Surface illumination device

Abstract

To achieve appearances from two directions simultaneously, and to improve non-uniformity in luminance in each of the directions.SOLUTION: A planar illumination device according to an embodiment includes: a plurality of light sources aligned two-dimensionally; a first optical element provided on a light emission side of the light source for collecting the light emitted from the plurality of light sources; and a fourth optical element in which a second optical element, which is provided on the light emission side of the first optical element and inclines light distribution of the light collected by the first optical element in one direction is combined with a third optical element which expands the light collected by the first optical element in the one direction. The fourth optical element has different contact angles depending on a position in the segment defined by each of the light sources.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a planar lighting device.

Background Art

[0002] A so-called direct-type planar lighting device having a substrate on which a plurality of light sources are two-dimensionally arranged and a reflector disposed on the substrate and having a reflecting surface surrounding the emission side of each light source is known. In such a direct-type planar lighting device, light from a light source is condensed by a linear Fresnel lens in which grooves of unevenness extend in one direction (for example, the horizontal direction, the lateral direction when visually observing the emission surface directly or indirectly from a user), and the optical axis is tilted by a peak shift prism in which grooves of unevenness extend in the same direction as the linear Fresnel lens, and narrow light distribution may be realized in a direction orthogonal to the grooves (for example, the vertical direction). A direct-type planar lighting device provided with a linear Fresnel lens and a peak shift prism is used, for example, in a head-up display (HUD) that requires high brightness.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, generally, in a display device including an HUD, browsing from two directions such as the front direction (H = 0 deg) and the oblique direction (for example, H = 30 deg) is assumed, and a backlight (planar lighting device) that illuminates a liquid crystal display panel as a display device is required to achieve good appearance from two directions while improving luminance non-uniformity in each direction. For this reason, various improvement methods have been proposed for planar lighting devices, but further improvement is desired.

[0005] The problem that this invention aims to solve is to provide a planar lighting device that can improve the non-uniformity of brightness in each direction while maintaining a good appearance from two directions. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, a planar illumination device according to one aspect of the present invention , multiple The device comprises several light sources, a first optical element positioned on the emission side of the light sources and collecting the light emitted from the multiple light sources, a second optical element positioned on the emission side of the first optical element and tilting the light distribution of the light collected by the first optical element in one direction, and a fourth optical element which is a composite of a third optical element that spreads the light collected by the first optical element in the one direction, The second optical element tilts the optical axis of the light emitted from the fourth optical element in a direction different from the optical axis of the light incident on the fourth optical element. The fourth optical element has different contact angles depending on its position within the segment defined by each light source. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the configuration of a planar illumination device according to an embodiment. [Figure 2] Figure 2 is a diagram illustrating an example of the configuration of a light distribution lens according to an embodiment. [Figure 3A] Figure 3A shows an example of the luminance distribution using a composite prism in a comparative example. [Figure 3B] Figure 3B shows an example of the luminance distribution using a composite prism in a comparative example. [Figure 4A] Figure 4A shows an example of relative brightness due to a composite prism in the comparative example. [Figure 4B] Figure 4B shows an example of relative brightness due to a composite prism in the comparative example. [Figure 5] Figure 5 illustrates the decrease in brightness in the upper subregion S1 in the front view. [Figure 6]Figure 6 is a diagram illustrating the continuous change in the contact angle depending on the position of the composite prism according to the embodiment. [Figure 7A] Figure 7A shows an example of the luminance distribution using a composite prism according to the embodiment. [Figure 7B] Figure 7B shows an example of the luminance distribution using a composite prism according to the embodiment. [Figure 8A] Figure 8A shows an example of relative brightness using a composite prism according to an embodiment. [Figure 8B] Figure 8B shows an example of relative brightness using a composite prism according to the embodiment. [Figure 9A] Figure 9A is a diagram illustrating the effects of the planar illumination device according to the embodiment. [Figure 9B] Figure 9B is a diagram illustrating the effects of the planar illumination device according to the embodiment. [Modes for carrying out the invention]

[0008] The following description of a planar illumination device according to an embodiment will be given with reference to the drawings. However, this embodiment does not limit the present invention. Furthermore, the dimensional relationships and ratios of the elements in the drawings may differ from reality. There may also be differences in dimensional relationships and ratios between different drawings. In principle, the contents described in one embodiment or modification apply similarly to other embodiments and modifications.

