US20020008830A1 - Active matrix liquid crystal display device - Google Patents

Active matrix liquid crystal display device Download PDF

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Publication number
US20020008830A1
US20020008830A1 US09/906,073 US90607301A US2002008830A1 US 20020008830 A1 US20020008830 A1 US 20020008830A1 US 90607301 A US90607301 A US 90607301A US 2002008830 A1 US2002008830 A1 US 2002008830A1
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liquid crystal
electrode
electric field
drain electrode
parallel
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Kimikazu Matsumoto
Shinichi Nishida
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Tianma Japan Ltd
Getner Foundation LLC
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NEC Corp
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Priority to US10/656,138 priority Critical patent/US7009673B2/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1343—Electrodes
    • G02F1/134309—Electrodes characterised by their geometrical arrangement
    • G02F1/134363—Electrodes characterised by their geometrical arrangement for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G02F1/13378—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation
    • G02F1/133784—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation by rubbing
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/136—Liquid crystal cells structurally associated with a semi-conducting layer or substrate, e.g. cells forming part of an integrated circuit
    • G02F1/1362—Active matrix addressed cells
    • G02F1/1368—Active matrix addressed cells in which the switching element is a three-electrode device

Definitions

  • the present invention relates to an active matrix liquid crystal display device and, more particularly, to an active matrix liquid crystal display device in which the residual image phenomenon is prevented.
  • a liquid crystal display device is adopted in many fields such as a viewfinder for a video camera, a pocket TV, a high-resolution projection TV, a personal computer, and the like.
  • an active matrix liquid crystal display device using a thin-film-transistor (TFT) as a switching element has a major feature that it can maintain a high contrast even when it performs high-capacity display, and accordingly it has been developed and commercialized actively.
  • TFT thin-film-transistor
  • the above active matrix liquid crystal display device widely employs the TN (Twisted-Nematic)-method NW (Normally-White) mode as the liquid crystal display mode.
  • NW Normally-White
  • a panel which is formed of electrode substrates sandwiching a liquid crystal layer such that liquid crystal molecules are twisted by about 90°, is sandwiched between two polarizing plates.
  • NW mode two polarizing plates are arranged such that their polarizing axes are orthogonal and become parallel or perpendicular to the major axis of liquid crystal molecules in contact with one substrate.
  • the liquid crystal display device displays white.
  • the light transmittance of the liquid crystal display device gradually decreases, and the liquid crystal display device displays black.
  • Japanese Examined Patent Publication No. 63-21907, Japanese Unexamined Patent Publication No. 7-36058, and the like propose so-called transverse electric field method IPS (In-Plane-Switching), with which an electric field is not applied in a direction perpendicular to the substrates, as in the TN liquid crystal display method, but the electric field to be applied to the liquid crystal is set substantially parallel to the substrates, and the direction of liquid crystal molecules is controlled within the substrate surfaces, thus modulating light.
  • IPS In-Plane-Switching
  • a normally-black IPS liquid crystal display device (shown in FIG. 1) utilizing the TFT characteristics will be described as an example.
  • Normally-black is a display method for a liquid crystal display device, with which the polarizing axes of the polarizing layers are arranged such that the display device displays black when no voltage difference is produced between a pixel electrode 24 for driving the liquid crystal and a common electrode 14 and the liquid crystal is orientated at the initial alignment angle, and such that the display device displays white when a voltage difference is applied between the pixel electrode 24 and common electrode 14 and the liquid crystal is rotated (ideally through 45°) from initial alignment.
  • the liquid crystal is initially aligned with an inclination of about 15°, as indicated by an alternate long and short dashed line, with respect to the pixel electrode 24 and common electrode 14 which form comb electrodes fitted with each other, and rotates in only a specific direction upon application of a voltage between the pixel electrode 24 and common electrode 14 .
  • the absorbing axes of the polarizing plates are aligned with the initial alignment direction of the liquid crystal, and an appropriate retardation ⁇ nd (product of a refractive index anisotropy ⁇ n of the liquid crystal and the effective thickness d0 of the liquid crystal layer) is set, so the display device can perform colorless white display and black display.
  • a TFT element serves as a switch which is turned on/off by the voltage applied to the gate electrode.
  • a sufficiently negative potential approximately about ⁇ 10 V although it may differ depending on the arrangement of the TFT element
  • movement of the charges in a-Si decreases, so a signal voltage from the drain electrode is not transmitted to the source electrode.
  • the signal voltage is not applied to a pixel electrode electrically connected to the source electrode, either.
