JP2018180415A - Optical structure and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical structure capable of suppressing in a simple manner unevenness in color within a view angle while keeping well display quality in front view of the display device.SOLUTION: An optical structure 100 includes a high refractive index layer 102, and a low refractive index layer 103 which is laminated on the high refractive index layer 102 with lower refractive index less than the high refractive index layer 102, being arranged on a display surface 15A of a display device 10. An interface between the high refractive index layer 102 and the low refractive index layer 103 has a rough shape 120, and each of a recess part 121 and a protruding part 122 of the rough shape 120 has flat pats 121A and 122A extending along a surface direction of the high refractive index layer 102 and the low refractive index layer 103. A side surface 120S of the rough shape 120 extending between the flat part 121A of the recess part 121 and the flat part 122A of the protruding part 122 has a curved surface or a folded surface expanding toward the low refractive index layer 103 side. The low refractive index layer 103 is arranged to face the display surface 15A side of the display device 10.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical structure that exerts an optical function on light emitted from a display surface of a display device. The present invention also relates to a display device provided with the optical structure.

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

  Among them, in the TN liquid crystal panel, when the voltage is off, the liquid crystal molecules are aligned in a direction parallel to the display surface and light is transmitted, and the voltage is gradually increased to make the liquid crystal molecules By raising to the side along the linear direction, the light transmittance is gradually reduced. In the VA mode liquid crystal panel, when the voltage is off, the liquid crystal molecules are aligned along the normal direction of the display surface and light is blocked, and the voltage is gradually increased to make the liquid crystal molecules the display surface. By inclining along the side, the light transmittance is gradually increased. In the liquid crystal panel of the IPS system, light transmittance is adjusted by rotating liquid crystal molecules aligned along the display surface according to application of a voltage.

  In the liquid crystal panel, control of the amount and range of light traveling to the front side is generally regarded as important, and a device for suitably securing the luminance, the contrast ratio and the color reproduction degree in the front view is made. On the other hand, control of light traveling in a direction inclined with respect to the normal direction of the liquid crystal panel is relatively complicated, and a wide viewing angle can be secured, and variations in luminance, contrast ratio and color reproduction within the viewing angle In order to sufficiently suppress the problem, the structure becomes complicated and the cost may be undesirably increased. For such problems, for example, Patent Documents 1 to 4 disclose an optical member provided on the display surface of the liquid crystal panel to expand the viewing angle by the action of diffusion or the like. With such a member, the viewing angle can be simply improved.

Japanese Patent Application Laid-Open No. 7-43704 Patent No. 3272833 Patent No. 3621959 JP, 2016-126350, A

  By the way, in the liquid crystal panel adopting the VA method among the above-mentioned respective methods, black is displayed when the voltage to the liquid crystal molecules is off, and this black becomes very close to the actual black in front view. The visual contrast ratio can be very high. On the other hand, when viewed from a direction inclined with respect to the normal direction of the display surface, the amount of light leaking from the pixel turned black in the front view is relatively large, and this is compared to the case of the front view. As a result, the contrast ratio may be significantly reduced, and as a result, the contrast ratio within the viewing angle may greatly vary. When an optical member for simply diffusing light is provided to such a liquid crystal panel, the contrast ratio in front view may be undesirably lowered, and the advantage of the VA method may be lost. Similarly, an optical member merely for diffusing light may also undesirably reduce the brightness of the front view.

  In addition, when the VA type liquid crystal panel is viewed from the direction inclined with respect to the normal direction of the display surface, the shape of the emission spectrum in the direction of the inclination changes, and the degree of color reproducibility is lowered. The cause is that the emission spectrum shape change with respect to the viewing angle of blue display is strong (compared to red display and green display). Specifically, "the intensity of the wavelength component corresponding to green" corresponds to "blue" The inventors of the present invention have found that the display color tends to yellow due to a change that increases with respect to the “intensity of the wavelength component”. It is useful if this problem can be solved by the optical member as described above. However, in the above-described conventional techniques, it is difficult to say that a device for effectively suppressing a color change according to the viewing angle is made.

  The present invention has been made in consideration of the above circumstances, and can easily suppress variation in color change in a viewing angle while maintaining good display quality in a front view of a display device. An object of the present invention is to provide an optical structure and a display device provided with the optical structure.

  An optical structure according to the present invention is an optical structure disposed on a display surface of a display device, which is laminated on a high refractive index layer and the high refractive index layer, and the high refractive index layer has a refractive index A lower refractive index layer lower than the lower refractive index layer, the interface between the high refractive index layer and the low refractive index layer has a concavo-convex shape, and each of the concave and convex portions in the concavo-convex shape has the high refractive index Layer and a flat portion extending along the surface direction of the low refractive index layer, and the side surface of the uneven shape extending between the flat portion of the concave portion and the flat portion of the convex portion is the low refractive index layer side The optical structure is a curved surface or a bent surface which is convex, and the low refractive index layer is arranged to be directed to the display surface side of the display device.

  In the optical structure according to the present invention, the difference between the maximum angle and the minimum angle between the side surface of the uneven shape and the normal direction of the high refractive index layer and the low refractive index layer is 3 degrees or more and 60 degrees or less It is preferable that

  Further, in the optical structure according to the present invention, the ratio of the total length of the flat portion to the length of one period of the concave and convex portions of the concavo-convex shape is 0.50 or more and less than 1.00. Is preferred.

  In the optical structure according to the present invention, the concavo-convex shape is defined by a straight line connecting both end points of the side surface of the concavo-convex shape and a normal direction of the high refractive index layer and the low refractive index layer. It is preferable that the average slope angle of the side surface is 9 degrees or more and 18 degrees or less.

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

  A display device according to the present invention includes: a liquid crystal panel having the display surface; and a back surface disposed to face the display surface; and a surface light source device disposed to face the back surface of the liquid crystal panel You may have.

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

  According to the present invention, it is possible to simply suppress the variation in color change in the viewing angle while maintaining the display quality in a front view of the display device favorably.

