JP6447654B2 - Optical structure and display device - Google Patents

Description

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

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

  Among these, in the TN liquid crystal panel, when the voltage is turned 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 so that the liquid crystal molecules are aligned with the display surface method. It has a configuration in which the light transmittance is gradually lowered by rising to the side along the line direction. 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 bring the liquid crystal molecules to the display surface. The light transmission rate is gradually increased by inclining toward the side. An IPS liquid crystal panel adjusts light transmittance by rotating liquid crystal molecules aligned along a display surface in accordance with voltage application.

  In a liquid crystal panel, control of the amount and range of light traveling to the front side is usually regarded as important, and contrivances have been made to favorably ensure brightness, contrast ratio, and color reproducibility in front view. 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, ensuring a wide viewing angle, and variations in luminance, contrast ratio, and color reproduction within the viewing angle. In order to sufficiently suppress the above, the structure becomes complicated and the cost may increase undesirably. In order to deal with such a problem, for example, Patent Documents 1 to 4 disclose optical members provided on the display surface of a liquid crystal panel so as to expand a viewing angle by an action such as diffusion. With such a member, the viewing angle can be easily improved.

JP 7-43704 A Japanese Patent No. 3272833 Japanese Patent No. 3621959 JP-A-2006-126350

  By the way, in the liquid crystal panel adopting the VA method among the above-described methods, black is displayed when the voltage to the liquid crystal molecules is off, and this black is 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, a relatively large amount of light leaks from the pixels that are black in front view, which is compared with that in front view. As a result, the contrast ratio may be significantly reduced. As a result, the contrast ratio within the viewing angle may vary greatly. When an optical member for simply diffusing light is provided for such a liquid crystal panel, the contrast ratio in the front view is undesirably lowered, and the advantages of the VA method may be impaired. Similarly, an optical member for simply diffusing light can undesirably reduce the brightness of the front view.

  Further, when the VA liquid crystal panel is viewed from a direction inclined with respect to the normal direction of the display surface, the shape of the emission spectrum in the inclined direction changes, resulting in a decrease in color reproducibility. 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 present inventors have found that the display color tends to yellow due to a change that increases with respect to the “intensity of the wavelength component to be performed”. It is useful if this problem can be solved by the optical member as described above. However, it is difficult to say that the above-described conventional technology has been devised to effectively suppress the color change according to the viewing angle.

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

  An optical structure according to the present invention is an optical structure disposed on a display surface of a display device, and is laminated on a high refractive index layer and the high refractive index layer, and the refractive index is the high refractive index layer. An 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. A flat portion extending along the surface direction of the layer and the low refractive index layer, and the concave and convex side surface extending between the flat portion of the concave portion and the flat portion of the convex portion is on the low refractive index layer side It is an optical structure that is a curved surface or a bent surface that is convex, and is arranged so that the low refractive index layer faces 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 that the side surface of the uneven shape forms a 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

  In the optical structure according to the present invention, the ratio of the total length of the flat portion to the length of one cycle of the concave and convex portions of the concave and convex shapes is 0.50 or more and less than 1.00. Preferably it is.

  Further, in the optical structure according to the present invention, the uneven shape defined by the straight line connecting both end points of the side surface of the uneven shape and the normal direction of the high refractive index layer and the low refractive index layer. The average slope angle of the side surface is preferably 9 degrees or more and 18 degrees or less.

  The 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, 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.

  The liquid crystal panel is in a state where 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 a 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. A panel may be sufficient.

  ADVANTAGE OF THE INVENTION According to this invention, the dispersion | variation in the color change within a viewing angle can be simply suppressed, maintaining the display quality in the front view of a display apparatus favorable.

It is a schematic sectional drawing of a display apparatus provided with the optical structure concerning one embodiment of the present invention. It is a schematic sectional drawing of the display apparatus for demonstrating the behavior of the light in the display apparatus which concerns on the embodiment. It is an expanded sectional view of the optical structure concerning 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 same 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 some uneven | corrugated shaped side surface from which a curvature mutually differs. The graph which showed the color change within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the curvature (difference between the maximum angle and the minimum angle) of the uneven | corrugated side surface of an optical structure was shown. FIG. The figure which showed the graph which shows the grade of the color change of the light radiate | emitted from an optical structure through a display apparatus according to the curvature (difference between the maximum angle and the minimum angle) of the uneven | corrugated side surface of an optical structure. is there. The graph which showed the radiance within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the curvature (difference between the maximum angle and the minimum angle) of the uneven | corrugated side surface of an optical structure was shown. FIG. A graph showing the degree of decrease in radiance of light emitted from the optical structure through the display device according to the curvature of the side surface of the concave and convex shape of the optical structure (difference between the maximum angle and the minimum angle) is shown. FIG. The figure which showed the graph which shows the contrast within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the curvature (difference between the maximum angle and the minimum angle) of the uneven | corrugated side surface of an optical structure It is. The figure which showed the graph which shows the grade of the fall of the contrast of the light radiate | emitted from an optical structure via a display apparatus according to the curvature (difference between the maximum angle and the minimum angle) of the uneven | corrugated side surface of an optical structure. It is. It is a figure which shows the uneven | corrugated shaped side surface of an optical structure, Comprising: It is the figure which showed the several uneven | corrugated shaped side surface from which an average slope angle differs mutually. It is the figure which showed the graph which shows the color change within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the uneven | corrugated shaped side surface 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 uneven | corrugated shaped side surface of an optical structure. It is the figure which showed the graph which shows the radiance within the viewing angle of the light radiate | emitted from an optical structure through a display apparatus according to the average slope angle of the uneven | corrugated shaped side surface of an optical structure. It is the figure which showed the graph which shows the grade 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 uneven | corrugated shaped side surface of an optical structure. It is the figure which showed the graph which shows the contrast within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the average slope angle of the uneven | corrugated shaped side surface of an optical structure. It is the figure which showed the graph which shows the grade 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 uneven | corrugated shaped side surface of an optical structure. It is the figure which showed the graph which shows the color change within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the uneven | corrugated shaped flat part 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 uneven | corrugated shaped flat part of an optical structure. It is the figure which showed the graph which shows the radiance within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the uneven | corrugated flat part of an optical structure. It is the figure which showed the graph which shows the grade 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 uneven | corrugated shaped flat part of an optical structure. It is the figure which showed the graph which shows the contrast within the viewing angle of the light radiate | emitted from an optical structure via a display apparatus according to the ratio of the uneven | corrugated shaped flat part of an optical structure. It is the figure which showed the graph which shows the grade 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 uneven | corrugated shaped flat part 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”, and “layer” are not distinguished from each other only based on the difference in names. Therefore, for example, a “sheet” is a concept including a member that can also be called a film, a plate, or a layer. Further, in this specification, the “sheet surface (plate surface, film surface)” means the planar direction (surface direction) of the target sheet-like member when the target sheet-like member is viewed as a whole and globally. ) Refers to the surface that matches. Furthermore, in this specification, the normal line direction of a sheet-like member refers to the normal line direction to the sheet | seat surface of the sheet-like member used as object.

