Liquid crystal display device

Abstract

Provided is a liquid crystal display device that suppresses reflection and light leakage from an oblique direction. A liquid crystal display device includes, in order from a back surface side, a first polarizing element, a liquid crystal panel, a second polarizing element, a first phase difference layer, and a third polarizing element, and light transmitted in an oblique direction between the second polarizing element and the third polarizing element is elliptically polarized light.

Description

Technical Field

[0001] This invention relates to liquid crystal display devices. Background Technology

[0002] Liquid crystal display (LCD) devices typically consist of an LCD panel, a backlight, and optical components such as polarizing elements. Due to their superior display characteristics, LCD devices are widely used in electronic devices such as smartphones, laptops, and automotive displays.

[0003] As a method to improve the visual recognizability of liquid crystal display devices, methods to suppress surface reflection of liquid crystal display devices have been studied. For example, Patent Document 1 discloses a display device having a display panel and a protective plate disposed opposite to the display panel. The protective plate has a protective substrate and a first polarizing plate. The display panel has a second polarizing plate with a polarization axis parallel to the first polarizing plate. The light transmitted between the first polarizing plate and the second polarizing plate is linearly polarized light. Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-252934 Summary of the Invention The technical problem to be solved by the present invention

[0005] Liquid crystal displays (LCDs) are used in smartphones, laptops, automotive displays, etc., but in bright environments, they sometimes appear washed out due to external light reflection, resulting in reduced contrast (CR) and decreased visual clarity. This reduction in visual clarity caused by external light reflection occurs not only in bright outdoor environments with illuminance of several thousand to tens of thousands of lux, but also in indoor environments with illuminance of around 500 lux.

[0006] Reflections in liquid crystal display devices can be broadly categorized into surface reflections and internal reflections. Surface reflections can be suppressed by applying anti-reflective coatings or similar materials to the surface of the liquid crystal display device. On the other hand, internal reflections are based on the reflections from various metals, transparent electrodes, resists, and other components that make up the liquid crystal panel, and cannot be suppressed even with anti-reflective coatings.

[0007] Furthermore, the liquid crystal display device uses a polarizing element with a viewing angle dependence, so light leakage sometimes occurs in a direction tilted relative to the normal direction of the liquid crystal panel when displaying black. Due to this light leakage, especially when displaying dark images, the contrast ratio (CR) is low, and sometimes blacks do not appear black.

[0008] The following uses Figure 19 and Figure 20 To provide a more specific explanation. Figure 19This is a cross-sectional schematic diagram showing an example of a liquid crystal display device involved in comparison method 1. For example... Figure 19 As shown, the liquid crystal display device 100A involved in Comparison Method 1 includes, in sequence from the backlight 140 and the backlight 140 side (rear side), a reflective polarizing element 114, a first polarizing element 111, a liquid crystal panel 120, and a second polarizing element 112. The first polarizing element 111 and the second polarizing element 112 are absorption polarizing elements and are arranged in orthogonal Nicol configuration. The second polarizing element 112 and the reflective polarizing element 114 are arranged in parallel Nicol configuration.

[0009] In the liquid crystal display device 100A, such as in Figure 19 As indicated by the solid arrow, due to surface and internal reflections in the liquid crystal display device, visual discernibility in tilted directions is sometimes reduced. Furthermore, when viewed from a tilted direction in blackout mode, as in... Figure 19 As indicated by the dashed arrow, a portion of the light emitted from the backlight 140 to the liquid crystal panel 120 is transmitted through the observer's side, which is sometimes observed as light leakage.

[0010] Figure 20 This is a cross-sectional schematic diagram illustrating an example of a liquid crystal display device involved in comparison method 2. For example... Figure 20 As shown, the liquid crystal display device 100B involved in Comparison Method 2 also includes a first retardation layer 131 on the back side of the first polarizing element 111. Compared with the liquid crystal display device 100A, as indicated by the dashed arrow, the liquid crystal display device 100B is able to suppress light leakage from the backlight 140. However, there is still room for further research to reduce surface reflection and internal reflection of the liquid crystal display device.

[0011] The present invention was made in view of the above-mentioned situation, and its object is to provide a liquid crystal display device that suppresses reflection and light leakage from the tilt direction. Solution to the problem

[0012] (1) A liquid crystal display device according to one embodiment of the present invention includes, in sequence from the back side, a first polarizing element, a liquid crystal panel, a second polarizing element, a first phase difference layer, and a third polarizing element, wherein the light transmitted between the second polarizing element and the third polarizing element along the inclined direction is elliptical polarized light.

[0013] (2) In addition, the liquid crystal display device of a certain embodiment of the present invention is based on the configuration described in (1) above, wherein the transmittance of at least one of the second polarizing element and the third polarizing element is greater than or equal to the transmittance of the first polarizing element.

[0014] (3) Furthermore, in a certain embodiment of the present invention, the liquid crystal display device is based on the configuration described in (1) or (2) above, wherein the polarization degree of at least one of the second polarizing element and the third polarizing element is less than or equal to the polarization degree of the first polarizing element.

[0015] (4) In addition, the liquid crystal display device of a certain embodiment of the present invention is based on any one of the above (1) to (3) configurations, wherein the transmittance or polarization of the second polarizing element and the third polarizing element are different.

[0016] (5) In addition, the liquid crystal display device of a certain embodiment of the present invention is based on any one of the above (1) to (4), wherein the second polarizing element and the third polarizing element are linear polarizing elements, and the transmission axis of the second polarizing element is parallel to the transmission axis of the third polarizing element.

[0017] (6) In addition, in a certain embodiment of the present invention, the liquid crystal display device is based on the above (5) configuration, wherein the difference between the transmittance of the light transmitted through the second polarizing element and the third polarizing element and the transmittance of the first polarizing element is 1% or less, or the difference between the polarization degree of the light transmitted through the second polarizing element and the third polarizing element and the polarization degree of the first polarizing element is 1% or less.

[0018] (7) In addition, the liquid crystal display device of a certain embodiment of the present invention is based on any one of the above (1) to (6) configurations, wherein the second polarizing element has a higher transmittance or polarization degree than the third polarizing element.

[0019] (8) In addition, a liquid crystal display device according to a certain embodiment of the present invention is based on any one of the above (1) to (7) configurations, and further includes a second phase difference layer between the second polarizing element and the third polarizing element. Invention Effects

[0020] According to the present invention, a liquid crystal display device is provided that suppresses reflections and light leakage from the tilt direction. Attached Figure Description

