JP2019109992A - Lens and planar lighting device - Google Patents

Abstract

To improve uniformity of brightness.SOLUTION: A lens according to an embodiment includes: a reflection part which is provided on a rear surface being a major surface facing a point light source and reflects light, which is reflected from an emission surface being a major surface facing the rear surface to the rear surface side, to the emission surface side; a recessed part recessed from the emission surface in a thickness direction at an immediately above part of the point light source; and a transmission part which is provided at an outer periphery part of the recessed part and transmits the light from the emission surface.SELECTED DRAWING: Figure 6A

Description

  The present invention relates to a lens and a surface illumination device.

  In recent years, there is a planar illumination device that illuminates a display panel of a liquid crystal display device from the back side. A planar illumination device is roughly classified into an edge light type and a direct type. Further, in the planar illumination device, so-called local dimming (area light emission) -compliant planar illumination device capable of adjusting the brightness for each area of the light emitting surface by controlling the light quantity of each point light source. It has been known.

  In addition, a direct type planar illumination device compatible with local dimming (area light emission) includes a lens for diffusing light emitted from a point light source, and spreads out light from the point light source to emit light, whereby the brightness of each area is obtained. It can be made uniform.

JP, 2010-8837, A

  However, due to the recent demand for thinning the planar illumination device, it has become impossible to ensure sufficient uniformity of luminance. For example, in the case of using a planar illumination device as a backlight of an information display of a vehicle, the installation space is limited, and in order to ensure uniform brightness, it is not possible to meet the demand for thinning.

  This invention is made in view of the above, Comprising: It aims at providing the lens and planar illumination device which can improve the uniformity of luminosity.

  In order to solve the problems described above and achieve the object, the lens according to one aspect of the present invention is provided on the back surface that is the main surface facing the point light source, and from the emission surface that is the main surface facing the back surface The reflecting portion for reflecting the light reflected to the back surface side to the emission surface side, the concave portion recessed in the thickness direction from the emission surface immediately above the point light source, and the outer peripheral portion of the concave portion And a light transmitting portion for transmitting light from the light source.

  According to one embodiment of the present invention, the uniformity of luminance can be improved.

FIG. 1: is a top view which shows an example of the external appearance of the planar illuminating device which concerns on embodiment. FIG. 2 is a top view showing an example of arrangement of lenses according to the first embodiment. FIG. 3A is a schematic cross-sectional view (No. 1) along the line AA shown in FIG. FIG. 3B is a schematic cross-sectional view (No. 2) along the line AA shown in FIG. FIG. 4 is a top view of the reflector according to the first embodiment. FIG. 5 is a top view of the lens according to the first embodiment. 6A is a schematic cross-sectional view taken along the line B-B shown in FIG. 6B is a schematic cross-sectional view taken along the line B-B shown in FIG. FIG. 7 is a schematic view showing light distribution characteristics of the lens according to the first embodiment. FIG. 8 is a diagram showing the comparison result of the luminance distribution according to the presence or absence of the transmission part. FIG. 9 is a top view showing an exemplary arrangement of lenses according to the second embodiment. FIG. 10 is a schematic cross-sectional view taken along the line C-C shown in FIG. FIG. 11 is a schematic cross-sectional view of a lens according to a third embodiment. FIG. 12 is a perspective view of the lens according to the third embodiment as viewed from the back surface side. FIG. 13 is a view showing the light distribution characteristic of the lens according to the third embodiment. FIG. 14 is a schematic cross-sectional view of a lens according to a fourth embodiment. FIG. 15 is a perspective view of the lens according to the fourth embodiment as viewed from the back surface side.

  Hereinafter, a lens and a planar illumination device according to an embodiment will be described with reference to the drawings. Note that the present invention is not limited by the embodiments described below. In addition, the dimensional relationships among the elements in the drawings, the proportions of the elements, and the like may differ from reality. In addition, parts having different dimensional relationships and ratios may be included among the drawings.

  First, the outline of the planar illumination device according to the embodiment will be described with reference to FIG. FIG. 1: is a front view which shows an example of the external appearance of the planar illuminating device which concerns on embodiment. The planar illumination device 1 according to the present embodiment is a direct-type planar illumination device, and is used as a backlight of various liquid crystal display devices. Such a liquid crystal display device is, for example, an electronic speedometer of a vehicle, but is not limited thereto.

