Semi-transmissive liquid crystal display device

Abstract

To provide a semi-transmissive liquid crystal display device that can be manufactured at a low cost, has excellent viewing angle characteristics, and is useful also as an in-cell type touch panel.SOLUTION: A semi-transmissive liquid crystal display device has a plurality of pixels, and comprises a first polarizing plate, a first phase difference layer, a first substrate, a liquid crystal layer, a second substrate, a second phase difference layer, and a second polarizing plate. The first substrate has a reflecting layer, a pair of electrodes that can generate a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer. The second substrate has a second horizontal alignment film in contact with the liquid crystal layer. The first phase difference layer includes a first λ / 2 plate, and a first λ / 4 plate. The second phase difference layer includes a second λ / 2 plate, and a second λ / 4 plate. At least one of the first phase difference layer and the second phase difference layer further includes a positive C-plate. The liquid crystal layer takes twist alignment when no voltage is applied. The pixels each have a reflecting area for reflecting light on the reflecting layer to perform display, and a transmission area for transmitting light to perform display.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] Liquid crystal display devices can also be broadly classified according to the driving method of the liquid crystal. For example, there are a vertical electric field type in which a liquid crystal layer is driven by an electric field in a direction substantially perpendicular to the substrate surface to perform display, and a horizontal electric field type in which a liquid crystal layer is driven by an electric field in a direction substantially parallel to the substrate surface to perform display. Examples of the vertical electric field type include the Twisted Nematic (TN) mode and the Multi-domain Vertical Alignment (MVA) mode, while examples of the horizontal electric field type include the In-plane Switching (IPS) mode and the Fringe Field Switching (FFS) mode. Patent Documents 1 to 3 disclose transflective liquid crystal display devices using the horizontal electric field type. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-126551 A [Patent Document 2] JP 2005-338256 A [Patent Document 3] JP 2005-338264 A Summary of the Invention [Problem to be solved by the invention]

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

[0006] Built-in touch panels are classified into on-cell type and in-cell type. The term "cell" refers to a display panel (also called a liquid crystal panel) that includes an active matrix substrate, typically a thin film transistor (TFT) substrate, an opposing substrate arranged to face the active matrix substrate, and a liquid crystal layer disposed between the substrates. In general, in the in-cell type, a layer that performs the touch sensor function is disposed within the display panel, while in the on-cell type, a layer that performs the touch sensor function is disposed between the display panel and a polarizing plate provided on the viewing surface side of the display panel. Of these, the in-cell type can, in principle, realize the thinnest and lightest touch panel.

[0007] The present inventors have therefore investigated liquid crystal display devices that can be used as in-cell touch panels, and have found that in environments with high illuminance (i.e., bright environments) such as outdoors under direct sunlight, the luminance of a transmissive liquid crystal display device is insufficient and visibility is poor, whereas the visibility of a reflective liquid crystal display device is good (see FIG. 36A). In environments with low illuminance (i.e., dark environments) such as indoors or at night, the reflective liquid crystal display device is darker and visibility is poorer than that of a transmissive liquid crystal display device (see FIG. 36B). FIG. 36A shows observation photographs of images displayed on the transmissive liquid crystal display device 1T and the reflective liquid crystal display device 1R outdoors under direct sunlight (illuminance was about 70,000 lx). It can be seen that the visibility of the transmissive liquid crystal display device 1T is poor, whereas the visibility of the reflective liquid crystal display device 1R is good. FIG. 36B shows observation photographs of images displayed on the transmissive liquid crystal display device 1T and the reflective liquid crystal display device 1R indoors (illuminance was about 1,000 lx). It can be seen that the transmissive liquid crystal display device 1T has good visibility, whereas the reflective liquid crystal display device 1R has poor visibility.

[0008] On the other hand, the researchers also noted that an in-cell touch panel capable of displaying in reflective mode has not yet been realized, and believed that the reason for this is that in current reflective LCD devices, one of a pair of electrodes for applying voltage to the liquid crystal layer (also called the opposing electrode or common electrode) is arranged on the opposing substrate side.

[0009] Therefore, in order to ensure good visibility in all environments, we focused on semi-transmissive liquid crystal display devices, and in particular, we conducted extensive research into transverse electric field semi-transmissive liquid crystal display devices in which a pair of electrodes are provided only on one of the substrates. However, conventional devices (see, for example, Patent Documents 1 to 3) had problems, particularly with viewing angle characteristics. We also considered using special optical films to configure the device, but in that case, we were unable to achieve cost reduction.

[0010] The present invention has been made in consideration of the above-mentioned current situation, and has an object to provide a semi-transmissive liquid crystal display device that is low-cost, has excellent viewing angle characteristics, and is also useful as an in-cell touch panel. [Means for solving the problem]

[0011] (1) One embodiment of the present invention is a liquid crystal display device having a plurality of pixels, the liquid crystal display device comprising, in order from a rear surface side to an observation surface side, a first polarizing plate, a first retardation layer, a first substrate, a liquid crystal layer, a second substrate, a second retardation layer, and a second polarizing plate, the first substrate having a reflective layer, a pair of electrodes capable of generating a transverse electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, the first retardation layer includes a first λ / 2 plate and a first λ / 4 plate, the second retardation layer includes a second λ / 2 plate and a second λ / 4 plate, at least one of the first retardation layer and the second retardation layer further includes a positive C plate, the liquid crystal layer has a twisted orientation when no voltage is applied, and each pixel has a reflective region that reflects light by the reflective layer to perform display, and a transmissive region that transmits light to perform display.

[0012] (2) Moreover, an embodiment of the present invention is a semi-transmissive liquid crystal display device having the configuration as described above in (1), wherein the liquid crystal layer contains a liquid crystal material having a positive dielectric anisotropy.

[0013] (3) According to another embodiment of the present invention, in addition to the configuration of (1) or (2) above, a semi-transmissive liquid crystal display device satisfies any one of the following (i) to (iii): (i) The second retardation layer includes one positive C plate, and the first retardation layer does not include a positive C plate. (ii) The first retardation layer and the second retardation layer each include one of the positive C plates. (iii) The first retardation layer and the second retardation layer each include two of the positive C plates.

[0014] (4) Furthermore, in an embodiment of the present invention, in addition to the configuration of (1), (2), or (3), the first λ / 2 plate and the first λ / 4 plate are positioned in this order from the rear surface side, the second λ / 2 plate and the second λ / 4 plate are positioned in this order from the observation surface side, the first λ / 2 plate and the second λ / 2 plate have approximately the same in-plane retardation Re, and the first λ / 4 plate and the second λ / 4 plate have approximately the same in-plane retardation Re.

[0015] (5) Furthermore, an embodiment of the present invention is a semi-transmissive liquid crystal display device, in which, in addition to the configuration of (1), (2), (3), or (4), the positive C plate is located between the first λ / 2 plate and the first λ / 4 plate, and / or between the second λ / 2 plate and the second λ / 4 plate.

[0016] (6) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), or (5), the positive C plate has an absolute value of a thickness direction retardation Rth (nm) of 150 to 270 nm.

[0017] (7) Furthermore, in an embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), or (6), the retardation layer further includes a second positive C plate, and the second positive C plate is located between the first λ / 2 plate and the first polarizing plate, and between the second λ / 2 plate and the second polarizing plate.

[0018] (8) Furthermore, in accordance with another embodiment of the present invention, in addition to the configuration (7), the second positive C plate has a thickness direction retardation Rth (nm) whose absolute value is 50 to 130 nm.

[0019] (9) Furthermore, one embodiment of the present invention is a semi-transmissive liquid crystal display device having the configuration as described above in (1), (2), (3), (4), (5), (6), (7), or (8), wherein the twist angle of the liquid crystal layer when no voltage is applied is 70° or more and 85° or less.

[0020] (10) Furthermore, an embodiment of the present invention is a semi-transmissive liquid crystal display device, in which, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), or (9), the product (dΔn) of the thickness d of the liquid crystal layer and the birefringence Δn of a liquid crystal material constituting the liquid crystal layer is 218 nm or more and 255 nm or less.

[0021] (11) Furthermore, in an embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9) or (10), a semi-transmissive liquid crystal display device is configured such that, when the alignment direction of liquid crystal molecules defined by the first horizontal alignment film is taken as a reference (0°) and the twist direction is taken as a positive angle, the polarization axis of the first polarizing plate, the in-plane slow axis of the first λ / 2 plate, and the in-plane slow axis of the first λ / 4 plate are positioned at angles of -6.6 to 1.4°, 70.9 to 74.9°, and 10.0 to 17.8°, respectively.

[0022] (12) Furthermore, in an embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10) or (11), a semi-transmissive liquid crystal display device is configured such that, when the alignment direction of the liquid crystal molecules defined by the first horizontal alignment film is taken as the reference (0°) and the twist direction is taken as a positive angle, the polarization axis of the second polarizing plate, the in-plane slow axis of the second λ / 2 plate, and the in-plane slow axis of the second λ / 4 plate are positioned at angles of -70.5° to -63.5°, -52.5° to -47.5°, and -27.9° to -22.9°, respectively.

[0023] (13) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11) or (12), at least one of the pair of electrodes has a plurality of strip portions and a slit located between two adjacent strip portions among the plurality of strip portions.

[0024] (14) Furthermore, one embodiment of the present invention is a semi-transmissive liquid crystal display device, which has the configuration as described above in (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12) or (13), and further has an alignment direction of liquid crystal molecules determined by the first horizontal alignment film that is in the range of -30° to 30° with respect to the direction in which the multiple strip-shaped portions extend (0°).

[0025] (15) Furthermore, one embodiment of the present invention is a semi-transmissive liquid crystal display device having the configuration described above in (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13) or (14), and further having a single domain orientation.

[0026] (16) Furthermore, an embodiment of the present invention is a semi-transmissive liquid crystal display device that performs display in a normally black mode in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), or (15) above.

[0027] (17) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15) or (16), one of the pair of electrodes is a pixel electrode provided in each of the plurality of pixels, and the other is a common electrode including a plurality of segments each capable of functioning as a touch sensor electrode, and the first substrate has a plurality of touch wirings each connected to a corresponding one of the touch sensor electrodes.

[0028] (18) Furthermore, an embodiment of the present invention is a semi-transmissive liquid crystal display device further comprising a light source in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), or (17). Effect of the Invention

[0029] According to the present invention, it is possible to provide a semi-transmissive liquid crystal display device which is low in cost, has excellent viewing angle characteristics, and is also useful as an in-cell touch panel. [Brief description of the drawings]

[0030] [Figure 1] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. [Diagram 3] FIG. 1 is a schematic plan view of the entire liquid crystal display device 1 as viewed from the observation surface side. [Figure 4] 1 is a schematic plan view conceptually illustrating that each pixel P in a liquid crystal display device 1 has a reflective region Rf and a transmissive region Tr. [Diagram 5] 1 is a diagram for explaining the slit angle of positive type liquid crystal molecules. FIG. [Figure 6] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 7A] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 7B] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 7C] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 7D] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 7E] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 7F] FIG. 2 is a schematic plan view showing a specific example of a pixel. [Figure 8] 1 is a plan view conceptually illustrating the relationship between the major axis directions of liquid crystal molecules 21A in a liquid crystal layer 20 and the optical axes of each optical film in a liquid crystal display device 1 when no voltage is applied. [Figure 9] FIG. 2 is a diagram for explaining the optical axis angle of an optical film. [Figure 10] FIG. 13 is a diagram conceptually showing optical axis settings. [Figure 11] 13 is a graph showing black transmittance mode efficiency. [Figure 12A] 13 is a graph showing black transmittance mode efficiency. [Figure 12B] 13 is a graph showing black transmittance mode efficiency. [Figure 12C] 13 is a graph showing black transmittance mode efficiency. [Figure 13] 2 is a plan view illustrating a schematic arrangement of touch sensor electrodes TX and touch wirings TL included in the liquid crystal display device 1. FIG. [Figure 14] FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. [Figure 15] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Figure 16] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Figure 17] 1 is a schematic cross-sectional view of a liquid crystal display device 1. FIG. [Figure 18A] 1 is a schematic plan view showing the structure of a liquid crystal cell 1100 when viewed from the front. [Figure 18B]18B is a schematic cross-sectional view (cross-sectional view taken along line AA') in FIG. 18A. [Figure 19A] FIG. 1 is a schematic cross-sectional view of a test cell 1000. [Figure 19B] FIG. 2 is a schematic cross-sectional view of a test cell 2000. [Figure 19C] FIG. 3 is a schematic cross-sectional view of a test cell 3000. [Figure 19D] FIG. 4 is a schematic cross-sectional view of a test cell 4000. [Figure 19E] FIG. 5 is a schematic cross-sectional view of a test cell 5000. [Figure 19F] FIG. 6 is a schematic cross-sectional view of a test cell 6000. [Figure 19G] FIG. 7 is a schematic cross-sectional view of a test cell 7000. [Figure 19H] FIG. 8 is a schematic cross-sectional view of a test cell 8000. [Figure 19I] FIG. 9 is a schematic cross-sectional view of a test cell 9000. [Figure 20] FIG. 13 is a diagram showing the results of verification example 1. [Figure 21] FIG. 13 is a diagram showing the results of verification example 1. [Figure 22] FIG. 13 is a diagram showing the results of verification example 1. [Diagram 23] FIG. 13 is a diagram showing the results of verification example 1. [Figure 24] FIG. 13 is a diagram conceptually showing optical axis settings. [Diagram 25] FIG. 13 is a diagram conceptually showing optical axis settings. [Figure 26] FIG. 13 is a diagram conceptually showing optical axis settings. [Figure 27A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 27B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 27C] FIG. 13 is a diagram showing the results of verification example 3. [Figure 28A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 28B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 28C] FIG. 13 is a diagram showing the results of verification example 3. [Figure 29A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 29B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 29C] FIG. 13 is a diagram showing the results of verification example 3. [Figure 30A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 30B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 30C] FIG. 13 is a diagram showing the results of verification example 3. [Diagram 31] This is the original image from the front. [Figure 32A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 32B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 32C] FIG. 13 is a diagram showing the results of verification example 3. [Fig. 32D] FIG. 13 is a diagram showing the results of verification example 3. [Figure 33A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 33B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 33C] FIG. 13 is a diagram showing the results of verification example 3. [Figure 33D] FIG. 13 is a diagram showing the results of verification example 3. [Figure 34A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 34B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 34C] FIG. 13 is a diagram showing the results of verification example 3. [Fig. 34D] FIG. 13 is a diagram showing the results of verification example 3. [Figure 35A] FIG. 13 is a diagram showing the results of verification example 3. [Figure 35B] FIG. 13 is a diagram showing the results of verification example 3. [Figure 35C] FIG. 13 is a diagram showing the results of verification example 3. [Figure 35D] FIG. 13 is a diagram showing the results of verification example 3. [Figure 36A]The photographs are observation photographs taken when images are displayed on a transmissive liquid crystal display device 1T and a reflective liquid crystal display device 1R outdoors under direct sunlight. [Figure 36B] The photographs are observation photographs taken indoors when images are displayed on a transmissive liquid crystal display device 1T and a reflective liquid crystal display device 1R. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0033] The polar angle means the angle between the direction of interest (for example, the measurement direction) and the normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction when the target direction is projected onto the screen of the liquid crystal panel, and is expressed as the angle (azimuth angle) between the target direction and a reference direction. Here, unless otherwise specified, the reference direction (0°) is set to the vertically upward direction (i.e., the upward direction of the y-axis) of the screen of the liquid crystal panel. For angles and azimuth angles, positive angles are counterclockwise from the reference orientation, and negative angles are clockwise from the reference orientation. Both counterclockwise and clockwise refer to the direction of rotation when the LCD panel screen is viewed from the observation side (front). Additionally, angles refer to values ​​measured when the LCD panel screen is viewed in a flat view, and refer to acute angles unless otherwise specified, such as the direction of rotation.

