LCD display device

Abstract

A liquid crystal display device is provided that can achieve high brightness and high CR in the frontal direction, making it particularly useful as a head-mounted liquid crystal display device. The liquid crystal display device includes, from the viewing surface side, a liquid crystal panel, optical elements, and a backlight. The optical elements include a first polarizer, a retardation layer, and a second polarizer. The first polarizer, the retardation layer, and the second polarizer are arranged sequentially from the viewing surface side. The first polarizer and the second polarizer are reflective polarizers, with the reflection axis of the first polarizer parallel to the reflection axis of the second polarizer. The light incident on the first polarizer is elliptically polarized in oblique directions with a polar angle of 60° and azimuths of 0°, 45°, and 90°.

Description

Technical Field

[0001] The following disclosure relates to liquid crystal display devices. Background Technology

[0002] Liquid crystal display (LCD) devices utilize liquid crystal materials for display. They are typically composed of an LCD panel, a backlight, and optical components such as polarizers and retardation plates. LCD devices are widely used due to their excellent display characteristics, thinness, light weight, and low power consumption.

[0003] In the field of liquid crystal display devices, techniques are known for using optical elements such as polarizers and phase retardation plates to control the viewing angle characteristics of light emitted from a backlight. For example, Patent Document 1 discloses a liquid crystal display device that sequentially comprises a liquid crystal panel, a first polarizer, a birefringence layer, a second polarizer, and a backlight. The transmission axes of the first and second polarizers are parallel to each other, the biaxiality parameter value of the birefringence layer is limited to a specified range, and the phase difference in the thickness direction of the birefringence layer or the angle between the transmission axis of the first polarizer and the in-plane hysteresis axis of the birefringence layer is limited to a specified range.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2012 / 090769 Summary of the Invention

[0007] The technical problem to be solved by the present invention

[0008] In recent years, the development and improvement of wearable devices worn on the user's body have made progress. Head-mounted displays (HMDs) are a well-known example of wearable devices. An HMD is a display device that outputs images in a way that allows the user to see them while wearing it on their head. Examples include monocular HMDs, where an image output unit is located in front of one eye, allowing both the image from the output unit and the external scenery to enter the user's field of vision simultaneously; and binocular HMDs, which completely cover both eyes, allowing the user to see only the HMD's display in their field of vision. Furthermore, HMDs that use liquid crystal displays are also called head-mounted liquid crystal displays.

[0009] HMDs display images at the closest distance to the user's eyes, therefore they do not require the wide viewing angles of other LCD devices (such as televisions). Instead, they require high brightness and high contrast ratio (CR) in the frontal direction corresponding to the user's eyes (e.g., within ±30° of the polar angle). However, in conventional LCD devices, brightness and CR in the frontal direction are insufficient.

[0010] Figure 6 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device without a polarizing louver (liquid crystal display device 100R of Comparative Example 1) and a conceptual diagram showing the axial orientation of each optical element. For example... Figure 6 As shown, the liquid crystal display device 100R, from the viewing surface side, sequentially includes a first absorptive polarizer 40, a liquid crystal panel 10, a second absorptive polarizer 24 orthogonally arranged with the first absorptive polarizer 40, a reflective polarizer 23 orthogonally arranged with the second absorptive polarizer 24, and a backlight 30. In this device, oblique light incident obliquely onto the liquid crystal panel 10 is first transmitted from the backlight 30 through the reflective polarizer 23 and the second absorptive polarizer 24, and modulated into elliptically polarized light by the liquid crystal layer or the like in the liquid crystal panel 10. Subsequently, due to scattering in the pair of substrates or liquid crystal layers in the liquid crystal panel 10, the direction of travel changes in the normal direction (the polarization state hardly changes before and after scattering). Moreover, since the elliptically polarized light is transmitted through the first absorptive polarizer 40, leakage light is observed based on the ellipticity. Therefore, the CR in the front direction (also called front CR) is insufficient, and the brightness in the front direction (also called front brightness) cannot be sufficiently obtained.

[0011] Figure 8 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device with a polarizing louver configuration (liquid crystal display device 100R of Comparative Example 2), and a conceptual diagram showing the axial orientation of each optical element. For example... Figure 8 As shown, the liquid crystal display device 100R, from the viewing surface side, sequentially includes a first absorptive polarizer 40, a liquid crystal panel 10, a second absorptive polarizer 24 orthogonally arranged with the first absorptive polarizer 40, a retardation plate 22 having a phase difference in the thickness direction, a reflective polarizer 23 orthogonally arranged with the second absorptive polarizer 24, and a backlight 30. The in-plane hysteresis axis of the retardation plate 22 is orthogonal to the absorption axis of the second absorptive polarizer 24 and the reflection axis of the reflective polarizer 23. In this device, the tilted light transmitted from the backlight 30 through the reflective polarizer 23 rotates its polarization axis through the retardation plate 22 and is absorbed by the second absorptive polarizer 24. Therefore, compared with the liquid crystal display device of Comparative Example 1, the front CR is improved, but on the other hand, the total beam amount is reduced. That is, the light emitted from the backlight 30 cannot be used efficiently as display light. Therefore, the front brightness is not sufficient. In addition, the portion from the second absorptive polarizer 24 to the reflective polarizer 23 is also called a polarizer venetian because it functions as an optical venetian.

[0012] Figure 10This is a cross-sectional schematic diagram showing an example of a liquid crystal display device (liquid crystal display device 100R of Comparative Example 3) with an increased aperture configuration of the polarizing louver compared to the liquid crystal display device of Comparative Example 2, and a conceptual diagram showing the axial orientation of each optical element. In this device, the front CR can be further improved compared to the liquid crystal display device of Comparative Example 2, but the front brightness is still insufficient.

[0013] The liquid crystal display device described in Patent Document 1 boasts excellent productivity and high CR (chromatic refractory) performance, making it useful for various applications. This device is particularly valuable for applications requiring wide viewing angles, such as televisions. However, there is still room for design improvement to further enhance brightness and CR in the front view, making it even more suitable for HMDs (High-Definition Displays).

[0014] The present invention was made in view of the above-mentioned situation, and its object is to provide a liquid crystal display device that can achieve high brightness and high CR in the frontal direction, and is particularly useful as a head-mounted liquid crystal display device.

[0015] Technical solutions for solving technical problems

[0016] (1) A liquid crystal display device according to an embodiment of the present invention has a liquid crystal panel, an optical element and a backlight in sequence from the observation surface side. The optical element includes a first polarizer, a phase difference layer and a second polarizer. The first polarizer, the phase difference layer and the second polarizer are arranged in sequence from the observation surface side. The first polarizer and the second polarizer are reflective polarizers. The reflection axis of the first polarizer and the reflection axis of the second polarizer are parallel to each other. The polarization state of the light incident on the first polarizer is elliptically polarized light in tilt directions with a polar angle of 60° and an azimuth of 0°, azimuth of 45° and azimuth of 90°.

[0017] (2) Furthermore, in a certain embodiment of the liquid crystal display device of the present invention, based on the above-described (1) configuration, the optical element further includes an absorption polarizer, the absorption polarizer being disposed on the observation surface side of the first polarizer, and the absorption axis of the absorption polarizer, the reflection axis of the first polarizer, and the reflection axis of the second polarizer being parallel to each other.

[0018] (3) Furthermore, in a certain embodiment of the present invention, the liquid crystal display device, based on the above-described (2) configuration, has a transmittance of 60° at the polar angle of the structure composed of the absorption polarizer, the first polarizer, the phase difference layer and the second polarizer, which is 60% or less in the three orientations of 0°, 45° and 90°, and a front transmittance of 100%.

[0019] (4) Furthermore, in a certain embodiment of the liquid crystal display device of the present invention, based on the above-described (1), (2) or (3), the angle between the hysteresis axis of the phase difference layer and the reflection axis of the first polarizer is 30° or more and 60° or less.

[0020] (5) Furthermore, in a certain embodiment of the liquid crystal display device of the present invention, based on the above-described (1), (2), (3) or (4), the phase difference layer is configured to include two layers: a first phase difference layer and a second phase difference layer. The first phase difference layer and the second phase difference layer are biaxial phase difference layers including an in-plane phase difference R0 and a thickness direction phase difference Rth. The first phase difference layer is disposed on the first polarizer side. The hysteresis axis of the first phase difference layer is 30° or more and 60° or less relative to the reflection axis of the first polarizer. The hysteresis axis of the second phase difference layer is orthogonal to the hysteresis axis of the first phase difference layer.

