JP2021173974A - Optical structure, polarizer with optical structure, display panel with optical structure, and display device with optical structure - Google Patents

Abstract

To suppress color change according to an observation angle.SOLUTION: An optical structure 40 includes: a first layer 50 having a plurality of protruding parts 52 arranged in a first direction D1 separately; and a second layer 55 laminated on the first layer 50 from the direction of the protruding parts 52, the second layer forming a refraction index interface B between the first layer 50 and the second layer. The first layer has a fine irregular surface in at least one of the top surface of the protruding parts and the bottom surface of the recessed part between protruding parts next to each other.SELECTED DRAWING: Figure 4

Description

The present invention relates to an optical structure, a polarizing plate with an optical structure, a display panel with an optical structure, and a display device with an optical structure.

For example, as disclosed in Patent Document 1, there is known a problem that an image displayed by a display device is observed in a different color as the angle at which the display device is observed changes. The color change according to the observation angle can occur in various display devices such as a liquid crystal display device and an EL (Electroluminescence) display device. The reason for the color change differs depending on the type of display device, but the optical path length of the image light traveling in the direction inclined in the front direction is longer than the optical path length of the image light traveling mainly in the front direction. It is due. In a normal display device, the color is adjusted so as to obtain the expected color when observed from the front direction, and a deviation from the planned color may occur as the observation angle is tilted from the front direction.

Japanese Unexamined Patent Publication No. 2012-2477883

For the purpose of solving such a problem, for example, as disclosed in Patent Document 1, it has been studied to arrange a member having a light diffusing function on the display surface of the display device. This member is expected to diffuse mainly by refraction. However, in the conventional technique, the color change according to the observation angle cannot be sufficiently suppressed.

The present invention has been made in consideration of the above points, and an object of the present invention is to suppress a color change according to an observation angle.

The first optical structure according to the present invention is
A first layer having a plurality of convex portions arranged apart from each other in the first direction,
A second layer, which is laminated on the first layer from the side of the convex portion and forms a refractive index interface with the first layer, is provided.
The first layer has a fine concavo-convex surface on at least one of the top surface of the convex portion and the bottom surface of the concave portion located between the adjacent convex portions.

The second optical structure according to the present invention is
A first layer having a plurality of convex portions arranged apart from each other in the first direction,
A second layer, which is laminated on the first layer from the side of the convex portion and forms a refractive index interface with the first layer, is provided.
The first layer has a diffraction structure on at least one of the top surface of the convex portion and the bottom surface of the concave portion located between the adjacent convex portions.

In the first and second optical structures according to the present invention
The light incident from the side of the second layer is arranged so as to be emitted from the side of the first layer.
The first layer may have the fine concavo-convex surface on the bottom surface of the recess.

In the first and second optical structures according to the present invention
The refractive index of the first layer is larger than the refractive index of the second layer.
The first layer may have the fine concavo-convex surface on the bottom surface of the recess.

In the first and second optical structures according to the present invention
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The pitch of the protruding elements may be 0.3 μm or more and 2.0 μm or less.

In the first and second optical structures according to the present invention
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The pitch of the protruding elements may be 0.3 μm or more and 0.78 μm or less.

In the first and second optical structures according to the present invention
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The ratio of the height to the width of the protruding element may be smaller than the ratio of the height to the width of the convex portion.

In the first and second optical structures according to the present invention
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The inclination angle of the surface of the protruding element may be smaller than 70 ° and smaller than the inclination angle of the side surface of the convex portion.

In the first and second optical structures according to the present invention
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The plurality of protruding elements may be arranged in the first direction.

In the first and second optical structures according to the present invention
Each of the plurality of convex portions extends linearly in a direction non-parallel to the first direction.
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The plurality of projecting elements may be arranged in the first direction, and each of the plurality of projecting elements may extend linearly in a direction non-parallel to the first direction.

In the first and second optical structures according to the present invention, the first layer may have a diffraction structure constituting the fine concavo-convex surface.

The polarizing plate with an optical structure according to the present invention
Polarizing plate and
It includes any of the above-mentioned optical structures according to the present invention, which are laminated with the polarizing plate.

The display panel with an optical structure according to the present invention
Display panel and
It includes any of the above-mentioned optical structures according to the present invention, which are laminated with the display panel.

The display device with an optical structure according to the present invention
Display device and
It comprises any of the above-mentioned optical structures according to the present invention, which are laminated with a display device.

According to the present invention, the color change according to the observation angle can be effectively suppressed.

FIG. 1 is a diagram for explaining an embodiment of the present invention, and is a schematic view showing a display device, a display panel, and a polarizing plate including an optical structure. FIG. 2 is a vertical cross-sectional view showing a surface light source device that can be included in the display device of FIG. 1, and is a diagram for explaining the operation of the surface light source device. FIG. 3 is a perspective view showing an optical structure that can be included in the display device of FIG. FIG. 4 is a cross-sectional view of the optical structure taken along the line IV-IV of FIG. FIG. 5 is a cross-sectional view showing a fine concavo-convex surface of the optical structure of FIG. 4 enlarged with the same cross section as that of FIG. FIG. 6 is a cross-sectional view showing the optical structure in the same cross section as in FIG. 4, and is a diagram for explaining the operation of the optical structure. FIG. 7 is a vertical cross-sectional view corresponding to FIG. 6 and is a diagram for explaining a modification of the optical structure. FIG. 8 is a vertical cross-sectional view corresponding to FIG. 6 for explaining another modification of the optical structure. FIG. 9 is a vertical cross-sectional view corresponding to FIG. 6 for explaining still another modification of the optical structure. FIG. 10 is a graph showing the measurement results of the optical characteristics of the optical structure.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the convenience of illustration and comprehension. In addition, hatching may be omitted in the cross-sectional view for convenience of understanding. Further, the configurations shown in one or more figures may be omitted in another figure.

In the present specification, terms such as "sheet", "film", "board", and "layer" are not distinguished from each other based only on the difference in designation. Thus, for example, "sheet" is a concept that includes members that can also be called films, plates, or layers.

Further, in the present specification, the "sheet surface (plate surface, film surface)" refers to the plane direction (plane direction) of the target sheet-like member when the target sheet-like member is viewed as a whole and in a broad view. Refers to the surface that coincides with the direction). Further, in the present specification, the perpendicular direction (normal direction) of the sheet-shaped member refers to the direction of the perpendicular line with respect to the seat surface of the target sheet-shaped member.

Furthermore, as used in the present specification, the terms such as "parallel", "orthogonal", and "identical", and the values of length and angle, which specify the shape and geometric conditions and their degrees, are strictly referred to. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.

FIG. 1 shows a display device 10A with an optical structure including the optical structure 40 according to the embodiment of the present invention. As shown in FIG. 1, the display device 10A with an optical structure includes a display device 10 having a display surface 11 and an optical structure 40 arranged to face the display surface 11 of the display device 10. .. The optical structure 40 is joined to, for example, the display surface 11. Note that FIG. 1 is a cross-sectional view of the display device 10A with an optical structure on a surface including the perpendicular direction of the display surface 11.

