JP2020016881A - Optical structure, polarizing plate with optical structure and display device - Google Patents

Abstract

To provide an optical structure for obtaining good display quality locally in a given angle range on a higher angle side within a viewing angle of a display device, while maintaining good display quality in a frontal view of the display device.SOLUTION: An optical structure 100 includes a low refractive index layer 102 and a high refractive index layer 103. An interface between the low refractive index layer 102 and the high refractive index layer 103 has a rugged pattern, in which a recess 121 in the rugged pattern is concave on the low refractive index layer 102 side, a projection 122 is convex on the high refractive index layer 103 side, and each of the recess 121 and the projection 122 has a flat portion extending in a plane direction of the low refractive index layer 102 and the high refractive index layer 103. In side faces 120S of the rugged pattern, two side faces 120S adjoining to each other and interposing the flat portion of the recess 121 form a tapered shape toward the low refractive index layer side; and two side faces 120S adjoining to each other and interposing the flat portion 122A of the projection 122 form a tapered shape toward the high refractive index layer side. The optical structure is disposed in such a manner that the high refractive index layer 103 faces a display screen side of a display device.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical structure having an optical effect on light emitted from a display surface of a display device. Further, the present invention relates to a polarizing plate with an optical structure provided with the optical structure and a display device.

  2. Description of the Related Art A liquid crystal display device, which is an example of a display device, is used in various fields. Liquid crystal panels of a liquid crystal display device are roughly classified into a TN (Twisted Nematic) system, a VA (Vertical Alignment) system, and an IPS (In-Plane Switching) system.

  In a liquid crystal display device, a color is expressed by mixing a plurality of lights having different wavelengths. However, depending on the angle of the light transmitted through the liquid crystal, there may be a case where a large difference occurs in the intensity of light having different wavelengths. Specifically, for example, the difference between the intensity of the light of one wavelength and the intensity of the light of the other wavelength of the two different wavelengths may be significantly different between the front view and the high angle side. In a liquid crystal display device including a liquid crystal panel having such characteristics, the color when viewed from an oblique direction can greatly change from the color when viewed from the front.

  For example, in a VA liquid crystal panel, black is displayed when the voltage applied to the liquid crystal molecules is off, and very little light leaks from the black display portion to the front, so that the contrast ratio in front view is extremely low. Can be higher. On the other hand, when viewed from a direction inclined with respect to the normal direction of the display surface, a relatively large amount of light leaks obliquely from pixels that are black when viewed from the front. As compared with the case, the contrast ratio may be remarkably reduced and the color may greatly change. As a result, the contrast ratio and the color within the viewing angle may vary greatly.

In a VA liquid crystal panel, for example, when displaying or displaying blue by weakening or blocking the intensity of red and green light of red, green and blue, red and green light obliquely leaks. In addition, a situation in which the tint greatly changes when viewed from the front and when viewed from an oblique direction is likely to occur.
In addition, since the emission spectrum shape change with respect to the viewing angle of blue display is strong (compared with red display and green display), specifically, the “intensity of the wavelength component corresponding to green” is changed to “the wavelength component corresponding to blue”. Due to a change that increases with respect to “intensity”, the display color when viewed obliquely tends to turn yellow when viewed from the front.

  In view of the above-described problems of contrast ratio variation and color change, in a VA liquid crystal panel, cells may be formed in a color filter in a plurality of types of patterns. In this method, for example, by making light distribution characteristics of light transmitted through cells having different patterns different from each other, it is possible to suppress a difference between a color when viewed obliquely and a color when viewed from the front.

  However, in recent years, high definition of liquid crystal display devices has been rapidly progressing, and when it is attempted to form a plurality of types of cells as described above on a color filter corresponding to a desired high resolution, processing is extremely troublesome. Or processing may not be possible depending on the desired resolution. In particular, in the VA system, it is generally necessary to make the cell division finer than in other formats such as the IPS system. Therefore, it is necessary to obtain a cell structure that can effectively suppress color change while achieving a desired high resolution. May be difficult. On the other hand, a proposal has been made in which the color change is not suppressed by the liquid crystal panel side but by an optical sheet provided on the display surface of the liquid crystal panel. Such an optical sheet is disclosed in, for example, Patent Documents 1 to 6.

JP-A-7-43704 Patent No. 3272833 Patent No. 3621959 JP-A-2006-126350 JP 2012-145944 A JP 2011-118393 A

  In a display device, it is generally desired that the display quality in the entire viewing angle range is not significantly reduced as compared with the front view while maintaining the display quality in the front view in the best condition. On the other hand, there is a demand that good display quality is required in a part of the angle range on the front view and on the high angle side, and that display quality in other angle ranges is not strongly required. However, an optical sheet that can meet such a demand has not been known so far.

  The inventor of the present invention has intensively studied to realize a structure capable of meeting the above-mentioned demands. Then, it has been found that it is effective to use total reflection when locally obtaining good display quality in a part of the angle range inclined toward the high angle side with respect to the front view direction.

  In some cases, an optical member as disclosed in Patent Documents 1 to 6 is provided with a surface material that forms the outermost surface on the light emission side outside a layer that has an optical effect on incident light. Although such a surface material can function as a protective layer, it sometimes lowers the luminance of light emitted from the outermost surface, and particularly greatly lowers the luminance on the high-angle side. Therefore, such a surface material may undesirably inhibit the effect of improving the viewing angle by the layer exerting an optical effect.

  The present invention has been made in view of the above circumstances, and while maintaining good display quality in front view of the display device, locally in a partial angle range on the high angle side within the viewing angle. An object of the present invention is to provide an optical structure capable of obtaining good display quality, a polarizing plate with the optical structure provided with the same, and a display device.

  The optical structure according to the present invention is an optical structure disposed on a display surface of a display device, and has a low-refractive-index layer and a low-refractive-index layer laminated on the low-refractive-index layer. Higher refractive index layer, the interface between the low refractive index layer and the high refractive index layer has an uneven shape, the concave and convex portions forming the uneven shape is a sheet-shaped low refractive index Layer and the high refractive index layer are alternately arranged in a first direction parallel to the main surface, extend linearly in a second direction parallel to the main surface and intersecting the first direction, and the concave portion and the convex portion Each of the portions has a flat portion extending along the surface direction of the low-refractive-index layer and the high-refractive-index layer, the concave portion is a portion that is concave toward the low-refractive-index layer, and the convex portion Is a portion that is convex toward the high refractive index layer side, and the uneven shape is between a flat portion of the concave portion and a flat portion of the convex portion. A side surface is formed, and two side surfaces of the concavo-convex shape adjacent to each other across the flat portion of the concave portion form a tapered shape from the high-refractive-index layer side toward the low-refractive-index layer side. Two side surfaces of the concavo-convex shape adjacent to each other across a flat portion form a tapered shape from the low refractive index layer side to the high refractive index layer side, and the high refractive index layer is a display surface of the display device. An optical structure arranged to face side.

  In the optical structure according to the present invention, the side surface of the concave-convex shape has at least one curved surface, a bent surface, or a curved surface convex to the high refractive index layer side, or at least one curved surface convex to the high refractive index layer side. The plane may include two planes.

  In the optical structure according to the present invention, a side surface of the uneven shape defined by a straight line connecting both end points of the side surface of the uneven shape and a normal direction of the low refractive index layer and the high refractive index layer. May be 11 degrees or more and 17 degrees or less.

  In the optical structure according to the present invention, the difference between the maximum angle and the minimum angle formed by the side surfaces of the uneven shape and the normal direction of the low refractive index layer and the high refractive index layer is 14 degrees or more and 18 degrees or less. It may be.

  In the optical structure according to the present invention, a ratio of a total length of the flat portion to a length of one period of the concave portion and the convex portion may be 0.75 or more and 0.85 or less.

  In the optical structure according to the present invention, light projected from the display surface of the display device to the outside through the optical structure is parallel to a normal direction of the low refractive index layer and the high refractive index layer. When viewed from the front view direction of the display device and a direction inclined with respect to the front view direction in a plane including the front view direction and the first direction, the light projected in the front view direction The color change Δu′v ′ of light projected in the inclined direction with respect to color gradually increases from the front view direction to a tendency change angle set between 40 ° and 55 ° with respect to the front view direction. However, after the tendency change angle, the tendency may start to decrease.

  The color change Δu′v ′ at the tendency change angle of the light projected from the display surface to the outside via the optical structure is a color change Δu′v ′ of the light projected from the display surface to the outside without passing through the optical structure. The color change Δu′v ′ at an angle corresponding to the tendency change angle may be smaller.

  Each value of the color change Δu′v ′ of light projected from the display surface to the outside through the optical structure in the range of 60 ° or more and 70 ° or less with respect to the front view direction is from the display surface. The value of the color change Δu′v ′ at a position corresponding to each of the values of the light projected outside without passing through the optical structure may be half or less.

  The optical structure according to the present invention may further include a surface material disposed on a side of the low refractive index layer opposite to the high refractive index layer side, and a refractive index of the surface material may be 1.40 or less. .

  The surface material may form an outermost surface on a side opposite to a display surface side of the display device.

  A polarizing plate with an optical structure according to the present invention is a polarizing plate with an optical structure, comprising: a polarizing plate; and the optical structure on a surface of the polarizing plate.

  The display device according to the present invention is a display device in which the optical structure is arranged on a display surface.

  The display device may include: a liquid crystal panel having the display surface, a back surface arranged to face the display surface, and a surface light source device arranged to face the back surface of the liquid crystal panel. Good.

