Liquid crystal display device

Abstract

To provide a liquid crystal display device which can realize a high reflectance at a low voltage, has a sufficiently high contrast, and is useful as well as an in-cell type touch panel capable of displaying in a reflection mode.SOLUTION: The liquid crystal display device includes a first substrate, a second substrate facing the first substrate, and a liquid crystal layer provided between the first and second substrates, and has plural pixels. The first substrate includes a reflective layer 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 orientation film in contact with the liquid crystal layer. The electrode arranged on the liquid crystal layer side has a plurality of band-like parts and a slit located between two next to each other of the band-like parts. The band-like parts include linear shapes extending in the same direction and in practically parallel to one another. The liquid crystal layer is made of a liquid crystal material including liquid crystal molecules, the liquid crystal material is a positive type, the second substrate has a second horizontal orientation film in contact with the liquid crystal layer, and the liquid crystal layer takes on a twist orientation when no voltages is applied.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The following disclosure relates to liquid crystal displays. [Background technology]

[0002] Liquid crystal display devices are display devices that use liquid crystal material for display, and are generally broadly classified into transmissive liquid crystal display devices and reflective liquid crystal display devices according to the display method. Transmissive liquid crystal display devices are devices that perform display in a transmissive mode using transmitted light from a backlight behind the screen, while reflective liquid crystal display devices are devices that perform display in a reflective mode using external light (also called ambient light) instead of backlight light. As a display device that combines these characteristics, a semi-transmissive liquid crystal display device has been proposed in which each pixel has an area that performs display in a transmissive mode and an area that performs display in a reflective mode (see, for example, Patent Document 1).

[0003] Liquid crystal display devices can also be broadly classified according to the liquid crystal driving method, and there are known liquid crystal display devices of a vertical electric field type that drives a liquid crystal layer with an electric field in a direction approximately perpendicular to the substrate surface to perform display, and a horizontal electric field type that drives a liquid crystal layer with an electric field in a direction approximately parallel to the substrate surface to perform display. Examples of the vertical electric field type include the twisted nematic (TN) mode and the multi-domain vertical alignment (MVA) mode, and examples of the horizontal electric field type include the in-plane switching (IPS) mode and the fringe field switching (FFS) mode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-47734 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, liquid crystal display devices used in smartphones, tablets, and the like are usually provided with a touch sensor function. There are various types of touch sensors known, such as resistive film type, electrostatic capacitance type, and optical type. Liquid crystal display devices equipped with a touch sensor (also called touch panel) include a type in which the touch sensor is attached externally (external type) and a type in which the touch sensor is built-in (built-in type). The built-in type touch panel is advantageous in terms of narrowing the frame, reducing the thickness, and reducing the weight, etc., compared to the external type touch panel, and also has the advantage of increasing the light transmittance.

[0006] Built-in touch panels are classified into on-cell type and in-cell type. The cell means a display panel (also called a liquid crystal panel) that includes an active matrix substrate, typically a thin film transistor (TFT) substrate, an opposing substrate arranged to face the active matrix substrate, and a liquid crystal layer arranged between the substrates. In general, in the in-cell type, a layer that performs the touch sensor function is arranged inside the display panel, whereas in the on-cell type, a layer that performs the touch sensor function is arranged between the display panel and a polarizing plate arranged on the observation surface side of the display panel. Among these, the in-cell type can theoretically realize the thinnest and lightest touch panel. In addition, liquid crystal display devices capable of displaying in a reflective mode are suitable for outdoor use, so there is a demand for an in-cell type touch panel that can display in a reflective mode. However, this has not yet been realized.

[0007] The reason why this has not been realized is believed to be that in current reflective liquid crystal display devices, one of a pair of electrodes for applying a voltage to the liquid crystal layer (also called a counter electrode or a common electrode) is arranged on the counter substrate side. Therefore, the inventors thought that if a horizontal electric field method such as the FFS mode is used, both of the pair of electrodes are provided only on the active matrix substrate side, and therefore an in-cell type touch panel capable of displaying in the reflective mode can be realized.

[0008] Therefore, further investigations were carried out on FFS mode devices that display in normally black mode, for example. However, while this device is capable of displaying in reflective mode, it was discovered that when a positive-type liquid crystal material is used for the liquid crystal layer, high reflectivity may not be obtained, particularly in white display, and when a negative-type liquid crystal material is used, high reflectivity can be obtained in white display, but low voltage operation is difficult (see verification example below). Furthermore, in recent years, there has been a demand for low power consumption due to the increasing need to make display devices smaller and reduce costs. Therefore, it would be ideal if it were possible to display at low voltage with high reflectivity, but such a device has not yet been realized.

[0009] Patent Document 1 describes that when twist alignment is used in the reflective display region, the reflectance of black display is 1% or less by adjusting the twist angle to a range of 0° to 73° and the product of the cell thickness and the refractive index difference of the liquid crystal layer to a range of 140 nm to 261 nm. However, there is no mention of the reflectance of white display (also called white reflectance) or a method for increasing the white reflectance, so high contrast cannot be expected. Regarding the liquid crystal properties, only Δn=0.1 and Δε=11.3 are specified, and the relationship with the white reflectance is not considered at all.

[0010] The present invention has been made in consideration of the above-mentioned current situation, and aims to provide a liquid crystal display device that can achieve high reflectance at a low voltage, has sufficiently high contrast, and is also useful, for example, as an in-cell type touch panel capable of displaying in a reflective mode. [Means for solving the problem]

[0011] (1) One embodiment of the present invention is a liquid crystal display device having a first substrate, a second substrate opposed to the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate, the liquid crystal display device having a plurality of pixels, the first substrate having a reflective layer that reflects light, a first electrode and a second electrode that can generate a transverse electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer, the first electrode and the second electrode that are disposed on the liquid crystal layer side have a plurality of strip portions and a slit located between two adjacent strip portions of the plurality of strip portions, the plurality of strip portions include linear shapes that are approximately parallel to each other and extend in the same direction, and the liquid crystal layer includes liquid crystal molecules. a first substrate having a first horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first substrate having a second horizontal alignment film in contact with the liquid crystal layer,

[0012] (2) Moreover, one embodiment of the present invention is a liquid crystal display device having the configuration as described above in (1), wherein the product (dΔn) of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal material is 236 nm or more and 252 nm or less.

[0013] (3) Moreover, an embodiment of the present invention is a liquid crystal display device having the configuration of (1) or (2) above, wherein the twist angle when no voltage is applied is equal to or greater than 83° and equal to or less than 87°.

[0014] (4) Furthermore, one embodiment of the present invention is a liquid crystal display device having the configuration of (1), (2), or (3) above, wherein the average azimuth angle φLCave of the liquid crystal molecules when a voltage is applied is 150° or more and 156° or less.

[0015] (5) In addition to the configuration of (1), (2), (3), or (4), an embodiment of the present invention further comprises the liquid crystal material having a birefringence Δn at 60° C. 60 and birefringence Δn at 20°C 20 The ratio of (Δn 60 / Δn 20 ) is 0.84 or more.

[0016] (6) Moreover, an embodiment of the present invention is a liquid crystal display device having the configuration of (1), (2), (3), (4) or (5) above, wherein the liquid crystal material has a dielectric anisotropy Δε of 7 or less.

[0017] (7) Furthermore, in addition to the configuration of (1), (2), (3), (4), (5) or (6), an embodiment of the present invention is a liquid crystal display device further comprising: a polarizing plate disposed on the outer side of the first substrate and / or the second substrate; and a retardation layer disposed between the substrate and the polarizing plate, the retardation layer including a λ / 4 plate and a λ / 2 plate.

[0018] (8) Furthermore, one embodiment of the present invention is a liquid crystal display device having the configuration described above in (1), (2), (3), (4), (5), (6) or (7), and further having a single domain alignment.

[0019] (9) Furthermore, an embodiment of the present invention is a liquid crystal display device that performs display in a normally black mode in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), or (8) above.

[0020] (10) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8) or (9), one of the first electrode or the second electrode is a pixel electrode provided in each of the plurality of pixels, and the other is a common electrode including a plurality of segments each capable of functioning as a touch sensor electrode, and the first substrate has a plurality of touch wirings each connected to a corresponding one of the touch sensor electrodes.

[0021] (11) Furthermore, an embodiment of the present invention is a liquid crystal display device further comprising a light source in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9) or (10). Effect of the Invention

[0022] According to the present invention, it is possible to provide a liquid crystal display device which can realize high reflectance at a low voltage, has sufficiently high contrast, and is useful, for example, as an in-cell touch panel capable of displaying in a reflective mode. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. [Diagram 3] FIG. 1 is a schematic plan view of the entire liquid crystal display device 1 as viewed from the observation surface side. [Figure 4] FIG. 13 is a diagram for explaining the definition of an angle. [Diagram 5] FIG. 2 is a plan view showing one pixel. [Figure 6] FIG. 6 is a schematic enlarged plan view of a portion of FIG. 5. [Figure 7] 1 is a cross-sectional view of the liquid crystal director distribution. [Figure 8A] FIG. 6 is a schematic enlarged plan view of a portion of FIG. 5. [Figure 8B]1 is a cross-sectional view of the liquid crystal director distribution. [Figure 9A] FIG. 6 is a schematic enlarged plan view of a portion of FIG. 5. [Figure 9B] 1 is a cross-sectional view of the liquid crystal director distribution. [Figure 10A] FIG. 6 is a schematic enlarged plan view of a portion of FIG. 5. [Figure 10B] 1 is a cross-sectional view of the liquid crystal director distribution. [Figure 11A] FIG. 6 is a schematic enlarged plan view of a portion of FIG. 5. [Figure 11B] 1 is a cross-sectional view of the liquid crystal director distribution. [Figure 12A] FIG. 13 is a diagram showing a calculation model of a liquid crystal director distribution diagram. [Figure 12B] FIG. 13 is a diagram showing an example of calculation of a VR curve. [Figure 12C] 1 is a cross-sectional view of the liquid crystal director distribution. [Figure 13A] 6 is a schematic cross-sectional view taken along line AA' in FIG. 5 (cross-sectional view taken along line AA'), conceptually illustrating the behavior of liquid crystal molecules 21 when no voltage is applied. [Figure 13B] 6 is a schematic enlarged plan view of a part of FIG. 5, conceptually showing the twist direction of liquid crystal molecules 21 when no voltage is applied. [Figure 14A] 6 is a schematic cross-sectional view taken along line AA' in FIG. 5 (cross-sectional view taken along line AA'), conceptually illustrating the behavior of liquid crystal molecules 21 when a voltage is applied. [Figure 14B] FIG. 6 is a schematic enlarged plan view of a part of FIG. 5, conceptually illustrating the twist direction of liquid crystal molecules 21 when a voltage is applied. [Figure 15] 2 is a plan view illustrating a schematic arrangement of touch sensor electrodes TX and touch wirings TL included in the liquid crystal display device 1. FIG. [Figure 16] FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. [Figure 17] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Figure 18] FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. [Figure 19] FIG. 1 is a plan view illustrating the axial angles of each optical film in a liquid crystal display device 1 that includes, from the rear 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. [Figure 20A] FIG. 1 is a conceptual diagram for explaining the principle of black display. [Figure 20B] FIG. 1 is a conceptual diagram for explaining the principle of white display. [Figure 21] FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. [Figure 22] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Diagram 23] 1 is a schematic plan view conceptually illustrating that each pixel P in a liquid crystal display device 1 has a reflective region Rf and a transmissive region Tr. [Figure 24] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Diagram 25] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Figure 26] 13 is a graph showing reflective mode efficiency when each liquid crystal material is used. [Figure 27] FIG. 27 is an analysis diagram of the VR curve shown in FIG. 26. [Figure 28] This is a cross-sectional view of the reflectance profile at VRmax. [Figure 29] This is the analysis result of the average azimuth angle φLCave of the liquid crystal molecules in the Z direction. [Diagram 30] This is a graph in which the VR curve of Example 2-6 is added to the graph of FIG. [Diagram 31] 1 is a graph examining the temperature characteristics of Δn of various liquid crystal materials. [Diagram 32] 1 is a graph examining the temperature dependency of contrast. [Diagram 33] 13 is a graph examining the temperature dependence of reflective mode efficiency in black display. [Diagram 34] 13 is a graph examining the temperature dependence of reflective mode efficiency in white display. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] (Definition of terms) In this specification, the observation side means the side closer to the screen (display surface) of the liquid crystal display device, and the rear side means the side farther from the screen (display surface) of the liquid crystal display device.

