Stereoscopic image display device and optical sheet

Abstract

The present invention addresses the problem of providing: a stereoscopic image display device having high display contrast; and an optical sheet capable of attaining high display contrast when used in the stereoscopic image display device. The present invention solves this problem with a configuration in which a lens array, a directional control layer, and a self-luminous image display element are provided in that order. The lens array has one surface having a planar shape and another surface having a curved shape. The directional control layer is disposed on the planar surface side of the lens array. The directional control layer is such that when light is emitted from one surface side, the luminance is the highest in the normal direction of another surface.

Description

Stereoscopic image display device and optical sheet

[0001] The present invention relates to a stereoscopic image display device and an optical sheet used in the stereoscopic image display device.

[0002] 2. Description of the Related Art There is known a stereoscopic image display device that displays a stereoscopic image by combining an image display element such as a liquid crystal display with a lens array such as a lenticular lens and a microlens array.

[0003] For example, Patent Document 1 describes a stereoscopic image display device (three-dimensional image display device) that includes: a display device unit having a display panel that is capable of simultaneously displaying multiple images with parallax, with multiple display pixels that each display the multiple images with parallax as a set, and these display pixel sets being arranged in a matrix; a lenticular lens that is provided on the image light output side of the display panel, with multiple unit lenses that are in the shape of a part of an approximately cylindrical shape or a part of an approximately elliptical cylindrical shape, arranged on the output side surface, and that outputs the image light of the multiple images with parallax in predetermined directions; and a light control sheet that is arranged between the lenticular lens and the display panel, with light-transmitting portions and light-absorbing portions arranged alternately along the arrangement direction of the unit lenses.

[0004] JP 2012-93631 A

[0005] A stereoscopic image display device using such a lens array divides a plurality of images corresponding to the parallax between the left and right eyes according to the lens array, and the divided images are arranged and displayed by the image display device. When an observer views the images through the lens array, the images are reconstructed at the positions of the observer's left and right eyes, and the image is observed as a stereoscopic image. In other words, a stereoscopic image display device using such a lens array and image display element allows an observer to view a stereoscopic image with the naked eye, without using special glasses such as glasses using polarizers.

[0006] However, conventional stereoscopic image display devices that allow stereoscopic images to be viewed with the naked eye do not have sufficient display contrast, and improvements are required.

[0007] The object of the present invention is to solve the problems of the conventional technology and to provide a stereoscopic image display device with high display contrast, and an optical sheet that can improve the display contrast when used in a stereoscopic image display device.

[0008] To achieve these objects, the present invention has the following configuration: [1] A stereoscopic image display device having, in this order, a lens array in which a plurality of lenses are arranged in a plane, a directivity control layer, and a self-luminous image display element, wherein one surface of the lens array is planar and the other surface of the lens array is curved, and the directivity control layer is arranged on the planar surface side of the lens array, and the directivity control layer is selected from the group consisting of an anisotropic absorption layer containing a dichroic material, a diffractive element, a metasurface structure, and a laminate of a polarizer, a retardation layer, and another polarizer, and the directivity control layer is a layer that, when light is irradiated from one surface side of the directivity control layer, has the highest luminance in the normal direction to the other surface of the directivity control layer. [2] The stereoscopic image display device according to [1], wherein the directivity control layer is an anisotropic absorption layer containing a dichroic material, and the transmittance central axis is parallel to the normal direction to the planar surface of the lens array. [3] The stereoscopic image display device according to [2], wherein the anisotropic absorbing layer contains a vertically aligned liquid crystal compound. [4] The stereoscopic image display device according to any one of [1] to [3], wherein the lens array is a lenticular lens. [5] The stereoscopic image display device according to [4], further comprising a polarizer between the image display element and the directivity control layer, wherein the transmission axis of the polarizer is perpendicular to the longitudinal direction of the lenses constituting the lenticular lens. [6] The stereoscopic image display device according to any one of [1] to [3], wherein the lens array is a microlens array. [7] An optical sheet comprising a lens array in which a plurality of lenses are arranged in a plane, and an anisotropic absorbing layer containing a dichroic material, wherein one surface of the lens array is planar and the other surface of the lens array is curved, wherein the anisotropic absorbing layer is disposed on the planar surface side of the lens array, and wherein the transmittance central axis of the anisotropic absorbing layer is parallel to the normal direction of the planar surface of the lens array. [8] The optical sheet according to [7], wherein the anisotropic absorbing layer contains a vertically aligned liquid crystal compound. [9] The optical sheet according to [7] or [8], wherein the lens array is a lenticular lens.

