JP2014186913A - Lighting unit and display device - Google Patents

Abstract

Provided are an illumination unit capable of making a light control element visible from an observer side and preventing a hot spot, and having high emission efficiency and uniform luminance, and a display device using the same. .
Light that deflects incident light toward a light exit surface 13 in each of the regions Ra, Rb, and Rc divided into a plurality of regions in a direction in which the light reflecting surface 14 of the light guide plate 10 is separated from the light incident surface 12. Control elements 11A, 11B, and 11C are formed, and the light control elements in the respective regions are formed of a plurality of reflective recesses 11a, 11b, and 11c arranged in a two-dimensional direction along the surface of the respective regions. The vertical width of each reflective recess in the direction parallel to the light incident surface 12 increases from the region adjacent to the light incident surface 12 to the region where the distance from the light incident surface increases, and the shape of the reflective recess in plan view The area was increased.
[Selection] Figure 4

Description

  The present invention relates to an illumination unit using a light guide plate mainly used for illumination optical path control and a display device incorporating the illumination unit.

  As a flat panel display typified by a liquid crystal display device (LCD), a type having a built-in lighting device necessary for recognizing provided information is widespread. The optical characteristics of the liquid crystal display device such as the luminance, the viewing angle distribution of the luminance, and the luminance spatial distribution are greatly influenced by the performance of the lighting device. Therefore, improving the optical characteristics of the lighting device directly leads to an improvement in the optical characteristics of the liquid crystal display device.

  As a lighting device used in a liquid crystal display device, there are mainly a direct type and an edge light type. Since the direct type illumination device can arrange a large number of light sources, it is mainly applied to a large-sized liquid crystal display device of 20 inches or more. On the other hand, the edge light method cannot be applied to a large display device because the arrangement position of the light source is limited to the side surface, and is mainly applied to a small display device such as a notebook personal computer, a liquid crystal monitor, and a portable information terminal.

  Recently, however, LED (Light Emitting Diode) has begun to be used instead of cold-cathode tubes as the light source for lighting devices. Lighting devices have begun to be used in medium-sized or large-sized liquid crystal display devices of 20 inches or more.

  In general, in the edge light system, a light source is disposed on an end surface of a light-transmitting plate called a light guide plate, and light is emitted from the entire surface substantially orthogonal to the end surface. That is, since the light source is disposed only on the end face of the light guide plate, the number of light sources to be installed is limited. Therefore, it becomes difficult to improve the luminance as the liquid crystal display device becomes larger. Even if the liquid crystal display device is not a large-sized liquid crystal display device, the number of light sources is often reduced in order to reduce power consumption and cost, and it is difficult to improve luminance in this respect as well.

Therefore, in an edge light type lighting device, it is desired to make the entire screen uniform and bright. For example, a backlight device described in Patent Document 1 has been proposed as a method for satisfying these.
In Patent Document 1, which is a prior art, on the reflecting surface of the light guide plate, the light control elements that reflect incident light are arranged at the same interval and the size of the light control element is increased as the light control elements are separated from the light source. A configuration has been proposed in which the density is increased by changing the arrangement interval in the two-dimensional direction to make it smaller without changing the size. As the light control element, for example, white diffuse reflection dots are printed on the reflecting surface of the light guide plate, minute irregularities are formed, or a prism-like structure extending in one direction is formed. doing.

  However, there is no description about a clear shape of a structure such as a minute unevenness or a prism shape extending in one direction. For example, a prism-shaped structure has a problem that the prism is directly visible from the observer side in the vicinity of the light incident surface of the light guide plate. Furthermore, in the case of a prism-shaped structure, in the vicinity of the light incident surface of the light guide plate, brightness nonuniformity, so-called hot spots, in which the brightness is different between the position closest to the light source and the position between the light sources. This also causes a problem that occurs.

  Patent Document 2 which is a prior art discloses a technique for making a light control element into a shape composed of a set of ellipses or quadrangles whose area increases as the distance from the light source increases. However, there is no technical description regarding the height (depth) of the shape, and the shape may change greatly depending on the distance from the light source. Further, there is no technical description regarding the arrangement of the light control elements, and the problem of visibility of the light control elements and the problem of hot spots are not solved.

Japanese Patent Laid-Open No. 3-6525 JP 09-311223 A

  Therefore, the present invention uses an illumination unit that can make the light control element visible from the viewer side and prevent hot spots, and has high emission efficiency and uniform luminance, and the illumination unit. An object is to provide a display device.

  In order to achieve the above object, the invention according to claim 1 is characterized in that one surface in the thickness direction is a light emission surface, the other surface in the thickness direction is a light reflection surface, and the light emission is performed. A light guide plate having at least a part of an end face connecting the edge of the surface and the edge of the light reflecting surface as a light incident surface, and a light source disposed to face the light incident surface. The light reflecting surface is divided into a plurality of regions in a direction away from the light incident surface, and light incident from the light source through the light incident surface is transmitted to each of the plurality of regions. A light control element that deflects toward the exit surface is formed, and the light control element in each region includes a plurality of reflective recesses arranged in a two-dimensional direction along the surface of each region. Each of the reflective recesses has a plan view shape with an ellipse, square or irregular outline. The vertical width of each reflective recess in each region increases as the distance from the region adjacent to the light incident surface increases to the region where the distance from the light incident surface increases, and the plane of the reflective recess The area of the visual shape is configured to increase, and the ratio of the total area of the total reflection recesses in the region when viewed in plan with respect to the surface area of each region is from the region adjacent to the light incident surface. It is configured to increase as the distance from the light incident surface increases.

  According to a second aspect of the present invention, in the illumination unit according to the first aspect, the reflection recesses in the respective regions are reflected in a direction orthogonal to the light incident surface as they are separated from the light incident surface for each region. The concave portions are arranged so that the arrangement pitch decreases.

