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 improving contrast at low cost. The liquid crystal display device includes 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, and has a plurality of pixels arranged in a matrix. The first substrate has a reflective layer that reflects light, a first electrode and a second electrode capable of generating a lateral electric field in the liquid crystal layer, and a first horizontal alignment film in contact with the liquid crystal layer, and the second substrate has a second horizontal alignment film in contact with the liquid crystal layer. The liquid crystal layer contains a positive-type liquid crystal material or a negative-type liquid crystal material and is twisted and oriented when no voltage is applied, and 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 within a specified range.

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. According to the display mode, they are generally divided into transmissive liquid crystal display devices and reflective liquid crystal display devices. Transmissive liquid crystal display devices are devices that use transmitted light based on the backlight source 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 source to display in a reflective mode. As a display device having these characteristics at the same time, a semi-transmissive liquid crystal display device has an area for displaying in a transmissive mode and an area for displaying in a reflective mode in each pixel (for example, refer to 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 examples of the longitudinal electric field method, TN (Twisted Nematic) mode, MVA (Multi-domain Vertical Alignment) mode, etc. can be exemplified, and as the transverse electric field method, IPS (In-plane Switching) mode, FFS (Fringe Field Switching) mode, etc. can be exemplified. 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, liquid crystal display devices used in smart phones or tablet computers usually have touch sensor functions. As touch sensor methods, various methods such as resistive film, electrostatic capacitance, and optical are known. In liquid crystal display devices (also called touch panels) equipped with touch sensors, there are external touch sensor methods (external type) and built-in touch sensor methods (built-in type). Compared with external touch panels, built-in touch panels are more conducive to narrow frame, thin and lightweight, etc., and also have the advantage of improving light transmittance.

[0006] There are two types of built-in touch panels: On-Cell (external embedded) type and In-Cell (internal embedded) type. 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, a relative substrate arranged opposite to the substrate, and a liquid crystal layer sandwiched between these substrates. However, generally speaking, in the internal embedded type, a layer that performs the touch sensor function is arranged in the display panel, and in the external embedded type, the layer that performs the touch sensor function is arranged between the display panel and the polarizing plate arranged on the viewing side of the display panel. Among them, the internal embedded type can, in principle, realize the thinnest and lightest touch panel. In addition, since liquid crystal display devices capable of displaying in a reflective mode are suitable for outdoor use, although there is currently a demand for internal embedded touch panels capable of displaying in a reflective mode, it has not yet been realized.

[0007] The reason for not being realized 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 relative electrode or a common electrode) is arranged on the opposite substrate side. Therefore, the inventors believe that if it is a lateral electric field mode such as the FFS mode, since a pair of electrodes are only arranged on the active matrix substrate side, it is possible to realize an embedded touch panel that can display a reflective mode. However, further research has found that even if the existing lateral electric field method is simply applied to a reflective liquid crystal display device, its reflectivity is low. For example, the reflectivity when the VA mode, which is a type of longitudinal electric field method, is adopted, is about 60%. In this way, if the reflectivity is low, the contrast ratio becomes small, so it is considered that it cannot be used as an embedded touch panel.

[0008] Therefore, an in-depth study was conducted, and as a result, the inventor of the present invention discovered a liquid crystal display device, which is provided with 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 liquid crystal layer, and a first horizontal alignment film connected to the liquid crystal layer, the second substrate having a second horizontal alignment film connected to the liquid crystal layer, and the liquid crystal layer is configured to be a liquid crystal display device of a lateral electric field mode when a twisted orientation is taken when no voltage is applied, and the contrast ratio can be improved, and it is useful as an embedded touch panel that can display in a reflective mode. However, in this device, since a special phase difference plate is preferably used as a phase difference layer, a new problem of increased cost is found. In addition, in the field of optical films, in order to seek cost reduction, 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 can improve the contrast ratio at low cost and is also useful as an in-cell touch panel capable of displaying in a reflective mode. Solutions for solving problems

[0010] (1) One embodiment of the present invention is a liquid crystal display device, which is a liquid crystal display device that includes, from the back side, a first substrate, a liquid crystal layer, a second substrate, a retardation layer, and a polarizing plate in order, and has a plurality of pixels arranged in a matrix, wherein the first substrate has a reflective layer that reflects light, a first electrode and a second electrode that can generate a lateral electric field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer, the second substrate has a second horizontal alignment film that is in contact with the liquid crystal layer, the retardation layer includes: a λ / 4 plate and a λ / 2 plate, the liquid crystal layer contains a positive liquid crystal material or a negative liquid crystal material, and takes a twisted orientation when no voltage is applied, when the liquid crystal layer contains 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 specified by the first horizontal alignment film is greater than 63.5° and less than 71.5°, and when the liquid crystal layer contains the negative liquid crystal material, the angle formed by the polarization axis of the polarizing plate and the alignment direction of the liquid crystal molecules specified by the first horizontal alignment film is greater than 20.5° and less than 26°.

[0011] (2) In addition, one embodiment of the present invention is a liquid crystal display device, in which, in addition to the configuration of (1) above, the retardation layer further includes a positive C plate.

[0012] (3) In addition, an embodiment of the present invention is a liquid crystal display device, in which, in addition to the configuration of (2) above, the positive C plate is located between the λ / 4 plate and the λ / 2 plate.

[0013] (4) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (2) or (3), has an absolute value of the thickness direction phase difference Rth (nm) of the positive C plate of 150 to 270 nm.

[0014] (5) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (2), the above (3) or the above (4), the phase difference layer also includes a second positive C plate, and the second positive C plate is located between the λ / 2 plate and the polarizing plate.

[0015] (6) In addition, an embodiment of the present invention is a liquid crystal display device, in which, in addition to the configuration of (5), the absolute value of the thickness direction phase difference Rth (nm) of the second positive C plate is 50 to 130 nm.

[0016] (7) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of the above (1), the above (2), the above (3), the above (4), the above (5) or the above (6), has a twist angle of the liquid crystal layer when no voltage is applied that is greater than 70° and less than 85°.

[0017] (8) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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), 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.

[0018] (9) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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), 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°.

[0019] (10) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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), 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.

[0020] (11) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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), 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°.

[0021] (12) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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), at least one of the first electrode and the second electrode has a plurality of strip-shaped portions and a slit, and the slit is located between two adjacent strip-shaped portions among the plurality of strip-shaped portions.

[0022] (13) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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) or the above (12), the liquid crystal layer is monodomain oriented.

[0023] (14) In addition, a certain embodiment of the present invention is a liquid crystal display device, which displays in a normally black mode 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).

[0024] (15) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, 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), the above (13) or the above (14), one of the first electrode or the second electrode is a pixel electrode respectively arranged on the plurality of pixels, and the other is a common electrode including a plurality of segments that can function as touch sensor electrodes respectively, and the first substrate has a plurality of touch wirings respectively connected to the corresponding touch sensor electrodes.

[0025] (16) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14) or (15), has the first substrate having thin film transistors respectively arranged on the plurality of pixels and including an oxide semiconductor layer, and the oxide semiconductor layer includes an In-Ga-Zn-O based semiconductor.

[0026] (17) In addition, a certain embodiment of the present invention is a liquid crystal display device, which, based on the structure of (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15) or (16), further includes a light source. Effects of the Invention

[0027] According to the present invention, there is provided a liquid crystal display device which can improve the contrast ratio at low cost and is also useful as an in-cell touch panel capable of displaying in a reflective mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the first embodiment. Figure 2 FIG. 1 is a schematic cross-sectional view showing a liquid crystal display device 1 according to an example of Embodiment 1 in more detail. Figure 3 This is a schematic plan view of the entire liquid crystal display device 1 according to an example of the first embodiment when viewed from the observation surface side. Figure 4 The top view conceptually shows the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, 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 polarizing plate 50 in a liquid crystal display device 1 which 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 polarizing plate 50 in sequence. 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 becomes 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. 9The top view conceptually shows the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, 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 polarizing plate 50 in a liquid crystal display device 1 which 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 polarizing plate 50 in sequence. 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 becomes minimum. This is also a diagram conceptually showing the setting of the optical axis in Example 3. Fig.12 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.13 It is a schematic cross-sectional view showing the liquid crystal display device 1 according to the first modification of the first embodiment in more detail. Fig.14 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the second embodiment. Fig.15A This is a diagram showing simulation results when the liquid crystal material is a positive type in the second embodiment. Fig. 15B This is a diagram showing simulation results when the liquid crystal material is a positive type in the second embodiment. Fig.16 3 is a diagram showing the simulation results of Example 1 and Example 3. Fig.17 This is a graph showing the distribution of the maximum value of black brightness for Examples 1 to 4. Fig.18 This is a diagram showing simulation results when the liquid crystal material is a negative type in the second embodiment. Fig.19 This is a graph showing the distribution of the maximum value of black brightness for Examples 11 to 14. Fig. 20 It is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the third embodiment. Fig.21 This is a diagram showing simulation results when the liquid crystal material is a positive type in the third embodiment. Fig. 22 This is a graph showing the distribution of the maximum value of black brightness for Examples 21 to 23. Fig.23 This is a diagram showing simulation results when the liquid crystal material is a negative type in the third embodiment. Fig.24 This is a graph showing the distribution of the maximum value of black brightness for Examples 31 to 33. Fig.25 It is a schematic cross-sectional view of a liquid crystal display device according to an example of the fourth embodiment. Fig.26 1 is a schematic plan view conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 according to the fourth embodiment. Fig. 27 It is a schematic cross-sectional view of a liquid crystal display device according to an example of the fifth embodiment. Fig.28A 1 is a schematic plan view showing the structure of the liquid crystal cell 1100 when viewed from the front. Fig.28B Yes Fig.28A The AA line in the figure is used as a cross-sectional schematic diagram of the cut surface (AA line cross-sectional diagram). Fig.29 is a cross-sectional schematic diagram of the test unit 1000 . Fig. 30A 1 is a schematic plan view showing the structure of the test unit 2100 (and the liquid crystal unit 2100 ) when viewed from the front. Fig. 30B Yes Fig. 30A The AA line in the figure is used as a cross-sectional schematic diagram of the cut surface (AA line cross-sectional diagram). Fig.31 is a cross-sectional schematic diagram of the test unit 2000. Fig.32 This is a diagram conceptually showing the setting of the optical axis in Comparative Example 1. Fig.33 It is a graph showing the results of Examples 1 and 2 and Comparative Example 1. Fig.34 It is a graph showing the results of Examples 1 and 2. Fig.35 It is a graph showing the results of Example 1. Fig.36 It is a graph showing the results of Example 1. Fig.37 It is a graph showing the results of Examples 3 and 4 and Comparative Example 1. Fig.38 It is a graph showing the results of Examples 3 and 4. Fig.39It is a graph showing the results of Example 3. Fig.40 It is a graph showing the results of Example 3. Fig.41A It is a graph showing the waveforms of Examples 1 and 3. Fig.41B It is a graph showing the waveforms of Examples 2 and 4. Fig.42A It is a figure which shows the results of Examples 6 and 7. Fig.42B It is a figure which shows the result of Example 8 and 9. Fig.42C It is a graph showing the results of Comparative Example 2. Fig.43A It is a figure which shows the results of Examples 6 and 7. Fig.43B It is a figure which shows the result of Example 8 and 9. Fig.43C It is a graph showing the results of Comparative Example 2. Fig.44 This is a diagram conceptually showing the azimuth angle. Fig.45 This is an image taken from the front. Fig.46A It is a figure which shows the results of Examples 6 and 7. Fig.46B It is a figure which shows the result of Example 8 and 9. Fig.46C It is a graph showing the results of Comparative Example 2. DETAILED DESCRIPTION

[0029] (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.

[0030] The non-voltage-applied state refers to a state in which the voltage applied to the liquid crystal layer is less than the threshold voltage (including no voltage application). The voltage-applied state refers to a state in which the voltage applied to the liquid crystal layer is greater than the threshold voltage. In this specification, the non-voltage-applied state is also referred to as the non-voltage-applied state, and the voltage-applied state is referred to as the voltage-applied state.

[0031] The polar angle refers to an angle formed between a target direction (eg, a measurement direction) and a normal direction of the screen of the liquid crystal panel. The azimuth refers to the direction when the direction to be the object is projected onto the screen of the liquid crystal panel, and is expressed by the angle (azimuth angle) 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. For the angle and the azimuth angle, the counterclockwise direction is set as the positive angle starting from the reference azimuth, and the clockwise direction is set as the negative angle starting from the reference azimuth. Both the counterclockwise and clockwise directions represent the rotation direction when observing the screen of the liquid crystal panel from the observation surface side (front). In addition, the angle represents the value measured in the state of observing the screen of the liquid crystal panel from above, and represents an acute angle as long as there is no description of the rotation direction, etc.

[0032] Regarding the axis azimuth of the optical film, if it is a polarizing plate, it refers to the azimuth of the polarization axis of the polarizing plate, and if it is a retardation layer, it refers to the azimuth of the slow axis. Regarding the polarization axis of the polarizing plate, if it is an absorption type polarizing plate, it refers to the absorption axis, and if it is a reflection type polarizing plate, it refers to the reflection axis. The axis azimuth of the retardation layer refers to the azimuth of the in-plane slow axis of the retardation layer, unless otherwise specified.

[0033] The retardation layer refers to a layer in which at least one of the in-plane retardation (also called in-plane phase difference) Re and the thickness direction retardation (also called thickness direction phase difference) Rth has a value of 10 nm or more (≥10 nm). Preferably, it refers to a layer having a value of 20 nm or more. In addition, in this specification, the values described as Re and Rth are absolute values, unless otherwise specified.

[0034] The in-plane phase difference Re is defined by Re = (nx - ny) × d. The thickness direction phase difference Rth is defined by Rth = {nz - (nx + ny) / 2} × d. nx represents the principal refractive index in the in-plane slow axis direction 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 the plane of 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.

