Liquid crystal display device

Abstract

Provided is a liquid crystal display device which can be used as an in-cell touch panel capable of display in a reflective mode, while being low-cost and capable of improving contrast and angle of view. A liquid crystal display device provided with a first substrate, a liquid crystal layer, a second substrate, a phase difference layer, and a polarizing plate in this order from the rear surface side, the liquid crystal display device having a plurality of pixels arranged in a matrix, the first substrate having: a reflective layer that reflects light; a first electrode and a second electrode capable of generating a transverse electric field in the liquid crystal layer; and a first horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer exhibiting torsional alignment when a voltage is not applied, and the retardation layer including a [lambda] / 4 plate, a [lambda] / 2 plate, and a positive C plate.

Description

Technical Field

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

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

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

[0004] Patent Document 1: Japanese Patent No. 5767195 Summary of the invention Technical Problems to be Solved by the Invention

[0005] However, in recent years, touch sensor functions are generally given 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 narrowing the frame, thinning, and lightening, etc., and improving the transmittance of light than the external touch panel.

[0006] Among the built-in touch panels, there are "on-cell" and "in-cell". 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 on-cell type, a layer that performs the touch sensor function is arranged in the display panel, and in the off-cell type, the layer that performs the touch sensor function is arranged between the display panel and a polarizer arranged on the viewing side of the display panel. Among them, the on-cell type can realize the thinnest and lightest touch panel in principle. In addition, liquid crystal display devices that can display in reflective mode are suitable for outdoor use. Therefore, although an on-cell touch panel that can display in reflective mode is sought, it has not yet been realized.

[0007] The reason why this cannot be achieved is that in the current reflective liquid crystal display device, one of a pair of electrodes for applying voltage to the liquid crystal layer (also called a counter electrode or a common electrode) is arranged on the opposite substrate side. Therefore, the inventors believe that if it is a transverse electric field mode such as the FFS mode, both sides of a pair of electrodes are only provided on the active matrix substrate side, so that an embedded touch panel capable of displaying a reflective mode can be realized. As a result of further research, it was found that even if the existing transverse electric field mode is simply adopted in a reflective liquid crystal display device, the reflectivity is low. For example, the reflectivity is about 60% when the VA mode, which is a type of longitudinal electric field mode, is adopted. If the reflectivity is so low, the contrast becomes small, so it is considered unacceptable for practical use as an embedded touch panel.

[0008] Here, in-depth research is conducted, and as a result, the inventor of the present invention has found a liquid crystal display device, which has a first substrate, a liquid crystal layer, a second substrate, a phase difference layer and a polarizing plate in sequence from the back side, and has a plurality of pixels arranged in a matrix, the first substrate having a reflective layer for reflecting light, a first electrode and a second electrode capable of generating a lateral electric field in the above-mentioned liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer, the second substrate having a second horizontal alignment film in contact with the liquid crystal layer, and the liquid crystal layer is set to obtain a twisted orientation when no voltage is applied. When the liquid crystal layer is configured, it is a liquid crystal display device of a lateral electric field mode, and the contrast ratio can be improved, and it is useful as an embedded touch panel that can display a reflective mode. However, in this device, since a special phase difference plate is preferably used as a phase difference layer, it is found that there is a new problem of increased cost. On the other hand, if a general phase difference plate is used, it is also found that there are problems in physical properties such as field angle and contrast (for example, refer to Test Example 2 described later). In addition, in order to seek cost reduction in the field of optical films, it is considered to use a film with a large circulation production volume, reduce material loss, and improve productivity.

[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 is low-cost, can improve the contrast ratio and the viewing angle, and is also useful as an in-cell touch panel capable of displaying in a reflective mode. Technical solutions for solving technical problems

[0010] (1) A liquid crystal display device according to one embodiment of the present invention comprises, from the back side, a first substrate, a liquid crystal layer, a second substrate, a phase difference layer and a polarizing plate, the liquid crystal display device having a plurality of pixels arranged in a matrix, the first substrate comprising: a reflective layer that reflects light; a first electrode and a second electrode that can generate a transverse electric field in the liquid crystal layer; and a first horizontal orientation film that is in contact with the liquid crystal layer, the second substrate comprising a second horizontal orientation film that is in contact with the liquid crystal layer, the liquid crystal layer exhibits a twisted orientation when no voltage is applied, and the phase difference layer comprises a λ / 4 plate, a λ / 2 plate and a positive C plate.

[0011] (2) In one embodiment of the present invention, in addition to the configuration of (1), the liquid crystal layer includes a positive liquid crystal material or a negative liquid crystal material.

[0012] (3) In addition, in a certain embodiment of the present invention, based on the construction of (2), when the liquid crystal layer includes the positive liquid crystal material, the angle formed by the polarization axis of the polarizing plate and the orientation direction of the liquid crystal molecules specified by the first horizontal orientation film is greater than 63.5° and less than 71.5°, and when the liquid crystal layer includes the negative liquid crystal material, the angle formed by the polarization axis of the polarizing plate and the orientation direction of the liquid crystal molecules specified by the first horizontal orientation film is greater than 20.5° and less than 26°.

[0013] (4) In addition, in one embodiment of the present invention, in a liquid crystal display device according to the configuration of (1), (2) or (3), the positive C plate is located between the λ / 4 plate and the λ / 2 plate.

[0014] (5) In addition, in a certain embodiment of the present invention, the liquid crystal display device is based on the structure of the above (1), the above (2), the above (3) or the above (4), and the absolute value of the thickness direction phase difference Rth (nm) of the positive C plate is 150 to 270nm.

[0015] (6) In addition, a liquid crystal display device according to a certain embodiment of the present invention is based on the structure of (1), (2), (3), (4) or (5), wherein the phase difference layer further includes a second positive C plate, and the second positive C plate is located between the λ / 2 plate and the polarizing plate.

[0016] (7) In a liquid crystal display device according to an embodiment of the present invention, in addition to the configuration of (6) above, the absolute value of the thickness direction phase difference Rth (nm) of the second positive C plate is 50 to 130 nm.

[0017] (8) In addition, a liquid crystal display device according to a certain embodiment of the present invention is based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5), the above (6) or the above (7), and the twist angle of the liquid crystal layer when no voltage is applied is greater than 70° and less than 85°.

[0018] (9) In addition, a liquid crystal display device according to a certain embodiment of the present invention is 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) or the above (8), and when the liquid crystal layer contains the positive liquid crystal material, the product dΔn of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal material is greater than 218nm and less than 255nm.

[0019] (10) In addition, a liquid crystal display device according to a certain embodiment of the present invention is 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), and when the liquid crystal layer contains the positive liquid crystal material, the angle formed by the in-plane slow axis of the λ / 2 plate and the orientation direction of the liquid crystal material specified by the first horizontal orientation film is greater than 47.5° and less than 52.5°.

[0020] (11) In addition, a liquid crystal display device according to a certain embodiment of the present invention is 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), the above (9) or the above (10), and when the liquid crystal layer contains the negative liquid crystal material, the product dΔn of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal material is greater than 230nm and less than 260nm.

[0021] (12) In addition, a liquid crystal display device according to a certain embodiment of the present invention is 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), the above (9), the above (10) or the above (11), and when the liquid crystal layer contains the negative liquid crystal material, the angle formed by the in-plane slow axis of the λ / 2 plate and the orientation direction of the liquid crystal material specified by the first horizontal orientation film is greater than 38.5° and less than 42.5°.

[0022] (13) 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) or (12), at least one of the first electrode and the second electrode has a plurality of strip-shaped portions and a slit between two adjacent strip-shaped portions among the plurality of strip-shaped portions.

[0023] (14) In addition, a liquid crystal display device according to a certain embodiment of the present invention is 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), the above (9), the above (10), the above (11), the above (12) or the above (13), and the liquid crystal display device is single-domain oriented.

[0024] (15) 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 configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13) or (14).

[0025] (16) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the configuration of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14) or (15), one of the first electrode and the second electrode is a pixel electrode provided in each of the plurality of pixels, the other of the first electrode or 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.

[0026] (17) 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), (13), (14), (15) or (16), the first substrate has a thin film transistor, the thin film transistor is arranged in each of the multiple pixels and contains an oxide semiconductor layer, and the oxide semiconductor layer contains an In-Ga-Zn-O based semiconductor.

[0027] (18) 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), (12), (13), (14), (15), (16) or (17). Beneficial Effects

[0028] According to the present invention, it is possible to provide a liquid crystal display device which is low-cost, can improve contrast and viewing angle, and is also useful as an in-cell touch panel capable of displaying in a reflective mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic cross-sectional view of the liquid crystal display device 1 . Figure 2 It is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. Figure 3 It is a schematic plan view of the entire liquid crystal display device 1 as viewed from the observation surface side. Figure 4 This is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 and the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42, and the polarization axis 50AA of the polarization plate 50 when no voltage is applied, in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 4 plate 41, a λ / 2 plate 42, and a polarization plate 50. Figure 5A It is a schematic plan view of the first substrate 10 as viewed from the first horizontal alignment film 140 side. Figure 5B It is a schematic plan view of the second substrate 30 as viewed from the second horizontal alignment film 340 side. Figure 5C This is a schematic plan view of the liquid crystal panel 1X after the first substrate 10 and the second substrate 30 are bonded together, as seen from the second substrate 30 side. Figure 6 This is a diagram conceptually showing the setting of the optical axis at which the black reflectance is the minimum. This is also a diagram conceptually showing the setting of the optical axis in Example 1. Figure 7 It is a graph showing the evaluation results of black brightness. Figure 8 It is a graph showing the evaluation results of contrast. Fig. 9This is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 and the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42, and the polarization axis 50AA of the polarization plate 50 when no voltage is applied, in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 4 plate 41, a λ / 2 plate 42, and a polarization plate 50. Fig. 10A It is a schematic plan view of the first substrate 10 as viewed from the first horizontal alignment film 140 side. Fig. 10B It is a schematic plan view of the second substrate 30 as viewed from the second horizontal alignment film 340 side. Fig. 10C This is a schematic plan view of the liquid crystal panel 1X after the first substrate 10 and the second substrate 30 are bonded together, as seen from the second substrate 30 side. Fig.11 This is a diagram conceptually showing the setting of the optical axis at which the black reflectance is the minimum. This is also a diagram conceptually showing the setting of the optical axis in Example 3. Fig. 12A 1 is a diagram showing simulation results in the case where the liquid crystal material is a positive type. Fig. 12B 1 is a diagram showing simulation results in the case where the liquid crystal material is a positive type. Fig.13 It is a figure which shows the simulation result about Example 1 and Example 3. Fig.14 This is a graph showing the distribution of the maximum value of black brightness in Examples 1 to 4. Fig.15 It is a diagram showing simulation results in the case where the liquid crystal material is a negative type. Fig.16 This is a graph showing the distribution of the maximum value of black brightness in Examples 11 to 14. Fig.17 1 is a schematic plan view illustrating an arrangement relationship between the touch sensor electrodes TX and the touch wirings TL included in the liquid crystal display device 1 . Fig.18 It is a schematic cross-sectional view showing the liquid crystal display device 1 in more detail. Fig.19 is a schematic cross-sectional view of the liquid crystal display device 1 . Fig. 20 It is a diagram showing simulation results when the liquid crystal material is a positive type. Fig.21 This is a graph showing the distribution of the maximum value of black brightness for Examples 21 to 23. Fig. 22 It is a diagram showing simulation results in the case where the liquid crystal material is a negative type. Fig.23 This is a graph showing the distribution of the maximum value of black brightness for Examples 31 to 33. Fig.24 is a schematic cross-sectional view of the liquid crystal display device 1 . Fig.25 1 is a schematic plan view conceptually showing that each pixel P in the liquid crystal display device 1 has a reflective region Rf and a transmissive region Tr. Fig.26 is a schematic cross-sectional view of a liquid crystal display device. Fig.27A 1 is a schematic plan view showing the structure of the liquid crystal cell 1100 when viewed from the front. Fig.27B Yes Fig.27A The A-A' line in the figure is used as a cross-sectional schematic diagram of the cross section (A-A' line cross-sectional diagram). Fig.28 is a cross-sectional schematic diagram of the test unit 1000 . Fig.29A 1 is a schematic plan view showing the structure of the test cell 3000 (and the liquid crystal cell 3000 ) when viewed from the front. Fig.29B Yes Fig.29A The A-A' line in the figure is used as a cross-sectional schematic diagram of the cross section (A-A' line cross-sectional diagram). Fig.30 is a schematic cross-sectional view of the test unit 3000 . Fig.31 This is a diagram conceptually showing the setting of the optical axis in Test Example 5. Fig.32A It is a figure which shows the result of test examples 1 and 2. Fig.32B It is a figure which shows the result of the test examples 3 and 4. Fig.32C It is a graph showing the results of Test Example 5. Fig.33A It is a figure which shows the result of test examples 1 and 2. Fig.33B It is a figure which shows the result of the test examples 3 and 4. Fig.33C It is a graph showing the results of Test Example 5. Fig.34 This is a diagram conceptually showing the azimuth angle. Fig.35 This is an image taken from the front. Fig.36A It is a figure which shows the result of test examples 1 and 2. Fig.36B It is a figure which shows the result of the test examples 3 and 4. Fig.36C It is a graph showing the results of Test Example 5. DETAILED DESCRIPTION

[0030] (Definition of terms) In this specification, the observer side refers to the side closer to the screen (display surface) of the liquid crystal display device, and the rear side refers to the side farther from the screen (display surface) of the liquid crystal display device.

