WO2013168545A1 - 液晶駆動方法及び液晶表示装置 - Google Patents
液晶駆動方法及び液晶表示装置 Download PDFInfo
- Publication number
- WO2013168545A1 WO2013168545A1 PCT/JP2013/061719 JP2013061719W WO2013168545A1 WO 2013168545 A1 WO2013168545 A1 WO 2013168545A1 JP 2013061719 W JP2013061719 W JP 2013061719W WO 2013168545 A1 WO2013168545 A1 WO 2013168545A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- liquid crystal
- electrode
- voltage
- electrodes
- pair
- Prior art date
Links
Images
Classifications
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3614—Control of polarity reversal in general
-
- 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
- G02F1/13306—Circuit arrangements or driving methods for the control of single liquid crystal cells
-
- 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
- G02F1/133345—Insulating 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
- G02F1/136—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
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3648—Control of matrices with row and column drivers using an active matrix
-
- 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
- G02F1/134381—Hybrid switching mode, i.e. for applying an electric field with components parallel and orthogonal to the substrates
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/04—Structural and physical details of display devices
- G09G2300/0421—Structural details of the set of electrodes
- G09G2300/0426—Layout of electrodes and connections
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/04—Structural and physical details of display devices
- G09G2300/0421—Structural details of the set of electrodes
- G09G2300/0434—Flat panel display in which a field is applied parallel to the display plane
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/04—Structural and physical details of display devices
- G09G2300/0469—Details of the physics of pixel operation
- G09G2300/0478—Details of the physics of pixel operation related to liquid crystal pixels
- G09G2300/0482—Use of memory effects in nematic liquid crystals
- G09G2300/0486—Cholesteric liquid crystals, including chiral-nematic liquid crystals, with transitions between focal conic, planar, and homeotropic states
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0204—Compensation of DC component across the pixels in flat panels
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0252—Improving the response speed
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0257—Reduction of after-image effects
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/04—Maintaining the quality of display appearance
- G09G2320/043—Preventing or counteracting the effects of ageing
- G09G2320/046—Dealing with screen burn-in prevention or compensation of the effects thereof
Definitions
- the present invention relates to a liquid crystal driving method and a liquid crystal display device. More specifically, the present invention relates to a liquid crystal driving method and a liquid crystal display device that perform display by applying an electric field using a pair of electrodes.
- the liquid crystal driving method is a method in which liquid crystal molecules in a liquid crystal layer sandwiched between a pair of substrates are moved by generating an electric field between electrodes, thereby changing the optical characteristics of the liquid crystal layer, so that light can pass through the liquid crystal panel. It can be transmitted or not transmitted to generate an on state or an off state.
- various types of liquid crystal display devices are provided in various applications by taking advantage of thin, light weight and low power consumption.
- various driving methods have been devised and put into practical use in in-vehicle devices such as personal computers, televisions, car navigation systems, and displays of portable information terminals such as smartphones and tablet terminals.
- Display modes have been developed for liquid crystal display devices depending on the characteristics of liquid crystal, electrode arrangement, substrate design, and the like.
- Display modes that have been widely used in recent years can be broadly classified as a vertical alignment (VA) mode in which liquid crystal molecules having negative dielectric anisotropy are vertically aligned with respect to the substrate surface, In-plane switching (IPS) mode in which liquid crystal molecules having negative dielectric anisotropy are horizontally aligned with respect to the substrate surface and a horizontal electric field is applied to the liquid crystal layer, and striped electric field switching (FFS) Fringe Field Switching).
- VA vertical alignment
- IPS In-plane switching
- FFS striped electric field switching
- an FFS driving type liquid crystal display device a thin film transistor type liquid crystal display having high-speed response and a wide viewing angle, a first substrate having a first common electrode layer, a pixel electrode layer, and a second common A second substrate having both electrode layers, a liquid crystal sandwiched between the first substrate and the second substrate, high-speed response to a high input data transfer rate, and a wide field of view for a viewer An electric field is generated between the first common electrode layer on the first substrate and both the pixel electrode layer and the second common electrode layer on the second substrate to provide a corner.
- a display including the means is disclosed (for example, refer to Patent Document 1).
- a liquid crystal device for applying a lateral electric field by a plurality of electrodes a liquid crystal device in which a liquid crystal layer made of a liquid crystal having a positive dielectric anisotropy is sandwiched between a pair of substrates arranged opposite to each other, The first substrate and the second substrate constituting the substrate are opposed to each other with the liquid crystal layer sandwiched therebetween, and an electrode for applying a vertical electric field to the liquid crystal layer is provided.
- a liquid crystal device provided with a plurality of electrodes for applying a lateral electric field to the liquid crystal layer is disclosed (for example, see Patent Document 2).
- the rising edge (while the display state changes from the dark state [black display] to the bright state [white display]) occurs between the upper slit electrode and the lower surface electrode of the lower substrate.
- the fringe electric field (FFS drive) causes the liquid crystal molecules to fall by the vertical electric field generated by the potential difference between the substrates during the fall (while the display state changes from the bright state [white display] to the dark state [black display]). It can be rotated for high speed response.
- FIG. 16 is a schematic cross-sectional view of a liquid crystal display device.
- FIG. 17 is a schematic diagram showing simulation results showing the director distribution, the electric field distribution, and the transmittance distribution in the liquid crystal display device shown in FIG.
- FIG. 16 shows a structure of a liquid crystal display device, in which a constant voltage is applied between a pair of comb electrodes (in the figure, 5 V and ⁇ 5 V. The potential difference between the pair of electrodes may be equal to or greater than a threshold value.
- the threshold means an electric field and / or a voltage value that generates an electric field that causes an optical change in the liquid crystal layer and a display state in the liquid crystal display device.
- the counter electrodes 813 and 823 are disposed on the counter substrate, respectively.
- the counter electrodes 813 and 823 are at 0V.
- FIG. 17 shows the simulation result at the rising edge, and shows the voltage distribution, the distribution of the director D, and the transmittance distribution (solid line t).
- Patent Document 2 describes that a response speed is improved by using comb driving in a liquid crystal display device having a three-layer electrode structure.
- a response speed is improved by using comb driving in a liquid crystal display device having a three-layer electrode structure.
- TN twisted nematic
- Patent Document 2 describes that a response speed is improved by using comb driving in a liquid crystal display device having a three-layer electrode structure.
- TN twisted nematic
- the present invention has been made in view of the above situation, and in a liquid crystal driving method for driving a liquid crystal by generating a potential difference between a pair of electrodes provided on one of upper and lower substrates, DC image sticking is sufficiently reduced together with flicker. It is an object of the present invention to provide a liquid crystal driving method and a liquid crystal display device driven using the liquid crystal driving method.
- the present inventors have also proposed a liquid crystal display device (for example, TBA [Transverse Bend Alignment] mode, FFS mode, etc.) that determines liquid crystal orientation by an electric field including a lateral component other than a liquid crystal display device having a vertical alignment type three-layer electrode structure.
- a liquid crystal display device for example, TBA [Transverse Bend Alignment] mode, FFS mode, etc.
- the liquid crystal is bent when a pair of comb electrodes such as an upper comb electrode generates an electric field including a lateral component (for example, a horizontal electric field or a fringe electric field with respect to the main surface of the substrate). It has been found that it has a region to be oriented or splay oriented.
- the present inventors examined the cause, and in the mode in which the alignment of the liquid crystal is determined by the electric field including the lateral component, the liquid crystal is obliquely aligned, so that the splay alignment or the bend alignment occurs, and such an alignment occurs.
- the inventors found that macroscopic polarization occurs (flexo polarization) because the symmetry of the molecular arrangement of the liquid crystal is lost.
- flexopolarization is a phenomenon observed in all nematic liquid crystals regardless of the shape of the molecule. Due to the occurrence of flexopolarization, a difference in orientation occurs between the positive polarity and the negative polarity, resulting in a difference in transmittance.
- the present inventors set the upper layer electrode of the lower substrate to comb-teeth drive, so that the rise is a lateral electric field, the rise of the potential difference between the comb teeth.
- On-on switching mode that generates a vertical electric field due to the potential difference between the substrates, rotates the liquid crystal molecules by the electric field at both rising and falling, and achieves high response by a lateral electric field driven by a comb.
- Various liquid crystal display devices are being studied.
- a driving method for producing a halftone and a 1TFT or 2TFT driving method other than 3TFT driving for improving the aperture ratio are also proposed (for example, Japanese Patent Application No. 2011-142346, Japanese Patent Application No. 2011-142348, Application No. 2011-142350, Japanese Patent Application No. 2011-229221, etc.).
- FIG. 14 shows the simulation result when the voltage applied to one of the pair of electrodes is positive, and FIG. 15 shows that the voltage applied to one of the pair of electrodes is negative. Both show the voltage distribution, the distribution of the director D, and the transmittance distribution (solid line t), with the orientation being significantly different between the positive polarity case and the negative polarity case.) .
- the present inventors have made a detailed study in order to eliminate flicker in a driving method for driving a liquid crystal by an electric field including such a lateral component.
- DC (Direct Current) due to DC (Direct Current) offset can be used.
- Burn-in becomes a problem. That is, normally, the counter electrode voltage (counter voltage) at which the flicker is minimized is set as the optimum counter voltage, but in the on-on switching mode and other lateral electric field modes, the flicker is set to be minimum.
- the transmittance difference between the positive polarity and the negative polarity due to flexopolarization is adjusted by the electric field strength, so that a large DC offset is applied to the electrode.
- the voltage setting that is optically matched (the voltage setting that minimizes flicker) is not electrically symmetric, so there is a concern about burn-in due to DC offset.
- each electrode in addition to the counter electrode of the counter substrate, and these three electrodes are adjusted when performing gradation expression, and each of the three electrodes is offset. Voltage is present. That is, each electrode can have an offset voltage with respect to the counter electrode. Normally, it is desirable that the offset voltage be 0 V, but in this case, flicker remains.
- a potential difference can be suitably generated in a pair of electrodes provided on one of the upper and lower substrates to sufficiently reduce flicker.
- the inventors of the present invention are not limited to the liquid crystal display device having such a vertical alignment type three-layer electrode structure, but the liquid crystal display device that determines the alignment of the liquid crystal by an electric field including other lateral components.
