresults for transient response in cases both with
`(a) and without (b) pre-charge. Both (a) and (b) show response forlevels
`from the current source of from 0 to 80 nA.
`
`charge. Both show responsefor levels from the current
`source of from 0 to 80 nA. As may be seen in Fig. 8(b),
`without pre-charge, the value of the current fiom the cur-
`rent source cannot be programmedinto the pixel circuit
`becausethat current, 80 nA,is too small to discharge, within
`tht horizontal period, T5 gate capacitance and data-line
`capacitancesufficiently for 80 nA to flow through T5. By
`way of contrast, as may be seen in Fig. 8(a), with pre-charge,
`programming can be performed because both the T5 gate
`capacitance and data-line capacitance can be discharged
`sufficiently within the pre-charge period by the voltage-fol-
`lower amplifier in the pre-chargecircuit.
`Figure 9 showssimulation results for OLED current
`accuracy vs. emission ratio (emission period/maximum
`emission period, expressed in %) for three cases of pre-
`chargeerrorwith respect to green (G), which has the small-
`est OLED current value among R, G, and B. We have
`confirmed that setting smaller emission periods makes
`higher accuracy possible. We havealso foundthat a 64-level
`gray scale can be achieved by setting the emission ratio to
`
`SAMSUNG, EXH. 1021, P. 9
`
`Simulation results
`3.3
`Figures 8(a) and 8(b) show, respectively, simulation results
`for transient response in cases both with and without pre-
`
`464
`
`Shimoda et al. /An integrated poly-Si TFT current data driver
`
`SAMSUNG, EXH. 1021, P. 9
`
`

`

`60
`
`80
`
`100
`
`
`
`FIGURE 10 — Image onthe fabricated AMOLED display.
`This figure is reproduced in color on page 592.
`
`increases reliability in AMOLEDdisplay systems, and the
`novel current-programming approach improves the accu-
`racy of current programmingat low brightness. Thesecir-
`cuits make it possible to produce AMOLEDdisplays with
`good gray-scale imagequality and goodpixel-to-pixel lumi-
`nance uniformity.
`
`
`Acknowledgments
`Weare very grateful to Mr. S. Kaneko, head of the SOG
`Research Labs for his important guidance and encourage-
`ment. We also thank the members of the SOG Research
`Labs for their help in fabricating the poly-Si TFT sub-
`strates, and we further wish to express our appreciation to
`the membersof the R&D Technical Support Center in NEC
`for thier valuable support during the course of this work,
`
`
`References
`1 R Dawsonet al, IEEE IEDM ‘98, 875 (1998).
`2 K Inukai et al, SID Intl Symp Digest Tech Papers, 924 (2000).
`3 M Kimuraet al, Proc IDW ‘99, 171 (1999).
`41M Hunteret al, AMLCD2000 Digest, 249 (2000).
`5 R Hattori et al, AMLCD2001 Digest, 223 (2001).
`6 T Sasaoka et al, SID Intl Symp Digest Tech Papers, 384 (2001).
`7 A Yumoto etal, Proc IDW ‘01, 1395(2001).
`8 K Abeet al, Proc EuroDisplay, 279 (2002).
`
`cuits and their application devices.
`
`Masamichi Shimodareceived his B.E. degree in
`electrical engineering from Meiji University in
`1988. He joined NEC Corporation in 1988 and
`has recently been engaged in the research and
`development of polycrystalline-silicon TFT cir-
`
`Journal of the SID 11/3, 2003
`
`465
`
`SAMSUNG, EXH. 1021, P. 10
`
`Emission ratio (9%
`
`FIGURE 9 — Simulation results for OLED current accuracy vs. emission
`ratio (emission period/maximum emission period, expressed in %) for
`three cases of pre-chargeerror.
`
`roughly 15% at 0.5 V of pre-charge error, about 40% at 0.2
`V, and about 70% at 0.1 V.
`
` 4
`
`Displays
`We have fabricated an AMOLED display based on the
`design presented here. Specifications for the developeddis-
`play are summarized in Table 1. The display contains gate
`drivers, a current data driver, andlevel shifters. Both RGB
`digital data signals (6 bits each) and digital control signals
`are supplied at 3 V from an external controller. Figure 10
`shows a sample display image. Here, the emission ratio is
`about 40%. Good pixel-to-pixel luminance uniformity and
`gray-scale images have been achieved with this display.
`
` 5
`
`Conclusion
`Wehave developed an integrated poly-Si TFT current data
`driver based on a current-copier technique and a novel cur-
`rent-programming approach with a data-line pre-charge
`function. The integrated current data driver eliminates of
`the need for external current sources, reduces cost, and
`
`
`
`TABLE 1 — Display specifications.
`
`Display size
`1.9 in.
`
`Pixel count
`120 x RGB x 136
`
`Pixel pitch
`96 ppi
`
`Peak luminance
`>150 cd/m?
`
`Inputdata
`Digital 6 bit x RGB
`Input level
`3VIF
`Current data driver
`Gate driver
`Integrated circuits
`
`__
`Level shifter
`
`(%)
`
`Accuracy
`
`0
`
`20
`
`40
`
`SAMSUNG, EXH. 1021, P. 10
`
`

`

`in nuclear engineering from Kyoto University in
`1993 and 1995, respectively. He joined NEC
`Corporation in 1995, and in 2002, he moved to
`NEC Electronics Corporation. In recent years,
`he has been engagedin the research and devel-
`opmentof polycrystalline-silicon TFT circuits
`and their application devices. Mr. Abe is a
`memberof the Society for Information Display.
`
`Hiroshi Haga received his B.E. degree in image
`science and technology from Chiba University
`in 1994.Since joining the Display Device Research
`Laboratory, Functional Devices Research Labo-
`ratories of NEC Corporation in 1994, he has
`been engaged in the research and development
`of polycrystalline-silicon TFT circuits and their
`application devices. Mr. Haga is a member of
`the Society for Information Display, the Institute
`of Electronics, Information and Communication
`Engineers, and the Institute of Image Information and Television Engi-
`neers.
`
` Katsumi Abe received his B.S. and M.S. degrees
` Hideki Asada received his B.E. and M.E. degrees
`
`in electrical engineering from Keio University in
`19B5 and 1987, respectively. In 1987, he joined
`the Central Research Laboratories, NEC Corpo-
`ration. Since then, he has been engagedin the
`research and development of polycrystalline-
`silicon TFT circuits and their application
`devices. Mr. Asada is a memberof the Society
`of Information Display.
`
`Hiroshi Hayama received his B.S., M.S., and
`Ph.D. degrees from the Tokyo Institute of Tech-
`nology, Tokya, Japan in 1978, 1980, and 1995,
`respectively. He joined the Central Research
`Laboratories, NEC Corporation, Kawasaki,
`Japan in 1980, where he has been engaged in
`research on highspeed CMOS/SOS, three-dimen-
`sional integration of ICs, display-driver LSlIs,
`thin-film transistors on amorphous substrates,
`and TFT-LCDs. Dr. Hayamais a memberof the
`Society of Information D