Transflective type liquid crystal display device

Abstract

To provide a transflective type liquid crystal display device in which flickering hardly occurs even with low frequency drive, and which is superior also in response characteristics, and useful also as an in-cell type touch panel allowing display in a reflection mode.SOLUTION: A transflective type liquid crystal display device comprises: a first substrate; a second substrate facing the first substrate; a liquid crystal layer interposed between the first substrate and the second substrate; and a plurality of pixels. The first substrate includes: a reflective layer that reflects light; a pair of electrodes that can generate a lateral electric field on the liquid crystal layer; and a first horizontal orientation film. The second substrate includes a second horizontal orientation film. The liquid crystal layer assumes a twist orientation when no voltage is applied, and contains a chemical compound having a structure represented by -CF2-O- in a molecule, in the total amount of 100 mass% of a liquid crystal material constituting the liquid crystal layer. Further, in the liquid crystal layer, a content of a positive type liquid crystal material with a positive dielectric anisotropy is 45 mass% or less. Each of the pixels includes: a reflective region for performing display by reflecting light on the reflective layer; and a transmission region for performing display by transmitting light.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 broadly classified into transmissive and reflective types depending on the image display method. Transmissive display devices display in transmissive mode, using transmitted light from a backlight behind the screen. Reflective display devices display in reflective mode, using external light (also called ambient light) instead of backlight. As a display device that combines these features, a semi-transmissive display device has also been proposed, in which each pixel has a region that displays in transmissive mode (transmissive region) and a region that displays in reflective mode (reflective region).

[0003] Liquid crystal display devices can also be broadly classified by the liquid crystal driving method. For example, there are known vertical electric field display devices that display by driving a liquid crystal layer with an electric field in a direction approximately perpendicular to the substrate surface, and horizontal electric field display devices that display by driving a liquid crystal layer with an electric field in a direction approximately parallel to the substrate surface. Examples of vertical electric field modes include TN (Twisted Nematic) mode and MVA (Multi-domain Vertical Alignment) mode, while examples of horizontal electric field modes include IPS (In-plane Switching) mode and FFS (Fringe Field Switching) mode. For example, Patent Document 1 discloses an IPS-mode transmissive liquid crystal display device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5315136 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, liquid crystal display devices used in smartphones, tablets, and the like are usually provided with a touch sensor function. Various types of touch sensors are known, such as resistive, capacitive, and optical types. Liquid crystal display devices equipped with a touch sensor (also called touch panels) are classified into two types: one in which the touch sensor is externally attached (external type) and one in which the touch sensor is built-in (built-in type). Built-in touch panels are advantageous over external touch panels in that they can have a narrower frame, be thinner, and lighter, and also have the advantage of being able to increase light transmittance.

[0006] Built-in touch panels are classified into on-cell and in-cell types. 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, a counter substrate facing the active matrix substrate, and a liquid crystal layer sandwiched between these substrates. Typically, in-cell touch panels have a touch sensor layer located within the display panel, while in on-cell touch panels, the touch sensor layer is located between the display panel and a polarizer on the viewing side of the display panel. In principle, the in-cell type offers the thinnest and lightest touch panels. Furthermore, because liquid crystal display devices capable of reflective mode display are suitable for outdoor use, there is a demand for in-cell touch panels capable of reflective mode display, but these have yet to be realized.

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

[0008] The present inventors further investigated FFS mode devices that display in a normally black mode, for example. Specifically, a test cell 1R was prepared using liquid crystal material No. 4, which has a positive dielectric anisotropy and is used in conventional reflective liquid crystal displays (see Comparative Example 1, described below). However, this test cell 1R exhibited flickering, a flashing phenomenon known as "flicker," on the screen. Particularly at low frequencies, such as 1 Hz, a downward-biased waveform occurred when the applied voltage reversed polarity (see Figures 27 and 29), resulting in noticeable flickering. While lowering the drive frequency of a liquid crystal display device is desirable because it reduces power consumption, low-frequency drive tends to increase flickering. Furthermore, this test cell 1R exhibited a slow fall response time Td, posing a problem with its response characteristics.

[0009] The present disclosure has been made in consideration of the above-mentioned current situation, and aims to provide a semi-transmissive liquid crystal display device that is less likely to cause flicker even when driven at low frequencies, has excellent response properties, and is also useful as an in-cell touch panel capable of displaying in reflective mode. [Means for solving the problem]

[0010] (1) One embodiment of the present disclosure is a semi-transmissive liquid crystal display device having a first substrate, a second substrate opposite the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate, the liquid crystal display device having a plurality of pixels, the first substrate having a reflective layer that reflects light, a pair of electrodes that can generate a transverse electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer having a twisted alignment when no voltage is applied, the liquid crystal layer containing a compound having a structure represented by -CF2-O- in its molecule and having positive dielectric anisotropy, with a content of 45% by mass or less out of a total of 100% by mass of liquid crystal material constituting the liquid crystal layer, and each pixel having a reflective region that reflects light by the reflective layer to perform display, and a transmissive region that transmits light to perform display.

[0011] (2) In one embodiment of the present disclosure, in addition to the configuration of (1) above, 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, and in each pixel, the plurality of strip portions have linear shapes that are approximately parallel to each other and extend in the same direction, and when no voltage is applied, the orientation direction of the liquid crystal molecules on the first substrate side is between -4° and 0°, with the direction in which the plurality of strip portions extend being taken as the reference 0°.

[0012] (3) In an embodiment of the present disclosure, in addition to the configuration of (1) or (2), a compound represented by the following formula (1): RP value = γ1 / K 22 (1) (In the formula, γ1 represents the rotational viscosity coefficient (mPa·sec) of the liquid crystal material constituting the liquid crystal layer. K 22 represents the twist elastic constant (unit: pN). The semi-transmissive liquid crystal display device has an RP value represented by ) of 17 or less.

[0013] (4) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device that includes, in addition to the configuration of (1), (2), or (3), a first polarizing plate, a first retardation layer, the first substrate, the liquid crystal layer, the second substrate, a second retardation layer, and a second polarizing plate, in this order from the rear side, wherein 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, and at least one of the first retardation layer and the second retardation layer further includes a positive C plate.

[0014] (5) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device in which, in addition to the configuration (4), the second retardation layer includes one of the positive C plates, and the first retardation layer does not include a positive C plate or includes one of the positive C plates.

[0015] (6) In one embodiment of the present disclosure, in addition to the configuration of (4) or (5) above, the first λ / 2 plate and the first λ / 4 plate are positioned in this order from the rear side, the second λ / 2 plate and the second λ / 4 plate are positioned in this order from the observation side, the in-plane retardation Re of the first λ / 2 plate and the second λ / 2 plate are approximately the same, and the in-plane retardation Re of the first λ / 4 plate and the second λ / 4 plate are approximately the same.

[0016] (7) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device, in which, in addition to the configuration of (4), (5), or (6), 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.

[0017] (8) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device having the configuration of (1), (2), (3), (4), (5), (6), or (7) above, wherein the twist angle of the liquid crystal layer when no voltage is applied is 58.3° or more and 89.9° or less.

[0018] (9) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device having the configuration of (1), (2), (3), (4), (5), (6), (7), or (8) above, wherein the ratio L / S of the width L per strip in plan view to the width S per slit in plan view is 0.4 to 0.7 / 1.

[0019] (10) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device having a single domain orientation in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), or (9).

[0020] (11) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device that displays in a normally black mode in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), or (10) above.

[0021] (12) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), or (11) above, wherein one of the first electrode or the second electrode is a pixel electrode provided in each of the plurality of pixels, and the other is a common electrode including a plurality of segments each capable of functioning as a touch sensor electrode, and the first substrate has a plurality of touch wirings each connected to the corresponding touch sensor electrode.

[0022] (13) An embodiment of the present disclosure is a semi-transmissive liquid crystal display device that further includes a light source in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), or (12) above. [Effects of the Invention]

