JP6859703B2 - Liquid crystal display device - Google Patents

Description

The present invention relates to a liquid crystal display device.

In the liquid crystal display panel, a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, an IPS (In-Plane Switching) / FFS (Fringe Field Switching) mode, and the like are used. Further, the VA mode, the IPS / FFS mode, and the like are mainly used because of the demand for a wide viewing angle and a high contrast ratio. However, the VA mode and the IPS / FFS mode do not have sufficient responsiveness, and there is a problem in displaying moving images. In addition, OCB (Optically Compensated Bend) mode and TBA (Transverse Bend Alignment) mode, which can improve responsiveness and support moving image display, have also been proposed.

While the OCB mode exhibits high-speed responsiveness, it requires a transition operation from the initial orientation of the spray orientation to the bend orientation at the time of driving (for example, applying a voltage of 10 V or more) when the power is turned on. In addition to the circuit, a drive circuit for initial transition is required. Therefore, the OCB mode may increase the cost and may not be suitable for mobile devices having limited power supply.

Further, in the TBA mode, since the dielectric film is provided on the common electrode on the color filter substrate side, seizure is likely to occur due to the DC imbalance caused by the dielectric film. Further, since the oblique electric field is weak at a normal driving voltage (for example, about 5 V), the transmittance becomes low.

JP-A-2010-217853

The present invention provides a liquid crystal display device capable of improving response speed and display characteristics.

The liquid crystal display device according to one aspect of the present invention includes the first and second substrates, a liquid crystal layer filled between the first and second substrates, a switching element provided on the first substrate, and the first. A pixel electrode provided on one substrate and electrically connected to the switching element, a first common electrode provided on the first substrate and surrounding the pixel electrode, and provided on the second substrate in a plan view. It includes a second common electrode that covers the first common electrode. The pixel electrodes include a first electrode extending in the first direction, first and second protrusions extending from the first electrode in the second direction intersecting the first direction, and the second direction from the first electrode. Includes third and fourth protrusions extending in a third direction opposite to the above. The second common electrode includes second and third electrodes extending in the first direction, fifth and sixth protrusions extending in the third direction from the second electrode, and the second direction from the third electrode. Includes 7th and 8th protrusions extending into. The first and second protrusions and the fifth and sixth protrusions are alternately arranged along the first direction. The third and fourth protrusions and the seventh and eighth protrusions are alternately arranged along the first direction.

According to the present invention, it is possible to provide a liquid crystal display device capable of improving the response speed and the display characteristics.

The block diagram of the liquid crystal display device which concerns on 1st Embodiment. The circuit diagram of the display panel shown in FIG. The plan view of the display panel which concerns on 1st Embodiment. The plan view of the display panel which mainly showed the electrode structure on the TFT substrate side which concerns on 1st Embodiment. The plan view of the display panel which mainly showed the electrode structure on the CF substrate side which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view of the display panel along the AA'line of FIG. FIG. 3 is a cross-sectional view of the display panel along the BB'line of FIG. The figure explaining the operation of the display panel in the off state. FIG. 8 is a cross-sectional view of the display panel along the AA'line of FIG. The figure explaining the operation of the display panel in the on state. FIG. 4 is a cross-sectional view of the display panel along the AA'line of FIG. The figure explaining the operation of the display panel which concerns on a modification. FIG. 2 is a cross-sectional view of the display panel along the AA'line of FIG. The figure explaining the operation of the display panel which concerns on a modification. FIG. 4 is a cross-sectional view of the display panel along the AA'line of FIG. The plan view of the display panel which concerns on 1st comparative example. FIG. 6 is a cross-sectional view of the display panel along the AA'line of FIG. The plan view of the display panel which concerns on 2nd comparative example. FIG. 6 is a cross-sectional view of the display panel along the AA'line of FIG. The plan view of the display panel which concerns on 2nd Embodiment. The plan view of the display panel which mainly showed the electrode structure on the TFT substrate side which concerns on 2nd Embodiment. FIG. 2 is a cross-sectional view of the display panel along the AA'line of FIG.

Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of each drawing are not necessarily the same as the actual ones. Further, even when the same part is represented between the drawings, the relationship and ratio of the dimensions of each other may be represented differently. In particular, some embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and depending on the shape, structure, arrangement, etc. of the components, the technical idea of the present invention. Is not specified. In the following description, elements having the same function and configuration are designated by the same reference numerals, and duplicate explanations will be given only when necessary.

[First Embodiment]
[1] Overall Configuration of Liquid Crystal Display Device FIG. 1 is a block diagram of the liquid crystal display device 10 according to the first embodiment of the present invention. The liquid crystal display device 10 includes a display panel 11, a backlight (lighting device) 12, a scanning driver (scanning line drive circuit) 13, a signal driver (signal line drive circuit) 14, a common electrode driver (common electrode drive circuit) 15, and a voltage. A generation circuit 16 and a control circuit 17 are provided.

The display panel 11 includes a pixel array in which a plurality of pixels are arranged in a matrix. The display panel 11 is provided with a plurality of scanning lines GL, each extending in the low direction (X direction), and a plurality of signal lines SL, each extending in the column direction (Y direction). Pixels are arranged in the intersection region of the scanning line GL and the signal line SL.

The backlight 12 is a surface light source that irradiates the back surface of the display panel 11 with light. As the backlight 12, for example, a direct type or side light type (edge light type) LED backlight is used.

The scanning driver 13 is connected to a plurality of scanning lines GL. The scanning driver 13 sends a scanning signal for turning on / off the switching element included in the pixel to the display panel 11 based on the vertical control signal sent from the control circuit 17.

The signal driver 14 is connected to a plurality of signal lines SL. The signal driver 14 receives a horizontal control signal and display data from the control circuit 17. The signal driver 14 sends a gradation signal (driving voltage) corresponding to the display data to the display panel 11 based on the horizontal control signal.

