Liquid crystal display device

Abstract

Provided is a liquid crystal display device which can sufficiently suppress the occurrence of alignment defects and is also useful as an In-cell touch panel capable of display in a reflection mode. The liquid crystal display device includes a first substrate, a second substrate, and a liquid crystal layer. The first substrate includes: a reflective layer that reflects light; the first electrode and the second electrode can generate a transverse electric field on the liquid crystal layer; and a first horizontal alignment film that is in contact with the liquid crystal layer, and at least one of the first electrode and the second electrode has: a plurality of belt-shaped sections; and a slit located between two adjacent band-shaped portions among the plurality of band-shaped portions, in each pixel, the plurality of band-shaped portions are composed of linear shapes substantially parallel to each other and extending in the same direction, and do not include a curved portion, and 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 positive dielectric anisotropy, and is twisted and oriented when a voltage is not applied.

Description

Technical Field

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

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

[0003] Liquid crystal display devices can also be roughly divided according to the driving method of the liquid crystal. For example, there are known liquid crystal display devices of a longitudinal electric field method that uses an electric field in a direction substantially perpendicular to the substrate surface to drive the liquid crystal layer for display, and liquid crystal display devices of a transverse electric field method that uses an electric field in a direction substantially parallel to the substrate surface to drive the liquid crystal layer for display. As the longitudinal electric field method, examples such as TN (Twisted Nematic) mode and MVA (Multi-domain Vertical Alignment) mode can be exemplified, and as the transverse electric field method, examples such as IPS (In-plane Switching) mode and FFS (Fringe Field Switching) mode can be exemplified. For example, a liquid crystal display suitable as a liquid crystal display device of a transverse electric field method is disclosed in Patent Document 1. This liquid crystal display can suppress adverse conditions caused by process deviations and improve display performance, and is particularly useful as a transmissive liquid crystal display device. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent No. 5756860 Summary of the invention Technical problem to be solved by the invention

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

[0006] Among the built-in touch panels, there are "On-cell (surface covered) type" and "In-cell (embedded) touch panel". A cell refers to a display panel (also called a liquid crystal panel) having an active matrix substrate represented by a thin film transistor (TFT) substrate, an opposing substrate arranged opposite to the substrate, and a liquid crystal layer sandwiched between these substrates. Usually, in the In-cell type, a layer that performs the touch sensor function is arranged in the display panel, and in the On-cell type, the layer that performs the touch sensor function is arranged between the display panel and a polarizing plate provided on the viewing side of the display panel. Among them, the In-cell type can realize the thinnest and lightest touch panel in principle. In addition, since liquid crystal display devices that can display in reflective mode are suitable for outdoor use, an In-cell touch panel that can display in reflective mode is required, but the current situation is that it has not yet been realized.

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

[0008] Therefore, further research has been conducted on devices in FFS mode, for example, which display in a normally black mode. For example, the following device has been studied: a positive liquid crystal material is used in the liquid crystal layer, and at least one of a pair of electrodes is made into a slit electrode having a slit-shaped opening. However, it was found that just after a voltage of 5V or more (above 5V) is applied from a voltage-unapplied state (0V), an orientation defect (also called orientation disorder) in which the liquid crystal orientation becomes unstable and the liquid crystal orientation is discontinuous is sometimes generated (refer to Test Example 4 described later, etc.). If an orientation defect occurs, problems such as deterioration of the liquid crystal response, reduction of the reflection mode efficiency, reduction of the transmission mode efficiency, and squinting will occur. In particular, as a liquid crystal display device for animation display, a device with uneven and unstable liquid crystal orientation is not suitable for practical use.

[0009] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a liquid crystal display device which can sufficiently suppress the occurrence of alignment defects and is also useful as an In-cell type touch panel capable of displaying in a reflective mode. Solutions to the problem

[0010] (1) A liquid crystal display device according to one embodiment of the present invention has a plurality of pixels. The liquid crystal display device includes: a first substrate; a second substrate opposed to the first substrate; and a liquid crystal layer provided between the first substrate and the second substrate, the first substrate having: a reflective layer for reflecting light; a first electrode and a second electrode, the first electrode and the second electrode being capable of generating a transverse electric field in the liquid crystal layer; and a first horizontal alignment film in contact with the liquid crystal layer, at least one of the first electrode and the second electrode having: a plurality of strip-shaped portions; and a slit located between two adjacent strip-shaped portions of the plurality of strip-shaped portions, wherein in each pixel, the plurality of strip-shaped portions are linear shapes extending substantially parallel to each other and in the same direction and do not include a bent portion, the second substrate having the second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer including liquid crystal molecules having a positive dielectric anisotropy and being twistedly aligned when no voltage is applied, and when the direction in which the plurality of strip-shaped portions extend is 0° or more and 16° or less, the alignment direction of the liquid crystal molecules on the first substrate side when no voltage is applied is 0° or more and 16° or less, with the direction in which the plurality of strip-shaped portions extend being the reference direction.

[0011] (2) In a liquid crystal display device according to an embodiment of the present invention, in addition to the configuration of (1) above, the plurality of strip-shaped portions do not include a cutout portion.

[0012] (3) In a liquid crystal display device according to an embodiment of the present invention, in addition to the configuration of (1) above, the directions in which the plurality of strip-shaped portions extend are the same at least in adjacent pixels or in a display area.

[0013] (4) In addition, a liquid crystal display device according to a certain embodiment of the present invention, based on the structure of (1) above, comprises, starting from the back side, a first polarizing plate, a first phase difference layer, the first substrate, the liquid crystal layer, the second substrate, a second phase difference layer and a second polarizing plate, wherein the first phase difference layer includes a first λ / 2 plate and a first λ / 4 plate, the second phase difference layer includes a second λ / 2 plate and a second λ / 4 plate, and at least one of the first phase difference layer and the second phase difference layer further includes a positive C plate.

[0014] (5) In addition, in a liquid crystal display device of a certain embodiment of the present invention, based on the structure of (4) above, the second phase difference layer includes one positive C plate, the first phase difference layer does not include a positive C plate, or the first phase difference layer includes two positive C plates.

[0015] (6) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the structure of (4) or (5), the first λ / 2 plate and the first λ / 4 plate are arranged in sequence from the back side, the second λ / 2 plate and the second λ / 4 plate are arranged in sequence from the observation side, the in-plane phase difference Re of the first λ / 2 plate is substantially the same as that of the second λ / 2 plate, and the in-plane phase difference Re of the first λ / 4 plate is substantially the same as that of the second λ / 4 plate.

[0016] (7) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the structure of (4), (5) or (6), the positive C plate is located between the first λ / 2 plate and the first λ / 4 plate, and / or between the second λ / 2 plate and the second λ / 4 plate.

[0017] (8) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the structure of (1), (2), (3), (4), (5), (6) or (7), the twist angle of the liquid crystal layer when no voltage is applied is greater than 58.3° and less than 89.9°.

[0018] (9) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the structure of (1), (2), (3), (4), (5), (6), (7) or (8), the ratio L / S of the width L of each of the plurality of strip-like portions when viewed from above to the width S of each slit when viewed from above is 0.4 to 0.7 / 1.

[0019] (10) In addition, a liquid crystal display device according to a certain embodiment of the present invention obtains a single-domain orientation based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6), the above (7), the above (8) or the above (9).

[0020] (11) In addition, a liquid crystal display device according to a certain embodiment of the present invention displays in a normally black mode based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9) or (10).

[0021] (12) In addition, in a liquid crystal display device of a certain embodiment of the present invention, based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10) or (11), one of the first electrode and the second electrode is a pixel electrode arranged in each of the multiple pixels, the other of the first electrode and the second electrode is a common electrode, the common electrode includes a plurality of segments that can respectively function as touch sensor electrodes, and the first substrate has a plurality of touch wirings, and the plurality of touch wirings are respectively connected to the corresponding touch sensor electrodes.

[0022] (13) In addition, a liquid crystal display device according to a certain embodiment of the present invention further includes a light source based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11) or (12).

[0023] (14) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12) or (13), each pixel has a reflective area and a transmissive area, the reflective area reflects light through the reflective layer to display, and the transmissive area transmits light to display. Effects of the Invention

[0024] According to the present invention, it is possible to provide a liquid crystal display device which can sufficiently suppress the occurrence of alignment defects and is also useful as an In-cell type touch panel capable of performing display in a reflective mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic cross-sectional view of the liquid crystal display device 1 . Figure 2 It is a more detailed schematic cross-sectional view of the liquid crystal display device 1 . Figure 3 It is a schematic plan view of the entire liquid crystal display device 1 as viewed from the observation surface side. Figure 4 It is a diagram for explaining the slit angle of liquid crystal molecules. Figure 5 1 is a schematic plan view showing a configuration example of a pixel (angle X is 0°). Fig. 6A 1 is a schematic plan view showing an example of pixel arrangement (angle X is 0°). Figure 6B 1 is a schematic plan view showing an example of pixel arrangement (angle X is -10°). Figure 6C 1 is a schematic plan view showing an example of pixel arrangement (angle X is +10°). Fig.6D 1 is a schematic plan view showing an example of pixel arrangement (angle X is -90°). Fig. 6E 1 is a schematic plan view showing an example of pixel arrangement (angle X is -100°). Fig. 6F 1 is a schematic plan view showing an example of pixel arrangement (angle X is -80°). Figure 7 1 is a schematic plan view illustrating an arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1 . Figure 8 is a schematic cross-sectional view of a liquid crystal display device. Fig. 9 is a schematic cross-sectional view of a liquid crystal display device. Fig.10 It is a more detailed schematic cross-sectional view of the liquid crystal display device 1 . Fig.11 1 is a schematic plan view conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr. Fig.12 1 is a schematic plan view showing a configuration example of a pixel (angle X is 0°). Fig.13A 1 is a schematic plan view showing an example of pixel arrangement (angle X is 0°). Fig. 13B 1 is a schematic plan view showing an example of pixel arrangement (angle X is -10°). Fig. 13C 1 is a schematic plan view showing an example of pixel arrangement (angle X is +10°). Fig.13D 1 is a schematic plan view showing an example of pixel arrangement (angle X is -90°). Fig.13E 1 is a schematic plan view showing an example of pixel arrangement (angle X is -100°). Fig.13F 1 is a schematic plan view showing an example of pixel arrangement (angle X is -80°). Fig.14 It is a plan view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 included in the liquid crystal layer 20 and the optical axis of each optical film when no voltage is applied. Fig.15 It is a diagram for explaining the optical axis angle of the optical film. Fig.16 is a schematic cross-sectional view of a liquid crystal display device. Fig.17 is a schematic cross-sectional view of a liquid crystal display device. Fig.18 is a schematic cross-sectional view of a liquid crystal display device. Fig.19 This is a diagram conceptually showing the most preferable optical axis setting. Fig. 20 1 is a schematic cross-sectional view of a liquid crystal panel 1X included in the device assumed in Test Example 1. Fig.21 1 is a schematic diagram conceptually showing the electrode structure of the pixel electrode PE and the common electrode CE when the slit angle is 0°. Fig. 22 is a graph showing the results of Test Example 1. Fig.23 is a graph showing the results of Test Example 1. Fig.24 is a graph showing the results of Test Example 1. Fig.25A 1 is a schematic plan view showing the structure of the liquid crystal cell 1100 when viewed from the front. Fig.25B So Fig.25A The AA line in the figure is a schematic cross-sectional view of the cross section (AA line cross-sectional view). Fig.26A 1 is a schematic cross-sectional view of the test unit 1000 during reflection observation. Fig.26B 1 is a schematic cross-sectional view of the test unit 1000 during transmission observation. Fig. 27 This is a diagram showing the results of Test Example 2. Fig.28A It is a schematic diagram showing the research results of Test Example 3-1. Fig.28B It is a schematic diagram showing the research results of Test Example 3-1. Fig.28C It is a schematic diagram showing the research results of Test Example 3-1. Fig.29A It is a schematic diagram showing the research results of Test Example 3-2. Fig.29B It is a schematic diagram showing the research results of Test Example 3-2. Fig.29C It is a schematic diagram showing the results of the studies of Test Examples 3-1 and 3-2. Fig.30 It is a graph showing the results of Test Example 4. Fig.31This is a schematic diagram when a voltage is applied in Test Example 4. Fig.32A is a graph showing the results of Test Example 5. Fig.32B is a graph showing the results of Test Example 5. Fig.33 This is a schematic diagram when voltage is applied in Test Examples 5 and 6. Fig.34A : is a graph showing the results of Test Example 6. Fig.34B : is a graph showing the results of Test Example 6. Fig.35 is a graph showing the results of Test Example 7. Fig.36 This is a schematic diagram when a voltage is applied in Test Example 7. Fig.37 is a graph showing the results of Test Example 8. Fig.38 is a graph showing the results of Test Example 8. Fig.39A 1 is a schematic plan view showing the structure of the test cell 2000 (and the liquid crystal cell 2100 ) when viewed from the front. Fig.39B So Fig.39A The AA line in the figure is a schematic cross-sectional view of the cross section (AA line cross-sectional view). Fig.40 is a cross-sectional schematic diagram of the test unit 2000. Fig.41 This is a diagram conceptually showing the optical axis setting of Test Example 9. Fig.42 : is a graph showing the results of Test Example 9. DETAILED DESCRIPTION

[0026] (Definition of terms) In this specification, the “observation side” refers to the side closer to the screen (display surface) of the liquid crystal display device, and the “back side” refers to the side farther from the screen (display surface) of the liquid crystal display device.

