JP2020013067A - Optical structure and display device - Google Patents

Abstract

To provide an optical structure capable of maintaining good visibility of a display device by uniformly varying the luminance and colors within a viewing angle toward a high angle side while enlarging the viewing angle of the device.SOLUTION: The optical structure includes a high refractive index layer and a low refractive index layer, in which the high refractive index layer has a plurality of projections which are arranged in a first direction parallel to the main surface of the sheet-like high refractive index layer and the low refractive index layer and are convex toward the low refractive index layer side. The projections have a first projection and a second projection: a side face of the first projection facing one side of the first direction forms a curved face, while a side face of the first projection facing the other side forms a flat face; and a side face of the second projection facing the other side of the first direction forms a curved face, while a side face of the second projection facing the one side forms a flat face. The first projection and the second projection are linearly symmetric to each other about an axis as the axis of symmetry parallel to the normal direction of the high refractive index layer and the low refractive index layer. The high refractive index layer is disposed to face a screen side of a display device.SELECTED DRAWING: Figure 3

Description

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

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

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

  For example, in a VA liquid crystal panel, black is displayed when the voltage to the liquid crystal molecules is off, and this black becomes very close to the actual black in a front view, so that the contrast ratio in a front view becomes very high. Can be. 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 pixels that are black when viewed from the front is relatively large, and compared with the case when viewed from the front. As a result, the contrast ratio may be significantly reduced, and the color may change significantly. As a result, the contrast ratio and the color within the viewing angle may vary greatly. For example, when weakening or blocking the intensity of red and green light of red, green, and blue, and displaying blue, the red and green light leaks obliquely, so that when viewed from the front and obliquely It is easy to cause a situation in which the color tone is greatly changed from when viewed from above.

In addition, in the VA liquid crystal panel, the emission spectrum shape change with respect to the viewing angle of blue display is strong (compared to red display and green display), and specifically, “the intensity of the wavelength component corresponding to green” is “ Due to a change that increases with respect to the “intensity of the wavelength component corresponding to blue”, the display color when viewed obliquely tends to turn yellow when viewed from the front.
Note that the above-described color problem that may occur in the VA liquid crystal panel may also occur in the TN method.

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

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

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

  The above optical sheet basically expands the viewing angle and improves the display quality within the viewing angle by adjusting the shape and the refractive index difference of the boundary between the low refractive index layer and the high refractive index layer. Aim. However, the conventional optical sheet has a monotonous shape at the boundary between the low-refractive-index layer and the high-refractive-index layer, so that the viewing angle cannot be sufficiently enlarged, and the change in brightness and color during the viewing angle is constant. In some cases, visibility was impaired.

  The present invention has been made in consideration of the above-described circumstances, and has a good visual recognition by uniformly changing a luminance change and a color change within a viewing angle toward a high angle side while expanding a viewing angle. It is an object of the present invention to provide an optical structure capable of ensuring the performance and a display device having the same.

  The optical structure according to the present invention is an optical structure disposed on a display surface of a display device, and has a high refractive index layer, which is laminated on the high refractive index layer, and whose refractive index is the high refractive index layer. Lower refractive index layer, wherein the high refractive index layer is arranged in a first direction parallel to a main surface of the sheet-like high refractive index layer and the low refractive index layer, and the low refractive index layer A plurality of convex portions that are convex on the side, the low refractive index layer is stacked on the high refractive index layer so as to enter between the plurality of convex portions, and the convex portion is a first convex portion And a second convex portion, wherein a side surface of the first convex portion facing one side in the first direction forms a curved surface or a bent surface, and a side surface of the first convex portion facing the other side in the first direction. Has a shape different from the side surface of the first projection facing one side in the first direction, and the side surface of the second projection facing the other side in the first direction is a curved surface or A side surface of the second convex portion facing one side in the first direction has a shape different from a side surface of the second convex portion facing the other side in the first direction; When viewed in a cross-section on a plane including the normal direction of the high-refractive-index layer and the low-refractive-index layer, the first convex portion and the second convex portion include the high-refractive index layer and the low-refractive index layer. An optical structure which is line-symmetric with respect to an axis parallel to a normal direction of a layer and which is a line of symmetry, and which is arranged so that the high refractive index layer is directed to a display surface side of the display device.

  In the optical structure according to the aspect of the invention, the side surface of the first protrusion facing the other side in the first direction, and the side surface of the second protrusion facing one side in the first direction are planes. Is also good.

