Optical structure, polarizing plate with optical structure, and display device

Abstract

To provide an optical structure that sufficiently condenses light for display image formation by using two prism sheets.SOLUTION: An optical structure according to an embodiment comprises: a first prism sheet in which a plurality of first prism parts is arranged and the first prism parts linearly extend in a direction intersecting the direction in which the first prism parts are arranged; and a second prism sheet in which a plurality of second prism parts is arranged and the second prism parts linearly extend in a direction intersecting the direction in which the second prism parts are arranged. A cross-sectional shape of the first and second prism parts is a triangular shape. The second prism sheet is arranged on vertex angles of the first prism parts so that the vertex angles of the first prism parts and the vertex angles of the second prism parts are directed in a same direction, and a direction in which the first prism parts linearly extend and a direction in which the second prism parts linearly extend are not in parallel to each other. The first and second prism parts have refractive indices of 1.475 or more and less than 1.725, respectively, and the first and second prism parts have vertical angles of 96 degrees or more and 108 degrees of less, respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical structure that exerts an optical effect on light for forming a display image, and also to a polarizing plate and a display device that include the optical structure. [Background technology]

[0002] Liquid crystal display devices, which are an example of display devices, are used in various fields. Liquid crystal panels of liquid crystal display devices are roughly classified into TN (Twisted Nematic) type, VA (Vertical Alignment) type, and IPS (In-Plane Switching) type.

[0003] In a liquid crystal display device, light from a backlight such as a surface light source device is incident on a liquid crystal panel, and the liquid crystal panel switches between transmitting and blocking the light and adjusts the light transmittance to adjust the color and gradation of the image.

[0004] For example, in a VA LCD panel, black is displayed when the voltage applied to the liquid crystal molecules is off. In other words, black is displayed by blocking the light from the backlight when the voltage is off. In a VA LCD panel, very little light leaks from the part that displays black toward the front, which allows for a very high contrast ratio when viewed from the front.

[0005] In such a VA type liquid crystal panel, the contrast ratio can be improved as the light from the backlight is concentrated in a range closer to perpendicular to the liquid crystal panel. Therefore, in liquid crystal display devices equipped with a VA type liquid crystal panel, a collimator is sometimes provided between the backlight and the liquid crystal panel. Various technologies related to such collimators have been proposed in the past (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2008-197752 A Summary of the Invention [Problem to be solved by the invention]

[0007] A collimator for a typical liquid crystal display device is constructed by laminating multiple optical sheets that control the direction of light. In a collimator constructed in this way, the more the number of optical sheets is increased, the more the light-collecting performance can be improved.

[0008] However, an increase in the number of optical sheets constituting the collimator may lead to an increase in the thickness of the collimator and an increase in manufacturing costs. It may also lead to a decrease in the brightness of the liquid crystal display device due to a decrease in light transmittance. In liquid crystal display devices that are generally required to be thin, low-cost, and power-saving, it is desirable to avoid an increase in the thickness and manufacturing costs of the collimator and a decrease in light transmittance.

[0009] Optical sheets that make up a collimator include prism sheets and louver sheets. Prism sheets generally produce side lobes, which can reduce light-collecting performance. On the other hand, when a louver sheet is placed on a prism sheet, it can improve light-collecting performance by absorbing the side lobes or reflecting them to a lower angle, but it can affect brightness because it absorbs some light. Prism sheets usually allow light to pass through overall, which is beneficial in terms of brightness.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an optical structure that can achieve high contrast and high brightness of a display image while suppressing an increase in the thickness of the display device by sufficiently concentrating light for forming a display image using two prism sheets, and a polarizing plate with an optical structure and a display device that include the same. [Means for solving the problem]

[0011] The optical structure of the present invention comprises a first prism sheet on which a plurality of first prism portions are arranged, the first prism portions extending linearly in a direction intersecting a direction in which the first prism portions are arranged, and a second prism sheet on which a plurality of second prism portions are arranged, the second prism portions extending linearly in a direction intersecting a direction in which the second prism portions are arranged, wherein the cross-sectional shapes of the first prism portions and the second prism portions are triangular, the second prism sheet is disposed on the apex angles of the first prism portions so that the apex angles of the first prism portions and the apex angles of the second prism portions face in the same direction, the linear extension direction of the first prism portions and the linear extension direction of the second prism portions are non-parallel, the refractive index of the first prism portions and the refractive index of the second prism portions are each 1.475 or more and less than 1.725, and the apex angle of the first prism portions and the apex angle of the second prism portions are each 96 degrees or more and 108 degrees or less.

[0012] The first prism sheet and the second prism sheet may be arranged such that a direction in which the first prism portions extend linearly and a direction in which the second prism portions extend linearly form an angle of 80 degrees or more and 100 degrees or less.

[0013] The first prism portion may have a refractive index of 1.475 or greater and less than 1.525, the second prism portion may have a refractive index of 1.625 or greater and less than 1.725, the first prism portion may have an apex angle of 100 degrees or greater and 108 degrees or less, and the second prism portion may have an apex angle of 96 degrees or greater and 104 degrees or less.

[0014] The refractive index of the first prism portion may be greater than or equal to 1.525 and less than 1.575, the refractive index of the second prism portion may be greater than or equal to 1.475 and less than 1.575, the apex angle of the first prism portion may be greater than or equal to 96 degrees and less than 100 degrees, and the apex angle of the second prism portion may be greater than or equal to 96 degrees and less than 100 degrees.

[0015] The refractive index of the first prism portion may be greater than or equal to 1.525 and less than 1.575, the refractive index of the second prism portion may be greater than or equal to 1.575 and less than 1.625, the apex angle of the first prism portion may be greater than or equal to 96 degrees and less than or equal to 100 degrees, and the apex angle of the second prism portion may be greater than or equal to 100 degrees and less than or equal to 108 degrees.

[0016] The first prism portion may have a refractive index of not less than 1.525 and less than 1.575, and the second prism portion may have a refractive index of not less than 1.625 and less than 1.725.

[0017] The first prism portion may have a refractive index of not less than 1.575 and less than 1.625. In this case, the second prism portion may have a refractive index of not less than 1.475 and less than 1.525, the first prism portion may have an apex angle of not less than 96 degrees and not more than 104 degrees, and the second prism portion may have an apex angle of not less than 96 degrees and not more than 100 degrees. The second prism portion may have a refractive index of not less than 1.525 and not more than 1.725, the first prism portion may have an apex angle of not less than 96 degrees and not more than 104 degrees, and the second prism portion may have an apex angle of not less than 100 degrees and not more than 108 degrees.