[0027] The voltage non-applied state refers to a state where the voltage applied to the liquid crystal layer is less than the threshold voltage (including no voltage applied). The voltage applied state refers to a state where the voltage applied to the liquid crystal layer is greater than the threshold voltage. In this specification, the voltage non-applied state is also referred to as the voltage non-applied state, and the voltage applied state is also referred to as the voltage applied state.

[0028] The polar angle refers to an angle formed between a target direction (eg, a measurement direction) and a normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction when the direction of the object is projected on the screen of the liquid crystal panel, and is expressed by the angle (azimuth) formed with the reference azimuth. Unless otherwise specified, the reference azimuth (0°) is the horizontal right direction of the screen of the liquid crystal panel. Angles and azimuths are positive angles in the counterclockwise direction from the reference azimuth, and negative angles in the clockwise direction from the reference azimuth. Both the counterclockwise direction and the clockwise direction indicate the rotation direction when the screen of the liquid crystal panel is observed from the observation side (front). In addition, the angle represents the value measured when looking down at the screen of the liquid crystal panel, and unless there is an explanation of the rotation direction, etc., it means an acute angle.

[0029] In the case of a polarizing plate, the axis orientation of the optical film refers to the orientation of the polarization axis of the polarizing plate. In the case of a phase difference layer, the axis orientation of the optical film refers to the orientation of the slow axis. In the case of an absorption-type polarizing plate, the polarization axis of the polarizing plate refers to the absorption axis. In the case of a reflection-type polarizing plate, the polarization axis of the polarizing plate refers to the reflection axis. Unless otherwise specified, the axis orientation of the phase difference layer refers to the orientation of the slow axis in the plane of the phase difference layer.

[0030] The so-called phase difference layer refers to a layer in which at least one of the in-plane delay (also referred to as in-plane phase difference) Re and the thickness direction delay (also referred to as thickness direction phase difference) Rth has a value of 10nm or more. Preferably, it is a layer having a value of 20nm or more. In addition, in this specification, unless otherwise specified, the values ​​recorded as Re and Rth are absolute values.

[0031] The in-plane phase difference Re is defined by Re=(nx-ny)×d. The thickness direction phase difference Rth is defined by Rth={nz-(nx+ny) / 2}×d. nx represents the principal refractive index in the slow axis direction within the plane of each retardation layer. Ny represents the principal refractive index in the fast axis direction within 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 refers to the direction with the largest refractive index, and the fast axis direction refers to the direction with the smallest refractive index. d represents the thickness of the phase difference layer.

[0032] The A plate is a phase difference plate that satisfies “nx>ny≈nz”.

[0033] Unless otherwise specified, the measurement wavelength of optical parameters such as refractive index and phase difference was set to 550 nm.

[0034] Approximately parallel means that the angle (absolute value) formed by the two is within the range of 0°±10°, preferably within the range of 0°±5°, and more preferably within 0° (i.e. parallel in a narrow sense). In addition, approximately orthogonal (or approximately perpendicular) means that the angle (absolute value) formed by the two forms an angle within the range of 90°±10°, preferably within the range of 90°±5°, and more preferably within 90° (i.e. orthogonal or perpendicular in a narrow sense).

[0035] 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 embodiments, and the design can be appropriately changed within the scope of the configuration satisfying the present invention.

[0036] (Implementation Method 1) Figure 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Figure 2 It is a more detailed schematic cross-sectional view of the liquid crystal display device 1 according to an example of the present embodiment. Figure 3 1 is a schematic plan view of the entire liquid crystal display device 1 of an example of this embodiment when viewed from the observation surface side. Figure 1 As shown, the liquid crystal display device 1 includes a first substrate 10, a liquid crystal layer 20, and a second substrate 30 in order from the back side. In this embodiment, a TFT substrate is used as the first substrate 10. In addition, a portion or a structure consisting of a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0037] The liquid crystal display device 1 has a plurality of pixels P. Preferably, the plurality of pixels P are as follows: Figure 3 The plurality of pixels P are typically arranged in a matrix. The plurality of pixels P typically include three types of pixels, namely, red pixels, green pixels, and blue pixels, but the types of pixels may be two or less, or four or more. Each pixel P includes a thin film transistor (TFT) 110 and a first electrode 121 and a second electrode 122 capable of generating a lateral electric field in the liquid crystal layer 20. The gate electrode of the TFT 110 is electrically connected to a corresponding gate wiring (also called a scanning wiring) GL, and the source electrode of the TFT 110 is electrically connected to a corresponding source wiring (also called a signal wiring) SL. The drain electrode of the TFT 110 is electrically connected to the second electrode 122.

[0038] <First Substrate> like Figure 2As shown, the first substrate 10 has a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 that contacts the liquid crystal layer 20 in sequence from the back side to the observation side. The first substrate 10 further preferably has a supporting substrate 100 and a backplane circuit BP on the back side of the reflective layer 130. An insulating layer (also called an insulating film) is provided between each layer as needed. For example, a first interlayer insulating layer 151 is provided in a manner covering the backplane circuit BP, a second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 with the reflective layer 130 interposed therebetween, and a dielectric layer (also called a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

[0039] The support substrate 100 is preferably transparent and insulating, and examples of the support substrate 100 include a glass substrate and a plastic substrate.

[0040] The back plate circuit BP is provided on the support substrate 100. The back plate circuit BP is a circuit for driving the plurality of pixels P, and includes the TFTs 110, the gate wiring GL, the source wiring SL, etc. Furthermore, it generally includes a gate insulating film 150G.

[0041] TFT110 is provided corresponding to each of the plurality of pixels P. As TFT110, a TFT including an oxide semiconductor layer as an active layer (also referred to as an oxide semiconductor TFT) is preferably used. In recent years, the oxide semiconductor contained in the oxide semiconductor layer has attracted attention as an active layer material replacing amorphous silicon or polycrystalline silicon, and has a higher mobility than amorphous silicon. Therefore, the oxide semiconductor TFT has the ability to operate at a higher speed than amorphous silicon. In addition, the oxide semiconductor film can be formed using a simpler process than the polycrystalline silicon layer, so it can also be used in devices requiring a large area.

[0042] Oxide semiconductor TFT also has excellent off-leak characteristics, so it is also possible to use a driving method that reduces the frequency of image rewriting for display. For example, when a still image is displayed, it is possible to rewrite the image data at a frequency of once per second. This driving method is called a dormant drive or a low-frequency drive, and can significantly reduce the power consumption of the liquid crystal display device. By adopting a pause drive and performing touch detection during the period when the image is not rewritten, the sensitivity of the touch operation caused by the noise from the drive circuit can be suppressed, and the S / N ratio (signal-to-noise ratio) can be made, for example, about 10 times the existing one.

[0043] Oxide semiconductor TFTs are also advantageous in reducing the size of TFTs, and therefore, a configuration in which a memory circuit is provided for each pixel P (referred to as MIP (Memory In Pixels)) can be preferably realized.

[0044] The oxide semiconductor may be an amorphous oxide semiconductor or a crystalline oxide semiconductor having a crystal portion. Examples of the crystalline oxide semiconductor include polycrystalline oxide semiconductors, microcrystalline oxide semiconductors, and crystalline oxide semiconductors whose c-axis is oriented substantially perpendicular to the layer surface.

[0045] The oxide semiconductor layer may be a single layer or may have a stacked structure of two or more layers. The oxide semiconductor layer having a stacked structure may include an amorphous oxide semiconductor layer and a crystalline oxide semiconductor layer, may include multiple crystalline oxide semiconductor layers of different crystal structures, or may include multiple amorphous oxide semiconductor layers. In the case where the oxide semiconductor layer has a double-layer structure including an upper layer and a lower layer, the energy gap of the oxide semiconductor contained in the lower layer may be different from the energy gap of the oxide semiconductor contained in the upper layer.

[0046] The materials, structures, film formation methods of amorphous oxide semiconductors and crystalline oxide semiconductors, and the composition of oxide semiconductor layers having a stacked structure are described in, for example, Japanese Patent Application Laid-Open No. 2014-007399. The entire disclosure of Japanese Patent Application Laid-Open No. 2014-007399 is cited in this specification for reference.

[0047] As an oxide semiconductor layer, specifically, it is preferred to contain at least one metal element selected from In (indium), Ga (gallium) and Zn (zinc). Among them, an oxide semiconductor film containing a ternary oxide of In, Ga and Zn is more preferred. As a ternary oxide of In, Ga and Zn, for example, indium gallium zinc oxide is preferably exemplified. A semiconductor containing a ternary oxide of In, Ga and Zn is called an In-Ga-Zn-O semiconductor, but in the semiconductor, the ratio (composition ratio) of In, Ga and Zn is not particularly limited, for example, In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, In:Ga:Zn=1:1:2, etc. can be exemplified.

[0048] In-Ga-Zn-O semiconductors may be amorphous or crystalline. As crystalline In-Ga-Zn-O semiconductors, preferably, the c-axis is oriented substantially perpendicular to the layer.

[0049] The crystal structure of the semiconductor of the crystalline In-Ga-Zn-O system is disclosed in, for example, Japanese Patent Laid-Open No. 2014-007399, Japanese Patent Laid-Open No. 2012-134475, and Japanese Patent Laid-Open No. 2014-209727. For reference, the entire disclosure of Japanese Patent Laid-Open No. 2012-134475 and Japanese Patent Laid-Open No. 2014-209727 is cited in this specification. The TFT having an In-Ga-Zn-O system semiconductor layer has a high mobility (more than 20 times compared to a-SiTFT) and a low leakage current (less than one percent compared to a-SiTFT), and is therefore preferably used as a driving TFT (for example, a TFT included in a driving circuit, which is arranged around a display area including a plurality of pixels and on the same substrate as the display area) and a pixel TFT (a TFT arranged in a pixel).

[0050] The oxide semiconductor layer may also include an oxide semiconductor other than an In-Ga-Zn-O semiconductor. For example, a ternary oxide of In, Sn (tin) and Zn may be cited, for example, preferably In2O3-SnO2-ZnO; InSnZnO. A semiconductor including a ternary oxide of In, Sn and Zn is called an In-Sn-Zn-O semiconductor. Alternatively, the oxide semiconductor layer 11a may also include In-Al-Zn-O series semiconductors, In-Al-Sn-Zn-O series semiconductors, Zn-O series semiconductors, In-Zn-O series semiconductors, Zn-Ti-O series semiconductors, Cd-Ge-O series semiconductors, Cd-Pb-O series semiconductors, CdO (cadmium oxide) series semiconductors, Mg-Zn-O series semiconductors, In-Ga-Sn-O series semiconductors, In-Ga-O series semiconductors, Zr-In-Zn-O series semiconductors, Hf-In-Zn-O series semiconductors, Al-Ga-Zn-O series semiconductors, Ga-Zn-O series semiconductors, In-Ga-Zn-Sn-O series semiconductors, etc.

[0051] The first interlayer insulating layer 151 is provided in a manner covering the backplane circuit BP. The surface of the first interlayer insulating layer 151 on the side of the reflective layer 130 preferably has a concavo-convex shape (also referred to as a concavo-convex surface structure). Thus, the reflective layer 130 can have a concavo-convex surface structure reflecting the shape. The first interlayer insulating layer 151 having a concavo-convex surface structure can be suitably formed using a photosensitive resin as described in Japanese Patent No. 3394926, for example.

[0052] The reflective layer (also called reflective film) 130 is provided on the first interlayer insulating layer 151. The reflective layer 130 is formed of a material that reflects light. Among them, it is preferably formed of a metal material with high reflectivity. As the material of the reflective layer 130, for example, a silver alloy, an aluminum alloy, etc. can be used.

[0053] The reflective layer 130 preferably has a concave-convex shape that reflects the concave-convex surface structure that the first interlayer insulating layer 151 preferably has. That is, the reflective layer 130 also preferably has a concave-convex surface structure. The concave-convex surface structure is also called MRS (MicroReflective Structure), which is provided to diffusely reflect ambient light to achieve a display close to paper white. The concave-convex surface structure can be composed of a plurality of convex portions p randomly arranged in such a manner that the center spacing of adjacent convex portions p is greater than 5 μm and less than 50 μm. The center spacing of adjacent convex portions p is more preferably greater than 10 μm and less than 20 μm. The shape of the convex portion p is preferably approximately circular or approximately polygonal when viewed from the normal direction of the supporting substrate. The convex portion p occupies, for example, approximately 20 to 40% of the area of ​​a pixel P, and the height of the convex portion p is, for example, preferably greater than 1 μm and less than 5 μm.

[0054] In addition, when the liquid crystal display device 1 includes the reflective layer 130 and the phase difference layer with the broadband λ / 4 condition, the light loss is sufficiently reduced because the polarization conversion (e.g., conversion between circularly polarized light and linearly polarized light) unique to the reflective liquid crystal display device can be performed. The broadband λ / 4 condition refers to the condition for obtaining polarized light close to circularly polarized light in a wide range within the visible light wavelength.