  In the optical structure according to the aspect of the invention, a side surface of the first protrusion facing the other side of the first direction and a side surface of the second protrusion facing one side of the first direction may be a curved surface or a bent surface. The difference between the maximum angle and the minimum angle formed by the side surface of the first convex portion facing one side of the first direction with the normal direction of the high refractive index layer and the low refractive index layer is the first angle. The side of the first convex portion facing the other side of the direction is larger than the difference between the maximum angle and the minimum angle between the normal direction of the high refractive index layer and the low refractive index layer, and the other side of the first direction. The difference between the maximum angle and the minimum angle formed by the side surface of the second convex portion facing the normal direction of the high-refractive-index layer and the low-refractive-index layer is different from that of the second convex portion facing one side in the first direction. The side surface of the portion may be larger than the difference between the maximum angle and the minimum angle between the normal direction of the high refractive index layer and the low refractive index layer. .

  In the optical structure according to the present invention, a straight line connecting both end points of the side surface of the first convex portion facing one side in the first direction and the side surface of the second convex portion facing the other side in the first direction. The average slope angle of each side surface formed by a straight line connecting both end points of the high refractive index layer and the normal direction of the low refractive index layer is 20 degrees or more and 30 degrees or less, and the other side in the first direction. A straight line connecting both end points of the side surface of the first convex portion facing the first direction and a straight line connecting both end points of the side surface of the second convex portion facing one side in the first direction are formed by the high refractive index layer and the low refractive index layer. The average slope angle of each side surface formed with the normal direction of the refractive index layer may be not less than 5 degrees and not more than 15 degrees.

  In the optical structure according to the present invention, a maximum angle and a minimum angle formed by a side surface of the first convex portion facing one side of the first direction with a normal direction of the high refractive index layer and the low refractive index layer. May be 15 degrees or more and 35 degrees or less.

  In the optical structure according to the present invention, the side surface of the first convex portion facing one side in the first direction and the side surface of the second convex portion facing the other side in the first direction may have the low refractive index. A curved surface or a bent surface that is convex toward the layer side may be formed.

  In the optical structure according to the present invention, tips of the first convex portion and the second convex portion may form a plane parallel to the first direction.

  In the optical structure according to the present invention, the tip of the low-refractive-index layer that enters between the adjacent convex portions may form a plane parallel to the first direction.

  In the optical structure according to the present invention, the first convex portions and the second convex portions may be alternately arranged.

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

  The display device 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. Is also good.

  ADVANTAGE OF THE INVENTION According to this invention, favorable visibility can be ensured by changing the brightness | luminance change and color change within a viewing angle uniformly toward the high angle side, expanding the viewing angle of a display apparatus.

1 is a schematic cross-sectional view of a display device including an optical structure according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the display device for explaining the behavior of light in the display device shown in FIG. 1. FIG. 2 is an enlarged sectional view of an optical structure provided in the display device shown in FIG. 1. FIG. 2 is an enlarged view of an interface between a high refractive index layer and a low refractive index layer of the optical structure shown in FIG. 1. FIG. 2 is a diagram for explaining an optical function of an optical structure provided in the display device shown in FIG. 1. FIG. 4 is a diagram illustrating a simulation result of a luminance distribution of an image displayed by a display device including the optical structure illustrated in FIG. 1 and a luminance distribution of an image displayed by a display device according to a comparative example. FIG. 7 is a schematic cross-sectional view of an optical sheet provided in a display device according to a comparative example showing a simulation result of a luminance distribution in FIG.

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

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

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

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

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

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

  In the present embodiment, liquid crystal panel 15 is, for example, a VA (Vertical Alignment) liquid crystal panel. Therefore, when the voltage to the liquid crystal molecules in the liquid crystal layer 12 is off or at the minimum value, the liquid crystal panels 15 are oriented along the normal direction of the display surface 15A, so that the light from the surface light source device 20 is blocked. In this configuration, the transmittance of light from the surface light source device 20 is gradually increased by gradually increasing the voltage with respect to the liquid crystal molecules and gradually tilting the liquid crystal molecules to the side along the display surface 15A. Have. The liquid crystal panel 15 is not limited to the VA type, but may be a TN (Twisted Nematic) type liquid crystal panel or an IPS (In-Plane Switching) type liquid crystal panel. The details of the liquid crystal panel 15 are described in various publicly known documents (for example, “Flat Panel Display Dictionary (Tatsuo Uchida, Supervised by Uchiike Hiraki)”, published by the Industrial Research Institute, 2001). Detailed description is omitted.