[0031] The state of no voltage application refers to a state in which the voltage applied to the liquid crystal layer is less than the threshold voltage (including no voltage application). The state of voltage application refers to a state in which the voltage applied to the liquid crystal layer is greater than the threshold voltage. In this specification, the state of no voltage application refers to the state in which the voltage is not applied, and the state of voltage application refers to the state in which the voltage is applied.

[0032] The polar angle refers to the angle between the direction of the object (such as the measurement direction) and the normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction when the direction of the object is projected onto the screen of the liquid crystal panel, and is expressed by the angle (azimuth) formed with the reference azimuth. Here, the reference azimuth (0°) is set to the horizontal right direction of the screen of the liquid crystal panel. Angles and azimuths are 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 observing the screen of the liquid crystal panel from the observation side (front). In addition, the angle represents the value measured in the state of looking down at the screen of the liquid crystal panel, and unless there is an explanation of the rotation direction, etc., it means the angle of the acute angle.

[0033] The axis orientation of an optical film refers to the orientation of the polarization axis of the polarizer if it is a polarizer, and refers to the orientation of the slow axis if it is a phase difference layer. The polarization axis of the polarizer refers to the absorption axis if it is an absorption-type polarizer, and refers to the reflection axis if it is a reflection-type polarizer. Unless otherwise specified, the axis orientation of the phase difference layer means the orientation of the slow axis in the plane of the phase difference layer.

[0034] 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 has a value of 20nm or more. In addition, in this specification, the numerical values ​​recorded as Re and Rth are absolute values ​​unless otherwise specified.

[0035] The in-plane phase difference Re is defined by Re=(nx-ny)×d. The thickness direction retardation Rth is defined by Rth={nz-(nx+ny) / 2}×d. nx represents the principal refractive index in the slow axis direction in the plane of each retardation layer. ny represents the principal refractive index in the in-plane fast axis direction of each retardation layer. nz represents the principal refractive index in the direction perpendicular to each retardation layer. The slow axis direction refers to the azimuth with the maximum refractive index, and the fast axis direction refers to the azimuth with the minimum refractive index. d represents the thickness of the retardation layer.

[0036] The A plate is a retardation plate that satisfies "nx > ny ≒ nz". Among C plates, the positive C plate (also called +C-plate) is a retardation plate that satisfies "nz > nx ≒ ny", and Rth represents a positive value. The negative C plate (also called -C-plate) is a retardation plate that satisfies "nz < nx ≒ ny", and Rth represents a negative value.

[0037] Unless otherwise specified, the measurement wavelength of optical parameters such as the principal refractive index and retardation is 550 nm.

[0038] Substantially parallel means that the angle (absolute value) formed by the two is in the range of 0° ± 10°, preferably in the range of 0° ± 5°, and more preferably 0° (i.e., strictly parallel). In addition, substantially orthogonal (or substantially perpendicular) means that the angle (absolute value) formed by the two is in the range of 90° ± 10°, preferably in the range of 90° ± 5°, and more preferably 90° (i.e., strictly orthogonal or perpendicular).

[0039] 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 content described in the following embodiments, and design changes can be appropriately made within the scope that satisfies the configuration of the present invention.

[0040] (Embodiment 1) Figure 1 is a schematic cross-sectional view of a liquid crystal display device 1 which is an example of this embodiment, Figure 2 is a more specific schematic cross-sectional view of a liquid crystal display device 1 which is an example of this embodiment. Figure 3 is a top view schematic when observing the whole of a liquid crystal display device 1 which is an example of this embodiment from the observation surface side. As Figure 1 shown, the liquid crystal display device 1 sequentially includes a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40, and a polarizing plate 50 from the back side. The retardation layer 40 includes a positive C plate 43 in addition to a λ / 4 plate 41 and a λ / 2 plate 42. In this embodiment, a TFT substrate is used as the first substrate 10. In addition, a part or structure formed by a structure that sandwiches the liquid crystal layer 20 between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0041] As Figure 3As shown, the liquid crystal display device 1 has a plurality of pixels P arranged in a matrix. The plurality of pixels P typically include three types of pixels, namely, red pixels, green pixels, and blue pixels, but the types of pixels may be two or less, or four or more. Each pixel P includes a thin film transistor (TFT) 110 and a first electrode 121 and a second electrode 122 capable of generating a lateral electric field in the liquid crystal layer 20. The gate electrode of the TFT 110 is electrically connected to 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.

[0042] <First Substrate> like Figure 2 As shown, the first substrate 10 has a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 that contacts the liquid crystal layer 20 in order from the back side to the observation side. The first substrate 10 preferably has a supporting substrate 100 and a bottom board circuit BP on the back side of the reflective layer 130. An insulating layer (also referred to as an insulating film) is provided between each layer as required. For example, a first interlayer insulating layer 151 is provided in a manner covering the bottom board circuit BP, a second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 with the reflective layer 130 interposed therebetween, and a dielectric layer (also referred to as a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

[0043] The supporting substrate 100 is preferably transparent and insulating, and examples of the supporting substrate 100 include a glass substrate and a plastic substrate.

[0044] The backplane circuit BP is provided on the support substrate 100. The backplane circuit BP is a circuit for driving a plurality of pixels P, and includes a TFT 110, a gate wiring GL, a source wiring SL, etc. In addition, it also generally includes a gate insulating film.

[0045] 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 that require a large area.

[0046] Oxide semiconductor TFTs have excellent off-leak characteristics, so they can also be used to reduce the frequency of image rewriting for display. For example, when displaying static images, the image data can be rewritten once per second. This driving method is called pause driving or low-frequency driving, and can significantly reduce the power consumption of liquid crystal display devices. By adopting pause driving, touch detection is performed during the period when the image is not rewritten, which can suppress the reduction in sensitivity of touch operations caused by noise from the drive circuit, and can make the S / N ratio (signal-to-noise ratio) about 10 times the existing one.

[0047] Oxide semiconductor TFTs are also advantageous in miniaturizing 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.

[0048] The oxide semiconductor may be an amorphous oxide semiconductor or a crystalline oxide semiconductor having a crystalline portion. Examples of the crystalline oxide semiconductor include polycrystalline oxide semiconductors, microcrystalline oxide semiconductors, and crystalline oxide semiconductors whose c-axis is oriented substantially perpendicular to the layer.

[0049] 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 with different crystal structures, or may include multiple amorphous oxide semiconductor layers. In the case where the oxide semiconductor layer has a two-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.

[0050] The materials, structures, film forming methods, and the composition of the oxide semiconductor layer having a stacked structure of the amorphous oxide semiconductor and each crystalline oxide semiconductor are described in, for example, Japanese Patent Laid-Open No. 2014-007399. For reference, the entire disclosure of Japanese Patent Laid-Open No. 2014-007399 is cited in this specification.

[0051] Specifically, the oxide semiconductor layer preferably contains at least one metal element selected from In (indium), Ga (gallium) and Zn (zinc). Among them, an oxide semiconductor film containing a ternary oxide of In, Ga and Zn is more 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, and examples thereof include In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, In:Ga:Zn=1:1:2, etc.

[0052] The In-Ga-Zn-O semiconductor may be amorphous or crystalline. As a crystalline In-Ga-Zn-O semiconductor, a crystalline In-Ga-Zn-O semiconductor whose c-axis is oriented substantially perpendicular to the layer is preferably used.

[0053] The crystal structure of the crystalline In-Ga-Zn-O semiconductor is disclosed in, for example, the above-mentioned Japanese Patent Publication No. 2014-0073 99, Japanese Patent Publication No. 2012-134475, and Japanese Patent Publication No. 2014-209727. For reference, the entire disclosure of Japanese Patent Publication No. 2012-134475 and Japanese Patent Publication No. 2014-209727 is cited in this specification. A TFT having a semiconductor layer of the In-Ga-Zn-O system has high mobility (more than 20 times that of an a-Si TFT) and low leakage current (less than one percent of that of an a-Si TFT), and is therefore preferably used as a driving TFT (for example, a TFT present in a driving circuit, which is provided in the periphery of a display region including a plurality of pixels and on the same substrate as the display region) and a pixel TFT (a TFT provided in a pixel).

[0054] 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 based semiconductors, In-Al-Sn-Zn-O based semiconductors, Zn-O based semiconductors, In-Zn-O based semiconductors, Zn-Ti-O based semiconductors, Cd-Ge-O based semiconductors, Cd-Pb-O based semiconductors, CdO (cadmium oxide), Mg-Zn-O based semiconductors, In-Ga-Sn-O based semiconductors, In-Ga-O based semiconductors, Zr-In-Zn-O based semiconductors, Hf-In-Zn-O based semiconductors, Al-Ga-Zn-O based semiconductors, Ga-Zn-O based semiconductors, In-Ga-Zn-Sn-O based semiconductors, etc.

[0055] The first interlayer insulating layer 151 is provided to cover the backplane circuit BP. It is preferred that the surface of the first interlayer insulating layer 151 on the side of the reflective layer 130 has a concavo-convex shape (also referred to as a concavo-convex surface structure). Thus, the reflective layer 130 can have a concavo-convex surface structure reflecting the shape. The first interlayer insulating layer 151 having a concavo-convex surface structure can be formed using a photosensitive resin as described in Japanese Patent Gazette No. 3394926, for example.

[0056] 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 or an aluminum alloy can be used.

[0057] The reflective layer 130 has a concavo-convex shape reflecting the concavo-convex surface structure of the first interlayer insulating layer 151. That is, the reflective layer 130 also preferably has a concavo-convex surface structure. The concavo-convex surface structure is also called MRS (Micro Reflective Structure), which is provided to diffusely reflect ambient light to achieve a display close to paper white. The concavo-convex surface structure can be composed of a plurality of convex portions p randomly arranged in such a way 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.

[0058] 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.

[0059] Here, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably formed of an organic insulating material or an inorganic insulating material. For example, as an organic insulating film obtained using an organic insulating material, organic films such as acrylic resin, polyimide resin, and phenolic varnish resin (dielectric constant ε = 2 to 5), and their stacked bodies can be cited. The film thickness of the organic insulating film is not particularly limited, and for example, it is greater than and less than 2 μm. 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 to 7), and their stacked films can be cited. The thickness of each insulating film is not particularly limited, and for example, it is preferably Above and In addition, it may be a stack of organic layers and inorganic layers. The first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably formed of an organic insulating material.

[0060] In addition, 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 be in a form with low transmittance or may be opaque. From the viewpoint of light utilization efficiency, the second interlayer insulating layer 152 may be in a form with high transparency or may be formed of a material with high transmittance different from that of the first interlayer insulating layer 151.