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 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 each of the above sectional views, hatching may be omitted for convenience of explanation. 1 to 4 are cross sections in a plane including a first direction d ₁ to be described later and a common normal direction of the sheet-like base material 101 of the liquid crystal panel 15 and the optical structure 100 in the display device 10. The figure is shown. In the present embodiment, the first direction d ₁ is the direction in which the light source 24 of the edge light type surface light source device 20 emits light to the light guide plate 30 as described later in the display device 10.

(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 that is arranged facing the back surface 15B of the liquid crystal panel 15 and illuminates the liquid crystal panel 15 in a planar shape from the back surface 15B side. The apparatus 20 includes a sheet-like optical structure 100 disposed on the display surface 15 </ b> A of the liquid crystal panel 15. The liquid crystal panel 15 includes 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 that controls transmission or blocking of light from the surface light source device 20 for each region (subpixel) in which a pixel is formed, and the liquid crystal panel 15 drives the display surface 15 </ b> A. An image is displayed.

  The illustrated liquid crystal panel 15 includes an upper polarizing plate 13 disposed on the light exit 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. Layer 12. The polarizing plates 14 and 13 decompose the incident light into two orthogonal polarization components (for example, P wave and S wave) and vibrate in one direction (direction parallel to the transmission axis) (for example, P wave). And has a function of absorbing a linearly polarized light component (for example, an S wave) that transmits in the other direction (a 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 alignment direction of the liquid crystal molecules in the liquid crystal layer 12 changes depending on whether or not the voltage is applied. As an example, the polarization component in a specific direction that has passed through the lower polarizing plate 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. The polarization direction is maintained when passing through the liquid crystal layer 12 to which a voltage is applied. In this case, whether the polarization component that vibrates in a specific direction transmitted through the lower polarizing plate 14 further transmits through the upper polarizing plate 13 disposed on the light output side of the lower polarizing plate 14 depending on whether or not voltage is applied to the liquid crystal layer 12. Alternatively, it is possible to control whether the light is absorbed and blocked by the upper polarizing plate 13. In this way, the liquid crystal panel 15 can control the transmission or blocking of light from the surface light source device 20 for each region where pixels are formed.

  In the present embodiment, the liquid crystal panel 15 is a VA (Vertical Alignment) type liquid crystal panel as an example. Therefore, in the liquid crystal panel 15, when the voltage with respect to the liquid crystal molecules in the liquid crystal layer 12 is off or at a 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. In this configuration, the transmittance of light from the surface light source device 20 is gradually increased by gradually increasing the voltage to the liquid crystal molecules and gradually tilting the liquid crystal molecules toward the side 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) type liquid crystal panel or an IPS (In-Plane Switching) type liquid crystal panel. Details of the liquid crystal panel 15 are described in various well-known documents (for example, “Flat Panel Display Dictionary (supervised by Tatsuo Uchida, Hiraki Uchiike)” published in 2001 by the Industrial Research Council). The detailed explanation 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. In the present embodiment, the surface light source device 20 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 an edge light type surface light source device as an example, and the light guide plate 30 and a side of one side of the light guide plate 30 (left side in FIG. 1). And the optical sheet (prism sheet) 60 and the reflective sheet 28 disposed so as to face the light guide plate 30 respectively. In the illustrated example, the optical sheet 60 is disposed facing the liquid crystal panel 15. A light emitting surface 21 of the surface light source device 20 is defined by the light exit surface 61 of the optical sheet 60.

  In the illustrated example, the light emitting surface 31 of the light guide plate 30 has a rectangular shape in plan view (a 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. 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 exit surface 31 and the back surface 32) in which the sides in the thickness direction are smaller than the other sides. A 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 having relatively thin sides in the thickness direction than other sides.