  According to a third aspect of the present invention, in the illumination unit according to the first or second aspect, the reflective recesses in the respective regions are arranged at a constant arrangement pitch that is different in a direction parallel to the light incident surface for each region. It is characterized by being.

  According to a fourth aspect of the present invention, in the illumination unit according to any one of the first to third aspects, the lateral widths of the respective reflective recesses in the respective regions are all the same.

  According to a fifth aspect of the present invention, in the illumination unit according to any one of the first to fourth aspects, the depths of the reflective recesses in the respective regions are all the same.

  The invention according to claim 6 is the illumination unit according to any one of claims 1 to 5, wherein a plurality of lenticular lenses extending in a direction perpendicular to the light incident surface are provided on the light emitting surface. Are arranged in parallel with each other in the extending direction of the light incident surface.

  The invention according to claim 7 is a display device, wherein the illumination unit according to any one of claims 1 to 6 and an image display element that is disposed on a light emission side of the illumination unit and defines a display image. It is characterized by providing.

  According to an eighth aspect of the present invention, in the display device according to the seventh aspect, the image display element displays an image by transmission / shielding in pixel units.

  According to the illumination unit using the light guide plate and the display device using the illumination unit according to the present invention, the light incident surface is divided into a plurality of regions divided in a direction in which the light reflecting surface of the light guide plate is separated from the light incident surface. Light control elements for deflecting light incident through the light source are formed on the light exit surface side, and the light control elements in each region are formed by a plurality of reflections arranged in a two-dimensional direction along the surface of each region. The vertical width of each reflective recess in each region in the direction parallel to the light incident surface increases as the distance from the region adjacent to the light incident surface increases to the region where the distance from the light incident surface increases. In addition, the ratio of the total area of the total reflection recesses in the region to the surface area of each region is large from the region adjacent to the light incident surface to the light incident surface. In the area As the light control element increases, the light control element can be efficiently emitted while preventing the light control element from being viewed from the observer side, suppressing the occurrence of hot spots, and making the luminance distribution uniform. It is also possible to do.

It is a schematic sectional drawing of the principal part which shows the display apparatus using the illumination unit by embodiment of this invention in the isolation | separation state. It is the schematic perspective view which looked at the light-guide plate in embodiment of this invention from the light reflection surface side. An example of the light control element arranged in the light reflection surface of the light-guide plate which concerns on this invention is shown, (a) is a perspective view of the reflective recessed part which exhibits a planar view ellipse which comprises a light control element, (b). These are a top view and a side view in the major axis direction and minor axis direction of a reflective recess that exhibits an elliptical shape in plan view. It is the schematic top view which looked at the light-guide plate in embodiment of this invention when the light source is arrange | positioned at the end surface of the light-guide plate which exhibits a planar view shape from the light reflection surface side. The example of the light control element formed in the light reflection surface of a light-guide plate is shown, (a) is a top view of the light-guide plate which shows the case of a semi-cylindrical cylindrical lens, (b) is elliptical view planarly It is a top view of the light-guide plate which shows the case of the reflective recessed part which exhibits. It is the schematic diagram showing the breadth to the Y direction when the light control element is not arranged in the light reflection surface of a light-guide plate. It is the schematic diagram showing the breadth to the Y direction when the light control element is arranged in the light reflection surface of a light-guide plate. It is the schematic top view which looked at the light-guide plate in embodiment of this invention from the light reflection surface side at the time of arrange | positioning a light source to the opposing both end surfaces of the light-guide plate which exhibits a planar view shape. (A)-(f) is explanatory drawing which shows the example of a shape of the reflective recessed part which comprises a light control element. (A), (b) is explanatory drawing which shows the example of a shape of the reflective recessed part which comprises the light control element of the position away from the light-incidence surface of the light-guide plate. (A)-(c) is explanatory drawing which shows the example of arrangement | positioning of the light control element to the light-guide plate light-incidence surface. The relationship between the light control element density and a schematic top view of the light guide plate in the embodiment of the present invention when viewed from the reflective surface side when a light source is arranged on one end surface of the light guide plate having a planar view shape is shown. FIG. It is a fragmentary longitudinal cross-sectional view of the light-guide plate explaining the relationship between the shape of a light control element and incident light, (a) is a light control element of a recessed part, (b) is a figure which shows the light control element of a convex part. It is a perspective view of the light-guide plate by the modification of this invention, and has shown the example by which the lenticular lens is provided in the light-projection surface. It is a figure which shows the screen front brightness | luminance in the Example and comparative example of this invention, the visibility of a light control element, and the evaluation result of a hot spot.

  Below, the illumination unit by embodiment of this invention and the display apparatus provided with this illumination unit are demonstrated. FIGS. 1 to 13 are schematic views, and the size and shape of each part are appropriately exaggerated for easy understanding.

As shown in FIG. 1, the display device 1 includes an image display panel 2 and an illumination unit 3 arranged facing the light incident side of the image display panel 2.
The image display panel 2 arranged closest to the viewer side F includes two polarizing plates (polarizing films) 4 and 5 and an image display element 6 sandwiched therebetween. The image display panel 2 is constituted by, for example, a liquid crystal display panel, and the image display element 6 is constituted by filling a liquid crystal layer between two glass substrates. The liquid crystal display element selected as the image display element 6 is a typical element that transmits and blocks light in pixel units and displays an image, and can improve image quality compared to other display elements. .

The image display panel 2 is preferably an element that displays an image by transmitting / blocking light in pixel units. A display device 1 that can uniformly brighten the entire screen with the illumination unit 3 can be obtained as long as the image is displayed by transmitting / blocking light in pixel units.
Further, the illumination unit 3 is an edge light type illumination device, is disposed facing the light incident side of the image display panel 2, and includes a surface light source unit 7 and an optical sheet 8. The surface light source unit 7 is provided with a light source 9 and a light guide plate 10 along an optical path of light.

