JP6751452B2 - Area lighting device - Google Patents

Description

The present invention relates to a planar lighting device.

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

Further, in a direct-type planar lighting device compatible with local dimming (area light emission), a lens for diffusing light emitted from a light source is provided, and the light from the light source is spread and emitted to make the luminance uniform for each region. can do.

JP, 2008-140653, A

However, in recent years, the number of light sources arranged on the substrate has been increasing in the direct type planar lighting device, and as the number of light sources increases, the positional deviation between the lenses and the light sources arranged directly above each light source is increased. When it occurs, the luminance of the light emitting surface may be 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 lighting device capable of improving the uniformity of brightness.

In order to solve the problems described above and achieve the object, a planar lighting device according to an aspect of the present invention includes a substrate, a diffusion plate, and a lens. A plurality of light sources are arranged on the substrate. The diffusion plate diffuses the light of the light source. The lens is a plate-like member that is arranged 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 surfaces. In the incident surface, an optical element is formed in which a plurality of first optical portions having a portion that tapers from the bottom surface of the hexagon toward the tip is in a staggered arrangement. Turning on and off of the light source can be individually controlled. The lens is than the distance from the incident surface to the light source, the incident is disposed towards longer located a distance from the incident surface to the diffusion plate, the light emitted from the light source without total reflection 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 light is incident on the surface, refracts and spreads the incident light to enter the diffusion plate. is there.

According to one embodiment of the present invention, the uniformity of luminance 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 light sources according to the embodiment. FIG. 5B is a diagram showing another arrangement example of the light sources according to the embodiment. FIG. 6 is an explanatory diagram of the positional relationship among the diffusion plate, the lens, and the light source. FIG. 7A is a diagram showing an arrangement example of the first recesses and the second recesses according to the embodiment. FIG. 7B is a diagram showing an arrangement example of the first recesses and the second recesses according to the modification. FIG. 8 is a diagram for explaining the luminance distribution of the light source according to the embodiment. FIG. 9: is sectional drawing of the planar illuminating device which concerns on a modification. FIG. 10 is an exploded perspective view of an optical sheet according to a modification. FIG. 11 is a diagram (No. 1) showing a comparison result of luminance distributions with and without the optical element according to the embodiment. FIG. 12 is a diagram (No. 2) showing the comparison result of the luminance distributions with and without the optical element according to the embodiment. FIG. 13 is a diagram showing a comparison result of luminance distributions depending on the angle of the optical element. FIG. 14 is a diagram showing a comparison result of luminance distributions due to differences in the lengths of optical elements. FIG. 15 is a diagram showing a comparison result of luminance distributions due to the displacement of the lens according to the embodiment. FIG. 16A is a top view of a lens according to a modification. FIG. 16B is a sectional view taken along line BB in FIG. 14A. FIG. 17A is a diagram showing a tip shape of the first recess according to the modification. FIG. 17B is a diagram showing the tip shape of the first recess according to the modification. FIG. 17C is a diagram showing a tip shape of the first recess according to the modification. FIG. 17D is a diagram showing the tip shape of the first recess according to the modification. FIG. 18 is a sectional view of a planar lighting device according to a modification. FIG. 19A is a diagram showing a configuration of an optical sheet according to a modification. FIG. 19B is a diagram showing the configuration of the optical sheet according to the modification. 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 modification is provided. FIG. 21A is a side view of the lens according to the modification. FIG. 21B is an enlarged view of the first optical portion according to the modification.

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 described below. In addition, the dimensional relationship of each element in the drawings, the ratio of each element, and the like may be different from reality. In addition, the drawings may include portions having different dimensional relationships and ratios. In the drawings shown below, for convenience of description, a three-dimensional orthogonal coordinate system in which the light emission direction of the planar lighting device is the positive Z-axis direction is shown. Such an orthogonal coordinate system may 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 taken 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 below 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 on-vehicle device such as an electronic meter or an indicator, but the target is not limited to the on-vehicle device and may be any liquid crystal display device.

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

Further, the planar lighting device 1 that is a direct type is compatible with so-called local dimming in which the brightness of the emission region R is partially adjusted by individually controlling each of a plurality of light sources 20 described below.

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

Further, as shown in FIGS. 2 and 3, the planar lighting device 1 according to the embodiment includes a substrate 2, a reflection plate 3, a lens (lens sheet) 4, a spacer 5, a diffusion plate 6, and a frame. 10, the light source 20, and the optical sheet 70.

The frame 10 is a sheet metal frame having high rigidity, for example, made of stainless steel. The frame 10 includes an upper frame 11 and a lower frame 12, and accommodates each part of the planar lighting device 1 such as the substrate 2, the reflection plate 3, the lens 4, the spacer 5, the diffusion plate 6, the light source 20 and the optical sheet 70. To do.