[0035] The A plate refers to a retardation plate that satisfies "nx > ny ≈ nz". The positive C plate (also called +C-plate) in the 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.

[0036] Unless otherwise specified, the measurement wavelength of optical parameters such as refractive index and phase difference is 550 nm.

[0037] Substantially parallel means that the angle (absolute value) formed by the two is within the range of 0°±10°, preferably within the range of 0°±5°, and more preferably 0° (i.e., parallel in a narrow sense). In addition, substantially orthogonal (or substantially perpendicular) means that the angle (absolute value) formed by the two is within the range of 90°±10°, preferably within the range of 90°±5°, and more preferably 90° (i.e., perpendicular or perpendicular in a narrow sense).

[0038] Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiment, and the design can be appropriately changed within the scope of the configuration satisfying the present invention.

[0039] [Implementation Method 1] Figure 1 is a schematic cross-sectional view of a liquid crystal display device 1 according to an example of the present embodiment. Figure 2 It is a schematic cross-sectional view showing the liquid crystal display device 1 according to an example of the present embodiment in more detail. Figure 3 1 is a schematic plan view of the entire liquid crystal display device 1 of one example of the present embodiment when viewed from the observation surface side. Figure 1 As shown, the liquid crystal display device 1 includes a first substrate 10, a liquid crystal layer 20, a second substrate 30, a phase difference layer 40, and a polarizing plate 50 in order from the back side. In this embodiment, a TFT substrate is used as the first substrate 10. In addition, a portion or a structure composed of a structure in which the liquid crystal layer 20 is sandwiched between the first substrate 10 and the second substrate 30 is also referred to as a liquid crystal panel 1X.

[0040] like Figure 3 As 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 less than two or more than four. Each pixel P includes a thin film transistor (TFT) 110, a first electrode 121 and a second electrode 122 capable of generating a lateral electric field on the liquid crystal layer 20. The gate electrode of the TFT 110 is electrically connected to the corresponding gate wiring (also called scanning wiring) GL, and the source electrode of the TFT 110 is electrically connected to the corresponding source wiring (also called signal wiring) SL. The drain of the TFT 110 is electrically connected to the second electrode 122.

[0041] <First Substrate> like Figure 2As shown, the first substrate 10 has a reflective layer 130 that reflects light, a first electrode 121, a second electrode 122, and a first horizontal alignment film 140 connected to the liquid crystal layer 20 in sequence from the back side to the observation side. The first substrate 10 also preferably has a supporting substrate 100 and a backplane circuit BP on the back side of the reflective layer 130. An insulating layer (also called an insulating film) is provided between each layer as needed. For example, a first interlayer insulating layer 151 is provided in a manner covering the backplane circuit BP, a second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 with the reflective layer 130 sandwiched therebetween, and a dielectric layer (also called a third interlayer insulating layer) 153 is provided between the first electrode 121 and the second electrode 122.

[0042] The support substrate 100 is preferably transparent and insulating, and examples of the support substrate 100 include a glass substrate and a plastic substrate.

[0043] The backplane circuit BP is provided on the support substrate 100. The backplane circuit BP is a circuit for driving the plurality of pixels P, and includes the TFTs 110, the gate wiring GL, the source wiring SL, etc. In addition, it is usually provided with a gate insulating film.

[0044] TFT110 is provided in each of the plurality of pixels P. As TFT110, a TFT containing 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, compared with amorphous silicon TFT, the oxide semiconductor TFT can operate at a higher speed. In addition, the oxide semiconductor layer is formed by a simpler process than the polycrystalline silicon layer, so it can also be applied to devices requiring a large area.

[0045] Since oxide semiconductor TFT has excellent off-leakage characteristics, it is also possible to use a driving method that reduces the frequency of image rewriting for display. For example, when displaying a static image, the image data can be rewritten once per second. This driving method is called dormant drive or low-frequency drive, etc., which can significantly reduce the power consumption of the liquid crystal display device. By adopting dormant drive, by performing touch detection during the period when the image is not rewritten, the reduction in the sensitivity of the touch operation caused by the noise from the drive circuit can be suppressed, and the S / N ratio (signal-to-noise ratio) can be made, for example, about 10 times that of the past.

[0046] Oxide semiconductor TFTs are also advantageous in reducing the size of TFTs, and thus a configuration in which a memory circuit is provided for each pixel P (also referred to as MIP (Memory In Pixels)) can be appropriately realized.

[0047] 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 in which the c-axis is oriented substantially perpendicular to the layer surface.

[0048] The oxide semiconductor layer may be a single layer or may have a stacked structure of more than two 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 crystalline 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 included in the lower layer and the energy gap of the oxide semiconductor included in the upper layer may also be different.

[0049] The materials, structures, and film formation methods of amorphous oxide semiconductors and crystalline oxide semiconductors, and the composition of oxide semiconductor layers having a stacked structure are described in, for example, Japanese Patent Application Laid-Open No. 2014-007399. For reference, the disclosure of Japanese Patent Application Laid-Open No. 2014-007399 is incorporated herein in its entirety.

[0050] Specifically, as an oxide semiconductor layer, it is preferred to contain at least one metal element selected from In (indium), Ga (gallium) and Zn (zinc). Among them, an oxide semiconductor film containing a ternary oxide of In, Ga and Zn is more preferred. As a ternary oxide of In, Ga and Zn, for example, indium gallium zinc oxide is preferably exemplified. A semiconductor containing a ternary oxide of In, Ga and Zn is called an In-Ga-Zn-O semiconductor, but in this semiconductor, the ratio (composition ratio) of In, Ga and Zn is not particularly limited, for example, In:Ga:Zn=2:2:1, In:Ga:Zn=1:1:1, In:Ga:Zn=1:1:2, etc.

[0051] The In-Ga-Zn-O semiconductor may be amorphous or crystalline. As a crystalline In-Ga-Zn-O semiconductor, a semiconductor whose c-axis is oriented substantially perpendicular to the layer surface is preferably used.

[0052] In addition, the crystal structure of the crystalline In-Ga-Zn-O semiconductor is disclosed in, for example, the above-mentioned Japanese Patent Publication No. 2014-007399, Japanese Patent Publication No. 2012-134475, Japanese Patent Publication No. 2014-209727, etc. For reference, the disclosures of Japanese Patent Publication No. 2012-134475 and Japanese Patent Publication No. 2014-209727 are all cited in this specification. The TFT with the In-Ga-Zn-O semiconductor layer has a high mobility (more than 20 times compared with a-SiTFT) and a low leakage current (less than 1 / 100 compared with a-SiTFT), so it is suitable for use as a driving TFT (for example, a TFT included in a driving circuit provided on the same substrate as the display area around a display area including a plurality of pixels) and a pixel TFT (a TFT provided in a pixel).

[0053] The oxide semiconductor layer may include an oxide semiconductor other than an In-Ga-Zn-O semiconductor. For example, a ternary oxide of In, Sn (tin) and Zn is listed, such as In2O3-SnO2-ZnO, and InSnZnO is preferably exemplified. A semiconductor containing a ternary oxide of In, Sn and Zn is called an In-Sn-Zn-O semiconductor. Alternatively, the oxide semiconductor layer may also include In-Al-Zn-O series semiconductors, In-Al-Sn-Zn-O series semiconductors, Zn-O series semiconductors, In-Zn-O series semiconductors, Zn-Ti-O series semiconductors, Cd-Ge-O series semiconductors, Cd-Pb-O series semiconductors, CdO (cadmium oxide), Mg-Zn-O series semiconductors, In-Ga-Sn-O series semiconductors, In-Ga-O series semiconductors, Zr-In-Zn-O series semiconductors, Hf-In-Zn-O series semiconductors, Al-Ga-Zn-O series semiconductors, Ga-Zn-O series semiconductors, In-Ga-Zn-Sn-O series semiconductors, etc.

[0054] The first interlayer insulating layer 151 is provided to cover the backplane circuit BP. The surface of the first interlayer insulating layer 151 on the side of the reflective layer 130 preferably has a concavo-convex shape (also referred to as a concavo-convex surface structure). Thus, the reflective layer 130 can have a concavo-convex surface structure reflecting the shape. The first interlayer insulating layer 151 having a concavo-convex surface structure can be formed using a photosensitive resin, for example, as described in Patent Gazette No. 3394926.

[0055] The reflective layer (also referred to as a reflective film) 130 is provided on the first interlayer insulating layer 151. The reflective layer 130 is formed of a material that reflects light. Among them, it is preferably formed of a metal material with high reflectivity. Examples of the material of the reflective layer 130 include silver alloys and aluminum alloys.

[0056] Preferably, the reflective layer 130 has a concave-convex shape reflecting the concave-convex surface structure preferably possessed by the first interlayer insulating layer 151. That is, the reflective layer 130 also preferably has a concave-convex surface structure. The concave-convex surface structure is also referred to as MRS (MicroReflective Structure), which is provided to diffusely reflect ambient light and realize a white display close to paper white. Preferably, the concave-convex surface structure is composed of a plurality of convex portions p randomly arranged in such a manner that the center spacing of adjacent convex portions p is 5 μm or more and 50 μm or less. The center spacing of adjacent convex portions p is more preferably 10 μm or more and 20 μm or less. Observed from the normal direction of the supporting substrate, the shape of the convex portion p is preferably approximately circular or approximately polygonal. The area occupied by the convex portion p in one pixel P is preferably, for example, approximately 20 to 40%, and the height of the convex portion p is, for example, 1 μm or more and 5 μm or less.

[0057] The second interlayer insulating layer 152 is provided on the first interlayer insulating layer 151 so as to cover the reflective layer 130. That is, the reflective layer 130 is arranged between the first interlayer insulating layer 151 and the second interlayer insulating layer 152.

[0058] 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 (relative dielectric constant ε=2~5) such as acrylic resin, polyimide resin, and phenolic varnish resin, or stacked bodies thereof can be listed. The film thickness of the organic insulating film is not particularly limited, but for example, it is greater than 2μm and less than 4μm. As an inorganic insulating film obtained using an inorganic insulating material, for example, inorganic films (relative dielectric constant ε=5~7) such as silicon nitride (SiNx) and silicon oxide (SiO2), or stacked films thereof can be listed. The film thickness of the inorganic insulating film is not particularly limited, but for example, it is Above and In addition, a laminate of an organic insulating film and an inorganic insulating film may be used. Among them, the first interlayer insulating layer 151 and the second interlayer insulating layer 152 are preferably organic insulating films.

[0059] 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 surface side than the reflective layer 130 may also be in a form with low transmittance or opaque. From the viewpoint of light utilization efficiency, the second interlayer insulating layer 152 may be in a form with high transparency, or may use a material with high transmittance different from that of the first interlayer insulating layer 151.

[0060] 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 side closer to the back than the first electrode 121 and the second electrode 122) relative to the first electrode 121 and the second electrode 122. In addition, in the first electrode 121 and the second electrode 122, in this embodiment, the second electrode 122 is relatively located on the observation surface side, and the first electrode 121 is located on the back side. The electrode relatively located on the observation surface side is also called an upper electrode, and the electrode relatively located on the back side is also called a lower electrode.

[0061] One of the first electrode 121 and the second electrode 122 is a pixel electrode PE, and the other is a common electrode CE. The pixel electrode is provided on each of the plurality of pixels P. The pixel electrode is electrically connected to the backplane circuit BP. In the present embodiment, the first electrode 121 (lower electrode) is the common electrode CE, and the second electrode 122 (upper electrode) is the pixel electrode PE.

[0062] At least one of the first electrode 121 and the second electrode 122 preferably has a plurality of strip-shaped portions SP and a slit S1 between two adjacent strip-shaped portions among the plurality of strip-shaped portions. The strip-shaped portion SP is equivalent to the electrode portion, and the slit S1 is equivalent to the opening portion, but such an electrode is also called a slit electrode or a finger electrode. From the viewpoint of easy generation of a transverse electric field, it is preferred that at least the upper electrode (the pixel electrode PE in this embodiment) is a slit electrode. At this time, 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.

[0063] The multiple strips SP constituting the slit electrode preferably extend in directions that are substantially parallel to each other. In addition, it is preferably a straight line shape extending in the same direction. The straight line shape means that the center line of the strip SP is a straight line shape, rather than the outer edge of the strip SP, and the center line of the strip SP refers to the line that divides the strip SP into two equal parts in the width direction. The width direction refers to a direction that is substantially perpendicular to the direction in which the strip SP extends when viewed from above. In addition, there may be a bend (also called a kink) in the middle of the strip SP (for example, at the end), but it is preferred that there is no bend.

[0064] 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.

[0065] In addition, in the top 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 the finger angle) may be 0°, or may be greater than 0° and less than 30°. The form in which the finger angle is 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.

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

[0067] However, in the present embodiment, the configuration in which the pixel electrode PE is disposed above the common electrode CE is described, but in a relatively large liquid crystal display device, that is, in a liquid crystal display device in which the area of ​​the pixel P is relatively large, it is preferred that the pixel electrode PE is disposed above the common electrode CE. In this configuration (also referred to as the V2 configuration), since it is not necessary to form a slit on the common electrode CE that becomes the lower electrode, the increase in the resistivity (surface resistivity) of the common electrode CE is suppressed compared to the configuration in which the common electrode CE is disposed above the pixel electrode PE (also referred to as the V3 configuration), thereby suppressing the weakening of the edge electric field applied to the liquid crystal layer 20. In this configuration (V2 configuration), when the pixel electrode PE is set as a slit electrode, although the resistivity of the pixel electrode PE increases, since a voltage input from the outside is applied to the pixel electrode PE, it is easy to reduce the influence of the increase in resistivity (that is, suppress the weakening of the edge electric field). In addition, in order to suppress the increase in the resistivity of the common electrode CE, it is also considered to use low-resistance wiring formed by a metal material (for example, connecting the low-resistance wiring to the common electrode), but in such a structure, sometimes adverse effects on the display (such as glare, rainbow diffraction, interference patterns) are caused by regular reflection of the low-resistance wiring, etc., and it is necessary to use a black matrix or the like for shading, and sometimes it is impossible to fully increase the reflective aperture ratio.

