Optical element and display device

Abstract

Provided are an optical element capable of suppressing light leakage in an inclined direction of a vertical orientation and suppressing coloring in the inclined direction, and a display device provided with the optical element. The optical element has a first polarizing plate, a first phase difference layer, a second phase difference layer, and a second polarizing plate in this order from the observation surface side, and the inclination angle of the first anisotropic molecules located on the first polarizing plate side is larger than the inclination angle of the first anisotropic molecules located on the opposite side. The inclination angle of the first anisotropic molecules continuously changes in the thickness direction of the first retardation layer, the inclination angle of the second anisotropic molecules located on the second polarizer side is larger than the inclination angle of the second anisotropic molecules located on the opposite side, and the inclination angle of the second anisotropic molecules continuously changes in the thickness direction of the second retardation layer. The transmission axes of the first and second polarizing plates are parallel, the slow axes of the first and second retardation layers are parallel, and the transmission axis of the first polarizing plate is parallel or orthogonal to the slow axis of the first retardation layer and the slow axis of the second retardation layer.

Description

Technical Field

[0001] The following disclosure relates to an optical element and a display device including the optical element. Background Art

[0002] Conventionally, various display devices such as liquid crystal display devices and organic electroluminescence (EL: Electro-Luminescence) display devices are widely used as devices for displaying images (moving images and still images). In order to improve the visibility of such display devices, optical elements are used.

[0003] For example, Patent Document 1 discloses an optical element which is a transmissive optical element, which comprises, in order from the viewing side, a polarizing plate and at least one obliquely oriented phase difference film, wherein (i) the absorption axis of the polarizing plate and the slow axis of the obliquely oriented phase difference film are at +15 degrees. degrees and -15 degrees degrees, and (ii) the above-mentioned inclined orientation phase difference film has an in-plane phase difference of At the same time, the average tilt angle γ relative to the film surface is 22 degrees Spend. Prior art literature Patent Literature

[0004] Patent Document 1: International Publication No. 2017 / 110216 Summary of the invention Technical Problems to be Solved by the Invention

[0005] Liquid crystal display devices are roughly divided into reflective type and transmissive type according to the method of light transmission to the liquid crystal layer. Transmissive type liquid crystal display devices have a backlight with a light source, and display is performed by transmitting the light emitted from the backlight through the liquid crystal layer. In the above-mentioned backlight, a prism sheet (lens sheet) is provided on the observation side of the light source in order to focus the light from the light source on the front.

[0006] In a backlight provided with a prism sheet, the light component with a large polar angle in the light incident from the light source to the prism sheet will be scattered by the prism (concave-convex structure) of the prism sheet, and will not be focused on the front but will be emitted from the prism sheet at a larger polar angle. This light component that leaks out at a large polar angle without being focused by a lens sheet is called "side lobe light". Side lobe light is originally a light component that is not needed for image display, and it is easy to become stray light in the liquid crystal panel. It becomes the leakage of oblique light (light with a large polar angle) in the black display, which becomes a reason for reducing the contrast when viewed from an oblique direction.

[0007] According to the inventor's research, side lobe light is easily generated in the upper and lower directions due to the configuration of the backlight, so there is room for research to suppress light leakage in the oblique direction of the upper and lower directions. In addition, according to the research of the inventor and others, when viewed from an oblique direction, the displayed image is sometimes colored in an undesirable color, and there is room for further research.

[0008] Patent Document 1 above studies the placement of specific optical elements on the viewing surface side of a display device to suppress a decrease in visibility due to external light reflection, but does not study a decrease in contrast due to sidelobe light or coloring in an oblique direction.

[0009] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide an optical element capable of suppressing light leakage in an oblique direction in the vertical direction and suppressing coloration in an oblique direction, and a display device having the optical element. Technical solutions for solving technical problems

[0010] (1) An optical element according to one embodiment of the present invention comprises, in order from the observation surface side, a first polarizer, a first phase difference layer containing first anisotropic molecules, a second phase difference layer containing second anisotropic molecules, and a second polarizer, when the tilt angle of the first anisotropic molecules of the first phase difference layer located on the first polarizer side is set to θ1-1, the tilt angle of the first anisotropic molecules of the first phase difference layer located on the interface side with the second phase difference layer is set to θ1-2, the tilt angle of the second anisotropic molecules of the second phase difference layer located on the second polarizer side is set to θ2-1, and the tilt angle of the second anisotropic molecules of the second phase difference layer located on the interface side with the first phase difference layer is set to θ2-1. When the tilt angle of the second anisotropic molecule on the interface side is set to θ2-2, the above θ1-1 is larger than the above θ1-2, the above-mentioned first anisotropic molecules are oriented in a manner that the tilt angle continuously changes in the thickness direction of the above-mentioned first phase difference layer, the above-mentioned θ2-1 is larger than the above-mentioned θ2-2, the above-mentioned second anisotropic molecules are oriented in a manner that the tilt angle continuously changes in the thickness direction of the above-mentioned second phase difference layer, the transmission axis of the above-mentioned first polarizer is parallel to the transmission axis of the above-mentioned second polarizer, the slow axis of the above-mentioned first phase difference layer is parallel to the slow axis of the above-mentioned second phase difference layer, and the transmission axis of the above-mentioned first polarizer is parallel to the slow axis of the above-mentioned first phase difference layer and the slow axis of the above-mentioned second phase difference layer.

[0011] (2) In another embodiment of the present invention, the optical element comprises, in order from the observation surface side, a first polarizer, a first phase difference layer comprising first anisotropic molecules, a second phase difference layer comprising second anisotropic molecules, and a second polarizer, when the tilt angle of the first anisotropic molecules of the first phase difference layer located on the first polarizer side is set to θ1-1, the tilt angle of the first anisotropic molecules of the first phase difference layer located on the interface side with the second phase difference layer is set to θ1-2, the tilt angle of the second anisotropic molecules of the second phase difference layer located on the second polarizer side is set to θ2-1, and the tilt angle of the second anisotropic molecules of the second phase difference layer located on the interface side with the first phase difference layer is set to θ2-1. When the tilt angle of the second anisotropic molecule on the interface side is set to θ2-2, the above θ1-1 is larger than the above θ1-2, the above-mentioned first anisotropic molecules are oriented in a manner that the tilt angle continuously changes in the thickness direction of the above-mentioned first phase difference layer, the above-mentioned θ2-1 is larger than the above-mentioned θ2-2, the above-mentioned second anisotropic molecules are oriented in a manner that the tilt angle continuously changes in the thickness direction of the above-mentioned second phase difference layer, the transmission axis of the above-mentioned first polarizer is parallel to the transmission axis of the above-mentioned second polarizer, the slow axis of the above-mentioned first phase difference layer is parallel to the slow axis of the above-mentioned second phase difference layer, and the transmission axis of the above-mentioned first polarizer is orthogonal to the slow axis of the above-mentioned first phase difference layer and the slow axis of the above-mentioned second phase difference layer.

[0012] (3) In one embodiment of the present invention, in addition to the configuration of (1), the angles θ1-1 and θ2-1 are not less than 65° and not more than 90°.

[0013] (4) In one embodiment of the present invention, in addition to the configuration of (2), the angles of θ1-1 and θ2-1 are not less than 70° and not more than 90°.

[0014] (5) In one embodiment of the present invention, in addition to the configuration of (1) or (2), the angles θ1-1 and θ2-1 are not less than 70° and not more than 80°.

[0015] (6) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (5), the difference between θ1-1 and θ2-1 is 3° or less.

[0016] (7) In addition, in a certain embodiment of the present invention, based on the structure of any one of (1) to (6), the first anisotropic molecule and the second anisotropic molecule respectively use the interface between the first phase difference layer and the second phase difference layer as the symmetry plane, and the inclination angle changes along the thickness direction of the first phase difference layer or the thickness direction of the second phase difference layer.

[0017] (8) In addition, in a certain embodiment of the present invention, based on the structure of any one of (1) to (7), the first polarizer is an absorptive polarizer or a stack of an absorptive polarizer and a reflective polarizer, and the second polarizer is a reflective polarizer or a stack of an absorptive polarizer and a reflective polarizer.

[0018] (9) A display device according to another embodiment of the present invention includes a liquid crystal panel, an optical element described in any one of (1) to (8), and a backlight in sequence, wherein the optical element is configured such that the first polarizing plate is located on the liquid crystal panel side.