As shown in FIG. 1 and FIG. 2, the light guide plate 30 includes the above-described light exit surface 31 configured by one main surface on the liquid crystal panel 15 side and the back surface 32 including the other main surface facing the light output surface 31. And a side surface extending between the light exit surface 31 and the back surface 32, and _one side surface of the two surfaces facing the first direction d ₁ of the side surfaces forms the light incident surface 33. . As shown in FIGS. 1 and 2, a light source 24 is provided facing the light incident surface 33. As shown in FIG. 2, the light incident on the light guide plate 30 from the light incident surface 33 is generally 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 arrangement is not particularly limited, and the display device may be arranged in another manner. 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 other types such as a direct type and a backside illumination 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. Specifically, 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, a connection surface 39 extending in the plate surface direction of the light guide plate 30, and have. The light guide in the light guide plate 30 is performed by a total reflection action on 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 exit surface 31 from the light incident surface 33 side toward the opposite surface 34 side. Therefore, the incident angle when the light reflected by the inclined surface 37 enters the pair of main surfaces 31 and 32 becomes small. When the incident angle to the pair of main surfaces 31 and 32 becomes less than the total reflection critical angle by reflecting on the inclined surface 37, the 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.

  The light source 24 may be configured in various modes such as 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-like light emitters 25, specifically, a large number of light emitting diodes (LEDs) arranged along the longitudinal direction of the light incident surface 33.

  The reflection sheet 28 is a member disposed so as to face the back surface 32 of the light guide plate 30, reflects light leaked from the back surface 32 of the light guide plate 30, and reenters the light guide plate 30. 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 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. Or the like. 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, unit units) formed on a 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 65, and each unit prism 70 is formed in a column shape and extends in a direction intersecting with 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 direction of the groove of the prism of each optical sheet 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 and polarization state and is incident on the liquid crystal panel 15. As described above, the 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 accordance with voltage application, 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 FIG. 2 and FIG. 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 arranged to face the light exit surface 101A, and a base The film-like high refractive index layer 102 provided on the back surface 101B of the material 101 and extending along the base material 101, and the base material provided on the surface opposite to the base material 101 side of the high refractive index layer 102 And a low-refractive index layer 103 having a lower refractive index than that of the high-refractive index layer 102, and an antireflection layer 104 provided on the light exit surface 101A of the substrate 101. .

  The base material 101 is a transparent base material made of resin, glass or the like and having optical transparency, and examples of the material include polyolefin, polycarbonate, polyacrylate, polyamide, and glass. 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, and in the illustrated example, the low refractive index layer 103 is directly on the display device 10, that is, the display surface 15A. Is in contact with The antireflection layer 104 is provided to suppress surface reflection of external light incident on the optical structure 100. Thereby, it can prevent that the visibility of the image displayed on the display apparatus 10 by the surface reflection of external light is impaired. Note that such an antireflection 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 portions 110 on the surface opposite to the substrate 101 side, and the lens portion 110 includes the high refractive index layer 102. Is formed so as to protrude toward the low refractive index layer 103 along the normal direction. That is, the high refractive index layer 102 includes a film-shaped layer main body 102A having a surface facing the base material 101 side and a back surface facing the surface and facing the low refractive index layer 103 side, and on the back surface of the layer main body 102A. And a plurality of lens portions 110 arranged side by side. 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 fill 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 an uneven shape 120.

The concavo-convex shape 120 is formed by forming one cycle shape with one concave portion 121 and the convex portion 122 and repeatedly forming the one cycle shape. Note that a portion recessed toward the high refractive index layer 102 with respect to the reference line SL extending in the plane direction passing through the midpoint 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. A portion that protrudes toward the refractive index layer 103 corresponds to the protrusion 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, 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 high refractive index layer 102 and the low refractive index layer 103, as shown in FIG. Specifically, the bottom of the recess 121 is a flat part 121A, and the top of the convex part 122 is a flat part 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 that is convex toward the low refractive index layer 103 side. The side surface 120S is formed so as not to cross the straight line extending in the normal direction from the end point of the flat portion 121A to which the side surface 120S is connected. Thereby, the high refractive index layer 102 having the lens part 110 forming the side surface 120S can be punched. In this embodiment, the side surface 120S is a curved surface, but the side surface 120S may be a bent surface (polygonal shape) that protrudes 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 the light for displaying the image emitted from the display surface 15A. It is provided to improve the display quality of the image.

  In this embodiment, the high refractive index layer 102 is set so 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 to 0.25. The low refractive index layer 103 is selected. The high refractive index layer 102 is disposed so as to face the front side of the display device 10, and the low refractive index layer 103 is disposed so as to face the display surface 15 </ b> A side of the liquid crystal panel 15. In the illustrated example, the low refractive index layer 103 is an adhesive layer, and the optical structure 100 is bonded to the display surface 15A of the liquid crystal panel 15 by the low refractive index layer 103 as shown in FIG. . These high-refractive index layer 102 and low-refractive index layer 103 are also light transmissive members, and the materials thereof are not particularly limited.

