Liquid crystal display device

Abstract

Provided is a liquid crystal display device which is capable of sufficiently suppressing generation of afterimage and is also useful as an in-cell touch panel capable of display in a reflection mode. The liquid crystal display device includes: a first substrate; a second substrate opposite to the first substrate; and a liquid crystal layer provided between the first substrate and the second substrate and having a plurality of pixels arranged in a matrix, the first substrate having a reflective layer for reflecting light, a first electrode and a second electrode capable of generating a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer. At least one of the first electrode and the second electrode has a plurality of strip-shaped portions and slits, the slits are located between two adjacent strip-shaped portions among the plurality of strip-shaped portions, and in each pixel, the plurality of strip-shaped portions are formed by linear shapes substantially parallel to each other and extending in the same direction, and do not include curved portions. The second substrate has a second horizontal alignment film in contact with the liquid crystal layer, and the liquid crystal layer is twisted and aligned when no voltage is applied.

Description

Technical Field

[0001] The following disclosure relates to a liquid crystal display device. Background Art

[0002] Liquid crystal display devices are display devices that use liquid crystal materials for display, and are generally divided into transmissive liquid crystal display devices and reflective liquid crystal display devices according to the display mode. A transmissive liquid crystal display device is a device that performs a transmissive mode display using transmitted light based on the backlight source on the back of the screen, and a reflective liquid crystal display device is a device that performs a reflective mode display using external light (also called ambient light) instead of the backlight source. As a display device having these characteristics at the same time, a semi-transmissive liquid crystal display device has an area for displaying in a transmissive mode and an area for displaying in a reflective mode in each pixel (for example, refer to Patent Document 1).

[0003] Liquid crystal display devices can also be roughly divided according to the driving method of the liquid crystal. For example, there are known liquid crystal display devices of a longitudinal electric field method that uses an electric field in a direction substantially perpendicular to the substrate surface to drive the liquid crystal layer for display, and liquid crystal display devices of a transverse electric field method that uses an electric field in a direction substantially parallel to the substrate surface to drive the liquid crystal layer for display. As the longitudinal electric field method, for example, TN (Twisted Nematic) mode, MVA (Multi-domain Vertical Alignment) mode, etc. can be exemplified, and as the transverse electric field method, IPS (In-plane Switching) mode, FFS (Fringe Field Switching) mode, etc. can be exemplified. For example, in Patent Document 2, a liquid crystal display suitable as a liquid crystal display device of a transverse electric field method is disclosed. This liquid crystal display can suppress adverse conditions caused by process deviations and improve display performance, and is particularly useful as a transmissive liquid crystal display device. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent No. 5767195 Patent Document 2: Japanese Patent No. 5756860 Summary of the invention Technical Problems to be Solved by the Invention

[0005] However, in recent years, liquid crystal display devices used in smart phones or tablet computers usually have touch sensor functions. As touch sensor methods, various methods such as resistive film, electrostatic capacitance, and optical are known. In liquid crystal display devices (also called touch panels) equipped with touch sensors, there are external touch sensor methods (external type) and built-in touch sensor methods (built-in type). Compared with external touch panels, built-in touch panels are more conducive to narrow frame, thin and lightweight, etc., and also have the advantage of improving light transmittance.

[0006] There are two types of built-in touch panels: On-Cell (external embedded) type and In-Cell (internal embedded) type. Cell refers to a display panel (also called a liquid crystal panel) having an active matrix substrate represented by a thin film transistor (TFT) substrate, a relative substrate arranged opposite to the substrate, and a liquid crystal layer sandwiched between these substrates. However, generally speaking, in the internal embedded type, a layer that performs the touch sensor function is arranged in the display panel, and in the external embedded type, the layer that performs the touch sensor function is arranged between the display panel and the polarizing plate arranged on the viewing side of the display panel. Among them, the internal embedded type can, in principle, realize the thinnest and lightest touch panel. In addition, since liquid crystal display devices capable of displaying in a reflective mode are suitable for outdoor use, although an internal embedded touch panel capable of displaying in a reflective mode is required, it has not yet been realized.

[0007] The reason why this has not been realized is that in the current reflective liquid crystal display device, one of a pair of electrodes for applying voltage to the liquid crystal layer (also referred to as a counter electrode or a common electrode) is disposed on the opposite substrate side. Therefore, the inventors believe that if a lateral electric field mode such as the FFS mode is used, since a pair of electrodes are only disposed on the active matrix substrate side, an in-cell touch panel capable of displaying a reflective mode can be realized, and therefore in-depth research has been conducted on lateral electric field mode liquid crystal display devices.

[0008] That is, specifically, a mobile TFT substrate is used, pixel electrodes and common electrodes for applying voltage to the liquid crystal layer are arranged on the TFT substrate side, and the common electrode is used as a slit electrode with a slit-shaped opening, and a negative liquid crystal material is used to produce a device capable of displaying an FFS mode of a reflective mode (refer to Verification Example 1 described later). In such a device, since the orientation disorder occurs due to the influence of the electric field at the end of the pixel, the strip portion constituting the slit electrode is usually formed into a shape in which a straight line is bent in the middle. The device is set to a white display state, and after black characters are written to the device in this state, when the written characters are erased (i.e., returned to the white display state), the afterimage of the characters is visually recognized as a burn-in (refer to Fig. 20C). Such afterimages may also occur during normal screen operations and dynamic image playback. Therefore, such devices have the problem of generating afterimages.

[0009] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a liquid crystal display device which can sufficiently suppress the occurrence of an afterimage and is also useful as an in-cell touch panel capable of displaying in a reflective mode. Solutions for solving problems

[0010] (1) One embodiment of the present invention is a liquid crystal display device, which includes: a first substrate; a second substrate, which is opposite to the first substrate; and a liquid crystal layer, which is provided between the first substrate and the second substrate and has a plurality of pixels arranged in a matrix, the first substrate having a reflective layer that reflects light, a first electrode and a second electrode that can generate a lateral electric field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer, at least one of the first electrode and the second electrode having a plurality of strip-shaped portions and a slit, the slit being located between two adjacent strip-shaped portions among the plurality of strip-shaped portions, in each pixel, the plurality of strip-shaped portions are composed of straight lines that are substantially parallel to each other and extend in the same direction and do not include a bent portion, the second substrate having a second horizontal alignment film that is in contact with the liquid crystal layer, and the liquid crystal layer has a twisted orientation when no voltage is applied.

[0011] (2) In addition, one embodiment of the present invention is a liquid crystal display device, wherein, in addition to the configuration of (1) above, the plurality of strip-shaped portions do not include a cutout portion.

[0012] (3) In addition, an embodiment of the present invention is a liquid crystal display device, which, in addition to the structure of (1) or (2) above, has the directions in which the plurality of strip-shaped portions extend in the same direction at least in adjacent pixels or in a display area.

[0013] (4) In addition, an embodiment of the present invention is a liquid crystal display device, in which, in addition to the structure of (1), (2) or (3), the liquid crystal layer contains a positive liquid crystal material.

[0014] (5) In addition, an embodiment of the present invention is a liquid crystal display device, in which, in addition to the structure of (1), (2) or (3), the liquid crystal layer contains a negative liquid crystal material.

[0015] (6) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (1), the above (2), the above (3), the above (4) or the above (5), has a twist angle of the liquid crystal layer when no voltage is applied that is greater than 58.3° and less than 89.9°.

[0016] (7) In addition, a certain embodiment of the present invention is a liquid crystal display device, in which, based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5) or the above (6), the liquid crystal layer is monodomain oriented.

[0017] (8) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6) or the above (7), has the orientation direction of the liquid crystal molecules on the first substrate side when no voltage is applied, with the direction in which the multiple strip-shaped portions extend as a reference (0°), and is greater than -30° and less than 30°.

[0018] (9) In addition, one embodiment of the present invention is a liquid crystal display device, which, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7) or (8), For the plurality of strip-shaped portions, a ratio L / S of a width L of each strip-shaped portion in a plan view to a width S of each slit in a plan view is 0.4 to 0.7 / 1.

[0019] (10) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6), the above (7), the above (8) or the above (9), also includes a polarizing plate arranged on the outside of the first substrate and / or the second substrate, and a phase difference layer arranged between the substrate and the polarizing plate.

[0020] (11) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above-mentioned (10), the liquid crystal layer contains a positive liquid crystal material, the polarizer is an absorption-type polarizer, and the light absorption axis of the polarizer is greater than 5° and less than 35°, with the direction orthogonal to the direction in which the multiple strip portions extend as a reference (0°).

[0021] (12) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (10) or the above (11), the liquid crystal layer includes a positive liquid crystal material, the phase difference layer includes a λ / 2 plate, and the in-plane slow axis of the λ / 2 plate is greater than 25° and less than 50° with respect to the direction orthogonal to the direction in which the multiple strip-shaped portions extend as a reference (0°).

[0022] (13) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (10), the above (11) or the above (12), the liquid crystal layer includes a positive liquid crystal material, the phase difference layer includes a λ / 4 plate, and the in-plane slow axis of the λ / 4 plate is greater than 45° and less than 70° with respect to the direction orthogonal to the direction in which the multiple strip-shaped portions extend as a reference (0°).

[0023] (14) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above-mentioned (10), the liquid crystal layer contains a negative liquid crystal material, the polarizer is an absorption-type polarizer, and the absorption axis of the polarizer is greater than -85° and less than -55°, with the direction orthogonal to the direction in which the multiple strip portions extend as a reference (0°).

[0024] (15) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (10) or the above (14), the liquid crystal layer includes a negative liquid crystal material, the phase difference layer includes a λ / 2 plate, and the in-plane slow axis of the λ / 2 plate is greater than -65° and less than -40° with respect to the direction orthogonal to the direction in which the multiple strip-shaped portions extend as a reference (0°).

[0025] (16) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (10), the above (14) or the above (15), the liquid crystal layer includes a negative liquid crystal material, the phase difference layer includes a λ / 4 plate, and the in-plane slow axis of the λ / 4 plate is greater than -40° and less than -15° with respect to the direction orthogonal to the direction in which the multiple strip-shaped portions extend as a reference (0°).

[0026] (17) In addition, a certain embodiment of the present invention is a liquid crystal display device, which displays in a normally black mode based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6), the above (7), the above (8), the above (9), the above (10), the above (11), the above (12), the above (13), the above (14), the above (15) or the above (16).

[0027] (18) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6), the above (7), the above (8), the above (9), the above (10), the above (11), the above (12), the above (13), the above (14), the above (15), the above (16) or the above (17), one of the first electrode or the second electrode is a pixel electrode respectively arranged on the plurality of pixels, and the other is a common electrode including a plurality of segments that can respectively function as touch sensor electrodes, and the first substrate has a plurality of touch wirings respectively connected to the corresponding touch sensor electrodes.