[0061] The first electrode 121 is arranged on the reflective layer 130 via the second interlayer insulating layer 152, and a dielectric layer 153 is arranged between the first electrode 121 and the second electrode 122. Therefore, the reflective layer 130 is located on the side opposite to the liquid crystal layer 20 (i.e., the back side of the first electrode 121 and the second electrode 122) relative to the first electrode 121 and the second electrode 122. It should be noted that, of the first electrode 121 and the second electrode 122, in this embodiment, the second electrode 122 is relatively located on the observation side, and the first electrode 121 is located on the back side. The electrode relatively located on the observation side is also referred to as the upper electrode, and the electrode relatively located on the back side is also referred to as the lower electrode.

[0062] 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 electrodes are 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.

[0063] Preferably, at least one of the first electrode 121 and the second electrode 122 has a plurality of strip-shaped portions SP and a slit S1 located between two adjacent strip-shaped portions among the plurality of strip-shaped portions. The strip-shaped portion SP is equivalent to the electrode portion, and the slit S1 is equivalent to the opening portion. Such an electrode is also called a slit electrode or a finger electrode. From the perspective of facilitating the generation of a transverse electric field, it is preferred that at least the upper electrode (the pixel electrode PE in this embodiment) is a slit electrode. In this case, the lower electrode (the common electrode CE in this embodiment) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode.

[0064] The multiple strips SP constituting the slit electrode preferably extend in directions substantially parallel to each other. In addition, they are preferably in a straight line shape extending in the same direction. The so-called straight line shape means that the center line of the strip SP is a straight line shape instead of the outer edge of the strip SP, and the so-called center line of the strip SP refers to a line that divides the strip SP into two equal parts in the width direction. The width direction refers to a direction substantially perpendicular to the direction in which the strip SP extends when viewed from above. In addition, the strip SP may have a curved portion (also called a kink portion) in the middle (for example, at the end), but it is preferred that there is no curved portion.

[0065] The extending directions of the plurality of strip-shaped portions SP may be different for each pixel, but are preferably the same in two or more adjacent pixels. However, from the viewpoint of maximizing display performance, it is most preferable that all pixels are the same.

[0066] In addition, in a plan view, the angle formed by the orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 and the direction in which the plurality of strip-shaped portions SP extend (this angle is also referred to as a finger angle) may be 0° or may be greater than 0° and less than 30°. The finger angle of 0° means that the orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 is substantially parallel to the direction in which the plurality of strip-shaped portions SP extend. In addition, it is preferable to study the finger angle in consideration of the twist angle described later.

[0067] 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 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.

[0068] However, in the present embodiment, the structure in which the pixel electrode PE is disposed above the common electrode CE is described, but in a relatively large liquid crystal display device, that is, a liquid crystal display device in which the area of ​​the pixel P is relatively large, it is preferable that the pixel electrode PE is disposed above the common electrode CE. In this structure (also referred to as the V2 structure), it is not necessary to form a slit in the lower electrode, that is, the common electrode CE, so compared with the structure in which the common electrode CE is disposed above the pixel electrode PE (also referred to as the V3 structure), the increase in the resistivity (surface resistivity) of the common electrode CE is suppressed, thereby suppressing the weakening of the fringe electric field applied to the liquid crystal layer 20. In this configuration (V2 structure), when the pixel electrode PE is used as a slit electrode, although the resistivity of the pixel electrode PE increases, since a voltage input from the outside is applied to the pixel electrode PE, it is easy to reduce the influence of the increase in resistivity (that is, suppress the weakening of the 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 a low-resistance wiring formed by a metal material (connecting the low-resistance wiring to the common electrode CE). However, in such a structure, due to the adverse effects on the display caused by regular reflection caused by the low-resistance wiring (such as glare, rainbow diffraction, interference pattern), it is necessary to use a black matrix or the like for shading, and there may be a situation where the reflective aperture ratio cannot be fully increased.

[0069] 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 be reduced compared to the configuration in which the common electrode CE is arranged above the pixel electrode PE. Since the area of ​​the region that does not contribute to the reflective display such as the contact hole 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 reflectivity. Conversely, in a relatively large liquid crystal display device, it is easy to further reduce the proportion of the region that does not contribute to the reflective display in the pixel P, so it is easy to suppress the reduction in the above reflectivity. For these reasons, in a relatively large liquid crystal display device, the configuration in which the pixel electrode PE is arranged above the common electrode CE is advantageous.

[0070] On the other hand, as described above, as the area of ​​the pixel P is smaller (i.e., the higher the precision), the reflectivity decreases because the area where the second contact hole CH2 is formed does not contribute to the reflective display. Therefore, in a relatively high-definition liquid crystal display device, 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).

[0071] The first electrode 121 and the second electrode 122 are preferably formed of a transparent conductive material. Examples of the transparent conductive material include indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), or a mixture thereof.

[0072] exist Figure 2 In the manner shown, the pixel electrode PE (the second electrode 122 in this embodiment) is electrically connected to the backplane circuit (more specifically, the drain electrode of the TFT 110) via the contact electrode 160. The contact electrode 160 is formed in the same layer as the reflective film 130 and is formed of the same material (metal film, etc.) as the reflective film 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.

[0073] The dielectric layer 153 is provided so as to cover the first electrode 121. It is preferable that the dielectric layer 153 is formed of an inorganic insulating material. The inorganic insulating film obtained by using the inorganic insulating material is as described above.

[0074] 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.

[0075] 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 orientation (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.

[0076] 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°.

[0077] The orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 and the orientation of the liquid crystal molecules 21 defined by the second horizontal alignment film 340 are different from each other. Therefore, the liquid crystal layer 20 has a twisted orientation when no voltage is applied (refer to 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).

[0078] <Liquid Crystal Layer> The liquid crystal layer 20 is located between the first substrate 10 and the second substrate 30, and includes a positive liquid crystal material or a negative liquid crystal material. The positive liquid crystal material refers to a nematic liquid crystal material with a positive dielectric constant anisotropy Δε, and the negative liquid crystal material refers to a nematic liquid crystal material with a negative dielectric constant anisotropy Δε. The dielectric constant anisotropy Δε is the difference between the dielectric constant ε / / in the long axis direction and the dielectric constant ε⊥ in the short axis direction of the liquid crystal molecule 21 (i.e., ε / / -ε ⊥ ).

[0079] In a positive liquid crystal material, the birefringence Δn of the liquid crystal material is preferably, for example, 0.12 or less, and more preferably 0.119 or less. In addition, considering the manufacturing point of view (yield, etc.), the thickness d of the liquid crystal layer 20 is preferably 2 μm or more, but in this case, Δn is preferably 0.119 or less. It is further preferred that d is 2.5 μm or more and Δn is 0.095 or less. However, from the viewpoint of response, it is preferred that the cell thickness is small. In addition, the dielectric anisotropy Δε of the liquid crystal material is preferably, for example, 10 or more.

[0080] In a negative liquid crystal material, the birefringence Δn of the liquid crystal material is preferably, for example, 0.123 or less, and more preferably 0.12 or less. It is particularly preferred that the thickness d of the liquid crystal layer 20 is 2 μm or more, and Δn is 0.123 or less. It is further preferred that d is 2.5 μm or more, and Δn is 0.098 or less. In addition, the dielectric anisotropy Δε of the liquid crystal material is preferably, for example, -5 or less. In addition, when Δε is small (or the absolute value of Δε is large), the VR curve (threshold value, reflectivity Max value, etc.) shifts to the low voltage side.

[0081] When selecting a positive type or a negative type, it is preferred to consider the application, the desired performance, etc. For example, from the perspective of achieving flicker-free (also called flicker-free), it is preferred to use a negative type liquid crystal material. This is due to the following reasons. In the lateral electric field method of the FFS mode using a positive type liquid crystal material, when a voltage is applied, due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field), flexible polarization is spontaneously generated in the liquid crystal layer. Since the liquid crystal responds to the above-mentioned flexible polarization, it is believed that the brightness changes when the polarity is reversed, which is easily perceived as flicker. From the perspective of reliability, it is preferred to use a positive type liquid crystal material.

[0082] The liquid crystal layer 20 may further contain a chiral agent as needed. The liquid crystal layer 20 may be formed by, for example, a dropping method.

[0083] The thickness d (also referred to as the cell gap or cell thickness) of the liquid crystal layer 20 is preferably 3.6 μm or less. More preferably, it is 2.0 to 3.4 μm. In addition, from the viewpoint of response speed, it is preferably 3 μm or less. In addition, since a small cell thickness can reduce the number of material members, it is suitable from the viewpoint of cost reduction. However, if it is too small, sometimes the display quality cannot be improved due to uneven cell thickness or foreign matter, which becomes a compromise relationship of the incidence rate of poor display quality. From the viewpoint of yield, it is preferably 2 μm or more as described above.

[0084] The liquid crystal layer 20 may be in a multi-domain orientation such as a dual-domain orientation. However, from the viewpoint of maximizing the liquid crystal mode reflection efficiency and the liquid crystal mode transmission efficiency, a single domain orientation (also referred to as a single domain orientation) is preferred.

[0085] <Second Substrate> The second substrate 30 has a second horizontal alignment film 340 disposed opposite to the first substrate 10 via the liquid crystal layer 20 and in contact with the liquid crystal layer 20. The second substrate 30 more preferably has a supporting substrate 300 and a color filter layer 310. Figure 2 As shown, the second substrate 30 has a second horizontal alignment film 340, a color filter layer 310, and a support substrate 300 in order from the liquid crystal layer 20 side. The second substrate 30 preferably has a plurality of columnar spacers (not shown). In addition, the first substrate 10 may also have a plurality of columnar spacers.

[0086] The support substrate 300 is preferably transparent and insulating, and examples of the support substrate 300 include a glass substrate and a plastic substrate. Figure 2In the embodiment, the surface of the phase difference layer 40 side of the support substrate 300 is formed with a high resistance transparent conductive film to deal with electrostatic burn of the liquid crystal unit. In order to suppress the decrease of transmittance and the increase of reflectivity, the high resistance transparent conductive film may be a multilayer structure.

[0087] The color filter layer 310 typically includes: a red color filter, which is provided in an area corresponding to a red pixel and allows red light to pass through; a green color filter, which is provided in an area corresponding to a green pixel and allows green light to pass through; and a blue color filter, which is provided in an area corresponding to a blue pixel and allows blue light to pass through. However, the types of color filters may be two or less, or four or more. In addition, when color display is not performed, the color filter layer 310 is omitted.

[0088] If necessary, an outer coating layer (also called a flattening layer) covering the color filter layer 310 may be provided. In addition, as the material for forming the electrode (e.g., transparent conductive material), the material for forming the interlayer insulating layer or dielectric layer, and the material for forming the alignment film, sometimes the white display has a yellow tint. In this case, the chromaticity adjustment (i.e., blue shift) may be performed by forming the outer coating layer with a blue resist, so that the chromaticity of the white display is close to the chromaticity of the D65 light source, for example. The D65 light source is the CIE standard light source D65.

[0089] <Phase difference layer> The phase difference layer 40 is located between the second substrate 30 and the polarizing plate 50, and includes a λ / 4 plate 41, a λ / 2 plate 42 and a positive C plate 43 (see Figure 1 as well as Figure 2 ). Thus, as the phase difference layer 40, in addition to the λ / 4 plate 41 and the λ / 2 plate 42, the positive C plate 43 is also provided, so that it is possible to improve the viewing angle and the contrast at a high level at the same time, which is extremely useful. In particular, the brightness fluctuation (also called black floating) during black display is fully suppressed, and the viewing angle of black display is expanded. From the viewpoint of further exerting such an effect, it is preferred that the arrangement order of the λ / 4 plate 41, the λ / 2 plate 42, and the positive C plate 43 is, from the liquid crystal layer 20 (and the second substrate 30) side, the λ / 4 plate 41, the positive C plate 43, the λ / 2 plate 42 (see Figure 1 ).