[0021] Figure 1 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device according to the first embodiment. Figure 2 This is a cross-sectional schematic diagram showing another example of the liquid crystal display device according to the first embodiment. Figure 3 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device according to the second embodiment. Figure 4This is a contour diagram showing the reflection field of view of the liquid crystal display device according to Embodiment 1, and a contour diagram showing the transmission field of view in the black display state. Figure 5 These are outline diagrams showing the reflection field of view of the liquid crystal display device according to Embodiment 2, and outline diagrams showing the transmission field of view in the black display state. Figure 6 This is a contour diagram showing the reflection field of view of the liquid crystal display device according to Embodiment 3, and a contour diagram showing the transmission field of view in the black display state. Figure 7 The diagram shows a contour view of the reflected viewing angle of the liquid crystal display device involved in Comparative Example 1, and a contour view of the transmitted viewing angle in the black display state. Figure 8 The diagram shows the outline of the reflected viewing angle of the liquid crystal display device involved in Comparative Example 2, and the outline of the transmitted viewing angle in the black display state. Figure 9 The diagram shows a contour view of the reflected viewing angle of the liquid crystal display device involved in Comparative Example 3, and a contour view of the transmitted viewing angle in the black display state. Figure 10 This is a graph showing the measurement results of the internal reflectivity at a polar angle of 30° for the liquid crystal display devices involved in Examples 2 and 3 and Comparative Examples 1 and 3 when the azimuth angle of the incident light is changed. Figure 11 These are outline diagrams showing the reflection field of view of the liquid crystal display device according to Embodiments 1-2, and outline diagrams showing the transmission field of view in the black display state. Figure 12 These are outline diagrams showing the reflection viewing angle of the liquid crystal display device according to Embodiments 1-3, and outline diagrams showing the transmission viewing angle in the black display state. Figure 13 These are outline diagrams showing the reflection viewing angle of the liquid crystal display device according to Embodiments 1-4, and outline diagrams showing the transmission viewing angle in the black display state. Figure 14 These are outline diagrams showing the reflection viewing angle of the liquid crystal display device according to Embodiments 1-5, and outline diagrams showing the transmission viewing angle in the black display state. Figure 15 These are outline diagrams showing the reflection viewing angle of the liquid crystal display device according to Embodiments 1-6, and outline diagrams showing the transmission viewing angle in the black display state. Figure 16 These are outline diagrams showing the reflection viewing angle of the liquid crystal display device according to Embodiments 1-7, and outline diagrams showing the transmission viewing angle in the black display state. Figure 17This is a graph showing the measurement results of the transmittance in the black display state when the polar angle is changed, for the liquid crystal display devices involved in Examples 1-5 to 1-7 and Comparative Example 1, when viewed from an azimuth angle of 45°. Figure 18 This is a graph showing the measurement results of reflectivity in white display state when the polar angle is changed, for the liquid crystal display devices involved in Examples 1-5 to 1-7 and Comparative Example 1, when viewed from an azimuth angle of 45°. Figure 19 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device involved in comparison method 1. Figure 20 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device involved in comparison method 2. Detailed Implementation

[0022] [Definitions of the term] In this specification, a polarizing element refers to an element that extracts polarized light (linearly polarized light) that vibrates only in a specific direction from unpolarized light (natural light), partially polarized light, or polarized light, as opposed to a circularly polarized element. An absorptive polarizing element absorbs light vibrating in a specific direction and transmits polarized light (linearly polarized light) vibrating in a direction perpendicular to it. A reflective polarizing element reflects light vibrating in a specific direction and transmits polarized light (linearly polarized light) vibrating in a direction perpendicular to it.

[0023] In this specification, the in-plane phase difference R is defined by R = (ns - nf)d. Furthermore, the thickness-direction phase difference Rth is defined by Rth = (nz - (nx + ny) / 2)d. And, the NZ coefficient (biaxiality parameter) is defined by NZ = (ns - nz) / (ns - nf). ns refers to the larger of nx and ny, and nf is the smaller. Additionally, nx and ny represent the principal refractive indices in the in-plane direction of the retardation layer, nz represents the principal refractive index in the out-of-plane direction, i.e., the direction perpendicular to the plane of the retardation layer, and d represents the thickness of the retardation layer.

[0024] In addition, unless otherwise specified, the wavelength for measuring optical parameters such as principal refractive index, phase difference, and NZ coefficient in this specification is 550 nm.

[0025] In this specification, a phase difference layer refers to a layer in which either the absolute value of the in-plane phase difference R or the thickness direction phase difference Rth has a value of 10 nm or more, preferably a value of 20 nm or more.

[0026] In this specification, the term "observer side" refers to the side closer to the screen (display surface) of the liquid crystal display device, and the term "rear side" refers to the side farther from the screen (display surface) of the liquid crystal display device.

[0027] In this specification, the polar angle refers to the angle between the normal direction of the LCD panel's screen and the direction of the object (e.g., the measurement direction, the viewing direction), with the normal direction of the LCD panel's screen set to 0°. The azimuth angle φ refers to the direction in which the object's direction is projected onto the LCD panel's screen, expressed as the angle (azimuth angle) formed between the azimuth and a reference azimuth. Here, the reference azimuth (φ = 0°) is set to the horizontal right direction of the LCD panel's screen. The azimuth angle is positive for counter-clockwise rotation and negative for clockwise rotation. Both counter-clockwise and clockwise rotation represent the rotation direction when viewing the LCD panel's screen from the observer's side (front). Furthermore, the angle represents the value measured when looking down at the LCD panel; two orthogonal lines (axis, direction) mean orthogonal when looking down at the LCD panel.

[0028] In this specification, "two straight lines (axis, direction) are parallel or arranged in parallel Nicol configuration" means that the angle between the two straight lines is within the range of 0°±10°, preferably within the range of 0°±5°, and more preferably within the range of 0°±1°. Furthermore, "two straight lines (axis, direction) are orthogonal or arranged in orthogonal Nicol configuration" means that the angle between the two straight lines is within the range of 90°±10°, preferably within the range of 90°±5°, and more preferably within the range of 90°±1°.

[0029] In this specification, unless otherwise specified, the axis orientation refers to the orientation of the absorption axis (reflection axis) of the polarizing element or the in-plane hysteresis axis of the phase difference layer.

[0030] The embodiments of the present invention will now be described. The present invention is not limited to the contents described in the following embodiments, and design changes may be appropriately made within the scope of satisfying the structure of the present invention.

[0031] <First Implementation Method> The liquid crystal display device according to the first embodiment includes, in sequence from the back side, a first polarizing element, a liquid crystal panel, a second polarizing element, a first phase difference layer, and a third polarizing element, wherein the light transmitted between the second polarizing element and the third polarizing element along the inclined direction is elliptical polarized light.

[0032] Figure 1 This is a cross-sectional schematic diagram showing an example of the liquid crystal display device according to the first embodiment. The liquid crystal display device 1 of the first embodiment may also be a transmissive liquid crystal display device, or as... Figure 1As shown, it includes a backlight 40, and sequentially comprises a first polarizing element 11, a liquid crystal panel 20, a second polarizing element 12, a first retardation layer 31, and a third polarizing element 13 from the back side (backlight 40 side). A fourth polarizing element 14 may also be provided on the backlight 40 side of the first polarizing element 11. Figure 1 The solid arrows represent external light incident on the liquid crystal panel 20 from an oblique direction, and reflected light reflected inside the liquid crystal panel 20 and emitted from the oblique direction. The dashed arrows represent light emitted obliquely from the backlight 40 side toward the liquid crystal panel 20 and transmitted through the liquid crystal panel 20.