[0021] (6) Furthermore, in a certain embodiment of the liquid crystal display device of the present invention, based on the above-described (5) configuration, the first phase difference layer and the second phase difference layer are any of the following (1), (2) or (3) forms.

[0022] (1) The NZ coefficient is 1.4≤NZ<1.6, and the absolute value of the in-plane phase difference R0, |R0|, satisfies the form of the following equations (1-1) and (1-2).

[0023] |R0|≧-325×NZ+710(1-1)

[0024] |R0|≤225 × NZ-50 (1-2)

[0025] (2) The NZ coefficient is 1.6≤NZ<3.0, and the absolute value of the in-plane phase difference R0, |R0|, satisfies the form of the following equations (2-1) and (2-2).

[0026] |R0|≧-57×NZ+281(2-1)

[0027] |R0|≤-114 × NZ+493 (2-2)

[0028] (3) The NZ coefficient is 3.0≤NZ≤4.0, and the absolute value of the plane phase difference R0, |R0|, satisfies the form of the following equations (3-1) and (3-2).

[0029] |R0|≧-10×NZ+140(3-1)

[0030] |R0|≤-40 × NZ+270 (3-2)

[0031] (7) Furthermore, in a certain embodiment of the present invention, the liquid crystal display device, based on the above-described configurations (1), (2), (3), (4), (5) or (6), also has an absorption polarizer on the viewing surface side of the liquid crystal panel.

[0032] (8) Furthermore, in a certain embodiment of the present invention, the liquid crystal display device is a head-mounted liquid crystal display device based on the above-described configurations (1), (2), (3), (4), (5), (6) or (7).

[0033] Beneficial effects

[0034] According to the present invention, high brightness and high CR can be achieved in the frontal direction, for example, providing a liquid crystal display device that is particularly useful as a head-mounted liquid crystal display device. Attached Figure Description

[0035] Figure 1 This is a cross-sectional schematic diagram showing an example of the liquid crystal display device according to the first embodiment.

[0036] Figure 2 This is a cross-sectional schematic diagram showing another example of the liquid crystal display device according to the first embodiment.

[0037] Figure 3 This is a perspective schematic diagram showing an example of the appearance of the liquid crystal display device of the first embodiment when used as an HMD.

[0038] Figure 4 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device according to the second embodiment.

[0039] Figure 5 This is a cross-sectional schematic diagram showing an example of a liquid crystal display device according to the third embodiment.

[0040] Figure 6 This is a cross-sectional schematic diagram showing the configuration of the liquid crystal display device of Comparative Example 1 and a conceptual diagram showing the axial orientation of each optical element.

[0041] Figure 7 The result is the result of calculating the transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Comparative Example 1.

[0042] Figure 8 This is a cross-sectional schematic diagram showing the configuration of the liquid crystal display device of Comparative Example 2 and a conceptual diagram showing the axial orientation of each optical element.

[0043] Figure 9 The result is the result of calculating the transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Comparative Example 2.

[0044] Figure 10This is a cross-sectional schematic diagram showing the configuration of the liquid crystal display device of Comparative Example 3 and a conceptual diagram showing the axial orientation of each optical element.

[0045] Figure 11 The result is the result of calculating the transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Comparative Example 3.

[0046] Figure 12 These are cross-sectional schematic diagrams showing the configuration of the liquid crystal display devices of Examples 1 to 4, and conceptual diagrams showing the axial orientation of each optical element.

[0047] Figure 13 The result is the calculated transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Example 1.

[0048] Figure 14 The graph is based on the transmission angle calculation results of the portion represented by 20X in the liquid crystal display device of Embodiment 1, with the transmission angles of 0° and 45° at polar angles of 60° or 80° as the vertical axis and the in-plane phase difference R0 as the horizontal axis.

[0049] Figure 15 The result is the result of calculating the transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Embodiment 2.

[0050] Figure 16 The graph is based on the transmission angle calculation results of the portion represented by 20X in the liquid crystal display device of Embodiment 2, with the transmission angles of 0° and 45° at polar angles of 60° or 80° as the vertical axis and the in-plane phase difference R0 as the horizontal axis.

[0051] Figure 17 The result is the calculated transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Example 3.

[0052] Figure 18 The graph is based on the transmission angle calculation results of the portion represented by 20X in the liquid crystal display device of Embodiment 3, with the transmission angles of 0° and 45° at polar angles of 60° or 80° as the vertical axis and the in-plane phase difference R0 as the horizontal axis.

[0053] Figure 19 The result is the calculated transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Example 4.

[0054] Figure 20The graph is based on the transmission angle calculation results of the portion represented by 20X in the liquid crystal display device of Embodiment 4, with the transmission angles of 0° and 45° at polar angles of 60° or 80° as the vertical axis and the in-plane phase difference R0 as the horizontal axis.

[0055] Figure 21 This is a cross-sectional schematic diagram showing the structure of the liquid crystal display device in Reference Example 1 and a conceptual diagram showing the axial orientation of each optical element.

[0056] Figure 22 The result is the result of calculating the transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Reference Example 1.

[0057] Figure 23 This is a cross-sectional schematic diagram showing the structure of the liquid crystal display device in Reference Example 2 and a conceptual diagram showing the axial orientation of each optical element.

[0058] Figure 24 The result is the result of calculating the transmittance viewing angle for the portion represented by 20X in the liquid crystal display device of Reference Example 2. Detailed Implementation

[0059] (Definition of the term)

[0060] In this specification, the viewing side refers to the side closer to the screen (display surface) of the liquid crystal display device, and the back side refers to the side farther from the screen (display surface) of the liquid crystal display device.

[0061] A polarizer is a device that extracts linearly polarized light (vibrating only in a specific direction) from unpolarized light (natural light), partially polarized light, or polarized light. This distinguishes it from a circular polarizer (circular polarizing plate). An absorption polarizer absorbs light vibrating in a specific direction and allows linearly polarized light vibrating in a direction perpendicular to it to pass through. A reflection polarizer reflects light vibrating in a specific direction and allows linearly polarized light vibrating in a direction perpendicular to it to pass through.

[0062] A phase difference layer refers to a layer in which either the absolute value of the in-plane phase difference R0, |R0|, or the absolute value of the thickness-direction phase difference (also known as the thickness-direction phase difference), Rth, |Rth|, has a value of 10 nm or more. Preferably, it has a value of 20 nm or more.

[0063] The in-plane phase difference R0 is defined by R0 = (ns - nf)d. The thickness-direction phase difference Rth is defined by Rth = {nz - (nx + ny) / 2}d. The NZ coefficient (a 2-axis parameter) is defined by NZ = (nz - nx) / (ny - nx) = (Rth / R0) + 0.5.

[0064] Here, ns refers to the larger of nx and ny, and nf refers to the smaller one. nx and ny represent the principal refractive index 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. d represents the thickness of the retardation layer. Furthermore, unless otherwise specified, the measurement wavelength for optical parameters such as principal refractive index, phase difference, and NZ coefficient is 550 nm.

[0065] The polar angle θ refers to the angle between the direction of the object (e.g., the measurement direction) and the normal direction of the LCD screen. The azimuth Φ refers to the direction when the object's direction is projected onto the LCD screen, expressed as the angle (azimuth angle) formed between it and a reference azimuth. Here, the reference azimuth... The horizontal rightward direction of the LCD panel screen is set. Angles and azimuths are positive angles rotating counter-clockwise from the reference direction and negative angles rotating clockwise from the reference direction. Both counter-clockwise and clockwise directions indicate the rotation direction when viewing the LCD panel screen from the viewing side (front). Furthermore, angles represent values ​​measured when looking down at the LCD panel; two straight lines (including axes, directions, and edges) being orthogonal means they are orthogonal when viewed from above.

[0066] Unless otherwise specified, the orientation of the axis refers to the orientation of the absorption axis (reflection axis) of the polarizer or the hysteresis axis of the phase retardation layer. The hysteresis axis of the phase retardation layer refers to the in-plane hysteresis axis.

[0067] Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and appropriate design changes can be made within the scope of satisfying the configuration of the present invention.

[0068] (First Implementation)

[0069] Figure 1 This is a cross-sectional schematic diagram illustrating an example of the liquid crystal display device according to this embodiment. Figure 1 As shown, the liquid crystal display device 100 includes, from the viewing surface side, a liquid crystal panel 10, an optical element 20, and a backlight 30. The optical element 20 includes, from the viewing surface side, a first polarizer 21, a retardation layer 22, and a second polarizer 23. Both the first polarizer 21 and the second polarizer 23 are reflective polarizers. Hereinafter, the first polarizer will also be referred to as a "first reflective polarizer," and the second polarizer will also be referred to as a "second reflective polarizer."