[0028] (19) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17) or (18), further includes a light source. Effects of the Invention

[0029] According to the present invention, it is possible to provide a liquid crystal display device which can sufficiently suppress the occurrence of an afterimage and is also useful as an in-cell touch panel capable of performing a display in a reflective mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the first embodiment. Figure 2 FIG. 1 is a schematic cross-sectional view showing a liquid crystal display device 1 according to an example of Embodiment 1 in more detail. Figure 3 This is a schematic plan view of the entire liquid crystal display device 1 according to an example of the first embodiment when viewed from the observation surface side. Figure 4A It is a diagram for explaining the slit angle of positive liquid crystal molecules. Figure 4B It is a diagram for explaining the slit angle of negative liquid crystal molecules. Figure 5 1 is a schematic plan view showing a configuration example of a pixel (angle X is 0°). Fig. 6A 1 is a schematic plan view showing an example of pixel arrangement (angle X is 0°). Figure 6B 1 is a schematic plan view showing an example of pixel arrangement (angle X is -10°). Figure 6C1 is a schematic plan view showing an example of pixel arrangement (angle X is +10°). Fig.6D 1 is a schematic plan view showing an example of pixel arrangement (angle X is -90°). Fig. 6E 1 is a schematic plan view showing an example of pixel arrangement (angle X is -100°). Fig. 6F 1 is a schematic plan view showing an example of pixel arrangement (angle X is -80°). Figure 7 1 is a schematic plan view illustrating an arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1 . Figure 8 It is a schematic cross-sectional view showing the liquid crystal display device 1 according to the first modification of the first embodiment in more detail. Fig. 9 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the second embodiment. Fig.10 FIG. 1 is a schematic cross-sectional view showing a liquid crystal display device 1 according to an example of the second embodiment in more detail. Fig.11 This is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42 and the polarization axis 50A of the polarizing plate 50 in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 4 plate 41, a λ / 2 plate 42 and a polarizing plate 50. Fig.12 This is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42 and the polarization axis 50A of the polarizing plate 50 in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 4 plate 41, a λ / 2 plate 42 and a polarizing plate 50. Fig.13 It is a schematic cross-sectional view showing the liquid crystal display device 1 according to the first modification of the second embodiment in more detail. Fig.14 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the third embodiment. Fig.15 1 is a schematic plan view conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 according to the third embodiment. Fig.16 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the fourth embodiment. Fig.17A This is a schematic cross-sectional view of the device produced in Verification Example 1. Fig. 17B This is a schematic cross-sectional view of the device envisioned in Test Examples 1 and 2. Fig.18 This is a CAD diagram showing only the pixel electrode PE and the common electrode CE on the TFT substrate side in a plan view. Fig.19 This is an image (top view image) of the inside of the device observed with a microscope in Verification Example 1. Fig. 20A This is a top view photograph of the initial state of the device taken from the observation surface side in Verification Example 1. Fig. 20B This is a top view photograph of the device in the initial state in Verification Example 1, taken from the observation surface side, showing a state where black characters are written. Fig. 20C This is a top view photograph taken from the observation surface side in Verification Example 1, showing a state where the written characters have been erased. Fig.21 This is a plan view conceptually showing that the rotation directions of the liquid crystal molecules 21 (negative liquid crystal) are different in the center of a pixel (a) and the edge of the pixel (b). Fig. 22 is Fig.18 A conceptual diagram showing the rotation direction of the liquid crystal molecules 21 is superimposed thereon. Fig.23 is Fig.19 A conceptual diagram showing the rotation direction of the liquid crystal molecules 21 is superimposed thereon. Fig.24A It is a figure which conceptually shows the simulation result of the test example 1 (refer to (a)) and a some strip|belt part SP based on this result (refer to (b)). Fig. 24B It is a figure which conceptually shows the simulation result of the test example 2 (refer to (a)) and a some strip|belt part SP based on this result (refer to (b)). Fig.25 1 is a schematic cross-sectional view of a liquid crystal panel 1X included in the device assumed in Test Examples 3 and 4. Fig.26 1 is a schematic diagram conceptually showing the electrode structure of the pixel electrode PE and the common electrode CE. Fig. 27 This is a plan view conceptually showing the axis settings of each optical film used in Test Example 3. Fig.28 This is a plan view conceptually showing the axis settings of each optical film used in Test Example 4. Fig.293 is a graph showing the results of Test Example 3. Fig.30 is a graph showing the results of Test Example 4. Fig.31 This is a plan view conceptually showing the axis settings of each optical film used in Test Example 5. Fig.32 This is a plan view conceptually showing the axis settings of each optical film used in Test Example 6. Fig.33 : is a graph showing the results of Test Example 5. Fig.34 3 is a graph showing the results of Test Example 6. DETAILED DESCRIPTION

[0031] (Definition of terms) In this specification, the observer side refers to the side closer to the screen (display surface) of the liquid crystal display device, and the rear side refers to the side farther from the screen (display surface) of the liquid crystal display device.

[0032] The no voltage applied state refers to a state where the voltage applied to the liquid crystal layer is less than the threshold voltage (including no voltage applied). The voltage applied state refers to a state where the voltage applied to the liquid crystal layer is greater than the threshold voltage. In this specification, the no voltage applied state is also referred to as the no voltage applied state, and the voltage applied state is referred to as the voltage applied state.

[0033] The polar angle refers to an angle formed between a target direction (eg, a measurement direction) and a normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction of the object when it is projected onto the screen of the liquid crystal panel, and is expressed by the angle (azimuth) formed with the reference azimuth. Here, the reference azimuth (0°) is set to the horizontal right direction of the screen of the liquid crystal panel. For angles and azimuths, the counterclockwise angle is set as a positive angle from the reference azimuth, and the clockwise angle is set as a negative angle from the reference azimuth. Counterclockwise and clockwise both represent the rotation direction when the screen of the liquid crystal panel is observed from the observation side (front). In addition, the angle represents the value measured when the screen of the liquid crystal panel is viewed from above, and unless there is a description of the rotation direction, the angle of the acute angle is represented.

[0034] The axis orientation of an optical film refers to the orientation of the polarization axis of the polarizing plate if it is a polarizing plate, and the orientation of the slow axis if it is a phase difference layer. The polarization axis of the polarizing plate refers to the absorption axis if it is an absorption-type polarizing plate, and the reflection axis if it is a reflection-type polarizing plate. The axis orientation of the phase difference layer refers to the orientation of the slow axis in the plane of the phase difference layer, unless otherwise specified.

[0035] The phase difference layer refers to a layer in which at least one of the in-plane delay (also referred to as in-plane phase difference) Re and the thickness direction delay (also referred to as thickness direction phase difference) Rth has a value of 10 nm or more. Preferably, it refers to a value of 20 nm or more (≥20 nm). In addition, in this specification, the numerical values ​​recorded as Re and Rth are absolute values ​​unless otherwise specified.

[0036] The in-plane phase difference Re is defined by Re=(nx-ny)×d. The thickness direction retardation Rth is defined by Rth={nz-(nx+ny) / 2}×d. nx represents the principal refractive index in the slow axis direction in the plane of each retardation layer. Ny represents the principal refractive index in the fast axis direction within the plane of each retardation layer. Nz represents the principal refractive index in the direction perpendicular to the surface of each retardation layer. The slow axis direction is the direction with the largest refractive index, and the fast axis direction is the direction with the smallest refractive index. d represents the thickness of the phase difference layer.

[0037] The A plate is a phase difference plate that satisfies “nx>ny≈nz”.

[0038] Unless otherwise specified, the measurement wavelength of optical parameters such as refractive index and phase difference is 550 nm.

[0039] Substantially parallel means that the angle (absolute value) formed by the two is within the range of 0°±10°, preferably within the range of 0°±5°, and more preferably 0° (i.e., parallel in a narrow sense). In addition, substantially orthogonal (or substantially perpendicular) means that the angle (absolute value) formed by the two is within the range of 90°±10°, preferably within the range of 90°±5°, and more preferably 90° (i.e., perpendicular or perpendicular in a narrow sense).

[0040] Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiment, and the design can be appropriately changed within the scope of the configuration satisfying the present invention.

[0041] (Implementation Method 1) Figure 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Figure 2 It is a schematic cross-sectional view showing the liquid crystal display device 1 according to an example of the present embodiment in more detail. Figure 3 1 is a schematic plan view of the entire liquid crystal display device 1 of one example of the present embodiment when viewed from the observation surface side. Figure 1As shown, the liquid crystal display device 1 includes a first substrate 10, a liquid crystal layer 20, and a second substrate 30 in order from the back side. In this embodiment, a TFT substrate is used as the first substrate 10. In addition, a portion or a structure consisting of a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0042] like Figure 3 As shown, the liquid crystal display device 1 has a plurality of pixels P arranged in a matrix. The plurality of pixels P typically include three types of pixels, namely red pixels, green pixels and blue pixels, but the types of pixels may be less than two or more than four. Each pixel P includes a thin film transistor (TFT) 110, a first electrode 121 and a second electrode 122 capable of generating a lateral electric field on the liquid crystal layer 20. The gate electrode of the TFT 110 is electrically connected to the corresponding gate wiring (also called scanning wiring) GL, and the source electrode of the TFT 110 is electrically connected to the corresponding source wiring (also called signal wiring) SL. The drain of the TFT 110 is electrically connected to the second electrode 122.

[0043] <First Substrate> like Figure 2 As shown, the first substrate 10 has a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 connected to the liquid crystal layer 20 in sequence from the back side to the observation side. The first substrate 10 also preferably has a supporting substrate 100 and a backplane circuit BP on the back side of the reflective layer 130. An insulating layer (also called an insulating film) is provided between each layer as needed. For example, a first interlayer insulating layer 151 is provided in a manner covering the backplane circuit BP, a second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 with the reflective layer 130 sandwiched therebetween, and a dielectric layer (also called a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

[0044] The support substrate 100 is preferably transparent and insulating, and examples of the support substrate 100 include a glass substrate and a plastic substrate.

[0045] The backplane circuit BP is provided on the support substrate 100. The backplane circuit BP is a circuit for driving the plurality of pixels P, and includes the TFTs 110, the gate wiring GL, the source wiring SL, etc. In addition, the backplane circuit BP is generally provided with a gate insulating film 150G.

[0046] TFT110 is provided in each of the plurality of pixels P. As TFT110, a TFT containing an oxide semiconductor layer as an active layer (also referred to as an oxide semiconductor TFT) is preferably used. In recent years, the oxide semiconductor contained in the oxide semiconductor layer has attracted attention as an active layer material replacing amorphous silicon or polycrystalline silicon, and has a higher mobility than amorphous silicon. Therefore, compared with amorphous silicon TFT, the oxide semiconductor TFT can operate at a higher speed. In addition, the oxide semiconductor layer is formed by a simpler process than the polycrystalline silicon layer, so it can also be applied to devices requiring a large area.

[0047] Since oxide semiconductor TFT has excellent off-leakage characteristics, it is also possible to use a driving method that reduces the frequency of image rewriting for display. For example, when displaying a static image, the image data can be rewritten once per second. This driving method is called dormant drive or low-frequency drive, etc., which can significantly reduce the power consumption of the liquid crystal display device. By adopting dormant drive, by performing touch detection during the period when the image is not rewritten, the reduction in the sensitivity of the touch operation caused by the noise from the drive circuit can be suppressed, and the S / N ratio (signal-to-noise ratio) can be made, for example, about 10 times that of the past.

[0048] Oxide semiconductor TFTs are also advantageous in reducing the size of TFTs, and thus a configuration in which a memory circuit is provided for each pixel P (also referred to as MIP (Memory In Pixels)) can be appropriately realized.

[0049] The oxide semiconductor may be an amorphous oxide semiconductor or a crystalline oxide semiconductor having a crystalline portion. Examples of the crystalline oxide semiconductor include polycrystalline oxide semiconductors, microcrystalline oxide semiconductors, and crystalline oxide semiconductors in which the c-axis is oriented substantially perpendicular to the layer surface.

[0050] The oxide semiconductor layer may be a single layer or may have a stacked structure of more than two layers. The oxide semiconductor layer having a stacked structure may include an amorphous oxide semiconductor layer and a crystalline oxide semiconductor layer, may include multiple crystalline oxide semiconductor layers with different crystalline structures, or may include multiple amorphous oxide semiconductor layers. In the case where the oxide semiconductor layer has a two-layer structure including an upper layer and a lower layer, the energy gap of the oxide semiconductor included in the lower layer and the energy gap of the oxide semiconductor included in the upper layer may also be different.

[0051] The materials, structures, and film formation methods of amorphous oxide semiconductors and crystalline oxide semiconductors, and the composition of oxide semiconductor layers having a stacked structure are described in, for example, Japanese Patent Application Laid-Open No. 2014-007399. For reference, the disclosure of Japanese Patent Application Laid-Open No. 2014-007399 is incorporated herein in its entirety.

[0052] Specifically, as an oxide semiconductor layer, it is preferred to contain at least one metal element of In (indium), Ga (gallium) and Zn (zinc). Among them, an oxide semiconductor film containing a ternary oxide of In, Ga and Zn is more preferred. As a ternary oxide of In, Ga and Zn, for example, indium gallium zinc oxide is preferably exemplified. A semiconductor containing a ternary oxide of In, Ga and Zn is called an In-Ga-Zn-O semiconductor, but in this semiconductor, the ratio (composition ratio) of In, Ga and Zn is not particularly limited, for example, In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, In:Ga:Zn=1:1:2, etc.

