Optical element and display unit

Abstract

To provide an optical element that can prevent leakage of light in an oblique direction in the vertical orientation and prevent coloring in the oblique direction, and a display unit including the optical element.SOLUTION: An optical element has a first polarizer, a first phase difference layer, a second phase difference layer, and a second polarizer in this order from an observation surface side. A tilt angle of first anisotropic molecules on a side of the first polarizer is larger than a tilt angle of first anisotropic molecules on a side of an interface between the first phase difference layer and the second phase difference layer, and the tilt angle of the first anisotropic molecules continuously changes in a thickness direction. A tilt angle of second anisotropic molecules on a side of the second polarizer is larger than a tilt angle of second anisotropic molecules on a side of an interface between the second phase difference layer and the first phase difference layer, and the tilt angle of the second anisotropic molecules continuously changes in the thickness direction. The transmission axes of the first and second polarizers are parallel to each other. The slow axes of the first and second phase difference layers are parallel to each other. The transmission axis of the first polarizer is orthogonal to the slow axes of the first and second phase difference layers.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, various display devices such as liquid crystal display devices and organic electroluminescence (EL: Electro-Luminescence) display devices have been 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 sometimes used.

[0003] For example, Patent Document 1 discloses a transmissive optical element comprising, from the viewing side, a polarizing plate and at least one inclined-oriented retardation film, in that order, (i) the absorption axis of the polarizing plate and the slow axis of the inclined-oriented retardation film are in the ranges of +15 degrees to +55 degrees and -15 degrees to -55 degrees, respectively, and (ii) the inclined-oriented retardation film has an in-plane retardation of 110 nm to 240 nm and an average tilt angle γ relative to the film plane of 22 degrees to 55 degrees. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 110216 Summary of the Invention [Problem to be solved by the invention]

[0005] Liquid crystal display devices are broadly classified into reflective and transmissive types depending on the method of transmitting light to the liquid crystal layer. Transmissive liquid crystal display devices are equipped with a backlight having a light source, and display is performed by transmitting light emitted from the backlight through the liquid crystal layer. The backlight may be provided with a prism sheet (lens sheet) on the observation side of the light source in order to focus the light from the light source to the front.

[0006] In a backlight equipped with a prism sheet, light components with large polar angles from the light source incident on the prism sheet are scattered by the prisms (convex and concave structures) of the prism sheet, and may be emitted from the prism sheet at an even larger polar angle without being focused in front. Such light components that are not focused by the lens sheet and leak out at a large polar angle are called "side lobe light." Side lobe light is a light component that is not necessary for image display and is prone to becoming stray light within the liquid crystal panel, which causes light leakage of oblique light (light with a large polar angle) during black display, which can be a factor in reducing contrast when viewed from an oblique direction.

[0007] According to the inventors' study, since side lobe light is likely to occur in the up and down directions depending on the configuration of the backlight, there is room for further study to suppress light leakage in the diagonal directions in the up and down directions. Furthermore, according to the inventors' study, when viewed from an oblique direction, the displayed image may be colored in an unintended color, so there is room for further study.

[0008] The above-mentioned Patent Document 1 considers placing a specific optical element on the observation surface side of the display device to suppress the decrease in visibility due to external light reflection, but does not consider the decrease in contrast due to side lobe light or coloring in oblique directions.

[0009] The present invention has been made in consideration of the above-mentioned current situation, and aims to provide an optical element that can suppress light leakage in diagonal directions in the upward and downward directions and suppress coloring in diagonal directions, and a display device equipped with the optical element. [Means for solving the problem]

[0010] (1) One embodiment of the present invention has, from an observation side, a first polarizer, a first retardation layer including first anisotropic molecules, a second retardation layer including second anisotropic molecules, and a second polarizer in this order, wherein a tilt angle of a first anisotropic molecule located on the first polarizer side of the first retardation layer is θ1-1, a tilt angle of a first anisotropic molecule located on the interface side of the first retardation layer with the second retardation layer is θ1-2, a tilt angle of a second anisotropic molecule located on the second polarizer side of the second retardation layer is θ2-1, and a tilt angle of a second anisotropic molecule located on the interface side of the second retardation layer with the first retardation layer is θ2-2. Then, the θ1-1 is larger than the θ1-2, the first anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the first retardation layer, the θ2-1 is larger than the θ2-2, the second anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the second retardation layer, the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel, the slow axis of the first retardation layer and the slow axis of the second retardation layer are parallel, and the transmission axis of the first polarizer is parallel to the slow axis of the first retardation layer and the slow axis of the second retardation layer.

[0011] (2) Another embodiment of the present invention has, from the observation surface side, a first polarizer, a first retardation layer including first anisotropic molecules, a second retardation layer including second anisotropic molecules, and a second polarizer in this order, and the tilt angle of the first anisotropic molecule located on the first polarizer side of the first retardation layer is θ1-1, the tilt angle of the first anisotropic molecule located on the interface side with the second retardation layer of the first retardation layer is θ1-2, the tilt angle of the second anisotropic molecule located on the second polarizer side of the second retardation layer is θ2-1, and the tilt angle of the second anisotropic molecule located on the interface side with the first retardation layer of the second retardation layer is θ2-2. an optical element in which the θ1-1 is larger than the θ1-2, the first anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the first retardation layer, the θ2-1 is larger than the θ2-2, the second anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the second retardation layer, the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel, the slow axis of the first retardation layer and the slow axis of the second retardation layer are parallel, and the transmission axis of the first polarizer is perpendicular to the slow axis of the first retardation layer and the slow axis of the second retardation layer.

[0012] (3) Moreover, in an embodiment of the present invention, in addition to the configuration of (1) above, the optical element is such that the θ1-1 and the θ2-1 are not less than 65° and not more than 90°.

[0013] (4) Moreover, in an embodiment of the present invention, in addition to the configuration of (2) above, the optical element is such that the θ1-1 and the θ2-1 are not less than 70° and not more than 90°.

[0014] (5) Moreover, in an embodiment of the present invention, in addition to the configuration of (1) or (2) above, the optical element is such that the θ1-1 and the θ2-1 are not less than 70° and not more than 80°.

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

[0016] (7) Furthermore, in an embodiment of the present invention, in addition to any one of the configurations (1) to (6) above, the first anisotropic molecule and the second anisotropic molecule each have a tilt angle that changes along a thickness direction of the first retardation layer or a thickness direction of the second retardation layer, with an interface between the first retardation layer and the second retardation layer as a plane of symmetry.

[0017] (8) Furthermore, in addition to the configuration of any one of (1) to (7) above, an embodiment of the present invention is an optical element, wherein the first polarizer is an absorptive polarizer or a laminate of an absorptive polarizer and a reflective polarizer, and the second polarizer is a reflective polarizer or a laminate of an absorptive polarizer and a reflective polarizer.

[0018] (9) Yet another embodiment of the present invention is a display device comprising a liquid crystal panel, an optical element according to any one of (1) to (8) above, and a backlight, in that order, the optical element being positioned so that the first polarizer faces the liquid crystal panel.