[0090] The λ / 4 plate is a phase difference plate that gives an in-plane phase difference of 1 / 4 wavelength to incident light of wavelength λ, and is also called a λ / 4 wave plate or QWP (Quarter-Wave Plate). Specifically, the λ / 4 plate 41 can convert linear polarized light into circular polarized light or convert circular polarized light into linear polarized light. For example, linear polarized light incident on the λ / 4 plate 41 becomes circular polarized light when it exits the λ / 4 plate 41.

[0091] The λ / 2 plate is a phase difference plate that gives an in-plane phase difference of 1 / 2 wavelength to incident light of wavelength λ, and is also called a λ / 2 wavelength plate, a half-wavelength plate, or an HWP (Half-Wave Plate). Specifically, the λ / 2 plate 42 can rotate the vibration direction of the incident light by approximately 90°. For example, circularly polarized light incident on the λ / 2 plate 42 becomes circularly polarized light with the opposite rotation direction when it is emitted.

[0092] As the λ / 4 plate 41 and the λ / 2 plate 42, a general phase difference plate can be used. More specifically, for example, as a circular polarizer of an anti-reflection film, it is preferred to use a generally circulated phase difference plate. In the present invention, it is preferred that, as described later, by controlling the angle formed by the polarization axis of the polarizer and the orientation azimuth of the liquid crystal molecules specified by the first horizontal orientation film 140 within a specified range, as the λ / 4 plate 41 and the λ / 2 plate 42, even if a general phase difference plate is used instead of a special phase difference plate, the liquid crystal display device of the lateral electric field mode can improve the contrast and the viewing angle, and is also useful as an embedded touch panel capable of displaying in a reflective mode, so that cost reduction can be achieved. In particular, it is very useful because it can reduce the total cost from the user's point of view. The liquid crystal display device of the present invention can achieve cost reduction not only when used as a built-in touch panel such as an embedded type, but also when used as an external touch panel.

[0093] Specifically, it is preferable to use a uniaxial A plate as the λ / 4 plate 41 and the λ / 2 plate 42 .

[0094] The positive C plate 43 (and the positive C plate 44 described later) may be composed of a single film or a laminate of two or more retardation films.

[0095] As the positive C plate 43 (and 44), 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.

[0096] Specific examples of the positive C plate 43 (and 44) ​​include positive C plates manufactured by ENEOS or Hayashi Tenrenfu, and positive-C retardation films manufactured by Nippon Kayaku Co., Ltd.

[0097] From the viewpoint of further improving the viewing angle, the thickness direction phase difference Rth of the positive C plate 43 is preferably More preferably More preferably

[0098] The thickness of the positive C plate 43 is preferably If it is within this range, the mechanical strength and display uniformity are more excellent. It is more preferably 0.1 to 80 μm, and further preferably 0.1 to 50 μm. In addition, when the positive C plate 43 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 may be the same or different.

[0099] <Polarizing plate> The polarizing plate 50 is located closer to the observation surface than the phase difference layer 40 (see Figure 1 as well as Figure 2 ). The polarizing plate 50 may be either a circular polarizing plate or a linear polarizing plate. Here, a linear polarizing plate refers to a 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, and is distinguished from a circular polarizing plate. Among them, a linear polarizing plate is preferred.

[0100] The polarizing plate 50 may be an absorption type polarizing plate or a reflection type polarizing plate. An absorption type polarizing plate 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 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.

[0101] 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. Usually, in order to ensure mechanical strength or moisture and heat resistance, a polyvinyl alcohol film is provided for practical use in a state where a protective film such as a triacetyl cellulose film is laminated on both sides. In addition, as a reflection type polarizing plate, for example, a film formed by laminating multiple dielectric films, a film formed by laminating multiple films with different refractive index anisotropy, a nanowire grid polarizing plate, a polarizing plate using selective reflection of cholesteric liquid crystals, etc. can be cited.

[0102] <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. Thus, the contrast ratio of the reflective display can be sufficiently improved. The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably greater than 70° and less than 85°. The preferred range will be described later.

[0103] The twist angle θ1 of the liquid crystal layer 20 is an angle formed by the alignment direction of the liquid crystal molecules 21 specified by the first horizontal alignment film 140 and the alignment direction of the liquid crystal molecules 21 specified by the second horizontal alignment film 340. That is, it is also called the angle formed by the long axis direction of the liquid crystal molecules 21A near the first horizontal alignment film 140 (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 called the liquid crystal molecules 21B on the second substrate 30 side when voltage is applied).

[0104] The liquid crystal display device 1 is preferably in a normally black mode from the viewpoint of further improving the contrast. 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.

[0105] In addition to the above components, the liquid crystal display device 1 is composed of multiple components such as TCP (tape carrier package), PCB (printed wiring board) and other external circuits, optical films such as viewing angle expansion film and brightness enhancement film, and outer frame (frame), and can also be assembled from components to other components. There is no special limitation on the above, and components commonly used in the field of liquid crystal display devices can be used, so the description is omitted.

[0106] <Preferred Optical Setting Example> Hereinafter, the preferred settings of the twist angle of the liquid crystal layer 20, the optical axis settings of each optical film (i.e., the polarizing plate 50 and the phase difference layer 40), the delay dΔn of the liquid crystal layer 20, etc. in this embodiment and the verification results for achieving the settings are further described by dividing into the case where the liquid crystal material constituting the liquid crystal layer 20 is positive and the case where the liquid crystal material constituting the liquid crystal layer 20 is negative. As the polarizing plate 50, an absorption-type polarizing plate is used. In addition, since the slow axis angle of the positive C plate 43 is the film normal direction (i.e., it is 90° when the orientation direction of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 is set to 0°), the method without the positive C plate was studied. In the case where the positive C plate is provided, the preferred settings are also the same.

[0107] (i) When the liquid crystal material is positive type (i-1) Preferred settings The following describes an example of particularly preferred optical settings from the viewpoint of improving the contrast ratio. Figure 4 This is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 and the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42, and the polarization axis 50AA of the polarization plate 50 when no voltage is applied in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 4 plate 41, a λ / 2 plate 42, and a polarization plate 50. Figure 4In FIG. 1 , as the liquid crystal molecules 21 , the liquid crystal molecules 21A near the first horizontal alignment film 140 and the liquid crystal molecules 21B near the second horizontal alignment film 340 are described.

[0108] In the following description, the angle when the reference direction is 0° is Figure 4 When used as a clock face, the reference orientation, i.e., the orientation orientation of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is in the 0° direction (3 o'clock direction), and the twisting direction is positive (counterclockwise). The twisting direction refers to the direction of twisting from the orientation orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 to the orientation orientation of the liquid crystal molecules 21 defined by the second horizontal alignment film 340 when the liquid crystal display device 1 is observed from the observation surface side.

[0109] The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably 70° to 85°, more preferably 75° to 85°, further preferably 80° to 85°, particularly preferably 81° to 84°, and most preferably around 83° (approximately 83°).

[0110] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 and the orientation azimuth of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 63.5° or more and 71.5° or less. It is more preferably 64.5° or more and 71.5° or less, in which case, a contrast ratio of 20 or more can be easily achieved. Moreover, 63.5° or more and 70.5° or less is also one of the preferred ranges. It is further preferably 64.5° or more and 70.5° or less, and particularly preferably 66.3° or more and 70° or less. In addition, when the reference azimuth is set to 0° and the twisting direction (counterclockwise direction) is set to positive, it is preferably -71.5° or more and -63.5° or less, more preferably -71.5° or more and -64.5° or less, further preferably -70.5° or more and -64.5° or less, and particularly preferably -70° or more and -66.3° or less.

[0111] The angle θ3 formed by the in-plane slow axis 42SA of the λ / 2 plate 42 and the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 47.5° or more and 52.5° or less. It is more preferably 48° or more and 52° or less, further preferably 49° or more and 51° or less, and particularly preferably 49° or more and 50° or less. In addition, when the reference orientation is set to 0° and the twisting direction (counterclockwise direction) is set to positive, it is preferably -52.5° or more and -47.5° or less, more preferably -52° or more and -48° or less, further preferably -51° or more and -49° or less, and particularly preferably -50° or more and -49° or less.

[0112] The angle θ4 formed by the in-plane slow axis 41SA of the λ / 4 plate 41 and the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 20° or more and 30° or less. It is more preferably 22° or more and 28° or less, further preferably 23° or more and 26° or less, and particularly preferably 24° or more and 25.5° or less. In addition, when the reference orientation is set to 0° and the twisting direction (counterclockwise direction) is set to positive, it is preferably -30° or more and -20° or less, more preferably -28° or more and -22° or less, further preferably -26° or more and -23° or less, and particularly preferably -25.5° or more and -24° or less.

[0113] The retardation of the liquid crystal layer 20, that is, the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material (dΔn), is preferably 218 nm or more and 255 nm or less. Among them, from the viewpoint of making the response performance better, the retardation dΔn is preferably 252 nm or less. From the viewpoint of further improving the contrast, it is more preferably 224 nm or more and 252 nm or less, further preferably 230 nm or more and 250 nm or less, and particularly preferably 236 nm or more and 248 nm or less.

[0114] (i-2) Verification results using optical simulation The above-mentioned preferred setting was discovered by the inventors of the present application through verification using optical simulation. The verification results are described below.

[0115] Assume that the liquid crystal display device 1 includes a reflective liquid crystal panel 1X using a positive liquid crystal material, a λ / 4 plate 41, a λ / 2 plate 42, and a polarizing plate 50. For optical simulation, assume that Figure 5A , Figure 5B and Figure 5C A liquid crystal layer with a monodomain structure (a liquid crystal layer that performs normally black display) is shown. Figure 5A It is a schematic plan view of the first substrate 10 (TFT substrate) viewed from the first horizontal alignment film 140 side. Figure 5B It is a schematic plan view of the second substrate 30 (counter substrate) viewed from the second horizontal alignment film 340 side. Figure 5C 1 is a schematic plan view of the liquid crystal panel 1X after the first substrate 10 and the second substrate 30 are bonded together, as viewed from the second substrate 30 side.

[0116] In the following description, Figure 5A , Figure 5B and Figure 5C Each of them is regarded as a clock face, and the reference direction, that is, the orientation direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140, is set to the 0° direction (3 o'clock direction). Figure 5A and Figure 5B In the figure, the arrows indicate the orientation of the liquid crystal molecules 21.

[0117] The upper electrode is set as a slit electrode (refer to Figure 5A and Figure 5B ). With respect to the reference orientation (0°), the direction in which the plurality of strip-shaped portions SP of the slit electrode extend (which is also equivalent to the direction in which each slit S1 extends) is set to +10°. That is, the finger angle is 10°. In addition, when viewed from above, the width of each strip-shaped portion SP is set to 1.6 μm, and the interval between two adjacent strip-shaped portions SP is set to 3 μm. The orientation direction of the liquid crystal molecules 21B defined by the second horizontal orientation film 340 is Figure 5B The +97° direction is in the Figure 5C The torsion angle θ1 is +83°.

[0118] First, a simulation was performed using LCD Master 1D manufactured by SHINTECH to optimize the next parameter condition where the reflectance of black display (also called black reflectance) becomes the minimum. Unit thickness d: 3.2~3.6μm Torsion angle θ1: 70~85° The axial orientation of the optical film (polarizing plate 50, λ / 2 plate 42, λ / 4 plate 41) is as follows: ±90° for the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm is used, and for the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm is used, and the wavelength dispersion of these phase difference plates is set to be flat. In addition, only one of the above parameters was changed and the other parameters were fixed to repeat the calculation.

[0119] Figure 6 2 shows the settings of the optical axes of the λ / 4 plate 41, the λ / 2 plate 42, and the polarizing plate 50 so as to minimize the black reflectance. Figure 6 This is a diagram conceptually showing the setting of the optical axis at which the black reflectance is minimum. Figure 6 As shown, the optimal setting of the polarization axis 50AA of the polarizing plate 50 is also -68.3° (+111.7°). The optimal setting of the slow axis 42SA of the λ / 2 plate 42 is -49.5° (or +130.5°), and the optimal setting of the slow axis 41SA of the λ / 4 plate 41 is -24.9° (or +155.1°).

