(12) United States Patent
`Kurahashi et al.
`
`USOO66.00541B2
`(10) Patent No.:
`US 6,600,541 B2
`(45) Date of Patent:
`Jul. 29, 2003
`
`(54) LIQUID CRYSTAL DISPLAY
`(75) Inventors: Nagatoshi Kurahashi, Mobara (JP);
`Masahiro Ishii, Mobara (JP); Yoshiaki
`Nakayoshi, Ooami (JP)
`(73) Assignee: Hitachi, Ltd., Tokyo (JP)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 99 days.
`
`(21) Appl. No.: 09/977,352
`(22) Filed:
`Oct. 16, 2001
`(65)
`Prior Publication Data
`US 2002/0051101A1 May 2, 2002
`Foreign Application Priority Data
`(30)
`Oct. 27, 2000 (JP) ....................................... 2000-328666
`(51) Int. Cl. ............................................. G02F 11/1336
`(52) U.S. Cl. ................
`... 349/141; 349/111
`(58) Field of Search .................................. 349/141, 111
`(56)
`References Cited
`U.S. PATENT DOCUMENTS
`6,097.454. A * 8/2000 Zhang et al. ................. 349/43
`
`6,160,601. A 12/2000 Sato ........................... 349/138
`
`* cited by examiner
`
`Primary Examiner James Dudek
`(57)
`ABSTRACT
`A liquid crystal display device which can prevent light leaks
`due to the influence of Signal lines includes, in each pixel
`area on a liquid-crystal-side Surface of one of Substrates
`disposed in opposition to each other with a liquid crystal
`interposed therebetween, a Switching element to be driven
`by Supply of a Scanning Signal from a gate Signal line, a pixel
`electrode to be Supplied with a Video signal from a drain
`Signal line via the Switching element, and a counter electrode
`which causes an electric field to be generated between the
`counter electrode and the pixel electrode. The counter elec
`trode is formed in a layer overlying the pixel electrode with
`an insulating film interposed between the counter electrode
`and the pixel electrode, and a conductive layer is formed in
`the same layer as the counter electrode and over a signal line
`which is at least one of the drain Signal line and the gate
`Signal line which lie in a layer underlying the insulating film,
`the conductive layer being Superposed on the Signal line.
`
`20 Claims, 10 Drawing Sheets
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`Page 1 of 20
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`

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`U.S. Patent
`
`Jul. 29, 2003
`
`Sheet 1 of 10
`
`US 6,600,541 B2
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`U.S. Patent
`
`Jul. 29, 2003
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`Sheet 2 of 10
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`U.S. Patent
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`Jul. 29, 2003
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`Sheet 3 of 10
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`US 6,600,541 B2
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`U.S. Patent
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`Jul. 29, 2003
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`Sheet 5 of 10
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`US 6,600,541 B2
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`ul. 29, 2003
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`U.S. Patent
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`Jul. 29, 2003
`
`Sheet 10 Of 10
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`US 6,600,541 B2
`
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`Page 11 of 20
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`1
`LIQUID CRYSTAL DISPLAY
`
`US 6,600,541 B2
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`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a liquid crystal display
`device and, more particularly, to a liquid crystal display
`device which is called In-Plane Switching Mode.
`2. Description of the Related Art
`A liquid crystal display device of the type which is called
`In-Plane Switching Mode has a construction in which a pixel
`electrode and a counter electrode are formed in each liquid
`crystal-Side pixel area of either one of the Substrates dis
`posed in opposition to each other with a liquid crystal
`interposed therebetween, So that the optical transmissivity of
`the liquid crystal is controlled by a component which is
`contained in an electric field generated between the pixel
`electrode and the counter electrode and which is nearly
`parallel to the Substrates.
`It has been known that one type of Such a liquid crystal
`display device has a construction in which its pixel electrode
`and its counter electrode are respectively formed in different
`layers with an insulating film interposed there between, and
`either one of the pixel and counter electrodes is formed as a
`transparent electrode formed in nearly the whole of each
`pixel area, while the other is formed as plural Stripe-shaped
`electrodes which are disposed in nearly the whole of each
`pixel are a in Such a manner as to be extended in one direct
`ion and to be juxtaposed in a direction traverse to the one
`direction.