The common electrode driver 15 generates a common voltage Vcom and supplies it to the common electrode in the display panel 11. The voltage generation circuit 16 generates various voltages necessary for the operation of the liquid crystal display device 10 and supplies them to each circuit.

The control circuit 17 receives image data from the outside. The control circuit 17 sends various control signals to the above-mentioned circuits based on the image data.

[2] Pixel Circuit Configuration Next, the pixel circuit configuration included in the display panel 11 will be described. FIG. 2 is a circuit diagram of the display panel 11. In FIG. 2, four pixels are extracted and shown.

The pixel 18 includes a switching element (active element) 19, a liquid crystal capacity (liquid crystal element) Clc, and a storage capacity Cs. As the switching element 19, for example, a TFT (Thin Film Transistor) is used, and an n-channel TFT is used.

The source of the TFT 19 is electrically connected to the signal line SL, its gate is electrically connected to the scanning line GL, and its drain is electrically connected to the liquid crystal capacitance Clc. The liquid crystal capacity Clc as a liquid crystal element is composed of a pixel electrode, a common electrode, and a liquid crystal layer sandwiched between them.

The storage capacity Cs is connected in parallel to the liquid crystal capacity Clc. The storage capacity Cs has a function of suppressing potential fluctuations that occur in the pixel electrodes and holding the drive voltage applied to the pixel electrodes until a drive voltage corresponding to the next signal is applied. The storage capacity Cs is composed of a pixel electrode, a storage electrode (storage capacity line), and an insulating film sandwiched between them. A common voltage Vcom is applied to the common electrode and the storage electrode by the common electrode driver 15.

[3] Configuration of Display Panel 11 Next, the configuration of the display panel 11 will be described. In this embodiment, a semi-transparent display panel will be described as an example. The transflective display panel has a reflection region for displaying an image by reflecting external light and a transmissive region for displaying an image by transmitting backlight light in one pixel.

FIG. 3 is a plan view of the display panel 11 according to the first embodiment. FIG. 4 is a plan view of the display panel 11 mainly showing the electrode structure on the TFT substrate 20 side. FIG. 5 is a plan view of the display panel 11 mainly showing the electrode structure on the CF substrate 21 side. By superimposing FIGS. 4 and 5, FIG. 3 is obtained. FIG. 6 is a cross-sectional view of the display panel 11 along the line AA'of FIG. FIG. 7 is a cross-sectional view of the display panel 11 along the line BB'of FIG. Note that FIG. 3 shows one pixel 18 extracted, and in reality, a plurality of pixels 18 in FIG. 3 are arranged in a matrix in the X direction and the Y direction.

The display panel 11 includes a TFT substrate 20 on which a switching element (TFT), pixel electrodes, and the like are formed, and a color filter substrate (CF substrate) 21 on which a color filter and the like are formed and arranged to face the TFT substrate 20. Each of the TFT substrate 20 and the CF substrate 21 is composed of a transparent substrate (for example, a glass substrate or a plastic substrate). The TFT substrate 20 is arranged to face the backlight 12, and the illumination light from the backlight 12 enters the display panel 11 from the TFT substrate 20 side.

The liquid crystal layer 22 is filled between the TFT substrate 20 and the CF substrate 21. Specifically, the liquid crystal layer 22 is enclosed in a display area surrounded by the TFT substrate 20, the CF substrate 21, and a sealing material (not shown). The sealing material is made of, for example, an ultraviolet curable resin, a thermosetting resin, an ultraviolet / heat combined type curable resin, etc., is applied to the TFT substrate 20 or the CF substrate 21 in the manufacturing process, and then cured by ultraviolet irradiation, heating, or the like. Be made to.

The liquid crystal material constituting the liquid crystal layer 22 changes its optical characteristics by manipulating the orientation of the liquid crystal molecules according to the electric field applied between the TFT substrate 20 and the CF substrate 21. In the present embodiment, as the liquid crystal layer 22, a positive type (P type) nematic liquid crystal having a positive dielectric anisotropy is used. The liquid crystal molecules are oriented substantially perpendicular to the substrate surface when there is no voltage (no electric field). That is, the long axis (director) of the liquid crystal molecules is vertically oriented when there is no voltage (no electric field), and the director of the liquid crystal molecules is tilted toward the electric field when a voltage is applied (electric field is applied).

A plurality of TFTs 19 are provided on the liquid crystal layer 22 side of the TFT substrate 20 so as to correspond to the plurality of pixels 18. As will be described later, the TFT 19 has a gate electrode electrically connected to the scanning line, a gate insulating film provided on the gate electrode, a semiconductor layer provided on the gate insulating film, and each other on the semiconductor layer. It includes a source electrode and a drain electrode provided apart from each other. The source electrode is electrically connected to the signal line SL.

A plurality of gate electrodes 23, each extending in the X direction, are provided on the TFT substrate 20. A plurality of pixels 18 for one row arranged in the X direction share one gate electrode 23. The gate electrode 23 functions as a scanning line GL. Further, a plurality of storage electrodes 24, each extending in the X direction, are provided on the TFT substrate 20. The storage electrode 24 is arranged adjacent to the gate electrode 23, for example. The same voltage as the common voltage applied to the common electrode described later is applied to the storage electrode 24. A gate insulating film 25 is provided on the gate electrode 23 and the storage electrode 24 and on the TFT substrate 20.

A plurality of semiconductor layers 26 corresponding to the plurality of pixels 18 are provided on the gate insulating film 25. As the semiconductor layer 26, for example, an amorphous silicon layer is used.

