`
`
`
`
`
`
`Journal of the
`“SOCIETY FOR
`
`INFOR MATION
`-DISP Lay.
`
`
`
`
`
`CombinedSpecial Issues on
`Selected Papers from the 9th International
`Display Workshops (IDW ’02)
`and
`Selected Papers from the 22ndInternational
`Display Research Conference (EuroDisplay ’02)
`
`Volume 11
`Number3
`
`
`
`Fe Previously published as
`
`___|Proceedings of the Society for Information Display
`
`
`
`
`
`SOCIETY FOR INFORMATION DISPLAY
`
`SAMSUNG, EXH. 1020, P. 1
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`

`

`I J
`
`
`
`Vision Science/HumanFactors
`Haruo Isono, HumanScience Research Division, NHK Science and Technical
`Research Labs., 1-10-11, Kinuta, Setagaya-ku, Tokyo 157-8510, Japan
`4+81-3-5494-2340,fax: +81-3-5494-2371, isono@strl.nhk.or.jp
`Alan R. Jacobsen, Boeing Commercial Airplane Group, P.O. Box 3707,
`MC 02-JH, Seattle, WA 98124-2207 USA
`425/294-0562, fax -0515, alan.r.jacobsen@boeing.com
`
`ournal of the SID
`The quarterly Journal of the SID publishes original work dealing with the
`theory and practice of information display. Coverage includes hard andsoft
`copy; the underlying chemistry, physics, physiology, and psychology;
`measurement techniques; and all aspects of the interaction between
`equipmentandits users.
`The Society also publishes Symposium Digests, containing extended
`abstracts of papers presented at the annualInternational Symposia, and the
`monthly magazine Information Display. We cooperate in publishing the
`digests of technical papers presented at the annualInternational Display
`Research Conferences. Information aboutall 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 or to the Editor.
`
`Light-Emitting Displays (LEDs, OLEDs, ELDs, Phosphors,etc.)
`GhassanE. Jabbour, Optical Science Center, The University of Arizona,
`1630 E. University Blvd., Tucson, AZ 85721 USA
`520/626-8324, fax 520/621-4442, gej@optics.Arizona.edu
`Webster E. Howard, 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 Proceedingsof the SID from 1963 through 1991 (Volumes 1-32)9_—________
`Plasma Displays
`Munisamy Anandan, Organic Lighting Technologies, LLC,
`13009 ThomeValley Dr., Del Valle, TX 78617-3489 USA
`phone/fax 512/247-6863, manandan@o-lite.com
`Heiju Uchiike, Saga University, Dept. of Electronics,
`1, Honjo-machi, Saga 840-8502 Japan;
`+81-952-28-8640,fax -8651, uchiike@cc.saga-u.ac.jp
`
`Editor
`Andras |. Lakatos
`4681 S. Golden Arrow Drive, Green Valley, AZ 85614-5474 USA
`520/625-1457,fax -9855, e-mail: editor@sid.org
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`
`
`Associate Editors
`
`
`LCDs
`Allan R. Kmetz, 50 Edgewood Road, Chatham, NJ 07928-2002 USA
`akmetz@aya.yale.edu
`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 Stuttgart, Germany, and Electro-Optical
`Consultancy, LLC, 9471 E. Yucca St., Scottsdale, AZ 85260 USA
`phone/fax 480/451-8074, e.lueder@att.net
`Martin Schadt, ROLIC, Ltd., Gewerbestrasse 18,
`CH-4123 Allschwil, Switzerland
`+41-61-487-2222, fax -2288, Martin.Schadt@rolic.ch
`
`
`Display Manufacturing
`Jin Jang, Head, TFT-LCD Nationa! Lab, Kyung Hee University,
`Dongdaemoon-ku, Seoul, 130-701, Korea
`+82-2-961-0270,fax +82-2-968-6924, jjang@khu.ac.kr
`
`
`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, Higashi-Nakajima,
`Higashi-Yodagawa-ku, Osaka, 533-0033 Japan
`+81-6-4809-4125, fax: -4127, s.morozumi@crystage.com
`
`Managing Editor
`CRTs
`Jay Morreale, Palisades Convention Management
`A. A. Seyno Sluyterman, LG.Philips Displays, Bldg. RAF-1, P.O. Box 807,
`411 Lafayette Street, 2nd Floor, New York, NY 10003, USA
`5600 AV, Eindhoven, The Netherlands
`212/460-8090 x21 2, fax -5460, jmorreale@pcm41 1.com
`+31-40-2782817, fax -2786185, seyno.sluyterman@lgphilips-displays.com
`
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`SAMSUNG, EXH. 1020, P. 2
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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
`
`Number 3
`
`2003
`
`429
`
`Announcement: W. E. Howard, S$. Morozumi, and P. Seats Become Associate Editors
`
`SELECTED PAPERS FROM THE 9TH INTERNATIONAL DISPLAY WORKSHOPS
`
`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 al., Tokyo University of Science, Japan
`
`437—Electrically commandedsurfaces: A new LCD concept
`L. Komitov, Chalmers University of Technology & Géteborg University, Sweden
`
`431
`
`433
`
`443
`
`449
`
`457
`
`461
`
`467
`
`473
`
`
`
`Domain walls in photoaligned double-domain twisted-nematic LCDs
`D. K. G. de Boer et al., Philips Research Labs, The Netherlands
`F. A, Fernandéz etal., University College of London, U.K.
