Liquid crystal display device

Abstract

A liquid crystal display device which is provided with a first substrate, a second substrate facing the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate, and which has a plurality of pixels, the first substrate includes a reflective layer that reflects light, a first electrode and a second electrode capable of generating a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer. The electrode disposed on the liquid crystal layer side has a plurality of band-shaped portions and slits located between two band-shaped portions adjacent to each other among the plurality of band-shaped portions, the plurality of band-shaped portions include linear shapes substantially parallel to each other and extending in the same direction, the liquid crystal layer is made of a liquid crystal material containing liquid crystal molecules, the liquid crystal material is of a positive type, and the liquid crystal molecules are arranged in the liquid crystal layer. The second substrate has a second horizontal alignment film in contact with the liquid crystal layer, and the liquid crystal layer adopts twist alignment when no voltage is applied.

Description

Technical Field

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

[0002] Liquid crystal display devices are display devices that use liquid crystal materials for display, and are generally divided into transmissive liquid crystal display devices and reflective liquid crystal display devices according to the display mode. Transmissive liquid crystal display devices are devices that use the transmitted light of the backlight on the back of the screen to display in a transmissive mode, and reflective liquid crystal display devices are devices that use external light (also called ambient light) instead of backlight to display in a reflective mode. As a display device having both of these characteristics, a semi-transmissive liquid crystal display device has been proposed in which each pixel has an area for displaying in a transmissive mode and an area for displaying in a reflective mode (for example, see Patent Document 1).

[0003] Liquid crystal display devices can also be roughly divided according to the driving method of the liquid crystal. For example, there are known liquid crystal display devices of a longitudinal electric field method that uses an electric field in a direction substantially perpendicular to the substrate surface to drive the liquid crystal layer for display, and liquid crystal display devices of a transverse electric field method that uses an electric field in a direction substantially parallel to the substrate surface to drive the liquid crystal layer for display. As the longitudinal electric field method, examples include TN (Twisted Nematic) mode and MVA (Multi-domain Vertical Alignment) mode, and as the transverse electric field method, examples include IPS (In-plane Switching) mode and FFS (Fringe Field Switching) mode. Prior art literature Patent Literature

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2007-47734 Summary of the invention Problems to be solved by the invention

[0005] However, in recent years, liquid crystal display devices used in smartphones and tablet computers are generally given touch sensor functions. As touch sensor methods, various methods such as resistive film, electrostatic capacitance, and optical are known. In a liquid crystal display device with a touch sensor (also called a touch panel), there is an external touch sensor method (external type) and a built-in touch sensor method (built-in type). The built-in touch panel is more conducive to narrow frame, thinness, and lightness than the external touch panel, and also has the advantage of improving the transmittance of light.

[0006] Among the built-in touch panels, there are On-cell type and In-cell type. The so-called unit refers to a display panel (also called a liquid crystal panel), which has an active matrix substrate represented by a thin film transistor (TFT) substrate, an opposing substrate arranged opposite to the substrate, and a liquid crystal layer sandwiched between these substrates. Usually, in the In-cell type, relative to the layer that assumes the function of the touch sensor being arranged in the display panel, in the On-cell type, the layer that assumes the function of the touch sensor is arranged between the display panel and the polarizing plate arranged on the viewing side of the display panel. Among them, the embedded type can realize the lightest and thinnest touch panel in principle. In addition, a liquid crystal display device capable of displaying in a reflective mode is suitable for outdoor use, so an embedded touch panel capable of displaying in a reflective mode is required. However, the current situation is that it has not yet been realized.

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

[0008] Therefore, further research has been conducted on devices in FFS mode, for example, which display in a normally black mode. However, in this device, although a reflective mode display can be performed, it is found that if a positive liquid crystal material is used for the liquid crystal layer, high reflectivity cannot be obtained, especially sometimes when displayed in white. In addition, if a negative liquid crystal material is used, although a high reflectivity is obtained when displayed in white, it is difficult to achieve low voltage (refer to the verification example described later). In addition, in recent years, due to the increased demand for miniaturization and cost reduction of display devices, low power consumption is required. Therefore, it would be ideal if it could display at low voltage and high reflectivity, but such a device has not yet been realized.

[0009] Patent Document 1 states that when twisting the display area, the twist angle is set to a range of 0° to 73°, and the product of the cell thickness and the refractive index difference of the liquid crystal layer is adjusted to a range of 140nm to 261nm, thereby achieving a black display reflectivity of less than 1%. However, there is no mention of the reflectivity of the white display (also called white reflectivity) or a method for further improving the white reflectivity, so high contrast cannot be foreseen. Regarding the physical properties of liquid crystal, only Δn=0.1 and Δε=11.3 are stated, and there is no research on the relationship with the white reflectivity.

[0010] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a liquid crystal display device which can achieve high reflectivity at a low voltage and has a sufficiently high contrast ratio and is also useful as an in-cell touch panel capable of displaying in a reflective mode, for example. Solutions to Solve Problems

[0011] (1) One embodiment of the present invention is to provide a liquid crystal display device, comprising a first substrate, a second substrate opposed to the first substrate, and a liquid crystal layer disposed between the first substrate and the second substrate, and having a plurality of pixels, wherein the first substrate comprises: a reflective layer for reflecting light, a first electrode and a second electrode capable of generating a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer; the electrode disposed on the liquid crystal layer side of the first electrode and the second electrode comprises a plurality of strip-shaped portions and a slit between two adjacent strip-shaped portions among the plurality of strip-shaped portions, the plurality of strip-shaped portions comprising straight lines substantially parallel to each other and extending in the same direction, and the liquid crystal layer The layer is composed of a liquid crystal material containing liquid crystal molecules, the liquid crystal material is positive, the second substrate has a second horizontal alignment film connected to the liquid crystal layer, the liquid crystal layer obtains a twisted orientation when no voltage is applied, and the twist angle when no voltage is applied is greater than 78° and less than 90°; when the liquid crystal layer of each pixel is looked down upon when no voltage is applied, at least in the central part of the surface direction of the liquid crystal layer, the extension direction of the multiple strip-shaped parts is located between the long axis direction of the liquid crystal molecules on the first substrate side and the long axis direction of the liquid crystal molecules on the second substrate side, and when the liquid crystal layer of each pixel is looked down upon, at least the liquid crystal molecules in the central part in the thickness direction of the liquid crystal layer rotate in the twist direction when no voltage is applied.

[0012] (2) In one embodiment of the present invention, in addition to the structure of (1) above, the liquid crystal display device is characterized in that the product of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal material (dΔn) is greater than or equal to 236 nm and less than or equal to 252 nm.

[0013] (3) In one embodiment of the present invention, in addition to the structure of (1) or (2) above, the liquid crystal display device has a twist angle of 83° to 87° when no voltage is applied.

[0014] (4) In addition, in one embodiment of the present invention, in addition to the structure of the above (1), the above (2) or the above (3), the average azimuth angle ΦLCave of the liquid crystal molecules when voltage is applied is greater than 150° and less than 156°.

[0015] (5) In addition, in one embodiment of the present invention, in addition to the structure of the above (1), the above (2), the above (3) or the above (4), the liquid crystal display device has a ratio of the birefringence index Δn60 of the liquid crystal material at 60°C to the birefringence index Δn20 at 20°C (Δn60 / Δn20) of 0.84 or more.

[0016] (6) In addition, in one embodiment of the present invention, in addition to the structure of (1), (2), (3), (4) or (5), the liquid crystal display device has a dielectric anisotropy Δε of less than 7.

[0017] (7) In addition, in one embodiment of the present invention, the liquid crystal display device, in addition to the structure of (1), (2), (3), (4), (5) or (6), further comprises: a polarizing plate arranged on the outside of the first substrate and / or the second substrate; and a phase difference layer arranged between the first substrate and the polarizing plate and / or between the second substrate and the polarizing plate, the phase difference layer including a λ / 4 plate and a λ / 2 plate.

[0018] (8) In addition, in one embodiment of the present invention, the liquid crystal display device is a single-domain orientation in addition to the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6) or the above (7).

[0019] (9) In addition, in one embodiment of the present invention, the liquid crystal display device displays in a normally black mode in addition to the structure of above-mentioned (1), above-mentioned (2), above-mentioned (3), above-mentioned (4), above-mentioned (5), above-mentioned (6), above-mentioned (7) or above-mentioned (8).

[0020] (10) In addition, in one embodiment of the present invention, in addition to the structure of (1), (2), (3), (4), (5), (6), (7), (8) or (9), the liquid crystal display device is characterized in that one of the first electrode or the second electrode is a pixel electrode arranged in each of the plurality of pixels, and the other is a common electrode including a plurality of segments that can respectively function as touch sensor electrodes, and the first substrate has a plurality of touch wirings respectively connected to the corresponding touch sensor electrodes.

[0021] (11) In addition, in one embodiment of the present invention, the liquid crystal display device has a light source in addition to the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6), the above (7), the above (8), the above (9) or the above (10). Effects of the Invention

[0022] According to the present invention, it is possible to provide a liquid crystal display device that can achieve high reflectivity at a low voltage and has a sufficiently high contrast ratio and is also useful as, for example, an in-cell touch panel capable of displaying in a reflective mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic cross-sectional view of the liquid crystal display device 1 . Figure 2 It is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. Figure 3 It is a schematic plan view of the entire liquid crystal display device 1 as viewed from the observation surface side. Figure 4 This is a diagram for explaining the definition of an angle. Figure 5 is a plan view schematically showing one pixel. Figure 6 It is magnified Figure 5 A schematic top view of a portion of. Figure 7 It is a liquid crystal director distribution diagram (cross-sectional diagram). Fig. 8A Yes Figure 5 An enlarged schematic plan view of a portion of the Figure 8B It is a liquid crystal director distribution diagram (cross-sectional diagram). Fig. 9A Yes Figure 5 A schematic top view of a portion of the enlarged image. Fig. 9B It is a liquid crystal director distribution diagram (cross-sectional diagram). Fig. 10A Yes Figure 5 A schematic top view of a portion of the enlarged image. Fig. 10B It is a liquid crystal director distribution diagram (cross-sectional diagram). Fig.11A Yes Figure 5 An enlarged schematic plan view of a portion of the Fig. 11B It is a liquid crystal director distribution diagram (cross-sectional diagram). Fig. 12A It is a diagram showing a calculation model of a liquid crystal director distribution pattern. Fig. 12B It is a diagram showing an example of calculation of a VR curve. Fig. 12C It is a liquid crystal director distribution diagram (cross-sectional diagram). Fig.13A So Figure 5The AA′ line in FIG. 1 is a schematic cross-sectional view (AA′ line cross-sectional view), which conceptually shows the behavior of the liquid crystal molecules 21 when no voltage is applied. Fig. 13B Yes Figure 5 2 is a partially enlarged plan view schematically showing the twisting direction of the liquid crystal molecules 21 when no voltage is applied. Fig.14A So Figure 5 The AA′ line in FIG. 1 is a schematic cross-sectional view (AA′ line cross-sectional view), which conceptually shows the behavior of the liquid crystal molecules 21 when a voltage is applied. Fig. 14B Yes Figure 5 2 is a schematic plan view in which a portion of FIG. 1 is enlarged, and is a diagram conceptually showing the twisting direction of the liquid crystal molecules 21 when a voltage is applied. Fig.15 1 is a schematic plan view illustrating an arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1 . Fig.16 It is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. Fig.17 is a schematic cross-sectional view of the liquid crystal display device 1 . Fig.18 It is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. Fig.19 A plan view for explaining the axis angles of the optical films in the liquid crystal display device 1 including the first substrate 10 , the liquid crystal layer 20 , the second substrate 30 , the λ / 4 plate 41 , the λ / 2 plate 42 , and the polarizing plate 50 in order from the back side. Fig. 20A This is a conceptual diagram for explaining the principle of black display. Fig. 20B This is a conceptual diagram for explaining the principle of white display. Fig.21 It is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. Fig. 22 is a schematic cross-sectional view of the liquid crystal display device 1 . Fig.23 1 is a schematic plan view conceptually showing that each pixel P in the liquid crystal display device 1 has a reflective region Rf and a transmissive region Tr. Fig.24 is a schematic cross-sectional view of the liquid crystal display device 1 . Fig.25 is a schematic cross-sectional view of the liquid crystal display device 1 . Fig.26 It is a graph showing the reflection mode efficiency when each liquid crystal material is used. Fig. 27 Yes Fig.26 A graph of the VR curve is shown. Fig.28 It is the reflectivity curve under VRmax (cross-sectional view). Fig.29 It is the analysis result of the average azimuth angle ΦLCave of the liquid crystal molecules in the Z direction. Fig.30 is Fig.26 A graph of the VR curve of Example 2-6 is added to the figure. Fig.31 This is a graph showing the temperature characteristics of Δn of various liquid crystal materials. Fig.32 This is a graph showing the temperature dependence of contrast. Fig.33 This is a graph showing the temperature dependence of the reflective mode efficiency in a black display. Fig.34 This is a graph showing the temperature dependence of the reflective mode efficiency in a white display. DETAILED DESCRIPTION