`This kind of art is described in detail in, for example, K.
`Tarumi, M. Bremer, and B. Shuler, IEICE TRANS.
`ELECTRON, VOL. E79-C No. 8, pp. 1035-1039,
`AUGUST 1996.
`Incidentally, a So-called active matrix System is applied to
`Such a liquid crystal display device; for example, each of its
`pixel areas is Surrounded by adjacent ones of gate Signal
`lines disposed to be extended in the X direction and to be
`juxtaposed in they direction and by adjacent ones of drain
`Signal lines disposed to be extended in they direction and to
`be juxtaposed in the X direction, and each of the pixel areas
`is provided with a switching element to be driven by the
`Supply of a Scanning Signal from one of the adjacent gate
`Signal lines, and a pixel electrode to which a video signal is
`to be Supplied from one of the adjacent drain signal lines via
`this Switching element.
`However, it has been known that Such a liquid crystal
`display device Suffer light leaks which occur by its liquid
`crystal being driven by electric fields which are generated
`between its drain Signal lines or its gate Signal lines and
`electrodes disposed adjacently thereto.
`AS a counter measure against this phenomenon, there is a
`method which blockS light due to Such light leaks by means
`of a black matrix formed on the opposite transparent Sub
`strate. However, in this method, the width of the black
`matrix needs to be ensured to Some extent, So that a
`disadvantage Such as a reduction in the aperture ratio of each
`pixel can not be avoided. Accordingly, a Solution using
`another method has been desired.
`A thin film transistor which is a Switch element is made
`of a Stacked Structure in which a gate electrode connected to
`a gate signal, a gate insulating film, a Semiconductor layer,
`a drain electrode connected to a drain signal line, and a
`Source electrode connected to a pixel electrode are Stacked
`in that order on the substrate. However, it has been pointed
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`out that electric charge is easily irregularly charged on the
`side of the surface of the semiconductor layer on which the
`individual electrodes are formed (this phenomenon is called
`a back channel), So that non-uniformity occurs in the char
`acteristics of individual thin film transistors.
`SUMMARY OF THE INVENTION
`The invention has been made in view of the above
`described problems, and provides a liquid crystal display
`device in which light leaks due to the influence of Signal
`lines are prevented.
`The invention also provides a liquid crystal display device
`provided with thin film transistors having Stable character
`istics in which no back channels occur.
`Representative aspects of the invention disclosed in the
`present application will be described below in brief.
`A liquid crystal display device includes, for example, in
`each pixel area on a liquid-crystal-Side Surface of one of
`Substrates disposed in opposition to each other with a liquid
`crystal inter posed there between, a Switching element to be
`driven by Supply of a Scanning Signal from a gate Signal line,
`a pixel electrode to be Supplied with a video Signal from a
`drain Signal line via the Switching element, and a counter
`electrode which causes an electric field to be generated
`between the counter electrode and the pixel electrode. The
`counter electrode is formed in a layer overlying the pixel
`electrode with an insulating film interposed between the
`counter electrode and the pixel electrode, and a conductive
`layer is formed in the same layer as the counter electrode and
`over a signal line which is at least one of the drain Signal line
`and the gate Signal line which lie in a layer underlying the
`insulating film, the conductive layer being Superposed on the
`Signal line.
`According to the liquid crystal display device constructed
`in this manner, the conductive layer can have the function of
`a light Shielding film, and can prevent light leaks due to the
`influence of Signal lines.
`In addition, Since this light Shielding film is formed on a
`Substrate on which the Signal lines are formed, the light
`shielding film can be formed to have a width sufficient to
`prevent the light leaks, whereby the width can be set to be
`comparatively Small.
`In the case where the conductive layer is formed to cover
`the gate Signal line, the conductive layer is also formed to
`cover the thin film transistor formed to be superposed on the
`gate signal line (with the insulating film being interposed
`between the conductive layer and the thin film transistor).