`
`Novel liquid-crystal materials for AMLCDs
`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 of the FastIntelligent Tracking (F!T) tube
`H. B. van den Brink and O. H. Willemsen, Philips Research Laboratories, The Netherlands
`The oxide cathoderevisited
`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., Ltd., Japan
`
`485
`
`493
`
`499
`
`|New metacodecoding concept for improving PDP gray-scale quality
`5. Weitbruch et al., Thomson Multimedia Research Laboratory, Germany
`
`Development of new high-luminance green EL devices based on Eu-doped calcium
`thioaluminate materials system
`A. M. Nakuaetal., Fire Technology, Canada
`
`Properties and cathodoluminescence of Y,0,S:Eu thin films
`M. M. Sychov, St. Petersburg State Institute of Technology, Russia
`Y. Hatanaka, Aichi University, Japan
`Y. Nakanishi et al., Shizuoka University, Japan
`
`continued
`
`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 SID Headquarters.
`Subscriptions for non-members are $100/year ($110/year outside
`North America). Single copies are $25; consult SID 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 Headquarters for 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 payment of
`copying fees to the Copyright Clearance Center (CCC), 27 CongressSt.,
`Salem, MA 01970. The fee and article code numberarelisted at the
`bottom of thefirst page of each paper.All other copying of any material
`in this Journal withoutthe specific permission of the Society is prohibited.
`Journal of 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. 1020, 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)
`
`Volume 11. Number 3
`
`2003
`
`Table of Contents (Continued)
`
`505
`
`Characteristics of aluminum oxinitride film grown by plasma-enhanced atomic layer deposition
`as the insulator of an electroluminescent device
`J. W. Lim et al., ETRI, Korea
`
`511~~A retinal scanning display with a wavefront curvature modulator
`M. Watanabeetal., Brother Industries, Ltd., Japan
`
`SELECTED PAPERS FROM THE 22nd INTERNATIONAL DISPLAY RESEARCH CONFERENCE
`
`517
`
`519
`
`Introduction
`
`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 et al., 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 etal., Thales Avionics LCD, France
`
`Organic-polymerthin-film transistors for active-matrix flat-panel displays
`S. Martin et al., The University of Michigan, U.S.A.
`
`Improvement of PDP discharge efficiency based on macro-cell studies
`L. Tessier et al., Thomson Plasma, France
`J. 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. Yamadaand Y. Ishii, Sharp Corp., Japan
`
`~Azo-dyealigning layers for liquid-crystal cells
`V. Chigrinov et al., The Hong Kong University of Science and Technology
`H. Akiyamaet al., Dai Nippon Ink & Chemicals, Inc., Japan
`
`Novel screen technologyfor high-contrast front-projection display by controlling ambient-light reflection
`B. Katagiri et al., Tohoku University, Japan
`
`SAMSUNG, EXH. 1020, P. 4
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`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`An integrated 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
`
`1
`
`‘Introduction
`
`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 (t0.8%) current determined by 6-bit digital input data.