[0023] According to the present disclosure, it is possible to provide a semi-transmissive liquid crystal display device that is less likely to cause flicker even when driven at low frequencies, has excellent response properties, and is useful as an in-cell touch panel capable of displaying in reflective mode. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view showing a structure of a semi-transmissive liquid crystal display device 1 according to first to third embodiments. [Figure 2] 1 is a cross-sectional view schematically illustrating a pixel included in a semi-transmissive liquid crystal display device 1 according to Embodiment 1. FIG. [Figure 3] FIG. 1 is a plan view schematically illustrating the entire semi-transmissive liquid crystal display device 1 according to the first to third embodiments, as viewed from the observation surface side. [Figure 4] FIG. 1 is a plan view schematically illustrating that each pixel P has a reflective region Rf and a transmissive region Tr in a transflective liquid crystal display device 1 according to first to third embodiments. [Figure 5] FIG. 10 is a diagram for explaining the slit angle of liquid crystal molecules. [Figure 6] FIG. 10 is a diagram for explaining the definition of an angle. [Figure 7] FIG. 2 is a plan view schematically illustrating one pixel. [Figure 8] FIG. 8 is a schematic plan view showing an enlarged portion of FIG. 7. [Figure 9] 1 is a schematic plan view showing an example of the structure of a pixel (angle X is 0°). [Figure 10A] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is 0°). [Figure 10B] FIG. 1 is a plan view showing an example of a pixel arrangement (angle X is −10°). [Figure 10C] FIG. 1 is a plan view showing an example of a pixel arrangement (angle X is +10°). [Figure 10D] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −90°). [Figure 10E] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −100°). [Figure 10F] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −80°). [Figure 11] FIG. 1 is a diagram conceptually showing the polarized structure of a compound represented by formula (I). [Figure 12] 2 is a plan view schematically illustrating the arrangement relationship between touch sensor electrodes TX and touch wirings TL included in the transflective liquid crystal display device 1 according to the first embodiment. FIG. [Figure 13] 1 is a cross-sectional view showing a structure of a semi-transmissive liquid crystal display device 1 according to a first modification of the first embodiment. [Figure 14] 10 is a cross-sectional view showing a pixel included in a semi-transmissive liquid crystal display device 1 according to a second embodiment. FIG. [Figure 15] FIG. 2 is a plan view schematically illustrating an example of the structure of a pixel. [Figure 16A] FIG. 2 is a plan view schematically illustrating an example of an arrangement of pixels. [Figure 16B] FIG. 2 is a plan view schematically illustrating an example of an arrangement of pixels. [Figure 16C] FIG. 2 is a plan view schematically illustrating an example of an arrangement of pixels. [Figure 16D]FIG. 2 is a plan view schematically illustrating an example of an arrangement of pixels. [Figure 16E] FIG. 2 is a plan view schematically illustrating an example of an arrangement of pixels. [Figure 16F] FIG. 2 is a plan view schematically illustrating an example of an arrangement of pixels. [Figure 17] FIG. 2 is a plan view conceptually showing the relationship between the long axis direction of liquid crystal molecules 21 in a liquid crystal layer 20 and the optical axes of each optical film when no voltage is applied. [Figure 18] FIG. 2 is a diagram for explaining the optical axis angle of an optical film. [Figure 19] FIG. 10 is a diagram conceptually showing the most preferable optical axis setting in the second embodiment. [Figure 20] 10 is a cross-sectional view showing a pixel included in a semi-transmissive liquid crystal display device 1 according to a third embodiment. FIG. [Figure 21A] FIG. 1 is a plan view showing the structure of a liquid crystal cell 1100 as viewed from the front. [Figure 21B] 21B is a schematic cross-sectional view (cross-sectional view taken along line AA') in FIG. 21A. [Figure 22A] 1A to 1C are cross-sectional schematic diagrams of test cells 1A, 2A, 3A, 1R, and 2R during reflection observation. [Figure 22B] 1A, 1B, 1C, and 1D are cross-sectional schematic views of test cells 1A, 2A, 3A, 1R, and 2R during transmission observation. [Figure 23A] FIG. 10 is a plan view showing the structure of test cell 3R (and liquid crystal cell 2100) as viewed from the front. [Figure 23B] 23B is a schematic cross-sectional view (cross-sectional view taken along line AA') in FIG. 23A. [Figure 24] FIG. 2 is a schematic cross-sectional view of test cell 3R. [Figure 25] FIG. 10 is a diagram conceptually showing the optical axis setting of the test cell 3R. [Figure 26] 10 is a graph showing the evaluation results when each test cell was used. [Figure 27] 10 is a graph showing the evaluation results when each test cell was used. [Figure 28]10 is a graph showing the evaluation results when each test cell was used. [Figure 29] 10 is a graph showing the evaluation results when each test cell was used. [Figure 30A] 10 is a graph showing the evaluation results when each test cell was used. [Figure 30B] 10 is a graph showing the evaluation results when each test cell was used. [Figure 31A] 10 is a graph showing the evaluation results when each test cell was used. [Figure 31B] 10 is a graph showing the evaluation results when each test cell was used. [Figure 32A] 10 is a graph showing the evaluation results when each test cell was used. [Figure 32B] 10 is a graph showing the evaluation results when each test cell was used. [Figure 32C] 10 is a graph showing the evaluation results when each test cell was used. [Figure 33A] 10 is a luminance profile image when test cell 1A (Example 1) is used. [Figure 33B] 10 is a luminance profile image when test cell 2A (Example 2) is used. [Figure 33C] 10 is a luminance profile image when test cell 3A (Example 3) is used. [Figure 33D] 10 is a luminance profile image when Test Cell 1R (Comparative Example 1) is used. [Figure 34A] 10 is a graph showing the evaluation results when each test cell was used. [Figure 34B] 10 is a graph showing the evaluation results when each test cell was used. [Figure 35A] 10 is a graph showing the evaluation results when each test cell was used. [Figure 35B] 10 is a graph showing the evaluation results when each test cell was used. DETAILED DESCRIPTION OF THE INVENTION

[0025] (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.

[0026] 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.

[0027] 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 of the target direction when projected onto the screen of the LCD panel, and is expressed as the angle (azimuth angle) between the target direction and a reference direction. Unless otherwise specified, the reference orientation (0°) is the horizontal right direction of the LCD panel screen (3 o'clock direction). Angles and azimuth angles are defined as positive angles (+) counterclockwise from the reference orientation and negative angles (-) clockwise from the reference orientation (see Figure 6). Figure 6 is a diagram for explaining the definition of angles, with the horizontal right direction of the screen defined as 0°. Both counterclockwise and clockwise directions represent the rotation direction when the LCD panel screen is viewed from the observation side (front). Angles represent values ​​measured when the LCD panel screen is viewed flat, and refer to acute angles unless otherwise specified, such as the rotation direction.

[0028] The axial direction of an optical film means the direction of the polarization axis of a polarizing plate if it is a polarizing plate, and means the direction of the slow axis if it is a retardation layer. The polarization axis of a polarizing plate means the absorption axis if it is an absorptive polarizing plate, and means the reflection axis if it is a reflective polarizing plate. The axial direction of a retardation layer means the direction of the in-plane slow axis of the retardation layer, unless otherwise specified.

[0029] The retardation layer refers to a layer having at least one of an in-plane retardation (also referred to as an in-plane retardation) Re and a thickness direction retardation (also referred to as a thickness direction retardation) Rth of 10 nm or more. Preferably, it refers to a layer having a value of 20 nm or more. In this specification, the numerical values ​​given for Re and Rth are absolute values ​​unless otherwise specified.

[0030] The in-plane retardation Re is defined as Re=(nx-ny)×d. The thickness direction retardation Rth is defined as Rth={nz−(nx+ny) / 2}×d. nx represents the principal refractive index in the slow axis direction in the plane of each retardation layer. ny represents the principal refractive index in the fast axis direction in the plane of each retardation layer. nz represents the principal refractive index in the direction perpendicular to the surface of each retardation layer. The slow axis direction is the direction in which the refractive index is maximum, and the fast axis direction is the direction in which the refractive index is minimum. d represents the thickness of the retardation layer.

[0031] An A plate is a retardation plate that satisfies "nx>ny≒nz."

[0032] The wavelength for measuring optical parameters such as refractive index and phase difference is 550 nm unless otherwise specified.

[0033] "Approximately parallel" means that the angle (absolute value) between them 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 them 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).

[0034] A semi-transmissive liquid crystal display device 1 (also simply referred to as a liquid crystal display device 1) according to an embodiment of the present disclosure will be described below. The present disclosure is not limited to the contents described in the following embodiment, and appropriate design modifications can be made within the scope of the configuration of the present disclosure. In the following description, the same reference numerals will be used appropriately in different drawings for the same parts or parts having similar functions, and repeated description will be omitted as appropriate. The various aspects of the present disclosure may be combined as appropriate within the scope of the gist of the present disclosure.

[0035] (Embodiment 1) FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display device 1 according to the present embodiment (and embodiments 2 and 3 described later), and FIG. 2 is a cross-sectional view showing a pixel included in the liquid crystal display device 1 according to the present embodiment. FIG. 3 is a plan view showing the entire liquid crystal display device 1 according to the present embodiment (and embodiments 2 and 3 described later) as viewed from the observation side. The liquid crystal display device 1 according to the present embodiment comprises, in this order from the rear side to the observation side, a first substrate 10, a liquid crystal layer 20, and a second substrate 30. In the present embodiment, a TFT substrate is used as the first substrate 10. Note that a portion or structure having a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0036] The liquid crystal display device 1 has a plurality of pixels P. The plurality of pixels P are preferably arranged in a matrix as shown in FIG. 3. The plurality of pixels P typically include three types of pixels: red pixels, green pixels, and blue pixels. However, the number of pixel types may be two or less, or four or more. Each of the plurality of pixels P has a reflective region Rf (i.e., a region that displays in reflective mode) that reflects light using the reflective layer 130 to perform display, and a transmissive region Tr (a region that displays in transmissive mode) that transmits light to perform display (see FIG. 4). This allows for good visibility in any environment. FIG. 4 is a plan view schematic diagram conceptually illustrating that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of this embodiment (and embodiments 2 and 3 described below).

[0037] The proportion of the area of ​​the transmissive region Tr within 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 within the pixel P can also be set appropriately depending on the application, etc.

[0038] A reflective layer 130 is disposed in the reflective region Rf. For example, light L1 from the observation surface side (e.g., external light) enters the liquid crystal display device 1, 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, if 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). The arrows in FIG. 2 indicate the optical path and traveling direction of light from the observation surface side (e.g., external light) or light from the rear side (e.g., backlight light).

[0039] <First board> As shown in FIG. 2, the first substrate 10 includes, in order from the rear surface side to the viewing surface 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 includes a support substrate 100 and a backplane circuit BP on the rear surface side of the reflective layer 130. Insulating layers (also referred to as insulating films) are provided between the various layers as needed. For example, a first interlayer insulating layer 151 is provided 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 referred to as a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

[0040] The support substrate 100 is preferably transparent and insulating, and examples of the support substrate 100 include a glass substrate and a plastic substrate.

[0041] 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 TFTs 110, gate lines GL, source lines SL, etc. It is to be noted that the backplane circuit BP also typically includes a gate insulating film.

[0042] The TFT 110 is provided in each of the plurality of pixels P. The gate electrode of the TFT 110 is electrically connected to the corresponding gate line (also referred to as the scanning line) GL, and the source electrode of the TFT 110 is electrically connected to the corresponding source line (also referred to as the signal line) SL. The drain electrode of the TFT 110 is electrically connected to the second electrode 122.

[0043] The TFT 110 is preferably one that includes an oxide semiconductor layer as an active layer (also referred to as an oxide semiconductor TFT). Oxide semiconductors included in the oxide semiconductor layer have recently been attracting attention as an alternative active layer material to amorphous silicon and polycrystalline silicon, and have higher mobility than amorphous silicon. Therefore, oxide semiconductor TFTs can operate at higher speeds than amorphous silicon TFTs. Furthermore, oxide semiconductor layers can be formed using a simpler process than polycrystalline silicon layers, making them suitable for use in devices requiring large areas.

[0044] Oxide semiconductor TFTs also have excellent off-leak characteristics, making it possible to use a drive method that reduces the frequency of image rewriting. For example, when displaying a still image, the image data can be rewritten once per second. This type of drive method, known as pause drive or low-frequency drive, can significantly reduce the power consumption of LCD devices. By employing pause drive and performing touch detection during periods when the image is not being rewritten, it is possible to suppress the reduction in sensitivity of touch operations due to noise from the drive circuit, and to increase the S / N ratio (signal-to-noise ratio), for example, by approximately 10 times that of conventional methods.

[0045] The oxide semiconductor TFT is also advantageous in terms of miniaturizing the TFT size, 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)).

[0046] 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 plane.

[0047] The oxide semiconductor layer may be a single layer or may have a stacked structure of two or more layers. An oxide semiconductor layer having a stacked structure may include an amorphous oxide semiconductor layer and a crystalline oxide semiconductor layer, or may include multiple crystalline oxide semiconductor layers with different crystal structures, or may include multiple 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.

[0048] 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 stacked 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.

[0049] Specifically, the oxide semiconductor layer preferably contains at least one metal element selected from the group consisting of In (indium), Ga (gallium), and Zn (zinc). Among these, an oxide semiconductor film containing a ternary oxide of In, Ga, and Zn is more preferable. A preferred example of a 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. In this semiconductor, the ratio (composition ratio) of In, Ga, and Zn is not particularly limited, and examples include In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, and In:Ga:Zn=1:1:2.