[0033] exist Figures 1 to 3 , Figure 19 and Figure 20 In the diagram, the angles (°) marked on the right side of each component indicate the axial orientation. Absorption-type polarizing elements indicate the axial orientation of the absorption axis, and reflection-type polarizing elements indicate the axial orientation of the reflection axis. For the phase retardation layers other than the positive C-plate and the negative C-plate, the axial orientation of the in-plane hysteresis axis is shown. Since the optical axis aligns with the normal direction for both the positive and negative C-plates, the in-plane hysteresis axis is not defined and is therefore marked with "-". Hereinafter, without distinguishing between the positive and negative C-plates, it will simply be referred to as C-plate.

[0034] By distributing a first phase retardation layer 31 between the second polarizing element 12 and the third polarizing element 13, the light transmitted between the second polarizing element 12 and the third polarizing element 13 along the tilt direction becomes elliptically polarized light. The light transmitted between the second polarizing element 12 and the third polarizing element 13 along the tilt direction only needs to be elliptically polarized if at least a wavelength of 550 nm is present. Furthermore, at least one of the light transmitted from the second polarizing element 12 side to the third polarizing element 13 side and the light transmitted from the third polarizing element 13 side to the second polarizing element 12 side needs to be elliptically polarized, but preferably both are elliptically polarized. The tilt direction refers to a direction other than the normal direction of the liquid crystal panel 20. The light transmitted between the second polarizing element 12 and the third polarizing element 13 does not need to be elliptically polarized in all tilt directions other than the normal direction of the liquid crystal panel 20, as long as it is elliptically polarized in at least one tilt direction.

[0035] The combination of the second polarizing element 12, the first retardation layer 31, and the third polarizing element 13 functions as an optical veil, and is therefore referred to hereinafter as a polarizing element veil. The liquid crystal display device according to the first embodiment has a polarizing element veil on the observer side of the liquid crystal panel 20. By setting the light transmitted between the second polarizing element 12 and the third polarizing element 13 as elliptically polarized light, in a black display state, such as Figure 1As indicated by the dashed arrow, leakage of light transmitted from the backlight 40 side in the tilted direction can be suppressed, thus improving contrast ratio (CR). Furthermore, by arranging polarizing element louvers on the observer side of the liquid crystal panel 20, the amount of external light incident from the tilted direction and reaching the interior of the liquid crystal panel 20 can be reduced, and, as... Figure 1 As indicated by the arrow in the solid line, the amount of reflected light that is reflected internally in the liquid crystal panel 20 and then emitted in an oblique direction can be reduced, thereby suppressing internal reflection in the liquid crystal panel 20.

[0036] Furthermore, regarding reflected light incident and emitted along the normal direction, it is generally not a problem even if an external light source exists in the normal direction of the display, as it will be blocked by the observer's own shadow. When there is a light source between the observer and the liquid crystal panel 20, reflection in the normal direction becomes a problem, but since this is a special case, it is sufficient to suppress reflection in the tilt direction if we consider the actual use of the liquid crystal display device.

[0037] The first polarizing element 11, the second polarizing element 12, and the third polarizing element 13 can also be absorption-type polarizing elements. An absorption-type polarizing element has a transmission axis and an absorption axis orthogonal to the transmission axis.

[0038] Examples of absorptive polarizing elements include a polyvinyl alcohol (PVA) film containing an anisotropic material such as an iodine complex with dichroism that is adsorbed and oriented. To ensure mechanical strength and resistance to damp heat, a protective film such as a triacetyl cellulose (TAC) film may be laminated onto at least one side of the aforementioned PVA film.

[0039] The first polarizing element 11 and the second polarizing element 12 clamp the liquid crystal panel 20. The first polarizing element 11, the second polarizing element 12, and the third polarizing element 13 are preferably linear polarizing elements. The first polarizing element 11 and the second polarizing element 12 can also be orthogonally arranged. That is, the transmission axis of the first polarizing element 11 and the transmission axis of the second polarizing element 12 can also be orthogonal to each other.

[0040] Furthermore, the first polarizing element 11 and the second polarizing element 12 can also be configured in parallel Nicol configuration, but from the viewpoint of obtaining high contrast, it is preferable to configure them in orthogonal Nicol configuration.

[0041] Preferably, the transmission axis of the second polarizing element 12 is parallel to the transmission axis of the third polarizing element 13. With this configuration, a bright white display can be obtained in the normal direction and the vertical and horizontal directions of the liquid crystal panel 20.

[0042] The second polarizing element 12 and the third polarizing element 13 do not necessarily need to have higher performance than the first polarizing element 11. If the combined performance of the second polarizing element 12 and the third polarizing element 13 is equivalent to that of the first polarizing element 11, compared with the configuration without the third polarizing element 13, the transmittance of the liquid crystal display device 1A in the white display state can be prevented from decreasing, and the contrast ratio can be prevented from decreasing compared with the configuration without the third polarizing element 13.

[0043] The transmission axis of the second polarizing element 12 is parallel to the transmission axis of the third polarizing element 13. The difference between the transmittance of the light transmitted through the second polarizing element 12 and the third polarizing element 13 and the transmittance of the first polarizing element 11 can be less than 1%, or the difference between the polarization of the light transmitted through the second polarizing element 12 and the third polarizing element 13 and the polarization of the first polarizing element 11 can also be less than 1%. In this specification, the transmittance of the polarizing element refers to the transmittance of light with a wavelength of 550 nm. Unless otherwise stated, the transmittance of the polarizing element refers to the individual transmittance Ts described later.

[0044] From the viewpoint of preventing the transmittance of the liquid crystal display device 1A in the white display state from being lower than that of a configuration without the third polarizing element 13, the transmittance of at least one of the second polarizing element 12 and the third polarizing element 13 can also be higher than the transmittance of the first polarizing element 11. By making the transmittance of at least one of the second polarizing element 12 and the third polarizing element 13 higher than the transmittance of the first polarizing element 11, the reduction in transmittance of the liquid crystal display device 1A in the white display state can be prevented compared to a configuration without the third polarizing element 13.

[0045] The polarization degree of at least one of the second polarizing element 12 and the third polarizing element 13 may be lower than that of the first polarizing element 11. Generally, since the transmittance and polarization degree of a polarizing element are in a trade-off, this configuration prevents a decrease in transmittance in the white display state of the liquid crystal display device 1A compared to a configuration without the third polarizing element 13. In this specification, the polarization degree of a polarizing element refers to the polarization degree of light with a wavelength of 550 nm.

[0046] The polarization degree of a polarizing element represents the degree of polarization deviation of light after it passes through the element when natural light is incident on it, and is expressed as a variable of contrast. The parallel Nicol transmittance (parallel transmittance) of each polarizing element is defined as Tp, the orthogonal Nicol transmittance (orthogonal transmittance) as Tc, the polarization degree as P, and the contrast as C. These are expressed as C = Tp / Tc and P = Sqrt((Tp-Tc) / (Tp+Tc)). If the equations are rearranged, they become P = Sqrt((CR-1) / (CR+1)) or C = (1+P^2) / (1-P^2). In these equations, "Sqrt" represents the square root, and "^2" represents the square.