`A novel current-programming approach employing a data-line pre-charge function helps achieve
`accurate current programmingat 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-
`programmingtimes at low brightness and achieves accurate
`current programming. We also demonstrate a 1.9-in. poly-Si
`TFT OLEDdisplay which employs thesecircuits.
`
`2
`
`Current data driver
`
`Poly-Si thin-film-transistor (TFT) OLED displays 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 eachpixel circuit, and an
`importantissue for poly-Si TFT OLED displays has been
`the pixel-driving technology needed to achieve uniformity
`in OLEDcurrents. 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 ofthe poly-Si TFT 6-bit current
`form part of the pixel circuit. A numberof 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. 1-7 Amongthem,those that employ a current-program-
`digital-to-current converters (DCCs), a standard current
`ming approach,*5 which works to compensateforvariations
`source circuit, pre-charge circuits, and 1-to-2 selectors.
`a,
`«6
`in both V; and mobility in poly-Si TFTs, are effective in
`These last five components form 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-
`lownessof its current for a dark gray scale meansthat(1)
`scale data when scanningsignals are output from 60-bit shift
`programming time will berelatively 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 DCCscarry out two different operations.
`example, drivers composed of crystal-Si MOSFETsthat
`Oneis 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 timefur-
`grated standard current source circuit in the driver. The
`ther because of the increase in high parasitic capacitance
`otheris to output the gray-scale currents (Is, Is x 2,..., Is X
`inducedbythe connection betweenthedata drivers and the
`62, or Is x 63) determinedbythe digital data from the 6-bit
`display panel. Whatis needed,then, is to integrate high-
`data latch. Each 6-bit DCC is composed of 6 1-bit DCCs
`accuracy current data drivers into the AMOLED display
`connected in parallel. Each 6-bit DCC sends an analog cur-
`substrate itself.
`rent signal to the pre-charge circuit. A 1-to-2 selector out-
`Further,thereis also high parasitic capacitancein the
`puts the signals to each of two outputs of the driver, one
`after the other. This is accomplished overa single horizontal
`data-line capacitors, and the need at low currentlevels to
`period. 60-bit shift register 2 outputs scanning signals to
`charge these data-line capacitors would also increase pro-
`
`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 LSI Division, 2nd Business Development Operations Unit, NEC Electronics Corp., Japan
`© Copyright 2003 Society for Information Display 1071-0922/03/1103-0461$1.00
`
`Journal of the SID 11/3, 2003
`
`461
`
`
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`J Voltage signal
`J Current signal
`
`
`6- bit data registers
`
`Data shift signals
`
`6- bit digital signals
`+ RGB
`
`
`
`Latch signals,
`
`Memorization signals,
`
`6- bit standard current
`source circuit+ RGB
`
`Standard current,
`control voltages
`
`Pre-charge signal,
`
`Selector signals.
`
`MS1.MS2_°H"/Digitaldata“L”
`+ lout=0
`
` rizin
`eewieQe;
`
`Driving TFT
`
`
` 60- bit shift- register 1
`
`
`
`
`
`60 6- bit Digital- to- C urrent C onverters
`
`
`(60 6-bitDCC)* RGB
`
`fa
`
`pre-charge circuits
`
`
`i
`Sw3 /
`'
`
`1-to-2 selectors
`Digital data “L” ----t----.---a
`Digital data “H” ------I--------oa
`aH
`
`
`St8ee
`120 Outputs > RGB
`
`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-charge circuits, 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
`sourcecircuit.
`
` =1-bit digital-to-current converter
`2.2
`The current-copier-type 1-bit DCCs of which the 6-bit
`DCCis composedare able to outputa highly accurate cur-
`
`Signal for memorization
`MS
`
`1- bit digital data
`Do 5
`
`(1- to- 60)
`
`(1-to- 60)
`
`capacitor
`Driving TFT
`
`SW2:TFT2
`
`Standard current line
`
`
`
`
`
`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
`
`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 makesthis
`accuracypossible, we give a detailed explanation ofthe 1-bit
`DCC’s design and operations.
`Figure 2 showsthe basic circuit of a 1-bit DCC. It is
`composedof a current-copier circuit and a switching TFT
`(SW3) controlled by 1-bit digital data signals sent from a
`6-bit data latch. The current-copier circuit is composedof 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 holdcapacitor.