[0120] Next, we conducted simulations using LCD Master 2D manufactured by Shintech to examine the optimal range of optical conditions. At this time, we simulated the parameter of interest (the parameter for which we wanted to obtain the optimal range) by changing the value around the optimal value (reference value) while fixing other parameters at their optimal values.

[0121] It was found that when the delay dΔn exceeds 252nm, that is, when the birefringence Δn of the liquid crystal material is 0.07 and the cell thickness d exceeds 3.6μm, the response performance may not be better. It was found that the response performance may not be better even when the twist angle θ1 exceeds 85°. Considering the response performance, it is known that the optimal setting of the twist angle θ1 is 83°, the optimal setting of the delay dΔn is 245nm, and the optimal setting of the optical axis of the λ / 4 plate 41, the λ / 2 plate 42 and the polarizing plate 50 is Figure 6 The settings shown.

[0122] In order to study the influence of the delay dΔn and the twist angle θ1 on the brightness of black display (also called black brightness) and contrast, the delay dΔn was changed in the range of 224 to 252nm, and the twist angle θ1 was changed in the range of 70 to 85°, and simulation was performed. The evaluation results of the black brightness are shown in Table 1 and Figure 7 The contrast evaluation results are shown in Table 2 and Figure 8 From these results, it can be seen that the preferred range of the twist angle θ1 is 70° or more and 85° or less, and the preferred range of the retardation dΔn is 236 nm or more and 252 nm or less. Figure 7 is a graph showing the evaluation results of black brightness, Figure 8 It is a graph showing the evaluation results of contrast.

[0123] In addition, regarding the conditions of the liquid crystal layer with a delay of dΔn=217nm (Δn=0.069928 at a wavelength of 550nm), a unit thickness of 3.11μm, and a twist angle θ1=74°, and a combination with special phase difference plates (λ / 4 plate with a delay of 110nm and λ / 2 plate with a delay of 260nm), the black brightness and contrast were calculated and the results showed that the black brightness was 0.02 (au) and the contrast was 1789.

[0124] [Table 1]

[0125] [Table 2]

[0126] (ii) When the liquid crystal material is positive type (ii-1) Preferred setting From the viewpoint of improving the contrast ratio, particularly preferred optical setting examples are shown below. Fig. 9This is a top view conceptually showing the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 and the in-plane slow axis 41SA of the λ / 4 plate 41, the in-plane slow axis 42SA of the λ / 2 plate 42, and the polarization axis 50AA of the polarization plate 50 when no voltage is applied in a liquid crystal display device 1 that includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a λ / 4 plate 41, a λ / 2 plate 42, and a polarization plate 50. Fig. 9 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 shown.

[0127] In the following description, the angle when the reference direction is 0° is Fig. 9 As a clock face, the reference orientation, that is, the orientation orientation of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is the 0° direction (3 o'clock direction), and the twisting direction is the angle when it is positive (counterclockwise).

[0128] The twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is preferably 70° to 85°, more preferably 75° to 85°, further preferably 80° to 85°, particularly preferably 81° to 84°, and most preferably around 83° (approximately 83°).

[0129] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 and the orientation azimuth of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 64° or more and 69.5° or less. It is more preferably 65° or more and 69.3° or less, further preferably 66° or more and 69° or less, and particularly preferably 67° or more and 68.7° or less. In addition, it is preferred that the angle θ2 is within the above range (all positive values) when the reference azimuth is set to 0° and the twisting direction (counterclockwise direction) is set to positive.

[0130] The angle θ3 formed by the in-plane slow axis 42SA of the λ / 2 plate 42 and the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 47.5° or more and 51.5° or less. It is more preferably 48° or more and 51° or less, further preferably 40° or more and 41.5° or less, and particularly preferably 48.5° or more and 50.0° or less. In addition, it is preferred that the angle θ3 is within the above range (all positive values) when the reference orientation is set to 0° and the twisting direction (counterclockwise direction) is set to positive.

[0131] The angle θ4 formed by the in-plane slow axis 41SA of the λ / 4 plate 41 and the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 15° or more and 35° or less. It is more preferably 17° or more and 32° or less, further preferably 20° or more and 30° or less, and particularly preferably 24° or more and 28° or less. In addition, it is preferred that the angle θ4 be within the above range (all positive values) when the reference orientation is set to 0° and the twisting direction (counterclockwise direction) is set to positive.

[0132] The retardation dΔn of the liquid crystal layer 20, that is, the product dΔn of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material, is preferably 230 nm to 260 nm. From the viewpoint of further improving the contrast, it is more preferably 232 nm to 250 nm, further preferably 235 nm to 246 nm, and particularly preferably 236 nm to 245 nm.

[0133] (ii-2) Verification results using optical simulation The above-mentioned preferred setting was discovered by the inventors of the present application through verification using optical simulation. The verification results are described below.

[0134] Assume that the liquid crystal display device 1 includes a reflective liquid crystal panel 1X using a negative liquid crystal material, a λ / 4 plate 41, a λ / 2 plate 42, and a polarizing plate 50. For optical simulation, assume that Fig. 10A , Fig. 10B and Fig. 10C A liquid crystal layer with a monodomain structure (a liquid crystal layer that performs normally black display) is shown. Fig. 10A It is a schematic plan view of the first substrate 10 (TFT substrate) viewed from the first horizontal alignment film 140 side. Fig. 10B It is a schematic plan view of the second substrate 30 (counter substrate) viewed from the second horizontal alignment film 340 side. Fig. 10C 1 is a schematic plan view of the liquid crystal panel 1X after the first substrate 10 and the second substrate 30 are bonded together, as viewed from the second substrate 30 side.

[0135] In the following description, Fig. 10A , Fig. 10B and Fig. 10C Consider them as the dial of a clock, set the 3 o'clock direction to 0°, set clockwise rotation to negative, and counterclockwise rotation to positive. Fig. 10A , Fig. 10B In the figure, the arrows indicate the orientation of the liquid crystal molecules 21.

[0136] In this example, the upper electrode is set as a slit electrode (refer to Fig. 10A and Fig. 10B). The orientation direction of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is set to the 90° direction (12 o'clock direction), and the direction in which the multiple strip-shaped portions SP of the upper electrode (slit electrode) extend (also equivalent to the direction in which each slit S1 extends) is set to the +10° direction. That is, the finger angle is 10°. In addition, when viewed from above, the width of each strip-shaped portion SP is set to 1.6μm, and the interval between two adjacent strip-shaped portions SP is set to 3μm. The orientation direction of the liquid crystal molecules 21B defined by the second horizontal alignment film 340 is set to Fig. 10B The direction is set to +7°, Fig. 10C The direction is set to +83°. That is, the torsion angle θ1 is +83°.

[0137] LCD Master 1D manufactured by SHINTECH was used, and the twist angle θ1 was fixed at 83° to obtain the conditions of the cell thickness d at which the black reflectance becomes minimum, the angle of the polarization axis 50AA of the polarizing plate 50, the angle and delay of the slow axis 42SA of the λ / 2 plate 42, and the angle and delay of the slow axis 41SA of the λ / 4 plate 41. In addition, only one of the above parameters was changed, and the other parameters were fixed and the calculation was repeated.

[0138] Fig.11 2 shows the settings of the optical axes of the λ / 4 plate 41, the λ / 2 plate 42, and the polarizing plate 50 so as to minimize the black reflectance. Fig.11 This is a diagram conceptually showing the setting of the optical axis at which the black reflectance is minimum. Fig.11 As shown, the optimal setting of the polarization axis 50AA of the polarizing plate 50 is the +21.7° direction (-158.3° direction). In addition, the optimal setting of the slow axis 42SA of the λ / 2 plate 42 is the +40.5° direction (or -139.5° direction), and the optimal setting of the slow axis 41SA of the λ / 4 plate 41 is the +65.1° direction (or -114.9° direction).

[0139] [Simulation Verification Results] The effects of the positive C plate 43 described above were discovered by the inventors of the present application through verification using optical simulation. The verification results are described below by dividing them into the case where the liquid crystal material constituting the liquid crystal layer 20 is positive and the case where the liquid crystal material is negative. In addition, an absorption-type polarizing plate is used as the polarizing plate 50.

[0140] (i) When the liquid crystal material is positive In a liquid crystal display device 1 having a reflective liquid crystal panel 1X using a positive liquid crystal material, a phase difference layer 40, and a polarizing plate 50, a three-layer structure of a λ / 4 plate 41, a λ / 2 plate 42, and a positive C plate 43 or a negative C plate 43R is assumed as the phase difference layer 40, and the influence of the addition of the C plate on the viewing angle caused by changing the position of the C plate is studied. LCD Master 1D manufactured by SHINTECH is used as the simulation software. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm is used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm is used, and the wavelength dispersion of these phase difference plates is set to be flat. The other settings are set as the optimal settings obtained by (i) of the above-mentioned <Preferred Optical Setting Example> when the liquid crystal material is positive. The results are shown in Fig. 12A as well as Fig. 12B .

[0141] Figure 12 and Fig. 12B 1 is a diagram showing simulation results for the case where the liquid crystal material is a positive type in this embodiment. In addition, an example without a C plate is shown as Example 1. Fig. 12A and Fig. 12B The upper part shows a schematic cross-sectional view of the liquid crystal display device 1 in each example (only the reflective layer 130 is shown separately from the liquid crystal panel 1X), and the lower part shows the viewing angle under black display (0V) (when light is incident at a polar angle of 30°). The thickness direction phase difference Rth of the C plate used in each example is shown in parentheses after the reference numeral 43 or 43R indicating the C plate (the same applies to other similar figures).

[0142] According to Figure 12 and Fig. 12B It can be seen that the viewing angle improvement effect of the examples (Examples 2, 3 and 4) in which the phase difference layer 40 includes the positive C plate 43 is superior to that of the examples (Examples 5, 6 and 7) in which the phase difference layer 40 includes the negative C plate 43R. Among them, in the example (Example 3) in which the positive C plate 43 is located between the λ / 4 plate 41 and the λ / 2 plate 42, the black float is significantly improved, and the viewing angle improvement effect can be significantly confirmed. In addition, using the stock of the positive C plate (Rth: 200nm), a test unit with the same configuration as Example 3 was made and verified, and the result confirmed that the viewing angle improvement effect is also visually observed. In order to make the comparison easier to understand, Fig.13 Schematic cross-sectional views of the liquid crystal display devices 1 of Examples 1 and 3 and the viewing angles in black display (0 V) (when light is incident at a polar angle of 30°) are shown. Fig.13 It is a figure which shows the simulation result about Example 1 and Example 3.

[0143] In addition, for the method including the positive C plate 43 in addition to the λ / 4 plate 41 and the λ / 2 plate 42, the optical conditions for minimizing black floating were optimized for the phase difference layer 40. That is, for each configuration example of Example 1 to Example 4, in the black display (0V) state, as the incident light at a polar angle of 30°, the luminance distribution of the azimuth angle: 0 to 360° (15° step) and the polar angle: 0 to 80° (10° step) was analyzed. The results are shown in Fig.14 middle. Fig.14 Graph showing the distribution of the maximum values ​​of black brightness in Examples 1 to 4. Fig.14 In the figure, the horizontal axis is the Rth (nm) of the positive C plate 43, and the vertical axis is the maximum value of the black brightness.

[0144] according to Fig.14 It can be seen that in In the distribution curve of Example 3, the maximum value of black brightness is the lowest. In addition, the value (arrow) at which the vertical axis (maximum value of black brightness) in the distribution curve of Example 3 becomes the minimum value is shown as a reference. Within 30% is the case where the Rth of the positive C plate 43 is 150nm or more and 270nm or less, within 15% is the case where the Rth is 160nm or more and 250nm or less, and within 10% is the case where the Rth is 170nm or more and 240nm or less. Based on this result, it is found that the preferred range of the thickness direction phase difference Rth is as described above.