  • a light-shielding layer is formed on a color filter unit side.
  • Light entering a region (non-open portion) other than the pixel electrodes and common electrode which form comb teeth is shielded by the light-shielding layer.
  • the state of alignment of the liquid crystal is the same as that of the open region, so display is not adversely affected.
  • the present inventors found that residual image which was not conventionally solved in the liquid crystal display device was related to a change in TFT characteristics of each pixel. More specifically, according to the findings of the present inventors, when the liquid crystal display device displays a fixed pattern, a change occurs in the characteristics of the TFT element of a pixel which displays white and of the TFT. element of a pixel which displays black, thus causing a residual image.
  • the alignment state of the liquid crystal molecules on the TFT element gradually shifts from the initial state due to the electric field generated between the drain electrode and source electrode. Due to this shift, the electric field enters the amorphous silicon portion of the TFT element differently in the case of white display and in the case of black display. As a result, the subsequent display state changes.
  • the present invention has been made in view of the above situation of the prior art, and has as its object to provide an active matrix liquid crystal display device in which even if the TFT element operates, the orientation of the liquid crystal on the TFT element does not change from the initial alignment angle. Therefore, a liquid crystal display device is provided in which the characteristics of the TFT element do not change during display, and even after a fixed pattern is kept displayed for a long period of time, no residual image phenomenon occurs.
  • the shapes of the drain electrode and source electrode are determined such that the direction of the electric field generated between the drain electrode and source electrode coincides with the rubbing direction.
  • the drain electrode and source electrode are formed such that their opposing edges are perpendicular to the rubbing direction.
  • the shape of amorphous silicon may be inclined to match the rubbing direction.
  • Partial rubbing is performed by using an alignment film which can be imparted with an alignment function upon being irradiated with light (the sixth embodiment to be described later).
  • a liquid crystal with a negative dielectric constant anisotropy is used.
  • the liquid crystal must be imparted with initial alignment in a direction perpendicular to the direction of the electric field generated between the drain electrode and source electrode (the seventh embodiment to be described later).
  • the drain electrode, the source electrode, and amorphous silicon are formed inclined to be parallel to the rubbing direction. (the eighth embodiment to be described later).
  • the electric field generated by the source electrode and drain electrode in the TFT element is set parallel to the rubbing direction, and a pixel electrode and common electrode within at least the display region are formed parallel to the rubbing direction (the ninth embodiment to be described later).
  • the electric field generated by the source electrode and drain electrode in the TFT element is set parallel to the rubbing direction, and a pixel electrode and common electrode at least within the display region are formed to have an L shape (the 10th and 11th embodiments to be described later).
  • the liquid crystal alignment on the TFT element is always constant and does not change in accordance with the state of liquid crystal display.
  • occurrence of the residual image phenomenon accompanying a change in TFT characteristics can be suppressed, so a high-quality active matrix liquid crystal display device can be provided.
  • FIG. 1 is a plan view showing an active element substrate unit in a conventional active matrix liquid crystal display device
  • FIG. 2 is a graph of TFT characteristics that change such that the OFF voltage increases
  • FIG. 3 is a graph of TFT characteristics that change such that the ON voltage increases
  • FIG. 4 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the first embodiment of the present invention
  • FIG. 5 is a sectional view taken along the line V-V of FIG. 4;
  • FIG. 6 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the second embodiment of the present invention.
  • FIG. 7 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the third embodiment of the present invention.
  • FIG. 8 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the fourth embodiment of the present invention.
  • FIG. 9 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the seventh embodiment of the present invention.
  • FIG. 10 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the eighth embodiment of the present invention.
  • FIG. 11 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the ninth embodiment of the present invention.
  • FIG. 12 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the 10th embodiment of the present invention.
  • FIG. 13 is a plan view showing an active element substrate unit in an active matrix liquid crystal display device according to the 11 th embodiment of the present invention.
  • FIG. 14 is a plan view showing a modification to the eighth embodiment shown in FIG. 10.
  • FIG. 4 is a plan view
  • FIG. 5 is a sectional view taken along the line V-V of FIG. 4.
  • a liquid crystal panel 2 is comprised of an active element substrate unit 4 , color filter unit 6 , and liquid crystal.
  • the active element substrate unit 4 will be described first.
  • Cr is sputtered to about 1,000 ⁇ (10,000 nm) at a predetermined region on a first glass substrate (TFT substrate) 10 , and is patterned to form a scanning signal line 12 and common electrode 14 . Then, a silicon nitride film and silicon oxide film as insulators are formed on the glass substrate 10 by CVD to a total of about 5,000 ⁇ so as to cover the scanning signal line 12 and common electrode 14 , thus forming a gate insulating film 16 .