- the inventors have found that the present invention can be suitably applied, and have conceived that the above problems can be solved brilliantly, and have reached the present invention.
- the present invention is a method of driving a liquid crystal by generating a potential difference between a pair of electrodes provided on one of upper and lower substrates, and one of the pair of electrodes changes an applied voltage in accordance with gradation.
- the pair of electrodes is one in which the polarity of the applied voltage is reversed, and a planar electrode is provided on one and / or the other of the upper and lower substrates, and the liquid crystal driving method includes the pair of electrodes.
- the difference obtained by subtracting the voltage applied to the planar electrode from the average value of the positive voltage and the negative voltage applied to one of the electrodes is applied to the first offset voltage and the other of the pair of electrodes.
- the absolute value of the second offset voltage is the first offset LCD drive larger than absolute voltage Performing a driving operation is a method.
- the liquid crystal is usually sandwiched between upper and lower substrates.
- the offset voltage is a value indicating how much the average value of the positive voltage and the negative voltage when the polarity is inverted is deviated from a certain reference (in this specification, for example, the counter voltage of the counter electrode).
- a difference obtained by subtracting the voltage applied to the planar electrode from the average value of the positive voltage and the negative voltage applied to one of the pair of electrodes “1 offset voltage” means a voltage applied to one of the pair of electrodes with respect to a voltage applied to the planar electrode as a reference when a positive voltage is applied to one of the pair of electrodes. And an average value of a voltage applied to one of the pair of electrodes with respect to a voltage applied to the planar electrode as a reference when a negative voltage is applied to one of the pair of electrodes.
- “Second offset voltage that is a difference obtained by subtracting a voltage applied to the planar electrode from an average value of a positive voltage and a negative voltage applied to the other of the pair of electrodes” according to the present invention.
- a voltage applied to the other of the pair of electrodes with respect to a voltage applied to the planar electrode as a reference when a positive voltage is applied to the other of the pair of electrodes
- a negative voltage when a negative voltage is applied to the other of the pair of electrodes, it means an average value of a voltage applied to the planar electrode as a reference and a voltage applied to the other of the pair of electrodes.
- the average value of the positive voltage and the negative voltage is a value obtained by adding the positive voltage and the negative voltage and dividing by two.
- + 7.1V / ⁇ 7.5V is re-labeled as “ ⁇ 7.3V ⁇ 0.2V”, and ⁇ 0.2V min That is, it deviates from 0V on average.
- each voltage is preferably constant, but may vary as long as the effect of the present invention is exhibited. When changing, each voltage can be its average value.
- the polarity of the applied voltage is reversed may mean that the absolute value of the applied voltage itself changes.
- the voltages applied to the pair of electrodes in the present invention are usually those whose polarities are reversed at regular intervals.
- the voltage applied to the pair of electrodes is usually an alternating voltage.
- the AC voltage is a voltage whose magnitude periodically changes with time. Normally, the potential changes so as to have substantially the same amplitude above and below the center voltage, but in the liquid crystal driving method of the present invention, driving is performed so that at least the second offset voltage does not become 0V. Become.
- the second offset voltage may be positive or negative, but is preferably negative.
- the first offset voltage may be substantially 0V, and is substantially 0V, which is one of the preferable modes in the liquid crystal driving method of the present invention.
- One of the pair of electrodes sets a voltage according to the gradation and changes the applied voltage to express gradation luminance.
- One of the pair of electrodes also reverses the polarity of the applied voltage. For example, it can be said that the polarity of the applied voltage is reversed even at ⁇ 0 V, and this is one preferred form.
- the other of the pair of electrodes may basically be an electrode that fixes the voltage regardless of the gradation and serves as a reference for the gradation electrode. (For example, in the case of the on-on switching mode and the TBA mode.)
- the voltage is set according to the gradation and the applied voltage is changed to express the gradation luminance.
- the FFS mode for example, in the case of the FFS mode.
- the pair of electrodes is preferably, for example, a pair of comb electrodes, and more preferably two comb electrodes are arranged so as to face each other when the main surface of the substrate is viewed in plan.
- These comb electrodes can generate a transverse electric field between the comb electrodes, so that when the liquid crystal layer includes liquid crystal molecules having positive dielectric anisotropy, the response performance and transmittance at the time of rising are
- the liquid crystal layer includes liquid crystal molecules having negative dielectric anisotropy
- the liquid crystal molecules can be rotated at a high speed by a horizontal electric field at the time of falling.
- the pair of comb-tooth electrodes it is preferable that the comb-tooth portions are respectively along when the main surface of the substrate is viewed in plan.
- the comb-tooth portions of the pair of comb-tooth electrodes are substantially parallel, in other words, each of the pair of comb-tooth electrodes has a plurality of substantially parallel slits.
- one comb-tooth electrode has two or more comb-tooth portions.
- the pair of comb electrodes may be provided in the same layer, and may be provided in different layers as long as the effects of the present invention can be exhibited, but the pair of electrodes are provided in the same layer. It is preferable that A pair of electrodes is provided in the same layer means that each electrode has a common member (for example, an insulating layer, a liquid crystal layer, etc.) on the liquid crystal layer side and / or on the side opposite to the liquid crystal layer side. Say that you are in contact with.
- a common member for example, an insulating layer, a liquid crystal layer, etc.
- the planar electrode is provided on one and / or the other of the upper and lower substrates
- the planar electrode may be (1) the planar electrode may be provided on both the upper and lower substrates, and (2) A planar electrode may be provided on only one of the upper and lower substrates (one on which a pair of electrodes are disposed), and (3) a planar electrode is provided only on the other of the upper and lower substrates. It may be.
- one of the pair of electrodes is positive and negative with reference to the voltage of one of the planar electrodes.
- the average value of the voltage applied to the first offset voltage may be the first offset voltage
- the average value of the voltage applied to the other of the pair of electrodes of the positive polarity and the negative polarity may be the second offset voltage.
- the average value of the voltage applied to one of the pair of electrodes is a first offset voltage
- the average value of the voltage applied to the other of the pair of electrodes is positive and negative. .
- the liquid crystal driving method further includes a driving operation for driving a liquid crystal by generating a potential difference between a pair of electrodes composed of planar electrodes provided on both upper and lower substrates. It is preferable to carry out.
- the planar electrode may be planar as long as it corresponds to (superimposes) pixels when the substrate main surface is viewed in plan.
- the liquid crystal driving method of the present invention is a method of driving a liquid crystal by generating a potential difference between two pairs of electrodes provided on the upper and lower substrates, and is particularly excellent in response speed.
- any planar electrode may be used as a reference when obtaining the offset voltage.
- the planar electrodes are provided on the other of the upper and lower substrates (counter substrate). It can be based on the planar electrode.
- a driving operation for driving a liquid crystal by generating a potential difference between the pair of planar electrodes is preferably performed.
- the pair of planar electrodes can usually apply a potential difference between the substrates.
- the planar electrode includes a form electrically connected in a plurality of pixels, for example, a form electrically connected in all pixels, and electrically in the same pixel column.
- a connected form is preferable.
- the planar shape only has to be a planar shape in the technical field of the present invention.
- the planar shape has an orientation regulation structure such as a rib or a slit in a part of the region, or when the main surface of the substrate is viewed in plan view
- the alignment regulating structure may be provided at the center of the pixel, but those having substantially no alignment regulating structure are suitable.
- planar electrode provided on one of the pair of substrates it is preferable that at least a portion overlapping with a pixel when the main surface of the substrate is viewed in a planar shape.
- the planar electrode provided on the other of the pair of substrates (counter substrate) preferably has no opening.
- the structure of the electrode is the same for the following forms (2) and (3).
- a planar electrode is provided on only one of the upper and lower substrates.
- the pair of electrodes provided on one of the upper and lower substrates is preferably provided on the planar electrode via an insulating layer.
- the liquid crystal driving method of the present invention may execute a driving operation in which a fringe electric field is applied between a pair of electrodes and a planar electrode, and this is also a preferred embodiment.
- a planar electrode is disposed only on the other of the upper and lower substrates.
- a dielectric layer is provided on at least one of the upper and lower substrates.
- a dielectric layer is preferably provided on the other of the upper and lower substrates.
- one of the upper and lower substrates includes a thin film transistor element, and the thin film transistor element includes an oxide semiconductor.
- the liquid crystal driving method is a method of driving by an active matrix driving method, and the active matrix driving method is driven by a plurality of bus lines using thin film transistors, and an electrode on the Nth bus line and the (N + 1) th bus. It is preferable to execute the driving operation by reversing the potential change applied to the electrodes in the line. Reversing the potential change applied to the electrode in the Nth bus line and the electrode in the (N + 1) th bus line means that a positive potential change and a negative potential change are performed with respect to a certain potential. .
- Examples of the bus line include a gate bus line and a source bus line.
- the liquid crystal preferably includes liquid crystal molecules that are aligned in a direction perpendicular to the main surface of the substrate when no voltage is applied.
- the term “orienting in the direction perpendicular to the main surface of the substrate” may be anything that can be said to be oriented in the direction perpendicular to the main surface of the substrate in the technical field of the present invention.
- the liquid crystal is substantially composed of liquid crystal molecules that are aligned in a direction perpendicular to the main surface of the substrate when no voltage is applied.
- the “when no voltage is applied” may be anything as long as it can be said that substantially no voltage is applied in the technical field of the present invention.
- Such vertical alignment type liquid crystal is an advantageous method for obtaining a wide viewing angle, high contrast characteristics, and the like, and its application is expanding.
- the driving operation is preferably a driving operation for driving a liquid crystal by generating a potential difference between a pair of comb electrodes.
- the pair of comb electrodes can be set to different potentials at a threshold voltage or higher.
- the threshold voltage means, for example, a voltage value that gives a transmittance of 5% when the transmittance in the bright state is set to 100%.
- the potential different from the threshold voltage can be any voltage as long as it can realize a driving operation with a potential different from the threshold voltage. This makes it possible to suitably control the electric field applied to the liquid crystal layer. Become.
- a preferable upper limit value of the different potential is, for example, 20V.
- one electrode of a pair of electrodes is driven by a certain TFT and the other electrode is driven by another TFT, or the lower electrode of the other electrode.