[0047] When ideally linearly polarized light is incident, the transmittance when its vibration orientation is aligned with the transmission axis of the polarizing element is defined as the first principal transmittance k1, and the transmittance when its vibration orientation is orthogonal to the transmission axis of the polarizing element is defined as the second principal transmittance k2. The transmittance when unpolarized light is incident on a single polarizing element is defined as the single-element transmittance Ts. The transmittance when two identical polarizing elements are overlapped in a parallel Nicol relationship and unpolarized light is incident on them is defined as the parallel Nicol transmittance Tp. The transmittance when two identical polarizing elements are overlapped in an orthogonal Nicol relationship and unpolarized light is incident on them is defined as the orthogonal Nicol transmittance Tc. If unpolarized light of intensity 1 is considered to be the sum of linearly polarized light vibrating in direction A with intensity 1 / 2 and linearly polarized light vibrating in a direction orthogonal to direction A with intensity 1 / 2, then Ts, Tp, and Tc can be expressed using kl and k2, respectively, by the following formula. Ts=(1 / 2)×k1+(1 / 2)×k2=(1 / 2)×(k1+k2) Tp=(1 / 2)×k1×k1+(1 / 2)×k2×k2=(1 / 2)×(k1^2+k2^2) Tc=(1 / 2)×k1×k2+(1 / 2)×k2×k1=(1 / 2)×(2k1×k2)

[0048] The performance of the second polarizing element 12 and the third polarizing element 13 can also be different. In other words, the transmittance or polarization degree of the third polarizing element 13 and the second polarizing element 12 can also be different. When the second polarizing element 12 is configured to form an orthogonal Nicol relationship with the first polarizing element 11, it cooperates with the first polarizing element 11 to determine the transmission display performance of the liquid crystal display device 1A. Therefore, it is preferable that the performance of the second polarizing element 12 is as high as possible. The performance of the second polarizing element 12 is preferably higher than that of the third polarizing element 13. However, as mentioned above, since the transmittance and polarization degree of a polarizing element are usually in a trade-off relationship, it is preferable that the second polarizing element 12 has a higher transmittance or polarization degree than the third polarizing element 13.

[0049] Focusing on anti-reflective performance, the performance of the second polarizing element 12 can be equivalent to that of the third polarizing element 13. When the second polarizing element 12 and the third polarizing element 13 are arranged in a parallel Nicol configuration, they cooperate to create a Venetian blind effect, thus determining the anti-reflective performance of the display device. Therefore, regardless of whether the second polarizing element 12 and the third polarizing element 13 are high-performance, as long as their performance is the same when combined and considered as a single polarizing element, the anti-reflective performance will not change. In other words, the performance distribution between the second polarizing element 12 and the third polarizing element 13 is not very important. The difference between the transmittance of the second polarizing element 12 and the transmittance of the third polarizing element 13 can be less than 1%, or the difference between the polarization degree of the second polarizing element 12 and the polarization degree of the third polarizing element 13 can also be less than 1%.

[0050] Furthermore, when the second polarizing element 12 and the third polarizing element 13 are combined and considered as a single polarizing element, if the first principal transmittance of the second polarizing element 12 is set as k1, the second principal transmittance as k2, the first principal transmittance of the third polarizing element 13 is set as k1', and the second principal transmittance as k2', then the parallel Nicol transmittance Tp and the cross Nicol transmittance Tc when the second polarizing element 12 and the third polarizing element 13 are combined can be calculated as follows. The difference between the parallel Nicol transmittance Tp when the second polarizing element 12 and the third polarizing element 13 are combined and the transmittance of the first polarizing element 11 can also be less than 1%. In addition, the difference between the polarization degree of the combined second polarizing element 12 and the third polarizing element 13 calculated according to the following Tp and Tc and the polarization degree of the first polarizing element 11 can also be less than 1%. Tp=(1 / 2)×k1×k1'+(1 / 2)×k2×k2'=(1 / 2)×(k1×k1'+k2×k2') Tc=(1 / 2)×k1×k2'+(1 / 2)×k2×k1'=(1 / 2)×(k1×k2'+k2×k1')

[0051] The first phase retardation layer 31 is disposed between the second polarizing element 12 and the third polarizing element 13. The first phase retardation layer 31 is not particularly limited as long as it can make the light transmitted along the tilt direction between the second polarizing element 12 and the third polarizing element 13 elliptically polarized. The in-plane phase difference R of the first phase retardation layer 31 is preferably 250 nm or more and 310 nm or less.

[0052] The thickness direction retardation Rth of the first retardation layer 31 (1) may be less than 400 nm (preferably 300 nm or less), or (2) may be 400 nm or more (preferably 500 nm or more). In the case of the above (1), the thickness direction retardation Rth of the first retardation layer 31 is preferably 120 nm or more, more preferably 140 nm or more. In the case of the above (2), the thickness direction retardation Rth of the first retardation layer 31 is preferably 610 nm or less.

[0053] Furthermore, the absolute value of the total sum of the thickness direction retardation Rth between the second polarizing element 12 and the third polarizing element 13 may also satisfy the above (1) or (2). In this specification, the total sum of the thickness direction retardation Rth between the second polarizing element 12 and the third polarizing element 13 refers to the total sum of the thickness direction retardation Rth of each of all layers (films) located between the second polarizing element 12 and the third polarizing element 13.

[0054] The birefringence parameter NZ of the first retardation layer 31 may satisfy (I) 0.9≦NZ<10 (preferably 1.5≦NZ<5.0), may satisfy (II) 10≦NZ (preferably 100≦NZ), may satisfy (III) -11<NZ≦-0.9, or may satisfy (IV) NZ≦-11 (preferably NZ≦-100).

[0055] In the case of the above (I), the in-plane slow axis of the first retardation layer 31 may be parallel (I-1) to the transmission axis of the second polarizing element 12 or the transmission axis of the third polarizing element 13, or may be orthogonal (I-2) thereto. The slow axis when viewed from an oblique direction depends on the viewing angle and the NZ coefficient, and the retardation when viewed from an oblique direction depends on the viewing angle, the NZ coefficient, and the in-plane retardation R (or the thickness direction retardation Rth). Regardless of whether the angle formed by the slow axis of the first retardation layer 31 and the absorption axis of the second polarizing plate 12 is 0° or 90°, if the NZ coefficient is increased, the first retardation layer 31 approaches a negative C-plate, and under the limit of 1<<NZ (NZ→+∞), the first retardation layer 31 completely becomes a negative C-plate. Conversely, if the NZ coefficient is decreased, the first retardation layer 31 approaches a positive C-plate.

[0056] In the case of the above (II), the upper limit of the birefringence parameter NZ of the first retardation layer 31 is not particularly limited, and may be NZ=+∞. In this case, the first retardation layer 31 becomes a negative C-plate.

[0057] In the case of the above (IV), the lower limit of the birefringence parameter NZ of the first retardation layer 31 is not particularly limited, and may be NZ=-∞. In this case, the first retardation layer 31 becomes a positive C-plate.

[0058] In cases (II) and (IV) above, the in-plane phase difference R of the first phase difference layer 31 is small enough to be considered optically isotropic in-plane. Therefore, the orientation of the in-plane axis of the first phase difference layer 31 is not particularly restricted.

[0059] exist Figure 1 The example illustrates the use of a negative C-plate or a positive C-plate as the first retardation layer 31. As described above, in the case of a negative C-plate or a positive C-plate, the orientation of the in-plane axis of the first retardation layer 31 is not particularly limited.