  The liquid crystal panel is in a state where when the voltage to the liquid crystal molecules is off or at a minimum value, the liquid crystal molecules are aligned along the normal direction of the display surface and light from the surface light source device is blocked, A VA-type liquid crystal configured to gradually increase the voltage for the molecules to gradually increase the transmittance of light from the surface light source device by gradually tilting the liquid crystal molecules to a side along the display surface. It may be a panel.

  ADVANTAGE OF THE INVENTION According to this invention, while maintaining the favorable display quality in the front view of a display apparatus, a favorable display quality can be locally obtained in a partial angle range on the high angle side within the viewing angle.

1 is a schematic cross-sectional view of a display device including an optical structure according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the display device for explaining the behavior of light in the display device shown in FIG. 1. It is an expanded sectional view of the optical structure shown in FIG. FIG. 2 is an enlarged view of an uneven shape formed at an interface between a high refractive index layer and a low refractive index layer of the optical structure shown in FIG. 1. FIG. 6 shows a color change Δu′v ′ within a viewing angle of a display device including the optical structure shown in FIG. 1 and a color change Δu′v ′ within a viewing angle of the display device without the optical structure attached. FIG. It is sectional drawing of the optical structure which concerns on one modification. It is sectional drawing of the optical structure which concerns on one modification. It is sectional drawing of the optical structure which concerns on one modification. It is sectional drawing of the optical structure which concerns on one modification. It is sectional drawing of the optical structure which concerns on one modification.

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

  In this specification, terms such as “sheet”, “film”, “plate”, and “layer” are not distinguished from each other based only on the difference in the names. Therefore, for example, the “sheet” is a concept including a member that can also be called a film, a plate, or a layer. In the present specification, the “sheet surface (plate surface, film surface)” refers to the plane direction (plane direction) of the target sheet member when the target sheet member is viewed as a whole and globally. ). The “sheet surface (plate surface, film surface)” may be referred to as a main surface. Furthermore, in this specification, the normal direction of the sheet-shaped member refers to the direction of the normal to the sheet surface of the target sheet-shaped member.

First, a basic configuration of a display device 10 including an optical structure 100 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a display device 10 including an optical structure 100, and FIG. 2 is a schematic cross-sectional view of the display device 10 for explaining the behavior of light in the display device 10. FIG. 3 is an enlarged cross-sectional view of the optical structure 100, and FIG. 4 is an enlarged view of a concavo-convex shape formed at an interface between the high refractive index layer and the low refractive index layer of the optical structure 100. In each of the cross-sectional views described above, hatching may be omitted for convenience of description. Further, FIGS. 1-4, the display device and the first direction d ₁ parallel to each sheet surface of the optical structure 100 of the liquid crystal panel 15 and sheet at 10, the optical liquid crystal panel 15 and the sheet in the display device 10 FIG. 3 is a cross-sectional view of a plane including the normal direction of the structure 100. In the present embodiment, the first direction d ₁ is a direction parallel to the direction in which the light source 24 of the surface light source device 20 of the edge light type in the display device 10 emits light to the light guide plate 30 as described later. This is the direction in which concave portions 121 and convex portions 122 of the concave-convex shape 120 described later formed on the optical structure 100 are alternately arranged.

(Display device)
First, the overall configuration of the display device 10 will be described. As shown in FIG. 1, a display device 10 according to the present embodiment includes a liquid crystal panel 15 and a surface light source arranged to face rear surface 15 </ b> B of liquid crystal panel 15 and illuminating liquid crystal panel 15 in a planar manner from rear surface 15 </ b> B side. The liquid crystal display includes a device 20 and a sheet-shaped optical structure 100 disposed on a display surface 15A of the liquid crystal panel 15. The liquid crystal panel 15 has a display surface 15A for displaying a still image or a moving image, and a back surface 15B arranged opposite to the display surface 15A. In the display device 10, the liquid crystal panel 15 functions as a shutter that controls transmission or blocking of light from the surface light source device 20 for each region (sub-pixel) in which a pixel is formed. An image is displayed.

  The illustrated liquid crystal panel 15 includes an upper polarizer 13 disposed on the light exit side, a lower polarizer 14 disposed on the light incident side, and a liquid crystal disposed between the upper polarizer 13 and the lower polarizer 14. And a layer 12. The polarizing plates 14 and 13 decompose incident light into two orthogonal polarization components (for example, a P-wave and an S-wave) and oscillate in one direction (a direction parallel to the transmission axis) (for example, a P-polarization component). Wave), and has a function of absorbing a linearly polarized component (for example, S-wave) oscillating in the other direction (parallel to the absorption axis) orthogonal to the one direction.

  In the liquid crystal layer 12, a voltage can be applied to each region where one pixel is formed, and the orientation of liquid crystal molecules in the liquid crystal layer 12 changes depending on whether or not a voltage is applied. As an example, the polarization component in a specific direction that has passed through the lower polarizer 14 disposed on the light incident side rotates the polarization direction by 90 ° when passing through the liquid crystal layer 12 to which no voltage is applied, and on the other hand, The polarization direction is maintained when passing through the liquid crystal layer 12 to which a voltage is applied. In this case, depending on whether or not a voltage is applied to the liquid crystal layer 12, whether the polarized component oscillating in a specific direction transmitted through the lower polarizing plate 14 further transmits through the upper polarizing plate 13 disposed on the light exit side of the lower polarizing plate 14. Alternatively, it is possible to control whether the light is absorbed and blocked by the upper polarizing plate 13. In this manner, in the liquid crystal panel 15, transmission or blocking of light from the surface light source device 20 can be controlled for each region where pixels are formed.

  In the present embodiment, liquid crystal panel 15 is, for example, a VA (Vertical Alignment) liquid crystal panel. Therefore, when the voltage to the liquid crystal molecules in the liquid crystal layer 12 is off or at the minimum value, the liquid crystal panels 15 are oriented along the normal direction of the display surface 15A, so that the light from the surface light source device 20 is blocked. In this configuration, the transmittance of light from the surface light source device 20 is gradually increased by gradually increasing the voltage with respect to the liquid crystal molecules and gradually tilting the liquid crystal molecules to the side along the display surface 15A. Have. The liquid crystal panel 15 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. The details of the liquid crystal panel 15 are described in various publicly known documents (for example, “Flat Panel Display Dictionary (Tatsuo Uchida, Supervised by Uchiike Hiraki)”, published by the Industrial Research Institute, 2001). Detailed description is omitted.

  Next, the surface light source device 20 will be described. The surface light source device 20 has a light emitting surface 21 that emits light in a planar shape, and in the present embodiment, is used as a device that illuminates the liquid crystal panel 15 from the back surface 15B side. As shown in FIG. 1, the surface light source device 20 is configured as, for example, an edge light type surface light source device, and includes a light guide plate 30 and one side (left side in FIG. 1) of the light guide plate 30. And an optical sheet (prism sheet) 60 and a reflection sheet 28 arranged so as to face the light guide plate 30, respectively. In the illustrated example, the optical sheet 60 is arranged so as to face the liquid crystal panel 15. The light emitting surface 21 of the surface light source device 20 is defined by the light emitting surface 61 of the optical sheet 60.

  In the illustrated example, the light-emitting surface 31 of the light guide plate 30 has a square shape in plan view (shape viewed from above) similarly to the display surface 15A of the liquid crystal panel 15 and the light-emitting surface 21 of the surface light source device 20. Is formed. As a result, as a whole, the light guide plate 30 is configured as a rectangular parallelepiped member having a pair of main surfaces (the light output surface 31 and the back surface 32), and whose sides in the thickness direction are smaller than the other sides. The side surface defined between the pair of main surfaces includes four surfaces. Similarly, the optical sheet 60 and the reflection sheet 28 are generally configured as rectangular parallelepiped members whose sides in the thickness direction are smaller than the other sides.

As shown in FIGS. 1 and 2, the light guide plate 30 includes the above-described light emitting surface 31 formed by one main surface on the liquid crystal panel 15 side, and a back surface 32 formed by the other main surface facing the light emitting surface 31. And a side surface extending between the light emitting surface 31 and the back surface 32, and _one of the two surfaces of the side surfaces facing the first direction d ₁ forms a light incident surface 33. . As shown in FIGS. 1 and 2, the light source 24 is provided so as to face the light incident surface 33. As shown in FIG. 2, the light that has entered the light guide plate 30 from the light incident surface 33 is substantially directed toward the opposite surface 34 facing the light incident surface 33 along the first direction (light guide direction) d _1. the first direction (light guide direction) light guide plate 30 along the d ₁ comes to be guided. Here, the display device 10 according to this embodiment, which first direction d ₁ is assumed to be arranged along the horizontal direction, that is the horizontal direction, in this case, the light from the light source 24 is The light is guided in the left-right direction. However, such an arrangement is not particularly limited, and the display device may be arranged in another mode. Further, in the present embodiment, the surface light source device 20 is of an edge light type, but the surface light source device 20 may be of another type such as a direct type or a back side illuminated type.

  The light guide plate 30 will be described in more detail. In the present embodiment, the back surface 32 of the light guide plate 30 is formed as an uneven surface. As a specific configuration, as shown in FIG. 2, the back surface 32 has an inclined surface 37, a step surface 38 extending in the normal direction of the light guide plate 30, a connection surface 39 extending in the plate surface direction of the light guide plate 30, have. Light is guided in the light guide plate 30 by total reflection at the pair of main surfaces 31 and 32 of the light guide plate 30. On the other hand, the inclined surface 37 is inclined with respect to the plate surface of the light guide plate 30 so as to approach the light emitting surface 31 from the light incident surface 33 side to the opposite surface 34 side. Therefore, the incident angle of the light reflected on the inclined surface 37 when entering the pair of main surfaces 31 and 32 becomes small. When the light is reflected by the inclined surface 37 and the incident angle on the pair of main surfaces 31 and 32 becomes smaller than the total reflection critical angle, the light is emitted from the light guide plate 30 as indicated by L1 in FIG. Become. That is, the inclined surface 37 functions as an element for extracting light from the light guide plate 30. The light guide plate 30 is not limited to the mode in the present embodiment, but may be another mode such as a dot pattern system.