[0025] The no-voltage-applied state refers to a state in which the voltage applied to the liquid crystal layer is less than the threshold voltage (including no voltage application). The voltage-applied state refers to a state in which the voltage applied to the liquid crystal layer is equal to or greater than the threshold voltage. In this specification, the no-voltage-applied state is also referred to as when no voltage is applied, and the voltage-applied state is also referred to as when a voltage is applied.

[0026] The polar angle means the angle between the direction of interest (for example, the measurement direction) and the normal direction of the screen of the liquid crystal panel. Azimuth refers to the direction of a target direction when it is projected onto the screen of an LCD panel, and is expressed as the angle (azimuth angle) between the target direction and a reference direction. Here, the reference orientation (0°) is set to the horizontal right direction of the screen of the liquid crystal panel. For angles and azimuth angles, a counterclockwise angle from the reference orientation is a positive angle, and a clockwise angle from the reference orientation is a negative angle (see FIG. 4). FIG. 4 is a diagram for explaining the definition of angles. Both counterclockwise and clockwise indicate the rotation direction when the screen of the liquid crystal panel is viewed from the observation surface side (front). Also, the angle indicates a value measured when the screen of the liquid crystal panel is viewed in a planar state.

[0027] The axial direction of the optical film means the direction of the polarization axis of the polarizing plate if it is a polarizing plate, and means the direction of the slow axis if it is a retardation layer. The polarization axis of the polarizing plate means the absorption axis if it is an absorption type polarizing plate, and means the reflection axis if it is a reflection type polarizing plate. The axial direction of the retardation layer means the direction of the in-plane slow axis of the retardation layer, unless otherwise specified.

[0028] The retardation layer means a layer having at least one of the in-plane retardation (also called in-plane retardation) Re and the thickness direction retardation (also called thickness direction retardation) Rth of 10 nm or more.Preferably, it means a layer having a value of 20 nm or more.In this specification, the numerical values ​​described as Re and Rth are absolute values ​​unless otherwise specified.

[0029] The in-plane retardation Re is defined as Re=(nx-ny)×d. The thickness direction retardation Rth is defined as 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 in 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 in which the refractive index is maximum, and the fast axis direction is the direction in which the refractive index is minimum. d represents the thickness of the retardation layer.

[0030] An A plate is a retardation plate that satisfies "nx>ny≒nz."

[0031] The measurement wavelength for optical parameters such as refractive index and phase difference is 550 nm unless otherwise specified.

[0032] "Approximately parallel" means that the angle (absolute value) between the two is within the range of 0°±10°, and this angle is preferably within the range of 0°±5°, and more preferably 0° (i.e., parallel in the narrow sense). "Approximately perpendicular" (or approximately perpendicular) means that the angle (absolute value) between the two is within the range of 90°±10°, and this angle is preferably within the range of 90°±5°, and more preferably 90° (i.e., orthogonal or perpendicular in the narrow sense).

[0033] 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 appropriate design changes can be made within the scope of the configuration of the present invention.

[0034] (Embodiment 1) FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 1 of this embodiment, and FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 of this embodiment in more detail. FIG. 3 is a schematic plan view of the entire liquid crystal display device 1 of this embodiment as viewed from the observation surface side. As shown in FIG. 1, the liquid crystal display device 1 includes, in order from the rear side, a first substrate 10, a liquid crystal layer 20, and a second substrate 30. In this embodiment, a TFT substrate is used as the first substrate 10. Note that a portion or structure having 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.

[0035] As shown in Fig. 3, 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 number of types of pixels may be two or less, or may be four or more. Each pixel P includes a thin film transistor (TFT) 110, and a first electrode 121 and a second electrode 122 capable of generating a transverse electric field in the liquid crystal layer 20. A gate electrode of the TFT 110 is electrically connected to a corresponding gate line (also referred to as a scanning line) GL, and a source electrode of the TFT 110 is electrically connected to a corresponding source line (also referred to as a signal line) SL. A drain electrode of the TFT 110 is electrically connected to the second electrode 122.

[0036] <First substrate> As shown in FIG. 2, the first substrate 10 has, in order from the back side to the observation side, a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 that contacts the liquid crystal layer 20. The first substrate 10 preferably further has a support 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, etc., as necessary. For example, a first interlayer insulating layer 151 is provided so as to cover 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.

[0037] The supporting substrate 100 is preferably transparent and insulating, and examples of the supporting substrate 100 include a glass substrate and a plastic substrate.

[0038] The backplane circuit BP is provided on a support substrate 100. The backplane circuit BP is a circuit for driving a plurality of pixels P, and includes a TFT 110, a gate line GL, a source line SL, etc. Usually, the backplane circuit BP also includes a gate insulating film.

[0039] The TFT 110 is provided in each of the pixels P. The TFT 110 is preferably one including an oxide semiconductor layer as an active layer (also referred to as an oxide semiconductor TFT). Specifically, the oxide semiconductor layer is preferably one including at least one metal element selected from In (indium), Ga (gallium), and Zn (zinc). Among them, an oxide semiconductor film including a ternary oxide of In, Ga, and Zn is more preferable. A preferred example of the ternary oxide of In, Ga, and Zn is indium gallium zinc oxide. A semiconductor including a ternary oxide of In, Ga, and Zn is called an In-Ga-Zn-O-based semiconductor, but the ratio (composition ratio) of In, Ga, and Zn in this semiconductor is not particularly limited, and examples include In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, and In:Ga:Zn=1:1:2. The In-Ga-Zn-O-based semiconductor may be amorphous or crystalline. As the crystalline In-Ga-Zn-O based semiconductor, one in which the c-axis is oriented approximately perpendicular to the layer surface is preferable.

[0040] The first interlayer insulating layer 151 is provided so as to cover the backplane circuit BP. The surface of the first interlayer insulating layer 151 on the reflective layer 130 side preferably has an uneven shape (also referred to as an uneven surface structure). This allows the reflective layer 130 to have an uneven surface structure that reflects this shape. The first interlayer insulating layer 151 having an uneven surface structure can be suitably formed using a photosensitive resin, for example, as described in Japanese Patent No. 3394926.

[0041] 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 from a material that reflects light. In particular, it is preferable that the reflective layer 130 is formed from a metal material having a high reflectance. Examples of materials for the reflective layer 130 include a silver alloy, an aluminum alloy, and an aluminum alloy.

[0042] The reflective layer 130 preferably has an uneven shape that reflects the uneven surface structure that the first interlayer insulating layer 151 preferably has. That is, the reflective layer 130 also preferably has an uneven surface structure. This uneven surface structure is also called MRS (Micro Reflective Structure) and is provided to diffusely reflect ambient light and realize a white display close to paper white. The uneven surface structure is preferably composed of a plurality of convex parts p arranged randomly so that the center distance between adjacent convex parts p is 5 μm or more and 50 μm or less. The center distance between adjacent convex parts p is more preferably 10 μm or more and 20 μm or less. The shape of the convex parts p is preferably approximately circular or approximately polygonal when viewed from the normal direction of the support substrate. The area of ​​the convex parts p that occupies one pixel P is preferably, for example, about 20 to 40%, and the height of the convex parts p is preferably, for example, 1 μm or more and 5 μm or less.

[0043] 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 disposed between the first interlayer insulating layer 151 and the second interlayer insulating layer 152.

[0044] Here, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably formed from an organic insulating material or an inorganic insulating material. For example, organic insulating films obtained using an organic insulating material include organic films (relative dielectric constant ε=2 to 5) of acrylic resin, polyimide resin, novolac resin, etc., and laminates thereof. The thickness of the organic insulating film is not particularly limited, but is, for example, 2 μm or more and 4 μm or less. For example, inorganic insulating films obtained using an inorganic insulating material include inorganic films (relative dielectric constant ε=5 to 7) of silicon nitride (SiNx), silicon oxide (SiO2), etc., and laminates thereof. The thickness of the inorganic insulating film is not particularly limited, but is, for example, 1500 Å or more and 3500 Å or less. Alternatively, the inorganic insulating film may be a laminate of an organic insulating film and an inorganic insulating film. Among them, it is preferable that the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are organic insulating films.

[0045] The thickness of each interlayer insulating layer is not particularly limited, but is preferably, for example, 0.2 to 0.5 μm.

[0046] The first electrode 121 is disposed on the reflective layer 130 via the second interlayer insulating layer 152, and a dielectric layer 153 is disposed between the first electrode 121 and the second electrode 122. Therefore, the reflective layer 130 is located on the opposite side of the liquid crystal layer 20 with respect to the first electrode 121 and the second electrode 122 (i.e., on the rear side of the first electrode 121 and the second electrode 122). In this embodiment, of the first electrode 121 and the second electrode 122, the second electrode 122 is located relatively closer to the observation surface, and the first electrode 121 is located on the rear surface. The electrode located relatively closer to the observation surface is also referred to as an upper layer electrode, and the electrode located relatively closer to the rear surface is also referred to as a lower layer electrode.

[0047] 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 in each of the multiple pixels P. The pixel electrode is electrically connected to the backplane circuit BP. In this embodiment, the first electrode 121 (lower layer electrode) is the common electrode CE, and the second electrode 122 (upper layer electrode) is the pixel electrode PE.

[0048] At least one of the first electrode 121 and the second electrode 122 has a plurality of strip portions SP and a slit Sl located between two adjacent strip portions of the plurality of strip portions. The strip portions SP correspond to electrode portions, and the slits Sl correspond to openings, and such electrodes are also called slit electrodes or finger electrodes. From the viewpoint of easily generating a transverse electric field, it is preferable that at least the upper layer electrode (the pixel electrode PE in this embodiment) is a slit electrode. In this case, it is preferable that the lower layer electrode (the common electrode CE in this embodiment) is a planar electrode, that is, a so-called solid electrode.

[0049] The strip portions SP constituting the slit electrode include linear shapes extending substantially parallel to each other and in the same direction. This makes the alignment of the liquid crystal molecules uniform, and sufficiently suppresses the occurrence of alignment disturbance. The linear shape means that the center line of the strip portion SP, not the outer edge of the strip portion SP, is linear, and the center line of the strip portion SP means a line that divides the strip portion SP in half in the width direction. The width direction means a direction substantially perpendicular to the direction in which the strip portion SP extends in a plan view. The strip portion SP may have a bent portion (also called a kink portion) in the middle (for example, at an end portion), but it is preferable that the strip portion SP does not have a bent portion.

[0050] In each pixel P, the directions in which the strip portions SP extend (also referred to as the extension directions of the strip portions SP) are approximately parallel to one another. The extension directions of the strip portions SP may differ for each pixel, but are preferably the same for two or more adjacent pixels. From the viewpoint of manufacturing, it is more preferable that the extension directions of the strip portions SP are the same for at least adjacent pixels. It is also more preferable that the extension directions of the strip portions SP are the same in the display region.

[0051] The width L of each strip-shaped portion SP differs depending on the applied voltage, etc., but is preferably, for example, 0.3 to 10 μm, and more preferably 1 to 5 μm. The interval between two adjacent strip-shaped portions SP (i.e., the interval between the center lines of each strip-shaped portion) also differs depending on the applied voltage, etc., but is preferably, for example, 0.3 to 10 μm, and more preferably 1 to 5 μm.

[0052] The ratio L / S (also referred to as the L / S condition) of the width L of each belt-like portion in a plan view to the width S of each slit in a plan view is preferably 0.4 to 0.7 / 1, which further improves the reflectance and therefore the contrast ratio.

[0053] FIG. 5 is a schematic plan view showing one pixel. FIG. 6 is a schematic plan view showing an enlarged portion of FIG. 5. FIGS. 5 and 6 show, as schematic plan views, a configuration in which the extension direction of a plurality of strip portions SP constituting a slit electrode (a pixel electrode PE in this embodiment) is arranged parallel to a plurality of source lines SL and a plurality of gate lines GL are arranged so as to be perpendicular to the plurality of source lines SL. The extension direction of the plurality of strip portions SP is located in a direction of 90° (see also FIG. 4), where the direction parallel to the gate lines GL (the left-right direction in the drawing) is taken as the reference (0°) and the angle rotated clockwise is taken as a positive angle (+) and the angle rotated counterclockwise is taken as a negative angle (-). This angle, that is, the angle of the extension direction of the plurality of strip portions SP when the direction parallel to the gate lines GL is taken as the reference (0°), is called the slit angle θ SP It is called.