[0034] The axial direction of the optical film means the azimuth of the polarization axis of the polarizing plate if it is a polarizing plate, and the azimuth of the slow axis if it is a retardation layer. The polarization axis of the polarizing plate means the absorption axis if it is an absorption type polarizing plate, and the reflection axis if it is a reflection type polarizing plate. The axial direction of the retardation layer means the azimuth of the in-plane slow axis of the retardation layer unless otherwise specified.

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

[0036] The in-plane phase difference Re is defined as Re = (nx - ny) × d. The thickness direction phase difference Rth is defined as Rth = {nz - (nx + ny) / 2} × d. nx represents the principal refractive index in the slow axis direction in the plane of each retardation layer. ny represents the principal refractive index in the fast axis direction in the plane of each retardation layer. nz represents the principal refractive index in the direction perpendicular to the plane of each retardation layer. The slow axis direction is the azimuth in which the refractive index is maximum, and the fast axis direction is the azimuth in which the refractive index is minimum. d indicates the thickness of the retardation layer.

[0037] An A plate is a retardation plate that satisfies "nx > ny ≒ nz". Among C plates, a positive C plate (also referred to as +C-plate) is a retardation plate that satisfies "nz > nx ≒ ny", and Rth shows a positive value. A negative C plate (also referred to as -C-plate) is a retardation plate that satisfies "nz < nx ≒ ny", and Rth shows a negative value.

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

[0039] "Approximately parallel" means that the angle (absolute value) between the two is within the range of 0°±10°, and this angle is preferably within the range of 0°±5°, and more preferably 0° (i.e., parallel in the narrow sense). "Approximately perpendicular" (or approximately perpendicular) means that the angle (absolute value) between the two is within the range of 90°±10°, and this angle is preferably within the range of 90°±5°, and more preferably 90° (i.e., orthogonal or perpendicular in the narrow sense).

[0040] A semi-transmissive liquid crystal display device (also simply referred to as a "liquid crystal display device") according to an embodiment of the present invention will be described below. The present invention is not limited to the contents described in the following embodiment, and appropriate design changes can be made within the scope of the configuration of the present invention.

[0041] (Embodiment 1) FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment, and FIG. 2 is a schematic cross-sectional view showing the liquid crystal display device 1 according to an example of the present embodiment in more detail. FIG. 3 is a schematic plan view of the entire liquid crystal display device 1 according to an example of the present embodiment, as viewed from the observation surface side. As shown in FIG. 1, the liquid crystal display device 1 includes, in order from the back surface side to the observation surface side, a first polarizing plate 51, a first retardation layer 41, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a second retardation layer 42, and a second polarizing plate 52. The first substrate 10 includes a reflective layer 130, as described later. In addition, the first retardation layer 41 includes a λ / 4 plate 411 and a λ / 2 plate 412, and the second retardation layer 42 includes a λ / 4 plate 421 and a λ / 2 plate 422. The second retardation layer 42 further includes a positive C plate 44. In this embodiment, a TFT substrate is used as the first substrate 10. Incidentally, a portion or structure having a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0042] In the liquid crystal display device 1 of this embodiment, each pixel P has a reflective region Rf (i.e., a region that displays in a reflective mode) that reflects light and displays, and a transmissive region Tr (a region that displays in a transmissive mode) that transmits light and displays (see FIG. 4). This allows good visibility to be achieved in any environment. FIG. 4 is a plan view schematic diagram conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of this embodiment.

[0043] A reflective layer 130 is disposed in the reflective region Rf. For example, light L1 (e.g., external light) enters the liquid crystal display device 1 from the observation surface side, is reflected by the reflective layer 130, and then exits from the observation surface side (see FIG. 2). On the other hand, the reflective layer 130 is not disposed in the transmissive region Tr (see FIG. 2). For example, when a backlight 61 is disposed on the rear side, light L2 from the backlight 61 passes through a region (transmissive region Tr) where the reflective layer 130 is not disposed, and exits from the observation surface side (see FIG. 2).

[0044] The ratio of the area of ​​the transmissive region Tr in each pixel P (aperture ratio) can be set appropriately depending on the application, etc., but is preferably 5% to 95% when the area of ​​one pixel P is 100%. In addition, the position and shape of the transmissive region Tr in the pixel P can also be set appropriately depending on the application, etc.

[0045] As shown in Fig. 3, the liquid crystal display device 1 has a plurality of pixels P arranged in a matrix. The plurality of pixels P typically include three types of pixels, namely red pixels, green pixels, and blue pixels, but the number of types of pixels may be two or less, or may be four or more. Each pixel P includes a thin film transistor (TFT) 110, and a first electrode 121 and a second electrode 122 capable of generating a transverse electric field in the liquid crystal layer 20. A gate electrode of the TFT 110 is electrically connected to a corresponding gate line (also referred to as a scanning line) GL, and a source electrode of the TFT 110 is electrically connected to a corresponding source line (also referred to as a signal line) SL. A drain electrode of the TFT 110 is electrically connected to the second electrode 122.

[0046] <First substrate> As shown in FIG. 2, the first substrate 10 has, in order from the back side to the observation side, a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 that contacts the liquid crystal layer 20. The first substrate 10 preferably further has a support substrate 100 and a backplane circuit BP on the back side of the reflective layer 130. An insulating layer (also called an insulating film) is provided between each layer, etc., as necessary. For example, a first interlayer insulating layer 151 is provided so as to cover the backplane circuit BP, a second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 with the reflective layer 130 sandwiched therebetween, and a dielectric layer (also called a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

[0047] The supporting substrate 100 is preferably transparent and insulating, and examples of the supporting substrate 100 include a glass substrate and a plastic substrate.

[0048] The backplane circuit BP is provided on a support substrate 100. The backplane circuit BP is a circuit for driving a plurality of pixels P, and includes a TFT 110, a gate line GL, a source line SL, etc. Usually, the backplane circuit BP also includes a gate insulating film.

[0049] The TFT 110 is provided in each of the pixels P. The TFT 110 is preferably one including an oxide semiconductor layer as an active layer (also referred to as an oxide semiconductor TFT). The oxide semiconductor included in the oxide semiconductor layer has been attracting attention in recent years as an active layer material to replace amorphous silicon and polycrystalline silicon, and has a higher mobility than amorphous silicon. Therefore, the oxide semiconductor TFT can operate at a higher speed than the amorphous silicon TFT. In addition, the oxide semiconductor layer can be formed by a simpler process than the polycrystalline silicon layer, and can be applied to devices requiring a large area.

[0050] Since oxide semiconductor TFTs also have excellent off-leak characteristics, a driving method can be used to display images by reducing the frequency of rewriting. For example, when displaying a still image, image data can be rewritten once per second. This type of driving method is called pause driving or low-frequency driving, and can significantly reduce the power consumption of a liquid crystal display device. By employing pause driving and performing touch detection during periods when images are not being rewritten, it is possible to suppress a decrease in sensitivity of touch operations due to noise from the driving circuit, and the S / N ratio (signal-to-noise ratio) can be increased, for example, to about 10 times that of conventional devices.

[0051] The oxide semiconductor TFT is also advantageous in terms of reducing the size of the TFT, and therefore can suitably realize a configuration in which a memory circuit is provided for each pixel P (also referred to as MIP (Memory In Pixels)).

[0052] The oxide semiconductor may be an amorphous oxide semiconductor or a crystalline oxide semiconductor having a crystalline portion. Examples of the crystalline oxide semiconductor include a polycrystalline oxide semiconductor, a microcrystalline oxide semiconductor, and a crystalline oxide semiconductor whose c-axis is oriented substantially perpendicular to the layer surface.

[0053] The oxide semiconductor layer may be a single layer or may have a laminated structure of two or more layers. The oxide semiconductor layer having a laminated structure may include an amorphous oxide semiconductor layer and a crystalline oxide semiconductor layer, may include a plurality of crystalline oxide semiconductor layers having different crystal structures, or may include a plurality of amorphous oxide semiconductor layers. When the oxide semiconductor layer has a two-layer structure including an upper layer and a lower layer, the energy gap of the oxide semiconductor included in the lower layer may be different from the energy gap of the oxide semiconductor included in the upper layer.

[0054] The materials and structures of the amorphous oxide semiconductor and each crystalline oxide semiconductor, the film formation method, and the configuration of the oxide semiconductor layer having a laminated structure are described in, for example, JP 2014-007399 A. For reference, the entire disclosure of JP 2014-007399 A is incorporated herein by reference.

[0055] Specifically, the oxide semiconductor layer preferably contains at least one metal element selected from In (indium), Ga (gallium), and Zn (zinc). Among them, an oxide semiconductor film containing a ternary oxide of In, Ga, and Zn is more preferable. A preferred example of the ternary oxide of In, Ga, and Zn is indium gallium zinc oxide. A semiconductor containing a ternary oxide of In, Ga, and Zn is called an In-Ga-Zn-O-based semiconductor, and the ratio (composition ratio) of In, Ga, and Zn in this semiconductor is not particularly limited, and examples thereof include In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, and In:Ga:Zn=1:1:2.

[0056] The In-Ga-Zn-O based semiconductor may be amorphous or crystalline. As a crystalline In-Ga-Zn-O based semiconductor, one in which the c-axis is oriented approximately perpendicular to the layer surface is preferable.

[0057] The crystal structure of the crystalline In-Ga-Zn-O-based semiconductor is disclosed in, for example, JP 2014-007399 A, JP 2012-134475 A, JP 2014-209727 A, etc. For reference, the entire disclosures of JP 2012-134475 A and JP 2014-209727 A are incorporated herein by reference. Since a TFT having an In-Ga-Zn-O-based semiconductor layer has high mobility (more than 20 times that of an a-Si TFT) and low leakage current (less than 1 / 100 that of an a-Si TFT), it is suitable for use as a driving TFT (for example, a TFT included in a driving circuit provided on the same substrate as the display area around a display area including a plurality of pixels) and a pixel TFT (a TFT provided in a pixel).

[0058] The oxide semiconductor layer may contain an oxide semiconductor other than an In-Ga-Zn-O-based semiconductor. For example, a ternary oxide of In, Sn (tin) and Zn may be used. For example, In 2 O 3 -SnO 2 Preferred examples include In-ZnO; InSnZnO. A semiconductor containing a ternary oxide of In, Sn, and Zn is called an In-Sn-Zn-O-based semiconductor. Alternatively, the oxide semiconductor layer may contain an In-Al-Zn-O-based semiconductor, an In-Al-Sn-Zn-O-based semiconductor, a Zn-O-based semiconductor, an In-Zn-O-based semiconductor, a Zn-Ti-O-based semiconductor, a Cd-Ge-O-based semiconductor, a Cd-Pb-O-based semiconductor, CdO (cadmium oxide), an Mg-Zn-O-based semiconductor, an In-Ga-Sn-O-based semiconductor, an In-Ga-O-based semiconductor, a Zr-In-Zn-O-based semiconductor, an Hf-In-Zn-O-based semiconductor, an Al-Ga-Zn-O-based semiconductor, a Ga-Zn-O-based semiconductor, an In-Ga-Zn-Sn-O-based semiconductor, or the like.

[0059] The first interlayer insulating layer 151 is provided so as to cover the backplane circuit BP. The surface of the first interlayer insulating layer 151 on the reflective layer 130 side preferably has an uneven shape (also referred to as an uneven surface structure). This allows the reflective layer 130 to have an uneven surface structure that reflects this shape. The first interlayer insulating layer 151 having an uneven surface structure can be suitably formed using a photosensitive resin, for example, as described in Japanese Patent No. 3394926.

[0060] The reflective layer (also referred to as a reflective film) 130 is provided on the first interlayer insulating layer 151. The reflective layer 130 is formed from a material that reflects light. In particular, it is preferable that the reflective layer 130 is formed from a metal material having a high reflectance. Examples of materials for the reflective layer 130 include a silver alloy, an aluminum alloy, and an aluminum alloy.

[0061] The reflective layer 130 preferably has an uneven shape that reflects the uneven surface structure that the first interlayer insulating layer 151 preferably has. That is, the reflective layer 130 also preferably has an uneven surface structure. This uneven surface structure is also called MRS (Micro Reflective Structure) and is provided to diffusely reflect ambient light and realize a white display close to paper white. The uneven surface structure is preferably composed of a plurality of convex parts p arranged randomly so that the center distance between adjacent convex parts p is 5 μm or more and 50 μm or less. The center distance between adjacent convex parts p is more preferably 10 μm or more and 20 μm or less. The shape of the convex parts p is preferably approximately circular or approximately polygonal when viewed from the normal direction of the support substrate. The area of ​​the convex parts p that occupies one pixel P is preferably, for example, about 20 to 40%, and the height of the convex parts p is preferably, for example, 1 μm or more and 5 μm or less.

[0062] As described above, the transmissive region Tr does not have a reflective layer 130. For example, during the manufacture of the first substrate 10, the reflective layer 130 is formed, and then a part of the reflective layer 130 is removed, thereby forming a reflective region Rf including the reflective layer 130 and a transmissive region Tr not including the reflective layer 130.

[0063] The second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 so as to cover the reflective layer 130. That is, the reflective layer 130 is disposed between the first interlayer insulating layer 151 and the second interlayer insulating layer 152.