  FIG. 4 is an enlarged view showing the uneven shape 120. Hereinafter, the uneven shape 120 will be described in more detail with reference to FIG. In FIG. 4, symbol θ <b> 1 indicates the minimum angle that the side surface 120 </ b> S of the uneven shape 120 forms with the normal direction of the high refractive index layer 102 and the low refractive index layer 103, and symbol θ <b> 2 indicates that the side surface 120 </ b> S of the uneven shape 120 is highly refractive. The maximum angle between 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 a tangent line passing through the end point on the concave portion 121 side of the side surface 120S and 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 angle formed by the tangent line passing through the end point on the convex portion 122 side and the normal direction of the interface between the high refractive index layer 102 and the low refractive index layer 103. When the side surface 120S is a bent surface, the minimum angle θ1 is such that the straight line passing through the element surface including the end point on the concave portion 121 side of 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 a straight line passing through the element surface including the end point on the convex portion 122 side of 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 θ0 indicates an “average slope angle” of the side surface 120S defined by a straight line connecting both end points of the uneven side surface 120S and the normal direction of the high refractive index layer 102 and the low refractive index layer 103. ing. Further, the symbol P indicates a pitch that is an interval of one period between one concave portion 121 and the convex portion 122 in the concave-convex shape 120. Further, 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 both end points of the side surface 120S.

  A “slope angle range α” is defined by the difference between the maximum angle θ2 and the minimum angle θ1, and the curvature of the side surface 120S increases as the slope angle range α increases. As a result of earnest research, the present inventor has found that the slope angle range α is preferably 3 degrees or more and 60 degrees or less. The present inventor has also found that the above-mentioned “average slope angle θ0” is preferably 9 degrees or more and 18 degrees or less. Further, the present inventor refers to 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 and convex shape 120, that is, β = (a + b) with reference to FIG. It was also found that / P is particularly preferably from 0.60 to 0.90. 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. Further, the present inventor has also found that the particularly preferable range of the slope angle range α varies depending on the ratio β. For example, as will be described later, when the ratio β is 0.80, it has been found that the slope angle range α is particularly preferably 9 degrees or more and 16 degrees or less, but when the ratio β changes, Such a particularly preferable range of the slope angle range α changes.

  The concavo-convex shape 120 is formed so as to satisfy the above three dimensional conditions at the same time, so that the color change within the viewing angle is extremely effective while maintaining the display quality of the display device 10 in the front view. Can be suppressed. However, even when only a part of the above dimensional conditions is satisfied, the uneven shape 120 can effectively suppress the color change within 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 described will be described.

(Relationship between slope angle range (curvature) and color change of side surface of uneven shape)
First, as an example, it will be described that when the ratio β is 0.80, the slope angle range α is particularly preferably a range of 9 degrees to 16 degrees. FIG. 5 shows the side surfaces 120S of a plurality of (three) concavo-convex shapes 120 having different curvatures, and the slope angle range α of the side surface 120S increases as the concavo-convex shape 120 shown on the right side in the figure. That is, the curvature is also large. 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, on the side surface 120S shown on the left side in the drawing, the slope angle range α is 0 degree and the radius of curvature is infinite (Inf). The side surface 120S in which the slope angle range α is 0 degrees is not included in the concept of “curved surface”, but is illustrated for convenience of explanation. In the side surface 120S shown in the center of the figure, the slope angle range α is 12 degrees and the radius of curvature is 55 μm. In the side surface 120S shown on the right side in the figure, the slope angle range α is 22 degrees, and the radius of curvature is 31 μm. 5 and 6, the distance L between the two end points of the side surface 120S is fixed to a constant value between the different uneven shapes 120, and the distance between the two end points of the side surface 120S is connected by a straight line. The slope length is also fixed at a certain value. Further, the width a of the flat portion 122A of the convex portion 122 is also fixed to a constant value.

  7A and 7B evaluated the color change within the viewing angle for the optical structure 100 corresponding to the three concavo-convex shapes 120 (α = 0 degree, 12 degrees, and 22 degrees) shown in FIG. A graph is shown. Specifically, FIGS. 7A and 7B show the case where 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 concave and convex shape 120 is 0.80. It is a graph which evaluates the color change of the optical structure 100 corresponding to each above-mentioned uneven | corrugated shape 120. FIG. 7A is a graph in which the horizontal axis indicates the angle in the viewing angle of the light emitted from the optical structure 100 and the vertical axis indicates the color change Δu′v ′. A 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-described conditions is shown. In addition, when the angle shown on the horizontal axis is 0 degree (deg), it means that it is visually recognized along the normal direction. For example, 30 degrees is in a direction inclined by 30 degrees with respect to the normal direction. It means that it was visually recognized along. The color change Δu′v ′ indicates a 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 formula (1).

  U ′ and v ′, which are color coordinates in the uniform color space in Expression (1), are expressed by the following Expressions (2-1) and (2-2), respectively.

  In the above equations, x and y are color coordinates defined in the CIE 1931 color space (CIE xyY color space).

  FIG. 7B is a graph in which the horizontal axis indicates the value of the slope angle range α, and the vertical axis indicates the color change score, which is incident from the main body (the liquid crystal panel 15 side) of the display device 10 and satisfies the above-described various conditions. A color change score of light emitted from the optical structure 100 is shown. Here, the color change score indicates that the smaller the value, the more drastically and effectively the color change is suppressed in the entire range of viewing angles of 0 to 60 degrees compared to the case where the optical structure 100 is not provided. It is an indicator. The color change score is calculated by the following equation (3). In Expression (3), θ represents an angle within the viewing angle, Film means that the optical structure 100 is provided in the display device 10, and NonFilm means that the optical structure 100 is in the display device 10. It means the case where it is not provided. The color change score is an index uniquely created by the inventor in order to evaluate the degree of color change. If the color change Δu′v ′ can be specified, this color change score can be used in the evaluation of the color change of the member similar to the optical structure 100 according to the present embodiment.