[0054] Slit angle θ SP The preferred range of varies depending on the condition of the width L of each strip portion SP and the width S of each slit Sl (also referred to as the L / S condition), the twist angle, and various physical properties of the liquid crystal material, but is preferably, for example, 30° or more. More preferably, it is 60° or more, and even more preferably, it is 80° or more. The upper limit is preferably 150° or less. More preferably, it is 120° or less, and even more preferably, it is 100° or less.

[0055] The first electrode 121 and the second electrode 122 are preferably each made of a transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), a mixture thereof, or the like.

[0056] In the embodiment shown in FIG. 2, the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, to the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed in the same layer as the reflective layer 130 and is made of the same material (metal film, etc.) as the reflective layer 130. The first interlayer insulating layer 151 is formed with a first contact hole CH1 that exposes a part of the backplane circuit BP (more specifically, at least a part of the drain electrode of the TFT 110), and the contact electrode 160 is connected to the backplane circuit BP at the first contact hole CH1. The second interlayer insulating layer 152 is formed with a second contact hole CH2 that exposes a part of the contact electrode 160, and the pixel electrode PE (the second electrode 122 in this embodiment) is connected to the contact electrode 160 at the second contact hole CH2.

[0057] The dielectric layer 153 is provided so as to cover the first electrode 121. The dielectric layer 153 is preferably formed from an inorganic insulating material. The inorganic insulating film obtained using the inorganic insulating material is as described above.

[0058] 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 disposed between the second interlayer insulating layer 152 and the first horizontal alignment film 140.

[0059] The first horizontal alignment film 140 and the second horizontal alignment film 340 described later are each subjected to an alignment treatment, and define the alignment direction (also referred to as the alignment direction) of the liquid crystal molecules 21 contained in the liquid crystal layer 20. For example, the alignment treatment is preferably performed by a photo-alignment treatment or a rubbing treatment. In the photo-alignment treatment, a photodecomposition type photo-alignment film material can be used, and in the rubbing treatment, it is preferable to use an alignment film material such as polyimide.

[0060] Both the first horizontal alignment film 140 and the second horizontal alignment film 340 are horizontal alignment films that align the liquid crystal molecules 21 in a direction horizontal to the first substrate 10 and the second substrate 30 when no voltage is applied to the liquid crystal layer 20. That is, the liquid crystal molecules 21 are horizontally aligned when no voltage is applied to the liquid crystal layer 20. The pretilt angle is substantially 0°.

[0061] The alignment direction of the liquid crystal molecules 21 determined by the first horizontal alignment film 140 is different from the alignment direction of the liquid crystal molecules 21 determined by the second horizontal alignment film 340. Therefore, the liquid crystal layer 20 has a twisted alignment when no voltage is applied (see FIG. 2). When a voltage is applied to the liquid crystal layer 20, that is, when a transverse electric field is generated in 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).

[0062] The thickness of each horizontal alignment film is not particularly limited, but is preferably, for example, 0.06 to 0.14 μm.

[0063] <Second board> The second substrate 30 is disposed opposite the first substrate 10 with the liquid crystal layer 20 interposed therebetween, and has a second horizontal alignment film 340 in contact with the liquid crystal layer 20. The second substrate 30 preferably further has a support substrate 300 and a color filter layer 310. For example, as shown in FIG. 2, the second substrate 30 has, in order from the liquid crystal layer 20 side, the second horizontal alignment film 340, the color filter layer 310, and the support substrate 300. The second substrate 30 preferably also has a plurality of columnar spacers (not shown). Note that the first substrate 10 may have a plurality of columnar spacers.

[0064] The supporting substrate 300 is preferably transparent and insulating, and examples of the supporting substrate 300 include a glass substrate and a plastic substrate.

[0065] The color filter layer 310 typically includes a red color filter provided in an area corresponding to a red pixel and transmitting red light, a green color filter provided in an area corresponding to a green pixel and transmitting green light, and a blue color filter provided in an area corresponding to a blue pixel and transmitting blue light. However, the number of types of color filters may be two or less, or may be four or more. When color display is not performed, the color filter layer 310 is omitted. In addition, when a color filter layer is formed on the first substrate 10, it is preferable that the second substrate 30 does not have a color filter layer.

[0066] If necessary, an overcoat layer (also called a planarizing layer) may be provided to cover the color filter layer 310. Note that the white display may have a yellowish tinge depending on the material (e.g., transparent conductive material) forming the electrodes, the material forming the interlayer insulating layer and the dielectric layer, and the material forming the alignment film. In that case, the chromaticity of the white display may be adjusted (i.e., blue shift) by forming the overcoat layer from a blue resist, so that the chromaticity of the white display may be brought closer to that of a D65 light source, for example. The D65 light source is the CIE standard illuminant D65.

[0067] <Liquid crystal layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and contains a positive type liquid crystal material. The positive type liquid crystal material means a nematic liquid crystal material having a positive dielectric anisotropy Δε. The negative type liquid crystal material means a nematic liquid crystal material having a negative dielectric anisotropy Δε. The dielectric anisotropy Δε is the dielectric constant ε in the long axis direction of the liquid crystal molecules 21. / / and the dielectric constant in the minor axis direction ε ⊥ (i.e., ε / / -ε ⊥ ).

[0068] The liquid crystal layer 20 may further include a chiral agent, if necessary. The liquid crystal layer 20 can be formed by, for example, a dropping method.

[0069] The thickness d of the liquid crystal layer 20 (also referred to as the cell gap or cell thickness) is preferably, for example, 1.5 μm or more. There is no particular upper limit, but it is preferably, for example, 10 μm or less. More preferably, it is 5 μm or less.

[0070] The liquid crystal layer 20 may have a multi-domain orientation such as a dual-domain orientation. However, if the dual-domain design of the transmissive FFS is directly applied to the reflective type, the pixel will act as a pixel with low reflectance when θa exceeds 90 degrees, and a loss in reflectance may occur. Therefore, a single-domain orientation (also called a mono-domain orientation) is preferable.

[0071] The liquid crystal material constituting the liquid crystal layer 20 has a positive dielectric anisotropy Δε. Generally, when the absolute value of Δε is less than 2, it is considered that there is no dielectric anisotropy, so the lower limit of Δε is preferably 2 or more, and more preferably 3 or more. From the viewpoint of further increasing the reflectance (for example, white reflectance in a normally black mode), the upper limit is preferably 15 or less, more preferably 10 or less, and even more preferably 7 or less.

[0072] Considering the absolute Δn value of the liquid crystal molecule with the lowest refractive index (Δn=0.038 for the alkenyl derivative with the lowest refractive index), the liquid crystal material preferably has a birefringence Δn of more than 0.05. More preferably, it is 0.06 or more, and most preferably, it is 0.077 or more. Furthermore, from the viewpoint of having a well-balanced performance as a liquid crystal mixture for displays, the upper limit is preferably 0.2 or less. More preferably, it is 0.1 or less, and most preferably, it is 0.09 or less.

[0073] The above liquid crystal material has a twist elastic constant K 22 (unit: pN) is preferably 2 or more, and more preferably 3 or more. From the viewpoint of lowering the voltage, the upper limit is preferably 10 or less, more preferably 7 or less, and even more preferably 6 or less.

[0074] The liquid crystal material has a splay elastic constant K11 (Unit: pN) is K 22 Since the bending elastic constant K tends to be directly proportional to the bending moment, it is preferable that the bending moment is 4 or more and 20 or less. More preferably, the bending elastic constant K is 6 or more and 14 or less. 33 Although the value (unit: pN) does not have a significant effect on the optical characteristics of this mode, it is preferably in the range of 6 to 20. More preferably, it is in the range of 10 to 16. In addition, each elastic constant (K 11 , K 22 , K 33 ) can be calculated by fitting a theoretical equation using the measured values ​​of the capacitance-voltage characteristic curve.

[0075] The liquid crystal material contains liquid crystal molecules (also called positive liquid crystal molecules), and the average azimuth angle φLCave of the liquid crystal molecules when a voltage is applied is preferably 150° or more and 156° or less. Within this range, it becomes easier to make the positional relationship between the extension direction of the multiple strip-shaped portions SP and the liquid crystal molecules 21 when no voltage is applied, and the rotation direction of the liquid crystal molecules 21 when a voltage is applied, into the form described above. It is more preferable that the lower limit is 151° or more. Also, it is more preferable that the upper limit is 155° or less, even more preferably 154° or less, and particularly preferably 153° or less.

[0076] In this specification, the average azimuth angle φLCave of the liquid crystal molecules when a voltage is applied is a value obtained by calculating the liquid crystal director at the voltage at which the reflectance is maximized using simulation software (LCD Master 2D) manufactured by Shintech Co., Ltd., and calculating the azimuth angle distribution of the liquid crystal molecules. The details of the calculation method are described below. (Calculation method for φLCave) (1) A calculation model shown in FIG. 12A is created. The width of a pixel is 4.6 μm. The first electrode 121 is a common electrode CE, and the second electrode 122 is a pixel electrode PE. The common electrode CE is a solid electrode, and the pixel electrode PE (122) is a slit electrode with a width L of 1.6 μm per stripe and a width S of 3.0 μm per slit. The liquid crystal layer 20 is arranged in increments of 0.05 μm in the X direction (horizontal direction) and 0.025 μm in the Z direction (thickness direction). In this calculation model, the liquid crystal layer 20 is in a matrix shape consisting of 21 points in the X direction × 31 points in the Z direction, a total of 651 points, and the azimuth angle and polar angle of the liquid crystal molecules in each matrix are calculated according to the applied voltage. FIG. 12A is a diagram showing a calculation model of a liquid crystal director distribution diagram. (2) In this calculation model, a voltage of, for example, 0 to 8 V is applied to the pixel electrode PE (122) in increments of 0.1 V to calculate a VR curve. An example of this calculation is shown in FIG. 12B. In this calculation example, the maximum reflectance was obtained at an applied voltage of 4.2 V (see FIG. 12B). FIG. 12B is a diagram showing an example of a calculation of a VR curve. (3) The liquid crystal molecule director distribution at the applied voltage (i.e., 4.2V) showing the maximum reflectance is calculated using simulation software (LCD Master 2D) manufactured by Shintech Co., Ltd. The obtained liquid crystal molecule director distribution diagram (also called liquid crystal director distribution diagram) is shown in Figure 12C. Figure 12C is a liquid crystal director distribution diagram (cross-sectional view). (4) The azimuth angle φ and polar angle θ are extracted for the director of each liquid crystal molecule obtained in (3) above (i.e., 21 points in the X direction × 31 points in the Z direction = 651 directors in total). (5) The average value for all azimuth angles (i.e., the sum of the azimuth angles of a total of 651 points / 651) is calculated. The value calculated in this way is the average azimuth angle φLCave of the liquid crystal molecules when a voltage is applied.

[0077] The above liquid crystal material has a birefringence Δn 60 and birefringence Δn at 20°C 20 The ratio of (Δn 60 / Δn 20) is preferably 0.80 or more. In general, the upper limit of the actual operating temperature of a liquid crystal display device is about 50° C. Therefore, Δn 60 / Δn 20 Within the above range, a display in which the influence of temperature is sufficiently suppressed can be obtained at the actual use temperature. In particular, black floating during black display is sufficiently suppressed. More preferably, it is 0.82 or more, and even more preferably, it is 0.84 or more. From the viewpoint of suppressing a decrease in contrast, the upper limit is preferably 0.97 or less, and more preferably 0.95 or less.

[0078] The retardation (dΔn) of the liquid crystal layer 20, which is expressed as the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material, is preferably 180 nm or more and 280 nm or less. This allows a lower voltage to be realized and the reflectance to be further improved. It is more preferably 200 nm or more and 260 nm or less, even more preferably 220 nm or more and 252 nm or less, and particularly preferably 236 nm or more and 252 nm or less. It is even more preferably 250 nm or less.

[0079] As described above, the liquid crystal layer 20 has a twisted orientation when no voltage is applied. That is, in the liquid crystal display device 1 of this embodiment, display is performed by the lateral electric field mode in which the liquid crystal layer 20 has a twisted orientation when no voltage is applied. This allows the cell gap to be increased, and the range of contrast fluctuations relative to cell gap fluctuations to be reduced. Therefore, the occurrence of display unevenness is sufficiently suppressed, and the contrast of the reflective display is improved. The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied will be described later.