[0064] Here, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably formed from an organic insulating material or an inorganic insulating material. For example, organic insulating films obtained using organic insulating materials include organic films (relative dielectric constant ε=2 to 5) such as acrylic resin, polyimide resin, and novolac resin, and laminates thereof. The thickness of the organic insulating film is not particularly limited, but is, for example, 2 μm or more and 4 μm or less. For example, inorganic insulating films obtained using inorganic insulating materials include silicon nitride (SiNx), silicon oxide (SiO 2) or a laminated film thereof. The thickness of the inorganic insulating film is not particularly limited, but is, for example, 1500 Å or more and 3500 Å or less. Alternatively, it may be a laminated body of an organic insulating film and an inorganic insulating film. Among them, it is preferable that the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are organic insulating films.

[0065] From the viewpoint of manufacturing, it is preferable that the interlayer insulating layers 151 and 152 are highly transparent, and it is suitable to form them from the same material with high transmittance. Also, the first interlayer insulating layer 151, which is farther from the observation surface side than the reflective layer 130, may have a low transmittance or may be opaque. From the viewpoint of light utilization efficiency, the second interlayer insulating layer 152 may have a high transparency, and may be made of a material with high transmittance different from that of the first interlayer insulating layer 151.

[0066] The first electrode 121 is disposed on the reflective layer 130 via the second interlayer insulating layer 152, and a dielectric layer 153 is disposed between the first electrode 121 and the second electrode 122. Therefore, the reflective layer 130 is located on the opposite side of the liquid crystal layer 20 with respect to the first electrode 121 and the second electrode 122 (i.e., on the rear side of the first electrode 121 and the second electrode 122). In this embodiment, of the first electrode 121 and the second electrode 122, the second electrode 122 is located relatively closer to the observation surface, and the first electrode 121 is located on the rear surface. The electrode located relatively closer to the observation surface is also referred to as an upper layer electrode, and the electrode located relatively closer to the rear surface is also referred to as a lower layer electrode.

[0067] One of the first electrode 121 and the second electrode 122 is a pixel electrode PE, and the other is a common electrode CE. The pixel electrode is provided in each of the multiple pixels P. The pixel electrode is electrically connected to the backplane circuit BP. In this embodiment, the first electrode 121 (lower layer electrode) is the common electrode CE, and the second electrode 122 (upper layer electrode) is the pixel electrode PE.

[0068] At least one of the first electrode 121 and the second electrode 122 preferably has a plurality of strip portions SP and a slit Sl located between two adjacent strip portions among the plurality of strip portions. The strip portion SP corresponds to an electrode portion, and the slit Sl corresponds to an opening, and such an electrode is also called a slit electrode or a finger electrode. From the viewpoint of easily generating a transverse electric field, it is preferable that at least the upper layer electrode (pixel electrode PE in this embodiment) is a slit electrode. In this case, the lower layer electrode (common electrode CE in this embodiment) may be a planar electrode, that is, a so-called solid electrode, or may be a slit electrode.

[0069] The extension directions of the multiple strip portions SP constituting the slit electrode are preferably approximately parallel to each other. Also, it is preferable that they have a linear shape extending in the same direction. A linear shape means that the center line of the strip portion SP, not the outer edge of the strip portion SP, is linear, and the center line of the strip portion SP means a line that divides the strip portion SP in half in the width direction. The width direction means a direction approximately perpendicular to the direction in which the strip portion SP extends in a plan view. Note that the strip portion SP may have a bent portion (also called a kink portion) in the middle (for example, at the end portion), but it is preferable that the strip portion SP does not have a bent portion.

[0070] The extension direction of the strip portions SP may be different for each pixel, but is preferably the same for two or more adjacent pixels, and is most preferably the same for all pixels from the viewpoint of maximizing display performance.

[0071] The width L of each strip-shaped portion SP differs depending on the applied voltage, etc., but is preferably, for example, 0.3 to 10 μm, and more preferably 1 to 5 μm. The interval between two adjacent strip-shaped portions SP (i.e., the interval between the center lines of each strip-shaped portion) also differs depending on the applied voltage, etc., but is preferably, for example, 0.3 to 10 μm, and more preferably 1 to 5 μm.

[0072] The ratio L / S (also referred to as L / S condition) of the width L per belt-like portion in plan view to the width S per slit in plan view is preferably 0.4 to 0.7 / 1. This improves the reflectance of white display (also referred to as white reflectance), and thus the contrast ratio (also simply referred to as "contrast"). Specific examples include L / S=1.6 / 3 (i.e., 0.533 / 1), L / S=2.2 / 4.1 (i.e., 0.537 / 1), and L / S=3 / 5 (i.e., 0.6 / 1).

[0073] Here, the alignment direction of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied (i.e., the alignment direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140) is preferably -30° or more and 30° or less with respect to the extension direction of the strip portions SP as the reference (0°). This angle, that is, the angle formed by the alignment direction of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied, when the extension direction of the strip portions SP is the reference (0°) and the angle rotated clockwise is a positive angle (+) and the angle rotated counterclockwise is a negative angle (-), is called the slit angle. The definition of the slit angle will be described with reference to FIG. 5. FIG. 5 is a diagram for explaining the slit angle of the liquid crystal molecules. The (p) suffixed to the symbol of the liquid crystal molecule means a positive type. In this specification, the liquid crystal molecules 21 near the first horizontal alignment film 140 (i.e., the liquid crystal molecules on the first substrate 10 side) are also referred to as liquid crystal molecules 21A, and the liquid crystal molecules 21 near the second horizontal alignment film 340 (i.e., the liquid crystal molecules on the second substrate 30 side) are also referred to as liquid crystal molecules 21B.

[0074] As described later, in this embodiment, a positive type liquid crystal material (and liquid crystal molecules) is used. In the case of positive type liquid crystal molecules, the alignment direction of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied corresponds to the long axis direction of the liquid crystal molecules 21A. When the long axis direction of the liquid crystal molecules 21A and the extension direction of the strip portions SP are parallel to each other, the slit angle is 0° (see the "0°" column in FIG. 5). When the extension direction of the strip portions SP rotates clockwise with the long axis direction of the liquid crystal molecules 21A as the reference (0°), the slit angle is a positive angle (+) (see the "Positive (+)" column in FIG. 5). When the extension direction of the strip portions SP rotates counterclockwise with the long axis direction of the liquid crystal molecules 21A as the reference (0°), the slit angle is a negative angle (-) (see the "Negative (-)" column in FIG. 5).

[0075] Therefore, the slit angle can also be said to be the angle formed by the axis of the liquid crystal molecule 21A on the first substrate 10 side with the extension direction of the multiple strip-shaped portions as the reference (0°) and the axis having the larger absolute value of the dielectric constant when no voltage is applied.

[0076] The suitable range of the slit angle varies depending on the condition of the width L of each belt-shaped portion SP and the width S of each slit Sl (also called the L / S condition), the twist angle, whether the liquid crystal material is positive type or negative type, etc. In particular, with a monodomain structure, the reflectance (especially the white reflectance) can be maximized by selecting the optimal slit angle depending on the L / S condition.

[0077] 6 and 7A show an example in which the extension direction of the strip-shaped portions SP is 0° (this angle is referred to as angle X) when the extension direction of the source wiring SL is taken as the reference (0°), and the angle rotated clockwise is taken as a positive angle (+), and the angle rotated counterclockwise is taken as a negative angle (-). Also, examples in which the angle X is -10°, +10°, -90°, -100°, and -80° are shown in Figs. 7B, 7C, 7D, 7E, and 7F, respectively. The aspect in which the angle X is 0° (see Figs. 6 and 7A) corresponds to the aspect in which the extension direction of the strip-shaped portions SP is parallel to the extension direction of the source wiring SL, and the aspect in which the angle X is -90° (see Fig. 7D) corresponds to the aspect in which the extension direction of the strip-shaped portions SP is parallel to the extension direction of the gate wiring GL. Figs. 6 and 7A to 7F are schematic plan views showing specific examples of pixels. 6 is a schematic plan view showing an example of a pixel structure, and Figs. 7A to 7F are schematic plan views showing an example of a pixel arrangement. Figs. 7A to 7F also show the twisted orientation of liquid crystal molecules 21.

[0078] The first electrode 121 and the second electrode 122 are preferably each made of a transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), a mixture thereof, or the like.

[0079] In the embodiment shown in FIG. 2, the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, to the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed in the same layer as the reflective film 130 and is made of the same material (metal film, etc.) as the reflective film 130. The first interlayer insulating layer 151 is formed with a first contact hole CH1 that exposes a part of the backplane circuit BP (more specifically, at least a part of the drain electrode of the TFT 110), and the contact electrode 160 is connected to the backplane circuit BP at the first contact hole CH1. The second interlayer insulating layer 152 is formed with a second contact hole CH2 that exposes a part of the contact electrode 160, and the pixel electrode PE (the second electrode 122 in this embodiment) is connected to the contact electrode 160 at the second contact hole CH2.

[0080] The dielectric layer 153 is provided so as to cover the first electrode 121. The dielectric layer 153 is preferably formed from an inorganic insulating material. The inorganic insulating film obtained using the inorganic insulating material is as described above.

[0081] The first horizontal alignment film 140 is provided on the second electrode 122 and is in contact with the liquid crystal layer 20. Therefore, it can be said that the first electrode 121 and the second electrode 122 are disposed between the second interlayer insulating layer 152 and the first horizontal alignment film 140.

[0082] The first horizontal alignment film 140 and the second horizontal alignment film 340 described later are each subjected to an alignment treatment, and define the alignment direction (also referred to as the alignment direction) of the liquid crystal molecules 21 contained in the liquid crystal layer 20. For example, the alignment treatment is preferably performed by a photo-alignment treatment or a rubbing treatment. In the photo-alignment treatment, a photodecomposition type photo-alignment film material can be used, and in the rubbing treatment, it is preferable to use an alignment film material such as polyimide.

[0083] Both the first horizontal alignment film 140 and the second horizontal alignment film 340 are horizontal alignment films that align the liquid crystal molecules 21 in a direction horizontal to the first substrate 10 and the second substrate 30 when no voltage is applied to the liquid crystal layer 20. That is, the liquid crystal molecules 21 are horizontally aligned when no voltage is applied to the liquid crystal layer 20. The pretilt angle is substantially 0°.

[0084] The alignment direction of the liquid crystal molecules 21 determined by the first horizontal alignment film 140 is different from the alignment direction of the liquid crystal molecules 21 determined by the second horizontal alignment film 340. Therefore, the liquid crystal layer 20 has a twisted alignment when no voltage is applied (see FIG. 2). When a voltage is applied to the liquid crystal layer 20, that is, when a transverse electric field is generated in the liquid crystal layer 20 by the first electrode 121 and the second electrode 122, the alignment state of the liquid crystal layer 20 changes due to the transverse electric field (fringe electric field).

[0085] In the present embodiment, the pixel electrode PE is provided above the common electrode CE. However, in a relatively large liquid crystal display device, that is, in a liquid crystal display device in which the area of ​​the pixel P is relatively large, it is preferable that the pixel electrode PE is provided above the common electrode CE. In this configuration (also referred to as the V2 structure), since there is no need to form a slit in the common electrode CE, which is the lower electrode, the increase in resistivity (sheet resistivity) of the common electrode CE is suppressed more than in the configuration (also referred to as the V3 structure) in which the common electrode CE is provided above the pixel electrode PE, and therefore the fringe electric field applied to the liquid crystal layer 20 is suppressed from weakening. In this configuration (V2 structure), when the pixel electrode PE is a slit electrode, the resistivity of the pixel electrode PE increases, but since an externally input voltage is applied to the pixel electrode PE, it is easy to reduce the effect of the increase in resistivity (i.e., to suppress the fringe electric field from weakening). In order to suppress the increase in resistivity of the common electrode CE, it is possible to use low-resistance wiring made of a metal material (for example, connecting the low-resistance wiring to the common electrode). However, in such a configuration, adverse effects on the display due to specular reflection from the low-resistance wiring (for example, glare, rainbow-colored diffraction, interference patterns) may occur, making it necessary to block light with a black matrix or the like, and it may not be possible to sufficiently improve the reflective aperture ratio.

[0086] In the configuration in which the pixel electrode PE is provided above the common electrode CE, the common electrode CE is not present in the region in which the second contact hole CH2 is formed, and the region does not contribute to reflective display, so that the reflectance may be lower than in the configuration in which the common electrode CE is provided above the pixel electrode PE. Since the area of ​​the region that does not contribute to reflective display, such as the contact hole, is required to a certain extent regardless of the size of the area of ​​the pixel P, the ratio of the region that does not contribute to reflective display in the pixel P increases as the area of ​​the pixel P decreases (i.e., the resolution increases), and the above-mentioned decrease in reflectance increases. In other words, in a relatively large liquid crystal display device, the ratio of the region that does not contribute to reflective display in the pixel P is easier to reduce, so that the above-mentioned decrease in reflectance is easier to suppress. For these reasons, in a relatively large liquid crystal display device, a configuration in which the pixel electrode PE is provided above the common electrode CE is advantageous.

[0087] On the other hand, as described above, the reduction in reflectance due to the region in which the second contact hole CH2 is formed not contributing to the reflective display becomes greater as the area of ​​the pixel P becomes smaller (i.e., as the resolution increases). Therefore, in a relatively high-resolution liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively small, it is preferable that the common electrode CE is provided above the pixel electrode PE (see Variant 1 of Embodiment 1 described below).

[0088] <Liquid crystal layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and contains a liquid crystal material. In this embodiment, the liquid crystal material constituting the liquid crystal layer 20 is preferably a positive type liquid crystal material. A positive type liquid crystal material means a liquid crystal material having a positive dielectric anisotropy, that is, a nematic liquid crystal material having a positive dielectric anisotropy Δε. Note that a negative type liquid crystal material means a liquid crystal material having a negative dielectric anisotropy, that is, a nematic liquid crystal material having a negative dielectric anisotropy Δε. The dielectric anisotropy Δε is determined by the dielectric constant ε in the long axis direction of the liquid crystal molecules 21. / / and the dielectric constant in the minor axis direction ε ⊥ (i.e., ε / / -ε ⊥ ).

[0089] The birefringence Δn of the positive type liquid crystal material is preferably, for example, 0.12 or less, and more preferably 0.119 or less. From the viewpoint of manufacturing (yield rate, etc.), the thickness d of the liquid crystal layer 20 is preferably 2 μm or more, and in this case, it is preferable that Δn is 0.119 or less. More preferably, d is 2.5 μm or more and Δn is 0.095 or less. However, from the viewpoint of response, a smaller cell thickness is preferable.

[0090] The liquid crystal layer 20 may further include a chiral agent, if necessary. The liquid crystal layer 20 can be formed by, for example, a dropping method.