[0070] (Optical components)

[0071] The optical element 20, which includes a first reflective polarizer 21, a phase retardation layer 22, and a second reflective polarizer 23, functions as an optical venetian blind and is therefore also called a polarizing venetian blind. The optical element 20 is typically attached to the liquid crystal panel 10 via an adhesive layer (not shown).

[0072] The reflection axis of the first polarizer 21 and the reflection axis of the second polarizer 23 are configured to be parallel to each other. That is, the first polarizer 21 and the second polarizer 23 are in a parallel Nicol configuration. More specifically, the reflection axis of the first polarizer 21 and the reflection axis of the second polarizer 23 form an angle within the range of 0° ± 10°. This angle is preferably within the range of 0° ± 5°.

[0073] In the tilt directions of 60° polar angle and 0°, 45° and 90° azimuth, the polarization state of the light incident on the first polarizer 21 is elliptically polarized. "Light incident on the first polarizer 21" refers to the light that is incident on the first polarizer 21 from the backlight 30 at least through the second polarizer 23 and the phase difference layer 22.

[0074] Furthermore, elliptically polarized light is not limited to right-handed or left-handed polarization. As a polarization state, it is not necessarily completely polarized light; it can also be partially polarized light, including some unpolarized light.

[0075] In the liquid crystal display device of this embodiment, by having an optical element 20 consisting of a phase retardation layer 22 sandwiched between a pair of reflective polarizers 21 and 23 to provide a polarizing veil function, it is possible to reflect the tilted light that is absorbed in conventional polarizing veils (such as the polarizing veil of the liquid crystal display device of Comparative Example 2 described later, which consists of a phase retardation plate 22 with a phase difference in the thickness direction disposed between a second absorptive polarizer 24 and a reflective polarizer 23) to the backlight 30 side. The light reflected to the backlight 30 side is reflected again to the liquid crystal panel 10 side by lenses, light guide plates, reflectors, etc. in the backlight 30. A portion of the reflected light is re-emitted (i.e., reused) in the front direction of the liquid crystal panel 10 during repeated multiple reflections. That is, by actively returning the tilted light to the backlight 30 side and recovering it in the front direction through multiple reflections in the backlight 30, the utilization efficiency of the light from the backlight 30 is improved without impairing the beam amount, thereby efficiently improving the front brightness. In addition to this configuration, as described above, in the tilt directions of 60° polar angle and 0°, 45° and 90° azimuth, the polarization state of the light incident on the first polarizer 21 is elliptically polarized, thereby achieving the high level of front brightness and front CR required by HMD.

[0076] The first reflective polarizer 21 has a transmission axis and a reflection axis orthogonal to the transmission axis. The second reflective polarizer 23 has a transmission axis and a reflection axis orthogonal to the transmission axis. As long as these polarizers are reflective polarizers, there are no particular limitations on the materials or optical properties. Specifically, for example, reflective polarizers obtained by uniaxially stretching a co-extruded film composed of two resins (such as APCF manufactured by Nitto Denko Corporation, DBEF manufactured by 3M Corporation, etc.) and reflective polarizers in which the wires of metal wires are arranged periodically (so-called wire grid polarizers) can be used.

[0077] The polarizers (reflective polarizers and absorptive polarizers) included in the liquid crystal display device of the present invention can also be plate-shaped polarizers (called polarizing plates). That is, each polarizer is preferably a polarizing plate. Specifically, as a polarizing plate, for example, to ensure mechanical strength, resistance to damp heat, etc., a polarizing plate in which a protective film (not shown) such as a triacetyl cellulose (TAC) film is laminated on at least one side of the observation surface side and the back side side of the element having the function of polarizing light can be used. The protective film is attached to the element by any suitable adhesive layer (not shown).

[0078] In this specification, "adhesive layer" refers to an adhesive layer that joins the surfaces of adjacent optical elements, integrating them in a practically effective manner with sufficient adhesive strength and bonding time. Examples of materials forming the adhesive layer include adhesives and tackifying coatings. The adhesive layer can also be a multi-layered structure, such as a tackifying coating layer formed on the surface of the adherends, upon which an adhesive layer is formed. Furthermore, it can be a thin layer invisible to the naked eye.

[0079] The axial orientation of the first reflective polarizer 21 and the second reflective polarizer 23 can be appropriately set, but it is preferably set within the range of 0°±10° or 90°±10°. More preferably, it is set within the range of 0°±5° or 90°±5°, and even more preferably substantially set to 0° or 90°. As a result, a bright display can be obtained in the normal direction and in the up, down, left, and right directions.

[0080] The angle between the hysteresis axis of the retardation layer 22 and the reflection axis of the first reflective polarizer 21 is preferably 30° or more and 60° or less. This further improves the front brightness and front CR (radius contrast). More preferably, it is 45° ± 10°, and even more preferably, it is 45° ± 5°. For example, when the axial orientation of the first reflective polarizer 21 is 90°, the hysteresis axis of the retardation layer 22 is preferably 30–60° or 120–150°. More preferably, it is 45° ± 10° or 135° ± 10°, even more preferably, it is 45° ± 5° or 135° ± 5°, and particularly preferably, it is 45° ± 1° or 135° ± 1°.

[0081] As described above, the retardation layer 22 has a value of 10 nm or more (preferably 20 nm or more) for either the absolute value of the in-plane phase difference R0 |R0| or the absolute value of the thickness direction phase difference Rth |Rth|, but is preferably a biaxial retardation layer including both the in-plane phase difference R0 and the thickness direction phase difference Rth. Specifically, both |R0| and |Rth| are preferably 10 nm or more, and more preferably 20 nm or more.

[0082] As described above, the phase retardation layer 22 is preferably a biaxial phase retardation layer. Preferably, the NZ coefficient, which is an indicator of biaxiality, satisfies 1 ≤ NZ < 10. This facilitates control over the polarization state of light incident on the first reflective polarizer 21. Specifically, in tilt directions with a polar angle of 60° and azimuths of 0°, 45°, and 90°, the polarization state of light incident on the first polarizer 21 is easily made close to linearly polarized light parallel to the absorption axis of the first polarizer 21. More preferably, 1.2 ≤ NZ ≤ 5.0, and even more preferably, 1.4 ≤ NZ ≤ 4.0.

[0083] Here, in the case where the phase difference layer 22 is composed of two or more layers (the case of (B) below), it is preferable that at least one of the phase difference layers 22 satisfies the above range. However, from the viewpoint of making it easier to control the polarization state, it is more preferable that the NZ coefficients of all phase difference layers 22 between the first reflective polarizer 21 and the second reflective polarizer 23 satisfy 1≤NZ<10.

[0084] The absolute value of the in-plane phase difference R0 of the retardation layer 22, |R0|, is preferably 50 nm or more. More preferably, it is 80 nm or more, and even more preferably, it is 100 nm or more. Furthermore, it is preferably 500 nm or less. More preferably, it is 400 nm or less, and even more preferably, it is 350 nm or less. In addition, it is preferable to set the absolute value of the phase difference Rth in the thickness direction of the retardation layer 22, |Rth|, so that the NZ coefficient is within the above-mentioned range.

[0085] Phase difference layer 22 can (A) as Figure 1 As shown, only one is set (i.e., phase difference layer 22 can also be composed of a single layer), and (B) can also be set as shown. Figure 2 Multiple layers can be set up as shown (i.e., the phase difference layer 22 can also be composed of two or more layers).

[0086] In the case described in (B) above, it is preferable that the hysteresis axes of each of the plurality of phase retardation layers 22 (22a, 22b, etc.) form an angle of 30° or more and 60° or less with respect to the reflection axis of the first reflective polarizer 21. A more preferred range of this angle is as described above. Furthermore, the hysteresis axes of adjacent phase retardation layers are preferably orthogonal to each other. That is, it is preferable that the hysteresis axis of phase retardation layer 22a is orthogonal to the hysteresis axis of phase retardation layer 22b. Here, "orthogonal" means forming an angle within the range of 90° ± 10°. More preferably, an angle within the range of 90° ± 5° is formed.