A source electrode 27A and a drain electrode 28A that are separated from each other in the Y direction are provided on one semiconductor layer 26 and the gate insulating film 25. Specifically, the source electrode 27A is formed so as to overlap a part of the semiconductor layer 26 and extend in the Y direction. The drain electrode 28A is formed so as to overlap a part of the semiconductor layer 26 and extend in the direction opposite to the source electrode 27A. As shown in FIG. 4, for example, the source electrode 27A has a T-shape having a wider end portion overlapping with the semiconductor layer 26 than the extending portion extending in the Y direction, and similarly, the drain electrode 28A has a drain electrode 28A. It has an inverted T shape.

A plurality of signal lines SL, each of which extends in the Y direction, are provided on the gate insulating film 25. The signal line SL is arranged at the boundary portion of the pixels 18 adjacent to each other in the X direction. A plurality of pixels 18 for one row arranged in the Y direction are commonly connected to one signal line SL. The connection electrode 27B is provided on the gate insulating film 25 so as to extend in the X direction, and electrically connects the source electrode 27A and the signal line SL.

A connection electrode 28B electrically connected to the end of the drain electrode 28A is provided on the gate insulating film 25. The length of the connection electrode 28B in the X direction is longer than the length of the drain electrode 28A in the X direction. The area of the connection electrode 28B is large in order to reliably compensate for the electrical connection with the pixel electrode 32 even when a misalignment occurs in the manufacturing process, for example. An insulating film 29 is provided on the source electrode 27A, the connection electrode 27B, the signal line SL, the drain electrode 28A, and the connection electrode 28B, and on the gate insulating film 25.

A plurality of reflective films 30 each extending in the X direction are provided on the insulating film 29. The region of the pixel provided with the reflective film 30 is the reflective region, and the other region is the transmissive region. The reflective film 30 reflects light incident from the liquid crystal layer 22 side. The reflective film 30 is arranged so as to cover the TFT 19. As a result, the TFT 19 is shielded from light by the reflective film 30, so that it is possible to prevent the TFT 19 from malfunctioning. The same voltage as the common voltage applied to the common electrode is applied to the reflective film 30. An insulating film 31 is provided on the reflective film 30 and the insulating film 29.

A pixel electrode 32 extending in the Y direction is provided on the insulating film 31. The specific configuration of the pixel electrode 32 (composed of members 32-1, 32-2, 32A, and 32B) will be described later. The pixel electrode 32 is electrically connected to the connection electrode 28B via the contact plug 33.

A common electrode 34 is provided on the insulating film 31. The common electrode 34 is configured to surround the pixel electrode 32. The specific configuration of the common electrode 34 (composed of members 34-1 to 3-4-4, 34A, and 34B) will be described later.

An alignment film 35 that controls the orientation of the liquid crystal layer 22 is provided on the pixel electrode 32, the common electrode 34, and the insulating film 31. The alignment film 35 is composed of a material that vertically orients liquid crystal molecules in the initial state of the liquid crystal layer 22.

Next, the configuration on the CF substrate 21 side will be described. A black matrix (also referred to as a black mask or a light-shielding film) 40 for shading is provided on the liquid crystal layer 22 side of the CF substrate 21. The black matrix 40 is arranged at the boundary of the pixels 18 and is formed in a mesh pattern. The black matrix 40 has a function of shielding the TFT 19 and a function of improving the contrast by shielding unnecessary light between color filters having different colors.

A plurality of color filters 41 are provided on the CF substrate 21 and the black matrix 40. The plurality of color filters (color members) 41 include a plurality of red filters 41-R, a plurality of green filters 41-G, and a plurality of blue filters 41-B. A general color filter is composed of the three primary colors of light, red (R), green (G), and blue (B). A set of three adjacent colors R, G, and B is a display unit (pixel), and the single color part of any one of R, G, and B in one pixel is the minimum called a sub pixel (sub pixel). It is a drive unit. The TFT 19 and the pixel electrode 32 are provided for each subpixel. In the description of the present specification, a sub-pixel is referred to as a pixel unless it is particularly necessary to distinguish between a pixel and a sub-pixel. As the color filter array, any array including a stripe array, a mosaic array, and a delta array can be applied.

A common electrode 42 is provided on the color filter 41 and the black matrix 40. That is, the common electrode 42 is configured to face the common electrode 34, that is, to cover the common electrode 34 in a plan view. The specific configuration of the common electrode 42 (composed of members 42-1 to 42-4, 42A, and 42B) will be described later. A common voltage Vcom is applied to the common electrode 42 from the common electrode driver 15. An overcoat film (flattening film) made of a transparent insulating material may be provided on the color filter 41 and the black matrix 40 in order to improve the flatness.

An alignment film 43 for controlling the orientation of the liquid crystal layer 22 is provided on the color filter 41 and the common electrode 42. The alignment film 43 is composed of a material that vertically orients liquid crystal molecules in the initial state of the liquid crystal layer 22.

A retardation plate 44 and a polarizing plate 46 are laminated in this order on the side of the TFT substrate 20 opposite to the liquid crystal layer 22. A retardation plate 45, a diffusion member 48, and a polarizing plate 47 are laminated in this order on the side of the CF substrate 21 opposite to the liquid crystal layer 22. The retardation plate 44 and the polarizing plate 46 form a circular polarizing plate, and the retardation plate 45 and the polarizing plate 47 form a circular polarizing plate.

Each of the polarizing plates (linear polarizers) 46 and 47 has a transmission axis and an absorption axis that are orthogonal to each other in a plane orthogonal to the traveling direction of light. Each of the polarizing plates 46 and 47 transmits linearly polarized light (linearly polarized light component) having a vibrating surface parallel to the transmission axis among light having a vibrating surface in a random direction, and the vibrating surface parallel to the absorption axis. Absorbs linearly polarized light (linearly polarized light component). The polarizing plates 46 and 47 are arranged so that their transmission axes are orthogonal to each other, that is, in an orthogonal Nicol state.