[0009] FIG. 1 is a diagram showing a configuration example of the planar lighting device 1 according to the embodiment, and is an end view showing the state inside the thickness. For convenience, the light emitting surface of the planar lighting device 1 is in the X-Y plane, and the thickness direction of the planar lighting device 1 is the Z direction. Further, in the usage state where the light emitted by the planar lighting device 1 is incident on a liquid crystal panel (not shown) or the like mounted on the planar lighting device 1 and is visible to the user, the X-axis direction corresponds to the horizontal direction (H), and the Y-axis direction corresponds to the vertical direction (V). Specifically, in the usage state of the planar lighting device 1, the positive Y-axis side corresponds to the "upper side", and the negative Y-axis side corresponds to the "lower side". Note that the usage state of the planar lighting device 1 is not limited to the above directions, and it can be used in any direction.

[0010] In this embodiment, the planar lighting device 1 is assumed to be viewed from two directions, the front direction (H = 0 deg) and the diagonal direction (H = 30 deg), and the case where the optical axis of the emitted light is inclined (peak shift) in the V = -12 deg direction will be described, but the present invention is not limited to this.

[0011] As shown in FIG. 1, the planar lighting device 1 includes a bottom frame 2, a substrate 3, a light source 4, a reflector 5, a condenser lens 6, a light distribution lens 7, and a reflective polarizing film 8.

[0012] The bottom frame 2 is a substantially bottomed box-shaped member that houses the substrate 3 and the like described later. The bottom frame 2 forms the exterior of the planar lighting device 1 by being fitted with a top frame (not shown) provided with an opening for emitting light. Although not described in detail, the bottom frame 2 is appropriately provided with a structure (protrusions, holes, etc.) for housing the substrate 3 and other members, and a connector for electrical connection.

[0013] The substrate 3 is provided at the bottom of the bottom frame 2 and is a member provided with electronic components such as the light source 4 described later.

[0014] The light source 4 is composed of an LED (Light Emitting Diode) or the like, and a plurality of them are arranged two-dimensionally (e.g., in a grid pattern) on the substrate 3. The light source 4 preferably has a light distribution called, for example, a top hat type. Further, each of the plurality of light sources 4 can be individually driven and can support so-called local dimming driving.

[0015] The reflector 5 is arranged on the side of the substrate 3 where the light source 4 is arranged, and includes a reflecting wall 51 extending along the Y-axis direction and a reflecting wall 52 extending along the X-axis direction. The reflector 5 forms a reflecting surface that surrounds the emission side of each individual light source 4 in a rectangular shape by arranging the reflecting wall 51 and the reflecting wall 52 at equal intervals between each of the plurality of light sources 4. Thereby, the contrast when the plurality of light sources 4 are driven by local dimming can be improved. The unit area in which each individual light source 4 is separated by the reflector 5 is described as a "segment (or zone)". Also, the height of the reflector 5 can be arbitrarily set, but in order to reduce stray light, it is preferable that the reflecting wall 52 is higher than the reflecting wall 51 as shown in the figure.

[0016] The condenser lens 6 is an optical member arranged on the emission side of the reflector 5 and condenses the light from the light source 4 in the Y-axis direction. For example, the condenser lens 6 is an optical member having a lenticular lens with uneven grooves extending along the Y-axis direction in the incident surface and a linear Fresnel lens (corresponding to the first optical element) with uneven grooves extending along the X-axis direction in the emission surface. The grooves of the linear Fresnel lens are periodically formed in accordance with the interval (pitch) of the plurality of light sources 4.

[0017] The light distribution lens 7 is positioned on the exit side of the condensing lens 6 and is an optical element that tilts the light distribution of the light focused by the condensing lens 6 in the Y-axis direction. For example, the light distribution lens 7 has a composite prism in which a linear prism with uneven grooves extending along the X-axis direction within the incident plane and a lenticular lens with uneven grooves extending along the X-axis direction are combined. With this configuration, the composite prism can simultaneously realize the function of a linear prism that tilts the light (peak shift in the V=-12deg direction) and the function of a lenticular lens that spreads the light. In addition, the light distribution lens 7 has a lenticular lens with uneven grooves extending along the Y-axis direction within the exit plane.