[0068] In the configuration in which the pixel electrode PE is disposed 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 reflective display, and the reflectivity may be reduced compared to the configuration in which the common electrode CE is disposed above the pixel electrode PE. Regardless of the size of the area of ​​the pixel P, the area of ​​the contact hole and the like that does not contribute to reflective display needs to be of a certain degree, and therefore, the smaller the area of ​​the pixel P (i.e., the higher the precision), the higher the proportion of the region that does not contribute to reflective display in the pixel P, and the greater the reduction in the above-mentioned reflectivity. In other words, in a relatively large liquid crystal display device, it is easy to make the proportion of the region that does not contribute to reflective display in the pixel P lower, and therefore it is easy to suppress the reduction in the above-mentioned reflectivity. For these reasons, in a relatively large liquid crystal display device, it is advantageous to have the pixel electrode PE disposed above the common electrode CE.

[0069] On the other hand, as described above, the smaller the area of ​​the pixel P (i.e., the higher the precision), the greater the reduction in reflectivity caused by the region where the second contact hole CH2 is formed not contributing to reflective display. Therefore, in a relatively high-precision liquid crystal display device, i.e., a liquid crystal display device where the area of ​​the pixel P is relatively small, the common electrode CE is preferably arranged above the pixel electrode PE (refer to variant example 1 of embodiment 1 described later).

[0070] The first electrode 121 and the second electrode 122 are preferably formed of a transparent conductive material, respectively. Examples of the transparent conductive material include indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), and a mixture thereof.

[0071] 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 on 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 on the first interlayer insulating layer 151 to expose a portion of the backplane circuit BP (more specifically, at least a portion of the drain electrode of the TFT 110), and the contact electrode 160 is connected to the backplane circuit BP in the first contact hole CH1. In addition, a second contact hole CH2 is formed on 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.

[0072] The dielectric layer 153 is provided so as to cover the first electrode 121. The dielectric layer 153 is preferably formed of an inorganic insulating material. The inorganic insulating film obtained using the inorganic insulating material is as described above.

[0073] 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.

[0074] The first horizontal alignment film 140 and the second horizontal alignment film 340 described later are respectively subjected to alignment treatment and define the alignment azimuth (also referred to as alignment direction) of the liquid crystal molecules 21 contained in the liquid crystal layer 20. Preferably, the alignment treatment is performed by, for example, a photo-alignment treatment or a rubbing treatment. Preferably, 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 can be used.

[0075] 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, when no voltage is applied to the liquid crystal layer 20, the liquid crystal molecules 21 are horizontally aligned. The pretilt angle is substantially 0°.

[0076] The orientation of the liquid crystal molecules 21 defined by the first horizontal alignment film 140 is different from the orientation of the liquid crystal molecules 21 defined by the second horizontal alignment film 340. Therefore, the liquid crystal layer 20 is in a twisted orientation when no voltage is applied (see Figure 2 When a voltage is applied to the liquid crystal layer 20, that is, when a lateral electric field is generated on the liquid crystal layer 20 by the first electrode 121 and the second electrode 122, the alignment state of the liquid crystal layer 20 changes due to the lateral electric field (fringe electric field).

[0077] <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⊥).

[0078] In a positive liquid crystal material, the birefringence Δn of the liquid crystal material is preferably, for example, less than 0.12, and more preferably less than 0.119. In addition, considering the manufacturing point of view (yield, etc.), the thickness d of the liquid crystal layer 20 is preferably greater than 2 μm, in which case Δn is preferably less than 0.119. More preferably, d is greater than 2.5 μm and Δn is less than 0.095. However, from the viewpoint of response, it is preferred that the unit thickness is small. In addition, preferably, the dielectric anisotropy Δε of the liquid crystal material is, for example, less than 10.

[0079] In a negative liquid crystal material, the birefringence Δn of the liquid crystal material is preferably, for example, less than 0.123, and more preferably less than 0.12. In particular, preferably, the thickness d of the liquid crystal layer 20 is greater than 2 μm, and Δn is less than 0.123. More preferably, d is greater than 2.5 μm, and Δn is less than 0.098. In addition, preferably, the dielectric anisotropy Δε of the liquid crystal material is, for example, less than -5. In addition, the smaller Δε (or the larger the absolute value of Δε), the VR curve (threshold value, reflectivity Max value, etc.) shifts toward the low voltage side.

[0080] 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 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, flexible polarization is spontaneously generated in the liquid crystal layer due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field). Since the liquid crystal responds to this flexible polarization, the brightness changes when the polarity is reversed, so it is easily visually recognized as flicker. In addition, from the perspective of reliability, it is preferred to use a positive liquid crystal material.

[0081] The liquid crystal layer 20 may further contain a chiral agent as required. The liquid crystal layer 20 may be formed by, for example, a dropping method.

[0082] Preferably, the thickness d (also called the cell gap or cell thickness) of the liquid crystal layer 20 is less than 3.6 μm. More preferably, it is 2.0 to 3.4 μm. In addition, from the viewpoint of response speed, it is preferably less than 3 μm. In addition, the smaller the cell thickness, the less the number of material components, so it is preferred from the viewpoint of cost reduction. However, if it is too small, sometimes the display quality cannot be improved due to uneven cell thickness and foreign matter, which becomes a compromise relationship with the incidence rate of poor display quality. From the viewpoint of yield, it is preferred to be more than 2 μm as described above.

[0083] The liquid crystal layer 20 may be in a multi-domain alignment such as a dual main alignment, but is preferably in a mono-domain alignment (also referred to as a mono domain alignment) from the viewpoint of maximizing the liquid crystal mode reflection efficiency and the liquid crystal mode transmission efficiency.

[0084] <Second Substrate> The second substrate 30 is disposed opposite to the first substrate 10 with the liquid crystal layer 20 sandwiched therebetween, and has a second horizontal alignment film 340 in contact with the liquid crystal layer 20. The second substrate 30 also preferably has a supporting substrate 300 and a color filter layer 310. For example, Figure 2As 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 also preferably has a plurality of columnar spacers (not shown). In addition, the first substrate 10 may also have a plurality of columnar spacers.

[0085] The support substrate 300 is preferably transparent and insulating, and examples of the support substrate 300 include a glass substrate and a plastic substrate. Figure 2 In the embodiment of the present invention, a high-resistance transparent conductive film may be formed on the surface of the phase difference layer 40 side of the supporting substrate 300 to prevent static sintering of the liquid crystal unit. In order to suppress the decrease in transmittance or the increase in reflectivity, the high-resistance transparent conductive film may also have a multilayer structure.

[0086] The color filter layer 310 typically includes a red filter disposed in an area corresponding to a red pixel and transmitting red light, a green filter disposed in an area corresponding to a green pixel and transmitting green light, and a blue filter disposed in an area corresponding to a blue pixel and transmitting blue light. However, the types of color filters may be less than 2 or more than 4. In addition, when color display is not performed, the color filter layer 310 is omitted.

[0087] If necessary, an outer coating layer (also called a planarization layer) covering the color filter layer 310 may also be provided. In addition, depending on the material forming the electrode (e.g., a transparent conductive material), the material forming the interlayer insulating layer or the dielectric layer, and the material forming the alignment film, the white display may sometimes have a yellow tint. In this case, the chromaticity adjustment (i.e., blue shift) may also be performed by forming an 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 refers to the CIE standard light source D65.

[0088] <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 and a λ / 2 plate 42 (see Figure 1 and Figure 2 ). Preferably, in terms of the arrangement order, the λ / 4 plate 41 and the λ / 2 plate 42 are arranged in the order of 1:1 from the liquid crystal layer 20 (and the second substrate 30) side (refer to Figure 1 and Figure 2 ).

[0089] 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 wavelength 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.

[0090] 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, the circularly polarized light incident on the λ / 2 plate 42 becomes circularly polarized light with the opposite rotation direction when it is emitted.

[0091] 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 polarizing plate of an anti-reflection film, it is preferred to use a generally circulated phase difference plate. In the present invention, it is preferred as described later that by controlling the angle formed by the polarization axis of the polarizing plate 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 without using a special phase difference plate, although it is a liquid crystal display device of a lateral electric field mode, it can improve the contrast ratio, and it is also useful as an embedded touch panel capable of displaying a reflective mode, so that cost reduction can be achieved. In particular, from the user's perspective, it is very useful because it can reduce the total cost. The liquid crystal display device of the present invention can be used not only as a built-in touch panel such as an embedded type, but also as an external touch panel. When used, cost reduction can be achieved.

[0092] Specifically, it is preferable to use a uniaxial A plate as the λ / 4 plate 41 and the λ / 2 plate 42 .

[0093] <Polarizing Plate> The polarizing plate 50 is located closer to the observation surface side than the phase difference layer 40 (see Figure 1 and Figure 2 ). The polarizing plate 50 may be a circular polarizing plate or a linear polarizing plate. Here, the linear polarizing plate refers to a polarizing plate having the function of extracting polarized light (linear polarized light) that vibrates only in a specific direction from unpolarized light (natural light), partially polarized light or polarized light, and is distinguished from a circular polarizing plate. Among them, a linear polarizing plate is preferred.

[0094] The polarizing plate 50 may be an absorption-type polarizing plate or a reflection-type polarizing plate. An absorption-type polarizing plate refers to a polarizing plate that has the function of absorbing light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. A reflection-type polarizing plate refers to a polarizing plate that has the function of reflecting light vibrating in a specific direction and transmitting polarized light (linear polarized light) vibrating in a direction perpendicular thereto. Among them, an absorption-type polarizing plate is preferred. It is particularly preferred to use an absorption-type linear polarizing plate.

[0095] As an absorption type polarizing plate, for example, a polarizing plate in which a polyvinyl alcohol film is dyed and an anisotropic material such as an iodine complex (or dye) is adsorbed and then stretched and oriented can be listed. Generally speaking, in order to ensure mechanical strength and moisture and heat resistance, a polyvinyl alcohol film is used 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 in which a plurality of dielectric thin films are laminated, a film in which a plurality of thin films with different refractive index anisotropy are laminated, a nanowire grid polarizing plate, a polarizing plate using selective reflection of cholesteric liquid crystal, etc. can be listed.

[0096] In the liquid crystal display device 1 of this embodiment, the liquid crystal layer 20 displays in a transverse electric field mode with twisted orientation when no voltage is applied. As a result, the contrast ratio of the reflective display can be fully improved. Preferably, the twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is not less than 70° and not more than 85°. A more preferred range will be described later.

[0097] The twist angle θ1 of the liquid crystal layer 20 is an angle formed by the orientation direction of the liquid crystal molecules 21 specified by the first horizontal alignment film 140 and the orientation direction of the liquid crystal molecules 21 specified by the second horizontal alignment film 340. That is, it is an angle formed by the long axis direction of the liquid crystal molecules 21A near the first horizontal alignment film 140 (also referred to as the liquid crystal molecules 21A on the first substrate 10 side when no voltage is applied) and the long axis direction of the liquid crystal molecules 21B near the second horizontal alignment film 340 (also referred to as the liquid crystal molecules 21B on the second substrate 30 side when voltage is applied).

[0098] From the viewpoint of further improving the contrast ratio, the liquid crystal display device 1 is preferably in a normally black mode. The normally black mode is a display mode in which a black display is displayed when no voltage is applied and a white display is displayed when a voltage is applied.

[0099] The liquid crystal display device 1 is composed of multiple components, such as TCP (tape, carrier, package), PCB (printed circuit board), etc., in addition to the above-mentioned components, optical films such as viewing angle magnification film and brightness enhancement film, and frame (frame), and can be assembled into other components according to the components. These are not particularly limited, and devices commonly used in the field of liquid crystal display devices can be used, so the description is omitted.

[0100] <Optimal settings and simulation verification results> Hereinafter, in this embodiment, preferred settings of the twist angle of the liquid crystal layer 20, the polarization axis of the polarizing plate 50, the in-plane slow axis of the λ / 2 plate 41, the in-plane slow axis of the λ / 4 plate 42, and the retardation dΔn of the liquid crystal layer 20, and verification results of the settings are further described, divided into the case where the liquid crystal material constituting the liquid crystal layer 20 is a positive type and the case where the liquid crystal material constituting the liquid crystal layer 20 is a negative type. In addition, as the polarizing plate 50, an absorption type polarizing plate is used.

[0101] (i) When the liquid crystal material is positive type (i-1) Preferred settings The following describes an example of optical settings that are particularly preferable 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 when no voltage is applied, 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 50A of the polarizing plate 50 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 polarizing plate 50. Figure 4 In FIG. 1 , as the liquid crystal molecules 21 , liquid crystal molecules 21A near the first horizontal alignment film 140 and liquid crystal molecules 21B near the second horizontal alignment film 340 are described.

[0102] In the following description, the angle when the reference direction is set to 0° is: Figure 4 Comparing it to the dial of a clock, the reference orientation, i.e., the orientation orientation of the liquid crystal molecules 21A defined by the first horizontal alignment film 140, is set to the 0° direction (3 o'clock direction), and the twist direction is set to the positive (counterclockwise direction). The twist 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 140 when the liquid crystal display device 1 is observed from the observation surface side.

[0103] Preferably, the twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is 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°).