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

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

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

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

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

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

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

  The surface light source device 20 as described above includes the optical sheet 60 so that the light from the light guide plate 30 is converted into a desired traveling direction and is incident on the liquid crystal panel 15. Specifically, the optical sheet 60 emits light so that most of the light incident on the liquid crystal panel 15 is parallel to the normal direction of the surface light source device 20. Thus, the surface light source device 20 according to the present embodiment is configured as a so-called parallel light backlight. As described above, the transmission or blocking of the light incident on the liquid crystal panel 15 in the liquid crystal layer 12 is controlled for each pixel forming region in accordance with the application of the voltage, whereby an image is formed on the display surface 15A of the liquid crystal panel 15. Will be displayed. Then, the image displayed on the display surface 15A is visually recognized through the optical structure 100.

(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-shaped or film-shaped base material 101 having a front surface 101A and a back surface 101B arranged opposite to the front surface 101A. A high-refractive-index layer 102 formed on a surface 101A of the substrate 101 and formed in a sheet or film shape extending along the substrate 101 and having a pair of main surfaces opposed in a thickness direction; 102 is formed on a surface opposite to the substrate 101 side and formed in a sheet or film shape extending along the substrate 101, and has a pair of main surfaces opposed in the thickness direction, and has a refractive index. Comprises a low-refractive-index layer 103 having a lower refractive index than the high-refractive-index layer 102, and a sheet-like or film-like surface material 104 disposed on the opposite side of the low-refractive-index layer 103 from the high-refractive-index layer 102 side. hand That. Although the surface material 104 in this embodiment forms the outermost surface on the light (image) emission side, a protective film or the like may be further laminated on the surface material 104.

  The base material 101 is a light-transmitting transparent base material made of resin, glass, or the like, and examples of the material include polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, polyamide, glass, triacetyl cellulose, and the like. . As shown in FIG. 2, the optical structure 100 is disposed so that the high refractive index layer 102 faces the display surface 15A of the display device 10. In the illustrated example, the back surface 101B of the base material 101 is formed of an adhesive layer. The liquid crystal panel 15, that is, the display surface 15 </ b> A of the liquid crystal panel 15 is bonded to the display surface 15 </ b> A.

  FIG. 3 shows, precisely, the optical structure 100 before being joined to the liquid crystal panel 15. As shown in FIG. 3, in the optical structure 100 according to the present embodiment, before being bonded to the liquid crystal panel 15, the adhesive layer 105 is bonded to the base material 101 and is opposite to the base material 101 side. A release film 106 is provided on the side surface.

  The surface member 104 forms the outermost surface on the side opposite to the display surface 15A side of the liquid crystal panel 15 in the optical structure 100. The surface material 104 is provided, for example, to suppress surface reflection of external light incident on the optical structure 100, and thereby, the visibility of an image displayed on the display device 10 by the surface reflection of external light. Is suppressed from being impaired. Specifically, the surface material 104 functions as an anti-reflection layer for external light by setting its refractive index lower than that of the low refractive index layer 103. Although the surface material 104 in this embodiment functions as an anti-reflection layer, it may be a mere protective layer, for example, a layer provided for scratch resistance prevention or stain resistance, or provided for antistatic. May be used. The surface material 104 may not be provided. In this case, the low refractive index layer 103 may form the outermost surface of the optical structure 100.

In this embodiment, a high refractive index layer 102 and a low refractive index layer 103 are provided between the base material 101 and the surface material 104 as described above. High refractive index layer 102 are aligned in the first direction d ₁ parallel to the main surface of the sheet of the high refractive index layer 102 and the low refractive index layer 103, a plurality of the convex in the low refractive index layer 103 side protrusion 120 The low-refractive-index layer 103 is laminated on the high-refractive-index layer 102 so as to enter between the plurality of convex portions 120. The convex portion 120 extends linearly in a second direction d ₂ that is non-parallel to the first direction d ₁ , specifically, a second direction d ₂ orthogonal to the first direction d ₁ , and has a low refractive index that enters between the convex portions 120. entry portion of the layer 103 is in a state extending linearly along the second direction d _2. In addition, the high refractive index layer 102 in the present embodiment is formed in a flat film shape in which a pair of flat surfaces are opposed to the plurality of convex portions 120 described above, and the convex portions 120 are formed on one flat surface. And a base 120 </ b> B that is integrated with and supports the protrusion 120. In the present embodiment, similarly to the high refractive index layer 102, the low refractive index layer 103 also supports one of the flat surfaces of the flat film-shaped base portion to support the intruding portion that enters between the convex portions 120. ing.

