Liquid crystal display device

Abstract

To provide a liquid crystal display device with which occurrence of alignment defects is sufficiently suppressed, high reflectance can be achieved at low voltage, and contrast is sufficiently high, and which is useful as an in-cell type touch panel capable of displaying in a reflection mode.SOLUTION: The liquid crystal display device comprises a first substrate, a liquid crystal layer, and a second substrate, and includes a plurality of pixels. The first substrate includes a reflection layer, first and second electrodes, and a first horizontal alignment film. At least one of the first and second electrodes includes a plurality of belt-like sections and a slit. In each pixel, the plurality of belt-like sections is composed of linear shapes extending parallel to each other and in the same direction and does not include a bent section. The second substrate has a second horizontal alignment film. The liquid crystal layer includes a liquid crystal molecule whose dielectric anisotropy is positive type and takes twist alignment when no voltages are applied. The alignment direction of the liquid crystal molecules on the first substrate side at a time when no voltages are applied is -6° or more and -1°or less, when the direction in which the plurality of belt-like sections extends is taken as reference 0°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] Liquid crystal display devices can also be broadly classified by the liquid crystal driving method. For example, there are known vertical electric field liquid crystal 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 liquid crystal 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 twisted nematic (TN) mode and multi-domain vertical alignment (MVA) mode, while examples of horizontal electric field modes include in-plane switching (IPS) mode and fringe field switching (FFS) mode. For example, Patent Document 1 discloses a liquid crystal display suitable as a horizontal electric field liquid crystal display device. This liquid crystal display is capable of suppressing defects caused by process variations and improving display performance, and is particularly useful as a transmissive liquid crystal display device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5756860 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, 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 can realize 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 current 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 provided only on the active matrix substrate side, and therefore an in-cell touch panel capable of displaying in reflective mode could be realized.

[0008] Therefore, we further investigated FFS-mode devices that display in a normally black mode. For example, we investigated devices using a positive-type liquid crystal material for the liquid crystal layer and a slit electrode with a slit-shaped opening as at least one of the pair of electrodes. However, we found that immediately after applying a voltage (5 V or higher) from a no-voltage state (0 V), the liquid crystal alignment becomes unstable, resulting in alignment defects (also called alignment disturbances) in which the liquid crystal alignment becomes discontinuous (see Test Example 4, etc., described below). The occurrence of alignment defects can lead to problems such as poor liquid crystal response, reduced reflective mode efficiency, reduced transmissive mode efficiency, and concerns about graininess when viewed obliquely. In particular, liquid crystal display devices with nonuniform and unstable liquid crystal alignment are not suitable for practical use as moving image display devices.

[0009] The present invention has been made in consideration of the above-mentioned current situation, and aims to provide a liquid crystal display device that sufficiently suppresses the occurrence of orientation defects, achieves high reflectivity at low voltage, has sufficiently high contrast, and is also useful as an in-cell type touch panel capable of displaying in reflective mode. [Means for solving the problem]

[0010] (1) One embodiment of the present invention is a liquid crystal display device having a plurality of pixels, the liquid crystal display device comprising a first substrate, a second substrate facing the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate, the first substrate having a reflective layer that reflects light, a first electrode and a second electrode that can generate a transverse electric field in the liquid crystal layer, and a first horizontal alignment film that contacts the liquid crystal layer, and at least one of the first electrode and the second electrode has a plurality of strip-shaped portions and two adjacent strip-shaped portions of the plurality of strip-shaped portions. and slits located between the strip-shaped portions, wherein in each pixel, the plurality of strip-shaped portions are linear and extend substantially parallel to one another in the same direction, and do not include any bent portions, the second substrate has a second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer contains liquid crystal molecules with positive dielectric anisotropy and exhibits a twisted alignment when no voltage is applied, and the alignment direction of the liquid crystal molecules on the first substrate side when no voltage is applied is between -6° and -1° when the direction in which the plurality of strip-shaped portions extend is taken as the reference 0°.

[0011] (2) In one embodiment of the present invention, in addition to the configuration (1) above, the plurality of strip-shaped portions do not include any notches.

[0012] (3) In one embodiment of the present invention, in addition to the configuration of (1) or (2) above, when the liquid crystal layer of each pixel is viewed in a plane with no applied voltage, the extension direction of the multiple strip-shaped portions, at least in the center of the plane direction of the liquid crystal layer, is located between the alignment direction of the liquid crystal molecules on the first substrate side and the alignment direction of the liquid crystal molecules on the second substrate side, and when the liquid crystal layer of each pixel is viewed in a plane, the liquid crystal molecules at least in the center of the thickness direction of the liquid crystal layer rotate in the twist direction when no voltage is applied when voltage is applied.

[0013] (4) An embodiment of the present invention is a liquid crystal display device having the configuration of (1), (2), or (3) above, wherein the dielectric anisotropy Δε of the liquid crystal molecules is 3 or more and 5 or less.

[0014] (5) One embodiment of the present invention is a liquid crystal display device having the configuration of (1), (2), (3), or (4) above, wherein the thickness of the liquid crystal layer is 2.5 μm or more and 3 μm or less.

[0015] (6) In one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4) or (5), the alignment direction of the liquid crystal molecules on the first substrate side when no voltage is applied is between -6° and -3° when the direction in which the multiple strip portions extend is taken as 0°, and the thickness of the liquid crystal layer is between 2.8 μm and 3 μm.

[0016] (7) In one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), or (6), the alignment direction of the liquid crystal molecules on the first substrate side when no voltage is applied is between -5° and -1° when the direction in which the multiple strip portions extend is taken as 0°, and the thickness of the liquid crystal layer is between 3.1 μm and 3.4 μm.

[0017] (8) One embodiment of the present invention is a liquid crystal display device having the configuration of (1), (2), (3), (4), (5), (6), or (7) above, in which the direction in which the multiple strip portions extend is the same at least in adjacent pixels or in the display area.

[0018] (9) In an embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), or (8), the liquid crystal display device further includes 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.

[0019] (10) An embodiment of the present invention is a liquid crystal display device having the configuration (9) above, wherein the second retardation layer includes one positive C plate, and the first retardation layer does not include a positive C plate or includes two positive C plates.

[0020] (11) In one embodiment of the present invention, in addition to the configuration of (9) or (10) 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.

[0021] (12) An embodiment of the present invention is a liquid crystal display device having the configuration of (9), (10), or (11) above, wherein 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.

[0022] (13) An embodiment of the present invention is a liquid crystal display device having the configuration described above in (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), or (12), wherein the twist angle of the liquid crystal layer when no voltage is applied is 58.3° or more and 89.9° or less.

[0023] (14) In one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), or (13), the plurality of strip portions are a liquid crystal display device in which the ratio L / S of the width L per strip portion in a planar view to the width S per slit in a planar view is 0.4 to 0.7 / 1.

[0024] (15) An embodiment of the present invention is a liquid crystal display device having a single domain alignment in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), or (14).

[0025] (16) An embodiment of the present invention is a 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), (10), (11), (12), (13), (14), or (15) above.

[0026] (17) In one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), or (16), one of the 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, and the first substrate is a liquid crystal display device having a plurality of touch wirings each connected to a corresponding one of the touch sensor electrodes.

[0027] (18) An embodiment of the present invention is a liquid crystal display device that further comprises a light source in addition to the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), or (17) above.