[0019] (10) In addition, in a certain embodiment of the present invention, based on the structure of (9), the backlight source has a prism sheet arranged on the optical element side of the backlight source, and the surface of the prism sheet on the observation side has a plurality of rows of linear protrusions extending parallel to each other, and the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to or orthogonal to the ridges of the linear protrusions. Beneficial Effects

[0020] According to the present invention, it is possible to provide an optical element capable of suppressing light leakage in an oblique direction in the vertical direction and suppressing coloration in an oblique direction, and a display device including the optical element. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a diagram illustrating polar angle and azimuth angle. Figure 2 It is a schematic cross-sectional view of the optical element involved in Embodiment 1. Figure 3 This is a diagram showing the axial orientation of each component of the optical element involved in Embodiment 1. Figure 4 It is a schematic cross-sectional view when the first polarizing plate and the second polarizing plate are a laminated body in the optical element according to Embodiment 1. Figure 5 It is a schematic cross-sectional view of the optical element involved in embodiment 2. Figure 6 This is a diagram showing the axial orientation of each component of the optical element involved in embodiment 2. Figure 7 It is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 3. Figure 8 It is a perspective view showing an example of a prism sheet included in the backlight. Fig. 9 It is a graph showing the transmittance of Example 1 and Example 2 when the tilt angle is changed. Fig.10It is the simulation result of the chromaticity transmittance field angle of the optical element of Example 1. Fig.11 This is an xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° of the optical element of Example 1. Fig.12 This is the simulation result of the chromatic transmittance viewing angle of the optical element of Example 2. Fig.13 This is an xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° of the optical element of Example 2. Fig.14 It is the simulation result of the transmittance field angle of the optical element of Example 1. Fig.15 This is the simulation result of the transmittance field angle of the optical element of Example 2. Fig.16 It is a schematic cross-sectional view of the optical element of Comparative Example 1. Fig.17 3 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 1. Fig.18 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 1. Fig.19 It is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 1. Fig. 20 It is a schematic cross-sectional view of the optical element of Comparative Example 2. Fig.21 It is a diagram showing the axial orientation of each member of the optical element of Comparative Example 2. Fig. 22 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 2. Fig.23 It is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 2. Fig.24 It is a schematic cross-sectional view of the optical element of Comparative Example 3. Fig.25 3 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 3. Fig.26 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 3. Fig. 27 It is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 3. Fig.28 It is a schematic cross-sectional view of the optical element of Comparative Example 4. Fig.29 3 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 4. Fig.30It is the simulation result of the transmittance field angle of the optical element of Comparative Example 4. Fig.31 It is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 4. Fig.32 It is a schematic cross-sectional view of the optical element of Comparative Example 5. Fig.33 3 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 5. Fig.34 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 5. Fig.35 It is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 5. Fig.36 It is a schematic cross-sectional view of the optical element of Comparative Example 6. Fig.37 3 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 6. Fig.38 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 6. Fig.39 It is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 6. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and design changes can be appropriately made within the scope of the present invention. In addition, in the following description, the same symbols are used in common between different drawings for the parts that are the same or have the same functions, and the repeated descriptions thereof are appropriately omitted. Aspects of the present invention can be appropriately combined within the scope of not departing from the gist of the present invention.

[0023] <Definition of terms> Figure 1 is a diagram illustrating polar angles and azimuth angles. Figure 1 As shown, the polar angle θ refers to the angle between the direction of the object (e.g., the measurement direction F) and the normal direction of the main surface of the optical element. That is, the direction parallel to the normal (z) of the main surface (xy plane) of the optical element is a polar angle of 0°. The direction parallel to the normal is also called the normal direction. In addition, the azimuth refers to the direction when the direction of the object is projected onto the main surface of the optical element, and is expressed by the angle (azimuth) formed with the azimuth that serves as the reference. In this specification, the azimuth that serves as the reference (azimuth 0°) is set to the horizontal right direction of the screen of the optical element.

[0024] In this specification, two axes (directions) are "parallel to each other" means that the angle (absolute value) formed by the two is in the range of 0±3°, preferably in the range of 0±1°, more preferably in the range of 0±0.5°, and particularly preferably 0° (completely parallel). In addition, in this specification, two axes (directions) are "orthogonal to each other" means that the angle (absolute value) formed by the two is in the range of 90±3°, preferably in the range of 90±1°, more preferably in the range of 90±0.5°, and particularly preferably 90° (completely orthogonal). As the above-mentioned axis, the transmission axis, reflection axis and slow axis of the phase difference layer of the polarizer can be cited.

[0025] In this specification, the observation side refers to the side closer to the observer with respect to the object component when the object component and the observer are arranged opposite to each other, and the rear side refers to the side farther from the observer with respect to the object component.

[0026] (Implementation Method 1) The optical element of embodiment 1 comprises, from the observation surface side, a first polarizer, a first phase difference layer containing first anisotropic molecules, a second phase difference layer containing second anisotropic molecules, and a second polarizer, when the tilt angle of the first anisotropic molecules of the first phase difference layer located on the first polarizer side is set to θ1-1, the tilt angle of the first anisotropic molecules of the first phase difference layer located on the interface side with the second phase difference layer is set to θ1-2, the tilt angle of the second anisotropic molecules of the second phase difference layer located on the second polarizer side is set to θ2-1, and the tilt angle of the second anisotropic molecules of the second phase difference layer located on the interface side with the first phase difference layer is set to θ2-1. When the tilt angle of the two anisotropic molecules is set to θ2-2, the above θ1-1 is larger than the above θ1-2, the above-mentioned first anisotropic molecules are oriented in a manner that the tilt angle continuously changes in the thickness direction of the above-mentioned first phase difference layer, the above-mentioned θ2-1 is larger than the above-mentioned θ2-2, the above-mentioned second anisotropic molecules are oriented in a manner that the tilt angle continuously changes in the thickness direction of the above-mentioned second phase difference layer, the transmission axis of the above-mentioned first polarizer is parallel to the transmission axis of the above-mentioned second polarizer, the slow axis of the above-mentioned first phase difference layer is parallel to the slow axis of the above-mentioned second phase difference layer, and the transmission axis of the above-mentioned first polarizer is parallel to the slow axis of the above-mentioned first phase difference layer and the slow axis of the above-mentioned second phase difference layer.

[0027] Figure 2 Schematic diagram of the cross section of the optical element involved in Embodiment 1. Figure 2As shown, the optical element 100A involved in Embodiment 1 has a first polarizer 10, a first phase difference layer 20, a second phase difference layer 30, and a second polarizer 40 in order from the observation surface side. Since the optical element 100A functions as an optical blind, it is also called a polarizer blind. In this specification, an optical element composed of all the components from the first polarizer 10 to the second polarizer 40 is called a polarizer blind.

[0028] (Polarizing Plate) Here, the first polarizer 10 and the second polarizer 40 refer to those having the function of extracting polarized light (linear polarized light) vibrating only in a specific direction from non-polarized light (natural light), partially polarized light or polarized light, and are called linear polarizers. The first polarizer 10 and the second polarizer 40 can be absorption polarizers or reflection polarizers. The absorption polarizer has: an absorption axis that absorbs light vibrating in a specific direction; a transmission axis that transmits polarized light (linear polarized light) vibrating in a direction orthogonal to the specific direction. The reflection polarizer has: a reflection axis that reflects light vibrating in a specific direction; and a transmission axis that transmits polarized light (linear polarized light) vibrating in a direction orthogonal to the specific direction.

[0029] The first polarizer 10 and the second polarizer 40 may both be absorptive polarizers. When a backlight is disposed on the back side of the optical element 100A, side lobe light can be absorbed, further improving the light shielding property in the oblique direction of the upper and lower directions.

[0030] The first polarizer 10 is an absorption polarizer, and the second polarizer 40 may also be a reflection polarizer. By using the second polarizer 40 on the back side as a reflection polarizer, when a backlight is arranged on the back side of the optical element 100A, the side lobe light is reflected to the backlight side, and the reflected light is emitted again to the observation side by using a reflection plate of the backlight, so that the light can be reused and the brightness in the normal direction during white display can be improved.

[0031] The first polarizer 10 and the second polarizer 40 can be a laminate of an absorption polarizer and a reflection polarizer, respectively. Although the reflection polarizer has the effect of increasing the brightness in the normal direction during white display, since its polarization degree is lower than that of the absorption polarizer, if only the reflection polarizer is used, the contrast of the polarizer blind will be reduced. Therefore, by laminating the absorption polarizer and the reflection polarizer, the brightness in the normal direction can be increased and the contrast can be improved.

[0032] Figure 4 : is a schematic cross-sectional view of the optical element according to Embodiment 1 when the first polarizer and the second polarizer are a laminate. Figure 4In the example, the case where the first polarizer and the second polarizer are a laminate of an absorbing polarizer and a reflecting polarizer is illustrated. When the first polarizer 10 is a laminate, it is preferably laminated in the order of the absorbing polarizer 10A and the reflecting polarizer 10B from the observation side. When the second polarizer 40 is a laminate, it is preferably laminated in the order of the absorbing polarizer 40A and the reflecting polarizer 40B from the observation side. When the absorbing polarizer and the reflecting polarizer are laminated, it is preferred that the transmission axis of the absorbing polarizer 10A is parallel to the transmission axis of the reflecting polarizer 10B. In addition, the transmission axis of the absorbing polarizer 40A is preferably parallel to the transmission axis of the reflecting polarizer 40B.

[0033] Either one of the first polarizer 10 and the second polarizer 40 is a single-layer absorption polarizer or a reflection polarizer, and the other is a laminate of an absorption polarizer and a reflection polarizer. The first polarizer 10 and the second polarizer 40 are both more preferably laminated bodies of absorption polarizers and reflection polarizers. It is more preferred that the first polarizer 10 and the second polarizer 40 are both laminated reflective polarizers on the back side of the absorption polarizer. In a display device in which a liquid crystal panel is configured on the front side of an optical element and a backlight source is configured on the back side of an optical element, the brightness and contrast can be further improved. By setting the second polarizer 40 located on the backlight side as a laminate of an absorption polarizer and a reflection polarizer, the outgoing light from the backlight can be more efficiently reflected to the backlight side, thereby improving the light reuse efficiency. By setting the first polarizer 10 configured on the liquid crystal panel side as a laminate of an absorption polarizer and a reflection polarizer, the light incident from the backlight source side can be further reflected to the backlight side, thereby improving the front brightness of the liquid crystal panel.