First, the display device 10 will be described. The display device 10 has a display surface 11 for displaying an image. The illustrated display device 10 is configured as a liquid crystal display device. As shown in FIG. 1, the display device 10 which is a liquid crystal display device has a display panel 15 as a liquid crystal display panel and a surface light source device 20 arranged to face the display panel 15. The surface light source device 20 faces the liquid crystal display panel 15 in a plane shape. The surface of the display panel 15 opposite to the side illuminated by the surface light source device 20 forms the display surface 11 of the display device 10. In the display device 10, the liquid crystal display panel 15 can function as a shutter that controls the transmission or blocking of light from the surface light source device 20 for each region (sub-pixel) forming a pixel. An image can be displayed on the display surface 11 by controlling the transmission or blocking of light for each region forming the pixel.

The illustrated liquid crystal display panel 15 is arranged between the upper polarizing plate 16 arranged on the light emitting side, the lower polarizing plate 18 arranged on the light entering side, and the upper polarizing plate 16 and the lower polarizing plate 18. It has a liquid crystal layer 17. The polarizing plates 16 and 18 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). It has a function of transmitting a wave) and absorbing a linearly polarized light component (for example, an S wave) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

In the liquid crystal layer 17, a voltage can be applied to each region forming one pixel. The orientation of the liquid crystal molecules in the liquid crystal layer 17 changes depending on the presence or absence of voltage application. As an example, as the display panel 15, a VA (Vertical Alignment) type liquid crystal display panel can be adopted. In the VA type display panel 15, when no voltage is applied to the liquid crystal molecules in the liquid crystal layer 17 or the applied voltage is the minimum value, the liquid crystal molecules are displayed on the sheet surface of the liquid crystal display panel 15, that is, the display. Oriented in the perpendicular direction of the surface 11. At this time, the polarized state of the light transmitted through the lower polarizing plate 18 is maintained, and after passing through the liquid crystal layer 17, it is absorbed by the upper polarizing plate 16. That is, the light from the surface light source device 20 is blocked by the display panel 15. When the voltage applied to the liquid crystal molecules is gradually increased, the liquid crystal molecules gradually incline toward the side along the sheet surface of the liquid crystal display panel 15. As a result, the polarized state of the light transmitted through the lower polarizing plate 18 changes the vibration direction by transmitting through the liquid crystal layer 17. As a result, the transmittance of light from the surface light source device 20 gradually increases as the applied voltage is increased. In this way, the display panel 15 can control the transmission or blocking of light from the surface light source device 20 for each sub-pixel.

The display panel 15 is not limited to the VA type liquid crystal display panel, and may be a TN (Twisted Nematic) type liquid crystal display panel, or an IPS (In-Plane Switching) type liquid crystal display panel. There may be. The details of the display panel 15 are described in various publicly known documents (for example, "Flat Panel Display Dictionary (supervised by Tatsuo Uchida and Hiraki Uchiike)" published by Kogyo Chosakai in 2001), and further details are described here. 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. The surface light source device 20 is used as a device for illuminating the display panel 15 from the back surface side (light entry side). As shown in FIGS. 1 and 2, the surface light source device 20 can be configured as an edge light type surface light source device as an example. However, the surface light source device 20 is not limited to the illustrated edge light type, and may be another type such as a direct type or a back-illuminated type.

The illustrated edge light type surface light source device 20 includes a light guide plate 30, a light source 23 arranged on one side of the light guide plate 30 (left side in FIGS. 1 and 2), and a light guide plate. It has an optical sheet (prism sheet) 25 and a reflective sheet 22 arranged so as to face each of the 30s. In the illustrated example, the optical sheet 25 is arranged facing the liquid crystal display panel 15. The light emitting surface of the optical sheet 25 forms the light emitting surface 21 of the surface light source device 20.

In the illustrated example, the light guide plate 30 has a rectangular parallelepiped outer contour whose side in the thickness direction is smaller than the other side. The light guide plate 30 has a light emitting surface 31 composed of one main surface facing the liquid crystal display panel 15, a back surface 32 composed of the other main surface facing the light emitting surface 31, and the light emitting surface 31 and the back surface 32. It has a side surface extending between them. The light emitting surface 31 and the back surface 32 as the pair of main surfaces have a rectangular shape in a plan view (when observed from the perpendicular direction of the light guide plate 30). Correspondingly, the display surface 11 of the display device 10 and the light emitting surface 21 of the surface light source device 20 have a rectangular shape in a plan view. Further, the optical sheet 25 and the reflective sheet 22 also have a rectangular shape in a plan view like the light guide plate 30.

In the illustrated light guide plate 30, one side surface of the two side surfaces facing the first direction D1 forms the light entry surface 33. As shown in FIGS. 1 and 2, the light source 23 is provided facing the light entering surface 33. As shown in FIG. 2, the light incident on the light guide plate 30 from the light entry surface 33 is directed to the opposite surface 34 facing the light entry surface 33 along the first direction (light guide direction) D1 and is substantially the first. The light guide plate 30 is guided along the direction (light guide direction) D1.

In order to clarify the directional relationship between the display device 10 and the optical structure 40 between the drawings, in some drawings, the first direction D1 and the second direction D2 and the front direction FD, which will be described later, are shown between the drawings. The common direction is indicated by an arrow. The tip side of the arrow is one side of each direction D1, D2, FD. Further, an arrow pointing toward the back of the paper surface in a direction perpendicular to the paper surface of the drawing is indicated by a symbol in which an X is provided in a circle, for example, as shown in FIG.

More specifically, the light guide plate 30 is formed as an uneven surface on the back surface 32 of the illustrated light guide plate 30. As shown in FIG. 2, the back surface 32 has a stepped surface 38 extending in the perpendicular direction of the light guide plate 30, a connecting surface 39 extending in the plate surface direction of the light guide plate 30, and both the stepped surface 38 and the connecting surface 39. It has an inclined inclined surface 37 and an inclined surface 37. The light guiding in the light guide plate 30 is performed by reflection on the pair of main surfaces 31 and 32 of the light guide plate 30, particularly total reflection action. 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 entering surface 33 side toward the opposite surface 34 side. Therefore, for the light reflected by the inclined surface 37, the incident angle when it is incident on the pair of main surfaces 31 and 32 becomes small. Therefore, by reflecting the light on the inclined surface 37, the angle of incidence of the light on the pair of main surfaces 31 and 32 tends to be less than the total reflection critical angle. Then, as shown in FIG. 2, the lights L21 and L22, which are reflected by the inclined surface 37 and whose incident angle to the pair of main surfaces 31 and 32 is less than the total reflection critical angle, are emitted from the light guide plate 30. In the illustrated example, the inclined surface 37 functions as a light extraction element for extracting light from the light guide plate 30. However, the light extraction element applied to the light guide plate 30 is not limited to the inclined surface 37. As the light extraction element of the light guide plate 30, a dot pattern containing a diffuser provided on the back surface 32 or a diffuser dispersed in the light guide plate may be used instead of the inclined surface 37 or in addition to the inclined surface 37. can.

The light source 23 may be configured in various forms such as a fluorescent lamp such as a linear cold cathode tube, a point LED (light emitting diode), and an incandescent lamp. The illustrated light source 23 is composed of a large number of point-shaped light emitters 24 arranged side by side along the longitudinal direction of the light entry surface 33, specifically, a large number of LEDs. In the illustrated example, the longitudinal direction of the light entering surface 33 is the second direction orthogonal to the first direction D1.