The upper frame 11 is arranged on the Z-axis positive direction side of the lower frame 12 on the light emission direction side, and functions as a lid of the frame 10. The upper frame 11 is composed of a top plate 11a and side walls 11b. An opening is formed in the center of the top plate 11a in a top view (as viewed from the Z-axis positive direction), and the exit region R is defined by the opening. The side wall 11b is continuous with the peripheral end portion (the side opposite to 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 Z axis negative direction side with respect to the upper frame 11, and functions as a base of the frame 10. The lower frame 12 is composed of a bottom portion 12a and a side wall 12b. The bottom portion 12a has a rectangular shape in a top view, and defines a top view shape of the planar lighting device 1. 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 substrate made of epoxy resin or PI (polyimide), and for example, a flexible printed circuit (FPC: Flexible Printed Circuit) can be adopted.

The light source 20 is a point 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 to this. 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 array. Here, an arrangement example 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 sources 20 according to the embodiment. FIG. 5A shows a top view of a part of the substrate 2 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 shape) on the substrate 2. In the example shown in FIG. 5A, six light sources 20 are arranged around the arbitrary one light source 20. Specifically, they are arranged at equal intervals (for example, 60° intervals) around the center light source 20. In other words, one light source 20 is surrounded by six light sources 20 and arranged at a predetermined interval.

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

The reflection plate 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, white resin and has a light reflecting function. Specifically, when the light of the light source 20 that once enters the lens 4 leaks back to the light source 20 side and returns, the reflecting plate 3 reflects the returned light toward the lens 4 again. Thereby, the emission efficiency of the planar lighting 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 and spread by the lens 4 and then emitted. The lens 4 is, for example, a plate-shaped member made of a material such as PMMA (polymethylmethacrylate), polycarbonate, PET (polyethylene terephthalate), or silicone, and integrally covers the plurality of light sources 20 arranged on the substrate 2.

Further, the lens 4 has two main surfaces 41a and 41b. The one main surface 41a is a surface facing the light source 20, and is an incident surface on which light from the light source 20 is incident (hereinafter referred to as an incident surface 41a). The other main surface 41b is a back surface of the incident surface 41a, and is an emission surface (hereinafter referred to as an emission surface 41b) that emits the light incident from the incident surface 41a. Further, as shown in FIG. 3, an optical element (prism in this embodiment) 40 having a fine concavo-convex shape is formed on the incident surface 41a, which 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 diffusion plate 6, and keeps the distance between the lens 4 and the diffusion plate 6 constant. The spacer 5 presses the diffusion plate 6 from the lower surface side along the longitudinal direction (X axis) of the planar lighting 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 emission surface 41b of the lens 4 toward the light source 20, which is on the Z axis negative direction side. Further, the spacer 5 presses the peripheral edge of the diffusion plate 6 described later toward the light emission direction side which is the Z axis positive direction side. As a result, the lens 4 and the diffusion plate 6 are held at a constant interval, so that the brightness of the light emitted from the lens 4 can be made uniform.

The spacer 5 can be made of, for example, a hard member, an elastic member, or the like, but the material and physical properties are not particularly limited as long as the lens 4 and the diffusion plate 6 can be held at a constant interval. Alternatively, the spacer 5 may be made of a white resin material or the like to further have a light reflecting function. Further, although the spacer 5 is shown as an example in the case of being formed in a square shape in a top view, the present invention is not limited to this.

The diffusion plate 6 is made of 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 light emission direction, which is the Z-axis positive direction side. That is, the light emitted from the lens 4 is diffused by the diffusion plate 6 and guided to the optical sheet 70.

Here, the positional relationship between the diffusion 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 among the diffusion plate 6, the lens 4, and the light source 20.

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

Further, in the lens 4, the distance Gb from the optical element 40 to the diffusion 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 diffusion plate is set to a predetermined value. Will be placed in the position. Specifically, the distance from the incident surface 41a of the lens 4 (optical element 40) to the incident surface 6a of the diffusion plate 6 is more than the distance Ga from the upper surface 20a of the light source 20 to the incident surface 41a of the lens 4 (optical element 40). The distance Gb is long.

Thus, by shortening the distance Ga from the upper surface 20a of the light source 20 to the incident surface 41a of the lens 4, it is possible to increase the distance Gb from the incident surface 41a to the incident surface 6a of the diffusion plate 6. As a result, the optical path length from the lens 4 to the diffusion plate 6 can be increased, so that the light refracted and emitted from the lens 4 is further spread and is incident on the diffusion 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 diffusion plate is set to a predetermined value, the effect of spreading the light of the lens 4 is obtained. Is effectively exhibited, and the brightness can be made uniform. Alternatively, the arrangement pitch of the light sources 20 can be widened to reduce the number of lights of the light sources 20.

In FIG. 6, the distance Ga and the incident surface 41a of the lens 4, that is, the bottom surface 40a2 of the first optical portion 40a or the bottom surface 40b2 of the second optical portion 40b (see FIG. 4B), which will be described later, of the optical element 40 are used as a reference. Although the distance Gb is 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 of the optical element 40.