`Accordingly, if electric charge is present in the insulating
`film on the thin film transistor, the distribution of the electric
`charge can be Stabilized by the conductive layer, whereby it
`is possible to obtain Stable characteristics which do not
`allow back channels to occur in the thin film transistor.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The invention will become more readily appreciated and
`understood from the following detailed description of pre
`ferred embodiments of the invention when taken in con
`junction with the accompanying drawings, in which:
`FIG. 1 is a cross-sectional view, taken along line I-I of
`FIG. 3, of a pixel of a liquid crystal display device according
`to the invention;
`FIG. 2 is an equivalent circuit diagram showing one
`embodiment of the liquid crystal display device according to
`the invention;
`FIG. 3 is a plan view showing one embodiment of a pixel
`of the liquid crystal display device according to the inven
`tion;
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`US 6,600,541 B2
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`3
`FIG. 4 is across-sectional view taken along line IV-IV of
`FIG. 3;
`FIG. 5 is a cross-sectional view taken along line V V of
`FIG. 3;
`FIG. 6 is a plan view showing another embodiment of a
`pixel of the liquid crystal display device according to the
`invention;
`FIG. 7 is a cross-sectional view taken along line VII-VII
`of FIG. 6;
`FIG. 8 is a plan view showing another embodiment of a
`pixel of the liquid crystal display device according to the
`invention.
`FIG. 9 is a plan view showing another embodiment of a
`pixel of the liquid crystal display device according to the
`invention;
`FIG. 10 is a plan view showing another embodiment of a
`pixel of the liquid crystal display device according to the
`invention;
`FIG. 11 is a plan view showing another embodiment of a
`pixel of the liquid crystal display device according to the
`invention;
`FIG. 12 is a cross-sectional view taken along line XII
`XII of FIG. 11; and
`25
`FIG. 13 is a cross-sectional view taken along line XIII
`XIII of FIG. 11.
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`from one of the adjacent gate Signal line S GL, and a video
`Signal (voltage) is Supplied to the pixel electrode PX from
`one of the adjacent drain Signal lines DL via the thin film
`transistor TFT.
`A capacitance element Cstg is formed between the pixel
`electrode PX and the other of the adjacent gate Signal lines
`GL so that when the thin film transistor TFT is turned off, a
`video signal supplied to the pixel electrode PX is stored for
`along time by this capacitance element Cstg.
`The pixel electrode PX in each of the pixel areas is
`arranged to cause an electric field having a component
`nearly parallel to the transparent substrate SUB1 to be
`generated between this pixel electrode PX and an adjacent
`one of the counter electrodes CT, there by controlling the
`optical transmissivity of the liquid crystal in the correspond
`ing one of the pixel areas.
`One end of each of the gate signal lines GL is formed to
`be extended to one side (in FIG. 2, the left-hand side) of the
`transparent Substrate SUB1, and the extended portion is
`formed as a terminal part GTM which is connected to a
`bump of a semiconductor integrated circuit GDRC made of
`a vertical Scanning circuit mounted on the transparent Sub
`strate SUB1. In addition, one end of each of the drain signal
`lines DL is formed to be extended to one side (in FIG. 2, the
`top side) of the transparent substrate SUB1, and the
`extended portion is formed as a terminal part DTM which is
`connected to a bump of a Semiconductor integrated circuit
`DDRC made of a video signal driver circuit made mounted
`on the transparent substrate SUB1.
`The semiconductor integrated circuits GDRC and DDRC
`in themselves are completely mounted on the transparent
`substrate SUB1 by a technique which is called COG (chip on
`glass).
`The input-Side bumps of each of the Semiconductor
`integrated circuits GDRC and DDRC are respectively con
`nected to terminal parts GTM2 and DTM2 formed on the
`transparent substrate SUB1. These terminal parts GTM2 and
`DTM2 are respectively connected via individual inter con
`nection layers to terminal parts GTM3 and DTM3 which are
`disposed in the peripheral portions of the transparent Sub
`strate SUB1 that are respectively closest to different side
`edges of the transparent substrate SUB1.
`The counter Voltage Signal lines CL are connected in
`common at their ends (in FIG. 2, their right-hand ends) and
`are extended to one side of the transparent Substrate SUB1
`and connected to a terminal part CTM.