The optical sheet 8 is disposed on the observer direction F side, which is the light traveling direction of the light guide plate 10, and at least one sheet preferably has a diffusion function. Moire generated between the light guide plate 10 and the optical sheet 8 or between the optical sheet 8 and the image display panel 2 can be eliminated, and a bright spot due to the light guide plate 10 can be eliminated. As the optical sheet 8, for example, a microlens sheet 18 and a prism lens sheet 19 are laminated and arranged to face the light exit surface 13 of the light guide plate 10. The light diffusion / condensing effect by the microlens sheet 18 and the condensing effect by the prism lens 19 can be exhibited.
As the optical sheet 8, in addition to a microlens sheet and a prism sheet, a diffusion sheet having an uneven surface, a diffusion sheet in which fine particles having different refractive indexes are mixed, a lenticular lens sheet, a polarization separation sheet, and the like can be installed. . Further, a plurality of optical sheets 8 may be arranged, or a single sheet may be used.

Next, the surface light source unit 7 will be described in detail.
As shown in FIG. 1, the surface light source unit 7 includes a light guide plate 10, a light source 9 disposed corresponding to a light incident surface 12 that is an opposite end surface of the light guide plate 10, and a light reflecting surface of the light guide plate 10. And a reflection sheet 15 provided so as to cover the entire area of 14 and the outer periphery of the light source 9. The reflection sheet 15 reflects the light emitted from the light reflection surface 14 side opposite to the light emission surface 13 of the light guide plate 8 and leads it to the light guide plate 10 again so that it can be used effectively. It becomes possible to raise.
Examples of the reflective sheet 15 include: (1) a resin sheet in which a void is formed by kneading and stretching a filler in PET, PP, etc. to increase the reflectance, and (2) aluminum is deposited on the surface of a transparent or white resin sheet. (3) A metal foil such as aluminum or a resin sheet carrying a metal foil, (4) a metal thin plate having sufficient reflectivity on the surface, or the like may be used.

  Examples of the light source 9 include a linear light source and a point light source. Examples of the linear light source include fluorescent tubes such as CCFL, HCFL, and EEFL. Moreover, LED is mentioned as a point light source, White LED, RGB-LED, etc. are mentioned as LED.

The light guide plate 10 has, for example, a rectangular parallel plate shape or a rectangular wedge shape.
Such a light guide plate 10 has one surface in the thickness direction as a light emitting surface 13, the other surface in the thickness direction as a light reflecting surface 14, and an edge of the light emitting surface 13 and the light reflecting surface 14. Among the end faces that form the four sides of the square connecting the edges, the two opposite facets are used as the light incident face 12. However, the number of light incident surfaces 12 of the light guide plate 10 is not limited to two, and at least one end surface may be the light incident surface 12 as shown in FIG.
Further, the light source 9 may be disposed opposite to the two light incident surfaces 12 which are end surfaces facing each other as shown in FIG. 1, or only one light incident surface 12 as shown in FIG. You may arrange opposite. In this case, the plurality of light sources 9 are arranged at regular intervals in the longitudinal direction of the light incident surface 12.

  The light guide plate 10 is molded on a light-transmitting substrate using UV or radiation curable resin, or PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer). Can be formed by an extrusion molding method, an injection molding method, or a hot press molding method well known in the art.

  The light reflecting surface 14 of the light guide plate 10 reflects light that is not directly emitted from the light emitting surface 13 out of light incident from the light source 9 through the light incident surface 12 in various directions in the light guide plate 10. It is a reflective surface for making it go to the light-projection surface 13 side.

  As shown in FIGS. 2 and 4, the light reflecting surface 14 has a plurality of regions Ra, Rb, Rc in a direction away from the light incident surface 12 of the light guide plate 10 (the direction of the arrow X orthogonal to the light incident surface 12). It is divided into In each of the regions Ra, Rb, and Rc, light control elements 11A, 11B, and 11C that deflect light incident from the light source 9 through the light incident surface 12 toward the light exit surface 13 are formed.

Each light control element 11A, 11B, 11C in each region Ra, Rb, Rc is formed from a plurality of reflective recesses 11a, 11b, 11c arranged in a two-dimensional direction along the surface of each region Ra, Rb, Rc. Thus, the respective reflective recesses 11a, 11b, and 11c in each of the regions Ra, Rb, and Rc have an elliptical shape in plan view and are arranged as shown in FIG. Further, in each of the regions Ra, Rb, and Rc, the lengths WYa, WYb, and WYc of the major axes of the ellipses of the reflecting recesses 11a, 11b, and 11c that are elliptical in plan view (the light incident surface 12 described in the claims) 4 corresponds to the vertical width in the direction of the arrow y in FIG. 4, and increases as the distance Ra from the region Ra adjacent to the light incident surface 12 increases to the regions Rb and Rc, as shown in FIG. In addition, the reflective recesses 11a, 11b, and 11c are configured to have an elliptical area in plan view.
Note that there is a relationship of WYa <WYb <WYc between the major axis lengths WYa, WYb, WYc of the ellipses of the reflective recesses 11a, 11b, 11c.
For each region Ra, Rb, Rc, the ratio of the total area of the total reflection recess 11a in the region Ra when viewed in plan with respect to the surface area of the region Ra, the region in the region Rb with respect to the surface area of the region Rb The ratio of the total area of the total reflection concave portion 11b and the ratio of the total area of the total reflection concave portion 11c in the region Rc to the surface area of the region Rc are such that the distance from the region Ra adjacent to the light incident surface 12 to the light incident surface 12 is large. It is configured to increase as it reaches the regions Rb and Rc.