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

[0025] The state of no voltage application 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 state of voltage application refers to a state in which the voltage applied to the liquid crystal layer is greater than the threshold voltage. In this specification, the state of no voltage application is referred to as the state of no voltage application, and the state of voltage application is referred to as the state of voltage application.

[0026] The polar angle refers to an angle formed between a target direction (eg, a measurement direction) and a normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction when the direction of the object is projected onto the screen of the liquid crystal panel, and is expressed by the angle (azimuth) formed with the reference azimuth. Here, the reference azimuth (0°) is set to the horizontal right direction of the screen of the liquid crystal panel. Angles and azimuths are set to positive angles counterclockwise from the reference azimuth, and negative angles clockwise from the reference azimuth (refer to Figure 4 ). Figure 4 This is a diagram for explaining the definition of angles. Counterclockwise and clockwise both represent the rotation direction when the screen of the liquid crystal panel is viewed from the viewing surface side (front). In addition, the angle represents a value measured in a state of looking down at the screen of the liquid crystal panel.

[0027] The axis orientation of an optical film refers to the orientation of the polarization axis of the polarizer if it is a polarizer, and the orientation of the phase lag axis if it is a phase difference layer. The polarization axis of the polarizer refers to the absorption axis if it is an absorption-type polarizer, and the reflection axis if it is a reflection-type polarizer. The axis orientation of the phase difference layer refers to the orientation of the phase lag axis in the plane of the phase difference layer, unless otherwise specified.

[0028] The so-called phase difference layer refers to a layer in which at least one of the in-plane delay (also referred to as in-plane phase difference) Re and the thickness direction delay (also referred to as thickness direction phase difference) Rth has a value of 10nm or more. Preferably, it refers to a layer having a value of 20nm or more. In addition, in this specification, unless otherwise specified, the values ​​recorded as Re and Rth are absolute values.

[0029] The in-plane phase difference Re is defined by Re=(nx-ny)×d. The thickness direction retardation Rth is defined by Rth={nz-(nx+ny) / 2}×d. nx represents the principal refractive index in the slow axis direction in the plane of each retardation layer. Ny represents the principal refractive index in the fast axis direction within the plane of each retardation layer, and Nz represents the principal refractive index in the direction perpendicular to the plane of each retardation layer. The slow axis direction refers to the direction with the largest refractive index, and the fast axis direction refers to the direction with the smallest refractive index. d represents the thickness of the phase difference layer.

[0030] The A plate is a phase difference plate that satisfies "nx>ny≒nz".

[0031] Unless otherwise specified, the measurement wavelength of optical parameters such as refractive index and phase difference was 550 nm.

[0032] Approximately parallel means that the angle (absolute value) formed by the two is within the range of 0°±10°, preferably within the range of 0°±5°, and more preferably 0° (i.e., parallel in a narrow sense). In addition, approximately orthogonal (or approximately perpendicular) means that the angle (absolute value) formed by the two forms an angle within the range of 90°±10°, preferably within the range of 90°±5°, and more preferably 90° (i.e., orthogonal or perpendicular in a 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 the design can be appropriately changed within the scope of the configuration satisfying the present invention.

[0034] (Implementation Method 1) Figure 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to this embodiment, Figure 2It is a schematic cross-sectional view showing the liquid crystal display device 1 according to the present embodiment in more detail. Figure 3 1 is a schematic plan view of the entire liquid crystal display device 1 of this embodiment when viewed from the observation surface side. Figure 1 As shown, the liquid crystal display device 1 includes a first substrate 10, a liquid crystal layer 20, and a second substrate 30 in order from the back side. In this embodiment, a TFT substrate is used as the first substrate 10. In addition, a portion or a structure consisting of a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0035] like Figure 3 As shown, the liquid crystal display device 1 has a plurality of pixels P arranged in a matrix. The plurality of pixels P typically include three types of pixels, namely red pixels, green pixels and blue pixels, but the types of pixels may be two or less, or 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 lateral electric field in the liquid crystal layer 20. The gate electrode of the TFT 110 is electrically connected to the corresponding gate wiring (also called scanning wiring) GL, and the source electrode of the TFT 110 is electrically connected to the corresponding source wiring (also called signal wiring) SL. The drain electrode of the TFT 110 is electrically connected to the second electrode 122.

[0036] <First substrate> like Figure 2 As shown, the first substrate 10 has a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 that contacts the liquid crystal layer 20 in order from the back side to the observation side. The first substrate 10 further preferably has a supporting substrate 100 and a bottom board circuit BP on the back side of the reflective layer 130. An insulating layer (also referred to as an insulating film) is provided between each layer as required. For example, a first interlayer insulating layer 151 is provided in a manner covering the bottom board circuit BP, a second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 with the reflective layer 130 interposed therebetween, and a dielectric layer (also referred to as a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

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

[0038] The backplane circuit BP is provided on the support substrate 100. The backplane circuit BP is a circuit for driving the plurality of pixels P, and includes the TFTs 110, the gate wiring GL, the source wiring SL, etc. In addition, it also generally includes a gate insulating film.

[0039] TFT110 is provided in each of the plurality of pixels P. As TFT110, a TFT including an oxide semiconductor layer as an active layer (also referred to as an oxide semiconductor TFT) is preferably used. As the oxide semiconductor layer, specifically, it is preferred to contain at least one metal element of In (indium), Ga (gallium) and Zn (zinc). Among them, an oxide semiconductor film containing a ternary oxide of In, Ga and Zn is more preferred. As a ternary oxide of In, Ga and Zn, for example, indium gallium zinc oxide is preferably exemplified. A semiconductor containing a ternary oxide of In, Ga and Zn is called an In-Ga-Zn-O semiconductor, but in the semiconductor, the ratio (composition ratio) of In, Ga and Zn is not particularly limited, for example, In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, In:Ga:Zn=1:1:2, etc. can be exemplified. In-Ga-Zn-O semiconductors can be amorphous or crystalline. As the crystalline In-Ga-Zn-O-based semiconductor, a semiconductor having a c-axis oriented substantially perpendicularly to the layer surface is preferred.

[0040] The first interlayer insulating layer 151 is provided so as to cover the backplane circuit BP. It is preferred that the surface of the first interlayer insulating layer 151 on the side of the reflective layer 130 has a concavo-convex shape (also referred to as a concavo-convex surface structure). Thus, the reflective layer 130 can have a concavo-convex surface structure reflecting the shape. The first interlayer insulating layer 151 having a concavo-convex surface structure can be appropriately formed using a photosensitive resin 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 of a material that reflects light. Among them, it is preferably formed of a metal material with high reflectivity. As the material of the reflective layer 130, for example, silver alloy, aluminum alloy, etc. can be cited.

[0042] Preferably, the reflective layer 130 has a concave-convex shape reflecting the concave-convex surface structure preferably possessed by the first interlayer insulating layer 151. That is, the reflective layer 130 also preferably has a concave-convex surface structure. The concave-convex surface structure is also referred to as MRS (MicroReflective Structure), which is configured to diffusely reflect ambient light to achieve a white display close to paper white. Preferably, the concave-convex surface structure is composed of a plurality of convex portions p randomly arranged in such a manner that the center spacing of adjacent convex portions p is 5 μm or more and 50 μm or less. The center spacing of adjacent convex portions p is more preferably 10 μm or more and 20 μm or less. The shape of the convex portion p is preferably roughly circular or roughly polygonal when viewed from the normal direction of the supporting substrate. The convex portion p occupies, for example, preferably about 20 to 40% of the area of ​​a pixel P, and the height of the convex portion p is, for example, preferably 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 arranged 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 of an organic insulating material or an inorganic insulating material. For example, as an organic insulating film obtained using an organic insulating material, organic films (relative dielectric constant ε = 2 to 5) of acrylic resin, polyimide resin, novolac resin, etc. and their stacks can be cited. The film thickness of the organic insulating film is not particularly limited, for example, it is greater than 2μm and less than 4μm. As an inorganic insulating film obtained using an inorganic insulating material, for example, inorganic films (relative dielectric constant ε = 5 to 7) of silicon nitride (SiNx), silicon oxide (SiO2), etc. and their stacks can be cited. The film thickness of the inorganic insulating film is not particularly limited, for example, it is greater than 1500A and less than 3500A. In addition, it can also be a stack of an organic insulating film and an inorganic insulating film. Among them, it is preferred 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 0.2 to 0.5 μm, for example.

[0046] The first electrode 121 is arranged on the reflective layer 130 via the second interlayer insulating layer 152, and a dielectric layer 153 is arranged between the first electrode 121 and the second electrode 122. Therefore, the reflective layer 130 is located on the side opposite to the liquid crystal layer 20 (i.e., the back side of the first electrode 121 and the second electrode 122) relative to the first electrode 121 and the second electrode 122. It should be noted that, of the first electrode 121 and the second electrode 122, in this embodiment, the second electrode 122 is relatively located on the observation surface side, and the first electrode 121 is located on the back side. The electrode relatively located on the observation surface side is also referred to as the upper electrode, and the electrode relatively located on the back side is also referred to as the lower 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 plurality of pixels P. The pixel electrode is electrically connected to the backplane circuit BP. In the present embodiment, the first electrode 121 (lower electrode) is the common electrode CE, and the second electrode 122 (upper electrode) is the pixel electrode PE.

[0048] At least one of the first electrode 121 and the second electrode 122 has a plurality of strip-shaped portions SP and a slit S1 located between two adjacent strip-shaped portions among the plurality of strip-shaped portions. The strip-shaped portion SP is equivalent to the electrode portion, and the slit S1 is equivalent to the opening portion. Such an electrode is also called a slit electrode or a finger electrode. From the perspective of facilitating the generation of a transverse electric field, it is preferred that at least the upper electrode (the pixel electrode PE in this embodiment) is a slit electrode. In this case, the lower electrode (the common electrode CE in this embodiment) is preferably a planar electrode, i.e., a so-called full-surface electrode.

