JP6853405B2 - Planar lighting device - Google Patents

Description

The present invention relates to a planar lighting device.

Conventionally, there is a planar lighting device that illuminates the display panel of a liquid crystal display device from the back side. The surface lighting device is roughly classified into an edge light type and a direct type. Further, in the planar illumination device, a planar illumination device compatible with so-called local dimming (area emission) capable of adjusting the brightness for each region of the light emitting surface by controlling the amount of light of each light source. Are known.

In addition, in a direct-type planar lighting device that supports local dimming (area emission), a lens that diffuses the light emitted from the light source is provided, and the light from the light source is spread and emitted to make the brightness of each area uniform. can do.

Japanese Unexamined Patent Publication No. 2008-140653

However, in recent years, the number of light sources arranged on a substrate has increased in a direct-type planar illumination device, and as the number of light sources increases, a positional shift between a lens arranged directly above each light source and the light source shifts. As a result, the brightness of the light emitting surface may become non-uniform.

The present invention has been made in view of the above, and an object of the present invention is to provide a planar illumination device capable of improving the uniformity of brightness.

In order to solve the above-mentioned problems and achieve the object, the planar illumination device according to one aspect of the present invention includes a substrate, a diffuser plate, and a lens. A plurality of light sources are arranged on the substrate. The diffuser diffuses the light of the light source. The lens is arranged at a distance between the diffuser plate and each of the light sources, and has a plate shape having two main surfaces, an incident surface facing the plurality of light sources and an exit surface facing the incident surface. An optical element including a plurality of first optical portions having a portion that tapers from the bottom surface of the polygon toward the tip end is formed on the incident surface. The lighting and extinguishing of the light source can be controlled individually. The lens is arranged at a position where the distance from the incident surface to the diffuser is longer than the distance from the incident surface to the light source, and the incident light emitted from the light source is not totally reflected. The angle between the bottom surface and the inclined surface intersecting the bottom surface is 44 ° or more and 58 ° or less so that the incident light is incident from a surface and the incident light is refracted and spread to be incident on the diffuser plate. is there.

According to one aspect of the present invention, the uniformity of brightness can be improved.

FIG. 1 is a top view of the planar lighting device according to the embodiment. FIG. 2 is an exploded perspective view of the planar lighting device according to the embodiment. FIG. 3 is a cross-sectional view of the planar lighting device according to the embodiment. FIG. 4A is a diagram showing an optical element. FIG. 4B is a diagram showing an optical element. FIG. 4C is a diagram showing an optical element. FIG. 5A is a diagram showing an arrangement example of the light source according to the embodiment. FIG. 5B is a diagram showing another arrangement example of the light source according to the embodiment. FIG. 6 is an explanatory diagram of the positional relationship between the diffuser plate, the lens, and the light source. FIG. 7A is a diagram showing an arrangement example of the first recess and the second recess according to the embodiment. FIG. 7B is a diagram showing an arrangement example of the first recess and the second recess according to the modified example. FIG. 8 is a diagram for explaining the brightness distribution of the light source according to the embodiment. FIG. 9 is a cross-sectional view of the planar lighting device according to the modified example. FIG. 10 is an exploded perspective view of the optical sheet according to the modified example. FIG. 11 is a diagram (No. 1) showing a comparison result of the luminance distribution depending on the presence or absence of the optical element according to the embodiment. FIG. 12 is a diagram (No. 2) showing a comparison result of the luminance distribution depending on the presence or absence of the optical element according to the embodiment. FIG. 13 is a diagram showing a comparison result of the luminance distribution due to the difference in the angle of the optical element. FIG. 14 is a diagram showing a comparison result of the luminance distribution due to the difference in the length of the optical element. FIG. 15 is a diagram showing a comparison result of the luminance distribution due to the misalignment of the lens according to the embodiment. FIG. 16A is a top view of the lens according to the modified example. 16B is a cross-sectional view taken along the line BB in FIG. 14A. FIG. 17A is a diagram showing the tip shape of the first concave portion according to the modified example. FIG. 17B is a diagram showing the tip shape of the first concave portion according to the modified example. FIG. 17C is a diagram showing the tip shape of the first concave portion according to the modified example. FIG. 17D is a diagram showing the tip shape of the first concave portion according to the modified example. FIG. 18 is a cross-sectional view of the planar lighting device according to the modified example. FIG. 19A is a diagram showing a configuration of an optical sheet according to a modified example. FIG. 19B is a diagram showing a configuration of an optical sheet according to a modified example. FIG. 19C is a diagram showing a configuration of an optical sheet according to a modified example. FIG. 20 is a diagram showing light distribution characteristics when the optical sheet according to the modified example is provided. FIG. 21A is a side view of the lens according to the modified example. FIG. 21B is an enlarged view of the first optical portion according to the modified example.

Hereinafter, the planar lighting device according to the embodiment will be described with reference to the drawings. The present invention is not limited to the embodiments shown below. In addition, the relationship between the dimensions of each element in the drawing, the ratio of each element, etc. may differ from the reality. In addition, there are cases where parts having different dimensional relationships and ratios are included between the drawings. In the drawings shown below, for convenience of explanation, a three-dimensional Cartesian coordinate system in which the light emission direction of the planar lighting device is the positive direction of the Z axis is shown. Such a Cartesian coordinate system may also be shown in other drawings used in the following description.

First, the outline of the planar lighting device according to the embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a top view of the planar lighting device according to the embodiment. FIG. 2 is an exploded perspective view of the planar lighting device according to the embodiment. FIG. 3 is a cross-sectional view of the planar lighting device according to the embodiment. FIG. 3 shows a cross section cut along the line AA shown in FIG.

The planar lighting device 1 according to the embodiment is a lighting device used as a backlight of various liquid crystal display devices, and is a so-called direct type planar lighting device in which a light source 20 described later is arranged directly under the liquid crystal display device. Is. The liquid crystal display device that is the target of the planar lighting device 1 is, for example, an electronic meter or an indicator that is an on-board unit, but the target is not limited to the on-board unit and may be any liquid crystal display device.

As shown in FIG. 1, the planar illumination device 1 according to the embodiment has an emission region R defined by an upper frame 11 described later. The planar illumination device 1 emits light in a planar manner by the emission region R, and functions as a backlight of the liquid crystal display device described above.

Further, the direct type planar illumination device 1 can cope with so-called local dimming in which the brightness of the emission region R is partially adjusted by individually controlling each of the plurality of light sources 20 described later.

Further, as shown in FIG. 1, the planar illumination device 1 according to the embodiment has a connector C. For example, power supply wiring, signal wiring, and the like are connected to the connector C. That is, power and signals are supplied to the planar illumination device 1 according to the embodiment via the connector C.

Further, as shown in FIGS. 2 and 3, the planar illumination device 1 according to the embodiment includes a substrate 2, a reflector 3, a lens (lens sheet) 4, a spacer 5, a diffuser 6, and a frame. 10, a light source 20, and an optical sheet 70 are provided.

The frame 10 is a sheet metal frame made of stainless steel, for example, which has high rigidity. The frame 10 includes an upper frame 11 and a lower frame 12, and houses each part of the planar illumination device 1 such as a substrate 2, a reflector 3, a lens 4, a spacer 5, a diffuser 6, a light source 20, and an optical sheet 70. To do.

The upper frame 11 is arranged on the light emitting direction side, which is the Z-axis positive direction side with respect to the lower frame 12, and functions as a lid in the frame 10. Further, the upper frame 11 is composed of a top plate 11a and a side wall 11b. An opening is formed in the central portion of the top plate 11a when viewed from above (when viewed from the positive direction of the Z axis), and the above-mentioned emission region R is defined by the opening. The side wall 11b is continuous with the peripheral end portion (opposite side of the opening) of the top plate 11a and extends along the side wall 12b of the lower frame 12 described later.