[0028] (19) An embodiment of the present invention is a liquid crystal display device having the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17), or (18) above, wherein each pixel has a reflective region that reflects light by the reflective layer to display an image, and a transmissive region that transmits light to display an image. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide a liquid crystal display device that sufficiently suppresses the occurrence of alignment defects, achieves high reflectivity at low voltage, has sufficiently high contrast, and is also useful as an in-cell touch panel capable of displaying in reflective mode. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view of a liquid crystal display device 1. FIG. [Figure 2] FIG. 2 is a more detailed schematic cross-sectional view of the liquid crystal display device 1. [Figure 3] FIG. 1 is a schematic plan view of the entire liquid crystal display device 1 as viewed from the observation surface side. [Figure 4] FIG. 10 is a diagram for explaining the slit angle of liquid crystal molecules. [Figure 5] FIG. 10 is a diagram for explaining the definition of an angle. [Figure 6] FIG. 2 is a plan view schematically illustrating one pixel. [Figure 7] FIG. 7 is a schematic plan view showing an enlarged portion of FIG. 6. [Figure 8] 1 is a schematic plan view showing an example of the structure of a pixel (angle X is 0°). [Figure 9A] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is 0°). [Figure 9B] FIG. 1 is a plan view showing an example of a pixel arrangement (angle X is −10°). [Figure 9C] FIG. 1 is a plan view showing an example of a pixel arrangement (angle X is +10°). [Figure 9D] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −90°). [Figure 9E] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −100°). [Figure 9F] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −80°). [Figure 10] 2 is a plan view schematically illustrating the arrangement relationship between touch sensor electrodes TX and touch wirings TL included in the liquid crystal display device 1. FIG. [Figure 11] 1 is a cross-sectional view of a liquid crystal display device 1. FIG. [Figure 12] 1 is a liquid crystal director distribution diagram (cross-sectional view). [Figure 13] 1 is a liquid crystal director distribution diagram (cross-sectional view). [Figure 14] 1 is a liquid crystal director distribution diagram (cross-sectional view). [Figure 15] FIG. 10 is a diagram showing a calculation model of a liquid crystal director distribution map. [Figure 16A] 7 is a schematic cross-sectional view (cross-sectional view taken along line AA' in FIG. 6) conceptually illustrating the behavior of liquid crystal molecules 21 when no voltage is applied. [Figure 16B] 7 is a schematic plan view showing an enlarged portion of FIG. 6, conceptually illustrating the twist direction of liquid crystal molecules 21 when no voltage is applied. [Figure 17A] 7 is a schematic cross-sectional view (cross-sectional view taken along line AA') in FIG. 6, conceptually illustrating the behavior of liquid crystal molecules 21 when a voltage is applied. [Figure 17B] 7 is a schematic plan view showing an enlarged portion of FIG. 6, conceptually illustrating the twist direction of liquid crystal molecules 21 when a voltage is applied. [Figure 18] 1 is a cross-sectional view of a liquid crystal display device 1. FIG. [Figure 19] FIG. 2 is a more detailed schematic cross-sectional view of the liquid crystal display device 1. [Figure 20] FIG. 1 is a schematic plan view conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr. [Figure 21] 1 is a schematic plan view showing an example of the structure of a pixel (angle X is 0°). [Figure 22A] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is 0°). [Figure 22B] FIG. 1 is a plan view showing an example of a pixel arrangement (angle X is −10°). [Figure 22C] FIG. 1 is a plan view showing an example of a pixel arrangement (angle X is +10°). [Figure 22D] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −90°). [Figure 22E] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −100°). [Figure 22F] FIG. 2 is a plan view showing an example of a pixel arrangement (angle X is −80°). [Figure 23] 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 24] FIG. 2 is a diagram for explaining the optical axis angle of an optical film. [Figure 25] FIG. 10 is a diagram conceptually showing the most preferable optical axis setting. [Figure 26] 1 is a cross-sectional view of a liquid crystal display device 1. FIG. [Figure 27] 1 is a cross-sectional view of a liquid crystal display device 1. FIG. [Figure 28] 1 is a cross-sectional view of a liquid crystal display device 1. FIG. [Figure 29] 1 is a cross-sectional view of a liquid crystal display device 1 assumed in Test Examples 1 to 3. FIG. [Figure 30] 10 is a diagram conceptually showing the slit angle θZ and the like in each of Test Examples 1 to 3. FIG. [Figure 31] FIG. 10 is a diagram showing the results of verification 1 in test example 3. [Figure 32] FIG. 1 is a diagram showing the results of verification 1 in test examples 1 to 3. [Figure 33] FIG. 10 is an image diagram of when a voltage is applied in Verification 2(1) of Test Examples 1 to 3. [Figure 34] FIG. 10 is an image diagram of when a voltage is applied in Verification 2(2) of Test Examples 1 to 3. [Figure 35A]FIG. 10 is a diagram showing the results of verification 2(1) of Test Examples 1 to 3. [Figure 35B] FIG. 10 is a diagram showing the results of verification 2(2) of Test Examples 1 to 3. [Figure 35C] FIG. 10 is a diagram showing the results of verification 2(3) of Test Examples 1 to 3. [Figure 36A] FIG. 10 is a diagram showing the results of verification 3 in test example 1. [Figure 36B] FIG. 10 is a diagram showing the results of verification 3 in test example 1. [Figure 36C] FIG. 10 is a diagram showing the results of verification 3 in test example 1. [Figure 36D] FIG. 10 is a diagram showing a calculation model of a liquid crystal director distribution map. [Figure 37] FIG. 10 is a diagram showing the results of verification 3 in test example 1. [Figure 38] 1 is a diagram conceptually showing the twist angle orientation T and the reverse twist orientation R in Test Example 1. FIG. [Figure 39A] FIG. 10 is a diagram showing the results of verification 4 in Test Examples 3 and 4. [Figure 39B] FIG. 10 is a diagram showing the results of verification 4 in Test Examples 3 and 4. [Figure 39C] FIG. 10 is a diagram showing the results of verification 4 in Test Examples 3 and 4. [Figure 39D] FIG. 10 is a diagram showing the results of verification 4 in Test Examples 3 and 4. [Figure 39E] FIG. 10 is a diagram showing the results of verification 4 in Test Examples 3 and 4. [Figure 40A] FIG. 10 is a diagram conceptually illustrating the twist angle orientation T and the reverse twist orientation R in Test Examples 3 and 4. [Figure 40B] FIG. 10 is a diagram conceptually illustrating the twist angle orientation T and the reverse twist orientation R in Test Examples 3 and 4. [Figure 41A] FIG. 10 is a diagram showing the results of verification 5 in test examples 1 to 3. [Figure 41B] FIG. 10 is a diagram showing the results of verification 5 in test examples 1 to 3. [Figure 41C] FIG. 10 is a diagram showing the results of verification 5 in test examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

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

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

[0033] The polar angle means the angle between the direction of interest (for example, the measurement direction) and the normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction 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 5). Figure 5 is a diagram for explaining the definition of angles, with the horizontal right direction of the screen defined as 0°. Counterclockwise and clockwise directions both 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] An A plate is a retardation plate that satisfies "nx>ny≒nz."

[0038] The wavelength for measuring optical parameters such as refractive index and phase difference is 550 nm unless otherwise specified.

[0039] "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).

[0040] Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiment, and appropriate design modifications can be made within the scope of the configuration of the present invention. In the following description, the same reference numerals will be used in different drawings as appropriate for the same parts or parts having similar functions, and repeated description thereof will be omitted as appropriate. Each aspect of the present invention may be combined as appropriate within the scope of the gist of the present invention.

[0041] (Embodiment 1) FIG. 1 is a cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment, and FIG. 2 is a more detailed cross-sectional view of the liquid crystal display device 1 according to an example of the present embodiment. FIG. 3 is a plan view of the entire liquid crystal display device 1 according to an example of the present embodiment, as viewed from the observation side. As shown in FIG. 1, the liquid crystal display device 1 includes, in this order from the rear side, a first substrate 10, a liquid crystal layer 20, and a second substrate 30. In this embodiment, a TFT substrate is used as the first substrate 10. Note that a portion or structure having a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0042] 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 pixel P includes a thin film transistor (TFT) 110 and a first electrode 121 and a second electrode 122 capable of generating a transverse electric field in the liquid crystal layer 20. A gate electrode of the TFT 110 is electrically connected to a corresponding gate line (also referred to as a scanning line) GL, and a source electrode of the TFT 110 is electrically connected to a corresponding source line (also referred to as a signal line) SL. A drain electrode of the TFT 110 is electrically connected to the second electrode 122.