  In addition, as shown in FIG. 12, the reflective recesses 11a in the region Ra are arranged so that the arrangement pitch Pxa of the reflective recesses 11a in the direction orthogonal to the light incident surface 12 decreases as the distance from the light incident surface 12 increases. . Similarly, the reflective concave portions 11b in the region Rb are also arranged so that the arrangement pitch Pxb of the reflective concave portions 11b in the direction orthogonal to the light incident surface 12 decreases as the distance from the light incident surface 12 increases. Similarly, the reflective concave portions 11c in the region Rc are also arranged so that the arrangement pitch Pxc of the reflective concave portions 11b in the direction orthogonal to the light incident surface 12 decreases as the distance from the light incident surface 12 increases.

  Further, as shown in FIG. 12, the reflective recesses 11 a in the region Ra are arranged at a constant arrangement pitch Pya in a direction parallel to the light incident surface 12. Similarly, the reflective recesses 11b in the region Rb are arranged at a constant arrangement pitch Pyb in a direction different from the arrangement pitch Pya and parallel to the light incident surface 12. Similarly, the reflective recesses 11c in the region Rc are arranged at a constant arrangement pitch Pyc in a direction different from the arrangement pitches Pya and Pyb and parallel to the light incident surface 12.

Further, in each of the regions Ra, Rb, and Rc, the length of the minor axis of the ellipse of each of the reflective recesses 11a, 11b, and 11c having an elliptical shape in plan view (in the x-axis direction shown in FIG. 3 is described in the claims) (Corresponding to the horizontal width in the direction of the arrow x orthogonal to the light incident surface 12) is the same.
Further, in each of the regions Ra, Rb, and Rc, the depths H (see FIG. 3) of the reflecting recesses 11a, 11b, and 11c that are elliptical in plan view are all the same.
Note that there is a relationship of WYa <WYb <WYc between the major axis lengths WYa, WYb, WYc of the ellipses of the reflective recesses 11a, 11b, 11c.
Here, the lengths in the x and y directions of the reflective recesses 11a, 11b, and 11c are the cross-sectional shapes in the x and y directions at the center positions of the respective reflective recesses 11a, 11b, and 11c, as in WX (WY) shown in FIG. It shall indicate the width in which

  In the light guide plate of the present invention, the vertical width in the arrow y direction parallel to the light incident surface 12 is the length of the major axis of the ellipse of each of the reflective recesses 11a, 11b, and 11c, and the direction of the arrow x orthogonal to the light incident surface 12. Is the length of the minor axis of the ellipse of each of the reflective recesses 11a, 11b, and 11c, but the present invention is not limited to this. The vertical width in the direction of the arrow y parallel to the light incident surface 12 is the length of the minor axis of the ellipse of each reflective recess 11a, 11b, 11c, and the horizontal width in the direction of the arrow x perpendicular to the light incident surface 12 is the respective reflective recess 11a, 11b. , 11c may be the length of the major axis of the ellipse. In particular, in a region approaching the light incident surface 12 (for example, the region Ra in FIG. 2, the region Ra in FIG. 4, the region Ra and the region Ra ′ in FIG. 8, and the region Ra in FIG. 12), an arrow parallel to the light incident surface 12 The vertical width in the y direction can be the length of the minor axis of the ellipse of each reflecting recess, and the horizontal width in the direction of the arrow x perpendicular to the light incident surface 12 can be the length of the major axis of the ellipse of each reflecting recess.

  In the display device configured as described above, the respective reflective recesses 11a, 11b, and 11c in the respective regions Ra, Rb, and Rc are arranged in a two-dimensional direction along the surfaces of the respective regions Ra, Rb, and Rc. Therefore, it is possible to prevent the reflective concave portions 11a, 11b, and 11c from being viewed from the viewer side, that is, to hide the reflective concave portions 11a, 11b, and 11c.

  The light guided through the light guide plate 10 is reflected by the reflective recesses 11a, 11b, and 11c and is emitted from the exit surface 13 to the viewer side. For this reason, the portions without the reflective concave portions 11a, 11b, and 11c appear dark, but the reflective concave portions 11a, 11b, and 11c appear bright and shining.

  FIG. 5A shows a case where the light control element 111 has a lenticular lens shape only in a one-dimensional direction, and FIG. 5B shows the light control element 11 according to the embodiment of the present invention. Thus, the state of the dot form which arranged the reflective recessed part in the two-dimensional direction is shown. The ratio of the light control element 111 shown in FIG. 5A with respect to the light reflection surface 14 of the light guide plate is substantially equal to the ratio of the light control element 11 shown in FIG. 5B with respect to the reflection surface 14. However, it can be seen that the light control element 11 formed by arranging the reflective concave portions in the form of dots in the two-dimensional direction is closer to the adjacent reflective concave portions. Therefore, it can be easily imagined that the case of FIG. 5B in which the reflective concave portions that shine brightly are evenly arranged is less visible from the observer side.

  Further, since the reflection concave portion in the region where the distance from the light incident surface 12 of the light guide plate 10 is smaller, the length WY in the y direction is shorter, the concealment of the region Ra near the light incident surface 12 where the light control element is most easily observed. Can increase the sex. The shorter the length WY in the y direction, the more reflective recesses are required to obtain the same optical characteristics. If there are a large number of reflection recesses, similar to the above-described case, adjacent reflection recesses are close to each other, so that the reflection recesses are not easily seen from the viewer side.

  On the other hand, since the reflective recesses in the region where the distance from the light incident surface 12 of the light guide plate 10 is larger, the length WY in the y direction is longer, the light emission efficiency can be increased. This is because, in the shape having a short length WY in the y direction, a part of the light irradiated to the reflective recess is diffused in the y direction. The light spreading in the y direction escapes to the outside from the side end surface 17 other than the light incident surface 12 of the light guide plate 10 shown in FIG. 2, and the loss of light increases.