[10] The optical sheet according to [9], further comprising a polarizer on the side of the anisotropic absorbing layer opposite to the lens array side, wherein the transmission axis of the polarizer is perpendicular to the longitudinal direction of the lenses constituting the lenticular lenses.

[11] The optical sheet according to [7] or [8], wherein the lens array is a microlens array.

[0009] According to the present invention, there are provided a stereoscopic image display device with high display contrast, and an optical sheet that can provide high display contrast when used in a stereoscopic image display device.

[0010] FIG. 1 is a conceptual diagram showing an example of a stereoscopic image display device of the present invention. FIG. 2 is a conceptual diagram showing an example of the light-emitting characteristics of a light-emitting element of an image display element. FIG. 3 is a graph showing an example of the light-emitting characteristics of a light-emitting element of an image display element. FIG. 4 is a graph showing a simulation result of the absorption characteristics of an anisotropic absorbing layer. FIG. 5 is a graph showing a simulation result of the light quantity distribution of light transmitted through an anisotropic absorbing layer. FIG. 6 is a conceptual diagram showing another example of a stereoscopic image display device of the present invention. FIG. 7 is a graph showing a simulation result of the light transmittance in a laminate of an anisotropic absorbing layer and a polarizer. FIG. 8 is a graph showing a simulation result of the light quantity distribution of light transmitted through a laminate of an anisotropic absorbing layer and a polarizer.

[0011] The stereoscopic image display device and optical sheet of the present invention will be described in detail below. The following description is based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In addition, all of the figures shown below are conceptual diagrams for explaining the present invention. Therefore, the shape, size, thickness, and positional relationships, such as the placement position and spacing, of each component in each figure do not necessarily match those of the actual device.

[0012] Fig. 1 conceptually shows an example of a stereoscopic image display device of the present invention. The stereoscopic image display device 10 shown in Fig. 1 includes an image display element 12, an anisotropic absorption layer 14, and a microlens array 16, in this order. The anisotropic absorption layer 14 corresponds to the directivity control layer of the present invention. The microlens array 16 corresponds to the lens array of the present invention.

[0013] In the stereoscopic image display device of the present invention, the lens array is a surface arrangement (arrangement) of multiple lenses, one surface of which is planar and the other surface of which has a curved shape. Note that, in the present invention, the term "plane" is not limited to a completely flat surface, but also includes a substantially flat surface, such as a surface having unavoidable irregularities. In the present invention, "one surface of the lens array having a curved shape" means that this surface does not include a vertex where two straight lines intersect, or a ridge where two planes intersect. Specifically, this means that the lenses constituting the lens array are lenses that do not include a vertex like an axicon lens or a ridge like a prism.

[0014] The anisotropic absorbing layer 14 contains a dichroic material, and the transmittance central axis is parallel to the normal direction of the planar surface of the microlens array 16 (lens array). The normal direction is a direction perpendicular to the surface of the sheet-like material (layer, film, plate-like material). The normal line is a line perpendicular to the surface of the sheet-like material. In other words, the combination of the anisotropic absorbing layer 14 and the microlens array 16 (lens array) constitutes the optical sheet of the present invention. Therefore, the stereoscopic image display device 10 shown in FIG. 1 is a stereoscopic image display device of the present invention that uses the optical sheet of the present invention.

[0015] In the stereoscopic image display device of the present invention, in addition to the anisotropic absorption layer 14 shown in the figure, a diffraction element, a metasurface structure, and a laminate of a polarizer, a retardation layer, and another polarizer can also be used as the directivity control layer. This will be described in detail later.

[0016] In the stereoscopic image display device 10 of the present invention, the image display element 12 is a self-luminous image display element. Any known image display element (image display device, display) can be used as the image display element 12 as long as it is a self-luminous image display element. Suitable examples of the image display element include an LED (Light Emitting Diode) display element, a micro LED display element, and an organic EL (Electro Luminescence) display element (OLED (Organic Light Emitting Diode)).

[0017] In the stereoscopic image display device 10 of the present invention, the image display element 12 is a general self-luminous image display element. In the stereoscopic image display device 10, the image display element 12, like the image display element of a known stereoscopic image display device that uses a lens array and that can be viewed with the naked eye, divides and arranges a plurality of images according to the observer's viewpoint according to the microlens array 16 for display. This point is the same even when the stereoscopic image display device of the present invention uses another lens array such as a lenticular lens.

[0018] In the stereoscopic image display device 10 of the present invention, the microlens array 16 can also be any of various known microlens arrays used in stereoscopic image display devices that use lens arrays to display stereoscopic images to the naked eye, as long as one surface is flat and the other surface has a curved shape.