Each of the retardation plates 44 and 45 has refractive index anisotropy, and has a slow-phase axis and a phase-advance axis orthogonal to each other in a plane orthogonal to the traveling direction of light. Each of the retardation plates 44 and 45 has a phase difference of λ / 4 between the light having a predetermined wavelength transmitted through the slow axis and the phase advance axis, respectively, with a predetermined retardation (when the wavelength of the light transmitted through λ is used). ) Has the function of giving. That is, the retardation plates 44 and 45 are composed of 1/4 wave plates (λ / 4 plates). The slow axis of the retardation plate 44 is set so as to form an angle of approximately 45 ° with respect to the transmission axis of the polarizing plate 46. The slow axis of the retardation plate 45 is set so as to form an angle of approximately 45 ° with respect to the transmission axis of the polarizing plate 47.

The angles that define the polarizing plate and the retardation plate described above include an error that enables the desired operation and an error that is caused by the manufacturing process. For example, the above-mentioned approximately 45 ° includes a range of 45 ° ± 5 °. For example, the above-mentioned orthogonality shall include a range of 90 ° ± 5 °.

The diffusing member 48 has a function of equalizing the transmitted light by diffusing (scattering) the transmitted light in a random direction. The diffusion member 48 is composed of a diffusion adhesive material, a diffusion film, a diffusion plate, or the like. When a diffusing adhesive is used as the diffusing member 48, the diffusing adhesive has a function of adhering the members on both sides in addition to the function of diffusing the incident light. The stacking order of the diffusion member 48 and the retardation plate 45 may be reversed. The diffusing member 48 particularly diffuses the reflected light reflected by the reflective film 30, and the diffused reflected light is observed by the observer. By using the diffusion member 48, the viewing angle can be improved with respect to the reflection display in the reflection region.

A diffusion member and a brightness improving film may be laminated in this order on the backlight side of the polarizing plate 46. The brightness improving film has a function of improving the utilization efficiency of the light from the backlight 12 and improving the brightness of the liquid crystal display device 10. The brightness improving film is composed of a reflective polarizing film, a prism sheet, or the like.

(Example of material)
Examples of the gate electrode 23, the storage electrode 24, the source electrode 27A, the connection electrode 27B, the signal line SL, the drain electrode 28A, and the connection electrode 28B include aluminum (Al), molybdenum (Mo), chromium (Cr), and tungsten ( An alloy containing any one of W) or one or more of these is used. As the reflective film 30, for example, aluminum (Al) is used. The pixel electrode 32, the contact plug 33, and the common electrodes 34 and 42 are composed of transparent electrodes, and for example, ITO (indium tin oxide) is used. The gate insulating film 25, the insulating film 29, and the insulating film 31 are made of a transparent insulating material, and for example, silicon nitride (SiN) is used.

[3-1] Details of Pixel Electrode 32 Next, a specific configuration of the pixel electrode 32 will be described. As shown in FIG. 4, the pixel electrode 32 includes an electrode 32-1, an electrode 32-2, a plurality of protrusions 32A, and a plurality of protrusions 32B.

Electrode 32-1 extends in the Y direction. Each of the plurality of protrusions 32A extends in the X direction from the electrode 32-1. The plurality of protrusions 32A are arranged at equal intervals, for example, in the Y direction. Each of the plurality of protrusions 32B extends from the electrode 32-1 in the X direction (direction opposite to the protrusion 32A). The plurality of protrusions 32B are arranged at equal intervals, for example, in the Y direction.

One protrusion 32A and one protrusion 32B are arranged in a straight line, that is, at the same position in the Y direction. In other words, the electrode 32-1, the protrusion 32A, and the protrusion 32B form a T-shape or a cross shape. The configuration is not limited to the configuration in which the protrusion 32A and the protrusion 32B are arranged in a straight line, and the protrusion 32A and the protrusion 32B may be arranged at different positions in the Y direction.

In the configuration example of FIG. 4, a configuration example having five protrusions 32A is shown, but the number of protrusions 32A is not limited to five. The number of protrusions 32A may be two, or the number of protrusions 32A may be three or more other than five. Similarly, the number of protrusions 32B may be two, or the number of protrusions 32B may be three or more other than five.

The electrode 32-2 has a function of more reliably connecting the pixel electrode 32 and the contact plug 33 and a function of increasing the storage capacity between the storage electrode 24 and the storage electrode 24. The width of the electrode 32-2 (length in the X direction) is thicker than the width of the electrode 32-1. The electrodes 32-2 are arranged so as to overlap the storage electrode 24 in a plan view. The electrode 32-2 constitutes a storage capacity with the storage electrode 24. In order to increase the storage capacity, it is desirable that the area of the electrode 32-2 is larger.

[3-2] Details of Common Electrode 34 Next, a specific configuration of the common electrode 34 provided on the TFT substrate 20 side will be described. As shown in FIG. 4, the common electrode 34 includes electrodes 34-1 to 3-4-4, a plurality of protrusions 34A, and a plurality of protrusions 34B.

The electrodes 34-1 to 3-4-4 are configured to surround the pixel electrodes 32. Electrodes 34-1 and 34-2 extend in the Y direction. The electrodes 34-3 and 34-4 extend in the X direction and electrically connect the electrodes 34-1 and 34-2. The electrodes 34-1 to 3-4-4 are arranged at the boundary portion of the pixel. The electrodes 34-1 to 3-4-4 are shared by four pixels adjacent to each other in the X direction and the Y direction, respectively.

Each of the plurality of protrusions 34A extends in the X direction from the electrode 34-1. The plurality of protrusions 34A are arranged at equal intervals, for example, in the Y direction. One protrusion 34A is arranged between two adjacent protrusions 32A. That is, the plurality of protrusions 32A and the plurality of protrusions 34A are arranged alternately. In other words, in a plan view, the gap (space) between the pixel electrode 32 and the common electrode 34 has a zigzag shape. The end of the protrusion 34A is arranged in the X direction to be the same as the end of the protrusion 32A or closer to the electrode 32-1 than the end of the protrusion 32A. The number of protrusions 34A is set to be the same as the number of protrusions 32A, for example.