  That is, the light incident surface 12 of the light guide plate 10 in which the visibility of the light control element is a problem is made a dot-shaped reflection concave portion having a small length WY in the y direction so as to ensure concealment and light incident on the light guide plate 10. The farther from the surface 12, the closer to the wrench-shaped reflective recess having a longer y-direction length WY, the brightness is improved. Thereby, loss of luminance can be suppressed while visual recognition is prevented. At the position farthest from the light incident surface 12, the length WY in the y direction may be substantially infinite, that is, a wrench shape.

  In addition, by reducing the length WY in the y direction of the reflective recess 11a in the region Ra adjacent to the light incident surface 12 of the light guide plate 10, the brightness and darkness and the brightness that occur near the light source 9 and between the adjacent light sources 9 are reduced. Uniformity (hot spot) can also be eliminated.

As shown in FIGS. 6 and 7, in the vicinity of the light incident surface 12 of the light guide plate 10, light and darkness is likely to occur between the light source 9 and between the light sources 9. In order to prevent this, it is necessary to sufficiently spread the light from the light source 9 in the y direction in the vicinity of the light incident surface 12. As described above, the light in the y direction can be further expanded by forming the dot-shaped reflective concave portion having a short y direction length WY. In that sense as well, it is preferable that the reflective concave portion in the form of dots is a short Y-direction length WY of the reflective concave portion in the vicinity region Ra of the light incident surface 12. Further, as the distance from the light incident surface 12 is increased, the reflection concave portion in the form of a dot having a long y-direction length WY can prevent the spread of light more than necessary and prevent a decrease in luminance.
Here, FIG. 6 shows the spread of light when the light control element 11 is not arranged. On the other hand, FIG. 7 shows the spread of light when the light control element 11 is arranged. Further, the distance x0 from the light incident surface 12 of the light guide plate 10 to the position where the light is sufficiently uniform is smaller in the case of FIG.

  As described above, according to the embodiment of the present invention, it is possible to increase the emission efficiency as the light guide plate while preventing the light control element 11 from being visually recognized in the vicinity of the light incident surface of the light guide plate 10. In addition, it is possible to eliminate luminance non-uniformity (hot spot) in the vicinity of the light incident surface of the light guide plate 10.

  As shown in FIG. 1, the same applies to the case where the light source 9 is disposed on the light incident surface 12 provided on the two opposite end surfaces of the light guide plate 10. In that case, a top view of the light guide plate 10 viewed from the light reflecting surface 14 side is as shown in FIG. In addition, the shapes and arrangement of the reflective recesses 11a, 11b, and 11c formed in the regions Ra, Rb, and Rc of the light reflecting surface 14 are as shown in FIG. That is, the y-direction length WY of the reflective concave portion increases as the central portion of the light guide plate is located farthest from the light incident surface 12.

  FIG. 4 shows an example in which the light reflecting surface 14 of the light guide plate 10 is divided into three regions Ra, Rb, and Rc in a direction orthogonal to the light incident surface 12, but naturally the number of divisions is three. There is no need. Preferably, the number is several to a dozen. As the number of divisions increases, the effect of the present invention can be obtained. However, in this case, it takes much time to design and manufacture the light control element 11.

  The depth H of the reflective recess is preferably substantially constant regardless of the region. Thereby, generation | occurrence | production of the thickness shift of the light-guide plate 10 by the arrangement | sequence density of a reflective recessed part can be suppressed, and the difficulty on manufacture of a light-guide plate can be reduced. In this case, the depth H of the reflective recess is preferably in the range of 0.5% to 3% of the thickness of the light guide plate 10. If it exceeds 3%, it is necessary to reduce the number of reflection recesses in order to ensure luminance uniformity, and the concealability deteriorates even if the dot-shaped reflection recesses. On the other hand, when the ratio is 0.5% or less, the ratio of the depth H of the reflective recess to the thickness of the light guide plate 10 becomes too small, so that it becomes difficult for the light to be irradiated to the reflective recess, and the emission efficiency decreases. End up. Here, “substantially constant” means that the difference in the depth of each reflecting recess is within 20% of the average depth H of each reflecting recess.

  Further, the length WX in the x direction of the reflective recess with respect to the direction orthogonal to the extending direction of the light incident surface 12 of the light guide plate 10 (hereinafter referred to as the x direction) is preferably substantially constant regardless of the region. In other words, the shape of the light control element 11 in the region away from the light incident surface 12 is preferably a shape that extends only in the y direction with respect to the shape of the light control element 11 in the region near the light incident surface 12. Thereby, difficulty in production can be prevented, and at the same time, changes in optical characteristics such as viewing angle characteristics of light emitted from the light guide plate 10 can be suppressed. That is, uniform optical characteristics can be obtained in the effective range.

  As described above, the length of the reflective recess in the x and y directions refers to the width of the cross-sectional shape in the x and y directions at the center position of each reflective recess as shown by WX (WY) shown in FIG. Shall be shown. Also, “substantially constant” means that the difference between WX and WY is within 20% of the average value of WX and WY, as in the case of the depth H of the reflective recess.

  Here, the aspect ratio H / WX, which indicates the ratio of the depth H to the length WX in the x direction of the reflective recess, is preferably 0.1 to 0.4. When the aspect ratio H / WX changes, the light distribution of the light emitted from the light guide plate 10 changes. If the aspect ratio H / WX is high, the light emitted from the light exit surface 13 is emitted in the front direction. If the aspect ratio H / WX is low, the light exits in an oblique direction inclined with respect to the front direction. However, if the aspect ratio H / WX is higher than 0.4, there is a disadvantage that light is emitted from the light reflecting surface 14 instead of the light emitting surface 13 side, and as a result, the emission efficiency is lowered. On the other hand, when the aspect ratio H / WX is lower than 0.1, there arises a problem that not only the emitted light becomes oblique but also the light that is not emitted from the light guide plate 10 increases. In this case as well, the injection efficiency similarly decreases.