  • An a-Si layer and n + a-Si layer are formed by CVD in a predetermined region to about 3,000 ⁇ and 500 ⁇ , respectively, and are patterned to form island-like amorphous silicon 18 .
  • Cr is sputtered to about 1,000 ⁇ on the gate insulating film 16 and island-like amorphous silicon 18 , and is patterned to form a drain electrode 20 , data line 21 , source electrode 22 , and pixel electrode 24 .
  • the island-like amorphous silicon 18 , drain electrode 20 , and source electrode 22 make up a TFT element.
  • the drain electrode 20 and source electrode 22 are formed such that their opposing edges are inclined by an angle ⁇ , and an initial alignment angle ⁇ formed by rubbing (to be described above) and the angle ⁇ coincide with each other.
  • the initial alignment angle ⁇ and angle ⁇ are angles measured with reference to the longitudinal directions of the pixel electrode 24 and common electrode 14 (also called a comb electrode).
  • SiN as an insulator is formed on the entire region on the gate insulating film 16 to about 3,000 ⁇ by CVD to form a passivation film 32 .
  • the passivation film 32 and gate insulating film 16 are etched in a predetermined region to form a hole communicating with the scanning signal line 12 . This hole is filled with Cr or the like to form a contact (not shown).
  • the unit formed in this manner is called the active element substrate unit 4 . Note that the widths of the pixel electrode 24 and common electrode 14 are set to 4.5 ⁇ m and that the distance between the pixel electrode 24 and common electrode 14 is set to 10 ⁇ m.
  • the color filter unit 6 is formed by forming a light-shielding layer 42 , color layer 44 , and planarized film 46 into a predetermined pattern in a predetermined region on the inner surface of a second glass substrate (counter substrate) 40 .
  • a transparent conductive film 48 made of ITO or the like is formed on the lower surface of the second glass substrate 40 by sputtering in order to prevent display nonuniformity which is caused by charge-up when the operator touches the liquid crystal panel with his hand.
  • An alignment film 60 is formed on the surface of each of the active element substrate unit 4 and color filter unit 6 by off set printing or the like, and is subjected to rubbing by the rubbing method such that the initial alignment angle becomes ⁇ .
  • the initial alignment direction is indicated by an alternate long and short dashed line.
  • An inner-cell spacer or the like (not shown) is placed between the active element substrate unit 4 and color filter unit 6 to form a predetermined gap, and a nematic liquid crystal 50 is sealed in it with a sealing agent (not shown) and a hole closing material (not shown), thus forming the liquid crystal panel 2 .
  • the liquid crystal molecules of the nematic liquid crystal 50 are initially aligned parallel such that they are inclined with respect to the pixel electrode 24 and common electrode 14 at the angle ⁇ (15°; the angle need not be 15° but may take other values).
  • liquid crystal material a nematic liquid crystal with a positive dielectric constant anisotropy ⁇ of 8.0 (589 nm, 20° C.), a refractive index anisotropy ⁇ n of 0.075, and a liquid crystal resistivity of 1.0 ⁇ 10 12 ⁇ cm is used.
  • the thickness of the liquid crystal layer (cell gap) is set to 4.0 ⁇ m.
  • Polarizing plates 62 are arranged on the upper and lower surfaces of the liquid crystal panel 2 .
  • the state of alignment of the nematic liquid crystal 50 is changed upon application of an external signal voltage, to control the strength of light transmitted through the liquid crystal panel 2 , so that the liquid crystal display device (not shown) performs gradation display.
  • the liquid crystal display device When no potential difference is applied between the pixel electrode 24 and common electrode 14 , the liquid crystal display device displays black. When a potential difference is applied between the pixel electrode 24 and common electrode 14 to form an electric field almost parallel to the glass substrate 10 , and the liquid crystal is rotated through almost 45° from the initial alignment angle so the strength of the transmitted light becomes the maximum, the liquid crystal display device displays white (normally-black method).
  • the liquid crystal panel 2 obtained in this manner was built as a liquid crystal display device in a driving unit (not shown), and was subjected to a residual image test.
  • an active element substrate unit 4 is formed in the following manner. A description on the same steps, members, and the like as those in the first embodiment will be omitted.
  • the opposing edges of a drain electrode 20 and source electrode 22 form the right angles with the longitudinal direction of the comb electrode formed of a pixel electrode 24 and common electrode 14 , and an alignment film 60 is rubbed to have an initial alignment angle ⁇ .