[0053] The In-Ga-Zn-O semiconductor may be amorphous or crystalline. As a crystalline In-Ga-Zn-O semiconductor, a semiconductor whose c-axis is oriented substantially perpendicular to the layer surface is preferably used.

[0054] In addition, the crystal structure of the crystalline In-Ga-Zn-O semiconductor is disclosed in, for example, the above-mentioned Japanese Patent Publication No. 2014-007399, Japanese Patent Publication No. 2012-134475, Japanese Patent Publication No. 2014-209727, etc. For reference, the disclosures of Japanese Patent Publication No. 2012-134475 and Japanese Patent Publication No. 2014-209727 are all cited in this specification. The TFT with the In-Ga-Zn-O semiconductor layer has a high mobility (more than 20 times compared with a-SiTFT) and a low leakage current (less than 1 / 100 compared with a-SiTFT), so it is suitable for use as a driving TFT (for example, a TFT included in a driving circuit provided on the same substrate as the display area around a display area including a plurality of pixels) and a pixel TFT (a TFT provided in a pixel).

[0055] The oxide semiconductor layer may include an oxide semiconductor other than an In-Ga-Zn-O semiconductor. For example, a ternary oxide of In, Sn (tin) and Zn is listed, such as In2O3-SnO2-ZnO, and InSnZnO is preferably exemplified. A semiconductor containing a ternary oxide of In, Sn and Zn is called an In-Sn-Zn-O semiconductor. Alternatively, the oxide semiconductor layer may also include In-Al-Zn-O series semiconductors, In-Al-Sn-Zn-O series semiconductors, Zn-O series semiconductors, In-Zn-O series semiconductors, Zn-Ti-O series semiconductors, Cd-Ge-O series semiconductors, Cd-Pb-O series semiconductors, CdO (cadmium oxide), Mg-Zn-O series semiconductors, In-Ga-Sn-O series semiconductors, In-Ga-O series semiconductors, Zr-In-Zn-O series semiconductors, Hf-In-Zn-O series semiconductors, Al-Ga-Zn-O series semiconductors, Ga-Zn-O series semiconductors, In-Ga-Zn-Sn-O series semiconductors, etc.

[0056] The first interlayer insulating layer 151 is provided to cover the backplane circuit BP. The surface of the first interlayer insulating layer 151 on the side of the reflective layer 130 preferably has a concavo-convex shape (also referred to as a concavo-convex surface structure). Thus, the reflective layer 130 can have a concavo-convex surface structure reflecting the shape. The first interlayer insulating layer 151 having a concavo-convex surface structure can be formed using a photosensitive resin, for example, as described in Patent Gazette No. 3394926.

[0057] The reflective layer (also referred to as a reflective film) 130 is provided on the first interlayer insulating layer 151. The reflective layer 130 is formed of a material that reflects light. Among them, it is preferably formed of a metal material with high reflectivity. Examples of the material of the reflective layer 130 include silver alloys and aluminum alloys.

[0058] Preferably, the reflective layer 130 has a concave-convex shape reflecting the concave-convex surface structure preferably possessed by the first interlayer insulating layer 151. That is, the reflective layer 130 also preferably has a concave-convex surface structure. The concave-convex surface structure is also referred to as MRS (MicroReflective Structure), which is provided to diffusely reflect ambient light and realize a white display close to paper white. Preferably, the concave-convex surface structure is composed of a plurality of convex portions p randomly arranged in such a manner that the center spacing of adjacent convex portions p is 5 μm or more and 50 μm or less. The center spacing of adjacent convex portions p is more preferably 10 μm or more and 20 μm or less. Observed from the normal direction of the supporting substrate, the shape of the convex portion p is preferably approximately circular or approximately polygonal. The area occupied by the convex portion p in one pixel P is preferably, for example, approximately 20 to 40%, and the height of the convex portion p is, for example, 1 μm or more (≥1 μm) and 5 μm or less.

[0059] By having the reflective layer 130 and introducing a phase difference layer with a broadband λ / 4 condition, polarization conversion (e.g., conversion between circularly polarized light and linearly polarized light) unique to a reflective liquid crystal display device can be performed, and thus light loss is sufficiently reduced. The broadband λ / 4 condition refers to a condition for obtaining polarized light close to circularly polarized light in a wide range within the visible wavelength.

[0060] The second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 so as to cover the reflective layer 130. That is, the reflective layer 130 is arranged between the first interlayer insulating layer 151 and the second interlayer insulating layer 152.

[0061] Here, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably formed of an organic insulating material or an inorganic insulating material. For example, as an organic insulating film obtained using an organic insulating material, organic films (relative dielectric constant ε=2~5) such as acrylic resin, polyimide resin, and phenolic varnish resin, or stacked bodies thereof can be listed. The film thickness of the organic insulating film is not particularly limited, but for example, it is greater than 2μm and less than 4μm. As an inorganic insulating film obtained using an inorganic insulating material, for example, inorganic films (relative dielectric constant ε=5~7) such as silicon nitride (SiNx) and silicon oxide (SiO2), or stacked films thereof can be listed. The film thickness of the inorganic insulating film is not particularly limited, but for example, it is Above and In addition, a laminate of an organic insulating film and an inorganic insulating film may be used. Among them, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably organic insulating films.

[0062] The first electrode 121 is arranged on the reflective layer 130 via the second interlayer insulating layer 152, and a dielectric layer 153 is arranged between the first electrode 121 and the second electrode 122. Therefore, the reflective layer 130 is located on the side opposite to the liquid crystal layer 20 (i.e., the side closer to the back than the first electrode 121 and the second electrode 122) relative to the first electrode 121 and the second electrode 122. In addition, in the first electrode 121 and the second electrode 122, in this embodiment, the second electrode 122 is relatively located on the observation surface side, and the first electrode 121 is located on the back side. The electrode relatively located on the observation surface side is also called an upper electrode, and the electrode relatively located on the back side is also called a lower electrode.

[0063] One of the first electrode 121 and the second electrode 122 is a pixel electrode PE, and the other is a common electrode CE. The pixel electrode is provided on each of the plurality of pixels P. The pixel electrode is electrically connected to the backplane circuit BP. In the present embodiment, the first electrode 121 (lower electrode) is the common electrode CE, and the second electrode 122 (upper electrode) is the pixel electrode PE.

[0064] At least one of the first electrode 121 and the second electrode 122 has a plurality of strip-shaped portions SP and a slit S1 between two adjacent strip-shaped portions among the plurality of strip-shaped portions. The strip-shaped portion SP is equivalent to the electrode portion, and the slit S1 is equivalent to the opening portion, but such an electrode is also called a slit electrode or a finger electrode. From the perspective of easy generation of a lateral electric field, it is preferred that at least the upper electrode (the pixel electrode PE in this embodiment) is a slit electrode. At this time, the lower electrode (the common electrode CE in this embodiment) can be a planar electrode, that is, a so-called full-surface electrode, or a slit electrode.

[0065] In each pixel P, the plurality of strip-shaped portions SP constituting the slit electrode (the second electrode 12 of the pixel electrode PE in this embodiment) are composed of straight lines substantially parallel to each other and extending in the same direction, and do not include a bent portion. As a result, the orientation of the liquid crystal molecules becomes uniform, and the occurrence of orientation disorder can be fully suppressed.

[0066] Here, the strip portion SP "is composed of a straight line shape and does not include a bent portion" means that the center line of the strip portion SP is a straight line shape without a bend, not the outer edge of the strip portion SP. The center line of the strip portion SP refers to a line that divides the strip portion SP into two equal parts in the width direction. The width direction refers to a direction that is approximately perpendicular to the direction in which the strip portion SP extends when viewed from above. Therefore, even if the outer edge of the front end portion of the strip portion SP is circular, as long as the center line of the strip portion SP is a straight line without a bend, it is included in the shape of "being composed of a straight line shape and does not include a bend." For comparison, Fig.24A (b) shows the shape of the strip portion SP when it includes a curved portion. Fig. 24B (b) shows the shape without the bent portion.

[0067] It is also preferable that the strip-shaped portion SP does not include a cutout portion. This further suppresses the occurrence of disordered orientation. “The strip-shaped portion SP does not include a cutout portion” means that a part of the strip-shaped portion SP is not cut out or pulled out.

[0068] In each pixel P, the directions in which the plurality of strip-shaped portions SP extend (also referred to as the directions in which the plurality of strip-shaped portions SP extend) are substantially parallel to each other. In addition, the directions in which the plurality of strip-shaped portions SP extend may be different for each pixel, but are preferably the same in two or more adjacent pixels. However, from the viewpoint of image quality and manufacturing, it is preferred that the directions in which the plurality of strip-shaped portions SP extend are at least the same in adjacent pixels. Figure 6A to Figure 6F The example in which the extending directions of the plurality of strip-shaped portions SP are the same in adjacent pixels is shown. It is more preferable that the extending directions of the plurality of strip-shaped portions SP are the same in the display area.

[0069] The width L of each strip-shaped portion SP is, for example, 0.3 to 10 μm, more preferably 1 to 5 μm. Preferably, the interval between two adjacent strip-shaped portions SP (ie, the interval between the center lines of each strip-shaped portion) is also, for example, 0.3 to 10 μm, more preferably 1 to 5 μm.

[0070] The ratio L / S (also referred to as the L / S condition) of the width L of each strip portion in plan view to the width S of each slit in plan view is preferably 0.4 to 0.7 / 1. This improves the reflectance of white display (also referred to as white reflectance), thereby further improving the contrast ratio.

[0071] Here, the orientation direction of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied is preferably -30° or more and 30° or less, based on the extension direction of the plurality of strip-shaped portions XP (0°). For this angle, that is, based on the extension direction of the plurality of strip-shaped portions SP (0°), when the clockwise angle is set as a positive angle (+) and the counterclockwise angle is set as a negative angle (-), the angle formed by the orientation direction of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied is called the slit angle. Figure 4A and Figure 4B Explain the definition of slit angle. Figure 4A is a diagram for explaining the slit angle of positive liquid crystal molecules. Figure 4B This is a diagram for explaining the slit angle of negative liquid crystal molecules. The liquid crystal molecules 21A refer to the liquid crystal molecules 21 near the first horizontal alignment film 140 (i.e., the liquid crystal molecules on the first substrate 10 side when no voltage is applied). The (p) added to the end of the symbol of the liquid crystal molecule indicates a positive type, and (n) indicates a negative type.

[0072] In the case of positive liquid crystal molecules, the orientation direction of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied corresponds to the long axis direction of the liquid crystal molecules 21A. When the long axis direction of the liquid crystal molecules 21A is parallel to the extending direction of the plurality of strip-shaped portions SP, the slit angle is 0° (see Figure 4A ). With the long axis direction of the liquid crystal molecule 21A as a reference (0°), when the extending direction of the plurality of strip-shaped portions XP is rotated clockwise, the slit angle becomes a positive angle (+) (refer to Figure 4A The “positive (+)” column). With the long axis direction of the liquid crystal molecule 21A as a reference (0°), when the extension direction of the plurality of strip-shaped portions XP rotates counterclockwise, the slit angle becomes a negative angle (+) (refer to Figure 4A in the “Negative (-)” column).

[0073] In the case of negative liquid crystal molecules, the orientation direction of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied corresponds to the short axis direction of the liquid crystal molecules 21A. When the short axis direction of the liquid crystal molecules 21A is parallel to the extending direction of the plurality of strip-shaped portions SP, the slit angle is 0° (see Figure 4B ). With the short axis direction of the liquid crystal molecule 21A as a reference (0°), when the extending direction of the plurality of strip-shaped portions XP is rotated clockwise, the slit angle becomes a positive angle (+) (refer to Figure 4B The “positive (+)” column). With the short axis direction of the liquid crystal molecule 21A as a reference (0°), when the extension direction of the plurality of strip-shaped portions XP is rotated counterclockwise, the slit angle becomes a negative angle (+) (refer to Figure 4B in the “Negative (-)” column).

[0074] Therefore, the slit angle can also be regarded as the angle formed by axes having a larger absolute value of dielectric constant in the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied, with reference to the extending direction of the plurality of strip-shaped portions (0°).