  Note that, in the present embodiment, the above-mentioned state “parallel to the main surface of the high refractive index layer 102 and the low refractive index layer 103” is one of the flat main layers of the high refractive index layer 102 and the low refractive index layer 103. Direction extending parallel to the surface (the main surface on the side where the convex portion 120 and the entering portion are not provided), and the direction in which the convex portion 120 of the high refractive index layer 102 and the entering portion of the low refractive index layer 103 are arranged; This means a state in which each of the high refractive index layer 102 and the low refractive index layer 103, which is a plane including a direction extending linearly, extends in parallel with the other main surface.

When 4 is also described in detail protrusion 120 with reference convex portion 120 in this embodiment includes a first convex portion 121 has a second projection 122, the first direction d ₁ and high refraction when viewed in cross section (cross section shown in FIGS. 3 and 4) in a plane including the normal line direction d ₃ rate layer 102 and the low refractive index layer 103, a first protrusion 121 second protrusion 122, law linear direction d ₃ axis of symmetry an axis parallel to a (e.g., n1 and n2 in FIG. 4), which is in line symmetry.

Specifically, the first one side of the direction _{d 1} without the side 121A is a curved surface of the first convex portion 121 facing (left side in FIG. 3 and 4), the first direction _{d 1} of the other side (right side in FIGS. 3 and 4) The side surface 121B of the first convex portion 121 facing the side has a shape different from that of the side surface 121A, and specifically forms a flat surface. On the other hand the second projection 122, the side surface 122B facing the first other side in the direction _{d 1} forms the curved surface, side surfaces 122A facing the first one side of the direction _{d 1} is the side surface 122B of a different shape, Specifically, it is flat. Then, as shown in FIG. 4, the side surface 122B side 121A and a second projection 122 of the first convex portion 121 that forms the curved surface becomes axisymmetric an axis parallel to the normal direction d ₃ as a symmetrical axis, side 121B of the first convex portion 121 and the side surface 122A of the second projection 122 is in line symmetry with an axis parallel to the normal direction _{d 3} as a symmetrical axis forming a plane.

In the present embodiment has first protrusion 121 and second protrusion 122 are alternately arranged in the first direction d _1, the sequence of the first protrusion 121 and second protrusion 122 is limited to this aspect Instead, the first protrusions 121 and the second protrusions 122 may be randomly arranged. Further, in the present embodiment, the side surface 121A of the first convex portion 121 and the side surface 122B of the second convex portion 122, which are curved surfaces, are curved surfaces projecting toward the low refractive index layer 103 side. The curved surface may be concave on the side opposite to the 103 side. The shape of the side surface formed as a curved surface is not particularly limited, and may be formed along a circular arc of a perfect circle, may be formed along an arc of an ellipse, or may be a quadratic function. Or a cubic function.

Incidentally, in FIG. 4, the angle at which the straight line connecting the end points of the side surface 121A of the first convex portion 121 facing the first one side of the direction d ₁ makes with the normal line direction d _3, expressed as the mean slope angle .theta.1a, the angle at which the straight line connecting the end points of the side surface 122B of the second convex portion 122 facing the first other side in the direction d ₁ makes with the normal line direction d _3, is shown as an average slope angle [theta] 2B. Further, the angle that the straight line connecting the end points of the side surface 121B of the first convex portion 121 facing the first other side in the direction d ₁ makes with the normal line direction d _3, expressed as the mean slope angle Shita1B, the first direction d ₁ while connecting the end points of the side surface 122A of the second convex portion 122 facing the side straight line an angle formed between the normal direction d _3, it is shown as an average slope angle θ2A of. Here, in the present embodiment, the average slope angle θ1A = the average slope angle θ2B, the average slope angle θ1B = the average slope angle θ2A, the average slope angle θ1A> the average slope angle θ1B, and the average slope angle θ2B> the average slope angle θ2A. The relationship holds. Incidentally, strictly speaking, the average slope angle is that straight line connecting the end points of the side surface of the protrusion 120 of the angle of the smaller of the angles formed between the normal direction d _3.

  The average slope angle θ1A of the side surface 121A of the first protrusion 121 and the average slope angle θ2B of the side surface 122B of the second protrusion 122 are preferably not less than 20 degrees and not more than 30 degrees. It is 8 degrees. The average slope angle θ1B of the side surface 121B of the first protrusion 121 and the average slope angle θ2A of the side surface 122A of the second protrusion 122 are preferably 5 degrees or more and 15 degrees or less, and in the present embodiment, as an example. It is 9.0 degrees.