[0060] Figure 2 This is a cross-sectional schematic diagram illustrating another example of the liquid crystal display device according to the first embodiment. Figure 2 In the example shown, the first phase retardation layer 31 uses layers other than the negative C-plate and the positive C-plate, and the in-plane hysteresis axis of the first phase retardation layer 31 is orthogonal to the transmission axis of the second polarizing element 12 or the transmission axis of the third polarizing element 13 (as described in (I-2)).

[0061] There are no particular limitations on the material of the first phase difference layer 31. For example, a material after stretching a polymer film, a material after fixing the orientation of a liquid crystal material, or a thin plate made of inorganic material can be used.

[0062] There are no particular limitations on the method for forming each phase difference layer. When forming from a polymer film, methods such as solvent casting and melt extrusion can be used. Multiple phase difference layers can also be formed simultaneously using co-extrusion. Even if the desired phase difference is achieved, stretching can be performed or no stretching is required. The stretching method is also not particularly limited; in addition to roll stretching, roll compression stretching, tenter frame transverse uniaxial stretching, tilt stretching, and longitudinal and transverse biaxial stretching, special stretching methods that stretch under the shrinkage force of a heat-shrinkable film can also be used. Furthermore, when forming from a liquid crystal material, for example, a method can be used to coat the liquid crystal material onto a substrate film that has undergone alignment treatment and then fix the alignment. As long as the desired phase difference is achieved, methods can be used without special alignment treatment of the substrate film, or by peeling the substrate film after alignment fixation and transferring it to another film. Moreover, methods that do not fix the alignment of the liquid crystal material can also be used. Additionally, when forming from a non-liquid crystal material, the same formation method as when forming from a liquid crystal material can be used.

[0063] As the first retardation layer 31 satisfying 0.9≦NZ<10, a retardation layer obtained by stretching a film containing a material with inherently positive birefringence can be appropriately used. Examples of materials with inherently positive birefringence include polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, cellulose triacetate, and diethyl cellulose.

[0064] As the first phase difference layer 31 satisfying 10≦NZ, a so-called negative C-plate can be appropriately used. For example, a negative C-plate can be made by stretching a film containing a material with inherent positive birefringence in both longitudinal and transverse axes, or a negative C-plate coated with liquid crystal materials such as cholesteric liquid crystal (chiral nematic) liquid crystal or disk liquid crystal, or a negative C-plate coated with non-liquid crystal materials such as polyimide or polyamide.

[0065] As the first phase retardation layer 31 satisfying -11 < NZ ≦ -0.9, a phase retardation layer obtained by stretching a film containing a material with inherently negative birefringence, or a phase retardation layer obtained by stretching a film containing a material with inherently positive birefringence under the shrinkage force of a heat-shrinkable film, can be appropriately used. From the viewpoint of simplifying the manufacturing process, materials obtained by stretching a film containing a material with inherently negative birefringence are preferred. Examples of materials with inherently negative birefringence include: resin compositions containing acrylic resins and styrene resins, polystyrene, polyvinyl naphthalene, polyvinyl biphenyl, polyvinylpyridine, polymethyl methacrylate, polymethyl acrylate, N-substituted maleimide copolymers, polycarbonate with a fluorene backbone, and triacetyl cellulose (especially substances with low acetylation).

[0066] As the first phase difference layer 31 satisfying NZ≦-11, a so-called positive C-plate or the like can be appropriately used. For example, a positive C-plate obtained by biaxial stretching of a film containing a material with inherently negative birefringence, or a positive C-plate made by coating a liquid crystal material such as nematic liquid crystal, can be appropriately used.

[0067] The fourth polarizing element 14 is preferably a linear polarizing element, but it can also be a reflective polarizing element. A reflective polarizing element has a transmission axis and a reflection axis orthogonal to the transmission axis. The reflective polarizing element has the effect of recovering backlight light; therefore, by arranging a reflective polarizing element on the back side of the first polarizing element 11, the transmittance of the liquid crystal display device 1A in white display mode can be improved.

[0068] When the first polarizing element 11 is an absorption polarizing element and the fourth polarizing element 14 is a reflection polarizing element, the orientation of the absorption axis of the first polarizing element 11 and the orientation of the reflection axis of the fourth polarizing element 14 can be configured to be orthogonal or parallel.

[0069] Examples of reflective polarizing elements include reflective polarizing elements obtained by uniaxially stretching a co-extruded film composed of two resins (e.g., APCF manufactured by Nitto Denko Corporation and DBEF manufactured by 3M Corporation), and reflective polarizing elements that periodically arrange fine metal wires (so-called wire grid polarizing elements).

[0070] The liquid crystal mode of the liquid crystal panel 20 is not particularly limited. Black display can be achieved by aligning the liquid crystal molecules in the liquid crystal layer perpendicular to the substrate surface, or by aligning the liquid crystal molecules in the liquid crystal layer parallel to the substrate surface or in a direction that is neither perpendicular nor parallel. In addition, as for the driving method of the liquid crystal panel 20, besides TFT method (active matrix method), it can also be simple matrix method (passive matrix method), plasma addressing method, etc.

[0071] The liquid crystal panel 20 can be, for example, a liquid crystal panel in which a liquid crystal layer is sandwiched between a pair of substrates on which pixel electrodes and a common electrode are formed, and a voltage is applied between the pixel electrodes and the common electrode to apply a lateral electric field (including an edge electric field) to the liquid crystal layer, thereby enabling display. Alternatively, it can be a liquid crystal panel in which a liquid crystal layer is sandwiched between a pair of substrates on which pixel electrodes are formed, and a voltage is applied between the pixel electrodes and the common electrode to apply a vertical electric field to the liquid crystal layer, thereby enabling display.

[0072] More specifically, examples of lateral electric field modes include the FFS (Fringe Field Switching) mode, in which the liquid crystal molecules in the liquid crystal layer are aligned parallel to the substrate surface when no voltage is applied, and the IPS (In Plane Switching) mode. Examples of longitudinal electric field modes include the vertical alignment (VA), in which the liquid crystal molecules in the liquid crystal layer are aligned perpendicularly to the substrate surface when no voltage is applied.

[0073] While it is known to suppress internal reflections by configuring circular polarizers, in principle, circular polarizers cannot be used to prevent reflections in transverse electric field modes (FFS mode, IPS mode). The light-blocking venetian blind of this embodiment can be appropriately used as a reflection suppression unit in FFS mode and IPS mode.

[0074] The backlight 40 is not particularly limited and can be any backlight commonly used in the field of liquid crystal display devices. It can be a direct-lit backlight in which the light source is disposed at a position overlapping the display area of ​​the liquid crystal panel 20, or it can be an edge-lit backlight in which a light guide plate is provided and the light source is disposed at the end of the light guide plate.

[0075] <Second Implementation Method> The liquid crystal display device according to the second embodiment has multiple phase difference layers between the second polarizing element 12 and the third polarizing element 13. In this embodiment, the description of components that have the same reference numerals as those in this embodiment and the first embodiment, or that have the same function, is appropriately omitted.

[0076] Figure 3 This is a cross-sectional schematic diagram illustrating an example of a liquid crystal display device according to the second embodiment. For example... Figure 3 As shown, the liquid crystal display device 1C according to the second embodiment also includes a second phase retardation layer 32 between the second polarizing element 12 and the third polarizing element 13. In the second embodiment, the combination of the second polarizing element 12, the first phase retardation layer 31, the second phase retardation layer 32 and the third polarizing element 13 is also referred to as a polarizing element venetian blind.