[0050] The In-Ga-Zn-O based semiconductor may be amorphous or crystalline. For crystalline In-Ga-Zn-O based semiconductors, those with the c-axis oriented approximately perpendicular to the layer plane are preferred.

[0051] The crystal structure of crystalline In-Ga-Zn-O-based semiconductors is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2014-007399, 2012-134475, and 2014-209727. The entire disclosures of Japanese Patent Application Laid-Open Nos. 2012-134475 and 2014-209727 are incorporated herein by reference. TFTs having an In-Ga-Zn-O-based semiconductor layer have high mobility (more than 20 times that of an a-Si TFT) and low leakage current (less than one-hundredth that of an a-Si TFT). Therefore, they are suitable for use as driver TFTs (e.g., TFTs included in a driver circuit provided on the same substrate as a display area, around a display area including multiple pixels) and pixel TFTs (TFTs provided in pixels).

[0052] 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 can be mentioned, and preferred examples include In2O3-SnO2-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 include 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.

[0053] 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 facing the reflective layer 130 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.

[0054] 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 made of a material that reflects light. In particular, it is preferable that the reflective layer 130 be made of a metal material with high reflectivity. Examples of materials for the reflective layer 130 include a silver alloy and an aluminum alloy.

[0055] The reflective layer 130 preferably has an uneven shape that reflects the uneven surface structure preferably possessed by the first interlayer insulating layer 151. That is, it is preferable that the reflective layer 130 also has an uneven surface structure. This uneven surface structure, also called an MRS (Micro Reflective Structure), 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 randomly arranged convex portions p, for example, such that the center-to-center distance between adjacent convex portions p is 5 μm to 50 μm. The center-to-center distance between adjacent convex portions p is more preferably 10 μm to 20 μm. The shape of the convex portions p is preferably approximately circular or approximately polygonal when viewed from the normal direction of the support substrate. The area of ​​the convex portions p occupying one pixel P is preferably, for example, approximately 20 to 40%, and the height of the convex portions p is preferably, for example, 1 μm to 5 μm.

[0056] If the liquid crystal display device 1 includes the reflective layer 130 and a retardation layer that satisfies the broadband λ / 4 condition, polarization conversion (e.g., conversion between circularly polarized light and linearly polarized light) specific to reflective liquid crystal display devices becomes possible, thereby sufficiently reducing light loss. The broadband λ / 4 condition is a condition under which polarized light close to circularly polarized light can be obtained over a wide range of visible wavelengths.

[0057] 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.

[0058] 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) of acrylic resin, polyimide resin, novolac resin, etc., and laminates thereof. The thickness of the organic insulating film is not particularly limited, but is, for example, 2 μm or more and 4 μm or less. Examples of inorganic insulating films obtained using inorganic insulating materials include inorganic films (relative dielectric constant ε=5 to 7) of silicon nitride (SiNx), silicon oxide (SiO2), etc., and laminates thereof. The thickness of the inorganic insulating film is not particularly limited, but is, for example, 1500 Å or more and 3500 Å or less. Alternatively, they may be laminates of organic insulating films and inorganic insulating films. In particular, it is preferable that the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are organic insulating films.

[0059] From a manufacturing standpoint, it is preferable that the interlayer insulating layers 151 and 152 be highly transparent, and it is suitable that they are formed from the same material with high transmittance. Furthermore, the first interlayer insulating layer 151, which is farther from the observation surface side than the reflective layer 130, may have low transmittance or may be opaque. From the standpoint of light utilization efficiency, the second interlayer insulating layer 152 may be highly transparent, or may be made of a material with high transmittance different from that of the first interlayer insulating layer 151.

[0060] The first electrode 121 is disposed on the reflective layer 130 via a 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 relatively closer to 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.

[0061] One of the first electrode 121 and the second electrode 122 is a pixel electrode PE, and the other is a common electrode CE. A pixel electrode is provided for each of the plurality of pixels P. The pixel electrode is electrically connected to a 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.

[0062] At least one of the first electrode 121 and the second electrode 122 has a plurality of strip portions SP and a slit Sl located between two adjacent strip portions of the plurality of strip portions. The strip portions SP correspond to electrode portions, and the slits Sl correspond to openings. Such electrodes are also referred to as slit electrodes or finger electrodes. From the viewpoint of facilitating the generation of a transverse electric field, it is preferable that at least the upper-layer electrode (the pixel electrode PE in this embodiment) is a slit electrode. In this case, the lower-layer electrode (the common electrode CE in this embodiment) may be a planar electrode, i.e., a so-called solid electrode, or may be a slit electrode.

[0063] In each pixel P, the multiple strip portions SP constituting the slit electrode (in this embodiment, the second electrode 122, which is the pixel electrode PE) preferably have a linear shape that is approximately parallel to one another and extends in the same direction. When the strip portions SP are "linear," it means that the center line of the strip portions SP, not the outer edge of the strip portions SP, is linear. The center line of the strip portions SP refers to the line that divides the strip portions SP into two equal parts in the width direction. The width direction refers to the direction that is approximately perpendicular to the direction in which the strip portions SP extend in a plan view.

[0064] It is also preferable that the strip portion SP does not include a cutout portion, which further suppresses the occurrence of alignment disturbance. "The strip portion SP does not include a cutout portion" means that no part of the strip portion SP has been cut out or removed.

[0065] In each pixel P, the directions in which the strip portions SP extend (also referred to as the extension directions of the strip portions SP) are substantially parallel to one another. The extension directions of the strip portions SP may differ for each pixel, but are preferably the same for two or more adjacent pixels. From the standpoints of image quality and manufacturing, it is particularly preferable that the extension directions of the strip portions SP be the same for at least adjacent pixels. Figures 10A to 10F, which will be described later, each show an example in which the extension directions of the strip portions SP are the same for adjacent pixels. It is also more preferable that the extension directions of the strip portions SP are the same throughout the display area.

[0066] The width L of each strip portion SP varies depending on the applied voltage, etc., but is preferably set to, for example, 0.3 to 10 μm. The above L is more preferably set to 1 to 5 μm. The interval between two adjacent strip portions SP (i.e., the interval between the center lines of each strip portion) also varies depending on the applied voltage, etc., but is preferably set to, for example, 0.3 to 10 μm. The above interval is more preferably set to 1 to 5 μm.

[0067] The ratio L / S (also referred to as the L / S condition), where L is the width per strip in plan view and S is the width 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), thereby further improving the contrast ratio (also simply referred to as "contrast"). The L / S condition is, for example, 1.6 / 3 (i.e., 0.533 / 1), L / S=2.2 / 4.1 (i.e., 0.537 / 1), or L / S=3 / 5 (i.e., 0.6 / 1).

[0068] In this embodiment, the alignment direction of the liquid crystal molecules 21 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 between −4° and 0°, with the extension direction of the plurality of strip portions SP as the reference (0°). This angle, that is, the angle rotated clockwise from the extension direction of the plurality of strip portions SP as the reference (0°) is defined as a positive angle (+) and an angle rotated counterclockwise is defined as a negative angle (−), and the angle formed by the alignment direction of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied is defined as the slit angle θ Z The definition of the slit angle will be explained with reference to FIG.

[0069] 5 is a diagram illustrating the slit angle of positive-type liquid crystal molecules. The (p) added to the end of the symbol for a liquid crystal molecule indicates 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. 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.

[0070] 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 multiple strip-shaped portions SP are parallel, the slit angle is 0° (see the "0°" column in FIG. 5). When the extension direction of the multiple strip-shaped 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 multiple strip-shaped 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).

[0071] 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 larger absolute value of the dielectric constant when no voltage is applied, with the extension direction of the multiple strip-shaped portions as the reference (0°).

[0072] In this embodiment, the slit angle is preferably between −4° and 0°, as described above. When the slit angle is within this range, the rotation directions of the liquid crystal molecules 21A on the first substrate 10 side and the liquid crystal molecules 21B on the second substrate 30 side coincide with each other, thereby sufficiently suppressing the occurrence of alignment defects, while simultaneously achieving high reflectance and high transmittance at a low voltage and improving response characteristics.

[0073] FIG. 7 is a schematic plan view showing one pixel. FIG. 8 is a schematic plan view showing an enlarged portion of FIG. 7. FIGS. 7 and 8 show, as schematic plan views, a configuration in which the extension direction of multiple strip portions SP constituting a slit electrode (pixel electrode PE in this embodiment) is arranged parallel to multiple source lines SL and multiple gate lines GL are arranged so as to be perpendicular to the multiple source lines SL. If the direction parallel to the gate lines GL (left and right directions in the drawing) is set to 0°, the extension direction of the multiple strip portions SP is positioned in a direction of 90°. In FIG. 7, θ Z is the slit angle, θ is the twist angle, and θ a is the angle of the alignment direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied.

[0074] 9 and 10A show an example in which the extension direction of the strip portions SP (this angle will be referred to as angle X) is 0° when the extension direction of the source wiring SL is taken as the reference (0°). Also, examples in which angle X is −10°, +10°, −90°, −100°, and −80° are shown in FIGS. 10B, 10C, 10D, 10E, and 10F, respectively. The case in which angle X is 0° (see FIGS. 9 and 10A) corresponds to the case in which the extension direction of the strip portions SP is parallel to the extension direction of the source wiring SL, and the case in which angle X is −90° (see FIG. 10D) corresponds to the case in which the extension direction of the strip portions SP is parallel to the extension direction of the gate wiring GL. FIGS. 9 and 10A to 10F are planar schematic diagrams illustrating specific examples of pixels. 9 is a plan view showing an example of the pixel structure, and FIGS. 10A to 10F are plan views showing an example of the pixel arrangement. FIGS. 10A to 10F also show the twisted orientation of liquid crystal molecules 21.

[0075] 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)), or a mixture thereof.

[0076] In the embodiment shown in FIG. 2 , the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, to the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed in the same layer as the reflective layer 130 and is made of the same material (e.g., a metal film) as the reflective layer 130. A first contact hole CH1 is formed in the first interlayer insulating layer 151 to expose a portion of the backplane circuit BP (more specifically, at least a portion of the drain electrode of the TFT 110), and the contact electrode 160 is connected to the backplane circuit BP through the first contact hole CH1. Furthermore, a second contact hole CH2 is formed in the second interlayer insulating layer 152 to expose a portion of the contact electrode 160, and the pixel electrode PE (the second electrode 122 in this embodiment) is connected to the contact electrode 160 through the second contact hole CH2.

[0077] 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.

[0078] 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.

[0079] The first horizontal alignment film 140 and the second horizontal alignment film 340 (described later) have each been 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 photodegradable photo-alignment film material can be used, and in the rubbing treatment, it is preferable to use an alignment film material such as polyimide.