The optical sheet 70 is a member that performs optical adjustments such as light distribution control such as homogenization and focusing of the light emitted from the diffusion plate 6. For example, the optical sheet 70 is a member also called a prism sheet, and a prism having a triangular sectional shape is formed on the principal surface on the light emission 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 Company), and the second sheet 72 is a reflective polarizing sheet (for example, Dual Brightness Enhancement Film manufactured by 3M Company). It can be arbitrarily changed depending on the light emission mode required for the planar lighting device 1. Further, the optical sheet 70 is fixed to the emission surface of the diffusion plate 6 with an adhesive or an adhesive member such as a double-sided tape, for example.

The configuration of the planar lighting device 1 shown in FIGS. 2 and 3 is an example, and for example, an elastic member such as rubber or sponge is provided 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. Accordingly, when the planar lighting device 1 vibrates, the elastic member absorbs the vibration, and thus the displacement 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 the 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 the substrate, it is difficult to align the light source and the lens. For this reason, in a general direct-type planar lighting device, when a plurality of light sources are spread over a substrate and arranged, if there is a positional shift between the light source and the lens, there is a possibility that the uniformity of brightness may deteriorate.

Therefore, in the planar lighting 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 concave portions that are recessed in a hexagonal pyramid shape in the direction away from the light source 20 (Z axis positive direction) on the incident surface 41a. Thereby, on the substrate 2 on which the plurality of light sources 20 are arranged, a plurality of hexagonal pyramid-shaped concave portions arranged at a pitch smaller than the pitch of the light sources 20 are formed on the incident surface 41 a facing the light sources 20. By integrally covering with the lens 4 having the element 40, even when a large number of light sources 20 are arranged on the substrate 2, it is possible to make the luminance of the light emitting surface uniform without performing alignment.

In this way, by integrally covering the substrate 2 on which the plurality of light sources 20 are arranged 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 with the lens 4 is required. That is, according to the planar lighting device 1 according to the embodiment, since the positional deviation between the light source 20 and the lens 4 can be substantially nullified, 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. 4A shows a view of the optical element 40 viewed from the negative Z-axis side, FIG. 4B shows a cross section taken along line BB shown in FIG. 4A, and FIG. 4C shows a first optical path of the optical element 40. The perspective view of the site|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 (a hatched area shown in FIG. 4A) in a top view as shown in FIGS. 4A to 4C, and a bottom surface as shown in FIGS. 4B and 4C. It is a conical recess that tapers from 40a2 toward the tip that is on the Z axis positive direction side, that is, a recess that is recessed into a hexagonal pyramid shape (hereinafter sometimes referred to as the first recess 40a). In other words, the first optical portion 40a has a shape having a portion in which the area of the cross section substantially parallel to the bottom surface 40a2 becomes smaller toward the tip.

The first optical parts 40a are staggered in a top view, which will be described later with reference to 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 the conical shape, and may be any shape such as an arc shape. In other words, 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 that is on the Z axis positive direction side. In addition, the first optical portion 40a does not have to be an exact cone shape. That is, the first optical portion 40a having the conical shape may be regarded as the conical shape even if the tip has a slightly arcuate shape due to 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. In the first optical portion 40a, the angle α between the inclined surface 40a1 and the bottom surface 40a2 is 44° or more and 58° or less. Alternatively, in the first optical portion 40a, the angle α between the hexagonal pyramid-shaped bottom surface 40a2 and the hexagonal pyramid-shaped inclined surface 40a1 is preferably, for example, 44° or more and 55° or less. More preferably, in the first optical portion 40a, the angle α between the inclined surface 40a1 and the bottom surface 40a2 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 1/2 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 1/2 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 a top view, even if the positional displacement between the light source 20 and the first optical portion 40a occurs, the positional displacement is substantially nullified. Therefore, it is possible to prevent the uniformity of brightness from being deteriorated. When a space (flat portion) is provided between the adjacent first optical portions 40a, the length D of the first optical portions 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 the rectangular shape, and may be another shape such as a circle or a polygon. For example, in the case of the circular light source 20, it is preferable that the length D of the first optical portion 40a be ½ or less of the diameter of the light source 20. That is, the length (length D) between the opposite sides of the hexagonal bottom surface of 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 of the first optical portion 40a and the height H (distance from the bottom surface to the tip) may be arbitrary, and all the plurality of first optical portions 40a have the same length D and height. It need not be H. That is, the plurality of first optical portions 40a may have different lengths D and heights H, and may have the same length.

Furthermore, the above-described length and height of the second optical portion 40b described later may be arbitrary as well. That is, the plurality of second optical portions 40b may have different lengths and heights, and may have the same length.

In addition, the second optical portion 40b is a triangular bottom surface 40b2 (a region with dots shown in FIG. 4A) in a top view as shown in FIG. 4A, and as shown in FIG. It is a conical concave portion that tapers toward the tip that is the direction side, that is, a concave portion that is concave in a triangular pyramid shape (hereinafter, may be referred to as a second concave portion 40b). In other words, the second optical portion 40b has a shape having a portion in which the area of the cross section 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 the conical shape, and may be an arbitrary shape such as an arc shape. In other words, 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. Further, the second optical portion 40b does not have to be an exact cone shape. That is, the conical second optical portion 40b may be regarded as a conical shape even when the tip has a slightly spherical shape due to 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 of the second recess 40b from the bottom surface 40b2 to the tip is shorter than the length from the bottom surface 40a2 of the first recess 40a to the tip. 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, or the first optical portion 40a may be a concave portion and the second optical portion 40b may be a convex portion. May be. Moreover, 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 into a star 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 of 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 such that the bottom sides are shared. However, 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.