[0043] <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.

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

[0045] The backplane circuit BP is provided on 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.

[0046] The TFT 110 is provided for each of the multiple pixels P. The TFT 110 preferably 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 active layer materials to replace 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, and therefore can be applied to devices requiring a large area.

[0047] 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.

[0048] 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)).

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

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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).

[0055] 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.

[0056] 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.

[0057] The reflective layer (also referred to as a reflective film) 130 is provided on the first interlayer insulating layer 151. The reflective layer 130 is 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, an aluminum alloy, and an aluminum alloy.

[0058] 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.

[0059] 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.

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

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] In each pixel P, the strip portions SP constituting the slit electrode (in this embodiment, the second electrode 122 that is the pixel electrode PE) are linear and extend substantially parallel to each other in the same direction, without including any bent portions, which makes the alignment of the liquid crystal molecules uniform and sufficiently suppresses the occurrence of alignment defects.

[0067] The band-shaped portion SP being "linear and not including any bent portions" means that the center line of the band-shaped portion SP, not the outer edge of the band-shaped portion SP, is linear and not bent. The center line of the band-shaped portion SP refers to the line that divides the band-shaped portion SP into two equal parts in the width direction. The width direction refers to the direction approximately perpendicular to the direction in which the band-shaped portion SP extends in a plan view. Therefore, even if the outer edge of the tip of the band-shaped portion SP is circular, if the center line of the band-shaped portion SP is linear and not bent, it falls under the category of "linear and not including any bent portions."

[0068] 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.

[0069] 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. In particular, from the standpoints of image quality and manufacturing, it is more preferable that the extension directions of the strip portions SP are the same for at least adjacent pixels. Figures 6A to 6F, 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.

[0070] 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.

[0071] 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"). Examples of the L / S condition are 1.6 / 3 (i.e., 0.533 / 1), L / S=2.2 / 4.1 (i.e., 0.537 / 1), and L / S=3 / 5 (i.e., 0.6 / 1).

[0072] 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 −6° or more and −2° or less 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 the 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.

[0073] 4 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.

[0074] 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. 4). 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. 4). 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. 4).

[0075] 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°).

[0076] In this embodiment, the slit angle is -6° to -1° as described above, and preferably -6° to -2°. A slit angle within this range ensures that the rotation directions of the liquid crystal molecules 21A on the first substrate 10 and the liquid crystal molecules 21B on the second substrate 30 are aligned, thereby sufficiently suppressing the occurrence of alignment defects. At the same time, high reflectance and transmittance are achieved at low voltage, and response characteristics are also improved. To further suppress the occurrence of alignment defects, the slit angle is particularly preferably -6° to -3°. Furthermore, as described below, to suppress the occurrence of reverse twist alignment when the cell thickness d is 3.1 μm to 3.4 μm, the slit angle is preferably -5° to -1°.

[0077] FIG. 6 is a schematic plan view showing one pixel. FIG. 7 is a schematic plan view showing an enlarged portion of FIG. 6. FIGS. 6 and 7 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. 6, 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.

[0078] 8 and 9A 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. 9B, 9C, 9D, 9E, and 9F, respectively. The case in which angle X is 0° (see FIGS. 8 and 9A) 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. 9D) 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. 8 and 9A to 9F are schematic plan views illustrating specific examples of pixels. 8 is a plan view showing an example of the pixel structure, and FIGS. 9A to 9F are plan views showing an example of the pixel arrangement. 9A to 9F also show the twisted orientation of liquid crystal molecules 21.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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°.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] 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).

[0089] <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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] <Liquid crystal layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and contains a liquid crystal material. In this embodiment, the liquid crystal layer 20 contains positive liquid crystal molecules. That is, the liquid crystal material constituting the liquid crystal layer 20 is a liquid crystal material with positive dielectric anisotropy (meaning a nematic liquid crystal material with a positive dielectric anisotropy Δε). Note that a negative liquid crystal material means a liquid crystal material with negative dielectric anisotropy, i.e., a nematic liquid crystal material with a negative dielectric anisotropy Δε. The dielectric anisotropy Δε is determined by the dielectric constant ε in the long axis direction of the liquid crystal molecules 21. / / and the permittivity in the minor axis direction ε ⊥ The difference between (i.e., ε / / -ε ⊥ )

[0094] 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.

[0095] 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).

[0096] 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.

[0097] In this embodiment, the slit angle θ Z It is preferable that the angle of the alignment direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied is -6° or more and -3° or less (i.e., when the direction in which the multiple strip-shaped portions SP extend is taken as the reference 0°), and that the thickness d of the liquid crystal layer 20 is 2.7 μm or more and 3 μm or less (more preferably 2.8 μm or more and 3 μm or less). In this case, the effects of suppressing the occurrence of alignment defects, achieving high reflectivity at low voltage, and increasing contrast are even more effectively exerted.

[0098] 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. In particular, from the viewpoint of achieving high reflectance, high transmittance, and high-speed response and suppressing the occurrence of reverse twist alignment, which will be described later, the slit angle θ Z is preferably in the range of −5° to −1°, and the thickness d of the liquid crystal layer 20 is preferably in the range of 3.1 μm to 3.4 μm.

[0099] The liquid crystal material (liquid crystal molecules) constituting the liquid crystal layer 20 has a positive dielectric anisotropy Δε. Generally, when the absolute value of Δε is less than 2, it is not considered to have dielectric anisotropy, and therefore, the lower limit of Δε is preferably 2 or greater. In particular, from the viewpoint of further increasing transmittance, Δε is preferably 3 or greater. Furthermore, from the viewpoints of further increasing reflectance, further suppressing the occurrence of alignment defects, and further improving response characteristics, Δε is preferably 10 or less, more preferably 7 or less, even more preferably 6 or less, and most preferably 5 or less. Therefore, the range of Δε is preferably 2 or greater and 10 or less, more preferably 3 or greater and 10 or less, even more preferably 3 or greater and 7 or less, particularly preferably 3 or greater and 6 or less, and most preferably 3 or greater and 5 or less.

[0100] Considering the absolute value of Δn possessed by the liquid crystal molecules with the lowest refractive index (Δn = 0.038 for the alkenyl derivative with the lowest refractive index), the liquid crystal material preferably has a birefringence Δn of more than 0.05. Furthermore, considering the preferred range of dΔn (described below) and the cell thickness, it is more preferably 0.077 or more, and most preferably 0.081 or more (for example, when the cell thickness is 3.0 μm). Considering 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 elastic constant of the liquid crystal material is inversely proportional to the threshold voltage, so from the viewpoint of reducing the voltage, the twist elastic constant (also called twist elastic constant) K 22 (unit: pN) is preferably 2 or more, more preferably 3 or more. 22 In addition, from the viewpoint of preventing the white reflectance (VRmax) from increasing to a high voltage, it is preferably 8 or less, 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. 33Although 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.

[0102] From the viewpoint of increasing the response speed, the liquid crystal material preferably has a rotational viscosity coefficient γ1 of 100 mPa·sec or less, more preferably 90 mPa·sec or less, and preferably 50 mPa·sec or more, more preferably 60 mPa·sec or more, and even more preferably 70 mPa·sec or more.

[0103] 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.

[0104] 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.

[0105] 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).

[0106] <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.

[0107] 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.

[0108] <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.

[0109] 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.

[0110] 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.

[0111] <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.

[0112] 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.

[0113] An example in which the liquid crystal display device 1 is used in an in-cell touch panel will be further described. 10 is a plan view schematically illustrating the arrangement of touch sensor electrodes TX and touch wiring TL included in a liquid crystal display device 1. As shown in FIG. 10, the liquid crystal display device 1 has a display area DR and a non-display area FR. The display area DR is defined by a plurality of pixels P (see, for example, FIG. 3) arranged in a matrix. The non-display area FR is located on the periphery of the display area DR and is also referred to as a peripheral area or a frame area.