[0018] The first prism portion may have a refractive index of not less than 1.625 and less than 1.675, and the second prism portion may have a refractive index of not less than 1.475 and less than 1.625. In this case, the apex angle of the first prism portion may be equal to or greater than 96 degrees and equal to or less than 104 degrees.

[0019] The refractive index of the first prism portion may be greater than or equal to 1.625 and less than 1.675, the refractive index of the second prism portion may be greater than or equal to 1.625 and less than 1.725, the apex angle of the first prism portion may be greater than or equal to 100 degrees and less than or equal to 108 degrees, and the apex angle of the second prism portion may be greater than or equal to 104 degrees and less than or equal to 108 degrees.

[0020] The first prism portion may have a refractive index of 1.675 or greater and less than 1.725, the second prism portion may have a refractive index of 1.475 or greater and less than 1.625, the first prism portion may have an apex angle of 96 degrees or greater and 104 degrees or less, and the second prism portion may have an apex angle of 96 degrees or greater and 104 degrees or less.

[0021] The first prism portion may have a refractive index of 1.675 or greater and less than 1.725, the second prism portion may have a refractive index of 1.625 or greater and less than 1.725, the first prism portion may have an apex angle of 104 degrees or greater and 108 degrees or less, and the second prism portion may have an apex angle of 108 degrees.

[0022] Further, the polarizing plate with an optical structure according to the present invention is a polarizing plate with an optical structure in which the optical structure and a polarizing plate are integrated together.

[0023] Further, a display device according to the present invention is a display device in which the optical structure is disposed between a surface light source device and a liquid crystal panel.

[0024] The liquid crystal panel may be a VA type liquid crystal panel configured such that when the voltage applied to the liquid crystal molecules is off or at a minimum value, the liquid crystal molecules are oriented along the normal direction of the liquid crystal panel, thereby blocking light from the surface light source device, and the voltage applied to the liquid crystal molecules is gradually increased to gradually tilt the liquid crystal molecules toward the liquid crystal panel, thereby gradually increasing the transmittance of light from the surface light source device. The display device may further include a view angle control sheet on the liquid crystal panel. Effect of the Invention

[0025] According to the present invention, the light for forming a display image is sufficiently condensed by two prism sheets, thereby making it possible to realize high contrast and high brightness of a display image while suppressing an increase in the thickness of the display device. [Brief description of the drawings]

[0026] [Figure 1] 1 is a perspective view showing a schematic layer structure of a display device including an optical structure according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3]2 is a diagram showing the positional relationship between a first prism sheet and a second prism sheet which constitute an optical structure in the display device shown in FIG. [Figure 4A] 1. FIG. 4 is a diagram showing an example of a graph of the luminance of light transmitted through a first prism sheet and a second prism sheet (optical structure) from a surface light source device constituting the display device shown in FIG. [Figure 4B] 2 is a diagram showing an example of an angular distribution of light transmitted through a first prism sheet and a second prism sheet (optical structure) from a surface light source device constituting the display device shown in FIG. [Figure 5A] FIG. 1 is a graph showing the luminance of light transmitted through two typical prism sheets. [Figure 5B] FIG. 5B shows the angular distribution of light, corresponding to FIG. 5A. [Figure 6] FIG. 2 is a diagram showing a table showing the relationship between the apex angle and the refractive index of each prism portion of the first and second prism sheets constituting the optical structure according to the present invention, and the light collecting performance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0028] In this specification, the terms "sheet", "film", "plate", etc. are not distinguished from each other based only on the difference in name. Therefore, for example, "sheet" is a concept that includes members that can also be called films and plates. In addition, in this specification, "sheet surface (plate surface, film surface)" refers to a surface that coincides with the planar direction (surface direction) of the target sheet-like member when the target sheet-like member is viewed overall and in a global perspective. In addition, "sheet surface (plate surface, film surface)" may also be called the main surface. Furthermore, in this specification, the normal direction of a sheet-like member refers to the normal direction to the sheet surface of the target sheet-like member.

[0029] Fig. 1 is a perspective view showing a schematic layer structure of a display device 1 including an optical structure 100 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1, and more specifically, a cross-sectional view showing the display device 1 of Fig. 1 cut along line II-II in the stacking direction of each layer (members forming a layer) and viewed in the direction of an arrow extending from line II-II.

[0030] 1 and 2, adjacent members (layers) among the multiple members (layers) constituting the display device 1 are shown separated from each other for the sake of convenience of explanation. In reality, adjacent members are directly or indirectly in close contact or bonded to each other, or are adjacent to each other.

[0031] 1 and 2, reference symbol D1 indicates a first direction parallel to the sheet surface of first prism sheet 210 (described later) in which first prism portions 212 are arranged. Reference symbol D2 indicates a second direction parallel to the sheet surface of first prism sheet 210 and perpendicular to first direction D1. Reference symbol D3 indicates a third direction perpendicular to both first direction D1 and second direction D2, in which multiple members (layers) constituting display device 1 are stacked.

[0032] <Display device> First, the overall configuration of the display device 1 will be described. The display device 1 according to the present embodiment shown in Fig. 1 and Fig. 2 is configured by laminating a surface light source device 10, an optical structure 100, a liquid crystal panel 50, and a viewing angle control sheet 60 in this order. When viewed from the viewer's side, that is, when viewed from above and below in the third direction D3, the display device 1 has a rectangular shape, with the long sides of the display device 1 parallel to the first direction D1 and the short sides of the display device 1 parallel to the second direction D2. However, the shape of the display device 1 is not particularly limited.

[0033] (Surface light source device) The surface light source device 10 is a backlight having a light-emitting surface 11 that emits light in a planar manner, and the light from the light-emitting surface 11 illuminates the rear surface 50B of the liquid crystal panel 50 via the optical structure 100. That is, in the present embodiment, the optical structure 100 is disposed between the surface light source device 10 and the liquid crystal panel 50, so that the light from the light-emitting surface 11 enters the liquid crystal panel 50 via the optical structure 100. The type of the surface light source device 10 is not particularly limited, and may be an edge light type or another type such as a direct type.