[0104] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 and the orientation azimuth of the liquid crystal molecules 21A specified by the first horizontal orientation film 140 is preferably 63.5° to 71.5°. It is more preferably 64.5° to 71.5°, in which case a contrast ratio of 20 or more can be easily achieved. In addition, 63.5° to 70.5° is also one of the preferred ranges. It is more preferably 64.5° to 70.5°, and particularly preferably 66.3° to 70°. In addition, when the reference orientation is 0° and the twisting direction (counterclockwise) is set to positive, it is preferably -71.5° to -63.5°, more preferably -71.5° to -64.5°, further preferably -70.5° to -64.5°, and particularly preferably -70° to -66.3°.

[0105] 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° to 52.5°. It is more preferably 48° to 52°, further preferably 49° to 51°, and particularly preferably 49° to 50°. In addition, when the reference orientation is 0° and the twist direction (counterclockwise) is positive, it is preferably -52.5° to -47.5°, more preferably -52° to -48°, further preferably 51° to -49°, and particularly preferably -50° to -49°.

[0106] 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° to 30°. It is more preferably 22° to 28°, further preferably 23° to 26°, and particularly preferably 24° to 25.5°. In addition, when the reference orientation is 0° and the twist direction (counterclockwise) is positive, it is preferably -30° to -20°, more preferably -28° to -22°, further preferably -26° to -23°, and particularly preferably -25.5° to -24°.

[0107] 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 to 255 nm. 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 ratio, it is more preferably 224 nm to 252 nm, further preferably 230 nm to 250 nm, and particularly preferably 236 nm to 248 nm.

[0108] (i-2) Verification results based on optical simulation The above-mentioned preferred setting was found by the inventors of the present application in verification using optical simulation. The verification results are described below.

[0109] The liquid crystal display device 1 is assumed to include 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, it is assumed that Figure 5A , Figure 5B as well as 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 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.

[0110] In the following description, Figure 5A , Figure 5B and Figure 5C Each is compared to a clock face, and the reference direction, that is, the alignment 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 FIG. 2 , the alignment directions of the liquid crystal molecules 21 are indicated by arrows.

[0111] 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 a +10° direction. That is, the finger angle is set to 10°. In addition, in the top view, 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 orientation of the liquid crystal molecules 21B defined by the second horizontal alignment film 340 is Figure 5B The direction is set to +97°. Figure 5C In other words, the twist angle θ1 is set to +83°.

[0112] First, a simulation was performed using LCD Master 1D manufactured by Shintech, and the next parameter condition was optimized so that the reflectance of black display (also called black reflectance) would be the minimum. Cell thickness d: 3.2 to 3.6 μm Twist angle θ1: 70~85° The axial orientation of the optical film (polarizing plate 50, λ / 2 plate 42, λ / 4 plate 41) is: ±90°. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm is used. As the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm is used. The wavelength dispersion of these phase difference plates is set to be flat. In addition, only one of the above parameters is changed, and the other parameters are fixed and the calculation is repeated.

[0113] exist Figure 6 , the settings of the optical axes of the λ / 4 plate 41, the λ / 2 plate 42, and the polarizing plate 50 are shown so that the black reflectance becomes minimum. Figure 6 FIG. 2 is a diagram conceptually showing the setting of the optical axis at which the black reflectance is minimized. Figure 6 As shown, the optimal setting of the polarization axis 50AA of the polarizing plate 50 is the -68.3° direction (also called the +111.7° direction). In addition, the optimal setting of the slow axis 42SA of the λ / 2 plate 42 is the -49.5° direction (also called the +130.5° direction), and the optimal setting of the slow axis 41SA of the λ / 4 plate 41 is the -24.9° direction (also called the +155.1° direction).

[0114] Next, the simulation was performed using LCD Master 2D manufactured by Shintech to study the preferred range of optical conditions. At this time, for the parameter of interest (the parameter for which the preferred range is to be determined), the simulation was performed by changing the value around the optimal value (reference value) while the other parameters were fixed at the optimal values.

[0115] 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, it is found that there are cases where the response performance cannot be improved. It is found that the response performance cannot be improved 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.

[0116] In order to study the influence of retardation dΔn and twist angle θ1 on the brightness of black display (also called black brightness) and contrast, simulation was performed by changing the retardation dΔn in the range of 224 to 252 nm and the twist angle θ1 in the range of 70 to 85°. The evaluation results of black brightness are shown in Table 1 and Figure 7 The evaluation results of contrast are shown in Table 2 and Figure 8 From these results, it was found 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 7is a graph showing the evaluation results of black brightness, Figure 8 It is a graph showing the evaluation results of contrast.

[0117] In addition, for the conditions of liquid crystal layer with delay dΔn=217nm (Δn=0.069928 at wavelength of 550nm), unit thickness=3.11μm, twist angle θ1=74° and the combination of special phase difference plates (λ / 4 plate with delay of 110nm and λ / 2 plate with delay of 260nm), the black brightness and contrast were calculated and found to be 0.02 (au) and 1789.

[0118] [Table 1]

[0119] [Table 2]

[0120] (ii) When the liquid crystal material is negative type (ii-1) Preferred settings The following describes an example of optical settings that are particularly preferable from the viewpoint of improving the contrast ratio. Fig. 9 The top view conceptually shows the relationship between the long axis direction of the liquid crystal molecules 21 of the liquid crystal layer 20 when no voltage is applied, 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 polarizing plate 50 in a liquid crystal display device 1 which 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 polarizing plate 50 in sequence. Fig. 9 In FIG. 1 , as the liquid crystal molecules 21 , liquid crystal molecules 21A near the first horizontal alignment film 40 and liquid crystal molecules 21B near the second horizontal alignment film 340 are shown.

[0121] In the following description, the angle when the reference direction is set to 0° is: Fig. 9 Comparing it to the dial of a clock, the reference orientation, that is, the orientation orientation of the liquid crystal molecules 21A defined by the first horizontal alignment film 140 is set to the 0° direction (3 o'clock direction) and the twist direction is set to the positive angle (counterclockwise).

[0122] Preferably, the twist angle θ1 of the liquid crystal layer 20 when no voltage is applied is 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°).

[0123] The angle θ2 formed by the polarization axis 50AA of the polarizing plate 50 and the orientation direction of the liquid crystal molecules 21A defined by the first horizontal orientation film 140 is preferably 64° to 69.5°. It is more preferably 65° to 69.3°, further preferably 66° to 69°, and particularly preferably 67° to 68.7°. In addition, when the orientation to be the reference is set to 0° and the twisting direction (counterclockwise) is set to positive, the angle θ2 is also preferably within the above ranges (all positive values).

[0124] 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° to 51.5°. It is more preferably 48° to 51°, further preferably 40° to 41.5°, and particularly preferably 48.5° to 50.0°. In addition, when the reference orientation is set to 0° and the twist direction (counterclockwise) is set to positive, the angle θ3 is also preferably within the above ranges (all positive values).

[0125] 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° to 35°. It is more preferably 17° to 32°, further preferably 20° to 30°, and particularly preferably 24° to 28°. In addition, when the reference orientation is set to 0° and the twist direction (counterclockwise) is set to positive, the angle θ4 is also preferably within the above ranges (all positive values).

[0126] The retardation dΔn of the liquid crystal layer 20, i.e., the product of the thickness d of the liquid crystal layer 20 and the birefringence Δn of the liquid crystal material, is preferably 230 nm to 260 nm. From the viewpoint of further improving the contrast ratio, it is more preferably 232 nm to 250 nm, further preferably 235 nm to 246 nm, and particularly preferably 236 nm to 245 nm.

[0127] (ii-2) Verification results based on optical simulation The above-mentioned preferred setting was found by the inventors of the present application in verification using optical simulation. The verification results are described below.

[0128] The liquid crystal display device 1 is assumed to include 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, it is assumed that Fig. 10A , Fig. 10B as well as Fig. 10C A liquid crystal layer with a monodomain structure (a liquid crystal layer that performs normally black display) is shown. Fig. 10AIt 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 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.

[0129] In the following description, Fig. 10A , Fig. 10B and Fig. 10C Compared to the dial of a clock, the 3 o'clock direction is set to 0°, the clockwise direction is set to negative, and the counterclockwise direction is set to positive. Fig. 10A and Fig. 10B In FIG. 1 , the alignment directions of the liquid crystal molecules 21 are shown by arrows.

[0130] 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 set to 10°. In addition, in the top view, 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 +7° direction is in the Fig. 10C In other words, the twist angle θ1 is set to +83°.

[0131] LCD Master 1D manufactured by Shintech was used to obtain the cell thickness d at which the black reflectance becomes minimum when θ1 is fixed at 83°, the angle of the polarization axis 50AA of the polarizing plate 50, the angle of the slow axis 42SA of the λ / 2 plate 42, and the angle and delay of the slow axis 41SA of the delay 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.

[0132] exist Fig.11 , the settings of the optical axes of the λ / 4 plate 41, the λ / 2 plate 42, and the polarizing plate 50 are shown so that the black reflectance becomes minimum. Fig.11 FIG. 2 is a diagram conceptually showing the setting of the optical axis at which the black reflectance is minimized. Fig.11As shown, the polarization axis 50AA of the polarizing plate 50 is optimally set to the +21.7° direction (also referred to as the -158.3° direction). In addition, the slow axis 42SA of the λ / 2 plate 42 is optimally set to the +40.5° direction (also referred to as the -139.5° direction), and the slow axis 41SA of the λ / 4 plate 41 is optimally set to the +65.1° direction (also referred to as the -114.9 direction).

[0133] <Application Examples> The liquid crystal display device 1 of this embodiment is applicable to various applications. Among them, it is preferably applicable to a touch panel. Regardless of whether it is applied to an external touch panel or a built-in touch panel, it is lower in cost than each previous touch panel and can improve the contrast ratio, so it is useful. Among them, it can be applied to a built-in touch panel, and can be particularly applicable to an embedded touch panel. In this way, if the liquid crystal display device 1 of this embodiment is used, it is preferably possible to realize an embedded touch panel that can display a reflective mode, which has not been realized so far.

[0134] By realizing an embedded touch panel capable of displaying a reflective mode, for example, the necessary frame wiring area is not required in an external touch panel, so a narrow frame can be achieved. In addition, since the touch panel function can be equipped without a glass cover, it can also contribute to thinning and lightweighting. In addition, since the touch function and the display function are driven in a time-division manner, the LCD (liquid crystal display) noise, which can be the largest noise source in the touch panel, is not received. That is, since a suppression mode (killer pattern) is not generated, it is easy to tune (adjust) the touch signal. Furthermore, not only is the loss of reflected light small enough, but pen writing is more natural, and a display without a sense of incoordination can be obtained. Moreover, compared with an external touch screen, a reduction in total cost can be achieved from the user's perspective. Moreover, it is possible to combine finger input and pen input of electromagnetic induction (EMR) to achieve high-precision pen writing.

[0135] An example in which the liquid crystal display device 1 is used for an in-cell touch panel will be described further. Fig.12 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.12 As shown, the liquid crystal display device 1 includes a display region DR and a non-display region FR. The display region DR is composed of a plurality of pixels P arranged in a matrix (for example, Figure 3 The non-display region FR is located at the periphery of the display region DR, and is also referred to as a peripheral region or a frame region.

[0136] In the display region DR, the common electrode CE is divided into a plurality of segments TX. Each segment (common electrode portion) TX functions as a touch sensor electrode. Fig.12 In the example shown, each touch sensor electrode TX is provided corresponding to two or more pixels P.

[0137] 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 also referred to as a touch wiring contact portion TC.

[0138] 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, for example, switch between a display mode in which a plurality of touch sensor electrodes TX function as a common electrode CE and a touch detection mode in which the touch sensor electrodes TX function in a time-division manner. For example, in the display mode, the touch drive unit TD applies a common signal to the touch sensor electrode TX (common electrode CE) via the touch wiring TL. On the other hand, in the touch detection mode, the touch drive unit TD applies a touch drive signal to the touch sensor electrode TX via the touch wiring TL.

[0139] exist Fig.12 In the embodiment, a plurality of touch wirings TL extend in a column direction (the same direction as the source wiring SL). A portion of the touch wiring TL extends across another one or more touch sensor electrodes Tx to the corresponding touch sensor electrode Tx.

[0140] When focusing on a certain touch sensor electrode TX, the first touch wiring TL1 that supplies a signal to the touch sensor electrode TX extends to the touch wiring contact portion TC, and the second touch wiring TL2 that supplies a signal to another touch sensor electrode TX extends in a manner that crosses the touch sensor electrode TX. The second touch wiring TL2 and the touch sensor electrode TX overlap via an insulating layer. In addition, depending on the position of the touch sensor electrode TX, sometimes more than two touch wirings TL are configured in a manner that crosses the touch sensor electrode TX, and sometimes no touch wiring TL that crosses the touch sensor electrode TX is configured.

[0141] In the non-display region FR, in addition to the touch drive unit TD, a peripheral circuit (not shown) is also provided, which includes a gate driver that supplies a gate signal to the gate bus (gate wiring) GL, a source driver that supplies a source signal to the source bus (source wiring) SL, and other drive circuits. These drive circuits can be mounted on the first substrate (TFT substrate) 10, or can be formed as an integral unit (monolithic). A semiconductor chip including part or all of the drive circuits can also be mounted in the non-display region FR.

[0142] In the embedded touch panel, as TFT110, it is particularly preferred to use In-Ga-Zn-O semiconductor. In addition, from the perspective of achieving flicker-free (also called flicker-free), it is particularly 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, flexible polarization is spontaneously generated in the liquid crystal layer due to the influence of the fine slit electrodes on the electrodes (i.e., the fringe electric field). Since the liquid crystal responds to this flexible polarization, the brightness changes when the polarity is reversed, so it is easily visually recognized as flickering.