[0145] (ii) When the liquid crystal material is negative In a liquid crystal display device 1 having a reflective liquid crystal panel 1X using a negative liquid crystal material, a phase difference layer 40, and a polarizing plate 50, a three-layer structure of a λ / 4 plate 41, a λ / 2 plate 42, a positive C plate 43 or a negative C plate 43R is assumed as the phase difference layer 40, and the influence of the addition of the C plate on the viewing angle caused by changing the position of the C plate is studied. LCD Master 1D manufactured by SHINTECH is used as simulation software. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm is used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm is used, and the wavelength dispersion of these phase difference plates is set to be flat. The other settings are set as the optimal settings obtained by (i) of the above <Preferred Optical Setting Example> when the liquid crystal material is negative.

[0146] As a result, when the liquid crystal material is positive (refer to Fig. 12A and Fig. 12B ) get almost the same tendency, so Fig.15 In the example, only the simulation results of the example in which the positive C plate 43 is located between the λ / 4 plate 41 and the λ / 2 plate 42 (Example 13) and the example in which no C plate is included (Example 11) are extracted and shown. Fig.15This is a diagram showing simulation results when the liquid crystal material is a negative type in this embodiment. Fig.15 The upper part shows a cross-sectional schematic diagram of the liquid crystal display device 1 in each example (in which only the reflective layer 130 is recorded separately from the liquid crystal panel 1X), and the lower part shows the viewing angle under black display (0V) (when light is incident at a polar angle of 30°).

[0147] In addition, for the method including the positive C plate 43 in addition to the λ / 4 plate 41 and the λ / 2 plate 42, the optical conditions for minimizing black floating are optimized for the phase difference layer 40. That is, for each of the following examples 11 to 14, in the black display (0V) state, as the incident light at a polar angle of 30°, the brightness distribution of the azimuth angle: 0 to 360° (15° step) and the polar angle: 0 to 80° (10° step) is analyzed. The results are shown in Fig.16 middle. Fig.16 Graph showing the distribution of the maximum values ​​of black brightness in Examples 11 to 14. Fig.16 In the figure, the horizontal axis is the Rth (nm) of the positive C plate 43, and the vertical axis is the maximum value of the black brightness. Example 11: Example without C plate. Example 12: An example in which the configuration of each phase difference plate is set to a positive C plate 43 (thickness direction phase difference Rth: 50nm), a λ / 2 plate 42, and a λ / 4 plate 41 in order from the observation surface side. Example 13: An example in which the configuration of each phase difference plate is set to be a λ / 2 plate 42, a positive C plate 43 (thickness direction phase difference Rth: 210 nm), and a λ / 4 plate 41 in order from the observation surface side. Example 14: An example in which the configuration of each phase difference plate is set to λ / 2 plate 42, λ / 4 plate 41, and positive C plate 43 (thickness direction phase difference Rth: 10nm) in order from the observation surface side.

[0148] according to Fig.16 It can be seen that in Example 11 In Example 14, the maximum black brightness is the lowest in Example 13. In addition, the value (with arrow) at which the vertical axis (maximum black brightness) in the distribution curve of Example 13 becomes the minimum value is shown as a reference. Within 30% is the case where the Rth of the positive C plate 43 is 150nm or more and 270nm or less, within 15% is the case where the Rth is 160nm or more and 250nm or less, and within 10% is the case where the Rth is 170nm or more and 240nm or less. That is, it is possible to obtain the same as the case where the liquid crystal material is positive (refer to Fig.14 Based on this result, it was found that the preferred range of the thickness direction phase difference Rth is as described above.

[0149] <Application Examples> The liquid crystal display device 1 of this embodiment is applicable to various applications. Among them, it can be preferably applied to a touch panel. Regardless of whether it is applied to an external touch panel or a built-in touch panel, it can improve the contrast ratio at a lower cost than each touch panel in the past, so it is useful. Among them, it can be suitably applied to a built-in touch panel, and is particularly suitably applied to an embedded touch panel. In this way, if the liquid crystal display device 1 of this embodiment is used, it is possible to appropriately realize an embedded touch panel capable of displaying in a reflective mode, which has not been realized so far.

[0150] Since an embedded touch panel capable of displaying a reflective mode can be realized, for example, the frame wiring area required in an external touch panel is not required, so a narrow frame can be realized, and the touch panel function can be installed without a cover glass, which can also contribute to thinning and weight reduction. 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 color-fading pattern (killer pattern) is generated, it is easy to adjust the touch signal (tuning). In addition, the loss of reflected light is sufficiently small, and the pen writing is more natural and there is no sense of incongruity. On top of this, compared with an external touch panel, the total cost can be reduced from the user's point of view. In addition, it is possible to combine finger input and pen input of the electromagnetic induction method (EMR) to achieve high-precision pen writing.

[0151] An example in which the liquid crystal display device 1 is used for an in-cell touch panel will be described further. Fig.17 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. Fig.17 As shown, the liquid crystal display device 1 has a display area DR and a non-display area FR. Figure 3 The non-display region FR is located at the periphery of the display region DR and is sometimes referred to as a “peripheral region” or a “frame region”.

[0152] In the display area DR, the common electrode CE is divided into a plurality of segments TX. Each segment (common electrode portion) Tx functions as a touch sensor electrode. Fig.17 In the example shown, each touch sensor electrode Tx is arranged corresponding to more than two pixels P.

[0153] The liquid crystal display device 1 (more specifically, the first substrate 10 ) has a plurality of touch wirings TL. Each touch sensor electrode TX is electrically connected to 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.

[0154] The touch wiring TL is connected to a touch drive unit TD provided in the non-display region FR. The touch drive unit TD is configured to switch, for example, 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 in a time-sharing manner. For example, in the display mode, the touch drive unit TD applies a common signal to the touch sensor electrodes 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 electrodes TX via the touch wiring TL.

[0155] exist Fig.17 In the embodiment, a plurality of touch wirings TL extend along 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.

[0156] 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 may be a case where two or more touch wirings TL are arranged to extend across the touch sensor electrode Tx, and there may also be a case where no touch wiring TL that extends across the touch sensor electrode Tx is arranged.

[0157] In the non-display region FR, in addition to the touch drive unit TD, peripheral circuits including a gate driver that provides a gate signal to the gate bus (gate wiring) GL, a source driver that provides a source signal to the source bus (source wiring) SL, and other drive circuits are provided. These drive circuits can be mounted on the first substrate (TFT substrate) 10, or can be formed in one piece (monolithically). A semiconductor chip including a part or all of the drive circuits can also be mounted in the non-display region FR.

[0158] In the embedded touch panel, as TFT110, it is particularly preferred to use an In-Ga-Zn-O semiconductor. In addition, from the perspective of achieving flicker-free (also called flicker-free), it is preferred to use a negative liquid crystal material. This is due to the following reasons. In the lateral electric field method of the FFS mode using a positive liquid crystal material, when a voltage is applied, due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field), flexible polarization is spontaneously generated in the liquid crystal layer. Since the liquid crystal responds to the above-mentioned flexible polarization, it is believed that the brightness changes when the polarity is reversed, which is easily perceived as flicker.

[0159] (Variation 1 of Implementation Example 1) In Embodiment 1, the structure in which the first electrode 121 as the lower electrode is the common electrode CE and the second electrode 122 as the upper electrode is the pixel electrode PE is described. However, on the contrary, the second electrode 122 is the common electrode CE and the first electrode 121 is the pixel electrode PE. In this embodiment, the second electrode 121 (upper electrode) is the common electrode CE and the first electrode 122 (lower electrode) is the pixel electrode PE (refer to Fig.18 ).

[0160] Fig.18 : is a cross-sectional schematic diagram showing 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 common 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 modified example is particularly suitable as a relatively high-definition liquid crystal display device as described above, i.e., a liquid crystal display device with a relatively small area of ​​pixel P.

[0161] (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 is twisted 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.

[0162] (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. In addition to including a positive C plate 43 and a positive C plate 44 different from it, the phase difference layer 40 of this embodiment is substantially the same as that of the embodiment 1. For convenience, in the embodiment 1, the above-mentioned positive C plate 43 is referred to as the first positive C plate 43, and the positive C plate 44 added in this embodiment is referred to as the second positive C plate 44.

[0163] Fig.19 FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Fig.19 As shown, the liquid crystal display device 1 includes a first substrate 10, a liquid crystal layer 20, a second substrate 30, a phase difference layer 40, and a polarizing plate 50 in order from the back side. The phase difference layer 40 includes a first positive C plate 43 and a second positive C plate 44 in addition to a λ / 4 plate 41 and a λ / 2 plate 42. The positive C plate 44 may be composed of a single film or a laminate of two or more phase difference films.

[0164] When the phase difference layer 40 includes the first positive C plate 43 and the second positive C plate 44, it is possible to achieve both a further improvement in viewing angle and a further improvement in contrast ratio. In particular, compared with Embodiment 2, black floating is further suppressed. From the viewpoint of further exerting this effect, it is preferred that the second positive C plate 44 is located between the λ / 2 plate 42 and the polarizing plate 50. That is, it is preferred that the phase difference layer 40 is located in the order of the λ / 4 plate 41, the first positive C plate 43, the λ / 2 plate 42, and the second positive C plate 44 (see Fig.19 ).

[0165] As long as the second positive C plate 44 satisfies "nz>nx≒ny", it can be the same as the first positive C plate 43 (same physical properties, same thickness, etc.) or different. However, from the perspective of further exerting the viewing angle improvement effect, the thickness direction phase difference Rth (absolute value) of the second positive C plate 44 is preferably 50 to 130 nm. More preferably More preferably

[0166] The thickness of the second positive C plate 44 is preferably If it is within this range, the mechanical strength and display uniformity are more excellent. It is more preferably 0.1 to 80 μm, and further preferably 0.1 to 50 μm. In addition, when the positive C plate 44 has a laminated structure, it is preferably set to have a total thickness within the above range, and the thickness of each phase difference film may be the same or different.

[0167] The effects of the first positive C plate 43 and the second positive C plate 44 are found by the inventors of the present application through verification using optical simulation. The verification results are described below by dividing them into the case where the liquid crystal material constituting the liquid crystal layer 20 is positive and the case where the liquid crystal material is negative. In addition, an absorption-type polarizing plate is used as the polarizing plate 50.

[0168] (i) When the liquid crystal material is positive In a liquid crystal display device 1 having a reflective liquid crystal panel 1X using a positive liquid crystal material, a phase difference layer 40 and a polarizing plate 50, as the phase difference layer 40, a four-layer structure in which a λ / 2 plate 42, a first positive C plate 43 (thickness direction phase difference Rth: 210nm), a λ / 4 plate 41 and a second positive C plate 44 (thickness direction phase difference Rth: 110nm) are sequentially arranged from the observation side is assumed, and the effect of the addition of the second positive C plate 44 on the viewing angle is studied (Example 23). As the simulation software, LC Master 1D manufactured by SHINTECH is used. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm is used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm is used, and the wavelength dispersion of these phase difference plates is set to be flat. The other settings are set as the optimal settings obtained in embodiment 1 when the liquid crystal material is positive. The results are shown in Fig. 20 middle.

[0169] Fig. 20 21 is an example in which no C plate is included, and 22 is an example in which the first positive C plate 43 is included but the second positive C plate 44 is not included. Fig. 20 The upper part shows a cross-sectional schematic diagram of the liquid crystal display device 1 in each example (in which only the reflective layer 130 is recorded separately from the liquid crystal panel 1X), and the lower part shows the viewing angle under black display (0V) (when light is incident at a polar angle of 30°).

[0170] In addition, for Examples 21 to 23, in the black display (0V) state, as incident light at a polar angle of 30°, the luminance distribution of azimuth angle: 0 to 360° (15° steps) and polar angle: 0 to 80° (10° steps) was analyzed. The results are shown in Fig.21 middle. Fig.21 This is a graph showing the distribution of the maximum value of black brightness for Examples 21 to 23. Fig.21 In the figure, the horizontal axis is the Rth (nm) of the second positive C plate 44, and the vertical axis is the maximum value of the black brightness.