[0034] Some of the light emitted by the surface light source device 10 passes through the optical structure 100 in one go and enters the liquid crystal panel 50, while some is reflected by the optical structure 100 and returns to the surface light source device 10. In order to reflect the light reflected by the optical structure 100 in this manner and allow it to efficiently enter the optical structure 100 again, it is preferable to provide the surface light source device 10 with a reflective sheet.

[0035] (optical structure) The optical structure 100 includes a first prism sheet 210 and a second prism sheet 220. In the optical structure 100, a surface of the first prism sheet 210 opposite to the second prism sheet 220 side forms one of the outermost surfaces of the optical structure 100, and a surface of the second prism sheet 220 opposite to the first prism sheet 210 side forms the other of the outermost surfaces of the optical structure 100.

[0036] The optical structure 100 is disposed such that the first prism sheet 210 faces the surface light source device 10 and the second prism sheet 220 faces the liquid crystal panel 50. The optical structure 100 has a function of collecting light from the surface light source device 10 in a direction perpendicular to the liquid crystal panel 50 and making the light incident on the liquid crystal panel 50, that is, it has a function as a collimator.

[0037] 1 and 2, the first prism sheet 210 has a sheet-like first main body portion 211 having a pair of main surfaces, and a first prism portion 212 provided on one of the pair of main surfaces of the first main body portion 211. A plurality of the first prism portions 212 are arranged in a first direction D1, and extend linearly in a direction intersecting the direction in which the first prism portions 212 are arranged. In FIGS. 1 and 2, the boundary between the first main body portion 211 and the first prism portion 212 is shown by a dashed line, but the first prism sheet 210 is produced by forming irregularities (first prism portions 212) on a single sheet body using a mold, and in reality, there is no interface between the first main body portion 211 and the first prism portion 212. However, the first main body portion 211 and the first prism portion 212 may be formed from different materials.

[0038] In this embodiment, the direction in which the first prism portions 212 extend linearly is perpendicular to the first direction D1 (i.e., the direction in which the first prism portions 212 are arranged) and is parallel to the second direction D2. However, the direction in which the first prism portions 212 extend linearly may obliquely intersect with the first direction D1 (i.e., the direction in which the first prism portions 212 are arranged).

[0039] The second prism sheet 220 also has a sheet-like second main body portion 221 having a pair of main surfaces, and a second prism portion 222 provided on one of the pair of main surfaces of the second main body portion 221. A plurality of second prism portions 222 are arranged in a direction intersecting with the first direction D1. The second prism portions 222 extend linearly in a direction intersecting with the direction in which they are arranged. Note that the second prism sheet 220 is also manufactured by forming projections and recesses (second prism portions 222) on a single sheet body using a mold, similar to the first prism sheet 210. Therefore, there is no interface between the second main body portion 221 and the second prism portion 222, but the first main body portion 211 and the first prism portion 212 may be formed from different materials.

[0040] When viewed in the second direction D2 as shown in FIG. 2, the first prism portion 212 has an isosceles triangle shape with one corner facing the side opposite to the first main body portion 211 side. Hereinafter, the corner of the first prism portion 212 facing the side opposite to the first main body portion 211 side is referred to as an apex angle. In other words, this apex angle is a corner of the first prism portion 212 facing one side in the normal direction to the sheet surface of the first prism sheet 210. Also, referring to FIG. 1, the second prism portion 222 has an isosceles triangle shape with one corner facing the side opposite to the second main body portion 221 side. Hereinafter, similar to the case of the first prism portion 212, the corner of the second prism portion 222 facing the side opposite to the second main body portion 221 side is referred to as an apex angle. The cross-sectional shape of the first prism portion 212 and the second prism portion 222 is not limited to an isosceles triangle, but may be a scalene triangle. However, an isosceles triangle is preferable from the viewpoint of light collection and ease of manufacture.

[0041] The second prism sheet 220 is disposed on the apex angle of the first prism portion 212 so that the apex angle of the first prism portion 212 and the apex angle of the second prism portion 222 face the same direction. The direction in which the first prism portion 212 extends linearly and the direction in which the second prism portion 222 extends linearly are non-parallel. More specifically, the first prism sheet 210 and the second prism sheet 220 are disposed so that the direction in which the first prism portion 212 extends linearly and the direction in which the second prism portion 222 extends linearly form an angle of 80 degrees or more and 100 degrees or less. In the illustrated example, as shown in FIG. 3, the angle θ between the direction in which the first prism portion 212 extends linearly and the direction in which the second prism portion 222 extends linearly is 90 degrees, but this angle θ may be any angle between 80 degrees or more and 100 degrees or less.

[0042] The refractive index of the first prism portion 212 and the refractive index of the second prism portion 222 are each 1.475 or more and less than 1.725. The refractive index of the first main body portion 211 and the refractive index of the second main body portion 221 are also 1.475 or more and less than 1.725. The material of the first prism sheet 210 and the second prism sheet 220 is not particularly limited, but for example, each prism sheet 210, 220 (each prism portion) is made of a resin, glass, or the like and has optical transparency, and examples of the material include polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, polyamide, triacetyl cellulose, glass, and the like. That is, each prism sheet may be formed of, for example, a film mainly composed of polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, polyamide, triacetyl cellulose, glass, or the like.

[0043] The first prism sheet 210 totally reflects as much light as possible incident from the surface light source device 10 at the interface between an air layer formed between adjacent first prism portions 212 and a first prism portion 212 having a higher refractive index than the air layer, thereby minimizing light emitted in a direction significantly tilted from a direction perpendicular to the first prism sheet 210, thereby concentrating the light in a direction perpendicular to the first prism sheet 210. Similarly, the second prism sheet 220 totally reflects as much light as possible incident from the first prism sheet 210 at the interface between an air layer formed between adjacent second prism portions 222 and a second prism portion 222 having a higher refractive index than the air layer, thereby minimizing light emitted in a direction significantly tilted from a direction perpendicular to the second prism sheet 220, thereby concentrating the light in a direction perpendicular to the second prism sheet 220.

[0044] The light collecting performance of the first prism sheet 210 and the second prism sheet 220 varies depending on the refractive index and shape of each prism portion. As a result of intensive research, the inventors of the present invention have found that when the refractive index of the first prism portion 212 and the refractive index of the second prism portion 222 are each 1.475 or more and less than 1.725, it is preferable from the viewpoint of improving the light collecting performance that the apex angle of the first prism portion 212 and the apex angle of the second prism portion 222 are each 96 degrees or more and 108 degrees or less. More specifically, it has been found that the following ranges are better.