The reflective sheet 22 is arranged so as to face the back surface 32 of the light guide plate 30. The reflective sheet 22 reflects the light leaked from the back surface 32 of the light guide plate 30 and causes it to enter the light guide plate 30 again. The reflective sheet 22 includes a white scattered reflective sheet, a sheet made of a material having a high reflectance such as metal, and a thin film made of a material having a high reflectance (for example, a metal thin film or a dielectric multilayer film) as a surface layer. And so on. The reflection on the reflective sheet 22 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflective sheet 22 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

The optical sheet 25 has a function of changing the traveling direction of transmitted light. The optical sheet 25 is arranged so as to face the light emitting surface 31 of the light guide plate 30. The optical sheet 25 shown in FIG. 2 has a plate-shaped main body 26 and a plurality of unit prisms (unit shape element, unit optical element, unit lens) formed on the light entry side surface of the main body 26. 27 and. The main body 26 is a flat plate having a pair of parallel main surfaces. The plurality of unit prisms 27 are arranged in the arrangement direction, and each unit prism 27 extends linearly in a direction non-parallel to the arrangement direction. In the illustrated example, the plurality of unit prisms 27 are arranged in the first direction D1. Each unit prism 27 extends linearly in the second direction D2 orthogonal to the first direction D1. Note that, unlike the illustrated example, a plurality of optical sheets 25 may be laminated on the light guide plate 30. In this example, the arrangement directions of the unit prisms 27 may be non-parallel, especially orthogonal, among the plurality of optical sheets 25.

In the surface light source device 20 as described above, the optical sheet 25 bends the traveling direction of the light emitted from the light emitting surface 31 of the light guide plate 30. More specifically, the optical sheet 25 bends the traveling direction of the transmitted light so that the angle formed by the traveling direction of the light with respect to the perpendicular direction of the light guide plate 30 is reduced. The light transmitted through the optical sheet 25 is incident on the display panel 15. As described above, the light incident on the display panel 15 is controlled to be transmitted or blocked in the liquid crystal layer 17 for each pixel, whereby an image is formed on the display surface 11 of the display device 10.

Next, the optical structure 40 will be described with reference to FIGS. 3 to 6. As shown in FIG. 3, the optical structure 40 is arranged on the display surface 11 of the display device 10. The optical structure 40 exerts an optical action on the image light emitted from the display device 10. More specifically, the optical structure 40 diffuses the transmitted image light and suppresses the color change according to the observation angle of the image. The optical structure 40 is arranged on the display surface 11 of the display device 10. The optical structure 40, together with the display device 10, constitutes a display device 10A with an optical structure. Further, the optical structure 40, together with the upper polarizing plate 16, constitutes a polarizing plate 16A with an optical structure. Further, the optical structure 40, together with the liquid crystal display panel 15, constitutes a display panel 15A with an optical structure.

The optical structure 40 is a sheet-like member. The perpendicular direction of the optical structure 40 coincides with the perpendicular direction of the display surface 11. In the illustrated example, the perpendicular direction of the optical structure 40 is the perpendicular direction of the liquid crystal display panel 15, the perpendicular direction of the light emitting surface 21, the perpendicular direction of the reflective sheet 22, the perpendicular direction of the optical sheet 25, and the perpendicular direction of the light guide plate 30. Also agrees. The perpendicular direction of the optical structure 40 is referred to as a frontal FD. In the illustrated example, the frontal FD is orthogonal to the first direction D1 and is also orthogonal to the second direction D2.

The optical structure 40 has a first layer 50 and a second layer 55 laminated on each other in the front direction FD. The first layer 50 and the second layer 55 form a refractive index interface B adjacent to each other in the front direction FD. That is, the first layer 50 and the second layer 55 have different refractive indexes from each other. As will be described later, at the interface B between the first layer 50 and the second layer 55, optical actions such as refraction and diffraction can be exerted on the image light transmitted through the optical structure 40. The illustrated optical structure 40 further has a base material 42 and a functional layer 44. In the illustrated optical structure 40, the second layer 55, the first layer 50, the base material 42, and the functional layer 44 are laminated in this order from the side (light receiving side) of the display device 10 in the front direction FD. ..

The optical structure 40 is preferably transparent from the viewpoint of transmitting image light with a high transmittance. Therefore, it is preferable that each of the constituent elements constituting the optical structure 40, that is, the second layer 55, the first layer 50, the base material 42, and the functional layer 44 is also transparent. Here, "transparent" means having transparency to the extent that it can be seen through, and for example, it is visible at 30% or more, more preferably 50% or more, and further preferably 70% or more. It means that it has light transmittance. The visible light transmittance is the transmittance at each wavelength when measured within the measurement wavelength range of 380 nm to 780 nm using a spectrophotometer (“UV-3100PC” manufactured by Shimadzu Corporation, JIS K 0115 compliant product). Is specified as the average value of.

The base material 42 is a support base material that appropriately supports the first layer 50 and the second layer 55. As an example, the base material 42 is made of a resin film or glass. Examples of the resin material used for the base material 42 include triacetyl cellulose, polyethylene terephthalate, polyoliffin, polycarbonate, polyacrylate, and polyamide. The base material 42 preferably has a thickness of 20 μm or more and 80 μm or less in consideration of transparency, appropriate supportability of the optical structure 40, and the like. On the other hand, the base material 42 may be omitted.

The functional layer 44 is a layer expected to have various functions, and may include a plurality of layers, may include a single layer having two or more functions, or may include an optical structure 40. It is also possible to omit from. In the illustrated example, the functional layer 44 is located on the side of the optical structure 40 that is farthest from the display device 10 in the front direction FD. That is, the functional layer 44 is located on the most emitted side and forms the surface layer of the display device 10A with an optical structure. As such a functional layer 44, an antireflection layer having an antireflection function can be exemplified. Examples of the other functional layer 44 include an antiglare layer having an antiglare function, a hard coat layer imparting scratch resistance, an antifouling layer having an antifouling function, and an antistatic layer having an antistatic function. Can be done.

Next, the first layer 50 and the second layer 55 will be described. As shown in FIGS. 3 to 6, the first layer 50 and the second layer 55 are adjacent to the front FD. The first layer 50 and the second layer 55 have shapes complementary to each other, and form an interface B as an uneven surface. The surface of the first layer 50 opposite to the second layer 55 and the surface of the second layer 55 opposite to the first layer 50 are parallel to each other. That is, the first layer 50 and the second layer 55 form a laminated body having a pair of parallel main surfaces.

In the illustrated example, the first layer 50 is located on the light emitting side of the second layer 55 in the front direction FD. The light entering side surface 50a of the first layer 50 and the light emitting side surface 55b of the second layer 55 are adjacent to each other to form an interface B. The light entering side surface 50a of the first layer 50 and the light emitting side surface 55b of the second layer 55 are uneven surfaces. The light emitting side surface 50b of the first layer 50 is parallel to the light entering side surface 55a of the second layer 55. The light emitting side surface 50b of the first layer 50 and the light entering side surface 55a of the second layer 55 are flat surfaces orthogonal to the front direction FD.