  As shown in the example of FIG. 1, the planar illumination device 1 according to the embodiment emits light from an emission area not covered by the frame 10. The connector C is connected with power supply wiring, signal wiring, and the like. That is, the planar illumination device 1 according to the embodiment is supplied with power and signals via the connector C.

  By the way, in general, in a direct type planar illumination device, a plurality of point light sources are arranged in a grid, and a lens is provided for each point light source and a lens is provided for each of a plurality of point light sources arranged in a row. There is.

  The lens according to the present embodiment is applicable to both cases. First, the case where a lens is provided for each point light source will be described as the first embodiment. FIG. 2 is a top view showing the arrangement of lenses according to the first embodiment. In addition, in order to clarify the positional relationship of the lens 50 and the point light source 30, in FIG. 2, the point light source 30 is shown collectively.

  As shown in FIG. 2, the point light sources 30 are arranged in a grid. Each point light source 30 is provided with a lens 50 from the emission direction. That is, in the planar illumination device 1, since the point light sources 30 are arranged in a grid, the lenses 50 are also arranged in a grid.

  Next, an internal configuration of the spread illuminating apparatus 1 according to the first embodiment will be described using FIGS. 3A and 3B. 3A and 3B are schematic cross-sectional views along the line AA shown in FIG. As shown in FIG. 3A, the planar illumination device 1 according to the embodiment includes the frame 10, the substrate 20, the point light source 30, the reflection plate 40, the lens 50, the diffusion plate 60, the spacer 70, and optics. A seat 80 and an elastic member 90 are provided.

  The frame 10 is a sheet metal frame having high rigidity, for example, stainless steel, and accommodates the respective members of the planar illumination device 1. Also, the frame 10 includes, for example, an upper frame 11 and a lower frame 12.

  The upper frame 11 is disposed on the upper surface side of the lower frame 12. The upper frame 11 has a rectangular top plate 11 a having an opening formed at its central portion, and a side wall 11 b extending from the periphery of the top plate 11 a along the outer surface of the lower frame 12. The lower frame 12 has a rectangular bottom 12 a and a side wall 12 b extending from the periphery of the bottom 12 a along the inner side of the upper frame 11.

  The substrate 20 is made of, for example, an epoxy resin or PI (polyimide), and has a main surface on which a plurality of point light sources 30 are mounted in a lattice. The point light source 30 is, for example, a light emitting diode (LED). The point light source 30 is disposed on the substrate 20 such that the optical axis is substantially perpendicular to the lens 50.

  The reflection plate 40 is formed of, for example, a white resin or the like. The reflecting plate 40 reflects the light reflected by the lens 50 toward the reflecting plate 40 toward the lens 50 again. Thus, the emission efficiency can be improved. The configuration of the reflection plate 40 will be described later with reference to FIG.

  The lens 50 performs light distribution control of light emitted from the point light source 30, and the outer shape of the lens 50 is rectangular or substantially rectangular in top view. As a material of the lens 50, for example, PMMA (polymethyl methacrylate) or polycarbonate can be used, but it is not limited thereto. The light whose light distribution is controlled by the lens 50 is emitted to the diffusion plate 60. The lens 50 also has a leg 56 that protrudes toward the substrate 20. For example, in the lens 50, an adhesive member such as an adhesive is applied to the bottom of the leg 56, for example, and fixed to the substrate 20, but the fixing method is not limited thereto. The details of the lens 50 will be described later with reference to FIG.

  The diffusion plate 60 is made of a material such as resin and has a function of diffusing the light emitted from the lens 50. That is, the light emitted from the lens 50 is diffused by the diffusion plate 60 and guided to the optical sheet 80.

  The spacer 70 is disposed between the lens 50 and the diffusion plate 60, and keeps the distance between the lens 50 and the diffusion plate 60 constant. The material of the spacer 70 is not particularly limited. For example, the spacer 70 may be formed of a white resin and have a function of reflecting light emitted from the lens 50. The spacer 70 presses the diffusion plate 60 from the lower surface side along the longitudinal direction (X axis) of the planar illumination device 1, and presses the lens 50 from the upper surface side along the longitudinal direction. The spacer 70 may not necessarily hold the distance between the lens 50 and the diffusion plate 60 in the lateral direction (Y axis) of the planar illumination device 1.