[0045] When the refractive index of first prism portion 212 is greater than or equal to 1.475 and less than 1.525, it is preferable that the refractive index of second prism portion 222 is greater than or equal to 1.625 and less than 1.725, the apex angle of first prism portion 212 is greater than or equal to 100 degrees and less than 108 degrees, and the apex angle of second prism portion 222 is greater than or equal to 96 degrees and less than 104 degrees. In particular, when the refractive index of first prism portion 212 is greater than or equal to 1.475 and less than 1.525, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.625 and less than 1.675, the apex angle of first prism portion 212 is greater than or equal to 100 degrees and less than 108 degrees, and the apex angle of second prism portion 222 is greater than or equal to 96 degrees and less than 100 degrees.

[0046] When the refractive index of first prism portion 212 is greater than or equal to 1.525 and less than 1.575, it is preferable that the refractive index of second prism portion 222 is greater than or equal to 1.475 and less than 1.575, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 100 degrees, and the apex angle of second prism portion 222 is greater than or equal to 96 degrees and less than 100 degrees. In particular, when the refractive index of first prism portion 212 is equal to or greater than 1.525 and less than 1.575, it is more preferable that the refractive index of second prism portion 222 is equal to or greater than 1.475 and less than 1.525, the apex angle of first prism portion 212 is 96 degrees, and the apex angle of second prism portion 222 is 96 degrees. Furthermore, when the refractive index of first prism portion 212 is equal to or greater than 1.525 and less than 1.575, it is more preferable that the refractive index of second prism portion 222 is equal to or greater than 1.525 and less than 1.575, the apex angle of first prism portion 212 is 96 degrees, and the apex angle of second prism portion 222 is 100 degrees.

[0047] Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.525 and less than 1.575, it is preferable that the refractive index of second prism portion 222 is greater than or equal to 1.575 and less than 1.625, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 100 degrees, and the apex angle of second prism portion 222 is greater than or equal to 100 degrees and less than 108 degrees. It is also preferable that the refractive index of first prism portion 212 is equal to or greater than 1.525 and less than 1.575, and that the refractive index of second prism portion 222 is equal to or greater than 1.625 and less than 1.725.

[0048] It is preferable that the refractive index of first prism portion 212 is equal to or greater than 1.575 and less than 1.625. In this case, it is preferable that the refractive index of second prism portion 222 is equal to or greater than 1.475 and less than 1.525, the apex angle of first prism portion 212 is equal to or greater than 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is equal to or greater than 96 degrees and less than 100 degrees.

[0049] Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.575 and less than 1.625, it is preferable that the refractive index of second prism portion 222 is greater than or equal to 1.525 and less than 1.575, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 100 degrees and less than 104 degrees. Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.575 and less than 1.625, it is preferable that the refractive index of second prism portion 222 is greater than or equal to 1.575 and less than 1.625, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 100 degrees and less than 108 degrees. Furthermore, when the refractive index of first prism portion 212 is 1.575 or greater and less than 1.625, it is preferable that the refractive index of second prism portion 222 is 1.625 or greater and less than 1.675, the apex angle of first prism portion 212 is 100 degrees or greater and less than 108 degrees, and the apex angle of second prism portion 222 is 96 degrees or greater and less than 108 degrees. Furthermore, when the refractive index of first prism portion 212 is 1.575 or more and less than 1.625, it is preferable that the refractive index of second prism portion 222 is 1.675 or more and less than 1.725, the apex angle of first prism portion 212 is 96 degrees or more and less than 104 degrees, and the apex angle of second prism portion 222 is 104 degrees or more and 108 degrees or less.

[0050] When the refractive index of first prism portion 212 is equal to or greater than 1.625 and less than 1.675, it is preferable that the refractive index of second prism portion 222 is equal to or greater than 1.475 and less than 1.625. In this case, it is preferable that the apex angle of first prism portion 212 is equal to or greater than 96 degrees and less than 104 degrees. In particular, when the refractive index of first prism portion 212 is greater than or equal to 1.625 and less than 1.675, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.475 and less than 1.525, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 96 degrees and less than 104 degrees. Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.625 and less than 1.675, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.525 and less than 1.575, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 100 degrees and less than 104 degrees. Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.625 and less than 1.675, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.575 and less than 1.625, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 96 degrees and less than 108 degrees.

[0051] Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.625 and less than 1.675, it is preferable that the refractive index of second prism portion 222 is greater than or equal to 1.625 and less than 1.725, the apex angle of first prism portion 212 is greater than or equal to 100 degrees and less than 108 degrees, and the apex angle of second prism portion 222 is greater than or equal to 104 degrees and less than 108 degrees. In this case, it is more preferable that the refractive index of second prism portion 222 is not less than 1.625 and less than 1.675, the apex angle of first prism portion 212 is not less than 100 degrees and not more than 104 degrees, and the apex angle of second prism portion 222 is not less than 104 degrees and not more than 108 degrees. Furthermore, when the refractive index of first prism portion 212 is equal to or greater than 1.625 and less than 1.675, it is preferable that the refractive index of second prism portion 222 is equal to or greater than 1.675 and less than 1.725, the apex angle of first prism portion 212 is 104 degrees, and the apex angle of second prism portion 222 is 108 degrees.

[0052] When the refractive index of first prism portion 212 is 1.675 or greater and less than 1.725, it is preferable that the refractive index of second prism portion 222 is 1.475 or greater and less than 1.625, the apex angle of first prism portion 212 is 96 degrees or greater and 104 degrees or less, and the apex angle of second prism portion 222 is 96 degrees or greater and 104 degrees or less. In particular, when the refractive index of first prism portion 212 is greater than or equal to 1.675 and less than 1.725, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.475 and less than 1.525, the apex angle of first prism portion 212 is greater than or equal to 96 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 96 degrees and less than 104 degrees. In particular, when the refractive index of first prism portion 212 is greater than or equal to 1.675 and less than 1.725, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.525 and less than 1.575, the apex angle of first prism portion 212 is greater than or equal to 100 degrees and less than 104 degrees, and the apex angle of second prism portion 222 is 100 degrees. Furthermore, when the refractive index of first prism portion 212 is greater than or equal to 1.675 and less than 1.725, it is more preferable that the refractive index of second prism portion 222 is greater than or equal to 1.575 and less than 1.625, the apex angle of first prism portion 212 is 104 degrees, and the apex angle of second prism portion 222 is greater than or equal to 100 degrees and less than 104 degrees.