[0055] The second interlayer insulating layer 152 is disposed on the first interlayer insulating layer 151 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.

[0056] The first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably formed of an organic insulating material or an inorganic insulating material. For example, as an organic insulating film obtained using an organic insulating material, organic films such as acrylic resin, polyimide resin, and phenolic varnish resin (relative dielectric constant ε=2~5), and their stacked films can be cited. The film thickness of the organic insulating film is not particularly limited, and for example, it is greater than 2μm and less than 4μm. As an inorganic insulating film obtained using an inorganic insulating material, for example, inorganic films such as silicon nitride (SiNx) and silicon oxide (SiO2) (relative dielectric constant ε=5~7), and their stacked films can be cited. The thickness of the inorganic insulating film is not particularly limited, and for example, it is preferably Above and In addition, a laminate of an organic insulating film and an inorganic insulating film may be used. Among them, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably organic insulating films.

[0057] From the viewpoint of manufacturing, the interlayer insulating layers 151 and 152 are preferably highly transparent and preferably formed of the same material with high transmittance. In addition, the first interlayer insulating layer 151 which is farther from the observation side than the reflective layer 130 may also be in a form with low transmittance or opaque. From the viewpoint of light utilization efficiency, the second interlayer insulating layer 152 may be in a form with high transparency or may use a material with high transmittance different from that of the first interlayer insulating layer 151.

[0058] The first electrode 121 is arranged on the reflective layer 130 via the second interlayer insulating layer 152, and a dielectric layer 153 is arranged between the first electrode 121 and the second electrode 122. Therefore, the reflective layer 130 is located on the opposite side of the liquid crystal layer 20 (that is, closer to the back side than the first electrode 121 and the second electrode 122) relative to the first electrode 121 and the second electrode 122. In addition, of the first electrode 121 and the second electrode 122, in this embodiment, the second electrode 122 is relatively located on the observation surface side, and the first electrode 121 is located on the back side. The electrode relatively located on the observation surface side is also called the upper electrode, and the electrode relatively located on the back side is also called the lower electrode.

[0059] One of the first electrode 121 and the second electrode 122 is a pixel electrode PE, and the other is a common electrode CE. The pixel electrodes are provided in a plurality of pixels P. The pixel electrode PE is electrically connected to the backplane circuit BP. In this embodiment, the first electrode 121 (lower electrode) is the common electrode CE, and the second electrode 122 (upper electrode) is the pixel electrode PE.

[0060] At least one of the first electrode 121 and the second electrode 122 has a plurality of strip-shaped portions SP and a slit S1 between two adjacent strip-shaped portions among the plurality of strip-shaped portions. The strip-shaped portion SP is equivalent to the electrode portion, and the slit S1 is equivalent to the opening portion. Such an electrode is also called a slit electrode or a finger electrode. From the perspective of easy generation of a transverse electric field, it is preferred that at least the upper electrode (the pixel electrode PE in this embodiment) is a slit electrode. In this case, the lower electrode (the common electrode CE in this embodiment) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode.

[0061] In each pixel P, the plurality of strip-shaped portions SP constituting the slit electrode (the second electrode 122 as the pixel electrode PE in this embodiment) are composed of straight lines substantially parallel to each other and extending in the same direction, and do not include a bent portion. As a result, the orientation of the liquid crystal molecules becomes uniform, and the generation of orientation defects can be sufficiently suppressed.

[0062] The strip-shaped portion SP "is composed of a straight line shape and does not include a curved portion" means that the center line of the strip-shaped portion SP is a straight line shape without a curve, and the outer edge of the non-strip-shaped portion SP is a straight line shape without a curve. The center line of the strip-shaped portion SP refers to a line that divides the strip-shaped portion SP into two equal parts in the width direction. The width direction refers to a direction that is substantially perpendicular to the direction in which the strip-shaped portion SP extends when viewed from above. Therefore, even if the outer edge of the front end of the strip-shaped portion SP is round, as long as the center line of the strip-shaped portion SP is a straight line without a curve, it is included in the shape of "being composed of a straight line shape and does not include a curved portion".

[0063] It is preferable that the strip-shaped portion SP does not include a notch portion. This further suppresses the occurrence of orientation disorder. “The strip-shaped portion SP does not include a notch portion” means that a part of the strip-shaped portion SP is not cut out or dropped.

[0064] In each pixel P, the directions in which the plurality of strip-shaped portions SP extend (also referred to as the directions in which the plurality of strip-shaped portions SP extend) are substantially parallel to each other. In addition, the directions in which the plurality of strip-shaped portions SP extend may be different for each pixel, but are preferably the same in two or more adjacent pixels. Among them, from the viewpoints of image quality and manufacturing, it is more preferable that the directions in which the plurality of strip-shaped portions SP extend are the same at least in adjacent pixels. 6A to 6F The example in which the extending directions of the plurality of strip-shaped portions SP are the same in adjacent pixels is shown. It is further preferred that the extending directions of the plurality of strip-shaped portions SP are the same in the display area.

[0065] The width L of each strip-shaped portion SP varies depending on the applied voltage, etc., and is preferably set to 0.3 to 10 μm, for example. The above L is more preferably 1 to 5 μm. The interval between two adjacent strip-shaped portions SP (i.e., the interval between the center lines of each strip-shaped portion) also varies depending on the applied voltage, etc., and is preferably set to 0.3 to 10 μm, for example. The above interval is more preferably 1 to 5 μm.

[0066] Preferably, the ratio L / S (also referred to as the L / S condition) of the width L of each strip-shaped portion when viewed from above to the width S of each slit when viewed from above is 0.4 to 0.7 / 1. As a result, the reflectivity of the white display (also referred to as the white reflectivity) is improved, and thus the contrast ratio (also referred to as "contrast") is further improved. 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).

[0067] The orientation direction of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied (i.e., the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140) is greater than 0° and less than 16° with respect to the extension direction of the plurality of strip-shaped portions SP as a reference (0°). When the angle, i.e., the angle after rotating the extension direction of the plurality of strip-shaped portions SP clockwise with respect to the extension direction (0°) as a reference is set to a positive angle (+), and the angle after rotating the extension direction counterclockwise is set to a negative angle (-), the angle formed by the orientation directions of the liquid crystal molecules 21 on the first substrate 10 side when no voltage is applied is referred to as the slit angle. Figure 4 Explain the definition of slit angle.

[0068] Figure 4 This is a diagram for explaining the slit angle of a positive liquid crystal molecule. The suffix (p) added to the reference numeral of the liquid crystal molecule means positive type. In this specification, the liquid crystal molecule 21 near the first horizontal alignment film 140 (i.e., the liquid crystal molecule on the first substrate 10 side) is also referred to as a liquid crystal molecule 21A. The liquid crystal molecule 21 near the second horizontal alignment film 340 (i.e., the liquid crystal molecule on the second substrate 30 side) is also referred to as a liquid crystal molecule 21B.

[0069] In the case of positive liquid crystal molecules, the orientation 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 is parallel to the extending direction of the plurality of strip-shaped portions SP, the slit angle is 0° (see Figure 4 When the extending direction of the plurality of strip-shaped portions SP is rotated clockwise with the long axis direction of the liquid crystal molecule 21A as a reference (0°), the slit angle becomes a positive angle (+) (refer to Figure 4 When the direction of extension of the plurality of strip-shaped portions SP is rotated counterclockwise with the long axis direction of the liquid crystal molecule 21A as a reference (0°), the slit angle becomes a negative angle (-) (refer to Figure 4 in the “Negative (-)” column).

[0070] Therefore, the slit angle can also be said to be the angle formed by axes having a large absolute value of the dielectric constant in the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied with reference to the extending direction of the plurality of strip-shaped portions (0°).

[0071] In this embodiment, the slit angle is greater than or equal to 0° and less than or equal to 16°. By making the slit angle within this range, the rotation direction of the liquid crystal molecules 21A on the first substrate 10 side and the liquid crystal molecules 21B on the second substrate 30 side are consistent, thereby fully suppressing the generation of alignment defects. Among them, from the viewpoint of suppressing the generation of alignment defects and further improving the transmission efficiency, the slit angle is preferably greater than or equal to 0° and less than 14°, more preferably greater than or equal to 0° and less than 12°, further preferably greater than or equal to 0° and less than 10°, particularly preferably greater than or equal to 0° and less than 7°, and most preferably greater than or equal to 0° and less than 4°.

[0072] Figure 5 and Fig. 6A , an example is shown in which the extending direction of the plurality of strip-shaped portions SP (this angle is referred to as angle X) is 0° when the angle after clockwise rotation based on the extending direction of the source wiring SL is set as a positive angle (+) and the angle after counterclockwise rotation is set as a negative angle (-). In addition, Figure 6B , Figure 6C , Fig.6D , Fig. 6E and Fig. 6F Examples of angle X being -10°, +10°, -90°, -100°, and -80° are shown. Figure 5 and Fig. 6A ) corresponds to a mode in which the extending direction of the plurality of strip-shaped portions SP is parallel to the extending direction of the source wiring SL, and the angle X is -90° (refer to Fig.6D ) corresponds to a mode in which the extending direction of the plurality of strip-shaped portions SP is parallel to the extending direction of the gate wiring GL. Figure 5 and 6A to 6F is a top view schematically showing a specific example of a pixel. Figure 5 is a schematic plan view showing a structural example of a pixel, and 6A to 6F is a schematic top view showing an example of pixel arrangement. 6A to 6F , the twisted orientation of the liquid crystal molecules 21 is also shown.

[0073] The first electrode 121 and the second electrode 122 are preferably formed of a transparent conductive material, respectively. Examples of the transparent conductive material include indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), or a mixture thereof.

[0074] exist Figure 2In the manner shown, the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed in the same layer as the reflective layer 130 and is formed of the same material (metal film, etc.) as the reflective layer 130. A first contact hole CH1 is formed in the first interlayer insulating layer 151 to expose a portion of the backplane circuit BP (more specifically, at least a portion of the drain electrode of the TFT 110), and the contact electrode 10 is connected to the backplane circuit BP in the first contact hole CH1. In addition, a second contact hole CH2 is formed in the second interlayer insulating layer 152 to expose a portion of the contact electrode 160, and the pixel electrode PE (the second electrode 122 in this embodiment) is connected to the contact electrode 160 in the second contact hole CH2.

[0075] The dielectric layer 153 is provided so as to cover the first electrode 121. The dielectric layer 153 is preferably formed of an inorganic insulating material. The inorganic insulating film obtained using the inorganic insulating material is as described above.

[0076] The first horizontal alignment film 140 is provided on the second electrode 122 and is in contact with the liquid crystal layer 20. Therefore, it can be said that the first electrode 121 and the second electrode 122 are arranged between the second interlayer insulating layer 152 and the first horizontal alignment film 140.

[0077] The first horizontal alignment film 140 and the second horizontal alignment film 340 described later are respectively subjected to an alignment treatment to define the alignment azimuth (also referred to as alignment direction) of the liquid crystal molecules 21 contained in the liquid crystal layer 20. For example, the alignment treatment is preferably performed by a photo-alignment treatment or a rubbing treatment. In the photo-alignment treatment, a photo-decomposable photo-alignment film material can be used, and in the rubbing treatment, an alignment film material such as polyimide is preferably used.

[0078] The first horizontal alignment film 140 and the second horizontal alignment film 340 are both horizontal alignment films that align the liquid crystal molecules 21 in a horizontal direction relative to the first substrate 10 and the second substrate 30 when no voltage is applied to the liquid crystal layer 20. That is, the liquid crystal molecules 21 are horizontally aligned when no voltage is applied to the liquid crystal layer 20. The pretilt angle is substantially 0°.

[0079] The orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 and the orientation of the liquid crystal molecules 21 defined by the second horizontal alignment film 340 are different from each other. Therefore, the liquid crystal layer 20 exhibits a twisted orientation when no voltage is applied (see Figure 2 When a voltage is applied to the liquid crystal layer 20, that is, when a lateral 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 according to the lateral electric field (fringe electric field).

[0080] However, in the present embodiment, the configuration in which the pixel electrode PE is disposed above the common electrode CE is described, but in a relatively large liquid crystal display device, that is, a liquid crystal display device in which the area of ​​the pixel P is relatively large, it is preferred that the pixel electrode PE is disposed above the common electrode CE. In this configuration (also referred to as the V2 configuration), since it is not necessary to form a slit in the common electrode CE that becomes the lower electrode, the increase in the resistivity (surface resistivity) of the common electrode CE is suppressed compared to the configuration in which the common electrode CE is disposed above the pixel electrode PE (also referred to as the V3 configuration), thereby suppressing the weakening of the fringe electric field applied to the liquid crystal layer 20. In this configuration (V2 configuration), when the pixel electrode PE is set as a slit electrode, although the resistivity of the pixel electrode PE increases, since a voltage input from the outside is applied to the pixel electrode PE, it is easy to reduce the influence of the increase in resistivity (that is, suppress the weakening of the fringe electric field). In addition, in order to suppress the increase in the resistivity of the common electrode CE, it is also considered to use low-resistance wiring formed by a metal material (for example, connecting the low-resistance wiring to the common electrode), but in such a structure, there is a situation where adverse effects on the display (such as glare, rainbow color diffraction, interference patterns) are caused by regular reflection caused by the low-resistance wiring, etc., and it is necessary to use a black matrix or the like for shading, and sometimes it is impossible to fully increase the reflective aperture ratio.