[0034] Examples of absorption-type polarizers include polarizers having a polarizing layer on a polyvinyl alcohol (PVA) film on which anisotropic materials such as dichroic iodine complexes are adsorbed and oriented. A protective film such as a triacetylcellulose (TAC) film may be provided on at least one of the viewing side and the back side of the polarizing layer.

[0035] Examples of reflective polarizers include reflective polarizers obtained by uniaxially stretching a coextruded film composed of multiple resins (e.g., APCF manufactured by Nitto Denko Corporation, DBEF manufactured by 3M Co., Ltd., etc.), and reflective polarizers in which fine metal wires are periodically arranged (so-called wire grid polarizers).

[0036] (Phase difference layer) The first phase difference layer 20 and the second phase difference layer 40 have the following functions: using birefringent materials to make two orthogonal polarization components have a phase difference, thereby changing the state of the incident polarized light.

[0037] like Figure 2As shown, the first phase difference layer 20 includes first anisotropic molecules 21, and the second phase difference layer 30 includes second anisotropic molecules 31. Figure 2 , the tilt angle of the first anisotropic molecule 21A of the first phase difference layer 20 located on the first polarizer 10 side is set to θ1-1. The tilt angle of the first anisotropic molecule 21B of the first phase difference layer 20 located on the interface side with the second phase difference layer 30 is set to θ1-2. The tilt angle of the second anisotropic molecule 31A of the second phase difference layer 30 located on the second polarizer 40 side is set to θ2-1. The tilt angle of the second anisotropic molecule 31B of the second phase difference layer 30 located on the interface side with the first phase difference layer 20 is set to θ2-2.

[0038] The above θ1-1 is greater than the above θ1-2, and the first anisotropic molecule 21 is oriented in a manner that the tilt angle changes continuously in the thickness direction of the first phase difference layer 20. The first anisotropic molecule 21 increases or decreases in tilt angle as it moves from one side of the thickness direction of the first phase difference layer 20 toward the other side. The above θ2-1 is greater than the above θ2-2, and the second anisotropic molecule 31 is oriented in a manner that the tilt angle changes continuously in the thickness direction of the second phase difference layer 30. The second anisotropic molecule 31 increases or decreases in tilt angle as it moves from one side of the thickness direction of the second phase difference layer 30 toward the other side. The above θ1-1 is different from the above θ1-2, and the above θ2-1 is different from the above θ2-2. That is, it can be said that the first anisotropic molecule 21 and the second anisotropic molecule 31 are mixedly oriented. By adopting such a method, the coloring of the optical element 100A observed from the oblique direction can be set to a hue close to a single color. Specifically, yellowing can be suppressed to form a blue single-color coloring. Taking the first phase difference layer 20 as an example, in the thickness direction of the first phase difference layer 20, the first anisotropic molecules 21 (inclination angle θ 21 ) has an inclination angle θ 21 In the case where θ1-2<θ 21 Within the range of θ1-1, the tilt angle gradually changes along the thickness direction of the first retardation layer 20 .

[0039] Unless otherwise specified, the tilt angle of the first anisotropic molecule 21 refers to the angle at which the long axis of the first anisotropic molecule 21 tilts relative to the parallel plane of the surface on the first retardation layer 20 side of the first polarizer 10. The tilt angle of the second anisotropic molecule 31 refers to the angle at which the long axis of the second anisotropic molecule 31 tilts relative to the parallel plane of the surface on the second retardation layer 30 side of the second polarizer 40, unless otherwise specified. In addition, the tilt angle is defined as being greater than 0° and less than 90°.

[0040] Preferably, the first anisotropic molecules 21 change in the thickness direction of the first phase difference layer 20 so that the tilt angle increases from the interface between the first phase difference layer 20 and the second phase difference layer 30 toward the first polarizer 10, and the second anisotropic molecules 31 change in the thickness direction of the second phase difference layer 30 so that the tilt angle increases from the above interface toward the second polarizer 40. The first phase difference layer 20 and the second phase difference layer 30 together form a louver, so it is preferred that the first phase difference layer 20 and the second phase difference layer 30 are in contact with each other.

[0041] Preferably, the first anisotropic molecules 21 and the second anisotropic molecules 31 are symmetrically arranged at the interface between the first retardation layer 20 and the second retardation layer 30 , and the tilt angles thereof vary along the thickness direction of the first retardation layer 20 or the thickness direction of the second retardation layer 30 .

[0042] It is preferred that the direction of change of the tilt angle of the first anisotropic molecule 21 of the first phase difference layer 20 is the same as the direction of change of the tilt angle of the second anisotropic molecule 31 of the second phase difference layer 30. The direction of change of the tilt angle of the anisotropic molecule refers to the direction in which the long axis of the anisotropic molecule stands up (the tilt angle becomes larger). Specifically, the direction of change of the tilt angle of the anisotropic molecule is: when the main surface of the optical element is set as the xy plane, the plane of the long axis of each of the multiple anisotropic molecules orthogonal to the main surface of the optical element and containing the tilt angle continuously changing is set as the xz plane, along the direction of the x-axis, and from one end side to the other end side of the long axis of each of the multiple anisotropic molecules. Here, the multiple anisotropic molecules are away from the interface of the first phase difference layer 20 and the second phase difference layer 30, the first phase difference layer 20 and the first polarizer 10 of the opposite surface and the second phase difference layer 30 and the second polarizer 40 of the opposite surface (standing object surface), the other end of the long axis stands up from the above-mentioned standing object surface side more. The cross-section in the xz plane ( Figure 2 In the figure, the direction of the arrow indicates the direction of change of the tilt angle of the anisotropic molecule.

[0043] In Embodiment 1, from the viewpoint of further reducing the transmittance in the oblique direction of the vertical position, the above θ1-1 and the above θ2-1 are preferably 65° or more and 90° or less. From the viewpoint of further suppressing oblique coloring, the above θ1-1 and the above θ2-1 are preferably 70° or more and 80° or less.

[0044] The above θ1-2 and the above θ2-2 may be smaller than the above θ1-1 and the above θ2-1, and are, for example, preferably not less than 0° and not more than 10°, and more preferably not less than 1° and not more than 5°.

[0045] The difference between the above θ1-1 and the above θ2-1 is preferably 3° or less, more preferably 1° or less, and more preferably the above θ1-1 is the same as the above θ2-1. The difference between the above θ1-2 and the above θ2-2 is preferably 3° or less, more preferably 1° or less, and more preferably the above θ1-2 is the same as the above θ2-2.

[0046] In addition, it is preferred that the first anisotropic molecules 21 are not twisted in the thickness direction of the first phase difference layer 20, and it is preferred that the second anisotropic molecules 31 are not twisted in the thickness direction of the second phase difference layer 30. That is, in a top view observed from the observation surface side, the orientation direction of the first anisotropic molecules 21A located on the first polarizer 10 side of the first phase difference layer 20 is preferably parallel to the orientation direction of the first anisotropic molecules 21B located on the interface side of the first phase difference layer 20 and the second phase difference layer 30. In addition, it is preferred that the orientation direction of the second anisotropic molecules 31A located on the second polarizer 40 side of the second phase difference layer 30 is parallel to the orientation direction of the second anisotropic molecules 31B located on the interface side of the second phase difference layer 30 and the first phase difference layer 20 in a top view.

[0047] The in-plane phase difference of the first phase difference layer 20 and the second phase difference layer 30 is preferably greater than 180nm and less than 250nm. By adopting this method, it is possible to more effectively suppress the oblique light in the upper and lower directions. The in-plane phase difference of the first phase difference layer 20 and the second phase difference layer 30 is more preferably greater than 190nm and less than 240nm, and further preferably greater than 200nm and less than 230nm. In addition, in this specification, unless otherwise specified, the phase difference is set to 550nm and the measurement temperature is 23°C.

[0048] When the thickness of the phase difference layer is d, the refractive index in the x-axis direction is nx, the refractive index in the y-axis direction is ny, and the refractive index in the z-axis direction is nz, the above-mentioned in-plane phase difference Re is defined by the following formula. Here, the x-axis is set to an azimuth angle of 0°-180°, the y-axis is set to an azimuth angle of 90°-270°, and the z-axis is orthogonal to the x-axis and the y-axis. Re=(nx-ny)×d

[0049] Preferably, the coloring when the optical element 100A is observed from an oblique direction can be set to a single color. By designing the thickness of the liquid crystal layer included in the liquid crystal panel disposed on the front side of the optical element 100A, the viewing angle compensation film, etc., it is easy to correct the color tone of the display device when viewed from an oblique direction. Therefore, the above-mentioned coloring is more preferably a blue single color. Specifically, the values ​​of x and y in the xy chromaticity diagram of the CIE1931 color space are preferably x<0.33 and y<0.33, and more preferably x<0.30 and y<0.30. The above-mentioned values ​​of x and y refer to the average chromaticity values ​​of the values ​​of x and y at azimuth angles of 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° at a polar angle of 60°, respectively.