Thus, the light of the light source 20 that is incident from the Z-axis negative direction side of the lens 4 is refracted and incident by the first recess 40a and the second recess 40b, that is, when the light is incident on the lens 4, the refraction action is performed. The light emitted from the lens 4 can be prevented from becoming higher than the brightness of the portion directly above the light source 20. Therefore, it is possible to prevent the portion directly above the light source 20 from becoming too bright, and to make the luminance of the light emitting surface uniform even in the case of local dimming (area light emission) and all the light sources 20 are turned on (luminance is increased). be able to.

Further, in the lens 4 according to the embodiment, the optical elements 40 having the plurality of hexagonal pyramid-shaped first concave portions 40a and the second concave portions 40b are arranged in a staggered arrangement on the incident surface 41a facing the plural light sources 20, It is possible to make the luminance 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, in the planar lighting device 1 according to the embodiment, the luminance distribution of the light emitted from each light source 20 has a hexagonal shape (a polygonal shape whose sides are linear), so that the intervals between the light emitting areas are narrowed, High-density local dimming (area light emission) is possible. Further, when a plurality of adjacent light sources 20 are turned on (increase brightness) or when all the light sources 20 are turned on (increase brightness), the intervals between the light emitting areas are narrowed, so that the brightness of the light emitting surface is reduced. Be uniform. Therefore, the planar lighting device 1 according to the present embodiment can control the contrast more finely during local dimming (area emission) while uniformizing the brightness of the light emitting surface.

Further, in the planar lighting device 1 according to the embodiment, the triangular pyramid-shaped second concave portions 40b are arranged between the plurality of hexagonal-pyramid-shaped first concave portions 40a on the incident surface 41a of the lens 4 to obtain the first concave portion 40a. The flat area between the recesses 40a can be reduced. In other words, it is possible to increase the ratio of the optical element 40 (the first recess 40a and the second recess 40b) in the incident surface 41a. That is, by reducing the flat area on the incident surface 41a, the light spread by the refraction of the optical element 40 (prism) increases, and thus 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 shape) in a top view. The zigzag arrangement means that the first concave portions 40a are arranged at each vertex and the center of the hexagon, and the hexagonal arrangement 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 FIG. 7A and FIG. 7B , the plurality of first recesses 40a (first optical parts 40a) have respective vertices of the first recesses 40a (each vertex of the bottom surface 40a2 of the first recess 40a). Are arranged symmetrically with the boundary as. In this case, since the straight line is continuous, the manufacturing is easy. The plurality of first recesses 40a may be arranged symmetrically with each side of the first recesses 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. A space (flat portion) may be provided between the first recesses 40a to be arranged.

Specifically, in the example shown in FIG. 7A, when the arbitrary first recess 40a is centered, the first recesses 40a are arranged at intervals of approximately 60° 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 has a direction parallel to the X-axis direction (0° and 180°), a direction +30° to the Y-axis direction (120° and 300°), and a Y-axis direction. -30° to the direction (60° and 240°).

And the 2nd recessed part 40b is arrange|positioned between each of several 1st recessed part 40a. That is, the optical element 40 becomes a star-shaped hexagon in a top view by the one first recess 40a and the 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. It can be created by cutting. In other words, by forming the optical element 40 as a star-shaped hexagonal recess, the mold can be easily manufactured, 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 for example, 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 modification. FIG. 7B shows an arrangement obtained by rotating the arrangement shown in FIG. 7A by 90° (also referred to as 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 first recess 40a serving as the center. In other words, the first recess 40a has a direction parallel to the Y-axis direction (90° and 270°), a direction +30° to the X-axis direction (30° and 210°), and an X-axis direction. -30° with respect to each other (150° and 330°).

7B shows the case where the arrangement shown in FIG. 7A is rotated by 90° (also referred to as 30° or 60°), the rotation angle depends on the required light emission characteristics of the planar lighting 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 of the prism and is emitted from the emission surface 41b of the lens 4. As a result, it is possible to prevent the area directly above the light source 20 from becoming too bright, and to make the luminance of the light emitting surface uniform even in the case of local dimming (area light emission) and when all the light sources 20 are turned on (luminance is increased). Can be planned.

Further, the lens 4 according to the present embodiment has a zigzag arrangement of optical elements 40 each 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 luminance 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 intervals between the light emitting areas of the respective light sources 20 are narrowed, the brightness of the light emitting surface is made uniform, and finer contrast control is possible during local dimming (area light emission).

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

In the example illustrated 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). In (1), the number of the first recesses 40a whose center overlaps 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 Next, the number of the first recesses 40a with which the center of the first recess 40a overlaps is large.