[0019] It should be noted that the lens array in the stereoscopic image display device of the present invention is not limited to the microlens array 16. That is, in the stereoscopic image display device of the present invention, the lens array is a planar arrangement of a plurality of lenses, and various known lens arrays used in stereoscopic image display devices that can be viewed with the naked eye can be used as long as one surface is flat and the other surface has a curved shape as described above. In addition to the microlens array 16 shown in the drawings, examples of such lens arrays include lenticular lenses, fly's eye lenses, and other lenses having spherical crown or semi-cylindrical shapes arranged in a convex structure.

[0020] In the stereoscopic image display device 10 of the present invention, the microlens array 16, i.e., the lens array, is arranged with its planar surface facing the anisotropic absorption layer 14, i.e., the directivity control layer. That is, the microlens array 16 is arranged with its planar surface facing the image display element 12. In other words, the anisotropic absorption layer 14 is provided on the planar surface side of the microlens array 16.

[0021] The stereoscopic image display device of the present invention has a lens array, a directivity control layer, and an image display element, in this order. Therefore, in the stereoscopic image display device 10 of the present invention, an anisotropic absorption layer 14 is provided between the image display element 12 and the microlens array 16. That is, in the stereoscopic image display device 10, an image displayed by the image display element 12 passes through the anisotropic absorption layer 14 and enters the microlens array 16, where it is refracted and observed by the viewer as a stereoscopic image.

[0022] Here, the anisotropic absorption layer 14 is the directivity control layer of the present invention, and is a layer containing a dichroic material, whose transmittance central axis is parallel to the normal direction of the planar surface of the microlens array 16 (lens array). Note that, in the present invention, "parallel to the normal direction of the planar surface of the microlens array 16" not only means completely parallel to the normal direction of this planar surface, but also includes an angle range of ±5° with respect to the normal direction of the planar surface. In this regard, the same applies to expressions such as the normal direction of the directivity control layer and the main surfaces of components being parallel to each other.

[0023] In the present invention, the directivity control layer is a layer in which, when light is irradiated from one surface of the directivity control layer, the luminance is highest in the normal direction of the other surface of the directivity control layer. Specifically, the directivity control layer is a layer in which, when light is irradiated from one surface of the layer in various directions by changing the polar angle and azimuthal angle, the luminance of light that passes through and exits from the other surface of the layer is highest in the normal direction. As described above, in the present invention, the normal direction not only refers to a direction that is completely coincident with the normal to the main surface, i.e., a direction (a line perpendicular to the main surface) that is completely perpendicular to the main surface, but also includes an angle range of ±5° with respect to the normal to the main surface. That is, the directivity control layer transmits light that is incident from the normal direction to the main surface as is. In contrast, the directivity control layer absorbs light that is incident at an angle with respect to the normal direction to the main surface, or changes the optical path of the light to light that is parallel to the normal direction to the main surface and then emits the light. The main surface is the largest surface of a sheet-like material (film, plate, layer), and usually refers to both surfaces in the thickness direction of the sheet-like material.

[0024] As described above, the anisotropic absorbing layer 14 is a directivity control layer containing a dichroic material and having a transmittance central axis parallel to the normal to the planar surface of the microlens array 16. In the present invention, the transmittance central axis is the direction in which the transmittance is highest when the transmittance is measured in various directions from the surface of the layer by changing the polar angle and azimuthal angle. The anisotropic absorbing layer 14, whose transmittance central axis is parallel to the normal to the planar surface of the microlens array 16, transmits light incident from the normal to the planar surface of the microlens array 16 as is and absorbs light incident from a direction inclined relative to the normal, i.e., from an oblique direction. In the stereoscopic image display device 10 of the present invention, the anisotropic absorbing layer 14 is typically disposed with its principal surface parallel to the planar surface of the microlens array 16. Therefore, in the stereoscopic image display device 10, the normal to the planar surface of the microlens array 16 and the normal to the principal surface of the anisotropic absorbing layer 14 coincide with each other. In the following description, the normal direction to the planar surface of the microlens array 16 and the normal direction to the main surface of the anisotropic absorbing layer 14 will also be simply referred to as the "normal direction."

[0025] That is, the stereoscopic image display device 10 converts the light of an image displayed by the self-luminous image display element 12 into light that travels in the normal direction (approximately the normal direction) by the anisotropic absorption layer 14, and displays a stereoscopic image by causing this light traveling in the normal direction to be incident on the microlens array 16. The stereoscopic image display device 10 of the present invention is a stereoscopic image display device that uses a microlens array 16 (lens array) and allows stereoscopic images to be viewed with the naked eye, and by having such an anisotropic absorption layer 14 (directivity control layer) between the microlens array 16 and the image display element 12, the display contrast of the stereoscopic image is improved.

