US0077l 82.3482
`
`(12) United States Patent
`Tomioka et al.
`
`(10) Patent No.:
`
`(45) Date of Patent:
`
`US 7,718,234 B2
`May 18, 2010
`
`(SM
`
`LIQUID (IRYSTAI. DISPLAY AND MlC'l'il()l)
`FOR MANUF.-\(,'TURI.VG SAME
`
`(75)
`
`Inventors: Yasushi Tomioka, Hitacllinaka (JP);
`Hidetoshi Abe. Hitachinaka (J 1’);
`Katsumi Kondo. Mito (JP)
`
`428/1.1,
`(58) Field ofClassification Search
`428/1.31.1.5. 1.2.1.25. 1.26: 252/299.01;
`349/123. 134. 135
`Sec application tile for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DO(‘UMF.NTS
`
`(73)
`
`Assignee: Hitachi Displays, [.td.. Mobara-sl1i(.TP)
`
`4.345349 A
`
`8.-1982 Togashi
`
`Notice:
`
`Subject to any disclaimer. the term ofthis
`patent is extended or adjusted under 35
`U.S.C. l54(b) by 1369 days.
`
`El’
`
`(21)
`
`Appl. No.:
`
`10/537,825
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`X50975
`"‘
`7. I998
`
`(Continued)
`
`()'I‘llI;'R PUBLIC‘.-\'l‘IONS
`
`(22)
`
`PCT Filed:
`
`Dec. 8, 2003
`
`Wayne M. Gibbons. et al.. Nature. 351. pp. 49-50 (May 2. 1991).
`
`l’("l‘ No.:
`
`P(T'l'/JP03/15658
`
`§ 37] mt] ),
`(2). (4) Date:
`
`Jun. 8, 2005
`
`(Continued)
`
`Primmjv Examiner—Shcan C W11
`(74) .-trtorney, Agent. or Firm»—-~~Antonelli. Terry, Stout &
`Klaus, LLP.
`
`PC'1‘ Pub. No.: W02004/053582
`
`(57)
`
`ABSTRACT
`
`l’("l‘ Pub. Date: Jun. 24, 2004
`
`Prior Publication Data
`
`US 2006/0061719 Al
`
`Mar. 23. 2006
`
`(30)
`
`Foreign Application Priority Data
`
`Dec. 9. 2002
`
`(JP)
`
`........................... .. 2002-35646]
`
`(51)
`
`[nt.(‘|.
`(2006.01)
`(‘09K 19/00
`(2006.01)
`G021" 1/133
`(2006.01)
`G021" I/I337
`(52) U.S.Cl.
`.................... .. 428/l.2:428/1.25:428!l.26:
`428/1.271349/I23: 349/134: 349/135
`
`A liquid crystal display is provided which is capable ot’rcduc-
`ing the occurrence o.i‘dei'ectivc display due to variations in the
`initial alignment direction ofa liquid crystal alignment con-
`trol film in a liquid crystal display ofan IPS scheme. realizing
`the stable liquid crystal alignnicnt. providing excellent mass
`productivity. and having high image quality with a higher
`contrast ratio. The liquid crystal display has a liquid crystal
`layer disposed between a pair of substrates. at least one ofthe
`substrates being transparent. and an alignment control film
`formed between the liquid crystal layer and the substrate. At
`least one of the alignment control films comprises photore-
`activc polyimide and/or polyamic acid provided with em
`alignment control ability by imidiation of substantially lin-
`early polarized light.