[0080] In this embodiment, when the liquid crystal layer 20 of each pixel P is viewed in a plane when no voltage is applied, at least in the center of the plane direction of the liquid crystal layer 20, the extension direction of the multiple strip-shaped portions SP is located between the long axis direction a of the liquid crystal molecules 21 on the first substrate 10 side and the long axis direction b of the liquid crystal molecules 21 on the second substrate 30 side. When the liquid crystal layer 20 of each pixel P is viewed in a plane, at least the liquid crystal molecules 21 in the center of the thickness direction of the liquid crystal layer 20 rotate in the twist direction when no voltage is applied when a voltage is applied. This form can be realized, for example, by appropriately adjusting the twist angle θ1 and various physical properties of the above-mentioned liquid crystal material, and by adopting this form, a reverse twist orientation occurs in the liquid crystal layer 20. Therefore, for example, in the case of a normally black mode, when white is displayed, the entire liquid crystal molecules of the liquid crystal layer 20 are in an orientation state that is very similar to a homogeneous orientation. Therefore, the light utilization efficiency is increased and the white reflectance is improved, so that a high reflectance can be obtained even when white is displayed at a low driving voltage. The liquid crystal molecules 21 on the first substrate 10 side (i.e., the liquid crystal molecules 21 near the first horizontal alignment film 140) are also referred to as liquid crystal molecules 21A, and the liquid crystal molecules 21 on the second substrate 30 side (i.e., the liquid crystal molecules 21 near the second horizontal alignment film 340) are also referred to as liquid crystal molecules 21B.

[0081] The surface direction center of the liquid crystal layer 20 is also referred to as the horizontal direction center of the liquid crystal layer 20, and means the center of the liquid crystal layer 20 in plan view. That is, it means the vicinity of the center of the liquid crystal layer 20 when the liquid crystal panel 1X is viewed from the observation surface side. Moreover, the thickness direction center of the liquid crystal layer 20 means the center of the liquid crystal layer 20 in cross-sectional view. That is, it means the vicinity of the center of the liquid crystal layer 20 when the liquid crystal panel 1X is viewed from its side. Therefore, the liquid crystal molecule 21 located at the thickness direction center of the liquid crystal layer 20 is located approximately halfway between the liquid crystal molecule 21A on the first substrate 10 side and the liquid crystal molecule 21B on the second substrate 30 side. The liquid crystal molecule 21 located at the thickness direction center of the liquid crystal layer 20 is also referred to as the liquid crystal molecule 21C.

[0082] When the liquid crystal layer 20 of each pixel P is viewed in plan with no voltage applied, "at least in the center of the surface direction of the liquid crystal layer 20, the extension direction of the plurality of strip-shaped portions SP is located between the long axis direction a of the liquid crystal molecules 21A and the long axis direction b of the liquid crystal molecules 21B" means that at least in the center of the surface direction of the liquid crystal layer 20, with no voltage applied, the extension direction of the plurality of strip-shaped portions SP is located between the long axis direction a of the liquid crystal molecules 21A and the long axis direction b of the liquid crystal molecules 21B. θ a <θ SP <(θ a +θ1) (1) This means that

[0083] In the above formula, θ a is the angle of the alignment direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied, where the direction parallel to the gate line GL is taken as the reference (0°), a clockwise rotation angle is a positive angle (+), and a counterclockwise rotation angle is a negative angle (-). In the case of positive type liquid crystal molecules, the alignment direction of the liquid crystal molecules 21A corresponds to the long axis direction of the liquid crystal molecules 21A. θ SP is the angle (slit angle) from the reference (0°) to the extension direction of the multiple strip-shaped parts SP. (θ a +θ1) is θ a and θ1, where θ1 is the twist angle. The twist angle is the angle between the long axis direction a of the liquid crystal molecules 21A when no voltage is applied and the long axis direction b of the liquid crystal molecules 21B when no voltage is applied (i.e., the angle between the alignment direction of the liquid crystal molecules 21A determined by the first horizontal alignment film 140 and the alignment direction of the liquid crystal molecules 21B determined by the second horizontal alignment film 340).

[0084] θ a is preferably, for example, 10 to 90°. In other words, the above relational expression (1) is satisfied, and θ a It is preferable to control the alignment of the liquid crystal molecules 21A by the first horizontal alignment film so that the angle is this angle. The lower limit is more preferably 30° or more, even more preferably 45° or more, and particularly preferably 60° or more. The upper limit is more preferably 89° or less, even more preferably 85° or less, particularly preferably 83° or less, and most preferably 80° or less.

[0085] Slit angle θ SP is preferably, for example, 30 to 150°. In other words, the above relational expression (1) is satisfied, and θ SP It is preferable to design the slit electrode so that the angle is within this range. a Any numerical value exceeding this limit may be used, but for example, it is more preferably 45° or more, even more preferably 60° or more, and particularly preferably 80° or more. The upper limit is more preferably 120° or less, and even more preferably 100° or less.

[0086] The twist angle θ1 is 78° or more and 90° or less. Among them, from the viewpoint of realizing a lower voltage and further improving the reflectance, 80° or more is preferable, and 83° or more is more preferable. Furthermore, when the twist angle θ1 is 90°, there is a concern that alignment disorder may occur due to pressure applied to the liquid crystal panel surface, so it is preferable that the twist angle θ1 is less than 90°. From the viewpoint of further improving the response characteristics, 88° or less is more preferable, and 87° or less is even more preferable. From the viewpoint of the maximum reflectance, the maximum reflectance voltage, and the response characteristics, it is particularly preferable that the twist angle θ1 is 78° or more and 88° or less, even more preferably 83° or more and 87° or less, and 83° is most preferable.

[0087] For example, θ a =80°, slit angle θ SP When the twist angle θ1 is 90° and the twist angle θ2 is 83°, the liquid crystal molecules 21A, 21B, and the extension directions of the strip portions SP of the slit electrode conceptually have a positional relationship as shown in FIG.

[0088] In this embodiment, where the twist angle is in a positive numerical range, the twist direction when no voltage is applied is a positive direction (i.e., counterclockwise). Therefore, when the liquid crystal layer 20 of each pixel P is viewed in a plan view, "at least the liquid crystal molecules 21C in the center in the thickness direction of the liquid crystal layer 20 rotate in the twist direction when no voltage is applied when a voltage is applied" means that at least the liquid crystal molecules 21C rotate in the positive direction when a voltage is applied.

[0089] As described above, in this embodiment, a reverse twist alignment occurs in the liquid crystal layer 20, and the mechanism by which the reverse twist alignment occurs will be described below with reference to, for example, Figures 6, 7, 8A and 8B, and 9A and 9B. Additionally, the mechanism by which a positive twist alignment occurs will be described below with reference to Figures 6, 7, 10A and 10B, and 11A and 11B. Here, an example will be described in which the liquid crystal panel 1X is in a normally black mode.

[0090] 6, 8A, 9A, 10A, and 11A are schematic plan views enlarging a part of FIG. 5, and are schematic plan views conceptually showing the relationship between the extension direction of the strip portion SP of the second electrode 122 (pixel electrode PE in this example) and the alignment direction of the liquid crystal molecules 21. However, the first electrode 121 (common electrode CE in this example) and the like are omitted. FIGS. 7, 8B, 9B, 10B, and 11B are liquid crystal director distribution diagrams (cross-sectional views).

[0091] FIG. 6 conceptually shows the positional relationship between the stretching direction of the strip portion SP and the alignment direction of the liquid crystal molecules 21 when no voltage is applied (i.e., when a voltage of 0 V is applied). FIG. 7 shows a liquid crystal director distribution diagram (cross-sectional view) when no voltage is applied. FIG. 8A conceptually shows the positional relationship between the stretching direction of the strip portion SP and the alignment direction of the liquid crystal molecules 21 when a threshold voltage (for example, a voltage of 1.8 V) is applied, in the case of reverse twist alignment, and FIG. 10A conceptually shows the positional relationship between the stretching direction of the strip portion SP and the alignment direction of the liquid crystal molecules 21 when a threshold voltage (for example, a voltage of 1.8 V) is applied, in the case of reverse twist alignment, and in the case of forward twist alignment. FIG. 8B conceptually shows the liquid crystal director distribution diagram (cross-sectional view) when a threshold voltage is applied, in the case of reverse twist alignment, and in the case of forward twist alignment, in FIG. 10B. FIG. 9A conceptually shows the positional relationship between the stretching direction of the strip portion SP and the alignment direction of the liquid crystal molecules 21 when a white voltage (for example, 4.0 V) is applied, in the case of reverse twist alignment, and in the case of forward twist alignment, in FIG. 11A conceptually shows the positional relationship. The liquid crystal director distribution diagram (cross-sectional view) when a white voltage is applied is shown in Fig. 9B for the reverse twist orientation and in Fig. 11B for the normal twist orientation. For reference, a model of the liquid crystal director distribution diagram is shown in Fig. 12A.

[0092] For example, θ a = 80°, slit angle θ SPWhen the twist angle θ1 is 90° and the twist angle θ1 is 83°, conceptually, the extension direction of the strip portions SP when no voltage is applied and the alignment direction of the liquid crystal molecules 21 have the positional relationship shown in Fig. 6 in a plan view. In this case, the liquid crystal molecules 21 are twisted in the direction of the arrow shown in Fig. 7 (to the right in the drawing) in a cross-sectional view (see Fig. 7).

[0093] In a configuration where reverse twist alignment occurs, when a voltage (e.g., 1.8 V) near the liquid crystal threshold is applied, the equipotential lines reach the opposing substrate (i.e., the second substrate 30) (see x in FIG. 8B). As a result, the liquid crystal molecules 21 in the entire liquid crystal layer 20, including the liquid crystal molecule 21B at the interface on the second substrate 30 side, rotate simultaneously due to elastic action. For example, when the liquid crystal molecule 21C located at the center in the thickness direction of the liquid crystal layer 20 is viewed in plan from the observation surface side, it rotates counterclockwise, which is the twist direction (see FIG. 8A). When a white voltage (e.g., 4.0 V) is applied, the liquid crystal molecule 21C further rotates counterclockwise (see FIG. 9A). In a cross-sectional view, almost all of the liquid crystal molecules 21 included in the liquid crystal layer 20 are twisted in the untwisting direction (leftward in FIG. 9B) (see FIG. 9B).

[0094] On the other hand, in a configuration where a positive twist orientation occurs, when a voltage (e.g., 1.8 V) near the liquid crystal threshold is applied, the equipotential lines do not reach the opposing substrate (i.e., the second substrate 30) (see x in FIG. 10B). Therefore, the liquid crystal molecules 21A at the interface on the first substrate 10 side mainly rotate, and when the liquid crystal molecules 21C at the center in the thickness direction of the liquid crystal layer 20 are viewed in plan from the observation surface side, they rotate clockwise, which is the opposite direction to the twist direction (see FIG. 10A). Furthermore, when a white voltage (e.g., 4.0 V) is applied, the liquid crystal molecules 21C further rotate clockwise (see FIG. 11A). In a cross-sectional view, the liquid crystal molecules 21 further rotate in the initial twist direction (rightward in FIG. 11B) according to the electric field direction that starts to move near the threshold voltage (see FIG. 11B). Due to the influence of such a twist direction of the liquid crystal molecules 21, a mixed state of optical rotation and birefringence occurs, and the white reflectance does not improve.

[0095] The behavior of the liquid crystal molecules 21 in this embodiment will be further described below with reference to the drawings. Here, too, an embodiment in which the liquid crystal panel 1X is in a normally black mode will be described.

[0096] FIG. 13A is a schematic cross-sectional view (A-A' line cross-sectional view) taken along line A-A' in FIG. 5, and is a diagram conceptually showing the behavior of the liquid crystal molecules 21 when no voltage is applied (i.e., black display state). FIG. 13B is a schematic plan view enlarging a portion of FIG. 5, and is a diagram conceptually showing the twist direction of the liquid crystal molecules 21 when no voltage is applied (i.e., black display state). Meanwhile, FIG. 14A is a schematic cross-sectional view (A-A' line cross-sectional view) taken along line A-A' in FIG. 5, and is a diagram conceptually showing the behavior of the liquid crystal molecules 21 when a voltage is applied (i.e., white display state). FIG. 14B is a schematic plan view enlarging a portion of FIG. 5, and is a diagram conceptually showing the twist direction of the liquid crystal molecules 21 when a voltage is applied (i.e., white display state).