[0091] The thickness d of the liquid crystal layer 20 (also referred to as the cell gap or cell thickness) is preferably 3.6 μm or less, and more preferably 2.0 to 3.4 μm. From the viewpoint of response speed, it is preferably 3 μm or less. A smaller cell thickness is preferable from the viewpoint of cost reduction, since it allows the number of materials to be reduced. However, if the cell thickness is too small, the display quality may not be improved due to unevenness in the cell thickness or foreign matter, resulting in a trade-off with the occurrence rate of defective display quality. From the viewpoint of yield, it is preferable that the cell thickness is 2 μm or more, as described above.

[0092] The retardation dΔn of the liquid crystal layer 20, i.e., the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material, is preferably 230 nm or more and 260 nm or less. From the viewpoint of further improving the contrast ratio, it is more preferably 232 nm or more and 250 nm or less, even more preferably 235 nm or more and 246 nm or less, and particularly preferably 236 nm or more and 245 nm or less.

[0093] The liquid crystal layer 20 may have a multi-domain alignment such as a dual-domain alignment, but is preferably a single-domain alignment (also called a mono-domain alignment) from the viewpoint of maximizing the liquid crystal mode reflection efficiency and the liquid crystal mode transmission efficiency.

[0094] <Second board> The second substrate 30 is disposed opposite the first substrate 10 with the liquid crystal layer 20 interposed therebetween, and has a second horizontal alignment film 340 in contact with the liquid crystal layer 20. The second substrate 30 preferably further has a support substrate 300 and a color filter layer 310. For example, as shown in FIG. 2, the second substrate 30 has, in order from the liquid crystal layer 20 side, the second horizontal alignment film 340, the color filter layer 310, and the support substrate 300. The second substrate 30 preferably also has a plurality of columnar spacers (not shown). Note that the first substrate 10 may have a plurality of columnar spacers.

[0095] The support substrate 300 is preferably transparent and insulating, and examples of the support substrate 300 include a glass substrate and a plastic substrate. A high-resistance transparent conductive film may be formed on the surface of the support substrate 300 opposite to the liquid crystal layer 20 (for example, in FIG. 2, the surface of the support substrate 300 on the retardation layer 40 side) in order to prevent static electricity from sticking to the liquid crystal cell. This high-resistance transparent conductive film may have a multi-layer structure in consideration of suppressing a decrease in transmittance and suppressing an increase in reflectance.

[0096] The color filter layer 310 typically includes a red color filter provided in an area corresponding to a red pixel and transmitting red light, a green color filter provided in an area corresponding to a green pixel and transmitting green light, and a blue color filter provided in an area corresponding to a blue pixel and transmitting blue light. However, the number of types of color filters may be two or less, or four or more. If color display is not performed, the color filter layer 310 is omitted.

[0097] If necessary, an overcoat layer (also called a planarizing layer) may be provided to cover the color filter layer 310. Note that the white display may have a yellowish tinge depending on the material (e.g., transparent conductive material) forming the electrodes, the material forming the interlayer insulating layer and the dielectric layer, and the material forming the alignment film. In that case, the chromaticity of the white display may be adjusted (i.e., blue shift) by forming the overcoat layer from a blue resist, so that the chromaticity of the white display may be brought closer to that of a D65 light source, for example. The D65 light source is the CIE standard illuminant D65.

[0098] <Retardation layer> The first retardation layer 41 is located between the first substrate 10 and the first polarizing plate 51, and includes a λ / 4 plate 411 and a λ / 2 plate 412 (see FIGS. 1 and 2). The second retardation layer 42 is located between the second substrate 30 and the second polarizing plate 52, and includes a λ / 4 plate 421, a λ / 2 plate 422, and a positive C plate 44 (see FIGS. 1 and 2). The positional relationship between the λ / 4 plate and the λ / 2 plate in each retardation layer is preferably the λ / 2 plate 412 and the λ / 4 plate 411 from the back side in the first retardation layer 41, and preferably the λ / 2 plate 422 and the λ / 4 plate 421 from the observation side in the second retardation layer 42.

[0099] The λ / 4 plate means a retardation plate that imparts an in-plane phase difference of 1 / 4 wavelength to incident light of wavelength λ, and is also called a λ / 4 wave plate or QWP (Quarter-Wave Plate). Specifically, the λ / 4 plate can convert linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light. For example, linearly polarized light incident on the λ / 4 plate becomes circularly polarized light when it is output.

[0100] A λ / 2 plate means a retardation plate that imparts an in-plane phase difference of 1 / 2 wavelength to incident light of wavelength λ, and is also called a λ / 2 wave plate, half wave plate, or HWP (Half-Wave Plate). Specifically, a λ / 2 plate can rotate the vibration direction of an incident light beam by approximately 90°. For example, circularly polarized light that enters a λ / 2 plate becomes circularly polarized light with the rotation direction reversed when it is emitted.

[0101] It is preferable that the first λ / 4 plate 411 and the second λ / 4 plate 421 have substantially the same in-plane retardation Re. Substantially the same means that the difference between these in-plane retardation Re is less than 5 nm. The difference between the in-plane retardation Re is preferably less than 1 nm.

[0102] It is preferable that the first λ / 2 plate 412 and the second λ / 2 plate 422 have substantially the same in-plane retardation Re. Substantially the same means that the difference between these in-plane retardations Re is less than 5 nm. The difference between the in-plane retardations Re is preferably less than 1 nm.

[0103] As the λ / 4 plates 411, 421 and the λ / 2 plates 412, 422, general-purpose retardation plates can be used. More specifically, it is preferable to use retardation plates that are generally distributed as, for example, circularly polarizing plates of anti-reflection films. In the present invention, preferably, by controlling the optical axis setting of each optical film within a predetermined range described later, even if a general-purpose retardation plate is used as the λ / 4 plate and the λ / 2 plate instead of a special retardation plate, the contrast ratio and viewing angle can be improved while being a transverse electric field type semi-transmissive liquid crystal display device, and it is also useful as an in-cell type touch panel, so that cost reduction can be achieved. In particular, from the user's perspective, it is very useful because it can reduce the total cost. Cost reduction can be achieved similarly when the semi-transmissive liquid crystal display device of the present invention is used not only as a built-in touch panel such as an in-cell type, but also as an external touch panel.

[0104] Specifically, it is preferable to use uniaxial A-plates as the λ / 4 plates 411 and 421 and the λ / 2 plates 412 and 422.

[0105] As described above, in the present invention, each of the retardation layers 41 and 42 includes a λ / 4 plate and a λ / 2 plate, and at least one of the retardation layers 41 and 42 further includes a positive C plate, so that the obtained liquid crystal display device can achieve excellent viewing angle characteristics and high contrast. In particular, brightness floating during black display (also called black floating) is sufficiently suppressed, and the viewing angle during black display is expanded. From the viewpoint of further exerting the above effect, it is preferable that the positive C plate is located between the λ / 4 plate and the λ / 2 plate. In particular, when the retardation layer includes one positive C plate, this arrangement is preferable. In this embodiment, only the second retardation layer 42 includes one positive C plate 44, and in this case, it is preferable that the λ / 4 plate 421, the positive C plate 44, and the λ / 2 plate 422 are located in this order from the liquid crystal layer 20 (and the second substrate 30) side (see FIG. 1).

[0106] The positive C plate 44 (as well as 43, 45, 46, etc. described later) may be made of a single film, or may be a laminate of two or more retardation films.

[0107] In this specification, a portion (structure) that is sandwiched between layers other than the positive C plate and acts as a positive C plate is counted as "one positive C plate". In this case, it does not matter whether the positive C plate is a laminate or not. Therefore, for example, when the retardation layer includes a λ / 4 plate, a multilayered positive C plate, and a λ / 2 plate in this order, it is called "the retardation layer has one positive C plate". In addition, when the retardation layer includes a λ / 4 plate, two commercially available positive C plates, and a λ / 2 plate in this order, it is called "the retardation layer has one positive C plate". When the retardation layer includes a λ / 4 plate, a first positive C plate (whether it is a laminate or not), a λ / 2 plate, and a second positive C plate (whether it is a laminate or not), it is called "the retardation layer has two positive C plates".

[0108] As the positive C plate 44 (and 43, 45, 46, etc. described later), it is preferable to use, for example, a film containing a material with negative intrinsic birefringence as a component, which is biaxially stretched lengthwise and widthwise, or a film coated with a liquid crystal material such as nematic liquid crystal, etc. Examples of materials with negative intrinsic birefringence include resin compositions containing acrylic resins and styrene resins, polystyrene, polyvinylnaphthalene, polyvinylbiphenyl, polyvinylpyridine, polymethylmethacrylate, polymethylacrylate, N-substituted maleimide copolymers, polycarbonates having a fluorene skeleton, triacetylcellulose (especially those with a low degree of acetylation), etc.

[0109] Specific examples of the positive C plate 44 (and 43, 45, 46, etc.) include a positive C plate manufactured by ENEOS Corporation or Hayashi Telempu Corporation, and a Positive-C retardation film manufactured by Nippon Kayaku Co., Ltd.

[0110] In order to enhance the viewing angle improving effect, the thickness direction retardation Rth of the positive C plate 44 (and 43) is preferably 150 to 270 nm, more preferably 160 to 250 nm, and further preferably 170 to 240 nm.

[0111] The thickness of each of the positive C plates 44 (and 43) is preferably, for example, 0.1 to 100 μm. Within this range, mechanical strength and display uniformity are superior. The thickness is more preferably 0.1 to 80 μm, and even more preferably 0.1 to 50 μm. When the positive C plate 44 (and 43) has a laminated structure, it is preferable to set the total thickness of the whole to be within the above range, and the thicknesses of the respective retardation films may be the same or different.

[0112] The retardation layer having a positive C plate (corresponding to the second retardation layer 42 in this embodiment) may have a positive C plate (referred to as a second positive C plate) other than the positive C plate. In this case, it is preferable that the second positive C plate is located between the λ / 2 plate and the polarizing plate. In addition, in the later-described embodiment 3, the aspect in which the first retardation layer 41 and the second retardation layer 42 have a first positive C plate and a second positive C plate, respectively, will be described in detail.

[0113] In the present invention, from the viewpoint of improving the viewing angle characteristics and contrast, it is particularly preferable that any one of the following (i) to (iii) is satisfied. Among these, in this embodiment, an embodiment that satisfies the following (i) is described in detail (see FIG. 2). In the later-described embodiment 2, an embodiment that satisfies the following (ii) is described in detail, and in the later-described embodiment 3, an embodiment that satisfies the following (iii) is described in detail. (i) The second retardation layer 42 includes one positive C plate, and the first retardation layer 41 does not include a positive C plate. (ii) Each of the first retardation layer 41 and the second retardation layer 42 includes one positive C plate. (iii) Each of the first retardation layer 41 and the second retardation layer 42 includes two positive C plates.

[0114] <Polarizing plate> The first polarizing plate 51 is located on the rear side of the first retardation layer 41 (see FIGS. 1 and 2). The second polarizing plate 52 is located on the observation side of the second retardation layer 42 (see FIGS. 1 and 2). The polarizing plates 51 and 52 may be circular polarizing plates or linear polarizing plates. Here, the linear polarizing plate means a polarizing plate having a function of extracting polarized light (linearly polarized light) that vibrates only in a specific direction from unpolarized light (natural light), partially polarized light, or polarized light, and is distinguished from a circular polarizing plate. Among them, a linear polarizing plate is preferable.

[0115] The polarizing plates 51 and 52 may be either an absorptive polarizing plate or a reflective polarizing plate. An absorptive polarizing plate is a polarizing plate that has the function of absorbing light that vibrates in a specific direction and transmitting polarized light (linearly polarized light) that vibrates in a direction perpendicular thereto. A reflective polarizing plate is a polarizing plate that has the function of reflecting light that vibrates in a specific direction and transmitting polarized light (linearly polarized light) that vibrates in a direction perpendicular thereto. Among these, an absorptive polarizing plate is preferred. It is particularly suitable to use an absorptive linear polarizing plate.

[0116] Examples of the absorptive polarizing plate include a polarizing plate obtained by dyeing and adsorbing an anisotropic material such as an iodine complex (or dye) on a polyvinyl alcohol film and then stretching and aligning the film. In general, in order to ensure mechanical strength and resistance to moist heat, the polyvinyl alcohol film is used in practical use with a protective film such as a triacetyl cellulose film laminated on both sides. Examples of the reflective polarizing plate include a film in which multiple dielectric thin films are laminated, a film in which multiple thin films with different refractive index anisotropy are laminated, a nanowire grid polarizing plate, and a polarizing plate using selective reflection of a cholesteric liquid crystal.

[0117] <Other configurations, etc.> In the liquid crystal display device 1 of this embodiment, display is performed in a lateral electric field mode in which the liquid crystal layer 20 has a twisted alignment when no voltage is applied. This makes it possible to sufficiently improve the contrast ratio of the reflective display. The twist angle θ of the liquid crystal layer 20 when no voltage is applied is 1 It is preferable that the angle is between 70° and 85°. A more preferable range will be described later.

[0118] Twist angle θ of liquid crystal layer 20 1This is the angle between the alignment direction of the liquid crystal molecules 21 determined by the first horizontal alignment film 140 and the alignment direction of the liquid crystal molecules 21 determined by the second horizontal alignment film 340. That is, this is the angle between the long axis direction of the liquid crystal molecules 21A (also referred to as the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied) near the first horizontal alignment film 140 and the long axis direction of the liquid crystal molecules 21B (also referred to as the liquid crystal molecules 21B on the second substrate 30 side when voltage is applied) near the second horizontal alignment film 340.

[0119] From the viewpoint of increasing the contrast ratio, the liquid crystal display device 1 is preferably in a normally black mode. The normally black mode is a display mode in which black is displayed when no voltage is applied and white is displayed when a voltage is applied.

[0120] It is preferable that the liquid crystal display device 1 further includes a light source. In this embodiment, a light source 61 (also referred to as a backlight) is further provided on the rear side of the liquid crystal layer 20 (see FIG. 1). The light source 61 (backlight) is not particularly limited as long as it irradiates light, and may be a direct type, an edge type, or any other type. Specifically, for example, it is preferable that the light source includes a light emitting diode (LED), a light guide plate, and a reflective sheet, and may further include a diffusion sheet or a prism sheet.

[0121] The liquid crystal display device 1 is also configured with a plurality of components, such as the above-mentioned components, external circuits such as a TCP (tape carrier package) and a PCB (printed wiring board), optical films such as a viewing angle widening film and a brightness enhancing film, and a bezel (frame), and some of the components may be incorporated into other components. These are not particularly limited, and those commonly used in the field of liquid crystal display devices can be used, so their explanation will be omitted.