The shape of the reflective concave portion may be any shape as long as it has a dot shape exhibiting an elliptical shape in plan view, for example.
FIG. 9 shows an example in which the shape of the reflective recess 11 is different from that in FIG. For example, as shown in (a), the planar view outline may be a dot-shaped reflection concave portion 11 having a circular arc-shaped concave curved surface, or as shown in (b), the plan view outline may be a quadrangular pyramid shape. It may be a dot-shaped reflective recess 11 having a depression. Moreover, as shown in (c), the shape of the reflection recess 11 having a shape obtained by cutting the bottom of the reflection recess 11 having the shape shown in (a) into a flat surface, or the shape shown in (b) as shown in (d). The reflective concave portion 11 having a shape obtained by cutting the bottom of the reflective concave portion 11 into a flat surface may be used. As shown in (e), the plan view contour is quadrangular, and each triangular surface connected to each side of the quadrangular plan view contour extends in the depth direction and curves inward from each other. A reflective recess 11 having a shape that forms a curved bottom surface that is closed by a plurality of recesses, and a plurality of recesses that are elliptical in plan view and connected along the elliptical plan view contour as shown in FIG. The reflective concave portion 11 having a shape that forms a closed curved bottom surface by bending the forming curved surface inward while extending in the depth direction may be used.

Moreover, as the reflective recessed part 11 of the area | region away from the light-incidence surface 12 of the light-guide plate 10, as shown to Fig.10 (a), the shape of the depth direction of the reflective recessed part 11 whose planar view outline exhibits an elliptical shape is an ellipse. A shape having an arcuate curved surface obtained by cutting the body along a plane parallel to the major axis, or a shape in the depth direction of the reflective recess 11 having a plan view outline having an elliptical shape as shown in FIG. May have a structure that forms a bottom like a ship bottom. In particular, the reflective recess 11 having the shape shown in FIG. 10B is suitable for the purpose of improving the luminance.
In addition, the planar view outline of the reflective recess is not limited to the shape shown in FIG. 10, and for example, the planar view outline may be an indefinite shape formed by connecting a straight line and a curved line.

  In addition, the arrangement density S of the reflection recesses, which represents the number of the reflection recesses 11 existing in the unit area of the region, is preferably increased monotonously according to the distance x from the light incident surface 12 in the same region. Since the amount of light propagating in the light guide plate 10 is large in the portion close to the light incident surface 12, the arrangement density S of the reflective recesses is set small, and the amount of light propagating in the light guide plate 10 is small in the portion far from the light incident surface 12. The arrangement density S of the reflective recesses was set large. This makes it possible to uniformly brighten the area. Here, the range of calculation of the arrangement density S of the reflective concave portions is set to a range in which several reflective concave portions 11 are included.

  Further, in this case, the arrangement pitch of the reflective recesses in the y direction in the same region is substantially constant, and the arrangement pitch in the x direction is preferably changed so as to continuously decrease as the distance from the light incident surface 12 increases. In addition, it is possible to change the arrangement density S of the reflection recesses while arranging the reflection recesses in a line and keeping the arrangement pitch in the y direction substantially constant. Along with this, it is possible to prevent difficulty in manufacturing the light guide plate. In addition, since the arrangement pitch is substantially constant, the reflective concave portions are concentrated locally and do not become bright spots.

4, 5, 7, and 8, the rows of the reflective recesses in the y direction are alternately shifted in the y direction by ½ of the array pitch Py in the x direction. However, the arrangement pattern of the reflective recesses is not limited to this.
For example, as shown in FIG. 11B, the reflective recesses 11 may be aligned and arranged without shifting in the y direction. Alternatively, as shown in FIG. 11C, the reflective recesses 11 may be arranged slightly shifted in the y direction. Further, as shown in FIG. 11 (d), the deviation in the y direction of the reflective recess 11 may be set at random. Rather, taking into account other lenses and the optical sheet 8 installed on the light exit surface 13 side of the light guide plate 10, the deviation of the reflective concave portion 11 arranged in the y direction from the adjacent reflective concave portion 11 is random. It is preferable that it is so that moire does not occur.

  Also, the substantially constant arrangement pitch of the reflective recesses means that the difference in pitch is within 20% of the average value of the pitch, as in the case described above. However, the arrangement pitch here refers to the average value of the three distances around the reflective recesses 11 arranged in a row as the arrangement pitch.

Further, the arrangement pattern of the reflective recesses 11 changes at the boundary between the regions. The arrangement density S of the reflection concave portions changes discontinuously, and the arrangement density S of the reflection concave portions in the far region is smaller than the region near the light incident surface 12 near the region boundary. Based on the example shown in FIG. 4, a graph showing the relationship between the arrangement density S of the reflective recesses and the position x is shown in FIG.
In this graph, the reflection recess 11 in a region farther from the light incident surface 12 has a longer length WY in the y direction and a higher light extraction effect in one reflection recess. Therefore, in order to make the luminance uniform, the arrangement density S of the reflective recesses needs to be small. Further, since the shape changes discontinuously at the region boundary, the arrangement density S of the reflective recesses also changes discontinuously. Here, when the light extraction efficiency η of one reflection recess 11 is defined, it is necessary to arrange the reflection recess 11 so that η × S is constant in the vicinity of the region boundary.