[0171] In addition, the value (with arrow) at which the vertical axis (maximum value of black brightness) in the distribution curve of Example 22 becomes the minimum value is shown as a reference, and within 30% is the case where the Rth of the second positive C plate 44 is 50nm or more and 130nm or less, within 15% is the case where the Rth is 70nm or more and 120nm or less, and within 10% is the case where the Rth is 80nm or more and 115nm or less. Based on this result, it is found that the preferred range of the thickness direction phase difference Rth of the second positive C plate 44 is as described above.

[0172] (ii) When the liquid crystal material is positive In a liquid crystal display device 1 having a reflective liquid crystal panel 1X using a negative liquid crystal material, a phase difference layer 40 and a polarizing plate 50, as the phase difference layer 40, a four-layer structure in which a λ / 2 plate 42, a first positive C plate 43 (thickness direction phase difference Rth: 210nm), a λ / 4 plate 41 and a second positive C plate 44 (thickness direction phase difference Rth: 110nm) are sequentially arranged from the observation side is assumed, and the effect of the addition of the second positive C plate 44 on the viewing angle is studied (Example 23). As the simulation software, LC Master 1D manufactured by SHINTECH is used. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm is used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm is used, and the wavelength dispersion of these phase difference plates is set to be flat. The other settings are set as the optimal settings obtained in embodiment 1 when the liquid crystal material is positive. The results are shown in Fig. 22 middle.

[0173] Fig. 22 31 is an example in which no C plate is included, and 32 is an example in which the first positive C plate 43 is included but the second positive C plate 44 is not included. Fig. 22 The upper part shows a cross-sectional schematic diagram of the liquid crystal display device 1 in each example (in which only the reflective layer 130 is recorded separately from the liquid crystal panel 1X), and the lower part shows the viewing angle under black display (0V) (when light is incident at a polar angle of 30°).

[0174] In addition, for Examples 31 to 33, in the black display (0V) state, as incident light at a polar angle of 30°, the luminance distribution of azimuth angle: 0 to 360° (15° steps) and polar angle: 0 to 80° (10° steps) was analyzed. The results are shown in Fig.23 middle. Fig.23 This is a graph showing the distribution of the maximum value of black brightness for Examples 31 to 33. Fig.23 In the figure, the horizontal axis is the Rth (nm) of the second positive C plate 44, and the vertical axis is the maximum value of the black brightness.

[0175] Depend on Fig.23 The distribution curve of Example 32 shows that the value (with arrow) where the vertical axis (maximum value of black brightness) becomes the minimum value is used as a reference. Within 30% is the case where the Rth of the second positive C plate 44 is 50nm or more and 130nm or less, within 15% is the case where the Rth is 70nm or more and 120nm or less, and within 10% is the case where the Rth is 80nm or more and 115nm or less. That is, it is possible to obtain the same as the case where the liquid crystal material is positive (refer to Fig.21Based on this result, it was found that the preferred range of the thickness direction phase difference Rth of the second positive C plate 44 is as described above.

[0176] (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 embodiment 1 is omitted. In embodiment 1, a reflective liquid crystal display device is described as an example, but in this embodiment, a semi-transmissive liquid crystal display device is described. The liquid crystal display device of this embodiment is mainly different from the liquid crystal display device of embodiment 1 in that a light source is provided on the back side relative to the liquid crystal layer 20.

[0177] Fig.24 1 is a cross-sectional schematic diagram of a liquid crystal display device 1 according to an example of the present embodiment. The liquid crystal display device 1 further includes a light source 61 (also referred to as a backlight source) on the back side of the liquid crystal layer 20. In addition, it is preferred that a polarizing plate 50' and a phase difference layer 40' are further included. More preferably, Fig.24 As shown, from the back side, it includes a light source 61, a polarizing plate 50', a phase difference layer 40', a first substrate 10, a liquid crystal layer 20, a second substrate 30, a phase difference layer 40 and a polarizing plate 50. In this embodiment, the first substrate 10 is preferably a TFT substrate.

[0178] The light source 61 (backlight source) is not particularly limited as long as it is a light source that irradiates light, and can be a direct-down type, an edge type, or any other type. Specifically, for example, it is preferred to have a light source such as a light emitting diode (LED), a light guide plate, and a reflective sheet, and may further have a diffuser or a prism sheet.

[0179] The polarizing plate 50' is arranged on the back side of the liquid crystal layer 20. More specifically, it is arranged at a position closer to the back side than the first substrate 10. The polarizing plate 50' can be a circular polarizing plate or a linear polarizing plate, preferably a linear polarizing plate. In addition, it can be an absorption type polarizing plate or a reflection type polarizing plate, preferably an absorption type polarizing plate. In particular, an absorption type linear polarizing plate is preferred.

[0180] The polarization axis of the polarizing plate 50' may be arranged substantially orthogonal to the polarization axis of the polarizing plate 50, or may be arranged substantially parallel to the polarizing axis of the polarizing plate 50. That is, the polarizing plate 50' may be arranged in a cross-Nicol arrangement or in a parallel-Nicol arrangement with the polarizing plate 50. Among them, the cross-Nicol arrangement is preferred.

[0181] The phase difference layer 40' is arranged between the polarizing plate 50' and the liquid crystal layer 20. More specifically, it is arranged between the polarizing plate 50' and the TFT substrate 10. The phase difference layer 40' may include, for example, a λ / 4 plate and a λ / 2 plate. It is preferred that these are arranged in the order of, for example, the λ / 2 plate and the λ / 4 plate are arranged in sequence from the back side.

[0182] In the liquid crystal display device 1 of the present embodiment, each pixel P includes a reflective region Rf for displaying in a reflective mode and a transmissive region Tr for displaying in a transmissive mode. Fig.25 The schematic plan view conceptually shows that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of the present embodiment. A reflective layer 130 (see, for example, FIG. 1 ) is disposed in the reflective region Rf. Figure 2 ), but the reflective layer 130 is not configured in the transmission region Tr. The ratio of the area of ​​the transmission region Tr in each pixel P can be appropriately set according to the purpose, for example, 20% to 90%. In addition, the position and shape of the transmission region Tr in the pixel P can also be appropriately set according to the purpose, etc.

[0183] In the liquid crystal display device and the semi-transmissive liquid crystal display device of this embodiment, similarly to the reflective liquid crystal display device, the liquid crystal layer 20 performs display in the transverse electric field mode in which the orientation is twisted when no voltage is applied, thereby sufficiently improving the contrast ratio of the reflective display. Therefore, the liquid crystal display device 1 of this embodiment can also be low-cost and have an improved contrast, and is also useful as an in-cell touch panel capable of displaying in the reflective mode.

[0184] (Implementation 4) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiment 1 is omitted. The liquid crystal display device of this embodiment mainly differs from the liquid crystal display device of embodiment 1 in that a light source is provided on the observation surface side relative to the liquid crystal layer 20. In addition, the liquid crystal display device of this embodiment is a reflective liquid crystal display device.

[0185] Fig.26 2 is a schematic 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. Fig.26 As shown, from the back side, it is provided with a first substrate 10, a liquid crystal layer 20, a second substrate 30, a phase difference layer 40, a polarizing plate 50, and a light source 62. In this embodiment, as the first substrate 10, a TFT substrate is preferably used.

[0186] The light source 62 (front light source) is not particularly limited as long as it is a light source that irradiates light. Specifically, for example, it is preferable to have a light source such as a light emitting diode (LED) or a light guide plate, and it is preferable to have a light guide plate. The reflective liquid crystal display device 1 has such a light source 62, so that even in an environment where the ambient light cannot be fully obtained, it can also perform bright reflective display.

[0187] Although the embodiments of the present invention have been described above, all of the matters described are applicable to the present invention as a whole.

[0188] Although the embodiments are disclosed below and the present invention is described in more detail, the present invention is not limited to these embodiments. As the polarizing plate 50, an absorption type polarizing plate is used.

[0189] (Test Examples 1 to 4) like Fig.27B As shown, the liquid crystal cell 1100 used to obtain the test cell 1000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 disposed between these substrates. Fig.27A 1 is a schematic plan view showing the structure of the liquid crystal cell 1100 when viewed from the front. Fig.27B Yes Fig.27A The A-A' line in the figure is used as a cross-sectional schematic diagram of the cross section (A-A' line cross-sectional diagram).

[0190] like Fig.27B 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 alignment film 140 are sequentially provided. The common electrode CE is formed of ITO, and the thickness of the common electrode CE is 100 nm. The dielectric layer 153 is formed of silicon nitride (SiNx), and the thickness of the dielectric layer 153 is 300 nm. The pixel electrode PE is formed of ITO, and the thickness of the pixel electrode PE is 100 nm. The pixel electrode PE has a plurality of strip portions SP and a plurality of slits S1. The width of each strip portion SP is 3 μm, and the width of each slit S1 (the interval between two adjacent strip portions SP) is 5 μm. Each strip portion SP is bent in a "<" shape. That is, each strip portion SP includes a first portion SPa extending in a certain direction (first direction) and a second portion SPb extending in a direction different from the first direction (second direction). Bending angle (the first part SPa and the second part SPb of the strip-shaped portion SP are respectively relative to Fig.27A The angle formed by the left and right directions in the image is 7°.

[0191] like Fig.27B As shown, the second substrate 30 includes a glass substrate 300 and a second horizontal alignment film 340 disposed on the glass substrate 300.

[0192] The thickness (cell gap) of the liquid crystal layer 20 is defined by plastic beads (not shown).

[0193] 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.

[0194] When using photo-alignment treatment, a photo-decomposable 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 non-polarized UV light emitted from the UV lamp unit is used as polarized UV light by the wire grid polarization element, and the polarized UV light is irradiated to the alignment film, thereby performing photo-alignment treatment. The extinction ratio of the wire grid polarization 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).

[0195] When the rubbing treatment is used, a horizontal alignment film is formed, and the rubbing treatment is performed by a rubbing roller (e.g., a roller wrapped with cloth), thereby performing the alignment treatment. Thus, the 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 cause pretilt due to the rubbing treatment is preferred, and such a material is commercially available. The liquid crystal molecules are aligned approximately parallel to the rubbing direction.

[0196] 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.).

[0197] Then, if Fig.28 As shown, a λ / 4 plate 41, a λ / 2 plate 42 and a polarizing plate 50 are sequentially attached to the second substrate 30 side of the liquid crystal unit 1100 (the adhesive layer is not shown).

[0198] Then, 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 facing downward. In this way, the test unit 1000 is manufactured. In addition, in this state, the voltage applied between the pixel electrode PE and the common electrode CE is changed, and the reflectivity is measured. The voltage application to the pixel electrode PE and the common electrode CE is performed using a function signal generator ("AFG1022" manufactured by TEKTRONIX) that can apply a voltage of 0V to 10V in a rectangular wave of 30Hz. The reflectivity is measured using a spectrophotometer ("CM-2600d" manufactured by MINOLTA). Fig.28 is a cross-sectional schematic diagram of the test unit 1000 .

[0199] Furthermore, in the manufacturing process of the test unit 1000, the test unit 2000 is manufactured in the same manner as the manufacturing method of the above-mentioned test unit 1000, except that the process of pasting the optical film on the liquid crystal unit 1100 is changed to the process of pasting the λ / 4 plate 41, the positive C plate 43, the λ / 2 plate 42 and the polarizing plate 50 on the second substrate 30 side of the liquid crystal unit 1100.

[0200] It should be noted that, as the λ / 4 plate 41, Nitto Denko Corporation's "NZF-UFO1A" (delay: 140 nm) was used in Test Examples 2 and 3, and Nitto Denko Corporation's "NZF-UFO1A" (delay: 110 nm) was used in Test Examples 1 and 4. As the λ / 2 plate 42, Nitto Denko Corporation's "NZF-UFO1A" (delay: 270 nm) was used in Test Examples 2 and 3, and Nitto Denko Corporation's "NZF-UFO1A" (delay: 260 nm) was used in Test Examples 1 and 4. As the positive C plate 43, a plate with an Rth of 200 nm was used.