[0122] <Examples of favorable optical settings> The following describes the preferred optical axis settings of each optical film (i.e., polarizing plate and retardation layer) and the verification results that led to the setting. An absorption type polarizing plate is used as the polarizing plate. As the liquid crystal layer 20, a liquid crystal layer that has a monodomain structure and performs normally black display is assumed, and a positive type liquid crystal material is used as the liquid crystal material that constitutes the liquid crystal layer 20. In addition, since the slow axis angle of the positive C plate is the film normal direction (i.e., 90° when the alignment direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is 0°), an embodiment without a positive C plate was examined. When a positive C plate is provided, each preferable setting is similar.

[0123] (I) Preferred Settings 8 is a plan view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21A in the liquid crystal layer 20 and the optical axis of each optical film (i.e., the in-plane slow axis of the λ / 4 plate and the λ / 2 plate and the polarization axis of the polarizer) in the liquid crystal display device 1 (see FIG. 1) including, in order from the back side to the observation side, the first polarizer 51, the first retardation layer 41, the first substrate 10, the liquid crystal layer 20, the second substrate 30, the second retardation layer 42, and the second polarizer 52 when no voltage is applied. In FIG. 8, the liquid crystal molecules 21A near the first horizontal alignment film 140 and the liquid crystal molecules 21B near the second horizontal alignment film 340 are shown as the liquid crystal molecules 21.

[0124] In this specification, unless otherwise specified, each angle (e.g., twist angle, optical axis angle, etc.) is an angle when the liquid crystal panel 1X is likened to a clock face, the alignment direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is taken as the reference direction, i.e., the 0° direction (12 o'clock direction), and the twist direction is taken as the positive (counterclockwise) direction (see FIG. 9). FIG. 9 is a diagram for explaining the optical axis angle of the optical film.

[0125] Twist angle θ of the liquid crystal layer 20 when no voltage is applied 1is preferably 70° or more and 85° or less, more preferably 75° or more and 85° or less, even more preferably 80° or more and 85° or less, particularly preferably 81° or more and 84° or less, and most preferably around 83° (approximately 83°).

[0126] The angle of the polarization axis 51AA of the first polarizing plate 51 (θ 2 ) is preferably −6.6 to 1.4°, more preferably −6.0 to 0.9°, further preferably −5.3 to 0.2°, and particularly preferably −4.5 to −0.7°.

[0127] The angle of the in-plane slow axis 412SA of the first λ / 2 plate 412 (θ 3 ) is preferably 70.9 to 74.9°, more preferably 71.2 to 74.6°, further preferably 71.5 to 74.3°, and particularly preferably 72.0 to 73.8°.

[0128] The angle of the in-plane slow axis 411SA of the first λ / 4 plate 411 (θ 4 ) is preferably 10.0 to 17.8°, more preferably 10.6 to 17.2°, further preferably 11.2 to 16.6°, and particularly preferably 12.1 to 15.7°.

[0129] Therefore, the polarization axis 51AA of the first polarizing plate 51, the in-plane slow axis 412SA of the first λ / 2 plate 412, and the in-plane slow axis 411SA of the first λ / 4 plate 411 are preferably positioned at angles of -6.6 to 1.4°, 70.9 to 74.9°, and 10.0 to 17.8°, respectively, more preferably at angles of -6.0 to 0.9°, 71.2 to 74.6°, and 10.6 to 17.2°, respectively, even more preferably at angles of -5.3 to 0.2°, 71.5 to 74.3°, and 11.2 to 16.6°, respectively, and particularly preferably at angles of -4.5 to -0.7°, 72.0 to 73.8°, and 12.1 to 15.7°, respectively.

[0130] The angle of the in-plane slow axis 421SA of the second λ / 4 plate 421 (θ 4) is preferably −27.9° to −22.9°, more preferably −27.0° to −23.0°, further preferably −26.0° to −23.0°, and particularly preferably −25.5° to −24.0°.

[0131] The angle of the in-plane slow axis 422SA of the second λ / 2 plate 422 (θ 3 ) is preferably from −52.5° to −47.5°, more preferably from −52.0° to −48.0°, further preferably from −51.0° to −49.0°, and particularly preferably from −50.0° to −49.0°.

[0132] The angle of the polarization axis 52AA of the second polarizing plate 52 (θ 2 ) is preferably from −70.5° to −63.5°, more preferably from −70.5° to −64.0°, further preferably from −70.5° to −64.5°, and particularly preferably from −70.0° to −66.3°.

[0133] Therefore, it is preferable that the polarization axis 52AA of the second polarizing plate 52, the in-plane slow axis 422SA of the second λ / 2 plate 422, and the in-plane slow axis 421SA of the second λ / 4 plate 421 are located at angles of −70.5° to −63.5°, −52.5° to −47.5°, and −27.9° to −22.9°, respectively, and that the angles of the polarization axes 52AA, 422SA, and 421SA of the second λ / 4 plate 421 are located at angles of −70.5° to −64.0°, −52.0° to −48.0°, and −27.9° to −22.9°, respectively. It is more preferable that they are located at angles of -27.0° to -23.0°, further more preferable that they are located at angles of -70.5° to -64.5°, -51.0° to -49.0°, and -26.0° to -23.0°, respectively, and particularly preferable that they are located at angles of -70.0° to -66.3°, -50.0° to -49.0°, and -25.5° to -24.0°, respectively.

[0134] (II) Verification results by optical simulation The above-mentioned preferable settings were found by the inventors of the present application through verification using optical simulation. The simulation was performed using Shintech OpticsMaster manufactured by Shintech Co., Ltd. The verification results will be described below.

[0135] A liquid crystal display device 1 (see FIG. 1) was assumed in which a λ / 4 plate 411, a λ / 2 plate 412, and a polarizing plate 51 were provided on the rear side of a reflective liquid crystal panel 1X using a positive liquid crystal material, in that order from the liquid crystal panel 1X side, and a λ / 4 plate 421, a λ / 2 plate 422, and a polarizing plate 52 were provided on the observation side of the liquid crystal panel 1X, in that order from the liquid crystal panel 1X side. The retardation dΔn of the liquid crystal layer 20 was set to 245 nm. The λ / 4 plates 411 and 421 were uniaxial retardation plates with a retardation Re of 140 nm, and the λ / 2 plates 412 and 422 were uniaxial retardation plates with a retardation Re of 270 nm, and the wavelength dispersion of these retardation plates was set to be flat.

[0136] The alignment direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is set to a 90° direction (12 o'clock direction), and the twist angle θ 1 The angle was fixed at 83°. This verification was carried out with no voltage applied.

[0137] (II-1) The optical axis settings of the optical film (also referred to as the front optical film) located on the observation surface side of the liquid crystal panel 1X were fixed to the optimal value of the optical axis setting in a reflective liquid crystal display device. This is shown in Table 1. Then, the optical axis settings of the optical film (also referred to as the rear optical film) located on the rear side of the liquid crystal panel 1X were changed in increments of 0.5° from a predetermined start angle to an end angle, and the transmission mode efficiency for black display (i.e., when no voltage is applied) was calculated. The calculation range is shown in Table 2. The transmission mode efficiency for black display is also referred to as the "black transmission mode efficiency." In the calculation, only one of the optical axes was changed, and the calculation was repeated with the other optical axes fixed.

[0138] [Table 1]

[0139] [Table 2]

[0140] Here, the transmission mode efficiency is expressed by the following formula (1): Transmissive mode efficiency (%) = (Luminance with front polarizer) / (Luminance without front polarizer) x 100 The front polarizing plate refers to the polarizing plate located on the observation surface side of the liquid crystal panel 1X, that is, the second polarizing plate 52.

[0141] An example of the calculation results is shown in Fig. 11. Fig. 11 is a graph showing the black transmittance mode efficiency when the in-plane slow axis 411SA of the first λ / 4 plate 411 is fixed at 14°, the in-plane slow axis 412SA of the first λ / 2 plate 412 is fixed at 73°, and the polarization axis 51AA of the first polarizing plate 51 is changed.

[0142] (II-2) The black transmission mode efficiency was calculated by changing the vicinity of each axis setting where the black transmission mode efficiency calculated by (II-1) above is the minimum in increments of 0.1°. The calculation range is shown in Table 3.

[0143] [Table 3]

[0144] The calculation results are shown in Figures 12A to 12C. Figure 12A is a graph showing the black transmittance mode efficiency when the in-plane slow axis 412SA of the first λ / 2 plate 412 is fixed at 72.9°, the polarization axis 51AA of the first polarizer 51 is fixed at -2.6°, and the in-plane slow axis 411SA of the first λ / 4 plate 411 is changed. Figure 12B is a graph showing the black transmittance mode efficiency when the in-plane slow axis 411SA of the first λ / 4 plate 411 is fixed at 13.9°, the polarization axis 51AA of the first polarizer 51 is fixed at -2.6°, and the in-plane slow axis 412SA of the first λ / 2 plate 412 is changed. Figure 12C is a graph showing the black transmittance mode efficiency when the in-plane slow axis 411SA of the first λ / 4 plate 411 is fixed at 13.9°, the in-plane slow axis 412SA of the first λ / 2 plate 412 is fixed at 72.9°, and the polarization axis 51AA of the first polarizing plate 51 is changed.

[0145] (II-3) The axis setting at which the black transmission mode efficiency calculated in (II-2) above is minimized was determined to be the optimal value. This is shown in Table 4.

[0146] [Table 4]

[0147] 12A to 12C, the ranges where the black transmission mode efficiency is 0.20% or less, 0.15% or less, 0.10% or less, and 0.05% or less are respectively defined as the preferred range (corresponding to the range where black display is possible), the more preferred range, the even more preferred range, and the particularly preferred range for each optical axis setting. Note that, based on the results of a 3D simulation ("Shintech LCD Master3D" manufactured by Shintech Co., Ltd.), if the transmission mode efficiency during white display is 15%, the contrasts in the preferred range, the more preferred range, the even more preferred range, and the particularly preferred range for each optical axis setting are 75 or more, 100 or more, 150 or more, and 300 or more, respectively.

[0148] Fig. 10 shows the most preferable optical axis setting from the viewpoint of improving the contrast ratio. Fig. 10 is a conceptual diagram showing the most preferable optical axis setting. In this optical axis setting diagram, the in-plane retardation Re of the λ / 4 plates 411 and 421 is 140 nm, and the in-plane retardation Re of the λ / 2 plates 412 and 422 is 270 nm.

[0149] <Application Examples> The liquid crystal display device 1 of the present embodiment is suitable for various applications. In particular, it is preferably applicable to touch panels. Whether it is applied to an external touch panel or a built-in touch panel, it is useful because it can be produced at a lower cost than conventional touch panels and has an improved contrast ratio. In particular, it is preferably applicable to a built-in touch panel, and is particularly preferably applicable to an in-cell touch panel. In this way, by using the liquid crystal display device 1 of the present embodiment, an in-cell touch panel capable of displaying in a reflective mode can be preferably realized.

[0150] By realizing an in-cell touch panel capable of displaying in reflective mode, for example, a frame wiring area required for an external touch panel is not required, so that a narrow frame can be achieved, and since the touch panel function can be installed without a cover glass, it contributes to a thinner and lighter touch panel. In addition, since the touch function and the display function are driven in a time-division manner, the touch panel is not affected by LCD (liquid crystal display) noise, which can be the largest noise source in a touch panel. In other words, since no killer pattern occurs, tuning (adjustment) of the touch signal is easy. Furthermore, the loss of reflected light is sufficiently small, and a more natural and natural display can be obtained when writing with a pen. Moreover, compared to an external touch panel, a total cost reduction can be achieved from the user's perspective. Moreover, it is possible to combine finger input with pen input using the electromagnetic induction method (EMR), which allows for highly accurate pen writing.

[0151] An example in which the liquid crystal display device 1 is used in an in-cell touch panel will be further described. Fig. 13 is a plan view schematic illustrating the arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1. As shown in Fig. 13, the liquid crystal display device 1 has a display area DR and a non-display area FR. The display area DR is defined by a plurality of pixels P (see Fig. 3, for example) arranged in a matrix. The non-display area FR is located on the periphery of the display area DR and is also referred to as a peripheral area or a frame area.

[0152] In the display region DR, the common electrode CE is divided into a plurality of segments TX. Each segment (common electrode portion) TX functions as a touch sensor electrode. In the example shown in FIG. 13, each touch sensor electrode TX is provided corresponding to two or more pixels P.

[0153] 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.

[0154] The touch wiring TL is connected to a touch driving unit TD provided in the non-display region FR. The touch driving unit TD is configured to switch, for example, between a display mode in which a plurality of touch sensor electrodes TX function as a common electrode CE and a touch detection mode in which the touch sensor electrodes TX function as the touch sensor electrodes TX in a time-division manner. For example, in the display mode, the touch driving unit TD applies a common signal to the touch sensor electrodes TX (common electrodes CE) via the touch wiring TL. On the other hand, in the touch detection mode, the touch driving unit TD applies a touch driving signal to the touch sensor electrodes TX via the touch wiring TL.

[0155] 13, the touch wirings TL extend in the column direction (the same direction as the source wirings SL). Some of the touch wirings TL extend to the corresponding touch sensor electrode TX across one or more other touch sensor electrodes TX.

[0156] Focusing on a certain touch sensor electrode TX, a first touch wiring TL1 that supplies a signal to the touch sensor electrode TX extends to a touch wiring contact portion TC, and a second touch wiring TL2 that supplies a signal to another touch sensor electrode TX extends across the touch sensor electrode TX. The second touch wiring TL2 and the touch sensor electrode TX overlap with each other via an insulating layer. Depending on the position of the touch sensor electrode TX, two or more touch wirings TL may be arranged to extend across the touch sensor electrode TX, or no touch wiring TL may be arranged to cross the touch sensor electrode TX.

[0157] In addition to the touch drive unit TD, the non-display area FR is provided with peripheral circuits including drive circuits such as a gate driver that supplies gate signals to the gate bus lines (gate wiring) GL and a source driver that supplies source signals to the source bus lines (source wiring) SL (not shown). These drive circuits may be mounted on the first substrate (TFT substrate) 10, for example, or may be formed integrally (monolithically). A semiconductor chip including some or all of the drive circuits may be mounted on the non-display area FR.

[0158] In an in-cell touch panel, it is particularly preferable to use an In-Ga-Zn-O based semiconductor as the TFT 110.

[0159] (Modification 1 of the first embodiment) In the first embodiment, the first electrode 121, which is a lower layer electrode, is the common electrode CE, and the second electrode 122, which is an upper layer electrode, is the pixel electrode PE. However, the second electrode 122 may be the common electrode CE, and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper layer electrode) is the common electrode CE, and the first electrode 121 (lower layer electrode) is the pixel electrode PE (see FIG. 14).