- the pair of comb electrodes can be set to different potentials.
- the width of the comb-teeth portion of the pair of comb-teeth electrodes is preferably 2 ⁇ m or more, for example.
- the width between the comb tooth portions is preferably 2 ⁇ m to 7 ⁇ m, for example.
- the liquid crystal is preferably aligned with a horizontal component with respect to the main surface of the substrate when the potential difference between the pair of comb electrodes is equal to or higher than the threshold voltage. “Orienting in the horizontal direction” may be anything that can be said to be oriented in the horizontal direction in the technical field of the present invention. Accordingly, high-speed response can be achieved, and the transmittance can be improved when the liquid crystal contains liquid crystal molecules (positive liquid crystal molecules) having positive dielectric anisotropy. It is preferable that the liquid crystal is substantially composed of liquid crystal molecules that are aligned at a threshold voltage or higher and oriented in the horizontal direction with respect to the main surface of the substrate.
- the liquid crystal preferably contains liquid crystal molecules (positive liquid crystal molecules) having positive dielectric anisotropy.
- the liquid crystal molecules having positive dielectric anisotropy are aligned in a certain direction when an electric field is applied, and the alignment control is easy, and a faster response can be achieved.
- the liquid crystal layer preferably also includes liquid crystal molecules having negative dielectric anisotropy (negative liquid crystal molecules). Thereby, the transmittance can be further improved. That is, it is preferable that the liquid crystal molecules are substantially composed of liquid crystal molecules having positive dielectric anisotropy from the viewpoint of high-speed response, and the liquid crystal molecules are negative from the viewpoint of transmittance. It can be said that it is preferable to be substantially composed of liquid crystal molecules having a dielectric anisotropy of
- the upper and lower substrates usually have an alignment film on at least one liquid crystal layer side.
- the alignment film is preferably a vertical alignment film.
- Examples of the alignment film include an alignment film formed from an organic material and an inorganic material, a photo-alignment film formed from a photoactive material, and an alignment film that has been subjected to alignment treatment by rubbing or the like.
- the alignment film may be an alignment film that has not been subjected to an alignment process such as a rubbing process.
- the upper and lower substrates preferably have a polarizing plate on the side opposite to at least one liquid crystal layer side.
- the polarizing plate is preferably a circular polarizing plate. With such a configuration, the transmittance improvement effect can be further exhibited.
- the polarizing plate is also preferably a linear polarizing plate. With such a configuration, the viewing angle characteristics can be improved.
- the upper and lower substrates provided in the liquid crystal display panel of the present invention are usually a pair of substrates for sandwiching liquid crystal.
- an insulating substrate such as glass or resin is used as a base, and wiring, electrodes, color filters, etc. are formed on the insulating substrate. It is formed by making.
- a dielectric layer is provided on at least one of the upper and lower substrates.
- the liquid crystal driving method of the present invention can be applied to any of transmissive, reflective, and transflective liquid crystal display devices.
- the present invention is also a liquid crystal display device driven using the liquid crystal driving method of the present invention.
- the preferred form of the liquid crystal driving method in the liquid crystal display device of the present invention is the same as the preferred form of the liquid crystal driving method of the present invention described above.
- Examples of the liquid crystal display device include in-vehicle devices such as personal computers, televisions, and car navigation systems, and displays of portable information terminals such as smartphones and tablet terminals.
- the response speed is extremely excellent in a mode in which liquid crystal molecules can be rotated at high speed by rotating the liquid crystal molecules by an electric field. Therefore, the present invention can be suitably applied to in-vehicle liquid crystal display devices such as car navigation that may be used in a low-temperature environment, field-sequential liquid crystal display devices, and 3D (stereoscopic) display devices.
- the configuration of the liquid crystal driving method and the liquid crystal display device of the present invention is not particularly limited by other components as long as such components are formed as essential, and the liquid crystal driving method and the liquid crystal display are not limited. Other configurations normally used in the apparatus can be applied as appropriate.
- a liquid crystal driving method for driving a liquid crystal by generating a potential difference between a pair of electrodes provided on one of upper and lower substrates DC image sticking can be sufficiently reduced together with flicker.
- FIG. 3 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a lateral electric field is generated.
- FIG. 3 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a vertical electric field is generated.
- FIG. 3 is a schematic cross-sectional view conceptually showing an offset voltage of each electrode of the liquid crystal display device according to Embodiment 1.
- FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 1.
- FIG. 3 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a lateral electric field is generated.
- FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 2 when a horizontal electric field is generated.
- FIG. It is a simulation result about the orientation and transmittance distribution of liquid crystal molecules at the time of low gradation display of the liquid crystal display device. It is a simulation result about the orientation and transmittance distribution of liquid crystal molecules at the time of low gradation display of the liquid crystal display device.
- FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 3 when a horizontal electric field is generated.
- 10 is a schematic cross-sectional view of a liquid crystal display device according to a modification of Embodiment 3 when a lateral electric field is generated.
- FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 4 when a horizontal electric field is generated.
- FIG. It is a figure which shows the example of an evaluation image. It is a graph which shows the burn-in evaluation result when the offset voltage is strongly applied to the gradation electrode side and when the offset voltage is strongly applied to the reference electrode side. It is a simulation result about the orientation and transmittance
- a pixel may be a picture element (sub-pixel) unless otherwise specified.
- the planar electrode is a planar electrode in the technical field of the present invention, for example, dot-shaped ribs and / or slits may be formed, but the planar electrode substantially has an alignment regulating structure. What is not preferred is preferred.
- a pair of substrates sandwiching the liquid crystal layer is also referred to as an upper substrate and a lower substrate.
- a substrate on the display surface side is also referred to as an upper substrate
- a substrate on the opposite side to the display surface is also referred to as a lower substrate.
- the electrodes arranged on the substrate the electrode on the display surface side is also referred to as an upper layer electrode
- the electrode on the opposite side to the display surface is also referred to as a lower layer electrode.
- the circuit substrate (lower substrate) of this embodiment is also referred to as a TFT substrate or an array substrate because it includes a thin film transistor element (TFT).
- TFT thin film transistor element
- the TFT is turned on both at the rising (horizontal electric field application) and the falling (vertical electric field application).
- a voltage is applied to at least one electrode (pixel electrode) of the pair of comb electrodes.
- the member and part which exhibit the same function are attached
- (i) shows the potential of one of the comb-shaped electrodes on the upper layer of the lower substrate, and (ii) shows the other potential of the comb-shaped electrode on the upper layer of the lower substrate.
- (Iii) indicates the potential of the planar electrode on the lower layer of the lower substrate or the potential of the planar electrode on the upper substrate, and (iv) indicates the potential of the planar electrode on the upper substrate.
- the reference electrode is basically an electrode that fixes a voltage regardless of gradation and serves as a reference for the gradation electrode. It may be changed depending on the gradation.
- the gradation electrode is an electrode that sets a voltage according to the gradation and changes it mainly to express gradation luminance.
- the gradation electrode is also referred to as one of a pair of comb electrodes on the lower substrate, and the reference electrode is also referred to as the other of the pair of comb electrodes on the lower substrate.
- the FFS mode there is no particular distinction between the pair of electrodes on the upper layer of the lower substrate, and both the pair of comb electrodes set the voltage according to the gradation and mainly express the gradation luminance. Therefore, it can be said that this is an electrode to be changed.
- FIG. 1 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a lateral electric field is generated.
- FIG. 2 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a vertical electric field is generated. 1 and 2, the dotted line indicates the direction of the generated electric field.
- the liquid crystal display device has a vertical alignment type three-layer electrode structure using liquid crystal molecules 31 that are positive type liquid crystals (here, the upper layer electrode of the lower substrate located in the second layer is a comb electrode) ). As shown in FIG. 1, the rise occurs at a potential difference of 7.5 V between a pair of comb electrodes 16 (for example, composed of a reference electrode 17 having a potential of 0 V and a gradation electrode 19 having a potential of 7.5 V). The liquid crystal molecules are rotated by the transverse electric field.
- the potential difference between the substrates (between the counter electrode 13 having a potential of 7.5V and the counter electrode 23 having a potential of 0V) is 7.5V, but the potential difference between the substrates does not substantially occur. There may be. Note that the offset according to the present embodiment is not explicitly shown in FIG.
- the fall occurs between the substrates (for example, between the counter electrode 13, the reference electrode 17, and the gradation electrode 19 each having a potential of 7.5V, and the counter electrode 23 having a potential of 0V.
- the liquid crystal molecules are rotated by a vertical electric field generated at a potential difference of 7.5 V.
- a potential difference between the pair of comb electrodes 16 (for example, composed of the reference electrode 17 having a potential of 7.5V and the gradation electrode 19 having a potential of 7.5V) does not substantially occur.
- High-speed response is achieved by rotating the liquid crystal molecules by an electric field for both rising and falling. That is, at the rising edge, the lateral electric field between the pair of comb electrodes is turned on to increase the transmittance, and at the falling edge, the vertical electric field between the substrates is turned on to increase the response speed. Further, a high transmittance can be realized by a lateral electric field driven by a comb.
- a positive liquid crystal is used as the liquid crystal, but a negative liquid crystal may be used instead of the positive liquid crystal.
- the liquid crystal molecules are aligned in the horizontal direction due to the potential difference between the pair of substrates, and the liquid crystal molecules are aligned in the horizontal direction due to the potential difference between the pair of comb electrodes.
- the transmittance is excellent, and the liquid crystal molecules can be rotated by an electric field at both rising and falling, thereby achieving high-speed response.
- a driving operation for generating a potential difference between the electrodes of a pair of comb-teeth electrodes and a driving operation for generating a potential difference between the opposing electrodes arranged on the upper and lower substrates respectively. It is preferable to execute in this order.
- the potential of the pair of comb electrodes is indicated by (i) and (ii)
- the potential of the planar electrode of the lower substrate is indicated by (iii)
- the potential of the planar electrode of the upper substrate is ( iv).
- the liquid crystal display panel according to Embodiment 1 includes an array substrate 10, a liquid crystal layer 30, and a counter substrate 20 (color filter substrate) from the back side of the liquid crystal display panel to the observation surface side.
- the layers are stacked in this order.