[0081] In the configuration in which the pixel electrode PE is arranged above the common electrode CE, since the common electrode CE does not exist in the region where the second contact hole CH2 is formed, the region does not contribute to the reflective display, and the reflectivity may decrease compared to the configuration in which the common electrode CE is arranged above the pixel electrode PE. Since the area of ​​the contact hole and the like that does not contribute to the reflective display does not depend on the size of the area of ​​the pixel P but requires a certain degree of area, the smaller the area of ​​the pixel P (i.e., the higher the resolution), the higher the proportion of the region that does not contribute to the reflective display in the pixel P, and the greater the reduction in the above-mentioned reflectivity. Conversely, in a relatively large liquid crystal display device, since it is easy to further reduce the proportion of the region that does not contribute to the reflective display in the pixel P, it is easy to suppress the reduction in the above-mentioned reflectivity. For these reasons, in a relatively large liquid crystal display device, it is advantageous to arrange the pixel electrode PE above the common electrode CE.

[0082] On the other hand, as described above, the smaller the area of ​​the pixel P (i.e., the higher the resolution), the lower the reflectivity due to the fact that the area where the second contact hole CH2 is formed does not contribute to the reflective display. 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 preferred that the common electrode CE is arranged above the pixel electrode PE (refer to variant example 1 of embodiment 1 described later).

[0083] <Liquid Crystal Layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and includes a liquid crystal material. In the present embodiment, the liquid crystal layer 20 includes positive liquid crystal molecules. That is, the liquid crystal material constituting the liquid crystal layer 20 refers to a liquid crystal material with a positive dielectric anisotropy (a nematic liquid crystal material with a positive dielectric anisotropy Δε). In addition, a negative liquid crystal material refers to a liquid crystal material with a negative dielectric anisotropy, that is, a nematic liquid crystal material with a negative dielectric anisotropy Δε. The dielectric anisotropy Δε is the dielectric constant ε of the liquid crystal molecule 21 in the long axis direction. / / and the dielectric constant ε in the short axis direction ⊥ The difference (i.e. ε / / -ε ⊥ ).

[0084] From a manufacturing perspective (e.g., yield rate, etc.), the thickness d (also referred to as the cell gap or cell thickness) of the liquid crystal layer 20 is preferably greater than 2 μm, and the birefringence Δn of the liquid crystal material (i.e., positive liquid crystal material) is preferably less than 0.123. In addition, from a response perspective, the cell thickness d is preferably less than 3 μm, and the birefringence Δn of the liquid crystal material is preferably less than 0.082. In addition, from the perspective of improving reflectivity, the birefringence Δn of the liquid crystal material is preferably less than 0.08, and more preferably less than 0.07. In order to suppress the maximum voltage in the voltage-reflectivity characteristic and the voltage-transmittance characteristic to less than 6 V, the dielectric anisotropy Δε of the liquid crystal material is preferably greater than 10.

[0085] The liquid crystal layer 20 may further contain a chiral agent as necessary. The liquid crystal layer 20 can be formed by, for example, a dropping method.

[0086] From the viewpoint of suppressing alignment disorder, the liquid crystal layer 20 is preferably in a monodomain alignment (also referred to as a single domain alignment).

[0087] <Second Substrate> The second substrate 30 includes a second horizontal alignment film 340 disposed opposite to the first substrate 10 via the liquid crystal layer 20 and in contact with the liquid crystal layer 20. Preferably, the second substrate 30 further includes a supporting substrate 300 and a color filter layer 310. For example, Figure 2 As shown, the second substrate 30 has a second horizontal alignment film 340, a color filter layer 310, and a support substrate 300 in order from the liquid crystal layer 20 side. The second substrate 30 preferably has a plurality of columnar spacers (not shown). In addition, the first substrate 10 may also have a plurality of columnar spacers.

[0088] The support substrate 300 is preferably transparent and insulating, and examples of the support substrate 300 include a glass substrate and a plastic substrate. Figure 2 In the embodiment, a high-resistance transparent conductive film is formed on the surface of the phase difference layer 40 side of the support substrate 300 to cope with the electrostatic burn-in of the liquid crystal unit. In order to suppress the decrease in transmittance or the increase in reflectivity, the high-resistance transparent conductive film may be a multilayer structure.

[0089] The color filter layer 310 typically includes: a red color filter, which is arranged in an area corresponding to a red pixel and transmits red light; a green color filter, which is arranged in an area corresponding to a green pixel and transmits green light; and a blue color filter, which is arranged in an area corresponding to a blue pixel and transmits blue light. However, the types of color filters may be two or less, or four or more. In addition, when color display is not performed, the color filter layer 310 is omitted.

[0090] As required, an outer coating (also called a planarization layer) covering the color filter layer 310 may also be provided. In addition, depending on the material forming the electrode (e.g., a transparent conductive material), the material forming the interlayer insulating layer, the dielectric layer, and the material forming the alignment film, the white display may be yellowish. In this case, the chromaticity adjustment (i.e., blue shift) may also be performed by forming the outer coating with a blue resist, so that the chromaticity of the white display is close to the chromaticity of, for example, a D65 light source. The D65 light source is the CIE standard light source D65.

[0091] <Other components> In the liquid crystal display device 1 of the present embodiment, the liquid crystal layer 20 displays in a transverse electric field mode in which a twisted orientation is exhibited when no voltage is applied. As a result, the cell gap can be increased, and the fluctuation range of the contrast can be reduced relative to the fluctuation of the cell gap. Therefore, the occurrence of display unevenness is fully suppressed, and the contrast of the reflective display becomes good. The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably greater than 58.3° and less than 89.9°. The more preferred range will be described later.

[0092] The twist angle θ1 of the liquid crystal layer 20 is an angle formed by the orientation direction of the liquid crystal molecules 21 specified by the first horizontal alignment film 140 and the orientation direction of the liquid crystal molecules 21 specified by the second horizontal alignment film 340. That is, the angle formed by 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 voltage is applied).

[0093] From the viewpoint of further improving the contrast, the liquid crystal display device 1 is preferably in a normally black mode. The normally black mode is a display mode in which a black display is displayed when no voltage is applied and a white display is displayed when a voltage is applied.

[0094] In addition to the above components, the liquid crystal display device 1 is composed of the following multiple components: TCP (tape carrier package), PCB (printed wiring substrate) and other external circuits; optical films such as viewing angle expansion film and brightness enhancement film; outer frame (frame), etc., and the components can also be assembled to other components. The above is not particularly limited, and the components commonly used in the field of liquid crystal display devices can be used, so the description is omitted.

[0095] <Application Examples> The liquid crystal display device 1 of this embodiment is applicable to various applications. Among them, it can be preferably applied to a touch panel. Regardless of whether it is applied to an external touch panel or a built-in touch panel, it can improve the contrast ratio at a lower cost than each previous touch panel, so it is useful. Among them, it can be suitably applied to a built-in touch panel, and is particularly suitably applied to an In-cell touch panel. In this way, if the liquid crystal display device 1 of this embodiment is used, an In-cell touch panel capable of displaying in a reflective mode can be appropriately realized.

[0096] Since the In-cell touch panel that can realize the display of the reflective mode does not need the frame wiring area that is necessary in the external touch panel, it is possible to achieve a narrow frame, and the touch panel function can be equipped without a cover glass, so it can also contribute to thinning and lightweight. In addition, since the touch function and the display function are driven in a time-sharing manner, the LCD (liquid crystal display) noise, which can be the largest noise source, is not received in the touch panel. That is, since no killer pattern is generated, the tuning (adjustment) of the touch signal becomes easy. Moreover, the loss of reflected light is sufficiently small, and the pen writing is more natural, and there is no display of incoordination. Moreover, compared with the external touch panel, the total cost can be reduced from the user's perspective. Moreover, it is possible to combine the finger input and the pen input of the electromagnetic induction method (EMR), and high-precision pen writing can be achieved.

[0097] An example in which the liquid crystal display device 1 is used for an In-cell type touch panel will be described further. Figure 7 1 is a schematic plan view illustrating the arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1. Figure 7 As shown, the liquid crystal display device 1 includes a display region DR and a non-display region FR. The display region DR includes a plurality of pixels P arranged in a matrix (for example, Figure 3The non-display region FR is located at the periphery of the display region DR, and is sometimes also referred to as a peripheral region or a frame region.

[0098] 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. Figure 7 In the example shown, each touch sensor electrode Tx is provided corresponding to two or more pixels P.

[0099] 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 the corresponding touch wiring TL. The connection portion TC between the touch sensor electrode TX and the touch wiring TL is called a touch wiring contact portion TC.

[0100] 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, for example, to switch between a display mode in which a plurality of touch sensor electrodes TX function as a common electrode CE and a touch detection mode in which a plurality of touch sensor electrodes TX function as touch sensor electrodes TX in a time-sharing manner. For example, in the display mode, the touch drive unit TD applies a common signal to the touch sensor electrode TX (common electrode 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 electrode TX via the touch wiring TL.

[0101] exist Figure 7 In the embodiment, a plurality of touch wirings TL extend in a column direction (the same direction as the source bus line SL). A portion of the touch wirings TL extends across one or more other touch sensor electrodes TX to the corresponding touch sensor electrode TX.

[0102] If we focus on a certain touch sensor electrode TX, the first touch wiring TL1 that provides a signal to the touch sensor electrode TX extends to the touch wiring contact portion TC, and the second touch wiring TL2 that provides a signal to other touch sensor electrodes TX extends across the touch sensor electrode TX. The second touch wiring TL2 overlaps the touch sensor electrode TX via an insulating layer. In addition, depending on the position of the touch sensor electrode TX, there are cases where two or more touch wirings TL are configured to extend across the touch sensor electrode TX, and there are also cases where no touch wiring TL is configured to extend across the touch sensor electrode TX.

[0103] In the non-display area FR, in addition to the touch drive unit TD, a peripheral circuit (not shown) including a drive circuit such as a gate driver and a source driver is provided. The gate driver is used to provide a gate signal to the gate bus (gate wiring) GL, and the source driver is used to provide a source signal to the source bus (source wiring) SL. These drive circuits can be mounted on the first substrate (TFT substrate) 10, or they can be formed as one piece (monolithic). A semiconductor chip including part or all of the drive circuits can also be mounted in the non-display area FR.

[0104] In an In-cell touch panel, it is particularly preferable to use an In—Ga—Zn—O-based semiconductor as the TFT 110 .

[0105] (Variation 1 of Implementation Example 1) In Embodiment 1, the first electrode 121 as the lower electrode is the common electrode CE, and the second electrode 122 as the upper electrode is the pixel electrode PE. However, conversely, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE, and the first electrode 121 (lower electrode) is the pixel electrode PE (see Figure 8 ).

[0106] Figure 8 : is a cross-sectional schematic diagram of the liquid crystal display device 1 of this example. In this example, from the viewpoint of easy generation of a lateral electric field, at least the upper electrode (the common electrode CE in this example) is preferably a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this variation is particularly suitable for a relatively high-definition liquid crystal display device as described above, i.e., a liquid crystal display device with a relatively small area of ​​pixel P.

[0107] (Variation 2 of Implementation Example 1) In Embodiment 1, an FFS mode liquid crystal display device is described, but an IPS mode liquid crystal display device (wherein the liquid crystal layer 20 exhibits a twisted orientation when no voltage is applied) may also be used. This modification is an IPS mode liquid crystal display device. In this modification, it is preferred that the first electrode 121 and the second electrode 122 are provided in the same layer, and both the first electrode 121 and the second electrode 122 are slit electrodes.

[0108] (Implementation Method 2) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiment 1 is omitted. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 1 in that the liquid crystal display device of this embodiment has a phase difference layer and a polarizing plate on both sides of the liquid crystal panel 1X, and has a light source on the back side of the liquid crystal layer 20.

[0109] Fig. 9 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Fig.10 FIG. 1 is a more detailed cross-sectional schematic diagram of a liquid crystal display device 1 according to an example of the present embodiment. Fig. 9 As shown, the liquid crystal display device 1 includes, from the back side to the observation side, the first polarizing plate 51, the first phase difference layer 41, the first substrate 10, the liquid crystal layer 20, the second substrate 30, the second phase difference layer 42, and the second polarizing plate 52. The first phase difference layer 41 includes a first λ / 2 plate 412 and a first λ / 4 plate 411. The second phase difference layer 42 includes a first λ / 2 plate 422 and a first λ / 4 plate 421. At least one of the first phase difference layer 41 and the second phase difference layer also includes a positive C plate 44. Fig. 9 and Fig.10 In FIG. 1 , as an example of this embodiment, an example in which the second retardation layer further includes a positive C plate 44 is shown.