[0050] Here, as the first anisotropic molecule 21 and the second anisotropic molecule 31, a substance having a positive wavelength dispersion characteristic in which the birefringence (phase difference) decreases as the wavelength becomes longer can be cited. When anisotropic molecules having positive wavelength dispersion characteristics are used, since the transmittance of the optical element 100A in the tilted direction is different for each wavelength, the coloring is perceived as a mixture of multiple colors. As a method for correcting such coloring from the tilted direction, it is also considered to further configure a phase difference layer containing anisotropic molecules having a reverse wavelength dispersion characteristic in which the birefringence increases as the wavelength becomes longer, but anisotropic molecules having an ideal wavelength dispersion characteristic capable of correcting the coloring have not yet been realized. Therefore, in this embodiment, by setting the coloring of the optical element 100A observed from the tilted direction to be monochrome, the coloring of the display device observed from the tilted direction can be corrected by designing the thickness of the liquid crystal layer contained in the liquid crystal panel disposed on the front side of the optical element 100A, the viewing angle compensation film, etc. For example, the coloring when the above-mentioned liquid crystal panel is viewed from the tilted direction is adjusted so that the optical element 100A becomes a coloring opposite to the coloring when viewed from the tilted direction. When the coloring of the optical element 100A in the oblique direction is blue, the color tone of the liquid crystal panel in the oblique direction is designed to be yellow.

[0051] The first anisotropic molecules 21 and the second anisotropic molecules 31 are molecules that make the first phase difference layer 20 and the second phase difference layer 30 show birefringence, respectively. The first anisotropic molecules 21 and the second anisotropic molecules 31 are molecules that show anisotropy of the refractive index of light by orienting the molecules in a specific direction. As the first anisotropic molecules 21 and the second anisotropic molecules 31, liquid crystal materials such as polymerizable liquid crystals and cured products of polymerizable liquid crystals can be cited. The details of the polymerizable liquid crystals will be described later.

[0052] The first phase difference layer 20 and the second phase difference layer 30 may also be, for example, an active mesogen layer (coated phase difference layer) composed of a cured product of a polymerizable liquid crystal (active mesogen). The coated phase difference layer may be formed, for example, by applying a composition containing a polymerizable liquid crystal on an orientation film that has been subjected to an orientation treatment, and curing by methods such as baking and light irradiation. The cured polymerizable liquid crystal is oriented according to the orientation orientation of the orientation film determined by the orientation treatment, showing a phase difference. The tilt angle of the polymerizable liquid crystal located on the side of the above-mentioned orientation film relative to the above-mentioned orientation film (the tilt angle of the long axis of the polymerizable liquid crystal) can be adjusted in units of a few degrees by an orientation treatment such as friction, and can be oriented, for example, in a roughly horizontal manner relative to the above-mentioned orientation film. On the other hand, the polymerizable liquid crystal on the surface (the surface in contact with the air) on the opposite side of the above-mentioned orientation film is oriented roughly vertically relative to the surface in contact with the above-mentioned air due to surface tension. The above-mentioned composition may contain a surfactant, and the tilt angle of the polymerizable liquid crystal relative to the surface in contact with the above-mentioned air can be adjusted by adjusting the concentration of the above-mentioned surfactant, etc. The tilt angle of the polymerizable liquid crystal in the obtained phase difference layer changes continuously along the thickness direction of the phase difference layer, and can be mixed and oriented. By adjusting the type of polymerizable liquid crystal, the type of surfactant, the conditions of firing, the conditions of light irradiation (the wavelength, intensity, and irradiation angle of the irradiated light), etc., the tilt angle of the first anisotropic molecule 21 and the second anisotropic molecule 31 can also be adjusted. The oriented film peeled off from the obtained phase difference layer can be attached to a polarizer or the like by an adhesive or the like.

[0053] The alignment film used as the base for coating the phase difference layer may be a general alignment film in the field of liquid crystal panels made of polyimide, etc. The alignment film may be aligned by rubbing, light irradiation, or the like.

[0054] (Axis configuration of each component) Figure 3 1 is a diagram showing the axial orientation of each component of the optical element involved in Embodiment 1. Figure 3 As shown, the transmission axis of the first polarizer 10 (hereinafter, also referred to as the first transmission axis) is parallel to the transmission axis of the second polarizer 40 (hereinafter, also referred to as the second transmission axis). The slow axis of the first phase difference layer 20 (hereinafter, also referred to as the first slow axis) is parallel to the slow axis of the second phase difference layer 30 (hereinafter, also referred to as the second slow axis). In the top view of the first phase difference layer 20 observed from the observation surface side, the long axis direction of the first anisotropic molecule 21 becomes the first slow axis. In the top view of the second phase difference layer 30 observed from the observation surface side, the long axis direction of the second anisotropic molecule 31 becomes the above-mentioned second slow axis. The above-mentioned first transmission axis is parallel to the above-mentioned first slow axis and the above-mentioned second slow axis. By adopting such a method, the contrast in the normal direction can be improved, and the transmittance in the inclined direction of the upper and lower positions can be reduced, thereby reducing light leakage.

[0055] In Embodiment 1, the first transmission axis is parallel to the first slow axis and the second slow axis. By making the first transmission axis parallel to the first slow axis and the second slow axis, the light shielding effect in the oblique direction of the upper position of Embodiment 2 can be further improved.

[0056] The above-mentioned slow axis can be measured using a phase difference measuring device (for example, "Axoscan" manufactured by Axometrics). Axoscan can measure phase difference, slow axis and tilt angle of anisotropic molecules. Specifically, by measuring and analyzing a matrix (Mueller matrix) composed of 16 4×4 representing the polarization state of light, it is possible to measure characteristics such as phase difference, slow axis and tilt angle of anisotropic molecules.

[0057] (Polymerized Liquid Crystal) As polymerizable liquid crystal, it is preferred to use a liquid crystal polymer with a photoreactive group. As a liquid crystal polymer with a photoreactive group, for example, a mesogenic group such as biphenyl, terphenyl, naphthyl, phenylbenzoate, azophenyl and their derivatives, and a side chain having a structure of a photoreactive group such as a cinnamoyl, chalcone, sub-cinnamyl, β-(2-phenyl) acryloyl, cinnamic acid and their derivatives, which are used as mesogenic components of liquid crystal polymers, can be cited, and the main chain has structures such as acrylate, methacrylate, maleimide, N-phenylmaleimide, siloxane.

[0058] The liquid crystal polymer may be a homopolymer composed of a single repeating unit, or a copolymer composed of two or more repeating units having different side chain structures. The copolymer includes any copolymers such as alternating type, random type, graft type, etc. In addition, in the copolymer, the side chain of at least one repeating unit may be a side chain having the structure of both the mesogen group and the photoreactive group, and the side chains of other repeating units may not have the mesogen group or the photoreactive group.

[0059] Preferred specific examples of the liquid crystalline polymer include copolymerizable (meth)acrylic polymers having a repeating unit represented by the following general formula (I).

[0060] [Chemistry 1]

[0061] In the above formula, R 1 is a hydrogen atom or a methyl group, R 2is an alkyl group or a phenyl group substituted by a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, ring A and ring B are each independently a group represented by the following general formulas (M1) to (M5), p and q are each independently an integer of 1 to 12, r and s are the molar fractions of each monomer in the copolymer, and satisfy the relationship of 0.65≤r≤0.95, 0.05≤s≤0.35, and r+s=1.

[0062] [Chemistry 2]

[0063] In the above formula, X 1 ~X 38 Each is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group.

[0064] The liquid crystalline polymer is preferably a copolymerizable (meth)acrylic polymer having a repeating unit represented by the following general formula (Ia).

[0065] [Chemistry 3]

[0066] In the above formula, R 1 is a hydrogen atom or a methyl group, R 2 is an alkyl group or a phenyl group substituted by a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X 1A ~X 4A They are independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group, ring B is a group represented by the following general formulas (M1a) to (M5a), p and q are independently integers of 1 to 12, r and s are the molar fractions of each monomer in the copolymer, satisfying the relationship of 0.65≤r≤0.95, 0.05≤s≤0.35, and r+s=1.

[0067] [Chemistry 4]

[0068] In the above formula, X 1B ~X 4B and X 31B ~X 38B Each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group.

[0069] Furthermore, the liquid crystalline polymer is preferably a copolymerizable (meth)acrylic polymer having a repeating unit represented by the following general formula (Ib) or (Ic).

[0070] [Chemistry 5]

[0071] In the above formula, R 1is a hydrogen atom or a methyl group, R 2 is an alkyl group or a phenyl group substituted by a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X 1A ~X 4A and X 31B ~X 38B They are independently hydrogen atoms, alkyl groups, alkoxy groups, halogen atoms or cyano groups, p and q are independently integers of 1 to 12, r and s are the molar fractions of the monomers in the copolymer, satisfying the relationship of 0.65≤r≤0.95, 0.05≤s≤0.35, and r+s=1.