`Figure 3 showsthe three operation states of the 1-bit
`DCC:the memorizing state, the outputting state for 1-bit
`data “H,” and the outputting state for 1-bit data “L.” In the
`memorizing state, SW1 and SW2 are ON, SW3is 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, SW3is ON or OFF, andthe driving TFT
`outputs “Is”or zero so thatthe hold capacitor and the driv-
`ing TF'T’s gate capacitorcan 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.
`Wehave experimentally 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 monotonyfor the current output. Figure 5
`shows deviations among the MSB (63 gray-scale) output
`currents for four outputsin each frame, as measuredforfive
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`
`
`1200
`
`
`
`
`
`
`
` Averageoutputcurrent(nA)
`
`
`200
`
`
`be SoSSs
`
`800
`
`600
`
`400
`
`
`
`0
`
`10
`
`20
`
`30
`
`40
`
`50
`
`60
`
`Digital gray- scale
`
`FIGURE 4 — Current driver output characteristics.
`
`
`
`
`
`
`
`
`
`
`
`
`
` DeviationoftheMSB_outputcurrents(%)
`
`
`
`
`
`
`
`lout-1
`
`Tout-2
`
`Tout-3
`
`lout-4
`
` 3
`
`Novel current-programming approach
`with data-line pre-charge function
`As previously noted,the 6-bit DCCsare able to output cur-
`rent accurately, with 6-bit resolution. The problem of long
`current-programming time remains, however, and in this
`section weexplain our novel current-programming approach,
`which employs a data-line pre-charge function in orderto
`reduce current-programmingtimesandto achieve accurate
`current-programming at low gray-scale levels, This
`approach has becomepossible because the current data
`driver has beenintegratedinto the display substrate itself.
`
`
`
`Circuit design
`3.1
`Figure 6 is a diagram of both the pixel circuit and the inte-
`grated current data driver containing a pre-chargecircuit.
`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 whichgeneratesan analog current on the
`basis of 6-bit digital data that has been inputto it, as was
`previously notedin Section 2. Theoutput 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
`sameas those ofthe driving TFT in the pre-chargecircuit.
`Theswitching TFTsare 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 used to initialize the
`OLED.
`
`FIGURE 5 — Deviation among four output currents for four outputs in
`each frame, as measured for five samples.
`
`samples. As may beseen, at MSB, wherethe output current
`is the highest, the current driver satisfies 6-bit accuracy
`(+0.8%) requirements.
`
`
`
`Voltage follower
`amplifier
`
`Pre-charge
`
`poqeecern rene cre reer
`
`
`
`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. 1020, P. 7
`
`SAMSUNG, EXH. 1020, P. 7
`
`

`

`WS1
`WS2A
`for Odd Line
`
`WS2B
`for Even Line
`
`1 frame
`—______——___,
`Horizontal period
`|
`|
`|
`
`|
`
`|
`
`;
`
`|
`;
`:
`|
`Emission period
`|
`| —_>
`
`Pre-charge period Current-programmingperiod
`
`Ve(T5) 10
`8
`(nA)
`80
`
`Pre-chargepei ra Current-programmingperiod
`Nerd
`0Coceaiell
`Pre-charge
`|
`|
`|
`eee
`|
`|
`|
`|
`0.00
`0.02
`0.04
`0.06
`0.08
`0.10
`Time (msec)
`(a) Pixel-driving with pre-charge
`
`i(T5)
`
`40
`
`illustrating current data driver and pixel
`FIGURE 7 — Timing chart
`Circuit operations. The signals Write scan1 (WS1), Write scan 2A/B
`(WS2A/B), andErase scan(ES) are output byan integrated gate driver,
`
`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 flowsinto T1. A volt-
`age-follower amplifier outputs the gate voltage of T1 into
`the gate electrode of T5, with T6 and T7 turned on. This
`pre-charge function rapidly pre-charges the voltage in the
`gate electrode of T5 so that a current roughly equivalent to
`the value ofthe current source flows through T5.
`In the subsequent current-programmingperiod, T4is
`turnedon, T2 and T3 are turned off, the pre-chargecircuit
`is disconnected, and the current from the currentsourceis
`directly supplied to the pixel circuit. While a pre-charge
`error may be generatedif 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
`accuracy of current programming significantly,
`After the horizontal period, T6 and T7 are turnedoff,
`T8 is turned on, and a current programmedby the data
`driveris supplied to the OLED.The emission periodis con-
`trolled by erase-scan signals which turn T8 andthe reset
`TFT T9 on andoff. Setting the emission period short makes
`it possible to set the current of the current source high
`enough to obtain the same average brightness over succes-
`sive frameperiods.