[0075] The preferred range of the slit angle varies depending on the conditions of the width L of each strip-shaped portion SP and the width S of each slit S1 (also referred to as the L / S condition), the twist angle, whether the liquid crystal material is positive or negative, etc. In particular, in a single domain structure, the reflectivity (especially white reflectivity) can be maximized by selecting the optimal slit angle according to the L / S condition.

[0076] For example, when a positive liquid crystal material is used and the twist angle is 74°, under the condition of L / S (μm) = 2.2 / 4.1 (i.e., L / S = 0.537 / 1), the preferred range of the slit angle is -25° to +18°, the more preferred range is -18° to +9°, and the further preferred range is -11.5° to +2° (refer to Experimental Example 3-1 described later). Under the condition of L / S (μm) = 1.6 / 3.0 (i.e., L / S = 0.533 / 1), the preferred range of the slit angle is -18° to +14°, the more preferred range is -11° to +9°, and the further preferred range is -9.5° to +0° (refer to Experimental Example 3-2 described later). Under the condition of L / S (μm) = 3.0 / 5.0 (ie, L / S = 0.6 / 1), the slit angle preferably ranges from -25° to +13°, and more preferably ranges from -13° to +5° (see Experimental Example 3-3 described later).

[0077] For example, when a negative liquid crystal material is used and the twist angle is 74°, under the condition of L / S (μm) = 2.2 / 4.1 (i.e., L / S = 0.537 / 1), the preferred range of the slit angle is -30° to +5°, and the more preferred range is -28° to -3° (refer to Experimental Example 4-1 described later). Under the condition of L / S (μm) = 1.6 / 3.0 (i.e., L / S = 0.533 / 1), the preferred range of the slit angle is -25° to +3°, and the more preferred range is -15° to -7° (refer to Experimental Example 4-2 described later). Under the condition of L / S (μm) = 3.0 / 5.0 (i.e., L / S = 0.6 / 1), the preferred range of the slit angle is -30° to 0°, and the more preferred range is -22° to -10° (refer to Experimental Example 4-3 described later).

[0078] For example, when a positive liquid crystal material is used and the twist angle is 83°, under the condition of L / S (μm) = 2.2 / 4.1 (i.e., L / S = 0.537 / 1), the preferred range of the slit angle is -27° to +16°, the more preferred range is -18° to +10°, and the further preferred range is -11.5° to 0° (refer to Experimental Example 5-1 described later). Under the condition of L / S (μm) = 1.6 / 3.0 (i.e., L / S = 0.533 / 1), the preferred range of the slit angle is -20° to +13°, the more preferred range is -12° to 7°, and the further preferred range is -9.5° to +0° (refer to Experimental Example 5-2 described later). Under the condition of L / S (μm) = 3.0 / 5.0 (ie, L / S = 0.6 / 1), the preferred range of the slit angle is -27° to +13°, and the more preferred range is -18° to +8° (see Experimental Example 5-3 described later).

[0079] For example, when a negative liquid crystal material is used and the twist angle is 83°, under the condition of L / S (μm) = 2.2 / 4.1 (i.e., L / S = 0.537 / 1), the preferred range of the slit angle is -30° to +5°, the more preferred range is -30° to -7°, and the further preferred range is -19° to -12° (refer to Experimental Example 6-1 described later). Under the condition of L / S (μm) = 1.6 / 3.0 (i.e., L / S = 0.533 / 1), the preferred range of the slit angle is -30° to +3°, and the more preferred range is -15° to -5° (refer to Experimental Example 6-2 described later). Under the condition of L / S (μm) = 3.0 / 5.0 (i.e., L / S = 0.6 / 1), the preferred range of the slit angle is -30° to +2°, and the more preferred range is -30° to -5° (refer to Experimental Example 6-3 described later).

[0080] Figure 5 and Fig. 6AThe example in which the extending direction of the plurality of strip-shaped portions SP (this angle is referred to as angle X) is 0° is shown, with the extending direction of the source wiring SL as a reference (0°), the angle rotated clockwise is a positive angle (+), and the angle rotated counterclockwise is a negative angle (-). In addition, examples in which the angle X is -10°, +10°, -90°, -100°, and -80° are respectively shown. Figure 6B , Figure 6C , Fig.6D , Fig. 6E , Fig. 6F The angle X is 0° (see Figure 5 and Fig. 6A ) corresponds to a mode in which the extending direction of the plurality of strip-shaped portions SP is parallel to the extending direction of the source wiring SL, and is -90° (refer to Fig.6D ) corresponds to a mode in which the extending direction of the plurality of strip-shaped portions SP is parallel to the extending direction of the gate wiring GL.

[0081] Figure 5 and Figure 6A to Figure 6F is a top view schematically showing a specific example of a pixel. Figure 5 is a schematic plan view showing a structural example of a pixel, Figure 6A to Figure 6F It is a schematic plan view showing an example of pixel arrangement. Figure 6A to Figure 6F , the twisted orientation of the liquid crystal molecules 21 is also shown. The liquid crystal molecules 21A refer to the liquid crystal molecules 21 near the first horizontal alignment film 140 (i.e., the liquid crystal molecules on the first substrate 10 side when no voltage is applied), and the liquid crystal molecules 21B refer to the liquid crystal molecules 21 near the second horizontal alignment film 340 (i.e., the liquid crystal molecules on the second substrate 30 side when voltage is applied). (p) added to the end of the symbol of each liquid crystal molecule indicates a positive type, and (n) indicates a negative type.

[0082] However, in the present embodiment, the configuration in which the pixel electrode PE is disposed above the common electrode CE is described, but preferably, in a relatively large liquid crystal display device, that is, in a liquid crystal display device in which the area of ​​the pixel P is relatively large, the pixel electrode PE is disposed above the common electrode CE. In this configuration (also referred to as the V2 configuration), since it is not necessary to form a slit on the common electrode CE that becomes the lower electrode, it is possible to suppress the increase in the resistivity (surface resistivity) of the common electrode CE compared to the configuration in which the common electrode CE is disposed above the pixel electrode PE (also referred to as the V3 configuration), and thus it is possible to suppress the weakening of the fringe electric field applied to the liquid crystal layer 20. In this configuration (V2 configuration), when the pixel electrode PE is set as a slit electrode, although the resistivity of the pixel electrode PE increases, since a voltage input from the outside is applied to the pixel electrode PE, it is easy to reduce the influence of the increase in resistivity (that is, suppress the weakening of the fringe electric field). In addition, in order to suppress the increase in the resistivity of the common electrode CE, it is also considered to use low-resistance wiring formed by a metal material (for example, connecting the low-resistance wiring to the common electrode), but in such a structure, sometimes adverse effects on the display (such as glare, rainbow diffraction, interference patterns) are caused by regular reflection of the low-resistance wiring, etc., and it is necessary to use a black matrix or the like for shading, and sometimes it is impossible to fully increase the reflective aperture ratio.

[0083] In the configuration in which the pixel electrode PE is disposed above the common electrode CE, since the common electrode CE does not exist in the region where the second contact hole CH2 is formed, the region does not contribute to reflective display, and the reflectivity may be reduced compared to the configuration in which the common electrode CE is disposed above the pixel electrode PE. Regardless of the size of the area of ​​the pixel P, the area of ​​the contact hole and the like that does not contribute to reflective display needs to be of a certain degree, and therefore, the smaller the area of ​​the pixel P (i.e., the higher the precision), the higher the proportion of the region that does not contribute to reflective display in the pixel P, and the greater the reduction in the above-mentioned reflectivity. In other words, in a relatively large liquid crystal display device, it is easy to make the proportion of the region that does not contribute to reflective display in the pixel P lower, and therefore it is easy to suppress the reduction in the above-mentioned reflectivity. For these reasons, in a relatively large liquid crystal display device, it is advantageous to have the pixel electrode PE disposed above the common electrode CE.

[0084] On the other hand, as described above, the smaller the area of ​​the pixel P (i.e., the higher the precision), the greater the reduction in reflectivity caused by the region where the second contact hole CH2 is formed not contributing to reflective display. Therefore, in a relatively high-precision liquid crystal display device, i.e., a liquid crystal display device where the area of ​​the pixel P is relatively small, the common electrode CE is preferably arranged above the pixel electrode PE (refer to variant example 1 of embodiment 1 described later).

[0085] The first electrode 121 and the second electrode 122 are preferably formed of a transparent conductive material, respectively. Examples of the transparent conductive material include indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), and a mixture thereof.

[0086] exist Figure 2 In the manner shown, the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed on the same layer as the reflective film 130 and is formed of the same material (metal film, etc.) as the reflective film 130. A first contact hole CH1 is formed on the first interlayer insulating layer 151 to expose a portion of the backplane circuit BP (more specifically, at least a portion of the drain electrode of the TFT 110), and is connected to the backplane circuit BP in the first contact hole CH1. In addition, a second contact hole CH2 is formed on the second interlayer insulating layer 152 to expose a portion of the contact electrode 160, and the pixel electrode PE (the second electrode 122 in this embodiment) is connected to the contact electrode 160 in the second contact hole CH2.

[0087] The dielectric layer 153 is provided so as to cover the first electrode 121. The dielectric layer 153 is preferably formed of an inorganic insulating material. The inorganic insulating film obtained using the inorganic insulating material is as described above.

[0088] The first horizontal alignment film 140 is provided on the second electrode 122 and is in contact with the liquid crystal layer 20. Therefore, it can be said that the first electrode 121 and the second electrode 122 are arranged between the second interlayer insulating layer 152 and the first horizontal alignment film 140.

[0089] The first horizontal alignment film 140 and the second horizontal alignment film 340 described later are respectively subjected to alignment treatment and define the alignment azimuth (also referred to as alignment direction) of the liquid crystal molecules 21 contained in the liquid crystal layer 20. Preferably, the alignment treatment is performed by, for example, a photo-alignment treatment or a rubbing treatment. Preferably, in the photo-alignment treatment, a photo-decomposable photo-alignment film material can be used, and in the rubbing treatment, an alignment film material such as polyimide can be used.

[0090] The first horizontal alignment film 140 and the second horizontal alignment film 340 are both horizontal alignment films that align the liquid crystal molecules 21 in a horizontal direction relative to the first substrate 10 and the second substrate 30 when no voltage is applied to the liquid crystal layer 20. That is, when no voltage is applied to the liquid crystal layer 20, the liquid crystal molecules 21 are horizontally aligned. The pretilt angle is substantially 0°.

[0091] The orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 is different from the orientation of the liquid crystal molecules 21 defined by the second horizontal alignment film 340. Therefore, the liquid crystal layer 20 takes a twisted orientation when no voltage is applied (see Figure 2 When a voltage is applied to the liquid crystal layer 20, that is, when a transverse electric field is generated on the liquid crystal layer 20 by the first electrode 121 and the second electrode 122, the alignment state of the liquid crystal layer 20 changes due to the transverse electric field (fringe electric field).

[0092] <Liquid Crystal Layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and includes a positive liquid crystal material or a negative liquid crystal material. The positive liquid crystal material refers to a nematic liquid crystal material with a positive dielectric constant anisotropy Δε, and the negative liquid crystal material refers to a nematic liquid crystal material with a negative dielectric constant anisotropy Δε. The dielectric constant anisotropy Δε is the difference between the dielectric constant ε / / in the long axis direction and the dielectric constant ε⊥ in the short axis direction of the liquid crystal molecule 21 (i.e., ε / / -ε⊥).

[0093] In a positive liquid crystal material, the birefringence Δn of the liquid crystal material is preferably, for example, less than 0.123, more preferably 0.12, and further preferably less than 0.119. In addition, considering the manufacturing point of view (yield, etc.), the thickness d of the liquid crystal layer 20 is preferably greater than 2 μm, in which case Δn is preferably less than 0.123. More preferably, d is greater than 2.5 μm and Δn is less than 0.098. However, from the viewpoint of response, it is preferred that the unit thickness is small. In addition, the dielectric anisotropy Δε of the liquid crystal material is preferably, for example, greater than 10.