[0026] The illustrated stereoscopic image display device 10 uses a microlens array 16 and is a so-called light field display. In such a stereoscopic image display device, a lens array, such as a microlens array, is provided between the image display element and the viewer, so that the image on the image display element is rearranged depending on the viewing angle, and the collection of images from each lens in the microlens array reconstructs the original image at the viewing point. By arranging the images on the image display element so that the reconstructed images at the respective positions of the viewer's left and right eyes reproduce the left-right parallax for the viewer, the viewer can experience a stereoscopic image display without using the naked eye. This is also true for stereoscopic image display devices that use lens arrays, such as lenticular lenses.

[0027] As mentioned above, the microlens array 16 can be a known microlens array used for stereoscopic image display. Therefore, the shape of the microlens array (lens array) can take various forms depending on the resolution of the image display element used, the pixel structure, and the image quality of the image to be displayed. For simplicity, a microlens array in which simple spherical plano-convex lenses are arranged will be described as an example. However, the scope of the present invention is not necessarily limited to this. For example, plano-concave lenses may be used instead of the plano-convex lens shape. Furthermore, the lenses may be aspherical instead of spherical.

[0028] When a plano-convex lens is used with its flat surface facing the image display element, it is preferable that light rays entering the lens from the image display element side be parallel to the optical axis of the lens. However, it is known that the light intensity distribution of individual pixels constituting an actual image display element, particularly individual pixels constituting a self-luminous display device, which is advantageous in terms of power consumption, has a certain degree of angular spread, even when an ideal point light source is assumed. Note that each pixel constituting an image display element is, for example, a single light-emitting point (point light source). Therefore, among the light intensity distribution of light emitted by a point light source, light emitted from the light-emitting point at an emission angle greater than a certain degree becomes stray light that does not form an image in the observer's pupil, thereby reducing the contrast of the displayed image. In other words, such stray light is emitted from the lenses constituting the lens array as light unrelated to the image and is perceived as background light distributed throughout the observer's field of view, and the greater the amount of light, the lower the display contrast.

[0029] The stereoscopic image display device of the present invention can reduce stray light components by providing a directivity control layer between the image display element and the lens array. As described above, the stereoscopic image display device 10 of the illustrated example reduces stray light components by providing an anisotropic absorption layer 14 as a directivity control layer between the image display element 12 and the microlens array 16. The stereoscopic image display device of the present invention has, as the directivity control layer, one or more selected from the anisotropic absorption layer 14 of the illustrated example, a diffraction element, a metasurface structure, and a laminate of a polarizer, a retardation layer, and a polarizer. That is, the stereoscopic image display device of the present invention has, as the directivity control layer, a superfine structure or a diffraction-type light path control element, and a directivity control layer using angle-selective reflection or absorption on a flat plate. This eliminates the need for precise alignment between the directivity control layer and the light-emitting elements (pixels) of the image display element, thereby achieving the desired stray light removal effect and improving contrast. In particular, when a high-resolution image display element exceeding 100 ppi is used to enable the display of a three-dimensional image that provides a natural three-dimensional effect, any misalignment affects the display contrast, making it essential to use the above-mentioned directivity control layer.

[0030] In order for a stereoscopic image display device to display a stereoscopic image that provides a natural sense of three-dimensionality, an angular resolution of approximately half the interpupillary distance of a human eye is required. The average interpupillary distance is approximately 5 cm. Therefore, assuming use at a distance of approximately 1 m from the stereoscopic image display device, each pixel (light-emitting point) on the image display element only needs to be repositioned within an angular range of approximately 1.5°. As an example, if a microlens array is used, in which a material with a refractive index of 1.6 is used and multiple lenses with a curvature radius of 1 mm and an outer diameter of 0.8 mm are arranged, the calculated spacing between light emitted from adjacent pixels (light-emitting points) to achieve such a configuration would be approximately 0.02 mm. Assuming that the light-emitting elements constituting each pixel are point light sources, light emitted at angles beyond this angular range will enter the range of light emitted by adjacent pixels that forms an image at the observer's pupil, resulting in stray light that reduces the display contrast as described above. Therefore, it is preferable to set a cone with the base diameter equal to the above-mentioned spacing (0.02 μm) and the height equal to the distance from the light-emitting element to the lens, and to remove light outside this cone. Furthermore, assuming that the distance from the light emitting element to the plane defined by the lens outer diameter is 0.4 mm, it is preferable to remove light outside the range of ±2.5° with respect to the direction parallel to the optical axis of the lens. In other words, the plane defined by the lens outer diameter is the planar surface of the microlens array.