[0160] FIG. 14 is a schematic cross-sectional view showing the liquid crystal display device 1 of this example in more detail. In this example as well, from the viewpoint of easily generating a transverse electric field, it is preferable that at least the upper layer electrode (common electrode CE in this example) is a slit electrode. The lower layer electrode (pixel electrode PE in this example) may be a planar electrode, i.e., a so-called solid electrode, or may be a slit electrode. As described above, the liquid crystal display device 1 of this example is particularly suitable as a relatively high-definition liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively small.

[0161] (Modification 2 of the first embodiment) In the first embodiment, an FFS mode liquid crystal display device has been described, but an IPS mode liquid crystal display device may also be used (however, the liquid crystal layer 20 has a twisted orientation when no voltage is applied). This modification is an IPS mode liquid crystal display device. In this modification, the first electrode 121 and the second electrode 122 are provided in the same layer, and it is preferable that both the first electrode 121 and the second electrode 122 are slit electrodes.

[0162] (Embodiment 2) In this embodiment, the features unique to this embodiment will be mainly described, and the description of the contents overlapping with the above-mentioned embodiment 1 will be omitted. In the embodiment 1, the embodiment in which only the second retardation layer 42 includes one positive C plate will be described, but in this embodiment, the embodiment in which both the first retardation layer 41 and the second retardation layer 42 each include one positive C plate (above (ii)) will be described. That is, the embodiment is substantially the same as the embodiment 1 except that the first retardation layer 41 further includes one positive C plate. The positive C plate of the first retardation layer 41 is referred to as a positive C plate 43, and the positive C plate of the second retardation layer 42 is referred to as a positive C plate 44.

[0163] Fig. 15 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. As shown in Fig. 15, the liquid crystal display device 1 includes, in order from the rear surface side to the observation surface side, a first polarizing plate 51, a first retardation layer 41, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a second retardation layer 42, and a second polarizing plate 52. The first retardation layer 41 includes a λ / 4 plate 411, a λ / 2 plate 412, and a positive C plate 43, and the second retardation layer 42 includes a λ / 4 plate 421, a λ / 2 plate 422, and a positive C plate 44.

[0164] The first retardation layer 41 and the second retardation layer 42 each include one positive C plate, so that the viewing angle characteristics are improved. From the viewpoint of exerting such an effect more fully, it is preferable that the positive C plate is located between the λ / 4 plate and the λ / 2 plate, as described above. In this embodiment, it is preferable that the first retardation layer 41 includes, in order from the back side, a λ / 2 plate 412, a positive C plate 43, and a λ / 4 plate 411, and it is preferable that the second retardation layer 42 includes, in order from the back side, a λ / 4 plate 421, a positive C plate 44, and a λ / 2 plate 422 (see FIG. 15).

[0165] (Embodiment 3) In this embodiment, the features unique to this embodiment will be mainly described, and the description of the contents overlapping with the above-mentioned embodiments 1 and 2 will be omitted. In the embodiment 2, the first retardation layer 41 and the second retardation layer 42 each include one positive C plate (above (ii)). In the embodiment 2, the first retardation layer 41 and the second retardation layer 42 each include two positive C plates (above (iii)). That is, the first retardation layer 41 includes a new positive C plate (also referred to as a second positive C plate) 45 in addition to the positive C plate (also referred to as a first positive C plate) 43, and the second retardation layer 42 includes a new positive C plate (also referred to as a second positive C plate) 46 in addition to the positive C plate (also referred to as a first positive C plate) 44. Other than these, the present embodiment is substantially the same as the embodiment 2.

[0166] 16 is a schematic cross-sectional view of a liquid crystal display device 1 according to an embodiment of the present invention. As shown in FIG. 16, the liquid crystal display device 1 includes, in order from the rear surface side to the observation surface side, a first polarizing plate 51, a first retardation layer 41, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a second retardation layer 42, and a second polarizing plate 52. The first retardation layer 41 includes a first positive C plate 43 and a second positive C plate 45 in addition to a λ / 4 plate 411 and a λ / 2 plate 412. The second retardation layer 42 includes a first positive C plate 44 and a second positive C plate 45 in addition to a λ / 4 plate 421 and a λ / 2 plate 422.

[0167] When the first retardation layer 41 includes the first positive C plate 43 and the second positive C plate 45, and the second retardation layer 42 includes the first positive C plate 44 and the second positive C plate 46, the viewing angle characteristics are even better than those of the embodiments 1 and 2. From the viewpoint of exerting such an effect more sufficiently, it is preferable that the first positive C plates 43 and 44 are located between the λ / 4 plate and the λ / 2 plate as described above, and it is preferable that the second positive C plates 45 and 46 are located between the λ / 2 plate and the polarizing plate. In this embodiment, it is preferable that the first retardation layer 41 includes, in order from the rear side, a second positive C plate 45, a λ / 2 plate 412, a first positive C plate 43, and a λ / 4 plate 411, and it is preferable that the second retardation layer 42 includes, in order from the rear side, a λ / 4 plate 421, a first positive C plate 44, a λ / 2 plate 422, and a second positive C plate 46 (see FIG. 16).

[0168] The second positive C plates 45, 46 may be the same as the first positive C plates 43, 44 (having the same physical properties and thickness, etc.) or may be different, so long as they are retardation plates that satisfy "nz>nx≈ny". However, from the viewpoint of further exerting the viewing angle improving effect, the thickness direction retardation Rth (absolute value) of the second positive C plates 45, 46 is preferably 50 to 130 nm, more preferably 70 to 120 nm, and further preferably 80 to 115 nm.

[0169] The thickness of each of the second positive C plates 45, 46 is preferably, for example, 0.1 to 100 μm. Within this range, mechanical strength and display uniformity are superior. The thickness is more preferably 0.1 to 80 μm, and even more preferably 0.1 to 50 μm. When the positive C plates 45, 46 have a laminated structure, it is preferable to set the total thickness of the entire plates to be within the above range, and the thicknesses of the retardation films may be the same or different.

[0170] (Embodiment 4) In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents overlapping with the above-mentioned embodiment 1 will be omitted. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 1 in that a light source is provided on the observation surface side of the liquid crystal layer 20.

[0171] Fig. 17 is a cross-sectional schematic diagram of a liquid crystal display device 1 as one example of this embodiment. The liquid crystal display device 1 of this embodiment further includes a light source 62 (also referred to as a front light) on the observation side of the liquid crystal layer 20. More preferably, as shown in Fig. 17, the liquid crystal display device 1 includes, in this order from the back side to the observation side, a first polarizing plate 51, a first retardation layer 41, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a second retardation layer 42, a second polarizing plate 52, and a light source 62. In this embodiment, a TFT substrate is also suitable as the first substrate 10.

[0172] The light source 62 (front light) is not particularly limited as long as it can emit light. Specifically, for example, it is preferable that the light source has a light source such as a light emitting diode (LED) and a light guide plate. By further including the light source 62, the liquid crystal display device 1 can perform bright reflective display even in an environment where sufficient ambient light cannot be obtained.

[0173] Although the embodiments of the present invention have been described above, the individual matters described above can all be applied to the present invention as a whole.

[0174] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, absorption type polarizers are used as the polarizers 51 and 52. The applied voltage for white display is 5 V, and the applied voltage for black display is 0 V (i.e., no voltage is applied).

[0175] (Prototype 1) A test cell 1000 was fabricated as follows. First, as shown in Fig. 18B, a liquid crystal cell 1100 for obtaining the test cell 1000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 provided between these substrates. Fig. 18A is a plan view showing the structure of the liquid crystal cell 1100 as viewed from the front. Fig. 18B is a cross-sectional view taken along line A-A' in Fig. 18A (cross-sectional view taken along line A-A').

[0176] As shown in FIG. 18B, the first substrate 10 includes a glass substrate 100, and includes a common electrode CE as the first electrode 121, a dielectric layer 153, a pixel electrode PE as the second electrode 122, and a first horizontal alignment film 140 on the glass substrate in this order. The common electrode CE is made of ITO, and has a thickness of 100 nm. The dielectric layer 153 is made of silicon nitride (SiNx), and has a thickness of 300 nm. The pixel electrode PE is made of ITO, and has a thickness of 100 nm. The pixel electrode PE has a plurality of strip portions SP and a plurality of slits Sl. The width of each strip portion SP is 3 μm, and the width of each slit Sl (the distance between two adjacent strip portions SP) is 5 μm. Each strip portion SP is bent in a dogleg shape. That is, each strip portion SP includes a first portion SPa extending in a certain direction (first direction) and a second portion SPb extending in a direction (second direction) different from the first direction. The bending angle (the angle that the first portion SPa and the second portion SPb of the strip portion SP make with respect to the left-right direction in FIG. 18A) is 7°.

[0177] The second substrate 30 has a glass substrate 300 and a second horizontal alignment film 340 provided on the glass substrate 300, as shown in FIG. 18B.

[0178] The thickness (cell gap) of the liquid crystal layer 20 is determined by plastic beads (not shown).

[0179] The alignment treatment for the first horizontal alignment film 140 and the second horizontal alignment film 340 was carried out by a photo-alignment treatment or a rubbing treatment.

[0180] When photo-alignment treatment was performed, a photodecomposition type photo-alignment film material was used. The photo-alignment film material was applied by spin coating, and the thickness of the alignment film was 1000 Å (i.e., 100 nm). The non-polarized UV light emitted from the UV lamp unit was converted to polarized UV light by a wire grid polarizer, and the alignment film was irradiated with the polarized UV light to perform the photo-alignment treatment. The extinction ratio of the wire grid polarizer was 100:1. The wavelength of UV light effective for photo-alignment was 220 to 260 nm, and the irradiation energy was 300 mJ / cm. 2 The alignment direction of the liquid crystal molecules is a direction substantially perpendicular to the transmission axis direction of the polarized UV light (particularly preferably at 90°).

[0181] When rubbing treatment is used, a horizontal alignment film is formed and then rubbed with a rubbing roller (e.g., a roller wrapped with cloth) to perform the alignment treatment. This results in a uniaxial alignment direction of the liquid crystal molecules. As an alignment film material suitable for operating the liquid crystal molecules with a transverse electric field, a polyimide-based material is suitable. In addition, a material that does not generate a pretilt due to the rubbing treatment is suitable, and such materials are commercially available. The liquid crystal molecules are aligned approximately parallel to the rubbing direction.

[0182] For the liquid crystal cell 1100 having the above structure, first, the retardation of the liquid crystal layer 20 was measured using a polarimeter ("AxoScan" manufactured by Axometrics Co., Ltd.) Next, the cell thickness was measured using a cell gap inspection device ("RetsQC" manufactured by Otsuka Electronics Co., Ltd.).

[0183] 19A, a λ / 4 plate 421, a λ / 2 plate 422, and a polarizing plate 52 were attached in this order to the second substrate 30 side of the liquid crystal cell 1100 (adhesive layer is not shown). Thereafter, for reflection observation, a drop of matching oil mo was dropped on a reflector 130 having a concave-convex surface structure (MRS) to reduce loss due to interface reflection, and the liquid crystal cell 1100 was placed on the reflector 130 with the first substrate 10 side facing down to perform verification (this corresponds to the test cell 1000 for reflection observation). For transmission observation, a λ / 4 plate 411, a λ / 2 plate 412, and a polarizing plate 51 were attached in this order to the first substrate 10 side of the liquid crystal cell 1100 to perform verification (this corresponds to the test cell 1000 for transmission observation). In this manner, the test cell 1000 was produced. The polarizing plates 51 and 52 were Nitto Denko Corporation's "NPF-CRT1794KDUHC3", the λ / 4 plates 411 and 421 were Nitto Denko Corporation's "NZF-UF01A" (retardation: 140 nm), and the λ / 2 plates 412 and 422 were Nitto Denko Corporation's "NZF-UF01A" (retardation: 270 nm).

[0184] In this state, the reflectance was measured by changing the voltage applied between the pixel electrode PE and the common electrode CE. A function generator ("AFG1022" manufactured by TEKTRONIX) capable of applying a voltage of 0V to 10V with a square wave of 30Hz was used to apply the voltage to the pixel electrode PE and the common electrode CE. Unless otherwise specified, the reflectance was measured using a spectrophotometer ("CM-2600d" manufactured by MINOLTA). FIG. 19A is a schematic cross-sectional view of the test cell 1000.

[0185] (Verification example 1) In this verification example, the following (a) and (b) were examined using the test cell 1000. The twist angle was 83°, and a positive type liquid crystal material was used. The optical axis settings (initial settings) and specifications of this verification example are shown in Table 5 and FIG. 10. FIG. 10 is also a diagram conceptually illustrating the optical axis settings of the test cell 1000. Note that in this verification example, the test cell 1000 was examined without a positive C plate, but the same tendency is obtained when a positive C plate is provided.

[0186] [Table 5]

[0187] (a) Relationship between the axial setting of the optical film and the transmission mode efficiency and transmission contrast The relationship between the axial setting of the rear optical film and each of the transmission mode efficiency and the transmission contrast was examined for the test cell 1000. The results are shown in Figures 20 and 21. Figures 20 and 21 are diagrams showing the results of Verification Example 1.

[0188] Each graph in FIG. 20 is a graph in which the transmission mode efficiency and the transmission contrast were measured by rotating only the first retardation layer 41 (i.e., the first λ / 2 plate 412 and the first λ / 4 plate 411). The first retardation layer 41 was rotated within a range of ±10° from the optimal value of the axis setting obtained in (II) above (see Table 4). The axis angle of the polarizing plate 51 was fixed to the initial setting. The angle between the slow axis 412SA of the λ / 2 plate 412 and the slow axis 411SA of the λ / 4 plate 411 was fixed, and the λ / 2 plate 412 and the λ / 4 plate 411 were rotated as a set. The horizontal axis represents the angle in the direction of the slow axis 411SA of the λ / 4 plate 411, and the vertical axis represents the transmission mode efficiency or the transmission contrast.

[0189] Each graph in Fig. 21 is a graph in which the transmission mode efficiency and the transmission contrast were measured by rotating only the first polarizing plate 51. The polarizing plate 51 was rotated within a range of ±10° from the optimal value of the axis setting obtained in (II) above (see Table 4). The axis angle of the first retardation layer 41 was fixed to the initial setting. The horizontal axis represents the angle of the polarization axis 51AA direction of the polarizing plate 51, and the vertical axis represents the transmission mode efficiency or the transmission contrast.

[0190] In Figures 20 and 21, the "0V" column shows a graph in which the transmissive mode efficiency of black display was measured. The "5V" column shows a graph in which the transmissive mode efficiency of white display was measured. The transmissive mode efficiency of each display was calculated using the above formula (1). The transmissive contrast was calculated from the transmissive mode efficiency of each display thus measured. That is, the transmission contrast is expressed by the following formula (2): Transmission contrast = Transmission mode efficiency of white display / Transmission mode efficiency of black display The approximate curves are also shown in each graph in the "0V" column.