  The optical sheet 80 performs optical adjustment such as equalization and orientation control on the light emitted from the diffusion plate 60, and emits the light subjected to the optical adjustment. The example shown in FIG. 3 exemplifies the case where the optical sheet 80 is composed of two sheets of the first sheet 81 and the second sheet 82.

  For example, the first sheet 81 is a BEF (Brightness Enhancement Film), and the second sheet 82 is a DBEF (Dual Brightness Enhancement Film), but the first sheet 81 may be arbitrarily changed according to the light emission mode required for the surface illumination device 1 Is possible. The optical sheet 80 is fixed to the exit surface of the diffusion plate 60 by, for example, an adhesive or an adhesive member such as a double-sided tape.

  The elastic member 90 is a frame-like member having elasticity, such as rubber or sponge. The elastic member 90 is provided on the optical sheet 80, holds the diffusion plate 60 and the optical sheet 80 between the spacer 70 and holds the same, and presses the lens 50 through the spacer 70 by its elastic force. In addition, when vibration occurs in the planar lighting device 1, the elastic member 90 absorbs the vibration. The elastic member 90 is disposed between the upper frame 11 and the diffusion plate 60, and presses the diffusion plate 60 from the top plate side of the upper frame 11. The elastic member 90 is not limited to the frame shape, and for example, a plurality of rod-like elastic members having a rectangular cross-sectional shape may be used.

  Further, as shown in FIG. 3B, the elastic member 90 may be provided so as to avoid the upper surface of the optical sheet 80. Specifically, as shown in FIG. 3B, the elastic member 90 is installed on the upper surface of the diffusion plate 60, and is pressed toward the diffusion plate 60 by the top plate 11a. Also, the optical sheet 80 is installed on the side surface of the elastic member 90. In such a case, the optical sheet 80 is smaller than the diffusion plate 60 in top view, and the elastic member 90 is provided in a region where the optical sheet 80 does not cover the diffusion plate 60. Accordingly, it is possible to suppress the wrinkles of the optical sheet 80 when the planar illumination device 1 is manufactured or when the planar illumination device 1 vibrates.

  Subsequently, the reflecting plate 40 will be described with reference to FIG. FIG. 4 is a top view of the reflecting plate 40 according to the embodiment. In FIG. 4, a part of the reflecting plate 40 is extracted and shown, and the point light source 30 and the lens 50 are shown together. As shown in FIG. 4, the reflection plate 40 includes a bottom surface 41 and a frame 42.

  The bottom surface 41 is provided with a plurality of openings, and the point light source 30 mounted on the substrate 20 is inserted from the substrate 20 side through the openings. The frame 42 encloses the side of each point light source 30. Since the point light sources 30 are arranged in a lattice, the frame portions 42 are formed in a lattice so as to surround the side surfaces of the point light sources 30 arranged in a lattice.

  Thus, the reflecting plate 40 which concerns on embodiment is provided so that each point light source 30 may be divided. Thereby, the light reflected to the reflecting plate 40 by the lens 50 can be prevented from leaking to the adjacent point light source 30. In other words, it is also possible to improve the contrast when the point light sources 30 are individually lit. For example, the frame portion 42 has a tapered shape that protrudes from the bottom surface 41 toward the lens 50 (the front side in the drawing) and narrows in width from the bottom surface 41 toward the lens 50.

  Subsequently, the lens 50 according to the first embodiment will be described with reference to FIG. FIG. 5 is a top view of the lens 50 according to the first embodiment. In addition, in FIG. 5, in order to clarify the positional relationship of the lens 50 and the point light source 30, the point light source 30 is shown collectively.

  As shown in FIG. 5, the exit surface 51 of the lens 50 has a flat portion 57, a transmission portion 52, and a recess 53. The flat portion 57 is a flat surface provided continuously with the recess 53 and emits light to the diffusion plate 60. The transmitting portion 52 has a function of promoting the emission of light to the boundary with the adjacent lens 50. The transmitting portion 52 may be a transmitting portion recessed in the thickness direction of the lens 50, and the shape thereof is not particularly limited.