As shown in FIG. 3, the first layer 50 has a sheet-shaped base portion 51 that spreads so as to be orthogonal to the front direction FD, and a plurality of convex portions 52 provided on the base portion 51. .. The plurality of convex portions 52 are arranged in the first direction D1. In the illustrated example, the convex portion 52 extends linearly in a direction non-parallel to the first direction D1. In particular, the illustrated convex portion 52 extends linearly in the second direction D2 orthogonal to the first direction D1. As a result, the plurality of convex portions 52 are linearly arranged, and the plurality of concave portions 53 are also linearly arranged.

As shown in FIGS. 3 to 6, the plurality of convex portions 52 are arranged apart from each other. Therefore, the concave portion 53 is formed between the two convex portions 52 adjacent to each other in the first direction D1. The recess 53 includes a bottom surface BS located on two adjacent convex portions 52. It can be said that the bottom surface BS is an exposed portion between two adjacent convex portions 52 in the surface of the base portion 51 facing the second layer 55 side in the front direction FD. Each convex portion 52 includes a top surface TS facing the second layer 55 side in the front direction FD, and a pair of side surface SSs connected to both ends of the top surface TS. Each side surface SS is located between the top surface TS and the bottom surface BS adjacent to each other in the first direction D1, and connects the top surface TS and the bottom surface BS. The pair of side surface SSs can be said to be a pair of side surfaces of the recess 53 connected to both ends of the bottom surface BS of the recess 53.

As shown in FIG. 4, the width WT of the top surface TS along the first direction D1 is smaller than the width W1 of the convex portion 52 including the top surface TS along the first direction D1. In the projection to the front direction FD, the top surface TS is located inside both ends of the convex portion 52 including the top surface TS in the first direction D1. Therefore, the pair of side surface SSs included in the convex portion 52 are not only the first direction D1 but also the surfaces inclined with respect to the front direction FD. Each of the pair of side surface SSs is inclined so as to approach each other as it separates from the base portion 51 in the front direction FD. The side surface SS is curved in the main cut surface of the convex portion 52 parallel to both the first direction D1 and the front direction FD shown in FIGS. 4 to 6. The curve formed by the side surface SS is a convex shape that bulges outward from both ends of the side surface SS. That is, the side surface SS is composed of a curved surface protruding outward.

However, the configuration of the side surface SS is not limited to the examples shown in FIGS. 4 to 6. The side surface SS may be configured as a concave curved surface as shown in FIG. 7, may be configured as a convex bent surface as shown in FIG. 8, or may be configured as a concave bent surface. You may. Further, the side surface SS may be formed of a flat surface and may be linear in the main cut surface. Further, the plurality of convex portions 52 included in the first layer 50 may have different configurations.

In the illustrated example, the cross-sectional shape of the convex portion 52 on the main cut surface is such that the convex portion 52 in the first direction D1 can be imparted with symmetrical optical characteristics centered on the front direction FD. It is line-symmetrical about the axis that passes through the center of the FD and extends in the front direction FD. Therefore, the pair of side surfaces SS are symmetrical with each other. However, the cross-sectional shape of the convex portion 52 on the main cut surface is not limited to this example, and may be asymmetrical.

The arrangement pitch P1 (see FIG. 4) along the first direction D1 of the convex portion 52 is preferably smaller than the pixel pitch of the display device 10. In particular, the arrangement pitch P1 along the first direction D1 of the convex portion 52 is preferably 1/5 or less, and more preferably 1/10 or less of the pixel pitch. Specifically, the arrangement pitch P1 along the first direction D1 of the convex portion 52 is preferably 10 μm or more and 60 μm or less, and more preferably 15 μm or more and 30 μm or less.

As the optical structure 40 capable of suppressing the color change according to the observation angle described later, other dimensions can be determined as follows. The width W1 of the convex portion 52 along the first direction D1 is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 25 μm or less. The width WT of the top surface TS of the convex portion 52 along the first direction D1 is preferably 3 μm or more and 20 μm or less, and more preferably 3 μm or more and 15 μm or less. The width WS along the first direction D1 of each side surface SS of the convex portion 52 is preferably 0.5 μm or more and 5 μm or less, and more preferably 1.5 μm or more and 3.5 μm or less. The height H1 along the frontal FD of the convex portion 52 is preferably 5 μm or more and 30 μm or less, and more preferably 8 μm or more and 20 μm or less. The inclination angle θ1 of each side surface SS of the convex portion 52 is preferably 60 ° or more and less than 90 °, more preferably 72 ° or more and 85 ° or less, and further preferably 76 ° or more and 83 ° or less. .. Here, as shown in FIG. 4, the inclination angle θ1 of the side surface SS is the smaller angle formed by the straight line connecting both ends of the side surface with respect to the seat surface of the optical structure 40. When the convex portions 52 are linearly arranged, the inclination angle θ1 of the side surface SS can be specified on the main cut surface of the convex portions 52.

Further, in the present embodiment, the first layer 50 has a fine uneven surface FUS on at least one of the top surface TS of the convex portion 52 and the bottom surface BS of the concave portion 53. In the examples shown in FIGS. 4 to 6, the fine uneven surface FUS is provided on the bottom surface BS of the recess 53. In this example, the fine uneven surface FUS is located on the most downstream side of the interface B of the first layer 50 and the second layer 55 in the direction in which the image light is transmitted. The fine uneven surface FUS suppresses the color change according to the observation angle by diffusing the image light. The diffusion of the image light on the fine uneven surface FUS is mainly due to the diffraction action due to the fine structure. That is, the fine uneven surface FUS is configured as a diffraction structure that causes a diffraction phenomenon. In FIG. 3, the illustration of the fine uneven surface FUS is omitted.

The fine concavo-convex surface FUS includes a plurality of projecting elements 54. The plurality of projecting elements 54 are arranged in the arrangement direction of at least the plurality of convex portions 52. In the illustrated example, the plurality of protruding elements 54 are arranged in the first direction D1. The arrangement pitch P2 of the protruding elements 54 (see FIG. 5) is smaller than the arrangement pitch P1 of the plurality of convex portions 52. The height H2 of the protruding element 54 (see FIG. 5) is smaller than the height H1 of the convex portion 52. "Fine" in the name of the fine concavo-convex surface FUS means that the pitch and height of the protruding element 54 are smaller than the pitch and height of the convex portion 52, respectively.

The plurality of protruding elements 54 are linearly arranged as an example. That is, each protruding element 54 extends linearly in a direction non-parallel to the first direction D1. The illustrated protruding element 54 extends linearly in the second direction D2 orthogonal to the first direction D1. However, the arrangement of the plurality of protruding elements 54 is not limited to this example. The plurality of projecting elements 54 are preferably arranged in the arrangement direction of the convex portions 52, but may be arranged two-dimensionally.

The cross-sectional shape of the projecting element 54 on the main cut surface of the projecting element 54 parallel to both the first direction D1 and the front direction FD is not particularly limited. However, in order to impart symmetrical optical characteristics centered on the frontal FD to the optical structure 40, the cross-sectional shape of the protruding element 54 on the main cut surface passes through the center of the protruding element 54 in the first direction D1. It is preferable that the axis is line-symmetrical with the axis extending in the front direction FD as the center.