[0094] In a negative liquid crystal material, the birefringence Δn of the liquid crystal material is preferably, for example, less than 0.123, and more preferably 0.12. In particular, preferably, the thickness d of the liquid crystal layer 20 is greater than 2 μm, and Δn is less than 0.123. More preferably, d is greater than 2.5, and Δn is less than 0.098. In addition, preferably, the dielectric anisotropy Δε of the liquid crystal material is, for example, less than -5. In addition, the smaller Δε (or the larger the absolute value of Δε), the VR curve (threshold value, reflectivity Max value, etc.) shifts toward the low voltage side.

[0095] When selecting a positive type or a negative type, it is preferred to consider the application, the desired performance, etc. For example, from the perspective of achieving flicker-free (also called flicker-free), it is preferred to use a negative liquid crystal material. This is due to the following reasons. In the lateral electric field method of the FFS mode using a positive liquid crystal material, when a voltage is applied, flexible polarization is spontaneously generated in the liquid crystal layer due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field). Since the liquid crystal responds to this flexible polarization, the brightness changes when the polarity is reversed, so it is easily visually recognized as flicker. In addition, from the perspective of reliability, it is preferred to use a positive liquid crystal material.

[0096] The liquid crystal layer 20 may further contain a chiral agent as required. The liquid crystal layer 20 may be formed by, for example, a dropping method.

[0097] Preferably, the thickness d (also referred to as the cell gap or cell thickness) of the liquid crystal layer 20 is, for example, less than 3.6 μm. More preferably, it is 2.0 to 3.4 μm. In addition, from the viewpoint of response speed, it is preferably less than 3 μm. In addition, the smaller the cell thickness, the less the number of material components, so it is preferred from the viewpoint of cost reduction. However, if it is too small, sometimes the display quality cannot be improved due to uneven cell thickness and foreign matter, which becomes a compromise relationship with the incidence rate of poor display quality. From the viewpoint of yield, it is preferred to be 2 μm or more as described above.

[0098] From the viewpoint of suppressing alignment disorder, the liquid crystal layer 20 is preferably in a monodomain alignment (also referred to as a single domain alignment).

[0099] <Second Substrate> The second substrate 30 is disposed opposite to the first substrate 10 with the liquid crystal layer 20 sandwiched therebetween, and has a second horizontal alignment film 340 in contact with the liquid crystal layer 20. The second substrate 30 also preferably has a supporting substrate 300 and a color filter layer 310. For example, Figure 2 As shown, the second substrate 30 has a second horizontal alignment film 340, a color filter layer 310 and a support substrate 300 in order from the liquid crystal layer 20 side. The second substrate 30 also preferably has a plurality of columnar spacers (not shown). In addition, the first substrate 10 may also have a plurality of columnar spacers.

[0100] The support substrate 300 is preferably transparent and insulating, and examples of the support substrate 300 include a glass substrate and a plastic substrate.

[0101] The color filter layer 310 typically includes a red filter disposed in an area corresponding to a red pixel and transmitting red light, a green filter disposed in an area corresponding to a green pixel and transmitting green light, and a blue filter disposed in an area corresponding to a blue pixel and transmitting blue light. However, the types of color filters may be less than 2 or more than 4. In addition, when color display is not performed, the color filter layer 310 is omitted.

[0102] If necessary, an outer coating layer (also called a planarization layer) covering the color filter layer 310 may also be provided. In addition, depending on the material forming the electrode (e.g., a transparent conductive material), the material forming the interlayer insulating layer or the dielectric layer, and the material forming the alignment film, the white display may sometimes have a yellow tint. In this case, the chromaticity adjustment (i.e., blue shift) may also be performed by forming an outer coating layer with a blue resist, so that the chromaticity of the white display is close to the chromaticity of the D65 light source, for example. The D65 light source refers to the CIE standard light source D65.

[0103] In the liquid crystal display device 1 of this embodiment, the liquid crystal layer 20 displays in a lateral electric field mode with twisted orientation when no voltage is applied. As a result, the cell gap can be increased, and the fluctuation range of the contrast can be reduced relative to the fluctuation of the cell gap. Therefore, the generation of display unevenness can be fully suppressed, and the contrast of the reflective display becomes good. The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably not less than 58.3° and not more than 89.9°. A more preferred range will be described later.

[0104] The twist angle θ1 of the liquid crystal layer 20 is an angle formed by the orientation direction of the liquid crystal molecules 21 specified by the first horizontal alignment film 140 and the orientation direction of the liquid crystal molecules 21 specified by the second horizontal alignment film 340. That is, it is an angle formed by the long axis direction of the liquid crystal molecules 21A near the first horizontal alignment film 140 (also referred to as the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied) and the long axis direction of the liquid crystal molecules 21B near the second horizontal alignment film 340 (also referred to as the liquid crystal molecules 21B on the second substrate 30 side when voltage is applied).

[0105] From the viewpoint of further improving the contrast, the liquid crystal display device 1 is preferably in a normally black mode. The normally black mode is a display mode in which a black display is displayed when no voltage is applied and a white display is displayed when a voltage is applied.

[0106] The liquid crystal display device 1 is composed of multiple components, such as TCP (tape, carrier, package), PCB (printed circuit board), etc., in addition to the above-mentioned components, optical films such as viewing angle magnification film and brightness enhancement film, and frame (frame), and can be assembled into other components according to the components. These are not particularly limited, and devices commonly used in the field of liquid crystal display devices can be used, so the description is omitted.

[0107] <Application Examples> The liquid crystal display device 1 of this embodiment is applicable to various applications. Among them, it is preferably applicable to a touch panel. Regardless of whether it is applied to an external touch panel or a built-in touch panel, it is lower in cost than each previous touch panel and can improve the contrast ratio, so it is useful. Among them, it can be applied to a built-in touch panel, and can be particularly applicable to an embedded touch panel. In this way, if the liquid crystal display device 1 of this embodiment is used, it is preferably possible to realize an embedded touch panel that can display a reflective mode, which has not been realized so far.

[0108] By realizing an embedded touch panel capable of displaying a reflective mode, for example, the necessary frame wiring area is not required in an external touch panel, so a narrow frame can be achieved. In addition, since the touch panel function can be equipped without a glass cover, it can also contribute to thinning and lightweighting. In addition, since the touch function and the display function are driven in a time-division manner, the LCD (liquid crystal display) noise, which can be the largest noise source in the touch panel, is not received. That is, since a suppression mode (killer pattern) is not generated, it is easy to tune (adjust) the touch signal. Furthermore, not only is the loss of reflected light small enough, but pen writing is more natural, and a display without a sense of incoordination can be obtained. Moreover, compared with an external touch screen, a reduction in total cost can be achieved from the user's perspective. Moreover, it is possible to combine finger input and pen input of electromagnetic induction (EMR) to achieve high-precision pen writing.

[0109] An example in which the liquid crystal display device 1 is used for an in-cell touch panel will be described further. Figure 7 1 is a schematic plan view illustrating the arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1. Figure 7 As shown, the liquid crystal display device 1 includes a display region DR and a non-display region FR. The display region DR is composed of a plurality of pixels P arranged in a matrix (for example, Figure 3 The non-display region FR is located at the periphery of the display region DR, and is also referred to as a peripheral region or a frame region.

[0110] In the display region DR, the common electrode CE is divided into a plurality of segments TX. Each segment (common electrode portion) TX functions as a touch sensor electrode. Figure 7 In the example shown, each touch sensor electrode TX is provided corresponding to two or more pixels P.

[0111] The liquid crystal display device 1 (more specifically, the first substrate 10 ) has a plurality of touch wirings TL. Each touch sensor electrode TX is electrically connected to the corresponding touch wiring TL. The connection portion TC between the touch sensor electrode TX and the touch wiring TL is also referred to as a touch wiring contact portion TC.

[0112] The touch wiring TL is connected to a touch drive unit TD provided in the non-display region FR. The touch drive unit TD is configured to, for example, switch between a display mode in which a plurality of touch sensor electrodes TX function as a common electrode CE and a touch detection mode in which the touch sensor electrodes TX function in a time-division manner. For example, in the display mode, the touch drive unit TD applies a common signal to the touch sensor electrode TX (common electrode CE) via the touch wiring TL. On the other hand, in the touch detection mode, the touch drive unit TD applies a touch drive signal to the touch sensor electrode TX via the touch wiring TL.

[0113] exist Figure 7 In the embodiment, a plurality of touch wirings TL extend in a column direction (the same direction as the source wiring SL). A portion of the touch wiring TL extends across another one or more touch sensor electrodes Tx to the corresponding touch sensor electrode Tx.

[0114] When focusing on a certain touch sensor electrode TX, the first touch wiring TL1 that supplies a signal to the touch sensor electrode TX extends to the touch wiring contact portion TC, and the second touch wiring TL2 that supplies a signal to another touch sensor electrode TX extends in a manner that crosses the touch sensor electrode TX. The second touch wiring TL2 and the touch sensor electrode TX overlap via an insulating layer. In addition, depending on the position of the touch sensor electrode TX, sometimes more than two touch wirings TL are configured in a manner that crosses the touch sensor electrode TX, and sometimes no touch wiring TL that crosses the touch sensor electrode TX is configured.

[0115] In the non-display region FR, in addition to the touch drive unit TD, a peripheral circuit (not shown) is also provided, which includes a gate driver that supplies a gate signal to the gate bus (gate wiring) GL, a source driver that supplies a source signal to the source bus (source wiring) SL, and other drive circuits. These drive circuits can be mounted on the first substrate (TFT substrate) 10, or can be formed as an integral unit (monolithic). A semiconductor chip including part or all of the drive circuits can also be mounted in the non-display region FR.

[0116] In the embedded touch panel, as TFT110, it is particularly preferred to use In-Ga-Zn-O semiconductor. In addition, from the perspective of achieving flicker-free (also called flicker-free), it is particularly preferred to use a negative liquid crystal material. This is due to the following reasons. In the lateral electric field method of the FFS mode using a positive liquid crystal material, when a voltage is applied, flexible polarization is spontaneously generated in the liquid crystal layer due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field). Since the liquid crystal responds to this flexible polarization, the brightness changes when the polarity is reversed, so it is easily visually recognized as flickering.

[0117] (Variation 1 of Embodiment 1) In the first embodiment, the first electrode 121 as the lower electrode is the common electrode CE, and the second electrode 122 as the upper electrode is the pixel electrode PE. However, on the contrary, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE, and the first electrode 121 (lower electrode) is the pixel electrode PE (see Figure 8 ).

[0118] Figure 8 is a cross-sectional schematic diagram showing the liquid crystal display device 1 of this example in more detail. In this example, from the viewpoint of easy generation of a lateral electric field, it is preferred that at least the upper electrode (the common electrode CE in this example) is a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this variant is particularly suitable as a relatively high-definition liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively small.

[0119] (Variation 2 of Embodiment 1) In the first embodiment, an FFS mode liquid crystal display device is described, but an IPS mode liquid crystal display device (wherein the liquid crystal layer 20 takes a twisted orientation when no voltage is applied) may also be used. This variation is an IPS mode liquid crystal display device. In this variation, preferably, the first electrode 121 and the second electrode 122 are provided in the same layer, and both the first electrode 121 and the second electrode 122 are slit electrodes.

[0120] (Implementation Method 2) In this embodiment, features unique to this embodiment are mainly described, and descriptions of contents overlapping with those of the above-described Embodiment 1 are omitted. This embodiment is substantially the same as Embodiment 1 except that the liquid crystal display device further includes a retardation layer 40 and a polarizing plate 50 .

[0121] Fig. 9is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Fig.10 1 is a cross-sectional schematic diagram showing a liquid crystal display device 1 according to an example of the present embodiment in more detail. Fig. 9 As shown, the liquid crystal display device 1 includes, in order from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40, and a polarizing plate 50. In this embodiment, a TFT substrate is used as the first substrate 10.

[0122] <Phase difference layer> Preferably, the phase difference layer 40 is located between the second substrate 30 and the polarizing plate 50, and includes a λ / 4 plate 41 and a λ / 2 plate 42 (see Fig. 9 and Fig.10 ). Preferably, in terms of the arrangement order, the λ / 4 plate 41 and the λ / 2 plate 42 are arranged in the order of 1:1 from the liquid crystal layer 20 (and the second substrate 30) side (refer to Fig. 9 and Fig.10 ).