[0080] 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°.

[0081] 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 assumes 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).

[0082] In the present embodiment, a configuration in which the pixel electrode PE is provided above the common electrode CE is described. However, in a relatively large liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively large, it is preferable to provide the pixel electrode PE above the common electrode CE. In this configuration (also referred to as the V2 structure), there is no need to form a slit in the common electrode CE, which is the lower electrode. Therefore, an increase in the resistivity (sheet resistivity) of the common electrode CE is suppressed compared to a configuration (also referred to as the V3 structure) in which the common electrode CE is provided above the pixel electrode PE, and therefore, a weakening of the fringe electric field applied to the liquid crystal layer 20 is suppressed. In this configuration (V2 structure), when the pixel electrode PE is a slit electrode, the resistivity of the pixel electrode PE increases. However, because 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 a weakening of the fringe electric field). 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), but such a configuration may cause adverse effects on the display due to specular reflection from the low-resistance wiring (for example, glare, rainbow-colored diffraction, and interference patterns), making it necessary to block light with a black matrix, etc., which may not be able to sufficiently improve the reflective aperture ratio.

[0083] In a configuration in which the pixel electrode PE is provided above the common electrode CE, the common electrode CE is not present in the region where the second contact hole CH2 is formed, and therefore this region does not contribute to reflective display, potentially resulting in a lower reflectance than in a configuration in which the common electrode CE is provided above the pixel electrode PE. A certain amount of area is required for the region that does not contribute to reflective display, such as the contact hole, regardless of the size of the pixel P. Therefore, the proportion of the region in the pixel P that does not contribute to reflective display increases as the pixel P becomes smaller (i.e., the higher the resolution), resulting in a greater decrease in reflectance. Conversely, in a relatively large liquid crystal display device, the proportion of the region in the pixel P that does not contribute to reflective display can be reduced, making it easier to suppress the decrease in reflectance described above. For these reasons, a configuration in which the pixel electrode PE is provided above the common electrode CE is advantageous in a relatively large liquid crystal display device.

[0084] On the other hand, as described above, the reduction in reflectivity due to the area where the second contact hole CH2 is formed not contributing to reflective display becomes greater the smaller the area of ​​the pixel P (i.e., the higher the resolution). Therefore, in a liquid crystal display device with a relatively high resolution, i.e., a liquid crystal display device with a relatively small area of ​​the pixel P, it is preferable that the common electrode CE be provided above the pixel electrode PE (see Variant 1 of Embodiment 1 described below).

[0085] <Second board> The second substrate 30 is disposed opposite the first substrate 10 with the liquid crystal layer 20 sandwiched therebetween, and has a second horizontal alignment film 340 in contact with the liquid crystal layer 20. The second substrate 30 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 also preferably has a plurality of columnar spacers (not shown). Note that the first substrate 10 may have a plurality of columnar spacers.

[0086] The support substrate 300 is preferably transparent and insulating, and examples of the support substrate 300 include a glass substrate and a plastic substrate. Note that 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) 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.

[0087] The color filter layer 310 typically includes a red color filter that is provided in an area corresponding to a red pixel and transmits red light, a green color filter that is provided in an area corresponding to a green pixel and transmits green light, and a blue color filter that is provided in an area corresponding to a blue pixel and transmits blue light. However, the number of types of color filters may be two or less, or four or more. Furthermore, if color display is not performed, the color filter layer 310 is omitted.

[0088] If necessary, an overcoat layer (also referred to as a planarizing layer) may be provided to cover the color filter layer 310. Note that depending on the material (e.g., transparent conductive material) forming the electrodes, the material forming the interlayer insulating layer and dielectric layer, and the material forming the alignment film, the white display may have a yellowish tinge. In such cases, the chromaticity of the white display may be adjusted (i.e., blue shifted) by forming the overcoat layer from a blue resist, so that the chromaticity of the white display approaches that of a D65 light source, for example. The D65 light source is the CIE standard illuminant D65.

[0089] <Liquid crystal layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30 and is made of a liquid crystal material. Among the liquid crystal materials, a nematic liquid crystal material having a positive dielectric anisotropy Δε is called a positive-type liquid crystal material, and a nematic liquid crystal material having a negative dielectric anisotropy Δε is called a negative-type liquid crystal material. The dielectric anisotropy Δε is determined by the dielectric constant ε in the long axis direction of the liquid crystal molecules 21. / / and the permittivity in the minor axis direction ε ⊥ The difference between / / -ε ⊥ )

[0090] The liquid crystal layer 20 is preferably made of a liquid crystal material having a positive dielectric anisotropy Δε. Generally, when the absolute value of Δε is less than 2, it is considered that the liquid crystal layer does not have dielectric anisotropy, so the lower limit of Δε is preferably 2 or more. In particular, from the viewpoint of further increasing the transmittance, Δε is preferably 3 or more. Furthermore, from the viewpoints of further increasing the reflectance, suppressing the occurrence of alignment defects, and further improving the response characteristics, Δε is preferably 12 or less, and more preferably 11 or less.

[0091] Particularly in this embodiment, the liquid crystal layer 20 contains 45 mass % or less of a positive liquid crystal material (also referred to as a positive liquid crystal material PL) that contains a compound having a structure represented by -CF2-O- in its molecule and has positive dielectric anisotropy, relative to the total mass 100% of the liquid crystal material that constitutes the liquid crystal layer 20. Note that, among the liquid crystal materials that constitute the liquid crystal layer, the liquid crystal materials other than the positive liquid crystal material PL are liquid crystal materials that make up the Δε of all the liquid crystal materials that constitute the liquid crystal layer 20 within the above range, and may include neutral liquid crystal materials that have no polarity.

[0092] The positive liquid crystal material PL contains a compound (also referred to as compound A) having a structure represented by -CF2-O- in the molecule. An example of such compound A is a compound represented by the following formula (I):

[0093] [ka]

[0094] Examples of compounds represented by the formula (I) include compounds represented by the formula (I) (R represents any hydrocarbon group). The compound represented by the formula (I) can be likened to a wedge-shaped molecule, as shown below the formula (I) in Figure 11 (see "EKISHO," Vol. 24, No. 4, 2020, p. 239, Fig. 8). Because the fluorine atom F is an electron-withdrawing group, it is thought that polarization occurs, with the thinner end of the wedge being positive and the thicker end being negative. Therefore, when a voltage is applied to a liquid crystal layer 20 formed using compound A, polarity bias occurs, potentially causing flicker in the display area. During polarity reversal, the polarizer moment temporarily returns to an equilibrium state. For example, when a liquid crystal material with a high content of positive-type liquid crystal material PL is used, a downward-angle waveform (a) is detected when the flicker rate per unit time is graphed (see Comparative Example 1 and Figures 27 and 29, described below). Figure 11 conceptually illustrates the polarization structure of the compound represented by formula (I).

[0095] The liquid crystal display device 1 of this embodiment, having the content ratio of the positive liquid crystal material PL within the above range, is less likely to cause flicker even when driven at low frequencies and exhibits excellent response properties. The content ratio of the positive liquid crystal material PL (hereinafter also referred to as the positive ratio) of the liquid crystal layer 20 relative to the total amount (100% by mass) of the liquid crystal material may be 45% by mass or less, preferably 42% by mass or less. Here, when the liquid crystal display device 1 is driven at, for example, 60 Hz, the fall response time Td, which is considered to have no effect on the video performance of the liquid crystal display device 1, is 10 ms or less. A positive ratio of 42% by mass or less makes it easy to achieve the fall response time Td of 10 ms or less (see Figure 31B described below). From the viewpoint of further improving response properties and flicker suppression, the positive ratio is more preferably 35% by mass or less, and particularly preferably 30% by mass or less. A positive ratio of 30% by mass or less not only exhibits excellent response properties but also further suppresses flicker in both reflective and transmissive display modes. Furthermore, from the viewpoint of maintaining Δε=10 required at a white voltage of 5V, the positive ratio is preferably more than 0% by mass, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

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

[0097] From the viewpoint of suppressing alignment disturbance, the liquid crystal layer 20 is preferably in a single domain alignment (also referred to as a monodomain alignment).

[0098] The thickness d (also referred to as cell gap or cell thickness) of the liquid crystal layer 20 is preferably 2 μm or more from a manufacturing viewpoint (e.g., yield, etc.). In particular, the cell thickness d is more preferably 2.5 μm or more, even more preferably 2.6 μm or more, particularly preferably 2.7 μm or more, and most preferably 2.8 μm or more, from the viewpoint of further increasing reflectance (e.g., white reflectance in normally black mode) and transmittance. Furthermore, the cell thickness d is preferably 3 μm or less, from the viewpoint of further suppressing the occurrence of alignment defects and further improving response characteristics. Therefore, the range of the cell thickness d is preferably 2 μm or more to 3 μm or less, more preferably 2.5 μm or more to 3 μm or less, even more preferably 2.6 μm or more to 3 μm or less, particularly preferably 2.7 μm or more to 3 μm or less, and most preferably 2.8 μm or more to 3 μm or less.

[0099] On the other hand, the liquid crystal display device 1 of this embodiment can achieve high reflectance and high transmittance even when the cell thickness d is 3 μm or more, so in applications where high reflectance and high transmittance are particularly required, the cell thickness d may be 3 μm or more. In such cases, the range of the cell thickness d is, for example, preferably 2 μm or more and 3.2 μm or less, more preferably 2.5 μm or more and 3.2 μm or less, even more preferably 2.6 μm or more and 3.2 μm or less, particularly preferably 2.7 μm or more and 3.2 μm or less, and most preferably 2.8 μm or more and 3.2 μm or less.

[0100] The liquid crystal material constituting the liquid crystal layer 20 preferably has a birefringence Δn of greater than 0.05, taking into account the absolute value of Δn possessed by liquid crystal molecules with the lowest refractive index (Δn=0.038 for the alkenyl derivative with the lowest refractive index). Furthermore, taking into account the preferred range of dΔn (described below) and the cell thickness, the birefringence Δn is more preferably 0.077 or greater, and most preferably 0.081 or greater (for example, when the cell thickness is 3.0 μm). Taking into account the range of dΔn, the upper limit of the birefringence Δn is preferably 0.09 or less (for example, when the cell thickness is 2.7 μm), and most preferably 0.087 or less (for example, when the cell thickness is 2.8 μm).

[0101] The retardation (dΔn) of the liquid crystal layer 20, which is expressed as the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material, is preferably 180 nm or more and 280 nm or less. This allows for a lower voltage to be achieved and further improves the reflectance. dΔn is more preferably 200 nm or more and 260 nm or less, even more preferably 220 nm or more and 252 nm or less, particularly preferably 236 nm or more and 252 nm or less, and most preferably 250 nm or less.