It is a schematic sectional drawing of a display provided with the optical structure which concerns on one embodiment of this invention. FIG. 6 is a schematic cross-sectional view of the display device for describing the behavior of light in the display device according to the same embodiment. It is an expanded sectional view of the optical structure which concerns on the embodiment. It is an enlarged view of the uneven | corrugated shape formed in the interface between the high refractive index layer of the optical structure which concerns on the embodiment, and a low refractive index layer. It is a figure which shows the uneven | corrugated shape of an optical structure, Comprising: It is the figure which showed the side surface of several uneven | corrugated shape from which a curvature mutually differs. It is the figure which showed the behavior of the light reflected in each of the side surface of several uneven | corrugated shape from which a curvature mutually differs. The graph shows the color change within the viewing angle of the light emitted from the optical structure through the display device according to the curvature (difference between the maximum angle and the minimum angle) of the side surface of the concavo-convex shape of the optical structure. FIG. In the figure which showed the graph which shows the extent of the color change of the light emitted from an optical structure via a display according to the curvature (difference between the maximum angle and the minimum angle) of the side of the concavo-convex shape of an optical structure. is there. The graph shows the radiance within the viewing angle of the light emitted from the optical structure through the display device according to the curvature (difference between the maximum angle and the minimum angle) of the side surface of the uneven shape of the optical structure. FIG. The graph shows the degree of decrease in radiance of light emitted from the optical structure through the display according to the curvature (difference between the maximum angle and the minimum angle) of the side surface of the uneven shape of the optical structure. FIG. Figure showing a graph showing the contrast within the viewing angle of light emitted from the optical structure through the display according to the curvature (difference between the maximum angle and the minimum angle) of the side surface of the concavo-convex shape of the optical structure It is. The figure which showed the graph which showed the grade of the contrast fall of the light emitted from an optical structure via a display according to the curvature (difference between the maximum angle and the minimum angle) of the side of the concavo-convex shape of an optical structure. It is. It is a figure which shows the side surface of the uneven | corrugated shape of an optical structure, Comprising: It is the figure which showed the side surface of several uneven | corrugated shape from which an average slope angle mutually differs. It is the figure which showed the graph which shows the color change in the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the side of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the grade of the color change of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the side of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the radiance in the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the side of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the extent of the fall of the radiance of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the side of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the contrast in the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the side of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the extent of the fall of the contrast of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the side of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the color change in the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the flat part of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the grade of the color change of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the flat part of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the radiance in the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the flat part of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the extent of the fall of the radiance of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the flat part of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph in the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the flat part of the uneven | corrugated shape of an optical structure. It is the figure which showed the graph which shows the extent of the fall of the contrast of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the flat part of the uneven | corrugated shape of an optical structure.

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

  In the present specification, terms such as “sheet”, “film”, “plate”, “layer” and the like are not distinguished from one another based only on the difference in designation. Thus, for example, "sheet" is a concept including members such as films, plates, and layers. Further, in the present specification, “sheet surface (plate surface, film surface)” refers to the plane direction (surface direction of the sheet-like member to be targeted when the target sheet-like member is viewed generally and globally) It refers to the face that coincides with). Furthermore, in the present specification, the normal direction of the sheet-like member refers to the normal direction to the sheet surface of the target sheet-like member.

First, the basic configuration of a display device 10 provided with an optical structure 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic cross-sectional view of a display device 10 provided with 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 the concavo-convex shape formed at the interface between the high refractive index layer and the low refractive index layer of the optical structure 100. In addition, in each said sectional view, hatching may be abbreviate | omitted for convenience of explanation. Moreover, Figures 1-4, cross-section in a plane including the first direction d ₁ to be described later, the common normal line direction of the sheet substrate 101 of the liquid crystal panel 15 and the optical structure 100 in the display device 10, the Figure is shown. In this embodiment, the first direction d ₁ is the direction of emitting light source 24 light guide plate 30 of the surface light source device 20 as the edge light type, as described below in the display device 10.

(Display device)
First, the entire configuration of the display device 10 will be described. As shown in FIG. 1, the display device 10 according to the present embodiment is a surface light source disposed facing the liquid crystal panel 15 and the back surface 15B of the liquid crystal panel 15 and illuminating the liquid crystal panel 15 from the back surface 15B side. The apparatus 20 and the sheet-like optical structure 100 disposed on the display surface 15A of the liquid crystal panel 15 are provided. The liquid crystal panel 15 has a display surface 15A that displays an image that is a still image or a moving image, and a back surface 15B that is disposed to face the display surface 15A. In the display device 10, the liquid crystal panel 15 functions as a shutter for controlling transmission or blocking of light from the surface light source device 20 for each area (sub-pixel) forming a pixel, and the liquid crystal panel 15 drives the display surface 15A. The image is to be displayed.

  The illustrated liquid crystal panel 15 includes an upper polarizing plate 13 disposed on the light output side, a lower polarizing plate 14 disposed on the light incident side, and a liquid crystal disposed between the upper polarizing plate 13 and the lower polarizing plate 14. And a layer 12. The polarizing plates 14 and 13 separate linearly incident light into two orthogonal polarization components (e.g., P wave and S wave) and oscillate in one direction (a direction parallel to the transmission axis) (e.g. Wave) and has a function of absorbing a linearly polarized light 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, voltage application can be performed for each area forming one pixel, and the alignment direction of liquid crystal molecules in the liquid crystal layer 12 changes depending on the presence or absence of voltage application. As an example, the polarization component in the specific direction transmitted through the lower polarization plate 14 disposed on the light entrance side rotates its polarization direction by 90 ° when passing through the liquid crystal layer 12 to which the voltage is not applied, When passing through the liquid crystal layer 12 to which a voltage is applied, the polarization direction is maintained. In this case, whether the polarized light component vibrating in the specific direction transmitted through the lower polarizing plate 14 is further transmitted through the upper polarizing plate 13 disposed on the light exit side of the lower polarizing plate 14 depending on the presence or absence of voltage application to the liquid crystal layer 12 Alternatively, it can be controlled to be absorbed by the upper polarizing plate 13 and blocked. 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 area forming a pixel.

  In the present embodiment, the liquid crystal panel 15 is, for example, a VA (Vertical Alignment) liquid crystal panel. Therefore, in the liquid crystal panel 15, when the voltage to the liquid crystal molecules in the liquid crystal layer 12 is off or at the minimum value, the liquid crystal molecules are aligned along the normal direction of the display surface 15A and the light from the surface light source device 20 is blocked. To gradually increase the transmittance of light from the surface light source device 20 by gradually increasing the voltage to the liquid crystal molecules and gradually tilting the liquid crystal molecules along the display surface 15A. Have. The liquid crystal panel 15 is not limited to the VA type, and may be a TN (Twisted Nematic) liquid crystal panel or an IPS (In-Plane Switching) liquid crystal panel. The details of the liquid crystal panel 15 are described in various well-known documents (for example, "Flat panel display large dictionary (Tatsuo Uchida, Hiraki Uchiike ed.)" Published by 2001 Industrial Research Committee), and here more details 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 for illuminating 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 an edge light type surface light source device as an example, and the light guide plate 30 and the side of 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 disposed to face the light guide plate 30, respectively. In the illustrated example, the optical sheet 60 is disposed 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 exit surface 31 of the light guide plate 30 has a square shape in plan view shape (shape viewed from above), like the display surface 15A of the liquid crystal panel 15 and the light emitting surface 21 of the surface light source device 20. It is formed. As a result, the light guide plate 30 is generally configured as a rectangular parallelepiped member having a pair of main surfaces (the light emitting surface 31 and the back surface 32) in which the side in the thickness direction is 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 reflective sheet 28 are generally configured as rectangular solid members whose sides in the thickness direction are relatively smaller than the other sides.