Further, in FIG. 4 shows the maximum angle θC and the minimum angle θD which side 121A of the first convex portion 121 facing the one side of the first direction d ₁ makes with the normal line direction d _3, in this embodiment, these The difference between the maximum angle θC and the minimum angle θD is defined as “slope angle range”. Maximum angle θC, the tip of the side surface 121A, an angle other words tangential side 121A through the endpoints of the distal end side of the side surface 121A of the protrusion 120 makes with the normal line direction _{d 3,} the minimum angle θD is the side 121A group end, in other words tangential sides 121A through an end point of the side surface 121A of the base end side of the convex portion 120 is an angle formed between the normal direction _{d 3.} The slope angle range of the side surface 121A of the first convex portion 121 is preferably 5 degrees or more and 55 degrees or less, and in the present embodiment, as an example, θC = 32.2 ° and θD = 9.9 °. . Similarly, the slope angle range of the side surface 122B of the second convex portion 122 is also preferably 5 degrees or more and 55 degrees or less. Has become. Incidentally, strictly speaking, the maximum angle and minimum angle, as well as the average slope angle is that tangential concerning aspects of angles smaller of the angles formed between the normal direction d _3.

In the present embodiment, the side surface 121A of the first convex portion 121 and the side surface 122B of the second convex portion 122, which are in a line-symmetric relationship, form curved surfaces, but these are bent surfaces, especially three or more element surfaces. May be formed. If a side 121A is folded surface of the first protrusion 121, the maximum angle θC described above, becomes an angle which the straight line passing through the element surface including the front end of the side surface 121A makes with the normal line direction d _3, the minimum angle θD is a side a straight line passing through the element surface including the proximal end is the angle formed between the normal direction d ₃ in 121A.

Further, in this embodiment, the side surface 121B of the first convex portion 121 facing the first other-side direction _{d 1,} and a side 122A of the second convex portion 122 facing the first one side of the direction _{d 1} is a plane However, these side surfaces 121B and 122A may be curved or bent. In this case, the side surface 121A of the first convex portion 121 facing the first one side of the direction _{d 1,} and, the slope angle range of the side surface 122B of the second convex portion 122 facing the other side in the first direction _{d 1} is respectively The value is set to a value larger than the slope angle range of the side surfaces 121B and 122A forming a curved surface or a bent surface on the opposite side.

Further, as shown in FIG. 4, the tip 121C of the first protrusion 121 of the present embodiment forms a plane parallel to the first direction _{d 1,} the distal end 122C of the second protrusion 122 in the first direction _{d 1} It forms a parallel plane. Also been between the convex portion 120 adjacent, i.e. the plane parallel intruded the tip also first direction d ₁ of the low refractive index layer 103 between the first protrusion 121 and the second projection 122 formed . Incidentally, the tip 121C and the tip 122C is may not be a plane, also may form a plane that is inclined with respect to the first direction d _1.

The high-refractive-index layer 102 and the low-refractive-index layer 103 as described above exert optical effects such as reflection, refraction, and transmission on light for displaying an image emitted from the display surface 15A, It is provided to improve the display quality of an image displayed on the display surface 15A. To be more specific, the side surface 122B forming the curved surface on the side surface 121A and the second projection 122 forms a curved surface in the first convex portion 121, a curved light parallel to the normal direction d ₃ emitted from the display surface 15A by reflection and refraction in the entire region can be diffused from the lower angle side in a wide range extending higher angle side light to the normal direction d _3. On the other hand, the side surface 121A and the side surface 122B forming the curved surface, from the subsequent one position toward the base end side from the distal end side of the projecting portion 120, formed by parallel light and side 121A and the side surface 122B in a direction normal to _{d 3} The angle becomes larger than the critical angle for total reflection, and light is totally reflected. At this time, although the totally reflected light is concentrated in a certain angle range, in this embodiment, on the high angle side, the intensity of the light diffused to the high angle side can be increased, but this high angle side In a different angle range, specifically, at the low angle side, the totally reflected light does not converge. As a result, the light intensity between the high angle side angle range and the lower angle side angle range is reduced. A situation may occur in which a difference occurs and visibility is impaired. On the other hand, in the present embodiment, the side surface 121B that forms a plane in the first convex portion 121 and the side surface 122A that forms a plane in the second convex portion 122 become light reflected by the side surfaces 121A and 122B that form a curved surface. The average inclination angles θ1B and θ2A are set so that the light is totally reflected in an angle range lower than the advancing angle range to compensate for the difference in light intensity described above. Thereby, the high refractive index layer 102 and the low refractive index layer 103 make the light distribution within a wide viewing angle from the front view direction to the high angle side closer to a normal distribution, and improve display quality at a wide viewing angle. It has become.