[0102] The liquid crystal layer 20 has the following formula (1): RP value = γ1 / K 22 (1) (In the formula, γ1 represents the rotational viscosity coefficient (mPa·sec) of the liquid crystal material constituting the liquid crystal layer 20. K 22 represents the torsional elastic constant (unit: pN). The RP value represented by is preferably 17 or less. When the RP value is 17 or less, it becomes easy to set the fall response time Td to 10 ms or less (see FIG. 31A described later). From the viewpoint of further improving the response properties, the RP value is more preferably 16 or less, and even more preferably 15 or less. The torsional elastic constant is also called the twist elastic constant.

[0103] Since the elastic constant is inversely proportional to the threshold voltage, from the viewpoint of reducing the voltage, the twist elastic constant K 22 is preferably 2 or more, more preferably 3 or more. 22 In addition, from the viewpoint of preventing the white reflectance (VRmax) from increasing at a high voltage, it is preferably 8 or less, and more preferably 7 or less. 11 (unit: pN) is K 22 Since the bending elastic constant K tends to be directly proportional to the bending elastic constant K, it is preferably 4 or more and 16 or less, and more preferably 6 or more and 14 or less. 33 Although the elastic constant (K pN) does not have a significant effect on the optical characteristics of this mode, it is preferably 6 or more and 20 or less, and more preferably 10 or more and 16 or less. 11 , K. 22 , K. 33 ) can be calculated by fitting a theoretical equation using the measured values ​​of the capacitance-voltage characteristic curve.

[0104] From the viewpoint of increasing the response speed, the rotational viscosity coefficient γ1 is preferably 100 mPa·sec or less, more preferably 90 mPa·sec or less, and is preferably 50 mPa·sec or more, more preferably 60 mPa·sec or more, and even more preferably 70 mPa·sec or more.

[0105] The liquid crystal layer 20 assumes a twisted orientation when no voltage is applied. That is, in the liquid crystal display device 1 of this embodiment, display is performed using the in-plane switching mode, in which the liquid crystal layer 20 assumes a twisted orientation when no voltage is applied. This allows the cell gap to be increased and the range of contrast fluctuations relative to cell gap fluctuations to be reduced. As a result, the occurrence of display unevenness is sufficiently suppressed, and the contrast of reflective display is improved. The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably 58.3° or more and 89.9° or less. A more preferable range will be described later.

[0106] The twist angle θ1 of the liquid crystal layer 20 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, it is the angle between the long axis direction of the liquid crystal molecules 21A near the first horizontal alignment film 140 (also referred to as the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied) and the long axis direction of the liquid crystal molecules 21B near the second horizontal alignment film 340 (also referred to as the liquid crystal molecules 21B on the second substrate 30 side when a voltage is applied).

[0107] <Light source> The liquid crystal display device 1 preferably includes a light source. In particular, the liquid crystal display device 1 preferably further includes a light source 61 (also referred to as a backlight) on the rear side of the liquid crystal layer 20. The light source 61 is not particularly limited as long as it emits light, and may be a direct type, an edge type, or any other type. The light source 61 preferably includes, for example, a light source such as a light-emitting diode (LED), a light guide plate, and a reflective sheet, and may further include a diffusion sheet or a prism sheet.

[0108] <Other configurations> From the viewpoint of further increasing the contrast ratio, the liquid crystal display device 1 is preferably in a normally black mode, which is a display mode in which black is displayed when no voltage is applied and white is displayed when a voltage is applied.

[0109] In addition to the components described above, the liquid crystal display device 1 is also configured with a plurality of components, such as 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 enhancement film, and a bezel (frame), and some of the components may be incorporated into other components. These are not particularly limited, and components commonly used in the field of liquid crystal display devices can be used, so their description will be omitted.

[0110] <Manufacturing method> The liquid crystal panel 1X can be manufactured, for example, by bonding a first substrate 10 and a second substrate 30 together, injecting a liquid crystal composition into the gap between them to form a liquid crystal layer 20, and then dividing the resulting structure.

[0111] As a manufacturing method for the first substrate 10 (e.g., a TFT substrate), it is preferable to adopt a general FFS mode TFT substrate manufacturing method using transparent electrodes. As described above, insulating films (also referred to as insulating layers) are formed as needed between electrodes or between each electrode and the gate line GL, source line SL, TFT 110, etc. As described above, the insulating film may be an inorganic film or an organic film. A color filter layer may be formed instead of the organic insulating film. It is also preferable to form the pixel electrode PE after forming the common electrode CE and then patterning the organic insulating film.

[0112] It is preferable to adopt a general method for producing an opposing substrate in FFS mode as a method for producing the second substrate 30. When a color filter layer is formed on the first substrate 10, it is preferable that the second substrate 30 does not have a color filter layer.

[0113] <Application example> The liquid crystal display device 1 of this 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 can improve the contrast ratio. In particular, it is preferably applicable to built-in touch panels, and particularly to in-cell touch panels. In this way, by using the liquid crystal display device 1 of this embodiment, it is possible to preferably realize an in-cell touch panel capable of displaying in a reflective mode.

[0114] By realizing an in-cell touch panel capable of reflective mode display, for example, the frame wiring area required for external touch panels is eliminated, allowing for a narrower frame. Furthermore, the touch panel function can be implemented without a cover glass, contributing to thinner and lighter devices. Furthermore, because the touch and display functions are driven using a time-division method, the panel is immune to LCD (liquid crystal display) noise, which is the largest noise source in touch panels. This means that killer patterns do not occur, making touch signal tuning easy. Furthermore, reflected light loss is sufficiently low, resulting in more natural and natural pen writing. Furthermore, compared to external touch panels, total costs can be reduced from the user's perspective. Furthermore, finger input and electromagnetic induction (EMR) pen input can be combined, enabling highly accurate pen writing.

[0115] An example in which the liquid crystal display device 1 is used in an in-cell touch panel will be further described. 12 is a plan view schematically illustrating the arrangement relationship between touch sensor electrodes TX and touch wiring TL included in a liquid crystal display device 1. As shown in FIG. 12, the liquid crystal display device 1 has a display region DR and a non-display region FR. The display region DR is defined by a plurality of pixels P (see, for example, FIG. 3) arranged in a matrix. The non-display region FR is located on the periphery of the display region DR and is also referred to as a peripheral region or a frame region.

[0116] 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. 12, each touch sensor electrode TX is provided corresponding to two or more pixels P.

[0117] 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.

[0118] The touch wiring TL is connected to a touch drive unit TD provided in the non-display region FR. The touch drive unit TD is configured to switch, for example, between a display mode in which a plurality of touch sensor electrodes TX function as common electrodes CE and a touch detection mode in which they function as touch sensor electrodes TX in a time-division manner. For example, in the display mode, the touch drive unit TD applies a common signal to the touch sensor electrodes TX (common electrodes CE) via the touch wiring TL. On the other hand, in the touch detection mode, the touch drive unit TD applies a touch drive signal to the touch sensor electrodes TX via the touch wiring TL.

[0119] 12, the touch wirings TL extend in the column direction (the same direction as the source wirings SL). Some of the touch wirings TL extend to the corresponding touch sensor electrodes TX, crossing one or more other touch sensor electrodes TX.

[0120] Focusing on a certain touch sensor electrode TX, a first touch wiring TL1 that supplies a signal to that touch sensor electrode TX extends to the touch wiring contact portion TC, and a second touch wiring TL2 that supplies a signal to another touch sensor electrode TX extends across that 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 that touch sensor electrode TX, or no touch wiring TL may be arranged to cross that touch sensor electrode TX.

[0121] In addition to the touch drive unit TD, the non-display area FR is provided with peripheral circuits (not shown) including drive circuits such as a gate driver that supplies gate signals to gate bus lines (gate wiring) GL and a source driver that supplies source signals to source bus lines (source wiring) SL. 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.

[0122] In an in-cell touch panel, it is particularly preferable to use an In—Ga—Zn—O based semiconductor as the TFT 110 .

[0123] (Modification 1 of Embodiment 1) In the first embodiment, the configuration in which 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 has been described, but the opposite may be true, in which the second electrode 122 is the common electrode CE and the first electrode 121 is 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. 13).

[0124] FIG. 13 is a cross-sectional view of a liquid crystal display device 1 according to this embodiment. In this embodiment, too, from the viewpoint of facilitating the generation of a transverse electric field, it is preferable that at least the upper-layer electrode (the common electrode CE in this embodiment) is a slit electrode. The lower-layer electrode (the pixel electrode PE in this embodiment) 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 according to this modification 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.

[0125] (Modification 2 of Embodiment 1) 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.

[0126] (Embodiment 2) In this embodiment, the features unique to this embodiment will be mainly described, and descriptions of the contents overlapping with those of the above-described Embodiments 1 and 2 will be omitted. The liquid crystal display device 1 of this embodiment is mainly different from the liquid crystal display device 1 of Embodiment 1 in that it has retardation layers and polarizing plates on both sides of the liquid crystal panel 1X and has a light source on the rear side of the liquid crystal layer 20.

[0127] FIG. 14 is a cross-sectional schematic diagram of a pixel included in a liquid crystal display device 1 of this embodiment. As shown in FIG. 14, the liquid crystal display device 1 includes, in order from the rear side to the viewing 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 λ / 2 plate 412 and a first λ / 4 plate 411. The second retardation layer 42 includes a first λ / 2 plate 422 and a first λ / 4 plate 421. At least one of the first retardation layer 41 and the second retardation layer further includes a positive C plate 44. FIG. 14 shows an example of this embodiment in which the second retardation layer further includes a positive C plate 44.

[0128] 15 and 16A show an example in which the extension direction (angle X) of the strip portions SP is 0° when the extension direction of the source wiring SL is taken as the reference (0°). Also, examples in which the angle X is −10°, +10°, −90°, −100°, and −80° are shown in FIGS. 16B, 16C, 16D, 16E, and 16F, respectively. The case in which the angle X is 0° (see FIGS. 15 and 16A) corresponds to the case in which the extension direction of the strip portions SP is parallel to the extension direction of the source wiring SL, and the case in which the angle X is −90° (see FIG. 16D) corresponds to the case in which the extension direction of the strip portions SP is parallel to the extension direction of the gate wiring GL. FIGS. 15 and 16A to 16F are planar schematic diagrams showing specific examples of pixels in this embodiment. 15 is a plan view showing an example of the pixel structure, and FIGS. 16A to 16F are plan views showing an example of the pixel arrangement. FIGS. 16A to 16F also show the twisted orientation of liquid crystal molecules 21.