[0143] (Variation 1 of Embodiment 1) In the first embodiment, the first electrode 121 as the lower electrode is the common electrode CE, and the second electrode 122 as the upper electrode is the pixel electrode PE. However, on the contrary, the second electrode 122 may be the common electrode CE and the first electrode 121 may be the pixel electrode PE. In this example, the second electrode 122 (upper electrode) is the common electrode CE, and the first electrode 121 (lower electrode) is the pixel electrode PE (see Fig.13 ).

[0144] Fig.13 is a cross-sectional schematic diagram showing the liquid crystal display device 1 of this example in more detail. In this example, from the viewpoint of easy generation of a lateral electric field, it is preferred that at least the upper electrode (the common electrode CE in this example) is a slit electrode. The lower electrode (the pixel electrode PE in this example) can be a planar electrode, i.e., a so-called full-surface electrode, or a slit electrode. The liquid crystal display device 1 involved in this variant is particularly suitable as a relatively high-definition liquid crystal display device, i.e., a liquid crystal display device in which the area of ​​the pixel P is relatively small.

[0145] (Variation 2 of Embodiment 1) In the first embodiment, an FFS mode liquid crystal display device is described, but an IPS mode liquid crystal display device (wherein the liquid crystal layer 20 takes a twisted orientation when no voltage is applied) may also be used. This variation is an IPS mode liquid crystal display device. In this variation, preferably, 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.

[0146] (Implementation Method 2) In this embodiment, the features unique to this embodiment are mainly described, and descriptions of contents overlapping with those of the above-mentioned Embodiment 1 are omitted. This embodiment is substantially the same as Embodiment 1 except that the phase difference layer 40 further includes a positive C plate 43 .

[0147] Fig.14 1 is a cross-sectional schematic diagram of a liquid crystal display device 1 according to an example of this embodiment. Fig.14 As shown, the liquid crystal display device 1 includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a phase difference layer 40, and a polarizing plate 50. The phase difference layer 40 includes a positive C plate 43 in addition to a λ / 4 plate 41 and a λ / 2 plate 42. The positive C plate 43 may be composed of a single film or a laminate of two or more phase difference films.

[0148] When the phase difference layer 40 further includes a positive C plate 43, it is very useful because it can achieve both an improved viewing angle and an improved contrast ratio at a higher level as a synergistic effect with the above-mentioned structure in the first embodiment. In particular, in the liquid crystal display device 1 of this embodiment, compared with the liquid crystal display device of the first embodiment, it is possible to fully suppress the brightness rise (also called black floating) during black display and fully expand the viewing angle during black display. From the viewpoint of further exerting such an effect, the positive C plate 43 is preferably located between the λ / 4 plate 41 and the λ / 2 plate 42 (see Fig.14 ).

[0149] From the viewpoint of further exerting the viewing angle improvement effect, the thickness direction retardation Rth of the positive C plate 43 is preferably 150 to 270 nm, more preferably 160 to 250 nm, and even more preferably 170 to 240 nm.

[0150] The thickness of the positive C plate 43 is, for example, 0.1 to 100 μm. 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 laminated structure, it is preferred to set the total thickness thereof to the above range, and the thickness of each phase difference film may be the same or different.

[0151] As the positive C plate 43 (and 44), for example, it is preferable to use a plate obtained by biaxially stretching a film containing a material having negative intrinsic birefringence as a component in the longitudinal and transverse directions, a plate obtained by coating a liquid crystal material such as a nematic liquid crystal, etc. As the material having negative intrinsic birefringence, for example, there can be listed: 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.

[0152] Specific examples of the positive C plate 43 (and 44) ​​include a positive C plate manufactured by ENEOS or Hayashi Telempu, and a positive C (Positive-C) retardation film manufactured by Nippon Kayaku Co., Ltd.

[0153] The above-mentioned effects brought about by including the positive C plate 43 are discovered by the inventors of the present application in 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. As the polarizing plate 50 , an absorption-type polarizing plate is used.

[0154] (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 changing the position of the C plate on the viewing angle caused by the addition of the C plate is studied. LCD Master 1D of Shintech Company was used as the simulation software. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm was used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm was used, and the wavelength dispersion of these phase difference plates was set to be flat. The settings other than these are the optimal settings when the liquid crystal material obtained in Implementation Example 1 is positive. The results are as follows. Fig.15A and Fig. 15B shown.

[0155] Fig.15A and Fig. 15B 1 is a diagram showing the simulation results when the liquid crystal material in this embodiment is a positive type. In addition, an example without a C plate is shown as Example 1. Fig.15A and Fig. 15B The upper section shows a schematic cross-sectional view of the liquid crystal display device 1 in each example (where only the reflective layer 130 and the liquid crystal panel 1X are described separately), and the lower section shows the viewing angle in black display (0V) (when the incident light is at a polar angle of 30°). The thickness direction phase difference Rth of the C plate used in each example is described in parentheses after the symbol 43 or 43R representing the C plate (the same is true in other similar figures).

[0156] according to Fig.15A and Fig. 15B 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 a positive C plate 43 is better than that of the examples (Examples 5, 6 and 7) in which the phase difference layer 40 includes a 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 floating is significantly improved, and the viewing angle improvement effect can be significantly confirmed. In addition, using a real positive C plate (Rth: 200nm), a test unit with the same configuration as Example 3 was made and verified. The result confirmed that the viewing angle improvement effect is achieved even by visual recognition. In order to make the comparison easier to understand, in Fig.16 Schematic cross-sectional views of the liquid crystal display devices 1 of Examples 1 and 3 and viewing angles in black display (0 V) (when light is incident at a polar angle of 30°) are shown. Fig.16 3 is a diagram showing the simulation results of Example 1 and Example 3.

[0157] In addition, for the phase difference layer 40, in addition to the λ / 4 plate 41 and the λ / 2 plate 42, the positive C plate 43 was included, and the optical conditions for minimizing black floating were optimized. That is, for each structure example of Example 1 to Example 4, in the black display (0V) state, as the incident light with 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 as follows: Fig.17 shown. Fig.17 Graph showing the distribution of the maximum value of black brightness for Examples 1 to 4. Fig.17 In the graph, the horizontal axis represents Rth (nm) of the positive C plate 43, and the vertical axis represents the maximum value of black brightness.

[0158] according to Fig.17 It is clear that even in Examples 1 to 4, the maximum value of black brightness is the lowest in Example 3. In addition, in the distribution curve of Example 3, it can be seen that the value (indicated by the arrow) with the vertical axis (maximum value of black brightness) as the minimum value is within 30% when the Rth of the positive C plate 43 is 150nm or more and 270nm or less, within 15% when the Rth is 160nm or more and 250nm or less, and within 10% when 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.

[0159] (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 envisioned as a phase difference layer 40, and the effect of changing the position of the C plate on the viewing angle caused by the addition of the C plate is studied. LCD Master 1D of Shintech was used as simulation software. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm was used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm was used, and the wavelength dispersion of these phase difference plates was set to be flat. The settings other than these are the optimal settings when the liquid crystal material obtained in Implementation Example 1 is negative.

[0160] As a result, the same as that when the liquid crystal material is positive (refer to Fig.15A and Fig. 15B ) have roughly the same tendency, so in Fig.18 In FIG. 1 , only simulation results of an example (Example 13) in which the positive C-plate 43 is located between the λ / 4 plate 41 and the λ / 2 plate 42 and an example (Example 11) in which no C-plate is included are extracted and shown. Fig.18 2 is a diagram showing simulation results when the liquid crystal material is a negative type in this embodiment. Fig.18 The upper section shows a schematic cross-sectional view of the liquid crystal display device 1 in each example (wherein only the reflective layer 130 and the liquid crystal panel 1X are described separately), and the lower section shows the viewing angle in black display (0 V) (when light is incident at a polar angle of 30°).

[0161] In addition, for the phase difference layer 40, in addition to the λ / 4 plate 41 and the λ / 2 plate 42, the optical conditions for minimizing black floating were optimized. That is, for each of the following examples 11 to 14, in the black display (0V) state, as the incident light with 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 as follows: Fig.19 shown. Fig.19 Graph showing the distribution of the maximum value of black brightness for Examples 11 to 14. Fig.19 In FIG. 1 , the horizontal axis is set to Rth (nm) of the positive C plate 43, and the vertical axis is set to the maximum value of the black brightness. Example 11: Example without C-plate. Example 12: An example in which the phase difference plates are arranged in the order of positive C plate 43 (thickness direction phase difference Rth: 50 nm), λ / 2 plate 42, and λ / 4 plate 41 from the observation surface side. Example 13: An example in which the phase difference plates are arranged in the order of the λ / 2 plate 42, the positive C plate 43 (thickness direction phase difference Rth: 210 nm), and the λ / 4 plate 41 from the observation surface side. Example 14: An example in which the phase difference plates are arranged in the order of λ / 2 plate 42, λ / 4 plate 41, and positive C plate 43 (thickness direction phase difference Rth: 10 nm) from the observation surface side.

[0162] according to Fig.19 It is clear that even in Examples 11 to 14, the maximum value of black brightness is the lowest in Example 13. In addition, in the distribution curve of Example 13, it can be seen that the value (with an arrow) with the vertical axis (maximum value of black brightness) as the minimum value is used as a reference to become within 30% when the Rth of the positive C plate 43 is 150nm or more and 270nm or less, within 15% when the Rth is 160nm or more and 250nm or less, and within 10% when the Rth is 170nm or more and 240nm or less. That is, the same as when the liquid crystal material is positive (refer to Fig.17Based on this result, it was found that the preferred range of the thickness direction phase difference Rth is as described above.

[0163] (Implementation Method 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. This embodiment is substantially the same as the second embodiment, except that the phase difference layer 40 further includes a positive C plate 44 different from the positive C plate 43. For the convenience of description, the positive C plate 43 described in the second embodiment is also referred to as the first positive C plate 43, and the positive C plate 44 added in this embodiment is also referred to as the second positive C plate 44.

[0164] Fig. 20 1 is a cross-sectional schematic diagram of a liquid crystal display device 1 according to an example of this embodiment. Fig. 20 As shown, the liquid crystal display device 1 includes, from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a phase difference layer 40, and a polarizing plate 50. 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.

[0165] 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 an improvement in contrast ratio. Compared with the second embodiment, black floating is further suppressed. From the viewpoint of further exerting such an effect, the second positive C plate 44 is preferably located between the λ / 4 plate 42 and the polarizing plate 50. That is, preferably, the phase difference layer 40 is provided with the λ / 4 plate 41, the first positive C plate 43, the λ / 2 plate 42, the second positive C plate 44 (see Fig. 20 ).

[0166] The second positive C plate 44 may be the same as the first positive C plate 43 (same physical properties, same thickness, etc.) or different as long as it satisfies "nz>nx≈ny". However, from the viewpoint of further exerting the viewing angle improvement effect, the thickness direction phase difference Rth (absolute value) of the second positive C plate 44 is preferably 50 to 130 nm. It is more preferably 70 to 120 nm, and even more preferably 8 to 115 nm.

[0167] The thickness of the second positive C plate 44 is, for example, 0.1 to 100 μm. If it is within this range, the mechanical strength and display uniformity are better. 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 stacked structure, it is preferred to set its total thickness to the above range, and the thickness of each phase difference film may be the same or different.

[0168] The above-mentioned effects brought about by including the first positive C plate 43 and the second positive C plate 44 are found by the inventors of the present application in verification using optical simulation. The verification results are described below by dividing into the case where the liquid crystal material constituting the liquid crystal layer 20 is a positive type and the case where the liquid crystal material is a negative type. In addition, as the polarizing plate 50, an absorption type polarizing plate is used.

[0169] (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, it is assumed that a four-layer structure of a λ / 2 plate 42, a first positive C plate 43 (phase difference Rth in the thickness direction: 210nm), a λ / 4 plate 41, and a second positive C plate 44 (phase difference Rth in the thickness direction: 110nm) is sequentially arranged from the observation side, and the effect of the addition of the second positive C plate 44 on the viewing angle is studied (Example 23). LCD Master 1D of Shintech Company was used as the simulation software. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm was used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm was used, and the wavelength dispersion of these phase difference plates was set to be flat. The settings other than these are the optimal settings when the liquid crystal material obtained in Implementation Example 1 is positive. The results are as follows. Fig.21 shown.

[0170] Fig.21 2 is a diagram showing the simulation results when the liquid crystal material is positive in this embodiment. In addition, an example without a C plate is referred to as Example 21, and an example including the first positive C plate 43 but not including the second positive C plate 44 is referred to as Example 22. Fig.21 The upper section shows a schematic cross-sectional view of the liquid crystal display device 1 in each example (wherein only the reflective layer 130 and the liquid crystal panel 1X are described separately), and the lower section shows the viewing angle in black display (0 V) (when light is incident at a polar angle of 30°).

[0171] In addition, for Examples 21 to 23, in the black display (0V) state, as incident light with a polar angle of 30°, the luminance distribution of azimuth angle: 0 to 360° (15° step) and polar angle: 0 to 80° (10° step) was analyzed. The results are as follows: Fig. 22 shown. Fig. 22 Graph showing the distribution of the maximum value of black brightness for Examples 21 to 23. Fig. 22 In FIG. 5 , the horizontal axis is set to Rth (nm) of the second positive C plate 44, and the vertical axis is set to the maximum value of the black brightness.

[0172] according to Fig. 22It can be seen that in the distribution curve of Example 22, the value (with an arrow) with the vertical axis (maximum value of black brightness) as the minimum value is within 30% when the Rth of the second positive C plate 44 is 50nm to 130nm, within 15% when the Rth is 70nm to 120nm, and within 10% when the Rth is 80nm to 115nm. 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.