In addition, the directions of “15°-195°”, “45°-225°”, “135°-315°” and “165°-345°” (hereinafter, the above four directions are collectively referred to as a third direction). (Described), the number of the first recesses 40a whose center overlaps 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 luminance on these three axes deviated by 60° is the largest. In addition, the brightness on the three axes that are deviated by 30° from these three axes becomes the next largest. Therefore, in the lens 4, the luminance distribution on the emission surface 41b has a hexagonal shape.

That is, the light emitted in the first direction has the largest number of light passing through the center of the first recess 40a, so that the brightness of the light emitted from the emission 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 luminance distribution in the first direction, the second direction, and the third direction. Are connected smoothly, so that the luminance distribution can be made into a uniform hexagonal shape. That is, according to the planar lighting device 1 according to the embodiment, it is possible to improve the uniformity of brightness.

As described above, the planar lighting device 1 according to the embodiment includes the substrate 2 and the lens 4. A plurality of light sources 20 are arranged on the substrate 2. In the lens 4, an optical element 40 in which a plurality of first optical portions 40a having a tapered portion from the hexagonal bottom surface toward the tip is formed in a staggered arrangement is formed 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 lenses 4 in which the fine hexagonal pyramid-shaped optical elements 40 (first optical portions 40a) are arranged at a pitch smaller than the pitch of the light sources 20, Alignment between the light source 20 and the lens 4 is unnecessary, and even when a large number of light sources 20 are arranged on the substrate 2, it is possible to make the luminance of the light emitting surface uniform without performing alignment.

Further, in the planar lighting device 1 according to the embodiment, the first concave portions 40a are arranged in a staggered arrangement, so that the luminance distribution on the emission surface 41b becomes a hexagonal shape. As a result, the intervals between the light emitting areas of the respective light sources 20 are narrowed, the brightness of the light emitting surface is made uniform, and finer contrast control is possible during local dimming (area light emission).

As described above, in the planar lighting device 1 according to the embodiment, the luminance distribution of the emitted light from each light source 20 has a hexagonal shape (a polygonal shape whose sides are linear), so that the intervals between the light emitting regions are narrowed. High density local dimming (area light emission) is possible. Further, when a plurality of adjacent light sources 20 are turned on (increase brightness) or when all the light sources 20 are turned on (increase brightness), the intervals between the light emitting areas are narrowed, so that the brightness of the light emitting surface is reduced. Be uniform. Therefore, the planar lighting device 1 according to the present embodiment can control the contrast more finely during local dimming (area emission) while uniformizing the brightness of the light emitting surface.

Furthermore, in the planar lighting device 1 according to the embodiment, the optical element 40 (first optical portion 40a) spreads the light directly above the light source 20 by refraction, and the area directly above the light source 20 is brighter than the surroundings. It can be prevented from becoming too much. Therefore, according to the planar lighting device 1 according to the embodiment, it is possible to improve the uniformity of brightness.

Further, as described above, in the planar lighting device 1 according to the embodiment, the plurality of light sources 20 are provided as the light source in which the optical element 40 having the fine hexagonal pyramid-shaped first recesses 40a and the triangular pyramid-shaped second recesses 40b is used. By integrally covering with the lens 4 arranged at a pitch smaller than the pitch of 20, the alignment between the light source 20 and the lens 4 becomes unnecessary, and even when a large number of the light sources 20 are arranged on the substrate 2, the alignment is not performed. It is possible to make the brightness of the light emitting surface uniform.

Further, in the planar lighting device 1 according to the embodiment, the optical elements 40 having the plurality of hexagonal pyramid-shaped first recesses 40a and the triangular pyramid-shaped second recesses 40b on the incident surface 41a facing the light source 20 are arranged in a staggered arrangement. By having the lens 4 arranged, it is possible to make the luminance 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, the intervals between the light emitting areas of the respective light sources 20 are narrowed, the brightness of the light emitting surface is made uniform, and finer contrast control is possible during local dimming (area light emission).

Further, in the planar lighting device 1 according to the embodiment, the plurality of optical elements 40 arranged in the lens 4 include hexagonal pyramid prisms and triangular pyramid prisms that 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 of the prism and is emitted from the emission surface 41b of the lens 4. As a result, it is possible to prevent the area directly above the light source 20 from becoming too bright, and to make the luminance of the light emitting surface uniform even in the case of local dimming (area light emission) and when all the light sources 20 are turned on (luminance is increased). Can be planned.

Further, in the surface 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 the light strikes the optical element 40, the light that enters the lens 4 without being totally reflected and that is emitted from the lens 4 is diffused outward, so that the luminance of the light emitting surface becomes uniform.

In addition to the configuration of the lens 4 described above, a plurality of convex diffusing elements 44 may be further provided on the emission 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 modification. Note that, in FIG. 9, the same configurations as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

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

As a result, in the planar lighting device 1 according to the embodiment, the diffusion effect of the plurality of diffusion elements 44 allows light to enter the region immediately above the light source 20 and make the luminance of the light emitting surface more uniform. Become.