In the examples shown in FIGS. 4 to 6, the cross-sectional shape of the projecting element 54 on the main cut surface is a triangular shape, particularly an isosceles triangular shape. The plurality of projecting elements 54 are arranged in the first direction D1 without a gap. However, the present invention is not limited to this example, and the plurality of projecting elements 54 may be arranged with a gap in the first direction D1. The triangular apex angle θx (see FIG. 5) formed by the projecting element 54 is not particularly limited and can be 45 ° or more and 120 ° or less.

In order to secure an excellent color change suppressing function in combination with the convex portion 52, the arrangement pitch P2 of the protruding elements 54 along the first direction D1 (see FIG. 5) and the width W2 of the protruding elements 54 (see FIG. 5). Is preferably 0.3 μm or more and 2 μm or less, more preferably 0.3 μm or more and 1.5 μm or less, and further preferably 0.3 μm or more and 0.78 μm or less. By setting the arrangement pitch P2 of the protruding elements 54 to 0.3 μm or more and 1.5 μm or less, the diffraction efficiency on the fine uneven surface FUS can be effectively improved. By setting the arrangement pitch P2 of the protruding element 54 to 0.3 μm or more and 0.78 μm or less, it is possible to improve the diffraction efficiency on the fine uneven surface FUS and effectively suppress the diffusion due to refraction by the protruding element 54. can.

Further, from the viewpoint of weakening the refraction action on the fine uneven surface FUS and making the optical action on the fine uneven surface FUS mainly a diffraction action, the inclination angle θ2 (see FIG. 5) of the surface of the protruding element 54 is set to 10 ° or more and 70 °. It is preferably smaller than °, more preferably 10 ° or more and less than 55 °, and even more preferably 10 ° or more and 45 ° or less. Here, as shown in FIG. 5, the inclination angle θ2 of the surface of the protruding element 54 is the smaller angle formed by the straight line connecting both ends of the side surface (surface) with respect to the sheet surface of the optical structure 40. be. When the projecting elements 54 are linearly arranged, the inclination angle θ2 can be specified on the main cutting surface of the projecting elements 54. On the other hand, as in the example shown in FIG. 9, it is more preferable that the inclination angle θ2 of the side surface (surface) of the projecting element 54 is 80 ° or more. According to such an example, the diffraction efficiency on the fine uneven surface FUS can be effectively improved.

As other dimensions, the height H2 of the protruding element 54 along the frontal FD is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 1 μm or less.

The second layer 55 is laminated on the first layer 50 having the above configuration from the side where the convex portion 52 protrudes. The first layer 50 and the second layer 55 are adjacent to the front FD. Therefore, the second layer 55 has a recess corresponding to the convex portion 52 of the first layer 50. Further, the second layer 55 has a convex portion corresponding to the concave portion 53 of the first layer 50. Further, the second layer 55 has a fine uneven surface corresponding to the fine uneven surface FUS of the first layer 50.

The first layer 50 and the second layer 55 have different refractive indexes from each other, and a refractive index interface B is formed between the first layer 50 and the second layer 55. When the difference between the refractive index of the first layer 50 and the refractive index of the second layer 55 becomes large, the optical action at the interface B between the first layer 50 and the second layer 55 is likely to be exhibited. The difference in refractive index between the first layer 50 and the second layer 55 is preferably 0.05 or more and 0.25 or less. With respect to the first layer 50 and the second layer 55 having the above-mentioned shapes, it is preferable that the refractive index of the first layer 50 is higher than that of the second layer 55. By setting the refractive indexes of the first layer 50 and the second layer 55 in this way, it is possible to effectively suppress the color change according to the observation angle. The refractive index of the first layer 50 can be, for example, 1.6 or more, and the refractive index of the second layer 55 can be, for example, 1.49 or less. The comparison between the refractive index of the first layer 50 and the refractive index of the second layer 55 is confirmed by, for example, the refraction direction of the light incident on the interface B between the first layer 50 and the second layer 55 and the total reflection conditions. can do. The specific value of the refractive index can also be measured with, for example, an Abbe refractive index meter (for example, RX-7000α manufactured by Atago Co., Ltd.).

The first layer 50 supplies, for example, an ionizing radiation curable resin composition between a mold having a mold surface obtained by reversing the shape of the desired first layer 50 and a resin film forming the base material 42, and the composition thereof. By curing the object, it can be formed on the base material 42. As the material of the first layer 50, for example, an ultraviolet curable resin such as urethane acrylate can be used. Further, the mold for molding the first layer 50 can be manufactured by cutting, etching or the like.

The second layer 55 can be produced by supplying a fluid resin composition onto the produced first layer 50 and curing the resin composition. Alternatively, it can be produced by laminating the produced first layer 50 on a softable resin film such as an acrylic thermoplastic resin and transferring the uneven shape of the first layer 50. The second layer 55 may be made to have adhesiveness so as to function as an adhesive layer. According to such a second layer 55, the optical structure 40 can be joined to the display device 10 via the second layer 55.

Next, the operation of the optical structure 40 and the display device 10A with an optical structure having the optical structure 40 will be described.

When displaying an image on the display device 10A with an optical structure, first, light is emitted from the light emitting body 24 of the light source 23. The light emitted from the light emitting body 24 enters the light guide plate 30 via the light incoming surface 33. The light incident on the light guide plate 30 is reflected by the pair of main surfaces 31 and 32, particularly totally reflected, and travels in the light guide plate 30 toward the opposite surface 34. Each time the light traveling through the light guide plate 30 is reflected by the inclined surface 37 in the back surface 32, the angle of incidence on the pair of main surfaces 31 and 32 is reduced. As shown in FIG. 2, when the angle of incidence on the main surface 31 is less than the total reflection critical angle, the lights L21 and L22 are emitted from the light guide plate 30. The light emitted from the light guide plate 30 is incident on the display panel 15 after being bent in the traveling direction by the optical sheet 25. In the display panel 15, light transmission and shielding are controlled for each pixel (sub-pixel). In this way, the image light is emitted from the display surface 11 of the display device 10. The image light emitted from the display surface 11 of the display device 10 is incident on the optical structure 40. The optical structure 40 diffuses and transmits image light. By emitting the image light from the optical structure 40, the observer can observe the image displayed by the display device 10A with the optical structure.

By the way, as described in the column of the prior art, when the image is displayed by the conventional display device, the color of the displayed image may be changed and observed depending on the observation angle at which the image is observed. When this defect occurs, even if the image can be observed in a desired color from any of the observation directions, the image is discolored and observed from the observation direction deviated from the observation direction. Normally, when observing from the front FD where the brightness should be the highest, the image is observed in an appropriate color. On the other hand, when the image is observed from the direction inclined from the front direction FD, the color of the observed image is observed in a color different from the original color. In recent years when the display of color images has become widespread, such a defect can be said to be a fatal problem in a display device.

On the other hand, the illustrated display device 10A with an optical structure is devised to effectively suppress the color change according to the observation angle. This point will be described below.