[0077] As the second phase retardation layer 32, the same phase retardation layer with the same configuration as the first phase retardation layer 31 can be used. The in-plane phase difference R of the second phase retardation layer 32 is preferably 250 nm or more and 310 nm or less.

[0078] The phase difference Rth in the thickness direction of the second phase difference layer 32 is similar to that of the first phase difference layer 31. (1) It can be less than 400 nm (preferably 300 nm or less), and (2) It can be 400 nm or more (preferably 500 nm or more). In the case of (1) above, the phase difference Rth in the thickness direction of the second phase difference layer 32 is preferably 120 nm or more, and more preferably 140 nm or more. In the case of (2) above, the phase difference Rth in the thickness direction of the second phase difference layer 32 is preferably 610 nm or less.

[0079] Furthermore, the absolute value of the total thickness direction phase difference Rth between the second polarizing element 12 and the third polarizing element 13 can satisfy either (1) or (2) above, but it is more preferable to satisfy (2) above.

[0080] The biaxial parameter NZ of the second phase retardation layer 32 is similar to that of the first phase retardation layer 31, and can also satisfy (I) 0.9≦NZ<10 (preferably 1.5≦NZ<5.0), (II) 10≦NZ (preferably 100≦NZ), (III) -11<NZ≦-0.9, and (IV) NZ≦-11 (preferably NZ≦-100). In the case of (I) above, the in-plane hysteresis axis of the second phase retardation layer 32 can be parallel (I-1) to the transmission axis of the second polarizing element 12 or the transmission axis of the third polarizing element 13, or orthogonal (I-2).

[0081] Preferably, the first phase difference layer 31 and the second phase difference layer 32 are substantially identical in configuration (made of substantially the same materials and manufactured in substantially the same processes, exhibiting substantially the same properties). By making the first phase difference layer 31 and the second phase difference layer 32 substantially identical, manufacturing costs can be suppressed. Furthermore, technically, by using identical phase difference layers, manufacturing deviations are eliminated. Therefore, particularly in the case equivalent to (I-3) described later, it is expected that the in-plane phase difference R will be completely eliminated, with a residual phase difference of zero.

[0082] The first phase difference layer 31 and the second phase difference layer 32 may each use biaxial parameters to satisfy the phase difference layers (I) to (IV) above, but the biaxial parameters of the first phase difference layer 31 and the second phase difference layer 32 may also satisfy (I) above.

[0083] When the first phase retardation layer 31 and the second phase retardation layer 32 satisfy the above (I), the in-plane hysteresis axes of the first phase retardation layer 31 and the second phase retardation layer 32 can also have the same configuration relationship with respect to the transmission axis of the second polarizing element 12. That is, the in-plane hysteresis axes of the first phase retardation layer 31 and the second phase retardation layer 32 can both be parallel to the transmission axis of the second polarizing element 12 (as described in (I-1) above), or orthogonal to the transmission axis of the second polarizing element 12 (as described in (I-2) above).

[0084] In addition, when the first phase difference layer 31 and the second phase difference layer 32 satisfy the above (I), (I-3) the angle between the in-plane hysteresis axis of the first phase difference layer 31 and the transmission axis of the second polarizing element 12 or the transmission axis of the third polarizing element 13 can be 30° or more and 60° or less (preferably 40° or more and 50° or less, more preferably 43° or more and 47° or less, and even more preferably substantially 45° or less).

[0085] When multiple phase lag layers are provided, and these multiple phase lag layers are equivalent to those described in (I-3) above, it is preferable that the in-plane hysteresis axes of each phase lag layer are mutually orthogonal. When there are an even number of phase lag layers (let's say 2n, where n is a natural number), it is preferable to arrange n phase lag layers and the remaining n phase lag layers in a manner where their in-plane hysteresis axes are mutually orthogonal. When there are an even number of phase lag layers and four or more, the stacking order is not limited. For example, whether the in-plane hysteresis axes are arranged sequentially at azimuth angles of 45° / 135° / 45° / 135° from the observer side, or arranged at azimuth angles of 45° / 45° / 135° / 135°, or arranged at azimuth angles of 45° / 135° / 135° / 45°, the same effect can be obtained.

[0086] On the other hand, when there is an odd number of phase retardation layers, in order to eliminate the influence in the frontal direction, it is preferable to configure the in-plane hysteresis axis so that the total in-plane phase difference is zero. For example, when there are three phase retardation layers, the in-plane hysteresis axis of the first phase retardation layer can be configured with an azimuth angle of 45°, the in-plane hysteresis axis of the second phase retardation layer (whose in-plane phase difference is twice that of the first phase retardation layer) can be configured with an azimuth angle of 135°, and the in-plane hysteresis axis of the third phase retardation layer (whose in-plane phase difference is the same as that of the first phase retardation layer) can be configured with an azimuth angle of 45°. [Example]

[0087] While embodiments and comparative examples are disclosed below, and the invention is described in more detail, the invention is not limited to these embodiments.

[0088] The transmittance T (%) and polarization (%) of the polarizing elements A to D used in the following examples and comparative examples are summarized in Table 1. As polarizing elements A to D, absorption-type polarizing elements were used, in which dichroic iodine complexes were adsorbed and oriented onto the polyvinyl alcohol (PVA) film.

[0089] (Methods for measuring the transmittance and polarization of polarizing elements) The transmittance T (%) and polarization (%) of polarizing elements A to D were determined by the following method. Measurements were performed using a UV-Vis spectrophotometer (manufactured by Nippon Spectrophotometer Co., Ltd., trade name: V-7100). Ideal polarizing elements, such as Gran Thompson prisms or Gran Foucault prisms, were used as optional equipment to ensure that the measurement light (incident light to the polarizing element sample) was linearly polarized. The transmittance in the visible light wavelength region (wavelength 380 nm to 780 nm) was measured, and the Y value, corrected for visual sensitivity using two fields of view (C light source) as specified in JIS Z 8701-1982, was taken as the transmittance T.

[0090] [Table 1] Types of polarizing elements T(％) Polarization degree (%) A 42.2 99.996 B 43.8 99.692 C 44.3 99.098 D 45.1 97.372

[0091] (Methods for determining R, Rth, NZ coefficients, nx, ny, and nz) The in-plane phase difference R, thickness-direction phase difference Rth, and NZ coefficient of the first and second retardation layers 31 and 32 shown in Tables 2 and 3 were determined using the following method. Measurements were performed using a polarimeter with a double-delay rotation method (trade name: Axo-scan, manufactured by Axometrics). The in-plane phase difference R was measured from the normal direction of the retardation layer. The principal refractive indices nx, ny, nz, thickness-direction phase difference Rth, and NZ coefficient were measured from the normal direction of the retardation layer and from various tilt directions tilted from -50° to 50°, and calculated using a known elliptic curve fitting method. The tilt orientation is the orientation orthogonal to the in-plane hysteresis axis. Furthermore, nx, ny, nz, Rth, and NZ are calculated based on the average refractive index = (nx + ny + nz) / 3 provided as a calculation condition for curve fitting, but the average refractive index of each retardation layer was uniformly set to 1.5. Regarding the phase difference layer, which differs from the actual average refractive index of 1.5, we also assume an average refractive index of 1.5 and perform the conversion.