`The transparent substrate SUB2 is disposed in opposition
`to the transparent substrate SUB1 in such a manner as to
`avoid an area in which the Semiconductor integrated circuits
`DDRC and GDRC are mounted, and the area of the trans
`parent substrate SUB2 is smaller than that of the transparent
`Substrate SUB1.
`The transparent substrate SUB2 is secured to the trans
`parent substrate SUB1 by a sealing material SL formed in
`the periphery of the transparent Substrate SUB2, and this
`Sealing material SL also has the function of Sealing the liquid
`crystal between the transparent substrates SUB1 and SUB2.
`Incidentally, the above description has referred to a liquid
`crystal display device of the type which uses a COG method,
`but the invention can also be applied to a liquid crystal
`display device of the type which uses a TCP method. The
`TCP method is to form a semiconductor integrated circuit by
`a tape carrier method, and the outer terminals of the Semi
`conductor integrated circuit are respectively connected to
`terminal parts formed on the transparent Substrate SUB1,
`while the input terminals of the Semiconductor integrated
`circuit are respectively connected to terminal parts on a
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`DETAILED DESCRIPTION OF THE
`INVENTION
`Embodiments of a liquid crystal display device according
`to the invention will be described below with reference to
`the accompanying drawings
`Embodiment 1
`<<Equivalent Circuitas
`FIG. 2 is a view showing the equivalent circuit of a liquid
`crystal display device according to the invention. FIG. 2 is
`an equivalent circuit diagram which is depicted in accor
`dance with the actual geometrical layout of the liquid crystal
`display device.
`In FIG. 2, there is shown a transparent substrate SUB1.
`This transparent substrate SUB1 is disposed in opposition to
`another transparent substrate SUB2 with a liquid crystal
`interposed therebetween.
`Gate Signal lines GL and drain Signal lines DL are formed
`on a liquid-crystal-Side Surface of the transparent Substrate
`SUB1 are. The gate signal lines GL are disposed to be
`extended in the X direction and to be juxtaposed in the y
`direction as viewed in FIG.2, while the drain signal lines DL
`are insulated from the gate Signal lines GL and are disposed
`50
`to be extended in they direction and to be juxtaposed in the
`X direction as viewed in FIG. 2. Rectangular are as each of
`which is Surrounded by adjacent ones of the gate Signal lines
`GL and adjacent ones of the drain Signal lines DL constitute
`pixel areas, respectively, and a display part AR is formed by
`an aggregation of these pixel areas.
`Counter Voltage Signal lines CL, which are disposed in
`parallel with the respective gate Signal lines GL, are formed
`between the respective gate signal lineS GL. Each of these
`counter Voltage Signal lines CL is Supplied with a signal
`(voltage) which serves as a reference for a video signal
`(which will be described later), and is connected to counter
`electrodes CT (which will be described later) in the corre
`sponding ones of the pixel areas, respectively.
`A thin film transistor TFT and a pixel electrode PX are
`formed in each of the pixel areas. The thin film transistor
`TFT is driven by the Supply of a Scanning signal (voltage)
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`printed circuit board which is disposed close to the trans
`parent substrate SUB1.
`<<Construction of Pixeld>
`FIG. 3 is a view showing the construction of one embodi
`ment of a pixel of the liquid crystal display device according
`to the invention, and is a plan view showing the portion
`surrounded by a dotted frame A in FIG. 2. FIG. 1 shows a
`cross-sectional view taken along line I-I of FIG. 3, FIG. 4
`shows a cross-sectional view taken along line IV-IV of
`FIG. 3, and FIG. 5 shows a cross-sectional view taken along
`line V-V of FIG. 3.
`Incidentally, the liquid crystal display device according to
`this embodiment is constructed to operate in a normally
`black mode in which black display is provided when electric
`fields having components nearly parallel to the transparent
`substrate SUB1 are not generated between its pixel elec
`trodes PX and its counter electrodes CT, and the normally
`black mode can be set according to the characteristic of
`liquid crystal (in this embodiment, for example, a p-type
`characteristic), the direction of an electric field between each
`of the pixel electrodes PX and the corresponding one of the
`counter electrodes CT, the rubbing direction of an alignment
`layer ORI, and the direction of the axis of transmission of
`light polarized by a polarizer POL.