As shown in FIG. 1 and FIG. 2, the light guide plate 30 has the above-described light emitting surface 31 formed by one main surface on the liquid crystal panel 15 side and a back surface 32 consisting of 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, _one of the two side surfaces facing the first direction d ₁ forms the light incident surface 33. . And as shown to FIG. 1 and FIG. 2, the light source 24 is provided facing the light-incidence surface 33. As shown in FIG. The light incident on the light guide plate 30 from the light incident surface 33, as shown in FIG. 2, toward the opposite surface 34 facing the first direction (light guide direction) d light incident surface 33 along _one generally 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 It will be guided in the left and right direction. However, such an arrangement is not particularly limited, and the display device may be arranged in other manners. Further, in the present embodiment, the surface light source device 20 is an edge light type, but the surface light source device 20 may be another type such as a direct type or a backside illumination type.

  More specifically, 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 includes an inclined surface 37, a step surface 38 extending in the normal direction of the light guide plate 30, and a connection surface 39 extending in the plate surface direction of the light guide plate 30. have. The light guide in the light guide plate 30 is performed by the total reflection action on the pair of main surfaces 31, 32 of the light guide plate 30. On the other hand, the inclined surface 37 is inclined with respect to the surface of the light guide plate 30 so as to approach the light exit surface 31 as it goes from the light incident surface 33 to the opposite surface 34. Therefore, with respect to the light reflected by the inclined surface 37, the incident angle when entering the pair of main surfaces 31, 32 becomes smaller. Then, when the incident angle on the pair of main surfaces 31 and 32 becomes smaller than the total reflection critical angle by reflection at the inclined surface 37, light is emitted from the light guide plate 30 as shown 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 aspect in the present embodiment, and may be another aspect such as a dot pattern method, for example.

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

  The reflective sheet 28 is a member disposed 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 causes the light to 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 high reflectance such as metal, a sheet including a thin film made of a material having high reflectance (for example, metal thin film or dielectric multilayer film) as a surface layer And so on. The reflection on the reflection sheet 28 may be regular 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 shown in FIG. 2, the optical sheet 60 according to this example includes a main body portion 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 portion 65. Optical element, unit lens) 70. The main body portion 65 is configured as a flat plate-like 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 portion 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 is provided with the optical sheet 60 so that the light from the light guide plate 30 is converted into a desired traveling direction or polarization state to be incident on the liquid crystal panel 15. The light incident on the liquid crystal panel 15 is controlled to be transmitted or blocked in the liquid crystal layer 12 for each formation region of the pixel in response to voltage application as described above, whereby an image is formed on the display surface 15A of the liquid crystal panel 15 It 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, the optical structure 100 according to the present embodiment includes a sheet-like base material 101 having a light exit surface 101A and a back surface 101B disposed opposite to the light exit surface 101A, and a base. The film-like high refractive index layer 102 provided on the back surface 101 B of the material 101 and extending along the substrate 101, and provided on the surface of the high refractive index layer 102 opposite to the substrate 101 side A film-like low refractive index layer 103 which extends along 101 and whose refractive index is lower than that of the high refractive index layer 102, and an antireflective layer 104 provided on the light exit surface 101A of the base material 101. .

  The base material 101 is a transparent base material made of resin, glass or the like and having light transmittance, and as its material, for example, polyoliphin, polycarbonate, polyacrylate, polyamide, glass and the like can be mentioned. The optical structure 100 is disposed such that the low refractive index layer 103 is directed to the display surface 15A side of the display device 10. In the illustrated example, the low refractive index layer 103 is directly on the display device 10, that is, the display surface 15A. I am in contact with The antireflection layer 104 is provided to suppress surface reflection of external light incident on the optical structure 100. Thereby, it is possible to prevent the visibility of the image displayed on the display device 10 from being impaired due to the surface reflection of the external light. Note that such an antireflective layer 104 may not be provided.

  As shown in FIG. 3, in the present embodiment, the high refractive index layer 102 has a plurality of lens sections 110 on the surface opposite to the base 101 side, and the lens section 110 is a high refractive index layer 102. It is formed to be convex toward the low refractive index layer 103 side along the normal direction of. That is, the high refractive index layer 102 has a film-like layer main body 102A having a surface facing the base material 101 and a back surface facing the surface facing the low refractive index layer 103, and a back surface of the layer main body 102A. And a plurality of lens portions 110 arranged in line with each other. On the other hand, the low refractive index layer 103 is laminated on the high refractive index layer 102 so as to cover the lens portion 110 and to be filled between the plurality of lens portions 110. As a result, in the present embodiment, the interface between the high refractive index layer 102 and the low refractive index layer 103 forms the concavo-convex shape 120.

The uneven | corrugated shape 120 makes | forms the shape of 1 period by one recessed part 121 and the convex part 122, and is comprised by repeating and forming the shape of this 1 period. A portion recessed toward the high refractive index layer 102 with respect to a reference line SL extending in the surface direction passing through the middle point between the bottom of the recess 121 and the top of the protrusion 122 corresponds to the recess 121 and is lower than the reference line SL. The portion that is convex toward the refractive index layer 103 corresponds to the convex portion 122. Each recess 121 and projection 122 are disposed in a first direction _{d 1,} the first direction _{d 1} and non-parallel, extending linearly in a direction for example perpendicular, respective recesses 121 and protrusions 122 of this embodiment, and it extends linearly in a direction orthogonal to the first direction d _1.

  Here, as shown in FIG. 3, each of the concave portion 121 and the convex portion 122 in the present embodiment has flat portions 121A and 122A extending along the surface direction of the high refractive index layer 102 and the low refractive index layer 103. 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 concavo-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 convex toward the low refractive index layer 103 side. The side surface 120S is formed so as not to exceed the straight line extending in the normal direction from the end point of the flat portion 121A to which it is connected in the surface direction. Thereby, it becomes possible to stamp out the high 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) that is convex toward the low refractive index layer 103 side. The uneven shape 120 as described above is displayed on the display surface 15A by exerting optical effects such as total reflection, refraction, and transmission on light for displaying an image emitted from the display surface 15A. Provided to improve the display quality of the image.

  Further, in the present embodiment, the high refractive index layer 102 is set such that the difference between the refractive index of the high refractive index layer 102 and the refractive index of the low refractive index layer 103 is in the range of 0.05 or more and 0.25 or less. And the low refractive index layer 103 is selected. The high refractive index layer 102 is disposed to face the front side of the display device 10, and the low refractive index layer 103 is disposed to face the display surface 15A of the liquid crystal panel 15. In the illustrated example, the low refractive index layer 103 is an adhesive layer, and as shown in FIG. 2, the optical structure 100 is joined to the display surface 15 A of the liquid crystal panel 15 by the low refractive index layer 103. . The high refractive index layer 102 and the low refractive index layer 103 are also members having optical transparency, and the material is not particularly limited.