[0049] The plurality of strip portions SP constituting the slit electrode include straight line shapes that are substantially parallel to each other and extend in the same direction. As a result, the orientation of the liquid crystal molecules becomes uniform, and the occurrence of orientation disorder can be fully suppressed. The so-called straight line shape does not refer to the outer edge of the strip portion SP, but refers to the center line of the strip portion SP being a straight line shape, and the so-called center line of the strip portion SP refers to the line that divides the strip portion SP into two equal parts in the width direction. The width direction refers to a direction that is substantially perpendicular to the direction in which the strip portion SP extends when viewed from above. In addition, a curved portion (also called a kinked portion) may be provided in the middle of the strip portion SP (for example, at the end), but it is preferred that there is no curved portion.

[0050] In each pixel P, the directions in which the plurality of strip-shaped portions SP extend (also referred to as the extending directions of the plurality of strip-shaped portions SP) are substantially parallel to each other. In addition, the extending directions of the plurality of strip-shaped portions SP may be different for each pixel, but are preferably the same in two or more adjacent pixels. Among them, from a manufacturing point of view, it is more preferred that the extending directions of the plurality of strip-shaped portions SP are the same at least in adjacent pixels. It is even more preferred that the extending directions of the plurality of strip-shaped portions SP are the same in the display area.

[0051] The width L of each strip-shaped portion SP varies depending on the applied voltage, etc., but is preferably set to 0.3 to 10 μm, for example. More preferably, it is 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 varies depending on the applied voltage, etc., and is preferably set to 0.3 to 10 μm, for example. More preferably, it is 1 to 5 μm.

[0052] Preferably, the ratio L / S (also referred to as the L / S condition) of the width L of each strip-shaped portion in plan view to the width S of each slit in plan view is 0.4 to 0.7 / 1. This further improves the reflectivity and thus the contrast ratio.

[0053] Figure 5 is a plan view schematically showing one pixel. Figure 6 It is magnified Figure 5 A schematic diagram of a portion of a plan. Figure 5 and Figure 6In the figure, the extension direction of the plurality of strip-shaped portions SP constituting the slit electrode (the pixel electrode PE in this embodiment) is arranged parallel to the plurality of source wirings SL, and the structure of the plurality of gate wirings GL arranged in a manner orthogonal to the plurality of source wirings SL is shown as a planar schematic diagram. If the direction parallel to the gate wiring GL (the left-right direction of the figure) is taken as a reference (0°), the clockwise angle is set as a positive angle (+), and the counterclockwise angle is set as a negative angle (-), then the extension direction of the plurality of strip-shaped portions SP is located in the direction of 90° (see also FIG. Figure 4 The angle of the extending direction of the plurality of strip-shaped portions SP when this angle, that is, the direction parallel to the gate wiring GL is taken as a reference (0°) is referred to as a slit angle θ. SP .

[0054] Slit angle θ SP The preferred range of varies depending on the conditions of the width L of each strip-shaped portion SP and the width S of each slit S1 (also referred to as the L / S condition), the twist angle, and various physical properties of the liquid crystal material, and is preferably 30° or more, more preferably 60° or more, and even more preferably 80° or more. In addition, the upper limit is preferably 150° or less, more preferably 120° or less, and even more preferably 100° or less.

[0055] The first electrode 121 and the second electrode 122 are preferably formed of a transparent conductive material, respectively. Examples of the transparent conductive material include indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), and a mixture thereof.

[0056] exist Figure 2 In the manner shown, the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed in the same layer as the reflective layer 130 and is formed of the same material (metal film, etc.) as the reflective layer 130. A first contact hole CH1 is formed in the first interlayer insulating layer 151 to expose a portion of the backplane circuit BP (more specifically, at least a portion of the drain electrode of the TFT 110), and the contact electrode 160 is connected to the backplane circuit BP at the first contact hole CH1. In addition, a second contact hole CH2 is formed in the second interlayer insulating layer 152 to expose a portion of the contact electrode 160, and the pixel electrode PE (the second electrode 122 in this embodiment) is connected to the contact electrode 160 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 of 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 arranged 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 respectively subjected to an alignment treatment to define the alignment azimuth (also referred to as 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 photo-decomposable photo-alignment film material can be used, and in the rubbing treatment, an alignment film material such as polyimide is preferably used.

[0060] The first horizontal alignment film 140 and the second horizontal alignment film 340 are both horizontal alignment films that align the liquid crystal molecules 21 in the horizontal direction relative to the first substrate 10 and the second substrate 30 when no voltage is applied to the liquid crystal layer 20. That is, 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 orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 and the orientation of the liquid crystal molecules 21 defined by the second horizontal alignment film 340 are different from each other. Therefore, the liquid crystal layer 20 has a twisted orientation when no voltage is applied (see Figure 2 When a voltage is applied to the liquid crystal layer 20, that is, when a transverse electric field is generated 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 substrate> The second substrate 30 includes a second horizontal alignment film 340 disposed opposite to the first substrate 10 via the liquid crystal layer 20 and in contact with the liquid crystal layer 20. The second substrate 30 further preferably includes a supporting substrate 300 and a color filter layer 310. Figure 2 As shown, the second substrate 30 has a second horizontal alignment film 340, a color filter layer 310, and a support substrate 300 in order from the liquid crystal layer 20 side. The second substrate 30 preferably has a plurality of columnar spacers (not shown). In addition, the first substrate 10 may also have a plurality of columnar spacers.

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

[0065] The color filter layer 310 typically includes: a red color filter, which is arranged in an area corresponding to a red pixel and allows red light to pass through; a green color filter, which is arranged in an area corresponding to a green pixel and allows green light to pass through; and a blue color filter, which is arranged in an area corresponding to a blue pixel and allows blue light to pass through. However, the types of color filters may be two or less or four or more. In the case where color display is not performed, the color filter layer 310 is omitted. In addition, in the case where a color filter layer is formed on the first substrate 10, it is preferred that the second substrate 30 does not have a color filter layer.

[0066] As required, an outer coating (also referred to as a planarization layer) covering the color filter layer 310 may also be provided. In addition, depending on the material forming the electrode (e.g., a transparent conductive material), the material forming the interlayer insulating layer or the dielectric layer, and the material forming the alignment film, the white display may sometimes be yellowish. In this case, the chromaticity adjustment (i.e., blue shift) may be performed by forming an outer coating with a blue resist, so that the chromaticity of the white display is close to the chromaticity of, for example, a D65 light source. The so-called D65 light source is the CIE standard light source D65.

[0067] <Liquid crystal layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and includes a positive liquid crystal material. A positive liquid crystal material refers to a nematic liquid crystal material with a positive dielectric anisotropy Δε. A negative liquid crystal material refers to a nematic liquid crystal material with a negative dielectric anisotropy Δε. The dielectric anisotropy Δε is the difference between the dielectric constant ε / / in the long axis direction and the dielectric constant ε⊥ in the short axis direction of the liquid crystal molecule 21 (i.e., ε / / -ε⊥).

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

[0069] The thickness d (also referred to as cell gap or cell thickness) of the liquid crystal layer 20 is preferably, for example, 1.5 μm or more. The upper limit is not particularly limited, but is, for example, preferably 10 μm or less, and more preferably 5 μm or less.

[0070] The liquid crystal layer 20 may be in a multi-domain orientation such as a dual-domain orientation. However, when the dual-domain design of the transmissive FFS is directly applied to the reflective type, when θa exceeds 90 degrees, it acts as a pixel with low reflectivity and may cause reflectivity loss, so a single-domain orientation is preferred.

[0071] The dielectric anisotropy Δε of the liquid crystal material constituting the liquid crystal layer 20 is a positive value. Generally speaking, 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. More preferably, it is 3 or more. In addition, from the viewpoint of further improving the reflectivity (for example, white reflectivity in a normally black mode), the upper limit is preferably 15 or less. More preferably, it is 10 or less, and even more preferably, it is 7 or less.

[0072] Considering the absolute value of Δn of the liquid crystal molecule with the lowest refractive index (Δn=0.038 in 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. In addition, from the perspective of a material composition having well-balanced performance as a liquid crystal mixture for a display, the upper limit is preferably 0.2 or less. The upper limit is more preferably 0.1 or less, and most preferably, it is 0.09 or less.

[0073] From the viewpoint of improving the response characteristics, the liquid crystal material preferably has a torsion elastic constant (also referred to as torsion elastic constant) K22 (unit: pN) of 2 or more. More preferably, it is 3 or more. In addition, from the viewpoint of low voltage, the upper limit is preferably 10 or less. The upper limit is more preferably 7 or less, and further preferably 6 or less.

[0074] The spray elastic constant K of the above liquid crystal material 11 (Unit: pN) 22 The bending elastic constant K is proportional to about 2 times of the bending elastic constant K, so it is preferably 4 or more and 20 or less. It is more preferably 6 or more and 14 or less. 33 (Unit: pN) has no significant effect on the optical characteristics of this mode, and is preferably 6 or more and 20 or less. More preferably, it is in the range of 10 or more and 16 or less. In addition, the elastic constants (K 11 , K 22 , K 33 ) can be calculated by fitting the theoretical formula using the measured values ​​of the capacitor-voltage characteristic curve.

[0075] The above-mentioned liquid crystal material contains liquid crystal molecules (also called positive liquid crystal molecules), but the average azimuth angle ΦLCave of the liquid crystal molecules when a voltage is applied is preferably greater than or equal to 150° and less than or equal to 156°. Within this range, it becomes easier to set the positional relationship between the extension direction of the plurality of 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 to the above-mentioned manner. The lower limit is more preferably greater than or equal to 151°. In addition, the upper limit is more preferably less than or equal to 155°, more preferably less than or equal to 154°, and particularly preferably less than or equal to 153°.

[0076] In this specification, the average azimuth angle ΦLCave of the liquid crystal molecules when a voltage is applied is a value derived by calculating the liquid crystal director at a voltage with the maximum reflectivity in the simulation software (LCD Master 2D) manufactured by Tester, and calculating the azimuth angle distribution of the liquid crystal molecules therein. The following is a detailed description of the calculation method. (Calculation method of ΦLCave) (1) Production Fig. 12A The calculation model shown. The lateral width of the pixel is 4.6μm. The first electrode 121 is set as the common electrode CE, and the second electrode 122 is set as the pixel electrode PE. The common electrode CE is a full-surface electrode, and the pixel electrode PE (122) is a slit electrode with a width L of each strip portion of 1.6μm and a width S of each slit of 3.0μm. The liquid crystal layer 20 is set to have a scale of 0.05μm in the X direction (lateral direction) and a scale of 0.025μm in the Z direction (thickness direction). In this calculation model, the liquid crystal layer 20 becomes a matrix of 651 points, 21 points in the X direction × 31 points in the Z direction, and the azimuth angle and polar angle of the liquid crystal molecules in each matrix are calculated according to the applied voltage. Fig. 12A It is a diagram showing a calculation model of a liquid crystal director distribution pattern. (2) In this calculation model, a voltage of 0 to 8 V is applied to the pixel electrode PE (122) at a scale of 0.1 V, for example, to calculate the VR curve. Fig. 12B In this calculation example, the maximum reflectivity was obtained by applying a voltage of 4.2 V (refer to Fig. 12B ). Fig. 12B It is a diagram showing an example of calculation of a VR curve. (3) The director distribution of the liquid crystal molecules at the applied voltage (i.e., 4.2 V) showing the maximum reflectivity was calculated using simulation software (LCD Master 2D) manufactured by SHINTECH. The director distribution diagram of the liquid crystal molecules (also referred to as the liquid crystal director distribution diagram) obtained is shown in Fig. 12C . Fig. 12C It is a liquid crystal director distribution diagram (cross-sectional diagram). (4) With respect to the directors of each liquid crystal molecule obtained in (3) above (i.e., 21 points in the X direction × 31 points in the Z direction = 651 points in total), extract the azimuth angle and the polar angle θ. (5) The average value of all azimuth angles is calculated (ie, the sum of the azimuth angles at a total of 651 points / 651). The value calculated in this way is the average azimuth angle ΦLCave of the liquid crystal molecules when a voltage is applied.