[0072] [Chemistry 6]

[0073] In the above formula, R 1 is a hydrogen atom or a methyl group, R 2 is an alkyl group or a phenyl group substituted by a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X 1A ~X 4A and X 1B ~X 4B They are independently hydrogen atoms, alkyl groups, alkoxy groups, halogen atoms or cyano groups, p and q are independently integers of 1 to 12, r and s are the molar fractions of the monomers in the copolymer, satisfying the relationship of 0.65≤r≤0.95, 0.05≤s≤0.35, and r+s=1.

[0074] In the above general formula (I) (including general formula (Ia), general formula (Ib) and general formula (Ic), the same applies hereinafter), R 1 , preferably methyl. 2 , preferably phenyl substituted by an alkyl group or a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, wherein phenyl substituted by an alkyl group or an alkoxy group or a cyano group is more preferred, and phenyl substituted by an alkyl group or an alkoxy group is particularly preferred.

[0075] As X 31B ~X 38B , preferably hydrogen atoms or halogen atoms, and most preferably all hydrogen atoms.

[0076] As for p and q, any integer of 3 to 9 is preferred, and any integer of 5 to 7 is preferred, and 6 is most preferred. As for r, the range of 0.75≤r≤0.85 is preferred, and 0.8 is most preferred. The corresponding preferred range of s is the range naturally determined from r+s=1. That is, the range of 0.15≤s≤0.25 is preferred, and 0.2 is most preferred.

[0077] In the above general formula (Ia), (Ib) or (Ic), X 1A ~X4A , preferably a hydrogen atom or a halogen atom, and particularly preferably X 1A ~X 4A In the case where any one of them is a halogen atom and the others are hydrogen atoms, or all of them are hydrogen atoms. 31B ~X 38B , preferably hydrogen atoms or halogen atoms, and most preferably all hydrogen atoms. 1B ~X 4B , preferably hydrogen atoms or halogen atoms, and most preferably all hydrogen atoms.

[0078] As R 2 Alkyl or R 2 The alkyl group as a substituent of the phenyl group may be an alkyl group having 1 to 12 carbon atoms, among which an alkyl group having 1 to 6 carbon atoms is preferred, an alkyl group having 1 to 4 carbon atoms is more preferred, and a methyl group is most preferred. 2 The alkoxy group as a substituent of the phenyl group may be an alkoxy group having 1 to 12 carbon atoms, preferably an alkoxy group having 1 to 6 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms, and most preferably a methoxy group. 2 The halogen atom as a substituent of the phenyl group includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and among them, a fluorine atom is preferred.

[0079] In x 1 ~x 38 In the above, as the alkyl group, alkyl groups having 1 to 4 carbon atoms are listed, among which methyl group is the most preferred; as the alkoxy group, alkoxy groups having 1 to 4 carbon atoms are listed, among which methoxy group is the most preferred; as the halogen atom, fluorine atom, chlorine atom, bromine atom and iodine atom are listed, among which fluorine atom is preferred.

[0080] In addition, in the present specification, regarding X as a substituent on Ring A or Ring B, 1 ~X 38 ,X 1A ~X 38A In the case where they are substituents on ring A, X 1B ~X 38B represents the case where they are substituents on ring B. Therefore, regarding X 1 ~X 38 The description can be directly applied to X 1A ~X 38A and X 1B ~X 38B .

[0081] The liquid crystal polymer may be dissolved in a solvent to form a phase difference layer composition. In addition to a photopolymerization initiator, a surfactant, and the like, components generally contained in a polymerizable composition that initiates polymerization by light or heat may be appropriately added to the phase difference layer composition.

[0082] Examples of the solvent used in the composition for the phase difference layer include toluene, ethylbenzene, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, dibutyl ether, acetone, methyl ethyl ketone, ethanol, propanol, cyclohexane, cyclopentanone, methylcyclohexane, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, methoxybutyl acetate, N-methylpyrrolidone, and dimethylacetamide.

[0083] As the photopolymerization initiator, a general-purpose photopolymerization initiator generally known for forming a uniform film by irradiation with a small amount of light can be used. Specific examples include: azonitrile-based photopolymerization initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile); α-aminoketone-based photopolymerization initiators such as Irgacure 907 (manufactured by Ciba Specialty Chemicals) and Irgacure 369 (manufactured by Ciba Specialty Chemicals); acetophenone-based photopolymerization initiators such as 4-phenoxydichloroacetophenone and 4-tert-butyl-dichloroacetophenone; benzoin-based photopolymerization initiators such as benzoin and benzoin methyl ether; benzophenone-based photopolymerization initiators such as benzophenone and benzoylbenzoic acid; triazine-based photopolymerization initiators such as 2,4,6-trichloro-S-triazine and 2-phenyl-4,6-bis(trichloromethyl)-S-triazine; carbazole-based photopolymerization initiators; and imidazole-based photopolymerization initiators. The photopolymerization initiators may be used alone or in combination of two or more.

[0084] As a surfactant, any surfactant commonly used to form a uniform film can be used. As specific examples, for example, anionic surfactants such as sodium lauryl sulfate and ammonium lauryl sulfate; nonionic surfactants such as polyethylene glycol monolaurate and sorbitan stearate; biotin surfactants such as stearyl trimethyl ammonium chloride and chlorobehenyl trimethyl ammonium; alkyl betaines such as lauryl betaine and alkyl sulfonate betaine, alkyl imidazoline, sodium lauroyl sarcosinate and other amphoteric surfactants; and BYK-361, BYK-306, BYK-307 (manufactured by BYK Chemical Japan Co., Ltd.); Fluorad FC430 (manufactured by Sumitomo 3M Co., Ltd.); Megaface F171, R08 (manufactured by Dainippon Ink and Chemicals Co., Ltd.) and other surfactants can be mentioned. Any one of these surfactants can be used alone, or two or more can be used simultaneously.

[0085] When a liquid crystal polymer having a photoreactive group is used as a polymerizable liquid crystal, it can be oriented by polarized light irradiation, etc., so it is possible to form a coating phase difference layer without providing an orientation film for a substrate. If a liquid crystal polymer having a photoreactive group is used to form a coating phase difference layer, the orientation film can be omitted, and thinning and simplification of the manufacturing process can be achieved.

[0086] (Implementation Method 2) The optical element of Embodiment 2 has the same configuration as that of Embodiment 1 except that the transmission axis of the first polarizing plate is orthogonal to the slow axes of the first retardation layer and the second retardation layer, and thus repeated descriptions are omitted.

[0087] The optical element of embodiment 2 comprises, in order from the observation surface side, a first polarizer, a first phase difference layer containing first anisotropic molecules, a second phase difference layer containing second anisotropic molecules, and a second polarizer, when the tilt angle of the first anisotropic molecules of the first phase difference layer located on the first polarizer side is set to θ1-1, the tilt angle of the first anisotropic molecules of the first phase difference layer located on the interface side with the second phase difference layer is set to θ1-2, the tilt angle of the second anisotropic molecules of the second phase difference layer located on the second polarizer side is set to θ2-1, and the tilt angle of the second anisotropic molecules of the second phase difference layer located on the interface side with the first phase difference layer is set to θ2-2. When the tilt angle of the second anisotropic molecule is set to θ2-2, the above θ1-1 is larger than the above θ1-2, the above first anisotropic molecule is oriented in a manner that the tilt angle changes continuously in the thickness direction of the above first phase difference layer, the above θ2-1 is larger than the above θ2-2, the above second anisotropic molecule is oriented in a manner that the tilt angle changes continuously in the thickness direction of the above second phase difference layer, the transmission axis of the above first polarizer is parallel to the transmission axis of the above second polarizer, the slow axis of the above first phase difference layer is parallel to the slow axis of the above second phase difference layer, and the transmission axis of the above first polarizer is orthogonal to the slow axis of the above first phase difference layer and the slow axis of the above second phase difference layer. By adopting such a method, the contrast in the normal direction can be improved, and the transmittance in the tilt direction of the upper and lower positions can be reduced, thereby reducing light leakage.

[0088] By making the first transmission axis orthogonal to the first slow axis and the second slow axis, it is possible to expand the light shielding range in the oblique direction at an upper and lower position than that in the first embodiment.

[0089] In Embodiment 2, from the viewpoint of further reducing the transmittance in the oblique direction of the vertical position, the θ1-1 and the θ2-1 are preferably 70° to 90°. From the viewpoint of further suppressing oblique coloring, the θ1-1 and the θ2-1 are preferably 70° to 80°.

[0090] The optical element 100B according to the second embodiment can suppress light leakage in the oblique directions of the upper and lower directions and suppress coloration in the oblique directions.

[0091] (Implementation 3) Figure 7 1 is a cross-sectional schematic diagram of a liquid crystal display device according to Embodiment 3. The display device 1 according to Embodiment 3 sequentially includes a liquid crystal panel 200, an optical element 100A, and a backlight 300, and the optical element 100A is arranged in such a manner that the first polarizing plate 10 is on the liquid crystal panel 200 side. As the optical element, either the optical element 100A according to Embodiment 1 or the optical element 100B according to Embodiment 2 may be used.

[0092] The observation surface side of the liquid crystal panel 200 may include an observation surface side polarizing plate 400. As the observation surface side polarizing plate 400, the above-mentioned absorption type polarizing plate or reflection type polarizing plate can be used, and an absorption type polarizing plate is preferable.