  FIG. 4 is an enlarged view showing the concavo-convex shape 120. Hereinafter, the uneven shape 120 will be described in more detail with reference to FIG. In FIG. 4, the symbol θ 1 indicates the minimum angle that the side surface 120 S of the concavo-convex shape 120 makes with the normal direction of the high refractive index layer 102 and the low refractive index layer 103, and the sign θ 2 indicates the high refraction of the side surface 120 S of the concavo-convex shape 120 The maximum angle with the normal direction of the refractive index layer 102 and the low refractive index layer 103 is shown. Specifically, the minimum angle θ1 is an angle formed by the tangent passing through the end point of the side surface 120S on the concave 121 side with the normal direction of the interface between the high refractive index layer 102 and the low refractive index layer 103, and the maximum angle θ2 is the side surface 120S The tangent line passing through the end point on the side of the convex portion 122 is an angle with the normal direction of the interface between the high refractive index layer 102 and the low refractive index layer 103. In the case where the side surface 120S is a broken surface, the minimum angle θ1 is such that a straight line passing through the element surface including the end point on the side of the recess 121 in the side surface 120S is the normal direction of the interface between the high refractive index layer 102 and the low refractive index layer 103. The maximum angle θ2 is an angle formed by the straight line passing through the element surface including the end point on the side of the convex portion 122 in the side surface 120S with the normal direction of the interface between the high refractive index layer 102 and the low refractive index layer 103. The symbol θ 0 indicates the “average slope angle” of the side surface 120S defined by a straight line connecting both end points of the side surface 120S of the uneven shape, and the normal direction of the high refractive index layer 102 and the low refractive index layer 103. ing. Further, a symbol P indicates a pitch which is an interval of one cycle of one concave portion 121 and one convex portion 122 in the concavo-convex shape 120. The symbol H indicates the height of the concavo-convex shape 120 along the normal direction from the concave portion 121 to the convex portion 122, and the symbol L indicates the distance in the surface direction between the end points of the side surface 120S.

  The “slope angle range α” is defined by the difference between the maximum angle θ2 and the minimum angle θ1. The larger the slope angle range α, the larger the curvature of the side surface 120S. The inventors of the present invention have found that it is preferable that the slope angle range α be 3 degrees or more and 60 degrees or less as a result of intensive research. The inventor also found that the above-mentioned “average slope angle θ0” is preferably 9 degrees or more and 18 degrees or less. Furthermore, the inventor of the present invention determines the ratio β of the total length of the flat portions 121A and 122A to the length of one cycle of the concave portion 121 and the convex portion 122 of the concavo-convex shape 120, that is, referring to FIG. It has also been found that it is particularly preferable that / P is 0.60 or more and 0.90 or less. The a is the width (length) of the flat portion 122A of the convex portion 122, and the b is the width (length) of the flat portion 121A of the recess 121. Further, the present inventor has also found that the slope angle range α varies in a particularly preferable range depending on the ratio β. For example, as described later, it has been found that the slope angle range α is particularly preferably 9 degrees or more and 16 degrees or less when the ratio β is 0.80, but if the ratio β changes, The range of such a particularly preferable slope angle range α changes.

  In the concavo-convex shape 120, by forming so as to simultaneously satisfy the three types of dimensional conditions described above, it is extremely effective to maintain the display quality in the front view of the display device 10 well and to change the color within the viewing angle. Can be suppressed. However, even when only a part of the above-described dimensional conditions are satisfied, the concavo-convex shape 120 can effectively suppress the color change in the viewing angle.

  Next, an example in which particularly preferable ranges of the slope angle range α, the average slope angle θ0, and the ratio β described above are specifically derived will be described.

(Relationship between slope angle range (curvature) of side of uneven shape and color change)
First, as an example, it will be described that it is particularly preferable that the slope angle range α be 9 degrees or more and 16 degrees or less when the ratio β is 0.80. FIG. 5 shows the side surfaces 120S of the plurality (three) of uneven shapes 120 having different curvatures, and the sloped angle range α of the side surface 120S becomes larger as the uneven shapes 120 shown on the right side in the figure That is, the curvature is also increasing. When the curvature of the side surface 120S is different, the behavior of light entering from the flat portion 122A of the convex portion 122 and totally reflected by the side surface 120S changes, as shown by the light trajectory LT in FIG. In FIG. 6, in the side surface 120S illustrated on the left side in the drawing, the slope angle range α is 0 degrees, and the curvature radius is infinite (Inf). Although the side surface 120S where the slope angle range α is 0 degree is not included in the concept of “curved surface”, it is illustrated for the convenience of description. Further, in the side surface 120S illustrated at the center in the drawing, the slope angle range α is 12 degrees, and the curvature radius is 55 μm. Further, in the side surface 120S illustrated on the right side in the drawing, the slope angle range α is 22 degrees, and the curvature radius is 31 μm. In FIGS. 5 and 6, the distance L in the surface direction between both end points of the side surface 120S is fixed to a constant value between different asperity shapes 120, and the distance between both end points of the side surface 120S is connected by a straight line The slope length is also fixed at a constant value. Further, the width a of the flat portion 122A of the convex portion 122 is also fixed at a constant value.

  And in FIG. 7A and FIG. 7B, the color change in the viewing angle about the optical structure 100 corresponding to the three uneven | corrugated shapes 120 ((alpha) = 0 degree, 12 degrees, 22 degrees) shown by FIG. 6 was evaluated. A graph is shown. More specifically, FIGS. 7A and 7B show that the ratio β of the total length of the flat portions 121A and 122A to the length of one cycle of the concave portion 121 and the convex portion 122 of the concavo-convex shape 120 is 0.80. It is a graph which evaluates the color change of optical structure 100 corresponding to each above-mentioned concavo-convex shape 120. Among them, FIG. 7A is a graph in which the horizontal axis represents the angle in the viewing angle of light emitted from the optical structure 100 and the vertical axis represents the color change Δu′v ′. The color change within the viewing angle of light incident from the liquid crystal panel 15 side and emitted from the optical structure 100 under the above-mentioned various conditions is shown. In addition, when the angle shown by the horizontal axis is 0 degree (deg), it means that it was visually recognized along the normal direction, for example, 30 degrees is a direction inclined 30 degrees with respect to the normal direction. It means being viewed along. The color change .DELTA.u'v 'indicates the color difference and 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 expressed by the following equation (1).

  The color coordinates u 'and v' in 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 formulas, x and y are color coordinates defined in the CIE 1931 color space (CIE xy Y color space).

  Further, FIG. 7B is a graph in which the horizontal axis shows the value of the slope angle range α and the vertical axis shows the color change score, and it is incident from the main body (the liquid crystal panel 15 side) of the display device 10 and The color change score of the light emitted from the optical structure 100 is shown. Here, the color change score indicates that the smaller the value, the more effectively and effectively the color change is suppressed over the entire range of the viewing angle 0 to 60 degrees with respect to the case where the optical structure 100 is not present. It is an index. The color change score is calculated by the following equation (3). In Equation (3), θ indicates an angle within the viewing angle, Film means that the optical structure 100 is provided in the display device 10, and NonFilm indicates that the optical structure 100 is displayed on the display device 10. It means the case where it is not provided. The color change score is an index created uniquely by the present inventor in order to evaluate the degree of color change. This color change score can be used in the evaluation of the color change of the same member as the optical structure 100 according to the present embodiment, as long as the color change Δu′v ′ can be specified.