[0031] For example, let us consider a micro LED display element as the image display element, and assume that the light intensity distribution from the bare chip of the light-emitting element is a uniform diffusion type light intensity distribution from a point light source, as shown in Figures 2 and 3. In this case, more than 90% of the light emitted from the light-emitting element becomes stray light, reducing the display contrast. In contrast, we simulate a case where an anisotropic absorbing layer is provided, containing a dichroic dye and having its transmittance central axis aligned with the normal direction, i.e., the normal direction to the planar surface of the lens array (the normal direction to the main layer surface) as described above. As an example, the transmittance of the anisotropic absorbing layer with respect to the angle of incidence of light within an arbitrary cross section of the anisotropic absorbing layer is shown in Figure 4. When such an anisotropic absorbing layer is disposed on the image display surface side (light exit surface side) of the image display element, the light intensity distribution of light emitted from the light-emitting element having the light intensity distribution shown in Figures 2 and 3 is changed to that shown in Figure 5. As a result, the amount of stray light can be reduced to approximately 60% of the light emitted from the bare chip.

[0032] That is, according to the stereoscopic image display device 10 of the present invention, light emitted from each pixel (light-emitting element / light-emitting point) of the self-luminous image display element 12 and entering the range of adjacent pixels as stray light is absorbed by the anisotropic absorption layer 14, and light traveling in the normal direction that forms an image at the observer's pupil can be selectively incident on the microlens array 16. As a result, the stereoscopic image display device 10 of the present invention can suppress a decrease in display contrast caused by stray light and display a stereoscopic image with high display contrast.

[0033] In the stereoscopic image display device 10 of the present invention, the anisotropic absorbing layer 14 contains a dichroic material, and the transmittance central axis is parallel to the normal direction. As described above, the main surface of the anisotropic absorbing layer 14 is parallel to the planar surface of the microlens array 16. Therefore, the anisotropic absorbing layer 14 may be, for example, a layer in which the dichroic material is oriented perpendicular to the main surface of the layer.

[0034] In the present invention, the dichroic material means a dye whose absorbance varies depending on the direction. The dichroic material may or may not exhibit liquid crystallinity.

[0035] The dichroic substance is not particularly limited, and examples thereof include visible light absorbing substances (dichroic dyes), luminescent substances (fluorescent substances, phosphorescent substances), ultraviolet absorbing substances, infrared absorbing substances, nonlinear optical substances, carbon nanotubes, and inorganic substances (e.g., quantum rods), and any conventionally known dichroic substance (dichroic dye) can be used. Specifically, for example, paragraphs

[0067] to

[0071] of JP 2013-228706 A, paragraphs

[0008] to

[0026] of JP 2013-227532 A, paragraphs

[0008] to

[0015] of JP 2013-209367 A, paragraphs

[0045] to

[0058] of JP 2013-14883 A, paragraphs

[0012] to

[0029] of JP 2013-109090 A, paragraphs

[0009] to

[0017] of JP 2013-101328 A, Paragraphs

[0051] to

[0065] of JP 2013-37353 A, paragraphs

[0049] to

[0073] of JP 2012-63387 A, paragraphs

[0016] to

[0018] of JP 11-305036 A, paragraphs

[0009] to

[0011] of JP 2001-133630 A, paragraphs

[0030] to

[0169] of JP 2011-215337 A, paragraphs

[0021] to

[0075] of JP 2010-106242 A, paragraphs

[0016] to

[0018] of JP 2010-215846 A Paragraphs

[0011] to

[0025] , paragraphs

[0017] to

[0069] of JP 2011-048311 A, paragraphs

[0013] to

[0133] of JP 2011-213610 A, paragraphs

[0074] to

[0246] of JP 2011-237513 A, paragraphs

[0005] to

[0051] of JP 2016-006502 A, paragraphs

[0014] to

[0032] of JP 2018-053167 A, paragraphs

[0014] to

[0033] of JP 2020-11716 A paragraphs

[0005] to

[0041] of International Publication No. 2016 / 060173, paragraphs

[0008] to

[0062] of International Publication No. 2016 / 136561, paragraphs

[0014] to

[0033] of International Publication No. 2017 / 154835, paragraphs

[0014] to

[0033] of International Publication No. 2017 / 154695, paragraphs

[0013] to

[0037] of International Publication No. 2017 / 195833, paragraphs

[0014] to

[0034] of International Publication No. 2018 / 164252,Examples include those described in paragraphs

[0021] to

[0030] of International Publication No. 2018 / 186503, paragraphs

[0043] to

[0063] of International Publication No. 2019 / 189345, paragraphs

[0043] to

[0085] of International Publication No. 2019 / 225468, paragraphs

[0050] to

[0074] of International Publication No. 2020 / 004106, and paragraphs

[0015] to

[0038] of International Publication No. 2021 / 044843.