[0077] In the above-mentioned liquid crystal material, the ratio of the birefringence Δn60 at 60°C to the birefringence Δn20 at 20°C (Δn60 / Δn20) is preferably greater than 0.80. Usually, the upper limit of the actual operating temperature of the liquid crystal display device is about 50°C. Therefore, if Δn60 / Δn20 is within the above range, a display in which the influence of temperature is fully suppressed can be obtained at the actual operating temperature. In particular, black floating during black display can be fully suppressed. It is more preferably greater than 0.82, and further preferably greater than 0.84. From the viewpoint of suppressing the reduction in contrast, the upper limit is preferably less than 0.97, and more preferably less than 0.95.

[0078] The retardation (dΔn) of the liquid crystal layer 20 represented by 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. Thus, a lower voltage can be achieved and the reflectivity can be further improved. It is more preferably 200 nm or more and 260 nm or less, further preferably 220 nm or more and 252 nm or less, and particularly preferably 236 nm or more and 252 nm or less. In addition, it is more preferably 250 nm or less.

[0079] As described above, the liquid crystal layer 20 exhibits a twisted orientation when no voltage is applied. That is, in the liquid crystal display device 1 of this embodiment, the liquid crystal layer 20 displays in a transverse electric field mode in which the liquid crystal layer 20 exhibits a twisted orientation when no voltage is applied. As a result, the cell gap can be increased, and the fluctuation range of the contrast can be reduced relative to the fluctuation of the cell gap. Therefore, the occurrence of display unevenness is fully suppressed, and the contrast of the reflective display becomes good. The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied will be described later.

[0080] In the present embodiment, when the liquid crystal layer 20 of each pixel P is viewed from above when no voltage is applied, at least in the central portion in the plane 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 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. In addition, when the liquid crystal layer 20 of each pixel P is viewed from above, at least the liquid crystal molecules 21 in the central portion in the thickness direction of the liquid crystal layer 20 rotate in the twisting direction when no voltage is applied when a voltage is applied. Such a form can be achieved, for example, by appropriately adjusting the twist angle θ1 and the various physical properties of the above-mentioned liquid crystal material, and by setting such a form, a reverse twist orientation is generated in the liquid crystal layer 20. Therefore, for example, in the case of a normally black mode, when white is displayed, the liquid crystal molecules of the liquid crystal layer 20 as a whole are in an orientation state close to a uniform orientation. Therefore, the light utilization efficiency is improved, and the white reflectivity is improved, so a high reflectivity can be obtained even when white is displayed at a low driving voltage. In addition, the liquid crystal molecules 21 on the first substrate 10 side (i.e., the liquid crystal molecules 21 near the first horizontal orientation 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 orientation film 340) are also referred to as liquid crystal molecules 21B.

[0081] The center portion of the liquid crystal layer 20 in the plane direction is also referred to as the center portion of the liquid crystal layer 20 in the horizontal direction, and refers to the center portion of the liquid crystal layer 20 when viewed from above. That is, it refers to the vicinity of the center of the liquid crystal layer 20 when the liquid crystal panel 1X is observed from the observation surface side. In addition, the center portion of the liquid crystal layer 20 in the thickness direction refers to the center portion of the liquid crystal layer 20 when viewed in section. That is, it refers to the vicinity of the center of the liquid crystal layer 20 when the liquid crystal panel 1X is observed from its side. Therefore, the liquid crystal molecule 21 located in the center portion of the liquid crystal layer 20 in the thickness direction is located approximately in the middle of 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 in the center portion of the liquid crystal layer 20 in the thickness direction is also referred to as a liquid crystal molecule 21C.

[0082] When looking down at the liquid crystal layer 20 of each pixel P when no voltage is applied, "at least in the central part 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 molecule 21A and the long axis direction b of the liquid crystal molecule 21B" means that at least in the central part of the surface direction of the liquid crystal layer 20, when no voltage is applied, the following relationship (1) is satisfied: θa<θ SP <(θa+θ1) (1).

[0083] In the above formula, θa 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, with the direction parallel to the gate wiring GL as a reference (0°), the clockwise angle as a positive angle (+), and the counterclockwise angle as a negative angle (-). In the case of positive 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 plurality of strip-shaped portions SP. (θa+θ1) represents the sum of θa and θ1, where θ1 is the twist angle. The twist angle refers to the angle formed by the long axis direction a of the liquid crystal molecule 21A when no voltage is applied and the long axis direction b of the liquid crystal molecule 21B when no voltage is applied (i.e., the angle formed by the orientation direction of the liquid crystal molecule 21A specified by the first horizontal alignment film 140 and the orientation direction of the liquid crystal molecule 21B specified by the second horizontal alignment film 340).

[0084] θa is preferably, for example, 10 to 90°. That is, it is preferred that the above-mentioned relational expression (1) is satisfied, and the first horizontal alignment film is used to control the orientation of the liquid crystal molecules 21A in such a manner that θa becomes this angle. The lower limit is more preferably 30° or more, further preferably 45° or more, and particularly preferably 60° or more. The upper limit is more preferably 89° or less, further preferably 85° or less, particularly preferably 83° or less, and most preferably 80° or less.

[0085] Slit angle θ SP For example, it is preferably 30 to 150°. That is, it is preferable to satisfy the above relational expression (1) and θ SP The slit electrode is designed in such a way that the angle is achieved. The lower limit may be a value exceeding θa, for example, more preferably 45° or more, further preferably 60° or more, and particularly preferably 80° or more. The upper limit is more preferably 120° or less, further preferably 100° or less.

[0086] The twist angle θ1 is greater than 78° and less than 90°. Among them, from the viewpoint of being able to achieve lower voltage and further improve reflectivity, it is preferably greater than 80°, and more preferably greater than 83°. In addition, when the twist angle θ1 is 90°, there is a concern about the possibility of orientation disorder due to pressure on the surface of the liquid crystal panel, etc., so it is preferably less than 90°. From the viewpoint of further improving the response characteristics, it is more preferably less than 88°, and more preferably less than 87°. From the viewpoint of maximum reflectivity, maximum reflectivity voltage and response characteristics, it is particularly preferably greater than 78° and less than 88°, more preferably greater than 83° and less than 87°, and most preferably 83°.

[0087] For example, when θa=80° and the slit angle θ SP =90° and the twist angle θ1=83°, the extending directions of the plurality of strip-shaped portions SP of the liquid crystal molecules 21A, 21B and the slit electrodes are conceptually expressed as Figure 6 The positional relationship shown.

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

[0089] As described above, in this embodiment, reverse twist alignment occurs in the liquid crystal layer 20, but in the following, referring to, for example Figure 6 , Figure 7 , Fig. 8A , Figure 8B as well as Fig. 9A, Fig. 9B , explaining the mechanism of producing reverse twist orientation. Figure 6 , Figure 7 , Fig. 10A , Fig. 10B as well as Fig.11A , Fig. 11B The mechanism of generating the positive twist alignment will be described below. Here, the description will be given by taking the case where the liquid crystal panel 1X is in the normally black mode as an example.

[0090] Figure 6 , Fig. 8A , Fig. 9A , Fig. 10A as well as Fig.11A It is magnified Figure 5 , is a schematic plan view of a portion of the second electrode 122 (pixel electrode PE in this example) and conceptually shows the relationship between the extending direction of the strip portion SP 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. Figure 7 , Figure 8B , Fig. 9B , Fig. 10B as well as Fig. 11B This is the distribution diagram of the liquid crystal director (cross-sectional view).

[0091] Figure 6 The positional relationship between the extending direction of the strip-shaped portion SP and the alignment direction of the liquid crystal molecules 21 when no voltage is applied (that is, when a voltage of 0 V is applied) is conceptually shown. Figure 7 The distribution diagram of the directors of the liquid crystal when no voltage is applied (cross-sectional view) is shown. The positional relationship between the extending direction of the strip portion SP and the orientation direction of the liquid crystal molecules 21 when a threshold voltage (e.g., a voltage of 1.8 V) is conceptually shown in the case of reverse twist orientation. Fig. 8A In the case of positive twist orientation, it is conceptually shown that Fig. 10A Regarding the reverse twist orientation, the distribution diagram (cross-sectional view) of the liquid crystal director when the threshold voltage is applied is shown in Figure 8B In the figure, regarding the positive twist orientation, the distribution diagram (cross-sectional diagram) of the liquid crystal director when the threshold voltage is applied is shown in Fig. 10B In addition, regarding the positional relationship between the extending direction of the strip-shaped portion SP and the alignment direction of the liquid crystal molecules 21 when a white voltage (for example, 4.0 V) is applied, the following is conceptually shown in the case of reverse twist alignment. Fig. 9A In the case of a positive twist orientation, the Fig.11A Regarding the reverse twist orientation, the distribution diagram (cross-sectional view) of the liquid crystal director when the white voltage is applied is shown in Fig. 9B In FIG. 1 , regarding the positive twist orientation, the liquid crystal director distribution diagram (cross-sectional view) when the white voltage is applied is shown in FIG. Fig. 11BFor reference, Fig. 12A A model of the liquid crystal director profile is shown in FIG.

[0092] For example, when θa=80° and the slit angle θ SP =90° and the twist angle θ1=83°, conceptually, the extending direction of the strip-shaped portion SP when no voltage is applied and the alignment direction of the liquid crystal molecules 21 are at the same angle in a plan view. Figure 6 The positional relationship is as shown in FIG. 2 . Figure 7 The direction of the arrow shown (right direction in the drawing) is reversed (refer to Figure 7 ).

[0093] In the structure that produces reverse twist orientation, when a voltage near the threshold value of the liquid crystal (e.g., 1.8 V) is applied, the equipotential line reaches the opposite substrate (i.e., the second substrate 30) (see Figure 8B As a result, the liquid crystal molecules 21 of the entire liquid crystal layer 20, including the liquid crystal molecules 21B at the interface on the second substrate 30 side, rotate simultaneously due to the elastic effect. For example, when the liquid crystal molecules 21C located in the center of the thickness direction of the liquid crystal layer 20 are viewed from the observation side, they rotate counterclockwise in the twisting direction (refer to Fig. 8A ). In addition, when a white voltage (eg, 4.0 V) is applied, the liquid crystal molecules 21C further rotate in the counterclockwise direction (see Fig. 9A When viewed in cross section, substantially all of the liquid crystal molecules 21 included in the liquid crystal layer 20 are in the direction of loosening the twist (in Fig. 9B (center is left) twist (refer to Fig. 9B ).