[0097] As shown in Fig. 13A, when no voltage is applied, the liquid crystal molecules 21 are horizontally aligned by the first horizontal alignment film 140 and the second horizontal alignment film 340. The liquid crystal molecules 21B defined by the second horizontal alignment film 340 are twisted by the twist angle θ1 from the liquid crystal molecules 21A defined by the first horizontal alignment film 140 (see Fig. 13B). On the other hand, when a voltage is applied, the liquid crystal molecules 21 rotate in the pixel plane so that the twist angle azimuths are different due to the influence of the transverse electric field EF generated between the first electrode 121 (common electrode CE in this embodiment) and the second electrode 122 (pixel electrode PE) (see Figs. 14A and 14B).

[0098] <Manufacturing method> The liquid crystal panel 1X can be manufactured, for example, by bonding a first substrate 10 and a second substrate 30 together, injecting a liquid crystal composition into the gap between them to form a liquid crystal layer 20, and then cutting the resulting structure.

[0099] As a manufacturing method for the first substrate 10 (e.g., a TFT substrate), it is preferable to adopt a general FFS mode TFT substrate manufacturing method using transparent electrodes. As described above, insulating films (also called insulating layers) are formed between the electrodes and between each electrode and the gate line GL, source line SL, TFT 110, etc. As described above, the insulating film may be an inorganic film or an organic film. A color filter layer may be formed instead of the organic insulating film. It is also preferable to form the pixel electrode PE after forming the common electrode CE and then forming the organic insulating film, and then patterning the organic insulating film.

[0100] It is preferable to adopt a method for producing a counter substrate in a general FFS mode as a method for producing the second substrate 30. When a color filter layer is formed on the first substrate 10, it is preferable that the second substrate 30 does not have a color filter layer.

[0101] <Other configurations etc.> From the viewpoint of further increasing contrast, the liquid crystal display device 1 is preferably in a normally black mode. The normally black mode is a display mode in which black is displayed when no voltage is applied and white is displayed when a voltage is applied.

[0102] In the present embodiment, the pixel electrode PE is provided above the common electrode CE. However, 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, it is preferable that the pixel electrode PE is provided above the common electrode CE. In this configuration (also referred to as the V2 structure), since there is no need to form a slit in the common electrode CE, which is the lower electrode, the increase in resistivity (sheet resistivity) of the common electrode CE is suppressed more than in the configuration (also referred to as the V3 structure) in which the common electrode CE is provided above the pixel electrode PE, and therefore the fringe electric field applied to the liquid crystal layer 20 is suppressed from weakening. In this configuration (V2 structure), when the pixel electrode PE is a slit electrode, the resistivity of the pixel electrode PE increases, but since an externally input voltage is applied to the pixel electrode PE, it is easy to reduce the effect of the increase in resistivity (i.e., to suppress the fringe electric field from weakening). In order to suppress the increase in resistivity of the common electrode CE, it is possible to use low-resistance wiring made of a metal material (for example, connecting the low-resistance wiring to the common electrode). However, in such a configuration, adverse effects on the display due to specular reflection from the low-resistance wiring (for example, glare, rainbow-colored diffraction, interference patterns) may occur, making it necessary to block light with a black matrix or the like, and it may not be possible to sufficiently improve the reflective aperture ratio.

[0103] In the configuration in which the pixel electrode PE is provided above the common electrode CE, the common electrode CE is not present in the region in which the second contact hole CH2 is formed, and the region does not contribute to reflective display, so that the reflectance may be lower than in the configuration in which the common electrode CE is provided above the pixel electrode PE. Since the area of ​​the region that does not contribute to reflective display, such as the contact hole, is required to a certain extent regardless of the size of the area of ​​the pixel P, the ratio of the region that does not contribute to reflective display in the pixel P increases as the area of ​​the pixel P decreases (i.e., the resolution increases), and the above-mentioned decrease in reflectance increases. In other words, in a relatively large liquid crystal display device, the ratio of the region that does not contribute to reflective display in the pixel P is easier to reduce, so that the above-mentioned decrease in reflectance is easier to suppress. For these reasons, in a relatively large liquid crystal display device, a configuration in which the pixel electrode PE is provided above the common electrode CE is advantageous.

[0104] On the other hand, as described above, the reduction in reflectance due to the region in which the second contact hole CH2 is formed not contributing to the reflective display becomes greater as the area of ​​the pixel P becomes smaller (i.e., as the resolution increases). Therefore, in a relatively high-resolution liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively small, it is preferable that the common electrode CE is provided above the pixel electrode PE (see Variant 1 of Embodiment 1 described below).

[0105] The liquid crystal display device 1 is also configured with a plurality of components, such as the above-mentioned components, external circuits such as a TCP (tape carrier package) and a PCB (printed wiring board), optical films such as a viewing angle widening film and a brightness enhancing film, and a bezel (frame), and some of the components may be incorporated into other components. These are not particularly limited, and those commonly used in the field of liquid crystal display devices can be used, so their explanation will be omitted.

[0106] <Application Examples> The liquid crystal display device 1 of the present embodiment is suitable for various applications. In particular, it is preferably applicable to touch panels. Whether it is applied to an external touch panel or a built-in touch panel, it is useful because it can be produced at a lower cost than conventional touch panels and has an improved contrast ratio. In particular, it is preferably applicable to a built-in touch panel, and is particularly preferably applicable to an in-cell touch panel. In this way, by using the liquid crystal display device 1 of the present embodiment, it is possible to preferably realize an in-cell touch panel capable of displaying in a reflective mode, which has not been possible until now.

[0107] By realizing an in-cell touch panel capable of displaying in reflective mode, for example, a frame wiring area required for an external touch panel is not required, so that a narrow frame can be achieved, and since the touch panel function can be installed without a cover glass, it contributes to a thinner and lighter touch panel. In addition, since the touch function and the display function are driven in a time-division manner, the touch panel is not affected by LCD (liquid crystal display) noise, which can be the largest noise source in a touch panel. In other words, since no killer pattern occurs, tuning (adjustment) of the touch signal is easy. Furthermore, the loss of reflected light is sufficiently small, and a more natural and natural display can be obtained when writing with a pen. Moreover, compared to an external touch panel, a total cost reduction can be achieved from the user's perspective. Moreover, it is possible to combine finger input with pen input using the electromagnetic induction method (EMR), which allows for highly accurate pen writing.

[0108] An example in which the liquid crystal display device 1 is used in an in-cell touch panel will be further described. Fig. 15 is a plan view schematic illustrating the arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1. As shown in Fig. 15, the liquid crystal display device 1 has a display area DR and a non-display area FR. The display area DR is defined by a plurality of pixels P (see Fig. 3, for example) arranged in a matrix. The non-display area FR is located on the periphery of the display area DR and is also referred to as a peripheral area or a frame area.

[0109] 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. In the example shown in FIG. 15, each touch sensor electrode TX is provided corresponding to two or more pixels P.

[0110] 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 a corresponding touch wiring TL. A 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.

[0111] The touch wiring TL is connected to a touch driving unit TD provided in the non-display region FR. The touch driving unit TD is configured to switch, for example, 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 as the touch sensor electrodes TX in a time-division manner. For example, in the display mode, the touch driving unit TD applies a common signal to the touch sensor electrodes TX (common electrodes CE) via the touch wiring TL. On the other hand, in the touch detection mode, the touch driving unit TD applies a touch driving signal to the touch sensor electrodes TX via the touch wiring TL.

[0112] 15, the touch wirings TL extend in the column direction (the same direction as the source wirings SL). Some of the touch wirings TL extend to the corresponding touch sensor electrodes TX, crossing one or more other touch sensor electrodes TX.

[0113] Focusing on a certain touch sensor electrode TX, a first touch wiring TL1 that supplies a signal to the touch sensor electrode TX extends to a touch wiring contact portion TC, and a second touch wiring TL2 that supplies a signal to another touch sensor electrode TX extends across the touch sensor electrode TX. The second touch wiring TL2 and the touch sensor electrode TX overlap with each other via an insulating layer. Depending on the position of the touch sensor electrode TX, two or more touch wirings TL may be arranged to extend across the touch sensor electrode TX, or no touch wiring TL may be arranged to cross the touch sensor electrode TX.

[0114] In addition to the touch drive unit TD, the non-display area FR is provided with peripheral circuits including drive circuits such as a gate driver that supplies gate signals to the gate bus lines (gate wiring) GL and a source driver that supplies source signals to the source bus lines (source wiring) SL (not shown). These drive circuits may be mounted on the first substrate (TFT substrate) 10, for example, or may be formed integrally (monolithically). A semiconductor chip including some or all of the drive circuits may be mounted on the non-display area FR.

[0115] In an in-cell touch panel, it is particularly preferable to use an In-Ga-Zn-O based semiconductor as the TFT 110. From the viewpoint of achieving flickerless (also called flicker-free), it is particularly preferable to use a negative type liquid crystal material. This is for the following reason. In the in-plane electric field method of the FFS mode using a positive type liquid crystal material, flexoelectric polarization occurs spontaneously in the liquid crystal layer due to the influence of the fine slit electrodes on the electrodes when a voltage is applied (i.e., the fringe electric field). Since the liquid crystal responds according to this flexoelectric polarization, the luminance changes when the polarity is inverted, which is thought to be easily visually recognized as flicker.

[0116] (Modification 1 of the first embodiment) In the first embodiment, the first electrode 121, which is a lower layer electrode, is the common electrode CE, and the second electrode 122, which is an upper layer electrode, is the pixel electrode PE. However, 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 layer electrode) is the common electrode CE, and the first electrode 121 (lower layer electrode) is the pixel electrode PE (see FIG. 16).

[0117] FIG. 16 is a schematic cross-sectional view showing the liquid crystal display device 1 of this example in more detail. In this example as well, from the viewpoint of easily generating a transverse electric field, it is preferable that at least the upper layer electrode (common electrode CE in this example) is a slit electrode. The lower layer electrode (pixel electrode PE in this example) may be a planar electrode, i.e., a so-called solid electrode, or may be a slit electrode. As described above, the liquid crystal display device 1 of this example 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.

[0118] (Modification 2 of the first embodiment) In the first embodiment, an FFS mode liquid crystal display device has been described, but an IPS mode liquid crystal display device may also be used (however, the liquid crystal layer 20 has a twisted orientation when no voltage is applied). This modification is an IPS mode liquid crystal display device. In this modification, the first electrode 121 and the second electrode 122 are provided in the same layer, and it is preferable that both the first electrode 121 and the second electrode 122 are slit electrodes.

[0119] (Embodiment 2) In this embodiment, the features unique to this embodiment will be mainly described, and the description of the contents overlapping with the above-mentioned embodiment 1 will be 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.

[0120] Fig. 17 is a schematic cross-sectional view of the liquid crystal display device 1 of this embodiment, and Fig. 18 is a schematic cross-sectional view showing the liquid crystal display device 1 of this embodiment in more detail. As shown in Fig. 17, the liquid crystal display device 1 includes, in order from the rear 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.

[0121] The retardation layer 40 is located between the second substrate 30 and the polarizing plate 50, and preferably includes a λ / 4 plate 41 and a λ / 2 plate 42 (see FIGS. 17 and 18). The arrangement order of these is preferably such that the λ / 4 plate 41 and the λ / 2 plate 42 are located from the liquid crystal layer 20 (and second substrate 30) side (see FIGS. 17 and 18).

[0122] The λ / 4 plate means a retardation plate that imparts an in-plane phase difference of 1 / 4 wavelength to incident light of wavelength λ, and is also called a λ / 4 wave plate or QWP (Quarter-Wave Plate). Specifically, the λ / 4 plate 41 can convert linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light. For example, linearly polarized light incident on the λ / 4 plate 41 becomes circularly polarized light when it is output from the λ / 4 plate 41.

[0123] The λ / 2 plate means a retardation plate that imparts an in-plane phase difference of 1 / 2 wavelength to incident light of wavelength λ, and is also called a λ / 2 wave plate, a half wave plate, or an HWP (Half-Wave Plate). Specifically, the λ / 2 plate 42 can rotate the vibration direction of the incident light beam by approximately 90°. For example, the circularly polarized light incident on the λ / 2 plate 42 becomes circularly polarized light with the rotation direction reversed when it is output.