The lower frame 12 is arranged on the negative side of the Z axis with respect to the upper frame 11 and functions as a base in the frame 10. Further, the lower frame 12 is composed of a bottom portion 12a and a side wall portion 12b. The bottom portion 12a has a rectangular shape when viewed from above, and defines the shape when viewed from above. The side wall 12b is continuous with the peripheral edge of the bottom portion 12a and extends along the side wall 11b of the upper frame 11.

The substrate 2 is, for example, a circuit board made of epoxy resin or PI (polyimide), and for example, a flexible printed circuit (FPC) can be adopted.

The light source 20 is a point-shaped light source, and for example, an LED (Light Emitting Diode) can be adopted. As the light source 20, for example, a package type LED or a chip type LED can be used, but the light source 20 is not limited thereto. When a chip type LED is used as the light source 20, it may be combined with a wavelength conversion member such as a phosphor sheet. The light source 20 is not limited to the LED, and any light emitting member can be adopted. Further, the plurality of light sources 20 are mounted on the substrate 2 in a predetermined arrangement. Here, an example of arrangement of the light source 20 will be described with reference to FIG. 5A.

FIG. 5A is a diagram showing an arrangement example of the light source 20 according to the embodiment. FIG. 5A shows a top view of a part of the substrate 2 as viewed from the Z-axis positive direction side. As shown in FIG. 5A, the plurality of light sources 20 are arranged in a staggered arrangement (arranged in a hexagonal lattice) with respect to the substrate 2. In the example shown in FIG. 5A, six light sources 20 are arranged around an arbitrary one light source 20. Specifically, they are arranged at equal intervals (for example, at 60 ° intervals) around the central light source 20. In other words, one light source 20 is arranged at a predetermined interval so as to be surrounded by the six light sources 20.

In the example shown in FIG. 5A, an example in which a plurality of light sources 20 are arranged in a staggered arrangement is shown, but the present invention is not limited to the staggered arrangement, and as shown in FIG. 5B, the arrangement of the plurality of light sources 20 is not limited to the staggered arrangement. It may be a rectangular array (for example, a matrix array, a lattice array, etc.). FIG. 5B is a top view showing another arrangement example of the light source 20 according to the embodiment. In the planar lighting device 1 according to the present embodiment, so-called local dimming (area light emission), in which the brightness is adjusted for each light emitting region corresponding to each light source 20, can be performed.

The reflector 3 is arranged on the substrate 2, and a hole in which the light source 20 is arranged is formed at a position corresponding to each light source 20 mounted on the substrate 2. The reflector 3 is made of, for example, a white resin or the like and has a light reflection function. Specifically, when the light of the light source 20 once incident on the lens 4 leaks to the light source 20 side and returns, the reflector 3 reflects the returned light toward the lens 4 again. As a result, the emission efficiency of the planar illumination device 1 can be improved.

The lens 4 controls the light distribution of the light emitted from the light source 20. Specifically, the light emitted from the light source 20 is refracted by the lens 4 and spread out. The lens 4 is a plate-shaped member made of a material such as PMMA (polymethylmethacrylate), polycarbonate, PET (polyethylene terephthalate), or silicone, and integrally covers a plurality of light sources 20 arranged on the substrate 2.

Further, the lens 4 has two main surfaces 41a and 41b. One main surface 41a is a surface facing the light source 20 and is an incident surface on which the light of the light source 20 is incident (hereinafter referred to as an incident surface 41a). The other main surface 41b is the back surface of the incident surface 41a, which is an exit surface (hereinafter referred to as an exit surface 41b) that emits light incident from the incident surface 41a. Further, as shown in FIG. 3, an optical element (prism in this embodiment) 40 having a fine uneven shape is formed on the incident surface 41a, and this point will be described later.

The spacer 5 is formed, for example, in a square shape when viewed from above. Further, the spacer 5 is arranged along the side wall 12b of the lower frame 12 and between the lens 4 and the diffuser plate 6 to keep the distance between the lens 4 and the diffuser plate 6 constant. The spacer 5 presses the diffuser plate 6 from the lower surface side along the longitudinal direction (X-axis) of the planar illumination device 1, and presses the lens 4 from the upper surface side along the longitudinal direction.

Specifically, the spacer 5 presses the peripheral edge of the exit surface 41b of the lens 4 toward the light source 20 on the negative direction side of the Z axis. Further, the spacer 5 presses the peripheral edge of the diffusion plate 6, which will be described later, toward the light emission direction side, which is the Z-axis positive direction side. As a result, the space between the lens 4 and the diffuser plate 6 is maintained at a constant interval, so that the brightness of the light emitted from the lens 4 can be made uniform.

For the spacer 5, for example, a hard member, an elastic member, or the like can be adopted, but the material, physical properties, and the like are not particularly limited as long as the space between the lens 4 and the diffusion plate 6 can be held at regular intervals. Alternatively, the spacer 5 may be made of a white resin material or the like to further have a light reflection function. Further, although the case where the spacer 5 is formed in a square shape when viewed from above is shown as an example, the spacer 5 is not limited to this.

The diffuser plate 6 is made of, for example, a material such as resin, and diffuses the light of the light source 20 emitted from the lens 4. The diffuser plate 6 diffuses the light emitted from the lens 4 and emits the light in the positive direction of the Z-axis toward the emission direction of the light. That is, the light emitted from the lens 4 is diffused by the diffuser plate 6 and guided to the optical sheet 70.

Here, the positional relationship between the diffuser plate 6, the lens 4, and the light source 20 will be described with reference to FIG. FIG. 6 is an explanatory diagram of the positional relationship between the diffuser plate 6, the lens 4, and the light source 20.

As shown in FIG. 6, the lens 4 is arranged between the diffuser plate 6 and the light source 20. Further, the lens 4 and the light source 20 are arranged apart from each other. Further, the lens 4 and the diffuser plate 6 are arranged apart from each other. That is, the lens 4 is arranged apart from each of the diffuser plate 6 and the light source 20.

Further, in the lens 4, the distance Gb from the optical element 40 to the diffuser plate 6 is longer than the distance Ga from the optical element 40 to the light source 20 in a state where the distance between the light source and the diffuser plate is set to a predetermined value. It is placed in the position where. Specifically, the distance Ga from the upper surface 20a of the light source 20 to the incident surface 41a (optical element 40) of the lens 4 is from the incident surface 41a (optical element 40) of the lens 4 to the incident surface 6a of the diffuser plate 6. The distance Gb is long.

By shortening the distance Ga from the upper surface 20a of the light source 20 to the incident surface 41a of the lens 4 in this way, the distance Gb from the incident surface 41a to the incident surface 6a of the diffuser plate 6 can be increased. As a result, the optical path length from the lens 4 to the diffuser plate 6 can be lengthened, so that the light refracted from the lens 4 and emitted is further spread and incident on the diffuser plate 6. In this way, by arranging the lens 4 at a position where the distance Gb is longer than the distance Ga in a state where the distance between the light source and the diffuser plate is set to a predetermined value, the effect of spreading the light of the lens 4 is widened. Is effectively exhibited and the brightness can be made uniform. Alternatively, it is possible to widen the arrangement pitch of the light sources 20 and reduce the number of lights of the light sources 20.

In FIG. 6, the distance Ga and the distance Ga and the distance Ga and the distance Ga and the distance Ga and the distance Ga and the bottom surface 40b2 (see FIG. Although the distance Gb has been calculated, the distance Ga and the distance Gb may be calculated with reference to the tip of the first optical portion 40a or the second optical portion 40b in the optical element 40.

The optical sheet 70 is a member that performs optical adjustment such as light distribution control such as homogenization and light collection with respect to the light emitted from the diffuser plate 6. For example, the optical sheet 70 is a member also called a prism sheet, and a prism having a triangular cross-sectional view is formed on a main surface on the light emitting direction side, which is the Z-axis positive direction side. Further, as shown in FIGS. 2 and 3, for example, the optical sheet 70 is composed of two sheets, a first sheet 71 and a second sheet 72.