[0019] (10) Furthermore, in one embodiment of the present invention, in addition to the configuration of (9) above, the backlight includes a prism sheet arranged 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 observation side surface, and the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to or perpendicular to the ridge lines of the linear convex portions. Effect of the Invention

[0020] According to the present invention, it is possible to provide an optical element capable of suppressing light leakage in oblique directions in the up and down directions and suppressing coloring in oblique directions, and a display device including the optical element. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a diagram illustrating a polar angle and an azimuth angle. [Diagram 2] 1 is a schematic cross-sectional view of an optical element according to a first embodiment. [Diagram 3]3 is a diagram showing the axial orientations of each member of the optical element according to the first embodiment. FIG. [Figure 4] 3 is a cross-sectional view illustrating the optical element according to the first embodiment, in which the first polarizer and the second polarizer are a laminate. FIG. [Diagram 5] 4 is a schematic cross-sectional view of an optical element according to embodiment 2. FIG. [Figure 6] 6 is a diagram showing the axial orientations of each member of an optical element according to embodiment 2. FIG. [Figure 7] FIG. 11 is a cross-sectional view illustrating a display device according to a third embodiment. [Figure 8] FIG. 2 is a perspective view showing an example of a prism sheet provided in the backlight. [Figure 9] 1 is a graph showing the transmittance of Example 1 and Example 2 when the tilt angle is changed. [Figure 10] 4 shows simulation results of chromaticity, transmittance and viewing angle of the optical element of Example 1. [Figure 11] FIG. 2 is an xy chromaticity diagram of the CIE 1931 color space at a polar angle of 60° for the optical element of Example 1. [Figure 12] 11 shows simulation results of chromaticity, transmittance and viewing angle of the optical element of Example 2. [Figure 13] FIG. 11 is an xy chromaticity diagram of the optical element of Example 2 in the CIE 1931 color space at a polar angle of 60°. [Figure 14] 1 shows a simulation result of the transmittance viewing angle of the optical element of Example 1. [Figure 15] 11 shows a simulation result of the transmittance viewing angle of the optical element of Example 2. [Figure 16] 3 is a schematic cross-sectional view of an optical element of Comparative Example 1. FIG. [Figure 17] 4 is a diagram showing the axial orientations of each member of the optical element of Comparative Example 1. FIG. [Figure 18] 13 is a simulation result of the transmittance viewing angle of the optical element of Comparative Example 1. [Figure 19] 13 is a simulation result of chromaticity, transmittance, and viewing angle of the optical element of Comparative Example 1. [Figure 20] 4 is a schematic cross-sectional view of an optical element of Comparative Example 2. FIG. [Figure 21] 13 is a diagram showing the axial orientations of each member of the optical element of Comparative Example 2. FIG. [Figure 22] 13 is a simulation result of the transmittance viewing angle of the optical element of Comparative Example 2. [Diagram 23] 13 is a simulation result of chromaticity, transmittance, and viewing angle of the optical element of Comparative Example 2. [Figure 24] 11 is a schematic cross-sectional view of an optical element of Comparative Example 3. FIG. [Diagram 25] FIG. 11 is a diagram showing the axial orientations of each member of the optical element of Comparative Example 3. [Figure 26] 13 is a simulation result of the transmittance viewing angle of the optical element of Comparative Example 3. [Figure 27] 13 is a simulation result of chromaticity, transmittance, and viewing angle of the optical element of Comparative Example 3. [Figure 28] 11 is a schematic cross-sectional view of an optical element of Comparative Example 4. FIG. [Figure 29] FIG. 11 is a diagram showing the axial orientations of each member of the optical element of Comparative Example 4. [Diagram 30] 13 is a simulation result of the transmittance viewing angle of the optical element of Comparative Example 4. [Diagram 31] 13 is a simulation result of chromaticity, transmittance, and viewing angle of the optical element of Comparative Example 4. [Diagram 32] 11 is a schematic cross-sectional view of an optical element of Comparative Example 5. FIG. [Diagram 33] FIG. 13 is a diagram showing the axial orientations of each member of the optical element of Comparative Example 5. [Diagram 34] 13 is a simulation result of the transmittance viewing angle of the optical element of Comparative Example 5. [Diagram 35] 13 is a simulation result of chromaticity, transmittance, and viewing angle of the optical element of Comparative Example 5. [Diagram 36] FIG. 11 is a schematic cross-sectional view of an optical element of Comparative Example 6. [Figure 37] FIG. 13 is a diagram showing the axial orientations of each member of the optical element of Comparative Example 6. [Figure 38] 13 is a simulation result of the transmittance viewing angle of the optical element of Comparative Example 6. [Figure 39]13 is a simulation result of chromaticity, transmittance, and viewing angle of the optical element of Comparative Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described. The present invention is not limited to the contents described in the following embodiment, and appropriate design changes can be made within the scope of the configuration of the present invention. In the following description, the same reference numerals are appropriately used in common between different drawings for parts having the same or similar functions, and repeated explanations thereof will be omitted as appropriate. Each aspect of the present invention may be appropriately combined within the scope of the gist of the present invention.

[0023] [Terminology definition] FIG. 1 is a diagram for explaining polar angles and azimuth angles. In this specification, the polar angle θ means the angle between the target direction (for example, the measurement direction F) and the direction parallel to the normal to the main surface of the optical element, as shown in FIG. 1. 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 means the direction when the target direction is projected onto the main surface of the optical element, and is expressed by the angle (also called the azimuth angle) between the target direction and the reference azimuth. In this specification, the reference azimuth (azimuth angle 0°) is set to the horizontal right direction of the screen of the optical element.

[0024] In this specification, the two axes (directions) being parallel means that the angle (absolute value) between them is within 0±3°, preferably within 0±1°, more preferably within 0±0.5°, and particularly preferably 0° (completely parallel). In addition, in this specification, the two axes (directions) being perpendicular to each other means that the angle (absolute value) between them is within 90±3°, preferably within 90±1°, more preferably within 90±0.5°, and particularly preferably 90° (completely perpendicular). The above-mentioned axes include the transmission axis and reflection axis of the polarizer and the slow axis of the retardation layer.

[0025] In this specification, the observation surface side means the side of the target component that is closer to the observer when the target component is placed facing the observer, and the back side means the side of the target component that is farther from the observer.

[0026] (Embodiment 1) The optical element according to the first embodiment has, from the observation surface side, a first polarizer, a first retardation layer including a first anisotropic molecule, a second retardation layer including a second anisotropic molecule, and a second polarizer in this order, and the tilt angle of the first anisotropic molecule located on the first polarizer side of the first retardation layer is θ1-1, the tilt angle of the first anisotropic molecule located on the interface side with the second retardation layer of the first retardation layer is θ1-2, the tilt angle of the second anisotropic molecule located on the second polarizer side of the second retardation layer is θ2-1, and the tilt angle of the second anisotropic molecule located on the interface side with the first retardation layer of the second retardation layer is θ2- 2, the θ1-1 is larger than the θ1-2, the first anisotropic molecules are oriented so that the tilt angle changes continuously in the thickness direction of the first retardation layer, the θ2-1 is larger than the θ2-2, the second anisotropic molecules are oriented so that the tilt angle changes continuously in the thickness direction of the second retardation layer, the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel, the slow axis of the first retardation layer and the slow axis of the second retardation layer are parallel, and the transmission axis of the first polarizer is parallel to the slow axis of the first retardation layer and the slow axis of the second retardation layer.

[0027] Fig. 2 is a cross-sectional schematic diagram of an optical element according to embodiment 1. As shown in Fig. 2, the optical element 100A according to embodiment 1 has a first polarizer 10, a first retardation layer 20, a second retardation layer 30, and a second polarizer 40 in this order from the observation surface side. The optical element 100A functions as an optical louver, and is therefore also called a polarizing plate louver. In this specification, an optical element constituted by all the members from the first polarizer 10 to the second polarizer 40 is called a polarizing plate louver.

[0028] (Polarizer) The first polarizer 10 and the second polarizer 40 have a function of extracting polarized light (linearly polarized light) that vibrates only in a specific direction from unpolarized light (natural light), partially polarized light, or polarized light, and are also called linear polarizing plates. The first polarizer 10 and the second polarizer 40 may each be an absorptive polarizer or a reflective polarizer. The absorptive polarizer has an absorption axis that absorbs light that vibrates in a specific direction and a transmission axis that transmits polarized light (linearly polarized light) that vibrates in a direction perpendicular to the specific direction. The reflective polarizer has a reflection axis that reflects light that vibrates in a specific direction and a transmission axis that transmits polarized light (linearly polarized light) that vibrates in a direction perpendicular to the specific direction.

[0029] Both the first polarizer 10 and the second polarizer 40 may be absorptive polarizers. By using absorptive polarizers for both the first polarizer 10 and the second polarizer 40, when a backlight is disposed on the rear side of the optical element 100A, side lobe light can be absorbed, and the light blocking properties in oblique directions in the up and down azimuths can be further improved.