[0036] In the present invention, two or more dichroic substances may be used in combination. For example, from the viewpoint of making the anisotropic absorption layer 14 closer to black, it is preferable to use in combination at least one dichroic substance having a maximum absorption wavelength in the wavelength range of 370 to 550 nm and at least one dichroic substance having a maximum absorption wavelength in the wavelength range of 500 to 700 nm.

[0037] The method for forming the anisotropic absorbing layer 14 is not particularly limited, and various known methods capable of aligning the dichroic material perpendicular to the major surface of the layer can be used. One example is a method using a liquid crystal composition containing a liquid crystal compound together with the dichroic material described above, from the viewpoint of aligning the dichroic material with a high degree of alignment. In the present invention, the liquid crystal compound is a liquid crystal compound that does not exhibit dichroism. While both low-molecular-weight and high-molecular-weight liquid crystal compounds can be used as the liquid crystal compound, high-molecular-weight liquid crystal compounds are preferred because they can achieve a high degree of alignment. Here, "low-molecular-weight liquid crystal compound" refers to a liquid crystal compound that does not have a repeating unit in its chemical structure. Furthermore, "high-molecular-weight liquid crystal compound" refers to a liquid crystal compound that has a repeating unit in its chemical structure. Examples of low-molecular-weight liquid crystal compounds include the liquid crystal compounds described in JP 2013-228706 A. Examples of high-molecular-weight liquid crystal compounds include the thermotropic liquid crystal polymers described in JP 2011-237513 A. The polymer liquid crystal compound may have a crosslinkable group (e.g., an acryloyl group or a methacryloyl group) at its terminal. The liquid crystal compound may be used alone or in combination of two or more. The liquid crystal compound preferably contains a polymer liquid crystal compound, since this provides a superior degree of alignment of the anisotropic absorption layer 14. The liquid crystal composition may also contain a solvent, a polymerization initiator, an interfacial improver, an alignment agent, and other components.

[0038] Such an anisotropic absorption layer 14 may be formed by a known method. For example, when forming an anisotropic absorption layer 14 using a liquid crystal composition, the liquid crystal composition is first applied to an alignment film to which an alignment property of the liquid crystal compound has been imparted. Next, the liquid crystal composition is heated and / or cooled, or heating and cooling are repeated, thereby aligning the liquid crystal compound in the thickness direction. This alignment of the liquid crystal compound also aligns the dichroic material in the thickness direction. Thereafter, if necessary, the liquid crystal layer is cured by irradiation with ultraviolet light or the like, thereby forming an anisotropic absorption layer 14 in which the dichroic material is oriented in the thickness direction.

[0039] As described above, in the stereoscopic image display device of the present invention, a lenticular lens can also be suitably used as the lens array. As described above, various known lenticular lenses used for displaying stereoscopic images with the naked eye can be used.

[0040] Here, as conceptually shown in Figure 6, when a lenticular lens 20 is used as the lens array, it is preferable to provide a polarizer 24 between the image display element 12 and the anisotropic absorption layer 14. Note that in Figure 6, only two lenses constituting the lenticular lens 20 are shown to simplify the drawing and make the configuration of the present invention easier to understand. However, as is well known, a lenticular lens is actually made up of a large number of long lenses arranged in a direction perpendicular to their longitudinal direction. In this case, the polarizer 24 is arranged with its transmission axis 24a perpendicular to the longitudinal direction of the lenses (cylindrical lenses) constituting the lenticular lens. In other words, this polarizer 24 blocks linearly polarized light in the longitudinal direction of the lenses constituting the lenticular lens.

[0041] As described above, the anisotropic absorbing layer 14 contains a dichroic material and has a transmittance central axis in the normal direction. That is, the anisotropic absorbing layer 14 is formed by aligning a layer of the dichroic material perpendicular to the principal surface. Such an anisotropic absorbing layer 14 transmits light incident in the normal direction and absorbs light incident in a direction inclined relative to the normal, i.e., from an oblique direction. Here, the anisotropic absorbing layer 14 can effectively absorb linearly polarized light normal to the principal surface among light incident from an oblique direction, but has low absorption rate for linearly polarized light perpendicular to the normal. In other words, the anisotropic absorbing layer 14 can effectively absorb linearly polarized light in the orientation direction of the dichroic material among light incident from an oblique direction, but has low absorption rate for linearly polarized light perpendicular to the orientation direction of the dichroic material. That is, the anisotropic absorption layer 14 preferably absorbs linearly polarized light that is incident from an oblique direction and that is perpendicular to the longitudinal direction of the lenses that make up the lenticular lens, but has a low absorption rate for linearly polarized light that is in the longitudinal direction of the lenses that make up the lenticular lens.