- the liquid crystal display panel of Embodiment 1 vertically aligns liquid crystal molecules when the voltage difference between the pair of comb electrodes 16 is less than the threshold voltage.
- the reference electrode 17 and the gradation electrode 19 (a pair of upper electrodes) formed on the glass substrate 11 (lower substrate) are formed.
- the amount of transmitted light is controlled by tilting the liquid crystal molecules in the horizontal direction between the comb electrodes by an electric field generated between the comb electrodes 16).
- the planar lower electrode (counter electrode) 13 is formed by sandwiching an insulating layer 15 between a reference electrode 17 and a gradation electrode 19 (a pair of comb electrodes 16).
- an oxide film SiO 2 , a nitride film SiN, an acrylic resin, or the like can be used, or a combination of these materials can also be used.
- FIG. 3 is a schematic cross-sectional view conceptually showing the offset voltage of each electrode of the liquid crystal display device according to the first embodiment.
- the offset specified as a condition in this specification is mainly the offset voltage of the reference electrode 17, the gradation electrode 19, and the lower layer electrode 13 with the counter electrode 23 as a reference. That is, with respect to the voltage applied to the counter electrode 23 (planar electrode), the voltage applied to each electrode, that is, the average value when the voltage applied to each electrode is positive and negative Is an offset voltage.
- These offset voltages are referred to as offset A, offset B, and offset C, respectively, as conceptually shown in FIG.
- FIG. 4 is a schematic cross-sectional view of the liquid crystal display device according to the first embodiment.
- FIG. 4 shows the lower layer electrode 13, the reference electrode 17, the gradation electrode 19, and the counter electrode 23 in a cross section different from that in FIG. 3 of the liquid crystal display device according to the first embodiment.
- the first embodiment and the embodiments described later propose a method for determining how to apply an offset voltage that suppresses flicker due to flexopolarization as much as possible and does not deteriorate the visual recognition level of burn-in.
- the counter electrode side may or may not have a dielectric layer (overcoat [OC] layer). 3 and 4, the case where the OC layer is provided has been described. However, the following description will also be made with reference to a diagram that does not show the OC layer. However, also in the following embodiments, a mode in which the counter substrate has an OC layer can be suitably applied.
- a dielectric layer overcoat [OC] layer
- FIG. 5 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 when a horizontal electric field is generated.
- the voltage applied to each electrode is shown.
- +7.1 V is applied as a positive voltage and ⁇ 7.5 V is applied as a negative voltage with respect to the voltage 0 V of the counter electrode 23.
- +0.2 V is applied as a positive voltage and ⁇ 0.0 V is applied as a negative voltage with respect to the voltage 0 V of the counter electrode 23.
- +3.95 V is applied as a positive voltage and ⁇ 3.75 V is applied as a negative voltage with respect to the voltage 0 V of the counter electrode 23.
- may be A> B when A is a positive value, or A ⁇ B when A is a negative value.
- the liquid crystal display device is easy to manufacture and can achieve high transmittance. Further, it is possible to reduce burn-in while suppressing flexopolarization, which is a cause of flicker. The same effect can be exhibited in the embodiments described later.
- the first embodiment related to the on-on switching mode, the second embodiment described later, and the third embodiment have such an effect in a mode capable of realizing a response speed capable of performing the field sequential method. It is particularly preferable.
- the voltage applied to the reference electrode 17 when the applied voltage is ⁇ 7.5 V, the voltage applied to the reference electrode 17 is positive, and the voltage applied to the reference electrode 17 is transparent compared to the case where the voltage applied to the reference electrode 17 is negative. The rate increases and flicker occurs.
- a polarizing plate is disposed on the opposite side of the liquid crystal layers of both substrates.
- the polarizing plate either a circular polarizing plate or a linear polarizing plate can be used.
- alignment films are respectively arranged on the liquid crystal layer sides of both substrates, and these alignment films stand liquid crystal molecules perpendicular to the film surfaces.
- an organic alignment film or an inorganic alignment film may be used.
- the voltage supplied from the video signal line is applied to the gradation electrode 19 that drives the liquid crystal through the thin film transistor element (TFT).
- TFT thin film transistor element
- the reference electrode 17 and the gradation electrode 19 are formed in the same layer, and a form formed in the same layer is preferable. However, as long as the effects of the present invention can be exhibited, they are formed in different layers. It may be done.
- the gradation electrode 19 is connected to a drain electrode extending from the TFT through a contact hole.
- the lower layer electrode 13 and the counter electrode 23 have a planar shape, and the lower layer electrode 13 can be commonly connected to each of the even and odd lines of the gate bus line. Such an electrode is also referred to as a planar electrode in this specification.
- the counter electrode 23 has no opening and is commonly connected corresponding to all pixels.
- the thin film transistor element will be described later, it is preferable to use an oxide semiconductor TFT (IGZO or the like) from the viewpoint of the transmittance improvement effect.
- IGZO oxide semiconductor TFT
- the electrode width L of the comb-tooth electrode is 3.0 ⁇ m, but is preferably 2 ⁇ m or more, for example.
- the electrode spacing S of the comb electrodes is 3.5 ⁇ m, but preferably 2 ⁇ m or more, for example.
- a preferable upper limit is, for example, 7 ⁇ m.
- the ratio (L / S) between the electrode spacing S and the electrode width L is 3.0 ⁇ m / 3.5 ⁇ m, and is preferably 0.4 to 3, for example.
- a more preferable lower limit value is 0.5, and a more preferable upper limit value is 1.5.
- the cell gap d is 3.5 ⁇ m, but may be 2 ⁇ m to 7 ⁇ m, and is preferably within the range.
- the cell gap d thickness of the liquid crystal layer
- the cell gap d is preferably calculated by averaging all the thicknesses of the liquid crystal layers in the liquid crystal display panel.
- the liquid crystal driving method of Embodiment 1 can appropriately execute the driving operation performed by the normal liquid crystal driving method.
- the liquid crystal display device of Embodiment 1 can be appropriately provided with a member (for example, a light source or the like) included in a normal liquid crystal display device. The same applies to the embodiments described later.
- FIG. 6 is a schematic cross-sectional view of the liquid crystal display device according to the second embodiment when a lateral electric field is generated.
- FIG. 6 shows a case where the A offset is ⁇ 0.2 V in the second embodiment.
- the DC component ( ⁇ 0.2 V) to be applied is shown.
- a ⁇ B C when
- is set so that the offset is strongly applied to the reference electrode side.
- Embodiment 2 is the same as that of Embodiment 1 mentioned above.
- FIGS. 7 and 8 are simulation results on the orientation and transmittance distribution of liquid crystal molecules during low-gradation display of a liquid crystal display device.
- FIG. 7 shows the case where the voltage of the lower layer electrode 213 (which is not shown in the drawing but is a planar electrode) is 7.2 V
- FIG. 8 is the lower layer electrode 313 (showing its shape in the drawing). This is a case where the voltage of the planar electrode is 6.0V.
- the electrode width L, the electrode spacing S, and the cell gap d of the comb electrodes in the simulation conditions of FIGS. 7 and 8 are the same as those of the first embodiment described above.
- 7 and 8 are diagrams showing a state where there is no offset.
- t is a graph indicating the transmittance
- D indicates a director.
- the thicknesses of the counter electrodes 223 and 323 are not clearly shown, respectively. The same applies to diagrams showing other simulation results described later.
- the liquid crystal near the edge on the reference electrode side (7.5 V side) is tilted to express gradation, and the gradation electrode side is almost vertical alignment. Therefore, if the gradation electrode side is burned with an offset, the burn-in becomes particularly visible on the gradation electrode side in the on-on switching mode. Conversely, when the image is burned with an offset on the reference electrode side as in the present invention, the degree of influence on the burn-in level of the display is small, and burn-in can be difficult to visually recognize.
- FIG. 9 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 3 when a horizontal electric field is generated.
- the electrode structure of the third embodiment is the same as that of the first and second embodiments except that there is no counter electrode.
- FIG. 9 shows a case where the offset A is 0.1V. That is, in the reference electrode 417, + 0.2V is applied as a positive voltage and ⁇ 0V is applied as a negative voltage with respect to the voltage 0V of the counter electrode 423.
- the offset A and the offset B are independent, and the offset A of the reference electrode 417> the offset B of the gradation electrode 419.
- the offset A and the offset B are not set as the common offset, and the above setting is performed, thereby obtaining a burn-in reduction effect.
- the DC component ( ⁇ 0.2 V) to be applied is shown.
- the polarity of the applied voltage is also reversed when the absolute value of the applied voltage itself changes, such as the reference electrode 417.
- Other configurations in the third embodiment are the same as those in the first embodiment.
- FIG. 10 is a schematic cross-sectional view of a liquid crystal display device according to a modification of Embodiment 3 when a horizontal electric field is generated.
- + 7.0V is applied as a positive voltage
- ⁇ 7.5V is applied as a negative voltage with respect to the voltage 0V of the counter electrode 523.
- FIG. 10 shows an electrode configuration in the on-on switching mode.
- the electrode structure in the TBA mode is the same as the electrode structure shown in FIG. 10 except that the lower layer electrode 513 is not provided.
- the other offset B is preferably 0V. That is, in FIG.
- FIG. 10 shows a case where the reference electrode offset A is a negative offset in the on-on switching mode. In this case, the burn-in becomes difficult to see with respect to the orientation during gradation display in this mode. It can be said that the polarity of the applied voltage is also reversed when the absolute value of the applied voltage itself is changed like the reference electrode 517 and when the voltage is ⁇ 0 V like the gradation electrode 519.
- FIG. 11 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 4 when a lateral electric field is generated.
- the comb electrode 617 for example, 2.8V is applied as a positive voltage and -3.0V is applied as a negative voltage.
- a voltage may be similarly applied to the comb electrode 619 instead of the comb electrode 617.
- the liquid crystal driving method of Embodiment 4 satisfies the following formula.
- the reference electrode when obtaining the electrode offset voltage is the planar electrode 613 provided on the array substrate 610. is there.
- a pair of comb electrodes is used (voltage of comb electrode 617) ⁇ (voltage of comb electrode 619) 2 TFT driving (driving with 2 TFTs per pixel, also referred to as comb driving).