As shown in FIG. 6, the lights L61 and L62 emitted from the display surface 11 of the display device 10 first enter the second layer 55 of the optical structure 40, and then the refraction of the first layer 50 and the second layer 55. Head toward the index interface B. The interface B of the first layer 50 and the second layer 55 formed by the side surface SS of the convex portion 52 bends the traveling direction of the transmitted light mainly by refraction. Typically, the light L61 traveling in a direction not significantly inclined with respect to the frontal FD or the frontal FD, that is, the rising light L61 is formed by the side surface SS so as to travel in a direction greatly inclined with respect to the frontal direction. The interface B bends the traveling direction of the light L61. On the other hand, the side surface SS is formed so that the light L62 traveling in a direction greatly inclined with respect to the front direction FD, that is, the sleeping light L62 travels in a direction not significantly inclined with respect to the front direction FD and the front direction FD. The interface B bends the traveling direction of the light L62. Due to the typical action at the interface B, the image light of an appropriate color traveling in the front direction FD is directed in a direction greatly inclined from the front direction FD. At the same time, the image light that has traveled in a direction that is greatly inclined from the front direction is directed in a direction that is not significantly inclined with respect to the front direction FD and the front direction FD. Due to the above optical action at the interface B formed by the top surface TS of the convex portion 52, images of different colors are superimposed and observed in various observation directions. This makes it possible to prevent the image from being observed in different colors depending on the observation direction.

As shown in FIG. 6, the interface B of the first layer 50 and the second layer 55 formed by the top surface TS of the convex portion 52 advances in a direction that is not significantly inclined with respect to the front direction FD and the front direction FD. The traveling direction of the light L63 is maintained without being significantly changed. Further, the interface B formed by the top surface TS can bend the traveling direction of the light L64 traveling in a direction greatly inclined with respect to the front direction FD in a direction not greatly inclined with respect to the front direction FD and the front direction FD. can. Due to these optical actions at the interface B formed by the top surface TS of the convex portion 52, the frontal brightness can be maintained.

In addition, according to the optical structure 40 according to the present embodiment, the first layer 50 is formed on at least one of the top surface TS of the convex portion 52 and the bottom surface BS of the concave portion 53 located between the adjacent convex portions 52. It has a fine uneven surface FUS. Then, the image light can be diffused also at the refractive index interface B of the first layer 50 and the second layer 55 formed by the fine uneven surface FUS. Diffusion at the interface B formed by the fine concavo-convex surface FUS is first due to refraction on the surface of the protruding element 54. In addition, the diffusion at the interface B formed by the fine concavo-convex surface FUS also depends on the diffraction caused by the fine concavo-convex structure. According to diffraction, the image light can be directed not only in the ± primary diffraction direction but also in the multi-order diffraction direction.

In the example shown in FIG. 6, the light L62 whose traveling direction is bent so as to reduce the angle formed with respect to the front direction FD by the interface B formed by the convex portion 52 is diffracted on the fine uneven surface FUS. Is spreading by. Further, the light L65 that travels in a direction that does not greatly incline with respect to the front direction FD and the front direction FD and heads toward the fine uneven surface FUS is also diffused by diffraction on the fine uneven surface FUS.

As described above, the diffusion at the interface B formed by the convex portion 52 and the diffusion at the interface B formed by the fine concavo-convex surface FUS having a pitch significantly finer than that of the convex portion 52 are combined. For example, the color change according to the observation angle can be effectively made inconspicuous. By increasing the side surface ratio indicating the ratio of the side surface SS in the first direction D1, the diffusivity by the refractive index interface B formed by the convex portion 52 is strengthened, and the color change according to the observation angle is alleviated. You can also do it. However, as demonstrated in the examples described later, instead of strengthening the diffusing ability by the refractive index interface B formed by the convex portion 52, the diffusion by the fine concavo-convex surface FUS is superimposed on the diffusion by the convex portion 52. By matching, it is possible to more effectively suppress the color change according to the observation angle. In particular, it was also confirmed that the fine uneven surface FUS adopting a configuration for improving the diffraction efficiency can suppress the color change according to the observation angle more remarkably.

The details of the phenomenon in which the color change is suppressed in this way are unknown, but it is presumed that the following points are one of the factors. Since the refractive index of the medium changes according to the wavelength, the refraction allows the direction of travel of short-wavelength light to be bent more. On the other hand, according to diffraction, it is possible to bend the traveling direction of long-wavelength light more greatly without depending on the refractive index. From such a point, according to the combination of the light diffusing function mainly at the convex portion 52 due to refraction and the light diffusing function at the fine uneven surface FUS using diffraction, the color change according to the observation angle is more effective. It is presumed that it can be suppressed.

Further, in the above-described specific example shown, the optical structure 40 is installed so that the image light incident from the side of the second layer 55 is emitted from the side of the first layer 50. The first layer 50 has a fine uneven surface FUS on the bottom surface BS of the recess 53. That is, a fine uneven surface FUS is provided on the bottom surface BS of the recess 53 of the first layer 50 located on the light emitting side. That is, after being diffused by the convex portion 52, it is diffused by the fine uneven surface FUS having a finer structure than the convex portion 52. Conversely, the image light can be diffused more uniformly at the refractive index interface B on the fine concavo-convex surface FUS and then transmitted through the optical structure 40 without being incident on the refractive index interface B at the convex portion 52. can. Therefore, according to the specific example described above, the image light passing through the optical structure 40 can be diffused more uniformly. As a result, the color change according to the observation angle can be suppressed more effectively.

Further, in the above-described specific example shown, the refractive index of the first layer 50 is larger than the refractive index of the second layer 55, and the first layer 50 has a fine uneven surface FUS on the bottom surface BS of the recess 53. .. Normally, the convex portion 52 of the first layer 50 is tapered toward the side of the second layer 55. The first layer 50 having the tapered convex portion 52 and having a high refractive index is preferably located on the light emitting side of the second layer 55. According to this arrangement, it becomes easy to set up the traveling direction of the light sleeping at the interface B of the first layer 50 and the second layer 55, and it becomes easy to set the traveling direction of the rising light to sleep. Then, as in the specific example described above, by providing the fine concavo-convex surface FUS on the bottom surface BS of the recess 53 of the first layer 50 located on the light emitting side, the image light is uniform at the refractive index interface B on the fine concavo-convex surface FUS. After being diffused into, it can pass through the optical structure 40 without being incident on the refractive index interface B at the convex portion 52. As a result, the image light that passes through the optical structure 40 can be diffused more uniformly. As a result, the color change according to the observation angle can be suppressed more effectively.

Further, in the above-described specific example shown, the first layer 50 has a plurality of projecting elements 54 forming a fine uneven surface FUS, and the pitch P2 of the projecting elements 54 is 0.3 μm or more and 2.0 μm or less. There is. By forming the fine concavo-convex surface FUS by the protruding elements 54 arranged at a short pitch in this way, diffraction on the fine concavo-convex surface FUS can be expected. As a result, the image light that passes through the optical structure 40 can be diffused more uniformly, and the color change according to the observation angle can be effectively suppressed.

Further, in the above-described specific example shown, the first layer 50 has a plurality of projecting elements 54 forming a fine uneven surface FUS, and the pitch of the projecting elements 54 is 0.3 μm or more and 0.78 μm or less. .. By forming the fine concavo-convex surface FUS by the protruding elements 54 arranged at a short pitch in this way, the diffraction efficiency on the fine concavo-convex surface FUS can be effectively improved. On the other hand, since the arrangement pitch of the protruding elements 54 is reduced to the range of the visible light wavelength region, the reflection and refraction of the protruding elements 54 at the refractive index interface B of the first layer 50 and the second layer 55 are effective. Can be suppressed. As a result, the image light passing through the optical structure 40 can be diffused more uniformly while effectively maintaining the brightness in the front direction, and the color change according to the observation angle can be effectively suppressed. ..