[0110] In the liquid crystal display device 1 of the present embodiment, each pixel P has a reflective region Rf that reflects light for display (i.e., a region that displays in a reflective mode); and a transmissive region Tr that transmits light for display (i.e., a region that displays in a transmissive mode) (see Fig.11 ). Thus, good visibility can be achieved in all environments. Therefore, the liquid crystal display device 1 of this embodiment is a semi-transmissive liquid crystal display device. Fig.11 1 is a schematic plan view conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of the present embodiment.

[0111] The reflective layer 130 is disposed in the reflective region Rf. For example, light L1 (for example, external light) enters the liquid crystal display device 1 from the observation surface side, is reflected by the reflective layer 130, and then is emitted from the observation surface side (see Fig.10 On the other hand, the reflective layer 130 is not arranged in the transmission region Tr (see Fig.11 For example, when the backlight source 61 is disposed on the back side, the light L2 from the backlight source 61 is transmitted through the region (transmission region Tr) where the reflective layer 130 is not disposed, and is emitted from the observation side (refer to Fig.10 ).

[0112] The ratio (aperture ratio) of the area of ​​the transmission region Tr in each pixel P can be appropriately set according to the purpose, for example, when the area of ​​one pixel P is set to 100%, it is preferably 5% or more and 95% or less. In addition, the position and shape of the transmission region Tr in the pixel P can also be appropriately set according to the purpose, etc.

[0113] Fig.12 and Fig.13A , an example is shown in which the extending direction (angle X) of the plurality of strip-shaped portions SP is 0° when the angle after clockwise rotation is set to a positive angle (+) and the angle after counterclockwise rotation is set to a negative angle (-) based on the extending direction of the source wiring SL as a reference (0°). In addition, Fig. 13B , Fig. 13C , Fig.13D , Fig.13E and Fig.13F Examples of angle X being -10°, +10°, -90°, -100°, and -80° are shown. Fig.12 and Fig.13A ) corresponds to a mode in which the extending direction of the plurality of strip-shaped portions SP is parallel to the extending direction of the source wiring SL, and the angle X is -90° (refer to Fig.13D ) corresponds to a mode in which the extending direction of the plurality of strip-shaped portions SP is parallel to the extending direction of the gate wiring GL. Fig.12 and FIG. 13A to FIG. 13F is a schematic top view schematically showing a specific example of a pixel in this embodiment. Fig.12 is a schematic plan view showing a structural example of a pixel, and FIG. 13A to FIG. 13F is a schematic top view showing an example of pixel arrangement. FIG. 13A to FIG. 13F , the twisted orientation of the liquid crystal molecules 21 is also shown.

[0114] <Phase difference layer> The first phase difference 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. In addition, the second phase difference 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. Preferably, in the first phase difference layer 41, the positional relationship between the λ / 4 plate and the λ / 2 plate in each phase difference layer is in the order of λ / 2 plate 412 and λ / 4 plate 411 from the back side, and in the second phase difference layer 42, the order is λ / 2 plate 422 and λ / 4 plate 421 from the observation side.

[0115] A λ / 4 plate is a phase difference plate that gives an in-plane phase difference of 1 / 4 wavelength to incident light of wavelength λ, and is also called a λ / 4 wave plate or QWP (Quarter-Wave Plate). Specifically, a λ / 4 plate can convert linearly polarized light into circularly polarized light or convert circularly polarized light into linearly polarized light. For example, linearly polarized light incident on a λ / 4 plate becomes circularly polarized light when it is emitted.

[0116] The λ / 2 plate is a phase difference plate that gives an in-plane phase difference of 1 / 2 wavelength to incident light of wavelength λ, and is also called a λ / 2 wavelength plate, a half-wavelength plate, or an HWP (Half-Wave Plate). Specifically, the λ / 2 plate can rotate the vibration direction of the incident light by approximately 90°. For example, circularly polarized light incident on the λ / 2 plate becomes circularly polarized light with the opposite rotation direction when it is emitted.

[0117] The first λ / 4 plate 411 and the second λ / 4 plate 421 preferably have substantially the same in-plane phase difference Re. Substantially the same means that the difference in in-plane phase difference Re is less than 5 nm. The difference in in-plane phase difference Re is preferably less than 1 nm.

[0118] The first λ / 2 plate 412 and the second λ / 2 plate 422 preferably have substantially the same in-plane phase difference Re. Substantially the same means that the difference between the in-plane phase differences Re is less than 5 nm. The difference between the in-plane phase differences Re is preferably less than 1 nm.

[0119] As the λ / 4 plates 411, 421 and the λ / 2 plates 412, 422, a general phase difference plate can be used. More specifically, for example, as a circular polarizing plate of an anti-reflection film, it is preferred to use a generally circulated phase difference plate. In the present invention, it is preferred that the optical axis setting of each optical film be controlled within the specified range described later, as the λ / 4 plate and the λ / 2 plate, even if a general phase difference plate is used without using a special phase difference plate, although it is a semi-transmissive liquid crystal display device of a lateral electric field mode, it can improve the contrast and the viewing angle, and it is also useful as an In-cell touch panel, so that cost reduction can be achieved. In particular, it is very useful because it can reduce the total cost from the user's perspective. The liquid crystal display device of the present invention is not only used as an In-cell type built-in touch panel, but also can achieve cost reduction when used as an external touch panel.

[0120] 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 .

[0121] As described above, in the present embodiment, each phase difference layer 41, 42 includes a λ / 4 plate and a λ / 2 plate, respectively, and at least one of the phase difference layers 41, 42 also includes a positive C plate. In this case, in the obtained liquid crystal display device, the viewing angle characteristics are excellent and a high contrast ratio can be achieved. In particular, the brightness disturbance during black display (also called black tone protrusion) is fully suppressed, and the viewing angle of black display is expanded. From the viewpoint of further exerting the above-mentioned effects, it is preferred that the positive C plate is located between the λ / 4 plate and the λ / 2 plate. In particular, in the case where the phase difference layer includes a positive C plate, it is preferred to set it to this configuration. In the present embodiment, only the second phase difference layer 42 has a positive C plate 44, but in this case, it is preferred that the λ / 4 plate 421, the positive C plate 44, and the λ / 2 plate 422 are arranged in sequence from the liquid crystal layer 20 (and the second substrate 30) side (refer to Fig.10 ).

[0122] The positive C plate 44 (and 43 , 45 , etc. described later) may be composed of a single film, or may be a laminate of two or more retardation films.

[0123] In this specification, the part (structure) that is sandwiched between layers other than the positive C plate and functions as a positive C plate is counted as "one positive C plate". At this time, it is not limited to whether the positive C plate is a laminated body. Therefore, for example, in the case where the phase difference layer includes a λ / 4 plate, a positive C plate of a multilayer structure, and a λ / 2 plate in sequence, it is referred to as "the phase difference layer has one positive C plate". In addition, the case where the phase difference layer includes a λ / 4 plate, two commercially available positive C plates, and a λ / 2 plate in sequence is also referred to as "the phase difference layer has one positive C plate". In the case where the phase difference layer includes a λ / 4 plate, a first positive C plate (not limited to whether it is a laminated body), a λ / 2 plate, and a second positive C plate (not limited to whether it is a laminated body) in sequence, it is referred to as "the phase difference layer has two positive C plates".

[0124] As the positive C plate 44 (and 43, 45, etc. described later), for example, a positive C plate obtained by biaxially stretching a film containing a material having negative intrinsic birefringence as a component in the longitudinal and transverse directions, a positive C plate obtained by coating a liquid crystal material such as a nematic liquid crystal, etc. can be appropriately used. As the material having negative intrinsic birefringence, for example, a resin composition containing an acrylic resin and a styrene resin, polystyrene, polyethylene naphthalene, polyethylene biphenyl, polyethylene pyridine, polymethyl methacrylate, polymethyl acrylate, N-substituted maleimide copolymer, polycarbonate having a fluorene skeleton, triacetyl cellulose (especially a material with a low degree of acetylation), etc. can be listed.

[0125] Specific examples of the positive C plate 44 (and 43 , 45 , etc.) include positive C plates manufactured by ENEOS or Hayashi Tenrenfu, and positive-C retardation films manufactured by Nippon Kayaku Co., Ltd.

[0126] From the viewpoint of further exerting the viewing angle improvement 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.

[0127] The thickness of each positive C plate 44 (and 43) is preferably, for example, 0.1 to 100 μm. If it is within this range, the mechanical strength and display uniformity are more excellent. The above-mentioned thicknesses are more preferably 0.1 to 80 μm, and further preferably 0.1 to 50 μm. In addition, when the positive C plate 44 (and 43) has a laminated structure, it is preferred to set the total thickness thereof to the above range, and the thicknesses of each phase difference film may be the same or different.

[0128] The phase difference layer having a positive C plate (equivalent to the second phase difference layer 42 in this embodiment) may also have a positive C plate different from the positive C plate (referred to as a second positive C plate). In this case, it is preferred that the second positive C plate is located between the λ / 2 plate and the polarizing plate. In addition, in Embodiment 3 described later, the first phase difference layer 41 and the second phase difference layer 42 respectively include the first positive C plate, and the first phase difference layer 41 also includes the second positive C plate. The method is described in detail.

[0129] From the viewpoint of further improving viewing angle characteristics and contrast, the liquid crystal display device 1 of the present embodiment particularly preferably 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 addition, in this embodiment, the description is particularly focused on the liquid crystal display device 1 that satisfies the above (i) (for example, see Fig. 9 as well as Fig.10 ). In the following embodiment 3, the description will focus on the liquid crystal display device 1 that satisfies the above condition (ii).

[0130] <Polarizing Plate> The first polarizing plate 51 is located at a position closer to the back side than the first phase difference layer 41. In addition, the second polarizing plate 52 is located at a position closer to the observation side than the second phase difference layer 42. Polarizing plates 51 and 52 can be either circular polarizing plates or linear polarizing plates. Here, a linear polarizing plate refers to a polarizing plate having the function of extracting polarized light (linear polarized light) that vibrates only in a specific direction from non-polarized light (natural light), partially polarized light or polarized light, which is different from a circular polarizing plate. Among them, a linear polarizing plate is preferred.

[0131] The polarizing plates 51 and 52 may be either absorption-type polarizing plates or reflection-type polarizing plates. An absorption-type polarizing plate refers to a polarizing plate that has the function of absorbing light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. A reflection-type polarizing plate refers to a polarizing plate that has the function of reflecting light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. Among them, an absorption-type polarizing plate is preferred. An absorption-type linear polarizing plate is particularly preferred.

[0132] As an absorption type polarizing plate, for example, a polarizing plate formed by dyeing a polyvinyl alcohol film and adsorbing an anisotropic material such as an iodine complex (or dye) and then stretching and aligning it can be cited. Generally speaking, in order to ensure mechanical strength and moisture and heat resistance, a protective film such as a triacetyl cellulose film is provided in a state of being stacked on both sides of the polyvinyl alcohol film. In addition, as a reflective polarizing plate, for example, a film formed by stacking multiple dielectric films, a film formed by stacking multiple films with different refractive index anisotropies, a nanowire grid polarizing plate, a selective reflection polarizing plate using cholesteric liquid crystals, etc. can be cited.

[0133] <Light Source> The liquid crystal display device 1 preferably further includes a light source. In the present embodiment, a light source 61 (also referred to as a backlight) is further provided on the back side of the liquid crystal layer 20 (see Fig. 9 The light source 61 is not particularly limited as long as it is a light source that irradiates light, and can be a direct-down type, an edge type, or any other type. The light source 61 preferably has a light source such as a light emitting diode (LED), a light guide plate, and a reflective sheet, and can further have a diffuser sheet and a prism sheet.

[0134] <Preferred Settings> The following further describes the preferred optical axis settings of each optical film (i.e., polarizing plate and phase difference layer). As a polarizing plate, an absorption-type polarizing plate is used. As the liquid crystal layer 20, a liquid crystal layer that displays normally black with a single-domain structure is assumed, and as a liquid crystal material constituting the liquid crystal layer 20, a positive liquid crystal material is used. In addition, since the slow axis angle of the positive C plate is the film normal direction (i.e., 90° when the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is set to 0°), the study was conducted in a manner without a positive C plate. In the case of having a positive C plate, the preferred settings are also the same.

[0135] Fig.14 The liquid crystal display device 1 includes 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 in this order from the back side toward the observation side (see Fig. 9) is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21A of the liquid crystal layer 20 and the optical axis of each optical film (i.e., the in-plane slow axis of the λ / 4 plate and the λ / 2 plate and the polarization axis of the polarizing plate) when no voltage is applied. Fig.14 In FIG. 1 , as the liquid crystal molecules 21 , liquid crystal molecules 21A near the first horizontal alignment film 140 and liquid crystal molecules 21B near the second horizontal alignment film 340 are described.

[0136] In this specification, unless otherwise specified, each angle (such as a twist angle or an optical axis angle) is an angle when the liquid crystal panel 1X is regarded as a dial of a clock and the direction perpendicular to the extending direction of the plurality of strip-shaped portions SP as a reference direction is set to the 0° direction (3 o'clock direction) and the twist direction is set to the positive direction (counterclockwise direction) (see Fig.15 ). Fig.15 3 is a diagram for explaining the optical axis angle of the optical film. The twist direction refers to the direction of twisting from the orientation of the liquid crystal molecule 21A defined by the first horizontal alignment film 140 to the orientation of the liquid crystal molecule 21B defined by the second horizontal alignment film 340 when the liquid crystal display device 1 is observed from the observation surface side. The liquid crystal molecule 21C is a liquid crystal molecule located between the liquid crystal molecule 21A and the liquid crystal molecule 21B.