It is further preferable that the reflective recess 11 is recessed with respect to the inner side of the light reflecting surface 14. This is because the concave shape allows light to be efficiently emitted.
FIG. 13A shows a case where the light control element is shaped as a concave reflection concave portion 11, and FIG. 13B shows a case where the light control element is shaped into a convex reflection portion 112. Further, α in the figure indicates the width of light irradiated on the reflective concave portion 11, and β in the figure indicates the width of light irradiated on the convex reflective portion 112. As is clear from FIG. 13, the width α of the light applied to the reflective concave portion 11 is larger than the width β of the light applied to the convex reflective portion 112. That is, the reflective recess 11 is more easily irradiated with light and has higher emission efficiency.

In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the meaning, it can change suitably. Hereinafter, although the modification of this invention is demonstrated, the same code | symbol is attached | subjected and demonstrated to the component or part etc. which are the same as that of the illumination unit 3 by the embodiment mentioned above, and the display apparatus 1, and are the same.
For example, the effect of the present invention can be obtained even if a light capturing structure is formed on the light incident surface 12 of the light guide plate 10 or a random structure is formed.

  As shown in FIG. 14, a plurality of lenticular lenses 16 extending in the x direction perpendicular to the extending direction of the light incident surface 12 are parallel to the light emitting surface 13 of the light guide plate 10 in the longitudinal direction. The light incident surfaces 12 are arranged adjacent to each other in the extending direction. Thereby, when the light incident on the light guide plate 10 is emitted from the light exit surface 13, it can be prevented from diffusing in the extending direction (y direction) of the light entrance surface 12.

  The effect of suppressing the spread of light in the y direction described above (hereinafter referred to as light confinement effect) obtained by arranging the lenticular lenses 16 on the light incident surface 12 of the light guide plate 10 is that the reflective recess 11 has two in the xy direction. Since the dot form has an array configuration in the dimensional direction, a higher effect can be obtained. In addition, the light propagating through the light guide plate 10 is spread in the y direction by the reflecting concave portion 11 while traveling in the x direction. However, when the lenticular lens 16 is arranged on the light exit surface 13 of the light guide plate 10, the light is confined. Since there is an effect, the diffusion effect in the y direction can be suppressed.

By applying this technique, local dimming that partially brightens or darkens the screen of the lighting unit 3 is possible. In addition, by using this, it is possible to perform scanning in which the brightness is changed in order. Furthermore, since the viewing angle distribution can be collected with respect to the extending direction of the light incident surface 12, the luminance can be improved.
Note that the optical sheet 8 may not be disposed in the illumination unit 3.

  The lighting unit 3 and the display device 1 including the lighting unit 3 according to the embodiment of the present invention have been described above. However, the lighting unit 3 is not applied only to the display device 1. Examples of the present invention will be described in detail below. However, it goes without saying that the present invention is not limited to the following examples.

Next, examples and comparative examples of the present invention will be described.
(Examples 1 and 2)
The light guide plate 10 used in the tests of Examples 1 and 2 was a rectangular flat plate made of acrylic, and had a length L of 200 mm and a thickness of 600 μm. A light control element is configured by arranging, in a two-dimensional direction, reflection concave portions 11 having a plurality of elliptical shapes in plan view as shown in FIG. 3 on the light reflection surface 14 of the light guide plate 10. The depth H of the reflective recess 11, the length WX in the x direction, and the length WY in the y direction were set as shown in the table of FIG.
(Comparative Examples 1, 2, 3)
Moreover, as Comparative Examples 1, 2, and 3, one region was prepared, that is, one in which one type of reflective concave portion was arranged in the entire region. It is the same except that the y-direction length WY is 90 μm, 50 μm, and 270 μm, respectively.

The arrangement of each element constituting the display device is set so that the luminance of the entire screen is uniform under the respective conditions, including the following comparative examples and examples. Further, as Comparative Example 4, it was divided into five regions, and from the light source side, regions 1, 2, 3, 4, and 5 were set to WY (μm) = 270, 220, 170, 130, and 90, respectively. As Example 1, it is divided into five areas and WY (μm) = 90, 130, 170, 220, and 270, respectively, from the light source side. As Example 2, it is divided into three areas and WY ( μm) = 90, 150, 270.
The illumination unit 3 used the white LED as the light source 9 facing the end surface of one side of the rectangular light guide plate 10 as the light incident surface 12. A reflection sheet 15 is disposed on the back surface side of the light guide plate 10 facing the light reflection surface 14, and a microlens sheet 18 is disposed as the optical sheet 8 on the light emission side facing the light emission surface 13 of the light guide plate 10. .

In these examples and comparative examples, the screen front brightness and appearance (visibility of light control elements and hot spots) of the lighting unit 3 were confirmed. The front brightness of the screen was measured with a spectral radiance meter SR-3A manufactured by Topcon, and the appearance was confirmed visually.
The evaluation results of Examples 1 and 2 and Comparative Examples 1, 2, and 3 are also shown in FIG. As for the front luminance, the result of Comparative Example 1 is set to 1.00, and other Comparative Examples and Examples have ratios to that. Regarding the visibility of the light control element, “X” indicates that the light control element appears bright, and “◯” indicates that the light control element cannot be seen. The hot spot was evaluated as “x” when the brightness was visible between the vicinity of the light source and between the adjacent light sources at a position 5 mm away from the light incident surface, and “◯” when it was not visible. As a comprehensive judgment, the front luminance exceeded 1.00, the visibility and hot spot of the light control element were both “good”, and at least one was “x” or less than “1.00” was “poor”.

  The front luminances of Examples 1 and 2 are 1.03 and 1.02, indicating that the luminance can be improved. It was also found that the visibility and hot spot of the light control element at that time had no problem (not visible). On the other hand, in Comparative Example 2, there is no problem in the visibility and hot spot of the light control element, but the front luminance is as low as 0.97. In Comparative Examples 3 and 4, the front luminance is 1.04. Although it improved with 1.03, the visibility and hot spot of the light control element were x.