  Specifically, as shown in FIG. 5, the transmitting portion 52 is formed concentrically at the outer peripheral portion of the recess 53, and is provided in contact with each side of the emission surface 51. That is, the transmitting portion 52 is provided on the outer peripheral portion of the emission surface 51. The transmitting portion 52 is a linear protrusion having a straight line or a curved line in a cross section and protruding from the emission surface. The transmitting unit 52 refracts and transmits a part of the emitted light, and promotes the emission of the light to the boundary with the adjacent lens 50. The transmitting portion 52 is not limited to the concentric shape, and may be formed in a linear shape as long as the transmitting portion 52 is formed on the outer peripheral portion of the emission surface 51. In the present embodiment, the boundary of the lens is the area above the gap with the adjacent lens 50, and it is difficult for the light from the point light source 30 to reach and the area easily darkens when the point light source 30 is lit. It is.

  The recess 53 has a shape that is recessed in the thickness direction from the emission surface 51 immediately above the point light source 30 of the emission surface 51. In other words, the concave portion 53 is provided at a position corresponding to the point light source 30 of the light emission surface 51, and the concave portion 53 is a shape recessed from the light emission surface 51 toward the back surface 54. It is formed in a conical shape (or a weir shape). The concave portion 53 has a function of reflecting the light emitted from the point light source 30 to the back surface 54 side. In the recess 53, it is not necessary to reflect all the light emitted from the point light source 30 to the back surface 54 side, and there may be light transmitted from the recess 53 to the diffusion plate 60.

  As described above, the recess 53 reflects the light emitted from the point light source 30 toward the back surface 54 side. The light intensity of the incident light is strong directly above the point light source 30 of the exit surface 51, but by reflecting most of the light emitted from the point light source 30 by the recess 53 toward the back surface 54, the light intensity directly above the point light source 30 Can be reduced. In other words, by reflecting the light from the point light source 30 by the concave portion 53, it is possible to suppress the increase in the luminance of the region corresponding to the portion immediately above the point light source 30 of the lens 50.

  As described above, the orientation of the light emitted from the point light source 30 is controlled so that the light intensity is uniform at the emission surface 51. In other words, the lens 50 can equalize the luminance by dispersing the light incident immediately above the light source having high light intensity over the entire emission surface 51.

  Subsequently, the cross-sectional shape of the lens 50 according to the embodiment will be described with reference to FIGS. 6A and 6B. 6A and 6B are schematic cross-sectional views taken along the line B-B shown in FIG. As shown in FIG. 6A, the lens 50 has a reflecting portion 55 on the back surface 54 in addition to the transmitting portion 52 and the recess portion 53 formed on the emitting surface 51.

  The reflective portion 55 is a dot that protrudes from the back surface 54 in the thickness direction of the lens 50, and is uniformly formed on the entire back surface 54, for example. The reflection unit 55 reflects the light reflected to the back surface 54 side at the emission surface 51 again to the emission surface 51 side.

  That is, the reflecting portion 55 reflects the light reflected to the back surface 54 side again to the emission surface 51 side by the concave portion 53 provided at the position corresponding to the point light source 30 of the lens 50. Thereby, the light reflected by the reflection part 55 is emitted from the flat part 57 provided continuously to the concave part 53 of the lens 50 to the diffusion plate 60. The reflecting portion 55 may have a dot shape which is recessed in the thickness direction of the lens 50 from the back surface 54. Also, the reflective portion 55 is not limited to dots.

  Further, FIG. 6A shows the case where the transmitting portion 52 has a triangular shape and the reflecting portion 55 has a dot shape in cross sectional view, but the present invention is not limited to this, and as shown in FIG. However, the cross-sectional view may have a rounded shape, such as a semicircular shape or a round shape, or the reflective portion 55 may have a triangular shape.

  Subsequently, the light distribution characteristic of the lens 50 will be described with reference to FIG. FIG. 7 is a schematic view showing light distribution characteristics of the lens 50 according to the first embodiment. In FIG. 7, the optical path of light is indicated by a broken line.

  As shown in FIG. 7, the light emitted from the point light source 30 is reflected by the recess 53 toward the back surface 54 as described above. Subsequently, the light is reflected by the reflection portion 55 provided on the back surface 54 again to the emission surface 51 side. Then, the light reflected by the reflection portion 55 is emitted from the flat portion 57 of the emission surface 51. That is, the light emitted from the point light source 30 is guided within the lens 50, converted to substantially surface light emission, and emitted. Further, a part of the outgoing light is refracted and transmitted by the transmission part 52, and the outgoing light is promoted to the boundary with the adjacent lens 50.