For example, the first sheet 71 is a prism sheet (for example, Brightness Enhancement Film manufactured by 3M), and the second sheet 72 is a reflective polarizing sheet (for example, Dual Brightness Enhancement Film manufactured by 3M). It can be arbitrarily changed depending on the light emitting mode required for the planar lighting device 1. Further, the optical sheet 70 is fixed to the exit surface of the diffusion plate 6 by, for example, an adhesive member such as an adhesive or double-sided tape.

The configuration of the planar illumination device 1 shown in FIGS. 2 and 3 is an example, and is, for example, an elastic member such as rubber or sponge between the top plate 11a of the upper frame 11 and the optical sheet 70. May be provided. The elastic member presses the diffusion plate 6 from the top plate 11a side of the upper frame 11 via the optical sheet 70. As a result, when vibration occurs in the planar lighting device 1, the elastic member absorbs the vibration, so that the position shift of the diffusion plate 6 due to the vibration can be prevented.

By the way, in a general direct-type planar lighting device, when a plurality of light sources are arranged on a substrate as described above and a lens is arranged directly above each light source, the light source and the lens can be aligned. It can be difficult. For example, when a large number of light sources are arranged on a substrate, it becomes difficult to align the light sources with the lens. For this reason, in a general direct-type planar lighting device, when a plurality of light sources are laid out on a substrate and arranged, there is a risk that the uniformity of brightness will decrease if the position of the light source and the lens is displaced.

Therefore, in the planar illumination device 1 according to the present embodiment, the optical element 40 is formed on the incident surface 41a of the lens 4. Specifically, the lens 4 has an optical element 40 having a plurality of recesses recessed in a hexagonal pyramid shape in a direction away from the light source 20 (Z-axis positive direction) on the incident surface 41a. As a result, with respect to the substrate 2 on which the plurality of light sources 20 are arranged, a plurality of hexagonal cone-shaped recesses arranged at a pitch smaller than the pitch of the light source 20 are formed on the incident surface 41a facing the light source 20. By integrally covering with the lens 4 having the element 40, it is possible to make the brightness of the light emitting surface uniform without alignment even when a large number of light sources 20 are arranged on the substrate 2.

In this way, the substrate 2 on which the plurality of light sources 20 are arranged is integrally covered with the lens 4 on which the optical elements 40 arranged at a pitch smaller than the pitch of the light sources 20 are formed. No alignment (positioning) with the lens 4 is required. That is, according to the planar illumination device 1 according to the embodiment, the positional deviation between the light source 20 and the lens 4 can be substantially nullified, so that the uniformity of brightness can be improved.

Here, the optical element 40 will be described in detail with reference to FIGS. 4A to 4C. 4A to 4C are views showing the optical element 40. FIG. 4A shows a view of the optical element 40 viewed from the negative direction side of the Z axis, FIG. 4B shows a cross section cut along the line BB shown in FIG. 4A, and FIG. 4C shows the first optical of the optical element 40. The perspective view of the part 40a is shown.

As shown in FIGS. 4A and 4B, the optical element 40 has a first optical portion 40a and a second optical portion 40b. The first optical portion 40a is a hexagonal bottom surface 40a2 (the shaded area shown in FIG. 4A) in top view as shown in FIGS. 4A to 4C, and is a bottom surface as shown in FIGS. 4B and 4C. It is a pyramid-shaped recess that tapers from 40a2 toward the tip on the Z-axis positive direction side, that is, a hexagonal pyramid-shaped recess (hereinafter, may be referred to as a first recess 40a). In other words, the first optical portion 40a has a shape having a portion whose cross-sectional area substantially parallel to the bottom surface 40a2 becomes smaller toward the tip.

Further, the first optical portion 40a has a staggered arrangement in a top view, and this point will be described later in FIG. 7A. The first optical portion 40a is not limited to the concave portion, but may be a convex portion, and the tip shape is not limited to a cone shape and may be an arbitrary shape such as an arc shape. That is, the first optical portion 40a can adopt any shape as long as it has a portion that tapers from the hexagonal bottom surface 40a2 toward the tip on the Z-axis positive direction side. Further, the first optical portion 40a does not have to have an accurate cone shape. That is, the cone-shaped first optical portion 40a may be regarded as a cone shape even when the tip is slightly arcuate due to, for example, a manufacturing error or the like.

Further, as shown in FIG. 4C, the first optical portion 40a is formed with an inclined surface 40a1 intersecting the bottom surface 40a2. The angle α between the inclined surface 40a1 and the bottom surface 40a2 of the first optical portion 40a is 44 ° or more and 58 ° or less. Alternatively, the first optical portion 40a preferably has an angle α between the hexagonal pyramid-shaped bottom surface 40a2 and the hexagonal pyramid-shaped inclined surface 40a1 of, for example, 44 ° or more and 55 ° or less. More preferably, the angle α between the inclined surface 40a1 and the bottom surface 40a2 of the first optical portion 40a is, for example, 50 ° in order to improve the uniformity of the brightness of the light emitting surface.

Further, as shown in FIG. 4C, the length D between the opposite sides of the first optical portion 40a is shorter than the length D20 between the diagonals of the light source 20 which is rectangular (top view), for example. Specifically, the length D of the first optical portion 40a is preferably ½ or less of the length D20 between the diagonals of the light source 20. In other words, the length D between the opposite sides of the first optical portion 40a is preferably ½ or less of the maximum distance of the light source 20 in the top view shape. Alternatively, the length D of the first optical portion 40a is more preferably 1/10 or less of the maximum distance of the light source 20 in the top view shape. That is, since the first optical portion 40a is smaller than the light source 20 in top view, even if a misalignment between the light source 20 and the first optical portion 40a occurs, the misalignment is substantially nullified. Therefore, it is possible to prevent the uniformity of brightness from being lowered. When a space (flat portion) is provided between the adjacent first optical portions 40a, the length D of the first optical portion 40a can be replaced with the pitch of the optical element 40.

The top view shape of the light source 20 is not limited to a rectangular shape, and may be another shape such as a circular shape or a polygonal shape, for example. For example, in the case of the circular light source 20, the length D of the first optical portion 40a is preferably 1/2 or less of the diameter of the light source 20. That is, the length (length D) between the opposite sides of the bottom surface of the hexagon in the first optical portion 40a is preferably 1/2 or less of the maximum distance of the light source 20 in the top view shape.

Further, the length D and the height H (distance from the bottom surface to the tip) of the first optical portion 40a may be arbitrary, and all of the plurality of first optical portions 40a have the same length D and height. It does not have to be H. That is, the plurality of first optical sites 40a may have different lengths D and heights H, and may be uniformly the same.

Further, the above-mentioned length and height of the second optical portion 40b, which will be described later, may also be arbitrary. That is, the plurality of second optical sites 40b may have different lengths and heights, and may be uniformly the same.

Further, the second optical portion 40b is a triangular bottom surface 40b2 (region with dots shown in FIG. 4A) in a top view as shown in FIG. 4A, and as shown in FIG. 4B, the bottom surface 40b2 to the Z-axis positive. It is a pyramidal recess that tapers toward the tip on the directional side, that is, a recess that is recessed in a triangular pyramid shape (hereinafter, may be referred to as a second recess 40b). In other words, the second optical portion 40b has a shape having a portion whose cross-sectional area substantially parallel to the bottom surface 40b2 becomes smaller toward the tip.

The second optical portion 40b is not limited to the concave portion, but may be a convex portion, and the tip shape is not limited to a cone shape and may be an arbitrary shape such as an arc shape. That is, the second optical portion 40b can adopt any shape as long as it has a portion that tapers from the bottom surface of the triangle toward the tip end. Further, the second optical portion 40b does not have to have an accurate cone shape. That is, the cone-shaped second optical portion 40b may be regarded as a cone even when the tip is slightly spherical due to, for example, a manufacturing error or the like.