[0087] The retardation layer 22 preferably has reverse wavelength dispersion characteristics. Therefore, when viewing the liquid crystal display device from an inclined direction, color distortion (especially white display) can be suppressed. Specifically, the ratio of the in-plane phase difference R0 at wavelength 450 nm to the in-plane phase difference R0 at wavelength 550 nm, i.e., (R450 / R550), is preferably 0.80 or more and 0.99 or less, more preferably 0.82 or more and 0.90 or less. Furthermore, the ratio of the in-plane phase difference R0 at wavelength 650 nm to the in-plane phase difference R0 at wavelength 550 nm, i.e., (R650 / R550), is preferably 1.01 or more and 1.20 or less, more preferably 1.02 or more and 1.18 or less. In addition, in the case of (B) above, as long as at least one of the retardation layers 22 has reverse wavelength dispersion characteristics, a slight color suppression effect is obtained; however, from the viewpoint of color suppression, it is more preferable that all the retardation layers 22 between the first polarizer 21 and the second polarizer 23 have reverse wavelength dispersion characteristics.

[0088] It is preferable that multiple phase retardation layers 22 (22a, 22b, etc.) are substantially identical (made of substantially the same material and manufactured in substantially the same process to achieve substantially the same properties). The first reason is economic rationality. When the phase retardation layer 22 is plate-shaped (phase retardation plate), it is generally manufactured in long, roll-shaped batches in large quantities. Therefore, minimizing the variety of products and using identical products can suppress manufacturing costs. Second, it has the following technical advantages: by using identical phase retardation layers, considering manufacturing deviations, the probability of the remaining phase difference becoming zero is increased.

[0089] Figure 2This is a cross-sectional schematic diagram showing a configuration example where the phase retardation layer 22 is configured as two layers including a first phase retardation layer 22a and a second phase retardation layer 22b. The first phase retardation layer 22a and the second phase retardation layer 22b are biaxial phase retardation layers containing an in-plane phase difference R0 and a thickness-direction phase difference Rth. The first phase retardation layer 22a is disposed on the side of the first reflective polarizer 21, i.e., the observation surface side. The hysteresis axis of the first phase retardation layer 22a is 30° or more and 60° or less relative to the reflection axis of the first reflective polarizer 21, preferably 45° ± 10°, more preferably 45° ± 5°. Furthermore, the hysteresis axis of the second phase retardation layer 22b is orthogonal to the hysteresis axis of the first phase retardation layer 22a. That is, the angle between the hysteresis axis of the first phase retardation layer 22a and the hysteresis axis of the second phase retardation layer 22b is in the range of 90° ± 10° (preferably 90° ± 5°).

[0090] like Figure 2 As shown, regarding the case where the phase difference layer 22 is configured as a two-layer structure including a first phase difference layer 22a and a second phase difference layer 22b, as described above, it is preferable that the first phase difference layer 22a and the second phase difference layer 22b are substantially the same, and it is particularly preferable that the NZ coefficients of both the first phase difference layer 22a and the second phase difference layer 22b satisfy 1.4≤NZ≤4.0. Specifically, in the case where (1) the NZ coefficients of the first phase difference layer 22a and the second phase difference layer 22b are 1.4≤NZ<1.6, it is preferable that the absolute value of the in-plane phase difference R0, |R0|, satisfies the following equations (1-1) and (1-2). This further improves the brightness and CR in the front direction.

[0091] |R0|≧-325×NZ+710(1-1)

[0092] |R0|≤225 × NZ-50 (1-2)

[0093] Furthermore, (2) when the NZ coefficients of the first phase difference layer 22a and the second phase difference layer 22b are 1.6≤NZ<3.0, it is preferable that the absolute value of the in-plane phase difference R0|R0| satisfies the following equations (2-1) and (2-2). As a result, the brightness and CR in the front direction can be further improved.

[0094] |R0|≧-57×NZ+281(2-1)

[0095] |R0|≤-114 × NZ+493 (2-2)

[0096] Furthermore, (3) when the NZ coefficients of the first phase difference layer 22a and the second phase difference layer 22b are 3.0≤NZ≤4.0, it is preferable that the absolute value of the in-plane phase difference R0, |R0|, satisfies the following equations (3-1) and (3-2). This further improves the brightness and CR in the front direction. |R0|≧10×NZ+140 (3-1)

[0097] |R0|≤-40 × NZ+270 (3-2)

[0098] The material used for the phase retardation layer 22 is not particularly limited. For example, materials formed by stretching a polymer film, materials formed by aligning a liquid crystal material, or thin plates made of inorganic materials can be used. The method for forming the phase retardation layer 22 is also not particularly limited. When formed from a polymer film, solvent casting or melt extrusion can be used, for example. Multiple phase retardation plates can also be formed simultaneously using co-extrusion. Even if the desired phase difference is achieved, stretching can be performed without stretching. The stretching method is also not particularly limited. In addition to roll stretching, roll compression stretching, tenter frame transverse uniaxial stretching, oblique 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 formed 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 such as not performing special alignment treatment on the substrate film or peeling it off from the substrate film after alignment fixation and then transferring it to other films can also be used. Furthermore, a method that does not fix the orientation of the liquid crystal material can also be used. Additionally, the same formation method can be used for cases formed from non-liquid crystal materials and cases formed from liquid crystal materials.

[0099] As the phase retardation layer 22, materials such as those formed 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, triacetyl cellulose, diethyl cellulose, and cyclic olefin polymers.

[0100] (LCD panel)

[0101] The liquid crystal mode of the liquid crystal panel 10 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 in a direction parallel to or neither perpendicular nor parallel to the substrate surface. In addition, as a driving method for the liquid crystal panel, besides TFT method (active matrix method), it can also be simple matrix method (passive matrix method), plasma addressing method, etc.

[0102] Examples of configurations for the liquid crystal panel 10 include: a configuration in which a liquid crystal layer is sandwiched between a pair of substrates on one substrate having pixel electrodes and a common electrode formed thereon, 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 for display; and a configuration in which a liquid crystal layer is sandwiched between a pair of substrates on one substrate having pixel electrodes and a common electrode formed thereon, and a voltage is applied between the pixel electrodes and the common electrode to apply a vertical electric field to the liquid crystal layer for display. More specifically, examples of lateral electric field types include the FFS (Fringe Field Switching) mode and the IPS (In Plane Switching) mode, where the liquid crystal molecules in the liquid crystal layer are aligned parallel to the substrate surface when no voltage is applied. Examples of vertical electric field types include vertical alignment (VA), where the liquid crystal molecules in the liquid crystal layer are aligned perpendicular to the substrate surface when no voltage is applied.

[0103] (Backlight)

[0104] The backlight 30 is not particularly limited in that it can be a direct-lit type, an edge-lit type, or any other type, as long as it is illuminated. Specifically, for example, the backlight 30 preferably includes a light source unit comprising a light guide plate and a light source, a reflector, and a diffuser. As a light source, for example, a light-emitting diode (LED) can be used.

[0105] (Other components)

[0106] In addition to the components described above, the liquid crystal display device 1 of this embodiment also includes external circuits such as TCP (with carrier package) and PCB (printed circuit board); optical films such as viewing angle magnification film and brightness enhancement film; an outer frame; and other components. Depending on the components, they may also be assembled into other components. Components other than those already described are not particularly limited, and components commonly used in the field of liquid crystal display devices can be used; therefore, their description is omitted.

[0107] (HMD)

[0108] Figure 3 This is a perspective view showing an example of the appearance of the liquid crystal display device of this embodiment when used as a head-mounted display (HMD), that is, when used as a head-mounted liquid crystal display device. Figure 3 As shown, the head-mounted display 1000 is a display device that includes a liquid crystal panel 10P for displaying images, optical elements 20, and a backlight (not shown), and can be worn on the head of a user U. Figure 3 The example shown is a binocular HMD, but the liquid crystal display device of the present invention can also be preferably used as a monocular HMD.

[0109] When the liquid crystal display device of this embodiment is used as an HMD, the display method is not particularly limited, and various display modes such as horizontal alignment mode and vertical alignment mode are preferred. For example, as an HMD utilizing the horizontal alignment mode, it is preferable to use a technique that features the opening shape of the electrodes used to form the edge electric field, as described in Japanese Patent Application Publication No. 2009-113584.

[0110] (Second Implementation)

[0111] In this embodiment, features unique to this embodiment will be described, and details repeated in the first embodiment will be omitted. The second embodiment will further describe the arrangement in which the optical element 20 has an absorption polarizer 24 on the observation surface side of the first reflective polarizer 21. Furthermore, the absorption polarizer 24, which can be located on the observation surface side of the liquid crystal panel and will be described later, is also referred to as the "second absorption polarizer".