[0114] 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. 10, each touch sensor electrode TX is provided corresponding to two or more pixels P.

[0115] 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.

[0116] 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.

[0117] 10, 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.

[0118] 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.

[0119] 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.

[0120] In an in-cell touch panel, it is particularly preferable to use an In—Ga—Zn—O based semiconductor as the TFT 110 .

[0121] (Modification 1 of Embodiment 1) In the first embodiment, a configuration has been described 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, 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. 11).

[0122] FIG. 11 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.

[0123] (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.

[0124] (Embodiment 2) In this embodiment, features unique to this embodiment will be mainly described, and descriptions of content overlapping with the first embodiment will be omitted. In this embodiment, when the liquid crystal layer 20 of each pixel P is viewed in a planar view with no voltage applied, the extension direction of the multiple strip portions SP, at least in the center of the plane direction of the liquid crystal layer 20, is located between the long axis direction a of the liquid crystal molecules 21 on the first substrate 10 side and the long axis direction b of the liquid crystal molecules 21 on the second substrate 30 side. Furthermore, when the liquid crystal layer 20 of each pixel P is viewed in a planar view, the liquid crystal molecules 21 at least in the center of the thickness direction of the liquid crystal layer 20 rotate in the twist direction when no voltage is applied. Other than these points, this embodiment is the same as the first embodiment.

[0125] This embodiment can be realized by appropriately adjusting, for example, the twist angle θ1 and the various physical properties of the liquid crystal material described above.

[0126] In the liquid crystal display device 1 of this embodiment, a reverse twist orientation occurs in the liquid crystal layer 20. Therefore, in the case of a normally black mode, for example, when white is displayed, the liquid crystal molecules in the liquid crystal layer 20 are all aligned in an orientation that closely resembles a homogeneous orientation. This increases the light utilization efficiency and improves the white reflectance, making it possible to obtain high reflectance even when white is displayed at a low driving voltage.

[0127] The central portion of the liquid crystal layer 20 in the plane direction is also referred to as the central portion of the liquid crystal layer 20 in the horizontal direction, and refers to the central portion of the liquid crystal layer 20 in a planar view. In other words, it refers to the vicinity of the center of the liquid crystal layer 20 when the liquid crystal panel 1X is viewed from the observation surface side. Furthermore, the central portion of the liquid crystal layer 20 in the thickness direction refers to the central portion of the liquid crystal layer 20 in a cross-sectional view. In other words, it refers to the vicinity of the center of the liquid crystal layer 20 when the liquid crystal panel 1X is viewed from its side. Therefore, the liquid crystal molecule 21 located in the central portion of the liquid crystal layer 20 in the thickness direction is located approximately midway between the liquid crystal molecule 21A on the first substrate 10 side and the liquid crystal molecule 21B on the second substrate 30 side. The liquid crystal molecule 21 located in the central portion of the liquid crystal layer 20 in the thickness direction is also referred to as the liquid crystal molecule 21C (and 21C').

[0128] When the liquid crystal layer 20 of each pixel P is viewed in plan with no voltage applied, the phrase "at least in the central portion of the liquid crystal layer 20 in the plane direction, the extension direction of the plurality of strip-shaped portions SP is located between the long axis direction a of the liquid crystal molecules 21A and the long axis direction b of the liquid crystal molecules 21B" means that at least in the central portion of the liquid crystal layer 20 in the plane direction, with no voltage applied, the following relational expression (1): θ a <θ SP <(θ a +θ1) (1) This means that

[0129] In the above formula, θ a is the angle of the alignment direction a of the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied, with the direction parallel to the gate line GL being the reference (0°), and the angle rotated clockwise being a positive angle (+), and the angle rotated counterclockwise being a negative angle (-). In the case of positive liquid crystal molecules, the alignment direction of the liquid crystal molecules 21A corresponds to the long axis direction of the liquid crystal molecules 21A. SP is the angle from the reference (0°) to the extension direction of the multiple strip portions SP. (θ a +θ1) is θ a and θ1, where θ1 is the twist angle.

[0130] θ a is preferably, for example, 10 to 90°. That is, the above relational expression (1) is satisfied, and θ a It is preferable to control the alignment of the liquid crystal molecules 21A by the first horizontal alignment film so that θ is at this angle. a The lower limit of θ is more preferably 30° or more, even more preferably 45° or more, and particularly preferably 60° or more. a The upper limit of the angle is more preferably 89° or less, even more preferably 85° or less, particularly preferably 83° or less, and most preferably 80° or less.

[0131] θ SP is preferably, for example, 30 to 150°. SP It is preferable to design the slit electrode so that θ is this angle. SP is θa Any value greater than θ SP The lower limit of θ is, for example, more preferably 45° or more, even more preferably 60° or more, and particularly preferably 80° or more. SP The upper limit is more preferably 120° or less, and even more preferably 100° or less.

[0132] The twist angle θ1 is preferably 58.3° or more and 89.9° or less. Within this range, high reflectance and high contrast can be obtained at a lower voltage, and the occurrence of alignment defects is further suppressed. In particular, the lower limit of θ1 is more preferably 70° or more, even more preferably 78° or more, and particularly preferably 83° or more. Furthermore, from the viewpoint of further improving response characteristics, the upper limit of θ1 is more preferably 88° or less, and even more preferably 87° or less. In consideration of the maximum reflectance, maximum reflectance voltage, and response characteristics, θ1 is particularly preferably 78° or more and 88° or less, even more preferably 83° or more and 87° or less, and most preferably 83°.

[0133] For example, θ a =80°, slit angle θ SP = 90° and twist angle θ1 = 83°, the liquid crystal molecules 21A, 21B, and the extension directions of the strip portions SP of the slit electrode conceptually have the positional relationship shown in FIG. Z is the slit angle.

[0134] When the twist angle θ1 is in a positive range, the twist direction when no voltage is applied is positive (i.e., counterclockwise). Therefore, when the liquid crystal layer 20 of each pixel P is viewed in a plan view, "at least the liquid crystal molecule 21C in the central portion in the thickness direction of the liquid crystal layer 20 rotates in the twist direction when no voltage is applied" means that at least the liquid crystal molecule 21C rotates in the positive direction when a voltage is applied (rotates from the liquid crystal molecule 21C' to the position of the liquid crystal molecule 21C in FIG. 24, which will be described later).

[0135] As described above, in this embodiment, a reverse twist alignment occurs in the liquid crystal layer 20. The mechanism by which the reverse twist alignment occurs will be described below with reference to, for example, Fig. 7 and Figs. 12 to 14. Here, an example in which the liquid crystal panel 1X is in a normally black mode will be described. Figs. 12 to 14 are liquid crystal director distribution diagrams (cross-sectional views).

[0136] For reference, a model of the liquid crystal director distribution diagram is shown in Figure 15. For example, using simulation software (LCD Master 2D) manufactured by Shintech, the liquid crystal director is calculated at the voltage (VRmax) at which the reflectance becomes maximum. In the calculation model shown in Figure 15, the pixel width is set to 4.6 μm. The first electrode 121 is the common electrode CE, and the second electrode 122 is the pixel electrode PE. The common electrode CE is a solid electrode, and the pixel electrode PE (122) is a slit electrode with a width L per stripe of 1.6 μm and a width S per slit of 3.0 μm. The liquid crystal layer 20 is arranged in 0.05 μm increments in the X direction (horizontal direction) and 0.025 μm increments in the Z direction (thickness direction). In this calculation model, the liquid crystal layer 20 is arranged in a matrix form consisting of 21 points in the X direction and 31 points in the Z direction, for a total of 651 points, and the azimuthal angle and polar angle of the liquid crystal molecules in each matrix are calculated according to the applied voltage.