[0093] The transmission axis of the observation side polarizer 400 and the transmission axis of the first polarizer 10 can be arranged orthogonally or in parallel, but from the perspective of obtaining high contrast, it is preferred that the transmission axis of the observation side polarizer 400 and the transmission axis of the first polarizer 10 are arranged orthogonally.

[0094] Usually, the liquid crystal panel is provided with polarizers on the observation side and the back side, respectively. Preferably, the first polarizer 10 also serves as a polarizer disposed on the back side of the above-mentioned liquid crystal panel. That is, preferably, there is no other polarizer between the liquid crystal panel and the first polarizer 10. The first polarizer 10 may also be attached to the back side of the liquid crystal panel 100, for example, by an adhesive layer or the like.

[0095] (LCD Panel) The liquid crystal panel 200 may include a pair of substrates and a liquid crystal layer sandwiched by the pair of substrates. The pair of substrates may be a color filter (CF) substrate including a color filter and a TFT substrate including a plurality of switching elements such as thin film transistors (TFTs).

[0096] The color filter substrate may also include, for example, a color filter and a black matrix separating the color filters. As a TFT substrate, there may be listed a structure including a gate wiring and a source wiring intersecting the gate wiring, a TFT disposed near the intersection of the gate wiring and the source wiring, and a pixel electrode electrically connected to the TFT.

[0097] Examples of the liquid crystal panel include VA (Vertical Alignment) mode, FFS (Fringe Field Switching) mode, IPS (In-Plane-Switching) mode, TN (Twisted Nematic) mode, and the like.

[0098] The above-mentioned VA mode may also be configured with a counter electrode on the CF substrate side, and the liquid crystal molecules in the liquid crystal layer are oriented approximately vertically relative to the substrate surface when no voltage is applied to the liquid crystal layer. The above-mentioned FFS and IPS modes may also be configured with a counter electrode on the TFT substrate side, and the liquid crystal molecules in the liquid crystal layer are oriented approximately horizontally relative to the substrate surface when no voltage is applied. The above-mentioned TN mode may also be configured with a counter electrode on the CF substrate side, and the liquid crystal molecules in the liquid crystal layer are spirally oriented in a manner of twisting from the TFT substrate to the CF substrate by friction treatment or the like. The orientation of the liquid crystal molecules changes according to the electric field generated in the liquid crystal layer by the voltage applied between the pixel electrode and the counter electrode, thereby controlling the amount of light transmitted. Liquid crystal panels in horizontal orientation modes such as FFS and IPS modes are preferably used because of their wide viewing angle in the tilt direction.

[0099] Orientation films may be provided between a pair of substrates and the liquid crystal layer. The orientation film is a layer that has been subjected to an orientation treatment for controlling the orientation of liquid crystal molecules. Examples of the material of the orientation film include polymers having a main chain such as polyimide, polyamic acid, and polysiloxane, and photo-orientation film materials having a photoreactive site (functional group) in the main chain or side chain may be used.

[0100] The dielectric anisotropy (Δε) of the liquid crystal molecules defined by the following formula (L) may have a positive value or a negative value. From the viewpoint of improving contrast, the liquid crystal molecules preferably have a negative Δε value. Δε=(dielectric constant in the long axis direction)-(dielectric constant in the short axis direction)(L)

[0101] (Backlight) The backlight 300 is not particularly limited as long as it is a light source for irradiating light to the liquid crystal panel 100, and may be a direct type, an edge type, or any other type. The backlight 300 may also include a light guide plate and a reflective plate.

[0102] The backlight 300 may include a light source and a prism sheet disposed on the observation surface side of the light source. The backlight 300 preferably includes a prism sheet disposed on the optical element side of the backlight 300. Examples of the light source include a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), and the like.

[0103] Figure 8FIG. 1 is a perspective view showing an example of a prism sheet included in a backlight source. Figure 8 As shown, the prism sheet 301 may include a prism sheet having multiple rows of prisms (linear convex portions) 301a extending parallel to each other on the surface of the observation surface side. The linear continuous portion of the vertices of the linear convex portion 301a is also referred to as the ridgeline 301b of the linear convex portion.

[0104] It is preferred that the edge 301b is arranged parallel to the azimuth angle of 0°. More specifically, the azimuth angle of the edge 301b is preferably 0°±3°. By arranging the edge 301b parallel to the azimuth angle of 0°, the focusing in the prism sheet in the left-right azimuth (azimuth angle of 0°-180°) is suppressed compared to the upper and lower azimuths (azimuth angle of 90°-270°), and the inclined brightness can be increased in the left-right azimuth, and a wide viewing angle can be achieved. At this time, the configuration orientation of the prism 301a is an azimuth angle of 90°. Such a form is particularly suitable for OEM standards that require a wider brightness viewing angle in the left-right azimuth.

[0105] It is preferable that the transmission axis of the first polarizing plate 10 and the transmission axis of the second polarizing plate 40 are parallel to or perpendicular to the ridge line 301b of the linear convex portion. By adopting such a configuration, it is possible to more effectively suppress oblique light in the upper and lower directions.

[0106] Here, the azimuth in which the side lobe light is generated varies, for example, according to the configuration of the ridgeline of the prism sheet provided by the backlight source. According to the research of the inventors, it is found that if a backlight source having a prism sheet 301 with the ridgeline 301b arranged parallel to the azimuth angle 0° (azimuth angle 0°-180°) or parallel to the azimuth angle 90° (azimuth angle 90°-270°) is used, side lobe light is easily generated in an inclined direction in the up-down orientation (azimuth angle 90°-270°). Therefore, by combining the optical element 100A of embodiment 1 or the optical element 100B of embodiment 2 on a backlight source of a prism sheet 301 having an edge 301b arranged parallel to an azimuth angle of 0° (azimuth angle 0°-180°) or parallel to an azimuth angle of 90° (azimuth angle 90°-270°), the azimuth and polar angle of the side lobe light can be made consistent with the azimuth and polar angle at which the transmittance can be reduced by the optical element 100A or 100, thereby effectively suppressing the side lobe light.

[0107] The backlight 300 may include a reflector on the back side of the light source. As the reflector, a reflector generally used in the field of display devices such as a metal vapor-deposited film can be used. [Example]

[0108] Hereinafter, although the present invention will be described in more detail with reference to Examples and Comparative Examples, the present invention is not limited to these Examples.

[0109] (Example 1) Example 1 is a specific example of Implementation Method 1. Figure 2 is a schematic cross-sectional view showing the optical element of Example 1. The optical element of Example 1 is also called a polarizing plate shutter. Figure 2 As shown, the optical element of Example 1 includes, in order from the observation surface side, a first polarizing plate 10, a first retardation layer 20 including first anisotropic molecules 21, a second retardation layer 30 including second anisotropic molecules 31, and a second polarizing plate 40.

[0110] Figure 3 : is a diagram showing the axial orientation of each component of the optical element of Example 1. Figure 3 As shown, in Example 1, the slow axis of the first phase difference layer (first slow axis), the slow axis of the second phase difference layer (second slow axis), the transmission axis of the first polarizer (first transmission axis) and the transmission axis of the second polarizer (second transmission axis) are all arranged in parallel (azimuth angle 0°-180°). As the first polarizer and the second polarizer, a single-layer absorption type linear polarizer is used.

[0111] like Figure 2 As shown, in Example 1, in the first phase difference layer 20 and the second phase difference layer 30, the tilt angles of the first anisotropic molecules 21 and the second anisotropic molecules 31 are continuously changed in a symmetrical manner with respect to the above-mentioned interface. The direction of change of the tilt angle of the first anisotropic molecule 21 is the same as the direction of change of the tilt angle of the second anisotropic molecule 31. The in-plane phase difference of each of the first phase difference layer 20 and the second phase difference layer 30 is 213nm.

[0112] (Example 2) Example 2 is a specific example of Implementation Method 2. Figure 5 1 is a schematic cross-sectional view showing an optical element of Example 2. Figure 6 2 is a diagram showing the axial orientation of each component of the optical element of Example 2. Example 2 has the same structure as Example 1 except that the first transmission axis and the second transmission axis are arranged differently. Figure 6 As shown, in Example 2, the first slow axis is parallel to the second slow axis (azimuth angle 0°-180°), and the first transmission axis is parallel to the second transmission axis (azimuth angle 90°-270°). The first transmission axis is orthogonal to the first slow axis and the second slow axis.

[0113] <Study of Tilt Angle and Transmittance> In the polarizing film shutter of the upper and lower apertures whose transmittance decreases in the upper and lower directions, it is preferred that the light transmittance at an azimuth angle of 90°-270° and a polar angle of 60° is 10% or less. In the following, regarding Examples 1 and 2, θ1-2 and θ2-2 are fixed at 4°, and θ1-1=θ2-1, and the angles of θ1-1 and θ2-1 are changed to 60°, 70°, 80°, and 90°, and the transmittance when observed from an azimuth angle of 90°-270° and a polar angle of 60° is simulated. LCD Master was used for the simulation.

[0114] Fig. 9 Graph showing the transmittance of Example 1 and Example 2 when the tilt angle is changed. Fig. 9 As shown, it is suggested that in Example 1, θ1-1 and θ2-1 are greater than 65°, and in Example 2, θ1-1 and θ2-1 are greater than 70°, and the transmittance is less than 10%, and excellent light-shielding properties can be obtained.