[0030] The first polarizer 10 may be an absorptive polarizer, and the second polarizer 40 may be a reflective polarizer. By using a reflective polarizer for the second polarizer 40 on the rear side, when a backlight is disposed on the rear side of the optical element 100A, the side lobe light is reflected toward the backlight and the reflected light is emitted again toward the observation surface by a reflector or the like of the backlight, thereby recycling the light and increasing the luminance in the normal direction during white display.

[0031] The first polarizer 10 and the second polarizer 40 may each be a laminate of an absorptive polarizer and a reflective polarizer. Although the reflective polarizer has the effect of improving the luminance in the normal direction during white display, the degree of polarization is lower than that of the absorptive polarizer, and therefore, if only the reflective polarizer is used, the contrast of the polarizing plate louver may decrease. Therefore, by laminating the absorptive polarizer and the reflective polarizer, it is possible to increase the contrast while improving the luminance in the normal direction.

[0032] FIG. 4 is a cross-sectional schematic diagram of the optical element according to embodiment 1 in which the first polarizer and the second polarizer are laminates. FIG. 4 illustrates an example in which the first polarizer and the second polarizer are laminates of an absorptive polarizer and a reflective polarizer. When the first polarizer 10 is a laminate, it is preferable that the absorptive polarizer 10A and the reflective polarizer 10B are laminated in this order from the observation side. When the second polarizer 40 is a laminate, it is preferable that the absorptive polarizer 40A and the reflective polarizer 40B are laminated in this order from the observation side. When the absorptive polarizer and the reflective polarizer are laminated, it is preferable that the transmission axis of the absorptive polarizer 10A and the transmission axis of the reflective polarizer 10B are parallel to each other. It is also preferable that the transmission axis of the absorptive polarizer 40A and the transmission axis of the reflective polarizer 40B are parallel to each other.

[0033] Either the first polarizer 10 or the second polarizer 40 may be a single-layer absorptive polarizer or a reflective polarizer, and the other may be a laminate of an absorptive polarizer and a reflective polarizer. It is more preferable that both the first polarizer 10 and the second polarizer 40 are laminates of an absorptive polarizer and a reflective polarizer. It is more preferable that a reflective polarizer is laminated on the back side of the absorptive polarizer for both the first polarizer 10 and the second polarizer 40. In a display device in which a liquid crystal panel is arranged on the front side of an optical element and a backlight is arranged on the back side of the optical element, the brightness and contrast can be further increased. By making the second polarizer 40 located on the backlight side a laminate of an absorptive polarizer and a reflective polarizer, the light emitted from the backlight can be more efficiently reflected to the backlight side, and the light recycling efficiency can be improved. By making the first polarizer 10 located on the liquid crystal panel side a laminate of an absorptive polarizer and a reflective polarizer, the light incident from the backlight side can be further reflected to the backlight side, and the front brightness of the liquid crystal panel can be improved.

[0034] An example of an absorptive polarizer is one having a polarizing layer in which an anisotropic material such as a dichroic iodine complex is adsorbed and aligned on a polyvinyl alcohol (PVA) film. At least one of the observation side and back side of the polarizing layer may have a protective film such as a triacetyl cellulose (TAC) film.

[0035] Examples of reflective polarizers include reflective polarizers obtained by uniaxially stretching a co-extruded film made of multiple types of resins (e.g., APCF manufactured by Nitto Denko Corporation and DBEF manufactured by 3M), and reflective polarizers in which thin metal wires are periodically arranged (so-called wire grid polarizers).

[0036] (phase contrast layer) The first retardation layer 20 and the second retardation layer 30 have a function of changing the state of incident polarized light by applying a phase difference between two orthogonal polarized light components using a birefringent material or the like.

[0037] As shown in FIG. 2, the first retardation layer 20 contains the first anisotropic molecule 21, and the second retardation layer 30 contains the second anisotropic molecule 31. In FIG. 2, the tilt angle of the first anisotropic molecule 21A located on the first polarizer 10 side of the first retardation layer 20 is θ1-1. The tilt angle of the first anisotropic molecule 21B located on the interface side of the first retardation layer 20 with the second retardation layer 30 is θ1-2. The tilt angle of the second anisotropic molecule 31A located on the second polarizer 40 side of the second retardation layer 30 is θ2-1. The tilt angle of the second anisotropic molecule 31B located on the interface side of the second retardation layer 30 with the first retardation layer 20 is θ2-2.

[0038] The θ1-1 is larger than the θ1-2, and the first anisotropic molecules 21 are aligned so that the tilt angle changes continuously in the thickness direction of the first retardation layer 20. The first anisotropic molecules 21 have a larger or smaller tilt angle from one side to the other side in the thickness direction of the first retardation layer 20. The θ2-1 is larger than the θ2-2, and the second anisotropic molecules 31 are aligned so that the tilt angle changes continuously in the thickness direction of the second retardation layer 30. The second anisotropic molecules 31 have a larger or smaller tilt angle from one side to the other side in the thickness direction of the second retardation layer 30. The θ1-1 is different from the θ1-2, and the θ2-1 is different from the θ2-2. That is, it can be said that the first anisotropic molecules 21 and the second anisotropic molecules 31 are aligned in a hybrid orientation. By adopting such an embodiment, the coloring of the optical element 100A when viewed from an oblique direction can be made to be close to a monochromatic color. Specifically, the yellowish color can be suppressed to give a single blue color. Taking the first retardation layer 20 as an example, the first anisotropic molecule 21 (having a tilt angle θ ) located between the first anisotropic molecule 21A and the first anisotropic molecule 21B in the thickness direction of the first retardation layer 20 is 21 ) is the tilt angle θ 21 The above θ1-2<θ 21 <Within the above range of θ1-1, the tilt angle gradually changes along the thickness direction of the first retardation layer 20.

[0039] The tilt angle of the first anisotropic molecule 21 refers to the angle at which the major axis of the first anisotropic molecule 21 is inclined with respect to a plane parallel to the surface of the first polarizer 10 on the first retardation layer 20 side, unless otherwise specified. The tilt angle of the second anisotropic molecule 31 refers to the angle at which the major axis of the second anisotropic molecule 31 is inclined with respect to a plane parallel to the surface of the second polarizer 40 on the second retardation layer 30 side, unless otherwise specified. The tilt angle is defined as 0° or more and 90° or less.

[0040] It is preferable that the first anisotropic molecules 21 change in the thickness direction of the first retardation layer 20 so that the tilt angle increases from the interface between the first retardation layer 20 and the second retardation layer 30 toward the first polarizer 10 side, and that the second anisotropic molecules 31 change in the thickness direction of the second retardation layer 30 so that the tilt angle increases from the interface toward the second polarizer 40 side. Since the first retardation layer 20 and the second retardation layer 30 are combined to form one louver, it is preferable that the first retardation layer 20 and the second retardation layer 30 are in contact with each other.

[0041] It is preferable that the tilt angle of the first anisotropic molecule 21 and the second anisotropic molecule 31 change along the thickness direction of the first retardation layer 20 or the thickness direction of the second retardation layer 30, with the interface between the first retardation layer 20 and the second retardation layer 30 as the plane of symmetry.

[0042] The change direction of the tilt angle of the first anisotropic molecule 21 of the first retardation layer 20 and the change direction of the tilt angle of the second anisotropic molecule 31 of the second retardation layer 30 are preferably the same. The change direction of the tilt angle of the anisotropic molecule refers to the direction in which the major axis of the anisotropic molecule rises (the tilt angle becomes larger). Specifically, the change direction of the tilt angle of the anisotropic molecule is the direction along the x-axis when the main surface of the optical element is the xy plane, and the plane perpendicular to the main surface of the optical element and including the major axes of the multiple anisotropic molecules whose tilt angles change continuously is the xz plane, and is the direction from one end side to the other end side of the major axis of each of the multiple anisotropic molecules. Here, the above-mentioned multiple anisotropic molecules are raised more from the other end of the long axis of the molecules as they move away from one of the surfaces (surfaces to be raised) among the interface between the first retardation layer 20 and the second retardation layer 30, the surface of the first retardation layer 20 facing the first polarizer 10, and the surface of the second retardation layer 30 facing the second polarizer 40. In the cross-sectional views (FIG. 2, etc.) in the xz plane, the direction of change of the tilt angle of the anisotropic molecules is indicated by the direction of the arrow.