Further, as shown in FIG. 4B, the second recess 40b has a shallower recess than the first recess 40a. That is, the length from the bottom surface 40b2 to the tip of the second recess 40b is shorter than the length from the bottom surface 40a2 to the tip of the first recess 40a. When the first optical portion 40a and the second optical portion 40b are convex portions, the second optical portion 40b is formed so that the height from the bottom surface to the apex is lower than that of the first optical portion 40a. That is, the length from the bottom surface to the tip of the second optical portion 40b is shorter than that of the first optical portion 40a.

Further, the first optical portion 40a and the second optical portion 40b may have a configuration in which concave portions and convex portions are mixed. That is, the first optical portion 40a may be a convex portion and the second optical portion 40b may be a concave portion, the first optical portion 40a may be a concave portion, and the second optical portion 40b may be a convex portion. You may. Further, if the optical element 40 has at least the first optical portion 40a of the first optical portion 40a and the second optical portion 40b, the second optical portion 40b may be omitted.

Then, as shown in FIG. 4A, the optical element 40 is recessed in a star-shaped hexagonal shape by the one first recess 40a and the plurality of second recesses 40b adjacent to the first recess 40a. Specifically, the plurality of second recesses 40b are adjacent to each other at positions corresponding to the respective bottom sides of the bottom surface 40a2 in the first recess 40Aa. More specifically, the bottom surface 40b2 of the second recess 40b and the bottom surface 40a2 of the first recess 40a are arranged so as to share the bottom surface. The present invention is not limited to this, and a space (flat portion) may be provided between the first recess 40a and the second recess 40b.

As a result, the light of the light source 20 incident from the negative Z-axis side of the lens 4 is refracted by the first recess 40a and the second recess 40b, that is, when the light is incident on the lens 4, it acts as a refraction. Since it is expanded by the lens 4 and emitted from the lens 4, it is possible to prevent the brightness directly above the light source 20 from becoming higher than the periphery immediately above the light source 20. Therefore, it is possible to prevent the area directly above the light source 20 from becoming too bright, and to make the brightness of the light emitting surface uniform regardless of whether the light source 20 is turned on (increasing the brightness) or in the case of local dimming (area light emission). be able to.

Further, in the lens 4 according to the embodiment, optical elements 40 having a plurality of hexagonal pyramid-shaped first recesses 40a and second recesses 40b are arranged in a staggered arrangement on an incident surface 41a facing the plurality of light sources 20. It is possible to make the brightness distribution of the emitted light from each light source 20 into a hexagonal shape. In other words, on the light emitting surface, the shape of the light emitting region corresponding to each light source 20 can be hexagonal.

As a result, in the planar illumination device 1 according to the embodiment, the brightness distribution of the emitted light from each light source 20 becomes a hexagonal shape (polygonal shape with straight sides), so that the distance between the light emitting regions becomes narrow. High-density local dimming (area emission) is possible. Further, when a plurality of adjacent light sources 20 are turned on (increasing the brightness) or when all the light sources 20 are turned on (increasing the brightness), the distance between the light emitting regions becomes narrow, so that the brightness of the light emitting surface becomes high. It becomes uniform. Therefore, the planar illumination device 1 according to the present embodiment can control the contrast more finely at the time of local dimming (area emission) while making the brightness of the light emitting surface uniform.

Further, in the planar illumination device 1 according to the embodiment, the first concave portion 40b having a triangular pyramid shape is arranged between the plurality of hexagonal pyramid-shaped first concave portions 40a on the incident surface 41a of the lens 4. The flat area between the recesses 40a can be reduced. In other words, the proportion of the optical element 40 (first recess 40a and second recess 40b) on the incident surface 41a can be increased. That is, by reducing the flat region on the incident surface 41a, the amount of light spread by the refraction action of the optical element 40 (prism) increases, so that the spread of light can be further strengthened. Therefore, the uniformity of brightness can be improved.

Next, the arrangement of the first recess 40a and the second recess 40b of the optical element 40 according to the embodiment will be described with reference to FIG. 7A. FIG. 7A is a diagram showing an arrangement example of the first recess 40a and the second recess 40b according to the embodiment.

As shown in FIG. 7A, the plurality of first recesses 40a are arranged in a staggered arrangement (arranged in a hexagonal lattice) in a top view. The staggered arrangement means that the first recess 40a is arranged at each vertex and center of the hexagon, and the arrangement of the hexagons is continuously arranged. That is, the plurality of first recesses 40a are arranged in a hexagonal shape on the incident surface 41a of the lens 4. In the present embodiment, as shown in FIGS. 7A and 7B, the plurality of first recesses 40a (first optical portions 40a) have each vertex of the first recess 40a (each vertex of the bottom surface 40a2 in the first recess 40a). Arranged symmetrically as boundaries. In this case, since the straight lines are continuous, manufacturing is easy. The plurality of first recesses 40a may be arranged symmetrically with each side of the first recess 40a as a boundary. In the example shown in FIG. 7A, one first recess 40a is surrounded by six first recesses 40a, and the six first recesses 40a are arranged so as to be in contact with each other, but the present invention is not limited to this, and the six first recesses 40a are adjacent to each other. A space (flat portion) may be provided between the first recesses 40a to be arranged.

Specifically, in the example shown in FIG. 7A, when any one first recess 40a is centered, the recesses 40a are arranged at intervals of approximately 60 ° in the rotational direction with respect to the center. That is, they are arranged at positions of 0 °, 60 °, 120 °, 180 °, 240 ° and 300 ° with respect to the central first recess 40a.

In other words, the first recess 40a is parallel to the X-axis direction (0 ° and 180 °), + 30 ° to the Y-axis direction (120 ° and 300 °), and the Y-axis direction. It is arranged in the direction (60 ° and 240 °) with respect to -30 °.

Then, a second recess 40b is arranged between the plurality of first recesses 40a. That is, the optical element 40 has a star-shaped hexagon in top view due to one first recess 40a and a plurality of (six in FIG. 7A) second recesses 40b adjacent to the first recess 40a.

Then, such a star-shaped hexagonal optical element 40 is molded in the directions of "0 ° -180 °", "60 ° -240 °" and "120 ° -300 °" as shown in FIG. 7A. Can be created by scraping. That is, by forming the optical element 40 as a star-shaped hexagonal recess, it is possible to facilitate the production of the mold, and thus it is possible to suppress an increase in cost.

The arrangement of the first recess 40a and the second recess 40b shown in FIG. 7A is an example, and the arrangement example shown in FIG. 7A may be rotated by a predetermined angle in the rotation direction. This point will be described with reference to FIG. 7B.

FIG. 7B is a diagram showing an arrangement example of the first recess 40a and the second recess 40b according to the modified example. FIG. 7B shows an arrangement in which the arrangement shown in FIG. 7A is rotated by 90 ° (which can also be said to be 30 ° or 60 °).

That is, the other first recesses 40a are arranged at positions of 30 °, 90 °, 150 °, 210 °, 270 ° and 330 ° with respect to the central first recess 40a. In other words, the first recess 40a is parallel to the Y-axis direction (90 ° and 270 °), + 30 ° to the X-axis direction (30 ° and 210 °), and the X-axis direction. It is arranged in the direction of −30 ° with respect to (150 ° and 330 °).

In addition, in FIG. 7B, the case where the arrangement shown in FIG. 7A is rotated by 90 ° (which can be said to be 30 ° or 60 °) is shown, but the rotation angle depends on the light emitting characteristics required for the planar illumination device 1. Any angle may be set accordingly.