(Examples 3 to 6)
In the third embodiment, as in the first embodiment, the shape of the reflective recess in each region is the same as that in the first embodiment. In the same region, the extending direction of the light incident surface 12 ( The arrangement pitch Py of the reflection concave portions 11 in the y direction) is made substantially constant, and the arrangement pitch Px of the reflection concave portions 11 in the direction orthogonal to the extending direction of the light incident surface 12 (x direction) becomes continuous as the distance from the light incident surface 12 increases. A light guide plate changed so as to be small was prepared. In addition, the arrangement density S of the reflection concave portions changes discontinuously at the boundary between the adjacent regions, and the arrangement density S of the reflection concave portions in the far region is smaller than that in the region near the light incident surface 12 near the region boundary. Here, the arrangement density S of the reflective concave portions represents the number of the reflective concave portions 11 existing in the unit area in the region.

  As Example 4, the same light guide plate 10 as Example 3 was prepared except that the arrangement pitch Py of the reflective recesses in the same region was not substantially constant. Here, the array pitch defines an average value of three distances around the reflective recesses 11 arranged in a row as an array pitch, and substantially constant means that the pitch difference is within 20% of the average pitch value. I shall refer to it. As Example 5, a light guide plate 10 that was the same as Example 3 was prepared except that a range in which the arrangement pitch Px of the reflective recesses in the same region was made constant was set. Furthermore, as Example 6, the same light guide plate 10 as Example 3 was prepared except that the arrangement density S of the reflective recesses was continuously changed at the boundary between adjacent regions.

  As in the first and second embodiments, the lighting unit 3 uses the end surface of one side of the rectangular light guide plate 10 as the light incident surface 12 and uses a white LED as the light source 9 facing the light incident surface 12. A reflection sheet 15 is disposed on the back surface side of the light guide plate 10 facing the light reflection surface 14, and a microlens sheet 18 is disposed as the optical sheet 8 on the light emission side facing the light emission surface 13 of the light guide plate 10. .

  In these Examples 3-6, the illumination unit 3 was visually evaluated for luminance uniformity. Here, the uniformity includes uniformity over the entire effective range and local non-uniformity that becomes a bright spot.

  As a result of visual evaluation, it was observed that Example 3 had uniform brightness. On the other hand, in Example 4, there were locally a portion where the reflective concave portion 11 was dense or a portion where it was sparse, and that portion became a bright and dark point, and the uniformity of luminance was lower than that in Example 3. In Example 5, the luminance distribution in a range in which the arrangement pitch Px was constant became dark in a band shape, and the uniformity of luminance was lower than that in Example 3. In Example 6, the luminance was different between the regions, the luminance distribution was like a step, and the luminance uniformity was lower than that in Example 3.

DESCRIPTION OF SYMBOLS 1 ... Display apparatus 2 ... Image display panel 3 ... Illumination unit 4,5 ... Polarizing plate 6 ... Image display element 7 ... Surface light source part 8 ... Optical sheet 9 ... Light source 10 ... Light guide plate 11A, 11B, 11C ... Light control element 11 , 11a, 11b, 11c ... reflective recess 12 ... light incident surface 13 ... light exit surface 14 ... light reflective surface 15 ... reflective sheet 16 ... lenticular lens 17 ... side end surface Ra, Rb, Rc ... region

Claims (8)

One surface in the thickness direction is a light emitting surface, the other surface in the thickness direction is a light reflecting surface, and at least one of the end surfaces connecting the edge of the light emitting surface and the edge of the light reflecting surface A light guide plate having a light incident surface as a part,
An illumination unit comprising a light source disposed facing the light incident surface,
The light reflecting surface is divided into a plurality of regions in a direction away from the light incident surface,
Each of the plurality of regions is formed with a light control element that deflects light incident from the light source through the light incident surface toward the light exit surface,
The light control element of each region comprises a plurality of reflective recesses arranged in a two-dimensional direction along the surface of each region.
Each of the reflective recesses in each of the regions has an elliptical or rectangular or irregular shape in plan view,
The vertical width of each reflective recess in each region increases as the distance from the region adjacent to the light incident surface increases to the region where the distance from the light incident surface increases, and the area of the reflective recess in plan view shape Is configured to increase,
Further, the ratio of the total area of the total reflection recesses in the region when viewed in plan with respect to the surface area of each region is a region in which the separation distance from the region adjacent to the light incident surface to the light incident surface is increased. Configured to increase over time,
A lighting unit characterized by that.   The reflective recesses in the regions are arranged so that the arrangement pitch of the reflective recesses in the direction orthogonal to the light incident surface decreases with increasing distance from the light incident surface for each region. The lighting unit according to claim 1.   3. The illumination unit according to claim 1, wherein the reflection recesses in the regions are arranged at a constant arrangement pitch that is different in a direction parallel to the light incident surface for each region.   The lighting unit according to any one of claims 1 to 3, wherein the horizontal widths of the reflective recesses in the regions are the same.   5. The illumination unit according to claim 1, wherein the depths of the reflection recesses in the regions are the same.   A plurality of lenticular lenses extending in a direction perpendicular to the light incident surface are arranged on the light emitting surface so that their longitudinal directions are parallel to each other and arranged in the extending direction of the light incident surface. The lighting unit according to any one of claims 1 to 5, wherein The lighting unit according to any one of claims 1 to 6,
An image display element disposed on the light exit side of the illumination unit and defining a display image;
A display device characterized by that.   The display device according to claim 7, wherein the image display element displays an image by transmission / shielding in pixel units.

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