[0043] In the first embodiment, from the viewpoint of lowering the transmittance in the oblique directions in the up and down directions, the angles θ1-1 and θ2-1 are preferably 65° or more and 90° or less. From the viewpoint of further suppressing coloring in the oblique directions, the angles θ1-1 and θ2-1 are preferably 70° or more and 80° or less.

[0044] The angles θ1-2 and θ2-2 may be smaller than the angles θ1-1 and θ2-1, and are preferably, for example, 0° or more and 10° or less, and more preferably 1° or more and 5° or less.

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

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

[0047] The in-plane retardation of the first retardation layer 20 and the second retardation layer 30 is preferably 180 nm or more and 250 nm or less. By adopting such an embodiment, it is possible to more effectively suppress oblique light in the up and down directions. The in-plane retardation of the first retardation layer 20 and the second retardation layer 30 is more preferably 190 nm or more and 240 nm or less, and further preferably 200 nm or more and 230 nm or less. In this specification, the retardation is 550 nm unless otherwise specified, and the measurement temperature is 23 ° C.

[0048] The in-plane retardation Re is defined by the following formula, where d is the thickness of the retardation layer, nx is the refractive index in the x-axis direction, ny is the refractive index in the y-axis direction, and nz is the refractive index in the z-axis direction, where 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 perpendicular to the x-axis and y-axis. Re = (nx-ny) × d

[0049] It is preferable that the color of the optical element 100A when viewed from an oblique direction can be monochromatic. Since the color of the display device when viewed from an oblique direction can be easily corrected by the thickness of the liquid crystal layer included in the liquid crystal panel arranged on the front side of the optical element 100A and the design of the viewing angle compensation film, etc., the color is more preferably monochromatic blue. Specifically, the values ​​of x and y in the xy chromaticity diagram of the CIE 1931 color space are preferably x<0.33 and y<0.33, and more preferably x<0.30 and y<0.30. The values ​​of x and y refer to the average chromaticity values ​​of the x and y values ​​at azimuth angles of 0°, 45°, 90°, 135°, 189°, 225°, 270°, and 315° at a polar angle of 60°, respectively.

[0050] Here, the first anisotropic molecule 21 and the second anisotropic molecule 31 may have a positive wavelength dispersion characteristic in which the birefringence (phase difference) decreases with increasing wavelength. When anisotropic molecules having a positive wavelength dispersion characteristic are used, the transmittance of the optical element 100A in the oblique direction differs for each wavelength, and the color is visually recognized as a mixture of multiple colors. As a method for correcting such coloring from an oblique direction, it is possible to further arrange a retardation layer containing anisotropic molecules having a reverse wavelength dispersion characteristic in which the birefringence increases with increasing wavelength, but anisotropic molecules having ideal wavelength dispersion characteristics capable of correcting coloring have not been realized. Therefore, in this embodiment, by making the coloring of the optical element 100A when viewed from an oblique direction monochromatic, the coloring of the display device when viewed from an oblique direction can be corrected 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 and the viewing angle compensation film. For example, the coloring of the liquid crystal panel when viewed from an oblique direction is adjusted to be the opposite color to the coloring of the optical element 100A when viewed from an oblique direction. When the color of the optical element 100A in the oblique direction is blue, the liquid crystal panel is designed to have a yellowish color in the oblique direction.

[0051] The first anisotropic molecule 21 and the second anisotropic molecule 31 are molecules that cause the first retardation layer 20 and the second retardation layer 30 to exhibit birefringence, respectively. The first anisotropic molecule 21 and the second anisotropic molecule 31 are molecules that exhibit anisotropy of the refractive index of light by being oriented in a specific direction. Examples of the first anisotropic molecule 21 and the second anisotropic molecule 31 include liquid crystal materials such as polymerizable liquid crystals and cured products of polymerizable liquid crystals. The details of polymerizable liquid crystals will be described later.

[0052] The first retardation layer 20 and the second retardation layer 30 may be, for example, a reactive mesogen layer (coating retardation layer) made of a cured product of a polymerizable liquid crystal (reactive mesogen). The coating retardation layer can be formed, for example, by applying a composition containing a polymerizable liquid crystal onto an alignment film that has been subjected to an alignment treatment, and curing the composition by baking, light irradiation, or other methods. The cured polymerizable liquid crystal is aligned according to the alignment direction of the alignment film determined by the alignment treatment, and exhibits retardation. The tilt angle (tilt angle of the long axis of the polymerizable liquid crystal) of the polymerizable liquid crystal located on the alignment film side relative to the alignment film can be adjusted in units of several degrees by an alignment treatment such as rubbing, and the polymerizable liquid crystal can be aligned, for example, to be nearly horizontal to the alignment film. On the other hand, the polymerizable liquid crystal located on the surface opposite to the alignment film (surface in contact with air) is aligned nearly perpendicular to the surface in contact with air due to surface tension. The composition may contain a surfactant, and the tilt angle of the polymerizable liquid crystal relative to the surface in contact with air can be adjusted by adjusting the concentration of the surfactant, etc. The polymerizable liquid crystal in the obtained retardation layer can be hybrid-oriented with a continuously changing tilt angle along the thickness direction of the retardation layer. The tilt angles of the first anisotropic molecules 21 and the second anisotropic molecules 31 can also be adjusted by adjusting the type of polymerizable liquid crystal, the type of surfactant, the baking conditions, the light irradiation conditions (wavelength, intensity, and irradiation angle of the irradiated light), etc. The alignment film can be peeled off from the obtained retardation layer and attached to a polarizer or the like with an adhesive or the like.

[0053] The alignment film used as the base of the coating retardation layer may be a film generally used in the field of liquid crystal panels, such as polyimide, etc. The alignment treatment of the alignment film may be performed by rubbing, light irradiation, or the like.

[0054] (Axial arrangement of each component) FIG. 3 is a diagram showing the axial orientation of each member of the optical element according to the first embodiment. As shown in FIG. 3, the transmission axis of the first polarizer 10 (hereinafter also referred to as the first transmission axis) and the transmission axis of the second polarizer 40 (hereinafter also referred to as the second transmission axis) are parallel. The slow axis of the first retardation layer 20 (hereinafter also referred to as the first slow axis) and the slow axis of the second retardation layer 30 (hereinafter also referred to as the second slow axis) are parallel. In a plan view in which the first retardation layer 20 is observed from the observation surface side, the long axis direction of the first anisotropic molecule 21 is the first slow axis. In a plan view in which the second retardation layer 30 is observed from the observation surface side, the long axis direction of the second anisotropic molecule 31 is the second slow axis. The first transmission axis is parallel to the first slow axis and the second slow axis. By adopting such an embodiment, it is possible to reduce light leakage by lowering the transmittance in the oblique direction in the up-down direction while increasing the contrast in the normal direction.

[0055] In the first embodiment, the first transmission axis is parallel to the first slow axis and the second slow axis. Since the first transmission axis is parallel to the first slow axis and the second slow axis, the light blocking effect in the oblique direction in the up-down direction can be further improved compared to the second embodiment.

[0056] The slow axis can be measured using a phase difference measuring device (for example, "Axoscan" manufactured by Axometrics). Axoscan can measure the phase difference, the slow axis, and the tilt angle of the anisotropic molecule. Specifically, the phase difference, the slow axis, the tilt angle of the anisotropic molecule, and other characteristics can be measured by measuring and analyzing a 4×4=16 matrix (Mueller matrix) that represents the polarization state of light.

[0057] (Polymerizable Liquid Crystal) As the polymerizable liquid crystal, the liquid crystal polymer having a photoreactive group is preferably used.As the liquid crystal polymer having a photoreactive group, for example, the polymer having a side chain structure that has a combination of mesogen group such as biphenyl group, terphenyl group, naphthalene group, phenylbenzoate group, azobenzene group, and their derivatives, which are frequently used as the mesogen component of liquid crystal polymer, and photoreactive group such as cinnamoyl group, chalcone group, cinnamylidene group, β-(2-phenyl)acryloyl group, cinnamic acid group, and their derivatives, and having a structure such as acrylate, methacrylate, maleimide, N-phenylmaleimide, siloxane, etc. in the main chain can be mentioned.