Further, the planar illumination device 1 according to the present embodiment is a hexagonal pyramid-shaped prism in which a plurality of optical elements 40 arranged in the lens 4 are recessed in a direction away from the plurality of light sources 20. The light emitted from the plurality of light sources 20 is spread by the refraction action of the prism and is emitted from the exit surface 41b of the lens 4. This prevents the area directly above the light source 20 from becoming too bright, and makes the brightness of the light emitting surface uniform regardless of whether it is local dimming (area emission) or lighting all the light sources 20 (increasing the brightness). Can be planned.

Further, the lens 4 according to the present embodiment has a staggered arrangement of optical elements 40 having a plurality of hexagonal pyramid-shaped first recesses 40a and triangular pyramid-shaped second recesses 40b on an incident surface 41a facing the plurality of light sources 20. By arranging them, it is possible to make the brightness distribution of the light emitted from each light source 20 into a hexagonal shape. In other words, on the light emitting surface, the shape of the light emitting region corresponding to each light source 20 can be hexagonal. As a result, the distance between the light emitting regions of each light source 20 is narrowed, the brightness of the light emitting surface becomes uniform, and finer contrast control becomes possible at the time of local dimming (area light emission).

Next, when the optical element 40 is applied with reference to FIG. 8, the luminance distribution will be described. FIG. 8 is a diagram for explaining the brightness distribution of the light source 20 according to the embodiment. FIG. 8 describes a case where one light source 20 is arranged at the center position of the first recess 40a. Further, FIG. 8 shows the diffusion of the optical element 40 in the azimuth angle range of 0 ° to 360 ° of the incident light emitted from the light source 20.

In the example shown in FIG. 8, first, the directions of "0 ° -180 °", "60 ° -240 °" and "120 ° -300 °" (hereinafter, the above three directions are collectively referred to as the first direction. The number of the first recesses 40a whose centers overlap each axis is larger than that of the other axes.

Further, in the directions of "30 ° -210 °", "90 ° -270 °" and "150 ° -330 °" (hereinafter, the above three directions are collectively referred to as the second direction), each axis. The number of first recesses 40a on which their centers overlap is the next largest.

Further, the directions of "15 ° -195 °", "45 ° -225 °", "135 ° -315 °" and "165 ° -345 °" (hereinafter, the above four directions are collectively referred to as the third direction. In (described), the number of the first recesses 40a whose centers overlap each axis is smaller than that of the other axes.

From these facts, the "axis in the 0 ° -180 ° direction", the "axis in the 60 ° -240 ° direction", and the "axis in the 120 ° -300 ° direction" that maximize the number of the first recesses 40a, that is, The brightness on these three axes, which are offset by 60 °, is the largest. In addition, the brightness on the three axes deviated by 30 ° from these three axes becomes the next largest. Therefore, in the lens 4, the brightness distribution on the exit surface 41b has a hexagonal shape.

That is, since the number of lights emitted in the first direction passes through the center of the first recess 40a is the largest, the brightness of the light emitted from the exit surface 41b is the highest. That is, the light emitted in the first direction, the second direction, and the third direction has a hexagonal luminance distribution on the emission surface 41b.

Further, the light emitted in the first direction, the second direction, and the third direction is diffused by the first recess 40a and the second recess 40b, so that the brightness distribution in the first direction, the second direction, and the third direction is obtained. Can be smoothly connected, so that the brightness distribution can be made into a uniform hexagonal shape. That is, according to the planar illumination device 1 according to the embodiment, the uniformity of brightness can be improved.

As described above, the planar illumination device 1 according to the embodiment includes a substrate 2 and a lens 4. A plurality of light sources 20 are arranged on the substrate 2. The lens 4 is formed with an optical element 40 in which a plurality of first optical portions 40a having a portion tapered from a hexagonal bottom surface toward the tip end in a staggered arrangement on an incident surface 41a facing the plurality of light sources 20. ..

In this way, the plurality of light sources 20 are integrally covered with the lens 4 in which the fine hexagonal pyramid-shaped optical element 40 (first optical portion 40a) is arranged at a pitch smaller than the pitch of the light source 20. Alignment between the light source 20 and the lens 4 becomes unnecessary, and even when a large number of light sources 20 are arranged on the substrate 2, the brightness of the light emitting surface can be made uniform without alignment.

Further, in the planar illumination device 1 according to the embodiment, by arranging the first recesses 40a in a staggered arrangement, the brightness distribution on the exit surface 41b becomes a hexagonal shape. As a result, the distance between the light emitting regions of each light source 20 is narrowed, the brightness of the light emitting surface becomes uniform, and finer contrast control becomes possible at the time of local dimming (area light emission).

As described above, in the planar illumination device 1 according to the embodiment, since the brightness distribution of the emitted light from each light source 20 has a hexagonal shape (polygonal shape with straight sides), the distance between the light emitting regions becomes narrow. , High-density local dimming (area emission) is possible. Further, when a plurality of adjacent light sources 20 are turned on (increasing the brightness) or when all the light sources 20 are turned on (increasing the brightness), the distance between the light emitting regions becomes narrow, so that the brightness of the light emitting surface becomes high. It becomes uniform. Therefore, the planar illumination device 1 according to the present embodiment can control the contrast more finely at the time of local dimming (area emission) while making the brightness of the light emitting surface uniform.

Further, in the planar illumination device 1 according to the embodiment, the optical element 40 (first optical portion 40a) spreads the light directly above the light source 20 by a refraction action, and the light directly above the light source 20 is brighter than the periphery. It can be prevented from becoming too much. Therefore, according to the planar illumination device 1 according to the embodiment, the uniformity of brightness can be improved.

Further, as described above, in the planar illumination device 1 according to the embodiment, the light source 20 is a plurality of light sources 20 and an optical element 40 having a fine hexagonal pyramid-shaped first recess 40a and a triangular pyramid-shaped second recess 40b. By integrally covering with the lens 4 arranged at a pitch smaller than the pitch of, the alignment between the light source 20 and the lens 4 becomes unnecessary, and even when a large number of light sources 20 are arranged on the substrate 2, light is emitted without alignment. It is possible to make the brightness of the surface uniform.

Further, in the planar illumination device 1 according to the embodiment, optical elements 40 having a plurality of hexagonal pyramid-shaped first recesses 40a and triangular pyramid-shaped second recesses 40b on an incident surface 41a facing the light source 20 are arranged in a staggered manner. By having the arranged lens 4, it is possible to make the brightness distribution of the light emitted from each light source 20 into a hexagonal shape. In other words, on the light emitting surface, the shape of the light emitting region corresponding to each light source 20 can be hexagonal. As a result, the distance between the light emitting regions of each light source 20 is narrowed, the brightness of the light emitting surface becomes uniform, and finer contrast control becomes possible at the time of local dimming (area light emission).

Further, the planar illumination device 1 according to the embodiment includes a hexagonal pyramid-shaped prism and a triangular pyramid-shaped prism in which a plurality of optical elements 40 arranged in the lens 4 are recessed in a direction away from the plurality of light sources 20. The light emitted from the plurality of light sources 20 is spread by the refraction action of the prism and is emitted from the exit surface 41b of the lens 4. This prevents the area directly above the light source 20 from becoming too bright, and makes the brightness of the light emitting surface uniform regardless of whether it is local dimming (area emission) or lighting all the light sources 20 (increasing the brightness). Can be planned.

Further, in the planar illumination device 1 according to the present embodiment, the angle α between the inclined surface 40a1 and the bottom surface 40a2 of the first recess 40a is set to 44 ° or more and 58 ° or less, so that the light emitted from the light source 20 is emitted. Even if it hits the optical element 40, it is incident inside the lens 4 without being totally reflected, and the light emitted from the lens 4 is diffused outward, so that the brightness of the light emitting surface becomes uniform.

In addition to the configuration of the lens 4 described above, a plurality of convex diffusion elements 44 may be further provided on the exit surface 41b. This point will be described with reference to FIG.