[0018] In this embodiment, the composite prism has a pitch smaller than the pitch of the light source 4 (i.e., multiple composite prisms exist within a single segment), and has different contact angles depending on its position in the Y-axis direction within the segment S defined by each light source 4. The configuration example and contact angle of the light distribution lens 7 will be described in detail later.

[0019] The reflective polarizing film 8 is an optical component positioned on the output side of the light distribution lens 7 to improve the brightness of the output light. The reflective polarizing film 8 is made of, for example, a roughly plate-shaped DBEF (Dual Brightness Enhancement Film) and has polarization that matches the liquid crystal panel provided on the output side of the surface illumination device 1.

[0020] Figure 2 is a diagram illustrating an example configuration of the light distribution lens 7 according to the embodiment. The right side of Figure 2 shows an example of the light distribution lens 7 according to the embodiment. The left side of Figure 2 shows an example of the light distribution lens 7' according to a comparative example. Note that "upper side" in Figure 2 corresponds to the "upper side" in the operating state of the surface illumination device 1, and "lower side" in Figure 2 corresponds to the "lower side" in the operating state of the surface illumination device 1.

[0021] In Figure 2, when linear prisms 71a and 71b are referred to collectively without distinction, they are written as "linear prism 71". Similarly, when lenticular lenses 72a and 72b are referred to collectively without distinction, they are written as "lenticular lens 72". Furthermore, when composite prisms 73a and 73b are referred to collectively without distinction, they are written as "composite prism 73".

[0022] As shown in Figure 2, the optical distribution lens 7 has a composite prism 73 (corresponding to the fourth optical element) which is a combination of a linear prism 71 (corresponding to the second optical element) with a triangular cross-section that tilts the optical distribution of the light focused by the condensing lens 6 in the Y-axis direction (for example, tilted in the direction of V = -12deg) and a lenticular lens 72 (corresponding to the third optical element) with an arc cross-section that spreads the light focused by the condensing lens 6 in the Y-axis direction. Specifically, the composite prism 73 is an optical element in which a lenticular lens 72 extending in the X-axis direction is formed on the main surface of the linear prism 71 extending in the X-axis direction, and multiple composite prisms are arranged in the Y-axis direction. The main surface of the linear prism 71 is the slope with the smaller inclination angle of a pair of inclined surfaces. In this embodiment, the lenticular lens 72 is formed as a curved surface (circular arc cross-section) with a constant curvature R, starting from the vertex side of the main surface of the linear prism 71, and is convex outward. Furthermore, although Figure 2 shows a boundary line between the linear prism 71 and the lenticular lens 72, in reality, since the two are molded as a single unit, no boundary line exists.

[0023] Furthermore, the light distribution lens 7' has a composite prism 73' which is a combination of a linear prism 71' and a lenticular lens 72'. Here, the basic configuration of the linear prism 71', lenticular lens 72', and composite prism 73' is the same as that of the linear prism 71, lenticular lens 72, and composite prism 73, so a detailed explanation is omitted.

[0024] Here, the height H and pitch length L of all composite prisms 73' in the optical distribution lens 7' of the comparative example are constant at any position within segment S. Therefore, the contact angle, which is the angle between the curved surface of the lenticular lens 72' in the composite prism 73' and the plane (XY plane) of the base portion of the optical distribution lens 7', is uniform regardless of the composite prism 73'.

[0025] On the other hand, the light distribution lens 7 according to this embodiment has different contact angles depending on its position within the segment S. In the example in Figure 2, the contact angle θa of the composite prism 73a is greater than the contact angle θb of the composite prism 73b. Since a larger contact angle increases the degree of light diffusion passing through a curved surface, the degree of light diffusion emitted from the composite prism 73a is greater than the degree of light diffusion emitted from the composite prism 73b.

[0026] Incidentally, in this embodiment, the contact angle of the composite prism 73 can be arbitrarily changed (designed) by varying the height to the vertex of each prism, since the curvature of the curved surface is constant. For example, in the manufacturing of a mold for forming the light distribution lens 7 by injection molding, the height of each composite prism 73 can be varied by varying the depth of the cutting tool (bit) used to cut the uneven surface of each composite prism 73. In this case, since the same cutting tool is used, the contact angle changes according to the height (depth of the mold groove), and the higher the height (deeper the mold groove), the larger the contact angle. In the example in Figure 2, by making the height Ha of the composite prism 73 higher than the height Hb of the composite prism 73b, the contact angle θa can be designed to be larger than the contact angle θb. The contact angle is calculated, for example, by the θ / 2 method, but known calculation methods can be applied as appropriate.