  The light source 24 can be configured in various forms such as a fluorescent lamp such as a linear cold-cathode tube, a point-like LED (light emitting diode), an incandescent lamp, and the like. The light source 24 in the present embodiment is constituted by a number of point-like light emitters 25 arranged in a line along the longitudinal direction of the light incident surface 33, specifically, a number of light emitting diodes (LEDs).

  The reflection sheet 28 is a member disposed so as to face the back surface 32 of the light guide plate 30, and reflects light leaked from the back surface 32 of the light guide plate 30 and makes the light enter the light guide plate 30 again. It is a member for. The reflection sheet 28 is a white scattering reflection sheet, a sheet made of a material having a high reflectance such as a metal, or a sheet containing a thin film (for example, a metal thin film or a dielectric multilayer film) made of a material having a high reflectance as a surface layer. And so on. The reflection on the reflection sheet 28 may be specular reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 28 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

  The optical sheet 60 is a member having a function of changing the traveling direction of transmitted light. As illustrated in FIG. 2, the optical sheet 60 according to the present example includes a main body 65 formed in a plate shape and a plurality of unit prisms (unit shape elements, units) formed on the light incident side surface 67 of the main body 65. Optical element, unit lens) 70. The main body 65 is configured as a flat plate-shaped member having a pair of parallel main surfaces. In the illustrated example, the unit prisms 70 are arranged side by side on the light incident side surface 67 of the main body 65, and each unit prism 70 is formed in a columnar shape and extends in a direction intersecting the arrangement direction. In the present embodiment, one optical sheet 60 is provided on the light guide plate 30, but a plurality of optical sheets may be provided on the light guide plate 30. In this case, the directions of the grooves of the prisms of the respective optical sheets may be different from each other.

  The surface light source device 20 as described above includes the optical sheet 60 so that the light from the light guide plate 30 is converted into a desired traveling direction and is incident on the liquid crystal panel 15. As described above, the transmission or blocking of the light incident on the liquid crystal panel 15 in the liquid crystal layer 12 is controlled for each pixel forming region in accordance with the application of the voltage, whereby an image is formed on the display surface 15A of the liquid crystal panel 15. Will be displayed.

(Optical structure)
Next, the optical structure 100 will be described in detail with reference to FIGS. As shown in FIGS. 2 and 3, an optical structure 100 according to the present embodiment has a sheet-like or film-like base material 101 having a light-emitting surface 101A and a back surface 101B disposed opposite to the light-emitting surface 101A. A low-refractive-index layer 102 formed on a back surface 101B of the substrate 101 and formed in a sheet or film shape extending along the substrate 101 and having a pair of main surfaces opposed in the thickness direction; A sheet or a film is provided on the surface of the rate layer 102 opposite to the substrate 101 and extends along the substrate 101, and has a pair of main surfaces opposed in the thickness direction, The high-refractive-index layer 103 having a higher refractive index than the low-refractive-index layer 102 and the low-refractive-index layer 102 are disposed on the side opposite to the high-refractive-index layer 103 side. Provided in It includes a sheet-shaped or film-shaped anti-reflection layer 104, a. The antireflection layer 104 in the present embodiment is a member corresponding to a so-called surface material that forms the outermost surface on the light emission side.

  The base material 101 is a light-transmitting transparent base material made of resin, glass, or the like, and examples of the material include polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, polyamide, glass, triacetyl cellulose, and the like. . That is, the base material 101 is made of, for example, a film mainly composed of polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, polyamide, triacetyl cellulose, glass, or the like. The thickness of the substrate 101 is, for example, not less than 10 μm and not more than 200 μm. The refractive index of the substrate 101 is, for example, 1.46 or more and 1.67 or less. Note that the main component means a component contained in a proportion of 50% or more or the component contained most in a whole substance among a plurality of components constituting a certain substance.

  As shown in FIG. 2, the optical structure 100 is arranged so that the high refractive index layer 103 faces the display surface 15A side of the display device 10 (the liquid crystal panel 15). In the illustrated example, the high refractive index layer 103 is used. Are in direct contact with the display surface 15A of the liquid crystal panel 15. The antireflection layer 104 forms the outermost surface on the side opposite to the display surface 15A side of the liquid crystal panel 15 in the optical structure 100, and suppresses surface reflection of external light incident on the optical structure 100. It is provided to control. This can prevent the visibility of an image displayed on the display device 10 from being impaired due to surface reflection of external light.

  The refractive index of the antireflection layer 104 is 1.40 or less, and more specifically, 1.35 in the present embodiment as an example. The general refractive index of a surface material such as an anti-reflection layer is about 1.45, and a member having such a refractive index can be obtained at relatively low cost, so that the cost can be suppressed. However, when a surface material having a refractive index of about 1.45 is used, the total reflection critical angle at which light to be emitted from the display device starts to be totally reflected at the interface with air becomes relatively small. The take-out amount is reduced. As a result, when the image on the display device is observed, the brightness of the image may be reduced, and particularly the brightness on the high-angle side may be significantly reduced. On the other hand, in the present embodiment, by setting the refractive index of the anti-reflection layer 104 to 1.40 or less, the total reflection critical angle at which light starts to be totally reflected at the interface between the anti-reflection layer 104 and air is increased. In this case, the light extraction amount is increased as compared with the case of a general surface material. This suppresses undesired reduction in luminance within the viewing angle.

  The inventor of the present invention has conducted intensive studies and found that the refractive index of the anti-reflection layer 104 as a surface material is 1.28 or more in order to prevent surface reflection of external light and sufficiently extract light from a display device. It was found from experiments and simulations that it is preferably 1.40 or less, and particularly preferably 1.30 or more and 1.36 or less. In this embodiment, the antireflection layer 104 as a surface material has a function of suppressing surface reflection of external light, but the surface material does not have to have such a function. Further, in the optical structure 100, the effect of suppressing color change in the viewing angle can be obtained by the optical action of the low refractive index layer 102 and the high refractive index layer 103 described below on light. Can be obtained even if the antireflection layer 104 is not provided.

  The anti-reflection layer 104 is transparent, and the thickness of the anti-reflection layer 104 is, for example, 0.05 μm or more. μm or less. The anti-reflection layer 104 may contain, for example, hollow silica fine particles and a base resin holding the hollow silica fine particles, but is not particularly limited as long as a desired refractive index can be obtained.

  When the anti-reflection layer 104 contains a hollow silica fine particle and a base resin holding the hollow silica fine particle, more specifically, for example, a (meth) acrylic resin, a hollow silica fine particle, a reactive silica fine particle, It may contain two kinds of antifouling agents.

  The (meth) acrylic resin corresponds to the base resin and is a component that functions as a binder component of the hollow silica fine particles and the reactive silica fine particles in the antireflection layer 104. In this specification, “(meth) acryl” means acryl or methacryl. Examples of the (meth) acrylic resin include a polymer or a copolymer of a (meth) acrylic monomer, and the (meth) acrylic monomer is not particularly limited. For example, pentaerythritol tri (meth) acrylate, dipenta Erythritol hexa (meth) acrylate, pentaerythritol (meth) tetraacrylate, dipentaerythritol penta (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, isocyanuric acid EO-modified tri (meth) Acrylates and the like are preferred. These (meth) acrylate monomers may have a part of the molecular skeleton modified, and have been modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol and the like. Things can also be used. These (meth) acrylic monomers may be used alone or in combination of two or more. These (meth) acrylic monomers have excellent curing reactivity and can improve the hardness of the obtained antireflection layer 104.

  The polymer or copolymer obtained by curing the (meth) acrylic monomer preferably has a refractive index of 1.47 or more and 1.53 or less. It is practically impossible to make the refractive index less than 1.47, and if it exceeds 1.53, an antireflection layer having a sufficiently low refractive index may not be obtained.

  The (meth) acrylic monomer preferably has a weight average molecular weight of 250 or more and 1000 or less. If it is less than 250, the number of functional groups is reduced, and the hardness of the obtained antireflection layer 104 may be reduced. If it exceeds 1,000, the functional group equivalent (the number of functional groups / molecular weight) generally becomes small, so that the crosslink density becomes low and the anti-reflection layer 104 having sufficient hardness may not be obtained. The weight average molecular weight of the (meth) acrylic monomer can be determined by gel permeation chromatography (GPC) in terms of polystyrene. As a solvent for the GPC mobile phase, tetrahydrofuran or chloroform can be used. The measurement column may be used in combination with a commercially available column for tetrahydrofuran or chloroform. Examples of the commercially available columns include Shodex GPC KF-801 and GPC-KF800D (both are trade names, manufactured by Showa Denko KK). As the detector, an RI (differential refractive index) detector and a UV detector may be used. Using such a solvent, column, and detector, the weight-average molecular weight can be appropriately measured by, for example, a GPC system such as Shodex GPC-101 (manufactured by Showa Denko KK).

  The hollow silica fine particles are components that serve to lower the refractive index while maintaining the layer strength of the antireflection layer 104. In this specification, the term “hollow silica fine particles” refers to a structure in which gas is filled and / or a porous structure containing gas, and the gas occupation ratio is smaller than the intrinsic refractive index of silica fine particles. Mean silica fine particles whose refractive index decreases in inverse proportion to The antireflection layer 104 can achieve a desired reflectance by containing hollow silica fine particles. Also, the anti-reflection layer 104 can be hard and have a lower refractive index.