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

[0059] A preferred specific example of the liquid crystal polymer is a copolymerizable (meth)acrylic acid polymer having a repeating unit represented by the following general formula (I).

[0060] [ka]

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

[0062] [ka]

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

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

[0065] [ka]

[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 with a group selected from an alkyl group, an alkoxy group, a cyano group, and a halogen atom; X 1A ~X 4A are each 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 formula (M1a) or (M5a); p and q are each independently an integer of 1 to 12; and r and s are the molar fractions of each monomer in the copolymer that satisfy the relationships 0.65≦r≦0.95, 0.05≦s≦0.35, and r+s=1.

[0067] [ka]

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

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

[0070] [ka]

[0071] 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 with 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 are each independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a cyano group, p and q are each independently an integer of 1 to 12, and r and s are the molar fractions of each monomer in the copolymer that satisfy the relationships 0.65≦r≦0.95, 0.05≦s≦0.35, and r+s=1.

[0072] [ka]

[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 with a group selected from an alkyl group, an alkoxy group, a cyano group, and a halogen atom; X 1A ~X4A and X 1B ~X 4B are each independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or a cyano group, p and q are each independently an integer of 1 to 12, and r and s are the molar fractions of each monomer in the copolymer that satisfy the relationships 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 below), R 1 R is preferably a methyl group. 2 is preferably an alkyl group, or a phenyl group substituted with one group selected from an alkyl group, an alkoxy group, a cyano group, and a halogen atom, of which a phenyl group substituted with an alkyl group, an alkoxy group, or a cyano group is more preferable, and a phenyl group substituted with an alkyl group or an alkoxy group is particularly preferable.

[0075] X 31B ~X 38B Each of the groups is preferably a hydrogen atom or a halogen atom, and it is most preferable that all of them are hydrogen atoms.

[0076] Each of p and q is preferably an integer between 3 and 9, more preferably an integer between 5 and 7, and most preferably 6. The preferred range for r is 0.75≦r≦0.85, and most preferably 0.8. The preferred range for the corresponding s is the range that is automatically determined by r+s=1. That is, the preferred range is 0.15≦s≦0.25, and most preferably 0.2.

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

[0078] R 2 or R 2 The alkyl group of the substituent of the phenyl group in R is an alkyl group having 1 to 12 carbon atoms, preferably having 1 to 6 carbon atoms, more preferably having 1 to 4 carbon atoms, and most preferably a methyl group. 2 The alkoxy group of the substituent of the phenyl group in R is 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 Examples of the halogen atom as a substituent of the phenyl group include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and among these, a fluorine atom is preferred.

[0079] X 1 ~X 38 In the above, examples of the alkyl group include those having 1 to 4 carbon atoms, of which a methyl group is most preferred, examples of the alkoxy group include those having 1 to 4 carbon atoms, of which a methoxy group is most preferred, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, of which a fluorine atom is preferred.

[0080] In this specification, X 1A ~X 38A is a substituent X on ring A or ring B. 1 ~X 38 where they are substituents on ring A, X 1B ~X 38Brepresents the case where they are substituents on ring B. Therefore, X 1 ~X 38 The explanation for X is as it is. 1A ~X 38A and X 1B ~X 38B This can also be applied to.

[0081] The liquid crystal polymer can be dissolved in a solvent to form a retardation layer composition. In addition, the retardation layer composition may appropriately contain a photopolymerization initiator, a surfactant, and other components that are generally contained in a polymerizable composition that is polymerized by light or heat.

[0082] Examples of the solvent used in the retardation layer composition 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, any of the general-purpose photopolymerization initiators generally known to form a uniform film by a small amount of light irradiation 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-t-butyl-dichloroacetophenone, benzoin, Examples of the photopolymerization initiator include benzoin-based photopolymerization initiators such as benzoin methyl ether, benzophenone-based photopolymerization initiators such as benzophenone and benzoylbenzoic acid, thioxanthone-based photopolymerization initiators such as 2-chlorothioxanthone and 2-methylthioxanthone, 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. Any of the photopolymerization initiators may be used alone, or two or more of them may be used in combination.

[0084] As the surfactant, any surfactant generally used to form a uniform film can be used. Specific examples include anionic surfactants such as sodium lauryl sulfate and ammonium lauryl sulfate; nonionic surfactants such as polyethylene glycol monolaurate and sorbitan stearate; cationic surfactants such as stearyl trimethylammonium chloride and behenyl trimethylammonium chloride; amphoteric surfactants such as alkyl betaines such as lauryl betaine and alkyl sulfobetaine, alkyl imidazolines, and sodium lauroyl sarcosine; and surfactants such as BYK-361, BYK-306, and BYK-307 (manufactured by BYK Japan), Fluorad FC430 (manufactured by Sumitomo 3M), Megafac F171, and R08 (manufactured by Dainippon Ink and Chemicals). These surfactants may be used alone or in combination of two or more.

[0085] When a liquid crystal polymer having a photoreactive group is used as the polymerizable liquid crystal, it can be oriented by polarized light irradiation, etc., so that the coating retardation layer can be formed without providing an underlying alignment film. If a coating retardation layer is formed using a liquid crystal polymer having a photoreactive group, the alignment film can be omitted, making it possible to reduce the thickness and simplify the manufacturing process.

[0086] (Embodiment 2) The optical element according to the second embodiment has the same configuration as that of the first embodiment, except that the transmission axis of the first polarizer is perpendicular to the slow axis of the first retardation layer and the slow axis of the second retardation layer, and therefore a duplicated description will be omitted.

[0087] The optical element according to the second embodiment has, from the observation surface side, a first polarizer, a first retardation layer including a first anisotropic molecule, a second retardation layer including a second anisotropic molecule, and a second polarizer in this order, and the tilt angle of the first anisotropic molecule located on the first polarizer side of the first retardation layer is θ1-1, the tilt angle of the first anisotropic molecule located on the interface side with the second retardation layer of the first retardation layer is θ1-2, the tilt angle of the second anisotropic molecule located on the second polarizer side of the second retardation layer is θ2-1, and the tilt angle of the second anisotropic molecule located on the interface side with the first retardation layer of the second retardation layer is θ2 When it is -2, the θ1-1 is larger than the θ1-2, the first anisotropic molecule is oriented so that the tilt angle changes continuously in the thickness direction of the first retardation layer, the θ2-1 is larger than the θ2-2, the second anisotropic molecule is oriented so that the tilt angle changes continuously in the thickness direction of the second retardation layer, the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel, the slow axis of the first retardation layer and the slow axis of the second retardation layer are parallel, and the transmission axis of the first polarizer is perpendicular to the slow axis of the first retardation layer and the slow axis of the second retardation layer. By adopting such an embodiment, it is possible to reduce light leakage by lowering the transmittance in the oblique direction in the up and down azimuths while increasing the contrast in the normal direction.

[0088] Since the first transmission axis is perpendicular to the first slow axis and the second slow axis, the range of oblique light blocking in the up and down azimuths can be made wider than that in the first embodiment.

[0089] In the second embodiment, from the viewpoint of lowering the transmittance in the oblique directions in the up and down directions, the angles θ1-1 and θ2-1 are preferably 70° or more and 90° or less. From the viewpoint of further suppressing coloring in the oblique directions, the angles θ1-1 and θ2-1 are preferably 70° or more and 80° or less.

[0090] The optical element 100B of the second embodiment can also suppress light leakage in oblique directions in the up and down azimuths, and suppress coloring in oblique directions.

[0091] (Embodiment 3) 7 is a cross-sectional schematic diagram of a display device according to embodiment 3. The display device 1 according to embodiment 3 includes a liquid crystal panel 200, an optical element 100A, and a backlight 300, in this order, and the optical element 100A is disposed so that the first polarizer 10 faces the liquid crystal panel 200. As the optical element, either the optical element 100A of embodiment 1 or the optical element 100B of embodiment 2 may be used.