[0027] Furthermore, since the height Hb of the composite prism 73b is Δh smaller than the height Ha, the pitch length Lb of the composite prism 73b also becomes Δl shorter than the length La. For this reason, it is preferable to place the composite prisms 73a and 73b close together so that no flat area (a portion where the composite prism 73 is not placed) is created between them.

[0028] Figures 3A and 3B show examples of luminance distribution using the composite prism 73' in the comparative example. Figures 4A and 4B show examples of relative luminance using the composite prism 73' in the comparative example. Figure 3A illustrates the luminance distribution in the forward direction (H=0deg), and Figure 3B illustrates the luminance distribution in the diagonal direction (H=30deg). In Figures 3A and 3B, "S" represents a segment, "S1" represents the upper subregion of segment S, and "S2" represents the lower subregion of segment S. Figures 4A and 4B illustrate the relative luminance for each position in the H and V directions.

[0029] As shown in Figures 3A and 4A, in the frontal direction, the upper subregion S1 was found to have the lowest brightness among the segments S. The lower subregion S2 was found to have the second lowest brightness after subregion S1. Furthermore, as shown in Figures 3B and 4B, in the diagonal direction, the ends of the segments S (subregions S1 and S2) were both found to have low brightness.

[0030] Figure 5 illustrates the decrease in brightness in the upper subregion S1 in the front direction. As shown in Figure 5, the optical distribution lens 7' is required to tilt the optical axis downward (negative Y-axis direction, V=-12deg direction), but the preceding condensing lens 6 is designed to be vertically symmetrical with respect to the optical axis and to spread (defocus) the light somewhat. Therefore, in the upper subregion S1, light mainly directed upward is emitted, and in the lower subregion S2, light mainly directed downward is emitted.

[0031] In this case, in subregion S1, upward-facing light may occur on the vertical surface 7'-2 of the light distribution lens 7' (composite prism 73') instead of the main surface 7'-1, resulting in the light distribution performance of the light distribution lens 7' not being properly utilized. Furthermore, even if the light occurs on the main surface 7'-1, it is difficult to tilt it in the desired direction (V=-12deg direction), so the brightness is likely to decrease in the upper subregion S1. In subregion S2, although there is more downward-facing light, making it easier for light to occur on the main surface 7'-1 compared to subregion S1, it is still difficult to tilt the incident light in the desired direction unless the incident light is nearly parallel.

[0032] Therefore, in order to compensate for the light distribution performance of the composite prism 73', the composite prism 73 is configured to have different contact angles and different heights (vertex positions) depending on the position within the segment S.

[0033] Figure 6 is a diagram illustrating the continuous change in the contact angle depending on the position of the composite prism 73 according to the embodiment. Figure 6 shows an example graph of the magnitude of the contact angle with respect to the vertex position of the composite prism 73 in the Y-axis direction.

[0034] As shown in Figure 6, the contact angle of the composite prism 73 in the subregion S1 is configured to be smaller compared to other regions. For example, the minimum contact angle in subregion S1 is 15.2 degrees. This suppresses the degree of diffusion in subregion S1, which is expected to improve brightness and reduce the dark lines that were present in the composite prism 73'.

[0035] Furthermore, the contact angle of the composite prism 73 near the center is configured to be larger compared to other regions. For example, the maximum contact angle near the center is 15.9 degrees. This increases the degree of diffusion near the center, which is expected to suppress brightness near the center and improve brightness uniformity in segment S.

[0036] Furthermore, the contact angle of the composite prism 73 on the lower side of the optical axis is configured to be generally larger than that on the upper side. This is because the brightness on the lower side of the optical axis tends to be higher than that on the upper side. In other words, this configuration increases the degree of diffusion on the lower side of the optical axis, which is expected to suppress the brightness on the lower side of the optical axis and improve the brightness uniformity in segment S.