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

In the present embodiment, light emitted from display surface 15A of liquid crystal panel 15 enters optical structure 100. At this time, light incident on the optical structure 100 from the liquid crystal panel 15 side is given an optical effect by reflection and transmission (refraction) by the high refractive index layer 102 and the low refractive index layer 103 as described above. That is, the side surface 122B forming the curved surface on the side surface 121A and the second projection 122 forms a curved surface in the first convex portion 121 is reflected across the curved surface parallel light in the normal direction _{d 3} emitted from the display surface 15A and by refracting, diffusing from the low angle of side a wide range extending high angle side with respect to the normal direction d _3.

Here, the side surface 121A and the side surface 122B forming the curved surface, from the subsequent one position toward the base end side from the distal end side of the convex portion 120 as described above, parallel light and side 121A and the side surface in the normal direction d ₃ The angle formed by the angle 122B is larger than the critical angle for total reflection, and the light is totally reflected. In FIG. 5, the light flux in the region A surrounded by the two-dot chain line corresponds to the light flux totally reflected by the curved side surfaces 121A and 122B. In the present embodiment, the curved side surfaces 121A and 122B totally reflect light as described above, so that light is collected on the high angle side, and as a result, the intensity of light diffused to the high angle side is increased. However, at the low angle side, the totally reflected light does not collect, and as a result, there may be a difference in light intensity between the high angle side angle range and the lower angle side angle range. . That is, in the angle range on the lower angle side than the region A in FIG. 5, the totally reflected light does not collect, so that the light intensity in the range may be smaller than the light intensity in the region A. Therefore, with the optical action of only the curved side surfaces 121A and 122B, the brightness when the image is viewed from the low angle side is undesirably low, or the brightness of the image when viewed from the high angle side is low. When the brightness becomes higher than when the image is viewed from the angle side, visibility may be impaired.

  However, in the present embodiment, the side surface 121B that forms a plane in the first convex portion 121 and the side surface 122A that forms a plane in the second convex portion 122 have an angle range in which light totally reflected by the side surface 121A and the side surface 122B forming a curved surface travels. Light is totally reflected in an angle range lower than the angle range. In FIG. 5, the bundle of light totally reflected by the side surface 121B that forms a plane in the first convex portion 121 and the side surface 122A that forms a plane in the second convex portion 122 is indicated by a region B surrounded by a two-dot chain line. I have. As is clear from FIG. 5, the second convex portion 121 has a second angle in a lower angle range in which the intensity of light can be smaller than that of the region A where the light reflected by the side surface 121A that forms the curved surface in the first convex portion 121 is totally reflected. The light totally reflected by the side surface 122 </ b> A forming a plane in the convex portion 122 advances. On the other hand, the first convex portion 121 forms a flat surface in an angle range on the low angle side where the light intensity can be smaller than the region A side where the light reflected by the side surface 122B that forms the curved surface in the second convex portion 122 is totally reflected. The light totally reflected by the side surface 121B advances. Accordingly, the light from the display surface 15A is diffused over a wide range, and the intensity of the light that changes from the front view toward the high angle side uniformly changes.

  Therefore, according to the present embodiment, good visibility can be secured by uniformly changing the luminance change and color change within the viewing angle toward the higher angle side while expanding the viewing angle.

  In this embodiment, the refractive index of the high refractive index layer 102 is 1.65 as an example, and the refractive index of the low refractive index layer 103 is 1.48 as an example. Referring to FIG. 4, an average slope angle θ1A of side surface 121A of first protrusion 121 and an average slope angle θ2B of side surface 122B of second protrusion 122 are 21.8 degrees, for example. The average slope angle θ1B of the side surface 121B of the first protrusion 121 and the average slope angle θ2A of the side surface 122A of the second protrusion 122 are, for example, 9.0 degrees. Further, the slope angle range of the side surface 121A of the first protrusion 121 and the slope angle range of the side surface 122B of the second protrusion 122 are, for example, θD = 9.9 ° and θC = 32.2 °. Under such conditions, it is possible to uniformly change the luminance change from the front view direction to a range where the angle with respect to the front view direction is about 75 degrees without significantly reducing the brightness in the front view direction. And good visibility in a wide viewing angle can be secured.