  The hollow silica fine particles preferably have an average particle diameter of 5 nm or more and 300 nm or less, more preferably 8 nm or more and 100 nm or less, and even more preferably 10 nm or more and 80 nm or less. If it is less than 5 nm, the porosity of the antireflection layer 104 is insufficient, and the refractive index cannot be sufficiently reduced. On the other hand, if the thickness exceeds 300 nm, irregularities are formed on the surface of the antireflection layer 104, the abrasion resistance of the optical structure 100 is deteriorated, and the strength of the hollow silica fine particles themselves is weakened. This leads to a decrease in film strength. A preferable lower limit of the average particle diameter of the hollow silica fine particles is 10 nm, and a preferable upper limit is 80 nm. Within this range, a desired reflectance can be achieved while maintaining the strength of the antireflection layer 104. The average particle diameter of the hollow silica fine particles means a value measured by, for example, observation by a dynamic light scattering method or a cross-sectional TEM method.

  Specific examples of the hollow silica fine particles are not particularly limited, and preferably include, for example, hollow silica fine particles prepared using the technique disclosed in JP-A-2001-233611. Since the hollow silica fine particles are easy to produce and have high hardness of themselves, when mixed with an organic binder component to form the antireflection layer 104, the layer strength is improved and the refractive index is reduced. It can be adjusted as follows.

  The porosity of the hollow silica fine particles is preferably 6.4% or more and 80.0% or less. When the porosity is less than 6.4%, the refractive index of the antireflection layer 104 cannot be sufficiently reduced. On the other hand, if the porosity exceeds 80.0%, the strength of the hollow silica fine particles may decrease, and the strength of the entire antireflection layer 104 may be insufficient. The porosity of the hollow silica fine particles has a more preferred lower limit of 8.5% and a more preferred upper limit of 76.4%. By having the porosity in this range, the antireflection layer 104 can have a sufficiently low refractive index and can have excellent strength.

  The hollow silica fine particles may be contained in an amount of 80 parts by mass or more and 200 parts by mass or less based on 100 parts by mass of the (meth) acrylic resin. The hollow silica fine particles are preferably contained in an amount of 100 parts by mass or more and 180 parts by mass or less based on 100 parts by mass of the acrylic resin. If the amount of the hollow silica fine particles is less than 80 parts by mass with respect to 100 parts by mass of the (meth) acrylic resin, the refractive index of the antireflection layer 104 cannot be sufficiently reduced. When the amount of the hollow silica fine particles exceeds 200 parts by mass with respect to 100 parts by mass of the (meth) acrylic resin, the scratch resistance is reduced. When the hollow silica fine particles are contained in an amount of 100 parts by mass or more and 180 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic resin, a desired reflectance can be obtained while maintaining the strength of the antireflection layer 104. Can be achieved.

  The reactive silica fine particles are silica fine particles having a reactive functional group on the surface. The reactive silica fine particles are components that play a role in increasing the surface hardness of the antireflection layer 104. The reactive functional group is not particularly limited, and is appropriately selected so as to be capable of crosslinking with the (meth) acrylic resin, and an ultraviolet curable functional group is suitably used. Specific examples of the reactive functional group include an ethylenically unsaturated bond such as a (meth) acryloyl group, a vinyl group and an allyl group, and an epoxy group. Among them, an ethylenically unsaturated bond is preferable.

  As such reactive silica fine particles, it is preferable that at least a part of the surface of the silica fine particles is coated with an organic component, and the surface has a reactive functional group introduced by the organic component. Here, the organic component is a component containing carbon. Further, as an embodiment in which at least a part of the surface of the silica fine particles is coated with an organic component, for example, a compound containing an organic component such as a silane coupling agent reacts with a hydroxyl group present on the surface of the silica fine particles to form a surface. In addition to the mode in which the organic component is bonded to a part of the silica fine particles, or the mode in which the compound containing the organic component having an isocyanate group in the hydroxyl group present on the surface of the silica fine particles reacts, and the organic component is bonded to a part of the surface, For example, an embodiment in which an organic component is attached to a hydroxyl group present on the surface of silica fine particles by an interaction such as a hydrogen bond is included.

  An organic component is coated on at least a part of the surface of the silica fine particles, and the method for preparing the reactive silica fine particles having a reactive functional group introduced by the organic component on the surface is not particularly limited, and a conventionally known method may be used. Can be used.

  The reactive silica fine particles preferably have an average particle diameter of 1 nm or more and 25 nm or less. If it is less than 1 nm, it may not be possible to contribute to the improvement of the hardness of the anti-reflection layer 104, and if it exceeds 25 nm, the transparency of the anti-reflection layer 104 may be reduced, and the transmittance may be deteriorated and the haze may be increased, Further, a defect may be caused in the antireflection layer 104 in some cases. A more preferred lower limit of the average particle size of the reactive silica fine particles is 5 nm, and a more preferred upper limit is 20 nm. In the present specification, the average particle diameter of the reactive silica fine particles is the 50% particle diameter when the reactive silica fine particles in the solution are measured by a dynamic light scattering method and the particle diameter distribution is represented by a cumulative distribution. (D50 median diameter). The average particle diameter can be measured using a Microtrac particle size analyzer manufactured by Nikkiso Co., Ltd. It can also be confirmed by observation by a cross-sectional TEM method.

  The reactive silica fine particles are preferably dispersed as single particles. For example, particles in which 3 to 20, preferably 3 to 10 reactive silica fine particles are bonded by an inorganic chemical bond are used. (Chain particles) may be contained. By containing such chain-like particles, the scratch resistance of the antireflection layer 104 can be improved. The chain particles are preferably contained in a ratio of 0 to 80% by mass based on 100% by mass of all the reactive silica fine particles (single particles + chain particles). If it exceeds 80% by mass, a defect may occur in the antireflection layer 104. A more preferable lower limit of the content ratio of the chain particles is 10% by mass, and a more preferable upper limit is 70% by mass.

  Examples of the inorganic chemical bond include an ionic bond, a metal bond, a coordination bond, and a covalent bond. Above all, even when the reactive silica fine particles are added to a polar solvent, a bond in which the bonded spherical silica fine particles are not dispersed, specifically, a metal bond, a coordination bond, and a covalent bond are preferable. Bonding is preferred. Examples of the polar solvent include water and lower alcohols such as methanol, ethanol, and isopropyl alcohol.

  The average bonding number of the reactive silica fine particles is determined by observing the cross section of the antireflection layer 104 using a SEM image or a TEM image, selecting 100 observed aggregated particles, and selecting the reactive silica contained in each chain particle. The fine particles can be counted and determined as an average value. The average particle diameter of the chain particles refers to the average of the major axis and the minor axis.

  Such chain particles to which the reactive silica fine particles are bonded can be obtained by a conventionally known method. For example, it can be obtained by adjusting the concentration or the pH of the dispersion of the reactive silica fine particles in a monodispersed state, and performing a hydrothermal treatment at a high temperature of 100 ° C. or higher. At this time, a binder component may be added as necessary to promote the binding of the reactive silica fine particles. Further, ions may be removed by passing a dispersion of the reactive silica fine particles to be used through an ion exchange resin. By such an ion exchange treatment, the binding of the reactive silica fine particles can be promoted. After the hydrothermal treatment, the ion exchange treatment may be performed again.

  The reactive silica fine particles described above are preferably contained in an amount of 5 parts by mass or more and 60 parts by mass or less based on 100 parts by mass of the (meth) acrylic resin. If the amount is less than 5 parts by mass, the hardness of the antireflection layer 104 cannot be sufficiently increased. If the amount exceeds 60 parts by mass, the adhesion to other layers may be insufficient. Further, the effect of merely adding the reactive silica fine particles is not seen, which leads to an increase in manufacturing cost and an increase in reflectance. A preferred lower limit of the content of the reactive silica fine particles is 10 parts by mass, and a preferred upper limit is 50 parts by mass. By being in this range, the film strength of the antireflection layer 104 can be improved without impairing the reflectance and the like.

  Further, since the scratch resistance of the antireflection layer 104 can be further improved, the content of the reactive silica fine particles in the antireflection layer 104 is appropriately adjusted in relation to the content of the hollow silica fine particles described above. Is preferred. Specifically, the compounding ratio of the hollow silica fine particles to the (meth) acrylic resin (content of hollow silica fine particles / content of (meth) acrylic resin) is 0.9 to 1.1 ((meth) acrylic resin). When the amount of the hollow silica fine particles is 90 parts by mass or more and 110 parts by mass or less with respect to 100 parts by mass of the acrylic resin, the content of the reactive silica fine particles is 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic resin. It is preferable that the amount is not less than 40 parts by mass or more. The mixing ratio of the hollow silica fine particles to the (meth) acrylic resin is from 1.1 to 1.4 (100 parts by weight of the (meth) acrylic resin, 110 to 140 parts by weight of the hollow silica fine particles. Below), the content of the reactive silica fine particles is preferably 40 parts by mass or more and 60 parts by mass or less based on 100 parts by mass of the (meth) acrylic resin.