  7A and 7B, the luminance evaluation shown in FIGS. 8A and 8B described later, and the contrast evaluation shown in FIGS. 9A and 9B, Sony is used as the main body of the display device provided with the optical structure 100. A multi-domain type VA type 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 or the like when a blue image is displayed by the pattern generator, and an image similar to the above is provided by providing the optical structure 100 in the main body of the display device. The color change at the time of display was evaluated using “Spectroradiometer SR-2” manufactured by Topcon Corporation. Note that evaluations shown in FIGS. 11A to 13B and evaluations shown in FIGS. 13A to 16B described later were also performed under the same conditions as described above.

  When the graph of FIG. 7A created as described above is viewed, 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 on the display device 10. When provided, it can be seen that the color change within 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 slope angle range α is 0 degree, it cannot be said that the color change graph smoothly transitions within the viewing angle in the range of 30 to 45 degrees within the viewing angle. It has become. From this tendency, the present inventor has found that when the slope angle range α is too small, the diffusion effect is weak and the effect of suppressing color change can be small. In FIG. 6, on the side surface 120S in which 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 effect of suppressing the color change tends to be small due to the phenomenon that the light diffusing angle becomes small.

  In addition, when the slope angle range α is 22 degrees, it can be seen that the effect of suppressing the color change is weaker in the range of 30 to 45 degrees within the viewing angle than the others. From this tendency, the present inventor has found that when the slope angle range α is too large, the diffusion effect is weak and the effect of suppressing the color change can be reduced. In FIG. 6, on the side surface 120S in which the slope angle range α is 22 degrees, light strikes the side surface 120S at an angle greater than the critical angle, and light is refracted and escapes. Due to such a phenomenon, it is considered that when the slope angle range α is too large, the diffusion effect is weak and the color change suppressing effect tends to be small.

  On the other hand, the color change score in FIG. 7B is calculated by the above-described equation (3), so that the smaller the value, the greater the color change with respect to the absence of the optical structure 100 and within the viewing angle. This is an index indicating that the color change is smoothly suppressed. 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. It should be noted that the range where the slope angle range α is not less than 7 degrees and not more than 20 degrees also has a tendency that the color change score tends to decrease with respect to the outer range. 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, which is a particularly preferable range. When attention is paid to this point and each of the above-described knowledge about the color change, the variation in the color change within the viewing angle is remarkably 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. Can be evaluated. 7B also shows a color change score in the optical structure 100 having an angle different from the slope angle range α illustrated in FIG. 7A.

  As described above, the present inventor, as an example, when the ratio β of the flat portions 121A and 122A to one cycle of the concavo-convex shape 120 is 0.80, the preferable range of the slope angle range α is 7 degrees or more and 20 degrees or less. In particular, the inventors have found that a particularly preferable range is 9 degrees or more and 16 degrees or less. In practice, it has been confirmed that the variation in the color change within the viewing angle can be effectively suppressed when it is within this range, as compared with the case where it is out of this range. In the graph of FIG. 7B, the color score decreases sharply when the slope angle range α exceeds 9 degrees, and the color change score decreases sharply when the slope angle range α falls below 16 degrees. When the position is 16 degrees, the value of the color change score is relatively sufficiently small as compared with the case where the color change score is larger than that, and the criticality can be found at each position. In the preferable range of the slope angle range α described above, the point at which such a color change score can be evaluated to be steeply lowered 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, when the inventor changes the value of the ratio β to a plus side from 0.80, the range in which the color change score sharply decreases as shown in FIG. 7B is the plus of the slope angle range α in FIG. 7B. There is a tendency to spread in the horizontal axis while displacing in the direction, and when the ratio β is changed to the negative side with respect to 0.80, the range of the slope angle range α in which the color change score rapidly decreases as shown in FIG. 7B Knows that it tends to be displaced in the negative direction in FIG. 7B. Therefore, when the ratio β is 0.80 as described above, the particularly preferable range of the slope angle range α is 9 degrees or more and 16 degrees or less, but when the ratio β is changed, such a preferable range is Will change.

  FIG. 8A is a graph showing the radiance at a wavelength of 450 nm within the viewing angle of the light incident from the main body (the liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, and the horizontal axis represents the viewing angle. The inside angle is shown, and the vertical axis shows the radiance. FIG. 8B is a graph showing the degree of decrease in 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, and the horizontal axis is a slope. The value of the angle range α is shown, and the vertical axis shows the radiance reduction rate (indicated as “luminance reduction rate” in the figure). The radiance decrease rate is an index indicating that the smaller the value, the smaller the decrease in radiance compared to the case without the optical structure 100.

  FIG. 9A is a graph showing the contrast within the viewing angle of the light incident from the main body (the 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. The vertical axis indicates contrast. FIG. 9B is a graph showing the degree of decrease in contrast of light incident from the main body (the liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above-described conditions, and the horizontal axis represents 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 without the optical structure 100.

  In the range where the 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 as compared with the case where the optical structure 100 is not provided. Therefore, in this range, the color change within the viewing angle can be effectively suppressed while maintaining the display quality of the display device 10 in a front view. Also from this point, it can be said that the slope angle range α is preferably 9 degrees or more and 16 degrees or less. In addition, such a numerical range is only an example of a particularly preferable range, and the present invention can obtain a useful effect even if it is different from the numerical range exemplified here.