  • the drain electrode 20 and source electrode 22 are subjected to rubbing such that they are parallel to the longitudinal direction of the comb electrode.
  • liquid crystal molecules are aligned parallel by rubbing such that they are inclined at ⁇ (15°) with respect to the longitudinal direction of the comb electrode.
  • a negative photosensitive resist is printed by a spin coater, and those portions of the resist which are on the drain electrode 20 and source electrode 22 are removed by photolithography.
  • a display device formed of the liquid crystal panel 2 obtained in this manner was subjected to a residual image test.
  • the direction of the electric field and the liquid crystal alignment coincide, in the same manner as in the first embodiment.
  • the liquid crystal molecules are not accordingly rotated by the electric field. An apparent residual image suppression effect was confirmed.
  • an initial alignment angle ⁇ obtained by rubbing and an inclination angle ⁇ of the drain electrode and source electrode are set to coincide with each other, in the same manner as in the first embodiment, and island-like amorphous silicon 18 is also inclined to match the inclination angle ⁇ .
  • the third embodiment is identical with the first embodiment. Residual image can be prevented more effectively also in this manner.
  • the opposing edges of a drain electrode 20 and source electrode 22 are set perpendicular to the longitudinal direction of the comb electrode, and the alignment direction of entire rubbing is set parallel to the longitudinal direction of the comb electrode. Then, no rotation force is applied to the liquid crystal molecules on the drain electrode 20 and source electrode 22 by the electric field generated between the drain electrode 20 and source electrode 22 , so residual image does not occur.
  • the open portion, i.e., the comb electrode applies a predetermined rotation force to the liquid crystal, so arbitrary display is performed.
  • alignment films 60 those to which an aligning capability is imparted by irradiation with light (ultraviolet rays, a laser beam, or the like) are used. These alignment films may set entire alignment as described above, or the alignment direction may differ from portion to portion.
  • an alignment film on a drain electrode 20 and source electrode 22 (on island-like amorphous silicon 18 ) is aligned by light, using a photomask, such that they are perpendicular to the opposing edges of the drain electrode 20 and source electrode 22 , i.e., such that it is parallel to the longitudinal direction of the comb electrode.
  • the alignment film is aligned by using another photomask such that they are inclined at ⁇ (15°) with respect to the longitudinal direction of the comb electrode.
  • a liquid crystal panel is formed in this manner.
  • alignment films 60 those that can be imparted with an alignment capability upon irradiation with light are employed, in the same manner as in the fifth embodiment, and are aligned by light such that the entire alignment direction is parallel to the longitudinal direction of the comb electrode. More specifically, the alignment films 60 , respectively formed on the surfaces of an active element substrate unit 4 and color filter unit 6 by offset printing or the like, are irradiated with light in a predetermined direction, so as to align liquid crystal molecules such that they are parallel to the longitudinal direction of the comb electrode, thus forming a liquid crystal panel. Alternatively, the liquid crystal molecules may be aligned in other directions by light or the like.
  • a drain electrode 20 , source electrode 22 , and island-like amorphous silicon 18 are inclined as shown in FIG. 9, so that they match an inclination angle ⁇ , in the same manner as in the third embodiment.
  • Alignment films 60 for an active element substrate unit 4 and color filter unit 6 are subjected to rubbing by the rubbing method such that they are inclined at an angle ⁇ (15°) with respect to the widthwide direction of the comb electrode, as shown in FIG. 9, and the liquid crystal molecules are aligned parallel.
  • a predetermined gap is formed between the active element substrate unit 4 and color filter unit 6 with an inner-cell spacer or the like (not shown), and a nematic liquid crystal 50 is sealed in it with a sealing agent (not shown) and a hole closing material (not shown), thus forming the liquid crystal panel.
  • a nematic liquid crystal with a negative dielectric constant anisotropy ⁇ of ⁇ 5.0 (589 nm, 20° C.), a refractive index anisotropy ⁇ n of 0.075, and a liquid crystal resistivity of 1.5 ⁇ 10 12 ⁇ cm is used.
  • the liquid crystal is imparted with a rotation force by the electric field, so it changes display.
  • the liquid crystal on the drain electrode 20 and source electrode 22 even when a voltage is applied between the drain electrode 20 and source electrode 22 , as the dielectric constant anisotropy ⁇ is negative, the electric field in this direction cannot impart a rotation force. Thus, a residual image does not occur.
  • a drain electrode 20 , source electrode 22 , and island-like amorphous silicon 18 are inclined as shown in FIG. 10, so that they match an inclination angle ⁇ .