FIG. 9 is a cross-sectional view of the planar lighting device 1 according to the modified example. In FIG. 9, the same configurations as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 9, in the planar illumination device 1 according to the modified example, a plurality of diffusion elements 44 are formed on the exit surface 41b, which is the back surface of the incident surface 41a. Specifically, a plurality of diffusion elements 44 (dots) protruding from the emission surface 41b are uniformly provided on the emission surface 41b of the lens 4.

As a result, in the planar illumination device 1 according to the embodiment, it is possible to make the brightness of the light emitting surface more uniform by allowing light to enter the region immediately above the light source 20 due to the diffusion effect of the plurality of diffusion elements 44. Become.

Further, since the exit surface 41b of the lens 4 is roughened by the plurality of diffusion elements 44, it is possible to prevent the exit surface 41 of the lens 4 from being directly scratched due to friction with other members.

In FIG. 9, the case where the diffusion element 44 is a dot is shown, but the configuration of the diffusion element 44 is not limited to this, and the surface of the emission surface 41b can be changed to the diffusion element 44, for example. It may be in a rough state. For example, the rough exit surface 41b may be formed by sand blasting, or the mold of the lens 4 may be textured and the texture may be transferred to the exit surface 41b.

Further, not only when the exit surface 41b is in a rough state, the incident surface 41a may be in a rough state. When the incident surface 41a is roughened, the entire incident surface 41a including the optical element 40 may be roughened, or only the optical element 40 of the incident surface 41a may be roughened. Further, of the optical elements 40, at least one of the first optical portion 40a and the second optical portion 40b may be in a roughened state.

In the above-described embodiment, the case where the first sheet 71 is a prism sheet and the second sheet 72 is a reflective polarizing sheet has been described for the optical sheet 70, but the present invention is not limited to this, and the first sheet 71 and Both the second sheet 72 may be a prism sheet. This point will be described with reference to FIG.

FIG. 10 is an exploded perspective view of the optical sheet 70 according to the modified example. As shown in FIG. 10, the first sheet 71 and the second sheet 72 are arranged so as to be overlapped with each other.

The first sheet 71 is, for example, a prism sheet, and has a plurality of first prisms 71a extending in the Y-axis direction, which is the lateral direction (first direction), and parallel to the X-axis direction, which is the longitudinal direction. Further, the second sheet 72 is, for example, a prism sheet, and has a second prism 72a extending in the X-axis direction which is the longitudinal direction (second direction) and parallel to the Y-axis direction which is the longitudinal direction.

The first prism 71a and the second prism 72a are projecting portions that project toward the light emission direction side, which is the Z-axis positive direction side. Further, the first prism 71a and the second prism 72a have, for example, a triangular cross-sectional view shape. Further, the first prism 71a and the second prism 72a are in a positional relationship in which the extending directions are orthogonal to each other.

The first prism 71a collects the emitted light in the Y-axis direction. Further, the second prism 72a collects the light emitted from the first prism 71a in the X-axis direction. That is, the light emitted through the first prism 71a and the second prism 72a is focused in a specific direction. As a result, the light can be focused in a specific direction, so that the light distribution in the specific direction can be controlled by the first sheet 71 and the second sheet 72.

The first prism 71a and the second prism 72a are not limited to being arranged so as to be orthogonal (intersect at 90 °), and an arbitrary intersection angle is set according to the required light distribution characteristics. Good.

Further, the lens 4 is not limited to the above-described embodiment, and for example, the lens 4 may be divided and configured. In such a case, the plurality of light sources 20 are arranged so that the gap between the plurality of lenses 4 is not located immediately above the light source 20. As a result, the refraction action of the optical element 40 of the lens 4 can guide the light directly above the gap, so that it is possible to prevent the brightness of the region of the gap from being lowered. That is, by using the lens 4 according to the embodiment, it is possible to prevent the gap between the lenses 4 from appearing as a dark portion, so that the uniformity of brightness can be improved.

Next, a simulation result showing the brightness distribution of the planar illumination device 1 according to the embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a diagram (No. 1) showing a comparison result of the luminance distribution depending on the presence or absence of the optical element 40 according to the embodiment. FIG. 12 is a diagram (No. 2) showing a comparison result of the luminance distribution depending on the presence or absence of the optical element 40 according to the embodiment. In addition, in FIGS. 11 and 12, the brightness is indicated by a shade, and the darker the shade, the stronger (brighter) the brightness.

First, the simulation result of the brightness distribution when the seven light sources 20 arranged in a staggered arrangement are turned on (seven lights are turned on) will be described with reference to FIG.

As shown in FIG. 11, in the planar illumination device provided with a lens without an optical element, which is a comparative example, the connection of the luminance distribution between the light sources is not smooth, whereas the surface provided with the lens 4 having the optical element 40 is provided. In the shape illuminating device 1, the connection of the brightness distributions between the light sources 20 is smooth. As described above, from the simulation results, it was found that in the case of the light sources 20 arranged in a staggered arrangement, the uniformity of brightness is improved by using the lens 4 having the optical elements 40. That is, when the brightness distribution is compared between the planar illumination device provided with the lens on which the optical element 40 is not arranged and the planar illumination device 1 according to the embodiment, the planar illumination device 1 is located between the light sources 20. It can be seen that the brightness distributions are smoothly connected and a clear hexagonal brightness distribution is obtained.

Further, as shown in FIG. 11, the planar illumination device 1 provided with the lens 4 having the optical element 40 has a substantially hexagonal shape of the brightness distribution. That is, in the planar illumination device 1 according to the embodiment, the brightness distribution of the light emitted from the light source 20 has a hexagonal shape (polygonal shape with straight sides), and the distance between the light emitting regions becomes narrower, so that the light emitting region The brightness can be made uniform, and the contrast can be controlled more finely during local dimming (area emission).

Next, a simulation result of the brightness distribution when nine light sources 20 arranged in a rectangular array are turned on (nine lights are turned on) will be described with reference to FIG.

As shown in FIG. 12, in the planar illumination device provided with a lens without an optical element, which is a comparative example, the connection of the luminance distribution between the light sources is not smooth, whereas the surface provided with the lens 4 having the optical element 40 is provided. In the shape illuminating device 1, the connection of the brightness distributions between the light sources 20 is smooth. As described above, from the simulation results, it was found that in the case of the light sources 20 arranged in a rectangular arrangement, the uniformity of brightness is improved by using the lens 4 having the optical elements 40.

Further, as shown in FIG. 12, in the planar illumination device 1 provided with the lens 4 having the optical element 40, when the light sources 20 are arranged in a rectangular arrangement, the shape of the brightness distribution becomes substantially rectangular. This is because, in the planar illumination device 1 according to the embodiment, the brightness distribution of the light emitted from the light source 20 has a hexagonal shape, but when the light sources 20 are arranged in a rectangular array, the hexagonal light emitted from the light source 20 This is because the luminance distributions of the shapes overlap each other, resulting in a substantially rectangular luminance distribution as a whole. That is, in the planar illumination device 1 according to the embodiment, when the light sources 20 are arranged in a rectangular array, the hexagonal brightness distributions overlap, so that the brightness of the light emitting region can be made uniform and local. Contrast can be controlled more finely during dimming (area emission).

Next, with reference to FIG. 13, the difference in the luminance distribution due to the difference in the angle α of the first optical portion 40a will be described. FIG. 13 is a diagram showing a comparison result of the luminance distribution due to the difference in the angle α of the first optical portion 40a. FIG. 13 shows the luminance distribution in an angle range from 40 ° to 62 °, specifically in 40 °, 44 °, 50 °, 58 ° and 62 °. Further, FIG. 13 shows the brightness distribution when all nine light sources 20 arranged in a rectangular arrangement are lit (when nine lights are lit).