`
`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
`
`Shimodaetal. /An integrated poly-Si TFT current data driver
`
`Current-programmingperiod So
`
`0.00
`
`0.02
`
`0.06
`0.04
`Time (msec)
`(b) Pixel-driving without pre-charge
`
`0.08
`
`0.10
`
`FIGURE 8 — Simulation results for transient responsein 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 maybe seen in Fig. 8(b),
`without pre-charge, the value of the current fiom the cur-
`rent source cannot be programmedinto the pixel circuit
`because that current, 80 nA,is too small to discharge,within
`the horizontal period, T5 gate capacitance and data-line
`capacitancesufficiently for 80 nA to flow through T5. By
`wayofcontrast, as maybeseenin 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 shows simulation results for OLED current
`accuracy vs. emission ratio (emission period/maximum
`emission period, expressed in %) for three cases of pre-
`chargeerror with 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 found that a 64-level
`gray scale can be achieved by setting the emission ratio to
`
`SAMSUNG, EXH. 1020, P. 8
`
`SAMSUNG, EXH. 1020, P. 8
`
`

`

`
`
`FIGURE 10 — Imageonthe fabricated AMOLED display.
`This figure is reproduced in color on page 592.
`
`increasesreliability in AMOLEDdisplay systems, and the
`novel current-programming approach improves the accu-
`racy of current programmingat low brightness. Thesecir-
`cuits makeit possible to produce AMOLEDdisplays with
`good gray-scale image quality 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
`Labsfor 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).
`4 1M 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 Yumotoet al, Proc IDW ‘01, 1395 (2001).
`8 K Abe et al, Proc EuroDisplay, 279 (2002).
`
`cifications.
`TABLE 1 — Displa
`
`
`Displaysize
`1.9 in.
`
`Pixel count
`120x RGBx 136
`
`Pixel pitch
`| 96 ppi
`
`Peak luminance
`>150 cd/m?
`
`Input data
`Digital 6 bit x RGB
`
`
`Inputlevel
`3VIUF
`
`
`Currentdata driver
`Gate driver
`
`Level shifter
`
`Integrated circuits
`
`
`
`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
`developmentof polycrystalline-silicon TFT cir-
`cuits and their application devices.
`
`Journal of the SID 11/3, 2003
`
`465
`
`SAMSUNG, EXH. 1020, P. 9
`
`pre-charge error 0.5V )
`
`w
`
`td
`
`Accuracy
`
`(“%)
`
`0
`
`20
`
`40
`
`60
`
`80
`
`100
`
`Emissionratio (%
`
`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-chargeerror, about40% at 0.2
`V, and about 70% at0.1 V.
`
` 4
`
`Displays
`We have fabricated an AMOLED display based on the
`design presented here. Specificationsfor the developed dis-
`play are summarizedin Table 1. The display contains gate
`drivers, a current data driver, andlevelshifters. Both RGB
`digital data signals (6 bits each) anddigital 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%. Goodpixel-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
`
`SAMSUNG, EXH. 1020, P. 9
`
`

`

`
`
`Katsumi Abe received his B.S. and M.S. degrees
`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.
`
`Hideki Asada received his B.E. and M.E. degrees
`in electrical engineering from Keio University in
`1985 and 1987, respectively. In 1987, he joined
`the Central Research Laboratories, NEC Corpo-
`ration. Since then, he has been engaged in the
`research and development of polycrystalline-
`silicon TFT circuits and their application
`devices. Mr. Asada is a memberof the Society
`of Information Display.
`
`
`
`
`
`
`
`
`
`Koichi Iguchi received his B.S degree in elec-
`tronic engineering from the University of Elec-
`tro-Communications in 1995. He joined NEC
`Corporation in 1995. He has recently been
`engaged in the research and development of
`polycrystalline-silicon TFT circuits and OLED
`displays.
`
`Daisuke Iga received his B.S. and M.S. degrees
`in electrical engineering and electronics from
`Aoyama Gakuin University, Tokyo