[0173] (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, as the phase difference layer 40, it is assumed that a four-layer structure of a λ / 2 plate 42, a first positive C plate 43 (phase difference Rth in the thickness direction: 210nm), a λ / 4 plate 41, and a second positive C plate 44 (phase difference Rth in the thickness direction: 110nm) is sequentially arranged from the observation side, and the effect of the addition of the second positive C plate 44 on the viewing angle is studied (Example 33). LCD Master 1D of Shintech Company was used as the simulation software. As the λ / 4 plate 41, a uniaxial phase difference plate with a delay of 140nm was used, and as the λ / 2 plate 42, a uniaxial phase difference plate with a delay of 270nm was used, and the wavelength dispersion of these phase difference plates was set to be flat. The settings other than these are the optimal settings when the liquid crystal material obtained in Implementation Example 1 is positive. The results are as follows. Fig.23 shown.

[0174] Fig.23 31 is an example that does not include a C plate, and an example that includes a first positive C plate 43 but does not include a second positive C plate 44 is an example 32. Fig.23 The upper section shows a schematic cross-sectional view of the liquid crystal display device 1 in each example (wherein only the reflective layer 130 and the liquid crystal panel 1X are described separately), and the lower section shows the viewing angle in black display (0 V) (when light is incident at a polar angle of 30°).

[0175] In addition, for Examples 31 to 33, in the black display (0V) state, as the incident light with 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 as follows: Fig.24 shown. Fig.24 Graph showing the distribution of the maximum value of black brightness for Examples 31 to 33. Fig.24 In FIG. 5 , the horizontal axis is set to Rth (nm) of the second positive C plate 44, and the vertical axis is set to the maximum value of the black brightness.

[0176] according to Fig.24 It can be seen that in the distribution curve of Example 32, the value (with an arrow) with the vertical axis (maximum value of black brightness) as the minimum value is within 30% when the Rth of the second positive C plate 44 is 50nm to 130nm, within 15% when the Rth is 70nm to 120nm, and within 10% when the Rth is 80nm to 115nm. That is, the same as when the liquid crystal material is positive (refer to Fig. 22 Based 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.

[0177] (Implementation method 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. In the embodiment 1, a reflective liquid crystal display device is exemplified, 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 at a position closer to the back side than the liquid crystal layer 20.

[0178] Fig.25 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) on the back side of the liquid crystal layer 20. In addition, it is preferred that the liquid crystal display device 1 further includes a polarizing plate 50' and a phase difference layer 40'. More preferably, Fig.25 As shown, the light source 61, polarizing plate 50', retardation layer 40', first substrate 10, liquid crystal layer 20, second substrate 30, retardation layer 40, and polarizing plate 50 are provided in order from the back side. In this embodiment, the first substrate 10 is preferably a TFT substrate.

[0179] The light source 61 (backlight source) is not particularly limited as long as it is a light source for irradiating light, and can be a direct-down type, an edge type, or any other type. Specifically, for example, a light source such as a light emitting diode (LED), a light guide plate, and a reflective sheet is preferred, and a diffuser or a prism sheet may be further provided.

[0180] The polarizing plate 50' is disposed on the back side of the liquid crystal layer 20. More specifically, it is disposed at a position closer to the back side than the first substrate 10. The polarizing plate 50' may be a circular polarizing plate or a linear polarizing plate, but is preferably a linear polarizing plate. In addition, it may be an absorption type polarizing plate or a reflection type polarizing plate, but is preferably an absorption type polarizing plate. It is particularly preferred to use an absorption type linear polarizing plate.

[0181] The polarization axis of the polarizing plate 50' may be arranged substantially orthogonal to or substantially parallel to the polarization axis of the polarizing plate 50. That is, the polarizing plate 50' may be arranged in a cross-Nicol arrangement or a parallel-Nicol arrangement with respect to the polarizing plate 50. Among them, the cross-Nicol arrangement is preferred.

[0182] 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 first substrate 10. The phase difference layer 40' can include, for example, a λ / 4 plate and a λ / 2 plate. Preferably, the arrangement order is, for example, λ / 2 plate, λ / 4 plate from the back side.

[0183] In the liquid crystal display device 1 of the present embodiment, each pixel P has a reflective region Rf for displaying in a reflective mode and a transmissive region Tr for displaying in a transmissive mode (see FIG. Fig.26 ). Fig.26 1 is a top view schematic diagram conceptually showing that each pixel P has a reflective region Rf and a transmissive region Tr in the liquid crystal display device 1 of this embodiment. A reflective layer 130 (for example, see Figure 2 ), but the reflective layer 130 is not arranged in the transmission region Tr. The ratio of the area occupied by the transmission region Tr in the pixel P can be appropriately set according to the purpose, but is preferably, for example, not less than 20% and not more than 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.

[0184] In the liquid crystal display device of this embodiment, that is, the semi-transmissive liquid crystal display device, similarly to the reflective liquid crystal display device, the contrast ratio of the reflective display can be sufficiently improved by displaying in a lateral electric field mode with twisted orientation when no voltage is applied to the liquid crystal layer 20. Therefore, the liquid crystal display device 1 of this embodiment is also useful as an in-cell touch panel that is low-cost, can improve the contrast ratio, and can display in a reflective mode.

[0185] (Implementation method five) In this embodiment, the features unique to this embodiment are mainly described, and the description of the contents repeated in the above-mentioned embodiment 1 is omitted. The main difference between the liquid crystal display device of this embodiment and the liquid crystal display device of embodiment 1 is that a light source is provided at a position closer to the observation surface side than the liquid crystal layer 20. In addition, the liquid crystal display device of this embodiment is a reflective liquid crystal display device.

[0186] Fig. 27 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 headlight) on the observation side of the liquid crystal layer 20. More preferably, Fig. 27As shown, the embodiment includes, in order from the back side, a first substrate 10, a liquid crystal layer 20, a second substrate 30, a retardation layer 40, a polarizing plate 50, and a light source 62. In this embodiment, the first substrate 10 is preferably a TFT substrate.

[0187] The light source 62 (headlight) is not particularly limited as long as it is a light source that irradiates light. Specifically, for example, a light source such as a light emitting diode (LED) and a light guide plate are preferably provided. Since the reflective liquid crystal display device 1 is also provided with the light source 62, a bright reflective display can be performed even in an environment where the ambient light is insufficient.

[0188] As mentioned above, although embodiment of this invention was demonstrated, each matter demonstrated can be applied to the whole invention.

[0189] The present invention will be described in further detail below with reference to Examples, but the present invention is not limited to these Examples. Hereinafter, an absorption-type polarizing plate is used as the polarizing plate 50 .

[0190] (Examples 1 and 2) like Fig.28B As shown, the liquid crystal cell 1100 for obtaining the test cell 1000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 disposed between these substrates. Fig.28A 1 is a schematic plan view showing the structure of the liquid crystal cell 1100 when viewed from the front. Fig.28B Yes Fig.28A The AA line in the figure is used as a cross-sectional schematic diagram of the cut surface (AA line cross-sectional diagram).

[0191] like Fig.28B As shown, the first substrate 10 includes a glass substrate 100, on which a common electrode CE as a first electrode 121, a dielectric layer 153, a pixel electrode PE as a second electrode 122, and a first horizontal alignment film 140 are sequentially provided. The common electrode CE is formed of ITO, and the thickness of the common electrode CE is 100nm. The dielectric layer 153 is formed of silicon nitride (SiNx), and the thickness of the dielectric layer 153 is 300nm. The pixel electrode PE is formed of ITO, and the thickness of the pixel electrode PE is 100nm. The pixel electrode PE has a plurality of strip portions SP and a plurality of slits Sl. The width of each strip portion SP is 3μm, and the width of each slit Sl (the interval between two adjacent strip portions SP) is 5μm. Each strip portion SP is bent into a "く" 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.28A The angle formed by the left and right directions in the image is 7°.

[0192] like Fig.28B As shown, the second substrate 30 includes a glass substrate 300 and a second horizontal alignment film 340 disposed on the glass substrate 300 .

[0193] The thickness (cell gap) of the liquid crystal layer 20 is defined by plastic beads (not shown).

[0194] The first horizontal alignment film 140 and the second horizontal alignment film 340 are subjected to an alignment treatment through a photo-alignment treatment or a rubbing treatment.

[0195] When using photo-alignment treatment, a photo-degradable photo-alignment film material is used. The photo-alignment film material is applied by spin coating, and the thickness of the alignment film is set to (i.e. 100nm). The unpolarized UV light emitted from the UV lamp unit is used as polarized UV light by a wire grid polarizer, and the polarized UV light is irradiated on the alignment film, thereby performing a photo-alignment treatment. The extinction ratio of the wire grid polarizer 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).

[0196] In the case of using friction treatment, a horizontal alignment film is formed, and the alignment treatment is performed by rubbing with a friction roller (e.g., a roller wound with a cloth). Thus, the uniaxial orientation of the liquid crystal molecules is obtained. As an alignment film material suitable for moving the liquid crystal molecules under a transverse electric field, a polyimide-based material is preferred. In addition, a material that does not produce pre-tilt by friction treatment is preferred, and the material is available on the market. The liquid crystal molecules are oriented approximately parallel to the rubbing direction.

[0197] For the liquid crystal cell 1100 having the above structure, the retardation of the liquid crystal layer 20 was first measured using a mass spectrometer ("AxoScan" manufactured by Axometrics), and then the cell thickness was measured using a cell gap inspection device ("RetQC" manufactured by Otsuka Electronics).

[0198] Then, if Fig.29As 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 (adhesive layer is not shown). As the polarizing plate 50, "NPF-CRT1794KDUHC3" manufactured by Nitto Denko Corporation is used. As the λ / 4 plate 41, "NZF-UF01A" (retardation: 140 nm) of Nitto Denko Corporation is used in Examples 1 and 3, and "NZF-UF01A" (retardation: 110 nm) of Nitto Denko Corporation is used in Examples 2 and 4. As the λ / 2 plate 42, "NZF-UF01A" (retardation: 270 nm) of Nitto Denko Corporation is used in Examples 1 and 3, and "NZF-UF01A" (retardation: 260 nm) of Nitto Denko Corporation is used in Examples 2 and 4.

[0199] Then, a drop of matching oil mo for reducing the loss caused by interface reflection is dripped on the reflector 130 having a concave-convex surface structure (MRS), and the liquid crystal unit 1100 is set on the reflector 130 with the first substrate 10 side at the bottom. In this way, the test unit 1000 is produced. In addition, in this state, the voltage applied between the pixel electrode PE and the common electrode CE is changed to measure the reflectivity. The voltage application to the pixel electrode PE and the common electrode CE is performed using a function generator ("AFG1022" manufactured by TEKTRONIX) that can apply a voltage of 0V to 10V with a rectangular wave of 30Hz. The reflectivity is measured using a spectrophotometer ("CM-2600d" manufactured by MINOLTA). Fig.29 is a cross-sectional schematic diagram of the test unit 1000 .

[0200] In Examples 1 and 2, the following studies (a) to (d) were conducted using the test unit 1000. In Examples 1 and 2, the liquid crystal material was positive type and the display mode was TW-FFS mode. The optical axis setting (initial setting) and specifications of Example 1 are shown in Tables 3 and Figure 6 As shown, the optical axis settings (initial settings) and specifications of Example 2 are shown in Table 3. Figure 6 This is a diagram conceptually showing the optical axis setting of Example 1.

[0201] [Table 3] unit Example 1 Example 2 liquid crystal material - Positive Positive Birefringence of Liquid Crystal Materials (550nm) - 0.069928 0.069928 Display Mode - TW-FFS TW-FFS Alignment orientation based on the first horizontal alignment film Spend 0 0 Alignment orientation based on the second horizontal alignment film Spend 83 74 Twist Angle Spend 83 74 Polarization axis angle of polarizing plate Spend -68.3 122.5 Slow axis angle of λ / 2 plate Spend -49.5 137 Slow axis angle of λ / 4 plate Spend -24.9 153.5 The width of the stripe portion of the pixel electrode μm 3 3 The slit width of the pixel electrode μm 5 5 Bending angle of strip Spend 7 7

[0202] (Comparative Example 1) like Fig. 30B As shown, the liquid crystal cell 2100 for obtaining the test cell 2000 includes a first substrate 10, a second substrate 30, and a liquid crystal layer 20 disposed between these substrates. Fig. 30A 1 is a schematic plan view showing the structure of the test unit 2100 (and the liquid crystal unit 2100 ) when viewed from the front. Fig. 30B Yes Fig. 30A The AA line in the figure is used as a cross-sectional schematic diagram of the cut surface (AA line cross-sectional diagram).

[0203] 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. Among the vertical alignment films, only the second vertical alignment film arranged on the observation surface side is subjected to a photo-alignment treatment. In addition, the alignment azimuth of the liquid crystal molecules 21 specified by the first vertical alignment film is in the 90° direction (pretilt angle is 88.4°).

[0204] like Fig.31 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 2100. As the polarizing plate 50, "NPF-CRT1794KDUHC3" manufactured by Nitto Denko Corporation was used, as the λ / 4 plate 41, "NZF-UF01A" (retardation: 110nm) manufactured by Nitto Denko Corporation was used, and as the λ / 2 plates 42a and 42b, "NZF-UF01A" (retardation: 260nm) manufactured by Nitto Denko Corporation was used. Then, a drop of matching oil mo was dripped on the reflector 130 having MRS, and the liquid crystal cell 2100 was placed on the reflector 130 with the first substrate 10 side facing downward. In this way, the test cell 2000 was manufactured. Fig.31 is a cross-sectional schematic diagram of the test unit 2000.

[0205] In Comparative Example 1, the following studies (a) to (d) were conducted using the test unit 2000. In Comparative Example 1, the liquid crystal material was a negative type with a negative dielectric anisotropy, and the display mode was a VA mode. The optical axis setting (initial setting) and specifications of Comparative Example 1 are shown in Tables 4 and Fig.32 shown.