[0037] Furthermore, the contact angle of the composite prism 73 in the subregion S2 is configured to be smaller than that near the center, but larger than that of other regions. This increases the degree of diffusion in the subregion S2, which is expected to suppress the brightness of the subregion S2 and improve the emission lines that were present in the composite prism 73'.

[0038] Figures 7A and 7B show an example of the luminance distribution by the composite prism 73 according to the embodiment. Figures 8A and 8B show an example of the relative luminance by the composite prism 73 according to the embodiment. Figure 7A illustrates the luminance distribution in the forward direction (H=0deg), and Figure 7B illustrates the luminance distribution in the oblique direction (H=30deg). Figures 8A and 8B illustrate the relative luminance for each position in the H direction and V direction.

[0039] As shown in Figures 7A to 8B, the luminance fluctuation range was small in both the frontal and oblique directions, and it was found that the bright and dark lines that occurred in the comparative example (composite prism 73') were improved.

[0040] Figures 9A and 9B are diagrams illustrating the effects of the planar illumination device 1 according to the embodiment. Figures 9A and 9B illustrate the results of comparing the relative brightness of the composite prism 73 (planar illumination device 1) and the composite prism 73' (comparative example) with respect to the V cross-section.

[0041] As shown in Figures 9A and 9B, in the forward direction (H=0deg), applying the composite prism 73 improved the relative brightness by up to approximately 2%. In the oblique direction (H=30deg), applying the composite prism 73 improved the relative brightness by up to approximately 4%. Furthermore, it was found that the improvement in appearance due to the composite prism 73 can be obtained regardless of the light distribution characteristics of the light source 4.

[0042] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention.

[0043] As described above, the planar illumination device according to the embodiment comprises a plurality of light sources arranged in two dimensions, a first optical element positioned on the emission side of the light sources and concentrating the light emitted from the plurality of light sources, a second optical element positioned on the emission side of the first optical element and tilting the light distribution of the light concentrated by the first optical element in one direction, and a fourth optical element which is a composite of a third optical element and a first optical element which spreads the light concentrated by the first optical element in the one direction, wherein the fourth optical element has different contact angles depending on its position within the segment defined by each light source. As a result, the planar illumination device can precisely improve the non-uniformity of brightness in each direction without using new materials, while maintaining a good appearance from two directions.

[0044] Furthermore, the aforementioned first direction is a first direction (for example, the Y-axis direction), and the fourth optical element is an optical element in which the third optical element, which has a circular arc cross-section extending along the second direction, is formed on one surface of the second optical element, which has a triangular cross-section extending along the second direction, and which has a triangular cross-section extending along the second direction. As a result, the planar illumination device can improve, for example, the non-uniformity of brightness in the Y-axis direction.

[0045] Furthermore, the fourth optical elements are arranged in multiples in the one direction, and the multiple fourth optical elements have different contact angles with each other because the curvature of the curved surface of the third optical element is constant, and the height to the vertex of each fourth optical element differs depending on its position in the one direction within the segment. As a result, the planar illumination device can improve the non-uniformity of brightness, particularly in the one direction.

[0046] Furthermore, the plurality of fourth optical elements have a large contact angle near the center in the one direction within the segment. As a result, the degree of diffusion near the center is increased, which suppresses the brightness near the center and improves the brightness uniformity in segment S.

[0047] Furthermore, the multiple fourth optical elements have a small contact angle near the end (partial region S1) within the segment that is opposite to the inclination direction side (e.g., downward side / negative Y-axis direction) caused by the second optical element. As a result, the degree of diffusion near the end is suppressed, which improves brightness and eliminates the dark lines that occurred in the comparative example.

[0048] Furthermore, the contact angle of the plurality of fourth optical elements on the side of the segment facing the inclination direction with respect to the second optical element is greater than the contact angle on the opposite side (upper side) from the inclination direction. As a result, the degree of diffusion on the lower side of the optical axis is increased, which suppresses the brightness on the lower side of the optical axis and improves the brightness uniformity in the segment.

[0049] Furthermore, the multiple fourth optical elements have a large contact angle near the end of the segment on the side of the inclination direction by the second optical element (partial region S2). As a result, the degree of diffusion in partial region S2 increases, which suppresses the brightness of partial region S2 and improves the emission lines that occurred in the comparative example.