Furthermore, the emission surface 41b of the lens 4 is roughened by the plurality of diffusion elements 44, so that the emission surface 41 of the lens 4 can be prevented from being directly scratched by friction with other members.

Note that, although the case where the diffusing element 44 is a dot is shown in FIG. 9, the configuration of the diffusing element 44 is not limited to this, and instead of the diffusing element 44, for example, the surface of the emission surface 41b is It may be in a rough state. For example, the light emitting surface 41b in a rough state may be formed by shaving by sandblasting, or the metal mold of the lens 4 may be subjected to embossing and the embossing may be transferred to the light emitting surface 41b.

Further, the incident surface 41a may be roughened as well as the case where the outgoing surface 41b is roughened. When the incident surface 41a is rough, the entire incident surface 41a including the optical element 40 may be rough, or only the optical element 40 of the incident surface 41a may be rough. Further, in the optical element 40, only at least one of the first optical portion 40a and the second optical portion 40b may be in a rough state.

It should be noted that in the above-described embodiment, the optical sheet 70 is described in which the first sheet 71 is a prism sheet and the second sheet 72 is a reflective polarizing sheet, but the present invention is not limited to this. 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 modification. As shown in FIG. 10, the first sheet 71 and the second sheet 72 are arranged in an overlapping manner.

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

The first prism 71a and the second prism 72a are protrusions that protrude toward the light emission direction side, which is the Z axis positive direction side. The first prism 71a and the second prism 72a have, for example, a triangular sectional shape. Further, the first prism 71a and the second prism 72a have 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. The second prism 72a also 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 condensed in a specific direction. Accordingly, light can be condensed in a specific direction, and thus the light distribution in the specific direction can be controlled by the first sheet 71 and the second sheet 72.

In addition, the first prism 71a and the second prism 72a are not limited to be arranged orthogonally (intersecting at 90°), and an arbitrary intersecting angle may be set according to the required light distribution characteristic. 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 gaps between the plurality of lenses 4 are not located directly above the light sources 20. With this, the refraction 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 luminance of the region of the gap from being lowered. That is, by using the lenses 4 according to the embodiment, it is possible to prevent the gap between the lenses 4 from appearing as a dark part, and thus it is possible to improve the uniformity of brightness.

Next, a simulation result showing the luminance distribution of the planar lighting device 1 according to the embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a diagram (part 1) showing a comparison result of luminance distributions with and without the optical element 40 according to the embodiment. FIG. 12 is a diagram (part 2) showing a comparison result of luminance distributions with and without the optical element 40 according to the embodiment. Note that in FIGS. 11 and 12, the brightness is shown by shading, and the darker the shading is, the stronger (brighter) the brightness is.

First, the simulation result of the brightness distribution when the seven light sources 20 arranged in the staggered arrangement are turned on (seven lights are turned on) will be described with reference to FIG. 11.

As shown in FIG. 11, in the planar illumination device including the lens without the optical element, which is a comparative example, the connection of the luminance distribution between the light sources is not smooth, whereas the surface including the lens 4 with the optical element 40 is not smooth. In the flat illumination device 1, the connection of the luminance distribution between the light sources 20 is smooth. As described above, the simulation result shows that in the case of the light sources 20 arranged in the staggered arrangement, the uniformity of the brightness is improved by using the lens 4 having the optical element 40. That is, when comparing the luminance distributions of the planar lighting device including the lens in which the optical element 40 is not arranged and the planar lighting device 1 according to the embodiment, the planar lighting device 1 is closer to the light source 20. It can be seen that the luminance distribution was smoothly connected to obtain a sharp hexagonal luminance distribution.

Further, as shown in FIG. 11, in the planar lighting device 1 including the lens 4 having the optical element 40, the shape of the luminance distribution is substantially hexagonal. That is, in the planar lighting device 1 according to the embodiment, the luminance distribution of the light emitted from the light source 20 has a hexagonal shape (a polygonal shape with straight sides), and the intervals between the respective light emitting areas are narrowed to cause the light emitting areas. The brightness can be made uniform, and the contrast can be controlled more finely during local dimming (area emission).

Next, the simulation result of the luminance distribution when the nine light sources 20 arranged in a rectangular array are turned on (9 lights are turned on) will be described with reference to FIG.

As shown in FIG. 12, in the planar illumination device including the lens without the optical element, which is a comparative example, the connection of the luminance distribution between the light sources is not smooth, while the surface including the lens 4 with the optical element 40 is not provided. In the flat illumination device 1, the connection of the luminance distribution between the light sources 20 is smooth. As described above, the simulation results show that in the case of the light sources 20 arranged in the rectangular array, the uniformity of the brightness is improved by using the lens 4 having the optical element 40.

Further, as shown in FIG. 12, in the planar lighting device 1 including the lens 4 having the optical element 40, when the light sources 20 are arranged in a rectangular array, the shape of the luminance distribution is substantially rectangular. This is because in the planar lighting device 1 according to the embodiment, the luminance 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 is hexagonal. This is because the luminance distributions of the shapes are overlapped with each other and the luminance distributions are substantially rectangular as a whole. That is, in the planar lighting device 1 according to the embodiment, when the light sources 20 are arranged in a rectangular array, the luminance distributions of the hexagons are overlapped with each other, so that the luminance of the light emitting region can be made uniform and the luminance of the light emitting region can be made uniform. The contrast can be controlled more finely during dimming (area emission).