[0129] <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. 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. The positional relationship between the λ / 4 plate and the λ / 2 plate in each retardation layer is preferably such that, in the first retardation layer 41, the λ / 2 plate 412 and the λ / 4 plate 411 are arranged in this order from the back surface side, and such that, in the second retardation layer 42, the λ / 2 plate 422 and the λ / 4 plate 421 are arranged in this order from the observation surface side.

[0130] A λ / 4 plate is a retardation plate that imparts an in-plane phase difference of ¼ wavelength to incident light of wavelength λ, and is also called a λ / 4 wave plate or QWP (Quarter-Wave Plate). Specifically, a 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 a λ / 4 plate becomes circularly polarized light when it exits.

[0131] A λ / 2 plate is 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 incident light by approximately 90°. For example, circularly polarized light incident on a λ / 2 plate becomes circularly polarized light with the opposite rotation direction when it exits.

[0132] It is preferable that the first λ / 4 plate 411 and the second λ / 4 plate 421 have approximately the same in-plane retardation Re. "Approximately the same" means that the difference in their in-plane retardation Re is less than 5 nm. The difference in their in-plane retardation Re is preferably less than 1 nm.

[0133] It is preferable that the first λ / 2 plate 412 and the second λ / 2 plate 422 have approximately the same in-plane retardation Re. "Approximately the same" means that the difference in their in-plane retardation Re is less than 5 nm. The difference in their in-plane retardation Re is preferably less than 1 nm.

[0134] General-purpose retardation plates can be used as the λ / 4 plates 411, 421 and the λ / 2 plates 412, 422. More specifically, it is preferable to use retardation plates commonly available as, for example, circular polarizers for anti-reflection films. In the present disclosure, by preferably controlling the optical axis setting of each optical film within a predetermined range described below, even if general-purpose retardation plates are used as the λ / 4 plates and λ / 2 plates instead of special retardation plates, the contrast ratio and viewing angle can be improved while the display device is a transflective IPS LCD device, and the display device is also useful as an in-cell touch panel, thereby achieving cost reduction. This is particularly useful from the user's perspective because it reduces total costs. Cost reduction can be achieved when the liquid crystal display device of the present disclosure is used not only as an in-cell or other built-in touch panel, but also as an external touch panel.

[0135] 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.

[0136] As described above, in this embodiment, the retardation layers 41 and 42 each include 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. In this case, the resulting liquid crystal display device can achieve excellent viewing angle characteristics and high contrast. In particular, brightness floating during black display (also referred to as black floating) is sufficiently suppressed, widening the viewing angle during black display. To further demonstrate the above effects, it is preferable that the positive C plate be 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. 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 second substrate 30) side (see FIG. 14 ).

[0137] The positive C plate 44 (and 43, etc., which will be described later) may be made of a single film, or may be a laminate of two or more retardation films.

[0138] In this specification, a portion (structure) sandwiched between layers other than a positive C plate and functioning as a positive C plate is counted as "one positive C plate." This does not matter whether the positive C plate is a laminate or not. Therefore, for example, when a retardation layer includes a λ / 4 plate, a multilayered positive C plate, and a λ / 2 plate in this order, it is referred to as "the retardation layer has one positive C plate." Also, when a retardation layer includes a λ / 4 plate, two commercially available positive C plates, and a λ / 2 plate in this order, it is referred to as "the retardation layer has one positive C plate." When a retardation layer includes a λ / 4 plate, a first positive C plate (whether or not it is a laminate), a λ / 2 plate, and a second positive C plate (whether or not it is a laminate), it is referred to as "the retardation layer has two positive C plates."

[0139] The positive C plate 44 (and 43, etc., described below) is preferably, for example, a film containing a material with negative intrinsic birefringence as a component, which has been biaxially stretched lengthwise and widthwise, or a film coated with a liquid crystalline material such as nematic liquid crystal, etc. Examples of materials with negative intrinsic birefringence include resin compositions containing acrylic resins and styrene resins, polystyrene, polyvinyl naphthalene, polyvinyl biphenyl, polyvinyl pyridine, polymethyl methacrylate, polymethyl acrylate, N-substituted maleimide copolymers, polycarbonates with a fluorene skeleton, and triacetyl cellulose (especially those with a low degree of acetylation).

[0140] Specific examples of the positive C plate 44 (and 43, etc.) include a positive C plate manufactured by ENEOS Corporation or Hayashi Telempu Co., Ltd., and a positive-C retardation film manufactured by Nippon Kayaku Co., Ltd.

[0141] 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 even more preferably 170 to 240 nm.

[0142] The thickness of each of the positive C plates 44 (and 43) is preferably, for example, 0.1 to 100 μm. Within this range, the mechanical strength and display uniformity are improved. Each of the thicknesses 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 entire plate to be within the above range, and the thicknesses of the respective retardation films may be the same or different.

[0143] The retardation layer including a positive C plate (corresponding to the second retardation layer 42 in this embodiment) may have a positive C plate (hereinafter referred to as a second positive C plate) separate from the positive C plate. In this case, it is preferable that the second positive C plate be located between the λ / 2 plate and the polarizing plate.

[0144] From the viewpoint of further improving the viewing angle characteristics and contrast, it is particularly preferable that the liquid crystal display device 1 of this embodiment satisfies the following (i) or (ii). (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) The second retardation layer 42 includes one positive C plate, and the first retardation layer 41 includes one positive C plate. In this embodiment, the liquid crystal display device 1 that satisfies the above condition (i) will be described in detail (see, for example, FIG. 14). In the below-described embodiment 3, the liquid crystal display device 1 that satisfies the above condition (ii) will be described in detail.

[0145] <Polarizing plate> The first polarizing plate 51 is located closer to the rear surface than the first retardation layer 41. The second polarizing plate 52 is located closer to the observation surface than the second retardation layer 42. The polarizing plates 51 and 52 may be circular polarizing plates or linear polarizing plates. Here, a linear polarizing plate refers to a polarizing plate that has the function of extracting polarized light that vibrates only in a specific direction (linearly polarized light) from unpolarized light (natural light), partially polarized light, or polarized light, and is distinguished from a circular polarizing plate. Among these, a linear polarizing plate is preferred.

[0146] The polarizing plates 51 and 52 may also be absorptive polarizing plates or reflective polarizing plates. An absorptive polarizing plate is a polarizing plate that has the function of absorbing light vibrating in a specific direction and transmitting polarized light vibrating in a direction perpendicular to that (linearly polarized light). A reflective polarizing plate is a polarizing plate that has the function of reflecting light vibrating in a specific direction and transmitting polarized light vibrating in a direction perpendicular to that (linearly polarized light). Among these, absorptive polarizing plates are preferred. It is particularly suitable to use absorptive linear polarizing plate.

[0147] Examples of absorptive polarizing plates include polarizing plates obtained by dyeing and adsorbing an anisotropic material such as an iodine complex (or dye) onto a polyvinyl alcohol film and then stretching and aligning the film. Generally, to ensure mechanical strength and resistance to moist heat, protective films such as triacetyl cellulose films are laminated on both sides of the polyvinyl alcohol film for practical use. Examples of reflective polarizing plates include films formed by laminating multiple dielectric thin films, films formed by laminating multiple thin films with different refractive index anisotropies, nanowire grid polarizing plates, and polarizing plates using selective reflection of cholesteric liquid crystals.

[0148] <Preferred Settings> The following further explains the preferred optical axis settings of each optical film (i.e., polarizer and retardation layer). An absorptive polarizer is used as the polarizer. The liquid crystal layer 20 is assumed to have a monodomain structure and provide normally black display, and a positive liquid crystal material is used as the liquid crystal material constituting the liquid crystal layer 20. Note that the slow axis angle of the positive C plate is in the direction normal to the film (i.e., 90° when the alignment direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is 0°), so an embodiment without a positive C plate was studied. The preferred settings are the same when a positive C plate is used.

[0149] 17 is a plan view conceptually illustrating the relationship between the long axis directions of liquid crystal molecules 21A in the liquid crystal layer 20 and the optical axes of each optical film (i.e., the in-plane slow axes of the λ / 4 plate and the λ / 2 plate and the polarization axes of the polarizers) when no voltage is applied in a liquid crystal display device 1 (see FIG. 14) including, in order from the back side to the viewing side, a first polarizer 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 polarizer 52. In FIG. 17, the liquid crystal molecules 21 are depicted as liquid crystal molecules 21A near the first horizontal alignment film 140 and liquid crystal molecules 21B near the second horizontal alignment film 340.

[0150] 18 is a diagram illustrating the optical axis angle of the optical film. The twist direction refers to the direction in which the liquid crystal molecules 21A are twisted from the alignment direction defined by the first horizontal alignment film 140 to the alignment direction of the liquid crystal molecules 21B defined by the second horizontal alignment film 340 when the liquid crystal display device 1 is viewed from the observation side. The liquid crystal molecules 21C and 21C' are liquid crystal molecules located approximately midway between the first substrate 10 and the second substrate 30, i.e., in the center of the liquid crystal layer 20 in the thickness direction.

[0151] The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably 58.3° or more and 89.9° or less. As a result, as described above, high reflectance and high contrast can be obtained at a lower voltage, and the occurrence of alignment defects can be further suppressed. Among these, as described above, a twist angle θ1 of 78° or more and 88° or less is particularly preferable, a twist angle of 83° or more and 87° or less is even more preferable, and 83° or less is the most preferable.

[0152] The angle of polarization axis 51AA of first polarizing plate 51 (θ2 in FIG. 18) is preferably 83.4 to 91.4°, more preferably 84.0 to 90.9°, still more preferably 84.7 to 90.2°, and particularly preferably 85.5 to 89.3°.

[0153] The angle (θ3 in FIG. 18) of the in-plane slow axis 412SA of the first λ / 2 plate 412 is preferably −19.1 to −15.1°, more preferably −18.8 to −15.4°, still more preferably −18.5 to −15.7°, and particularly preferably −18.0 to 16.2°.

[0154] The angle (θ4 in FIG. 18) of the in-plane slow axis 411SA of the first λ / 4 plate 411 is preferably −80.0 to −72.2°, more preferably −79.4 to −72.8°, still more preferably −78.8 to −73.4°, and particularly preferably −77.9 to −74.3°.

[0155] 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 83.4 to 91.4°, −19.1 to −15.1°, and −80.0 to −72.2°, respectively, more preferably at angles of 84.0 to 90.9°, −18.8 to −15.4°, and −79.4 to −72.8°, respectively, even more preferably at angles of 84.7 to 90.2°, −18.5 to −15.7°, and −78.8 to −73.4°, respectively, and particularly preferably at angles of 85.5 to 89.3°, −18.0 to 16.2°, and −77.9 to −74.3°, respectively.