[0050] Furthermore, the present invention is not limited to the embodiments described above. Configurations that appropriately combine the above-described components are also included in the present invention. Moreover, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the embodiments described above, and various modifications are possible. [Explanation of Symbols]

[0051] 1. Planar illumination device, 2. Bottom frame, 3. Substrate, 4. Light source, 5. Reflector, 51, 52. Reflective wall, 6. Focusing lens, 7. Light distribution lens, 71. Linear prism, 72. Lenticular lens, 73. Compound prism, 8. Reflective polarizing film

Claims

1. Multiple light sources, A first optical element is positioned on the emission side of the light source and collects the light emitted from the plurality of light sources, A fourth optical element is formed by combining a second optical element positioned on the output side of the first optical element and tilting the light distribution of the light focused by the first optical element in one direction, and a third optical element that spreads the light focused by the first optical element in the aforementioned one direction. Equipped with, The second optical element tilts the optical axis of the light emitted from the fourth optical element in a direction different from the optical axis of the light incident on the fourth optical element. The fourth optical element has different contact angles depending on its position within the segment defined by each light source. Surface illumination device.

2. The second optical element is arranged in a plurality within the segment, Each of the plurality of second optical elements tilts the light incident on the second optical element to one side in the first direction within the segment. The planar illumination device according to claim 1.

3. The fourth optical element is arranged in a plurality in the one direction, The main surface of each of the composite prisms constituting the plurality of fourth optical elements is arranged facing one side in the aforementioned direction. The planar illumination device according to claim 1.

4. Multiple light sources, A first optical element is positioned on the emission side of the light source and collects the light emitted from the plurality of light sources, A fourth optical element is formed by combining a second optical element positioned on the output side of the first optical element and tilting the light distribution of the light focused by the first optical element in one direction, and a third optical element that spreads the light focused by the first optical element in the aforementioned one direction. Equipped with, The fourth optical element has different contact angles depending on its position in one direction within the segment, so that the brightness within the segment defined by each light source is uniform. Surface illumination device.

5. The contact angles of the plurality of fourth optical elements within the segment are asymmetric with respect to the center in one direction within the segment. The planar illumination device according to claim 4.

6. The aforementioned direction one is the first direction, The fourth optical element is an optical element in which a third optical element, having a circular arc-shaped cross-section extending along the second direction, is formed on one surface of a second optical element, which has a triangular cross-section extending along the second direction. The planar illumination device according to claim 1 or 4.

7. The fourth optical element is arranged in multiples in the one direction, The plurality of fourth optical elements have different contact angles with each other, such that the curvature of the curved surface of the third optical element is constant, and the height to the vertex of each fourth optical element differs depending on its position in one direction within the segment. The planar illumination device according to claim 1 or 4.

8. Among the plurality of positions in the one direction within the segment, the fourth optical element corresponding to the position where the brightness is higher compared to the other positions when the contact angles of the plurality of fourth optical elements are constant has a larger contact angle than the fourth optical element corresponding to the other positions. Among the multiple positions in the one direction within the segment, the fourth optical element corresponding to the position with lower brightness compared to the other positions when the contact angles of the multiple fourth optical elements are constant has a smaller contact angle than the fourth optical element corresponding to the other positions. The planar illumination device according to claim 1 or 4.

9. The plurality of fourth optical elements have a contact angle near the center in one direction within the segment that is greater than the contact angles near both ends in the same direction within the segment. The planar illumination device according to claim 1 or 4.

10. The plurality of fourth optical elements have a contact angle near the end of the segment opposite to the side inclined by the second optical element that is smaller than the contact angle near the other end. The planar illumination device according to claim 1 or 4.

11. The plurality of fourth optical elements are such that the contact angle on the side of the segment facing the inclination direction by the second optical element is greater than the contact angle on the side opposite to the inclination direction. The planar illumination device according to claim 1 or 4.

12. The plurality of fourth optical elements have a contact angle near the end of the segment on the side facing the inclination direction of the second optical element that is greater than the contact angle near the end on the side opposite to the inclination direction. The planar illumination device according to claim 1 or 4.

13. The plurality of light sources are arranged in a grid pattern. The planar illumination device according to claim 1 or 4.

14. Each of the plurality of light sources is enclosed in a rectangular shape by the reflective surface of the reflector, defining the segment. The planar illumination device according to claim 1 or 4.

Images