[0094] On the other hand, in the structure that produces a positive twist orientation, when a voltage near the threshold value of the liquid crystal (e.g., 1.8 V) is applied, the equipotential line does not reach the opposite substrate (i.e., the second substrate 30) (see 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 of the thickness direction of the liquid crystal layer 20 are viewed from the observation surface side, they rotate in the clockwise direction, which is the opposite direction to the twisting direction (refer to Fig. 10A ). In addition, when a white voltage (eg, 4.0 V) is applied, the liquid crystal molecules 21C further rotate in the clockwise direction (see Fig.11A ). When viewed in cross section, the liquid crystal molecules 21 are twisted in the initial twist direction ( Fig. 11B in the right direction) to further rotate (refer to Fig. 11B ) Due to the influence of the twisting direction of the liquid crystal molecules 21, a mixed state of optical rotation and birefringence is achieved, and the white reflectivity is not improved.

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

[0096] Fig.13A So Figure 5 The AA′ line in FIG. 1 is a schematic cross-sectional view of a cut surface (AA′ line cross-sectional view), and conceptually shows the behavior of the liquid crystal molecules 21 when no voltage is applied (ie, in a black display state). Fig. 13B Yes Figure 5 The partially enlarged plan view schematically shows the twisting direction of the liquid crystal molecules 21 when no voltage is applied (ie, in a black display state). Fig.14A So Figure 5 The AA′ line in FIG. 1 is a schematic cross-sectional view (AA′ line cross-sectional view), which conceptually shows the behavior of the liquid crystal molecules 21 when a voltage is applied (ie, in a white display state). Fig. 14B Yes Figure 5 The partially enlarged plan view schematically shows the twisting direction of the liquid crystal molecules 21 when a voltage is applied (ie, in a white display state).

[0097] like Fig.13A and Fig. 13B As shown, 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 from the liquid crystal molecules 21A defined by the first horizontal alignment film 140 by only an amount of twist angle θ1 (see Fig. 13B On the other hand, when a voltage is applied, the liquid crystal molecules 21 rotate in different twist angles in the pixel plane due to the influence of the lateral electric field EF generated between the first electrode 121 (the common electrode CE in this embodiment) and the second electrode 122 (the pixel electrode PE) (see Fig.14A and Fig. 14B ).

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

[0099] As a manufacturing method of the first substrate 10 (e.g., a TFT substrate), it is preferred to adopt a manufacturing method of a TFT substrate in a conventional FFS mode using a transparent electrode. An insulating film (also referred to as an insulating layer) is formed between the electrodes, between each electrode and the gate wiring GL, the source wiring SL, the TFT110, etc. as described above. As described above, the insulating film can be either an inorganic film or an organic film. A color filter layer can also be formed instead of the organic insulating film. In addition, it is preferred to form an organic insulating film after forming the common electrode CE, and after patterning the organic insulating film, form the pixel electrode PE.

[0100] A general method for manufacturing a counter substrate in the FFS mode is preferably used as a method for manufacturing the second substrate 30. When a color filter layer is formed on the first substrate 10, the second substrate 30 preferably does not have a color filter layer.

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

[0102] However, in the present embodiment, the structure in which the pixel electrode PE is disposed above the common electrode CE is described, but in a relatively large liquid crystal display device, that is, a liquid crystal display device in which the area of ​​the pixel P is relatively large, it is preferred that the pixel electrode PE is disposed above the common electrode CE. In this structure (also referred to as the V2 structure), it is not necessary to form a slit in the common electrode CE that becomes the lower electrode, so compared with the structure in which the common electrode CE is disposed above the pixel electrode PE (also referred to as the V3 structure), the increase in the resistivity (surface resistivity) of the common electrode CE is suppressed, thereby suppressing the weakening of the edge electric field applied to the liquid crystal layer 20. In this structure (V2 structure), when the pixel electrode PE is used as a slit electrode, although the resistivity of the pixel electrode PE increases, since a voltage input from the outside is applied to the pixel electrode PE, it is easy to reduce the influence of the increase in resistivity (that is, suppress the weakening of the edge electric field). In addition, in order to suppress the increase in the resistivity of the common electrode CE, it is also considered to use low-resistance wiring formed by a metal material (for example, connecting the low-resistance wiring to the common electrode), but in such a structure, sometimes adverse effects on the display (such as glare, rainbow-colored diffraction, interference patterns) are caused by regular reflection caused by the low-resistance wiring, and it is necessary to use a black matrix or the like for shading, and sometimes it is impossible to fully increase the reflective aperture ratio.

[0103] In the structure where the pixel electrode PE is arranged above the common electrode CE, in addition, since the common electrode CE does not exist in the area where the second contact hole CH2 is formed, this area is not conducive to reflective display, and the reflectivity may decrease compared with the structure where the common electrode CE is arranged above the pixel electrode PE. The area of ​​the area that does not contribute to the reflective display of the contact hole, etc., needs to be of a certain degree regardless of the size of the area of ​​the pixel P. Therefore, the smaller the area of ​​the pixel P (that is, the higher the fineness), the higher the proportion of the area that does not contribute to the reflective display in the pixel P, and the greater the reduction in the above reflectivity. Conversely, in a relatively large liquid crystal display device, it is easy to further reduce the proportion of the area that does not contribute to the reflective display in the pixel P, so it is easy to suppress the reduction in the above reflectivity. For these reasons, in a relatively large liquid crystal display device, a structure where the pixel electrode PE is arranged above the common electrode CE is advantageous.

[0104] On the other hand, as described above, the area where the second contact hole CH2 is formed does not contribute to the decrease in reflectivity caused by reflective display, and the smaller the area of ​​the pixel P is (that is, the higher the precision is), the higher it is. Therefore, in a relatively high-definition liquid crystal display device, that is, a liquid crystal display device with a smaller area of ​​the pixel P, it is preferred that the common electrode CE is arranged above the pixel electrode PE (refer to variant example 1 of embodiment 1 described later).

[0105] The liquid crystal display device 1 is composed of a plurality of components, including TCP (tape-carrier-package), PCB (printed wiring board), etc., external circuits, optical films such as viewing angle expansion film and brightness enhancement film, and outer frame (frame), etc., in addition to the above components, and can also be assembled to other components through components. These are not particularly limited, and components commonly used in the field of liquid crystal display devices can be used, so the description is omitted.

[0106] <Application Examples> The liquid crystal display device 1 of this embodiment is applicable to various applications. Among them, it can be preferably applied to a touch panel. Regardless of whether it is applied to an external touch panel or a built-in touch panel, it can improve the contrast ratio at a lower cost than each touch panel in the past, so it is useful. Among them, it can be suitably applied to a built-in touch panel, and is particularly suitably applied to an embedded touch panel. In this way, if the liquid crystal display device 1 of this embodiment is used, it is possible to appropriately realize an embedded touch panel capable of displaying in a reflective mode, which has not been realized so far.

[0107] Since it is possible to realize an embedded touch panel capable of displaying a reflective mode, for example, the necessary frame wiring area is not required in an external touch panel, so a narrow frame can be realized, and the touch panel function can be equipped without a cover glass, so it can also contribute to thinning and lightweighting. In addition, since the touch function and the display function are driven in a time-sharing manner, the LCD (liquid crystal display) noise, which can be the largest noise source, is not received in the touch panel. That is, since no chiral pattern is generated, it is easy to adjust the touch signal. In addition, the loss of reflected light is sufficiently small, and the pen writing is more natural and there is no sense of incoordination. On this basis, compared with the external touch panel, the total cost can be reduced from the user's point of view. Moreover, it is possible to combine finger input and pen input of electromagnetic induction (EMR) to achieve high-precision pen writing.

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

[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. Fig.15 In the example shown, 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 drive unit TD provided in the non-display region FR. The touch drive unit TD is configured to, for example, switch between a display mode in which a plurality of touch sensor electrodes TX function as common electrodes CE and a touch detection mode in which the plurality of touch sensor electrodes TX function as touch sensor electrodes TX in a time-division manner. For example, in the display mode, the touch drive 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 drive unit TD applies a touch drive signal to the touch sensor electrodes TX via the touch wiring TL.

[0112] exist Fig.15 In the embodiment, a plurality of touch wirings TL extend in a column direction (the same direction as the source wiring SL). A portion of the touch wiring TL extends across another one or more touch sensor electrodes TX to the corresponding touch sensor electrode TX.

[0113] If we focus on a certain touch sensor electrode TX, the first touch wiring TL1 that supplies a signal to the touch sensor electrode TX extends to the touch wiring contact portion TC, and the second touch wiring TL2 that supplies a signal to other touch sensor electrodes TX extends in a manner that crosses the touch sensor electrode TX. The second touch wiring TL2 overlaps the touch sensor electrode TX via an insulating layer. In addition, depending on the position of the touch sensor electrode TX, sometimes more than two touch wirings TL are configured in a manner that extends across the touch sensor electrode TX, and there is also a case where a touch wiring TL that crosses the touch sensor electrode TX is not configured.

[0114] In the non-display region FR, in addition to the touch drive unit TD, a peripheral circuit (not shown) including a gate driver that provides a gate signal to the gate bus (gate wiring) GL, a source driver that provides a source signal to the source bus (source wiring) SL, and the like is provided. These drive circuits can be mounted on the first substrate (TFT substrate) 10, or can be formed as an integral unit (monolithic). A semiconductor chip including a part or all of the drive circuits can also be mounted on the non-display region FR.

[0115] In the embedded touch panel, as TFT110, it is particularly preferred to use In-Ga-Zn-O semiconductor. In addition, from the perspective of achieving flicker-free (also called stroboscopic) display, it is particularly preferred to use negative liquid crystal materials. This is based on the following reasons. In the lateral electric field method of the FFS mode using a positive liquid crystal material, when a voltage is applied, flexible polarization is spontaneously generated in the liquid crystal layer due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field). Since the liquid crystal responds to this flexible polarization, it is believed that the brightness changes when the polarity is reversed, which can be easily seen as flickering.

[0116] (Variation 1 of Implementation Example 1) In Embodiment 1, the structure in which the first electrode 121 as the lower electrode is the common electrode CE and the second electrode 122 as the upper electrode is the pixel electrode PE is described. However, conversely, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE and the first electrode 121 (lower electrode) is the pixel electrode PE (see Fig.16 ).

[0117] Fig.16 is a cross-sectional schematic diagram showing the liquid crystal display device 1 of this example in more detail. In this example, from the viewpoint of easy generation of a lateral electric field, at least the upper electrode (the common electrode CE in this example) is preferably a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this example is particularly suitable as a relatively high-definition liquid crystal display device as described above, i.e., a liquid crystal display device with a relatively small area of ​​pixel P.

[0118] (Variation 2 of Implementation Example 1) In Embodiment 1, an FFS mode liquid crystal display device is described, but an IPS mode liquid crystal display device (wherein the liquid crystal layer 20 adopts a twisted orientation when no voltage is applied) may also be used. This variation is an IPS mode liquid crystal display device. In this variation, it is preferred that the first electrode 121 and the second electrode 122 are provided in the same layer, and both the first electrode 121 and the second electrode 122 are slit electrodes.