[0156] The angle (θ4 in FIG. 18) of the in-plane slow axis 421SA of the second λ / 4 plate 421 is preferably 62.1 to 67.1°, more preferably 63.0 to 67.0°, still more preferably 64.0 to 67.0°, and particularly preferably 64.5 to 66.0°.

[0157] The angle (θ3 in FIG. 18) of the in-plane slow axis 422SA of the second λ / 2 plate 422 is preferably 37.5 to 42.5°, more preferably 38.0 to 42.0°, still more preferably 39.0 to 41.0°, and particularly preferably 40.0 to 41.0°.

[0158] The angle of the polarization axis 52AA of the second polarizing plate 52 (θ2 in FIG. 18) is preferably 19.5 to 26.5°, more preferably 19.5 to 26.0°, still more preferably 19.5 to 25.5°, and particularly preferably 20.0 to 23.7°.

[0159] Therefore, 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 preferably positioned at angles of 19.5 to 26.5°, 37.5 to 42.5°, and 62.1 to 67.1°, respectively, more preferably at angles of 19.5 to 26.0°, 38.0 to 42.0°, and 63.0 to 67.0°, respectively, even more preferably at angles of 19.5 to 25.5°, 39.0 to 41.0°, and 64.0 to 67.0°, respectively, and particularly preferably at angles of 20.0 to 23.7°, 40.0 to 41.0°, and 64.5 to 66.0°, respectively.

[0160] 19 is a conceptual diagram showing the most preferable optical axis setting in this embodiment, in which 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.

[0161] When the slit angle is changed, it is preferable to change the polarization axis direction of the polarizing plate, the slow axis direction of the λ / 4 plate, and the slow axis direction of the λ / 2 plate by the same angle in the same direction.

[0162] (Modification 1 of Embodiment 2) In the second embodiment, a configuration has been described in which the first electrode 121, which is a lower layer electrode, is a common electrode CE, and the second electrode 122, which is an upper layer electrode, is a pixel electrode PE. However, the configuration may be reversed, in which the second electrode 122 is a common electrode CE, and the first electrode 121 is a pixel electrode PE.

[0163] (Embodiment 3) In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents overlapping with those of the above-described Embodiments 1 and 2 will be omitted. In Embodiment 2, the description focused particularly on the liquid crystal display device 1 in which only the second retardation layer 42 includes one positive C plate. In this embodiment, however, the description focuses particularly on the liquid crystal display device 1 in which the first retardation layer 41 includes one positive C plate and the second retardation layer 42 includes one positive C plate (i.e., the liquid crystal display device 1 that satisfies the above (ii)). The liquid crystal display device 1 of this embodiment is substantially the same as the liquid crystal display device 1 of Embodiment 1 or 2, except that the first retardation layer 41 includes one positive C plate.

[0164] 20 is a cross-sectional view schematically illustrating a pixel included in a liquid crystal display device 1 according to the present embodiment. As illustrated in FIG. 20, 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 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 in addition to a λ / 4 plate 421 and a λ / 2 plate 422.

[0165] From the viewpoint of further improving the viewing angle characteristics and contrast, 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. 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 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 back side, a λ / 4 plate 421, a first positive C plate 44, and a λ / 2 plate 422 (see FIG. 20 ).

[0166] (Modification 1 of Embodiment 3) In the third embodiment, a configuration was described in which the first electrode 121, which is a lower layer electrode, is a common electrode CE, and the second electrode 122, which is an upper layer electrode, is a pixel electrode PE. However, the configuration may be reversed, in which the second electrode 122 is a common electrode CE, and the first electrode 121 is a pixel electrode PE.

[0167] The embodiments of the present disclosure have been described above, but the individual matters described can all be applied to the entire present disclosure.

[0168] The liquid crystal display device 1 of the present disclosure will be described in further detail below with reference to examples, but the liquid crystal display device 1 of the present disclosure is not limited to the embodiments of these examples.

[0169] Example 1 Test cell 1A was prepared as follows. First, as shown in Fig. 21B, a liquid crystal cell 1100 for obtaining test cell 1A includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 provided between these substrates. Fig. 21A is a plan view showing the structure of liquid crystal cell 1100 as viewed from the front. Fig. 21B is a cross-sectional view (cross-sectional view taken along line A-A') in Fig. 21A.

[0170] The first substrate 10 includes a glass substrate 100, on which a common electrode CE as a first electrode 121, a dielectric layer 153, a pixel electrode PE as a second electrode 122, and a first horizontal alignment film 140 are formed 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 L of each strip portion SP is 3 μm, and the width S of each slit Sl (the distance between two adjacent strip portions SP) is 5 μm. Therefore, the L / S condition is 3 / 5. 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.

[0171] As shown in FIG. 21B, the second substrate 30 has a glass substrate 300 and a second horizontal alignment film 340 provided on the glass substrate 300.

[0172] The thickness (cell gap) of the liquid crystal layer 20 is determined by plastic beads (not shown). In Example 1, liquid crystal material No. 1 shown in Table 1 was used as the liquid crystal material constituting the liquid crystal layer 20. Table 1 shows the physical properties of each liquid crystal material.

[0173] 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.

[0174] When photo-alignment treatment was performed, a photodegradable 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 into polarized UV light by a wire grid polarizer, and the polarized UV light was irradiated onto the alignment film 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 approximately perpendicular (particularly preferably at 90°) to the transmission axis direction of polarized UV light.

[0175] When using rubbing, a horizontal alignment film is formed and then rubbed with a rubbing roller (e.g., a roller wrapped in cloth) to perform the alignment process. This results in a uniaxial alignment direction for the liquid crystal molecules. Polyimide-based materials are suitable as alignment film materials for operating liquid crystal molecules in a transverse electric field. Materials that do not generate a pretilt due to rubbing are also suitable, and such materials are commercially available. The liquid crystal molecules are aligned approximately parallel to the rubbing direction.

[0176] 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), and then the cell thickness was measured using a cell gap inspection device ("RetsQC" manufactured by Otsuka Electronics).

[0177] Next, as shown in FIG. 22A, a λ / 4 plate 421, a positive C plate 44, 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 not shown). Then, for reflection observation, a drop of matching oil mo was placed on a reflector 130 having a roughened surface structure (MRS) to reduce loss due to interfacial reflection, and the liquid crystal cell 1100 was placed on the reflector 130 with the first substrate 10 side facing downwards for verification (this corresponds to the test cell for reflection observation; see FIG. 22A). 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 for verification (this corresponds to the test cell for transmission observation; see FIG. 22B).

[0178] Nitto Denko Corporation's "NPF-CRT1794KDUHC3" was used as the polarizing plates 51 and 52, Nitto Denko Corporation's "NZF-UF01A" (retardation: 140 nm) was used as the λ / 4 plates 411 and 421, and Nitto Denko Corporation's "NZF-UF01A" (retardation: 270 nm) was used as the λ / 2 plates 412 and 422. The axial conditions of each optical film were as shown in Table 2.

[0179] 22A is a cross-sectional view of test cell 1A (and test cells 2A, 3A, 1R, and 2R described below) during reflection observation, and Fig. 22B is a cross-sectional view of test cell 1A (and test cells 2A, 3A, 1R, and 2R described below) during transmission observation. When Figs. 22A and 22B represent test cell 2A described below, the symbol 1A in the figures is replaced with 2A, 3A, 1R, or 2R.

[0180] [Table 1]

[0181] In Table 1, the positive ratio is, as described above, the content ratio of positive liquid crystal material PL (i.e., liquid crystal material that contains a compound having a structure represented by -CF2-O- in its molecule and has positive dielectric anisotropy) out of the total amount of 100 mass% of the liquid crystal material that constitutes the liquid crystal layer 20. The RP value of liquid crystal material No. 6 is calculated using the following formula (2): RP value = γ1 / K 33 (2) (In the formula, γ1 represents the rotational viscosity coefficient (mPa·sec) of the liquid crystal material that constitutes the liquid crystal layer. K 33 represents the bending elastic constant (unit: pN).

[0182] [Table 2]

[0183] In Table 2, the "front optical film" refers to the optical film located on the viewing surface side of the liquid crystal panel 1X, and the "rear optical film" refers to the optical film located on the back side of the liquid crystal panel 1X. The axial angle of each optical film is the angle of each axis when no voltage is applied, with the horizontal right direction of the screen as the reference (0°), and the angle rotated clockwise is a positive angle (+) and the angle rotated counterclockwise is a negative angle (-). The slit angle (first portion SPa) is the angle formed by the alignment direction of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied, when the extension direction of the first portion SPa of each strip portion SP (i.e., the first direction) is set as the reference 0°. The slit angle (second portion SPb) is the angle formed by the alignment direction of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied, when the extension direction of the second portion SPb of each strip portion SP (i.e., the second direction) is set as the reference 0°.

[0184] Example 2 Test cell 2A was prepared in the same manner as in Example 1, except that liquid crystal material No. 2 shown in Table 1 was used as the liquid crystal material.

[0185] Example 3 Test cell 3A was prepared in the same manner as in Example 1, except that liquid crystal material No. 3 shown in Table 1 was used as the liquid crystal material and the slit angle was changed as shown in Table 2.

[0186] (Comparative Example 1) Test cell 1R was prepared in the same manner as in Example 3, except that liquid crystal material No. 4 shown in Table 1 was used as the liquid crystal material.

[0187] (Comparative Example 2) Test cell 2R was prepared in the same manner as in Example 1, except that it did not include the reflective layer 130, that liquid crystal material No. 5 shown in Table 1 was used as the liquid crystal material, and that the slit angle was changed as shown in Table 2. Test cell 2R corresponds to a transmissive liquid crystal display device.

[0188] (Comparative Example 3) A test cell 3R of the VA type, which is a vertical electric field type, was prepared as follows. First, as shown in FIG. 23B, the liquid crystal cell 2100 for obtaining the test cell 3R includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 provided between these substrates. FIG. 23A is a plan view showing the structure of the test cell 3R (and the liquid crystal cell 2100) as viewed from the front. FIG. 23B is a cross-sectional view (cross-sectional view taken along line A-A') in FIG. 23A. In this example, liquid crystal material No. 6 shown in Table 1 was used as the liquid crystal material.

[0189] The first substrate 10 includes a glass substrate 100, on which a pixel electrode PE and a first vertical alignment film (not shown) are disposed in this order. The second substrate 30 includes a glass substrate 300, on which a common electrode CE and a second vertical alignment film (not shown) are disposed in this order. Of the vertical alignment films, only the second vertical alignment film disposed on the observation surface side has undergone photo-alignment treatment. The alignment direction of the liquid crystal molecules 21 determined by the first vertical alignment film is the 90° direction (the pretilt angle is 88.4°).