`
`24 Claims, 8 Drawing Sheets
`
`(86)
`
`(87)
`
`(65)
`
`H3
`
`.\\‘1:€:1:3:3:3:3:3:~‘7IIIIl I
`
`I09 '
`
`
`
`
`
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`
`
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`"/3.’!//2
`
`
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`5
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`Page 1 of 30
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`Tianma Exhibit 1001
`
`

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`
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`US 7,718,234 B2
`Page 2
`
`
`US. PATENT DOCUMENTS
`
`
`
`
`J 3‘
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`J
`
`J)
`
`J)
`
`J
`
`J
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`J3
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`J
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`TW
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`W0
`
`7-209650
`
`7-209653
`
`07_2g7235
`
`g_361g3
`
`9.73101
`
`g_297313
`
`10_307295
`
`11_218765
`
`11.264932
`
`20oo-ogo164
`
`2000319510
`
`2000231671
`
`2001_517317
`
`2002431751
`
`3303766
`
`2002253262
`
`2002253303
`
`2003_73471
`
`2003_255349
`
`473497
`
`
`
`W0 91/1093“
`
`8/1995
`
`8/1995
`
`10’/1995
`
`2/1996
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`3/1997
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`11/1997
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`11/199g
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`8/1999
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`9/1999
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`3/2000
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`11/2000
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`10/2001
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`10/2001
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`5‘/2002
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`5/2002
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`9/2002
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`972002
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`3/2003
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`9/2003
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`1/2002
`
`
`7/1991
`
`
`
`OTHER PUBLICATIONS
`Japanese Official Action issued Jan. 26, 2010, in Application No.
`
`
`
`
`
`
`
`
`
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`2003403382.
`
`
`* cited by exaiuiner
`
`
`
`
`
`
`
`
`
`
`
`
`
`4,335,249 A 4‘
`
`
`5,612,450 A
`
`
`5,731,405 A *
`
`
`5,756,649 A
`
`
`5,928,733 A *
`
`
`5,929,201 A
`
`
`5.940.156 A ‘J
`
`
`3990.856 A *
`
`
`6,063,829 A
`
`
`
`6.242.060 B1 *
`
`6,294,639 B1
`
`
`6,344,889 B1 *
`
`
`6,433,764 131"‘
`
`
`6,685,997 B1
`
`
`6,746,730 B1
`
`
`2001/0048498 A1 ”‘
`
`
`2004/0012725 A1
`
`
`2005/0271833 Al"‘
`
`
`
`
`
`
`
`
`
`528/353
`
`
`
`
`
`
`
`
`349/156
`
`345/97
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`
`
`......... .. 528/353
`5/1989 Gallagher 61 a1.
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`
`
`
`
`3/1997 Mizushima et al.
`
`
`
`
`3/1998 Gibbons et a1.
`
`
`
`5/1998 Mizushima et al.
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`
`
`
`7/1999 Yoneyaet al.
`.............. .. 428/1.3
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`7/1999 Gibbons et al.
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`8/1999 Nisl1ig11chi at al.
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`
`11/1999 Takeda et a1.
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`5/2000 Endou et 31.
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`............ .. 428/1.23
`6/2001 Yoneya et al.
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`9/2001 Sawahata et al,
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`2/2002 Hasegawa 61:11.
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`8/2002 Hebiguchi et al.
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`12/"2005 Matsumoriet £11.
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`......... .. 349/129
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`.......... .. 345/87
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`
`
`........... .. 349/123
`
`
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`
`
`428/1.25
`
`
`FOREIGN PATENT DOCUMENTS
`
`
`
`1037092
`972000
`6341907
`5/1988
`6-160878
`6/1994
`6-202127
`7/1994
`
`
`
`7-36047
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`2/ 1 995
`
`EP
`
`JP
`JP
`JP
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`JP
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`
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`Page 2 of 30
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`Page 2 of 30
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`U.S. Patent
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`May18,2010
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`
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`Sheet10f8
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`US 7,718,234 132
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`U.S. Patent
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`May 13, 2010
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`Sheet 2 of8
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`US 7,718,234 B2
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`U.S. Patent
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`May 13, 2010
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`US 7,718,234 B2
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`May 18, 2010
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`May 13, 2010
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`US 7,718,234 B2
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`May 13, 2010
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`US 7,718,234 B2
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`May 18,2010
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`US 7,718,234 B2
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`1
`LIQUID CRYSTAL DISPLAY AND METHOD
`
`
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`FOR MANUFACTURING SAME
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`
`
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`TECHNICAL FIELD
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`
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`The present invention relates to a liquid crystal display of a
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`so-called IPS (In-Plane Switching) scheme in wlnch an elec-
`tric field substantially in parallel with a substrate is applied to
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`a liquid crystal layer for operation, and to a production pro-
`cess thereo T.