- the offsets A and B can be specified independently.
- both the comb electrodes 617 and 619 change the applied voltage in accordance with the gradation.
- Either offset A or offset B may be 0V (FIG. 11 shows the case where offset B is 0V).
- the upper electrode of the FFS mode liquid crystal display device is not a comb electrode but a slit electrode, and the comb electrode 617 and the comb electrode 619 shown in FIG. 11 are common electrodes.
- the counter voltage of the counter electrode is shifted to reduce the flicker, but the flicker is zero.
- offset A offset B ⁇ 0 V, burn-in occurs.
- the electrodes 617 and 619 are comb-shaped electrodes, and the offset is determined independently, so that the burn-in is reduced as compared with the case where the offset A and the offset B are offset by the same amount.
- the DC component ( ⁇ 0.1 V) that is applied is shown.
- the offset between the upper layer electrode and the lower layer electrode (at the insulating layer) can be reduced, which is a countermeasure against burn-in.
- the offset between the upper layer electrode and the lower layer electrode is considered to be more effective than between the comb-teeth electrodes. If both the offset A and the offset B are in an offset state, there is a possibility of burning.
- the counter substrate 620 does not have a counter electrode.
- the lower layer electrode 613 of the array substrate 610 serves as a counter electrode serving as a reference when the offset voltage is obtained. It can be said that the polarity of the applied voltage is reversed even when the absolute value of the applied voltage itself changes, such as the electrode 617.
- the driving operation as in the fourth embodiment is also a driving operation in which a potential difference is generated between the pair of electrodes 617 and 619 and the liquid crystal is driven. It can be said that there is.
- FIG. 12 is a diagram illustrating an example of an evaluation image.
- a burn-in level determination method for applying an offset voltage
- An arbitrary burn-in evaluation image is displayed.
- An arbitrary burn-in evaluation image is, for example, an image in which a window of a specific gradation (for example, 255 gradation: white) is displayed in 0 gradation (black screen) with the least burn-in (see FIG. 12).
- a plurality of different settings for applying the offset voltage are prepared and displayed side by side in the window (see FIG. 12).
- a standard such as 100 hours (H), 500 hours (H), and 1000 hours (H) is determined and left for a long time.
- the entire screen is displayed in a halftone solid screen (for example, 0 gradation, 24 gradation, 32 gradation, etc.) that is easy to see, and burn-in is performed using a filter called an ND filter.
- the level can be visually discriminated.
- the ND filter is a filter that reduces the amount of light without affecting the color.
- the burn-in level is quantified in the form of what percentage of the ND filter makes the burn-in invisible, and the respective burn-in levels are compared. .
- the burn-in level can be compared between the current offset setting and an offset setting different from the offset setting, and the effect of the offset setting on the burn-in level in the current setting can be verified.
- FIG. 13 is a graph showing burn-in evaluation results when the offset voltage is strongly applied to the gradation electrode side and when the offset voltage is strongly applied to the reference electrode side.
- FIG. 13 is an example of a burn-in evaluation result when an offset voltage is applied to the gradation electrode side and when an offset voltage is applied to the reference electrode side.
- the burn-in level is smaller as the numerical value is higher.
- the result of applying the same level of offset almost no burn-in progressed with the offset setting (reference electrode side negative offset) shown in the liquid crystal driving method of the present invention, but even with the offset voltage of the same level It shows that the burn-in level is greatly different when the voltage is applied differently.
- the liquid crystal driving method and the liquid crystal display device of the present invention can be obtained by verifying the driving voltage or performing microscopic observation such as SEM (Scanning / Electron / Microscope) on the TFT substrate and the counter substrate. The electrode structure and the like can be confirmed.
- SEM Sccanning / Electron / Microscope
- FIG. 14 is a simulation result on the orientation and transmittance distribution of liquid crystal molecules when one of a pair of electrodes of a liquid crystal display device having a vertical alignment type three-layer electrode structure is positive.
- FIG. 15 is a simulation result on the orientation and transmittance distribution of liquid crystal molecules when one of a pair of electrodes of a liquid crystal display device having a vertical alignment type three-layer electrode structure is negative.
- the OC layer has a thickness of 1.5 ⁇ m
- the liquid crystal layer 730 has a cell thickness of 3.7 ⁇ m
- the insulating layer 715 of the array substrate 710 has a thickness of 0.3 ⁇ m
- L / S is It is calculated as 2.5 ⁇ m / 3.0 ⁇ m.
- the orientation is greatly different between positive polarity and negative polarity (location surrounded by a broken-line circle in FIGS. 14 and 15). For this reason, flicker occurs.
- FIG. 16 is a schematic cross-sectional view of a liquid crystal display device having a vertical alignment type three-layer electrode structure.
- FIG. 17 is a simulation result on the alignment and transmittance distribution of liquid crystal molecules of a liquid crystal display device having a vertical alignment type three-layer electrode structure.
- the counter substrate 820 is not provided with an OC layer.
- This mode is the same mode as in Comparative Example 1, and flexopolarization always occurs. Therefore, a difference in transmittance, that is, flicker occurs due to the polarity inversion due to flexopolarization.
- the positive / negative transmittance difference may be adjusted by applying an electrical offset to the electrodes. However, when an offset voltage is equally applied to a pair of comb electrodes, DC burn-in due to DC offset becomes a problem.
- an oxide semiconductor TFT (IGZO or the like) is preferably used.
- the oxide semiconductor TFT will be described in detail below.
- At least one of the upper and lower substrates usually includes a thin film transistor element.
- the thin film transistor element preferably includes an oxide semiconductor. That is, in the thin film transistor element, it is preferable to form the active layer of the active drive element (TFT) using an oxide semiconductor film such as zinc oxide instead of the silicon semiconductor film.
- TFT active drive element
- An oxide semiconductor is characterized by exhibiting higher carrier mobility and less characteristic variation than amorphous silicon. For this reason, the oxide semiconductor TFT can operate at higher speed than the amorphous silicon TFT, has a high driving frequency, and is suitable for driving a next-generation display device with higher definition.
- the oxide semiconductor film is formed by a simpler process than the polycrystalline silicon film, there is an advantage that the oxide semiconductor film can be applied to a device requiring a large area.
- FIG. 18 is a schematic cross-sectional view showing an example of a liquid crystal display device used in the liquid crystal driving method of the present embodiment. Since a large capacitance is generated between the upper layer electrode and the lower layer electrode at a position indicated by an arrow, the pixel capacitance is larger than that of a normal vertical alignment (VA) mode liquid crystal display device.
- VA vertical alignment
- the merits when the oxide semiconductor TFT (IGZO or the like) is applied are as follows. For the reasons (1) and (2) above, it is about 20 times that of a model of 52 type with a pixel capacity of 240 Hz driven by UV2A. Therefore, when a conventional a-Si transistor is used to manufacture a transistor, there is a problem that the transistor becomes about 20 times larger and the aperture ratio cannot be sufficiently obtained. Since the mobility of IGZO is about 10 times that of a-Si, the size of the transistor is about 1/10. Since the three transistors in the liquid crystal display device using the color filter RGB are one, it can be manufactured with almost the same or smaller size than a-Si. As described above, since the capacitance of Cgd is reduced when the transistor is reduced, the burden on the source bus line is reduced accordingly.
- FIGS. 19 is a schematic plan view of the periphery of the active drive element used in the present embodiment.
- FIG. 20 is a schematic cross-sectional view around the active drive element used in the present embodiment.
- the symbol T indicates a gate / source terminal.
- a symbol Cs indicates an auxiliary capacity.
- An example (part concerned) of a manufacturing process of the oxide semiconductor TFT is described below.
- the active layer oxide semiconductor layers 905a and 905b of the active drive element (TFT) using the oxide semiconductor film can be formed as follows.
- an In—Ga—Zn—O-based semiconductor (IGZO) film with a thickness of, for example, 30 nm to 300 nm is formed over the insulating film 913i by a sputtering method. Thereafter, a resist mask covering a predetermined region of the IGZO film is formed by photolithography. Next, the portion of the IGZO film that is not covered with the resist mask is removed by wet etching. Thereafter, the resist mask is peeled off. In this manner, island-shaped oxide semiconductor layers 905a and 905b are obtained. Note that the oxide semiconductor layers 905a and 905b may be formed using another oxide semiconductor film instead of the IGZO film.
- the insulating layer 907 is patterned. Specifically, first, for example, a SiO 2 film (thickness: about 150 nm) is formed as the insulating layer 907 on the insulating film 913i and the oxide semiconductor layers 905a and 905b by a CVD method.
- the insulating layer 907 preferably includes an oxide film such as SiOy.
- the SiO 2 film when an oxide film is used, when oxygen vacancies are generated in the oxide semiconductor layers 905a and 905b, the oxygen vacancies can be recovered by oxygen contained in the oxide film, so that the oxide semiconductor layers 905a and 905b The oxidation deficiency can be reduced more effectively.
- the SiO 2 film as a lower layer may have a laminated structure of the SiNx film as an upper layer.
- the thickness of the insulating layer 907 (the total thickness of each layer in the case of a stacked structure) is preferably 50 nm or more and 200 nm or less.
- the thickness is 50 nm or more, the surfaces of the oxide semiconductor layers 905a and 905b can be more reliably protected in the patterning process of the source / drain electrodes. On the other hand, if it exceeds 200 nm, a larger step is generated in the source electrode and the drain electrode, which may cause disconnection or the like.
- the oxide semiconductor layers 905a and 905b in this embodiment include, for example, a Zn—O based semiconductor (ZnO), an In—Ga—Zn—O based semiconductor (IGZO), an In—Zn—O based semiconductor (IZO), or A layer made of a Zn—Ti—O based semiconductor (ZTO) or the like is preferable.
- ZnO Zn—O based semiconductor
- IGZO In—Ga—Zn—O-based semiconductor
- IGZO In—Ga—Zn—O-based semiconductor
- this mode has a certain function and effect in combination with the above-described oxide semiconductor TFT, it can also be driven using a known TFT element such as an amorphous Si TFT or a polycrystalline Si TFT.
- the counter substrate has no overcoat layer, but an overcoat layer may be provided.
- an overcoat layer may be provided.