[0119] (Implementation Method 2) In this embodiment, features unique to this embodiment are mainly described, and description of contents overlapping with those of the above-described Embodiment 1 is 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 a liquid crystal display device 1 according to this embodiment, Fig.18 1 is a schematic cross-sectional view showing the liquid crystal display device 1 of the present embodiment in more detail. Fig.17 As shown, the liquid crystal display device 1 includes, in order from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40, and a polarizing plate 50. In this embodiment, a TFT substrate is used as the first substrate 10.

[0121] The phase difference 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 Fig.17 and Fig.18 ). The arrangement order of these is preferably such that the λ / 4 plate 41 and the λ / 2 plate 42 are arranged in this order from the liquid crystal layer 20 (and the second substrate 30) side (see Fig.17 as well as Fig.18 ).

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

[0123] The λ / 2 plate is a phase difference plate that gives an in-plane phase difference of 1 / 2 wavelength to incident light of wavelength λ, and is also called a λ / 2 wavelength plate, a half-wavelength plate, or an HWP (Half-Wave Plate). Specifically, the λ / 2 plate 42 can rotate the vibration direction of the incident light by approximately 90°. For example, the circularly polarized light incident on the λ / 2 plate 42 rotates in the opposite direction when it is emitted.

[0124] Specifically, it is preferable to use a uniaxial A plate as the λ / 4 plate 41 and the λ / 2 plate 42 .

[0125] The polarizing plate 50 is located closer to the observation surface than the phase difference layer 40 (see Fig.17 as well as Fig.18 ). The polarizing plate 50 may be a circular polarizing plate or a linear polarizing plate. Here, the linear polarizing plate refers to a polarizing plate having the function of extracting polarized light (linear polarization) that vibrates only in a specific direction from non-polarized light (natural light), partially polarized light or polarized light, and is different from a circular polarizing plate. Among them, a linear polarizing plate is preferred.

[0126] The polarizing plate 50 may be an absorption type polarizing plate or a reflection type polarizing plate. An absorption type polarizing plate is a polarizing plate that has the function of absorbing light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. A reflection type polarizing plate is a polarizing plate that has the function of reflecting light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. Among them, an absorption type polarizing plate is preferred. It is particularly preferred to use an absorption type linear polarizing plate.

[0127] As an absorption type polarizing plate, for example, a polarizing plate in which an anisotropic material such as an iodine complex (or dye) is dyed and adsorbed on a polyvinyl alcohol film and then stretched and oriented can be cited. Usually, in order to ensure mechanical strength and moisture and heat resistance, a protective film such as a triacetyl cellulose film is laminated on both sides of the polyvinyl alcohol film for practical use. In addition, as a reflection type polarizing plate, for example, a film formed by laminating a plurality of dielectric films, a film formed by laminating a plurality of films with different refractive index anisotropies, a nanowire grid polarizing plate, a polarizing plate for selective reflection using cholesteric liquid crystals, etc. can be cited.

[0128] Hereinafter, preferred axis angles of the optical films (ie, polarizing plates and phase difference plates) will be described. As the polarizing plate 50, an absorption-type polarizing plate is used.

[0129] Fig.19 The liquid crystal display device 1 is provided with 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 order from the back side (see Fig.17 as well as Fig.18 ) is a top view used to illustrate the axis angle of each optical film. In the following description, the axis angle of each optical film is Fig.19 The angle when the dial of a clock is regarded as the 3 o'clock direction (0°) and the rotation direction is positive (counterclockwise). Fig.19 In FIG. 1 , for convenience, the angle θa of the alignment direction (ie, the long axis direction) a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied is 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 perspective of improving the contrast ratio, it is more preferably 8° or more and 20° or less, and further 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 perspective of improving the contrast ratio, it 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 perspective of improving the contrast ratio, it is more preferably 48° or more and 65° or less, and even more preferably 50° or more and 60° or less.

[0133] Next, the principle of white display and black display in the liquid crystal display device 1 of this embodiment is described. The liquid crystal display device 1 here includes 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 order from the back side (see Fig.17 as well as Fig.18 ), assuming the display is in normally black mode.

[0134] Fig. 20A This is a conceptual diagram for explaining the principle of black display. Fig. 20B This is a conceptual diagram for explaining the principle of white display. Fig. 20A and Fig. 20BFor convenience, only the reflective layer 130, the liquid crystal layer 20, the phase difference layer 40 (ie, the λ / 4 plate 41 and the λ / 2 plate 42), and the polarizing plate 50 are shown. As the polarizing plate 50, a linear polarizing plate is used.

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

[0136] When voltage is applied, Fig. 20B As shown, light (I) also passes through the polarizing plate 50 and becomes linearly polarized light (i). The linearly polarized light (i) is given a phase difference of (λ / 2+λ / 4) by the phase difference layer (40) and becomes elliptically polarized light (ii). When a voltage is applied to the liquid crystal layer 20, the phase difference is added to the liquid crystal layer 20, and the elliptically polarized light (ii) becomes linearly polarized light (iii) having a polarization direction that rotates the linearly polarized light (i) by approximately 90°. Even if the linearly polarized light (iii) is reflected by the reflective layer 130, the polarization direction does not change (it is set to linearly polarized light (iv). The linearly polarized light (iv) becomes elliptically polarized light (v) whose phase difference is returned on the liquid crystal layer 20 and whose rotation direction is opposite to that of the elliptically polarized light (ii). The elliptically polarized light (v) is given a phase difference of (λ / 2+λ / 4) by the phase difference layer 40, and 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 and becomes a white display.

[0137] (Variation 1 of Implementation Example 2) In Embodiment 2, the structure in which the first electrode 121 as the lower electrode is the common electrode CE and the second electrode 122 as the upper electrode is the pixel electrode PE is described. However, conversely, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE and the first electrode 121 (lower electrode) is the pixel electrode PE (see Fig.21 ).

[0138] Fig.21 is a cross-sectional schematic diagram showing the liquid crystal display device 1 of this example in more detail. In this example, from the viewpoint of easy generation of a lateral electric field, at least the upper electrode (the common electrode CE in this example) is preferably a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this variation is particularly suitable as a relatively high-definition liquid crystal display device as described above, i.e., a liquid crystal display device with a relatively small area of ​​pixel P.

[0139] (Implementation method 3) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiments 1 and 2 is omitted. In embodiments 1 and 2, the reflective liquid crystal display device is described as an example, but in this embodiment, a semi-transmissive liquid crystal display device is described. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 2 in that a light source is provided on the back side relative to the liquid crystal layer 20.

[0140] Fig. 22 2 is a schematic cross-sectional view of the 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 source) on the back side of the liquid crystal layer 20. In addition, it is preferred to further include a polarizing plate 50' and a phase difference layer 40'. More preferably, as Fig. 22 As shown, from the back side, a light source 61, a polarizing plate 50', a retardation layer 40', a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40 and a polarizing plate 50 are provided in order. In this embodiment, the first substrate 10 is preferably a TFT substrate.

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

[0142] The polarizing plate 50' is arranged on the back side of the liquid crystal layer 20. More specifically, it is arranged on the back side of the first substrate 10. The polarizing plate 50' can be a circular polarizing plate or a linear polarizing plate, preferably a linear polarizing plate. In addition, it can be an absorption type polarizing plate or a reflection type polarizing plate, but preferably an absorption type polarizing plate. In particular, it is preferable to use an absorption type linear polarizing plate.

[0143] The polarization axis of the polarizing plate 50' may be arranged substantially orthogonal to the polarization axis of the polarizing plate 50, or may be arranged substantially parallel to the polarization axis of the polarizing plate 50. That is, the polarizing plate 50' may be arranged in a cross-Nicol arrangement or a parallel-Nicol arrangement with the polarizing plate 50. Among them, the cross-Nicol arrangement is preferred.

[0144] The phase difference layer 40' is arranged between the polarizing plate 50' and the liquid crystal layer 20. More specifically, it is arranged between the polarizing plate 50' and the first substrate 10. The phase difference layer 40' may include, for example, a λ / 4 plate and a λ / 2 plate. The arrangement order thereof is preferably, for example, λ / 2 plate and λ / 4 plate are arranged in order from the back side.

[0145] In the liquid crystal display device 1 of the present embodiment, each pixel P has a reflective region Rf for displaying in a reflective mode and a transmissive region Tr for displaying in a transmissive mode (see FIG. Fig.23 ). Fig.23 The schematic plan view conceptually shows that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of the present embodiment. A reflective layer 130 (for example, see Figure 2 ), but the reflective layer 130 is not configured in the transmission region Tr. The proportion of the area of ​​the transmission region Tr in each pixel P can be appropriately set according to the purpose, for example, preferably more than 20% and less than 90%. In addition, the position and shape of the transmission region Tr in the pixel P can also be appropriately set according to the purpose, etc.

[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 liquid crystal layer 20 displays in a transverse electric field mode in which a twisted orientation is exhibited when no voltage is applied, thereby being able to sufficiently improve the contrast ratio of the reflective display. Therefore, the liquid crystal display device 1 of this embodiment can also achieve low cost and improve the contrast ratio, and is also useful as an embedded touch panel capable of displaying in a reflective mode.

[0147] (Implementation 4) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiment 1 is omitted. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 1 in that a light source is provided on the observation surface side relative to the liquid crystal layer 20. In addition, the liquid crystal display device of this embodiment is a reflective liquid crystal display device.

[0148] Fig.24 is a schematic cross-sectional view of the 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 source) on the observation side relative to the liquid crystal layer 20. More preferably, Fig.24As shown, the embodiment includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40, a polarizing plate 50, and a light source 62. In this embodiment, the first substrate 10 is preferably a TFT substrate.

[0149] The light source 62 (front light source) is not particularly limited as long as it is a light source that irradiates light. Specifically, for example, a light source such as a light emitting diode (LED) and a light guide plate are preferably provided. The reflective liquid crystal display device 1 further includes the light source 62, thereby enabling bright reflective display even in an environment where the ambient light cannot be fully obtained.

[0150] As mentioned above, although embodiment of this invention is described, each matter described is applicable to the whole present invention.

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

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

[0153] [Table 1]

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

[0155] In this example, the liquid crystal display device 1 of Embodiment 2 is assumed as an FFS mode liquid crystal display device. Fig.25 A schematic cross-sectional view of the liquid crystal display device 1 of this example is shown in , and the specific optical setting contents are shown in Table 2. The angles of each axis are the angles of each axis when no voltage is applied, with the direction parallel to the gate wiring GL as a reference (0°), the clockwise rotation angle as a positive angle (+), and the counterclockwise rotation angle as a negative angle (-). In addition, in Table 2 (and Table 4 and Table 7), PI refers to the polyimide film used as the horizontal orientation film 140, 340. As the liquid crystal layer 20, a liquid crystal layer with a single domain structure for normally black display is assumed, and a positive liquid crystal material de5 is used as a liquid crystal material constituting the liquid crystal layer 20. The twist angle θ1 is set to 78° to 90°, and the VR curve and response characteristics are studied by simulation software. The results are shown in Table 3.

[0156] [Table 2]

[0157] [Table 3]

[0158] In Table 3, "maximum reflectivity voltage" and "maximum reflectivity orientation" refer to the voltage and orientation state when the reflectivity shows the maximum value. The reflectivity here refers to the reflectivity of white display (also called white reflectivity). In the "maximum reflectivity orientation" column, PT refers to positive twist orientation and RT refers to reverse twist orientation. The values ​​recorded in the "response characteristics" column are the values ​​when the response speed (tr, td; both in msec) of, for example, 1-3 (twist angle 83°) is set to 100%.