As shown in FIG. 13, in the angle range of the angle α from 40 ° to 62 °, the brightness uniformity is highest when the angle α is 50 °. Further, the case of 44 ° and 58 ° has the next highest brightness uniformity, and the case of 40 ° and 62 ° has the lowest brightness uniformity.

That is, in the optical element 40, the closer the angle α of the first optical portion 40a is to 50 °, the higher the uniformity of brightness. Further, when the angle α is in the range of 44 ° to 58 °, the light emitted from the light source 20 is incident on the optical element 40 of the lens 4, is refracted and spreads out, so that the uneven brightness is less likely to become apparent. That is, the angle α of the first optical portion 40a is preferably 44 ° or more and 58 ° or less, and more preferably 50 °. By designing in such an angle α range, it is possible to make the brightness uniform.

Next, the difference in the luminance distribution due to the difference in the length D of the first optical portion 40a will be described with reference to FIGS. 14 and 15. FIG. 14 is a diagram showing a comparison result of the luminance distribution due to the difference in the length D of the first optical portion 40a. FIG. 15 is a diagram showing a comparison result of the luminance distribution due to the positional deviation of the lens 4 according to the embodiment. Further, FIG. 14 shows the brightness distribution when all nine light sources 20 arranged in a rectangular arrangement are lit (when nine lights are lit). Further, FIG. 15 shows the brightness distribution when one light source 20 is lit (when one light is lit).

14 and 15 show the ratio of the length D of the first optical portion 40a to the maximum distance (diagonal length D20) of the light source 20 (LED). For example, "1/2" indicates that the length D of the first optical portion 40a is 1/2 of the length D20 of the light source 20 (see FIG. 4C).

As shown in FIG. 14, the case of "1/10" has the highest brightness uniformity, and the brightness uniformity is higher in the order of "1/2" and "4/5". That is, the shorter the length D of the first optical portion 40a, the higher the uniformity of brightness. Further, if it is "1/2", the uneven brightness is less likely to become apparent. That is, the length D of the first optical portion 40a is preferably 1/2 or less, more preferably 1/10 or less of the maximum distance of the light source 20 in the top view shape. By designing the length D of the first optical portion 40a as described above, it is possible to make the brightness uniform.

Further, as shown in FIG. 15, for example, when the lens 4 is shifted (positionally deviated) by 0.5 mm with respect to the light source 20, the brightness distribution changes due to the misalignment at “4/5”. That is, "4/5" indicates that the appearance is not uniform due to the positional deviation between the light source 20 and the lens 4.

On the other hand, in "1/2" and "1/10", even if the lens 4 is shifted by 0.5 mm with respect to the light source 20, the change in the luminance distribution is extremely small. Further, the change in the luminance distribution is smaller in "1/10" than in "1/2". That is, the length D of the first optical portion 40a is preferably 1/2 or less, more preferably 1/10 or less of the maximum distance of the light source 20 in the top view shape. That is, since "1/2" and "1/10" can substantially nullify the positional deviation between the light source 20 and the lens 4, for example, the light source 20 and the lens 4 are caused by vibration or thermal expansion (contraction) of the lens 4. Even when the lens is misaligned, the brightness can be made uniform.

The lens 4 according to the above-described embodiment may have legs that support the lens 4. The legs of the lens 4 will be described with reference to FIGS. 12A and 12B. FIG. 12A is a top view of the lens 4 according to the modified example. FIG. 12B is a cross-sectional view taken along the line BB in FIG. 12A. Note that FIG. 12A shows a case where the plurality of light sources 20 have a rectangular arrangement.

As shown in FIGS. 16A and 16B, the lens 4 has a leg 400 projecting toward the substrate 2 on the incident surface 41a. The lens 4 is supported by the substrate 2 via the leg 400. As a result, the distance between the lens 4 and the light source 20 can be kept constant. Further, since it becomes easy to keep the distance between the lens 4 and the light source 20 constant, it is possible to contribute to the improvement of productivity. Further, by keeping the distance between the lens 4 and the light source 20 constant by the leg portion 400, it is possible to contribute to uniform brightness. The lens 4 may be fixed to the substrate 2 via the leg 400.

Further, as shown in FIGS. 16A and 16B, the legs 400 extend in a grid pattern (X-axis direction and Y-axis direction) and individually surround the plurality of light sources 20. As a result, it is possible to prevent the light from the adjacent light sources 20 from entering, so that the contrast can be improved during local dimming (area light emission).

Although FIGS. 16A and 16B show a case where the lens 4 and the leg 400 are integrally formed, the lens 4 and the leg 400 may be separately formed. Alternatively, the leg portion 400 may be integrally configured with the substrate 2.

Further, when the lens 4 and the leg portion 400 are integrally formed, the leg portion 400 may have a function as a reflecting portion by roughening the surface of the leg portion 400.

Further, in FIG. 16A, the case where the plurality of light sources 20 are arranged in a grid is shown. For example, when the plurality of light sources 20 are arranged in a staggered arrangement, the legs 400 extend in a staggered arrangement, so that the plurality of light sources are arranged in a staggered manner. 20 are individually enclosed.

In the above-described embodiment, the first recess 40a and the second recess 40b have a conical shape (a shape with a sharp tip), but the tips of the first recess 40a and the second recess 40b are sharp. It does not have to be a shape. For example, the tip shapes of the first recess 40a and the second recess 40b may be as shown in FIGS. 17A to 17D.

17A to 17D are views showing the tip shape of the first recess 40a according to the modified example. Although the tip shape of the first recess 40a is shown in FIGS. 17A to 17D, the second recess 40b may have a tip shape as shown in FIGS. 17A to 17D.

As shown in FIG. 17A, for example, the tip shape of the first recess 40a may be arcuate. Further, as shown in FIG. 17B, the tip shape of the first recess 40a may be a planar shape. Such a planar shape may be, for example, the same hexagon as the bottom surface 40a2 of the first recess 40a, or may be a polygon or a circle other than the hexagon.

Further, as shown in FIG. 17C, the tip shape of the first recess 40a may be a recessed recess. Further, as shown in FIG. 17D, the first concave portion 40a may have an arc shape in which the inclined surface 40a1 is concave. The inclined surface 40a1 may have a convex arc shape.

In addition to the tip shape of the first recess 40a shown in FIGS. 17A to 17D, any shape can be adopted. That is, the tip shape of the first recess 40a may be any shape as long as it has a portion that tapers from the bottom surface 40a2 toward the tip.

In the above-described embodiment, the optical sheet 70 is composed of the first sheet 71 and the second sheet 72, but the optical sheet 70 may be composed of three sheets. This point will be described with reference to FIGS. 18 to 20.

FIG. 18 is a cross-sectional view of the planar lighting device 1 according to the modified example. 19A to 19C are views showing the configuration of the optical sheet 70 according to the modified example. FIG. 20 is a diagram showing light distribution characteristics when the optical sheet 70 according to the modified example is provided. Note that FIG. 20 shows the brightness of the emitted light in the polar coordinate system in which the declination is shown in the range of 0 ° to 80 °, and the darker the shade, the stronger (brighter) the brightness.

As shown in FIG. 18, the optical sheet 70 is composed of, for example, three sheets. Specifically, the optical sheet 70 includes a first sheet 71, a second sheet 72, and a third sheet 73. Since the configurations of the first sheet 71 and the second sheet 72 are the same as those in the above-described embodiment, the description thereof will be omitted.

The third sheet 73 is a sheet-like member arranged on the light emitting direction side, which is the Z-axis positive direction side of the second sheet 72, and is, for example, an ALCF (Advanced Light Control Film) manufactured by 3M. It is a member in which a reflective polarizing sheet and a louver film are integrated. For example, the louver 73a of the third sheet 73 preferably has a light cutoff of 45 ° or less. Further, the third sheet 73 is arranged on the side farther from the lens 4 than the first sheet 71 and the second sheet 72.