[0092] The liquid crystal panel 200 may have an observation-side polarizer 400 on its observation-side surface. As the observation-side polarizer 400, the above-mentioned absorptive polarizer or reflective polarizer can be used, but an absorptive polarizer is preferable.

[0093] The transmission axis of the observation-side polarizer 400 and the transmission axis of the first polarizer 10 may be arranged perpendicular to each other or parallel to each other. From the viewpoint of obtaining high contrast, however, it is preferable that the transmission axis of the observation-side polarizer 400 and the transmission axis of the first polarizer 10 are arranged perpendicular to each other.

[0094] Typically, a liquid crystal panel has polarizers disposed on both the observation side and the back side. It is preferable that the first polarizer 10 also serves as the polarizer disposed on the back side of the liquid crystal panel. In other words, it is preferable that there is no other polarizer between the liquid crystal panel and the first polarizer 10. The first polarizer 10 may be attached to the back side of the liquid crystal panel 100 by, for example, an adhesive layer or the like.

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

[0096] The color filter substrate may have, for example, color filters and a black matrix that separates the color filters.The TFT substrate may have gate wiring and source wiring that intersects with the gate wiring, a TFT is disposed near the intersection of the gate wiring and the source wiring, and a pixel electrode electrically connected to the TFT is disposed.

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

[0098] In the VA mode, a counter electrode may be disposed on the CF substrate side, and liquid crystal molecules in the liquid crystal layer may be aligned approximately vertically to the substrate surface when no voltage is applied to the liquid crystal layer. In the FFS and IPS modes, a counter electrode may be disposed on the TFT substrate side, and liquid crystal molecules in the liquid crystal layer may be aligned approximately horizontally to the substrate surface when no voltage is applied. In the TN mode, a counter electrode may be disposed on the CF substrate side, and liquid crystal molecules in the liquid crystal layer may be aligned in a helical shape by rubbing treatment or the like so as to be twisted from the TFT substrate toward the CF substrate. The amount of light transmission is controlled by changing the alignment of the liquid crystal molecules in response to an electric field generated in the liquid crystal layer by a voltage applied between the pixel electrode and the counter electrode. Liquid crystal panels in horizontal alignment modes such as FFS and IPS modes are preferably used because they have a wide viewing angle in the oblique direction.

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

[0100] The liquid crystal molecules may have a positive or negative dielectric anisotropy (Δε) defined by the following formula (L): From the viewpoint of enhancing contrast, it is preferable that the liquid crystal molecules have a negative Δε. 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 irradiates light onto the liquid crystal panel 100, and may be of any type, such as a direct type or an edge type. The backlight 300 may further include a light guide plate, a reflector, etc.

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

[0103] Fig. 8 is a perspective view showing an example of a prism sheet provided in a backlight. As shown in Fig. 8, an example of prism sheet 301 has a plurality of rows of prisms (linear convex portions) 301a extending parallel to each other on the surface on the observation side. The linear convex portions 301a each have a continuous apex, which is also called a ridge line 301b of the linear convex portions.

[0104] It is preferable that the ridgeline 301b is arranged parallel to an azimuth angle of 0°. More specifically, it is preferable that the azimuth angle of the ridgeline 301b is 0°±3°. By arranging the ridgeline 301b parallel to an azimuth angle of 0°, the light collection in the prism sheet in the left and right azimuth (azimuth angle 0°-180°) is suppressed more than in the up and down azimuth (azimuth angle 90°-270°), making it possible to increase the diagonal brightness in the left and right azimuth, and realizing a wide viewing angle. In this case, the arrangement orientation of the prism 301a is an azimuth angle of 90°. Such an embodiment is particularly suitable for use with OEM standards that require a wide brightness viewing angle in the left and right azimuth.

[0105] The transmission axis of the first polarizer 10 and the transmission axis of the second polarizer 40 are preferably parallel to or perpendicular to the ridge line 301b of the linear convex portion. By adopting such an embodiment, it is possible to more effectively suppress oblique light in the upward and downward directions.

[0106] Here, the direction in which the side lobe light is generated varies depending on, for example, the arrangement of the ridges of a prism sheet included in the backlight. According to the study by the present inventors, it was found that when a backlight is used that includes a prism sheet 301 in which ridges 301b are arranged parallel to an azimuth angle of 0° (azimuth angles 0°-180°) or parallel to an azimuth angle of 90° (azimuth angles 90°-270°), side lobe light is likely to be generated in an oblique direction in the up and down azimuth directions (azimuth angles 90°-270°). Therefore, by combining optical element 100A of embodiment 1 or optical element 100B of embodiment 2 with a backlight having prism sheet 301 in which ridge line 301b is arranged parallel to an azimuth angle of 0° (azimuth angle 0°-180°) or parallel to an azimuth angle of 90° (azimuth angle 90°-270°), it becomes possible to match the azimuth and polar angle at which side lobe light is generated with the azimuth and polar angle at which transmittance can be reduced by optical element 100A or 100, and the side lobe light can be effectively suppressed.

[0107] The backlight 300 may include a reflector on the rear side of the light source. As the reflector, a metal deposition film or other reflector commonly used in the field of display devices can be used. EXAMPLES

[0108] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0109] Example 1 Example 1 is a specific example of embodiment 1. FIG. 2 is also a cross-sectional schematic diagram of the optical element of Example 1. The optical element of Example 1 is also called a polarizing plate louver. As shown in FIG. 2, the optical element of Example 1 has a first polarizer 10, a first retardation layer 20 including a first anisotropic molecule 21, a second retardation layer 30 including a second anisotropic molecule 31, and a second polarizer 40 in this order from the observation side.

[0110] Fig. 3 is also a diagram showing the axial orientation of each member of the optical element of Example 1. As shown in Fig. 3, in Example 1, the slow axis (first slow axis) of the first retardation layer, the slow axis (second slow axis) of the second retardation layer, the transmission axis (first transmission axis) of the first polarizer, and the transmission axis (second transmission axis) of the second polarizer were all arranged to be parallel (azimuth angle 0°-180°). As the first polarizer and the second polarizer, single-layer absorption-type linear polarizers were used.

[0111] As shown in Fig. 2, in Example 1, the tilt angles of the first anisotropic molecules 21 and the second anisotropic molecules 31 were continuously changed so as to be symmetrical with respect to the interface between the first retardation layer 20 and the second retardation layer 30. The direction of change in the tilt angle of the first anisotropic molecules 21 was set to be the same as the direction of change in the tilt angle of the second anisotropic molecules 31. The in-plane retardation of each of the first retardation layer 20 and the second retardation layer 30 was 213 nm.

[0112] Example 2 Example 2 is a specific example of embodiment 2. FIG. 5 is also a cross-sectional schematic diagram of the optical element of Example 2. FIG. 6 is also a diagram showing the axial orientation of each member of the optical element of Example 2. Example 2 has the same configuration as Example 1, except that the arrangement of the first transmission axis and the second transmission axis is different. As shown in FIG. 6, in Example 1, the first slow axis and the second slow axis are arranged (azimuth angle 0°-180°), and the first transmission axis and the second transmission axis are arranged parallel (azimuth angle 90°-270°). The first transmission axis, and the first slow axis and the second slow axis are arranged perpendicular to each other.

[0113] <Study of tilt angle and transmittance> In a polarizing plate louver with top and bottom apertures in which the transmittance in the top and bottom azimuths is reduced, it is desirable that the light transmittance at an azimuth angle of 90°-270° and a polar angle of 60° is 10% or less. In the following, for Examples 1 and 2, θ1-2 and θ2-2 are fixed at 4°, 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 is a graph showing the transmittance when the tilt angle is changed in Example 1 and Example 2. As shown in Fig. 9, in Example 1, when θ1-1 and θ2-1 are 65° or more, and in Example 2, when θ1-1 and θ2-1 are 70° or more, the transmittance is 10% or less, suggesting that excellent light blocking properties can be obtained.