[0159] According to Table 3, the torsion angle θ1 is above 83° and becomes a reverse twist orientation. It can also be seen that the voltage indicating the maximum reflectivity is less than 5V, which is an example of a torsion angle of 83° or more. Therefore, the torsion angle is preferably above 83°. In addition, it can be seen that when the torsion angle is below 87°, the response characteristic is controlled within 105% when the case of a torsion angle of 83° is set to 100%. This range is a range that can be allowed even if product deviations occur when production is completed. Therefore, the torsion angle is preferably below 87°. In this way, from the viewpoint of maximum reflectivity, maximum reflectivity voltage and response characteristics, it can be seen that the torsion angle is particularly preferably above 83° and below 87°, and most preferably 83°.

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

[0161] In this example as well, the liquid crystal display device 1 according to the second embodiment is assumed to be a FFS mode liquid crystal display device. Fig.25 The cross-sectional schematic diagram of the liquid crystal display device 1 of this example is shown in FIG. 4, and the specific optical setting contents are shown in Table 4. As the liquid crystal layer 20, a liquid crystal layer with a single domain structure for normally black display is assumed, and as the liquid crystal material constituting the liquid crystal layer 20, positive liquid crystal materials de5, de6, de7, de10 or de15 are used. The VR curve is calculated by simulation software and analyzed. The results are shown in FIG. Figure 26 to Figure 29 As shown in Table 5.

[0162] [Table 4]

[0163] [Table 5]

[0164] Fig.26is a graph showing the reflection mode efficiency when various liquid crystal materials are used. Fig.26 In the above table, the horizontal axis is the voltage applied to the liquid crystal layer 20 (V), and the vertical axis is the reflection mode efficiency (%). The obtained curve is called VR curve. Fig.26 In Table 5, "VRmax" refers to the voltage at which the reflection mode efficiency shows a maximum value, and "Rmax" refers to the maximum value of the reflection mode efficiency.

[0165] Fig. 27 is to focus on the liquid crystal director when voltage is applied. Fig.26 The VR curve shown in FIG. 1 is analyzed to obtain a graph (called reflectivity distribution). The reflectivity distribution under the voltage (i.e., VRmax) when the reflective mode efficiency shows the maximum value is analyzed, and it is found that the larger Δε is, the lower the reflectivity of the central portion between the first electrode 121 (CE) and the second electrode 122 (PE) is (refer to FIG. Fig. 27 ). In order to examine the reasons for the highs and lows in the reflectivity distribution, the average azimuth angle ΦLCave and polar angle of the liquid crystal molecules at VRmax were analyzed (see Fig.28 ).

[0166] Fig.28 is the reflectivity distribution under VRmax (cross-sectional view). The vertical axis represents the distance in the thickness direction (also called the Z direction) of the liquid crystal layer 20 from the first substrate 10 (the closer to the top of the figure, the greater the distance, which means the closer to the second substrate 30). Fig.28 , the average value of the liquid crystal director in the thickness direction was analyzed. Specifically, the liquid crystal display device 1 of this example is in FFS mode (lateral electric field), so the azimuth angle of the liquid crystal molecule 21 was analyzed. The results are as follows Fig.29 shown. Fig.29 is the analysis result of the average azimuth angle ΦLCave of the liquid crystal molecules in the Z direction. Fig.29 In FIG. 5 , the vertical axis represents the average azimuth angle ΦLCave of the liquid crystal molecules 21 .

[0167] In particular, according to Fig. 27 as well as Fig.29 , the following matters were determined. First, it can be seen that the average azimuth angle ΦLCave is different depending on whether the Δε of the liquid crystal molecules is less than 7 or more than 7. In addition, the example in which the white reflectivity is high and the reflectivity distribution is close to uniform is the example in which the liquid crystal material with Δε less than 7 is used. In this case, the average azimuth angle is about 150°, and the orientation of the liquid crystal molecules is close to homogeneous. That is, in these examples, the reverse twist orientation is obtained (see Fig. 9B). In contrast, examples where the white reflectivity is low and the reflectivity distribution has highs and lows and is uneven are examples where a liquid crystal material with Δε exceeding 7 is used. In this case, the average azimuth angle ΦLCave is about 90°, and the orientation of the liquid crystal molecules is further twisted. That is, in these examples, the orientation becomes positive twisted (see Fig. 11B ).

[0168] The above results are summarized in Table 6. In Examples 2-6, as reference examples, simulation results are also recorded for using a negative liquid crystal material instead of a positive liquid crystal material as a liquid crystal material. Fig.30 Shown in Fig.26 A graph of the VR curve of Example 2-6 (ie, the VR curve when a negative liquid crystal material (de-5) is used) is added to the graph of .

[0169] [Table 6]

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

[0171] From Table 6, the following can be known. In the example using a positive liquid crystal material, in Examples 2-3 to 2-5 using a liquid crystal material with a Δε greater than 7, a positive twist orientation is achieved when a white voltage is applied, and the maximum reflectivity (Rmax) is 32.8 to 36.7%. In Example 2-6 using a negative liquid crystal material, a reverse twist orientation is achieved, and the maximum reflectivity (Rmax) is 37.4%, which is a high reflectivity compared to Examples 2-3 to 2-5. Further analysis shows that in the example using a positive liquid crystal material with a Δε of less than 7 such as Examples 2-1 and 2-2, a reverse twist orientation is achieved, and the maximum reflectivity (Rmax) is higher than that of Example 2-6 using a negative liquid crystal material. In addition, in general, when the absolute value of Δε is less than 2, there is no dielectric anisotropy, so the lower limit value of Δε is particularly preferably greater than 3.

[0172] However, from the perspective of further realizing the low power consumption that is an advantage of the reflective type, it is preferred that the driving voltage (white voltage) be less than 5V. However, the negative liquid crystal material cannot structurally increase the polar component Δε compared to the positive liquid crystal material, and it is unrealistic to make the absolute value of Δε be, for example, greater than 7. Even if a liquid crystal material with a high Δε such as Δε=-7 is used, there will be a compromise problem such as a delay in response speed due to the increased viscosity of the liquid crystal layer, or a decrease in VHR due to the easy mixing of impurity ions. On the other hand, in the example of using a positive liquid crystal material with a Δε of less than 7 such as Examples 2-1 and 2-2, the driving voltage can be made less than 5V, and low power consumption can be achieved.

[0173] Therefore, from the viewpoint of achieving a driving voltage lower than 5V, obtaining a high reflectivity compared to the case of using a negative liquid crystal material, and realizing reverse twist orientation, it is found that Δε of the liquid crystal material is particularly preferably greater than 3 and less than 7. In addition, it is also found that the average azimuth angle ΦLCave of the liquid crystal molecules in the reverse twist orientation when a positive liquid crystal material is used is particularly preferably greater than 151° and less than 154°.

[0174] (Verification Example 3: Example 3-1 to Example 3-11) According to Verification Example 2, further improvement of the white reflectance is due to reverse twist alignment during white display. Therefore, in this example, the physical properties of the liquid crystal material were further investigated.

[0175] In this example as well, it is assumed that the liquid crystal display device 1 according to the second embodiment is a FFS mode liquid crystal display device. Fig.25 , and the specific optical setting contents are shown in Table 7. As the liquid crystal layer 20, a liquid crystal layer that performs normally black display with a single domain structure is assumed, and a positive liquid crystal material or a negative liquid crystal material is used as a liquid crystal material constituting the liquid crystal layer 20. VR curves were calculated and analyzed using simulation software.

[0176] [Table 7]

[0177] It is believed that when a white voltage is applied, the orientation of the liquid crystal director is affected by Δε and the torsional elastic constant K 22 The torque balance will be different. Therefore, we focus on Δε or K 22 The results of the analysis focusing on the difference in Δε are shown in Table 8. 22 The results after analysis are shown in Table 9.

[0178] [Table 8]

[0179] [Table 9]

[0180] According to Tables 8 and 9, it can be seen that when a positive liquid crystal material is used, the reverse twist orientation is achieved, and a higher white reflectance is shown when Δε is 7 or less and K is 0. 22 In the example of 6 or less. In addition, when the absolute value of Δε is less than 2, the optical change caused by the liquid crystal and the dielectric anisotropy is slight, and a high voltage may be formed. Therefore, the lower limit of Δε is preferably 3 or more.22 When the absolute value of K is less than 2, the response characteristic may rise later. 22 The lower limit of is particularly preferably 3 or more.

[0181] In summary, it can be seen that in order to achieve reverse twist orientation using a positive liquid crystal material, the Δε of the liquid crystal material is preferably greater than 3 and less than 7. 22 It is particularly preferably 3 or more and 6 or less. It is also 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 main reason for the positive twist orientation or the reverse twist orientation is considered to be that the behavior of the liquid crystal molecules is different depending on whether the equipotential line reaches the opposite substrate (second substrate 30) near the threshold voltage. Therefore, the retardation dΔn of the liquid crystal layer 20 is fixed, and it is studied whether the example with a large cell thickness and the example with a small cell thickness has a reverse twist orientation, and the physical properties of the liquid crystal material in each example are studied.

[0183] In this example as well, it is assumed that the liquid crystal display device 1 according to the second embodiment is a FFS mode liquid crystal display device. Fig.25 , and the specific optical setting contents (same as those in Verification Example 3) are shown in Table 7. As the liquid crystal layer 20, a liquid crystal layer that performs normally black display with a single domain structure is assumed, and a positive liquid crystal material is used as a liquid crystal material constituting the liquid crystal layer 20. VR curves were calculated and analyzed using simulation software.

[0184] As an example of a large cell thickness, for example, Table 10 shows the results of analyzing an example in which the cell thickness is d=4.05 μm and the birefringence Δn of the liquid crystal material is 0.06. In addition, as an example in which the cell thickness is small, Table 11 shows the results of analyzing an example in which the cell thickness is d=2.70 μm and the birefringence Δn of the liquid crystal material is 0.09.

[0185] [Table 10]

[0186] [Table 11]

[0187] According to Tables 10 and 11, it can be seen that the reverse twist orientation can be achieved using positive liquid crystal materials in Examples 4-6 to 4-10, which are examples with a small cell thickness (d = 2.70 μm), and among them, the high reflectivity is achieved in Examples 4-7 to 4-10, where Δε is 15 or less, compared with the case where a negative liquid crystal material is used (for example, refer to Examples 2-6 and 3-6, etc.). In Examples 4-1 to 4-5, which are examples with a large cell thickness (d = 4.05 μm), regardless of the value of Δε, positive twist orientation is achieved, and it can also be seen that when Rmax is low or VRmax is 5V or more, it becomes a high voltage compared with the case where a negative liquid crystal material is used.

[0188] Therefore, from the viewpoint of being able to achieve reverse twist orientation and obtaining a high reflectivity compared to the case of using a negative liquid crystal material, it is known that the birefringence Δn of the liquid crystal material is particularly preferably 0.077 or more and 0.09 or less. In addition, the average azimuth angle ΦLCave of the liquid crystal molecules is preferably 150° or more and 156° or less, more preferably 150° or more and 155° or less, and most preferably 151° or more and 153° or less.