`Referring first to FIG. 3, a gate signal line GL which is
`disposed to be extended in the X direction of FIG. 3 is
`formed on the surface of the transparent Substrate SUB1 on
`the bottom Side of the shown pixel area. This gate Signal line
`GL is made of, for example, Cr or a Cr alloy.
`This gate Signal line GL is formed to Surround the pixel
`area together with a corresponding gate signal line GL (not
`shown) which is positioned on the top side of the pixel area,
`a drain signal line DL which will be described later, and a
`corresponding drain signal line which is positioned on the
`right-hand Side of the pixel area.
`A counter Voltage Signal line CL which runs in parallel
`with the gate Signal lines GL is formed between the gate
`Signal line S GL. This counter Voltage Signal line CL is
`formed at the same time that, for example, the gate Signal
`lines GL are formed, and is made of, for example, Cr or a Cr
`alloy.
`In FIG. 2, this counter voltage signal line CL is shown to
`be disposed close to one of the gate Signal lines GL, but in
`this embodiment, the counter Voltage Signal line CL is
`formed to pass through nearly the center of the pixel area. In
`this case, it is possible to reliably prevent connection
`between the counter Voltage Signal line CL and the gate
`Signal lines GL, and it is possible to improve the manufac
`turing yield factor of the liquid crystal is play device.
`An insulating film GI made of, for example, SiN is formed
`to cover the gate signal line GL and others on the Surface of
`the transparent Substrate SUB1 on which the gate Signal
`lines GL and the counter Voltage signal lines CL are formed
`in the above-described manner (refer to FIGS. 1, 4 and 5).
`This insulating film GI has the function of an interlayer
`insulating film between the drain signal lines DL (which will
`be described later) and the gate Signal lines GL as well as the
`counter Voltage Signal lines CL, the function of gate insu
`lating films with respect to the thin film transistors TFT
`which will be described later, and the function of dielectric
`films with respect to the capacitance elements Cstg which
`will be described later.
`A Semiconductor layer AS made of, for example, amor
`phous Si (a-Si) is formed on the top surface of the portion
`of the insulating film GI that is Superposed on the gate Signal
`line GL.
`This Semiconductor layer as constitutes a Semiconductor
`layer of the thin film transistor TFT, and a drain electrode
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`SD1 and a source electrode SD2 are formed on the top
`Surface of the Semiconductor layer AS, the reby forming a
`MIS type transistor having a reversed-staggered Structure
`which uses part of the gate signal line GL as its gate
`electrode.
`Incidentally, the Semiconductor layer AS is formed not
`only in an area in which the thin film transistor TFT is
`formed, but also in an area in which the drain signal line DL
`which will be described later is formed. The reason for this
`is to give the Semiconductor layer AS as well as the
`insulating film GI the function of an interlayer insulating
`film between the drain Signal lines DL and the gate Signal
`lines GL as well as the counter Voltage Signal line S CL.
`The drain electrode SD1 of the thin film transistor TFT is
`formed at the Same time as the drain Signal line DL, and the
`Source electrode SD2 is formed at the same time as the pixel
`electrode PX.
`Specifically, the drain signal line DL which is extended in
`they direction in FIG. 3 is formed on the insulating film GI,
`and part of the drain signal line DL is formed to be extended
`onto the top Surface of the Semiconductor layer AS, whereby
`the drain electrode SD1 is formed. The drain signal line DL
`and the drain electrode SD1 are formed of, for example, Cr
`or a Cr alloy.
`In addition, plural (in FIG. 3, three) pixel electrodes PX
`which are disposed to be extended in they direction and to
`be juxtaposed in the X direction in FIG. 3 are formed in the
`central portion of the pixel area except a Small-width periph
`ery thereof, and these pixel electrodes PX are electrically
`connected to one another in the pattern of being connected
`to one another on the counter Voltage Signal line CL. These
`pixel electrodes PX are formed at the same time that the
`drain signal lines DL are formed, and are made of, for
`example, Cr or a Cr alloy.