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`BACKGROUND ART
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`In general, display ofa liquid crystal display is realized by
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`applying an electric field to liquid crystal molecules in a
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`liquid crystal layer sandwiched between a pair of sub strates to
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`change the alignment direction of the liquid crystal molecules
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`and utilizing the resulting change in the optical property ofthe
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`liquid crystal layer. Conventionally, a liquid crystal display of
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`a so—called active drive type having a switching device such as
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`a thin-film transistor for each pixel is represented by a TN
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`(Twisted Nematic) display scheme in which an electrode is
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`provided for each ofa pair of substrates sandwiching a liquid
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`crystal layer between them, the direction of an electric field
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`applied to the liquid crystal layer is set to be substantially
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`perpendicular to the interface between the substrates, and the
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`optical rotatory power of tlie liquid crystal molecules consti-
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`tuting the liquid crystal layer is utilized to achieve display. In
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`the liquid crystal display of the TN scheme, a small viewing
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`angle is regarded as the greatest problem.
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`On the other hand, “Patent Document l,” “Patent Docu-
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`ment 2,” “Patent Document 3,” “Patent Document 4," “Patent
`Document 5” and the like have disclosed an IPS scheme in
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`which an inter-digital electrode formed on one of a pair of
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`substrates is used to produce an electric field having a corn-
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`ponent substantially in parallel with the substrate surface to
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`rotate liquid crystal molecules constituting a liquid crystal
`layer in a plane substantially in parallel with the substrate and
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`the birefringence of the liquid crystal layer is used to realize
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`display, The IPS scheme has advantages such as a wider
`viewing angle and a lower load capacity due to the in-plane
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`switching of the liquid crystal molecules as compared with
`the conventional TN scheme. The IPS scheme is considered
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`as a new and promising liquid crystal display which will
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`replace the TN scheme and has made rapid advances in recent
`years. In addition, another type of the IPS scheme has been
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`disclosed in “Patent Document 6” iii which at least one of
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`paired electrodes for applying an electric field to a liquid
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`crystal layer is made of a transparent conductive film to
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`improve transmittance.
`The liquid crystal display of the IPS scheme (abbreviated
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`as IPS-TFT-LCD) with favorable viewing angle characteris-
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`tics (luminance contrast ratio, tone and color reversal) and
`bright display represents prospective technology formonitors
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`or televisions with a large display area. In the liquid crystal
`display, an alignment control film provided with a liquid
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`crystal alignment control ability is formed on the interface
`between a liquid crystal layer and each of a pair of substrates
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`sandwiching the liquid crystal layer between them. However,
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`to put IPS-TFT-LCDs for supporting large screens of 20
`inches or more into practiceuse in the future, it is necessary to
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`develop a new structure and process for large-size displays
`(large panels).
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`In particular, for an IPS-TFT-LCD having many stepped
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`structures on a surface opposite to a liquid crystal layer, it is
`difficult to perform u11ifon11 alig1n11ei1t processing 011 an
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`alignment control film over a large screen. A margin in per-
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`10
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`15
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`2(J
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`35
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`“
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`2
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`forming the alignment processing o11 the alignment control
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`film is significantly smaller than that of the conventional TN
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`scheme, especially a normally open type TN scheme which is
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`predominant at present (bright display at low voltage and dark
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`display at high voltage). The reasons for the small margin
`include three points described below as (l) to (3).
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`(1) Stepped Structure
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`In the IPS—TFT-LCD, it is necessary to provide a number of
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`elongated electrodes (which may be referred to as inter digital
`electrodes) having a width of approximately several microns
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`in principle. This causes minute stepped structures to be
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`formed therein. The height of the step depends on the thick-
`ness of the electrodes or the shapes of various films formed
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`thereon, andtypically is equal to 0.l micron (mp) orlarger.An
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`alignment control film (also referred to as an alignment film)
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`made of a polymer film such as polyimide is formed in the
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`uppenno st layer of the se films.