  As described above, in the lens 50 according to the first embodiment, the orientation is controlled so that the light incident from the point light source 30 is uniformly emitted from the entire emission surface 51. That is, according to the lens 50 which concerns on this embodiment, equalization | homogenization of brightness | luminance can be improved.

  Further, in the lens 50 according to the first embodiment, by refracting and transmitting a part of light by the transmitting unit 52, it is possible to suppress the light guided to the adjacent lens 50. In other words, the transmitting portion 52 can suppress the leakage of light to the adjacent lens 50. That is, the lens 50 according to the first embodiment can also improve the contrast when the point light sources 30 are individually lit by suppressing the light guided to the adjacent lens 50.

  Next, the comparison result by the presence or absence of the lens 50 which concerns on embodiment using FIG. 8 is demonstrated. FIG. 8 is a view showing the comparison result of the luminance distribution depending on the presence or absence of the transmission part 52. As shown in FIG. In addition, in FIG. 8, the simulation result of the luminance distribution at the time of making nine point light sources 30 emit light is shown. The circled area in FIG. 8 corresponds to the boundary between the lens 50 and the lens 50 adjacent to the lens 50.

  Comparing the circled area shown in FIG. 8 with the presence or absence of the transmission part 52, it can be seen that the luminance is improved more in the case where the transmission part 52 is provided than in the case where the transmission part 52 is not present.

  That is, in the planar illumination device 1 according to the embodiment, by providing the transmitting portion 52 on the outer peripheral portion of the emission surface 51 of the lens 50, the brightness between the adjacent lenses 50 can be improved.

  In other words, uneven brightness between adjacent lenses 50 can be suppressed. Therefore, according to the lens 50 which concerns on embodiment, equalization | homogenization of brightness | luminance can be improved.

  As described above, in the lens 50 according to the embodiment, the reflective portion 55 is provided on the back surface 54 that is the main surface that faces the point light source 30 and is the main surface that faces the back surface 54 Is reflected to the side of the exit surface 51. The recess 53 has a shape that is recessed in the thickness direction from the emission surface 51 immediately above the point light source 30. The transmitting portion 52 is provided on the outer peripheral portion of the recess 53, and refracts and transmits a part of light. As a result, emission of light is promoted by the transmitting portion 52 to the boundary with the adjacent lens 50, the luminance between the adjacent lenses 50 is improved, and the luminance becomes uniform. Furthermore, the light leakage to the adjacent lens 50 is suppressed by the transmission part 52, and the contrast when the point light sources 30 are individually lit is improved. Therefore, according to the lens 50 according to the first embodiment, it is possible to improve the contrast when the point light sources 30 are individually lit while improving the uniformity of the luminance of the planar illumination device 1.

Second Embodiment
Next, a lens 50B according to the second embodiment will be described with reference to FIGS. In the second embodiment, the case where the lens 50B covers a plurality of point light sources 30 alone will be described.

  First, an outline of the lens 50B according to the second embodiment will be described with reference to FIG. FIG. 9 is a top view showing an arrangement example of the lens 50B according to the second embodiment. As shown in FIG. 9, the lens 50B according to the second embodiment differs from the lens 50 according to the first embodiment in that the lens 50B covers a plurality of point light sources 30.

  Specifically, the lens 50B according to the second embodiment covers a plurality of point light sources 30 lined in the short direction (Y axis) among the plurality of point light sources 30 lined in a grid-like manner alone, They are arranged in parallel along the direction (X axis). The lens 50B is rectangular or substantially rectangular in top view. The lens 50B according to the present embodiment has a rectangular shape in which the side extending in parallel to the short direction (Y axis) is a long side and the side extending in a direction parallel to the longitudinal direction (X axis) is a short side in top view is there.

  Thus, by covering the plurality of point light sources 30 aligned in the short direction, the lens 50B can shorten the lens length as compared to the case of covering the plurality of point light sources 30 aligned in the longitudinal direction.