  • the drain electrode 20 and source electrode 22 not only their opposing edges but also those portions of them which are connected to a data line 21 are also set to match the angle ⁇ .
  • a liquid crystal panel 2 obtained in this manner was built as a liquid crystal display apparatus into a driving unit, and was subjected to a proper residual image test for a long period of time. No residual image occurred at all.
  • the orientation of the comb electrode is inclined. More specifically, rubbing is performed parallel to a data line 21 and the like. Regarding a drain electrode 20 and source electrode 22 , their opposing edges are perpendicular to the rubbing direction.
  • a liquid crystal panel 2 obtained in this manner was built as a liquid crystal display apparatus into a driving unit, and was subjected to a proper residual image test for a long period of time. No residual image occurred at all.
  • the comb electrode is formed to have an L shape.
  • the rubbing direction is identical with that of the ninth embodiment, and is parallel to a data line 21 and the like.
  • the liquid crystal molecules are rotated in the respective directions by the electric field, so display is changed.
  • the direction of the liquid crystal on a drain electrode 20 and source electrode 22 coincides with the direction of the electric field between the drain electrode 20 and source electrode 22 , no rotation force is imparted to the liquid crystal. Therefore, a residual image can be prevented.
  • the comb electrode When the comb electrode is formed with this shape, a portion where the liquid crystal molecules are rotated clockwise by the electric field of the comb electrode and a portion where the liquid crystal molecules are rotated counterclockwise by the electric field of the comb electrode are formed. Since the liquid crystal molecules are rotated in two directions, orientations of the liquid crystal molecules at the open portion can be dispersed, so that the visual easiness of the screen can be improved.
  • the L shape of the comb electrode is symmetric with respect to the rubbing direction. Alternatively, the orientations of the liquid crystals may be appropriately dispersed, or may be biased in any particular direction for the purpose of, e.g., improving the visual easiness of the screen.
  • FIG. 13 shows the 11th embodiment in which a comb electrode, a drain electrode 20 , and a source electrode 22 identical with those of the above ninth embodiment are rotated through 90°.
  • the liquid crystal alignment on the TFT element is always constant. Therefore, residual image accompanying a change in TFT characteristics can be suppressed.
  • the residual image suppression effect is particularly apparent in the third and eighth embodiments.
  • the liquid crystal panel can be manufactured with the same process as that for a panel with the conventional structure.
  • the driving voltage to be applied to the liquid crystal can be decreased.
  • the rotational direction of the liquid crystal differs between the right and left sides of the electrode or between the upper and lower sides of the electrode.
  • coloration that occurs when the liquid crystal panel is seen obliquely can be prevented, and the view angle is widened.
  • FIG. 14 shows a modification to the eighth embodiment shown in FIG. 10.
  • part of a scanning signal line 12 corresponding to inclined island-like amorphous silicon 18 is inclined to match the inclination of the island-like amorphous silicon 18 .

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  • General Physics & Mathematics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
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JP2000216202A JP3570974B2 (ja) 2000-07-17 2000-07-17 アクティブマトリクス型液晶表示装置
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US11/291,997 Expired - Fee Related US7492431B2 (en) 2000-07-17 2005-12-02 Active matrix liquid crystal display having a thin film transistor over which alignment of liquid crystal molecules does not change

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GB2405523A (en) * 2003-08-25 2005-03-02 Lg Philips Lcd Co Ltd LCD fabrication process with rubbed orientation layer
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US20050140897A1 (en) * 2003-12-29 2005-06-30 Woo-Hyun Kim In-plane switching mode liquid crystal display device having multi-domains
US7388639B2 (en) 2003-12-29 2008-06-17 Lg Display Co., Ltd. In-plane switching mode liquid crystal display device having multi-domains
US20140104555A1 (en) * 2011-02-01 2014-04-17 Samsung Display Co., Ltd. Vertical alignment layer and liquid crystal display including the same
US9244309B2 (en) * 2011-02-01 2016-01-26 Samsung Display Co., Ltd. Vertical alignment layer and liquid crystal display including the same

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JP2002031802A (ja) 2002-01-31
US7009673B2 (en) 2006-03-07
US7492431B2 (en) 2009-02-17
TWI238915B (en) 2005-09-01
US20060082713A1 (en) 2006-04-20
KR20020015003A (ko) 2002-02-27
US20040046903A1 (en) 2004-03-11
KR100396823B1 (ko) 2003-09-02
JP3570974B2 (ja) 2004-09-29

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