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`In conventional mass production teclmology, the align-
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`ment control film is subjected to rubbing processing to pro-
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`vide a liquid crystal alignment ability (initial alignment).
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`Meanwhile, a cloth for the rubbing is formed by binding thin
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`fibers with a thickness of approximately l0 to 30 microns.
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`Essentially, each of the thin fibers provides shearing force in
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`a predetermined direction for a local portion of the alignment
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`film to perform the processing of giving the liquid crystal
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`alignment ability. While very thin fibers of approximately
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`several microns are present the fibers, such very thin fibers
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`have not been put into practical use since rigidity for provid-
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`ing certain frictional force is required for the rubbing. The
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`interval between the electrodes in the IPS scheme is approxi-
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`mately IO to 30 microns which is substantially the same as the
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`diameter of the fibers, so that sufficient rubbing is not per-
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`formed near the steps and misalignment tends to occur. The
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`misalignment leads to reduced image quality such as a higher
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`black level, an associated lower contrast ratio, and uneven
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`luminance.
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`(2) Alignment Angle
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`In the IPS-TFT-LCD, the initial alignment direction needs
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`to be set in principle at a certain angle or more shi Fted from the
`direction in which the electrode extends or the direction per-
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`pendicular thereto. The electrode refers to a signal wiring
`electrode, a common electrode in pixels, and a pixel elec-
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`trode. The definition ofthe initial alignment direction through
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`the rubbing requires the fibers of approximately l0 to 30
`microns to rub in a predetermined angular direction as
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`described above. However, the step of the wire such as the
`signal wiring electrode. the common electrode in pixels, or
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`the pixel electrode extending in a certain direction at their
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`ends draws the fibers toward the step from the set angle to
`produce misalignment, thereby reducing image quality such
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`as a higher black level,
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`(3) Expression of Dark Level
`One ofthe characteristics of the IPS-TFT-LCD is excellent
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`expression of a dark level (black display). Thus, misalign-
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`ment is easily noticeable as compared with the other schemes.
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`In the conventionally normally open type TN scheme, the
`dark level is provided while a high voltage is applied. In this
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`case, most ofliquid crystal molecules align in the direction of
`the electric field which is one direction perpendicular to the
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`substrate surface at a high voltage, and the dark level is
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`provided from the relationship between the arrangement of
`the liquid crystal molecules and the placement of a polarizing
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`plate. Thus, the uniformity ofthe dark level hardly depends on
`the initial aligmnent state at a low voltage i11 principle. In
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`addition, since human eyes recognize uneven luminance as a
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`Page 11 of 30
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`US 7,718,234 B2
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`4
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`ciated with the rubbing processing technique such as TFT
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`breakage due to static electricity produced by friction, unfa-
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`vorable display due to misalignment from disordered fiber
`ends of a rubbing cloth or dust, and the need for frequent
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`exchanges of rubbing cloths. For the purpose of solving the
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`problems associated with the rubbing alignment processing, a
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`so-called “rubbing-less” alignment technique for aligning
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`liquid crystal molecules without the rubbing has been studied
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`and various processes thereof have been proposed. Among
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`other things, a process has been proposed in which polarized
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`ultraviolet rays or the like are irradiated to the surface of a
`polymer film to align liquid crystal molecules without the
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`rubbing.
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`As an example, a process disclosed in “Non-Patent Docu-
`ment 1” is characterized in that it does not require the con-
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`ventional rubbing proccssing and realizes the alignment of
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`liquid crystal molecules in a predetermined direction through
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`irradiation of polarized light. The process is advantageous in
`presenting no problems such as damages on the film surface
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`and static electricity associated with the rubbing technique
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`and providing a simpler production process in View of indus-
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`trial production. The process has attracted attention as a new
`liquid crystal aligmrtent processing process without using the
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`rubbing processing.