  This is because the lens 50B thermally expands (contracts) due to the heat generation of the point light source 30 and the ambient environment temperature, and the lens 50B is caused by positional deviation between the point light source 30 and the lens 50B due to the thermal expansion of the lens 50B. In order to suppress the deterioration of the optical characteristics of Assuming that the expansion coefficient per unit volume of the lens 50B is the same, the longer the lens length, the larger the expansion (contraction) volume, so the lens 50B expands (contracts) more.

  Further, as will be described later with reference to FIG. 10, the light emitting surface 51b is provided with a recess 53b provided at a position corresponding to the immediate upper part of the point light source 30, and a transmitting part 52b between the adjacent point light sources 30. The recess 53 b and the transmission part 52 b are designed based on the position of the point light source 30.

  When the relative position between each point light source 30 and the transmitting portion 52b or the recess 53b is deviated, the light distribution characteristic of the light emitting surface 51 or the recess 53b is deteriorated. That is, the lens 50B according to the second embodiment covers the point light sources 30 arranged in the short direction so that the lens length is relatively short, whereby the positional deviation between each point light source 30 and the transmitting portion 52b or the recess 53b Suppress. As a result, it is possible to suppress a decrease in light distribution characteristics due to thermal expansion or thermal contraction of the lens 50B.

  Further, as shown in FIG. 9, the lens 50B covers a row of point light sources 30. As a result, the width (length in the X-axis direction) of the lens 50B can be reduced, so that the lens 50B can be applied to the planar illumination device 1 having a curved exit surface.

  Subsequently, a schematic cross-sectional view of the lens 50B according to the second embodiment will be described with reference to FIG. FIG. 10 is a schematic cross-sectional view taken along the line C-C shown in FIG. As shown in FIG. 10, in the lens 50B according to the second embodiment, a plurality of transmission portions 52b, a plurality of recesses 53b, and a flat portion 57b are formed on the emission surface 51b.

  The transmitting portion 52 b is provided around the recess 53 b. For example, in the cross sectional view, the transmitting portion 52 b is provided in the boundary area between the corresponding point light source 30 and the point light source 30 adjacent to the point light source 30. In the lens 50 according to the present embodiment, the transmissive portion 52 b is a protrusion that has a straight line or a curved line in a cross section and that protrudes from the emission surface 51. Moreover, the transmission part 52 which concerns on this embodiment is arranged in the direction substantially orthogonal to the arrangement direction of the point light source 30 which the lens 50B covers. In other words, the transmitting portion 52b is formed along the longitudinal direction (X axis). In addition, the concave portion 53b is provided at a position corresponding to the immediate upper part of the corresponding point light source 30, and has a shape that is recessed from the emission surface 51b toward the back surface 54b. In the lens 50B according to the second embodiment, the back surface 54b is formed flat, and the reflecting portion 55b is uniformly formed on the entire surface.

  That is, the lens 50B according to the second embodiment reflects the light emitted from the plurality of point light sources 30 toward the back surface 54b by the corresponding concave portions 53b, and causes the light to be reflected again by the reflecting portion 55b. Then, the light is emitted from the flat portion 57b of the emission surface 51b.

As described above, in the lens 50B according to the second embodiment, the concave portions 53b are formed at positions corresponding to the point light sources 30, and the transmitting portions 52b are formed in the boundary region with the point light sources 30 adjacent to each other.
The transmitting portion 52b refracts and transmits a part of the emitted light and promotes the emission of light to the boundary portion with the adjacent emission surface 51b, as in the transmitting portion 52 according to the first embodiment. Thereby, even in the case of covering a plurality of point light sources, it is possible to improve the brightness of the boundary portion of the emission surface 51b. That is, as in the lens 50 according to the first embodiment, it is possible to improve the uniformity of the luminance. Furthermore, the transmitting portion 52b suppresses light guided to the adjacent emission surface 51b side (for example, suppresses light guided from the emission surface 51b-1 of FIG. 10 to the adjacent emission surface 51b-2 side) ). In other words, leakage of light to the adjacent emission surface 51b is suppressed by the transmission portion 52b. Thereby, when the point light sources 30 are individually lit, it is possible to improve the contrast. In the present embodiment, the boundary portion of the lens is a region above the boundary region of the emission surface 51, and it is a region where light from the point light source 30 is hard to reach and is likely to be dark when the point light source 30 is lit. is there.