[0201] The test unit 1000 described above was used in Test Examples 1, 2, and 4, and the test unit 2000 described above was used in Test Example 3, and the following studies (a) and (b) were conducted. In Experimental Examples 1 to 3, the liquid crystal material is positive type, and the display mode is TW-FFS mode. In Experimental Example 4, the liquid crystal material is negative type, and the display mode is TW-FFS mode. Figure 6 The optical axis settings (initial settings) and specifications of Test Examples 1 to 4 are shown. Figure 6 It also conceptually represents the test case Diagram of the optical axis setting (but excluding the positive C plate).

[0202] [Table 3]

[0203] (Test Example 5) like Fig.29B As shown, the liquid crystal unit 3100 used to obtain the test unit 3000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 disposed between these substrates. Fig.29A It is a schematic plan view showing the structure of the test cell 3000 (and the liquid crystal cell 3100 ) when viewed from the front. Fig.29B Yes Fig.29A The A-A' line in the figure is used as a cross-sectional schematic diagram of the cross section (A-A' line cross-sectional diagram).

[0204] 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 the 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°).

[0205] like Fig.30 As shown, a λ / 4 plate 41, a first λ / 2 plate 42a, a second λ / 2 plate 42b and a polarizing plate 50 (adhesive layer not shown) are sequentially attached to the second substrate 30 side of the liquid crystal cell 300. As the polarizing plate 50, "NPF-CRT1794KDUHC3" manufactured by Nitto Denko Corporation is used, as the λ / 4 plate 41, "NZF-UF01A" manufactured by Nitto Denko Corporation (retardation: 110nm) is used, and as the λ / 2 plates 42a and 42b, "NZF-UF01A" manufactured by Nitto Denko Corporation (retardation: 260nm) is used. Then, a drop of matching oil mo is dropped on the reflector 130 having MRS, and the liquid crystal cell 3100 is placed on the reflector 130 with the first substrate 10 side facing downward. In this way, the test cell 3000 is manufactured. Fig.30 is a schematic cross-sectional view of the test unit 3000 .

[0206] In Experimental Example 5, the above-mentioned test unit 3000 was used to conduct the following studies (a) and (b). In Experimental Example 5, the liquid crystal material is a negative type with a negative dielectric anisotropy, and the display mode is a VA mode. Fig.31 The optical axis settings (initial settings) and specifications of Comparative Example 1 are shown.

[0207] [Table 4]

[0208] In the following studies, the normalized reflectance was calculated using the following formula: Normalized reflectance (%)=(n gray reflectance−0 gray reflectance) / (255 gray reflectance−0 gray reflectance)×100.

[0209] (A) Evaluation of tilted γ characteristics The γ curve was analyzed with the polar angle set to 50°. The results are shown in Figures 32A to 32C. In these figures, the upper part shows a schematic cross-sectional view of the test unit in each example, the middle part shows a graph of the γ curve, and the lower part shows a distribution graph of the reflected brightness of the white display at a grayscale of 255. In the graph in the middle part, the horizontal axis is the grayscale (0 to 255 levels) in the front view, and the vertical axis is the standardized reflectance. The front side is corrected to γ ​​= 2.2. In each graph, the angle added to each γ curve (the azimuth is defined as 0° in the 3-point direction, and the polar angle is defined as 0° in the normal direction of the viewing surface of the panel) represents the angle in the azimuth direction (where the polar angle is 50°). For example, in the case of Test Example 1, "75°" represents the γ curve at an azimuth direction of 75° and a polar angle of 50°, "210°" represents the γ curve at an azimuth direction of 210° and a polar angle of 50°, and "285°" represents the γ curve at an azimuth direction of 285° and a polar angle of 50°. Figures 32A to 32C It is a figure which shows the results of Test Examples 1-5.

[0210] The gamma curve was analyzed by changing the polar angle. The results are shown in Figure 33A to Figure 33C In these figures, the upper graph shows the case of a polar angle of 30°, the middle graph shows the case of a polar angle of 40°, and the lower graph shows the case of a polar angle of 50°. In each graph, the horizontal axis is the grayscale (0 to 255 levels) in the front view, and the vertical axis is the normalized reflectance. Figure 33A to Figure 33C It is a figure which shows the results of Test Examples 1-5.

[0211] Depend on Figures 32A to 32C and Figure 33A to Figure 33B It can be seen that in the positive liquid crystal material (Test Examples 1 to 4), when the polar angle is 30°, the tilt γ characteristics are almost equal, and when the polar angle is 40° or more, the tilt γ characteristics become a problem in Test Example 3. However, by comparing Test Example 2 with Test Example 3, it can be seen that the tilt γ characteristics are improved by adding the positive C plate 43.

[0212] (b) Simulation evaluation from the oblique direction The oblique γ characteristics were evaluated relative to the γ characteristics observed from the front, and an image simulation was performed when the display screen was visually confirmed from an oblique direction. Specifically, each test unit was displayed with a color original image, and a camera was used to view the image from the oblique direction. Fig.34 The images shown are taken from all directions (the images shown are taken from all directions and at a polar angle of 50 degrees). The results are shown in Figure 36A to Figure 36C For comparison, Fig.35 The image shown is taken from the front (also called the original image). Fig.34 This is a diagram that conceptually shows the azimuth angle. Fig.35 is an image taken from the front, This is a test example Result graph.

[0213] exist Fig.35 and Figure 36A to Figure 36C In the example, the simulated image and its orientation (angle) when the image is most lifted are published in column (I), and the simulated image and its orientation (angle) when the image is most sunken are published in column (II). "Lifting image" means that the grayscale is higher than the front side, and "sunken image" means that the grayscale is lower than the front side.

[0214] according to In the test case The best example of the balance between white blur, black blur and natural color tone (chroma of facial color, etc.) is Test Example 3. White blur refers to the phenomenon that bright parts become uniformly brighter. For example, when the change of the γ curve is smaller than γ = 2.2, the image rises and the white blur becomes larger. Black blur refers to the phenomenon that dark parts become uniformly darker. For example, when the change of the γ curve is larger than γ = 2.2, the image sinks and the black blur becomes larger. For example, in Test Example 5, in the simulated image that is the most floating, the white blur is large (refer to Fig.36C In the simulated image at the bottom of the image, the facial color of the person is unnatural (refer to Fig.36C ).

[0215] Fig.36A and Fig.36B By comparing Test Example 2 with Test Example 3, it can be seen that by adding the positive C plate 43, both white blurring and black blurring can be suppressed (refer to Fig.36A s, t).

[0216] 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

[0217] 1: Liquid crystal display device 1X: LCD panel 10, 30: substrate 20: Liquid crystal layer 21, 21A, 21B: Liquid crystal molecules 40, 40': Phase difference layer 41: λ / 4 plate 42, 42a, 42b: λ / 2 plate 41SA, 42SA, 42aSA, 42bSA: In-plane slow axis 43, 43R, 44: Positive C plate 50, 50': polarizing plate 50AA: Polarization axis 61, 62: Light source 100, 300: Support substrate 110: TFT 121, 122: Electrode 130: Reflective layer 140, 340: horizontal orientation film 151, 152: Interlayer insulation layer 153: Dielectric layer 160: Contact electrode 210, 310: Color filter layer 1000, 2000, 3000: test unit 1100, 3100: Liquid crystal unit BP: Baseboard Circuit CE: Common Electrode PE: Pixel electrode CH1, CH2: contact holes DR: Display Region FR: Non-display area GL: Gate wiring SL: Source wiring p: convex part P: Pixel Rf: Reflection area Tr: Transmission area S1: Slit SP, SPa, SPb: Strip TC: Touch wiring contact TD: Touch driver TL, TL1, TL2: Touch wiring TX: Touch sensor electrode

Claims

1. A liquid crystal display device, comprising, from the back side, a first substrate, a liquid crystal layer, a second substrate, a phase difference layer and a polarizing plate, the liquid crystal display device having a plurality of pixels arranged in a matrix, characterized in that , The first substrate comprises: a reflective layer that reflects light; a first electrode and a second electrode that can generate a transverse electric field in the liquid crystal layer; and a first horizontal alignment film, which is in contact with the liquid crystal layer, The second substrate has a second horizontal alignment film in contact with the liquid crystal layer, and the liquid crystal layer exhibits a twisted alignment when no voltage is applied. The phase difference layer includes a λ / 4 plate, a λ / 2 plate and a positive C plate.

2. The liquid crystal display device according to claim 1, wherein: The liquid crystal layer includes a positive liquid crystal material or a negative liquid crystal material.

3. The liquid crystal display device according to claim 2, characterized in that: When the liquid crystal layer includes the positive liquid crystal material, the angle formed by the polarization axis of the polarizing plate and the alignment direction of the liquid crystal molecules defined by the first horizontal alignment film is greater than or equal to 63.5° and less than or equal to 71.5°, When the liquid crystal layer includes the negative liquid crystal material, an angle formed by a polarization axis of the polarizing plate and an alignment direction of liquid crystal molecules defined by the first horizontal alignment film is 20.5° or more and 26° or less.

4. The liquid crystal display device according to any one of claims 1 to 3, characterized in that: The positive C plate is located between the λ / 4 plate and the λ / 2 plate.

5. The liquid crystal display device according to any one of claims 1 to 4, characterized in that: The absolute value of the thickness direction phase difference Rth (nm) of the positive C plate is 150 to 270 nm.

6. The liquid crystal display device according to any one of claims 1 to 5, characterized in that: The phase difference layer further includes a second positive C plate, and the second positive C plate is located between the λ / 2 plate and the polarizing plate.

7. The liquid crystal display device according to claim 6, characterized in that: The absolute value of the thickness direction phase difference Rth (nm) of the second positive C plate is 50 to 130 nm.

8. The liquid crystal display device according to any one of claims 1 to 7, characterized in that: The twist angle of the liquid crystal layer when no voltage is applied is greater than or equal to 70° and less than or equal to 85°.

9. The liquid crystal display device according to any one of claims 2 to 8, characterized in that: When the liquid crystal layer includes the positive liquid crystal material, a product dΔn of a thickness d of the liquid crystal layer and a birefringence Δn of the liquid crystal material is greater than or equal to 218 nm and less than or equal to 255 nm.

10. The liquid crystal display device according to any one of claims 2 to 9, characterized in that: When the liquid crystal layer includes the positive liquid crystal material, the angle formed by the in-plane slow axis of the λ / 2 plate and the alignment direction of the liquid crystal material defined by the first horizontal alignment film is 47.5° or more and 52.5° or less.

11. The liquid crystal display device according to any one of claims 1 to 10, characterized in that: When the liquid crystal layer includes the negative liquid crystal material, a product dΔn of a thickness d of the liquid crystal layer and a birefringence Δn of the liquid crystal material is greater than or equal to 230 nm and less than or equal to 260 nm.

12. The liquid crystal display device according to any one of claims 1 to 11, characterized in that: When the liquid crystal layer includes the negative liquid crystal material, the angle formed by the in-plane slow axis of the λ / 2 plate and the alignment direction of the liquid crystal material defined by the first horizontal alignment film is 38.5° or more and 42.5° or less.

13. The liquid crystal display device according to any one of claims 1 to 12, characterized in that: At least one of the first electrode and the second electrode includes a plurality of strip-shaped portions and a slit located between two adjacent strip-shaped portions among the plurality of strip-shaped portions.

14. The liquid crystal display device according to any one of claims 1 to 13, characterized in that: The liquid crystal display device is monodomain oriented.

15. The liquid crystal display device according to any one of claims 1 to 14, characterized in that: The liquid crystal display device performs display in a normally black mode.

16. The liquid crystal display device according to any one of claims 1 to 15, characterized in that: One of the first electrode or the second electrode is a pixel electrode provided in each of the plurality of pixels, the other of the first electrode and the second electrode 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 the corresponding touch sensor electrodes.

17. The liquid crystal display device according to any one of claims 1 to 16, characterized in that: The first substrate has a thin film transistor, which is disposed in each of the plurality of pixels and includes an oxide semiconductor layer. The oxide semiconductor layer contains an In-Ga-Zn-O based semiconductor.

18. The liquid crystal display device according to any one of claims 1 to 17, characterized in that: Also includes a light source.

Images