- the electrode material ITO (Indium Tin Oxide) can be used, but a known material such as IZO (Indium Zinc Oxide) can be used instead.
- the liquid crystal driving method and liquid crystal display device of the present invention can also be applied to other lateral electric field type liquid crystal display devices in which liquid crystal molecules are not aligned in the vertical direction when no voltage is applied.
- the present invention can be applied to an IPS mode liquid crystal display device.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Theoretical Computer Science (AREA)
- Computer Hardware Design (AREA)
- Mathematical Physics (AREA)
- Optics & Photonics (AREA)
- Liquid Crystal (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
- Liquid Crystal Display Device Control (AREA)
Abstract
Description
このような液晶駆動により、種々の形態の液晶表示装置が薄型で軽量かつ低消費電力といった利点を活かして様々な用途において提供されている。例えば、パーソナルコンピュータ、テレビジョン、カーナビゲーション等の車載用の機器、スマートフォンやタブレット端末等の携帯情報端末のディスプレイ等において種々の駆動方法が考案されており、実用化されている。
上記一対の櫛歯電極は、通常は、閾値電圧以上で異なる電位とすることができるものである。閾値電圧は、例えば、明状態の透過率を100%に設定したとき、5%の透過率を与える電圧値を意味する。閾値電圧以上で異なる電位とすることができるとは、閾値電圧以上で異なる電位とする駆動操作を実現できるものであればよく、これにより液晶層に印加する電界を好適に制御することが可能となる。異なる電位の好ましい上限値は、例えば20Vである。異なる電位とすることができる構成としては、例えば、一対の電極のうち、一方の電極をあるTFTで駆動すると共に、他方の電極を、別のTFTで駆動したり、該他方の電極の下層電極と導通させたりすることにより、一対の櫛歯電極をそれぞれ異なる電位とすることができる。上記一対の櫛歯電極が一対の櫛歯電極である場合は、一対の櫛歯電極における櫛歯部分の幅は、例えば2μm以上が好ましい。また、櫛歯部分と櫛歯部分との間の幅(本明細書中、スペースともいう。)は、例えば2μm~7μmであることが好ましい。
先ず、オン-オンスイッチングモードの概要について説明する。図1は、実施形態1に係る液晶表示装置の横電界発生時における断面模式図である。図2は、実施形態1に係る液晶表示装置の縦電界発生時における断面模式図である。図1及び図2において、点線は、発生する電界の向きを示す。実施形態1に係る液晶表示装置は、ポジ型液晶である液晶分子31を用いた垂直配向型の3層電極構造(ここで、第2層目に位置する下側基板の上層電極は櫛歯電極である。)を有する。立ち上がりは、図1に示すように、一対の櫛歯電極16(例えば、電位0Vである基準電極17と電位7.5Vである階調電極19とからなる)間の電位差7.5Vで発生する横電界により、液晶分子を回転させる。このとき、基板間(電位7.5Vである対向電極13と電位0Vである対向電極23との間)の電位差は7.5Vであるが、基板間の電位差が実質的に生じていないものであってもよい。なお、本実施形態に係るオフセットについては、図1では明示していない。
一般的は、通常交流(AC)駆動(極性反転)により、DC(Direct Current)成分を極力減らして焼きつきを軽減させるが、オフセット電圧をかけると、それは液晶にかかるDC成分となるため、DC(Direct Current)焼きつきの原因となる。
実施形態1の液晶駆動方法は、下記式を満たす。
オフセットA=-0.2V(図5中、上方向にDC成分が残る。)
オフセットB=オフセットC=0.1V
また、|A|>|B|=|C|として基準電極側にオフセットが強くかかるようにする。なお、|A|>|B|とは、Aが正の値である場合に、A>Bであってもよく、Aが負の値である場合に、A<Bであってもよい。
一対の櫛歯電極間(基準電極17-階調電極19間)にオフセットがかかるため、フレクソ分極によるフリッカをキャンセルすることができる。すなわち、基準電極に正極性の電圧を印加した場合であっても、負極性の電圧を印加した場合であっても、透過率差をより小さなものとすることができる。
同時に、上層-下層間(基準電極17-下層電極13間)にもオフセットが生じてしまう。
このモードで主に焼きつきが見える階調(低階調)では、もともと階調電極側の液晶がほとんど倒れていない(図7、図8参照)。
そのため、階調電極19の周りで焼きつくと、液晶が倒れて表示が浮いてしまう。つまり、階調電極19-下層電極13間にオフセットが生じてしまうと、焼きつきが視認しやすいようなモードとなっており、逆に基準電極17-下層電極13間のオフセットによる焼きつきに対しては、視認しにくい表示モードとなっている。
そのため、基準電極側にオフセットを印加した場合の方が、焼きつきが視認しにくい。
図6は、実施形態2に係る液晶表示装置の横電界発生時における断面模式図である。図6は、実施例2においてAオフセットが-0.2Vの場合を示す。図6中、かかっていることになるDC成分(-0.2V)を示している。なお、このように、本実施形態では|A|>|B|=|C|として基準電極側にオフセットが強くかかるようにするところ、A<B=Cであることがより好ましい。例えば、Aが負であること、B=C=0であることが好ましい。基準電極117のように印加電圧の絶対値自体が変わるもの、階調電極119のように±0Vであるものも、印加電圧の極性が反転されると言える。なお、実施形態2におけるその他の構成は、上述した実施形態1の構成と同様である。
図7及び図8は、液晶表示装置の低階調表示時の液晶分子の配向と透過率分布についてのシミュレーション結果である。図7は、下層電極213(図ではその形状を示していないが、面状電極である。)の電圧が7.2Vの場合であり、図8は、下層電極313(図ではその形状を示していないが、面状電極である。)の電圧が6.0Vの場合である。図7及び図8のシミュレーション条件における櫛歯電極の電極幅L、電極間隔S、セルギャップdは、上述した実施形態1の構成と同様である。なお、図7及び図8は、オフセットが無い状態の図である。また、tは透過率を示すグラフであり、Dはダイレクタを示す。また、図7及び図8においては、それぞれ、対向電極223、323の厚みは特に明示していない。後述するその他のシミュレーション結果を示す図についても同様である。
図9は、実施形態3に係る液晶表示装置の横電界発生時における断面模式図である。実施形態3の電極構造は、対向電極が無い以外は、実施形態1、2と同様である。図9は、オフセットAが0.1Vの場合である。すなわち、基準電極417においては、対向電極423の電圧0Vに対して、正極性の電圧としては+0.2Vを印加し、負極性の電圧としては-0Vを印加する。
実施形態3の液晶駆動方法は、下記式を満たす。
オフセットA=0.1V
オフセットB=0V
図9に示すように、オフセットB=(対向電極423に印加される電圧を基準として、階調電極419に印加される正極性の電圧と、階調電極419に印加される負極性の電圧との平均値)={(+5V)-5V}/2=0Vであっても良い。
TBAモードにおいても、フレクソ分極の影響により、正負極性間の透過率差が出てフリッカが生じてしまうため、フリッカを消すためのオフセットをかける。
オフセットAとオフセットBとを共通オフセットとはせず、上記の設定にすることで、焼きつき低減効果を得る。なお、図9中、かかっていることになるDC成分(-0.2V)を示している。
オン-オンスイッチングモード、又は、TBAモードにおいて、オフセットAを負のオフセットとする。
図10は、実施形態3の変形例に係る液晶表示装置の横電界発生時における断面模式図である。基準電極517においては、対向電極523の電圧0Vに対して、正極性の電圧としては+7.0Vを印加し、負極性の電圧としては-7.5Vを印加する。図10では、オン-オンスイッチングモードの場合の電極構成を示す。TBAモードの電極構造は、下層電極513が無い以外は、図10に示した電極構造と同様である。
もう一方のオフセットBは、0Vが望ましい。すなわち、図10では、階調電極519においては、対向電極523の電圧0Vに対して、正極性の電圧としては+0Vを印加し、負極性の電圧としては-0Vを印加する。図10は、オン-オンスイッチングモードにおいて、基準電極オフセットAを負のオフセットとした場合である。この場合、本モードの階調表示時の配向に対して焼きつきが見えにくくなる。
基準電極517のように印加電圧の絶対値自体が変わるもの、階調電極519のように±0Vであるものも、印加電圧の極性が反転されると言える。
図11は、実施形態4に係る液晶表示装置の横電界発生時における断面模式図である。
櫛歯電極617においては、1例としては、正極性の電圧としては2.8Vを印加し、負極性の電圧としては-3.0Vを印加する。なお、実施形態4では、櫛歯電極617の代わりに、櫛歯電極619に同様に電圧を印加するものであってもよい。実施形態4の液晶駆動方法は、下記式を満たす。
オフセットA=-0.1V
オフセットB=0V
なお、実施形態4の液晶表示装置では、対向基板620に対向電極が設けられていないことから、電極のオフセット電圧を求める際に基準となる電極はアレイ基板610に設けられた面状電極613である。
FFSモードにおいて、通常は上層電極としてスリット電極を用い、(櫛歯電極617に相当する電極の電圧)=(櫛歯電極619に相当する電極の電圧)となっている。実施形態4では、敢えて一対の櫛歯電極を用いて(櫛歯電極617の電圧)≠(櫛歯電極619の電圧)の2TFT駆動(1絵素当たり2TFTによる駆動。櫛歯駆動とも言う。)とし、各オフセットA、Bを独立に指定できる構造とする。
このモードに一般的な意味での基準電極・階調電極の違いはないので、オフセットA>オフセットB(又はオフセットA<オフセットB)となっていればよく、通常のオフセットA=オフセットBでなければ良い。実施形態4では、櫛歯電極617、619の両方が階調に応じて印加電圧を変化させるものであると言える。
オフセットA又はオフセットBのいずれか一方が0Vであってもよい(図11では、オフセットBが0Vである場合を示す)。
そこで、電極617・619を櫛歯電極とし、独立にオフセットを決めることによって、オフセットA、オフセットBに同じだけ対向櫛歯間オフセットがかかる場合よりも焼きつきを軽減させる。なお、図11中、かかっていることになるDC成分(-0.1V)を示している。
また実施形態4において、上層電極-下層電極間(絶縁層のところ)のオフセットを軽減させることができる可能性があり、焼きつき対策となる。
焼きつきに対しては、櫛歯電極間よりも上層電極-下層電極間のオフセットが大きく効くと考えられ、オフセットA、オフセットBの両方にオフセットがかかる状態だと焼きついてしまうおそれがある。
実施形態4は、対向基板620が対向電極を有しない。この場合、上述したように、アレイ基板610の下層電極613がオフセット電圧を求める際に基準となる対向電極となる。
電極617のように印加電圧の絶対値自体が変わるものも、印加電圧の極性が反転されると言える。実施形態4におけるその他の構成は、実施形態1の構成と同様である。なお、実施形態4のような駆動操作も、一対の電極617・619間に電位差を生じさせるとともに、液晶を駆動することから、一対の電極間に電位差を生じさせて液晶を駆動する駆動操作であると言える。
図12は、評価画像例を示す図である。
本発明の効果を検証する方法の一つとして、焼きつきレベルの判定方法(オフセット電圧のかけ方に対して)を述べる。