  In the evaluation of color change shown in FIGS. 7A and 7B, the evaluation of luminance shown in FIGS. 8A and 8B described later, and the evaluation of contrast shown in FIGS. A multi-domain type VA liquid crystal display device manufactured by the company was used. Then, without the optical structure 100 in the main body of the display device, a color change etc. when a blue image is displayed by the pattern generator, and the optical structure 100 provided on the main body of the display device The color change etc. at the time of displaying were evaluated using "Spectroradiometer SR-2" manufactured by Topcon Corporation. In addition, the evaluation shown in FIG. 11A-FIG. 13B mentioned later and the evaluation shown in FIG. 13A-FIG. 16B were also performed on the conditions similar to the above-mentioned.

  Referring to the graph of FIG. 7A created as described above, the display unit 10 is provided with the optical structure 100 in which the concavo-convex shape 120 having the side surface 120S in which the slope angle range α is 0 degrees, 12 degrees, and 22 degrees is formed. When provided, it is understood that the color change in the viewing angle is suppressed as compared with the case where the optical structure 100 is not provided in the display device 10. On the other hand, in the case where the slope angle range α is 0 degree, it is not possible to say that the graph of the color change is smoothly transitioned in the viewing angle in the range of 30 to 45 in the viewing angle. It has become. From this tendency, the inventor found that the diffusion effect is weak and the effect of suppressing the color change can be reduced when the slope angle range α is too small. In FIG. 6, on the side surface 120S where the slope angle range α is 0 degree, the totally reflected light is emitted in the direction of a constant angle. When the slope angle range α is too small, it is considered that the diffusion effect is weak and the suppression effect of the color change tends to be small due to the phenomenon that the light diffusion angle becomes small as described above.

  Further, when the slope angle range α is 22 degrees, it can be seen that the color change suppression effect is weaker in the range of 30 to 45 degrees in the viewing angle than in the others. From such a tendency, the inventor found that the diffusion effect is weak and the effect of suppressing the color change can be reduced when the slope angle range α is too large. In FIG. 6, on the side surface 120S where the slope angle range α is 22 degrees, light strikes the side surface 120S at an angle equal to or greater than the critical angle, and is refracted to escape. It is considered that due to such a phenomenon, when the slope angle range α is too large, the diffusion effect is weak and the suppression effect of the color change tends to be small.

  On the other hand, the color change score in FIG. 7B is calculated according to the above equation (3), so that the smaller the value is, the color change significantly with respect to the case without the optical structure 100 and within the viewing angle. It is an index indicating that color change is suppressed smoothly. Here, it can be seen from FIG. 7B that the color change score tends to be significantly suppressed when the slope angle range α is in the range of 9 degrees to 16 degrees. The range of slope angle range α between 7 degrees and 20 degrees also tends to decrease with respect to the range outside the color change score, so it can be said that it is a preferable range in terms of suppression of color change. When α is in the range of 9 degrees or more and 16 degrees or less, the value of the color change score is relatively small, and thus it can be said to be a particularly preferable range. Focusing on this point and each knowledge on the change in color change described above, the variation in color change in the viewing angle is significantly suppressed in the range where the slope angle range α of the side surface 120S is 9 degrees or more and 16 degrees or less. It can be evaluated. In FIG. 7B, the color change score in the optical structure 100 at an angle different from the slope angle range α illustrated in FIG. 7A is also shown.

  From the above, the inventor of the present invention has, as an example, a preferable range of the slope angle range α of 7 degrees or more and 20 degrees or less when the ratio β of the flat portions 121A and 122A to one cycle of the uneven shape 120 is 0.80. It has been found that the particularly preferable range is 9 degrees or more and 16 degrees or less. And, in fact, it has been confirmed that the variation in color change in the viewing angle can be effectively suppressed as compared with the case of being outside this range to be within this range. In the graph of FIG. 7B, the color score drops sharply when the slope angle range α exceeds the position of 9 degrees, and the color change score drops sharply when the slope angle range α falls below the position of 16 degrees. If the position is 16 degrees, the value of the color change score is relatively small compared to the case where it is larger, and criticality can be found at each position. In the preferable range of the above-mentioned slope angle range α, the point which can be evaluated that such a color change score falls sharply is defined as the lower limit value and the upper limit value. The slope angle range α is preferably 9 degrees or more and 16 degrees or less, and more preferably 10 degrees or more and 15 degrees or less.

  Further, the inventor of the present invention changes the value of the ratio β to the positive side of 0.80, the range in which the color change score falls sharply as shown in FIG. 7B is the plus of the slope angle range α in FIG. 7B. There is a tendency to spread along the horizontal axis while displacing in the direction, and when the ratio β is changed to the minus side with respect to 0.80, the range of the slope angle range α in which the color change score falls sharply as shown in FIG. Has found that in FIG. 7B, it tends to be displaced in the negative direction. Therefore, as described above, when the ratio β is 0.80, the particularly preferable range of the slope angle range α is 9 degrees or more and 16 degrees or less. However, when the ratio β changes, such a preferable range is It will change.

  FIG. 8A is a graph showing the radiance at a wavelength of 450 nm within the viewing angle of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, the horizontal axis being the viewing angle The middle angle is shown, and the vertical axis is radiance. FIG. 8B is a graph showing the degree of reduction of the radiance of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above-mentioned conditions, the horizontal axis being a slope The value of the angular range α is shown, and the vertical axis shows the radiance reduction rate (denoted as “the luminance reduction rate” in the figure). The radiance reduction rate is an index indicating that the smaller the value, the smaller the degree of reduction in radiance compared to the case where the optical structure 100 is not present.

  FIG. 9A is a graph showing the contrast in the viewing angle of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, and the horizontal axis represents the angle in the viewing angle. And the vertical axis represents the contrast. FIG. 9B is a graph showing the degree of decrease in the contrast of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above conditions, the horizontal axis representing the slope angle The value of the range α is shown, and the vertical axis shows the contrast reduction rate. The contrast reduction rate is an index indicating that the smaller the value, the smaller the degree of contrast reduction compared to the case where the optical structure 100 is not present.

  In the range where the above-described slope angle range α is 9 degrees or more and 16 degrees or less, it can be evaluated that the decrease in luminance and contrast is not excessive compared to the case where the optical structure 100 is not present. Therefore, in the case of this range, it is possible to effectively suppress the color change in the viewing angle while keeping the display quality in the front view of the display device 10 good. From this point as well, it is preferable that the slope angle range α be 9 degrees or more and 16 degrees or less. Note that such a numerical range is only an example of a particularly preferable range, and the present invention can obtain useful effects even when it is different from the numerical range exemplified here.