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`As a material ofthe liquid crystal alignment filmused in the
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`previous reports, the use of a polymer compound having a
`photoreactive group in the side chain of a polymer has been
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`proposed for the need to provide photochemical sensitivity to
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`polarized light. A representative example thereof is polyvi-
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`nylcinnamate, in which case it is thought that dimerization in
`the side chain through light irradiation develops anisotropy in
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`a polymer film to align the liquid crystal. Another proposal
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`involves dispersing low-molecular dichroic azo dye in a poly-
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`mer material and irradiating a film surface with polarized
`light to allow the alignment of liquid crystal molecules in a
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`predetermined direction. In addition, the alignment of liquid
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`crystal molecules achieved by irradiating a particular poly-
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`imide film with polarized ultraviolet rays or the like has been
`reported. In this case, it is contemplated that the light irradia-
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`tion decomposes the polyimide main chain in a certain direc-
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`tion to develop the liquid crystal alignment.
`Patent Document 1: JP-B-63-21907
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`Patent Document 2: U.S. Pat. No. 4,345,249
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`Patent Document 3: W091/l 0936
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`Patent Document 4: JP-A-6-22739
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`Patent Document 5: JP-A-6-160878
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`Patent Document 6: JP-A-9-73101
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`Patent Document 7: Japanese Patent No. 3303766
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`Patent Document 8: JP-A-ll-218765
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`Non-Patent Document 1: W. M. Gibbons et al., Nature,
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`351, 49(l99l)
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`DISCLOSURE OF THE INVENTION
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`In this mamter, the photo-alignment process through light
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`irradiation has been proposed and studied as the rubbing-less
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`alignment teclmique for solving the problems in the rubbing
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`alignment technique, but it has the following problems from
`a practical standpoint. In a polymeric material obtained by
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`introducing a photoreactive group in the side chain ofa poly-
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`mer represented by polyvinylcinnamate, the heat stability of
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`alignment is insufficient and satisfactory reliability is not
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`ensured from a practical viewpoint. hi this case, since it is
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`thought that the side chain of the polymer corresponds to the
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`10
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`15
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`')t]
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`30
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`35
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`~
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`55
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`60
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`3
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`relative ratio of luminance and 111ake response close to a
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`logarithmic scale, they are sensitive to variations in the dark
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`level. From this viewpoint, the conventional nonnally open
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`type TN scheme in which the liquid crystal molecules are
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`forcedly arranged in one direction at a high voltage is advan-
`tageous in that it is not sensitive to the initial alignment state.
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`On the other hand, in the IPS scheme. display of a dark
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`level is performed at a low voltage or no voltage, so that it is
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`sensitive to disturbance of the initial alignment state. In par-
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`ticular, when liomogeneous alignment is used ir1 which the
`alignment directions of liquid crystal molecules are in paral-
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`lel with each other on an upper substrate and a lower sub-
`strate. and the light transmission axis of one of polarizing
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`plates is set in parallel with the alignment direction of the
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`liquid crystal molecules and the light transmission axis of
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`other polarizing plate is set orthogonally thereto (called a
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`birefringence mode), polarized light incident on the liquid
`crystal layer is transmitted with almost no disturbance of
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`lineal polarization. This is effective in providing excellent
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`expression of the dark level.
`The transmittance T in the birefringence mode is expressed
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`by the following equation:
`
`T‘7"0‘sin2 {29(E)}-sinz {(fl£'d,_,f[\71)/7\.}
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`where To represents a coefficient which is a numerical value
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`determined mainly by the transmittance of the polarizing
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`plate for use in the liquid crystal panel, E)(E) represents an
`angle between the alignment direction of liquid molecules
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`(the effective optical axis of the liquid crystal layer) and the
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`polarized light transmission axis, E represents an applied
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`electric field intensity, dqfrepresent the effective thickness of
`the liquid crystal layer, An represents the refractive index
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`anisotropy of liquid crystal, and A represents the wavelength
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`oflight. The product ofthe effective thicknes s defofthe liquid
`crystal layer and the refractive index anisotropy An of the
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`liquid crystal, that is, d,f~A11 is called retardation. The thick-
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`ness defof the liquid crystal layer does not refer to the tl1ick-
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`ness of the whole liquid crystal layer but corresponds to the
`thickness ofthe liquid crystal layer which actually changes in
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`the alignment direction when a voltage is applied thereto.