[0053] In addition, when the refractive index of first prism portion 212 is 1.675 or more and less than 1.725, it is also preferable that the refractive index of second prism portion 222 is 1.625 or more and less than 1.725, the apex angle of first prism portion 212 is 104 degrees or more and 108 degrees or less, and the apex angle of second prism portion 222 is 108 degrees.

[0054] Here, Fig. 4A shows an example of a graph of the luminance of light transmitted from the surface light source device 10 through the first prism sheet 210 and the second prism sheet 220 (optical structure 100). Fig. 4B shows an example of the angular distribution of light transmitted from the surface light source device 10 through the first prism sheet 210 and the second prism sheet 220 (optical structure 100). In the optical structure 100 used in specifying the graph of Fig. 4A and the angular distribution of Fig. 4B, the refractive index of the first prism sheet 210 is 1.60, the apex angle of the first prism portion 212 is 104 degrees, the refractive index of the second prism sheet 220 is 1.60, and the apex angle of the second prism portion 222 is 100 degrees.

[0055] The horizontal axis of the graph in FIG. 4A indicates the viewing angle, and the horizontal axis indicates the viewing angle within the viewing angle with respect to the perpendicular direction (0 degrees) of the first prism sheet 210. The vertical axis of the graph in FIG. 4A indicates the luminance value (%). This luminance value (%) is indicated as a relative value (relative luminance) to the maximum luminance (100%) when the light directly irradiated by the surface light source device 10 is specified by simulation. In FIG. 4A, the luminance at the viewing angle in the first direction D1 (the viewing angle in the plane including the first direction D1 and the third direction D3) is indicated by a solid line, and the luminance at the viewing angle in the second direction D2 (the viewing angle in the plane including the second direction D2 and the third direction D3) is indicated by a dashed line.

[0056] In the angle distribution of Fig. 4B, the horizontal axis indicates the viewing angle in the first direction D1, and the vertical axis indicates the viewing angle in the second direction D2. Fig. 4B also illustrates the relationship between the luminance value (%) and the hatching. The luminance value (%) on the seat surface is shown by different types of hatching (by different colors). The luminance value (%) in the angle distribution of Fig. 4B is also shown as a relative value to the maximum luminance (100%) when the light directly irradiated by the surface light source device 10 is identified by simulation.

[0057] The above-mentioned luminance graph shown in Fig. 4A and the angular distribution shown in Fig. 4B are specified by simulating the luminance of white light irradiated from the surface light source device 10 and emitted from the optical structure 100. The maximum luminance of light directly irradiated by the reference surface light source device 10 is also specified by simulation.

[0058] 4A and 4B, the light emitted from the optical structure 100 is effectively focused in the front viewing direction (third direction D3) while suppressing the occurrence of side lobes. Specifically, a light focusing performance (hereinafter referred to as "good light focusing performance") is obtained in which the luminance value at a viewing angle of 10 degrees is greater than 90%, the luminance value at a viewing angle of 20 degrees is greater than 80%, the luminance value at a viewing angle of 25 degrees is greater than 50%, the luminance value at a viewing angle of 30 degrees is less than 50% or is about 50%, the luminance value at a viewing angle of 40 degrees is less than 15%, and the luminance value at a viewing angle of 50 degrees or more is less than 10%. In the preferred ranges of the refractive index and apex angle of the prism parts 212 and 222 described above, this "good light focusing performance" is easily obtained.

[0059] Meanwhile, Fig. 5A shows a graph of the luminance of light passing through two general prism sheets, and Fig. 5B shows the angle distribution of the light corresponding to Fig. 5A. The two prism sheets used here have the same basic shapes as the first prism sheet 210 and the second prism sheet 220, respectively, but the refractive index of each prism portion is 1.50, and the apex angle is 92 degrees.

[0060] As in the case of FIG. 4A, the horizontal axis of the graph in FIG. 5A indicates the viewing angle, and the horizontal axis indicates the viewing angle in the viewing angle with respect to the vertical direction (0 degrees) of the prism sheet. The vertical axis of the graph in FIG. 5A indicates the luminance value (%). This luminance value (%) is shown as a relative value (relative luminance) to the maximum luminance (100%) when the light directly irradiated by the surface light source device 10 is specified by simulation. In FIG. 5A, the luminance at the viewing angle in the first direction D1 (the viewing angle in the plane including the first direction D1 and the third direction D3) is shown by a solid line, and the luminance at the viewing angle in the second direction D2 (the viewing angle in the plane including the second direction D2 and the third direction D3) is shown by a dashed line.

[0061] In the angle distribution of FIG. 5B, the horizontal axis indicates the viewing angle in the first direction D1, and the vertical axis indicates the viewing angle in the second direction D2. The luminance value (%) on the seat surface is shown by different hatching types (color-coded). The luminance value (%) in the angle distribution of FIG. 5B is also shown as a relative value to the maximum luminance (100%) when the light directly irradiated by the surface light source device 10 is specified by simulation. In FIG. 5A and FIG. 5B, many side lobes are generated, as shown by the area surrounded by the two-dot chain line. The effect of the optical structure 100 according to this embodiment can also be seen from the comparison of FIG. 5A and FIG. 5B with FIG. 4A and FIG. 4B.

[0062] 6 is a table showing the relationship between the refractive index and apex angle of the first prism portion 212 and the second prism portion 222 and the light collecting performance. In the table, horizontally arranged columns show a plurality of types of refractive index (1.50, 1.55, 1.60, 1.65, 1.70) set for the first prism portion 212, which is the lower prism portion, and below that, the values ​​of the apex angle of the first prism portion 212 set for each refractive index (72 to 108 degrees) are shown in increments of 4 degrees. Vertically arranged columns show a plurality of types of refractive index (1.50, 1.55, 1.60, 1.65, 1.70) set for the second prism portion 222, which is the upper prism portion, and next to that, the values ​​of the apex angle of the second prism portion 222 set for each refractive index (72 to 108 degrees) are shown in increments of 4 degrees.