Further, in the above-described specific example shown, the first layer 50 has a plurality of projecting elements 54 forming a fine concavo-convex surface FUS, and the ratio of the height H2 to the width W2 of the projecting elements 54 is the ratio of the convex portion 52. It is smaller than the ratio of the height H1 to the width W1. By reducing the aspect ratio of the protruding element 54 in this way, it is possible to suppress strong diffusion due to refraction on the fine uneven surface FUS. As a result, the image light passing through the optical structure 40 can be diffused more uniformly while effectively maintaining the brightness in the front direction, and the color change according to the observation angle can be effectively suppressed. ..

Further, in the above-described specific example shown, the first layer 50 has a plurality of projecting elements 54 forming a fine concavo-convex surface FUS, and the inclination angle θ2 of the surface of the projecting element 54 is smaller than 70 ° and the convex portion. It is smaller than the inclination angle θ1 of the side surface SS of 52. By reducing the inclination angle θ2 of the surface of the protruding element 54 in this way, strong diffusion due to refraction on the fine uneven surface FUS can be suppressed. As a result, the image light passing through the optical structure 40 can be diffused more uniformly while effectively maintaining the brightness in the front direction, and the color change according to the observation angle can be effectively suppressed. .. Further, the protruding element 54 having an inclination angle smaller than 45 ° can be relatively easily manufactured.

Further, in the above-described specific example shown, the first layer 50 has a plurality of projecting elements 54 forming a fine uneven surface FUS, and the plurality of projecting elements 54 are arranged in the first direction D1. More specifically, each convex portion 52 and each protruding element 54 extend linearly in a direction non-parallel to the first direction D1. According to such a configuration, the light diffusing function of the convex portion 52 and the light diffusing function of the fine concavo-convex surface FUS can be effectively combined, and the transmitted light of the optical structure 40 can be diffused more uniformly. Can be done. As a result, the image light transmitted through the optical structure 40 can be diffused more uniformly, and the color change according to the observation angle can be effectively suppressed.

In one embodiment described above, the optical structure 40 has a first layer 50 having a plurality of convex portions 52 arranged apart from each other in the first direction D1, and a first layer from the side of the convex portions 52. It has a second layer 55, which is laminated on the 50 and forms a refractive index interface B with the first layer 50. The first layer 50 has a fine uneven surface FUS on at least one of the top surface TS of the convex portion 52 and the bottom surface BS of the protruding element 54 located between the convex portions 52 adjacent to each other. According to this embodiment, the light traveling direction can be bent and diffused at the refractive index interface B of the first layer 50 and the second layer 55 on the side surface SS of the convex portion 52. Similarly, at the interface B of the first layer 50 and the second layer 55 on the fine concavo-convex surface FUS, the traveling direction of light can be bent and diffused. By combining the light diffusing function of the convex portion 52 and the light diffusing function of the fine uneven surface FUS, the transmitted light can be diffused more uniformly. As a result, it is possible to effectively suppress the problem that the displayed image is observed in different colors depending on the observation angle.

In particular, in the present embodiment, the light diffusing function at the convex portion 52 is mainly caused by refraction, and the light diffusing function at the fine concavo-convex surface FUS is caused not only by refraction but also by diffraction. Refraction allows the direction of travel of short wavelength light to be bent more. On the other hand, according to diffraction, the traveling direction of long-wavelength light can be bent more. Therefore, according to the combination of the light diffusing function of the convex portion 52 and the light diffusing function of the fine concavo-convex surface FUS, the color change according to the observation angle can be suppressed more effectively.

Although one embodiment has been described with reference to a plurality of specific examples, these specific examples are not intended to limit one embodiment. The above-described embodiment can be implemented in various other specific examples, and various omissions, replacements, changes, additions, and the like can be made without departing from the gist thereof.

Hereinafter, an example of modification will be described with reference to the drawings. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-mentioned specific examples are used for the parts that can be configured in the same manner as the above-mentioned specific examples, and the same reference numerals are used, and duplicate explanations are given. Is omitted.

For example, in the above-described embodiment, an example of the projecting element 54 constituting the fine concavo-convex surface FUS is shown, but the projecting element 54 is not limited to the above-described embodiment. For example, as shown in FIG. 9, the cross-sectional shape of the protruding element 54 on the main cut surface may be a trapezoidal shape or a rectangular shape. According to the protruding element 54 having a rectangular cross section, the diffraction efficiency on the fine uneven surface FUS can be effectively improved. Further, in the fine uneven surface FUS in which the cross-sectional shape of the protruding element 54 is rectangular, the amount of incident light on the side surface that stands out in the front direction FD is reduced, especially when the fine uneven surface FUS is provided on the bottom surface BS of the concave portion 53. This makes it possible to significantly reduce the degree of refraction.

That is, according to the example shown in FIG. 9, the first layer 50 has a plurality of projecting elements 54 forming the fine uneven surface FUS. The inclination angle θ2 of the side surface (surface) of the projecting element 54 is larger than 45 ° and larger than the inclination angle θ1 of the top surface TS of the convex portion 52. By increasing the inclination angle θ2 of the surface of the projecting element 54, diffusion due to refraction on the fine uneven surface FUS can be suppressed, and the diffraction efficiency on the fine uneven surface FUS can be effectively improved. .. As a result, the image light transmitted through the optical structure 40 can be diffused more uniformly while effectively maintaining the brightness in the front direction, and the color change according to the observation angle can be effectively suppressed. can.

Further, in the above-mentioned specific example, an example in which the fine concavo-convex surface FUS is provided on the bottom surface BS of the recess 53 is shown, but the present invention is not limited to this example. For example, as shown in FIG. 7, the fine concavo-convex surface FUS may be provided on the bottom surface BS of the concave portion 53 and may be provided on the top surface TS of the convex portion 52. Further, as shown in FIG. 8, the fine uneven surface FUS may be provided only on the top surface TS of the convex portion 52. Further, the fine uneven surface FUS may be provided only on a part of each bottom surface BS, or may be provided only on a part of each top surface TS. Further, the fine uneven surface FUS may be provided on the bottom surface BS of some of the concave portions 53, or may be provided on the top surface TS of some of the convex portions 52.

Further, as already described, the protruding three protruding elements 54 forming the fine concavo-convex surface FUS may be arranged two-dimensionally instead of being linearly arranged. The convex portions 52 may be arranged two-dimensionally instead of being linearly arranged.