Third Embodiment
Next, a lens 50C according to a third embodiment will be described with reference to FIGS. FIG. 11 is a schematic cross-sectional view of a lens 50C according to the third embodiment, which corresponds to the cross-sectional view along the line B-B shown in FIG. FIG. 12 is a perspective view of the lens 50C according to the third embodiment as viewed from the back surface 54c side. FIG. 13 is a view showing light distribution characteristics of the lens 50C according to the third embodiment.

  The lens 50C according to the third embodiment is a lens that covers one point light source 30 alone as in the lens 50 according to the first embodiment. The lens 50C according to the third embodiment is different in that the shapes of the lens 50 according to the first embodiment shown in FIG. 6 and the back surface 54c are different.

  The lens 50C according to the third embodiment includes a transmitting portion 52c, a recess 53c, and a flat portion 57c on the emission surface 51c, and a reflecting portion 55c on the back surface 54c. In addition, the lens 50C according to the third embodiment protrudes from the end of the back surface 54c toward the center in a bowl shape, and such a bowl-shaped tip is formed in a flat shape, for example.

  More specifically, as shown in FIG. 12, the back surface 54c has slopes 58 which are inclined from the respective end sides of the ridge toward the center. Moreover, in the example shown in FIG. 12, in the back surface 54c, although the front-end | tip of a ridge is a substantially plane, it is not limited to this. For example, such a tip may be dome-shaped or the like. Further, in the example shown in FIG. 12, in the lens 50C according to the third embodiment, the back surface 54c is formed in a pyramid shape, but it is not limited to this.

  Subsequently, the light distribution characteristic of the lens 50C according to the third embodiment will be described with reference to FIG. In addition, in FIG. 13, in order to simplify the description, the description of the transmitting portion 52c and the reflecting portion 55c is omitted.

  As shown in FIG. 13, light emitted from the point light source 30 enters the lens 50C from the back surface 54c. Then, the light which injected into the lens 50C is reflected by the recessed part 53c at the back surface 54c side. At this time, such light enters the inclined portion 58 with a predetermined incident angle. Thereby, the light reflected to the back surface 54 c side by the emission surface 51 c is reflected again to the emission surface 51 c side by the inclined portion 58.

  That is, the lens 50C according to the third embodiment promotes total reflection by the inclined portion 58 by providing the inclined portion 58 on the back surface 54c. That is, the inclined portion 58 suppresses transmission of light from the back surface 54c to the point light source 30 side. Thereby, the lens 50C according to the third embodiment can improve the emission efficiency and the luminance. Further, the inclined portion 58 can suppress leakage of light to the adjacent lens 50C. Therefore, the lens 50C according to the third embodiment can also improve the contrast when the point light sources 30 are individually lit. It is.

  As described above, the lens 50C according to the third embodiment further includes the transmitting portion 52c on the emission surface 51c and the reflecting portion 55c on the back surface 54c. The transmitting portion 52c refracts and transmits a part of the emitted light, thereby promoting the emission of the light to the boundary with the adjacent lens 50C, and making it possible to make the luminance of the emission surface 51c uniform. The reflection portion 55c suppresses the emission of light from the back surface 54c, and reflects the light toward the emission surface 51c.

  That is, in the lens 50C according to the third embodiment, by providing the sloped portion 58 on the back surface 54c in addition to the reflective portion 55c, light is reflected toward the emission surface 51c at both the reflective portion 55c and the sloped portion 58. Do.

  As a result, the lens 50C according to the third embodiment can improve the uniformity of luminance similarly to the lenses 50 and 50B according to the first and second embodiments. Further, the lens 50C according to the third embodiment can suppress leakage of light from the back surface 54c and light guided to the adjacent lens 50C by the inclined portion 58. Therefore, the emission efficiency can be improved and the luminance can be made uniform. Furthermore, it becomes possible to improve the contrast when the point light sources 30 are individually turned on.

Fourth Embodiment
Next, a lens 50D according to a fourth embodiment will be described using FIGS. 14 and 15. FIG. FIG. 14 is a schematic cross-sectional view of a lens 50D according to the fourth embodiment, which corresponds to a schematic cross-sectional view along the line C-C shown in FIG. FIG. 15 is a perspective view of the lens 50D according to the fourth embodiment as viewed from the back surface 54d side.