[0063] In the table of FIG. 6, a 0 or 1 is shown at a position determined by the apex angle of first prism portion 212 set to a certain refractive index and the apex angle of second prism portion 222 set to a certain refractive index. In FIG. 6, when 1 is shown, the above-mentioned condition of "good light collecting performance" is satisfied. On the other hand, when 0 is shown, the condition of "good light collecting performance" is not satisfied. In the table of FIG. 6, the part shown by "1" is given a background area. In addition, the range where the apex angle of the first prism portion 212 and the apex angle of the second prism portion 222 are 96 degrees or more and 108 degrees or less is surrounded by a solid line. In addition, the range surrounded by the dashed line indicates the range where the condition of "good light collecting performance" is more likely to be satisfied. Referring to FIG. 6, it can be seen that the above-mentioned preferable ranges (conditions) of the refractive index and apex angle of the prism portions 212 and 222 are preferable from the viewpoint of improving the light collecting performance.

[0064] The shapes of the first prism portion 212 and the second prism portion 222 and the apex angles can be specified, for example, by cutting the prism sheet in the thickness direction and observing the cross section with a microscope or SEM image. The refractive index of the first prism portion 212 and the second prism portion 222 can be obtained, for example, by fitting a reflection spectrum measured by a spectrophotometer to a spectrum calculated from an optical model of a thin film using Fresnel's equation. The refractive index may also be obtained by measurement using an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd.) or an ellipsometer. The refractive index can also be measured by the following procedure. That is, the first prism portion 212 or the second prism portion 222 is scraped off with a cutter or the like to prepare a powdered sample, and the Becke method according to JIS K 7142 (2008) Method B (for powdered or granular transparent materials) is used (Cargill reagent with a known refractive index is used, the powdered sample is placed on a slide glass or the like, the reagent is dropped onto the sample, and the sample is immersed in the reagent. The state is observed under a microscope, and the refractive index of the reagent at which the bright lines (Becke lines) that appear on the sample outline due to the difference in refractive index between the sample and the reagent cannot be observed with the naked eye is regarded as the refractive index of the sample).

[0065] In this embodiment, the preferred values ​​of the apex angle and refractive index of prism portions 212 and 222 are specified with a predetermined significant figure n, but if the apex angle and refractive index of prism portions 212 and 222 are specified to the n+1 digit, the n+1 digit is rounded off. That is, for example, the concept of the apex angle of the prism portion being 90 degrees or more and 108 degrees or less includes the concept of 89.5 degrees or more and 108.4 degrees or less. Also, for example, the concept of the refractive index of the prism portion being 1.65 includes the concept of 1.645 or more and 1.654 or less.

[0066] In the optical structure 100 according to the present embodiment described above, light incident on the first prism sheet 210 from the surface light source device 10 is condensed by the first prism portions 212 in a direction perpendicular to the first prism sheet 210 on a plane (the plane shown in FIG. 2) including the first direction D1 and the third direction D3. The condensed light emitted from the first prism sheet 210 is incident on the second prism sheet 220. The light incident on the second prism sheet 220 is condensed by the second prism portions 222 in a direction perpendicular to the second prism sheet 220 on a plane including the second direction D2 and the third direction D3. This allows the optical structure 100 to exhibit condensing performance in all directions.

[0067] In order to improve the light-collecting performance of the collimator, measures such as doubling the prism sheet to make the linear extension direction of the prism portion non-parallel and doubling the louver sheet to make the linear extension direction of the light-absorbing portion non-parallel can be considered. However, even if this measure improves the light-collecting performance, there is a risk that the light utilization efficiency will decrease and the thickness of the display device will increase. In contrast, the optical structure 100 according to the present embodiment can achieve both sufficient improvement in light-collecting performance and high light utilization efficiency while suppressing an increase in the thickness of the display device, thereby realizing high contrast and high brightness of the displayed image.

[0068] (Liquid crystal panel) 1 and 2, the liquid crystal panel 50 has a display surface 50A that displays an image, which is a still image or a moving image, using light incident from the optical structure 100, and a back surface 50B on the opposite side to the display surface 50A. In the display device 1, the liquid crystal panel 50 functions as a shutter that controls the transmission or blocking of light transmitted from the surface light source device 10 through the optical structure 100 for each region forming a pixel (subpixel). Then, an image is displayed on the display surface 50A by driving the liquid crystal panel 50.

[0069] The illustrated liquid crystal panel 50 has an upper polarizing plate 52 arranged on the light output side, a lower polarizing plate 53 arranged on the light input side, and a liquid crystal layer 51 arranged between the upper polarizing plate 52 and the lower polarizing plate 53. The polarizing plates 52 and 53 have the function of decomposing the incident light into two orthogonal polarized components (e.g., P waves and S waves), transmitting the linearly polarized component oscillating in one direction (parallel to the transmission axis) and absorbing the linearly polarized component oscillating in the other direction (parallel to the absorption axis) orthogonal to the one direction (e.g., S waves).

[0070] In the liquid crystal layer 51, a voltage can be applied to each region forming one pixel, and the orientation direction of the liquid crystal molecules in the liquid crystal layer 51 changes depending on whether or not a voltage is applied. As an example, a polarized component in a specific direction that has passed through the lower polarizing plate 53 arranged on the light-entering side rotates its polarization direction by 90 degrees when passing through the liquid crystal layer 51 to which no voltage is applied, and maintains its polarization direction when passing through the liquid crystal layer 51 to which a voltage is applied. In this case, depending on whether or not a voltage is applied to the liquid crystal layer 51, it is possible to control whether the polarized component vibrating in a specific direction that has passed through the lower polarizing plate 53 is further transmitted through the upper polarizing plate 52 arranged on the light-emitting side of the lower polarizing plate 53, or is absorbed and blocked by the upper polarizing plate 52. In this way, in the liquid crystal panel 50, the transmission or blocking of light from the surface light source device 10 can be controlled for each region forming a pixel.

[0071] In this embodiment, the liquid crystal panel 50 is a VA (Vertical Alignment) type liquid crystal panel. Therefore, the liquid crystal panel 50 has a configuration in which, when the voltage applied to the liquid crystal molecules in the liquid crystal layer 51 is off or at a minimum value, the liquid crystal molecules are oriented along the normal direction of the display surface 50A, and light from the optical structure 100 is blocked, and the voltage applied to the liquid crystal molecules is gradually increased to gradually tilt the liquid crystal molecules toward the side along the display surface 50A, thereby gradually increasing the transmittance of light from the optical structure 100.

[0072] The higher the light collecting ability (directivity) of light from the optical structure 100, the more the VA liquid crystal panel 50 can improve the contrast ratio of the displayed image when viewed from the front and when viewed from an oblique direction. Therefore, in a display device 1 in which the VA liquid crystal panel 50 and the optical structure 100 are combined, the light collecting performance of the optical structure 100 is sufficiently improved, thereby realizing a high contrast of the displayed image. In addition, since the optical structure 100 can achieve both a sufficient improvement in light collecting performance and high light utilization efficiency, the display image can also be made brighter. In addition, the thickness of the display device 1 can be suppressed in this case.