Each of the plurality of protrusions 34B extends from the electrode 34-2 in the X direction (direction opposite to the protrusion 34B). The plurality of protrusions 34B are arranged at equal intervals, for example, in the Y direction. One protrusion 34B is arranged between two adjacent protrusions 32B. That is, the plurality of protrusions 32B and the plurality of protrusions 34B are arranged alternately. The end of the protrusion 34B is arranged in the X direction on the same side as the end of the protrusion 32B or on the electrode 32-1 side of the end of the protrusion 32B. The number of protrusions 34B is set to be the same as the number of protrusions 32B, for example.

[3-3] Details of Common Electrode 42 Next, a specific configuration of the common electrode 42 provided on the CF substrate 21 side will be described. As shown in FIG. 5, the common electrode 42 includes electrodes 42-1 to 42-4, a plurality of protrusions 42A, and a plurality of protrusions 42B. Roughly speaking, the common electrode 42 provided on the CF substrate 21 side has the same shape as the common electrode 34 provided on the TFT substrate 20 side. The common electrode 42 is configured to cover the common electrode 34 in a plan view.

The electrodes 42-1 to 42-4 are configured to surround the pixel electrode 32. Electrodes 42-1 and 42-2 extend in the Y direction. The electrodes 42-3 and 42-4 extend in the X direction and electrically connect the electrodes 42-1 and 42-2. The electrodes 42-1 to 42-4 are arranged at the boundary portion of the pixel. The electrodes 42-1 to 42-4 are shared by four pixels adjacent to each other in the X direction and the Y direction, respectively.

The electrodes 42-1 to 42-4 are configured to cover the electrodes 34-1 to 3-4-4 in a plan view. The end of the electrode 42-1 is the same as the end of the electrode 34-1 or is arranged closer to the pixel electrode 32 than the end of the electrode 34-1. The end of the electrode 42-2 is the same as the end of the electrode 34-2, or is arranged closer to the pixel electrode 32 than the end of the electrode 34-2. The end of the electrode 42-3 is the same as the end of the electrode 34-3, or is arranged closer to the pixel electrode 32 than the end of the electrode 34-3. The end of the electrode 42-4 is the same as the end of the electrode 34-4, or is arranged closer to the pixel electrode 32 than the end of the electrode 34-4.

Each of the plurality of protrusions 42A extends in the X direction from the electrode 42-1. The plurality of protrusions 42A are arranged at equal intervals, for example, in the Y direction. As shown in FIG. 3, one protrusion 42A is arranged between two adjacent protrusions 32A. That is, the plurality of protrusions 32A and the plurality of protrusions 42A are arranged alternately. In other words, in a plan view, the gap between the pixel electrode 32 and the common electrode 42 has a zigzag shape. The end of the protrusion 42A is arranged in the X direction to be the same as the end of the protrusion 34A or closer to the electrode 32-1 than the end of the protrusion 34A. The number of protrusions 42A is set to be the same as the number of protrusions 34A. The protrusion 42A is configured to cover the protrusion 34A in a plan view. The width of the protrusion 42A (length in the Y direction) is set to be equal to or greater than the width of the protrusion 34A.

Each of the plurality of protrusions 42B extends in the X direction from the electrode 42-2. The plurality of protrusions 42B are arranged at equal intervals, for example, in the Y direction. As shown in FIG. 3, one protrusion 42B is arranged between two adjacent protrusions 32B. That is, the plurality of protrusions 32B and the plurality of protrusions 42B are arranged alternately. The end of the protrusion 42B is arranged in the X direction on the same side as the end of the protrusion 34B or on the electrode 32-1 side of the end of the protrusion 34B. The number of protrusions 42B is set to be the same as the number of protrusions 34B. The protrusion 42B is configured to cover the protrusion 34B in a plan view. The width of the protrusion 42B (length in the Y direction) is set to be equal to or greater than the width of the protrusion 34B.

[4] Operation Next, the operation of the liquid crystal display device 10 configured as described above will be described.

First, the operation of the liquid crystal display device 10 in the off state will be described. In the off state, the same voltage (for example, 0V) is applied to the pixel electrode 32 and the common electrodes 34 and 42, and no electric field is applied to the liquid crystal layer 22.

FIG. 8 is a diagram illustrating the operation of the display panel 11 in the off state. FIG. 9 is a cross-sectional view of the display panel 11 along the AA'line of FIG. In FIG. 9, the polarizing plate and the retardation plate are not shown. 8 and 9 schematically show the liquid crystal molecule 22A.

In the off state, no electric field is applied to the liquid crystal layer 22, and the liquid crystal layer 22 maintains its initial orientation. That is, the liquid crystal layer 22 is vertically oriented as a whole, and the long axis of the liquid crystal molecules 22A is oriented in the direction perpendicular to the substrate. In this off state, the illumination light from the backlight 12 passes through the polarizing plate 46, then passes through the liquid crystal layer 22 in a state where the retardation is almost zero, and the light transmitted through the liquid crystal layer 22 passes through the polarizing plate 47. Is absorbed by. As a result, the liquid crystal display device 10 becomes a black display.

Next, the operation of the liquid crystal display device 10 in the on state will be described. In the on state, different voltages are applied to the pixel electrode 32 and the common electrodes 34 and 42, and an electric field is applied to the liquid crystal layer 22. That is, in the on state, a positive voltage is applied to the pixel electrodes 32, and 0 V (= common voltage Vcom) is applied to the common electrodes 34 and 42. It is desirable that the polarities of the voltages applied to the pixel electrodes 32 and the common electrodes 34 and 42 are periodically reversed. That is, it is desirable that 0 V and a positive voltage are alternately applied to the pixel electrode 32 and the common electrodes 34 and 42 at predetermined intervals.