[0115] <Coloring Evaluation at a Polar Angle of 60°> As a way to improve the color tone when viewed from an oblique direction, the case where the color tone at a polar angle of 60° is a blue monochrome was studied. Below, regarding Examples 1 and 2, θ1-2 and θ2-2 were fixed at 4°, and θ1-1 = θ2-1, and the angles of θ1-1 and θ2-1 were changed to 60°, 70°, 80°, and 90°, to simulate the chromaticity values ​​(x, y) of all angles (azimuth angle 0° to 360°) at a polar angle of 60°. The above simulation used LCD Master. Fig.10 It is the simulation result of the chromaticity transmittance field angle of the optical element of Example 1. Fig.11 It is the xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° of the optical element of Example 1. Fig.12 This is the simulation result of the chromatic transmittance viewing angle of the optical element of Example 2. Fig.13 This is an xy chromaticity diagram of the CIE1931 color space at a polar angle of 60° for the optical element of Example 2. In the conversion diagram of chromaticity transmittance versus viewing angle, a darker colored portion indicates that coloration is observed.

[0116] Table 1 below shows Fig.10 The contour plot of chromatic transmittance versus viewing angle and Fig.11 The following table summarizes the values ​​of x and y in the xy chromaticity diagram. Fig.12 The contour plot of chromatic transmittance versus viewing angle and Fig.13The x and y values ​​in the xy chromaticity diagram are summarized in a table. The x and y values ​​are respectively the average chromaticity values ​​of the x and y values ​​at the azimuth angles of 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° at a polar angle of 60°. When the color tone at a polar angle of 60° is made a blue monochrome, the average chromaticity values ​​of x and y in the CIE 1931 color space at a polar angle of 60° are preferably x<0.33 and y<0.33, and more preferably x<0.30 and y<0.30.

[0117] [Table 1]

[0118] [Table 2]

[0119] According to the results of Tables 1 and 2, in Examples 1 and 2, θ1-1 and θ2-1 are 60° or more and 90° or less, and the average chromaticity values ​​are x<0.33 and y<0.33. In addition, when θ1-1 and θ2-1 are 70° or more and 80° or less, and the average chromaticity values ​​are x<0.30 and y<0.30, the yellow sense can be further suppressed, and coloring close to a blue monochromatic color can be formed.

[0120] When the general Fig. 9 The transmittance shown agrees with the results of Tables 1 and 2, and it can be seen that when θ1-1 and θ2-1 are 80°, light shielding properties are obtained in the vertical direction, and a color tone close to a blue monochromatic color can be formed.

[0121] <Transmittance in oblique directions> Regarding Examples 1 and 2, let θ1-1 = 70°, θ2-1 = 70°, θ1-2 = 4°, θ2-2 = 4°. Figure 2 As shown, in the first phase difference layer 20, the tilt angle of the first anisotropic molecules is mixedly oriented in such a manner that the tilt angle continuously increases from the interface between the first phase difference layer 20 and the second phase difference layer 30 toward the first polarizer 10 side. In the second phase difference layer 30, the tilt angle of the second anisotropic molecules is mixedly oriented in such a manner that the tilt angle continuously increases from the above interface toward the second polarizer 40 side.

[0122] The transmittance viewing angles of the optical elements of Examples 1 and 2 were simulated using LCD Master and shown in contour plots. Fig.14 It is the simulation result of the transmittance field angle of the optical element of Example 1. Fig.15 The following is a simulation result of the transmittance viewing angle of the optical element of Example 2. The circular dotted lines in the contour map represent polar angles of 20°, 40°, 60°, and 80° from the inside. The shades of the contour map of the transmittance viewing angle correspond to the transmittance shown on the right side of each figure. Fig.14 and Fig.15 As shown in FIG. 1 , it can be confirmed that the optical elements of Examples 1 and 2 can reduce the transmitted light in the oblique direction in the vertical and horizontal directions (azimuth angle 90°-270°), and can also shield light symmetrically with respect to the azimuth angle 90°-270°. ) is called "oblique light".

[0123] (Comparative Example 1) Fig.16 It is a schematic cross-sectional view of the optical element of Comparative Example 1. Fig.17 Schematic diagram of the cross section of the optical element of Comparative Example 1. Fig.17 As shown, the axis arrangement of each component is the same as that of Example 1. The optical element 1100A of Comparative Example 1 is set to θ1-1=70°, θ2-1=4°, θ1-2=4°, and θ2-2=70°. The in-plane retardation of each of the first retardation layer 20 and the second retardation layer 30 is 213 nm.

[0124] like Fig.16 As shown, in the first phase difference layer 20, the tilt angle of the first anisotropic molecule is mixedly oriented in such a manner that the tilt angle continuously increases from the interface between the first phase difference layer 20 and the second phase difference layer 30 toward the first polarizer 10 side. In the second phase difference layer 30, the tilt angle of the second anisotropic molecule is mixedly oriented in such a manner that the tilt angle continuously decreases from the above interface toward the second polarizing element 40 side. The change in the tilt angle of the first anisotropic molecule 21 and the second anisotropic molecule 31 is asymmetric with respect to the interface between the first phase difference layer 20 and the second phase difference layer 30. In addition, the change direction of the tilt angle of the first anisotropic molecule 21 and the change direction of the tilt angle of the second anisotropic molecule 31 are opposite to each other.

[0125] In the same manner as in Example 1, the transmittance, viewing angle, and coloring of the optical element of Comparative Example 1 were simulated. Fig.18 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 1. Fig.19 The following table 3 summarizes the simulation results of the chromaticity transmittance viewing angle of the optical element of Comparative Example 1. Fig.19 The table shows the values ​​of x and y in the xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° for the optical element of Comparative Example 1. Fig.18 As shown in FIG. 1 , comparative example 1 can reduce oblique light at an azimuth angle of 90°-270°, but the area that can block light is left-right asymmetric relative to the azimuth angle of 90°-270°. Fig.19 As shown in Table 3, at an inclined angle (polar angle 60°), a mixed coloration of blue and yellow was observed.

[0126] [Table 3]

[0127] (Comparative Example 2) Fig. 20 It is a schematic cross-sectional view of the optical element of Comparative Example 2. Fig.21 Schematic diagram of the cross section of the optical element of Comparative Example 2. Fig.21 As shown, the axis arrangement of each component is the same as that of Example 1. The optical element 1100B of Comparative Example 2 is set to θ1-1=4°, θ2-1=70°, θ1-2=70°, and θ2-2=4°. The in-plane retardation of each of the first retardation layer 20 and the second retardation layer 30 is 213 nm.

[0128] like Fig. 20 As shown, in the first phase difference layer 20, the tilt angle of the first anisotropic molecule is mixedly oriented in such a manner that the tilt angle continuously decreases from the interface between the first phase difference layer 20 and the second phase difference layer 30 toward the first polarizer 10 side. In the second phase difference layer 30, the tilt angle of the second anisotropic molecule is mixedly oriented in such a manner that the tilt angle continuously increases from the above interface toward the second polarizer 40 side. The change in the tilt angle of the first anisotropic molecule 21 and the second anisotropic molecule 31 is asymmetric with respect to the interface between the first phase difference layer 20 and the second phase difference layer 30. In addition, the change direction of the tilt angle of the first anisotropic molecule 21 and the change direction of the tilt angle of the second anisotropic molecule 31 are opposite.

[0129] In the same manner as in Example 1, the transmittance, viewing angle, and coloring of the optical element of Comparative Example 2 were simulated. Fig. 22 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 2. Fig.23 The following table 4 summarizes the simulation results of the chromaticity transmittance viewing angle of the optical element of Comparative Example 2. Fig.23 The table of x and y values ​​of the xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° for the optical element of Comparative Example 2 shown in FIG. Fig. 22 As shown in FIG. 1 , Comparative Example 2 can reduce oblique light at an azimuth angle of 90°-270°, but the area that can block light is left-right asymmetric relative to the azimuth angle of 90°-270°. Fig.23 As shown in Table 4, at an inclined angle (polar angle 60°), a mixed coloration of blue and yellow was observed.

[0130] [Table 4]

[0131] (Comparative Example 3) Fig.24 It is a schematic cross-sectional view of the optical element of Comparative Example 3. Fig.25 Schematic diagram of the cross section of the optical element of Comparative Example 3. Fig.25As shown, the axis arrangement of each component is the same as that of Example 2. The optical element 1100C of Comparative Example 3 is set to θ1-1 = 4°, θ2-1 = 70°, θ1-2 = 70°, and θ2-2 = 4°. Fig.24 As shown, similarly to Comparative Example 2, the first anisotropic molecules of the first retardation layer 20 and the second anisotropic molecules of the second retardation layer 30 were mixed and aligned.

[0132] In the same manner as in Example 1, the transmittance, viewing angle, and coloring of the optical element of Comparative Example 3 were simulated. Fig.26 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 3. Fig. 27 The following table 5 summarizes the simulation results of the chromaticity transmittance viewing angle of the optical element of comparative example 3. Fig. 27 The table of x and y values ​​of the xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° for the optical element of Comparative Example 3 shown in FIG. Fig.26 As shown, Comparative Example 3 can reduce the oblique light at an azimuth angle of 90°-270°, and although the area that can be shielded is improved compared with Comparative Example 1, it is left-right asymmetric with respect to the azimuth angle of 90°-270°. Fig. 27 As shown in Table 5, at an inclined angle (polar angle 60°), a mixed coloration of blue and yellow was observed.