(Relationship between mean slope angle and color change on the side of uneven shape)
Next, the reason why it is preferable that the average slope angle θ0 of the side surface 120S of the concavo-convex shape 120 is 9 degrees or more and 18 degrees or less will be described. In FIG. 10, the side surfaces 120S of the plurality (three) of uneven shapes 120 having different average slope angles θ0 from one another are shown, and it is meant that the average slope angle θ0 is larger the more to the right in the figure. The side surfaces 120S shown in FIG. 10 have the same curvature (i.e., a is constant). And in FIGS. 11A and 11B, an optical structure corresponding to the concavo-convex shape 120 which becomes the average slope angle θ0 = 6.0 degrees, 8.5 degrees, 11 degrees, 15.0 degrees, 17.5 degrees, and 20 degrees. A graph is shown evaluating the color change within the viewing angle for 100. More specifically, FIGS. 11A and 11B show that the ratio β of the total length of the flat portions 121A and 122A to the length of one cycle of the concave portion 121 and the convex portion 122 of the concavo-convex shape 120 is 0.80. It is a graph which evaluates the color change of optical structure 100 corresponding to each above-mentioned concavo-convex shape 120.

  FIG. 11A is a graph in which the horizontal axis represents the angle in the viewing angle of light emitted from the optical structure 100 and the vertical axis represents the color change Δu′v ′, and the main body of the display device 10 (liquid crystal panel 15 The color change in the viewing angle of the light emitted from the optical structure 100 under the above-mentioned conditions is shown. In the optical structure 100 under each condition, the curvatures of the side surface 120S are set to be equal to each other. Further, FIG. 11B is a graph in which the horizontal axis represents the value of the average slope angle θ0 and the vertical axis represents the color change score, which is incident from the main body (liquid crystal panel 15 side) of the display device 10 and The color change score of the light emitted from the optical structure 100 is shown. The color change score is calculated by the equation (3) described above.

  Referring to FIG. 11A created as described above, the optical structure 100 is displayed in which the concavo-convex shape 120 having the side surface 120S with the average slope angle θ0 of 11 degrees, 15 degrees, 17.5 degrees, and 20 degrees is formed. When provided in the device 10, it is understood that the color change in the viewing angle is suppressed as compared with the case where the optical structure 100 is not provided in the display device 10. On the other hand, when the optical structure 100 having the concavo-convex shape 120 having the side surface 120S having the average slope angle θ0 of 6 degrees and 8.5 degrees is provided in the display device 10, 15 to 25 within the viewing angle It can be seen that the color change in the range of degrees is greater than in the case where the optical structure 100 is not provided, and these are undesirable. From this tendency, when the average slope angle θ0 is too small, the present inventors have found that the diffusion effect is weak and the color change suppression effect can be reduced by reducing the amount of light totally reflected by the side surface 120S. I found out.

  On the other hand, it can be seen from FIG. 11B that the color change score is suitably suppressed when the average slope angle θ0 is in the range of 9 degrees to 18 degrees. Focusing on this point and the knowledge on the change in color change described above, it is considered that the variation in color change within the viewing angle is suitably suppressed in the range where the average slope angle θ0 of the side surface 120S is 9 degrees or more and 18 degrees or less. It can be evaluated.

  From the above, the inventor of the present invention defines the preferable range of the average slope angle θ0 as 9 degrees or more and 18 degrees or less. And, in fact, it has been confirmed that the variation in color change in the viewing angle can be effectively suppressed as compared with the case of being outside this range to be within this range. The average slope angle θ0 is preferably 9 degrees or more and 18 degrees or less, and more preferably 10 degrees or more and 17.5 degrees or less. More preferably, the average slope angle θ0 is 11 degrees or more and 15 degrees or less. Further, the graph of the color change shown in FIG. 11B changes depending on the value β of the total length of the flat portions 121A and 122A to the length of one cycle of the concave portion 121 and the convex portion 122 of the uneven shape 120. The inventors of the present invention have found that when the average slope angle θ0 is 9 degrees or more and 18 degrees or less, good color change suppression effects can be obtained regardless of the value of the ratio β.

  FIG. 12A is a graph showing the radiance at a wavelength of 450 nm within the viewing angle of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, the horizontal axis being the viewing angle The middle angle is shown, and the vertical axis is radiance. FIG. 12B is a graph showing the degree of decrease in radiance of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above-mentioned conditions, the horizontal axis being an average The value of the slope angle θ0 is shown, and the vertical axis shows the radiance reduction rate (denoted as “the luminance reduction rate” in the figure). The radiance reduction rate is an index indicating that the smaller the value, the smaller the degree of reduction in radiance compared to the case where the optical structure 100 is not present.

  FIG. 13A is a graph showing the contrast in the viewing angle of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, and the horizontal axis represents the angle in the viewing angle. And the vertical axis represents the contrast. FIG. 13B is a graph showing the degree of reduction in the contrast of light that is incident from the main body (liquid crystal panel 15 side) of the display device 10 and is emitted from the optical structure 100 under the above-mentioned conditions. The value of the angle θ0 is shown, and the vertical axis shows the contrast reduction rate. The contrast reduction rate is an index indicating that the smaller the value, the smaller the degree of contrast reduction compared to the case where the optical structure 100 is not present.

  From the results of FIGS. 12A to 13B, it was found that the brightness and the contrast and the color change have a trade-off relationship when the average slope angle θ0 is 9 degrees or more and 18 degrees or less.

(Relationship between the ratio of flat part of uneven shape and color change)
Next, when the ratio β of the sum of the widths of the flat portions 121A and 122A to the length of one cycle of the concave portion 121 and the convex portion 122 of the concavo-convex shape 120 is, for example, the slope angle range α is 12 degrees, The fact that it is particularly preferable to be 0.74 or more and 0.83 or less will be described. As described above, the inventor of the present invention has found that the range in which the ratio β is 0.60 or more and 0.90 or less is particularly preferable in the optical structure 100 as a result of earnest research. When the slope angle range α is 12 degrees, the fact that the ratio β is particularly preferably in the range of 0.74 or more and 0.83 or less will be described by way of an example derived from experiments or simulations. The graphs shown in FIG. 14A and FIG. 14B are graphs in the case where the slope angle range α is 12 degrees, and the uneven shape 120 with the ratio β = 0.90, 0.80, 0.75, 0.63 is obtained. A graph is shown that evaluates the color change within the viewing angle for the corresponding optical structure 100. FIG. 14A is a graph in which the horizontal axis represents the angle in the viewing angle of light emitted from the optical structure 100, and the vertical axis represents the color change Δu′v ′. The main body of the display device 10 (liquid crystal panel 15 The color change in the viewing angle of the light emitted from the optical structure 100 under the above-mentioned conditions is shown. Further, FIG. 14B is a graph in which the horizontal axis shows the value of the ratio β and the vertical axis shows the color change score, and it is incident from the main body (the liquid crystal panel 15 side) of the display device 10 and the optical structure of the above conditions. The color change score of the light emitted from the body 100 is shown. The color change score is calculated by the equation (3) described above.