[0123] The λ / 4 plate is a phase difference plate that gives an in-plane phase difference of 1 / 4 wavelength to incident light of wavelength λ, and is also called a λ / 4 wavelength plate or QWP (Quarter-Wave Plate). Specifically, the λ / 4 plate 41 can convert linear polarized light into circular polarized light or convert circular polarized light into linear polarized light. For example, linear polarized light incident on the λ / 4 plate 41 becomes circular polarized light when it exits the λ / 4 plate 41.

[0124] The λ / 2 plate is a phase difference plate that gives an in-plane phase difference of 1 / 2 wavelength to incident light of wavelength λ, and is also called a λ / 2 wavelength plate, a half-wavelength plate, or an HWP (Half-Wave Plate). Specifically, the λ / 2 plate 42 can rotate the vibration direction of the incident light by approximately 90°. For example, the circularly polarized light incident on the λ / 2 plate 42 becomes circularly polarized light with the opposite rotation direction when it is emitted.

[0125] Specifically, it is preferable to use a uniaxial A plate as the λ / 4 plate 41 and the λ / 2 plate 42 .

[0126] <Polarizing Plate> The polarizing plate 50 is located closer to the observation surface side than the phase difference layer 40 (see Fig. 9 and Fig.10 ). The polarizing plate 50 may be a circular polarizing plate or a linear polarizing plate. Here, the linear polarizing plate refers to a polarizing plate having the function of extracting polarized light (linear polarized light) that vibrates only in a specific direction from unpolarized light (natural light), partially polarized light or polarized light, and is distinguished from a circular polarizing plate. Among them, a linear polarizing plate is preferred.

[0127] The polarizing plate 50 may be an absorption-type polarizing plate or a reflection-type polarizing plate. An absorption-type polarizing plate refers to a polarizing plate that has the function of absorbing light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. A reflection-type polarizing plate refers to a polarizing plate that has the function of reflecting light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. Among them, an absorption-type polarizing plate is preferred. It is particularly preferred to use an absorption-type linear polarizing plate.

[0128] As an absorption type polarizing plate, for example, a polarizing plate in which a polyvinyl alcohol film is dyed and an anisotropic material such as an iodine complex (or dye) is adsorbed and then stretched and oriented can be listed. Generally speaking, in order to ensure mechanical strength and moisture and heat resistance, a polyvinyl alcohol film is used for practical use in a state where a protective film such as a triacetyl cellulose film is laminated on both sides. In addition, as a reflection type polarizing plate, for example, a film in which a plurality of dielectric thin films are laminated, a film in which a plurality of thin films with different refractive index anisotropy are laminated, a nanowire grid polarizing plate, a polarizing plate using selective reflection of cholesteric liquid crystal, etc. can be listed.

[0129] When the slit angle is changed, the polarization axis direction 50AA of the polarization plate 50 , the slow axis direction 41SA of the λ / 4 plate 41 , and the slow axis direction 42SA of the λ / 2 plate are changed in the same direction by the same angle.

[0130] <Preferred Settings> In the following, the preferred settings of the twist angle and retardation dΔn of the liquid crystal layer 20, the axis settings of the optical films (i.e., the polarizing plate and the phase difference plate) and the like in this embodiment are further described by dividing into the case where the liquid crystal material constituting the liquid crystal layer 20 is a positive type and the case where the liquid crystal material is a negative type. In addition, as the polarizing plate 50, an absorption type polarizing plate is used.

[0131] (i) When the liquid crystal material is positive type (i-1) Preferred settings Fig.11 From the viewpoint of improving the contrast ratio, an example of optical setting that is particularly preferable is shown. Fig.11 The top view conceptually shows the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42, and the polarization axis 50A of the polarizing plate 50 in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 41 plate 41, a λ / 2 plate 42, and a polarizing plate 50. Fig.11 In FIG. 1 , as the liquid crystal molecules 21 , liquid crystal molecules 21A near the first horizontal alignment film 140 and liquid crystal molecules 21B near the second horizontal alignment film 340 are shown.

[0132] In the following description, the angle when the reference direction is set to 0° is the angle when Fig.11 Comparing to the dial of a clock, the reference direction, i.e., the direction orthogonal to the extending direction of the plurality of strip-shaped portions SP is set to the 0° direction (3 o'clock direction), and the twist direction is set to the positive (counterclockwise) angle. The twist direction refers to the direction in which the alignment direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is twisted toward the alignment direction of the liquid crystal molecules 21B defined by the second horizontal alignment film 340 when the liquid crystal display device 1 is observed from the observation surface side.

[0133] The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably 58.3° to 89.9°. This improves the contrast ratio. From the viewpoint of further improving the contrast ratio, it is more preferably 64.0° to 88°, more preferably 6.4° to 86°, and particularly preferably 71.4° to 84°.

[0134] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 is preferably 5° to 35°, with the direction perpendicular to the direction in which the plurality of strip-shaped portions SP extend as a reference (0°). Thus, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably 15° to 34°, and further preferably 20° to 33°.

[0135] The angle θ3 formed by the in-plane slow axis 42SA of the λ / 2 plate 42 is preferably 25° to 50°, with the direction perpendicular to the direction in which the plurality of strip-shaped portions SP extend as a reference (0°). This improves the contrast ratio. From the viewpoint of further improving the contrast ratio, it is more preferably 35° to 49°, and even more preferably 40° to 48°.

[0136] The angle θ4 formed by the slow axis 41SA in the plane of the λ / 4 plate 41 is preferably 45° to 70°, with the direction perpendicular to the direction in which the plurality of strip-shaped portions SP extend as a reference (0°). As a result, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably 55° to 68°, and even more preferably 60° to 66°.

[0137] The retardation of the liquid crystal layer 20, that is, the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material (dΔn), is preferably 152.3 nm to 285.8 nm. Thus, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably 176.9 nm to 260.8 nm, further preferably 195.8 nm to 250 nm, and particularly preferably 207.0 nm to 248 nm.

[0138] (ii) When the liquid crystal material is negative type (ii-1) Preferred settings Fig.12 From the viewpoint of improving the contrast ratio, an example of optical setting that is particularly preferable is shown. Fig.12 The top view conceptually shows the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42 and the polarization axis 50A of the polarizing plate 50 in a liquid crystal display device 1 which includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 41 plate 41, a λ / 2 plate 42 and a polarizing plate 50 in sequence. Fig.12 In FIG. 1 , as the liquid crystal molecules 21 , liquid crystal molecules 21A near the first horizontal alignment film 140 and liquid crystal molecules 21B near the second horizontal alignment film 340 are shown.

[0139] In the following description, the angle when the reference direction is set to 0° is the angle when Fig.12 Comparing it to a clock face, the reference direction, that is, the direction perpendicular to the extending direction of the plurality of strip-shaped portions SP is set to the 0° direction (3 o'clock direction), and the twist direction is set to the positive (counterclockwise) angle.

[0140] The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably 58.3° to 89.9°. This improves the contrast ratio. From the viewpoint of further improving the contrast ratio, it is more preferably 64.0° to 88°, more preferably 6.4° to 86°, and particularly preferably 71.4° to 84°.

[0141] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 is preferably not less than -85° and not more than -55°, with the direction perpendicular to the direction in which the plurality of strip-shaped portions SP extend as a reference (0°). Thus, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably not less than -75° and not more than -56°, and further preferably not less than -70° and not more than -57°.

[0142] The angle θ3 formed by the in-plane slow axis 42SA of the λ / 2 plate 42 is preferably not less than -65° and not more than -40°, with the direction perpendicular to the direction in which the plurality of strip-shaped portions SP extend as a reference (0°). Thus, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably not less than -55° and not more than -41°, and further preferably not less than -50° and not more than -42°.

[0143] The angle θ4 formed by the slow axis 41SA in the plane of the λ / 4 plate 41 is preferably not less than -40° and not more than -15°, with the direction perpendicular to the direction in which the plurality of strip-shaped portions SP extend as a reference (0°). As a result, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably not less than -30° and not more than -20°, and further preferably not less than -27° and not more than -24°.

[0144] The retardation of the liquid crystal layer 20, that is, the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material (dΔn), is preferably 151.2 nm to 285.1 nm. Thus, the contrast ratio is improved. From the viewpoint of further improving the contrast ratio, it is more preferably 175.9 nm to 250 nm, further preferably 193.8 nm to 246 nm, and particularly preferably 204.7 nm to 245 nm.

[0145] (Variation 1 of Implementation Method 2) In the second embodiment, the first electrode 121 as the lower electrode is the common electrode CE, and the second electrode 122 as the upper electrode is the pixel electrode PE. However, on the contrary, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE, and the first electrode 121 (lower electrode) is the pixel electrode PE (see Fig.13 ).

[0146] Fig.13 is a cross-sectional schematic diagram showing the liquid crystal display device 1 of this example in more detail. In this example, from the viewpoint of easy generation of a lateral electric field, it is preferred that at least the upper electrode (the common electrode CE in this example) is a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this variant is particularly suitable as a relatively high-definition liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively small.

[0147] (Implementation Method 3) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiments 1 and 2 is omitted. In embodiments 1 and 2, a reflective liquid crystal display device is exemplified, but in this embodiment, a semi-transmissive liquid crystal display device is described. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 2 in that a light source is provided at a position closer to the back side than the liquid crystal layer 20.

[0148] Fig.141 is a cross-sectional schematic diagram of a liquid crystal display device 1 according to an example of the present embodiment. The liquid crystal display device 1 further includes a light source 61 (also referred to as a backlight) on the back side of the liquid crystal layer 20. In addition, it is preferred that the liquid crystal display device 1 further includes a polarizing plate 50' and a phase difference layer 40'. More preferably, Fig.14 As shown, the light source 61, polarizing plate 50', retardation layer 40', first substrate 10, liquid crystal layer 20, second substrate 30, retardation layer 40, and polarizing plate 50 are provided in order from the back side. In this embodiment, the first substrate 10 is preferably a TFT substrate.

[0149] The light source 61 (backlight source) is not particularly limited as long as it is a light source for irradiating light, and can be a direct-down type, an edge type, or any other type. Specifically, for example, a light source such as a light emitting diode (LED), a light guide plate, and a reflective sheet is preferred, and a diffuser or a prism sheet may be further provided.

[0150] The polarizing plate 50' is disposed on the back side of the liquid crystal layer 20. More specifically, it is disposed at a position closer to the back side than the first substrate 10. The polarizing plate 50' may be a circular polarizing plate or a linear polarizing plate, but is preferably a linear polarizing plate. In addition, it may be an absorption type polarizing plate or a reflection type polarizing plate, but is preferably an absorption type polarizing plate. It is particularly preferred to use an absorption type linear polarizing plate.

[0151] The phase difference layer 40' is arranged between the polarizing plate 50' and the liquid crystal layer 20. More specifically, it is arranged between the polarizing plate 50' and the first substrate 10. The phase difference layer 40' can include, for example, a λ / 4 plate and a λ / 2 plate. Preferably, the arrangement order is, for example, λ / 2 plate, λ / 4 plate from the back side.

[0152] In the liquid crystal display device 1 of the present embodiment, each pixel P has a reflective region Rf for displaying in a reflective mode and a transmissive region Tr for displaying in a transmissive mode (see FIG. Fig.15 ). Fig.15 1 is a top view schematic diagram conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of this embodiment. A reflective layer 130 (for example, see Figure 2 ), but the reflective layer 130 is not arranged in the transmission region Tr. The ratio of the area occupied by the transmission region Tr in the pixel P can be appropriately set according to the purpose, but is preferably, for example, not less than 20% and not more than 90%. In addition, the position and shape of the transmission region Tr in the pixel P can also be appropriately set according to the purpose, etc.