  As described above, the average slope angle θ1A of the side surface 121A of the first protrusion 121 and the average slope angle θ2B of the side surface 122B of the second protrusion 122 are preferably 20 degrees or more and 30 degrees or less. It is preferable that the average slope angle θ1B of the side surface 121B of the portion 121 and the average slope angle θ2A of the side surface 122A of the second convex portion 122 are not less than 5 degrees and not more than 15 degrees. In addition, it is preferable that the slope angle range of the side surface 121A of the first protrusion 121 and the slope angle range of the side surface 122B of the second protrusion 122 are not less than 5 degrees and not more than 55 degrees. When such an angle range is premised, the refractive index of the high refractive index layer 102 is preferably from 1.60 to 1.67, and the refractive index layer of the low refractive index layer 103 is from 1.46 to 1.46. It is preferably 50 or less. In this case, the present inventors have confirmed that good visibility can be ensured at a wide viewing angle.

  Here, FIG. 6 is a diagram illustrating a simulation result of a luminance distribution of an image displayed by the display device 10 including the optical structure 100 according to the present embodiment and a luminance distribution of an image displayed by the display device according to the comparative example. It is. FIG. 7 is a schematic cross-sectional view of an optical sheet provided in a display device according to a comparative example in which the simulation result of the luminance distribution is shown in FIG. The optical sheet provided in the display device according to the comparative example includes a high refractive index layer 202 and a low refractive index layer 202 shown in FIG. 7 instead of the high refractive index layer 102 and the low refractive index layer 103 of the optical structure 100 according to the present embodiment. A refractive index layer 203 is provided. The side surface of the convex portion 220 in the high refractive index layer 202 has a left-right symmetry in the figure and has a curved surface protruding toward the low refractive index layer 203 side.

  In FIG. 6, the horizontal axis indicates an angle inclined with respect to the front view direction, and the vertical axis indicates the image in a direction inclined with respect to the front view direction with respect to luminance when the image is viewed in the front view direction. It shows the ratio of the luminance (normalized luminance) at the time of this. In the simulation shown in FIG. 6, the light emitted from the display surface 15A of the liquid crystal panel 15 in accordance with the normal distribution shown by the solid line is emitted through the optical structure 100 and through the optical sheet according to the comparative example. The luminance distribution at the time of emission is calculated. The light emitted from the display surface 15A according to the normal distribution in this manner is hereinafter referred to as reference light. The reference light has a normal distribution with a standard deviation of 13.98 such that the luminance when viewed at an angle of ± 30 degrees with respect to the front view direction is 10% of the luminance in the front view direction. Also, the dashed line indicates the simulation result according to the present embodiment, and the two-dot chain line indicates the simulation result according to the comparative example.

  In the optical sheet according to the comparative example, although the light totally reflected on the side surface of the convex portion 220 forming the curved surface in the high refractive index layer 202 can concentrate and diffuse the light on the high angle side, the light is totally reflected on the low angle side. Since the collected light is not concentrated, the luminance near the ± 30 degrees in FIG. 6 is reduced, and the luminance near the ± 60 degrees is higher than the luminance near the ± 30 degrees. In such a case, when the image is viewed from the front view direction toward the high angle side, the image is perceived as suddenly becoming darker and then becoming brighter, so that visibility may be impaired. On the other hand, in the simulation result according to the present embodiment, the brightness gradually and uniformly decreases from the vicinity of ± 30 degrees to the vicinity of ± 60 degrees in FIG. Therefore, when the image is viewed from the front view direction toward the high angle side, the image is sensed to be gradually darkened, and the viewer does not feel uncomfortable.

  According to the present embodiment, from the simulation results as shown in FIG. 6, it is possible to uniformly change the luminance change and the color change within the viewing angle toward the higher angle side while expanding the viewing angle. It can be confirmed that good visibility can be secured.