[0133] [Table 5]

[0134] (Comparative Example 4) Fig.28 It is a schematic cross-sectional view of the optical element of Comparative Example 4. Fig.29 Schematic diagram of the cross section of the optical element of Comparative Example 4. Fig.29 As shown, the axis arrangement of each component is the same as that of Example 2. The optical element 1100D of Comparative Example 4 is set to θ1-1 = 4°, θ2-1 = 70°, θ1-2 = 70°, and θ2-2 = 4°. Fig.28 As shown, similarly to Comparative Example 2, the first anisotropic molecules of the first retardation layer 20 and the second anisotropic molecules of the second retardation layer 30 were mixed and aligned.

[0135] In the same manner as in Example 1, the transmittance, viewing angle, and coloring of the optical element of Comparative Example 4 were simulated. Fig.30 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 4. Fig.31 The simulation results of the chromaticity transmittance viewing angle of the optical element of Comparative Example 4 are summarized in Table 6 below. Fig.31 The table of x and y values ​​of the xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° for the optical element of Comparative Example 4 shown in FIG. Fig.30As shown, Comparative Example 4 can reduce the oblique light at an azimuth angle of 90°-270°, and although the area that can be shielded is improved compared with Comparative Example 1, it is left-right asymmetric with respect to the azimuth angle of 90°-270°. Fig.31 As shown in Table 6, at an inclined angle (polar angle 60°), a mixed coloration of blue and yellow was observed.

[0136] [Table 6]

[0137] (Comparative Example 5) Fig.32 It is a schematic cross-sectional view of the optical element of Comparative Example 5. Fig.33 Schematic diagram of the cross section of the optical element of Comparative Example 5. Fig.33 As shown, the axis arrangement of each component is the same as that of Example 2. The optical element 1100E of Comparative Example 5 is set to θ1-1=4°, θ2-1=4°, θ1-2=70°, and θ2-2=70°. The in-plane retardation of each of the first retardation layer 20 and the second retardation layer 30 is 213 nm.

[0138] like Fig.32 As shown, in the first phase difference layer 20, the tilt angle of the first anisotropic molecule is mixedly oriented in such a manner that the tilt angle continuously decreases from the interface between the first phase difference layer 20 and the second phase difference layer 30 toward the first polarizer 10 side. In the second phase difference layer 30, the tilt angle of the second anisotropic molecule is mixedly oriented in such a manner that the tilt angle continuously decreases from the above interface toward the second polarizing element 40 side. The change in the tilt angle of the first anisotropic molecule 21 and the second anisotropic molecule 31 is asymmetric with respect to the interface between the first phase difference layer 20 and the second phase difference layer 30, and the change direction of the tilt angle of the first anisotropic molecule 21 is the same as the change direction of the tilt angle of the second anisotropic molecule 31.

[0139] In the same manner as in Example 1, the transmittance viewing angle of the optical element of Comparative Example 5 was simulated. Fig.34 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 5. Fig.35 is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 5. Fig.34 and Fig.35 As shown, although the oblique light in the left and right azimuths (azimuth angle 0°-180°) is reduced in Comparative Example 5, the oblique light in the azimuth angle 90°-270° cannot be reduced.

[0140] (Comparative Example 6) Fig.36 It is a schematic cross-sectional view of the optical element of Comparative Example 6. Fig.37 Schematic diagram of the cross section of the optical element of Comparative Example 6. Fig.37As shown, the axis arrangement of each component is the same as that of Example 1. The optical element 1100F of Comparative Example 6 is set to θ1-1 = 4°, θ2-1 = 4°, θ1-2 = 70°, and θ2-2 = 70°. Fig.36 As shown, similarly to Comparative Example 5, the first anisotropic molecules of the first retardation layer 20 and the second anisotropic molecules of the second retardation layer 30 were mixed and aligned.

[0141] In the same manner as in Example 1, the transmittance viewing angle of the optical element of Comparative Example 6 was simulated. Fig.39 It is the simulation result of the transmittance field angle of the optical element of Comparative Example 6. Fig.39 is the simulation result of the chromaticity transmittance viewing angle of the optical element of Comparative Example 6. Fig.38 and Fig.39 As shown, the shading range of Comparative Example 6 is narrower than that of Example 1, and cannot fully reduce the transmitted light in the oblique direction (for example, polar angle 60°) in the upper and lower directions (azimuth angle 90°-270°). Description of Reference Numerals

[0142] 1: Display device 10: First polarizer 20: First phase difference layer 21: The first anisotropic molecule 30: Second phase difference layer 31: The second anisotropic molecule 40: Second polarizer 100A, 100B, 1100A, 1100B, 1100C, 1100D, 1100E, 1100F: Optical components 200: LCD panel 300: Backlight 301: Prism 301a: Prism 301b: Ridge 400: Observation side polarizer

Claims

1. An optical element, characterized in that: The first polarizing plate, the first phase difference layer containing the first anisotropic molecules, the second phase difference layer containing the second anisotropic molecules, and the second polarizing plate are provided in this order from the observation side. When the tilt angle of the first anisotropic molecules of the first phase difference layer located on the first polarizer side is set to θ1-1, the tilt angle of the first anisotropic molecules of the first phase difference layer located on the interface side with the second phase difference layer is set to θ1-2, the tilt angle of the second anisotropic molecules of the second phase difference layer located on the second polarizer side is set to θ2-1, and the tilt angle of the second anisotropic molecules of the second phase difference layer located on the interface side with the first phase difference layer is set to θ2-2, The θ1-1 is larger than the θ1-2, and the first anisotropic molecules are oriented in a manner such that the tilt angle continuously changes in the thickness direction of the first phase difference layer. The θ2-1 is greater than the θ2-2, and the second anisotropic molecules are oriented in a manner such that the tilt angle continuously changes in the thickness direction of the second phase difference layer. The transmission axis of the first polarizer is parallel to the transmission axis of the second polarizer, The slow axis of the first phase difference layer is parallel to the slow axis of the second phase difference layer. The transmission axis of the first polarizer is parallel to the slow axis of the first phase difference layer and the slow axis of the second phase difference layer.

2. An optical element, characterized in that: The first polarizing plate, the first phase difference layer containing the first anisotropic molecules, the second phase difference layer containing the second anisotropic molecules, and the second polarizing plate are provided in this order from the observation side. When the tilt angle of the first anisotropic molecules of the first phase difference layer located on the first polarizer side is set to θ1-1, the tilt angle of the first anisotropic molecules of the first phase difference layer located on the interface side with the second phase difference layer is set to θ1-2, the tilt angle of the second anisotropic molecules of the second phase difference layer located on the second polarizer side is set to θ2-1, and the tilt angle of the second anisotropic molecules of the second phase difference layer located on the interface side with the first phase difference layer is set to θ2-2, The θ1-1 is larger than the θ1-2, and the first anisotropic molecules are oriented in a manner such that the tilt angle continuously changes in the thickness direction of the first phase difference layer. The θ2-1 is greater than the θ2-2, and the second anisotropic molecules are oriented in a manner such that the tilt angle continuously changes in the thickness direction of the second phase difference layer. The transmission axis of the first polarizer is parallel to the transmission axis of the second polarizer, The slow axis of the first phase difference layer is parallel to the slow axis of the second phase difference layer. The transmission axis of the first polarizing plate is orthogonal to the slow axis of the first retardation layer and the slow axis of the second retardation layer.

3. The optical element according to claim 1, characterized in that The angles θ1-1 and θ2-1 are greater than or equal to 65° and less than or equal to 90°.

4. The optical element according to claim 2, characterized in that The angles θ1-1 and θ2-1 are not less than 70° and not more than 90°.

5. The optical element according to claim 1 or 2, characterized in that: The θ1-1 and the θ2-1 are greater than or equal to 70° and less than or equal to 80°.

6. The optical element according to claim 1 or 2, characterized in that: The difference between the θ1-1 and the θ2-1 is 3° or less.

7. The optical element according to claim 1 or 2, characterized in that: The first anisotropic molecules and the second anisotropic molecules respectively use the interface between the first phase difference layer and the second phase difference layer as a symmetry plane, and the tilt angles thereof vary along the thickness direction of the first phase difference layer or the thickness direction of the second phase difference layer.

8. The optical element according to claim 1 or 2, characterized in that: The first polarizer is an absorbing polarizer or a laminate of an absorbing polarizer and a reflecting polarizer. The second polarizer is a reflective polarizer or a laminate of an absorptive polarizer and a reflective polarizer.

9. A display device, characterized in that: A device having a liquid crystal panel, an optical element according to any one of claims 1 to 8, and a backlight in this order, The optical element is configured such that the first polarizing plate is located on the liquid crystal panel side.

10. The display device according to claim 9, characterized in that: The backlight includes a prism sheet disposed on the optical element side of the backlight. The prism sheet has a plurality of rows of linear convex portions extending parallel to each other on the surface of the observation surface side. The transmission axis of the first polarizing plate and the transmission axis of the second polarizing plate are parallel to or perpendicular to the ridgeline of the linear convex portion.

Images