[0137] For example, θ a = 80°, θ SP When the twist angle θ1 is 90° and the twist angle θ1 is 83°, conceptually, the extension direction of the strip portion SP and the alignment direction of the liquid crystal molecules 21 when no voltage is applied (i.e., when a voltage of 0 V is applied) have the positional relationship shown in Fig. 7 in plan view. In this case, the liquid crystal molecules 21 are twisted in the direction of the arrow shown in Fig. 12 (to the right in the drawing) in cross section (see Fig. 12). Fig. 12 is a liquid crystal director distribution diagram (cross section) when no voltage is applied.

[0138] In a configuration in which reverse twist alignment occurs, when a voltage (e.g., 1.8 V) near the liquid crystal threshold is applied, the equipotential lines reach the opposing substrate (i.e., the second substrate 30). This causes all of the liquid crystal molecules 21 in the liquid crystal layer 20, including the liquid crystal molecule 21B at the interface on the second substrate 30 side, to simultaneously rotate due to elastic action. For example, when viewed from the observation side, the liquid crystal molecule 21C located at the center of the thickness direction of the liquid crystal layer 20 rotates counterclockwise, which is the twist direction. Furthermore, when a white voltage (e.g., 4.0 V) is applied, the liquid crystal molecule 21C further rotates counterclockwise. In a cross-sectional view, almost all of the liquid crystal molecules 21 in the liquid crystal layer 20 are twisted in the untwisting direction (leftward in FIG. 13) (see FIG. 13). FIG. 13 is a cross-sectional view of the liquid crystal director distribution in reverse twist alignment when a white voltage is applied.

[0139] On the other hand, in a configuration in which a forward twist orientation (also referred to as a reverse twist orientation) is generated, when a voltage (e.g., 1.8 V) near the liquid crystal threshold is applied, the equipotential lines do not reach the opposing substrate (i.e., the second substrate 30). Therefore, liquid crystal molecules 21A at the interface on the first substrate 10 side primarily rotate, and liquid crystal molecules 21C at the center of the thickness direction of the liquid crystal layer 20 rotate clockwise, which is the opposite direction to the twist direction, when viewed from the observation side. Furthermore, when a white voltage (e.g., 4.0 V) is applied, liquid crystal molecules 21C further rotate clockwise (see FIG. 14). In cross-sectional view, liquid crystal molecules 21 further rotate in the initial twist direction (to the right in FIG. 14) in accordance with the electric field direction that begins to move near the threshold voltage (see FIG. 14). Due to the influence of this twist direction of liquid crystal molecules 21, a mixed state of optical rotation and birefringence occurs, and white reflectance does not improve. FIG. 14 is a diagram (cross-sectional view) showing the liquid crystal director distribution in the positive twist alignment when a white voltage is applied.

[0140] The behavior of the liquid crystal molecules 21 in this embodiment will be further described below with reference to the drawings. Here, too, an embodiment in which the liquid crystal panel 1X is in a normally black mode will be described.

[0141] FIG. 16A is a schematic cross-sectional view (A-A' cross-sectional view) taken along line A-A' in FIG. 6, conceptually illustrating the behavior of liquid crystal molecules 21 when no voltage is applied (i.e., black display state). FIG. 16B is a schematic plan view enlarged from a portion of FIG. 6, conceptually illustrating the twist direction of liquid crystal molecules 21 when no voltage is applied (i.e., black display state). Meanwhile, FIG. 17A is a schematic cross-sectional view (A-A' cross-sectional view) taken along line A-A' in FIG. 6, conceptually illustrating the behavior of liquid crystal molecules 21 when voltage is applied (i.e., white display state). FIG. 17B is a schematic plan view enlarged from a portion of FIG. 6, conceptually illustrating the twist direction of liquid crystal molecules 21 when voltage is applied (i.e., white display state).

[0142] As shown in Fig. 16A, when no voltage is applied, the liquid crystal molecules 21 are horizontally aligned by the first horizontal alignment film 140 and the second horizontal alignment film 340. The liquid crystal molecules 21B defined by the second horizontal alignment film 340 are twisted by a twist angle θ1 from the liquid crystal molecules 21A defined by the first horizontal alignment film 140 (see Fig. 16B). On the other hand, when a voltage is applied, the liquid crystal molecules 21 rotate in the pixel plane so that the twist angle orientation changes due to the influence of the transverse electric field EF generated between the first electrode 121 (common electrode CE in this embodiment) and the second electrode 122 (pixel electrode PE) (see Figs. 17A and 17B).

[0143] (Embodiment 3) 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 embodiment 1 or 2 will be omitted. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 1 or 2 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.

[0144] FIG. 18 is a cross-sectional view of a liquid crystal display device 1 according to an example of this embodiment. FIG. 19 is a more detailed cross-sectional view of the liquid crystal display device 1 according to this example of this embodiment. As shown in FIG. 18 , 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. FIGS. 18 and 19 show an example of this embodiment in which the second retardation layer further includes a positive C plate 44.

[0145] In the liquid crystal display device 1 of this embodiment, each pixel P has a reflective region Rf (i.e., a region that displays in reflective mode) that reflects light to display, and a transmissive region Tr (a region that displays in transmissive mode) that transmits light to display (see FIG. 20). This allows for good visibility in any environment. Therefore, the liquid crystal display device 1 of this embodiment is a semi-transmissive liquid crystal display device. FIG. 20 is a plan view schematic diagram conceptually illustrating that each pixel P in the liquid crystal display device 1 of this embodiment has a reflective region Rf and a transmissive region Tr.

[0146] A reflective layer 130 is disposed in the reflective region Rf. For example, light L1 (e.g., external light) enters the liquid crystal display device 1 from the observation side, is reflected by the reflective layer 130, and then exits from the observation side (see FIG. 19). On the other hand, no reflective layer 130 is disposed in the transmissive region Tr (see FIG. 20). 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 no reflective layer 130 is disposed, and exits from the observation side (see FIG. 19).

[0147] 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.

[0148] 21 and 22A 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. 22B, 22C, 22D, 22E, and 22F, respectively. The case in which the angle X is 0° (see FIGS. 21 and 22A) 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. 22D) 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. 21 and 22A to 22F are planar schematic diagrams illustrating specific examples of pixels in this embodiment. 21 is a plan view showing an example of the pixel structure, and FIGS. 22A to 22F are plan views showing an example of the pixel arrangement. 22A to 22F also show the twisted orientation of liquid crystal molecules 21.

[0149] <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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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 invention, by controlling the optical axis setting of each optical film within a predetermined range described below, it is possible to use general-purpose retardation plates instead of special retardation plates as the λ / 4 plates and λ / 2 plates. This allows for improved contrast ratio and viewing angle despite the transflective LCD device being an in-plane switching mode, and also makes the device useful as an in-cell touch panel, thereby achieving cost reduction. This is particularly useful from the user's perspective, as it reduces total costs. Cost reduction can be achieved when the LCD device of the present invention is used not only as an in-cell or other built-in touch panel, but also as an external touch panel.

[0155] 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.

[0156] 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. 19 ).

[0157] The positive C plate 44 (and 43, 45, etc., which will be described later) may be made of a single film, or may be a laminate of two or more retardation films.

[0158] 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."

[0159] The positive C plate 44 (and 43, 45, etc., described below) is preferably, for example, a film containing a material with negative intrinsic birefringence as a component that 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).

[0160] Specific examples of the positive C plate 44 (and 43, 45, 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.

[0161] 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.

[0162] 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.

[0163] The retardation layer including a positive C plate (corresponding to the second retardation layer 42 in this embodiment) may have a positive C plate (referred to as a second positive C plate) separate from the positive C plate. In this case, it is preferable that the second positive C plate is located between the λ / 2 plate and the polarizing plate. Note that in the later-described embodiment 3, an embodiment in which the first retardation layer 41 and the second retardation layer 42 each include a first positive C plate and the first retardation layer 41 further includes a second positive C plate will be described in detail.