  14A, the display apparatus 10 is provided with the optical structure 100 in which the concavo-convex shape 120 having the side surface 120S in which the ratio β of the flat portion is 0.63, 0.75, 0.80, 0, 90 is formed. In this case, it is understood that the color change in the viewing angle is suppressed as compared with the case where the optical structure 100 is not provided in the display device 10. However, in the concavo-convex shape 120 having the side surface 120S in which the ratio β is 0.90, it can be seen that the degree of color change is smaller as compared with the case where the optical structure 100 is not provided in the display device 10. From such a tendency, the inventor obtained the knowledge that the diffusion effect by the side surface 120S is weak and the suppression effect of the color change may be small when the ratio β is too large.

  On the other hand, it can be seen from FIG. 14B that when the ratio β of flat portions is 0.63, 0.75, 0.80, 0.90, color change in the viewing angle is suppressed. However, when the ratio β is 0.90, it can be evaluated that the color change score is relatively high, that is, the color change is relatively large. When the ratio β is 0.63, although the color change score is low, that is, although it can be evaluated that the color change is small, there is no continuity for values larger than this, and stable color change It is difficult to say that the suppression effect can be obtained. FIG. 14B also shows the color change score in the optical structure 100 at a ratio β different from the ratio β of the flat portion illustrated in FIG. 14A. Focusing on the above points, when the slope angle range α is 12 degrees, the inventor of the present invention changes the color change within the viewing angle in a stable state in the range where the ratio β is 0.70 or more and 0.86 or less. It was evaluated that the variation of Further, in this evaluation, it is considered particularly preferable that the ratio β is 0.74 or more and 0.83 or less in consideration of the graph.

  FIG. 15A is a graph showing the radiance at a wavelength of 450 nm within the viewing angle of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, the horizontal axis being the viewing angle The middle angle is shown, and the vertical axis is radiance. FIG. 15B is a graph showing the degree of decrease in radiance of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above-mentioned conditions, the horizontal axis being a ratio The value of β is shown, and the vertical axis shows the radiance reduction rate (denoted as “the luminance reduction rate” in the figure). The radiance reduction rate is an index indicating that the smaller the value, the smaller the degree of reduction in radiance compared to the case where the optical structure 100 is not present.

  FIG. 16A is a graph showing the contrast in the viewing angle of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, and the horizontal axis represents the angle in the viewing angle. And the vertical axis represents the contrast. FIG. 16B is a graph showing the degree of reduction in the contrast of light incident from the main body (liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above conditions, the horizontal axis being the ratio β The vertical axis represents the contrast reduction rate. The contrast reduction rate is an index indicating that the smaller the value, the smaller the degree of contrast reduction compared to the case where the optical structure 100 is not present.

  When the ratio β is in the range of 0.74 or more and 0.83 or less, it can be evaluated that the decrease in luminance and contrast is not excessive compared to the case where the optical structure 100 is not present. Therefore, in the case of this range, it is possible to effectively suppress the color change in the viewing angle without deteriorating the display quality in the front view of the display device 10. From this point as well, it can be said that the ratio β is preferably 0.74 or more and 0.83 or less.

Further, as described above, when the slope angle range α is 12 degrees, it is a particularly preferable range that the ratio β is 0.74 or more and 0.83 or less. On the other hand, as described above in "Relationship between the slope angle range (curvature) of the side surface of the uneven shape and the color change", when the ratio β is 0.80, the slope angle range α is 9 degrees or more and 16 degrees It is a particularly preferable range to be Then, as a result of intensive investigations of these results, the inventor of the present invention came to be able to determine the preferable value of the slope angle range α from the following relationship that changes in accordance with the value of the ratio β.
The slope angle range α is preferably 83.33β-59.67 degrees or more and 80β-44 degrees or less, and more preferably 66.67β-37.33 degrees or more and 100β-71 degrees or less. However, α is greater than 0 and β is less than 1. Note that, from the above formula, β is preferably 0.55 or more and less than 1.00, and α is preferably more than 0 and less than 36 degrees.
By manufacturing the optical structure 100 according to such conditions, it is possible to simply and effectively suppress the variation of the color change in the viewing angle while keeping the display quality in the front view of the display device 10 good. The optical structure 100 which can be obtained can be obtained.

Further, in the configuration of the display device 10 according to the present embodiment, the light from the surface light source device 20 is incident on the back surface of the optical structure 100. Under the present circumstances, even if the range of the radiation angle of the light from the surface light source device 20 is 0 degree or more and 90 degrees or less, the angle range of the light ray in the inside of the optical structure 100 is the radiation angle of the light from the surface light source device 20 It becomes narrower than the range of This is because light is refracted when the optical structure 100 is incident. Here, although depending on the refractive index of the surface light source device 20 and the optical structure 100, in the configuration of the display device 10 according to the present embodiment, the range of the radiation angle of light from the surface light source device 20 is 0 degree or more When the angle is 90 degrees or less, it is assumed that the angle range of the light beam inside the optical structure 100 can be approximately 0 degrees or more and 60 degrees or less. Specifically, when the refractive index of the high refractive index layer 102 is 1.15 or more, the angle range of light rays in the optical structure 100 can be approximately 0 degrees or more and 60 degrees or less. Moreover, when the refractive index of the high refractive index layer 102 is 1.29, the angle range of the light ray in the inside of the optical structure 100 can be suppressed to 0 degree or more and 51 degrees or less. Furthermore, as a range which facilitates manufacture, when the refractive index of the high refractive index layer 102 is 1.6 or more, the angle range of light rays in the inside of the optical structure 100 is suppressed to approximately 0 degrees or more and 40 degrees or less be able to.
Here, light of an angle larger than the light of the largest angle in the angle range of the light ray in the inside of the optical structure 100 does not need to exert an optical action on the side surface 120S of the uneven shape 120. In view of this point, the slope angle range α may be greater than 0 degrees and not more than 60 degrees in consideration of the maximum angle of the angle range of light rays inside the optical structure 100 assumed. Depending on the value of the refractive index, it may be more than 0 degrees and not more than 40 degrees. The inventor of the present invention has confirmed that when the slope angle range α is 3 degrees or more, the effect of suppressing the color change is visually recognizable. From this point, the slope angle range α is preferably 3 degrees or more and 60 degrees or less, and more preferably 3 degrees or more and 40 degrees or less depending on the value of the refractive index of the high refractive index layer 102. The high refractive index layer in the present invention is referred to as a high refractive index layer in the sense that its refractive index is higher than that of the low refractive index layer.

(The behavior of light in the display device)
Next, the behavior of light in the display device 10 of the present embodiment will be described again with reference to FIG. In the case of displaying an image in the display device 10 of the present embodiment, light is emitted from the light source 24 first. 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 in 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 incident angle on the main surface 31 becomes less than the total reflection critical angle, 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 or polarization state by the unit prism 70 when passing through the optical sheet 60, and enters the liquid crystal panel 15. Next, light incident on the liquid crystal panel 15 is controlled to be transmitted or blocked in the liquid crystal layer 12 for each pixel formation region in response to voltage application, whereby an image is displayed on the display surface 15A of the liquid crystal panel 15 .