[0206] [Table 4] unit Comparative Example 1 liquid crystal material - Negative Birefringence of liquid crystal materials (589nm) 0.093839 △ε of liquid crystal material - -4.2 Display Mode - VA Alignment direction based on the first vertical alignment film Spend 0 Alignment orientation based on the second vertical alignment film Spend 90 Polarization axis angle of polarizing plate Spend 110 The slow axis angle of the λ / 2 plate 42b Spend 185 The slow axis angle of the λ / 2 plate 42a Spend 115 Slow axis angle of λ / 4 plate Spend 195

[0207] (a) Relationship between twist angle and VR curve The relationship between the twist angle and the VR curve was studied. Fig.33 shown. Fig.33 Graph showing the results of Examples 1 and 2 and Comparative Example 1. Fig.33 In FIG. 1 , the horizontal axis represents the voltage (V) applied to the liquid crystal layer 20 and the vertical axis represents the reflection mode efficiency (%). The obtained curve is referred to as a VR curve.

[0208] according to Fig.33 It can be seen that the maximum reflectivity of Example 1 (twist angle: 83°) is higher than that of Example 2 (twist angle: 74°). The maximum reflectivity in Example 1 is about the same as that in Comparative Example 1 (VA mode).

[0209] (b) Relationship between delay and reflection mode efficiency and contrast The relationship between the delay (i.e., dΔn) and the reflective mode efficiency and contrast ratio was studied. Fig.34 shown. Fig.34 It is a graph showing the results of Examples 1 and 2.

[0210] exist Fig.34 In the black reflectivity column, a graph is described in which the reflection mode efficiency of a black display (applied voltage: 0 V) ​​is measured by varying the retardation. The horizontal axis is retardation (nm), and the vertical axis is the reflection mode efficiency of a black display. The column of white reflectivity shows a graph obtained by measuring the reflection mode efficiency of white display (applied voltage: 5 V) by changing the retardation. The horizontal axis represents the retardation (nm) and the vertical axis represents the reflection mode efficiency of white display. The Contrast Ratio column contains a graph of the contrast ratio measured by varying the retardation. The contrast ratio refers to the ratio of the contrast of 5 V to the contrast of 0 V (5 V / 0 V) (the same applies below). The horizontal axis is retardation (nm) and the vertical axis is contrast ratio. Approximate curves are recorded simultaneously in all figures.

[0211] Depend on Fig.34 It can be seen that the reflectivity of the black display of Example 1 (twist angle: 83°) is higher than that of Example 2 (twist angle: 74°). In addition, it is shown that when the twist angle is 83° (Example 1), the contrast ratio is greater than 20 when the delay dΔn is greater than 218nm and less than 255nm, and the contrast ratio is the maximum value (about 24) when the delay dΔn is 238nm (i.e., the unit thickness d: 3.41μm). The reflective mode efficiency of the white display is almost constant.

[0212] (c) Relationship between axis setting and contrast ratio of optical film For the test unit 1000 of Example 1, the relationship between axis setting and contrast ratio of the optical film (i.e., polarizing plate and phase difference plate) was studied. In addition, the cases where the retardation (dΔn) was 235nm, 238nm and 246nm were studied respectively. The results are as follows: Fig.35 shown. Fig.35 It is a graph showing the results of Example 1.

[0213] Fig.35In the graphs in the column (I), the contrast ratios were measured by rotating only the polarizing plate 50 (the phase difference plate was fixed to the initial setting). The horizontal axis is the angle of the polarization axis 50AA direction of the polarizing plate 50, and the vertical axis is the contrast ratio. The graphs in the column (II) are graphs obtained by rotating only the phase difference plate (i.e., the λ / 2 plate 42 and the λ / 4 plate 41) to measure the contrast ratio (the polarizing plate is fixed as the initial setting). The angle formed by the slow axis 42SA of the λ / 2 plate 42 and the slow axis 41SA of the λ / 4 plate 41 is fixed. The horizontal axis is set to the angle in the direction of the slow axis 42SA of the λ / 2 plate 42, and the vertical axis is set to the contrast ratio. The graphs in the column (III) are graphs obtained by rotating the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 at the same angle and measuring the contrast ratio. That is, the angle formed by the polarizing plate 50 and the λ / 2 plate 42, the angle formed by the polarizing plate 50 and the λ / 4 plate 41, and the angle formed by the λ / 2 plate 42 and the λ / 4 plate 41 are all fixed, and the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 are rotated as a set. The horizontal axis is the angle in the direction of the polarization axis 50AA of the polarizing plate 50, and the vertical axis is the contrast ratio. Approximate curves are recorded simultaneously in all figures.

[0214] according to Fig.35 , shows that when the delay dΔn is 238nm, in the initial setting (refer to Figure 6 ), the contrast ratio is at a maximum value (about 25). In this case, the margin for axis deviation is the largest. That is, the variation in contrast is minimal relative to the deviation of the film axes of the three optical films (i.e., the polarizing plate and the phase difference plate). In addition, it was found that the contrast ratio is about 10% lower than the maximum value when the angle in the direction of the polarization axis 50AA of the polarizing plate 50 is within ±2° centered on the angle at which the contrast ratio is at a maximum value. In addition, it can also be seen that when the angle in the direction of the polarization axis 50AA of the polarizing plate 50 is greater than -71.5° and less than 63.5° (refer to column (I)), when the slow axis 42SA of the λ / 2 plate 42 is greater than -52.5° and less than -47.5° (refer to column (II)), and when the angle in the direction of the polarization axis 50AA of the polarizing plate 50 is greater than -71.5° and less than -64.5° (refer to column (III)), the contrast ratio is greater than 20.

[0215] (d) Relationship between axis setting and chromaticity of optical film For the test unit 1000 of Example 1, the relationship between the axis setting of the optical film (i.e., the polarizing plate and the phase difference plate) and the chromaticity of the white display (applied voltage: 5V) and the black display (applied voltage: 0V) was studied. In addition, the cases where the delay (dΔn) was 235nm, 238nm and 246nm were studied respectively. The results are as follows: Fig.36 Chromaticity is evaluated using an xy chromaticity diagram. For reference, the chromaticity of the D65 illuminant is plotted in each figure. Fig.36 It is a graph showing the results of Example 1.

[0216] Fig.36 In FIG. 1 , each graph in the column (I) is a graph obtained by analyzing the chromaticity of white display by rotating only the polarizing plate 50 (the phase difference plate is fixed to the initial setting). The graphs in the column (II) are graphs obtained by rotating only the phase difference plates (i.e., the λ / 2 plate 42 and the λ / 4 plate 41) and analyzing the chromaticity of the white display (the polarizing plate is fixed as the initial setting). The angle between the slow axis 42SA of the λ / 2 plate 42 and the slow axis 41SA of the λ / 4 plate 41 is fixed. The graphs in the column (III) are graphs in which the chromaticity of white display is analyzed by rotating the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 at the same angle. That is, the angle formed by the polarizing plate 50 and the λ / 2 plate 42, the angle formed by the polarizing plate 50 and the λ / 4 plate 41, and the angle formed by the λ / 2 plate 42 and the λ / 4 plate 41 are all fixed, and the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 are rotated as a set.

[0217] from Fig.36 It can be seen that the chromaticity of the white display (0V) is less affected by the unit thickness and axis setting. In addition, the chromaticity of the black display (5V) can be adjusted by rotating only the polarizing plate 50 (refer to column (I)) or the group rotation of the optical film (polarizing plate and phase difference plate) (refer to column (III)). In the case where the chromaticity of the black display is adjusted to the vicinity of the chromaticity of the D65 light source, it is preferred to rotate only the polarizing plate 50, and make the angle of the polarization axis 50AA direction of the polarizing plate 50 be above -67.3° and below -66.3°. Within this range, the contrast ratio is not reduced.

[0218] (Examples 3 and 4) In Examples 3 and 4, the following studies (a) to (d) were conducted using the test unit 1000. In Examples 3 and 4, the liquid crystal material was negative type, and the display mode was TW-FFS mode. The optical axis setting (initial setting) and specifications of Example 3 are shown in Tables 5 and Fig.11 As shown, the optical axis settings (initial settings) and specifications of Example 4 are shown in Table 5. Fig.11 This is a diagram conceptually showing the optical axis setting of Example 3.

[0219] [Table 5] unit Example 3 Example 4 liquid crystal material - Positive Positive Birefringence of Liquid Crystal Materials (550nm) - 0.079224 0.079224 Display Mode - TW-FFS TW-FFS Alignment orientation based on the first horizontal alignment film Spend 90 90 Alignment orientation based on the second horizontal alignment film Spend 173 164 Twist Angle Spend 83 74 Polarization axis angle of polarizing plate Spend 21.7 32.5 Slow axis angle of λ / 2 plate Spend 40.5 47 Slow axis angle of λ / 4 plate Spend 65.1 63.5 The width of the stripe portion of the pixel electrode μm 3 3 The slit width of the pixel electrode μm 5 5 Bending angle of strip Spend 7 7

[0220] (a) Relationship between twist angle and VR curve The relationship between the twist angle and the VR curve was studied. Fig.37 As shown. Fig.37 In FIG. 1 , the horizontal axis represents the voltage (V) applied to the liquid crystal layer 20 and the vertical axis represents the reflection mode efficiency (%). The obtained curve is referred to as a VR curve. Fig.37 It is a graph showing the results of Examples 3 and 4 and Comparative Example 1.

[0221] according to Fig.37 It can be seen that, unlike the tendency of the positive type (Examples 1 and 2), the VR curves in Example 3 (twist angle: 83°) and Example 4 (twist angle: 74°) are substantially the same.

[0222] (b) Relationship between delay and reflection mode efficiency and contrast The relationship between retardation (i.e., dΔn) and reflective mode efficiency, and the relationship between retardation and contrast. Fig.38 shown. Fig.38 It is a graph showing the results of Examples 3 and 4.

[0223] exist Fig.38 In the black reflectivity column, a graph is described in which the reflection mode efficiency of a black display (applied voltage: 0 V) ​​is measured by varying the retardation. The horizontal axis is retardation (nm), and the vertical axis is the reflection mode efficiency of a black display. The column of white reflectivity shows a graph obtained by measuring the reflection mode efficiency of white display (applied voltage: 5 V) by changing the retardation. The horizontal axis represents the retardation (nm) and the vertical axis represents the reflection mode efficiency of white display. The Contrast Ratio column contains a graph of the contrast ratio measured by varying the retardation. The contrast ratio refers to the ratio of the contrast of 5 V to the contrast of 0 V (5 V / 0 V) (the same applies below). The horizontal axis is retardation (nm) and the vertical axis is contrast ratio. Approximate curves are recorded simultaneously in all figures.

[0224] Depend on Fig.38 It can be seen that the reflectivity of the black display of Example 4 (twist angle: 83°) is higher than that of Example 3 (twist angle: 74°). In addition, it is shown that when the twist angle is 83° (Example 3), the contrast ratio is greater than 20 when the delay dΔn is greater than 230nm and less than 260nm, and the contrast ratio is maximum (about 24) when the unit thickness d is 3.1μm (that is, the delay dΔn is about 245nm). The unit thickness d at which the contrast ratio is maximum is consistent with the optical simulation results. The reflective mode efficiency of the white display is almost constant. On the other hand, it can be seen that when the twist angle is 74° (Example 4), the contrast ratio is greater than 20 when the delay dΔn is greater than 207nm and less than 230nm.

[0225] (c) Relationship between the axis setting of the optical film and the contrast ratio For the test unit 1000 of Example 3, the relationship between the axis setting of the optical film (i.e., the polarizing plate and the phase difference plate) and the contrast ratio was studied. The delay was set to 246 nm. The results are as follows Fig.39 shown. Fig.39 It is a graph showing the results of Example 3.

[0226] Fig.39 In the graphs in the column (I), the contrast ratios were measured by rotating only the polarizing plate 50 (the phase difference plate was fixed to the initial setting). The horizontal axis is the angle of the polarization axis 50AA direction of the polarizing plate 50, and the vertical axis is the contrast ratio. The graphs in the column (II) are graphs obtained by rotating only the phase difference plate (i.e., the λ / 2 plate 42 and the λ / 4 plate 41) to measure the contrast ratio (the polarizing plate is fixed as the initial setting). The angle formed by the slow axis 42SA of the λ / 2 plate 42 and the slow axis 41SA of the λ / 4 plate 41 is fixed. The horizontal axis is set to the angle in the direction of the slow axis 42SA of the λ / 2 plate 42, and the vertical axis is set to the contrast ratio. The graphs in the column (III) are graphs obtained by rotating the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 at the same angle and measuring the contrast ratio. That is, the angle formed by the polarizing plate 50 and the λ / 2 plate 42, the angle formed by the polarizing plate 50 and the λ / 4 plate 41, and the angle formed by the λ / 2 plate 42 and the λ / 4 plate 41 are all fixed, and the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 are rotated as a set. The horizontal axis is the angle in the direction of the polarization axis 50AA of the polarizing plate 50, and the vertical axis is the contrast ratio. Approximate curves are recorded simultaneously in all figures.

[0227] according to Fig.39 , shows that when the delay dΔn is 246nm, in the initial setting (refer to Fig.11 ), the contrast ratio is at a maximum value (about 23). In this case, the margin with respect to the axis deviation is the largest. That is, the deviation of the angle (x-axis direction) of the arrow position of the maximum value is small. In addition, it is also found that the contrast ratio is a value about 10% lower than the maximum value when the angle in the direction of the polarization axis 50AA of the polarizing plate 50 is within ±2° centered on the angle at which the contrast ratio is at a maximum value. In addition, it can also be seen that the contrast ratio is greater than 20 when the angle in the direction of the polarization axis 50AA of the polarizing plate 50 is greater than 20.5° and less than 26.0° (refer to column (I)), when the slow axis 42SA of the λ / plate 42 is greater than 38.5° and less than 42.5° (refer to column (II)), and when the angle in the direction of the polarization axis 50AA of the polarizing plate 50 is greater than -18.0° and less than 25.5° (refer to column (III)).