[0137] 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. This improves contrast. From the viewpoint of improving contrast, the twist angle θ1 is more preferably 70° or more and 85° or less.

[0138] The angle of the polarization axis 51AA of the first polarizing plate 51 is ( Fig.14 The angle θ2) is preferably 83.4° to 91.4°. The angle is more preferably 84.0° to 90.9°, further preferably 84.7° to 90.2°, and particularly preferably 85.5° to 89.3°.

[0139] The angle of the in-plane slow axis 412SA of the first λ / 2 plate 412 is ( Fig.14 The angle θ3) is preferably -19.1° to -15.1°. The angle is more preferably -18.8° to -15.4°, further preferably -18.5° to -15.7°, and particularly preferably -18.0° to 16.2°.

[0140] The angle of the in-plane slow axis 411SA of the first λ / 4 plate 411 is ( Fig.14 The angle θ4) is preferably -80.0° to -72.2°. The above angle is more preferably -79.4° to -72.8°, further preferably -78.8° to -73.4°, and particularly preferably -77.9° to -74.3°.

[0141] 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 located at angles of 83.4° to 91.4°, -19.1° to -15.1° and -80.0° to -72.2°, more preferably located at angles of 84.0° to 90.9°, -18.8° to -15.4° and -79.4° to -72.8°, further preferably located at angles of 84.7° to 90.2°, -18.5° to -15.7° and -78.8° to -73.4°, and particularly preferably located at angles of 85.5° to 89.3°, -18.0° to 16.2° and -77.9 to -74.3°, respectively.

[0142] The angle of the in-plane slow axis 421SA of the second λ / 4 plate 421 is ( Fig.14 The angle θ4) is preferably 62.1° to 67.1°. The above angle is more preferably 63.0° to 67.0°, further preferably 64.0° to 67.0°, and particularly preferably 64.5° to 66.0°.

[0143] The angle of the in-plane slow axis 422SA of the second λ / 2 plate 422 is ( Fig.14 The angle θ3) is preferably 37.5° to 42.5°. The angle is more preferably 38.0° to 42.0°, further preferably 39.0° to 41.0°, and particularly preferably 40.0° to 41.0°.

[0144] The angle of the polarization axis 52AA of the second polarizing plate 52 is ( Fig.14 The angle θ2) is preferably 19.5° to 26.5°. The angle is more preferably 19.5° to 26.0°, further preferably 19.5° to 25.5°, and particularly preferably 20.0° to 23.7°.

[0145] 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 located at angles of 19.5° to 26.5°, 37.5° to 42.5° and 62.1° to 67.1°, more preferably located at angles of 19.5° to 26.0°, 38.0° to 42.0° and 63.0° to 67.0°, further preferably located at angles of 19.5° to 25.5°, 39.0° to 41.0° and 64.0° to 67.0°, and particularly preferably located at angles of 20.0° to 23.7°, 40.0° to 41.0° and 64.5° to 66.0°, respectively.

[0146] Fig.19Optimal optical axis settings from the viewpoint of improving contrast are shown in FIG. Fig.19 This is a diagram conceptually showing the most preferable optical axis setting. Fig.19 , the in-plane phase difference Re of the λ / 4 plates 411 and 421 is 140 nm, and the in-plane phase difference Re of the λ / 2 plates 412 and 422 is 270 nm.

[0147] When changing the slit angle, 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 in the same direction by the same angle.

[0148] (Variation 1 of Implementation Example 2) In Embodiment 2, the first electrode 121 as the lower electrode is the common electrode CE, and the second electrode 122 as the upper electrode is the pixel electrode PE. However, conversely, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE, and the first electrode 121 (lower electrode) is the pixel electrode PE (see Fig.16 ).

[0149] Fig.16 : is a cross-sectional schematic diagram of the liquid crystal display device 1 of this example. In this example, from the viewpoint of easy generation of a lateral electric field, at least the upper electrode (the common electrode CE in this example) is preferably a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this variation is particularly suitable for a relatively high-definition liquid crystal display device as described above, i.e., a liquid crystal display device with a relatively small area of ​​pixel P.

[0150] (Implementation 3) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiments 1 and 2 is omitted. In embodiment 2, the description is particularly focused on the liquid crystal display device 1 in which only the second phase difference layer 42 includes a positive C plate, but in this embodiment, the description is particularly focused on the liquid crystal display device 1 in which the first phase difference layer 41 includes two positive C plates and the second phase difference layer 42 includes a positive C plate (that is, the liquid crystal display device 1 that satisfies the above (ii)). The liquid crystal display device 1 of this embodiment is substantially the same as the liquid crystal display device 1 of embodiment 2, except that the first phase difference layer 41 includes two positive C plates.

[0151] Fig.17 FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Fig.17As shown, the liquid crystal display device 1 includes, from the back side toward the observation side, the first polarizing plate 51, the first retardation layer 41, the first substrate 10, the liquid crystal layer 20, the second substrate 30, the second retardation layer 42, and the second polarizing plate 52. The first retardation layer 41 includes a λ / 4 plate 411 and a λ / 2 plate 412, and also includes a first positive C plate 43 and a second positive C plate 45. The second retardation layer 42 includes a first positive C plate 44 in addition to a λ / 4 plate 421 and a λ / 2 plate 422.

[0152] From the viewpoint of making the viewing angle characteristics and contrast better, it is preferred that the first positive C plates 43 and 44 are located between the λ / 4 plate and the λ / 2 plate as described above, and it is preferred that the second positive C plate 45 is located between the λ / 2 plate and the polarizing plate. In this embodiment, the first phase difference layer 41 preferably includes the second positive C plate 45, the λ / 2 plate 412, the first positive C plate 43, and the λ / 4 plate 411 in order from the back side, and the second phase difference layer 42 preferably includes the λ / 4 plate 421, the first positive C plate 44, and the λ / 2 plate 422 in order from the back side (see Fig.17 ).

[0153] The second positive C plate 45 can be the same phase difference plate as the first positive C plates 43 and 44 (same physical properties, same thickness, etc.) or different phase difference plates as long as it satisfies "nz>nx≈ny". However, from the viewpoint of further exerting the viewing angle improvement effect, the thickness direction phase difference Rth (absolute value) of the second positive C plate 45 is preferably 50 to 130 nm. The above Rth is more preferably 70 to 120 nm, and further preferably 80 to 115 nm.

[0154] The thickness of the second positive C plate 45 is preferably 0.1 to 100 μm, for example. If it is within this range, the mechanical strength and display uniformity are more excellent. The above thickness is more preferably 0.1 to 80 μm, and further preferably 0.1 to 50 μm. In addition, when the positive C plate 45 has a stacked structure, it is preferably set to the above range for the total thickness of the whole, and the thickness of each phase difference film can be the same or different.

[0155] (Variation 1 of Implementation Method 3) In Embodiment 3, the first electrode 121 as the lower electrode is the common electrode CE and the second electrode 122 as the upper electrode is the pixel electrode PE. However, conversely, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE.

[0156] (Implementation 4) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiment 1 is omitted. The main difference between the liquid crystal display device of this embodiment and the liquid crystal display device of embodiment 1 is that the liquid crystal display device of this embodiment has a light source on the observation side closer to the liquid crystal layer 20.

[0157] Fig.18 1 is a cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. The liquid crystal display device 1 according to the present embodiment further includes a light source 62 (also referred to as a front light source) on the observation side of the liquid crystal layer 20. The liquid crystal display device 1 is preferably as follows: Fig.18 The embodiment shown in the figure includes, from the back side to the observation side, a first polarizing plate 51, a first retardation layer 41, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a second retardation layer 42, and a second polarizing plate 52. The first retardation layer 41 preferably includes a first λ / 2 plate 412 and a first λ / 4 plate 411, and the second retardation layer 42 preferably 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 preferably further includes a positive C plate 44. Fig.18 In FIG. 1 , as an example of this embodiment, an example in which the second retardation layer further includes a positive C plate 44 is shown.

[0158] The light source 62 (front light source) is not particularly limited as long as it is a light source that irradiates light. The light source 62 preferably includes a light source such as a light emitting diode (LED) and a light guide plate. The reflective liquid crystal display device 1 also includes the light source 62, so that bright reflective display can be performed even in an environment where the ambient light cannot be fully obtained.

[0159] As mentioned above, although embodiment of this invention was demonstrated, each matter demonstrated is applicable to this invention as a whole.

[0160] Although the present invention is described in more detail below by way of examples, the present invention is not limited to these examples. Hereinafter, as polarizing plates 51 and 52, absorption-type polarizing plates are used. In addition, the applied voltage for white display is set to 5V, and the applied voltage for black display is set to 0V (i.e., no voltage is applied).

[0161] (Test Example 1) Assuming a reflective liquid crystal display device 1 using a positive liquid crystal material, a change in reflective mode efficiency depending on the slit angle was evaluated and analyzed by three-dimensional optical simulation. "Shintech LCD Master 3D" manufactured by SHINTECH was used as simulation software.

[0162] In this test example, a liquid crystal display device 1 is assumed in which a λ / 4 plate 411, a λ / 2 plate 412, and a polarizing plate 51 are provided in order from the liquid crystal panel 1X side on the back side of a reflective liquid crystal panel 1X using a positive liquid crystal material, and a λ / 4 plate 421, a λ / 2 plate 422, and a polarizing plate 52 are provided in order from the liquid crystal panel 1X side on the observation side of the liquid crystal panel 1X. The twist angle θ1 is set to 83°, and the retardation dΔn of the liquid crystal layer 20 is set to 245nm. As the λ / 4 plates 411 and 421, a uniaxial phase difference plate with a retardation Re of 140nm is used, and as the λ / 2 plates 412 and 422, a uniaxial phase difference plate with a retardation Re of 270nm is used, and the wavelength dispersion of these phase difference plates is set to be flat.

[0163] As the liquid crystal panel 1X, a pixel electrode PE and a common electrode CE for applying a voltage to the liquid crystal layer 20 are arranged on the TFT substrate (first substrate) 10 side, and the common electrode CE as the upper electrode (second electrode 122) is set as a slit electrode having a plurality of strip-shaped portions SP and a slit S1 located between two adjacent strip-shaped portions (see Fig. 20 as well as Fig.21 ). The plurality of strip portions SP are composed of straight lines that are substantially parallel to each other and extend in the same direction, and do not include a curved portion. The slit angles of the strip portions SP are set to -10°, -7°, -4°, -2°, 0°, +2°, +4°, +7°, +10°, +12°, +14°, and +16°, respectively. For reference, Fig.21 2 shows an example of a case where the slit angle is 0°. The pixel electrode PE as the lower electrode (first electrode 121) is provided as a full-surface electrode. In addition, a liquid crystal layer of a single domain structure (a liquid crystal layer that performs a normally black display) is assumed.

[0164] The ratio of the width L of a strip portion SP to the width S of a slit S1 (i.e., the L / S condition) is L / S (μm) = 2.2 / 4.1 in Test Example 1-1, L / S (μm) = 1.6 / 3.0 in Test Example 1-2, and L / S (μm) = 3.0 / 5.0 in Test Example 1-3.

[0165] Fig. 20 It is a schematic cross-sectional view of a liquid crystal panel 1X assumed in this example. Fig. 20 In the figure, the film thickness of some layers is written in parentheses after the reference numerals indicating the layers. Fig.21 1 is a schematic diagram conceptually showing the electrode structure of the pixel electrode PE and the common electrode CE when the slit angle is 0°. Fig.21 In FIG. 1 , the orientation of the liquid crystal molecules 21A on the TFT substrate 10 side when no voltage is applied (ie, the initial orientation) is represented by the direction of the positive liquid crystal molecules 21A (p).

[0166] In the actual simulation, in order to simplify the condition setting, the pre-twist angle of the liquid crystal molecule 21 and the axis angle of the optical film are changed instead of changing the slit angle. However, the twist angle θ1 is fixed at 83°. Specifically, the pre-twist angle of the liquid crystal molecule 21 and the axis angle of each optical film are rotated to the same angle as the slit angle, with the axis setting of the optical film as a reference. The optical film refers to the polarizing plates 51, 52 and the phase difference layers 41, 42 (in this case, the λ / 4 plate and the λ / 2 plate). The pre-twist angle of the liquid crystal molecule 21 refers to the initial orientation angle of the liquid crystal molecule 21A on the TFT substrate (first substrate) 10 side relative to the reference. The reference (0°) here is the 12 o'clock direction when looking down at the liquid crystal panel from the observation side.

[0167] The voltage setting was set to 5V or 6V. The average reflection mode efficiency or average transmission mode efficiency of the brightness distribution was calculated for each slit angle. The results are shown in Figure 22 to Figure 24 The reflection mode efficiency and the transmission mode efficiency are obtained by the following formulas respectively. Reflection mode efficiency (%) = (brightness with polarizing plate) / (brightness without polarizing plate) × 100 Transmission mode efficiency (%) = (brightness with polarizing plate) / (brightness without polarizing plate) × 100 The front polarizing plate refers to a polarizing plate (ie, the second polarizing plate 52 ) located on the viewing surface side of the liquid crystal panel 1X.