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

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

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 enters the optical element 40 of the lens 4, is refracted and spreads out, and uneven brightness is less likely to be 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 within such a range of the angle α, 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 luminance distributions 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 distributions due to the displacement of the lens 4 according to the embodiment. Further, FIG. 14 shows the luminance distribution when all nine light sources 20 arranged in a rectangular array are lit (when nine lights are lit). In addition, FIG. 15 shows the luminance distribution when one light source 20 is turned on (when one lamp is turned on).

14 and 15 show the ratio of the length D of the first optical portion 40a to the maximum distance (distance D20 between diagonals) 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 brightness uniformity is highest in the case of "1/10", and the brightness uniformity is high 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. If it is "1/2", 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, and more preferably 1/10 or less of the maximum distance of the light source 20 in the top view shape. By designing such a length D of the first optical portion 40a, it is possible to make the brightness uniform.

Further, as shown in FIG. 15, for example, when the lens 4 is shifted (displaced) by 0.5 mm with respect to the light source 20, the luminance distribution changes due to the displacement 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, with "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. Furthermore, the change of 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, and more preferably 1/10 or less of the maximum distance of the light source 20 in the top view shape. That is, “1/2” and “1/10” can substantially nullify the positional deviation between the light source 20 and the lens 4, so that the light source 20 and the lens 4 are vibrated or thermally expanded (contracted), for example. Even if and are misaligned, the brightness can be made uniform.

The lens 4 according to the above-described embodiment may have a leg portion that supports 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 modification. FIG. 12B is a sectional view taken along line BB in FIG. 12A. Note that FIG. 12A shows a case where the plurality of light sources 20 are in a rectangular array.

As shown in FIGS. 16A and 16B, the lens 4 has a leg portion 400 that protrudes toward the substrate 2 on the incident surface 41a. The lens 4 is supported by the substrate 2 via the leg portion 400. Thereby, 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 improvement in productivity. Furthermore, 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 portion 400.

In addition, as shown in FIGS. 16A and 16B, the leg portion 400 extends in a lattice shape (X-axis direction and Y-axis direction) and individually surrounds the plurality of light sources 20. As a result, it is possible to prevent light from the adjacent light sources 20 from entering, so that it is possible to improve the contrast during local dimming (during area light emission).

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

When the lens 4 and the leg portion 400 are integrally configured, the surface of the leg portion 400 may be roughened to give the leg portion 400 a function as a reflecting portion.

16A shows the case where the plurality of light sources 20 is in a lattice arrangement, for example, when the plurality of light sources 20 is in a staggered arrangement, the leg portion 400 extends in a staggered arrangement, so that the plurality of light sources is arranged. Enclose 20 individually.

In addition, in the above-mentioned embodiment, although the 1st recessed part 40a and the 2nd recessed part 40b showed the case where it was pyramid-shaped (the shape where the tip was sharp), the tip of the 1st recessed part 40a and the 2nd recessed part 40b was sharp. The shape does not have to be. For example, the tip shapes of the first recess 40a and the second recess 40b may be the shapes shown in FIGS. 17A to 17D.

17A to 17D are diagrams showing the tip shape of the first recess 40a according to the modification. 17A to 17D show the tip shape of the first recess 40a, the second recess 40b may have the 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 an arc shape. Further, as shown in FIG. 17B, the tip shape of the first recess 40a may be a planar shape. The planar shape may be, for example, the same hexagon as the bottom surface 40a2 of the first recess 40a, or 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 recess 40a may have an arcuate shape in which the inclined surface 40a1 is concave. The inclined surface 40a1 may have a convex arc shape.

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

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

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

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. The configurations of the first sheet 71 and the second sheet 72 are the same as those in the above-described embodiment, and thus the description thereof is omitted.

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

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 the direction (second direction). The reflective polarizing sheet of the third sheet 73 may have any 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 characteristic is three-dimensionally represented by the polar coordinate system, it is possible to cut out the emitted light having a declination angle of a predetermined angle (approximately 45° in FIG. 20) or more. it can. That is, the spread of the emitted light in the longitudinal direction and the lateral direction of the planar lighting device 1 can be suppressed. Therefore, for example, when the planar lighting device 1 is applied to a vehicle-mounted device, it is possible to suppress the reflection on the windshield or the side window glass.

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 deviates from the first prism 71a by substantially the same angle as the rotation angle. Further, the second prism 72a is displaced from the louver 73a by substantially the same amount as the rotation angle. The rotation angle is preferably ±20° or less, for example. 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 lighting device 1, similarly to the positional relationship of FIG. 19A described above. Therefore, for example, when the planar lighting device 1 is applied to a vehicle-mounted device, it is possible to suppress the reflection on the windshield or the side window glass.