[0092] (Example 1) Example 1 is a specific example of the display device involved in the first embodiment, having the same characteristics as... Figure 1 The configuration shown is the same. Figure 1 This is a cross-sectional schematic diagram of the liquid crystal display device involved in Embodiment 1. For example... Figure 1 As shown, the liquid crystal display device according to Embodiment 1 includes a backlight 40, and from the backlight 40 side (back side), it sequentially includes a reflective polarizing element 14, a first polarizing element 11, a liquid crystal panel 20, a second polarizing element 12, a first retardation layer 31, and a third polarizing element 13. The liquid crystal panel 20 is an FFS mode liquid crystal panel using a lateral electric field method. The reflective polarizing element 14 is an APF (Advanced Persistent Polarizing Element) manufactured by 3M Corporation.

[0093] In Example 1, as shown in Table 2, the polarizing elements listed in Table 1 were used as the first, second, and third polarizing elements. A negative C-plate with a thickness-direction phase difference Rth of 250 nm was used as the first retardation layer. The in-plane phase difference R and thickness-direction phase difference Rth of the first retardation layer used in Example 1 are shown in Table 2. Furthermore, in Table 2 and Table 3 (described later), the phase difference R of the retardation layer other than the C-plate represents the in-plane phase difference. In the case of the C-plate, the in-plane phase difference is 0, therefore it represents the thickness-direction phase difference Rth.

[0094] (Example 2) Example 2 is another specific example of the display device involved in the first embodiment, having the same characteristics as... Figure 2 The configuration shown is the same. Figure 2 This is a cross-sectional schematic diagram of the liquid crystal display device according to Embodiment 2. Embodiment 2 uses a phase retardation layer other than the C-plate as the first phase retardation layer 31, such as... Figure 2 The in-plane hysteresis axis is configured as shown. The in-plane phase difference R, thickness direction phase difference Rth, and NZ coefficient of the first phase difference layer 31 used in Embodiment 2 are shown in Table 2.

[0095] (Example 3) Example 3 is a specific example of the display device involved in the second embodiment, having the same characteristics as... Figure 3 The configuration shown is the same. Figure 3 This is a cross-sectional schematic diagram of the liquid crystal display device according to Embodiment 3. In Embodiment 3, a two-layer phase retardation layer is used, serving as the first phase retardation layer 31 and the second phase retardation layer 32, and the phase retardation layer used in Embodiment 2 is employed. The in-plane hysteresis axes of the first phase retardation layer 31 and the second phase retardation layer 32 are as follows: Figure 3 Configure it as shown.

[0096] (Comparative Example 1) Comparative Example 1 is another specific example of the display device involved in Comparison Method 1, having the same characteristics as... Figure 19 The configuration shown is the same. Figure 19 This is a cross-sectional schematic diagram of the liquid crystal display device according to Comparative Example 1. The liquid crystal display device according to Comparative Example 1 includes a backlight 140, and from the backlight 140 side (back side), it sequentially includes a reflective polarizing element 114, a first polarizing element 111, a liquid crystal panel 120, and a second polarizing element 112. The backlight 140, the liquid crystal panel 120, and the reflective polarizing element 114 use the same configuration as in Example 1.

[0097] (Comparative Example 2) Comparative Example 2 is another specific example of a display device involved in Comparison Method 2, having the same characteristics as... Figure 20 The configuration shown is the same. Figure 20 This is a cross-sectional schematic diagram of the liquid crystal display device according to Comparative Example 2. The liquid crystal display device according to Comparative Example 2 includes a backlight 140, and from the backlight 140 side (back side), it sequentially includes a reflective polarizing element 114, a first retardation layer 131, a first polarizing element 111, a liquid crystal panel 120, and a second polarizing element 112. As the first retardation layer 131, the same negative C-plate as in Example 1 is used. The backlight 140, the liquid crystal panel 120, and the reflective polarizing element 114 use the same configuration as in Example 1.

[0098] (Comparative Example 3) The liquid crystal display device involved in Comparative Example 3 uses the same phase difference layer as in Example 2 as the first phase difference layer 131, and sets the axial orientation to 0°. Otherwise, it has the same configuration as Comparative Example 2.

[0099] (View of field characteristics) As for the viewing angle characteristics of the liquid crystal display devices in Examples 1-3 and Comparative Examples 1-3, the reflected viewing angle and the transmitted viewing angle were calculated. In the calculation, the reflectivity of the liquid crystal panel surface was simply replaced with that of an ideal mirror (100% reflectivity). The reflected viewing angle and the transmitted viewing angle were calculated using a liquid crystal optical simulator (trade name: LCD-MASTER).

[0100] The reflected viewing angle is calculated from the reflectance of the liquid crystal display device in white mode when the azimuth angle varies from 0 to 360° within a polar angle of 0 to 80°. The transmitted viewing angle is calculated from the transmittance of the liquid crystal display device in black mode when the azimuth angle varies from 0 to 360° within a polar angle of 0 to 80°. The results of the viewing angle characteristics are shown in... Figures 4 to 9 . Figures 4 to 9 These are contour diagrams showing the reflection viewing angle of the liquid crystal display devices involved in Examples 1-3 and Comparative Examples 1-3, and a contour diagram showing the transmission viewing angle in a black display state. The contour diagrams are contour plots representing brightness; higher values ​​indicate higher transmittance or reflectance. In the contour diagrams showing the reflection viewing angle, higher values ​​indicate high reflectance of the liquid crystal panel, including both internal and external reflections. In the contour diagrams showing the transmission viewing angle, higher values ​​indicate light leakage occurring in the black display state. Furthermore, the white display state refers to the state where the liquid crystal display device has the highest brightness, and the black display state refers to the state where the liquid crystal display device has the lowest brightness. In the black display state, the backlight is also set to be on.

[0101] (Front-facing transmittance in white display mode) The front transmittance of the liquid crystal display device in white display mode is calculated from the transmittance along the normal direction (polar angle 0°) of the image on the liquid crystal panel in white display mode. The aforementioned transmittance is calculated using a liquid crystal optical simulator (Sumitec, trade name: LCD-MASTER) to determine the spectral transmittance in the visible wavelength range (wavelength 380nm to 780nm). Table 2 shows the relative values ​​of the front transmittance when the front transmittance of Comparative Example 1 is set to 1, representing the front transmittance of each embodiment and comparative example.

[0102] [Table 2]

[0103] like Figures 4 to 9As shown, the reflectivity of the white display state in Examples 1-3 is lower than that in Comparative Examples 1-3. Furthermore, it can be confirmed that the transmittance of the liquid crystal display device in the black display state in Examples 1-3 is lower than that in Comparative Examples 1-3, resulting in less light leakage. In particular, in Example 3, where the hysteresis axes of the two phase difference layers are orthogonal, the reflectivity of the liquid crystal display device in the white display state is low, and light leakage is minimal.