[0073] The liquid crystal panel 50 is not limited to the VA type, but may be a TN (Twisted Nematic) type liquid crystal panel or an IPS (In-Plane Switching) type liquid crystal panel. A certain degree of effect can be expected even with a type other than the VA type. Also, a surface light source device using an organic LED may be combined with the optical structure 100 to configure a display device, in which case, for example, the contrast of a displayed image when viewed from the front may be improved.

[0074] In addition, in this embodiment, it is assumed that the liquid crystal panel 50 and the optical structure 100 are prepared separately and then combined when manufacturing the display device 1, but the display device 1 may also be constructed by preparing a polarizing plate with an optical structure in which the lower polarizing plate 53 that constitutes the liquid crystal panel 50 and the optical structure 100 are integrated, and combining this with a liquid crystal layer, etc.

[0075] (Viewing angle control sheet) The view angle control sheet 60 has a first view angle control sheet 61 and a second view angle control sheet 62, and is arranged so that the first view angle control sheet 61 faces the liquid crystal panel 50 and the second view angle control sheet 62 is located on the viewer side. Note that the configuration of the view angle control sheet 60 described below is merely an example, and other configurations may be used.

[0076] 2, the first view angle control sheet 61 has a high refractive index layer 61A shown with hatching, and a low refractive index layer 61B bonded to the high refractive index layer 61A and having a lower refractive index than the high refractive index layer 61A, and the low refractive index layer 61B faces the liquid crystal panel 50. The interface between the high refractive index layer 61A and the low refractive index layer 61B has an uneven shape, and the concave and convex parts in the uneven shape are alternately arranged in the first direction D1 in the illustrated example, and extend long in a direction intersecting the first direction D1, which is the second direction D2 in this example. The bottom surface of the concave part is flat, and the top of the convex part is flat. The side surface connecting the bottom surface of the concave part and the top of the convex part is an arc surface, and is an arc surface that is convex in the direction from the high refractive index layer 61A side to the low refractive index layer 61B side.

[0077] The second view angle control sheet 62 has the same configuration as the first view angle control sheet 61, and has a high refractive index layer 62A shown with hatching, and a low refractive index layer 62B bonded to the high refractive index layer 62A and having a lower refractive index than the high refractive index layer 62A. The second view angle control sheet 62 is arranged so that the low refractive index layer 62B faces the first view angle control sheet 61. The high refractive index layer 62A and the low refractive index layer 62B of the second view angle control sheet 62 have the same configuration as those of the first view angle control sheet 61, but the longitudinal directions of the concave and convex portions in the concave and convex shape are different. That is, in this embodiment, when viewed in the direction in which the first view angle control sheet 61 and the second view angle control sheet 62 overlap (third direction D3), the longitudinal direction of the concaves and convexities of the uneven shape at the interface between the high refractive index layer 61A and the low refractive index layer 61B of the first view angle control sheet 61 intersects with the longitudinal direction of the concaves and convexities of the uneven shape at the interface between the high refractive index layer 62A and the low refractive index layer 62B of the second view angle control sheet 62. The intersecting state may be perpendicular or oblique.

[0078] In VA type liquid crystal panels, color change within the viewing angle may become large, but the first viewing angle control sheet 61 and the second viewing angle control sheet 62 are configured to suppress color change within the viewing angle by reflecting and refracting light on the side surfaces of the uneven shape at the interface between the high refractive index layer and the low refractive index layer. Here, in this embodiment, the first viewing angle control sheet 61 and the second viewing angle control sheet 62 are arranged in a cross state, so that color change within the viewing angle in all directions can be suppressed.

[0079] The view angle control sheet 60 is not limited to the example of this embodiment, but preferably has a function of suppressing color change, a function of expanding the view angle, etc. For example, the view angle control sheet 60 may be composed of a single layer, or may be a single-layer matte layer or a prism layer. Also, for example, the arrangement positions of the high refractive index layer and the low refractive index layer in the first view angle control sheet 61 may be opposite to that in the illustrated example. Also, the shape of the interface between the high refractive index layer and the low refractive index layer is not limited to the illustrated embodiment.

[0080] <Light behavior> The behavior of light for forming a display image in the display device 1 according to the present embodiment will be described below.

[0081] When displaying an image on the display device 1, first, light is emitted from the surface light source device .

[0082] Light incident on the optical structure 100 from the surface light source device 10 is focused by the first prism portions 212 of the first prism sheet 210 in a direction perpendicular to the first prism sheet 210 on a plane including the first direction D1 and the third direction D3. The focused light emitted from the first prism sheet 210 then enters the second prism sheet 220. In the second prism sheet 220, the light is focused by the second prism portions 222 in a direction perpendicular to the second prism sheet 220 on a plane including the second direction D2 and the third direction D3. This allows light with high light focusing (directivity) to be incident on the liquid crystal panel 50 from the optical structure 100.

[0083] In addition, the higher the light collecting ability (directivity) of the light supplied from the optical structure 100, the more the VA liquid crystal panel 50 can improve the contrast ratio of the displayed image when viewed from the front and the contrast ratio when viewed from an oblique direction. This makes it possible to realize a high contrast display image. Furthermore, the optical structure 100 can achieve both sufficient improvement in light collecting performance and high light utilization efficiency, so that it is possible to realize a high brightness display image. In this case, the thickness of the display device 1 is suppressed.

[0084] In this embodiment, light for forming a display image from the liquid crystal panel 50 is incident on the view angle control sheet 60 and is given an optical effect. Since the view angle control sheet 60 is configured to be capable of suppressing color change, the display image displayed by the view angle control sheet 60 is also suppressed from changing in color within the viewing angle.

[0085] According to the present embodiment described above, the light for forming a display image is sufficiently concentrated by the two prism sheets (210, 220), thereby making it possible to realize high contrast and high brightness of the display image while suppressing an increase in the thickness of the display device. In particular, in this embodiment, the VA type liquid crystal panel 50 and the optical structure 100 are combined, thereby making it possible to effectively improve the contrast ratio and brightness of the display image. On the other hand, in the VA type liquid crystal panel, color change within the viewing angle may become large, but by providing a viewing angle control sheet 60 of a type capable of suppressing color change on the light output side of the liquid crystal panel 50, color change can also be effectively suppressed, making it possible to display a high quality image.