[0112] Figure 4 This is a cross-sectional schematic diagram illustrating an example of the liquid crystal display device according to this embodiment. More specifically, Figure 2 The diagram shows a cross-sectional view of an example configuration where the optical element 20 of the liquid crystal display device also includes an absorption polarizer 24. (See diagram for reference.) Figure 4 As shown, the liquid crystal display device 100 includes a liquid crystal panel 10, an optical element 20 and a backlight 30 in sequence from the viewing surface side. The optical element 20 includes an absorption polarizer 24, a first reflection polarizer 21, a phase difference layer 22 (first and second phase difference layers 22a and 22b) and a second reflection polarizer 23 in sequence from the viewing surface side.

[0113] The absorption axis of the second absorption polarizer 24, the reflection axis of the first reflection polarizer 21, and the reflection axis of the second reflection polarizer 23 are configured to be parallel to each other. That is, the second absorption polarizer 24, the first reflection polarizer 21, and the second reflection polarizer 23 are in a parallel Nicol configuration. More specifically, the absorption axis of the second absorption polarizer 24 forms an angle with the reflection axis of the first reflection polarizer 21 within the range of 0°±10° (preferably 0°±5°), and the reflection axis of the first reflection polarizer 21 forms an angle with the reflection axis of the second reflection polarizer 23 within the range of 0°±10° (preferably 0°±5°).

[0114] The second absorption polarizer 24, as long as it is an absorption polarizer, does not have any particular limitations on materials or optical properties. Specifically, for example, an absorption polarizer that uses anisotropic materials such as iodine complexes with dichroism adsorbed on a polyvinyl alcohol (PVA) film can be appropriately used.

[0115] Here, the transmittance at a polar angle of 60° of the structure composed of the absorptive polarizer 24, the first reflective polarizer 21, the retardation layer 22, and the second reflective polarizer 23 (i.e., the part composed of the back side part of the liquid crystal panel 10) is preferably 60% or less in the three azimuths of azimuth 0°, azimuth 45°, and azimuth 90°. However, the front transmittance is set to 100%. Thereby, an improvement in front brightness and front CR can be achieved. Among them, from the viewpoint of further improving the front CR, the above transmittance at azimuth 45° is preferably 40% or less, more preferably 30% or less, and further preferably 25% or less.

[0116] The front transmittance refers to the transmittance in the front direction (within a polar angle of ±30°) when the above structure does not have a retardation layer.

[0117] The above transmittance can be obtained by calculating the transmittance viewing angle (also referred to as the transmittance viewing angle characteristic) of the above structure. "LCD Master" manufactured by MACHINE TEC (in Japanese: Syntec Co., Ltd.) is used in the calculation. Since the above structure is located on the back side of the liquid crystal panel, by obtaining the transmittance viewing angle characteristic, the light distribution of the backlight incident on the liquid crystal panel can be grasped.

[0118] (Third Embodiment)

[0119] In the present embodiment, mainly the features unique to the present embodiment will be described, and the description of the content overlapping with the above first embodiment will be omitted. The third embodiment describes the case where the liquid crystal display device further includes an absorptive polarizer 40 on the viewing surface side of the liquid crystal panel 10. In addition, this absorptive polarizer 40 is also referred to as the "first absorptive polarizer".

[0120] Figure 5 It is a cross-sectional schematic diagram showing an example of the liquid crystal display device of the present embodiment. More specifically, Figure 4 The shown liquid crystal display device (second embodiment) is a cross-sectional schematic diagram showing a configuration example when the first absorptive polarizer 40 is further provided on the viewing surface side of the liquid crystal panel 10. As Figure 5 shown, the liquid crystal display device 100 sequentially includes a first absorptive polarizer 40, a liquid crystal panel 10, an optical element 20, and a backlight 30 from the viewing surface side. The optical element 20 sequentially includes an absorptive polarizer 24, a first reflective polarizer 21, a retardation layer 22 (first and second retardation layers 22a, 22b), and a second reflective polarizer 23 from the viewing surface side.

[0121] The axial direction of the absorption axis of the first absorptive polarizer 40 is not particularly limited, but it is preferably configured to be perpendicular to the reflection axes of the first reflective polarizer 21 and the second reflective polarizer. That is, the first absorptive polarizer 40 is preferably orthogonally Nichols-configured with the first and second reflective polarizers 21 and 23. More specifically, the absorption axis of the absorptive polarizer 24 is at an angle of 90° ± 10° (preferably 90° ± 5°) to the reflection axis of the first reflective polarizer 21, and the reflection axis of the first reflective polarizer 21 is at an angle of 0° ± 10° (preferably 0° ± 5°) to the reflection axis of the second reflective polarizer 23.

[0122] The first absorption polarizer 40 is an absorption polarizer, and there are no particular limitations on its materials or optical properties. Specifically, for example, an absorption polarizer that uses anisotropic materials such as iodine complexes with dichroism adsorbed on a polyvinyl alcohol (PVA) film can be appropriately used.

[0123] The present invention is illustrated in more detail below with examples and comparative examples, but the invention is not limited to these examples. Furthermore, Figure 6 , 8 In diagrams 10, 12, 21, and 23, the angles shown on the right side of each layer in the cross-sectional schematic diagrams are as follows: if it is an absorptive polarizer, it represents the azimuth angle of the absorption axis; if it is a reflective polarizer, it represents the azimuth angle of the reflection axis; if it is a phase difference plate, it represents the azimuth angle of the hysteresis axis; if it is a liquid crystal panel, it represents the azimuth angle of the hysteresis axis.

[0124] (Comparative Example 1)

[0125] The liquid crystal display device in Comparative Example 1 is Figure 3 A head-mounted liquid crystal display device as shown. Figure 6 As shown, the configuration includes, in sequence from the viewing surface side: a first absorptive polarizer 40; a liquid crystal panel 10; a second absorptive polarizer 24, which is orthogonally Nichols-configured with the first absorptive polarizer 40; a reflective polarizer 23, which is parallel to the second absorptive polarizer 24 in a Nichols-configured arrangement; and a backlight 30. Figure 6 This is a diagram illustrating the configuration of the liquid crystal display device in Comparative Example 1. The axial orientations of the optical elements between the liquid crystal panel 10 and the backlight 30 are also shown. Figure 6As absorptive polarizers 40 and 24, absorptive polarizers are used to adsorb and orient iodine complexes with dichroism onto the polyvinyl alcohol (PVA) film. As a reflective polarizer 23, a reflective polarizer APF manufactured by 3M is used. As a liquid crystal panel 10, a high-resolution liquid crystal panel (2.5-inch type, 1200ppi) for head-mounted applications is used. As a backlight 30, a cross-BEF (Brightness Enhancement Film) backlight is used, in which two lenses are diagonally crossed.

[0126] To determine the backlight distribution incident on the LCD panel of Comparative Example 1, the transmittance viewing angle of the portion further back than the LCD panel was calculated, specifically the 20X transmittance viewing angle of the portion formed by the second absorptive polarizer 24 and the reflective polarizer 23. The "LCD Master" optical sensor manufactured by MACHINE TEC was used. The results are as follows... Figure 7 As shown ( Figure 7 (a) Figure 7 A graph is also shown that is normalized by dividing the results of the transmittance angle calculated in this example by the results of Comparative Example 1. Figure 7 (b)). Since Comparative Example 1 is the benchmark, Figure 7 (b) shows the transmittance viewpoint as “1.000000” across the entire surface.

[0127] In the actual prototype of the liquid crystal display device (head-mounted liquid crystal display device) of Comparative Example 1, the white brightness and black brightness in the front direction were measured using the "SR-UL1" manufactured by TOPCON Corporation, and the ratio of these values ​​was used as the contrast ratio in the front direction (CR = white brightness / black brightness). The white brightness (referred to as front brightness) and the CR (referred to as front CR) in the front direction are shown in Table 1. All values ​​are actual measurements. As shown in Table 1, the front brightness and front CR in the liquid crystal display device of Comparative Example 1 are insufficient, for the reasons described above.

[0128] (Comparative Example 2)

[0129] The liquid crystal display device of Comparative Example 2 is the same as that of Comparative Example 1, except that a phase difference plate 22 is arranged between the second absorptive polarizer 24 and the reflective polarizer 23 so that its hysteresis axis is at a 90° angle to the absorption axis of the second absorptive polarizer 24. Figure 8 It indicates its composition. Figure 8 This is a diagram illustrating the configuration of the liquid crystal display device in Comparative Example 2. The axial orientations of the optical elements between the liquid crystal panel 10 and the backlight 30 are also shown. Figure 8 As the phase retardation plate 22, a biaxial phase retardation film with NZ coefficient = 1.6, in-plane phase difference R0 = 260 nm, and thickness direction phase difference Rth = 286 nm was used.