FIG. 10 is a diagram illustrating the operation of the display panel 11 in the on state. FIG. 11 is a cross-sectional view of the display panel 11 along the AA'line of FIG.

In the on state, a lateral electric field generated between the pixel electrode 32 and the common electrode 34 and an oblique electric field generated between the pixel electrode 32 and the common electrode 42 are applied to the liquid crystal layer 22. As a result, the liquid crystal layer 22 takes a half bend orientation (one side half of the bend orientation), and the liquid crystal molecules are tilted toward the common electrodes 34 and 42 with respect to the perpendicular line passing through the pixel electrode 32. Specifically, the closer to the pixel electrode 32 and the common electrode 34, the larger the inclination of the liquid crystal molecules, and the closer to the common electrode 42 from the pixel electrode 32, the smaller the inclination of the liquid crystal molecules. Further, by arranging the common electrode 42 in the oblique direction from the pixel electrode 32, a larger oblique electric field can be applied to the liquid crystal layer 22. As a result, the liquid crystal molecules above the pixel electrode 32 can also be tilted, so that the transmittance can be improved.

Further, as shown in FIG. 10, a plurality of liquid crystal molecules can be tilted in all directions. As a result, it is possible to prevent the transmittance from becoming non-uniform.

In this on state, the illumination light from the backlight 12 passes through the polarizing plate 46 and then passes through the liquid crystal layer 22 to impart a predetermined retardation, and the light transmitted through the liquid crystal layer 22 passes through the polarizing plate 47. To Penetrate. As a result, the liquid crystal display device 10 becomes a white display (actually, a color display corresponding to the color filter).

In FIG. 10, the aperture ratio of the present embodiment is the area (area effective for display) surrounded by the pixel electrode 32, the common electrode 34 (or the common electrode 42), and the storage electrode 24 in one pixel area. Defined as area ratio.

[5] Modification Example Next, a modification of the first embodiment will be described.

FIG. 12 is a diagram illustrating the operation of the display panel 11 according to the modified example. FIG. 12 shows the operation in the off state. FIG. 13 is a cross-sectional view of the display panel 11 along the AA'line of FIG.

In the modified example, the TFT substrate 20 and the CF substrate 21 are misaligned in the manufacturing process. As an example, in FIGS. 12 and 13, the CF substrate 21 is displaced to the right by the deviation amount Δ with respect to the TFT substrate 20. Due to this misalignment, the protrusion 42A of the common electrode 42 is closer to the pixel electrode 32, and the protrusion 42B of the common electrode 42 is further away from the pixel electrode 32.

FIG. 14 is a diagram illustrating the operation of the display panel 11 according to the modified example. FIG. 14 shows the operation in the on state. FIG. 15 is a cross-sectional view of the display panel 11 along the AA'line of FIG.

Even in the on state, the desired half-bend orientation is maintained, and the plurality of liquid crystal molecules are tilted in all directions. As a result, it is possible to prevent the transmittance from becoming non-uniform.

[6] Comparative Example Next, a display panel according to the comparative example will be described. FIG. 16 is a plan view of the display panel according to the first comparative example. FIG. 17 is a cross-sectional view of the display panel along the line AA'of FIG.

The pixel electrode 32 includes an electrode 32-1 extending in the Y direction and an electrode 32-2 having a width wider than that of the electrode 32-1. That is, the pixel electrode 32 of the comparative example does not have a protrusion.

The common electrode 34 is composed of a rectangular frame. That is, the common electrode 34 is composed of the first and second electrodes extending in the Y direction, and the third and fourth electrodes connecting both ends of the first and second electrodes and extending in the X direction. Similarly, the common electrode 42 is composed of a rectangular frame. That is, the common electrodes 34 and 42 of the comparative example do not have protrusions. The common electrodes 34 and 42 are configured to surround the pixel electrodes 32, respectively. Other configurations are the same as those in the first embodiment.

FIG. 18 is a plan view of the display panel according to the second comparative example. FIG. 19 is a cross-sectional view of the display panel along the AA'line of FIG. In the second comparative example, the TFT substrate 20 and the CF substrate 21 are misaligned. As an example, in FIGS. 18 and 19, the CF substrate 21 is displaced to the right by the deviation amount Δ with respect to the TFT substrate 20. Due to this misalignment, the distance between the pixel electrode 32 (electrode 32-1) and the common electrode 42 is different on the left and right.

In addition, FIGS. 18 and 19 also show the operation in the on state. In the comparative example, in the region on the left side of the pixel electrode 32 (half the region of the approximate pixel) of the pixels, the plurality of liquid crystal molecules are tilted in substantially the same direction. Similarly, in the region of the pixel on the right side of the pixel electrode 32 (the other half region of the approximate pixel), the plurality of liquid crystal molecules are tilted in substantially the same direction.

Here, in a state where no misalignment has occurred (FIGS. 16 and 17), the shortest horizontal distance between the common electrode 42 on the CF substrate 21 side and the pixel electrode 32 on the TFT substrate 20 side is t, and the TFT substrate 20 The shortest distance between the common electrode 34 and the pixel electrode 32 is L, the vertical distance (cell gap) between the common electrode 34 and the common electrode 42 is d, and the voltage between the common electrode 34 (and the common electrode 42) and the pixel electrode 32. Let V be the difference. The oblique electric field Ea and the transverse electric field Eb are represented by the following equations (1) and (2), respectively.