[0115] <Color evaluation at a polar angle of 60°> As an improvement of the color when viewed from an oblique direction, the case where the color becomes blue monochromatic at a polar angle of 60° was examined. In the following, for Examples 1 and 2, θ1-2 and θ2-2 were fixed at 4°, and θ1-1=θ2-1 was set, and the angles of θ1-1 and θ2-1 were changed to 60°, 70°, 80°, and 90°, and the chromaticity values ​​(x, y) of all azimuth angles (azimuth angles 0° to 360°) at a polar angle of 60° were simulated. LCD Master was used for the above simulation. FIG. 10 shows the simulation results of the chromaticity transmittance viewing angle of the optical element of Example 1. FIG. 11 shows the xy chromaticity diagram of the CIE 1931 color space of the optical element of Example 1 at a polar angle of 60°. FIG. 12 shows the simulation results of the chromaticity transmittance viewing angle of the optical element of Example 2. FIG. 13 shows the xy chromaticity diagram of the CIE 1931 color space of the optical element of Example 2 at a polar angle of 60°. In the contour diagram of chromaticity transmittance viewing angle, darker colored areas indicate that coloring was observed.

[0116] Table 1 below is a table summarizing the values ​​of x and y in the contour diagram of chromaticity transmittance viewing angle in FIG. 10 and the xy chromaticity diagram in FIG. 11. Table 2 below is a table summarizing the values ​​of x and y in the contour diagram of chromaticity transmittance viewing angle in FIG. 12 and the xy chromaticity diagram in FIG. 13. The above x and y values ​​refer to the average chromaticity values ​​of x and y at azimuth angles of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° at a polar angle of 60°. When the color at a polar angle of 60° is to be monochromatic blue, 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] From the results in Tables 1 and 2, in both Examples 1 and 2, when θ1-1 and θ2-1 were 60° or more and 90° or less, the average chromaticity values ​​were x<0.33 and y<0.33. In addition, when θ1-1 and θ2-1 were 70° or more and 80° or less, the average chromaticity values ​​were x<0.30 and y<0.30, so the yellowish tinge was further suppressed and a color close to a single blue color was achieved.

[0120] Combining the transmittance shown in Figure 9 with the results in Tables 1 and 2, it is clear that when θ1-1 and θ2-1 are 80°, it is possible to obtain a color close to monochrome blue while still obtaining light blocking properties in the upward and downward directions.

[0121] <Diagonal transmittance> In Examples 1 and 2, θ1-1=70°, θ2-1=70°, θ1-2=4°, and θ2-2=4° were set, and as shown in Fig. 2, in the first retardation layer 20, the tilt angle of the first anisotropic molecule was hybrid-oriented so that the tilt angle continuously increased from the interface between the first retardation layer 20 and the second retardation layer 30 toward the first polarizer 10 side. In the second retardation layer 30, the tilt angle of the second anisotropic molecule was hybrid-oriented so that the tilt angle continuously increased from the interface toward the second polarizer 40 side.

[0122] Using LCD Master, the transmittance viewing angle of the optical elements of Examples 1 and 2 was simulated and shown in a contour diagram. FIG. 14 shows the results of the simulation of the transmittance viewing angle of the optical element of Example 1. FIG. 15 shows the results of the simulation of the transmittance viewing angle of the optical element of Example 2. The circular dotted lines in the contour diagrams represent polar angles of 20°, 40°, 60°, and 80° from the inside. The shading of the contour diagrams of the transmittance viewing angle corresponds to the transmittance shown on the right side of each diagram. As shown in FIG. 14 and FIG. 15, it was confirmed that the optical elements of Examples 1 and 2 can narrow the transmitted light in the oblique direction in the up and down azimuth (azimuth angle 90°-270°), and can block light symmetrically with respect to the azimuth angle of 90°-270°. Hereinafter, the transmitted light in the oblique direction (particularly the polar angle of 60° to 80°) is also referred to as "oblique light".

[0123] Comparative Example 1 Fig. 16 is a cross-sectional schematic diagram of the optical element of Comparative Example 1. Fig. 17 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 1. As shown in Fig. 17, the axial arrangement of each member was the same as that of Example 1. In the optical element 1100A of Comparative Example 1, 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 was 213 nm.

[0124] As shown in FIG. 16, in the first retardation layer 20, the tilt angle of the first anisotropic molecule was hybrid-oriented so that the tilt angle continuously increased from the interface between the first retardation layer 20 and the second retardation layer 30 toward the first polarizer 10 side. In the second retardation layer 30, the tilt angle of the second anisotropic molecule was hybrid-oriented so that the tilt angle continuously decreased from the interface toward the second polarizer 40 side. The tilt angles of the first anisotropic molecule 21 and the second anisotropic molecule 31 were asymmetric with respect to the interface between the first retardation layer 20 and the second retardation layer 30. In addition, the tilt angle of the first anisotropic molecule 21 was changed in the opposite direction to the tilt angle of the second anisotropic molecule 31.

[0125] The transmittance viewing angle and coloring of the optical element of Comparative Example 1 were simulated in the same manner as in Example 1. FIG. 18 shows the results of simulating the transmittance viewing angle of the optical element of Comparative Example 1. FIG. 19 shows the results of simulating the chromaticity transmittance viewing angle of the optical element of Comparative Example 1. Table 3 below is a table summarizing 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 shown in FIG. 19. As shown in FIG. 18, Comparative Example 1 was able to narrow the oblique light at an azimuth angle of 90°-270°, but the region that could be blocked was asymmetrical with respect to the azimuth angle of 90°-270°. In addition, as shown in FIG. 19 and Table 3, a coloring with a mixture of bluish and yellowish was observed at an oblique angle (polar angle of 60°).

[0126] [Table 3]

[0127] Comparative Example 2 Fig. 20 is a cross-sectional schematic diagram of the optical element of Comparative Example 2. Fig. 21 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 2. As shown in Fig. 21, the axial arrangement of each member was the same as that of Example 1. In the optical element 1100B of Comparative Example 2, 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 was 213 nm.

[0128] As shown in FIG. 20, in the first retardation layer 20, the tilt angle of the first anisotropic molecule was hybrid-oriented so that the tilt angle was continuously decreased from the interface between the first retardation layer 20 and the second retardation layer 30 toward the first polarizer 10 side. In the second retardation layer 30, the tilt angle of the second anisotropic molecule was hybrid-oriented so that the tilt angle was continuously increased from the 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 was asymmetric with respect to the interface between the first retardation layer 20 and the second retardation 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 were opposite to each other.

[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 shows the results of simulating the transmittance viewing angle of the optical element of Comparative Example 2. FIG. 23 shows the results of simulating the chromaticity transmittance viewing angle of the optical element of Comparative Example 2. Table 4 below is a table summarizing 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 2 shown in FIG. 23. As shown in FIG. 22, Comparative Example 2 was able to narrow the oblique light at an azimuth angle of 90°-270°, but the region that could be blocked was asymmetrical with respect to the azimuth angle of 90°-270°. In addition, as shown in FIG. 23 and Table 4, a coloring with a mixture of bluish and yellowish was observed at an oblique angle (polar angle of 60°).

[0130] [Table 4]

[0131] Comparative Example 3 Fig. 24 is a cross-sectional schematic diagram of the optical element of Comparative Example 3. Fig. 25 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 3. As shown in Fig. 25, the axial arrangement of each member was the same as in Example 2. In the optical element 1100C of Comparative Example 3, θ1-1=4°, θ2-1=70°, θ1-2=70°, and θ2-2=4° were set, and as shown in Fig. 24, the first anisotropic molecules of the first retardation layer 20 and the second anisotropic molecules of the second retardation layer 30 were hybrid-oriented in the same manner as in Comparative Example 2.

[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 shows the results of simulating the transmittance viewing angle of the optical element of Comparative Example 3. FIG. 27 shows the results of simulating the chromaticity transmittance viewing angle of the optical element of Comparative Example 3. Table 5 below is a table summarizing 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 3 shown in FIG. 27. As shown in FIG. 26, Comparative Example 3 was able to narrow the oblique light at an azimuth angle of 90°-270°, but although the region that could be blocked was improved compared to Comparative Example 1, it was asymmetrical with respect to the azimuth angle of 90°-270°. In addition, as shown in FIG. 27 and Table 5, a coloring with a mixture of bluish and yellowish was observed at an oblique angle (polar angle of 60°).