[0042] In contrast, as shown in Fig. 6, when a lenticular lens 20 is used as the lens array, it is preferable to provide a polarizer 24 between the image display element 12 and the anisotropic absorption layer 14, with its transmission axis 24a oriented orthogonal to the longitudinal direction of the lenses constituting the lenticular lens 20. This allows the polarizer 24 to block, i.e., remove in advance, linearly polarized light in the longitudinal direction of the lenses constituting the lenticular lens 20, which has a low absorption rate by the anisotropic absorption layer 14, from among the light obliquely incident on the anisotropic absorption layer 14, and to allow only the obliquely incident light linearly polarized in the orthogonal direction to be incident on the anisotropic absorption layer 14. As a result, the stereoscopic image display device shown in Fig. 6 further reduces light that enters the range of adjacent pixels as stray light, more suitably suppresses a decrease in display contrast due to stray light, and can display a stereoscopic image with high display contrast.

[0043] The following shows the results of a simulation in which a polarizer 24 is provided between the anisotropic absorbing layer 14 and the image display element 12. As shown in FIG. 6 , when the polarizer 24 is provided between the anisotropic absorbing layer 14 and the image display element 12 with its transmission axis 24 a aligned perpendicular to the longitudinal direction of the lens, the transmittance of the laminate of the polarizer and the anisotropic absorbing layer versus the angle of incidence of light is as shown in FIG. 7 . This laminate changes the light intensity distribution of light emitted from the light-emitting element having the light intensity distribution shown in FIG. 3 as shown in FIG. 8 . This reduces the amount of stray light to about 20% compared to when light is directly incident on the lenticular lens 20 from the light-emitting element. This result indicates that in a stereoscopic image display device using a lenticular lens 20 as a lens array and an anisotropic absorbing layer 14 as a directivity control layer, a particularly favorable effect of improving display contrast can be achieved by arranging the polarizer 24 so that the longitudinal direction of the lenses constituting the lenticular lens 20 is perpendicular to the direction of the transmission axis 24 a.

[0044] For example, even when the light emitting element is a surface-emitting type, such as an OLED display element, if a high-resolution display element exceeding 100 ppi is used, the light emitting element is small enough that it can be treated as a pseudo-point light source, even if it is a surface-emitting type such as an OLED, and therefore the same effect as described above can be obtained.

[0045] Various known linear polarizers (linear polarizing plates) can be used as the polarizer 24. Therefore, the polarizer 24 may be either a reflective type or an absorptive type. Examples of the polarizer 24 include an iodine-based polarizer, a dye-based polarizer using a dichroic dye, a polyene-based polarizer, a wire grid polarizer, and a film obtained by stretching a dielectric multilayer film as described in JP 2011-053705 A, etc.

[0046] As described above, in the stereoscopic image display device of the present invention, the directivity control layer may be a diffraction element, a metasurface structure, or a laminate of a polarizer, a retardation layer, and another polarizer, in addition to the anisotropic absorption layer 14 containing a dichroic material shown in Figures 1 and 6. Note that a plurality of these directivity control layers may be used in combination as necessary.

[0047] Specifically, the diffraction element that serves as the directivity control layer may be a diffraction element that uses diffraction to diffract light components that make large angles with respect to the optical axis, so that the light components are directed in the optical axis direction, i.e., normal direction. Examples of such diffraction elements include diffraction elements that are composed of a surface relief hologram, a volume hologram, and a liquid crystal diffraction element.

[0048] Furthermore, a transmissive metasurface structure that changes the direction of light incident at an angle to the normal direction to the normal direction can also be used as the directivity control layer. Various known metasurface structures can be used, each consisting of an array of microstructures corresponding to the wavelength of the three-dimensional image to be displayed. Such metasurface structures can be designed using known methods according to the transmission characteristics of the target light (electromagnetic waves). As an example, the amplitude and phase of light passing through the microstructures used can be calculated using commercially available simulation software, and the arrangement of the microstructures can be set to achieve the desired distribution of phase modulation (refractive index).