`Each of the pixel electrodes PX is of a ZigZag shape
`having Several bends along its extension direction. This
`ZigZag shape will be described later together with the
`counter electrodes.
`Among the pixel electrodes PX, the pixel electrode PX
`closest to the thin film transistor TFT is extended on to the
`top Surface of the Semiconductor layer AS at one end,
`whereby the source electrode SD1 is formed.
`A protective film PSV which is made of a stacked
`structure in which an inorganic film PSV1 made of SiN or
`the like and an organic film PSV2 made of resin film of the
`like are stacked in that order is formed to cover the thin film
`transistor TFT and others on the surface of the transparent
`Substrate SUB1 on which the thin film transistors TFT, the
`drain signal lines DL and the pixel electrodes PX are formed
`in the above-described manner (refer to FIGS. 1, 4 and 5).
`This protective film PSV is formed chiefly in order to
`prevent the thin film transistor TFT from coming into direct
`contact with a liquid crystal LC.
`The reason why the organic film PSV2 made of resin film
`or the like is used as a part of the protective film PSV is that
`since the dielectric constant of the organic film PSV2 is low,
`it is possible to reduce a capacitance which occurs between
`an electrode or a signal line positioned to underlie the
`protective film PSV and an electrode or a signal line
`positioned to overlie the protective film PSV. The organic
`film PSV2 can easily be made thick compared to the
`inorganic film PSV1, and the surface of the organic film
`PSV2 can easily be made flat compared to the inorganic film
`PSV1. Accordingly, it is possible to obtain the advantage of
`preventing application defect of alignment film which
`occurs due to Steps of edge portions of interconnection lines
`on the transparent substrate SUB1, initial alignment defect
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`due to shadows during rubbing, and Switching abnormality
`(domain) of liquid crystal
`Plural (in FIG. 3, two) counter electrodes CT which are
`disposed to be extended in they direction and to be juxta
`posed in the X direction in FIG. 3 are formed on the top
`surface of the protective film PSV, and these counter elec
`trodes CT are formed so that the counter electrodes CT and
`the pixel electrodes PX are alternately arranged with Spaces
`being interposed between each of the counter electrodes CT
`and the adjacent ones of the pixel electrodes PX, respec
`tively The counter electrodes CT are formed from a trans
`parent conductive film Such as an ITO (Indium-Tin-Oxide)
`film or an IZO (Indium-Zinc-Oxide) film.
`The counter electrodes CT are constructed to be electri
`cally connected in the pattern of being connected to each
`other in an area which is Superposed on the counter Voltage
`Signal line CL, and in a portion of this area, the counter
`electrodes CT are connected to the counter Voltage Signal
`line CL via a contact hole TH which is formed in the
`protective film PSV (the organic film PSV2 and the inor
`ganic film PSV1).
`The formation of this contact hole TH is performed above
`the counter Voltage Signal line CL So that a reduction in
`aperture ratio can be avoided. In this case, a connection
`portion where the pixel electrodes PX are connected to one
`another is formed in a pattern which avoids a portion where
`the contact hole TH is formed, in order to prevent interfer
`ence between the connection portion and the contact hole
`TH.
`Each of the counter electrodes CT is formed in a ZigZag.
`shape in which it is extended from one end toward the other
`end in the state of being bent first in a 0 direction (with
`respect to the y direction in FIG. 3), then in a -0 direction
`(with respect to the y direction in FIG. 3), and again in the
`0 direction (with respect to they direction in FIG.3). In this
`ZigZag shape, the angle 0 is Set to be greater than 0 and
`less than 45 ), preferably with in the range of 5
`to 30).
`The pixel electrodes PX are bent similarly to the counter
`electrodes CT, and are formed in a pattern in which if either
`the pixel electrodes PX or the counter electrodes CT are
`shifted in an X direction in FIG. 3, both electrodes PX and
`CT can be Superposed on one another.
`The reason why the pixel electrodes PX and the counter
`electrodes CT are formed in this pattern is that this embodi
`ment adopts a So-called multi domain Scheme in which
`domains are formed So that the directions of electric fields to
`be generated between the pixel electrodes PX and the
`counter electrodes CT differ from domain to domain,
`thereby canceling variations in color tone which occur when
`the display area is viewed in different directions with respect
`to the display Surface of the liquid crystal display device.