[0191] 20, when the slow axis 411SA direction of the λ / 4 plate 411 is 13.9°, the slow axis 412SA direction of the λ / 2 plate 412 is 72.9°. It is confirmed from Fig. 20 and Fig. 21 that the transmission mode efficiency in black display is minimized and the transmission contrast is maximized at the optimal axis setting values ​​(see Table 4) obtained in (II) above.

[0192] (b) Relationship between the axis setting of the optical film and chromaticity For the test cell 1000, the relationship between the axis setting of the rear optical film and the chromaticity of the white display was examined. The chromaticity was evaluated using an xy chromaticity diagram. For reference, the chromaticity of a D65 light source (x=0.3127, y=0.3290) was plotted in each diagram. The results are shown in Fig. 22 and Fig. 23. Fig. 22 and Fig. 23 are diagrams showing the results of Verification Example 1.

[0193] The graph in Fig. 22 is a graph in which chromaticity was measured by rotating only the first retardation layer 41 (i.e., the first λ / 2 plate 412 and the first λ / 4 plate 411). The first retardation layer 41 was rotated within a range of ±10° from the optimal value of the axis setting obtained in (II) above (see Table 4). The axis angle of the polarizing plate 51 was fixed to the initial setting. The angle between the slow axis 412SA of the λ / 2 plate 412 and the slow axis 411SA of the λ / 4 plate 411 was fixed, and the λ / 2 plate 412 and the λ / 4 plate 411 were rotated as a set.

[0194] The graph in Fig. 23 is a graph in which the chromaticity was measured by rotating only the first polarizing plate 51. The polarizing plate 51 was rotated within a range of ±10° from the optimal value of the axis setting obtained in (II) above (see Table 4). The axis angle of the first retardation layer 41 was fixed to the initial setting.

[0195] 22 and 23, it was found that the axis settings close to the chromaticity of the D65 light source are 11.9° for the slow axis 411SA of the first λ / 4 plate 411 and 70.9° for the slow axis 412SA of the first λ / 2 plate 412. With these axis settings, it is believed that chromaticity approximately equivalent to that of the D65 light source can be obtained by adjusting the color tone (yellow shift) of the light source (backlight 61 in this verification example) and adjusting the color of the color filter.

[0196] (Prototype 2) Test cell 2000 was produced in the same manner as test cell 1000, except that during the production process of test cell 1000, the process of attaching an optical film to the first substrate 10 side of liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 411, a positive C plate 43, a λ / 2 plate 412 and a polarizing plate 51 in this order to the first substrate 10 side of liquid crystal cell 1100.

[0197] (Prototype 3) Test cell 3000 was produced in the same manner as test cell 1000, except that in the production process of test cell 1000, the process of attaching an optical film to the first substrate 10 side of liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 411, a first positive C plate 43, a λ / 2 plate 412, a second positive C plate 45 and a polarizing plate 51 in this order to the first substrate 10 side of liquid crystal cell 1100.

[0198] (Prototype 4) Test cell 4000 was produced in the same manner as test cell 1000, except that during the production process of test cell 1000, the process of attaching an optical film to the second substrate 30 side of liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 421, a positive C plate 44, a λ / 2 plate 422 and a polarizing plate 52 in this order to the second substrate 30 side of liquid crystal cell 1100.

[0199] (Prototype 5) Test cell 5000 was produced in the same manner as test cell 1000, except that in the process of producing test cell 1000, the process of attaching an optical film to liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 411, a positive C plate 43, a λ / 2 plate 412 and a polarizing plate 51 in this order to the first substrate 10 side of the liquid crystal cell 1100, and attaching a λ / 4 plate 421, a positive C plate 44, a λ / 2 plate 422 and a polarizing plate 52 in this order to the second substrate 30 side of the liquid crystal cell 1100.

[0200] (Prototype 6) During the production process of the above test cell 1000, the process of attaching an optical film to the liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 411, a first positive C plate 43, a λ / 2 plate 412, a second positive C plate 45 and a polarizing plate 51 in this order to the first substrate 10 side of the liquid crystal cell 1100, and attaching a λ / 4 plate 421, a positive C plate 44, a λ / 2 plate 422 and a polarizing plate 52 in this order to the second substrate 30 side of the liquid crystal cell 1100. Except for this, a test cell 6000 was produced in the same manner as the production method of the above test cell 1000.

[0201] (Prototype 7) Test cell 7000 was produced in the same manner as test cell 1000, except that in the process of producing test cell 1000, the process of attaching an optical film to the second substrate 30 side of liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 421, a first positive C plate 44, a λ / 2 plate 422, a second positive C plate 46 and a polarizing plate 52 in this order.

[0202] (Prototype Example 8) Test cell 8000 was produced in the same manner as test cell 1000, except that in the production process of test cell 1000, the process of attaching an optical film to liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 411, a positive C plate 43, a λ / 2 plate 412 and a polarizing plate 51 in this order to the first substrate 10 side of the liquid crystal cell 1100, and attaching a λ / 4 plate 421, a first positive C plate 44, a λ / 2 plate 422, a second positive C plate 46 and a polarizing plate 52 in this order to the second substrate 30 side of the liquid crystal cell 1100.

[0203] (Prototype Example 9) During the production process of the above test cell 1000, the process of attaching an optical film to the liquid crystal cell 1100 was changed to a process of attaching a λ / 4 plate 421, a first positive C plate 44, a λ / 2 plate 422, a second positive C plate 45 and a polarizing plate 52 in this order, and attaching a λ / 4 plate 421, a first positive C plate 44, a λ / 2 plate 422, a second positive C plate 46 and a polarizing plate 52 in this order to the second substrate 30 side of the liquid crystal cell 1100. Except for this, a test cell 9000 was produced in the same manner as the production method of the above test cell 1000.

[0204] In prototypes 2 to 9, films with an Rth of 200 nm were used as the positive C plates 43 and 44 disposed between the λ / 4 plate and the λ / 2 plate, and films with an Rth of 115 nm were used as the positive C plates 45 and 46 disposed between the λ / 2 plate and the polarizing plate. The layer structures of the test cells obtained in prototypes 2 to 9 are shown in Figures 19B to 19F, respectively. Figures 19B to 19F are cross-sectional schematic diagrams showing the layer structures of the test cells obtained in prototypes 2 to 9, respectively.

[0205] (Verification example 2) In this verification example, the following (c) and (d) were examined using test cells 1000 to 9000, respectively. The twist angle was set to 83°, and a positive-type liquid crystal material was used. The optical axis settings (initial settings) of this verification example are shown in Table 5 and Figs. 24 to 26. Fig. 24 is a conceptual diagram showing the optical axis setting in an example using test cell 4000, which corresponds to the most preferred optical axis setting in the above-mentioned embodiment 1. Fig. 25 is a conceptual diagram showing the optical axis setting in an example using test cell 5000, which corresponds to the most preferred optical axis setting in the above-mentioned embodiment 2. Fig. 26 is a conceptual diagram showing the optical axis setting in an example using test cell 9000, which corresponds to the most preferred optical axis setting in the above-mentioned embodiment 3.

[0206] (c) Front contrast and viewing angle characteristics of white display in reflective mode The front contrast ratio (also referred to as front CR) and the viewing angle characteristic of white display were measured for each of the test cells 1000, 4000, and 9000. Then, the cells were evaluated according to the following criteria. The results are shown in Table 6.

[0207] (Front contrast) The ratio of the reflectance at 5 V to the reflectance at 0 V in the reflective mode (5 V / 0 V) was determined. The values ​​are shown in Table 6. Based on these values, evaluation was performed according to the following criteria. ◎(Excellent): The above ratio is 45 or more. ◯ (Very good): The above ratio is 35 or more and less than 45. △(Good): The ratio is 20 or more and less than 35. × (Poor): The ratio is less than 20.

[0208] (Viewing angle characteristics) The viewing angle characteristics were evaluated in a total of eight directions, four directions (up, down, left, right) and four diagonal directions, according to the following criteria, with the 3 o'clock direction as 0°, the upward direction as 90°, the downward direction as 270°, the left direction as 180°, the right direction as 0°, and the diagonal directions as 45°, 135°, 225°, and 315°. The results are shown in Table 6. ◯ (Very good): The reflectance difference (maximum reflectance - minimum reflectance) at a polar angle of 60° is less than 2%. Δ(Good): The reflectance difference is 2% or more and less than 5%. × (Poor): The reflectance difference is 5% or more.

[0209] [Table 6]

[0210] From Table 6, it can be seen that in the reflective display, Example 2-4 using Test Cell 4000 has a higher front contrast ratio, and Example 2-9 has an even higher front contrast ratio, compared to Example 2-1 using Test Cell 1000. The viewing angle characteristics are also better in Examples 2-4 and 2-9 than in Example 2-1.

[0211] (d) Viewing angle characteristics of white display in transmissive mode The viewing angle characteristics of the white display were measured for each of the test cells 1000 to 9000. The viewing angle characteristics were evaluated in a total of eight directions, four directions, up and down, left and right, and four diagonal directions, according to the following criteria, after measuring the luminance (absolute value) in the azimuth angle range of 0 to 359° and the polar angle range of 0 to 88° in the white display in the transmission mode. The following criteria indicate how the azimuth angle symmetry of the transmission contrast in the corresponding example was compared with the azimuth angle symmetry of the transmission contrast in Example 2-1 using the test cell 1000. Note that the directions were set to 0°, with the 3 o'clock direction on a clock as 3 o'clock, an azimuth of 90° for the upward direction, 270° for the downward direction, 180° for the left direction, and 0° for the right direction, and the diagonal directions were azimuth of 45°, 135°, 225°, and 315°. For the measurements, "EZContrast" manufactured by ELDIM was used. The results are shown in Tables 7 to 9. ◎(Outstanding):The best. 〇〇(Excellent): Even better (a rating between ◎ and 〇). 〇(Very good):Good. △(Good): Somewhat good. ×(Poor): Same or worse.

[0212] [Table 7]

[0213] [Table 8]

[0214] [Table 9]

[0215] From Tables 7 to 9, it can be seen that in transmissive display, Examples 2-2, 2-4, 2-5, and 2-9 have better viewing angle characteristics than Example 2-1, which uses test cell 1000. Among these, Examples 2-4, 2-5, and 2-9 are better, Examples 2-5 and 2-9 are even better, and Example 2-9 is the best.

[0216] (Verification example 3) In this verification example, the viewing angle characteristics and the like were examined in more detail using each of the test cells 1000, 4000, 5000, and 9000. Specifically, the following (e) to (n) were examined. The twist angle was set to 83°, and a positive type liquid crystal material was used. The optical axis settings (initial settings) of this verification example are shown in Table 5 and Figures 24 to 26. In the following (e) to (i), when test cell 5000 was used (Example 3-5), the same results were obtained as in Example 3-4, in which test cell 4000 was used, so the results of Example 3-5 are omitted.

[0217] (e) Viewing angle characteristics of white display in reflective mode The distribution of reflectance in white display in reflective mode for each test cell was measured using a "Display Measuring System" (model number: DMS 803) manufactured by Instrument Systems. The orientation of the graph of reflectance characteristics was set to 0° at 3 o'clock on a clock, with the upward direction being 90°, the downward direction being 270°, the left direction being 180°, the right direction being 0°, and the diagonal directions being 45°, 135°, 225°, and 315°. In addition, the reflectance characteristics were graphed for the orientation with the widest distribution of reflectance (also referred to as orientation I) and the orientation with the narrowest distribution of reflectance (also referred to as orientation II). The results are shown in Figs. 27A to 27C. Figs. 27A to 27C are diagrams showing the results of Verification Example 3.

[0218] Comparing the white reflectance distribution diagrams in each figure, it can be seen that in Example 3-9, the distribution diagram is closest to a circle, and therefore the viewing angle characteristics in white display are the best. In each of Examples 3-1, 3-4, and 3-9, the orientation I is 120° and the orientation II is 30°.

[0219] From the graphs of white reflectance, it can be seen that in all of Examples 3-1, 3-4, and 3-9, there is no difference in reflectance between the upward and downward directions, and no difference in reflectance between the left and right directions. On the other hand, the difference in reflectance in oblique directions is smaller in Examples 3-4 and 3-9 than in Example 3-1, and the difference in reflectance between the orientation with the widest distribution and the orientation with the narrowest distribution is also smaller in Examples 3-4 and 3-9 than in Example 3-1.

[0220] Therefore, it was found that the viewing angle characteristics of white display were the best in Example 3-9 and also good in Example 3-4 (and Example 3-5), while being poor in Example 3-1.

[0221] (f) Viewing angle characteristics of black display in reflective mode The distribution of reflectance in black display for each test cell was measured using a "Display Measuring System" (model number: DMS 803) manufactured by Instrument Systems. The orientation of the graph of reflectance characteristics was set to 0° at 3 o'clock on a clock, with the upward direction being 90°, the downward direction being 270°, the left direction being 180°, the right direction being 0°, and the diagonal directions being 45°, 135°, 225°, and 315°. In addition, the reflectance characteristics were graphed for the orientation I with the widest distribution of reflectance and the orientation II with the narrowest distribution. The results are shown in Figs. 28A to 28C. Figs. 28A to 28C are diagrams showing the results of Verification Example 3.

[0222] From the black reflectance distribution diagrams in each figure, in Example 3-1, orientation I is 30° and orientation II is 165°, in Example 3-4, orientation I is 150° and orientation II is 105°, and in Example 3-9, orientation I is 135° and orientation II is 45°. Note that the shape of the reflectance distribution can be made symmetrical in the up-down and left-right directions by changing the direction of the initial alignment of the liquid crystal molecules.

[0223] From the graphs of black reflectance, it can be seen that in all of Examples 3-1, 3-4, and 3-9, there is no difference in reflectance between the upward and downward directions, and there is also no difference in reflectance between the left and right directions. On the other hand, it can be seen that the difference in reflectance in the diagonal directions is large in Example 3-1, but is small in Example 3-9, and even smaller in Example 3-4. It can be seen that the difference in reflectance between orientation I and orientation II is very large in Example 3-1, but is small in Examples 3-4 and 3-9.

[0224] Therefore, it was found that the viewing angle characteristics in black display were almost equally good in Example 3-9 and Example 3-4 (and Example 3-5), whereas the viewing angle characteristics were poor in Example 3-1.

[0225] (g) Isocontours in reflection mode For each test cell, the distribution of contrast in the reflective mode was obtained from the viewing angle characteristics of white display and the viewing angle characteristics of black display. Specifically, the reflectance ratio (reflectance of white display / reflectance of black display) was obtained at each azimuth angle and polar angle. The azimuth was set to 0° at 3 o'clock on a clock, 90° upward, 270° downward, 180° leftward, 0° rightward, and 45°, 135°, 225°, and 315° oblique directions. The results are shown in Figs. 29A to 29C. Figs. 29A to 29C are diagrams showing the results of Verification Example 3.