Further, the illustrated display device 10 is only an example. The above-mentioned optical structure 40 is not particularly limited, and can be applied to various display devices. For example, in the surface light source device 20 shown in FIG. 1, a reflective polarizer may be arranged between the liquid crystal display panel 15 and the optical sheet 25. Further, the surface light source device 20 may include a plurality of optical sheets 25. Further, the surface light source device 20 may include a light diffusing plate. Further, the display device 10 may be an EL (Electroluminescence) display device limited to the liquid crystal display device.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Optical structures according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were produced. Each optical structure has a base material, a first layer and a second layer of the above-mentioned optical structure shown in FIGS. 1 to 6. The first layer was made of a resin having a refractive index of 1.65, and the second layer was made of a resin having a refractive index of 1.48. The first layer was made to have linearly arranged protrusions. Regarding the optical structures according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the arrangement pitch P1 of the convex portion in the first direction is set to 22.5 μm, and the height of the convex portion along the front direction FD of the convex portion is set to 22.5 μm. H1 was set to 16 μm. Further, with respect to the optical structures according to Example 1, Example 2, and Comparative Example 1, the side surface ratio as the ratio occupied by the side surface of the convex portion in the first direction D1 (= ((W1-WT) / P1) / 100 [%]) was set to 25.3%. On the other hand, the side ratio of the optical structure according to Comparative Example 2 was set to 28.0%. Then, in the optical structures according to the first and second embodiments, a fine concavo-convex surface is provided on the bottom surface of the recess. On the other hand, in the optical structures according to Comparative Example 1 and Comparative Example 2, the bottom surface of the recess was made a flat surface, and a fine uneven surface was not provided. Regarding other configurations, the optical structures according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 have a common configuration.

In the optical structures according to Examples 1 and 2, a fine concavo-convex surface FUS was formed by linearly arranged protruding elements 54. The cross-sectional shape of the projecting element 54 was approximately an isosceles triangle, similar to the example shown in FIG. The design value of the apex angle θx of the approximately isosceles triangle shape forming the cross-sectional shape of the protruding element 54 was set to 80 °. In the optical structure according to the first embodiment, the arrangement pitch P2 of the protruding elements 54 was set to 2 μm, and in the optical structure according to the second embodiment, the arrangement pitch P2 of the protruding elements 54 was set to 0.5 μm.

Each of the produced optical structures was bonded to the display surface of a commercially available multi-domain type VA liquid crystal display device manufactured by Samsung, with the second layer as an adhesive layer, and the optical characteristics were compared. As the optical characteristics, the front luminance ratio [%] and the color washout angle [°] were evaluated. The front-direction brightness ratio is the front-direction brightness when the optical structures are laminated, which is measured when the entire display device with the optical structure is displayed in white, and the front-side direction when the optical structure is removed. The ratio to the brightness [%] was used. Luminance was measured using SPECTRORADIOMETER (CS-1000) manufactured by Minolta.

The color washout angle [°] is the angle formed by the measurement direction in which the saturation measured in the front direction is 20% different from the saturation measured in the front direction for each display device with an optical structure. .. In other words, the saturation measured from the direction inclined by the color washout angle [°] with respect to the front direction is 80% of the saturation measured from the front direction. Saturation is represented by ^{C *} = ((a ^* ) ² + (b ^* ) ² ) ^{1/2 in the L *} a ^* b ^* color system. The L ^* a ^* b ^* color system has been standardized by the CIE (Commission Internationale de l'Eclairage) and adopted in JIS Z 8781-4: 2013. Luminance was measured using SPECTRORADIOMETER (CS-1000) manufactured by Minolta. The saturation was measured from the direction in which the inclination angle with respect to the front direction was changed in the virtual plane parallel to both the front direction and the first direction.

The results are shown in Table 1 and FIG. In Comparative Example 2, the lateral ratio was increased as compared with Comparative Example 1. Therefore, the diffusion function due to refraction on the side surface in Comparative Example 2 was enhanced, and the color washout angle [°] was larger than that in Comparative Example 1. Example 1 and Example 2 had the same front-facing luminance ratio with respect to Comparative Example 2, while having a significantly expanded color washout angle [°] over Comparative Example 1. Example 2 in which the pitch P2 and the pitch of the protruding elements constituting the fine concavo-convex surface were reduced was superior to that of Example 1 in both the front luminance ratio and the color washout angle [°]. From this point, it is presumed that the diffusion on the fine concavo-convex surface FUS is preferably mainly diffraction rather than refraction.

10 Display device 10A Display device with optical structure 11 Display surface 15 Liquid crystal display panel 15A Display panel with optical structure 16 Upper polarizing plate 16A Polarizing plate with optical structure 17 Liquid crystal layer 18 Lower polarizing plate 20 Surface light source device 21 Light emitting surface 22 Reflective sheet 23 Light source 24 Light emitting body 25 Optical sheet 26 Main body 27 Unit prism 30 Light guide plate 31 Light emitting surface 32 Back surface 33 Incoming surface 34 Opposite surface 37 Inclined surface 38 Step surface 39 Connection surface 40 Optical structure 42 Base material 44 Functional layer 50 1st layer 50a Incoming side surface 50b Emitting side surface 51 Base part 52 Convex part 53 Recessing element 55 Protruding element 55 2nd layer 55a Incoming light side surface D1 1st direction D2 2nd direction FD Front direction FUS Fine uneven surface TS Top Surface BS Bottom SS Side B Interface

Claims (13)

A first layer having a plurality of convex portions arranged apart from each other in the first direction,
A second layer, which is laminated on the first layer from the side of the convex portion and forms a refractive index interface with the first layer, is provided.
The first layer is an optical structure having a fine concavo-convex surface on at least one of a top surface of the convex portion and a bottom surface of a concave portion located between the adjacent convex portions. The light incident from the side of the second layer is arranged so as to be emitted from the side of the first layer.
The optical structure according to claim 1, wherein the first layer has the fine concavo-convex surface on the bottom surface of the recess. The refractive index of the first layer is larger than the refractive index of the second layer.
The optical structure according to claim 1 or 2, wherein the first layer has the fine concavo-convex surface on the bottom surface of the recess. The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The optical structure according to any one of claims 1 to 3, wherein the pitch of the protruding elements is 0.3 μm or more and 2.0 μm or less. The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The optical structure according to any one of claims 1 to 4, wherein the pitch of the protruding elements is 0.3 μm or more and 0.78 μm or less. The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The optical structure according to any one of claims 1 to 5, wherein the ratio of the height to the width of the protruding element is smaller than the ratio of the height to the width of the convex portion. The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The optical structure according to any one of claims 1 to 6, wherein the inclination angle of the surface of the protruding element is smaller than 70 ° and smaller than the inclination angle of the side surface of the convex portion. The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The optical structure according to any one of claims 1 to 7, wherein the plurality of protruding elements are arranged in the first direction. Each of the plurality of convex portions extends linearly in a direction non-parallel to the first direction.
The first layer has a plurality of protruding elements forming the fine concavo-convex surface.
The plurality of projecting elements are arranged in the first direction, and each of the plurality of projecting elements extends linearly in a direction non-parallel to the first direction, according to any one of claims 1 to 8. The optical structure described. The optical structure according to any one of claims 1 to 9, wherein the first layer has a diffraction structure constituting the fine concavo-convex surface. Polarizing plate and
A polarizing plate with an optical structure comprising the optical structure according to any one of claims 1 to 10 laminated with the polarizing plate. Display panel and
A display panel with an optical structure comprising the optical structure according to any one of claims 1 to 10 laminated with the display panel. Display device and
A display device with an optical structure, comprising the optical structure according to any one of claims 1 to 10 laminated with the display device.

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