(Relationship between average slope angle of uneven side surface and color change)
Next, the reason why the average slope angle θ0 of the side surface 120S of the uneven shape 120 is preferably 9 degrees or more and 18 degrees or less will be described. FIG. 10 shows a plurality of (three) side surfaces 120S of the concavo-convex shape 120 having different average slope angles θ0 from each other, and it means that the average slope angle θ0 is larger as it is tilted to the right side in the figure. Note that the side surfaces 120S shown in FIG. 10 have the same curvature (that is, α is constant). 11A and 11B show an optical structure corresponding to the concave-convex shape 120 having an average slope angle θ0 = 6.0 degrees, 8.5 degrees, 11 degrees, 15.0 degrees, 17.5 degrees, and 20 degrees. A graph evaluating the color change within the viewing angle for 100 is shown. More specifically, FIGS. 11A and 11B show the case where 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 concave and convex shape 120 is 0.80. FIG. 11 is a graph for evaluating the color change of the optical structure 100 corresponding to each of the above-described uneven shapes 120. FIG.

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

  Referring to FIG. 11A created as described above, the optical structure 100 in which the uneven shape 120 having the side surface 120S having the average slope angle θ0 of 11 degrees, 15 degrees, 17.5 degrees, and 20 degrees is formed is displayed. When provided in the device 10, it can be seen that the color change within 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 display device 10 is provided with the optical structure 100 having the uneven shape 120 having the side surface 120S having the average slope angle θ0 of 6 degrees and 8.5 degrees, 15 to 25 within the viewing angle. It can be seen that the color change in the degree range is larger than that in the case where the optical structure 100 is not provided, and these are not preferable. From this tendency, when the average slope angle θ0 is too small, the present inventor has found that the amount of light totally reflected by the side surface 120S is reduced, so that the diffusion effect is weak and the color change suppressing effect can be reduced. Found.

  On the other hand, when FIG. 11B is seen, it turns out that a color change score is suitably suppressed in the range whose average slope angle (theta) 0 is 9 degrees or more and 18 degrees or less. Focusing on this point and the above-described knowledge about the change in color change, 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. Can be evaluated.

  As described above, the present inventor defines a preferable range of the average slope angle θ0 as 9 degrees or more and 18 degrees or less. In practice, it has been confirmed that the variation in the color change within the viewing angle can be effectively suppressed when it is within this range, as compared with the case where it is out of 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 not less than 11 degrees and not more than 15 degrees. In addition, the color change graph shown in FIG. 11B varies depending on the value of 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 and convex shape 120. The present inventors have found that, regardless of the value of the ratio β, when the average slope angle θ0 is 9 degrees or more and 18 degrees or less, a good color change suppression effect can be obtained.

  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 (the liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100, and the horizontal axis represents the viewing angle. The inside angle is shown, and the vertical axis shows the radiance. FIG. 12B is a graph showing the degree of decrease in 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-described conditions, and the horizontal axis represents the average. The value of the slope angle θ0 is shown, and the vertical axis shows the radiance reduction rate (indicated as “luminance reduction rate” in the figure). The radiance decrease rate is an index indicating that the smaller the value, the smaller the decrease in radiance compared to the case without the optical structure 100.

  FIG. 13A is a graph showing the contrast within the viewing angle of the light incident from the main body (the 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. The vertical axis indicates contrast. FIG. 13B is a graph showing the degree of decrease in 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-described conditions, and the horizontal axis is the average slope. 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 without the optical structure 100.

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

(Relationship between the ratio of uneven portions 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 concave and convex shape 120 is, for example, the slope angle range α is 12 degrees, The reason why it is particularly preferable that the ratio is 0.74 or more and 0.83 or less will be described. As described above, as a result of earnest research, the present inventor 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. The fact that the ratio β is particularly preferably in the range of 0.74 or more and 0.83 or less when the slope angle range α is 12 degrees will be described as an example derived from experiments or simulations. The graphs shown in FIGS. 14A and 14B are graphs when the slope angle range α is 12 degrees, and the uneven shape 120 having the ratio β = 0.90, 0.80, 0.75, 0.63 is obtained. A graph evaluating the color change within the viewing angle for the corresponding optical structure 100 is shown. FIG. 14A is a graph in which the horizontal axis indicates the angle in the viewing angle of the light emitted from the optical structure 100 and the vertical axis indicates the color change Δu′v ′, and the main body of the display device 10 (the liquid crystal panel 15). The color change within the viewing angle of the light incident from the side) and emitted from the optical structure 100 under the above-described conditions is shown. FIG. 14B is a graph in which the horizontal axis indicates the value of the ratio β and the vertical axis indicates the color change score. The optical structure is incident from the main body (the liquid crystal panel 15 side) of the display device 10 and has the above-described various conditions. A color change score of light emitted from the body 100 is shown. The color change score is calculated by the above-described equation (3).

  As shown in FIG. 14A, the display device 10 is provided with the optical structure 100 in which the concave-convex shape 120 having the side surface 120S having the flat portion ratio β of 0.63, 0.75, 0.80, 0, 90 is formed. In this case, it is understood that the color change within the viewing angle is suppressed as compared with the case where the optical structure 100 is not provided in the display device 10. However, it can be seen that the uneven shape 120 having the side surface 120S having the ratio β of 0.90 has a small color change compared to the case where the optical structure 100 is not provided in the display device 10. From this tendency, when the ratio β is too large, the present inventor has found that the diffusion effect by the side surface 120S is weak and the effect of suppressing color change can be small.