先ず、任意の焼きつき評価画像を表示する。任意の焼きつき評価画像とは、例えば焼きつきの最も少ない0階調(黒画面)の中に特定の階調(例えば255階調:白)のウィンドウが表示されているような画像である(図12参照)。
オフセット電圧のかけ方の異なる設定を複数用意し、それらをウィンドウ内に並べて表示する(図12参照)。
上記の評価画像を表示した状態で、例えば100時間(H)や500時間(H)、1000時間(H)など基準を決めて長時間放置する。
NDフィルタは、色彩に影響を与えることなく光量を低下させるフィルタであり、何%のNDフィルタで焼きつきが見えなくなるかという形で、焼きつきレベルを定量化し、それぞれの焼きつきレベルを比較する。
現行のオフセット設定と、該オフセット設定とは異なるオフセット設定とで、焼きつきレベルを比較し、現行設定における焼きつきレベルに対するオフセット設定の効果を検証することができる。
図13は、階調電極側にオフセット電圧を強くかけた場合と、基準電極側にオフセット電圧を強くかけた場合との、焼きつき評価結果を示すグラフである。
図13は、階調電極側にオフセット電圧をかけた場合と基準電極側にオフセット電圧をかけた場合の、焼きつき評価結果の一例である。
ここでは、焼きつきレベルは数値が高いほど、焼きつき度合が小さいこととしている。
それぞれ同レベルのオフセットをかけた結果となっており、本発明の液晶駆動方法で示すオフセット設定(基準電極側負オフセット)ではほとんど焼きつきが進行しないのに対して、同じレベルのオフセット電圧でもオフセット電圧のかけ方が異なると大きく焼きつきレベルが異なることを示している。
図14は、垂直配向型の3層電極構造を有する液晶表示装置の一対の電極の一方が正の場合の液晶分子の配向と透過率分布についてのシミュレーション結果である。図15は、垂直配向型の3層電極構造を有する液晶表示装置の一対の電極の一方が負の場合の液晶分子の配向と透過率分布についてのシミュレーション結果である。図14及び図15のシミュレーション条件は、OC層の層厚は1.5μm、液晶層730のセル厚は3.7μm、アレイ基板710の絶縁層715の層厚は0.3μm、L/Sは2.5μm/3.0μmとして計算している。
比較例1では、正極性と負極性とで配向が大きく異なる(図14及び図15の破線の円で囲んだ箇所)。このため、フリッカが生じることとなってしまう。
図16は、垂直配向型の3層電極構造を有する液晶表示装置の断面模式図である。図17は、垂直配向型の3層電極構造を有する液晶表示装置の液晶分子の配向と透過率分布についてのシミュレーション結果である。なお、比較例2では対向基板820にOC層が設けられていない。
本発明の各実施形態においては、酸化物半導体TFT(IGZO等)が好適に用いられる。この酸化物半導体TFTについて、以下に詳細に説明する。
(1)画素容量が通常のVA(垂直配向)モードよりも大きい(図18は、本実施形態の液晶駆動方法に用いられる液晶表示装置の一例を示す断面模式図であるところ、図18中、矢印で示される箇所において、上層電極と下層電極との間に大きな容量が発生するため、画素容量が通常の垂直配向〔VA:Vertical Alignment〕モードの液晶表示装置より大きい。)。(2)RGBの3画素が1画素になるため、1画素の容量が3倍である。(3)更に、240Hz以上の駆動が必要のためゲートオン時間が非常に短い。
上記(1)と(2)の理由より、52型で画素容量がUV2Aの240Hz駆動の機種の約20倍ある。
故に、従来のa-Siでトランジスタを作製するとトランジスタが約20倍以上大きくなり、開口率が充分にとれない課題があった。
IGZOの移動度はa-Siの約10倍であるため、トランジスタの大きさが約1/10になる。
カラーフィルタRGBを用いる液晶表示装置にあった3つのトランジスタが1つになっているので、a-Siとほぼ同等か小さいくらいで作製可能である。
上記のようにトランジスタが小さくなると、Cgdの容量も小さくなるので、その分ソースバスラインに対する負担も小さくなる。
酸化物半導体TFTの構成図(例示)を、図19、図20に示す。図19は、本実施形態に用いられるアクティブ駆動素子周辺の平面模式図である。図20は、本実施形態に用いられるアクティブ駆動素子周辺の断面模式図である。なお、符号Tは、ゲート・ソース端子を示す。符号Csは、補助容量を示す。
酸化物半導体TFTの作製工程の一例(当該部)を、以下に説明する。
酸化物半導体膜を用いたアクティブ駆動素子(TFT)の活性層酸化物半導体層905a、905bは、以下のようにして形成できる。
まず、スパッタリング法を用いて、例えば厚さが30nm以上、300nm以下のIn-Ga-Zn-O系半導体(IGZO)膜を絶縁膜913iの上に形成する。この後、フォトリソグラフィにより、IGZO膜の所定の領域を覆うレジストマスクを形成する。次いで、IGZO膜のうちレジストマスクで覆われていない部分をウェットエッチングにより除去する。この後、レジストマスクを剥離する。このようにして、島状の酸化物半導体層905a、905bを得る。なお、IGZO膜の代わりに、他の酸化物半導体膜を用いて酸化物半導体層905a、905bを形成してもよい。
具体的には、まず、絶縁膜913i及び酸化物半導体層905a、905bの上に、絶縁層907として例えばSiO2膜(厚さ:例えば約150nm)をCVD法によって形成する。
絶縁層907は、SiOy等の酸化物膜を含むことが好ましい。
絶縁層907の厚さ(積層構造を有する場合には各層の合計厚さ)は、50nm以上、200nm以下であることが好ましい。50nm以上であれば、ソース・ドレイン電極のパターニング工程等において、酸化物半導体層905a、905bの表面をより確実に保護できる。一方、200nmを超えると、ソース電極やドレイン電極により大きい段差が生じるので、断線等を引き起こすおそれがある。
また電極材料としては、ITO(Indium Tin Oxide;酸化インジウム錫)を用いることができるが、その代わりに、IZO(Indium Zinc Oxide;酸化インジウム亜鉛)等の公知の材料を用いることができる。
11、21、111、121、211、221、311、321、411、421、511、521、611、621、711、721、811、821、911、921:ガラス基板
13、113、213、313、513、613、713、813、913:下層電極(対向電極)
15、115、215、315、415、515、615、715、815、915:絶縁層
16:一対の櫛歯電極
17、117、217、317、417、517、717、817、917:基準電極
19、119、219、319、419、519、719、819、919:階調電極
20、120、420、520、620、720、820、920:対向基板
23、123、223、323、423、523、723、823、923:対向電極
25:誘電体層(オーバーコート層)
30、130、430、530、630、730、830、930:液晶層
31:液晶(液晶分子)
617、619:(櫛歯)電極
901a:ゲート配線
901b:補助容量配線
901c:接続部
911g:基板
913i:絶縁膜(ゲート絶縁膜)
905a、905b:酸化物半導体層(活性層)
907:絶縁層(エッチングストッパ、保護膜)
909as、909ad、909b、915b:開口部
911as:ソース配線
911ad:ドレイン配線
911c、917c:接続部
913p:保護膜
917pix:画素電極
901:画素部
902:端子配置領域
Cs:補助容量
T:ゲート・ソース端子
D:ダイレクタ
t:透過率
OC:OC(オーバーコート)層
Claims (11)
- 上下基板の一方に設けられた一対の電極に電位差を生じさせて液晶を駆動する方法であって、
該一対の電極の一方は、階調に応じて印加電圧を変化させるものであり、
該一対の電極は、それぞれ印加電圧の極性が反転されるものであり、
該上下基板の一方及び/又は他方に面状電極が設けられており、
該液晶駆動方法は、該一対の電極の一方に印加される正極性の電圧と負極性の電圧との平均値から、該面状電極に印加される電圧を差し引いた差を第1オフセット電圧、該一対の電極の他方に印加される正極性の電圧と負極性の電圧との平均値から、該面状電極に印加される電圧を差し引いた差を第2オフセット電圧とすると、第2オフセット電圧の絶対値は、第1オフセット電圧の絶対値よりも大きい駆動操作を実行する
ことを特徴とする液晶駆動方法。 - 前記第2オフセット電圧は、負である
ことを特徴とする請求項1に記載の液晶駆動方法。 - 前記液晶駆動方法は、前記駆動操作の後に、更に、上下基板の両方に設けられた面状電極から構成される一対の電極に電位差を生じさせて液晶を駆動する駆動操作を実行する
ことを特徴とする請求項1又は2に記載の液晶駆動方法。 - 前記上下基板の一方だけに面状電極が設けられている
ことを特徴とする請求項1又は2に記載の液晶駆動方法。 - 前記上下基板の一方に設けられた一対の電極は、該面状電極上に絶縁層を介して設けられたものである
ことを特徴とする請求項3又は4に記載の液晶駆動方法。 - 前記液晶駆動方法は、一対の電極と面状電極との間でフリンジ電界を印加する駆動操作を実行する
ことを特徴とする請求項4又は5に記載の液晶駆動方法。 - 前記上下基板の他方だけに面状電極が配置されている
ことを特徴とする請求項1又は2に記載の液晶駆動方法。 - 前記液晶は、電圧無印加時に基板主面に対して垂直方向に配向する液晶分子を含む
ことを特徴とする請求項1~7のいずれかに記載の液晶駆動方法。 - 前記上下基板の少なくとも一方には、誘電体層が設けられている
ことを特徴とする請求項1~8のいずれかに記載の液晶駆動方法。 - 前記上下基板の一方は、薄膜トランジスタ素子を備え、
該薄膜トランジスタ素子は、酸化物半導体を含む
ことを特徴とする請求項1~9のいずれかに記載の液晶駆動方法。 - 請求項1~10のいずれかに記載の液晶駆動方法を用いて駆動されることを特徴とする液晶表示装置。
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2014514432A JP5898307B2 (ja) | 2012-05-10 | 2013-04-22 | 液晶駆動方法及び液晶表示装置 |
CN201380023952.9A CN104272176B (zh) | 2012-05-10 | 2013-04-22 | 液晶驱动方法和液晶显示装置 |
KR1020147030980A KR101602091B1 (ko) | 2012-05-10 | 2013-04-22 | 액정 구동 방법 및 액정 표시 장치 |
US14/399,626 US9508297B2 (en) | 2012-05-10 | 2013-04-22 | Liquid-crystal-driving method and liquid crystal display device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2012108794 | 2012-05-10 | ||
JP2012-108794 | 2012-05-10 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2013168545A1 true WO2013168545A1 (ja) | 2013-11-14 |
Family
ID=49550596
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2013/061719 WO2013168545A1 (ja) | 2012-05-10 | 2013-04-22 | 液晶駆動方法及び液晶表示装置 |
Country Status (5)
Country | Link |
---|---|
US (1) | US9508297B2 (ja) |
JP (1) | JP5898307B2 (ja) |
KR (1) | KR101602091B1 (ja) |
CN (1) | CN104272176B (ja) |
WO (1) | WO2013168545A1 (ja) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2016118706A (ja) * | 2014-12-22 | 2016-06-30 | エルジー ディスプレイ カンパニー リミテッド | Ffsモード液晶表示装置及びその製造方法 |