[0168] Figure 22 to Figure 24 is a graph showing the results of Test Example 1. Specifically, Fig. 22 This is a graph showing the reflection mode efficiency when a voltage of 5 V is applied to the liquid crystal display device of Test Example 1-3. Fig.23 It is a graph showing the reflective mode efficiency when voltage is applied to each liquid crystal display device of Test Example 1-1, Test Example 1-2 and Test Example 1-3. Among them, the upper graph (5V column) is a graph when 5V voltage is applied, and the lower graph (6V column) is a graph when 6V voltage is applied. Fig.24 The graphs are graphs showing the transmission mode efficiency when voltage is applied to each liquid crystal display device of Test Example 1-1, Test Example 1-2, and Test Example 1-3. The upper graph (5V column) is a graph when 5V voltage is applied, and the lower graph (6V column) is a graph when 6V voltage is applied.

[0169] according to Fig. 22 It is known that the reflection mode efficiency tends to decrease as the absolute value of the slit angle increases to greater than 2°. In addition, as described later, when the slit angle is less than 0°, there is a possibility that the alignment may be disturbed.

[0170] However, in the case of the test cell using the VA (Vertical Alignment) method, the reflection mode efficiency is 37.2% (when the applied voltage is 5V), and the transmission mode efficiency is 15.8%. If the efficiency of each mode of the test cell using the VA method is considered, then according to Fig.23 and Fig.24 It can be seen that the spacing of the slit electrodes is preferably less than 6.3 (μm), and the L / S condition is preferably less than 2.2 / 4.1 (i.e., 0.54 / 1). Similarly, if the efficiency of each mode of the VA test unit is considered, then Fig.24 As can be seen from the lower graph (column 6V), the slit angle is particularly preferably not less than 0° and not more than 4°. The pitch of the slit electrodes is the sum of the width of one strip-shaped portion SP and the width of one slit S1, and is obtained by “L+S”.

[0171] (Trial Example 1) Next, the test unit 1000 was prototyped. First, if Fig.25B As shown, the liquid crystal cell 1100 for obtaining the test cell 1000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 disposed between these substrates. Fig.25A 1 is a schematic plan view showing the structure of the liquid crystal cell 1100 when viewed from the front. Fig.25B So Fig.25A The AA line in is a schematic cross-sectional view of the cross section (AA line cross-sectional view).

[0172] like Fig.25B As shown, the first substrate 10 has a glass substrate 100, on which a common electrode CE as a first electrode 121, a dielectric layer 153, a pixel electrode PE as a second electrode 122, and a first horizontal orientation film 140 are sequentially provided. The common electrode CE is formed of ITO, and the thickness of the common electrode CE is 100nm. The dielectric layer 153 is formed of silicon nitride (SiNx), and the thickness of the dielectric layer 153 is 300nm. The pixel electrode PE is formed of ITO, and the thickness of the pixel electrode PE is 100nm. The pixel electrode PE has a plurality of strip portions SP and a plurality of slits Sl. The width L of each strip portion SP is 3μm, and the width S of each slit Sl (the interval between two adjacent strip portions SP) is 5μm. Therefore, the L / S condition is 3 / 5. Each strip portion SP is bent in a "<" shape. That is, each strip-shaped portion SP includes a first portion SPa extending in a certain direction (first direction) and a second portion SPb extending in a direction (second direction) different from the first direction.

[0173] like Fig.25BAs shown, the second substrate 30 includes a glass substrate 300 and a second horizontal alignment film 340 disposed on the glass substrate 300 .

[0174] The thickness (cell gap) of the liquid crystal layer 20 is defined by plastic beads (not shown).

[0175] The alignment treatment of the first horizontal alignment film 140 and the second horizontal alignment film 340 is performed by a photo-alignment treatment or a rubbing treatment.

[0176] When using photo-alignment treatment, a photo-degradable photo-alignment film material is used. The photo-alignment film material is applied by spin coating, and the thickness of the alignment film is set to (i.e. 100nm). The unpolarized UV light emitted from the UV lamp unit is converted into polarized UV light by using a wire grid polarizing element, and the polarized UV light is irradiated on the alignment film, thereby performing a photo-alignment treatment. The extinction ratio of the wire grid polarizing element is 100:1. The wavelength of UV light effective for photo-alignment is 220 to 260nm, and the irradiation energy is 300mJ / cm 2 The orientation direction of the liquid crystal molecules is a direction substantially orthogonal to the transmission axis direction of the polarized UV light (particularly preferably a 90° direction).

[0177] In the case of using friction treatment, a horizontal alignment film is formed, and the friction treatment is performed by a friction roller (for example, a roller wrapped with cloth), thereby performing an alignment treatment. Thus, a uniaxial alignment direction of the liquid crystal molecules is obtained. As an alignment film material suitable for moving the liquid crystal molecules by a transverse electric field, a polyimide-based material is preferred. In addition, a material that does not pre-tilt due to the friction treatment is preferred, and the material is commercially available. The liquid crystal molecules are oriented approximately parallel to the rubbing direction.

[0178] Regarding the liquid crystal cell 1100 having the above structure, first, the retardation of the liquid crystal layer 20 was measured using a polarimeter ("AxoScan" manufactured by Axometrics), and then the cell thickness was measured using a cell gap inspection device (RetQC manufactured by Otsuka Electronics Co., Ltd.).

[0179] Then, if Fig.26A As shown, a λ / 4 plate 421, a positive C plate 44, a λ / 2 plate 422, and a polarizing plate 52 are sequentially attached to the second substrate 30 side of the liquid crystal unit 1100 (the adhesive layer is not shown). Then, during reflection observation, a drop of matching oil mo for reducing the loss caused by interface reflection is dropped on the reflector 130 having a concave-convex surface structure (MRS), and the liquid crystal unit 1100 is placed on the reflector 130 with the first substrate 10 side at the bottom for verification (this is equivalent to the test unit 1000 during reflection observation. Refer to Fig.26A). During transmission observation, the λ / 4 plate 411, the λ / 2 plate 412, and the polarizing plate 51 were sequentially attached to the first substrate 10 side of the liquid crystal unit 1100 and verified (this is equivalent to the test unit 1000 during transmission observation. Refer to Fig.26B ).

[0180] Fig.26A is a schematic cross-sectional view of the test unit 1000 during reflection observation, Fig.26B 1 is a schematic cross-sectional view of the test unit 1000 during transmission observation. In addition, as polarizing plates 51 and 52, "NPF-CRT1794KDUHC3" manufactured by Nitto Denko Corporation was used, as λ / 4 plates 411 and 421, "NZF-UF01A" manufactured by Nitto Denko Corporation (retardation: 140 nm) was used, and as λ / 2 plates 412 and 422, "NZF-UF01A" manufactured by Nitto Denko Corporation (retardation: 270 nm) was used. The axis conditions of each optical film are shown in Table 1.

[0181] The voltage application to the pixel electrode PE and the common electrode CE was performed using a function signal generator ("AFG1022" manufactured by TEKTRONIX) that can apply a voltage of 0V to 10V with a rectangular wave of 30Hz. Unless otherwise specified, the reflectivity was measured using a spectrophotometer ("CM-2600d" manufactured by MINOLTA), and the transmittance was measured using a spectrophotometer ("SR-UL2" manufactured by TOPCON).

[0182] [Table 1]

[0183] In Table 1, the front side optical film refers to the optical film located on the observation side of the liquid crystal panel 1X, and the back side optical film refers to the optical film located on the back side of the liquid crystal panel 1X. The axis angle of each optical film is the angle when viewed from the observation side, and each optical film is observed on the dial of a clock, with the 3 o'clock direction being 0° and the counterclockwise direction being positive.

[0184] (Test Example 2) The slit angle of the first portion SPa and the slit angle of the second portion SPb in the test unit 1000 obtained in the trial production example 1 are set to Fig. 27 The angles described in (Test Examples 2-1 to 2-6) were investigated for the relationship between the orientation of the liquid crystal molecules and the polarization direction. In this example, the twist angle was fixed at +83°.

[0185] Fig. 27 is a graph showing the results of Test Example 2. Fig. 27In the Slit Angle SPa column, the slit angle of the first part SPa is recorded, and the slit angle of the second part SPb is recorded in the Slit Angle SPb column. The "Liquid Crystal Orientation Diagram" is a schematic diagram showing the relationship between the slit angle and the orientation direction of the liquid crystal molecules. In the "Polarization Direction" diagram, the angle marked with the dotted arrow is the polarization direction of the polarized UV light subjected to the photo-orientation treatment in the second substrate 30, and the angle marked with the solid arrow is the polarization direction of the polarized UV light subjected to the photo-orientation treatment in the first substrate 10 (i.e., the TFT substrate including the slit electrode). In addition, the orientation direction of the liquid crystal molecules and the polarization direction are orthogonal to each other.

[0186] In this example, an electrode having a plurality of strip-shaped portions with bent portions is used as a slit electrode (a pixel electrode in this example), and a first portion SPa and a second portion SPb of the slit electrode are studied.

[0187] (Test Example 3) In this case, the mechanism of generating flow orientation disturbance was studied. In Experimental Example 3-1, the test unit obtained in Experimental Example 2-2 was used as the test unit to study the orientation defect. In Experimental Example 3-2, only the portion where the first portion SPa (slit angle was 0°) of the test unit obtained in Experimental Example 2-5 was located was used as the test unit to study the orientation defect.

[0188] Fig.28A , Fig.28B , Fig.28C as well as Fig.29C Schematic diagram showing the research results of Experimental Example 3-1. Fig.28A is a diagram showing the alignment of liquid crystal molecules when no voltage is applied in the test cell. Fig.28B The diagram shows the alignment of liquid crystal molecules when a voltage of 5 V is applied to the test cell. Fig.28C yes Fig.28B FIG. 1 is a cross-sectional view of a portion of the test unit where the first portion SPa is located. Fig.29C yes Fig.28B FIG. 4 is a cross-sectional view of a portion of the test unit where the second portion SPb is located.

[0189] like Fig.28B as well as Fig.28C As shown, if a voltage of 5V is applied to the above-mentioned test unit, in the portion where the first portion SPa is located, since the rotation direction of the liquid crystal molecules 21A on the first substrate 10 side is opposite to the rotation direction of the liquid crystal molecules 21B on the second substrate 30 side, a linear orientation defect De is generated at the boundary portion of the liquid crystal domains with different rotation directions. Fig.28CIn FIG. 1 , c(30) indicates the rotation direction of the liquid crystal molecule 21B on the second substrate 30 side. c(10) indicates the rotation direction of the liquid crystal molecule 21 on the first substrate 10 side. The liquid crystal molecules 21C′ and 21C are liquid crystal molecules located approximately in the middle of the first substrate 10 and the second substrate 30. Fig.28B As shown, a portion where the rotation direction of the liquid crystal molecules is inconsistent occurs in the liquid crystal layer 20 (for example, near X), and an alignment defect (discontinuous point) occurs near the X (see the reference numeral De). For example, an alignment defect may occur immediately after a 5V white voltage is applied (for example, 0.5 seconds after the white voltage is applied). When the portion where the alignment defect occurs is observed using an orthogonal Nicol polarized light transmission microscope (manufactured by Loressods, "BX51"), the alignment defect is visually recognized as a dark line (for example, see the reference numeral De). Fig.30 The orientation defect is a transient defect and is considered to be stabilized after about 1 second from the occurrence of the orientation defect.

[0190] On the other hand, Fig.28B as well as Fig.29C As shown, in the portion where the second portion SPb is located, the rotation direction of the liquid crystal molecules 21A on the first substrate 10 side is consistent with the rotation direction of the liquid crystal molecules 21B on the second substrate 30 side, so no alignment defect occurs.

[0191] Fig.29A , Fig.29B as well as Fig.29C Schematic diagram showing the research results of Experimental Example 3-2. Fig.29A is a diagram showing the alignment of liquid crystal molecules when no voltage is applied in the test cell. Fig.29B The diagram shows the alignment of liquid crystal molecules when a voltage of 5 V is applied to the test cell. Fig.29C yes Fig.29B A cross-sectional view of the test unit shown in FIG.

[0192] like Fig.29B and Fig.29C As shown, in the test cell used in Experimental Example 3-2, the rotation direction of the liquid crystal molecules 21A on the first substrate 10 side and the rotation direction of the liquid crystal molecules 21B on the second substrate 30 side are consistent, so no alignment defect occurs.

[0193] (Test Example 4) Using the test cells obtained in Experimental Examples 2-1 to 2-6, the change in the orientation of the liquid crystal molecules when a voltage of 5 V was applied from a state where no voltage was applied was observed. The observation was performed using an orthogonal Nicol polarizing light transmission microscope (manufactured by Loressage, "BX51"). Fig.31 ] shows an image when a voltage is applied in this example. Fig.31This is a schematic diagram when voltage is applied in this example.