  On the other hand, when FIG. 14B is seen, when the ratio β of the flat portion is 0.63, 0.75, 0.80, 0.90, it is understood that the color change within 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. On the other hand, when the ratio β is 0.63, although the color change score is low, that is, it can be evaluated that the color change is small, there is no continuity with respect to a value larger than this, and stable color change occurs. It is difficult to say that a suppression effect can be obtained. 14B also shows a color change score in the optical structure 100 having a ratio β different from the ratio β of the flat portion illustrated in FIG. 14A. Focusing on the above points, the present inventor, when the slope angle range α is 12 degrees, in the range where the ratio β is 0.70 or more and 0.86 or less, the color change within the viewing angle in a stable state. It was evaluated that the variation of the was suppressed. In this evaluation, it is considered that the ratio β is particularly preferably not less than 0.74 and not more than 0.83 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, and the horizontal axis represents the viewing angle. The inside angle is shown, and the vertical axis shows the radiance. FIG. 15B is a graph showing the degree of decrease in the radiance of light incident from the main body (the liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above-mentioned various conditions, and the horizontal axis represents the ratio. The value of β is shown, and the vertical axis shows the radiance reduction rate (indicated as “luminance reduction rate” in the figure). The radiance decrease rate is an index indicating that the smaller the value, the smaller the decrease in radiance compared to the case without the optical structure 100.

  FIG. 16A is a graph showing the contrast within the viewing angle of the light incident from the main body (the 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. The vertical axis indicates contrast. FIG. 16B is a graph showing the degree of decrease in contrast of light incident from the main body (the liquid crystal panel 15 side) of the display device 10 and emitted from the optical structure 100 under the above-described conditions, and the horizontal axis represents 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 without the optical structure 100.

  In the range where the ratio β is 0.74 or more and 0.83 or less, it can be evaluated that the decrease in luminance and contrast is not excessive as compared with the case where the optical structure 100 is not provided. Therefore, in this range, the color change within the viewing angle can be effectively suppressed without impairing the display quality of the display device 10 when viewed from the front. From this point, it can be said that the ratio β is preferably 0.74 or more and 0.83 or less.

As described above, when the slope angle range α is 12 degrees, the ratio β is particularly preferably in the range of 0.74 to 0.83. On the other hand, as described in the above-mentioned “Relationship between slope angle range (curvature) of side surface of uneven shape and color change”, when ratio β is 0.80, slope angle range α is 9 degrees or more and 16 degrees. It becomes a particularly preferable range. And as a result of intensive study of these results, the present inventor has come to be able to determine a preferable value of the slope angle range α from the following relationship that changes according to the value of the ratio β.
The slope angle range α is preferably 83.33β-59.67 degrees and 80β-44 degrees or less, more preferably 66.67β-37.33 degrees and 100β-71 degrees or less. However, α is greater than 0 and β is less than 1. From the above formula, it can be said that β is preferably 0.55 or more and less than 1.00, and α is preferably greater than 0 and less than 36 degrees.
If the optical structure 100 is manufactured according to such conditions, it is possible to easily and effectively suppress variations in color change within the viewing angle while maintaining good display quality in the front view of the display device 10. An optical structure 100 that can be obtained can be obtained.

In the configuration of display device 10 according to the present embodiment, light from surface light source device 20 is incident on the back surface of optical structure 100. At this time, even if the range of the light emission angle from the surface light source device 20 is not less than 0 degrees and not more than 90 degrees, the angle range of the light beam inside the optical structure 100 is the light emission angle from the surface light source device 20. It becomes narrower than the range. This is because refraction occurs when light enters the optical structure 100. 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 the light rays inside the optical structure 100 can be approximately 0 degree or more and 60 degrees or less. Further, when the refractive index of the high refractive index layer 102 is 1.29, the angle range of the light beam inside the optical structure 100 can be suppressed to 0 degree or more and 51 degrees or less. Furthermore, as a range that makes it easier to manufacture, when the refractive index of the high refractive index layer 102 is 1.6 or more, the angle range of the light rays inside the optical structure 100 is suppressed to approximately 0 degree or more and 40 degrees or less. be able to.
Here, light having an angle larger than the light having the maximum angle in the angle range of the light beam inside the optical structure 100 does not need to exert an optical action on the side surface 120S of the uneven shape 120. Considering this point, considering the maximum angle of the angle range of the light beam in the optical structure 100 that is assumed, the slope angle range α may be greater than 0 degree and 60 degrees or less. Depending on the value of the refractive index, it may be greater than 0 degree and 40 degrees or less. In addition, when this slope angle range (alpha) is 3 degree | times or more, this inventor has confirmed that the suppression effect of a color change will become a grade which can be recognized visually. In this respect, 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 refractive index value of the high refractive index layer 102. In addition, the high refractive index layer as used in the field of this invention is called a high refractive index layer in the meaning that the refractive index is higher than a low refractive index layer.