[0124] Specifically, it is preferable to use uniaxial A-plates as the λ / 4 plate 41 and the λ / 2 plate .

[0125] The polarizing plate 50 is located closer to the observation surface than the retardation layer 40 (see Figs. 17 and 18). The polarizing plate 50 may be a circular polarizing plate or a linear polarizing plate. Here, the linear polarizing plate means a polarizing plate having a function of extracting polarized light (linearly 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 preferable.

[0126] The polarizing plate 50 may be either an absorptive polarizing plate or a reflective polarizing plate. An absorptive polarizing plate is a polarizing plate that has the function of absorbing light that vibrates in a specific direction and transmitting polarized light (linearly polarized light) that vibrates in a direction perpendicular thereto. A reflective polarizing plate is a polarizing plate that has the function of reflecting light that vibrates in a specific direction and transmitting polarized light (linearly polarized light) that vibrates in a direction perpendicular thereto. Among these, an absorptive polarizing plate is preferred. It is particularly suitable to use an absorptive linear polarizing plate.

[0127] Examples of the absorptive polarizing plate include a polarizing plate obtained by dyeing and adsorbing an anisotropic material such as an iodine complex (or dye) on a polyvinyl alcohol film and then stretching and aligning the film. In general, in order to ensure mechanical strength and resistance to moist heat, the polyvinyl alcohol film is used in practical use with a protective film such as a triacetyl cellulose film laminated on both sides. Examples of the reflective polarizing plate include a film in which multiple dielectric thin films are laminated, a film in which multiple thin films with different refractive index anisotropy are laminated, a nanowire grid polarizing plate, and a polarizing plate using selective reflection of a cholesteric liquid crystal.

[0128] The following describes preferred axial angles of the optical films (that is, the polarizing plate and the retardation plate). As the polarizing plate 50, an absorptive polarizing plate is used.

[0129] FIG. 19 is a plan view for explaining the axial angle of each optical film in a liquid crystal display device 1 (see FIG. 17 and FIG. 18) including, in order from the rear 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. In the following explanation, the axial angle of each optical film is the angle when FIG. 19 is likened to a clock face, the reference direction is the 3 o'clock direction (0°), and the twist direction is positive (counterclockwise). For convenience, in FIG. 19, the angle θ of the alignment direction (i.e., the long axis direction) a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied is shown. a was set to 90°.

[0130] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 is preferably 5° or more and 25° or less. This improves the contrast ratio. From the viewpoint of further improving the contrast ratio, the angle θ2 is more preferably 8° or more and 20° or less, and even more preferably 10° or more and 15° or less.

[0131] The angle θ3 formed by the in-plane slow axis 42SA of the λ / 2 plate 42 is preferably 25° or more and 45° or less. This improves the contrast ratio. From the viewpoint of further improving the contrast ratio, the angle θ3 is more preferably 26° or more and 40° or less, and even more preferably 28° or more and 35° or less.

[0132] The angle θ4 formed by the in-plane slow axis 41SA of the λ / 4 plate 41 is preferably 45° or more and 70° or less. This improves the contrast ratio. From the viewpoint of further improving the contrast ratio, the angle θ4 is more preferably 48° or more and 65° or less, and even more preferably 50° or more and 60° or less.

[0133] Next, a description will be given of the principle of white display and black display in the liquid crystal display device 1 of this embodiment. The liquid crystal display device 1 here is assumed to include, in order from the rear 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 (see FIGS. 17 and 18), and to perform display in a normally black mode.

[0134] Fig. 20A is a conceptual diagram for explaining the principle of black display, and Fig. 20B is a conceptual diagram for explaining the principle of white display. For convenience, Fig. 20A and Fig. 20B show only the reflective layer 130, the liquid crystal layer 20, the retardation layer 40 (i.e., the λ / 4 plate 41 and the λ / 2 plate 42), and the polarizing plate 50. A linear polarizing plate is used as the polarizing plate 50.

[0135] As shown in FIG. 20A, light (I) becomes linearly polarized light (i) by passing through the polarizing plate 50. The linearly polarized light (i) is given a phase difference of (λ / 2+λ / 4) by the retardation layer 40, and becomes elliptically polarized light (ii). When no voltage is applied, the elliptically polarized light (ii) becomes elliptically polarized light (iii) by the liquid crystal layer 20, and becomes elliptically polarized light (iii). This elliptically polarized light (iii) is reflected by the reflective layer 130, and becomes elliptically polarized light (iv) whose rotation direction is opposite to that of the elliptically polarized light (iii). The elliptically polarized light (iv) becomes elliptically polarized light (v) by the liquid crystal layer 20, and becomes elliptically polarized light (v) by the retardation layer 40, and becomes linearly polarized light (vi) whose vibration direction is perpendicular to that of the linearly polarized light (i). Therefore, the polarized light (II) is not emitted from the polarizing plate 50, and a black display is displayed.

[0136] Even when a voltage is applied, as shown in FIG. 20B, the light (I) becomes linearly polarized light (i) by passing through the polarizing plate 50. The phase difference of (λ / 2+λ / 4) is imparted to the linearly polarized light (i) by the retardation layer 40, and the light becomes elliptically polarized light (ii). When a voltage is applied to the liquid crystal layer 20, a phase difference is added in the liquid crystal layer 20, and the elliptically polarized light (ii) becomes linearly polarized light (iii) having a polarization direction rotated by approximately 90° from the linearly polarized light (i). The polarization direction of the linearly polarized light (iii) does not change even when reflected by the reflective layer 130 (this is referred to as linearly polarized light (iv)). The phase difference of the linearly polarized light (iv) is returned in the liquid crystal layer 20, and the light becomes elliptically polarized light (v) having a rotation direction opposite to that of the elliptically polarized light (ii). The phase difference of (λ / 2+λ / 4) is imparted to the elliptically polarized light (v) by the retardation layer 40, and the light becomes linearly polarized light (vi) having the same vibration direction as the linearly polarized light (i). Therefore, the polarized light (II) passes through the polarizing plate 50, resulting in a white display.

[0137] (Modification 1 of the second embodiment) In the second embodiment, the first electrode 121, which is a lower layer electrode, is the common electrode CE, and the second electrode 122, which is an upper layer electrode, is the pixel electrode PE. However, 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 layer electrode) is the common electrode CE, and the first electrode 121 (lower layer electrode) is the pixel electrode PE (see FIG. 21).

[0138] FIG. 21 is a schematic cross-sectional view showing the liquid crystal display device 1 of this example in more detail. In this example as well, from the viewpoint of easily generating a transverse electric field, it is preferable that at least the upper layer electrode (common electrode CE in this example) is a slit electrode. The lower layer electrode (pixel electrode PE in this example) may be a planar electrode, i.e., a so-called solid electrode, or may be a slit electrode. As described above, the liquid crystal display device 1 of this modified example 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.

[0139] (Embodiment 3) In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents overlapping with the above-mentioned embodiments 1 and 2 will be omitted. In the embodiments 1 and 2, a reflective liquid crystal display device has been described as an example, but in this embodiment, a semi-transmissive liquid crystal display device will be described. The liquid crystal display device of this embodiment differs from the liquid crystal display device of embodiment 2 mainly in that a light source is provided on the rear side of the liquid crystal layer 20.

[0140] Fig. 22 is a cross-sectional schematic diagram of a liquid crystal display device 1 of this embodiment. The liquid crystal display device 1 further includes a light source 61 (also referred to as a backlight) on the rear side of the liquid crystal layer 20. It is preferable that the liquid crystal display device 1 further includes a polarizing plate 50' and a retardation layer 40'. More preferably, as shown in Fig. 22, the liquid crystal display device 1 includes, in this order from the rear side, the light source 61, the polarizing plate 50', the retardation layer 40', the first substrate 10, the liquid crystal layer 20, the second substrate 30, the retardation layer 40, and the polarizing plate 50. In this embodiment, a TFT substrate is also suitable as the first substrate 10.

[0141] The light source 61 (backlight) is not particularly limited as long as it irradiates light, and may be a direct type, an edge type, or any other type. Specifically, for example, it is preferable that the light source has a light emitting diode (LED) or other such light source, a light guide plate, and a reflective sheet, and may further have a diffusion sheet or a prism sheet.

[0142] The polarizing plate 50' is disposed on the rear side of the liquid crystal layer 20. More specifically, it is disposed on the rear side of 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. Also, it may be an absorptive polarizing plate or a reflective polarizing plate, but is preferably an absorptive polarizing plate. In particular, it is preferable to use an absorptive linear polarizing plate.

[0143] The polarization axis of the polarizing plate 50' may be arranged so as to be approximately perpendicular to or approximately parallel to the polarization axis of the polarizing plate 50. That is, the polarizing plate 50' may be arranged in a crossed Nicol state or a parallel Nicol state with the polarizing plate 50. Among these, the crossed Nicol state is preferable.

[0144] The retardation layer 40' is disposed between the polarizing plate 50' and the liquid crystal layer 20. More specifically, it is disposed between the polarizing plate 50' and the first substrate 10. The retardation layer 40' may include, for example, a λ / 4 plate and a λ / 2 plate. The arrangement order of these is preferably, for example, the λ / 2 plate and the λ / 4 plate from the rear side.

[0145] In the liquid crystal display device 1 of this embodiment, each pixel P has a reflective region Rf for performing display in a reflective mode and a transmissive region Tr for performing display in a transmissive mode (see FIG. 23). FIG. 23 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 of this embodiment. A reflective layer 130 (see FIG. 2, for example) is arranged in the reflective region Rf, but the reflective layer 130 is not arranged in the transmissive region Tr. The proportion of the area of ​​the transmissive region Tr in each pixel P can be appropriately set depending on the application, etc., but is preferably, for example, 20% or more and 90% or less. The position and shape of the transmissive region Tr in the pixel P can also be appropriately set depending on the application, etc.

[0146] In the liquid crystal display device of this embodiment, i.e., 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 performing display in the lateral electric field mode in which the liquid crystal layer 20 has a twisted orientation when no voltage is applied. Therefore, the liquid crystal display device 1 of this embodiment is also useful as an in-cell touch panel capable of displaying in the reflective mode at low cost and with an improved contrast ratio.

[0147] (Embodiment 4) In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents overlapping with the above-mentioned embodiment 1 will be omitted. The liquid crystal display device of this embodiment mainly differs from the liquid crystal display device of embodiment 1 in that a light source is provided on the observation surface side of the liquid crystal layer 20. The liquid crystal display device of this embodiment is a reflective liquid crystal display device.

[0148] Fig. 24 is a cross-sectional view of a liquid crystal display device 1 of this embodiment. The liquid crystal display device 1 of this embodiment further includes a light source 62 (also referred to as a front light) on the observation surface side of the liquid crystal layer 20. More preferably, as shown in Fig. 24, the liquid crystal display device 1 includes, in this order from the rear 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, a TFT substrate is also suitable as the first substrate 10.

[0149] The light source 62 (front light) is not particularly limited as long as it can irradiate light. Specifically, for example, it is preferable that the light source has a light emitting diode (LED) or other light source and a light guide plate. By further including the light source 62, the reflective liquid crystal display device 1 can perform bright reflective display even in an environment where sufficient ambient light cannot be obtained.

[0150] Although the embodiments of the present invention have been described above, the individual matters described above can all be applied to the present invention as a whole.

[0151] The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to these examples.

[0152] In the following verification examples, the simulation software used was LCD Master 2D manufactured by Shintech Co., Ltd. The various physical properties of the liquid crystal materials de5, de6, de7, de10, and de15 used in the verification examples are shown in the table below.

[0153] [Table 1]

[0154] (Verification example 1: Example 1-1 to Example 1-7) In this example, the angle θ of the alignment direction a of the liquid crystal molecules 21A when no voltage is applied is a In the case where the twist angle θ1 is 80°, a preferable range of the twist angle θ1 was considered.