[0226] 29A to 29C show that the contrast characteristics in the reflective mode are almost equally good in Example 3-9 and Example 3-4 (and Example 3-5), while they are poor in Example 3-1. Note that the shape of the contrast distribution can be made symmetrical in the vertical and horizontal directions by changing the initial orientation of the liquid crystal molecules.

[0227] (h) Viewing angle characteristics in reflective mode (diagonal gamma characteristics) For each test cell, a distribution diagram of the reflected luminance from a grayscale level of 255 in white display to a grayscale level of 0 in black display was measured for every 32 levels using a "Display Measuring System" (model number: DMS 803) manufactured by Instrument Systems. As a representative example, a distribution diagram of the reflected luminance at a grayscale level of 255 in white display is shown. The γ curve was calculated from the results of predetermined grayscales (255, 224, 192, 160, 128, 96, 64, 32, 0). From the obtained distribution diagram, the orientation (also called orientation III) where the grayscale is higher than the front (γ=2.2) and the orientation (also called orientation IV) where the grayscale is lower than the front (γ=2.2) or shows peculiar characteristics were obtained, and the γ curve was analyzed at these orientations with a polar angle of 50°. In the graph of the oblique γ characteristic, the horizontal axis is the grayscale (0 to 255 levels) when viewed from the front, and the vertical axis is the normalized reflectance. The front was corrected to γ=2.2. The results are shown in Figures 30A to 30C. Figures 30A to 30C are diagrams showing the results of Verification Example 3.

[0228] From the white luminance distribution diagrams in each figure, in Example 3-1, the orientation III is 300° and the orientation IV is 30°, in Example 3-4, the orientation III is 165° and the orientation IV is 270°, and in Example 3-9, the orientation III is 225° and the orientation IV is 330°. Each angle represents the angle of the orientation when the 3 o'clock direction on a clock is set as 0°.

[0229] (i) Viewing angle characteristics in reflective mode (image simulation) An image simulation was carried out when the display screen was viewed from each of orientations III and IV obtained from the distribution maps of Figures 30A to 30C. Specifically, a color original image was used as a front-view image (also called an original image), and the original image was converted according to the gamma curves for each azimuth angle and polar angle of 50°. The results are shown in Figures 30A to 30C. For comparison, a front-view image is shown in Figure 31.

[0230] 30A to 30C show that the display quality of an oblique image is the best in Example 3-9, and is also good in Example 3-4 (and Example 3-5), while it is poor in Example 3-1. Also, from the viewpoint of film cost and production yield, Example 3-4 using test cell 4000 (and Example 3-5 using test cell 5000) is the most effective.

[0231] (j) Viewing angle characteristics of white display in transmissive mode For each test cell, a distribution diagram of the transmission luminance at a grayscale level of 255 in white display was measured using "EZContrast" manufactured by ELDIM. The orientation of the graph of the luminance characteristics was 0°, with the 3 o'clock direction of the clock as the azimuth 90°, the downward direction as the azimuth 270°, the left direction as the azimuth 180°, the right direction as the azimuth 0°, and the diagonal directions as the azimuth 45°, 135°, 225°, and 315°. In addition, the luminance characteristics were graphed for the azimuth I, which has the widest distribution of white luminance, and the azimuth II, which has the narrowest distribution. The results are shown in Figs. 32A to 32D. Figs. 32A to 32D are diagrams showing the results of Verification Example 3.

[0232] From the white luminance distribution diagrams in each figure, in Example 3-1, orientation I is 130° and orientation II is 20°, in Example 3-4, orientation I is 150° and orientation II is 20°, in Example 3-4, orientation I is 170° and orientation II is 80°, and in Example 3-9, orientation I is 160° and orientation II is 70°.

[0233] 32A to 32D show that the viewing angle characteristics of white display in the transmissive mode are the best in Example 3-9, followed by Example 3-5, and then Example 3-4, while Example 3-1 is poor. From the viewpoints of film cost and production yield, Example 3-4 using test cell 4000 is the most effective.

[0234] (k) Viewing angle characteristics of black display in transmissive mode For each test cell, a distribution diagram of the transmission luminance at gradation level 0 of black display was measured using "EZContrast" manufactured by ELDIM. The orientation of the graph of the luminance characteristics was 0°, with the 3 o'clock direction of the clock as 0°, the upward direction was 90°, the downward direction was 270°, the left direction was 180°, the right direction was 0°, and the diagonal directions were 45°, 135°, 225°, and 315°. In addition, the luminance characteristics were graphed for the orientation I where the distribution of black luminance is the widest, and the orientation II where the distribution is the narrowest. The results are shown in Figs. 33A to 33D. Figs. 33A to 33D are diagrams showing the results of Verification Example 3.

[0235] From the black luminance distribution diagrams in each figure, in Example 3-1, orientation I is 30° and orientation II is 165°, in Example 3-4, orientation I is 135° and orientation II is 90°, in Example 3-4, orientation I is 135° and orientation II is 90°, and in Example 3-9, orientation I is 135° and orientation II is 90°.

[0236] 33A to 33D show that the viewing angle characteristics of black display in the transmissive mode are the best for Example 3-9, followed by Example 3-5, and then Example 3-4, while Example 3-1 is poor. From the viewpoints of film cost and production yield, Example 3-4 using test cell 4000 is the most effective.

[0237] (l) Isocontours in transparent mode For each test cell, the distribution of contrast in the transmissive mode was obtained from the white luminance distribution diagram and the black luminance distribution diagram. Specifically, the luminance ratio (luminance of white display / luminance of black display) was obtained at each azimuth angle and polar angle. The orientation of the luminance characteristic graph was set to 0° at 3 o'clock on a clock, with the upward direction being 90°, the downward direction being 270°, the left direction being 180°, the right direction being 0°, and the diagonal directions being 45°, 135°, 225°, and 315°. The results are shown in Figs. 34A to 34D. Figs. 34A to 34D are diagrams showing the results of Verification Example 3.

[0238] 34A to 34D show that the contrast characteristics in the transmissive mode are the best for Example 3-9, followed by Example 3-5, then Example 3-4, while Example 3-1 is poor. Example 3-9 has the best balance of vertical and horizontal viewing angles. In each contrast distribution diagram, the central value is 50 or more.

[0239] (m) Viewing angle characteristics in transmissive mode (diagonal gamma characteristics) For each test cell, a distribution diagram of the transmission luminance from a grayscale level of 255 in white display to a grayscale level of 0 in black display was measured for every 32 levels using "EZContrast" manufactured by ELDIM. As a representative example, a distribution diagram of the transmission luminance at a grayscale level of 255 in white display is shown. The γ curve was calculated from the results of predetermined grayscales (255, 224, 192, 160, 128, 96, 64, 32, 0). From the obtained distribution diagram, the orientation III where the grayscale is higher than the front (γ = 2.2) and the orientation IV where the grayscale is lower than the front (γ = 2.2) or shows peculiar characteristics were obtained, and the γ curve was analyzed at these orientations with a polar angle of 50°. In the graph of the oblique γ characteristic, the horizontal axis is the grayscale (0 to 255 levels) when viewed from the front, and the vertical axis is the normalized luminance. The front was corrected to γ ​​= 2.2. The results are shown in Figures 35A to 35D. 35A to 35D are diagrams showing the results of Verification Example 3.

[0240] From the white luminance distribution diagrams in each figure, in Example 3-1, the orientation III is 130° and the orientation IV is 202°, ​​in Example 3-4, the orientation III is 88° and the orientation IV is 5°, in Example 3-5, the orientation III is 220° and the orientation IV is 275°, and in Example 3-9, the orientation III is 240° and the orientation IV is 265°. Each angle represents the angle of the orientation when the 3 o'clock direction on a clock is set as 0°.

[0241] (n) Viewing angle characteristics in transmission mode (image simulation) An image simulation was carried out when the display screen was viewed from each of orientations III and IV obtained from the distribution maps of Figures 35A to 35D. Specifically, a color original image was used as a front-view image (also called an original image), and the original image was converted according to the gamma curves for each azimuth angle and polar angle of 50°. The results are shown in Figures 35A to 35D. For comparison, a front-view image is shown in Figure 31.

[0242] 35A to 35D show that the display quality of an obliquely viewed image is the best in Example 3-9, and is also good in Examples 3-4 and 3-5, while it is poor in Example 3-1. From the viewpoints of film cost and production yield, Example 3-4 using test cell 4000 is the most effective.

[0243] The above-described aspects of the present invention may be combined as appropriate without departing from the gist of the present invention. [Explanation of symbols]

[0244] 1: Semi-reflective liquid crystal display device 1T: Transmissive liquid crystal display device 1R: Reflective liquid crystal display device 1X: LCD panel 10, 30: PCB 20: Liquid crystal layer 21, 21A, 21B: Liquid crystal molecules 41, 42: Retardation layer 411, 421: λ / 4 board 412, 422: λ / 2 plate 411SA, 421SA, 412SA, 422SA: In-plane slow axis 43, 44, 45, 46: Positive C-plate 51, 52: Polarizing plate 51AA, 52AA: Polarization axis 61, 62: Light source 100, 300: Support substrate 110: TFT 121, 122: Electrode 130: Reflective layer 140, 340: Horizontal alignment film 151, 152: Interlayer insulating layer 153: Dielectric layer 160: Contact electrode 310: Color filter layer 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000: Test cells 1100: Liquid crystal cell BP: Backplane circuit CE: Common electrode PE: Pixel electrode CH1, CH2: Contact hole DR:Display area FR: Hidden area GL: Gate wiring SL: Source wiring p: protruding part P: Pixel Rf:Reflection area Tr:Transmission area Sl: Slit SP, SPa, SPb: Band TC: Touch wiring contact part TD: Touch drive unit TL, TL1, TL2: Touch wiring TX: Touch sensor electrode

Claims

1. A liquid crystal display device having a plurality of pixels, The liquid crystal display device includes, in order from a rear surface side to a viewing surface side, a first polarizing plate, a first retardation layer, a first substrate, a liquid crystal layer, a second substrate, a second retardation layer, and a second polarizing plate; the first substrate has a reflective layer, a pair of electrodes capable of generating a transverse electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer; the second substrate has a second horizontal alignment film in contact with the liquid crystal layer, the first retardation layer includes a first λ / 2 plate and a first λ / 4 plate, the second retardation layer includes a second λ / 2 plate and a second λ / 4 plate, At least one of the first retardation layer and the second retardation layer further includes a positive C plate, The liquid crystal layer has a twisted orientation when no voltage is applied, Each pixel has a reflective area that reflects light by the reflective layer to perform display, and a transmissive area that transmits light to perform display.

1. A semi-transmissive liquid crystal display device comprising:

2. The liquid crystal layer contains a liquid crystal material having a positive dielectric anisotropy.

2. The semi-transmissive liquid crystal display device according to claim 1.

3. Satisfy any of the following (i) to (iii):

2. The semi-transmissive liquid crystal display device according to claim 1. (i) The second retardation layer includes one positive C plate, and the first retardation layer does not include a positive C plate. (ii) The first retardation layer and the second retardation layer each include one positive C plate. (iii) Each of the first retardation layer and the second retardation layer includes two of the positive C plates.

4. the first λ / 2 plate and the first λ / 4 plate are located in this order from the rear side, the second λ / 2 plate and the second λ / 4 plate are located in this order from an observation surface side, The in-plane retardation Re of the first λ / 2 plate and the in-plane retardation Re of the second λ / 2 plate are substantially the same, The in-plane retardation Re of the first λ / 4 plate and the in-plane retardation Re of the second λ / 4 plate are substantially the same.

2. The semi-transmissive liquid crystal display device according to claim 1.

5. The positive C plate is located between the first λ / 2 plate and the first λ / 4 plate and / or between the second λ / 2 plate and the second λ / 4 plate.

2. The semi-transmissive liquid crystal display device according to claim 1.

6. The positive C plate has a thickness direction retardation Rth (nm) of 150 to 270 nm in absolute value.

2. The semi-transmissive liquid crystal display device according to claim 1.

7. The retardation layer further includes a second positive C plate, The second positive C plate is located between the first λ / 2 plate and the first polarizing plate, and between the second λ / 2 plate and the second polarizing plate.

2. The semi-transmissive liquid crystal display device according to claim 1.

8. The second positive C plate has a thickness direction retardation Rth (nm) of 50 to 130 nm in absolute value.

8. The semi-transmissive liquid crystal display device according to claim 7.

9. The twist angle of the liquid crystal layer when no voltage is applied is 70° or more and 85° or less.

2. The semi-transmissive liquid crystal display device according to claim 1.

10. The product (dΔn) of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal material constituting the liquid crystal layer is 218 nm or more and 255 nm or less.

2. The semi-transmissive liquid crystal display device according to claim 1.

11. When the alignment direction of the liquid crystal molecules defined by the first horizontal alignment film is taken as the reference (0°) and the twist direction is taken as a positive angle, The polarization axis of the first polarizing plate, the in-plane slow axis of the first λ / 2 plate, and the in-plane slow axis of the first λ / 4 plate are positioned at angles of −6.6 to 1.4°, 70.9 to 74.9°, and 10.0 to 17.8°, respectively.

2. The semi-transmissive liquid crystal display device according to claim 1.

12. When the alignment direction of the liquid crystal molecules defined by the first horizontal alignment film is taken as the reference (0°) and the twist direction is taken as a positive angle, The polarization axis of the second polarizing plate, the in-plane slow axis of the second λ / 2 plate, and the in-plane slow axis of the second λ / 4 plate are positioned at angles of −70.5° to −63.5°, −52.5° to −47.5°, and −27.9° to −22.9°, respectively.

2. The semi-transmissive liquid crystal display device according to claim 1.

13. At least one of the pair of electrodes has a plurality of strip portions and a slit located between two adjacent strip portions of the plurality of strip portions.

2. The semi-transmissive liquid crystal display device according to claim 1.

14. The alignment direction of the liquid crystal molecules defined by the first horizontal alignment film is in the range of −30° to 30° with respect to the direction in which the strip portions extend (0°).

2. The semi-transmissive liquid crystal display device according to claim 1.

15. Single domain orientation 2. The semi-transmissive liquid crystal display device according to claim 1.

16. Display in normally black mode 2. The semi-transmissive liquid crystal display device according to claim 1.

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

2. The semi-transmissive liquid crystal display device according to claim 1.

18. Further, a light source is provided.

18. The semi-transmissive liquid crystal display device according to claim 1,

Images