[0130] Similar to Comparative Example 1, only the transmittance viewing angle of the portion on the back side of the liquid crystal panel was calculated, that is, the transmittance viewing angle of the portion 20X (polarizing venetian blind) from the second absorptive polarizer 24 to the reflective polarizer 23 was calculated. The results are as follows: Figure 9 As shown ( Figure 9 (a)). Furthermore, in Figure 9 The diagram also shows a standardized graph obtained by dividing the transmittance angle calculated in this comparative example by the result of comparative example 1. Figure 9 (b)). Table 1 shows the relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60°. Furthermore, similar to Comparative Example 1, frontal brightness and frontal CR were measured. The results are shown in Table 1.

[0131] like Figure 9 As shown in Table 1, in Comparative Example 2, compared to Comparative Example 1, the transmittance decreased at tilt angles of 45°, -225°, 130°, and -315°, and at polar angles above 40°. Therefore, it can be seen that the polarizing venetian blind is effective. Furthermore, as shown in Table 1, in Comparative Example 2, compared to Comparative Example 1, the front CR increased, but the front brightness remained unchanged. This is because the tilted light at the tilt angles (45°, -225°, 130°, and -315°) that were contracted by the polarizing venetian blind was absorbed by the second absorptive polarizing plate 24 and was not reused.

[0132] (Comparative Example 3)

[0133] The liquid crystal display device of Comparative Example 3 uses a polarizing venetian blind configuration with a larger aperture for tilted light than that of Comparative Example 2. Specifically, except that the first phase retardation plate 22a and the second phase retardation plate 22b are positioned between the second absorptive polarizing plate 24 and the reflective polarizing plate 23 from the viewing surface side, the rest is the same as the liquid crystal display device of Comparative Example 2. Its configuration is as follows: Figure 10 As shown. Figure 10 This is a diagram illustrating the configuration of the liquid crystal display device in Comparative Example 3. The axial orientations of the optical elements between the liquid crystal panel 10 and the backlight 30 are also shown. Figure 10 The first and second phase retardation plates 22a and 22b are configured such that their hysteresis axes are at an angle of 45° to the absorption axis of the second absorption polarizer 24, and the angle between the hysteresis axis of the first phase retardation plate 22a and the hysteresis axis of the second phase retardation plate 22b is 90°. Two biaxial phase retardation films (first and second phase retardation plates 22a and 22b) used in Comparative Example 1 are used as phase retardation plates.

[0134] Similar to Comparative Example 1, only the transmittance of the portion on the back side of the liquid crystal panel was calculated, that is, the transmittance viewing angle of the portion 20X (polarizing venetian blind) from the second absorptive polarizing plate 24 to the reflective polarizing plate 23 was calculated. The results are as follows: Figure 11 ( Figure 11 As shown in (a)). Furthermore, a standardized graph is also shown, which divides the transmittance angle calculated in this example by the result of Comparative Example 1. Figure 11 ( Figure 11 (b)). Table 1 shows the relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60°. Furthermore, similar to Comparative Example 1, frontal brightness and frontal CR were measured. The results are shown in Table 1.

[0135] like Figure 11 As shown in Table 1, in Comparative Example 3, the omnidirectional transmittance is lower compared to Comparative Example 1. Therefore, it can be concluded that the polarizing venetian blind of Comparative Example 3 ( Figure 10 The aperture of the 20X portion of the polarizing plate venetian blind in Comparative Example 2 is larger. Furthermore, as shown in Table 1, in Comparative Example 3, the front CR is improved compared to Comparative Example 1 and Comparative Example 2, but the front brightness remains unchanged. This is believed to be because, similar to Comparative Example 1, the tilted light at the tilted azimuths (45°, -225°, 130°, and -315°) that is contracted by the polarizing plate venetian blind is absorbed by the second absorption-type polarizing plate 24 and is not reused.

[0136] (Example 1)

[0137] The liquid crystal display device of Example 1 has the same configuration as the liquid crystal display device of Comparative Example 3, except that a reflective polarizer (first reflective polarizer 21) is disposed between the second absorptive polarizer 24 and the first phase retardation plate 22a. Its configuration is as follows: Figure 12 As shown. Figure 12 This diagram illustrates the configuration of the liquid crystal display device according to Embodiment 1 and Embodiments 2 to 4 described below. The axial orientation of each optical element between the liquid crystal panel 10 and the backlight 30 is also shown. Figure 12 The first reflective polarizer 21 uses a reflective polarizer APF manufactured by 3M. The reflective polarizer 23 is also called the second reflective polarizer 23.

[0138] Similar to Comparative Example 1, only the transmittance viewing angle of the portion 20X (polarizing venetian blind) of the back side of the liquid crystal panel, i.e., the portion from the second absorptive polarizer 24 to the second reflective polarizer 23, is calculated. The calculation results are shown when both the first and second phase retardation plates 22a and 22b have an NZ coefficient of 1.6, an in-plane phase difference R0 of 260 nm, and a thickness-direction phase difference Rth of 286 nm. Figure 13 ( Figure 13 (a)). And, Figure 13 The diagram also shows a standardized graph obtained by dividing the transmittance angle calculated in this example by the result of Comparative Example 1. Figure 13 (b) The relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60° is shown in Table 1. Furthermore, frontal brightness and frontal CR were measured in the same manner as in Comparative Example 1. This measurement used an in-plane phase difference R0 = 260 nm. The results are shown in Table 1.

[0139] In the calculations using "LCD Master" in the measurements, the effect of light being reflected multiple times from the liquid crystal panel 10 to the backlight 30 side and then reused in the front direction cannot be taken into account; therefore, the results for the transmittance viewing angle ( Figure 13 The results (and Table 1) are the same as those in Comparative Example 3.

[0140] In order to study the dependence of transmittance on the in-plane phase difference R0, the NZ coefficient of the first and second phase difference plates 22a and 22b was set to 1.6, so that the in-plane phase difference R0 varied between 100nm and 380nm, thereby studying the transmittance. Figure 14 The calculation results are presented in a graph with the transmittance at azimuth angles of 0° and 45° (polar angle 60°) as the vertical axis and the in-plane phase difference R0 as the horizontal axis. Figure 14 (a) and a graph with the transmittance at polar angle 80° and azimuth angle 45° as the vertical axis and the in-plane phase difference R0 as the horizontal axis. Figure 14 (b) Figure 14 In the diagram, the transmittance shown on the vertical axis is a relative value when the transmittance of Comparative Example 1 is set to 100%. The transmittance of Comparative Example 1 corresponds to the transmittance in the front direction (also known as the front transmittance).

[0141] Depend on Figure 14 As shown in (a), the transmittance is minimized when R0 = 260 nm at a polar angle of 60° and an azimuth angle of 0°. Therefore, in the measurements of frontal brightness and frontal CR, a configuration with an in-plane phase difference R0 = 260 nm, where the transmittance is minimized at a polar angle of 60° and an azimuth angle of 0°, was used. Furthermore, according to Figure 14 In (a), R0 is 190 nm (y1) and 310 nm (y2) when the transmittance reaches 60% at an azimuth angle of 0°. According to Figure 14 In (b), the R0 when the transmittance reaches 60% at an azimuth angle of 0° is 148nm(x1) and 323nm(x2). Therefore, if R0 is in the range of 190 to 310nm (from y1 to y2), it can be known that the transmittance is less than 60% at polar angles above 60° and at azimuth angles of 0° and 45°.

[0142] As shown in Table 1, in Example 1, both the front CR and front brightness were improved compared to Comparative Example 1.

[0143] (Example 2)

[0144] The liquid crystal display device of Embodiment 2 is identical to the liquid crystal display device of Embodiment 1, except that the NZ coefficients of the first and second phase difference layers 22a and 22b are changed to 1.4. Figure 12 The middle part indicates its composition.

[0145] Similar to Comparative Example 1, the transmittance viewing angle of only the portion on the back side of the liquid crystal panel, namely the portion 20X (polarizing venetian blind) from the second absorptive polarizer 24 to the second reflective polarizer 23, was calculated. Figure 15 The figure shows the calculation results when the first and second phase difference plates 22a and 22b both have an NZ coefficient of 1.4, an in-plane phase difference R0 of 260 nm, and a thickness direction phase difference Rth of 234 nm. Figure 15 (a)). And, Figure 15 The diagram also shows a standardized graph obtained by dividing the transmittance angle calculated in this example by the result of Comparative Example 1. Figure 15 (b) The relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60° is shown in Table 1. Furthermore, frontal brightness and frontal CR were measured in the same manner as in Comparative Example 1. This measurement used an in-plane phase difference R0 = 260 nm. The results are shown in Table 1.