[0194] In this example, electrodes having multiple strip-shaped portions with curved portions are used as slit electrodes (pixel electrodes in this example), and the first portion SPa and the second portion SPb of the slit electrode are studied respectively. Test Examples 4-1 to 4-6 are examples of observing the orientation of liquid crystal molecules by focusing only on the portion where the first portion SPa is located in the test cells used in Test Examples 2-1 to 2-6. Test Examples 4-7 to 4-12 are examples of observing the orientation of liquid crystal molecules by focusing only on the portion where the second portion SPb is located in the test cells used in Test Examples 2-1 to 2-6. The results are shown in Fig.30 middle.

[0195] Fig.30 This is a diagram showing the results of Test Example 4 (see Test Example 4-1 to Test Example 4-12). Fig.30 In the table, “×” means that an orientation defect (also called flow orientation disorder) was visually recognized, and “○” means that an orientation defect was not visually recognized.

[0196] like Fig.30 As shown, in Test Examples 4-1 and 4-2, the alignment disorder occurred in the entire bright pixel with relatively high light transmittance. In Test Examples 4-3 and 4-4, the alignment disorder occurred in the bright pixel with relatively high light transmittance (refer to Fig.30 ). In contrast, in Test Examples 4-5 to 4-12, no alignment disorder was observed. Therefore, it can be seen that the occurrence of alignment defects can be sufficiently suppressed by setting the slit angle to be greater than 0° and less than 16°.

[0197] (Test Example 5) For the test cells obtained in Experimental Example 2-5, the reflection mode efficiency and transmission mode efficiency were evaluated when the voltage was gradually increased from a state where no voltage was applied. The voltage was set to 0 V to 10 V in units of 0.5 V. The results are shown in Fig.32A and Fig.32B middle. Fig.32A and Fig.32B is a graph showing the results of this example. Fig.32A and Fig.32B In the , the data when the VA method test unit is used is also recorded. Fig.33 ] shows an image when a voltage is applied in this example. Fig.33 This is a schematic diagram when voltage is applied in this example.

[0198] (Test Example 6) For the test cell obtained in Experimental Example 2-2, the reflection mode efficiency and transmission mode efficiency were evaluated when the voltage was gradually increased from a state where no voltage was applied. The voltage was set to 0 V to 10 V in units of 0.5 V. The results are shown in Fig.34A and Fig.34B middle. Fig.34A and Fig.34B is a graph showing the results of this example. Fig.34A and Fig.34B The data when using the VA method test unit is also recorded. Fig.33 This is also a schematic diagram when voltage is applied in this example.

[0199] (Test Example 7) The test cell obtained in Test Example 2-2 was evaluated for reflection mode efficiency when the voltage was increased stepwise from a voltage-unapplied state and when the voltage was decreased stepwise from a voltage-applied state of 10 V. The results are shown in Fig.35 middle. Fig.35 is a graph showing the results of this example. Fig.35 The data when using the VA method test unit is also recorded. Fig.36 This is a schematic diagram when voltage is applied in this example.

[0200] according to Fig.35 It can be seen that when the voltage is 5.5V or less during voltage drop, the reflectivity decreases compared to when the voltage is increased. Therefore, it is believed that an orientation defect occurs around 5.5V during voltage drop. Fig.35 In the figure, (a) indicates a voltage increase, and (b) indicates a voltage decrease.

[0201] (Trial Example 2) A test unit 1000 ′ for transmission observation was prepared in the same manner as in Prototype Example 1 except that the positive C plate 44 was not used.

[0202] (Test Example 8) The slit angle of the first portion SPa and the slit angle of the second portion SPb in the test unit 1000' obtained in the trial production example 2 are set to Fig. 27 The angles recorded in (refer to Test Example 2). The torsion angle is fixed at +83°. Using each test unit obtained in this way, the relationship between the slit angle and the response time is evaluated. The results are shown in Fig.37 and Fig.38 middle.

[0203] Fig.37 and Fig.38 is a graph showing the results of Test Example 8. Fig.37This is a graph evaluating the response time of the rising edge when a voltage of 5V is applied from a state where no voltage is applied (0V→5V). Fig.38 This is a graph for evaluating the response time of the falling edge when the voltage is changed from the state of 5V application to the state of no voltage application (5V→0V). Fig.37 as well as Fig.38 The data when the VA test unit was used is also recorded in the table. When the VA test unit was used, the response time of the rising edge was 15.3 milliseconds (ms), and the response time of the falling edge was 6.5 milliseconds (ms).

[0204] In this example, for the convenience of the experiment, multiple strip-shaped electrodes with curved portions are used as slit electrodes (pixel electrodes in this example), so each test unit has a first portion SPa and a second portion SPb with different slit angles. Fig.37 and Fig.38 The response time plotted in becomes the average value of the response time of the liquid crystal in the first portion SPa and the response time of the liquid crystal in the second portion SPb.

[0205] In this example, the response time (milliseconds) is obtained by correcting the response time normalized when the luminance ratio changes from 0.1 to 0.9 in the response waveform using the reference liquid crystal retardation dΔn (245 nm).

[0206] Fig.37 It can be seen that the response time of the rising edge becomes less than about 15 milliseconds (ms) when the slit angle is above -2°, that is, it tends to be saturated above -2°. Fig.37 In the figure, orientation disorder occurs in the ranges of (a) and (b), but no orientation disorder occurs in the range of (c).

[0207] Depend on Fig.38 It can be seen that the response time of the falling edge is less than about 20 milliseconds (ms) in the range of the slit angle being greater than -4°, that is, there is a saturation tendency above -4°.

[0208] (Test Example 9) The VA-type test cell used in Test Examples 5 to 8 and the like is a test cell 2000 produced as follows. like Fig.39B As shown, the liquid crystal cell 2100 for obtaining the test cell 2000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 disposed between these substrates. Fig.39A 1 is a schematic plan view showing the structure of the test cell 2000 (and the liquid crystal cell 2100 ) when viewed from the front. Fig.39B So Fig.39A The AA line in the figure is a schematic cross-sectional view of the cross section (AA line cross-sectional view).

[0209] The first substrate 10 includes a glass substrate 100, on which a pixel electrode PE and a first vertical alignment film (not shown) are sequentially arranged. The second substrate 30 includes a glass substrate 300, on which a common electrode CE and a second vertical alignment film (not shown) are sequentially arranged. Only the second vertical alignment film arranged on the observation surface side of the vertical alignment film is subjected to a photo-alignment treatment. In addition, the alignment azimuth of the liquid crystal molecules 21 specified by the first vertical alignment film is in the 90° direction (pretilt angle is 88.4°).

[0210] like Fig.40 As shown, a λ / 4 plate 41, a first λ / 2 plate 42a, a second λ / 2 plate 42b, and a polarizing plate 50 are sequentially attached to the second substrate 30 side of the liquid crystal cell 2100 (the adhesive layer is not shown). As the polarizing plate 50, "NPF-CRT1794KDUHC3" manufactured by Nitto Denko Corporation is used, as the λ / 4 plate 41, "NZF-UF01A" (retardation: 110nm) manufactured by Nitto Denko Corporation is used, and as the λ / 2 plates 42a and 42b, "NZF-UF01A" (retardation: 260nm) manufactured by Nitto Denko Corporation is used. Then, a drop of matching oil mo is dropped on the reflector 130 having MRS, and the liquid crystal cell 2100 is placed on the reflector 130 with the first substrate 10 side facing downward. In this way, the test cell 2000 is manufactured. Fig.40 is a cross-sectional schematic diagram of the test unit 2000.

[0211] The test unit 2000 is a structure using a liquid crystal material with negative dielectric anisotropy, and the display mode is VA mode. Fig.41 The optical axis settings (initial settings) and specifications are shown in . Fig.41 It is a diagram conceptually showing the optical axis setting of Test Example 9. In Table 2, CH (Chirality) refers to the twist angle of the liquid crystal molecules 21 between the upper and lower substrates (that is, between the first substrate 10 and the second substrate 30).

[0212] [Table 2]

[0213] The reflection mode efficiency of the test unit 2000 was evaluated when the voltage was gradually increased from the state where no voltage was applied. The voltage was set to 0V to 10V in units of 0.5V. The results are shown in Fig.42 middle. Fig.42 is a graph showing the results of this example.

[0214] according to Fig.42The reflection mode efficiency when no voltage is applied is 0.8%, and the reflection mode efficiency when voltage is applied is 37.2%. The contrast ratio (5V / 0V) obtained as their ratio is 48. Since the VA liquid crystal display device uses a longitudinal electric field, it is difficult to form an In-cell touch panel.

[0215] The various aspects of the present invention described above can be appropriately combined within the scope not departing from the gist of the present invention. Description of Reference Numerals

[0216] 1: Liquid crystal display device 1X: LCD panel 10, 30: substrate 20: Liquid crystal layer 21, 21A, 21B, 21C, 21C': Liquid crystal molecules 40: Phase difference layer 41: λ / 4 plate 42, 42a, 42b: λ / 2 plate 41SA, 42SA: In-plane slow axis 50, 51, 52: Polarizing plate 50AA: Polarization axis 61, 62: Light source 100, 300: Support substrate 121, 122: Electrode 130: Reflection layer 140, 340: Horizontal alignment film 150G: Gate insulating film 151, 152: interlayer insulation layer 153: dielectric layer 160: contact electrode 310: color filter layer BP: backplane circuit CE: Common Electrode PE: pixel electrode CH1, CH2: contact hole De: orientation defect DR: Display Region FR: Non-display area GL: Gate wiring SL: Source wiring p: convex part P: Pixel Rf: Reflection area Tr: Transmission area Sl: Slit SP: Strip SPa: Part I SPb: Part II TC: Touch wiring contact TD: Touch drive TL, TL1, TL2: Touch wiring TX: Touch sensor electrode.

Claims

1. A liquid crystal display device having a plurality of pixels, wherein the liquid crystal display device comprises: a first substrate; a second substrate, which is opposite to the first substrate; as well as a liquid crystal layer disposed between the first substrate and the second substrate, The first substrate comprises: a reflective layer for reflecting light; a first electrode and a second electrode, wherein the first electrode and the second electrode are capable of generating a lateral electric field in the liquid crystal layer; and a first horizontal alignment film, which 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 among the plurality of strip-shaped portions, In each pixel, the plurality of strip-shaped portions are composed of straight lines that are substantially parallel to each other and extend in the same direction and do not include a bent portion. The second substrate has a second horizontal alignment film in contact with the liquid crystal layer. The liquid crystal layer includes liquid crystal molecules having a positive dielectric anisotropy and taking a twisted orientation when no voltage is applied. When the direction in which the plurality of strip-shaped portions extend is defined as 0° as a reference, the alignment direction of the liquid crystal molecules on the first substrate side when no voltage is applied is greater than or equal to 0° and less than or equal to 16°.

2. The liquid crystal display device according to claim 1, wherein: The plurality of strip-shaped portions do not include a notch portion.

3. The liquid crystal display device according to claim 1, wherein: The directions in which the plurality of strip-shaped portions extend are the same at least in adjacent pixels or in a display area.

4. The liquid crystal display device according to claim 1, wherein: The invention comprises, in order from the back side, 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. The first phase difference layer includes a first λ / 2 plate and a first λ / 4 plate. The second phase difference layer includes a second λ / 2 plate and a second λ / 4 plate. At least one of the first retardation layer and the second retardation layer further includes a positive C plate.

5. The liquid crystal display device according to claim 4, characterized in that: The second phase difference layer includes a positive C plate. The first phase difference layer does not include a positive C plate, or the first phase difference layer includes two positive C plates.

6. The liquid crystal display device according to claim 4 or 5, characterized in that: The first λ / 2 plate and the first λ / 4 plate are arranged in this order from the back side, The second λ / 2 plate and the second λ / 4 plate are arranged in this order from the observation surface side, The in-plane phase difference Re of the first λ / 2 plate and the second λ / 2 plate is substantially the same, The in-plane phase difference Re of the first λ / 4 plate and the second λ / 4 plate are substantially the same.

7. The liquid crystal display device according to claim 4 or 5, characterized in that: 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.

8. The liquid crystal display device according to claim 1, wherein: The twist angle of the liquid crystal layer when no voltage is applied is greater than or equal to 58.3° and less than or equal to 89.9°.

9. The liquid crystal display device according to claim 1, characterized in that: A ratio L / S of a width L of each of the plurality of strip-shaped portions in a plan view to a width S of each of the slits in a plan view is 0.4 to 0.7 / 1.

10. The liquid crystal display device according to claim 1, characterized in that: Obtain a single domain orientation.

11. The liquid crystal display device according to claim 1, characterized in that: Display in normally black mode.

12. The liquid crystal display device according to claim 1, characterized in that: One of the first electrode and the second electrode is a pixel electrode provided in each of the plurality of pixels, and the other is a common electrode including a plurality of segments capable of functioning as touch sensor electrodes, respectively. The first substrate has a plurality of touch wirings, and the plurality of touch wirings are respectively connected to corresponding touch sensor electrodes.

13. The liquid crystal display device according to claim 1, characterized in that: It also has a light source.

14. The liquid crystal display device according to claim 1, 2, 3, 4, 5, 8, 9, 10, 11, 12 or 13, characterized in that: Each pixel has a reflective region and a transmissive region. The reflective region reflects light through the reflective layer to perform display, and the transmissive region transmits light to perform display.

Images