[0164] 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 two positive C plates. In this embodiment, the liquid crystal display device 1 that satisfies the above condition (i) will be described in detail (see, for example, FIGS. 18 and 19). In the fourth embodiment described below, the liquid crystal display device 1 that satisfies the above condition (ii) will be described in detail.

[0165] <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.

[0166] 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.

[0167] 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.

[0168] <Light source> The liquid crystal display device 1 preferably further includes a light source. In this embodiment, a light source 61 (also referred to as a backlight) is further provided on the rear side of the liquid crystal layer 20 (see FIG. 15). The light source 61 is not particularly limited as long as it can emit 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.

[0169] <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.

[0170] 23 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. 18) 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. 23, the liquid crystal molecules 21 are illustrated as liquid crystal molecules 21A near a first horizontal alignment film 140 and liquid crystal molecules 21B near a second horizontal alignment film 340.

[0171] 24 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.

[0172] 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.

[0173] The angle of the polarization axis 51AA of the first polarizing plate 51 (θ2 in FIG. 23) 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°.

[0174] The angle (θ3 in FIG. 23) 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°.

[0175] The angle (θ4 in FIG. 23) 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°.

[0176] 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.

[0177] The angle (θ4 in FIG. 23) 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°.

[0178] The angle (θ3 in FIG. 23) 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°.

[0179] The angle of the polarization axis 52AA of the second polarizing plate 52 (θ2 in FIG. 23) 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°.

[0180] 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.

[0181] Fig. 25 is a conceptual diagram showing the most preferable optical axis setting in this embodiment. In Fig. 25, 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.

[0182] 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.

[0183] (Modification 1 of Embodiment 3) In the third embodiment, a configuration has been described 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, 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. 26).

[0184] FIG. 26 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.

[0185] (Embodiment 4) 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 to 3 will be omitted. In embodiment 3, the description was given focusing particularly on the liquid crystal display device 1 in which only the second retardation layer 42 includes one positive C plate, but in this embodiment, the description will be given focusing particularly on the liquid crystal display device 1 in which the first retardation layer 41 includes two positive C plates and the second retardation layer 42 includes one positive C plate (i.e., the liquid crystal display device 1 satisfying 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, 2, or 3, except that the first retardation layer 41 includes two positive C plates.

[0186] 27 is a cross-sectional view schematically illustrating a liquid crystal display device 1 according to an embodiment of the present invention. As illustrated in FIG. 27, the liquid crystal display device 1 includes, in order from the rear surface side to the viewing surface side, a first polarizing plate 51, a first retardation layer 41, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a second retardation layer 42, and a second polarizing plate 52. The first retardation layer 41 includes a λ / 4 plate 411 and a λ / 2 plate 412, as well as a first positive C plate 43 and a second positive C plate 45. The second retardation layer 42 includes a λ / 4 plate 421 and a λ / 2 plate 422, as well as a first positive C plate 44.

[0187] From the viewpoint of further improving the viewing angle characteristics and contrast, the first positive C plates 43 and 44 are preferably positioned between the λ / 4 plate and the λ / 2 plate as described above, and the second positive C plate 45 is preferably positioned between the λ / 2 plate and the polarizing plate. In this embodiment, the first retardation layer 41 preferably includes, in order from the back side, the second positive C plate 45, the λ / 2 plate 412, the first positive C plate 43, and the λ / 4 plate 411, and the second retardation layer 42 preferably includes, in order from the back side, the λ / 4 plate 421, the first positive C plate 44, and the λ / 2 plate 422 (see FIG. 27 ).

[0188] The second positive C plate 45 may be the same as or different from the first positive C plates 43 and 44 (having the same physical properties and thickness, for example) as long as it is a retardation plate that satisfies "nz>nx≈ny." However, from the viewpoint of further enhancing the viewing angle improvement effect, the thickness direction retardation Rth (absolute value) of the second positive C plate 45 is preferably 50 to 130 nm. The Rth is more preferably 70 to 120 nm, and even more preferably 80 to 115 nm.

[0189] The thickness of the second positive C plate 45 is preferably, for example, 0.1 to 100 μm. Within this range, the mechanical strength and display uniformity are improved. The thickness is more preferably 0.1 to 80 μm, and even more preferably 0.1 to 50 μm. When the positive C plate 45 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.

[0190] (Modification 1 of Embodiment 4) In the fourth 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.

[0191] (Embodiment 5) In this embodiment, the features unique to this embodiment will be mainly described, and descriptions of the contents overlapping with those of the above-mentioned embodiments 1 to 4 will be omitted. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 1, 2, 3, or 4 in that a light source is provided on the observation surface side of the liquid crystal layer 20.

[0192] FIG. 28 is a cross-sectional view schematically illustrating a liquid crystal display device 1 according to an example of this embodiment. The liquid crystal display device 1 of this embodiment further includes a light source 62 (also referred to as a front light) located closer to the viewing surface than the liquid crystal layer 20. As shown in FIG. 28, the liquid crystal display device 1 preferably includes, in order from the back surface side to the viewing 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. Preferably, the first retardation layer 41 includes a first λ / 2 plate 412 and a first λ / 4 plate 411, and the second retardation layer 42 includes a first λ / 2 plate 422 and a first λ / 4 plate 421. Preferably, at least one of the first retardation layer 41 and the second retardation layer further includes a positive C plate 44. FIG. 28 shows an example of this embodiment in which the second retardation layer further includes a positive C plate 44.

[0193] The light source 62 (front light) is not particularly limited as long as it can emit light. The light source 62 preferably includes a light source such as a light emitting diode (LED) and a light guide plate. By further including the light source 62, the reflective liquid crystal display device 1 can provide bright reflective display even in an environment where sufficient ambient light is not available.

[0194] Although the embodiments of the present invention have been described above, the individual matters described can all be applied to the present invention as a whole.

[0195] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0196] (Test Examples 1 to 4) A reflective liquid crystal display device 1 using a positive liquid crystal material was assumed, and a study was carried out using simulation software (LCD Master2D) manufactured by Shintech Co., Ltd. Figure 29 is a cross-sectional view of the liquid crystal display device 1 assumed in this example. In Figure 29, the film thicknesses of some layers are written in parentheses after the reference numerals representing the layers.

[0197] The liquid crystal display device 1 assumed in this example is provided with, in order from the liquid crystal panel 1X side, a λ / 4 plate 411, a λ / 2 plate 412, and a polarizing plate 51 on the back side of a reflective liquid crystal panel 1X made of a positive liquid crystal material, and with, in order from the liquid crystal panel 1X side, a λ / 4 plate 421, a λ / 2 plate 422, and a polarizing plate 52 on the observation side of the liquid crystal panel 1X (see FIG. 29). Note that absorptive polarizing plates are used as the polarizing plates 51 and 52, and uniaxial retardation plates are used as the λ / 4 plates 411 and 421 and the λ / 2 plates 412 and 422, and the wavelength dispersion of the retardation plates is set to be flat.

[0198] The liquid crystal panel 1X includes a pixel electrode PE and a common electrode CE on the TFT substrate (first substrate) 10 side for applying a voltage to the liquid crystal layer 20, and a reflective layer 130 (0.1 μm thick) in the reflective region Rf (see FIG. 29). The pixel electrode PE, which is the upper-layer electrode (second electrode 122), is a slit electrode having multiple strip portions SP and a slit S1 located between two adjacent strip portions (see FIG. 29). The multiple strip portions SP are linear and extend substantially parallel to each other in the same direction, without any bends. The angle of the strip portions SP (pixel electrode angle) is +90°, with 3 o'clock being 0°. The common electrode CE, which is the lower-layer electrode (first electrode 121), is a solid electrode (0.1 μm thick). The liquid crystal layer 20 is assumed to have a monodomain structure and provide a normally black display.

[0199] Specific optical settings and other details are shown in Table 1. In Table 1, the angle of each axis 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 (-) (see Figure 5). PI refers to a polyimide film as the horizontal alignment film 140, 340. Furthermore, the physical properties of liquid crystal materials No. 1 to 34 are shown in Tables 2-1 to 2-4.