[0153] In the liquid crystal display device of this embodiment, that is, the semi-transmissive liquid crystal display device, similarly to the reflective liquid crystal display device, the contrast ratio of the reflective display can be sufficiently improved by displaying in a lateral electric field mode with twisted orientation when no voltage is applied to the liquid crystal layer 20. Therefore, the liquid crystal display device 1 of this embodiment is also useful as an in-cell touch panel that is low-cost, can improve the contrast ratio, and can display in a reflective mode.

[0154] (Implementation method 4) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiment 1 is omitted. The main difference between the liquid crystal display device of this embodiment and the liquid crystal display device of embodiment 1 is that a light source is provided at a position closer to the observation surface side than the liquid crystal layer 20. In addition, the liquid crystal display device of this embodiment is a reflective liquid crystal display device.

[0155] Fig.16 2 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. The liquid crystal display device 1 according to the present embodiment further includes a light source 62 (also referred to as a headlight) on the observation side of the liquid crystal layer 20. More preferably, Fig.16 As shown, the embodiment includes, in order from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40, a polarizing plate 50, and a light source 62. In this embodiment, the first substrate 10 is preferably a TFT substrate.

[0156] The light source 62 (headlight) is not particularly limited as long as it is a light source that irradiates light. Specifically, for example, a light source such as a light emitting diode (LED) and a light guide plate are preferably provided. Since the reflective liquid crystal display device 1 is also provided with the light source 62, a bright reflective display can be performed even in an environment where the ambient light is insufficient.

[0157] As mentioned above, although embodiment of this invention was demonstrated, each matter demonstrated can be applied to the whole invention.

[0158] The present invention will be described in further detail below with reference to Examples, but the present invention is not limited to these Examples. Hereinafter, an absorption-type polarizing plate is used as the polarizing plate 50 .

[0159] (Verification Example 1) Using the TFT substrate (first substrate) 10 of a mobile device, an FFS mode device capable of displaying in a reflective mode was manufactured (see FIG. 20 ). Fig.17A As shown, a pixel electrode PE and a common electrode CE for applying a voltage to the liquid crystal layer 20 are arranged on the TFT substrate 10 side, and as shown in FIG. Fig.18As shown in FIG. 1 , the common electrode CE as the upper electrode (second electrode 122) is set as a slit electrode having a plurality of strip-shaped portions SP and a slit S1 located between two adjacent strip-shaped portions. The width L of each strip-shaped portion SP is 1.6 μm, and the width of each slit S1 is 3.0 μm. The plurality of strip-shaped portions SP are composed of straight lines that are substantially parallel to each other and extend in the same direction, but are bent in the middle (see FIG. 1 ). Fig.18 f). The front end f of the bend is also called a kink or a bend. The liquid crystal layer 20 uses a negative liquid crystal material. The pixel electrode PE as the lower electrode (first electrode 121) is set as a full-surface electrode. In addition, no color filter is configured and it is set to black and white mode. Fig.17A is a schematic cross-sectional view of the device produced in this example, Fig.18 It is a CAD (Computer Aided Design) diagram showing only the pixel electrode PE and the common electrode CE on the TFT substrate side in a top view.

[0160] First, the device is set to an initial state, so that it is in a white display state (i.e., 255 grayscale display) (refer to Fig. 20A ). Next, when a black character is written in the device in this state, a black area is generated (refer to Fig. 20B Then, the written characters are erased (i.e., the display returns to the white state) (refer to Fig. 20C After doing this (see Figure 20A to Figure 20C ), the residual image of the characters is visually recognized as burn-in (refer to Fig. 20C within the dotted line). Fig. 20A This is a top view of the device in its initial state, taken from the observation side. Fig. 20B This is a top view photograph taken from the observation side of the device in the initial state with black characters written. Fig. 20C This is a top view photograph taken from the observation side of the state where the written characters have been erased. The part where the residual image is generated is observed with a microscope ("BX51" manufactured by OLYMPUS Corporation), and it is confirmed that the orientation disorder occurs at the end f of each common electrode CE, which is called a kink part (refer to Fig.19 ). Since the orientation disorder generated in the kink portion f causes a brightness difference (i.e., a reflectivity difference) between the kink portion f and other portions (e.g., the central portion of the pixel), it is considered that the afterimage is visually recognized. Fig.19 This is an image of the inside of the device observed with a microscope (top view image). Fig.19 The electrode structure of the portion shown is shown in a CAD diagram. Fig.18 .

[0161] The inventors have further studied the cause of this orientation disorder. Fig.18 and Fig.19 (a) in the vicinity) and the pixel end ( Fig.18 and Fig.19 In the example of the slit electrode, the slit angle is -10 degrees in the center of the pixel (a) and -20 degrees at the end of the pixel (b). The inventors speculate that due to the difference in the slit angle, the rotation direction of the liquid crystal molecules 21 when a voltage is applied is different (refer to Fig.21 ). Fig.21 This is a top view conceptually showing the different rotation directions of the liquid crystal molecules 21 (negative liquid crystal) in the center of the pixel (a) and the end of the pixel (b). The orientation of the liquid crystal molecules 21A on the TFT substrate 10 side when no voltage is applied (i.e., the initial orientation) is represented by the direction of the liquid crystal molecules 21A, and the orientation of the liquid crystal molecules 21A on the TFT substrate 10 side when voltage is applied is represented by the direction of the liquid crystal molecules 21A (A). The 3 o'clock direction is set to 0 degrees, the counterclockwise direction is set to positive (+), and the twist angle is set to +74 degrees. When a voltage is applied, the liquid crystal molecules 21A rotate clockwise (-) in the center of the pixel (refer to Fig.21 A), and rotate counterclockwise (+) at the end of the pixel (refer to Fig.21 B) The boundary between the center of the pixel and the end of the pixel corresponds to the portion where the slit angle changes, and the orientation of the liquid crystal molecules 21 is discontinuous here. Therefore, the orientation disorder occurs, and thus a brightness difference occurs between the pixel and the pixel without the orientation disorder, which is visually recognized as an afterimage.

[0162] For reference, as a conceptual diagram showing that the rotation directions of the liquid crystal molecules 21 (ie, the liquid crystal molecules 21A on the TFT substrate side) are different when a voltage is applied to the center of the pixel (a) and the end of the pixel (b), the following diagram is shown: Fig. 22 and Fig.23 . Fig. 22 is Fig.18 A conceptual diagram showing the rotation direction of the liquid crystal molecules 21 is superimposed on the Fig.21 ), Fig.23 is Fig.19 A conceptual diagram showing the rotation direction of the liquid crystal molecules 21 is superimposed on the Fig.21 )’s picture.

[0163] (Test Examples 1 and 2) Assuming a reflective liquid crystal display device 1 using a negative liquid crystal material, the occurrence of alignment disorder caused by the presence or absence of a kink portion was compared by three-dimensional optical simulation. Fig. 17BAs shown, a pixel electrode PE and a common electrode CE for applying a voltage to the liquid crystal layer 20 are arranged on the TFT substrate (first substrate) 10 side, and the common electrode CE as the upper electrode (second electrode 122) is set as a slit electrode having a plurality of strip-shaped portions SP and a slit S1 located between two adjacent strip-shaped portions. The width L of each strip-shaped portion SP is 2.4 μm, and the width of each slit S1 is set to 2.2 μm. A negative liquid crystal material is used for the liquid crystal layer 20. The pixel electrode PE as the lower electrode (first electrode 121) is set as a full-surface electrode. Fig. 17B is a schematic cross-sectional view of the device envisioned in this example.

[0164] Here, in Experimental Example 1, the plurality of strip-shaped portions SP constituting the slit electrode (common electrode CE) are configured to be linear shapes that are substantially parallel to each other and extend in the same direction, but have bent portions f at the ends (see Fig.24A (b)). In contrast, in Test Example 2, the linear shape is substantially parallel to each other and extends in the same direction, and does not include a bent portion f (refer to Fig. 24B (b)). Fig.24A It is a figure which conceptually shows the simulation result of the test example 1 (refer to (a)) and a some strip|belt part SP based on this result (refer to (b)). Fig. 24B It is a figure which conceptually shows the simulation result of the test example 2 (refer to (a)) and a some strip|belt part SP based on this result (refer to (b)).

[0165] As a result of evaluating the reflectivity distribution through three-dimensional optical simulation, Fig.24A (a) shows the results of Test Example 1. Fig. 24B The result of Test Example 2 is shown in (a). In Test Example 1, the orientation disorder occurred in the bent portion f called the kink portion, and the brightness of the kink portion f was low (refer to Fig.24A In contrast, in Test Example 2, no alignment disorder occurred, and the luminance of the end portion of the common electrode CE (corresponding to the kinked portion f of Test Example 1) increased compared to Test Example 1 (refer to Fig. 24B (a)). Therefore, it was confirmed that the alignment disorder would not occur by setting the plurality of strip-shaped portions SP constituting the slit electrode to be composed of straight lines that are substantially parallel to each other and extend in the same direction and do not include a bent portion. Since the relationship between the alignment of the liquid crystal molecules 21 and the slit angle becomes uniform in each pixel, it can be considered that the alignment disorder no longer occurs.

[0166] (Test Examples 3 and 4) In summary, it can be considered that the cause of the disordered orientation is due to the difference in the slit angles of the slit electrodes in the kinked portion and other portions. Therefore, the change in the reflection mode efficiency caused by the slit angle is evaluated and analyzed by three-dimensional optical simulation. Specifically, in a liquid crystal display device 1 having a reflective liquid crystal panel 1X, a phase difference layer 40, and a polarizing plate 50 in sequence, as the phase difference layer 40, a structure in which a λ / 4 plate 41 and a λ / 2 plate 42 are arranged in sequence from the liquid crystal panel 1X side is envisioned (refer to Fig. 9 ). As the λ / 4 plate 41, a uniaxial phase difference plate with a retardation of 110 nm was used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a retardation of 260 nm was used.

[0167] As a liquid crystal panel 1X, a pixel electrode PE and a common electrode CE for applying a voltage to a liquid crystal layer 20 are arranged on the TFT substrate (first substrate) 10 side, and the common electrode CE as an upper electrode (second electrode 122) is set as a slit electrode having a plurality of strip-shaped portions SP and a slit S1 located between two adjacent strip-shaped portions. The plurality of strip-shaped portions SP are composed of straight lines that are substantially parallel to each other and extend in the same direction, and do not include a bent portion, and the slit angle is set to 0° (refer to Fig.26 ). The pixel electrode PE as the lower electrode (first electrode 121) is set as a full-surface electrode. In addition, a liquid crystal layer with a single domain structure (a liquid crystal layer that performs a normally black display) is assumed. Fig.25 In the diagram, the film thickness of a partial layer is described in parentheses after the symbol indicating the layer.

[0168] An example in which a positive liquid crystal material is used in the liquid crystal layer 20 is referred to as Test Example 3, and an example in which a negative liquid crystal material is used is referred to as Test Example 4. The ratio of the width L of each strip-shaped portion SP to the width S of each slit S1 (referred to as the L / S condition) is set to L / S (μm) = 2.2 / 4.1 in Test Examples 3-1 and 4-1, to L / S (μm) = 1.6 / 3.0 in Test Examples 3-2 and 4-2, and to L / S (μm) = 3.0 / 5.0 in Test Examples 3-3 and 4-3.

[0169] Fig.25 It is a schematic cross-sectional view of a liquid crystal panel 1X included in the device assumed in this example. Fig.26 Schematic diagram conceptually showing the electrode structure of the pixel electrode PE and the common electrode CE, in which an example (Test Example 3-2 and Test Example 4-2) of L / S (μm)=1.6 / 3.0 is particularly shown. Fig.26 , the orientation of the liquid crystal molecules 21A on the TFT substrate 10 side when no voltage is applied (ie, the initial orientation) is represented by the directions of the positive liquid crystal molecules 21A(p) and the negative liquid crystal molecules 21A(n).