[0146] In order to study the dependence of transmittance on the in-plane phase difference R0, the NZ coefficient of the first and second phase difference plates 22a and 22b was set to 1.4, so that the in-plane phase difference R0 varied between 100nm and 380nm, thereby studying the transmittance. Figure 16 This is a graph showing the results of the calculation, with the transmittance at azimuth angles of 0° and 45° (polar angle 60°) set as the vertical axis and the in-plane phase difference R0 set as the horizontal axis. Figure 16 (a) and a graph showing the transmittance at polar angle 80° and azimuth angle 45° as the vertical axis and the in-plane phase difference R0 as the horizontal axis. Figure 16 (b) Figure 16 In the figure, the transmittance shown on the vertical axis is a relative value when the transmittance of Comparative Example 1 is set to 100%.

[0147] Depend on Figure 16As shown in (a), the transmittance is minimized when R0 = 260 nm at a polar angle of 60° and an azimuth angle of 0°. Therefore, in the measurements of frontal brightness and frontal CR, a configuration with an in-plane phase difference R0 = 260 nm, where the transmittance is minimized at a polar angle of 60° and an azimuth angle of 0°, was used. Furthermore, according to Figure 16 (a) When the transmittance reaches 60% at an azimuth angle of 0°, R0 is 255nm(y1) and 265nm(y2), according to Figure 16 (b) When the transmittance reaches 60% at an azimuth angle of 0°, R0 is 170nm(x1) and 323nm(x2). Therefore, in the range of R0 = 255 to 265nm (from y1 to y2), it can be known that the transmittance is less than 60% at polar angles above 60° and at azimuth angles of 0° and 45°.

[0148] As shown in Table 1, in Example 2, compared to Comparative Example 1, both the frontal CR and frontal brightness were improved. Furthermore, if we consider... Figure 15 Based on the results of the transmittance angle in Table 1 and the results of Example 1 above, when the NZ coefficient is less than 1.4, the transmittance at azimuth 0°, azimuth 45° and azimuth 90° becomes higher, that is, the aperture becomes weaker. Therefore, it is considered that the brightness improvement effect has reached its limit.

[0149] (Example 3)

[0150] The liquid crystal display device of Embodiment 3 has the same configuration as the liquid crystal display device of Embodiment 1, except that the NZ coefficients of the first and second phase difference layers 22a and 22b are changed to 3.0. Its configuration is as follows: Figure 12 As shown.

[0151] Similar to Comparative Example 1, the transmittance angle of only the portion on the back side of the liquid crystal panel, namely the portion 20X (polarizing venetian blind) from the second absorptive polarizer 24 to the second reflective polarizer 23, was calculated. Figure 17 The calculation results are shown when both the first phase difference plate 22a and the second phase difference plate 22b have an NZ coefficient of 3.0, an in-plane phase difference R0 of 140 nm, and a thickness-direction phase difference Rth of 350 nm. Figure 17 (a)). And, Figure 17 The figure also shows a normalized result obtained by dividing the transmittance angle calculated in this example by the result of Comparative Example 1. Figure 17 (b) The relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60° is shown in Table 1. Furthermore, frontal brightness and frontal CR were measured in the same manner as in Comparative Example 1. This measurement used an in-plane phase difference R0 = 140 nm. The results are shown in Table 1.

[0152] In order to study the dependence of transmittance on the in-plane phase difference R0, the NZ coefficient of the first and second phase difference plates 22a and 22b was set to 3.0, so that the in-plane phase difference R0 varied between 100nm and 380nm, thereby studying the transmittance. Figure 18 In this calculation result, a graph is created with the transmittance at azimuth angles of 0° and 45° (polar angle 60°) as the vertical axis and the in-plane phase difference R0 as the horizontal axis. Figure 18 (a) and a graph with the transmittance at polar angle 80° and azimuth angle 45° as the vertical axis and the in-plane phase difference R0 as the horizontal axis. Figure 18 (b) Figure 18 In the figure, the transmittance shown on the vertical axis is a relative value when the transmittance of Comparative Example 1 is set to 100%.

[0153] Depend on Figure 18 As shown in (a), the transmittance is minimized at a polar angle of 60° and an azimuth angle of 45° when R0 = 140 nm. Therefore, in the measurements of frontal brightness and frontal CR, a configuration with an in-plane phase difference R0 = 140 nm, where the transmittance is minimized at a polar angle of 60° and an azimuth angle of 45°, was used. Furthermore, according to Figure 18 In (a), R0 is 115 nm (y1) when the transmittance reaches 60% at an azimuth angle of 0°. According to Figure 18 In (b), the lower limit of measurement, R0, is 100 nm (x1) and 225 nm (y2) when the transmittance reaches 60% at an azimuth angle of 0°, and 150 nm (x2) when the transmittance reaches 60% at an azimuth angle of 45°. Therefore, within the range of R0 = 115 to 150 nm (from y1 to x2), it can be known that the transmittance is below 60% at polar angles above 60° and at azimuth angles of 0° and 45°.

[0154] As shown in Table 1, in Example 3, both the front CR and front brightness were improved compared to Comparative Example 1.

[0155] (Example 4)

[0156] The liquid crystal display device of Embodiment 4 has the same configuration as the liquid crystal display device of Embodiment 1, except that the NZ coefficients of the first and second phase difference layers 22a and 22b are changed to 4.0. Its configuration is as follows: Figure 12 As shown.

[0157] Similar to Comparative Example 1, the transmittance viewing angle of only the portion on the back side of the liquid crystal panel, namely the portion 20X (polarizing venetian blind) from the second absorptive polarizer 24 to the second reflective polarizer 23, was calculated. Figure 19The calculation results are shown for the first and second phase difference plates 22a and 22b, where the NZ coefficient is 4.0, the in-plane phase difference R0 is 100 nm, and the thickness direction phase difference Rth is 350 nm. Figure 19 (a)). And, Figure 19 The graph also shows a normalized result obtained by dividing the transmittance angle calculated in this example by the result of Comparative Example 1. Figure 19 (b) The relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60° is shown in Table 1. Furthermore, frontal brightness and frontal CR were measured in the same manner as in Comparative Example 1. This measurement used an in-plane phase difference R0 = 100 nm. The results are shown in Table 1.

[0158] In order to study the dependence of transmittance on the in-plane phase difference R0, the NZ coefficient of the first and second phase difference plates 22a and 22b was set to 4.0, so that the in-plane phase difference R0 varied between 100nm and 380nm, thereby studying the transmittance. Figure 20 This is a graph showing the results of the calculation, with the transmittance at azimuth angles of 0° and 45° (polar angle 60°) set as the vertical axis and the in-plane phase difference R0 set as the horizontal axis. Figure 20 (a) and a graph showing the transmittance at polar angle 80° and azimuth angle 45° as the vertical axis and the in-plane phase difference R0 as the horizontal axis. Figure 20 (b) Figure 20 In the figure, the transmittance shown on the vertical axis is a relative value when the transmittance of Comparative Example 1 is set to 100%.

[0159] Depend on Figure 20 As shown in (a), when R0 = 100 nm, the transmittance is minimized at a polar angle of 60° and an azimuth angle of 45°. Therefore, in the measurements of frontal brightness and frontal CR, a configuration with an in-plane phase difference R0 = 140 nm, where the transmittance is minimized at a polar angle of 60° and an azimuth angle of 45°, was used. Furthermore, according to Figure 20 In (a), R0 is the lower limit of measurement when the transmittance is 60% at azimuth angles of 0° (and 45°), i.e., 100nm(y1) and 153nm(y2). Figure 20 (b) indicates that R0, at azimuth angles of 0° (and 45°), is the lower limit of measurement when the transmittance is 60%, namely 100 nm (x1) and 110 nm (x2). Therefore, it can be seen that if R0 is in the range of 100 to 110 nm (y1 (=x1) to x2), then the transmittance at polar angles above 60° and azimuth angles of 0° and 45° is below 60%.

[0160] As shown in Table 1, in Example 4, compared to Comparative Example 1, both the front CR and front brightness were improved. Furthermore, if we consider... Figure 19 Based on the results of the transmittance angle in Table 1 and the results of Example 3 above, when the NZ coefficient becomes greater than 4.0, the transmittance at azimuth 0°, azimuth 45° and azimuth 90° becomes higher, that is, the aperture becomes weaker. Therefore, it is considered that the brightness improvement effect has reached its limit.