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

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

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

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

In addition, in the above-mentioned embodiment, although the lens 4 showed the case where it was a plane, 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 modification. FIG. 21B is an enlarged view of the first optical portion 40a according to the modification. 21A and 21B, the case where the first optical portion 40a has a convex shape will be described. Further, FIG. 21B shows an enlarged view of a region surrounded by a broken line shown in FIG. 21A.

As shown in FIG. 21A, the lens 4 has a curved surface shape curved in the Z-axis direction. Specifically, in the lens 4, the incident surface 41a has a convex shape and the emitting surface 41b has a concave curved surface shape. 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 shape, the first optical portion 40a preferably has an asymmetrical shape in a side view. Specifically, the first optical portion 40a has a shape that faces inward (a central side of the lens 4) with respect to an imaginary 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, the first optical portion 40a faces inward with respect to the vertical line VL, so that when the mold is pulled out in the Z-axis negative direction, the first optical portion 40a may be caught by the mold. It can be prevented. Therefore, when the lens 4 has a curved surface shape, it is possible to improve workability when removing the first optical portion 40a from the mold.

In FIG. 21A, the lens 4 has a curved surface shape that is convex on the Z axis negative direction side, but may be a curved surface shape that is convex on the Z axis positive direction side. In such a case, it is preferable that the first optical portion 40a has a shape that faces the outer side (the peripheral end side of the lens 4) with respect to the vertical line VL.

Further, the present invention is not limited to the above embodiment. The present invention also includes those configured by appropriately combining the constituent elements described above. Further, further effects and modified examples 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.

DESCRIPTION OF SYMBOLS 1 Planar illumination device, 2 substrate, 3 reflective plate, 4 lens, 5 spacer, 6 diffuser plate, 10 frame, 11 upper frame, 12 lower frame, 20 light source, 40 optical element, 40a 1st optical part, 40b 2nd Optical part, 44 Diffusing element, 70 Optical sheet, 71 First sheet, 72 Second sheet, 73 Third sheet

Claims (14)

A substrate on which a plurality of light sources are arranged,
Two diffuser plates for diffusing the light of the light source, an incident surface arranged between the diffuser plate and the light sources and facing the plurality of light sources, and an exit surface facing the incident surface are provided. A lens having an optical element formed in a plate shape having a main surface and having a plurality of first optical portions having a zigzag arrangement on the incident surface, the portions having a taper from the hexagonal bottom surface toward the tip. ,
Turning on and off the light source can be controlled individually,
The lens is
The distance from the incident surface to the diffusion 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 total reflection, in order to be incident on the diffusion plate spread refracts incident light; intersecting the bottom surface and the bottom surface A planar lighting device in which an angle with the inclined surface is 44° or more and 58° or less. The first optical portion is
The planar illumination device according to claim 1, wherein a length between opposite sides of the bottom surface is ½ or less of a maximum distance of the light source in a top view shape. The optical element is
The planar illumination device according to claim 1, wherein an angle between the bottom surface and an inclined surface intersecting the bottom surface is 44° or more and 55° or less. The lens is
The optical element further having a plurality of second optical portions that are adjacent to the first optical portion and have portions that taper from the bottom surface of the triangle toward the tip is formed. The planar illumination device described. The plurality of second optical parts,
The planar illumination device according to claim 4, wherein the planar illumination device is adjacent to each other at a position corresponding to each base of the bottom surface of the first optical portion. The optical element is
The planar illumination device according to claim 4 or 5, wherein the one first optical portion and the plurality of second optical portions adjacent to the first optical portion form a star-shaped hexagon in a top view. The second optical portion is
The planar illumination device according to claim 4, wherein the length from the bottom surface to the tip is shorter than that of the first optical portion. Further comprising an optical sheet arranged on the exit surface side of the lens,
The optical sheet,
8. 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 with the first direction. The planar lighting device according to any one of claims. The optical sheet,
A plurality of optical elements extending in a third direction, further comprising a third sheet arranged farther from the lens than the first sheet and the second sheet,
The third sheet is
The planar illumination device according to claim 8, wherein the third direction is defined by the first direction and the second direction. The lens is
The planar lighting device according to claim 1, further comprising a plurality of diffusion elements that project from the emission surface. The planar lighting device according to claim 1, wherein the plurality of light sources are arranged on the substrate in a staggered arrangement. The plurality of light sources are arranged in a rectangular array on the substrate,
The plurality of first optical portions arranged in a staggered arrangement are arranged linearly along the ridgeline of the first optical portion,
While the arrangement direction of the light source, a planar illumination device according to any one of claims 1 to 10 either the direction coincident to the first optical portion is arranged in a straight line. The lens is
13. The incident light is refracted and spread so that the luminance distribution of the emitted light emitted from the light source overlaps the luminance distribution of the emitted light emitted from the light source adjacent to the light source. The planar illumination device according to any one of the above. The lens has substantially the same shape as the substrate in a top view shape, has a leg portion that integrally covers the plurality of light sources arranged on the substrate, and supports the lens, and the leg portion has a plurality of legs. The planar lighting device according to claim 1, wherein the light source is individually surrounded.

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