  Further, the antireflection layer 104 contains an antifouling agent made of a fluorine-based compound and an antifouling agent made of a fluorine-silicone-based compound as the antifouling agent. By using two kinds of antifouling agents in this manner, for example, by containing the antifouling agent comprising the above-mentioned fluorine-based compound, the fingerprint adhesion preventing performance and the fingerprint wiping performance are excellent. Further, by containing the antifouling agent comprising the above-mentioned fluorine-silicone compound, the magic repelling performance, the magic wiping performance, the slipperiness and the scratch resistance are excellent, and furthermore, the antireflection layer 104 has a defect. Can be suppressed.

  The content of the fluorine-based compound is not particularly limited, but may be 1.0 part by mass or more and 10.0 parts by mass or less based on a total of 100 parts by mass of the hollow silica fine particles and the (meth) acrylic resin. preferable.

  When the antireflection layer 104 is configured as described above, the respective mass parts of the hollow silica fine particles, the (meth) acrylic resin serving as the base resin, and the reactive silica fine particles in the antireflection layer 104 are, for example, the antireflection layer 104. It can be estimated by specifying the area ratio of each component using the SEM image of the cross section, and considering the specific gravity of each component. Further, it can also be specified by specifying the manufacturing process of the antireflection layer 104.

Next, the low refractive index layer 102 and the high refractive index layer 103 will be described. As shown in FIG. 3, in the present embodiment, the low refractive index layer 102 has a plurality of lens portions 110 on a surface opposite to the base material 101 side, and the lens portion 110 includes the low refractive index layer 102. and it is formed so as to project the high refractive index layer 103 side along the common normal direction d ₃ of the high refractive index layer 103. That is, the low-refractive-index layer 102 includes a film-shaped layer main body 102A having a surface facing the substrate 101 side and a rear surface facing the high-refractive-index layer 103 side, and a rear surface of the layer main body 102A. And a plurality of lens units 110 arranged side by side. On the other hand, the high-refractive-index layer 103 is laminated on the low-refractive-index layer 102 so as to cover the lens unit 110 and fill the space between the plurality of lens units 110. As a result, in the present embodiment, the interface between the low refractive index layer 102 and the high refractive index layer 103 forms an uneven shape 120.

The concavo-convex shape 120 is formed by forming one cycle with one concave part 121 and one convex part 122, and repeatedly forming the shape with one cycle. In addition, it is recessed toward the low-refractive-index layer 102 side with respect to a reference line SL extending in parallel with the main surfaces of the low-refractive-index layer 102 and the high-refractive-index layer 103 through a midpoint between the bottom of the concave portion 121 and the top of the convex portion 122. The portion corresponds to the concave portion 121, and the portion that protrudes toward the high refractive index layer 103 with respect to the reference line SL corresponds to the convex portion 122. Each recess 121 and projection 122 are disposed in a first direction d ₁ parallel to the main surface of the low refractive index layer 102 and the high-refractive index layer 103, the first direction d ₁ and the non-parallel, in particular the first crossing the direction d _1, and extends linearly along the second direction d ₂ perpendicular in this example. As shown in FIG. 3, the normal direction d ₃ of the low refractive index layer 102 and the high-refractive index layer 103 have a relationship that is perpendicular to both the first direction d ₁ and the second direction d _2. In the present embodiment, the above-mentioned state “extending parallel to the main surfaces of the low-refractive-index layer 102 and the high-refractive-index layer 103” corresponds to one of the flat surfaces of the low-refractive-index layer 102 and the high-refractive-index layer 103. The low-refractive-index layer 102 is a plane that extends parallel to the main surface of the low-refractive-index layer 102 and the direction in which the concave portions 121 and the convex portions 122 at the interface between the low-refractive index layer 102 and the high This means a state in which the high refractive index layer 103 extends in parallel with the other main surface.

Here, each of the concave portion 121 and the convex portion 122 of the present embodiment has flat portions 121A and 122A extending along the surface direction of the low refractive index layer 102 and the high refractive index layer 103, as shown in FIG. More specifically, the bottom of the concave portion 121 is a flat portion 121A, and the top of the convex portion 122 is a flat portion 122A. The side surface 120S of the concave-convex shape 120 extending between the flat portion 121A of the concave portion 121 and the flat portion 122A of the convex portion 122 is a curved surface that protrudes toward the high refractive index layer 103 side. Side 120S, this is formed a straight line extending along a direction normal to d ₃ from the end point of the flat portion 121A so as not to exceed in the surface direction of connecting. Thereby, it becomes possible to cut out the low refractive index layer 102 having the lens portion 110 forming the side surface 120S. In the present embodiment, the side surface 120S is a curved surface, but the side surface 120S may be a bent surface (polygonal shape) convex toward the high refractive index layer 103 side. Further, the side surface 120S formed as a curved surface may be formed along a circular arc of a perfect circle, or may be formed along an arc of an ellipse.

  The uneven shape 120 as described above is displayed on the display surface 15A by exerting an optical effect such as reflection, refraction, and transmission on light for displaying an image emitted from the display surface 15A. It is provided to improve the display quality of an image. More specifically, in the optical structure 100 according to the present embodiment, the high-refractive-index layer 103 of the low-refractive-index layer 102 and the high-refractive-index layer 103 is connected to the display surface 15A of the display device 10 as described above. The flat portions 121A and 122A are formed on the concave and convex shape 120, and two side surfaces 120S adjacent to each other across the flat portion 121A of the concave portion 121 have a low refractive index from the high refractive index layer 103 side. A tapered shape is formed toward the refractive index layer 102 side, and two side surfaces 120S adjacent to each other across the flat portion 122A of the projection 122 have a tapered shape from the low refractive index layer 102 side to the high refractive index layer 103 side. Form. Thereby, while maintaining good display quality in front view of the display device 10, good display quality can be locally obtained in a part of the angle range on the high angle side within the viewing angle.

  More specifically, when the above-described various shapes are employed, light entering the low refractive index layer 102 from the flat portion 122A of the convex portion 122 and traveling from the low refractive index layer 102 to the side surface 120S is totally reflected by the side surface 120S. Instead, a part is reflected on the side surface 120S, and a part is refracted and transmitted. At this time, the reflected light is collected in the front view direction and an angle range close thereto. Light that does not enter the low refractive index layer 102 from the flat portion 122A of the convex portion 122 but goes from the side surface 120S to the low refractive index layer 102 side is totally reflected by the side surface 120S, and the angle range on the high angle side Gather in Here, the variation in the color change within the viewing angle that occurs in the liquid crystal display device may be caused by, for example, the ratio of the intensity of red, blue, and green light projected when displaying a color image varies with the angle. However, when the above-described shape is adopted, such red, blue, and green light can be collected in a front view direction and an angle range close thereto and an angle range on a high angle side. The present inventor has found that the concentration of light on the two regions allows the intensity of red, blue, and green light on the high angle side with respect to the ratio of the intensity of red, blue, and green light in the front view direction, for example. It has been found that the change of the ratio of the light can be suppressed, and the color change of the light in the angle range on the high angle side with respect to the color of the light projected in the front view direction can be locally and effectively suppressed. In the present invention, various shapes as described above are employed based on such knowledge.

  In addition, the present inventor proposes that when the side surface 120S is a curved surface that is convex toward the high refractive index layer 103 side or a bent surface (polygonal shape) as in the present embodiment, the high angle side within the viewing angle is used. By being able to disperse the light in a part of the angle range, the color change in the part of the high angle side with respect to the color of the light projected in the front view direction can be particularly effectively suppressed. According to the present embodiment, a configuration in which the side surface 120S is a curved surface is employed.

  Further, in the present embodiment, the low refractive index layer 102 is formed so that the difference between the refractive index of the low refractive index layer 102 and the refractive index of the high refractive index layer 103 is in the range of 0.05 to 0.25. And the high refractive index layer 103 are selected. The low-refractive-index layer 102 is disposed so as to face the front side of the display device 10, that is, in the direction in which light is projected, and the high-refractive-index layer 103 is directed toward the display surface 15A of the liquid crystal panel 15. Are located. In the illustrated example, the high refractive index layer 103 is an adhesive layer, and the optical structure 100 is joined to the display surface 15A of the liquid crystal panel 15 by the high refractive index layer 103, as shown in FIG. . The low-refractive-index layer 102 and the high-refractive-index layer 103 are also members having optical transparency, and their materials are not particularly limited. Note that the high refractive index layer 103 may be joined to the display surface 15A of the liquid crystal panel 15 via another layer, and may not be an adhesive layer.

  The low refractive index layer 102 may be formed by, for example, curing an ultraviolet curable resin, an electron beam curable resin, or a thermosetting resin. When the low refractive index layer 102 is formed by curing an ultraviolet curable resin, the ultraviolet curable resin may include an acrylic resin or may include an epoxy resin.

  Similarly, the high refractive index layer 103 may be formed by curing, for example, an ultraviolet curable resin, an electron beam curable resin, or a thermosetting resin. When the high refractive index layer 103 is formed by curing an ultraviolet curable resin, the ultraviolet curable resin may include an acrylic resin or may include an epoxy resin. When the high refractive index layer 103 is formed as an adhesive layer, the high refractive index layer 103 may be formed from an acrylic resin adhesive.

The behavior of light in the display device 10 of the present embodiment as described above will be described with reference to FIG. 2 and the like. When displaying an image on the display device 10 of the present embodiment, first, light is emitted from the light source 24. Irradiated. Thus the light incident from the light incident surface 33 into the light guide plate 30 is, as shown in FIG. 2, toward the opposite surface 34 facing the first direction d incidence surface 33 along _a generally first direction The light is guided inside the light guide plate 30 along d ₁ . The guided light repeats total reflection between the main surfaces 31 and 32 of the light guide plate 30, and when the angle of incidence on the main surface 31 becomes less than the critical angle for total reflection, as shown by L1 in FIG. Light is emitted from the light plate 30. The light emitted from the light guide plate 30 is converted into a desired traveling direction by the unit prism 70 when passing through the optical sheet 60 and enters the liquid crystal panel 15. Next, transmission or cutoff of the light incident on the liquid crystal panel 15 in the liquid crystal layer 12 is controlled for each pixel forming region in accordance with the application of a voltage, whereby an image is displayed on the display surface 15A of the liquid crystal panel 15. .