[0190] As shown in FIG. 24, a λ / 4 plate 41, a first λ / 2 plate 42a, a second λ / 2 plate 42b, and a polarizing plate 50 were attached in this order to the second substrate 30 side of the liquid crystal cell 2100 (adhesive layer not shown). The polarizing plate 50 was Nitto Denko Corporation's "NPF-CRT1794KDUHC3," the λ / 4 plate 41 was Nitto Denko Corporation's "NZF-UF01A" (retardation: 110 nm), and the λ / 2 plates 42a and 42b were Nitto Denko Corporation's "NZF-UF01A" (retardation: 260 nm). A drop of matching oil was then dropped onto the reflector 130 with the MRS, and the liquid crystal cell 2100 was placed on the reflector 130 with the first substrate 10 side facing down. In this manner, a test cell 3R was fabricated. FIG. 24 is a schematic cross-sectional view of the test cell 3R.

[0191] Test cell 3R uses a liquid crystal material with negative dielectric anisotropy, and its display mode is VA mode. The optical axis setting (initial setting) and specifications are shown in Table 3 and Figure 25. Figure 25 is a conceptual diagram showing the optical axis setting of test cell 3R.

[0192] [Table 3]

[0193] In Table 3, CH (Chirality) is the twist angle of the liquid crystal molecules 21 between the upper and lower substrates (that is, between the first substrate 10 and the second substrate 30).

[0194] (Evaluation test) The following evaluations were carried out using the test cells prepared in Examples 1 to 3 and Comparative Examples 1 to 3. Voltage application to the pixel electrode PE and the common electrode CE was carried out using a function generator ("AFG1022" manufactured by TEKTRONIX) capable of applying a voltage of 0 V to 10 V with a 30 Hz square wave.

[0195] (1) Reflectance and transmittance For the measurement of reflectance, a test cell for reflection observation (see FIG. 22A) was used, and the reflectance (also referred to as reflection mode efficiency) was measured using a spectrophotometer (MINOLTA "CM-2600d"). For the measurement of transmittance, a test cell for transmission observation (see FIG. 22B) was used, and the transmittance (also referred to as transmission mode efficiency) was measured using a spectrophotometer (TOPCON "SR-UL2"). The results are shown in Table 4.

[0196] [Table 4]

[0197] (2) Flicker rate (2-1) Flicker rate during reflection observation The test cell (see FIG. 22A) was driven at 1 Hz and the flicker was visually confirmed, and the flicker rate was calculated using the following formula: Flicker rate = reflectance change / average reflectance The results are shown in Table 5 and Fig. 26. In Table 5 and Fig. 26, the flicker rate is expressed as an absolute value. Based on this data, we created a graph (Fig. 27) with the horizontal axis representing time and the vertical axis representing the flicker rate at 96 gradations, a graph (Fig. 30A) with the horizontal axis representing the positive ratio and the vertical axis representing the flicker rate at 96 gradations, and a graph (Fig. 31A) with the horizontal axis representing the positive ratio and the vertical axis representing the logarithm of the flicker rate at 96 gradations.

[0198] [Table 5]

[0199] In each of the test cells of Examples 1 to 3, no flicker was visible when driven at 1 Hz. Table 5 also shows that the flicker rate was 5% or less at all gradations. On the other hand, in the test cell of Comparative Example 1 (positive ratio 71%), flicker was visible at gradations 64 to 192. Table 5 also shows that the flicker rate was 5% or more at these gradations.

[0200] (2-2) Flicker rate during transmitted light observation The test cell (see FIG. 22B) was driven at 1 Hz and the flicker was visually confirmed, and the flicker rate was calculated using the following formula: Flicker rate = Transmittance change / Average transmittance The results are shown in Table 5 and Fig. 28. In Table 6 and Fig. 28, the flicker rate is shown as an absolute value. Based on this data, we created a graph (Fig. 29) with the horizontal axis representing time and the vertical axis representing the flicker rate at 96 gradations, a graph (Fig. 30B) with the horizontal axis representing the positive ratio and the vertical axis representing the flicker rate at 96 gradations, and a graph (Fig. 31B) with the horizontal axis representing the positive ratio and the vertical axis representing the logarithm of the flicker rate at 96 gradations.

[0201] [Table 6]

[0202] In each of the test cells of Examples 1 and 2, no flicker was visible at 160 gradations or higher when driven at 1 Hz, and in the test cell of Example 3, no flicker was visible at 128 gradations or higher when driven at 1 Hz. Table 6 also shows that the flicker rate was 5% or less at these gradations. On the other hand, in the test cell of Comparative Example 1 (positive ratio 71%), flicker was visible at 32 to 192 gradations. Table 6 also shows that the flicker rate was 5% or more at these gradations. In the test cell of Comparative Example 2 (positive ratio 20%), no flicker was visible at any gradation, but the reflective mode efficiency was low (see Table 3).

[0203] 27 and 29, the waveform with a positive value is referred to as an upper angle waveform, and the waveform with a negative value is referred to as a lower angle waveform (see, for example, (a) of FIG. 27). The flicker rates at each of the 96 gray levels are shown in Table 4.

[0204] (3) Change in brightness profile (transmitted light observation) The test cell (see Figure 22B) was driven at 0.1 Hz (DC offset 0 V), and the change in luminance profile upon polarity inversion was observed in transmission mode. The luminance profile (128 gradations) for positive polarity is shown in Figure 32A, and the luminance profile (128 gradations) for negative polarity is shown in Figure 32B. The difference between the positive and negative average gradations (128 gradations) is shown in Figure 32C. The thin horizontal lines in each image in Figure 32C indicate the positions where the profiles were acquired. Furthermore, luminance profile images for positive and negative polarity are shown in Figures 33A to 33D.

[0205] (4) Response characteristics (transmitted light observation) (4-1) Rising response Using a test cell (see FIG. 22B), the luminance per unit time was measured when the voltage was increased from 0 V to 5 V. The results are shown in FIG. 34A. The time required for the luminance to change from 10% to 90% (referred to as the rise response time Tr) is shown in Table 4. ms stands for milliseconds. Table 4 shows that the rise response time Tr was slow in Comparative Example 1 and Comparative Example 3.

[0206] (4-2) Falling response Using a test cell (see FIG. 22B), the luminance per unit time was measured when the voltage was decreased from 5 V to 0 V. The results are shown in FIG. 34B. The time required for the luminance to change from 90% to 10% (referred to as the falling response time Td) is shown in Table 4. Table 4 shows that the falling response time Td was slow in Comparative Example 1 and Comparative Example 3.

[0207] (4-3) Consideration of fall response time Td Based on the fall response time Td calculated above, a graph (Figure 35A) was created in which the horizontal axis represents the RP value and the vertical axis represents the fall response time Td, and a graph (Figure 35B) was created in which the horizontal axis represents the positive ratio and the vertical axis represents the fall response time Td.

[0208] The above-described aspects of the present disclosure may be combined as appropriate within the scope of the gist of the present disclosure. [Explanation of symbols]

[0209] 1:LCD display device 1A, 2A, 3A, 1R, 2R, 3R: Test cell 1x: LCD panel 10, 30: PCB 20: Liquid crystal layer 21, 21A, 21B, 21C, 21C': Liquid crystal molecules 40, 41, 42: Retardation layer 411, 412: λ / 4 plate 412, 422, 42a, 42b: λ / 2 board 41SA, 42SA, 411SA, 412SA, 421SA, 422SA: In-plane slow axis 43, 44: Positive C-plate 51, 52: Polarizing plates 51AA, 52AA: Polarization axis 61 :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 1100, 2100: Liquid crystal cells for obtaining test cells BP: Backplane circuit CE: Common electrode PE: pixel electrode CH1, CH2: Contact holes DR:Display area FR: Hidden area GL: Gate wiring SL: Source wiring p: convex part P: pixel Rf:Reflection area Tr:Transmission area Sl: Slit SP: Belt SPa: 1st part SPb: 2nd part TC: Touch wiring contact area TD: Touch drive unit TL, TL1, TL2: Touch wiring TX: Touch sensor electrode (a) :Bottom angle waveform

Claims

1. a first substrate; a second substrate facing the first substrate; a liquid crystal layer provided between the first substrate and the second substrate; A liquid crystal display device having a plurality of pixels, the first substrate has a reflective layer that reflects light, a pair of electrodes that can generate a transverse electric field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer; the second substrate has a second horizontal alignment film in contact with the liquid crystal layer, The liquid crystal layer has a twisted orientation when no voltage is applied, In 100% by mass of the total amount of the liquid crystal material constituting the liquid crystal layer, -CF ２ the content of a positive liquid crystal material containing a compound having a structure represented by —O— and having positive dielectric anisotropy is 45% by mass or less, 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. A semi-transmissive liquid crystal display device characterized by:

2. At least one of the pair of electrodes has a plurality of strip-shaped portions and a slit located between two adjacent strip-shaped portions of the plurality of strip-shaped portions, In each pixel, the plurality of strip-shaped portions are linear and extend substantially parallel to one another in the same direction; When no voltage is applied, the alignment direction of the liquid crystal molecules on the first substrate side is between −4° and 0°, with the direction in which the strip portions extend being taken as the reference angle of 0°.

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

3. The liquid crystal layer has the following formula (1): RP value = γ １ / K ２２ (1) (In the formula, γ １ represents the rotational viscosity coefficient (mPa·sec) of the liquid crystal material constituting the liquid crystal layer. ２２ represents the torsional elastic constant (unit: pN). The RP value represented by 2. The semi-transmissive liquid crystal display device according to claim 1.

4. a first polarizing plate, a first retardation layer, the first substrate, the liquid crystal layer, the second substrate, a second retardation layer, and a second polarizing plate, in this order from the rear side; 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.

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

5. the second retardation layer includes one positive C plate, The first retardation layer does not include a positive C plate or includes one positive C plate.

5. The semi-transmissive liquid crystal display device according to claim 4.

6. 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 the observation surface side, the first λ / 2 plate and the second λ / 2 plate have substantially the same in-plane retardation Re; The in-plane retardation Re of the first λ / 4 plate and the second λ / 4 plate is approximately the same.

6. The semi-transmissive liquid crystal display device according to claim 4 or 5.

7. 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.

6. The semi-transmissive liquid crystal display device according to claim 4 or 5.

8. The twist angle of the liquid crystal layer when no voltage is applied is 58.3° or more and 89.9° or less.

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

9. The plurality of strip-shaped portions have a ratio L / S of a width L per strip-shaped portion in a plan view to a width S per slit in a plan view of 0.4 to 0.7 / 1.

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

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

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

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

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

13. Further, a light source is provided.

13. The semi-transmissive liquid crystal display device according to claim 1, 2, 3, 4, 8, 9, 10, 11 or 12.

Images