Ea = V / (t ² + d ² ) ^1/2 ... (1)
Eb = V / L ... (2)

As shown in FIG. 19, assuming that the TFT substrate 20 and the CF substrate 21 are misaligned by the amount of deviation Δ in the horizontal direction, the diagonal electric field Ea1 and the lateral electric field Eb1 on the left side of the pixel electrode 32-1 and the pixels. The diagonal electric field Ea2 and the lateral electric field Eb2 on the right side of the electrode 32 are represented by the following equations (3) to (5).

Ea1 = V / {(t−Δ) ² + d ² } ^1/2 ... (3)
Ea2 = V / {(t + Δ) ² + d ² } ^1/2 ... (4)
Eb1 = Eb2 = V / L ... (5)

In this way, the diagonal electric field Ea2 on the right side of the pixel electrode 32 becomes lower than the diagonal electric field Ea1 on the left side, and an imbalance of electric fields occurs on the left and right sides of the pixel electrode 32. As a result, the transmittance in the pixel becomes non-uniform on the left and right sides of the pixel electrode 32, and display unevenness occurs. Display unevenness (luminance unevenness and / or color unevenness) means that the color and brightness differ depending on the region. In addition, the transmittance becomes non-uniform on the left and right, which increases the dependence on the viewing angle. The viewing angle dependence is a property in which the appearance (contrast ratio and / or color) differs depending on the viewing angle (angle of viewing the screen).

On the other hand, in the present embodiment, since the liquid crystal molecules are tilted in all directions, it is possible to reduce the region where the transmittance is non-uniform. In particular, in the present embodiment, even when the above-mentioned misalignment occurs, display unevenness can be reduced and viewing angle dependence can be reduced.

[7] Effect of First Embodiment As described in detail above, in the first embodiment, the liquid crystal display device 10 is filled between the TFT substrate 20, the CF substrate 21, the TFT substrate 20, and the CF substrate 21, and the electric field is charged. The liquid crystal layer 22 is provided with a vertically oriented liquid crystal layer 22 in a state where the above is not applied. Further, the liquid crystal display device 10 is provided on the TFT substrate 20, a pixel electrode 32 electrically connected to the switching element 19, a common electrode 34 provided on the TFT substrate 20 and surrounding the pixel electrode 32, and a CF substrate 21. It is provided with a common electrode 42 that covers the common electrode 34 in a plan view. The pixel electrode 32 includes an electrode 32-1 extending in the first direction, a plurality of protrusions 32A extending in the second direction intersecting the electrode 32-1 in the first direction, and electrodes 32-1 opposite to the second direction. Includes a plurality of protrusions 32B extending in the third direction. The common electrode 34 includes electrodes 34-1 and 34-2 extending in the first direction, a plurality of protrusions 34A extending in the third direction from the electrode 34-1 and a plurality of protrusions extending in the second direction from the electrode 34-2. Including part 34B. The common electrode 42 includes electrodes 42-1 and 42-2 extending in the first direction, a plurality of protrusions 42A extending in the third direction from the electrode 42-1 and a plurality of protrusions extending in the second direction from the electrode 42-2. Including part 42B. The plurality of protrusions 32A and the plurality of protrusions 42A are alternately arranged along the first direction. The plurality of protrusions 32B and the plurality of protrusions 42B are alternately arranged along the first direction. In a plan view, the protrusion 42A covers the protrusion 34A, and the protrusion 42B covers the protrusion 34B.

Therefore, according to the first embodiment, a plurality of liquid crystal molecules can be tilted in all directions. As a result, it is possible to prevent the transmittance in the pixel from becoming non-uniform. As a result, display unevenness can be reduced. Further, since it is possible to suppress the display from becoming uneven depending on the viewing angle of the screen, it is possible to reduce the dependence on the viewing angle. As a result, the display characteristics of the liquid crystal display device 10 can be improved.

Further, since the region effective for display (the gap between the pixel electrode 32 and the common electrode 42) has a zigzag shape, the path length of this region can be lengthened. As a result, the transmittance of the pixels can be improved and the aperture ratio can be improved.

Further, when an electric field is applied to the liquid crystal layer 22, the liquid crystal molecules take a bend orientation (specifically, a half bend orientation), so that the VA (Vertical Alignment) mode and the IPS (In-Plane Switching) / The response speed of the display panel 11 can be improved as compared with the FFS (Fringe Field Switching) mode or the like.

Further, it is not necessary to form a dielectric film for adjusting the electric field applied to the liquid crystal layer, which is required in the conventional TBA (Transverse Bend Alignment) mode, on the common electrode 42 on the CF substrate 21 side. As a result, afterimages (so-called burn-in) generated due to DC (direct current) imbalance can be suppressed.

Further, by arranging the common electrode 42 on the CF substrate 21 side so as to overlap the common electrode 34 on the TFT substrate 20 side in the plane projection, the pixel electrode 32 on the TFT substrate 20 side and the common electrode 42 on the CF substrate 21 side are arranged. The diagonal electric field becomes stronger between them. As a result, the liquid crystal molecules can be tilted so as to have a desired half-bend orientation, so that the transmittance can be improved.

Further, in the TBA mode, it is difficult to reduce the cell gap because the transmittance is low. However, by adopting the structure of the present embodiment, the cell gap can be made smaller, and the response speed can be further increased.

Further, since the cell gap can be reduced, the circular polarizing plate can be used without deteriorating the viewing angle. Further, by arranging the circularly polarizing plate on the display panel 11, it is possible to extract light in a region where liquid crystal molecules that are tilted in the axial direction of the polarizing plate, which could not be extracted by the linear polarizing plate, can be extracted, further improving the transmittance. Is possible. Furthermore, since the optical design of the reflection display can be optimized, it becomes possible to support a semi-transmissive display panel.

[Second Embodiment]
In the second embodiment, the common electrode 34 on the TFT substrate 20 side is not provided with a protrusion, and the common electrode 34 is formed of a rectangular frame. Then, only the common electrode 42 on the CF substrate 21 side is provided with a plurality of protrusions 42A and 42B.