[0228] (d) Relationship between axis setting and chromaticity of optical film For the test unit 1000 of Example 3, the relationship between the axis setting of the optical film (i.e., the polarizing plate and the phase difference plate) and the chromaticity of the white display (applied voltage: 5V) and the black display (applied voltage: 0V) was studied. Fig.40 Chromaticity is evaluated using an xy chromaticity diagram. For reference, the chromaticity of the D65 illuminant is plotted in each figure. Fig.40 It is a graph showing the results of Example 3.

[0229] Fig.40 In FIG. 1 , each graph in the column (I) is a graph obtained by analyzing the chromaticity of white display by rotating only the polarizing plate 50 (the phase difference plate is fixed to the initial setting). The graphs in the middle section of column (II) are graphs obtained by rotating only the phase difference plates (i.e., the λ / 2 plate 42 and the λ / 4 plate 41) and analyzing the chromaticity of the white display (the polarizing plate is fixed as the initial setting). The angle between the slow axis 42SA of the λ / 2 plate 42 and the slow axis 41SA of the λ / 4 plate 41 is fixed. The graphs in the lower section of the column (III) are graphs analyzing the chromaticity of white display by rotating the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 at the same angle. That is, the angle formed by the polarizing plate 50 and the λ / 2 plate 42, the angle formed by the polarizing plate 50 and the λ / 4 plate 41, and the angle formed by the λ / 2 plate 42 and the λ / 4 plate 41 are all fixed, and the polarizing plate 50, the λ / 2 plate 42, and the λ / 4 plate 41 are rotated as a set.

[0230] from Fig.40 It can be seen that the chromaticity of the white display (5V) is less affected by the cell thickness and axis setting. In addition, the chromaticity of the black display (0V) can be adjusted by rotating only the polarizing plate 50 (refer to column (I)) or by rotating the optical film in groups (refer to column (III)). When adjusting the chromaticity of the black display to near the chromaticity of the D65 light source, it is preferred to rotate only the polarizing plate 50 and make the angle of the polarization axis 50AA direction of the polarizing plate 50 be greater than 21.7° and less than 22.7°.

[0231] For reference, the measured results of reflectivity mode efficiency of Comparative Example 1 (negative liquid crystal material, VA mode) are shown in Table 7 (see also Fig.37 ). As can be seen from the table, a sufficiently high contrast ratio can be obtained in Comparative Example 1. However, as described above, since the VA mode uses a longitudinal electric field method, it is difficult to adopt it in an in-cell touch panel.

[0232] [Table 6]

[0233] (Example 5) For each test unit used in Example 1 (twist angle of 83°, liquid crystal material is positive), Example 2 (twist angle of 74°, liquid crystal material is positive), Example 3 (twist angle of 83°, liquid crystal material is negative), and Example 4 (twist angle of 74°, liquid crystal material is negative), the visual recognition of flicker was evaluated when observed from the front. The results are as follows: Fig.41A , Fig.41B The results are shown in Tables 7 to 10. In Tables 7 to 10, ○ indicates that the flicker is visually recognized, and × indicates that the flicker is not visually recognized. Fig.41A is a graph showing the waveforms of Examples 1 and 3, Fig.41B It is a graph showing the waveforms of Examples 2 and 4.

[0234] [Table 7]

[0235] [Table 8]

[0236] [Table 9]

[0237] [Table 10]

[0238] according to Fig.41A , Fig.41B , Table 7 and Table 8, when the liquid crystal material is positive (Examples 1 and 2), flicker is visually recognized below 10 Hz when viewed from the front. The visually recognized range is the same when the twist angle is 83° and 74°. In addition, according to Fig.41A , Fig.41B , Table 10 and Table 11, when the liquid crystal material is a negative type (Examples 3 and 4), flicker is not visually recognized in all grayscales when observed from the front. That is, flicker-free can be achieved.

[0239] (Examples 6 to 9) In the test unit 1000 used in Examples 1 to 5, when manufacturing the second substrate 30, a substrate having a high-resistance ITO coated on the surface of the glass substrate was used as the glass substrate 300 (in order to increase the black reflectivity). However, when manufacturing the test unit 3000, the high-resistance ITO was not coated. Except for this, the test unit 3000 was manufactured in the same manner as the manufacturing method of the test unit 1000 described above.

[0240] In addition, in the production process of the test unit 3000, the test unit 4000 is produced in the same manner as the above-mentioned test unit 3000, except that the process of pasting the optical film on the liquid crystal unit 3100 is changed to the process of pasting the λ / 4 plate 41, the positive C plate 43, the λ / plate 42 and the polarizing plate 50 on the second substrate 30 side of the liquid crystal unit 300.

[0241] In addition, as the λ / 4 plate 41, "NZF-UF01A" (retardation: 140nm) of Nitto Denko Corporation was used in Examples 7 and 8, and "NZF-UF01A" (retardation: 110nm) of Nitto Denko Corporation was used in Examples 6 and 9. As the λ / 2 plate 42, "NZF-UF01A" (retardation: 270nm) of Nitto Denko Corporation was used in Examples 7 and 8, and "NZF-UF01A" (retardation: 260nm) of Nitto Denko Corporation was used in Examples 6 and 9. As the positive C plate 43, a plate with an Rth of 200nm was used.

[0242] The above-mentioned test unit 3000 was used in Examples 6, 7 and 9, and the above-mentioned test unit 4000 was used in Example 8 to conduct the following studies (e) and (f). In Examples 6 to 8, the liquid crystal material is positive type and the display mode is TW-FFS mode. In Example 9, the liquid crystal material is negative type and the display mode is TW-FFS mode. The optical axis settings (initial settings) and specifications of Examples 6 to 9 are shown in Table 11.

[0243] [Table 11] unit Example 6 Example 7 Example 8 Example 9 liquid crystal material - Positive Positive Positive Negative Birefringence of Liquid Crystal Materials (550nm) - 0.069928 0.069928 0.069928 0.079224 Display Mode - TW-FFS TW-FFS TW-FFS TW-FFS Alignment orientation based on the first horizontal alignment film Spend 0 0 0 90 Alignment orientation based on the second horizontal alignment film Spend 74 83 83 164 Twist Angle Spend 74 83 83 74 Polarization axis angle of polarizing plate Spend 122.5 -68.3 -68.3 32.5 Slow axis angle of λ / 2 plate Spend 137 -49.5 -49.5 47 Slow axis angle of λ / 4 plate Spend 153.5 -24.9 -24.9 63.5 The width of the stripe portion of the pixel electrode μm 3 3 3 3 The slit width of the pixel electrode μm 5 5 5 5 Bending angle of strip Spend 7 7 7 7

[0244] (Comparative Example 2) In the test cell 2000 used in Comparative Example 1, a glass substrate having a surface coated with high-resistance ITO was used as the glass substrate 300 when the second substrate 30 was produced. However, in the test cell 5000 used in this example, high-resistance ITO was not applied. The test cell 5000 was produced in the same manner as the test cell 2000 described above.

[0245] In Comparative Example 2, the following studies (e) and (f) were conducted using the test unit 5000. In Comparative Example 2, the liquid crystal material was negative type, and the display mode was VA mode. The optical axis setting (initial setting) and specifications of Comparative Example 2 are shown in Table 12.

[0246] [Table 12] unit Comparative Example 2 liquid crystal material - Negative Birefringence of liquid crystal materials (589nm) 0.093839 Display Mode - VA Alignment direction based on the first vertical alignment film Spend 0 Alignment orientation based on the second vertical alignment film Spend 90 Polarization axis angle of polarizing plate Spend 110 The slow axis angle of the γ / 2 plate 42b Spend 185 The slow axis angle of the γ / 2 plate 42a is Spend 115 Slow axis angle of γ / 4 plate Spend 195

[0247] 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.

[0248] (e) Evaluation of tilted γ characteristics The polar angle was set to 50° and the γ curve was analyzed. Figures 42A to 42C As shown. In these figures, the upper section shows a schematic cross-sectional view of the test unit in each example, the middle section shows a graph of the γ curve, and the lower section shows a distribution diagram of the reflected brightness of 255 gray levels of white display. In the graph in the middle section, the horizontal axis is set to the gray level (0 to 255 levels) when observed from the front, and the vertical axis is set to the standardized reflectivity. The front is corrected to γ ​​= 2.2. In each graph, the angle assigned to each γ curve (the azimuth defines the 3 o'clock direction as 0°, and the polar angle defines the normal direction of the observation surface of the panel as 0°) represents the angle in the azimuth direction (where the polar angle is set to 50°). For example, in Example 6, "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 42A to 42C It is a graph showing the results of Examples 6 to 9 and Comparative Example 2.

[0249] The polar angle was changed and the γ curve was analyzed. The results are as follows Figures 43A to 43C In these figures, the upper graph shows the case where the polar angle is 30°, the middle graph shows the case where the polar angle is 40°, and the lower graph shows the case where the polar angle is 50°. In each graph, the horizontal axis is set to the grayscale (0 to 255 grayscale) when viewed from the front, and the vertical axis is set to the standardized reflectance. Figures 43A to 43C It is also a graph showing the results of Examples 6 to 9 and Comparative Example 2.

[0250] according to Figures 42A to 42C and Figure 43A to Figure 43B It can be seen that in the positive liquid crystal material (Examples 6 to 8), the tilt γ characteristic is roughly the same when the polar angle is 30°, but when the polar angle is 40° or more, the tilt γ characteristic becomes a problem in Example 7. However, by comparing Example 7 with Example 8, it can be seen that the tilt γ characteristic is improved by adding the positive C plate 43.

[0251] (f) Simulation evaluation from the tilt direction The oblique γ characteristics were evaluated relative to the γ characteristics when viewed from the front, and an image simulation was performed when the display screen was visually recognized 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.44 The images shown are taken from all directions (taken from all directions and at a polar angle of 50 degrees). Figures 46A to 46CFor comparison, the image taken from the front (also called the original image) is shown as Fig.45 shown. Fig.44 is a diagram conceptually showing the azimuth angle. Fig.45 This is an image taken from the front. Figures 46A to 46C It is a figure which shows the results of Examples 6 to 9 and Comparative Example 2.

[0252] exist Fig.45 and Figures 46A to 46C In the figure, the simulated image and its orientation (angle) when the image is most floating are listed in the (I) column, and the simulated image and its orientation (angle) when the image is most sunken are listed in the (II) column. "Image floating" means that the grayscale is higher than the front side, and "image sinking" means that the grayscale is lower than the front side.

[0253] according to Figures 46A to 46C In Examples 6 to 9 and Comparative Example 2, Example 8 is the best example in terms of balance from the three viewpoints of whitish, black, and natural color tone (chroma of face, etc.). Whitish refers to the phenomenon that bright parts become uniformly brighter. For example, if the change in the γ curve is smaller than γ=2.2, the image will float up and the whitishness will increase. Blackening refers to the phenomenon that dark parts become uniformly darker. For example, if the change in the γ curve is larger than γ=2.2, the image will sink and the blackening will increase. For example, in Comparative Example 2, in the simulated image where the image floats the most, the whitishness is large (refer to Fig.46C s), in the simulated image with the image sunken the most, the person's face looks unnatural (refer to Fig.46C ).

[0254] exist Fig.46A and Fig.46B By comparing Example 7 with Example 8, it can be seen that by adding the positive C plate 43, whitening is suppressed and blackening is also suppressed (refer to Fig.46A s, t).

[0255] The above-described embodiments of the present invention may be appropriately combined within the scope of the present invention. Description of Reference Numerals

[0256] 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 310: Color filter layer 1000, 2000, 3000, 4000, 5000: test unit 1100, 2100, 3100: liquid crystal unit BP: Backplane 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, and having a plurality of pixels arranged in a matrix, wherein: The first substrate has a reflective layer that reflects light, a first electrode and a second electrode that can generate a lateral electric field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer, and the second substrate has a second horizontal alignment film that is in contact with the liquid crystal layer. The phase difference layer comprises: λ / 4 plate and λ / 2 plate, The liquid crystal layer contains a positive liquid crystal material or a negative liquid crystal material, and takes a twisted orientation when no voltage is applied. When the liquid crystal layer contains 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 contains 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.

2. The liquid crystal display device according to claim 1, wherein: The phase difference layer further includes a positive C plate.

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

4. The liquid crystal display device according to claim 2, characterized in that: The absolute value of the thickness direction phase difference Rth (nm) of the positive C plate is 150 to 270 nm.

5. The liquid crystal display device according to claim 2, characterized in that: The phase difference layer also includes a second positive C plate, The second positive C plate is located between the λ / 2 plate and the polarizing plate.

6. The liquid crystal display device according to claim 5, 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.

7. The liquid crystal display device according to claim 1, 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°.

8. The liquid crystal display device according to claim 1, wherein: 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.

9. The liquid crystal display device according to claim 1, characterized in that: 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 alignment direction of the liquid crystal material defined by the first horizontal alignment film is 47.5° or more and 52.5° or less.

10. The liquid crystal display device according to claim 1, characterized in that: When the liquid crystal layer contains 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.

11. The liquid crystal display device according to claim 1, characterized in that: 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 alignment direction of the liquid crystal material defined by the first horizontal alignment film is 38.5° or more and 42.5° or less.

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

13. The liquid crystal display device according to claim 1, characterized in that: The liquid crystal layer is in a single domain orientation.

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

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

16. The liquid crystal display device according to claim 1, characterized in that: The first substrate has a thin film transistor including an oxide semiconductor layer, which is respectively provided on each of the plurality of pixels. The oxide semiconductor layer includes an In-Ga-Zn-O-based semiconductor.

17. The liquid crystal display device according to any one of claims 1 to 16, characterized in that: Also includes a light source.

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