  In the present embodiment, light emitted from display surface 15A of liquid crystal panel 15 enters optical structure 100. At this time, the light incident on the optical structure 100 from the liquid crystal panel 15 side is given an optical action by reflection and transmission (refraction) by the uneven shape 120. That is, at this time, light that enters the low-refractive-index layer 102 from the flat portion 122A of the convex portion 122 and travels from the low-refractive-index layer 102 to the side surface 120S is not totally reflected at the side surface 120S, but is partially reflected. Some are refracted and transmitted. At this time, the reflected light is collected in the front view direction and an angle range close thereto. On the other hand, light that does not enter the low-refractive-index layer 102 from the flat portion 122A of the convex portion 122 but goes from the side surface 120S toward the low-refractive-index layer 102 is totally reflected by the side surface 120S and has an angle on the high-angle side. Gather in the range. Thereby, the color change of light in the angle range on the higher angle side with respect to the color of light projected in the front view direction is suppressed. On the other hand, the flat portions 121A and 122A of the concavo-convex shape 120 have a function of transmitting light vertically incident on the optical structure 100 in the front direction. Thereby, in the present embodiment, diffusion of light emitted to the front side is suppressed, and display quality in a front view is favorably maintained. At this time, as described above, the light reflected by the side surface 120S and collected in the front view direction and the angle range close to the front view direction does not largely diffuse, so that the light quality does not affect the display quality in the front view. .

  As described above, in the present embodiment, while maintaining good display quality in front view of the display device 10, locally good display quality is obtained in a part of the angle range on the high angle side within the viewing angle. Will be able to gain.

Hereinafter, the preferable conditions of the uneven shape 120 will be described in detail with reference to FIG. 4, reference numeral θ1 denotes the minimum angle of the side surface 120S of the uneven shape 120 makes with the normal line direction _{d 3} of the low refractive index layer 102 and the high-refractive index layer 103, reference numeral θ2 is the side 120S of the irregularities 120 It indicates the maximum angle formed between the normal direction d ₃ of the low refractive index layer 102 and the high-refractive index layer 103. Specifically, the minimum angle θ1, the angle (narrow angle of the tangent through the concave portion 121 side of the end point of the side surface 120S constituting the normal direction d ₃ of the low refractive index layer 102 and the high-refractive index layer 103, those causing other words acute angle a angle), the maximum angle θ2, the angle (narrow angle of the tangent passing through the convex portion 122 side of the end point of the side surface 120S constituting the normal direction d ₃ of the low refractive index layer 102 and the high-refractive index layer 103, in other words (The angle that becomes the acute angle). In the case where the side surface 120S is a broken surface, the minimum angle θ1 is determined by setting a straight line passing through the element surface including the end point of the side surface 120S on the concave portion 121 side as a normal direction d of the interface between the low refractive index layer 102 and the high refractive index layer 103. ₃ becomes the angle, the maximum angle θ2 is the angle which the straight line passing through the element surface including the end point of the convex portion 122 side of the lateral surface 120S makes with the normal line direction d ₃ of the interface of the low refractive index layer 102 and the high-refractive index layer 103 Becomes The code θ0 is a straight line connecting the end points of the side surface 120S of the irregularities, "average slope angle" of the side surface 120S which is defined as the normal direction d ₃ of the low refractive index layer 102 and the high-refractive index layer 103, a Is shown. The average slope angles, the straight line connecting the end points of the side surface 120S of irregular shape, narrow angle of the angle formed by the normal direction d _3, an angle of the direction of the other words acute angle. The symbol P indicates a pitch, which is an interval of one cycle between one concave portion 121 and one convex portion 122 in the concave-convex shape 120. Reference numeral H indicates a height of the concave-convex shape 120 along the normal direction from the concave portion 121 to the convex portion 122, and reference numeral L indicates a distance in a plane direction between both end points of the side surface 120S. The above angles or the like, a direction orthogonal to the main surface of the optical structure 100 in the second direction d _2, i.e. the first direction d _1, an angle or the like in the plane including the normal direction d _3.

  The present inventor has found that the above-mentioned “average slope angle θ0” is preferably 11 degrees or more and 17 degrees or less. When the average slope angle θ0 is set in the range of 11 degrees or more and 17 degrees or less, in the experiments and simulations of the present inventor, the light enters the low-refractive-index layer 102 from the flat portion 122A of the convex portion 122 and has a low refractive index. Part of the light traveling from the refractive index layer 102 to the side surface 120S is reflected by the side surface 120S, so that it is particularly easy to gather in the front view direction and an angle range close thereto, and the light going from the side surface 120S to the low refractive index layer 102 side is It has been found that the light is totally reflected by the side surface 120S and tends to gather in an angle range on the high angle side, particularly in a range of 60 degrees or more and 70 degrees or less. Therefore, when the average slope angle θ0 is set within the above angle range, the color change within the viewing angle with respect to the color of the light projected in the front view direction is performed in a part of the high angle side angle range. It becomes possible to suppress locally particularly effectively.

  The “slope angle range α” is defined by the difference between the maximum angle θ2 and the minimum angle θ1. As a result of earnest research, the present inventor has found that when the above-mentioned average slope angle θ0 is 11 degrees or more and 17 degrees or less, it is preferable that the slope angle range α is 14 degrees or more and 18 degrees or less. Specifically, as a result of earnest research, the present inventor has determined that when the slope angle range α is 14 degrees or more and 18 degrees or less, the slope angle range α is set to a relatively narrow range, so that the height within the viewing angle can be increased. While collecting light in a part of the angle range on the angle side, it is possible to effectively disperse light in this angle range, for example, when red, blue, green light is projected, the angle It has been found that the ratio of the intensity of these lights in the range can be equalized, and as a result, the color change of the light in the angle range on the high angle side with respect to the color of the light projected in the front view direction can be effectively suppressed.

  In addition, the present inventor has found that the ratio β of the total length of the flat portions 121A and 122A to the length of one period of the concave portion 121 and the convex portion 122 of the concave-convex shape 120, that is, with reference to FIG. 4, β = (a + b) It has also been found that / P is preferably 0.60 or more and 0.90 or less, and particularly preferably 0.75 or more and 0.85 or less. Note that a is the width (length) of the flat portion 122A of the convex portion 122, and b is the width (length) of the flat portion 121A of the concave portion 121. In a general liquid crystal panel, light traveling in the front view direction is controlled to an optimal state so that display quality in the front view direction is good, so that a member such as the optical structure 100 is provided. However, it is desirable to use such light effectively. If the ratio β is excessively small, that is, the ratio of the flat portions 121A and 122A is excessively small, the light traveling in the front view direction in which the liquid crystal panel is controlled to the optimum state cannot be effectively used, and the optical structure 100 causes display quality. May be undesirably damaged. Therefore, the inventor of the present invention has set the range of the ratio β as a preferable numerical value as a setting capable of securing a relatively large flat portion 121A, 122A while sufficiently obtaining the optical action by the side surface 120S.

  In the concavo-convex shape 120, particularly when the average slope angle θ0 is 11 degrees or more and 17 degrees or less, the slope angle range α is 14 degrees or more and 18 degrees or less, and the ratio β is 0.75 or more and 0.85 or less, Effectively maintaining good display quality in front view of the display device 10 and locally obtaining good display quality (color change suppressing effect) in a partial angle range on the high angle side within the viewing angle. Can be. However, the uneven shape 120 is useful even when only some of the above three types of dimensional conditions are satisfied.

  Note that the average slope angle θ0, the minimum angle θ1 and the maximum angle θ2 used when obtaining the slope angle range α, and the width a of the flat portion 121A of the concave portion 121 and the flat portion 122A of the convex portion 122 used when calculating the ratio β. The width b and the like can be specified, for example, by capturing and evaluating an SEM image of a cross section when the optical structure 100 is cut in the thickness direction, that is, an SEM image corresponding to the cross section shown in FIG.

  Further, the above three kinds of dimensional conditions, that is, the average slope angle θ0 is 11 ° or more and 17 ° or less, the slope angle range α is 14 ° or more and 18 ° or less, and the ratio β is 0.75 or more and 0.85 or less. In the following case, by adjusting the refractive index of the low-refractive-index layer 102 and the high-refractive-index layer 103, the color of light projected in the front-view direction is inclined in the direction inclined with respect to the front-view direction. The color change Δu′v ′ of the projected light gradually increases from the front view direction to a tendency change angle set between 40 ° and 55 ° with respect to the front view direction, and decreases after the trend change angle. It is possible to form a characteristic that turns into a tendency.

More specifically, light projected from the display surface 15A of the display device 10 (the liquid crystal panel 15) to the outside via the optical structure 100 is directed to the normal direction d of the low refractive index layer 102 and the high refractive index layer 103. ₃ and the front view direction of the parallel display device 10, when observed from the direction inclined with respect to the front view direction in the front view direction and the first plane including the direction d _1, projected to the front view direction The color change Δu′v ′ of the light projected in the inclined direction with respect to the color of the light to be emitted is set between 40 ° and 55 ° from the front view direction to the front view direction. It is possible to form a characteristic that gradually increases up to the angle and turns to decrease after the inclination angle. When such a characteristic occurs, the color change within the viewing angle with respect to the color of the light projected in the front view direction can be locally and effectively suppressed in a partial angle range on the high angle side. It can be said. Note that the tendency change angle means an angle at which a maximum value of a color change Δu′v ′ of light projected in an oblique direction with respect to a color of light projected in a front view direction occurs.