FIG. 20 is a plan view of the display panel 11 according to the second embodiment of the present invention. FIG. 21 is a plan view of the display panel 11 mainly showing the electrode structure on the TFT substrate 20 side. FIG. 22 is a cross-sectional view of the display panel 11 along the AA'line of FIG. The plan view of the common electrode 42 is the same as that of FIG. 5 shown in the first embodiment. The cross-sectional view taken along the line BB'of FIG. 20 is the same as that of FIG. 7 shown in the first embodiment. By superimposing FIGS. 21 and 5, FIG. 20 is obtained.

The common electrode 34 is composed of a rectangular frame and is configured to surround the pixel electrode 32. That is, the common electrode 34 connects the first and second electrodes 34-1 and 34-2 extending in the Y direction and both ends of the first and second electrodes 34-1 and 34-2 and extends in the X direction. The third and fourth electrodes 34-3 and 34-4 are provided. The electrodes 34-1 to 3-4-4 are arranged at the boundary portion of the pixel. The electrodes 34-1 to 3-4-4 are shared by four pixels adjacent to each other in the X direction and the Y direction, respectively.

The end of the electrode 42-1 is the same as the end of the electrode 34-1 or is arranged closer to the pixel electrode 32 than the end of the electrode 34-1. The end of the electrode 42-2 is the same as the end of the electrode 34-2, or is arranged closer to the pixel electrode 32 than the end of the electrode 34-2. The end of the electrode 42-3 is the same as the end of the electrode 34-3, or is arranged closer to the pixel electrode 32 than the end of the electrode 34-3. The end of the electrode 42-4 is the same as the end of the electrode 34-4, or is arranged closer to the pixel electrode 32 than the end of the electrode 34-4. Other configurations are the same as those in the first embodiment.

In the second embodiment, the same operation as in the first embodiment can be realized. The effect of the second embodiment is the same as that of the first embodiment.

In each of the above embodiments, a configuration example of a semi-transmissive display panel including a reflection region and a transmission region is shown. However, it is also possible to apply this embodiment to a transmissive display panel that does not include a reflective region. The transmissive display panel is configured by removing the reflective film from the structure of the transflective display panel.

In the present specification, the plate and the film are expressions exemplifying the members thereof, and are not limited to the configuration thereof. For example, the retardation plate is not limited to the plate-shaped member, and may be a film or other member having the functions described in the specification. The polarizing plate is not limited to the plate-shaped member, and may be a film or other member having the functions described in the specification.

The present invention is not limited to the above embodiment, and the constituent elements can be modified and embodied within a range that does not deviate from the gist thereof. Further, the above-described embodiment includes inventions at various stages, and by an appropriate combination of a plurality of components disclosed in one embodiment or an appropriate combination of components disclosed in different embodiments. Various inventions can be constructed. For example, even if some components are deleted from all the components disclosed in the embodiment, if the problem to be solved by the invention can be solved and the effect of the invention is obtained, these components are deleted. The embodiment can be extracted as an invention.

... 10 ... LCD display device, 11 ... Display panel, 12 ... Backlight, 13 ... Scan driver, 14 ... Signal driver, 15 ... Common electrode driver, 16 ... Voltage generation circuit, 17 ... Control circuit, 18 ... Pixel, 19 ... Switching element, 20 ... TFT substrate, 21 ... CF substrate, 22 ... liquid crystal layer, 23 ... gate electrode, 24 ... storage electrode, 25 ... gate insulating film, 26 ... semiconductor layer, 27A ... source electrode, 27B, 28B ... connection electrode , 28A ... drain electrode, 29, 31 ... insulating film, 30 ... reflective film, 32 ... pixel electrode, 33 ... contact plug, 34 ... common electrode, 35, 43 ... alignment film, 40 ... black matrix, 41 ... color filter, 42 ... common electrode, 44, 45 ... retardation plate, 46, 47 ... polarizing plate.

Claims (7)

1st and 2nd boards,
The liquid crystal layer filled between the first and second substrates,
The switching element provided on the first substrate and
A pixel electrode provided on the first substrate and electrically connected to the switching element,
A first common electrode provided on the first substrate, having a rectangular shape, and linearly surrounding the pixel electrode,
A second common electrode provided on the second substrate and covering the first common electrode in a plan view is provided.
The pixel electrodes include a first electrode extending in the first direction, first and second protrusions extending from the first electrode in the second direction intersecting the first direction, and the second direction from the first electrode. Includes third and fourth protrusions extending in the third direction opposite to
The second common electrode includes second and third electrodes extending in the first direction, fifth and sixth protrusions extending in the third direction from the second electrode, and the second direction from the third electrode. Including the 7th and 8th protrusions extending to
The first and second protrusions and the fifth and sixth protrusions are alternately arranged along the first direction.
A liquid crystal display device in which the third and fourth protrusions and the seventh and eighth protrusions are alternately arranged along the first direction. The liquid crystal display device according to claim 1, wherein the gap between the pixel electrode and the second common electrode has a zigzag shape in a plan view. The first common electrode includes a fourth and fifth electrode extending in the first direction,
The liquid crystal display device according to claim 1 or 2 , wherein the second and third electrodes cover the fourth and fifth electrodes, respectively, in a plan view. The liquid crystal display device according to any one of claims 1 to 3 , wherein the liquid crystal layer is made of a P-type liquid crystal material and is vertically oriented without applying an electric field. The liquid crystal display device according to any one of claims 1 to 4 , wherein the same voltage is applied to the first and second common electrodes. The liquid crystal display device according to any one of claims 1 to 5 , further comprising first and second circular polarizing plates arranged so as to sandwich the first and second substrates. The liquid crystal display device according to any one of claims 1 to 6 , further comprising a reflective film provided on the first substrate so as to cover the switching element.

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