[0104] The liquid crystal display devices of Examples 1-3 differ from those of Comparative Examples 1-3 in that they exhibit less unwanted reflection when viewed in bright light. In particular, unwanted reflection is reduced when viewed from an angle. Furthermore, it is evident that Examples 1-3 exhibit less light leakage in black display mode compared to Comparative Example 1, thus further improving contrast and enhancing visual discernibility.

[0105] (Determination of internal reflectivity) Regarding Examples 2 and 3 and Comparative Examples 1 and 3, the internal reflectivity at a polar angle of 30° was measured, and the results are shown in... Figure 10 A variable angle photometer (manufactured by Nippon Denshoku Kogyo Co., Ltd., trade name: GC5000L) was used in the measurement. Figure 10 This is a graph showing the measurement results of the internal reflectivity at a polar angle of 30° for the liquid crystal display devices according to Examples 2 and 3 and Comparative Examples 1 and 3, when the azimuth angle of the incident light is changed. The internal reflectivity referred to here is the reflectivity after removing the surface reflectivity (the surface reflectivity of the polarizing element reaching the outermost surface) from the reflectivity of the liquid crystal display device in the white display state described above. The reflectivity of the polarizing element disposed on the outermost surface of each liquid crystal display device is set to 4%.

[0106] like Figure 10 As shown, compared to Comparative Examples 1 and 3, the liquid crystal display devices of Examples 2 and 3 require less reflection when viewed in bright light, thus maintaining the quality of black display. When actually manufacturing the liquid crystal display devices of Examples 2 and 3 and Comparative Examples 1 and 3, and verifying the black display state of the liquid crystal display devices in a bright environment of 1000 lux, the same results as the above calculations were confirmed.

[0107] (Examples 1-2 to 1-7) Liquid crystal display devices according to Examples 1-2 to 1-7 were fabricated using polarizing elements with different transmittance and polarization as shown in Table 1. The liquid crystal display devices according to Examples 1-2 to 1-7 have the same configuration as those in Example 1, except for changes in the performance of the third and second polarizing elements. The configurations of Examples 1-2 to 1-7 are shown in Table 3.

[0108] Similar to Example 1, the reflection viewing angle, the transmission viewing angle in the black display state, and the front transmittance in the white display state (relative values ​​to Comparative Example 1) of the liquid crystal display device were calculated. The results of the front transmittance of the liquid crystal display device in the white display state are shown in Table 3, and the results of the viewing angle characteristics are shown in... Figures 11 to 16 . Figures 11 to 16 These are outline diagrams showing the reflection field of view of the liquid crystal display device involved in Embodiments 1-2 to 1-7, and outline diagrams showing the transmission field of view in the black display state.

[0109] [Table 3]

[0110] like Figure 4 , Figures 11 to 16 As shown, the liquid crystal display devices of Examples 1-2 to 1-7 improve the transmittance of the liquid crystal display device in the white display state compared with Example 1 by setting the transmittance of the third polarizing element and / or the second polarizing element to be higher than that of the first polarizing element. In particular, in Examples 1-5 to 1-7, the transmittance in the white display state can be further improved.

[0111] Furthermore, as can be seen from the results of Examples 1-5 to 1-7, it is preferable that the performance of the second polarizing element is higher than that of the third polarizing element. The reasons for this can be attributed to the following (i) and (ii), using... Figure 17 and Figure 18 Please provide an explanation. Figure 17 This is a graph showing the measurement results of the transmittance in the black display state when the polar angle is changed, for the liquid crystal display devices involved in Examples 1-5 to 1-7 and Comparative Example 1, when viewed from an azimuth angle of 45°. Figure 18 This is a graph showing the measurement results of reflectivity in white display state when the polar angle is changed, for the liquid crystal display devices involved in Examples 1-5 to 1-7 and Comparative Example 1, when viewed from an azimuth angle of 45°.

[0112] (i) The second polarizing element is configured to be in a cross-nicotinic relationship with the first polarizing element, and cooperates with the first polarizing element to determine the transmission display performance of the display device. Therefore, it is preferable that the performance of the second polarizing element is as high as possible. Figure 17 As shown, when comparing Examples 1-5, 1-6, and 1-7, the liquid crystal display device involved in Examples 1-5 has the lowest transmittance and less light leakage in the black display state.

[0113] (ii) The second polarizing element is configured to form a parallel nicotinic relationship with the third polarizing element, cooperating with the third polarizing element to present a venetian blind effect, thereby determining the anti-reflection performance of the liquid crystal display device. Therefore, regardless of which polarizing element, the second or the third, has higher performance, as long as their performance is the same when combined and considered as a single polarizing element, the anti-reflection performance will not change. That is, the performance distribution between the second and third polarizing elements is not very important. Figure 18 As shown, Examples 1-5, 1-6, and 1-7 all achieved a reflection reduction effect compared to Comparative Example 1. On the other hand, the graphs of Examples 1-5, 1-6, and 1-7 overlap, indicating that there is no difference in the reflection reduction effect among Comparative Examples 1-5, 1-6, and 1-7. Explanation of reference numerals in the attached figures

[0114] 1A, 1B, 1C, 100A, 100B: Liquid Crystal Display Devices 11, 111: First polarizing element 12, 112: Second polarizing element 13: Third polarizing element 14, 114: Fourth polarizing element (reflective polarizing element) 20, 120: LCD panel 31, 131: First phase difference layer 32: Second phase difference layer 40, 140: Backlight

Claims

1. A liquid crystal display device, characterized in that, Starting from the back side, it sequentially includes a first polarizing element, a liquid crystal panel, a second polarizing element, a first retardation layer, and a third polarizing element. It also includes a backlight source, which is located on the side opposite to the second polarizing element, the first retardation layer, and the third polarizing element relative to the liquid crystal panel, and is located on the back side of the first polarizing element. After being emitted from the backlight and transmitted through the liquid crystal panel, the light transmitted along the inclined direction between the second polarizing element and the third polarizing element is elliptically polarized light. The second polarizing element and the third polarizing element are linear polarizing elements. The transmission axis of the second polarizing element is parallel to the transmission axis of the third polarizing element. The first phase difference layer is a negative C-plate or a positive C-plate.

2. The liquid crystal display device according to claim 1, characterized in that, The transmittance of at least one of the second polarizing element and the third polarizing element is greater than the transmittance of the first polarizing element.

3. The liquid crystal display device according to claim 1 or 2, characterized in that, The polarization degree of at least one of the second polarizing element and the third polarizing element is lower than that of the first polarizing element.

4. The liquid crystal display device according to any one of claims 1 to 3, characterized in that, The second polarizing element and the third polarizing element have different transmittance or polarization.

5. The liquid crystal display device according to claim 1, characterized in that, The difference between the transmittance of light transmitted through the second and third polarizing elements and the transmittance of the first polarizing element is less than 1%, or... The difference between the polarization degree of the light transmitted through the second polarizing element and the third polarizing element and the polarization degree of the first polarizing element is less than 1%.

6. The liquid crystal display device according to any one of claims 1 to 5, characterized in that, The second polarizing element has a higher transmittance or polarization degree compared to the third polarizing element.

7. The liquid crystal display device according to any one of claims 1 to 6, characterized in that, A second phase détachology layer is also included between the second polarizing element and the third polarizing element.

Images