  Note that the color change Δu′v ′ indicates a color difference, and in the present embodiment, a smaller value indicates a smaller color difference with respect to light projected in the front view direction. The color change Δu′v ′ is calculated from the color defined by u ′ and v ′ in the uniform color space. The value of Δu′v ′ at an angle θ in a certain viewing angle is represented by the following equation (1).

  The color coordinates u 'and v' of the uniform color space in the equation (1) are expressed by the following equations (2-1) and (2-2), respectively.

  Here, in each of the above equations, x and y are color coordinates defined in the CIE1931 color space (CIE xyY color space).

  The above-described characteristic of the color change Δu′v ′ is basically generated by any light projected from the display surface 15 </ b> A of the display device 10 (the liquid crystal panel 15). Using a multi-domain VA liquid crystal display device manufactured by Sony Corporation as the main body (liquid crystal panel 15) of the display device provided with the structure 100, the characteristics of the color change Δu′v ′ were confirmed. More specifically, the optical structure 100 is attached to the main body of the display device, a blue image is displayed by a pattern generator, and the color change when the image is projected to the outside via the optical structure 100 is referred to as “Spectroscopy” manufactured by Topcon. It evaluated using the radiometer SR-2.

  When the above three types of dimensional conditions are satisfied, basically, the tendency change angle of the light projected from the display surface 15A to the outside via the optical structure 100 (change point to a decreasing tendency, that is, The color change Δu′v ′ at the maximum value) is the color change Δu′v at an angle corresponding to the tendency change angle of light projected outside from the display surface 15A of the display device 10 without passing through the optical structure 100. The characteristic that the value becomes smaller than 'is further generated. When such additional characteristics occur, the color change Δu′v ′ in a predetermined angle range higher than the tendency change angle of the light projected outside via the optical structure 100 is determined by the optical structure Compared to the case where 100 is not provided, it is possible to significantly suppress the color change, and it is possible to significantly suppress the color change on the high angle side.

  Further, under the above three types of dimensional conditions, the optical structure 100 can be adjusted from the display surface 15A of the display device 10 in the range of 60 degrees or more and 70 degrees or less with respect to the front view direction of the display device 10 by appropriate dimensional adjustment. Correspond to the respective values of the color change Δu′v ′ of the light projected to the outside via the display device 10 from the display surface 15A of the display device 10 without passing through the optical structure 100. The value can be set to half or less of the value of the color change Δu'v 'at the position. In this case, a remarkable color change suppression effect is obtained such that the observer can easily perceive the color change Δu′v ′ in the predetermined angle range on the high angle side.

  The ratio a: b between the width a of the flat portion 122A of the convex portion 122 and the width b of the flat portion 121A of the concave portion 121 is preferably in the range of 1: 6 to 3: 1. According to the inventor's earnest research, by setting a: b in the range of 1: 6 to 3: 1 when the ratio β is in the range of 0.75 or more and 0.85 or less, the side surface 120S increases the high angle. It has been found that light can be made to enter the low-refractive-index layer 102 from the flat portion 122A of the convex portion 122 to such an extent that the color change on the side can be sufficiently suppressed.

Note the thickness in the normal direction _{d 3} layer body 102A in the low refractive index layer 102 is, for example, 0.5μm or more 30μm or less. The thickness in the normal direction _{d 3} of the lens unit 110 in the low-refractive index layer 102 (height) is, for example, 1.0μm or more 30μm or less. The refractive index of the low refractive index layer 102 is, for example, not less than 1.40 and not more than 1.55. On the other hand, the thickness in the normal direction _{d 3} of the high refractive index layer 103 from the flat portion 122A of the projection 122 to the surface of the liquid crystal panel 15 side of the high refractive index layer 103 is 5μm or more 100μm or less. The refractive index of the high refractive index layer 103 is, for example, 1.55 or more and 1.90 or less, and is larger than the refractive index of the low refractive index layer 102.

Here, in the graph of FIG. 5, the color change Δu′v ′ within the viewing angle of the display device 10 including the optical structure 100 according to the present embodiment under a predetermined condition, and the optical structure 100 is attached. And a color change Δu′v ′ within the viewing angle of the display device 10 that is not shown. The color change Δu′v ′ of the display device 10 to which the optical structure 100 is not attached refers to the light projected from the display surface 15A of the display device 10 to the outside without passing through the optical structure 100 in the front view direction. This is a color change (color difference) of the light color when viewed from an oblique direction with respect to the light color. More particularly, the color change Δu'v within the field of view angle of the display device 10 having the optical structure 100 according to the embodiment in FIG 5 'is in the second direction d ₂ in the main surface of the optical structure 100 The color of light in the front view direction, which is the color of light when the light is viewed in a direction orthogonal to the front view direction on a plane including the first direction d ₁ and the normal direction d ₃ , which is orthogonal to the first direction d _1. Color change with respect to The color change Δu′v ′ within the viewing angle of the display device 10 to which the optical structure 100 is not attached is a direction orthogonal to the second direction d ₂ on the main surface of the optical structure 100, that is, the first direction d _1. When, in the normal direction d ₃ and the color of light at the time of viewing the light at an oblique direction with respect to the front view direction keep surface corresponding to the plane containing the, that color change with respect to the color of the front view direction of the light It is.

  In the example of FIG. 5, after setting the following conditions, the color change Δu′v ′ of light projected outside via the optical structure 100 and projected outside without passing through the optical structure 100. The color change Δu′v ′ of light was evaluated using “Spectroradiometer SR-2” manufactured by Topcon Corporation.

(Conditions of Optical Structure 100)
Shape of side surface 120S: curved surface convex toward high refractive index layer 103 side Average slope angle θ0: 12.0 degrees Slope angle range α: 15.0 degrees (minimum angle θ1: 5 degrees, maximum angle θ2: 20 degrees) )
・ Ratio β: 0.79

The dimensions and physical properties of each layer of the optical structure 100 are as follows.
The thickness of the layer main body 102A of the low refractive index layer 102 is 4 μm, the thickness of the lens portion 110 is 16 μm, and the refractive index is 1.48.
The thickness of the high refractive index layer 103 from the flat portion 122A of the convex portion 122 to the surface of the high refractive index layer 103 on the liquid crystal panel 15 side is 45 μm, and the refractive index is 1.65.
The thickness of the substrate 101 is 70 μm, and its refractive index is 1.49.
The thickness of the antireflection layer 104 is 12 μm, and its refractive index is 1.35.

(Light projected from the display surface 15A)
-Main body of display device provided with optical structure 100 (liquid crystal panel 15): multi-domain VA liquid crystal display device manufactured by Sony Corporation-Projected light: blue image

  In FIG. 5, a line L1 indicates a color change Δu′v ′ within a viewing angle of the display device 10 including the optical structure 100, and a line L2 indicates a visual field of the display device 10 to which the optical structure 100 is not attached. The color change Δu'v 'in the corner is shown. As is clear from the comparison between the line L1 and the line L2, the color change Δu′v ′ within the viewing angle of the display device 10 including the optical structure 100 is more suppressed than when the optical structure 100 is not attached. In particular, it is significantly suppressed in a range of angles larger than the tendency change angle CA. In the color change Δu′v ′ within the viewing angle of the display device 10 including the optical structure 100 shown in FIG. 5, the above-described tendency change angle CA is set to 48 degrees within the viewing angle. Each value of the color change Δu′v ′ projected outside through the optical structure 100 in the range of 60 degrees or more and 70 degrees or less within the viewing angle is the light projected outside without passing through the optical structure 100. Is less than half the value of the color change Δu'v 'at the position corresponding to each of the above values. In the visual check, no color difference was detected between the light projected in the front view direction via the optical structure 100 and the light projected in the front view direction without passing through the optical structure 100. .

  From the results of FIG. 5 as described above, the optical structure 100 also maintains a good display quality in front view of the display device 10 while maintaining a part of the angle range on the high angle side within the viewing angle, in particular, 60 °. It was confirmed that a good display quality could be locally obtained in the angle range from 70 degrees to 70 degrees.

  As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments, and further modifications can be made to these embodiments. For example, in the above-described embodiment, an example in which the surface light source device 20 is of the edge light type has been described, but the surface light source device 20 may be of a direct type.

  In the above-described embodiment, the optical structure 100 is attached to the upper polarizing plate 13 of the liquid crystal panel 15. At this time, the optical structure 100 may be attached to the upper polarizing plate 13 integrated with the liquid crystal panel 15, or may be attached to the upper polarizing plate 13 before being integrated with the liquid crystal panel 15. Good. That is, a polarizing plate with an optical structure in which the upper polarizing plate 13 and the optical structure 100 are integrated may be integrated with the liquid crystal layer 12 of the liquid crystal panel 15.

  6 to 10 show sectional views of modified examples of the above-described embodiment. The same components as those described in the above-described embodiment among the components in each modified example are denoted by the same reference numerals, and descriptions other than the differences will be omitted.

  In the modification example shown in FIG. 6, the side surface 120S is a bent surface, and has three element surfaces 131, a second element surface 132, and a third element surface 133, each of which is formed as a plane. . In the modification shown in FIG. 7, the side surface 120S includes a curved surface 134 and a bent surface having two element surfaces 135 and 136 configured as flat surfaces. In the modification shown in FIG. 8, the side surface 120S includes a curved surface 137 and a plane 138.