[0086] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made to the above-mentioned embodiment. [Explanation of symbols]

[0087] 1...Display device 10…Surface light source device 210…First prism sheet 211...First main body part 212…First prism section 220…Second prism sheet 221...Second body part 222…Second prism section 50...LCD panel 50A…display surface 50B…Back side 51...Liquid crystal layer 52...Upper polarizing plate 53...Lower polarizing plate 60...Viewing angle control sheet 100...Optical structure

Claims

1. a first prism sheet in which a plurality of first prism portions are arranged, the first prism portions extending linearly in a direction intersecting a direction in which the first prism portions are arranged; a second prism sheet in which a plurality of second prism portions are arranged, the second prism portions extending linearly in a direction intersecting a direction in which the second prism portions are arranged; Equipped with The first prism portion and the second prism portion have a triangular cross-sectional shape, the second prism sheet is disposed on the apex angle of the first prism portion such that the apex angle of the first prism portion and the apex angle of the second prism portion face in the same direction; a direction in which the first prism portion extends linearly and a direction in which the second prism portion extends linearly are non-parallel to each other, The refractive index of the first prism portion is equal to or greater than 1.575 and less than 1.625, The refractive index of the second prism portion is equal to or greater than 1.525 and less than 1.575, an apex angle of the first prism portion is greater than or equal to 96 degrees and less than or equal to 104 degrees, and an apex angle of the second prism portion is greater than or equal to 100 degrees and less than or equal to 104 degrees.

2. a first prism sheet in which a plurality of first prism portions are arranged, the first prism portions extending linearly in a direction intersecting a direction in which the first prism portions are arranged; a second prism sheet in which a plurality of second prism portions are arranged, the second prism portions extending linearly in a direction intersecting a direction in which the second prism portions are arranged; Equipped with The first prism portion and the second prism portion have a triangular cross-sectional shape, the second prism sheet is disposed on the apex angle of the first prism portion such that the apex angle of the first prism portion and the apex angle of the second prism portion face in the same direction; a direction in which the first prism portion extends linearly and a direction in which the second prism portion extends linearly are non-parallel to each other, The refractive index of the first prism portion is equal to or greater than 1.575 and less than 1.625, The refractive index of the second prism portion is equal to or greater than 1.625 and less than 1.675, an apex angle of the first prism portion is greater than or equal to 100 degrees and less than or equal to 108 degrees, and an apex angle of the second prism portion is greater than or equal to 96 degrees and less than or equal to 108 degrees.

3. a first prism sheet in which a plurality of first prism portions are arranged, the first prism portions extending linearly in a direction intersecting a direction in which the first prism portions are arranged; a second prism sheet in which a plurality of second prism portions are arranged, the second prism portions extending linearly in a direction intersecting a direction in which the second prism portions are arranged; Equipped with The first prism portion and the second prism portion have a triangular cross-sectional shape, the second prism sheet is disposed on the apex angle of the first prism portion such that the apex angle of the first prism portion and the apex angle of the second prism portion face in the same direction; a direction in which the first prism portion extends linearly and a direction in which the second prism portion extends linearly are non-parallel to each other, The refractive index of the first prism portion is equal to or greater than 1.575 and less than 1.625, The refractive index of the second prism portion is equal to or greater than 1.675 and less than 1.725, an apex angle of the first prism portion is greater than or equal to 96 degrees and less than or equal to 104 degrees, and an apex angle of the second prism portion is greater than or equal to 104 degrees and less than or equal to 108 degrees.

4. a first prism sheet in which a plurality of first prism portions are arranged, the first prism portions extending linearly in a direction intersecting a direction in which the first prism portions are arranged; a second prism sheet in which a plurality of second prism portions are arranged, the second prism portions extending linearly in a direction intersecting a direction in which the second prism portions are arranged; Equipped with The first prism portion and the second prism portion have a triangular cross-sectional shape, the second prism sheet is disposed on the apex angle of the first prism portion such that the apex angle of the first prism portion and the apex angle of the second prism portion face in the same direction; a direction in which the first prism portion extends linearly and a direction in which the second prism portion extends linearly are non-parallel to each other, The refractive index of the first prism portion is equal to or greater than 1.625 and less than 1.675, The refractive index of the second prism portion is equal to or greater than 1.625 and less than 1.725, the apex angle of the first prism portion is equal to or greater than 100 degrees and equal to or less than 108 degrees; the apex angle of the second prism portion is equal to or greater than 104 degrees and equal to or less than 108 degrees; An optical structure, wherein an apex angle of the first prism portion is different from an apex angle of the second prism portion.

5. a first prism sheet in which a plurality of first prism portions are arranged, the first prism portions extending linearly in a direction intersecting a direction in which the first prism portions are arranged; a second prism sheet in which a plurality of second prism portions are arranged, the second prism portions extending linearly in a direction intersecting a direction in which the second prism portions are arranged; Equipped with The first prism portion and the second prism portion have a triangular cross-sectional shape, the second prism sheet is disposed on the apex angle of the first prism portion such that the apex angle of the first prism portion and the apex angle of the second prism portion face in the same direction; a direction in which the first prism portion extends linearly and a direction in which the second prism portion extends linearly are non-parallel to each other, The refractive index of the first prism portion is equal to or greater than 1.675 and less than 1.725, The refractive index of the second prism portion is equal to or greater than 1.675 and less than 1.725, the apex angle of the first prism portion is equal to or greater than 104 degrees and equal to or less than 108 degrees; The optical structure, wherein the second prism portion has an apex angle of 108 degrees.

6. A polarizing plate with an optical structure, comprising the optical structure according to claim 1 and a polarizing plate integrated together.

7. A display device, comprising the optical structure according to claim 1 disposed between a surface light source device and a liquid crystal panel.

8. The display device described in claim 7, wherein the liquid crystal panel is a VA type liquid crystal panel configured such that when the voltage applied to the liquid crystal molecules is off or at a minimum value, the liquid crystal molecules are oriented along the normal direction of the liquid crystal panel, thereby blocking light from the surface light source device, and by gradually increasing the voltage applied to the liquid crystal molecules, the liquid crystal molecules are gradually tilted toward the liquid crystal panel, thereby gradually increasing the transmittance of light from the surface light source device.

Images