[0155] In this example, the liquid crystal display device 1 of the second embodiment was assumed as the liquid crystal display device of the FFS mode. FIG. 25 shows a schematic cross-sectional view of the liquid crystal display device 1 of this example, and Table 2 shows specific optical settings. The angle of each axis is the angle of each axis when no voltage is applied, with the direction parallel to the gate line GL as the reference (0°), the angle rotated clockwise as a positive angle (+), and the angle rotated counterclockwise as a negative angle (-). In Table 2 (and Tables 4 and 7), PI means a polyimide film as the horizontal alignment film 140, 340. Assuming that the liquid crystal layer 20 is a liquid crystal layer having a monodomain structure and performing normally black display, a positive type liquid crystal material de5 was used as the liquid crystal material constituting the liquid crystal layer 20. The twist angle θ1 was set to 78° to 90°, and the VR curve and response characteristics were examined using simulation software. The results are shown in Table 3.

[0156] [Table 2]

[0157] [Table 3]

[0158] In Table 3, "maximum reflectance voltage" and "maximum reflectance orientation" respectively refer to the voltage and orientation state when the reflectance is at its maximum value. Reflectance here refers to the reflectance of white display (also referred to as white reflectance). In the "maximum reflectance orientation" column, PT refers to forward twist orientation, and RT refers to reverse twist orientation. The values ​​listed in the "response characteristics" column are values ​​when the response speed (tr, td; both in msec) in Example 1-3 (twist angle 83°) is taken as 100%, respectively.

[0159] From Table 3, it can be seen that a reverse twist orientation occurs when the twist angle θ1 is 83° or more. It can also be seen that the voltage showing the maximum reflectance is less than 5V in the case where the twist angle is 83° or more. Therefore, it is preferable that the twist angle is 83° or more. It can also be seen that when the twist angle is 87° or less, the response characteristic falls within 105% when the case where the twist angle is 83° is taken as 100%. This range is an acceptable range even if product variations occur during production finishing. Therefore, it is also preferable that the twist angle is 87° or less. Thus, from the viewpoints of the maximum reflectance, the maximum reflectance voltage, and the response characteristics, it was found that the twist angle is particularly preferably 83° or more and 87° or less, and 83° is the most preferable.

[0160] (Verification Example 2: Example 2-1 to Example 2-6) In this example, the angle θ of the alignment direction a of the liquid crystal molecules 21A when no voltage is applied is a In the case where the angle is 80°, a preferable range of Δε of the liquid crystal material was examined.

[0161] In this example, the liquid crystal display device 1 of embodiment 2 was assumed as the FFS mode liquid crystal display device. FIG. 25 shows a schematic cross-sectional view of the liquid crystal display device 1 of this example, and Table 4 shows specific optical settings. As the liquid crystal layer 20, a liquid crystal layer having a monodomain structure and performing normally black display was assumed, and positive type liquid crystal materials de5, de6, de7, de10, and de15 were used as the liquid crystal materials constituting the liquid crystal layer 20. A VR curve was calculated and analyzed using simulation software. The results are shown in FIGS. 26 to 29 and Table 5.

[0162] [Table 4]

[0163] [Table 5]

[0164] FIG. 26 is a graph showing the reflective mode efficiency when each liquid crystal material is used. In FIG. 26, the horizontal axis represents the voltage (V) applied to the liquid crystal layer 20, and the vertical axis represents the reflective mode efficiency (%). The resulting curve is called a VR curve. Table 5 summarizes the results based on FIG. 26. In Table 5, "VRmax" means the voltage when the reflective mode efficiency is at its maximum value, and "Rmax" means the maximum value of the reflective mode efficiency.

[0165] Fig. 27 is a diagram (called a reflectance profile) obtained by analyzing the VR curve shown in Fig. 26, focusing on the liquid crystal director when a voltage is applied. As a result of analyzing the reflectance profile at the voltage (i.e., VRmax) at which the reflective mode efficiency is at its maximum, it was found that the reflectance at the center between the first electrode 121 (CE) and the second electrode 122 (PE) decreases as Δε increases (see Fig. 27). In order to consider the reason why the reflectance profile has highs and lows, the average azimuthal angle φLCave and polar angle of the liquid crystal molecules at VRmax were analyzed (see Fig. 28).

[0166] FIG. 28 is a reflectance profile (cross-sectional view) at VRmax. The vertical axis represents the distance from the first substrate 10 in the thickness direction (also referred to as the Z direction) of the liquid crystal layer 20 (the further up in the drawing the greater this distance is, meaning closer to the second substrate 30). Based on FIG. 28, the average value of the liquid crystal director in the thickness direction was analyzed. Specifically, since the liquid crystal display device 1 of this example is an FFS mode (horizontal electric field), the azimuth angle of the liquid crystal molecules 21 was analyzed. The results are shown in FIG. 29. FIG. 29 is the analysis result of the average azimuth angle φLCave of the liquid crystal molecules in the Z direction. In FIG. 29, the vertical axis represents the average azimuth angle φLCave of the liquid crystal molecules 21.

[0167] In particular, the following points became clear from Figures 27 and 29. First, it was found that the average azimuth angle φLCave differs depending on whether the Δε of the liquid crystal molecules is 7 or less or exceeds 7. In addition, examples in which the white reflectance is high and the reflectance profile is nearly uniform are examples using a liquid crystal material with a Δε of 7 or less. In this case, the average azimuth angle is around 150°, and the alignment of the liquid crystal molecules is nearly homogeneous. In other words, these examples have a reverse twist alignment (see Figure 9B). In contrast, examples in which the white reflectance is low and the reflectance profile has highs and lows and is non-uniform are examples using a liquid crystal material with a Δε of more than 7. In this case, the average azimuth angle φLCave is around 90°, and the alignment of the liquid crystal molecules is more twisted. In other words, these examples have a positive twist alignment (see Figure 11B).

[0168] The above results are summarized in Table 6. In Example 2-6, as a reference example, the simulation results using a negative type liquid crystal material instead of a positive type liquid crystal material are also shown. Also, Fig. 30 shows a graph in which the VR curve of Example 2-6 (i.e., the VR curve when a negative type liquid crystal material (de-5) is used) is added to the graph of Fig. 26.

[0169] [Table 6]

[0170] In Table 6, "orientation" refers to the orientation state when the white reflectance exhibits the maximum value, PT refers to a forward twist orientation, and RT refers to a reverse twist orientation.

[0171] The following points were found from Table 6. Among the examples using positive type liquid crystal materials, in Examples 2-3 to 2-5 using liquid crystal materials with Δε exceeding 7, a positive twist alignment was obtained when a white voltage was applied, and the maximum reflectance (Rmax) was 32.8 to 36.7%. In Example 2-6 using a negative type liquid crystal material, a reverse twist alignment was obtained, and the maximum reflectance (Rmax) was 37.4%, which was a higher reflectance than Examples 2-3 to 2-5. Further analysis revealed that in the examples using positive type liquid crystal materials with Δε of 7 or less, such as Examples 2-1 and 2-2, a reverse twist alignment was obtained, and the maximum reflectance (Rmax) was higher than that of Example 2-6 using a negative type liquid crystal material. In general, it is considered that an absolute value of Δε of less than 2 does not have dielectric anisotropy, so the lower limit of Δε is particularly preferably 3 or more.

[0172] Incidentally, from the viewpoint of realizing low power consumption, which is an advantage of the reflective type, it is considered preferable that the driving voltage (white voltage) is less than 5V. However, due to its structure, the Δε of the polar component of a negative type liquid crystal material cannot be made large compared to a positive type liquid crystal material, and it is not realistic to make the absolute value of Δε, for example, 7 or more. Even if a liquid crystal material with a high Δε such as Δε=-7 is used, there are trade-off issues such as a delay in response speed due to an increase in viscosity of the liquid crystal layer and a decrease in VHR due to the tendency to incorporate impurity ions. On the other hand, in examples using positive type liquid crystal materials with Δε of 7 or less, such as Example 2-1 and Example 2-2, the driving voltage can be made 5V or less, and low power consumption can be realized.

[0173] Therefore, from the viewpoint of achieving a drive voltage of less than 5V, obtaining a higher reflectance than when a negative type liquid crystal material is used, and realizing a reverse twist alignment, it was found that the Δε of the liquid crystal material is particularly preferably between 3 and 7. It was also found that when a positive type liquid crystal material is used, the average azimuth angle φLCave of the liquid crystal molecules when a reverse twist alignment is achieved is particularly preferably between 151° and 154°.

[0174] (Verification Example 3: Example 3-1 to Example 3-11) From verification example 2, it was found that the reason for increasing the white reflectance is that the liquid crystal has a reverse twist alignment during white display. Therefore, in this example, the physical properties of the liquid crystal material were further examined.

[0175] In this example, the liquid crystal display device 1 of embodiment 2 was assumed as the FFS mode liquid crystal display device. Fig. 25 shows a schematic cross-sectional view of the liquid crystal display device 1 of this example, and Table 7 shows specific optical settings. As the liquid crystal layer 20, a liquid crystal layer having a monodomain structure and performing normally black display was assumed, and a positive type liquid crystal material or a negative type liquid crystal material was used as the liquid crystal material constituting the liquid crystal layer 20. A VR curve was calculated and analyzed using simulation software.

[0176] [Table 7]

[0177] When a white voltage is applied, the liquid crystal director orientation is determined by Δε and the twist elastic constant K 22 It is believed that the electric field behavior differs depending on the torque balance of Δε or K 22 The analysis was conducted by focusing on the differences between them. The results of the analysis by focusing on the differences in Δε are shown in Table 8. 22 The results of the analysis focusing on the differences are shown in Table 9.

[0178] [Table 8]

[0179] [Table 9]

[0180] From Tables 8 and 9, when a positive-type liquid crystal material is used, a reverse twist alignment is obtained and a higher white reflectance is shown than when a negative-type liquid crystal material is used. 22It was found that this is an example where the absolute value of Δε is 6 or less. In addition, when the absolute value of Δε is less than 2, the optical change due to the liquid crystal and the dielectric anisotropy is slight, and a high voltage may be required, so that the lower limit of Δε is particularly preferably 3 or more. 22 If the absolute value of is less than 2, the rise of the response characteristic may be delayed. 22 The lower limit is particularly preferably 3 or more.

[0181] In summary, to realize a reverse twist alignment using a positive type liquid crystal material, it is particularly preferable that the Δε of the liquid crystal material is 3 or more and 7 or less. 22 It was found that the average azimuth angle φLCave of the liquid crystal molecules is particularly preferably 151° or more and 154° or less.

[0182] (Verification Example 4: Example 4-1 to Example 4-10) As described above, the reason why the orientation becomes forward twisted or reverse twisted is believed to be that the behavior of the liquid crystal molecules differs depending on whether the equipotential lines reach the opposing substrate (second substrate 30) near the threshold voltage. Therefore, by fixing the retardation dΔn of the liquid crystal layer 20, we investigated whether the reverse twist orientation occurs in an example with a large cell thickness or an example with a small cell thickness, and also investigated the physical properties of the liquid crystal material in each example.

[0183] In this example, the liquid crystal display device 1 of embodiment 2 was assumed as the FFS mode liquid crystal display device. Fig. 25 shows a schematic cross-sectional view of the liquid crystal display device 1 of this example, and Table 7 shows specific optical settings (similar to those in verification example 3). As the liquid crystal layer 20, a liquid crystal layer having a monodomain structure and performing normally black display was assumed, and a positive type liquid crystal material was used as the liquid crystal material constituting the liquid crystal layer 20. A VR curve was calculated and analyzed using simulation software.

[0184] As an example of a large cell thickness, for example, an example where the cell thickness is d=4.05 μm and the birefringence of the liquid crystal material is Δn=0.06 is analyzed, and the results are shown in Table 10. Also, as an example of a small cell thickness, for example, an example where the cell thickness is d=2.70 μm and the birefringence of the liquid crystal material is Δn=0.09 is analyzed, and the results are shown in Table 11.

[0185] [Table 10]

[0186] [Table 11]

[0187] From Tables 10 and 11, it was found that the examples 4-6 to 4-10, which have a small cell thickness (d=2.70 μm), can realize a reverse twist alignment using a positive type liquid crystal material, and among them, the examples 4-7 to 4-10, which have a Δε of 15 or less, have a higher reflectance than the case where a negative type liquid crystal material is used (see, for example, Examples 2-6 and 3-6, etc.). It was also found that the examples 4-1 to 4-5, which have a large cell thickness (d=4.05 μm), all have a positive twist alignment regardless of the value of Δε, and that either Rmax is lower or VRmax is a high voltage of 5 V or more, compared to the case where a negative type liquid crystal material is used.