  As shown in FIG. 14, in the lens 50D according to the fourth embodiment, the shapes of the lens 50B and the back surface 54d already described in FIG. 10 are different. That is, in the lens 50D according to the fourth embodiment, the transmitting portion 52d, the recess 53d, and the flat portion 57d are formed on the emission surface 51d, and the reflecting portion 55d is formed on the back surface 54d.

  In addition, the back surface 54d is the same in shape with respect to one point light source 30 as the lens 50C according to the third embodiment already described with reference to FIG. That is, as shown in FIG. 15, in the lens 50 </ b> D according to the fourth embodiment, the back surface 54 d has a shape projecting in a bowl shape toward each point light source 30. For example, the back surface 54d is configured by four inclined portions 58d with one ridge. A point light source 30 is disposed on the tip end side of the crucible.

  In the lens 50D according to the fourth embodiment, the inclined portion 58d can suppress transmission of light from the back surface 54d side. In addition, the lens 50D according to the fourth embodiment further includes a transmitting portion 52d on the emission surface 51d and a reflecting portion 55d on the back surface 54d.

  Therefore, the lens 50D according to the fourth embodiment improves the uniformity of the luminance as well as the lens 50C according to the third embodiment, and improves the emission efficiency and the contrast when the point light sources 30 are individually lit. It is possible to

  The present invention is not limited by the above embodiment. The present invention also includes those configured by appropriately combining the above-described components. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above embodiment, and various modifications are possible.

  Reference Signs List 1 planar illumination device, 20 substrates, 30 point light source, 40 reflectors, 50 lenses, 52 transmitting portions, 53 recessed portions, 55 reflecting portions, 57 flat portions

Claims (14)

A reflecting portion provided on a back surface that is a main surface facing a point light source, and reflecting light reflected to the back surface side from an emitting surface that is a main surface facing the back surface to the emitting surface side;
A recessed portion recessed in the thickness direction from the light emission surface at a portion immediately above the point light source;
A transmitting portion provided at an outer peripheral portion of the recess and transmitting light from the emission surface. The lens is
Provided for each point light source,
The transparent portion is
The lens according to claim 1, wherein the lens abuts on each side of the exit surface. The transparent portion is
The lens according to claim 1 or 2, which is a linear protrusion having a straight line in cross section and protruding from the light emitting surface. The transparent portion is
The lens according to claim 1 or 2, which is a streak-like protrusion having a curve in a cross section and protruding from the emission surface. The transparent portion is
The lens according to any one of claims 1 to 4, which is formed concentrically. The recess is
The cross-sectional shape is a substantially inverted conical shape,
The lens according to any one of claims 1 to 5. The lens is
The lens according to any one of claims 1 to 6, which covers a plurality of point light sources arranged in the lateral direction among the point light sources arranged in a lattice. The lens is
Substantially rectangular in top view,
The transparent portion is
The lens according to claim 7, wherein the lens is provided in a boundary area of the point light sources adjacent to each other. A substrate having a main surface on which a plurality of point light sources are mounted in a grid shape;
A plurality of lenses provided for each of the point light sources;
A planar illumination device comprising: a frame for containing the substrate and the plurality of lenses;
The lens is
A reflecting portion provided on a back surface that is a main surface facing the point light source, and reflecting light reflected to the back surface side from an emitting surface that is a main surface facing the back surface to the emitting surface side;
A recessed portion recessed in the thickness direction from the light emission surface at a portion immediately above the point light source;
A planar illumination device comprising: a transmitting portion provided on an outer peripheral portion of the recess and transmitting light from the emission surface. The transmission part of the lens is
The planar illumination device according to claim 9, wherein the planar illumination device abuts on each side of the emission surface. The transmission part of the lens is
The planar illumination device according to claim 9 or 10, wherein the projection is a linear projection having a straight line in cross section and protruding from the exit surface. The transmission part of the lens is
The planar illumination device according to claim 9, wherein the planar illumination device has a curvilinear cross section and is a stripe-like protrusion protruding from the exit surface. The transmission part of the lens is
The planar illuminating device as described in any one of Claims 9-12 formed concentrically. The recess of the lens is
The cross-sectional shape is a substantially inverted conical shape,
The planar illumination device as described in any one of Claims 9-13.

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