  In the modification of FIG. 9, a flat layer 105 is provided between the base material 101 and the low refractive index layer 102. The flat layer 105 is a layer interposed between the low-refractive-index layer 102 and the substrate 101 to stabilize the bonding state between the low-refractive-index layer 102 and the substrate 101. The flat layer 105 is made of a transparent material having a light-transmitting property. In this embodiment, the flat layer 105 is made of a material that can transmit visible light and ultraviolet light. For example, the flat layer 105 is mainly made of polyester resin, vinyl chloride / vinyl acetate resin, urethane resin, or the like. May be included. The flat layer 105 can be formed, for example, by drying a solution of a polyester resin, a vinyl chloride / vinyl acetate resin, or a urethane resin. The thickness of the flat layer 105 is, for example, 1 μm or more and 20 μm or less. The refractive index of the flat layer 105 is, for example, 1.46 or more and 1.1.67 or less.

  In the modification of FIG. 10, the positional relationship between the low refractive index layer 102 and the high refractive index layer 103 is different from that of the above-described embodiment. That is, the low refractive index layer 102 is disposed closer to the liquid crystal panel 15 than the high refractive index layer 103 is. The side surface 120S is a curved surface that is convex on the low refractive index layer 102 side, a bent surface, or a surface that includes at least one flat surface and a curved surface that is convex on the low refractive index layer 102 side, In the illustrated example, the curved surface is convex toward the low refractive index layer 102 side. Note that the dimensions and physical properties of the low-refractive-index layer 102, the high-refractive-index layer 103, the base material 101, and the antireflection layer 104 are set in the same manner as in the above-described embodiment.

  In the modification shown in FIG. 10, light incident on the optical structure 100 from the liquid crystal panel 15 side shown in FIG. Specifically, at this time, light that enters from the flat portion 122A of the convex portion 122 and travels on the high angle side of the viewing angle toward the curved side surface 120S that is convex toward the low refractive index layer 102 side is totally reflected by the side surface 120S. Then, the light is diffused widely in a direction including the low-angle side, and the light that is perpendicularly incident on the optical structure 100 travels in the front direction by the flat portions 121A and 122A of the concavo-convex shape 120, and the diffusion is suppressed. As a result, a change in color within the viewing angle is suppressed, and a decrease in brightness and contrast in a front view is suppressed.

  The slope angle range α, the average slope angle θ0, and the ratio β of the total length of the flat portions 121A and 122A to the length of one period of the concave portion 121 and the convex portion 122 of the uneven shape 120 described with reference to FIG. In the modification shown in FIG. 10, the slope angle range α is preferably 3 degrees or more and 60 degrees or less. The larger the slope angle range α, the more the light can be dispersed, and the angle is preferably 20 degrees or more, more preferably 30 degrees or more, and even more preferably 40 degrees or more. Further, it is preferable that the average slope angle θ0 is not less than 9 degrees and not more than 18 degrees. Furthermore, referring to the ratio β, that is, FIG. 4, it is particularly preferable that β = (a + b) / P be 0.60 or more and 0.90 or less.

  In consideration of facilitation of die cutting, the larger the ratio β, the easier the die cutting. In consideration of such a manufacturing advantage, the ratio β is preferably equal to or more than 0.50 and less than 1.00, and is 0.60 in consideration of facilitating securing the effect of suppressing color change. More preferably, it is less than 0.90.

  The uneven shape 120 is formed so as to satisfy the above three types of dimensional conditions at the same time, so that the color change within the viewing angle can be extremely effectively maintained while maintaining a good display quality in front view of the display device. It can be suppressed. However, even when only a part of the dimensional conditions described above is satisfied, the uneven shape 120 can effectively suppress a color change within a viewing angle.

  The reason why the dimension setting of the uneven shape 120 is desirable is described in Japanese Patent Application Laid-Open No. 2018-180415 (filed on Apr. 19, 2017, Japanese Patent Application No. 2017-82978) previously filed by the present applicant. The entire contents of Japanese Patent Application No. 2017-82978 are incorporated herein by reference. Further, the provision of the anti-reflection layer 104 suppresses a decrease in luminance, and can effectively improve display quality within a viewing angle as compared with a case where the anti-reflection layer 104 is not provided.

Reference Signs List 10 display device, 12 liquid crystal layer, 13 upper polarizing plate, 14 lower polarizing plate, 15 liquid crystal panel, 15A display surface, 15B back surface, 20 surface light source device, 21 light emitting surface, 24 light source , 28: reflection sheet, 30: light guide plate, 31: light exit surface, 32: back surface, 33: light entrance surface, 34: opposite surface, 37: inclined surface, 38: step surface, 39: connection surface, 60: optical sheet , 65: Main body part, 67: Light incident side surface, 70: Unit prism, 100: Optical structure, 101: Base material, 101A: Light emitting surface, 101B: Back surface, 102: Low refractive index layer, 102A: Layer body, 103 ... high refractive index layer, 104 ... antireflection layer, 110 ... lens part, 120 ... uneven shape, 120S ... side surface, 121 ... concave part, 121A ... flat part, 122 ... convex part, 122A ... flat part, SL ... reference line, d 1 _... the first direction, d 2 _... the second direction, _{d 3} The normal direction

Claims (14)

An optical structure disposed on a display surface of a display device,
A low refractive index layer,
A high refractive index layer laminated on the low refractive index layer and having a higher refractive index than the low refractive index layer,
The interface between the low refractive index layer and the high refractive index layer has an uneven shape,
The concave and convex portions forming the uneven shape are alternately arranged in a first direction parallel to a main surface of the sheet-like low refractive index layer and the high refractive index layer, and are parallel to the main surface in the first direction. Extend linearly along the intersecting second direction,
Each of the concave portion and the convex portion has a flat portion extending along a surface direction of the low refractive index layer and the high refractive index layer,
The concave portion is a portion concave toward the low refractive index layer side, the convex portion is a portion convex toward the high refractive index layer side, between the flat portion of the concave portion and the flat portion of the convex portion. Side surfaces of the uneven shape are formed,
Two side surfaces of the concavo-convex shape adjacent to each other across the flat portion of the concave portion form a tapered shape from the high refractive index layer side toward the low refractive index layer side, and sandwich the flat portion of the convex portion. The two side surfaces of the adjacent concavo-convex shape form a tapered shape from the low refractive index layer side toward the high refractive index layer side,
An optical structure, wherein the high refractive index layer is arranged so as to face a display surface side of the display device.   The side surface of the concave-convex shape is a curved surface convex to the high refractive index layer side, a bent surface, or a surface including at least one curved surface convex to the high refractive index layer side and at least one plane. The optical structure according to claim 1.   The average slope angle of the side surface of the irregular shape defined by a straight line connecting both end points of the side surface of the irregular shape and the normal direction of the low refractive index layer and the high refractive index layer is 11 degrees or more and 17 degrees or more. The optical structure according to claim 2, wherein the optical structure is less than or equal to degrees.   The difference between a maximum angle and a minimum angle that a side surface of the uneven shape forms with a normal direction of the low refractive index layer and the high refractive index layer is 14 degrees or more and 18 degrees or less. Optical structure.   5. The optical device according to claim 2, wherein a ratio of a total length of the flat portion to a length of one period of the concave portion and the convex portion is 0.75 or more and 0.85 or less. 6. Structure.   The light projected from the display surface of the display device to the outside through the optical structure, the front view direction of the display device parallel to the normal direction of the low refractive index layer and the high refractive index layer, When viewed from a direction including the front view direction and a direction inclined with respect to the front view direction on a plane including the first direction, the light is projected in the tilt direction with respect to the color of light projected in the front view direction. The color change Δu′v ′ of light gradually increases from the front view direction to a trend change angle set between 40 ° and 55 ° with respect to the front view direction, and decreases after the trend change angle. The optical structure according to claim 1, wherein   The color change Δu′v ′ at the tendency change angle of the light projected from the display surface to the outside via the optical structure is a color change Δu′v ′ of the light projected from the display surface to the outside without passing through the optical structure. The optical structure according to claim 6, wherein the color change is smaller than a color change Δu′v ′ at an angle corresponding to the tendency change angle.   Each value of the color change Δu′v ′ of light projected from the display surface to the outside through the optical structure in the range of 60 ° or more and 70 ° or less with respect to the front view direction is from the display surface. The optical structure according to claim 7, wherein the value of the color change Δu′v ′ at a position corresponding to each of the values of the light projected outside without passing through the optical structure is half or less. Further comprising a surface material disposed on a side of the low refractive index layer opposite to the high refractive index layer side,
The optical structure according to any one of claims 1 to 8, wherein the refractive index of the surface material is 1.40 or less.   The optical structure according to claim 9, wherein the surface material forms an outermost surface on a side opposite to a display surface side of the display device. A polarizing plate,
A polarizing plate with an optical structure, comprising: the optical structure according to claim 1 on a surface of the polarizing plate.   A display device, wherein the optical structure according to claim 1 is arranged on a display surface. The display device,
A liquid crystal panel having the display surface and a back surface arranged to face the display surface;
The display device according to claim 12, further comprising: a surface light source device disposed to face a back surface of the liquid crystal panel.   The liquid crystal panel is in a state where when the voltage to the liquid crystal molecules is off or at a minimum value, the liquid crystal molecules are aligned along the normal direction of the display surface and light from the surface light source device is blocked, A VA-type liquid crystal configured to gradually increase the voltage for the molecules to gradually increase the transmittance of light from the surface light source device by gradually tilting the liquid crystal molecules to a side along the display surface. The display device according to claim 13, which is a panel.