[0161] (Refer to Example 1)

[0162] The liquid crystal display device of Reference Example 1 has the same configuration as the liquid crystal display device of Comparative Example 2, except that a reflective polarizer (first reflective polarizer 21) is disposed between the second absorptive polarizer 24 and the phase retardation plate 22, such that its reflection axis is parallel to the absorption axis of the second absorptive polarizer 24. Its configuration is as follows: Figure 21 As shown.

[0163] Figure 21 This is a diagram illustrating the configuration of the liquid crystal display device of Reference Example 1. The axial orientations of the optical elements between the liquid crystal panel 10 and the backlight 30 are also shown. Figure 21 The first reflective polarizer 21 uses a reflective polarizer APF manufactured by 3M. The reflective polarizer 23 is also called the second reflective polarizer 23.

[0164] Similar to Comparative Example 1, only the transmittance viewing angle of the portion on the back side of the liquid crystal panel, namely the portion 20X (polarizing venetian blind) from the second absorptive polarizer 24 to the second reflective polarizer 23, was calculated. The results are as follows... Figure 22 ( Figure 22 As shown in (a)). Furthermore, the standardized graph, obtained by dividing the transmittance angle calculated in this example by the result of Comparative Example 1, is also shown in [the figure]. Figure 22 middle( Figure 22 (b)). Table 1 shows the relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60°. Furthermore, similar to Comparative Example 1, frontal brightness and frontal CR were measured. The results are shown in Table 1.

[0165] In this example, the liquid crystal display device is set as... Figure 21 The configuration shown is such that the tilted light at tilted azimuths (45°, -225°, 130°, and -315°) absorbed by the second absorptive polarizer 24 in Comparative Example 2 is reflected by the newly configured first reflective polarizer 21, with the aim of partially re-emitting in the forward direction during repeated reflections with the backlight 30. However, in the calculations of the "LCD Master" used in the measurement, the effect of light being reused in the forward direction after multiple reflections from the liquid crystal panel 10 to the backlight 30 side cannot be taken into account. Therefore, the result of the transmittance viewing angle ( Figure 22 And Table 1) becomes the same calculation result as Comparative Example 2.

[0166] As shown in Table 1, in Reference Example 1, compared with Comparative Example 1, both the front CR and front brightness were improved. However, compared with Examples 1-4, the improvement effect was small.

[0167] (See Example 2 for reference)

[0168] The liquid crystal display device of Reference Example 2 has the same configuration as the liquid crystal display device of Reference Example 1, except that it uses a biaxial retardation film with an NZ coefficient of 10, an in-plane phase difference R0 of 50 nm, and a thickness-direction phase difference Rth of 475 nm as the retardation layer 22. Its configuration is as follows: Figure 23 As shown. Figure 23 This is a diagram illustrating the configuration of the liquid crystal display device of Reference Example 2. The axial orientations of the optical elements between the liquid crystal panel 10 and the backlight 30 are also shown. Figure 23 middle.

[0169] Similar to Comparative Example 1, only the transmittance viewing angle of the portion on the back side of the liquid crystal panel, namely the portion 20X (polarizing venetian blind) from the second absorptive polarizer 24 to the second reflective polarizer 23, was calculated. The results are as follows... Figure 24 ( Figure 24 As shown in (a)). Furthermore, the standardized graph, obtained by dividing the transmittance angle calculated in this example by the result of Comparative Example 1, is also shown in [the graph]. Figure 24 middle( Figure 24 (b)). Table 1 shows the relative transmittance at azimuth angles of 0°, 45°, and 90° for a polar angle of 60°. Furthermore, similar to Comparative Example 1, frontal brightness and frontal CR were measured. The results are shown in Table 1.

[0170] like Figure 24 As shown in Table 1, in Reference Example 2, compared with Reference Example 1, the oblique light with oblique orientation (45°, -225°, 130° and -315°) was contracted, but there was no aperture at azimuth 0°, 180°, 90° and -270°.

[0171] As shown in Table 1, in Reference Example 2, compared to Comparative Example 1, both the front CR and front brightness were improved. However, compared to Examples 1-4, the improvement was small.

[0172] [Table 1]

[0173]

[0174] The various embodiments of the present invention shown above can also be appropriately combined without departing from the spirit of the present invention.

[0175] Explanation of reference numerals in the attached figures

[0176] 10, 10P: LCD panel

[0177] 20: Optical components

[0178] 20X: Components on the back side of the LCD panel

[0179] 21: First polarizer, (first) reflective polarizer, (first) reflective polarizer plate 22: Phase difference layer, phase difference plate

[0180] 22a: (First) phase difference layer, (First) phase difference plate

[0181] 22b: (Second) phase retardation layer, (second) phase retardation plate; 23: Second polarizer, (second) reflective polarizer, (second) reflective polarizer; 24: (Second) absorption polarizer, (second) absorption polarizer; 21A, 22A, 22aA, 22bA, 23A, 24A: Absorption axis or reflection axis of the polarizer, or hysteresis axis of the phase retardation layer.

[0182] 30: Backlight

[0183] 40: (First) Absorption polarizer, (First) Absorption polarizing plate

[0184] 100, 100R: Liquid crystal display device

[0185] 1000: Head-mounted display

[0186] U: User

Claims

1. A liquid crystal display device, comprising, sequentially from the viewing surface side, a liquid crystal panel, optical elements, and a backlight, characterized in that, The optical element includes a first polarizer, a phase difference layer, and a second polarizer. The first polarizer, the phase retardation layer, and the second polarizer are arranged sequentially from the observation plane side. The first polarizer and the second polarizer are reflective polarizers. The reflection axis of the first polarizer is parallel to the reflection axis of the second polarizer. In the tilt directions of 60° polar angle and 0°, 45° and 90° azimuth, the polarization state of the light from the backlight incident on the first polarizer is elliptically polarized light.

2. The liquid crystal display device according to claim 1, characterized in that, The optical element also includes an absorption polarizer. The absorption polarizer is positioned on the observation plane side of the first polarizer. The absorption axis of the absorption polarizer, the reflection axis of the first polarizer, and the reflection axis of the second polarizer are parallel to each other.

3. The liquid crystal display device according to claim 2, characterized in that, The transmittance of the structure composed of the absorptive polarizer, the first polarizer, the phase difference layer and the second polarizer at a polar angle of 60° is less than 60% in the three orientations of 0°, 45° and 90°, wherein the transmittance on the front is 100%.

4. The liquid crystal display device according to any one of claims 1 to 3, characterized in that, The angle between the hysteresis axis of the phase difference layer and the reflection axis of the first polarizer is greater than 30° and less than 60°.

5. The liquid crystal display device according to any one of claims 1 to 3, characterized in that, The phase difference layer is composed of two layers: a first phase difference layer and a second phase difference layer. The first phase difference layer and the second phase difference layer are biaxial phase difference layers including an in-plane phase difference R0 and a thickness-direction phase difference Rth. The first phase difference layer is disposed on the first polarizer side. The hysteresis axis of the first phase difference layer is between 30° and 60° relative to the reflection axis of the first polarizer. The hysteresis axis of the second phase difference layer is orthogonal to the hysteresis axis of the first phase difference layer.

6. The liquid crystal display device according to claim 5, characterized in that, The first phase difference layer and the second phase difference layer are any of the following forms (1), (2) or (3): (1) The NZ coefficient is 1.4 ≤ NZ < 1.6, and the absolute value of the in-plane phase difference R0, |R0|, satisfies the form of equations (1-1) and (1-2). |R0|≥-325 × NZ+710 (1-1); |R0|≤225 × NZ-50 (1-2); (2) The NZ coefficient is 1.6 ≤ NZ < 3.0, and the absolute value of the in-plane phase difference R0, |R0|, satisfies the form of equations (2-1) and (2-2). |R0|≥-57 × NZ+281 (2-1); |R0|≤-114 × NZ+493 (2-2); (3) The NZ coefficient is 3.0≤NZ≤4.0, and the absolute value of the in-plane phase difference R0, |R0|, satisfies the forms of equations (3-1) and (3-2). |R0|≥-10 × NZ+140 (3-1); |R0|≤-40 × NZ+270 (3-2).

7. The liquid crystal display device according to any one of claims 1 to 3, characterized in that, An absorption polarizer is also provided on the viewing side of the liquid crystal panel.

8. The liquid crystal display device according to any one of claims 1 to 3, characterized in that, The liquid crystal display device is a head-mounted liquid crystal display device.

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