[0133] [Table 5]

[0134] Comparative Example 4 Fig. 28 is a cross-sectional schematic diagram of the optical element of Comparative Example 4. Fig. 29 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 4. As shown in Fig. 29, the axial arrangement of each member was the same as in Example 2. In the optical element 1100D of Comparative Example 4, θ1-1=4°, θ2-1=70°, θ1-2=70°, and θ2-2=4°, and as shown in Fig. 28, the first anisotropic molecules of the first retardation layer 20 and the second anisotropic molecules of the second retardation layer 30 were hybrid-oriented in the same manner as in Comparative Example 2.

[0135] The transmittance viewing angle and coloring of the optical element of Comparative Example 4 were simulated in the same manner as in Example 1. FIG. 30 shows the results of simulating the transmittance viewing angle of the optical element of Comparative Example 4. FIG. 31 shows the results of simulating the chromaticity transmittance viewing angle of the optical element of Comparative Example 4. Table 6 below is a table summarizing 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 4 shown in FIG. 31. As shown in FIG. 30, Comparative Example 4 was able to narrow the oblique light at an azimuth angle of 90°-270°, which was an improvement over Comparative Example 1, but the light-shielding region was asymmetrical with respect to the azimuth angle of 90°-270°. In addition, as shown in FIG. 31 and Table 6, a coloring with a mixture of bluish and yellowish was observed at an oblique angle (polar angle of 60°).

[0136] [Table 6]

[0137] Comparative Example 5 Fig. 32 is a cross-sectional schematic diagram of the optical element of Comparative Example 5. Fig. 33 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 5. As shown in Fig. 33, the axial arrangement of each member was the same as that of Example 2. In the optical element 1100E of Comparative Example 5, 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 was 213 nm.

[0138] As shown in FIG. 32, in the first retardation layer 20, the tilt angle of the first anisotropic molecule was hybrid-oriented so that the tilt angle continuously decreased from the interface between the first retardation layer 20 and the second retardation layer 30 toward the first polarizer 10 side. In the second retardation layer 30, the tilt angle of the second anisotropic molecule was hybrid-oriented so that the tilt angle continuously decreased from the interface toward the second polarizer 40 side. The tilt angles of the first anisotropic molecule 21 and the second anisotropic molecule 31 were changed symmetrically with respect to the interface between the first retardation layer 20 and the second retardation layer 30, and the direction of change in the tilt angle of the first anisotropic molecule 21 was the same as the direction of change in the tilt angle of the second anisotropic molecule 31.

[0139] The transmittance viewing angle of the optical element of Comparative Example 5 was simulated in the same manner as in Example 1. Fig. 34 shows the results of simulating the transmittance viewing angle of the optical element of Comparative Example 5. Fig. 35 shows the results of simulating the chromaticity transmittance viewing angle of the optical element of Comparative Example 5. As shown in Figs. 34 and 35, Comparative Example 5 was able to narrow down oblique light in the left and right azimuths (azimuth angles of 0°-180°), but was unable to narrow down oblique light at azimuth angles of 90°-270°.

[0140] Comparative Example 6 Fig. 29 is a cross-sectional schematic diagram of the optical element of Comparative Example 6. Fig. 37 is a diagram showing the axial orientation of each member of the optical element of Comparative Example 6. As shown in Fig. 37, the axial arrangement of each member was the same as that of Example 1. In the optical element 1100F of Comparative Example 6, θ1-1=4°, θ2-1=4°, θ1-2=70°, and θ2-2=70°, and as shown in Fig. 36, the first anisotropic molecules of the first retardation layer 20 and the second anisotropic molecules of the second retardation layer 30 were hybrid-oriented in the same manner as in Comparative Example 5.

[0141] The transmittance viewing angle of the optical element of Comparative Example 6 was simulated in the same manner as in Example 1. Fig. 31 shows the results of simulating the transmittance viewing angle of the optical element of Comparative Example 6. Fig. 39 shows the results of simulating the chromaticity transmittance viewing angle of the optical element of Comparative Example 6. As shown in Figs. 38 and 39, Comparative Example 6 has a narrower light blocking range than Example 1, and it is not possible to sufficiently narrow down the transmitted light in the oblique direction (for example, polar angle 60°) in the up and down azimuths (azimuth angles 90°-270°). [Explanation of symbols]

[0142] 1:Display device 10:First polarizer 20: First retardation layer 21: First anisotropic molecule 30:Second retardation layer 31: Second anisotropic molecule 40:Second polarizer 100A, 100B, 1100A, 1100B, 1100C, 1100D, 1100E, 1100F: Optical elements 200: LCD panel 300: Backlight 301: Prism sheet 301a: Prism 301b: Ridgeline 400: Observation side polarizer

Claims

1. A first polarizer, a first retardation layer including first anisotropic molecules, a second retardation layer including second anisotropic molecules, and a second polarizer, in this order, from the observation side; The tilt angle of the first anisotropic molecule located on the first polarizer side of the first retardation layer is θ1-1, the tilt angle of the first anisotropic molecule located on the interface side with the second retardation layer of the first retardation layer is θ1-2, the tilt angle of the second anisotropic molecule located on the second polarizer side of the second retardation layer is θ2-1, and the tilt angle of the second anisotropic molecule located on the interface side with the first retardation layer of the second retardation layer is θ2-2. the θ1-1 is greater than the θ1-2, and the first anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the first retardation layer; the θ2-1 is greater than the θ2-2, and the second anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the second retardation layer; the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel; the slow axis of the first retardation layer and the slow axis of the second retardation layer are parallel to each other, an optical element, wherein a transmission axis of the first polarizer is parallel to a slow axis of the first retardation layer and a slow axis of the second retardation layer.

2. A first polarizer, a first retardation layer including first anisotropic molecules, a second retardation layer including second anisotropic molecules, and a second polarizer, in this order, from the observation side; The tilt angle of the first anisotropic molecule located on the first polarizer side of the first retardation layer is θ1-1, the tilt angle of the first anisotropic molecule located on the interface side with the second retardation layer of the first retardation layer is θ1-2, the tilt angle of the second anisotropic molecule located on the second polarizer side of the second retardation layer is θ2-1, and the tilt angle of the second anisotropic molecule located on the interface side with the first retardation layer of the second retardation layer is θ2-2. the θ1-1 is greater than the θ1-2, and the first anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the first retardation layer; the θ2-1 is greater than the θ2-2, and the second anisotropic molecules are oriented such that the tilt angle changes continuously in the thickness direction of the second retardation layer; the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel; the slow axis of the first retardation layer and the slow axis of the second retardation layer are parallel to each other, an optical element, wherein a transmission axis of the first polarizer is perpendicular to a slow axis of the first retardation layer and a slow axis of the second retardation layer;

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

4. 3. The optical element according to claim 2, wherein the angles θ1-1 and θ2-1 are equal to or greater than 70° and equal to or less than 90°.

5. 3. The optical element according to claim 1, wherein the angles θ1-1 and θ2-1 are equal to or greater than 70° and equal to or less than 80°.

6. 3. The optical element according to claim 1, wherein a difference between the angles θ1-1 and θ2-1 is 3° or less.

7. The first anisotropic molecule and the second anisotropic molecule each have a tilt angle that changes along the thickness direction of the first retardation layer or the thickness direction of the second retardation layer, with the interface between the first retardation layer and the second retardation layer as a plane of symmetry. The optical element according to claim 1 or 2.

8. the first polarizer is an absorptive polarizer or a laminate of an absorptive polarizer and a reflective polarizer, The optical element according to claim 1 , wherein the second polarizer is a reflective polarizer or a laminate of an absorptive polarizer and a reflective polarizer.

9. A liquid crystal panel, the optical element according to claim 1 or 2, and a backlight, in this order; The display device, wherein the optical element is disposed so that the first polarizer faces the liquid crystal panel.

10. 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 a surface on the observation surface side, The display device according to claim 9 , wherein a transmission axis of the first polarizer and a transmission axis of the second polarizer are parallel to or perpendicular to a ridge line of the linear convex portion.

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