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`This is because the liquid crystal molecules near the interface
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`of the liquid crystal layer do not change in the alignment
`direction due to the influence of anchoring at the interface
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`even when a voltage is applied thereto. Thus, assuming the
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`thickness of the whole liquid crystal
`layer sandwiched
`between the substrates is dm, the relationship de <dLC is
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`always found between the thicknesses dm and def The dif-
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`ference between them can be estimated at approximately 20
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`nm to 40 nm, although it depends on the liquid crystal mate-
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`rial used in the liquid crystal panel and the type of the inter-
`face in contact with the liquid crystal layer, for example the
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`material of the alignment film.
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`As apparent from the above equation, the term sing {26(E)}
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`depends on the electric field intensity, and the luminance can
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`be adjusted by changing the angle 6 in accordance with the
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`electric field intensity E. For the normally close type, polar-
`izing plates are set to satisfy 6"0 when no voltage is applied,
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`and it is sensitive to disturbance of the initial alignment direc-
`tion.
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`In this manner, the uniformity ofalignment is a very impor-
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`tant factor in the IPS scheme, and problems in the currently
`used rubbing tecmique have become apparent. In general, the
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`rubbing alignment processing includes many problems asso-
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`Page 12 of 30
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`Page 12 of 30
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`US 7,718,234 B2
`
`5
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`site of the structure which develops the alignment of liquid
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`crystal, it is difficult to say that the technique is preferable in
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`providing more uniform alignment of liquid crystal mol-
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`ecules and more resistant alignment. When low-molecular
`dichroic dye is dispersed in a polymer, the dye itself for
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`aligning liquid crystal is the low molecular substance, and
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`from the viewpoint ofpractical use, problems remain i11 terms
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`of reliability for heat and light.
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`ln addition, in the process ofirradiating particular polyim-
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`ide with polarized ultraviolet rays, the polyimide itself is
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`reliable in heat resistance or the like, but it is thought that the
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`alignment mechanism is caused by decomposition through
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`the light, and it is thus difficult to ensure sullicient reliability
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`for practical use. Specifically, when the liquid crystal align-
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`ment with the polarized light irradiation is applied in the
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`future, it is necessary not only to initially align the liquid
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`crystal but also to develop more stable alignment from the
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`viewpoint of reliability. lll view of actual industrial applica-
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`tion, selection of a thermally stable polymer structure is
`desired. From those points, the polymer material proposed
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`conventionally for the liquid ciystal alignment through light
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`irradiation is not sufficient in the alignment property and the
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`stability, which actually presents a significant problem in .
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`realizing the rubbing-less alignment through light irradiation.
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`Thus, it is an object of the present invention to provide,
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`particularly, a large-sized liquid crystal display capable of
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`solving the inherent problem of the small production margin
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`in the alignment processing in the lPS-TFT-LCD described 30
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`above, reducing the occurrence of defective display due to
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`variations in the initial alignment direction, realizing the
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`stable liquid crystal alignment, and having high image quality
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`with a higher contrast ratio. It is another object of the present
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`invention to provide a process ofproducing a high-quality and
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`high-definition liquid crystal display with excellent mass pro-
`ductivity.