  Then, in the present embodiment, the light emitted from the display surface 15A of the liquid crystal panel 15 enters the optical structure 100. At this time, light incident on the optical structure 100 from the liquid crystal panel 15 side is given an optical action by transmission and total reflection by the uneven shape 120. That is, at this time, the light traveling on the high angle side of the viewing angle is totally reflected by the curved side 120S convex on the low refractive index layer 103 side in the concavo-convex shape 120 and widely in the direction including the low angle side. While being diffused, the light vertically 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, the color change in the viewing angle is suppressed, and the decrease in luminance and contrast in front view is suppressed.

  Thereby, according to the present embodiment, it is possible to simply suppress the variation in color change in the viewing angle while maintaining the display quality in the front view of the display device 10 favorably. Further, in the present embodiment, for example, the difference between the maximum angle and the minimum angle (slope angle range α) formed by the side surface 120S of the concavo-convex shape 120 with the normal direction of the high refractive index layer 102 and the low refractive index layer 103 is When the ratio β is 0.80, the variation in color change within the viewing angle can be effectively suppressed by setting 9 degrees or more and 16 degrees or less, and excessive reduction in luminance and contrast is suppressed. can do. The average slope angle θ0 of the side surface 120S defined by the straight line connecting both end points of the side surface 120S of the concavo-convex shape 120 and the normal direction of the high refractive index layer 102 and the low refractive index layer 103 is 9 degrees or more 18 By setting the difference to less than or equal to, it is possible to effectively suppress the variation in color change in the viewing angle. In addition, such a numerical range is only an example of a preferable range, and the present invention can obtain useful effects even when it is different from the numerical range exemplified here.

  Further, as described above, 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, the diffusion of the emitted light is suppressed, and it is possible to suppress the reduction in the luminance and the contrast in the front view. On the other hand, the fact that the uneven shape 120 has the flat portions 121A and 122A has a great merit in manufacturing. Specifically, even if the ratio of the length of the flat portion 121A to the length of the flat portion 122A is arbitrarily changed to a certain extent under the condition that the shape of the side surface 120S of the concavo-convex shape 120 is fixed, the optical characteristics are almost changed do not do. Therefore, in the design stage, the ratio β of the flat portions 121A and 122A to one cycle of the concave portion 121 and the convex portion 122 of the concavo-convex shape 120 is fixed to a desired value, and the length of the flat portion 121A and the length of the flat portion 122A By changing the ratio to a certain degree arbitrarily, it is possible to manufacture the optical structure 100 having the desired optical characteristics in the desired manufacturing process. Specifically, when the ratio of the flat portion 121A of the concave portion 121 is increased, the filling of the low refractive index layer 103 is facilitated. When the ratio of the flat portion 122A of the convex portion 122 is made large, the high refractive index layer 102 can be easily demolded, and the problem of air being mixed in at the time of shaping on the high refractive index layer 102 can be suppressed. It has been found that such a manufacturing advantage can be obtained when the ratio of the flat portion 121A to the flat portion 122A is, for example, 7: 4. The optical characteristics hardly change unless the ratio between the flat portion 121A and the flat portion 122A is an extreme ratio. For example, when the average slope angle θ0 = 11 of the slope angle range α = 12, the ratio β = 0.80, the ratio of the flat portion changes between the flat portion 121A: flat portion 122A = 7: 3 to 3:10. Even when it was made, the optical properties hardly changed.

  Also, considering the facilitation of mold removal, the larger the ratio β, the easier the mold removal. In consideration of such manufacturing merits, the ratio β is preferably 0.50 or more and less than 1.00, and it is 0.60 in consideration of facilitating the effect of suppressing the color change. It is more preferable that it is not less than 0.90.

  As mentioned above, although embodiment of this invention and its modification were described, this invention is not limited to the above-mentioned embodiment, A change is further added with respect to these embodiment and its modification. Is possible. For example, in the above-described embodiment, an example in which the surface light source device 20 is an edge light type is shown, but the surface light source device 20 may be a direct type.

  DESCRIPTION OF SYMBOLS 10 display device 12 liquid crystal layer 13 upper polarizing plate 14 lower polarizing plate 15 liquid crystal panel 15 A display surface 15 B back surface 20 surface light source device 21 light emitting surface 24 light source 25: point-like light emitter, 28: reflection sheet, 30: light guide plate, 60: optical sheet, 100: optical structure, 101: base material, 101A: light exit surface, 101B: back surface, 102: high refractive index layer, 103: low refractive index layer, 104: antireflective layer, 110: lens portion, 120: concave and convex shape, 120S: side surface, 121: concave portion, 121A: flat portion, 122: convex portion, 122A: flat portion

Claims (7)

An optical structure disposed on a display surface of a display device, the optical structure comprising:
A high refractive index layer,
And a low refractive index layer laminated on the high refractive index layer and having a refractive index lower than that of the high refractive index layer.
The interface between the high refractive index layer and the low refractive index layer has a concavo-convex shape,
Each of the concave portion and the convex portion in the concavo-convex shape has a flat portion extending along the surface direction of the high refractive index layer and the low refractive index layer,
The side surface of the uneven shape extending between the flat portion of the concave portion and the flat portion of the convex portion is a curved surface or a bent surface which is convex toward the low refractive index layer side,
An optical structure, wherein the low refractive index layer is arranged to be directed to the display surface side of the display device.   The difference between the maximum angle and the minimum angle between the side surface of the uneven shape and the normal direction of the high refractive index layer and the low refractive index layer is 3 degrees or more and 60 degrees or less. Optical structure.   The optical structure according to claim 1, wherein a ratio of a total length of the flat portion to a length of one cycle of the concave and convex portions and the convex portion is 0.50 or more and less than 1.00.   The average slope angle of the side surface of the concavo-convex shape defined by the straight line connecting both end points of the side surface of the concavo-convex shape, and the normal direction of the high refractive index layer and the low refractive index layer is 9 degrees or more 18 The optical structure according to any one of claims 1 to 3, which is less   A display device, wherein the optical structure according to any one of claims 1 to 4 is disposed on a display surface. The display device is
A liquid crystal panel having the display surface and a back surface disposed to face the display surface;
The display apparatus according to claim 5, further comprising: a surface light source device disposed to face the back surface of the liquid crystal panel.   In the liquid crystal panel, the liquid crystal molecules are aligned along the normal direction of the display surface when the voltage to the liquid crystal molecules is off or at the minimum value, and the light from the surface light source device is blocked. A VA type liquid crystal configured to gradually increase the transmittance of light from the surface light source device by gradually increasing the voltage to the molecules and gradually tilting the liquid crystal molecules to the side along the display surface The display device according to claim 6, which is a panel.

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