(Light behavior in display devices)
Next, the behavior of light in the display device 10 according to the present embodiment will be described again with reference to FIG. When an image is displayed on the display device 10 of the present embodiment, light is first emitted from the light source 24. As a result, the light incident on the light guide plate 30 from the light incident surface 33 is generally in the first direction toward the opposite surface 34 facing the light incident surface 33 along the first direction d ₁ as shown in FIG. The light is guided through 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. When the light emitted from the light guide plate 30 passes through the optical sheet 60, it is converted into a desired traveling direction or polarization state by the unit prism 70 and enters the liquid crystal panel 15. Next, the 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 accordance with voltage application, whereby an image is displayed on the display surface 15A of the liquid crystal panel 15. .

  In the present embodiment, the light emitted from the display surface 15 </ b> A of the liquid crystal panel 15 enters the 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 transmission and total reflection by the concavo-convex shape 120. That is, at this time, the light that travels on the high angle side of the viewing angle is totally reflected by the curved side surface 120S that protrudes toward the low refractive index layer 103 side in the concavo-convex shape 120, and extends in a wide range in the direction including the low angle side. While being diffused, the flat portions 121A and 122A of the concavo-convex shape 120 allow light that is perpendicularly incident on the optical structure 100 to travel in the front direction, and diffusion is suppressed. Thereby, the color change within the viewing angle is suppressed, and the decrease in luminance and contrast in the front view is suppressed.

  Thereby, according to this Embodiment, the dispersion | variation in the color change within a viewing angle can be simply suppressed, maintaining the display quality in the front view of the display apparatus 10 favorable. In the present embodiment, for example, the difference (inclination angle range α) between the maximum angle and the minimum angle that the side surface 120S 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 is described above. When the ratio β is 0.80, the variation in color within the viewing angle can be effectively suppressed by setting the angle to 9 degrees or more and 16 degrees or less, and excessive reduction in luminance and contrast is suppressed. can do. Further, 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 and 18 By setting the angle to a degree or less, it is possible to effectively suppress variations in color change within the viewing angle. In addition, such a numerical range is only an example of a preferable range, and the present invention can obtain a useful effect even if 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 this Embodiment, the spreading | diffusion of the emitted light is suppressed and the fall of the brightness | luminance and contrast by a front view can be suppressed. On the other hand, the fact that the concavo-convex shape 120 has the flat portions 121A and 122A has a great merit in manufacturing. Specifically, even when the ratio of the length of the flat portion 121A and the length of the flat portion 122A is arbitrarily changed to some 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 concave and 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 are By changing the ratio arbitrarily to some extent, the optical structure 100 having desired optical characteristics can be manufactured by a desired manufacturing process. Specifically, if the ratio of the flat portion 121A of the recess 121 is increased, the low refractive index layer 103 can be easily filled. If the ratio of the flat portion 122A of the convex portion 122 is increased, the high refractive index layer 102 can be easily removed from the mold, and the problem of air being mixed when forming the high refractive index layer 102 can be suppressed. It has been found that when the ratio of the flat portion 121A and the flat portion 122A is, for example, 7: 4, such manufacturing merit can be obtained. The optical characteristics hardly change unless the ratio of the flat portion 121A to the flat portion 122A is an extreme ratio. For example, when the slope angle range α = 12, the ratio β = 0.80, and the average slope angle θ0 = 11, the flat portion ratio is changed between the flat portion 121A: the flat portion 122A = 7: 3 to 3:10. Even if it was made, optical characteristics hardly changed.

  In consideration of facilitating die cutting, the larger the ratio β, the easier the die cutting. In consideration of such manufacturing merit, the ratio β is preferably 0.50 or more and less than 1.00, and considering that it is easy to secure the effect of suppressing color change, 0.60 is considered. More preferably, it is less than 0.90.

  As mentioned above, although embodiment of this invention and its modification were described, this invention is not restricted to the above-mentioned embodiment, Further modification is 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 apparatus, 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 , 25 ... point-like illuminant, 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, DESCRIPTION OF SYMBOLS 103 ... Low 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

Claims (6)

An optical structure disposed on a display surface of a display device,
A high refractive index layer;
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 an uneven 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 uneven side surface 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 that is convex from the high refractive index layer side toward the low refractive index layer side. And
The low refractive index layer is disposed so as to face the display surface side of the display device,
An optical structure in which a difference between a maximum angle and a minimum angle formed by a side surface of the concavo-convex shape with a normal direction of the high refractive index layer and the low refractive index layer is 3 degrees or more and 60 degrees or less. An optical structure disposed on a display surface of a display device,
A high refractive index layer;
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 an uneven 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 uneven side surface 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 that is convex from the high refractive index layer side toward the low refractive index layer side. And
The low refractive index layer is disposed so as to face the display surface side of the display device,
The optical structure in which the ratio of the total length of the flat portion to the length of one cycle of the concave and convex portions having the concavo-convex shape is 0.50 or more and less than 1.00. An optical structure disposed on a display surface of a display device,
A high refractive index layer;
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 an uneven 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 uneven side surface 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 that is convex from the high refractive index layer side toward the low refractive index layer side. And
The low refractive index layer is disposed so as to face the display surface side of the display device,
An average slope angle of the side surface of the concavo-convex shape 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 is 9 degrees or more and 18 An optical structure that is less than or equal to degrees.   A display device, wherein the optical structure according to claim 1 is disposed on a display surface. The display device
A liquid crystal panel having the display surface and a back surface disposed to face the display surface;
The display device according to claim 4, further comprising: a surface light source device disposed to face the back surface of the liquid crystal panel.   The liquid crystal panel is in a state where 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 a 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 5, wherein the display device is a panel.

Images