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

  Reference Signs List 10 display device, 12 liquid crystal layer, 13 upper polarizing plate, 14 lower polarizing plate, 15 liquid crystal panel, 15A display surface, 15B back surface, 20 surface light source device, 21 light emitting surface, 24 light source Reference numerals 25, point light emitters, 28, reflection sheet, 30, light guide plate, 31, light outgoing surface, 32, back surface, 33, light incoming surface, 34, opposite surface, 37, inclined surface, 38, step surface, 39, Connection surface, 60 optical sheet, 61 light emitting surface, 65 body part, 67 light incident side surface, 70 unit prism, 100 optical structure, 101 substrate, 101A front surface, 101B back surface, 102 High refractive index layer, 103 low refractive index layer, 104 surface material, 105 adhesive layer, 106 release film, 120 convex part, 120B base part, 121 first convex part, 121A first convex part. Side of one side of the portion, 121B... Side of the other side of the first convex portion, 1 2 ... second convex portion, 122A ... one side surface of the second convex portion, 122B ... other side surface of the second protrusion

Claims (11)

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 lower refractive index than the high refractive index layer,
The high refractive index layer is arranged in a first direction parallel to a main surface of the sheet-like high refractive index layer and the low refractive index layer, and has a plurality of convex portions that are convex toward the low refractive index layer side. ,
The low-refractive-index layer is stacked on the high-refractive-index layer so as to enter between the plurality of convex portions,
The protrusion has a first protrusion and a second protrusion,
The side surface of the first convex portion facing one side in the first direction forms a curved surface or a bent surface, and the side surface of the first convex portion facing the other side in the first direction has one side in the first direction. Forming a shape different from the side surface of the first convex portion facing;
The side surface of the second convex portion facing the other side of the first direction forms a curved surface or a bent surface, and the side surface of the second convex portion facing one side of the first direction has the other side in the first direction. Forming a shape different from the side surface of the second convex portion facing;
When viewed in a cross section on a plane including the first direction and a normal direction of the high refractive index layer and the low refractive index layer, the first convex portion and the second convex portion include the high refractive index layer and With the axis parallel to the normal direction of the low refractive index layer as the axis of symmetry, it is line symmetric,
An optical structure, wherein the high refractive index layer is arranged so as to face a display surface side of the display device.   The optical structure according to claim 1, wherein a side surface of the first protrusion facing the other side in the first direction and a side surface of the second protrusion facing one side in the first direction form a plane. . The side surface of the first convex portion facing the other side of the first direction, and the side surface of the second convex portion facing one side of the first direction form a curved surface or a bent surface,
The difference between the maximum angle and the minimum angle formed by the side surface of the first convex portion facing one side of the first direction with the normal direction of the high refractive index layer and the low refractive index layer is the other of the first direction. The side of the first convex portion facing the side is larger than the difference between the maximum angle and the minimum angle between the normal direction of the high refractive index layer and the low refractive index layer,
The difference between the maximum angle and the minimum angle formed by the side surface of the second convex portion facing the other side of the first direction with the normal direction of the high refractive index layer and the low refractive index layer is one of the first direction. 2. The optical structure according to claim 1, wherein a side surface of the second convex portion facing the side is larger than a difference between a maximum angle and a minimum angle between normal directions of the high refractive index layer and the low refractive index layer. A straight line connecting both end points of a side surface of the first convex portion facing one side of the first direction and a straight line connecting both end points of a side surface of the second convex portion facing the other side in the first direction are the aforementioned. The average slope angle of each side surface forming the normal direction of the high refractive index layer and the low refractive index layer is 20 degrees or more and 30 degrees or less,
A straight line connecting both end points of the side surface of the first convex portion facing the other side of the first direction and a straight line connecting both end points of the side surface of the second convex portion facing one side in the first direction are the aforementioned. 4. The optical structure according to claim 2, wherein an average slope angle of each side surface formed by a normal direction of the high refractive index layer and the low refractive index layer is 5 degrees or more and 15 degrees or less. 5.   A difference between a maximum angle and a minimum angle formed by a side surface of the first convex portion facing one side of the first direction with a normal direction of the high refractive index layer and the low refractive index layer is 15 degrees or more and 35 degrees or less. The optical structure according to claim 4, wherein   The side surface of the first convex portion facing one side in the first direction and the side surface of the second convex portion facing the other side in the first direction have a curved surface or a bent surface convex toward the low refractive index layer. The optical structure according to any one of claims 1 to 5, wherein   The optical structure according to claim 1, wherein tips of the first protrusion and the second protrusion form a plane parallel to the first direction.   The optical structure according to any one of claims 1 to 7, wherein a tip of the low-refractive-index layer that enters between the adjacent protrusions forms a plane parallel to the first direction.   The optical structure according to claim 1, wherein the first protrusions and the second protrusions are alternately arranged.   A display device, wherein the optical structure according to claim 1 is arranged on a display surface. The display device,
A liquid crystal panel having the display surface and a back surface arranged to face the display surface;
The display device according to claim 10, further comprising: a surface light source device disposed to face a rear surface of the liquid crystal panel.

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