JP2016118683A (ja) * | 2014-12-22 | 2016-06-30 | エルジー ディスプレイ カンパニー リミテッド | Ffsモード液晶表示装置及びその製造方法 |
WO2016190211A1 (ja) * | 2015-05-22 | 2016-12-01 | シャープ株式会社 | 液晶表示装置 |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014097998A1 (ja) * | 2012-12-19 | 2014-06-26 | シャープ株式会社 | 液晶表示装置 |
CN105137661B (zh) * | 2015-10-09 | 2018-03-27 | 京东方科技集团股份有限公司 | 一种取向膜制造方法 |
KR102416410B1 (ko) * | 2015-12-21 | 2022-07-04 | 삼성디스플레이 주식회사 | 액정 표시 장치 |
JP2019184638A (ja) * | 2018-04-02 | 2019-10-24 | シャープ株式会社 | 液晶表示装置および電子機器 |
CN111540330B (zh) * | 2020-05-26 | 2022-03-08 | Tcl华星光电技术有限公司 | 液晶驱动电路、液晶驱动方法及液晶显示面板 |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003091014A (ja) * | 2001-09-19 | 2003-03-28 | Hitachi Ltd | 液晶表示パネル,液晶表示装置、及び液晶テレビ |
JP2006523850A (ja) * | 2002-08-26 | 2006-10-19 | ユニバーシティ・オブ・セントラル・フロリダ・リサーチ・ファウンデーション・インコーポレイテッド | 高速及び広視野角液晶ディスプレイ |
JP2008216859A (ja) * | 2007-03-07 | 2008-09-18 | Epson Imaging Devices Corp | 電気光学装置の駆動方法、電気光学装置、及び電子機器 |
JP2011112865A (ja) * | 2009-11-26 | 2011-06-09 | Toshiba Mobile Display Co Ltd | 液晶表示装置および液晶表示装置の駆動方法 |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1315002C (zh) * | 1994-06-24 | 2007-05-09 | 株式会社日立制作所 | 有源矩阵型液晶显示系统 |
JP3668844B2 (ja) * | 2000-10-04 | 2005-07-06 | 松下電器産業株式会社 | 表示装置及びその駆動方法 |
JP3900859B2 (ja) | 2001-06-07 | 2007-04-04 | セイコーエプソン株式会社 | 液晶装置、投射型表示装置および電子機器 |
KR20030091014A (ko) * | 2002-05-24 | 2003-12-01 | 김용신 | 자연석재 조경물의 제조방법 |
CN100363826C (zh) * | 2002-08-26 | 2008-01-23 | 中佛罗里达州大学研究基金会股份有限公司 | 高速、宽视角液晶显示器 |
CN100511408C (zh) * | 2006-12-11 | 2009-07-08 | 友达光电股份有限公司 | 改善液晶显示器上影像残留的显示方法 |
US9252282B2 (en) | 2011-03-18 | 2016-02-02 | Sharp Kabushiki Kaisha | Thin film transistor array substrate and liquid crystal display device |
US9372371B2 (en) | 2011-06-27 | 2016-06-21 | Sharp Kabushiki Kaisha | Liquid crystal display panel, and liquid crystal display device |
US9348178B2 (en) | 2011-06-27 | 2016-05-24 | Sharp Kabushiki Kaisha | Liquid crystal display panel and liquid crystal display device |
US20140111561A1 (en) | 2011-06-27 | 2014-04-24 | Sharp Kabushiki Kaisha | Liquid crystal drive device and liquid crystal display device |
CN103874955B (zh) | 2011-10-14 | 2016-10-19 | 夏普株式会社 | 液晶驱动方法和液晶显示装置 |
WO2013065529A1 (ja) | 2011-10-31 | 2013-05-10 | シャープ株式会社 | 薄膜トランジスタアレイ基板及び液晶表示装置 |
-
2013
- 2013-04-22 CN CN201380023952.9A patent/CN104272176B/zh not_active Expired - Fee Related
- 2013-04-22 JP JP2014514432A patent/JP5898307B2/ja not_active Expired - Fee Related
- 2013-04-22 WO PCT/JP2013/061719 patent/WO2013168545A1/ja active Application Filing
- 2013-04-22 KR KR1020147030980A patent/KR101602091B1/ko active IP Right Grant
- 2013-04-22 US US14/399,626 patent/US9508297B2/en active Active
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003091014A (ja) * | 2001-09-19 | 2003-03-28 | Hitachi Ltd | 液晶表示パネル,液晶表示装置、及び液晶テレビ |
JP2006523850A (ja) * | 2002-08-26 | 2006-10-19 | ユニバーシティ・オブ・セントラル・フロリダ・リサーチ・ファウンデーション・インコーポレイテッド | 高速及び広視野角液晶ディスプレイ |
JP2008216859A (ja) * | 2007-03-07 | 2008-09-18 | Epson Imaging Devices Corp | 電気光学装置の駆動方法、電気光学装置、及び電子機器 |
JP2011112865A (ja) * | 2009-11-26 | 2011-06-09 | Toshiba Mobile Display Co Ltd | 液晶表示装置および液晶表示装置の駆動方法 |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2016118706A (ja) * | 2014-12-22 | 2016-06-30 | エルジー ディスプレイ カンパニー リミテッド | Ffsモード液晶表示装置及びその製造方法 |
JP2016118683A (ja) * | 2014-12-22 | 2016-06-30 | エルジー ディスプレイ カンパニー リミテッド | Ffsモード液晶表示装置及びその製造方法 |
WO2016190211A1 (ja) * | 2015-05-22 | 2016-12-01 | シャープ株式会社 | 液晶表示装置 |
Also Published As
Publication number | Publication date |
---|---|
KR101602091B1 (ko) | 2016-03-09 |
JP5898307B2 (ja) | 2016-04-06 |
CN104272176B (zh) | 2017-02-22 |
US9508297B2 (en) | 2016-11-29 |
CN104272176A (zh) | 2015-01-07 |
US20150109274A1 (en) | 2015-04-23 |
JPWO2013168545A1 (ja) | 2016-01-07 |
KR20150002760A (ko) | 2015-01-07 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5898307B2 (ja) | 液晶駆動方法及び液晶表示装置 | |
JP5643422B2 (ja) | 液晶表示装置 | |
JP5654677B2 (ja) | 液晶表示パネル及び液晶表示装置 | |
WO2013146635A1 (ja) | 液晶駆動方法及び液晶表示装置 | |
JP5728587B2 (ja) | 液晶駆動方法及び液晶表示装置 | |
US9348178B2 (en) | Liquid crystal display panel and liquid crystal display device | |
JP5764665B2 (ja) | 薄膜トランジスタアレイ基板及び液晶表示装置 | |
US20150146125A1 (en) | Liquid crystal display panel, liquid crystal display apparatus, and thin film transistor array substrate | |
WO2012128061A1 (ja) | 液晶駆動方法及び液晶表示装置 | |
US9645453B2 (en) | Liquid crystal panel having a plurality of first common electrodes and a plurality of first pixel electrodes alternately arranged on a lower substrate, and display device incorporating the same | |
WO2013058157A1 (ja) | 液晶表示パネル及び液晶表示装置 | |
JP5878978B2 (ja) | 液晶駆動方法及び液晶表示装置 | |
WO2016080271A1 (ja) | 液晶表示装置 | |
US10558085B2 (en) | Liquid crystal display device | |
WO2016013500A1 (ja) | 液晶表示装置 | |
CN106125406B (zh) | 一种窄视角显示的垂直取向液晶显示器 | |
US20190121208A1 (en) | Liquid crystal display device | |
WO2013146856A1 (ja) | 液晶表示装置及び液晶駆動方法 | |
WO2012165312A1 (ja) | 液晶表示パネル及び液晶表示装置 | |
WO2016021527A1 (ja) | 液晶表示装置 | |
WO2016006506A1 (ja) | 液晶表示装置 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 13788229 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 2014514432 Country of ref document: JP Kind code of ref document: A |
|
ENP | Entry into the national phase |
Ref document number: 20147030980 Country of ref document: KR Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 14399626 Country of ref document: US |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 13788229 Country of ref document: EP Kind code of ref document: A1 |