[0189] From Tables 8 to 11, it can be seen that when the angle θa of the orientation direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied is 80°, the dielectric anisotropy Δε, birefringence Δn and torsional elastic constant K of the liquid crystal material are 22 The most preferred values ​​are 3≦Δε≦7, 0.077≦Δn≦0.09, and 3≦K. 22 ≦6. It was also found that the most preferred average azimuth angle ΦLCave of the liquid crystal material is 151°≦ΦLCave≦153°.

[0190] (Verification Example 5: Example 5-1 to Example 5-6) Next, the preferred range of the twist angle θ1 was examined when the angle θa of the alignment direction a of the liquid crystal molecules 21A when no voltage was applied was 83°.

[0191] In this example, in addition to setting θa to 83°, the same conditions as those in Verification Example 1 (see Table 2 above) were set, and the VR curve and response characteristics were studied using simulation software. The results are shown in Table 12. For reference, the results of Examples 1-3 are also recorded. The values ​​recorded in the "Response Characteristics" column are the values ​​when the response speeds in Examples 1-3 (torsion angle 83°) are set to 100%.

[0192] [Table 12]

[0193] According to Table 12, when θa is 83°, the reverse twist orientation is obtained within the entire range of the calculated twist angle θ1 (78° to 90°), and the voltage indicating the maximum reflectivity is less than 5V. Among them, from the viewpoints of maximum reflectivity, maximum reflectivity voltage, and response characteristics, it can be seen that the twist angle θ1 is particularly preferably 78° to 88°, more preferably 83° to 87°, and most preferably 83°. In addition, compared with the example where θa is 83° (Example 5-1 to Example 5-5), the maximum reflectivity voltage of the example where θa is 80° (Example 1-3) is lower. Therefore, from the viewpoint of being able to further achieve low power consumption, θa is also preferably 80° compared to 83°.

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

[0195] In this example, the same conditions as those in Verification Example 3 (see Table 7 above) were set except that θa 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, and the results of the analysis focusing on the difference in K 22 The results of the analysis of the differences are shown in Table 14.

[0196] [Table 13]

[0197] [Table 14]

[0198] According to Table 13 and Table 14, from the viewpoint of being able to achieve reverse twist orientation and obtaining a higher reflectivity than when using a negative liquid crystal material, it can be seen that Δε of the liquid crystal material is preferably 3 or more and 15 or less, and most preferably 3 or more and 10 or less, and K of the liquid crystal material is 22 It is particularly preferably 3 or more and 5 or less. It is also 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, in the case where θa was 83°, the physical properties of the liquid crystal material were further examined in the same manner as in the above-mentioned Verification Example 4.

[0200] In this example, except that θa was set to 83°, the same conditions as those of Verification Example 4 (see Table 7 above) were set, and the VR curve was calculated by simulation software and analyzed. As an example with a large cell thickness, for example, the results of analyzing an example with a cell thickness of d = 4.05 μm and a birefringence index Δn of the liquid crystal material of 0.06 are shown in Table 15. In addition, as an example with a small cell thickness, for example, the results of analyzing an example with a cell thickness of d = 2.70 μm and a birefringence index Δn of the liquid crystal material of 0.09 are shown in Table 16.

[0201] [Table 15]

[0202] [Table 16]

[0203] According to Tables 15 and 16, from the viewpoint of being able to achieve reverse twist orientation and obtaining a high reflectivity compared to the case of using a negative liquid crystal material, it can be seen that the birefringence Δn of the liquid crystal material is particularly preferably 0.06 or more and 0.09 or less. In addition, it is also found that the average azimuth angle ΦLCave of the liquid crystal molecules is particularly preferably 151° or more and 156° or less.

[0204] From Tables 13 to 16, it can be seen that when the angle θa of the orientation direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied is 83°, the dielectric anisotropy Δε, birefringence Δn and torsional elastic constant K of the liquid crystal material are 22 The most preferred values ​​are 3≦Δε≦10, 0.06≦Δn≦0.09, and 3≦K. 22 ≦5. It was also found that the most preferred average azimuth angle ΦLCave of the liquid crystal material is 151°≦ΦLCave≦156°.

[0205] (Verification Example 8: Example 8-1 to Example 8-5) Black display is achieved by compensating the λ / 4 condition determined by the delay 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) or the twist orientation with a phase difference layer. However, the birefringence Δn of the liquid crystal material has a temperature characteristic that Δn becomes smaller if the temperature rises. Usually, in the display mode that uses a phase difference layer to compensate for the delay of the liquid crystal layer to display black, in order to improve the temperature characteristics of Δn, most of them deal with it by increasing the Tni (nematic-isotropic phase transition temperature) of the liquid crystal material (for example, OCB method (Optically Compensated Bend Mode: optically compensated bend mode)). However, if Tni is increased, sometimes the elastic constant also increases in conjunction with it. In this case, there is a concern that the VT and VR curves will be high voltage. In order to improve this situation, measures such as increasing Δε are also considered, but if Δε is increased, the viscosity increases, so the response becomes slower, and therefore, sometimes the optical characteristics of the display are not optimal. Therefore, the inventors of the present invention focused on the ratio of the birefringence Δn60 at 60°C to the birefringence Δn20 at 20°C (Δn60 / Δn20) to improve the temperature characteristics of Δn of various liquid crystal materials while minimizing the increase in Tni of the liquid crystal material. The results are shown in Figure 31 to Figure 34 And Table 17. The configuration of the liquid crystal display device other than the liquid crystal material, optical settings, etc. were the same as those of Verification Example 5. That is, the conditions were the same as those of Verification Example 1 (see Table 2 above) except that θa was set to 83°.

[0206] [Table 17]

[0207] Fig.31 This is a graph that studies the temperature characteristics of Δn of various liquid crystal materials. In this graph, for each liquid crystal material, the birefringence Δn20 at 10°C, 20°C, 30°C, 40°C, 50°C, and 60°C is plotted. The horizontal axis is temperature, and the vertical axis is birefringence Δn (wherein the birefringence Δn20 at 20°C is set to 1). The birefringence Δn is the value at a wavelength of 550nm.

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

[0209] Fig.33This is a graph that studies the temperature dependence of the reflective mode efficiency in black 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 black display (i.e., no voltage applied).

[0210] Fig.34 This is a graph that studies the temperature dependence 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 (5V applied).

[0211] Considering that the actual use temperature range of the liquid crystal panel is 50° C. or less, the presence or absence of black floating at 50° C. is also evaluated in Table 17. The black floating is evaluated as follows. (Evaluation method) The black display state of each produced liquid crystal display device when heated to 50° C. was actually observed visually and evaluated according to the following criteria: ○: No problem in actual use. ×: Contrast ratio decreased after heating, and commercial quality was insufficient.

[0212] According to Table 17 and Figure 31 to Figure 34 It is known that if the ratio of the birefringence Δn60 at 60°C to the birefringence Δn20 at 20°C (Δn60 / Δn20) is 0.84 or more, a display without black floating at 50°C, i.e., without temperature change at 50°C, which is a general practical use temperature, can be obtained. In addition, the inventors have confirmed that the above ratio (Δn60 / Δn20) is 1.1 or less without a significant decrease in contrast.

[0213] The various aspects of the present invention described above may be appropriately combined within the scope not departing from the gist of the present invention. Description of Reference Numerals

[0214] 1: Liquid crystal display device 1X: LCD panel 10, 30: substrate 20: Liquid crystal layer 21, 21A, 21B: Liquid crystal molecules 40, 40': Phase difference layer 41: λ / 4 plate 42: λ / 2 plate 41SA, 42SA: In-plane hysteresis axis 50, 50': polarizing plate 50AA: Polarization axis 61, 62: Light source 100, 300: Support substrate 110: TFT 121, 122: Electrode 130: Reflective layer 140, 340: horizontal orientation film 150, 151, 152: Insulating film (insulating layer) 153: Dielectric layer 160: Contact electrode 310: Color filter layer BP: Baseboard Circuit CE: Common Electrode PE: Pixel electrode CH1, CH2: contact holes DR: Display Region FR: Hidden Area GL: Gate wiring SL: Source wiring EF: Transverse electric field p: convex part P: Pixel Rf: Reflection area Tr: Transmission area Sl: Slit SP: Strip TC: Touch wiring contact TD: Touch driver TL, TL1, TL2: Touch wiring TX: Touch sensor electrode

Claims

1. A liquid crystal display device, characterized in that: have: a first substrate; a second substrate, which is opposite to the first substrate; and a liquid crystal layer disposed between the first substrate and the second substrate, The liquid crystal display device has a plurality of pixels. The first substrate includes: a reflective layer for reflecting light, a first electrode and a second electrode capable of generating a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer. The electrode disposed on the liquid crystal layer side of the first electrode and the second electrode has a plurality of strip-shaped portions and a slit located between two adjacent strip-shaped portions among the plurality of strip-shaped portions. The plurality of strip-shaped portions include straight lines that are substantially parallel to each other and extend in the same direction. The liquid crystal layer is composed of a liquid crystal material including 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 adopts a twisted orientation when no voltage is applied, and the twist angle when no voltage is applied is greater than 78° and less than 90°. When the liquid crystal layer of each pixel is viewed from above when no voltage is applied, at least in the center of the plane direction of the liquid crystal layer, the extension direction of the plurality of strip-shaped portions is located between the long axis direction of the liquid crystal molecules on the first substrate side and the long axis direction of the liquid crystal molecules on the second substrate side. When the liquid crystal layer of each pixel is viewed from above, liquid crystal molecules in at least the center portion in the thickness direction of the liquid crystal layer rotate in the twisting direction when a voltage is applied, as compared to the twisting direction when no voltage is applied.

2. The liquid crystal display device according to claim 1, wherein: A product of a thickness d of the liquid crystal layer and a birefringence Δn of the liquid crystal material (dΔn) is greater than or equal to 236 nm and less than or equal to 252 nm.

3. The liquid crystal display device according to claim 1 or 2, characterized in that: The torsion angle when no voltage is applied is not less than 83° and not more than 87°.

4. The liquid crystal display device according to any one of claims 1 to 3, characterized in that: The average azimuth angle ΦLCave of the liquid crystal molecules when a voltage is applied is greater than or equal to 150° and less than or equal to 156°.

5. The liquid crystal display device according to any one of claims 1 to 4, characterized in that: The ratio of the birefringence Δn60 of the liquid crystal material at 60° C. to the birefringence Δn20 at 20° C. (Δn60 / Δn20) is 0.84 or more.

6. The liquid crystal display device according to any one of claims 1 to 5, characterized in that: The dielectric anisotropy Δε of the liquid crystal material is 7 or less.

7. The liquid crystal display device according to any one of claims 1 to 6, characterized in that: Further possesses: a polarizing plate disposed on an outer side of the first substrate and / or the second substrate; and a phase difference layer, which is arranged between the first substrate and the polarizing plate and / or between the second substrate and the polarizing plate; The phase difference layer includes a λ / 4 plate and a λ / 2 plate.

8. The liquid crystal display device according to any one of claims 1 to 7, characterized in that: The liquid crystal display device is of single domain orientation.

9. The liquid crystal display device according to any one of claims 1 to 8, characterized in that: Display in normally black mode.

10. The liquid crystal display device according to any one of claims 1 to 9, characterized in that: 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 capable of functioning as touch sensor electrodes. The first substrate has a plurality of touch wirings respectively connected to the corresponding touch sensor electrodes.

11. The liquid crystal display device according to any one of claims 1 to 10, characterized in that: It also has a light source.

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