[0170] In the actual simulation, in order to simplify the condition setting, the pre-twist angle of the liquid crystal molecule 21 and the axis angle of the optical film were changed instead of changing the slit angle. However, the twist angle θ1 is fixed (74° in Test Examples 3 and 4). Specifically, the axis setting of the optical film described below is used as a reference, and the pre-twist angle of the liquid crystal molecule 21 and the axis angle of each optical film are rotated to the same angle as the slit angle. The optical film refers to the polarizing plate 50 and the phase difference layer 40 (in this example, the λ / 4 plate 41 and the λ / 2 plate 42). In addition, the pre-twist angle of the liquid crystal molecule 21 refers to the initial orientation angle of the liquid crystal molecule 21A on the TFT substrate (first substrate) 10 side relative to the reference (in this specification, the 3 o'clock direction when observing the liquid crystal panel from the observation side is set as the reference 0°).

[0171] The axis settings of each optical film and the retardation dΔn of the liquid crystal layer 20 are as follows in Experimental Example 3 (positive liquid crystal): Fig. 27 As shown in Table 1, in Test Example 4 (negative liquid crystal) Fig.28 As shown in Table 1. Fig. 27 is a top view conceptually showing the axis setting of each optical film used in Test Example 3, Fig.28 FIG. 4 is a top view conceptually showing the axis settings of each optical film used in Test Example 4. Fig. 27 and Fig.28 In the diagram, each optical film is compared to a clock face, with the 3 o'clock direction being 0° and the counterclockwise direction being positive. The axis angle of each optical film is the angle when viewed from the observation surface side.

[0172] The voltage setting was set from 0 V to 6 V in increments of 0.5 V. The average reflection mode efficiency of the luminance distribution was found, and the reflection mode efficiency when 5 V was applied was plotted under L / S conditions. Here, the reflection mode efficiency is as follows: The result is obtained by reflection mode efficiency (%) = (brightness with polarizing plate) / (brightness without polarizing plate) × 100. Fig.29 and Fig.30 shown. Fig.29 is a graph showing the results of Test Example 3 (positive type, twist angle 74°), Fig.30 This is a graph showing the results of Test Example 4 (negative type, twist angle 74°).

[0173] [Table 1]

[0174] exist Fig.29(positive type, twist angle 74°), it was confirmed that the reflectivity changed greatly with a specific slit angle as the boundary. This is believed to be caused by the different rotation directions of the liquid crystal molecules when voltage is applied. In addition, it was confirmed that the slit angle at which the reflectivity is discontinuous changes according to the L / S condition. The slit angle at which the reflectivity is discontinuous is around -11.5° in Test Example 3-1 (L / S (μm) = 2.2 / 4.1), around -9.5° in Test Example 3-2 (L / S (μm) = 1.6 / 3.0), and around -13° in Test Example 3-3 (L / S (μm) = 3.0 / 5.0). Therefore, under each L / S condition, the slit angle when the reflection mode efficiency is above 30%, the slit angle when the reflection mode efficiency is above 33%, and the slit angle when the reflection mode efficiency is above 36%, are respectively set to the above-mentioned preferred range, more preferred range, and further preferred range, respectively.

[0175] exist Fig.30 (negative type, twist angle 74°), it was also confirmed that the reflectivity changed greatly with a specific slit angle as the boundary, and it was also confirmed that the slit angle at which the reflectivity was discontinuous changed according to the L / S condition. The slit angle at which the reflectivity was discontinuous was around -19° in Test Example 4-1 (L / S (μm) = 2.2 / 4.1), around -15° in Test Example 4-2 (L / S (μm) = 1.6 / 3.0), and around -22° in Test Example 4-3 (L / S (μm) = 3.0 / 5.0). Therefore, under each L / S condition, the slit angle when the reflection mode efficiency is above 30% and the slit angle when the reflection mode efficiency is above 33% are set to the above-mentioned preferred range and the more preferred range, respectively.

[0176] (Test Examples 5 and 6) Experimental Example 5 is as follows: except that the twist angle θ1 is set to 83°, the axis settings of each optical film and the retardation dΔn of the liquid crystal layer 20 are as follows: Fig.31 The conditions are substantially the same as those in Experimental Example 3 except that the twist angle θ1 is set to 83°, the axis of each optical film and the retardation dΔn of the liquid crystal layer 20 are set to Fig.32 Except for the conditions shown in Table 2, the conditions were substantially the same as those in Test Example 4. The L / S condition was set to L / S (μm) = 2.2 / 4.1 in Test Example 5-1 and Test Example 6-1, to L / S (μm) = 1.6 / 3.0 in Test Example 5-2 and Test Example 6-2, and to L / S (μm) = 3.0 / 5.0 in Test Example 5-3 and Test Example 6-3. Fig.31 is a top view conceptually showing the axis settings of each optical film used in Test Example 5, Fig.32 This is a plan view conceptually showing the axis settings of each optical film used in Test Example 6.

[0177] The voltage setting is set from 0V to 6V in 0.5V increments. The average reflection mode efficiency of the brightness distribution is calculated, and the reflection mode efficiency when 5V is applied is plotted according to the L / S condition. The results are shown in Fig.33 and Fig.34 shown. Fig.33 is a graph showing the results of Test Example 5 (positive type, twist angle 83°), Fig.34 This is a graph showing the results of Test Example 6 (negative type, twist angle 83°).

[0178] [Table 2]

[0179] exist Fig.33 (positive type, twist angle 83°), it was also confirmed that the reflectivity changed greatly with a specific slit angle as the boundary, and it was also confirmed that the slit angle at which the reflectivity was discontinuous changed according to the L / S condition. The slit angle at which the reflectivity was discontinuous was around -11.5° in Test Example 5-1 (L / S (μm) = 2.2 / 4.1), around -9.5° in Test Example 5-2 (L / S (μm) = 1.6 / 3.0), and around -13° in Test Example 5-3 (L / S (μm) = 3.0 / 5.0). Therefore, under each L / S condition, the slit angle when the reflection mode efficiency is above 30%, the slit angle when the reflection mode efficiency is above 33%, and the slit angle when the reflection mode efficiency is above 36% are set to the above-mentioned preferred range, more preferred range, and further preferred range, respectively.

[0180] exist Fig.34 (negative type, twist angle 83°), it was confirmed that the reflectivity changed greatly with a specific slit angle as the boundary, and it was also confirmed that the slit angle at which the reflectivity was discontinuous changed according to the L / S condition. The slit angle at which the reflectivity was discontinuous was around -19° in Test Example 6-1 (L / S (μm) = 2.2 / 4.1), around -15° in Test Example 6-2 (L / S (μm) = 1.6 / 3.0), and around -22° in Test Example 6-3 (L / S (μm) = 3.0 / 5.0). Therefore, under each L / S condition, the slit angle when the reflection mode efficiency is above 30%, the slit angle when the reflection mode efficiency is above 33%, and the slit angle when the reflection mode efficiency is above 36% are set to the above-mentioned preferred range, more preferred range, and further preferred range, respectively.

[0181] The above-described embodiments of the present invention may be appropriately combined within the scope of the present invention. Description of Reference Numerals

[0182] 1: Liquid crystal display device 1X: LCD panel 10, 30: substrate 20: Liquid crystal layer 21, 21A, 21B: Liquid crystal molecules 40, 40': Phase difference layer 41: λ / 4 plate 42: λ / 2 plate 41SA, 42SA: In-plane slow axis 50, 50': Polarizing plate 50AA: Polarization axis 61, 62: Light source 100, 300: Support substrate 110: TFT 121, 122: Electrode 130: Reflective layer 140, 340: horizontal orientation film 150G: Gate insulation film 151, 152: Interlayer insulation layer 153: Dielectric layer 160: Contact electrode 310: Color filter layer BP: Backplane circuit CE: Common Electrode PE: Pixel electrode CH1, CH2: contact holes DR: Display Region FR: Display area GL: Gate wiring SL: Source wiring f: Kink (bend) p: convex part P: Pixel Rf: Reflection area Tr: Transmission area S1: Slit SP: Strip TC: Touch wiring contact TD: Touch driver TL, TL1, TL2: Touch wiring TX: Touch sensor electrode

Claims

1. A liquid crystal display device, comprising: a first substrate; a second substrate, which is opposite to the first substrate; as well as a liquid crystal layer disposed between the first substrate and the second substrate, The liquid crystal display device has a plurality of pixels arranged in a matrix, and is characterized in that: The first substrate has a reflective layer for reflecting light, a first electrode and a second electrode capable of generating a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer. At least one of the first electrode and the second electrode has a plurality of strip-shaped portions and a slit, wherein the slit is located between two adjacent strip-shaped portions among the plurality of strip-shaped portions. In each pixel, the plurality of strip-shaped portions are composed of straight lines that are substantially parallel to each other and extend in the same direction and do not include a bent portion. The second substrate has a second horizontal alignment film in contact with the liquid crystal layer. The liquid crystal layer takes a twisted orientation when no voltage is applied.

2. The liquid crystal display device according to claim 1, wherein The plurality of strip-shaped portions do not include a cutout portion.

3. The liquid crystal display device according to claim 1, wherein The directions in which the plurality of strip-shaped portions extend are the same at least in adjacent pixels or in a display area.

4. The liquid crystal display device according to claim 1, wherein The liquid crystal layer includes a positive liquid crystal material.

5. The liquid crystal display device according to claim 1, wherein: The liquid crystal layer includes a negative liquid crystal material.

6. The liquid crystal display device according to claim 4 or 5, characterized in that: The twist angle of the liquid crystal layer when no voltage is applied is 58.3° or more and 89.9° or less.

7. The liquid crystal display device according to claim 1, wherein: The liquid crystal layer is in a single domain orientation.

8. The liquid crystal display device according to claim 4 or 5, characterized in that: The alignment direction of the liquid crystal molecules on the first substrate side when no voltage is applied is not less than -30° and not more than 30°, with respect to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

9. The liquid crystal display device according to claim 4 or 5, characterized in that: For the plurality of strip-shaped portions, a ratio L / S of a width L of each strip-shaped portion in a plan view to a width S of each slit in a plan view is 0.4 to 0.7 / 1.

10. The liquid crystal display device according to claim 1, wherein: The invention further includes a polarizing plate disposed outside the first substrate and / or the second substrate, and a phase difference layer disposed between the substrate and the polarizing plate.

11. The liquid crystal display device according to claim 10, wherein: The liquid crystal layer contains a positive liquid crystal material. The polarizing plate is an absorbing polarizing plate, The light absorption axis of the polarizing plate is 5° or more and 35° or less with respect to a direction perpendicular to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

12. The liquid crystal display device according to claim 10, wherein: The liquid crystal layer includes a positive liquid crystal material, and the phase difference layer includes a λ / 2 plate. The in-plane slow axis of the λ / 2 plate is 25° or more and 50° or less with respect to a direction perpendicular to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

13. The liquid crystal display device according to claim 10, wherein: The liquid crystal layer includes a positive liquid crystal material, and the phase difference layer includes a λ / 4 plate. The in-plane slow axis of the λ / 4 plate is not less than 45° and not more than 70° with respect to a direction perpendicular to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

14. The liquid crystal display device according to claim 10, wherein: The liquid crystal layer includes a negative liquid crystal material, and the polarizing plate is an absorption-type polarizing plate. The absorption axis of the polarizing plate is greater than or equal to -85° and less than or equal to -55°, with respect to a direction perpendicular to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

15. The liquid crystal display device according to claim 10, wherein: The liquid crystal layer includes a negative liquid crystal material, and the phase difference layer includes a λ / 2 plate. The in-plane slow axis of the λ / 2 plate is not less than -65° and not more than -40° with respect to a direction orthogonal to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

16. The liquid crystal display device according to claim 10, wherein: The liquid crystal layer includes a negative liquid crystal material, and the phase difference layer includes a λ / 4 plate. The in-plane slow axis of the λ / 4 plate is not less than -40° and not more than -15° with respect to a direction perpendicular to the direction in which the plurality of strip-shaped portions extend as a reference (0°).

17. The liquid crystal display device according to claim 1, wherein: Display in normally black mode.

18. The liquid crystal display device according to claim 1, wherein: One of the first electrode and the second electrode is a pixel electrode provided on each of the plurality of pixels, and the other is a common electrode including a plurality of segments capable of functioning as touch sensor electrodes, The first substrate has a plurality of touch wirings respectively connected to the corresponding touch sensor electrodes.

19. The liquid crystal display device according to claim 1, wherein: Also includes a light source.

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