[0200] [Table 1]

[0201] [Table 2-1]

[0202] [Table 2-2]

[0203] [Table 2-3]

[0204] [Table 2-4]

[0205] (Verification 1) The VR curve and VT curve were examined for each of the liquid crystal display devices 1 of Test Examples 1 to 3. The results are shown in Table 3, Fig. 31, and Fig. 32. Fig. 31 is a diagram showing the results of Test Example 3 (VR curve and VT curve), and Fig. 32 is a diagram showing the results of Test Examples 1 to 3 (VR curve and VT curve). Fig. 30 shows the relationship between the slit angle θ in each of Test Examples 1 to 3. Z 30 is a diagram conceptually showing the above, etc. Each diagram in FIG. 30 is a schematic plan view in which a part of FIG. 6 is enlarged.

[0206] The reflection efficiency (also referred to as reflection mode efficiency) and transmission efficiency (also referred to as transmission mode efficiency) of the luminance distribution are calculated by the following formulas, respectively. Reflection mode efficiency (%) = (Luminance with front polarizer) / (Luminance without front polarizer) × 100 Transmittance mode efficiency (%) = (Luminance with front polarizer) / (Luminance without front polarizer) × 100 The front polarizer refers to the polarizer located on the observation side of the liquid crystal panel 1X (i.e., the second polarizer 52). In the graph of reflective mode efficiency (VR curve), the maximum reflective mode efficiency is referred to as "Rmax," and the voltage at which the maximum reflective mode efficiency is obtained is referred to as "VRmax." In the graph of transmissive mode efficiency (VT curve), the transmissive mode efficiency at VRmax is referred to as "T" (see FIG. 31).

[0207] [Table 3]

[0208] In Table 3, "orientation disorder" was evaluated as follows. Alignment disturbance can be evaluated by applying a voltage (for example, applying 0V to VRmax in one go) to an FFS test cell (i.e., the liquid crystal display device 1 of each test example) created under the desired conditions, and visually checking the liquid crystal alignment state under transmission light with an optical microscope. If there is no alignment disturbance, a uniform alignment change will be observed through visual observation. If alignment disturbance occurs, a disclination line caused by reverse twist will appear between the pixel electrodes (for example, corresponding to the cut-out part of the pixel electrode PE in Figure 6). The disclination line that appears will spread throughout the entire pixel over time, making it easy to confirm visually.

[0209] From the results of Verification 1, it can be seen that the reflection efficiency and transmission efficiency are simultaneously increased in Test Example 3 compared to Test Example 2. This is because in Test Example 3, the slit angle θ Z This is thought to be because the VR curve and VT curve can both be kept steep since the angle is within the range of -6° to -2° and the alignment disorder is suppressed.

[0210] (Verification 2) The liquid crystal display devices 1 of Test Examples 1 to 3 were subjected to the following verification. (1) We investigated the liquid crystal director distribution when the voltage was increased stepwise from 0 V to 8 V in 1 V increments at 1-second intervals. The results are shown in Figure 35A. Figure 33 is an image of the applied voltage in this study. (2) We investigated the liquid crystal director distribution when the voltage was suddenly increased from 0 V to VRmax. The results are shown in Figure 35B. Figure 34 is an image of the applied voltage in this verification. (3) The response characteristics were investigated. The results are shown in Figure 35C. tr is the rise time (msec), and td is the fall time (msec). The tr ratio and td ratio are values ​​(unit: %) when the response speeds tr and td in Test Example 1 are set to 100, respectively.

[0211] The results of Verification 2 show that in Test Example 1, a reverse twist orientation occurs when the voltage is suddenly increased, and the response speed, especially the rise speed tr, is slow. In Test Example 2, the response speed, especially the rise speed tr, is significantly improved, and in Test Example 3, both the rise speed tr and the fall speed td are significantly improved.

[0212] (Verification 3) The mechanism by which reverse twist (positive twist) alignment occurs was analyzed in the liquid crystal display device 1 of Test Example 1. Specifically, the time change in the azimuth angle of the liquid crystal director was analyzed when the voltage was changed from 0 V to 4.8 V (Vmax) at point A (corresponding to point A in Figures 36A to 36D) where the electric field density is high in the cross section. The results are shown in Figures 36A to 36C and 37.

[0213] FIG. 36A is a liquid crystal director distribution diagram immediately (0 msec) after voltage (4.8 V) application, FIG. 36B is a liquid crystal director distribution diagram 5 msec after voltage application, and FIG. 36C is a liquid crystal director distribution diagram 15 msec after voltage application. FIG. 36D is a diagram showing a calculation model for the liquid crystal director distribution diagram. Note that the vertical axis (z) in FIGS. 36A to 36D represents the distance in the thickness direction of the liquid crystal layer 20, and the distance increases as one moves upward in the diagram, i.e., closer to the second substrate 30. Therefore, the maximum value of the vertical axis z (i.e., the length d in FIG. 36A) corresponds to the cell thickness d of the liquid crystal layer 20.

[0214] In Figure 37, the horizontal axis represents "z / d" and the vertical axis represents "azimuth angle." As described above, z represents the distance in the thickness direction of the liquid crystal layer 20, and d represents the cell thickness of the liquid crystal layer 20. θ a is the angle of the alignment direction a of the liquid crystal molecules 21A when no voltage is applied, with the direction parallel to the gate line GL (the 3 o'clock direction) being taken as the reference angle of 0°, and is 83° in this example. b is the angle of the alignment direction b of the liquid crystal molecules 21B when no voltage is applied, with the direction parallel to the gate line GL (the 3 o'clock direction) being taken as the reference angle of 0°, and is 166° in this example. b and θ a The difference between these corresponds to the twist angle θ1, which is 83° in this example. a The shaded area below is the region where the reverse twist orientation occurs.

[0215] 38 is a diagram conceptually showing the twist angle orientation T (corresponding to the twist direction) and the reverse twist orientation R in Test Example 1. This diagram is a schematic plan view enlarging a part of FIG.

[0216] (Verification 4) The azimuthal polar angle of the liquid crystal director was analyzed over time in each of the liquid crystal display devices 1 of Test Examples 3 and 4. The results are shown in Figs. 39A to 39E. In these figures, the horizontal axis represents "z / d" and the vertical axis represents "azimuthal angle," as in Fig. 37. Graph de5 is a graph of Test Example 3, and graph de10 is a graph of Test Example 4.

[0217] 40A and 40B are diagrams conceptually showing the twist angle orientation T and reverse twist orientation R in Test Examples 3 and 4. Fig. 40A shows the state when no voltage is applied (i.e., 0 msec after voltage application), and Fig. 40B shows the state 5 to 20 seconds after application of a white voltage (VRmax). These figures are schematic plan views enlarging a portion of Fig. 6.

[0218] The results of Verification 4 show that Test Example 3, in which the Δε of the liquid crystal molecules is 5 or less, exhibited smaller deviations in the azimuth angle in the reverse twist direction R immediately (5 msec) after application of a voltage of VRmax than Test Example 4, in which the Δε of the liquid crystal molecules is 10 (see Figure 39B). As a result, in Test Example 3, the reverse twist alignment was eliminated and an inverted twist alignment was obtained 20 msec after voltage application (see Figure 39E). On the other hand, in Test Example 4, a reverse twist alignment was obtained 20 msec after voltage application (see Figure 39E). Therefore, it was found that even with the same cell thickness, by setting Δε to 5 or less, the reverse twist alignment was eliminated and an inverted twist alignment was obtained.

[0219] (Verification 5) In each of the liquid crystal display devices 1 of Test Examples 1 to 3, the time variation of the azimuthal angle and polar angle of the liquid crystal director was analyzed when the voltage was changed from 0 V to Vmax at point A where the electric field density was high in the cross section. The results are shown in Figures 41A to 41C. In these figures, the horizontal axis represents "z / d" and the vertical axis represents "azimuthal angle," as in Figure 37.