Further, in the third sheet 73, the extending direction (third direction) of the louver 73a (optical element) of the louver film is the extending direction (first direction) of the first prism 71a and the extending direction of the second prism 72a. It is a member whose positional relationship is defined by a direction (second direction). The reflective polarizing sheet of the third sheet 73 may have an arbitrary extending direction regardless of the first prism 71a and the second prism 72a. 19A to 19C show the positional relationship between the louver 73a, the first prism 71a, and the second prism 72a.

The positional relationship shown in FIG. 19A will be described. In the example shown in FIG. 19A, the first prism 71a extends in the Y-axis direction, the second prism 72a extends in the X-axis direction, and the louver 73a extends in the X-axis direction.

That is, the louver 73a is substantially orthogonal to the first prism 71a and substantially parallel to the second prism 72a. As a result, as shown in FIG. 20, when the light distribution characteristics are three-dimensionally represented in a polar coordinate system, it is possible to cut the emitted light having an argument of a predetermined angle (approximately 45 ° in FIG. 20) or more. it can. That is, it is possible to suppress the spread of the emitted light in the longitudinal direction and the lateral direction of the planar illumination device 1. Therefore, for example, when the planar lighting device 1 is applied to an in-vehicle device, it is possible to suppress reflection on the windshield and the window glass on the side side.

Further, for example, as shown in FIG. 19B, the second prism 72a may be rotated by a predetermined angle in the rotation direction from the X-axis direction. That is, as shown in FIG. 19B, the second prism 72a is substantially orthogonal to the first prism 71a by the rotation angle. Further, the second prism 72a is substantially deviated from the louver 73a by the rotation angle. The rotation angle is preferably, for example, ± 20 ° or less. Even with such a configuration, it is possible to suppress the spread of the emitted light in the longitudinal direction and the lateral direction of the planar illumination device 1 as in the positional relationship shown in FIG. 19A. Therefore, for example, when the planar lighting device 1 is applied to an in-vehicle device, it is possible to suppress reflection on the windshield and the window glass on the side side.

Further, for example, as shown in FIG. 19C, the first prism 71a and the second prism 72a may be rotated by approximately 45 ° while maintaining an orthogonal relationship with each other. Specifically, the first prism 71a is rotated by approximately 45 ° from the Y-axis direction in the rotation direction (for example, counterclockwise). Further, the second prism 72a is rotated by approximately 45 ° from the X-axis direction in the rotation direction (for example, counterclockwise). Further, the louver 73a extends in the X-axis direction. That is, the louver 73a is arranged so as to be displaced by approximately 45 ° with respect to the first prism 71a and the second prism 72a. Similar to the positional relationship of FIGS. 19A and 19B described above, it is possible to suppress the spread of the emitted light in the longitudinal direction and the lateral direction of the planar illumination device 1. Therefore, for example, when the planar lighting device 1 is applied to an in-vehicle device, it is possible to suppress reflection on the windshield and the window glass on the side side.

In the example shown in FIG. 19C, the case where the first prism 71a and the second prism 72a are rotated by approximately 45 ° is shown, but if the orthogonal relationship between the first prism 71a and the second prism 72a is maintained, The rotation angle can be up to ± 60 °.

Further, in FIGS. 19A to 19C, the louver 73a extends substantially parallel to the X-axis direction, but the louver 73a may be rotated by a predetermined angle from the X-axis direction in the rotation direction. In such a case, the rotation angle of the louver 73a is preferably ± 10 ° or less.

Further, in the above description, the case where the reflective polarizing sheet and the louver film are integrally formed in the third sheet 73 has been described, but the reflective polarizing sheet and the louver film may be separately formed in the third sheet 73. ..

In the above-described embodiment, the lens 4 is a flat surface, but the lens 4 may be a curved surface. This point will be described with reference to FIGS. 21A and 21B. FIG. 21A is a side view of the lens 4 according to the modified example. FIG. 21B is an enlarged view of the first optical portion 40a according to the modified example. In addition, in FIG. 21A and FIG. 21B, the case where the first optical portion 40a is convex will be described. Further, FIG. 21B shows an enlarged view of the region surrounded by the broken line shown in FIG. 21A.

As shown in FIG. 21A, the lens 4 has a curved surface shape that is curved in the Z-axis direction. Specifically, the lens 4 has a curved surface shape in which the incident surface 41a is convex and the exit surface 41b is concave. The radius (R) of the curved lens 4 can be set within a range in which the angle α (see FIG. 4C) of the first recess 40a is approximately 44 ° or more and 58 ° or less.

Further, as shown in FIG. 21B, when the lens 4 has a curved surface shape, the first optical portion 40a preferably has an asymmetrical shape in a side view. Specifically, the first optical portion 40a has a shape facing inward (center side of the lens 4) with respect to the virtual vertical line VL parallel to the Z-axis direction. More specifically, in the first optical portion 40a, the apex of the hexagonal pyramid is located inside the vertical line VL. In other words, since the first optical portion 40a faces inward from the vertical line VL, the first optical portion 40a is caught in the mold when the mold is pulled out in the negative direction of the Z axis. Can be prevented. Therefore, when the lens 4 has a curved surface shape, the workability when the first optical portion 40a is pulled out from the mold can be improved.
In FIG. 21A, the lens 4 has a curved surface shape that is convex in the negative direction of the Z axis, but may have a curved surface shape that is convex in the positive direction of the Z axis. In such a case, it is preferable that the first optical portion 40a has a shape facing the outside (peripheral end side of the lens 4) with respect to the vertical line VL.

Moreover, the present invention is not limited by the above-described embodiment. The present invention also includes a configuration in which the above-mentioned constituent elements are appropriately combined. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

1 planar illuminator, 2 substrates, 3 reflectors, 4 lenses, 5 spacers, 6 diffusers, 10 frames, 11 upper frames, 12 lower frames, 20 light sources, 40 optics, 40a first optical part, 40b second Optical part, 44 Diffusing element, 70 Optical sheet, 71 1st sheet, 72 2nd sheet, 73 3rd sheet

Claims (5)

A board on which multiple light sources are placed and
A diffuser that diffuses the light from the light source,
It is a plate shape that is arranged apart from each other between the diffuser plate and each of the light sources and has two main surfaces, an incident surface facing the plurality of light sources and an exit surface facing the incident surface. A lens in which an optical element including a plurality of optical parts having a portion that tapers from the bottom surface of the polygon toward the tip on the incident surface is formed.
With
The lighting and extinguishing of the light source can be controlled individually.
The lens is
It is arranged at a position where the distance from the incident surface to the diffuser plate is longer than the distance from the incident surface to the light source.
The light emitted from the light source is incident from the incident surface without being totally reflected, and the incident light is refracted and spread to be incident on the diffuser plate so as to intersect the bottom surface and the bottom surface. A planar lighting device having an angle of 44 ° or more and 58 ° or less with an inclined surface. The plurality of light sources are arranged on the substrate in a rectangular arrangement.
The plurality of the optical parts are arranged linearly along the ridgeline of the optical part.
The planar lighting device according to claim 1, one of a direction of arrangement of the light source, any one of the direction in which the optical portion is arranged in a straight line coincide. An optical sheet arranged on the exit surface side of the lens is further provided.
The optical sheet is
Claim 1 or 2 includes a first sheet having a plurality of optical elements extending in a first direction and a second sheet having a plurality of optical elements extending in a second direction intersecting the first direction. The planar illuminator described. The optical sheet is
It further comprises a plurality of optical elements extending in a third direction, the first sheet and a third sheet located farther from the lens than the second sheet.
The third sheet is
The planar lighting device according to claim 3 , wherein the third direction is defined by the first direction and the second direction. The lens is
The planar illumination device according to any one of claims 1 to 4 , further comprising a plurality of diffusion elements projecting from the exit surface on the exit surface which is the back surface of the incident surface.

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