[0188] Therefore, from the viewpoint of realizing a reverse twist alignment and obtaining a higher reflectance than when a negative type liquid crystal material is used, it was found that the birefringence Δn of the liquid crystal material is particularly preferably 0.077 to 0.09. It was also found that the average azimuth angle φLCave of the liquid crystal molecules is preferably 150° to 156°, more preferably 150° to 155°, and most preferably 151° to 153°.

[0189] Taking Tables 8 to 11 together, the angle θ of the alignment direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied a When the angle is 80°, the dielectric anisotropy Δε, birefringence Δn and twist elastic constant K of the liquid crystal material are22 are 3≦Δε≦7, 0.077≦Δn≦0.09, and 3≦K, respectively. 22 It was also found that the average azimuth angle φLCave of the liquid crystal material is most preferably 151°≦φLCave≦153°.

[0190] (Verification Example 5: Example 5-1 to Example 5-6) Next, the angle θ of the alignment direction a of the liquid crystal molecules 21A when no voltage is applied a In the case where the twist angle θ1 is 83°, a preferable range of the twist angle θ1 was considered.

[0191] In this example, θ a The conditions were set to be the same as in Verification Example 1 (see Table 2 above), except that the twist angle was set to 83°, and the VR curve and response characteristics were examined using simulation software. The results are shown in Table 12. For reference, the results of Examples 1-3 are also shown. The values ​​shown in the "Response characteristics" column are the values ​​when the response speed in Example 1-3 (twist angle 83°) is set to 100%.

[0192] [Table 12]

[0193] From Table 12, θ a It was found that when the twist angle θ1 was 83°, the reverse twist orientation was obtained and the voltage at which the maximum reflectance was shown was less than 5 V over the entire range of the calculated twist angle θ1 (78° to 90°). Among these, from the viewpoints of the maximum reflectance, the maximum reflectance voltage and the response characteristics, it was found that the twist angle θ1 is particularly preferably 78° to 88°, more preferably 83° to 87°, and most preferably 83°. In addition, it was found that when the twist angle θ1 was 83°, the reverse twist orientation was obtained over the entire range of the calculated twist angle θ1 (78° to 90°), and the voltage at which the maximum reflectance was shown was less than 5 V. a θ is 83°, which is lower than the examples (Example 5-1 to Example 5-5). a The example where θ is 80° (Example 1-3) has a lower maximum reflectance voltage. Therefore, from the viewpoint of realizing lower power consumption, a It was also found that 80° was more preferable than 83°.

[0194] (Verification Example 6: Example 6-1 to Example 6-11) Next, θ a When the angle was 83°, the physical properties of the liquid crystal material were further examined in the same manner as in Verification Example 3 above.

[0195] In this example, θ a The conditions were the same as in Verification Example 3 (see Table 7 above), except that the angle was set to 83°, and the VR curve was calculated and analyzed using simulation software. The results of the analysis focusing on the difference in Δε are shown in Table 13. 22 The results of the analysis focusing on the differences are shown in Table 14.

[0196] [Table 13]

[0197] [Table 14]

[0198] From the viewpoint of realizing a reverse twist alignment and obtaining a higher reflectance than when a negative type liquid crystal material is used, it is particularly preferable that the Δε of the liquid crystal material is 3 or more and 15 or less, and most preferably 3 or more and 10 or less. 22 It was found that the average azimuth angle φLCave of the liquid crystal molecules is particularly preferably 151° or more and 156° or less.

[0199] (Verification Example 7: Example 7-1 to Example 7-10) Next, θ a When the angle was 83°, the physical properties of the liquid crystal material were further examined in the same manner as in Verification Example 4 above.

[0200] In this example, θ aExcept for the angle being set to 83°, the same conditions were set as in Verification Example 4 (see Table 7 above), and the VR curve was calculated and analyzed using simulation software. As an example of a large cell thickness, for example, a case where the cell thickness is d=4.05 μm and the birefringence index Δn of the liquid crystal material is 0.06 is analyzed, and the results are shown in Table 15. Also, as an example of a small cell thickness, for example, a case where the cell thickness is d=2.70 μm and the birefringence index Δn of the liquid crystal material is 0.09 is analyzed, and the results are shown in Table 16.

[0201] [Table 15]

[0202] [Table 16]

[0203] From Tables 15 and 16, it is found that the birefringence Δn of the liquid crystal material is particularly preferably 0.06 to 0.09 in order to realize a reverse twist alignment and obtain a higher reflectance than when a negative type liquid crystal material is used. It is also found that the average azimuth angle φLCave of the liquid crystal molecules is particularly preferably 151° to 156°.

[0204] Taking Tables 13 to 16 together, the angle θ of the alignment direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied a When the angle is 83°, the dielectric anisotropy Δε, birefringence Δn and twist elastic constant K of the liquid crystal material are 22 are 3≦Δε≦10, 0.06≦Δn≦0.09, and 3≦K, respectively. 22 It was also found that the average azimuth angle φLCave of the liquid crystal material is most preferably 151°≦φLCave≦156°.

[0205] (Verification Example 8: Example 8-1 to Example 8-5) The black display is realized by compensating the retardation dΔn of the liquid crystal layer (i.e., the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material) and the λ / 4 condition determined by the twisted orientation with a retardation layer. However, the birefringence Δn of the liquid crystal material has a temperature characteristic in which Δn decreases as the temperature increases. Generally, in a display mode in which the retardation of the liquid crystal layer is compensated for by a retardation layer to display black, the Tni (nematic-isotropic phase transition temperature) of the liquid crystal material is increased to improve the temperature characteristic of Δn (for example, OCB (Optically Compensated Bend Mode)). However, when Tni is increased, the elastic constant may also increase in conjunction with this, and in this case, there is a concern that the VT and VR curves will become high voltage. One possible solution to this problem is to increase Δε, but increasing Δε is accompanied by an increase in viscosity, which slows down the response and may result in the optical characteristics of the display not being optimal. Therefore, the present inventors have determined that the birefringence Δn at 60° C. is 100% in order to improve the temperature characteristics of Δn while minimizing the increase in Tni of the liquid crystal material. 60 and birefringence Δn at 20°C 20 Ratio to (Δn 60 / Δn 20 ), the temperature characteristics of Δn of various liquid crystal materials were compared. The results are shown in Figures 31 to 34 and Table 17. The configuration and optical settings of the liquid crystal display device other than the liquid crystal material were the same as those in Verification Example 5. That is, θ a The conditions were the same as those in Verification Example 1 (see Table 2 above), except that the angle was set to 83°.

[0206] [Table 17]

[0207] Figure 31 is a graph examining the temperature characteristics of Δn for various liquid crystal materials. In this graph, the birefringence Δn for each liquid crystal material at 20°C is 20 The birefringence Δn at temperatures of 10°C, 20°C, 30°C, 40°C, 50°C and 60°C when 20The horizontal axis is temperature, and the vertical axis is birefringence Δn (wherein the birefringence Δn at 20°C is 20 is set to 1.) All birefringence values ​​Δn are values ​​at a wavelength of 550 nm.

[0208] Fig. 32 is a graph examining the temperature dependency of contrast. That is, a VR curve was calculated and analyzed using simulation software. The horizontal axis is temperature, and the vertical axis is contrast (CR; i.e., the ratio of reflective mode efficiency in white display to reflective mode efficiency in black display).

[0209] Fig. 33 is a graph examining the temperature dependency of the reflective mode efficiency in black display. That is, a VR curve was calculated and analyzed using simulation software. The horizontal axis is temperature, and the vertical axis is the reflective mode efficiency in black display (i.e., when no voltage is applied).

[0210] Figure 34 is a graph examining the temperature dependency of the reflective mode efficiency in white display. That is, the VR curve was calculated and analyzed using simulation software. The horizontal axis is temperature, and the vertical axis is the reflective mode efficiency in white display (5 V applied).

[0211] Considering that the actual operating temperature range of liquid crystal panels is 50° C. or less, Table 17 also evaluates the presence or absence of black floating at 50° C. The black floating was evaluated as follows. (Evaluation method) The produced liquid crystal display devices were heated to 50° C., and the black display state was actually observed visually and evaluated according to the following criteria. 〇: No problems in actual use. ×: A decrease in contrast was observed after heating, and the product lacked marketability.

[0212] From Table 17 and Figures 31 to 34, the birefringence Δn 60 and birefringence Δn at 20°C 20 Ratio to (Δn 60 / Δn 20 It has been found that if the ratio (Δn60 / Δn 20 ) is less than 1.1, and it has already been demonstrated that there is no significant loss of contrast.

[0213] The above-described aspects of the present invention may be combined as appropriate without departing from the gist of the present invention. [Explanation of symbols]

[0214] 1:LCD display device 1X: LCD panel 10, 30: PCB 20: Liquid crystal layer 21, 21A, 21B: Liquid crystal molecules 40, 40': Retardation 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 alignment film 150, 151, 152: insulating film (insulating layer) 153: Dielectric layer 160: Contact electrode 310: Color filter layer BP: Backplane circuit CE: Common electrode PE: Pixel electrode CH1, CH2: Contact hole DR:Display area FR: Hidden area GL: Gate wiring SL: Source wiring EF: Horizontal electric field p: protruding part P: Pixel Rf:Reflection area Tr:Transmission area Sl: Slit SP: Belt TC: Touch wiring contact part TD: Touch drive unit TL, TL1, TL2: Touch wiring TX: Touch sensor electrode

Claims

1. A first substrate; a second substrate facing the first substrate; a liquid crystal layer provided between the first substrate and the second substrate; A liquid crystal display device having a plurality of pixels, the first substrate has a reflective layer that reflects light, a first electrode and a second electrode that can generate a transverse electric field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer; the first electrode and the second electrode, the electrode disposed on the liquid crystal layer side, has a plurality of strip-shaped portions and a slit located between two adjacent strip-shaped portions of the plurality of strip-shaped portions; The plurality of strip portions include linear shapes extending substantially parallel to one another and in the same direction, the liquid crystal layer is made of a liquid crystal material containing liquid crystal molecules; the liquid crystal material is positive type; the second substrate has a second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer has a twisted orientation when no voltage is applied, and the twist angle when no voltage is applied is 78° or more and 90° or less; when the liquid crystal layer of each pixel is viewed in a plane when no voltage is applied, at least in a central portion in a plane direction of the liquid crystal layer, an extension direction of the plurality of strip-shaped portions is located between a long axis direction of the liquid crystal molecules on the first substrate side and a long axis direction of the liquid crystal molecules on the second substrate side, When the liquid crystal layer of each pixel is viewed in a plan view, liquid crystal molecules at least in the center of the liquid crystal layer in the thickness direction rotate in the same twist direction as when no voltage is applied, when a voltage is applied. A liquid crystal display device comprising:

2. The product (dΔn) of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal material is 236 nm or more and 252 nm or less.

2. The liquid crystal display device according to claim 1 .

3. The twist angle when no voltage is applied is 83° or more and 87° or less.

2. The liquid crystal display device according to claim 1 .

4. The average azimuth angle φLCave of the liquid crystal molecules when a voltage is applied is 150° or more and 156° or less.

2. The liquid crystal display device according to claim 1 .

5. The liquid crystal material has a birefringence Δn ６０ and birefringence Δn at 20° C. ２０ The ratio of (Δn ６０ / Δn ２０ ) is 0.84 or more 2. The liquid crystal display device according to claim 1 .

6. The liquid crystal material has a dielectric anisotropy Δε of 7 or less.

2. The liquid crystal display device according to claim 1 .

7. Furthermore, a polarizing plate disposed on the outer side of the first substrate and / or the second substrate; a retardation layer disposed between the substrate and the polarizing plate; Equipped with The retardation layer includes a λ / 4 plate and a λ / 2 plate.

2. The liquid crystal display device according to claim 1 .

8. Single domain orientation 2. The liquid crystal display device according to claim 1 .

9. Display in normally black mode 2. The liquid crystal display device according to claim 1 .

10. One of the first electrode and the second electrode is a pixel electrode provided in each of the plurality of pixels, and the other is a common electrode including a plurality of segments each capable of functioning as a touch sensor electrode; The first substrate has a plurality of touch wirings each connected to a corresponding one of the touch sensor electrodes.

2. The liquid crystal display device according to claim 1 .

11. Further, a light source is provided.

11. The liquid crystal display device according to claim 1,

Images