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`To achieve the abovementioned objects, the present inven-
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`tion provides a liquid crystal display comprising: a pair of 40
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`substrates, at least one of the substrates being transparent; a
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`liquid crystal layer disposed between the pair of substrates; a
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`group ofelectrodes formed on one ofthe pair of substrates for
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`applying an electric field having a component substantially in
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`parallel with a surface of the substrate to the liquid crystal M
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`layer; a plurality of active devices connected to the group of
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`electrodes; an alignment control film disposed between the
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`liquid crystal layer and at least one of the pair of substrates;
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`and optical means formed on at least one of the pair of sub-
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`strates for changing the optical property of the liquid crystal <0
`layer in accordance with an alignnent state of molecules of i
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`said liquid crystal layer, wherein at least one of the alignment
`control films is an alignment control film comprising photo-
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`reactive polyimide andjor polyamic acid provided with an
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`alignment control ability by irradiation of substantially lin-
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`early polarized light.
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`The present invention is characterized in that liquid crystal
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`molecules in the liquid crystal layer on the alignment control
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`film have a long axis in a direction orthogonal to a polariza-
`tion axis of the substantially linearly polarized light for irra-
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`diation. In particular, it is desirable that the photoreactive
`alignment control film is polyamic acid or polyimide com-
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`prising at least cyclobutanetetracarboxylic acid dianhydride
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`as acid anhydride and at least aromatic diamine as diamine.
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`The present invention is characterized in that the cyclobu-
`tanetetracarboxylic acid dianhydride a11d its derivative are a
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`compound represented by a formula [l7]:
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`where R1, R2, R3, R4 each represent a hydrogen atom, a
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`fluorine atom, an alkyl group or alkoxyl group with a carbon
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`number of l to 6.
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`On the other hand, the aromatic diamine compound con-
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`tains at least one of compounds selected from a group of
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`compounds consisting of ones represented by formulas [18]
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`to [32]:
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`[13]
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`[19]
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`[20]
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`[31]
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`[22]
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`l
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`R
`_/_
`\ l /
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`R2
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`NH;
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`H7l\
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`NH;
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`Hzb
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`\ R2
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`Rt
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`HaN
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`NH)
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`R1)\\_..9\<‘R;
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`R
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`1
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`J?H2l\‘
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`’ /
`R2
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`X
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`R,
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`/ / NH;
`R4
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`R1
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`R3
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`.3”7.A XI
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`/1 \t
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`2F
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`5
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`10
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`15
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`35
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`55
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`Page 13 of 30
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`Page 13 of 30
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`US 7,718,234 B2
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`7
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`-continued
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`8
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`-continued
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`R3
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`R4
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`[31]
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`R1
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`R3/\‘—’/\R.1
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`R/\\_}‘~R,
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`l \
`l X
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`| \
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`HZN
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`H2N
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`R3
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`Page 14 of 30
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`10
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`15
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`[36]
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`[39]
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`5
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`R1
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`E
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`\
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`),Z°‘/
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`where R1, R2, R3, R4 each represent a hydrogen atom, a
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`fluorine atom, an alkyl group or alkoxyl group witl1 a carbon
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`number of 1 to 6, or a vinyl group 1 ———————(CHZ),,,———————CH:CH3.
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`111:0, 1, 2} or an acetyl group {—(CHZ)n—(‘,E(",H, 11:0, 1,
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`2}, and in the formula [5], X represents a bond group —S—,
`—CO-, ——NI~'I-—.
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`When the alignment control film is fonned as a thin film
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`l1avi11g a thickness from I 11111 to 10011111, the ligl1t transn1it-
`tance is improved and the efiiciency of light reaction with
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`polarized light irradiation is effectively improved. In addi-
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`tion, when the liquid crystal display is produced, the voltage
`for driving the liquid crystal is effectively applied to the liquid
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`crystal layer. Furthermore, when the alignment control filn1
`on the electrode is fonned as a thin film having a thickness
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`from 1 nm to 50 nm, and even from 1 nm to 30 nm, it is
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`possible to reduce a direct current voltage component (a
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`so-called residual DC voltage) remaining between the elec-
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`trode/alignment control film/liquid crystal layer/alignment
`control film/electrode in each pixel of the liquid crystal d's-
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`play, and after-image and persistence characteristics are
`effectively enhanced.
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`In addition. the present invention is characterized in tlr at
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`the liq