[0049] Furthermore, as the directivity control layer, a laminate having a polarizer, a retardation layer, and a polarizer in this order, with the transmission axes of the polarizers arranged parallel or orthogonal to each other, can be used. More specifically, a laminate having a polarizer, a λ / 2 wave plate, and a polarizer in this order, with the transmission axes of the polarizers being orthogonal to each other, and the λ / 2 plate being arranged at 45° to the transmission axes of each polarizer, and having negative biaxiality (nx>ny>nz) can be exemplified. In this laminate, as an example, light incident from the normal direction is transmitted only as P-polarized light by the first polarizer, and the P-polarized light is converted to S-polarized light by the λ / 2 plate, and the S-polarized light is transmitted by the second polarizer. On the other hand, the larger the polar angle of light incident from an oblique direction, the more phase change is added by the retardation Rth in the thickness direction of the λ / 2 plate, so that the light becomes elliptically polarized, and the transmittance of the second polarizer decreases. As a result, the transmitted light is mainly light in the normal direction, and the directionality of the light can be controlled. In other words, the polar angle is the angle with respect to the normal. The larger the λ / 2 thickness retardation Rth, the greater the angular selectivity that can be exhibited. The λ / 2 plate may be hybrid-oriented. In this laminate, various known polarizers and retardation layers can be used. The polarizer may be either an absorptive or reflective type. In this laminate, the polarizer, retardation layer, and polarizer may be laminated via other layers as long as they are arranged in this order, or they may be bonded to form a laminate structure.

[0050] 1 and 6 is more preferably used as the directivity control layer, in that it can suitably absorb and remove light that is angled with respect to the normal direction from the light emitted from the image display elements 12 (light-emitting elements), it can relatively increase the transmittance of light in the normal direction, thereby improving light utilization efficiency, and it requires fewer layers, thereby reducing interfacial reflection, etc. That is, in the stereoscopic image display device of the present invention, the optical sheet of the present invention is suitably used, which has a lens array and an anisotropic absorbing layer that contains a dichroic dye, one surface of the lens array is planar and the other surface is curved, the anisotropic absorbing layer is disposed on the planar surface side of the lens array, and the transmittance central axis of the anisotropic absorbing layer is parallel to the normal direction of the planar surface of the lens array.

[0051] The above describes in detail the stereoscopic image display device and optical sheet of the present invention, but the present invention is not limited to the above examples, and various improvements and modifications may be made within the scope of the gist of the present invention.

[0052] The present invention can be suitably used in head-mounted displays such as VR (Virtual Reality) goggles.

[0053] REFERENCE SIGNS LIST 10 stereoscopic image display device 12 image display element 14 anisotropic absorption layer 16 microlens array 20 lenticular lens 24 polarizer

Claims

1. A stereoscopic image display device having, in this order, a lens array in which a number of lenses are arranged in a plane, a directivity control layer, and a self-luminous image display element, wherein one surface of the lens array is planar and the other surface of the lens array has a curved shape, the directivity control layer is arranged on the planar surface side of the lens array, and the directivity control layer is selected from the group consisting of an anisotropic absorption layer containing a dichroic material, a diffraction element, a metasurface structure, and a laminate of a polarizer, a phase difference layer, and a polarizer, and the directivity control layer is a layer that has the highest brightness in the normal direction of the other surface of the directivity control layer when light is irradiated from one surface side of the directivity control layer.

2. The stereoscopic image display device according to claim 1, wherein the directivity control layer is an anisotropic absorption layer containing the dichroic material, and the central axis of transmittance is parallel to the normal direction of the planar surface of the lens array.

3. The stereoscopic image display device of claim 2, wherein said anisotropic absorbing layer comprises a vertically aligned liquid crystal compound.

4. The stereoscopic image display device according to claim 1 or 2, wherein the lens array is a lenticular lens.

5. The stereoscopic image display device according to claim 4, further comprising a polarizer between said image display element and said directivity control layer, the transmission axis of said polarizer being perpendicular to the longitudinal direction of the lenses constituting said lenticular lens.

6. The stereoscopic image display device according to claim 1 or 2, wherein the lens array is a microlens array.

7. An optical sheet comprising a lens array having a plurality of lenses arranged in a plane, and an anisotropic absorbing layer containing a dichroic material, wherein one surface of the lens array is planar and the other surface of the lens array has a curved shape, the anisotropic absorbing layer is arranged on the planar surface side of the lens array, and the central axis of transmittance of the anisotropic absorbing layer is parallel to the normal direction of the planar surface of the lens array.

8. The optical sheet of claim 7, wherein the anisotropic absorbing layer comprises a homeotropically aligned liquid crystal compound.

9. The optical sheet according to claim 7 or 8, wherein the lens array is a lenticular lens.

10. The optical sheet according to claim 9, further comprising a polarizer on the side of said anisotropic absorbing layer opposite said lens array, said polarizer having a transmission axis perpendicular to the longitudinal direction of the lenses constituting said lenticular lens.

11. The optical sheet according to claim 7 or 8, wherein the lens array is a microlens array.

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