[0220] From the results of Verification 5, a reverse twist orientation was observed in Test Example 1, but not in Test Example 2 (see Figures 41A and 41B). On the other hand, in Test Example 3, a reverse twist orientation occurred 5 msec and 15 msec after voltage application, but the reverse twist orientation disappeared 20 msec later (see Figure 41C). This is thought to be due to the fact that Test Example 3, compared with Test Examples 1 and 2, had a Δε of the liquid crystal molecules of 5 or less and a cell thickness of 3 μm or less. In other words, by reducing Δε and reducing the degree of change in director when the potential changes, and by thinning the cell thickness, the twist direction determined by the elastic modulus of the liquid crystal became dominant, allowing the liquid crystal molecules to rotate into a reverse twist orientation.

[0221] (Verification 6) A liquid crystal display device 1 was assumed to be under the same conditions as in Test Example 1, except that the liquid crystal material (dielectric anisotropy Δε), cell thickness, and angle of the alignment axis a of the liquid crystal molecules 21A were changed as shown in Tables 4 to 18. The twist angle θ1 was set to 83°, the same as in Test Example 1.

[0222] For each liquid crystal display device 1, VRmax, Rmax, transmittance T at VRmax, alignment disorder, tr ratio (referred to as Tr ratio in the table below), and td ratio (referred to as Td ratio in the table below) were confirmed by simulation, as in the above-mentioned (Verification 1) and (Verification 2). The results are shown in Tables 4 to 21. The names of the liquid crystal materials used in each test example (see Tables 2-1 to 2-4) are also listed in these tables. The liquid crystal display device 1 of Test Example 11-5 corresponds to the liquid crystal display device 1 of Test Example 1.

[0223] [Table 4]

[0224] [Table 5]

[0225] [Table 6]

[0226]

Table 7

[0227]

Table 8

[0228]

Table 9

[0229]

Table 10

[0230]

Table 11

[0231]

Table 12

[0232]

Table 13

[0233]

Table 14

[0234]

Table 15

[0235] Table 16

[0236] [Table 17]

[0237] [Table 18]

[0238] [Table 19]

[0239] [Table 20]

[0240] [Table 21]

[0241] (Verification 7) A liquid crystal display device 1 was assumed under the same conditions as in Test Example 1, except that the liquid crystal material (dielectric anisotropy Δε), cell thickness, and angle of alignment axis a of liquid crystal molecules 21A were changed as shown in Tables 23 to 36. The twist angle θ1 was set to 83°, the same as in Test Example 1. The physical properties of liquid crystal materials Nos. 101 to 120 are shown in Tables 22-1 to 22-4.

[0242] For each liquid crystal display device 1, VRmax, Rmax, transmittance T at VRmax, alignment disorder, tr ratio (referred to as Tr ratio in the table below), and td ratio (referred to as Td ratio in the table below) were confirmed by simulation, as in the above-mentioned (Verification 1) and (Verification 2). The results are shown in Tables 23 to 36. The names of the liquid crystal materials used in each test example (see Tables 22-1 to 22-4) are also listed in these tables.

[0243] [Table 22-1]

[0244]

Table 22-2

[0245]

Table 22-3

[0246]

Table 22-4

[0247] Table 23

[0248] Table 24

[0249] Table 25

[0250] Table 26

[0251] Table 27

[0252] Table 28

[0253] Table 29

[0254] Table 30

[0255] [Table 31]

[0256] [Table 32]

[0257] [Table 33]

[0258] [Table 34]

[0259] [Table 35]

[0260] [Table 36]

[0261] From the results of Verification 7, when the cell thickness d is 3.1 μm or more and 3.4 μm or less, the slit angle θ Z In addition, when the cell thickness d is 3.1 μm or more and the slit angle θ is 0.05 μm or less, the reverse twist orientation does not occur. Z The reflectance, transmittance, and response characteristics obtained when the angle was between -5° and -1° were almost as good as when the cell thickness d was 3.0 μm or less (see Verification 6, etc.).

[0262] The above-described aspects of the present invention may be combined as appropriate within the scope of the present invention. [Explanation of symbols]

[0263] 1:LCD display device 1x: LCD panel 10, 30: PCB 20: Liquid crystal layer 21, 21A, 21B, 21C: Liquid crystal molecules 40: Retardation layer 41:λ / 4 plate 42:λ / 2 plate 411SA, 412SA, 421SA, 422SA: In-plane slow axis 43, 44, 45: Positive C-plate 51, 52: Polarizing plates 51AA, 52AA: Polarization axis 61, 62: Light source 100, 300: Support substrate 110: TFT 121, 122: Electrode 130: Reflective layer 140, 340: horizontal alignment film 151, 152: Interlayer insulating layer 153: Dielectric layer 160: Contact electrode 310: Color filter layer T (arrow): Twist angle orientation R (arrow): Reverse twist direction BP: Backplane circuit CE: Common electrode PE: pixel electrode CH1, CH2: Contact holes De: orientation defect 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 TC: Touch wiring contact area TD: Touch drive unit TL, TL1, TL2: Touch wiring TX: Touch sensor electrode

Claims

1. a first substrate; a second substrate facing the first substrate; a liquid crystal layer provided between the first substrate and the second substrate; A liquid crystal display device having a plurality of pixels, the first substrate has a reflective layer that reflects light, a first electrode and a second electrode that can generate a transverse electric field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer; At least one of the first electrode and the second electrode has a plurality of strip-shaped portions and a slit located between two adjacent strip-shaped portions 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, and do not include any bent portions; the second substrate has a second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer contains liquid crystal molecules having a positive dielectric anisotropy and having a twisted orientation when no voltage is applied; When no voltage is applied, the alignment direction of the liquid crystal molecules on the first substrate side is −6° or more and −1° or less, when the direction in which the plurality of strip portions extend is taken as 0°. A liquid crystal display device characterized by:

2. The plurality of band-shaped portions do not include any notches.

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

3. when the liquid crystal layer of each pixel is viewed in a plane when no voltage is applied, the extension direction of the plurality of strip-shaped portions is located between the alignment direction of liquid crystal molecules on the first substrate side and the alignment direction of liquid crystal molecules on the second substrate side, at least in a central portion in a plane direction of the liquid crystal layer, When the liquid crystal layer of each pixel is viewed in a plan view, liquid crystal molecules at least in the center of the liquid crystal layer in the thickness direction rotate in the same twist direction as when no voltage is applied, when a voltage is applied.

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

4. The dielectric anisotropy Δε of the liquid crystal molecules is 3 or more and 5 or less.

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

5. The thickness of the liquid crystal layer is 2.5 μm or more and 3 μm or less.

5. The liquid crystal display device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

6. When no voltage is applied, the alignment direction of the liquid crystal molecules on the first substrate side is −6° or more and −3° or less when the direction in which the plurality of strip-shaped portions extend is taken as 0°, and the thickness of the liquid crystal layer is 2.8 μm or more and 3 μm or less.

5. The liquid crystal display device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

7. When no voltage is applied, the alignment direction of the liquid crystal molecules on the first substrate side is −5° or more and −1° or less, with the direction in which the strip portions extend being taken as the reference angle of 0°, and the thickness of the liquid crystal layer is 3.1 μm or more and 3.4 μm or less.

5. The liquid crystal display device according to claim 1, wherein the first and second electrodes are electrically connected to each other.

8. The extending direction of the plurality of strip-shaped portions is the same at least in adjacent pixels or in the display area.

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

9. 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 liquid crystal display device according to claim 1.

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

10. The liquid crystal display device according to claim 9.

11. 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.

11. The liquid crystal display device according to claim 9 or 10.

12. 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.

11. The liquid crystal display device according to claim 9 or 10.

13. 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 liquid crystal display device according to claim 1.

14. 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 liquid crystal display device according to claim 1.

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

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

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

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

18. Further, a light source is provided.

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

19. 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.

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

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