`In this embodiment, a first conductive layer CND1 which
`has nearly the same central ax is as the drain Signal line DL
`and is wider than the drain Signal line DL is formed over an
`area in which the drain signal line DL is formed. In other
`words, the first conductive layer CND1 is formed in the state
`of completely covering the drain Signal line DL without
`allowing the drain Signal line DL to be exposed when the
`transparent Substrate SUB1 is viewed in a direction perpen
`dicular thereto. The first conductive layer CND1 is formed
`at the same time that the counter electrodes CT are formed,
`so that the first conductive layer CND1 is made of an ITO
`film or an IZO film.
`The first conductive layer CND1 is held at the same
`potential as the counter electrodes CT.
`Although the first conductive layer CND1 is formed of a
`transparent conductive layer made of, for example, an ITO
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`film, the first conductive layer CND1 functions as a light
`Shielding film which prevents light leak due to an electric
`field which drives the liquid crystal in the vicinity of the
`drain Signal line DL.
`Specifically, as described previously, this liquid crystal
`display device is constructed to operate in a normally black
`mode in which black display is provided when electric fields
`having components nearly parallel to the transparent Sub
`strate SUB1 are not generated between the pixel electrodes
`PX and the counter electrodes CT. In this construction,
`above the first conductive layer CND1, a large number of
`electric fields are generated in a direction nearly perpen
`dicular to the transparent substrate SUB1 and no electric
`fields having components nearly parallel to the transparent
`substrate SUB1 are generated, where by black display is
`provided and the first conductive layer CND1 can be used in
`place of a light Shielding film.
`In addition, the first conductive layer CND1 can terminate
`electric fields generated from the drain Signal line DL, and
`can therefore restrain the electric fields from terminating on
`the side of the pixel electrode PX adjacent to the drain signal
`line DL.
`The first conductive layer CND1 is at the same potential
`as the counter electrodes CT, whereby the electric fields
`from the drain Signal line DL can easily be terminated in this
`first conductive layer CND1. In addition, in this case, the
`fact that the protective film PSV is constructed as a stacked
`structure in which the protective film PSV2 made of a resin
`layer of low dielectric constant is used as its upper layer
`makes it easy to terminate the electric fields from the drain
`signal line DL in the first conductive layer CND1.
`Owing to this fact, the pixel electrodes PX enable only
`electric fields based on a Video signal transmitted via the thin
`film transistor TFT to be generated between the pixel
`electrodes PX and the counter electrodes CT, and electric
`fields which become noise do not enter from the drain Signal
`line DL, whereby it is possible to realize a construction
`which can avoid display defect.
`In addition, since the first conductive layer CND1 is at the
`Same potential as the counter electrodes CT as described
`above, the first conductive layer CND1 also functions as a
`counter electrode CT which causes an electric field to be
`generated between the counter electrode CT and the pixel
`electrode PX disposed adjacent there to.
`This fact means that if the Space of the pixel area and the
`number of the electrodes PX and CT per pixel area are set
`in advance, a pair of counter electrodes CT can be disposed
`outside the pixel area (over the drain signal line DL),
`whereby the aperture ratio per pixel can be improved.
`An alignment film ORI1 which also covers the pixel
`electrodes PX is formed on the Sur face of the transparent
`substrate SUB1 on which the pixel electrodes PX are formed
`in this manner. This alignment film ORI1 is a film which is
`indirect contact with the liquid crystal LC to restrict the
`initial alignment direction of the molecules of the liquid
`crystal LC. In this embodiment, the rubbing direction of the
`alignment film ORI1 coincides with the direction of exten
`Sion of the drain Signal lines DL.
`Incidentally, a polarizer POL1 is formed on the surface of
`the transparent substrate SUB1 opposite to the liquid crystal
`LC, and the direction of the polarization axis of the polarizer
`POL1 is the same as or perpendicular to the rubbing direc
`tion of the alignment film ORI1.
`A black matrix BM is formed on the liquid-crystal-side
`surface of the transparent Substrate SUB2 which is disposed
`in oppos