Surface light source device, display device and light flux control member

Abstract

To provide a surface light source device capable of suppressing deterioration of image quality.SOLUTION: In a surface light source device having a plurality of light-emitting devices arranged on an XY plane of an XYZ coordinate system that defines an X direction, a Y direction and a Z direction orthogonal to each other, and a light diffusion plate arranged at a distance in the Z direction from the XY plane, each of the plurality of light-emitting devices has a light-emitting element, and a light flux control member for controlling light from the light-emitting element, and satisfies a condition 1, a condition 2, and a condition 3-1 or 3-2.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a surface light source device, a display device, and a light beam control member.

Background Art

[0002] Transmissive image display devices such as liquid crystal display devices are known. In a transmissive image display device, an image is displayed when light from a surface light source device hits a display member. For example, Patent Document 1 discloses such a surface light source device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] FIG. 1 shows a cross-sectional view of a surface light source device 10 as described above. As shown in FIG. 1, the surface light source device 10 includes a plurality of light-emitting devices 20 and a light diffusion plate 11 that diffuses light from the plurality of light-emitting devices 20. As shown in FIG. 1, in the surface light source device 10, when the plane in which the plurality of light-emitting devices 20 are arranged is defined as the XY plane, the light diffusion plate 11 is arranged at a distance in the Z direction. In the surface light source device 10, light from the plurality of light-emitting devices 20 is diffused by the light diffusion plate 11 to form planar light.

[0005] Here, when the light diffusion plate 11 is, for example, bent, the distance between the light diffusion plate 11 and the XY plane in which the light-emitting device 20 is arranged changes. More specifically, if the Z-direction distance OD between the light-reaching surface 11a located on the light-emitting device 20 side of the light diffusion plate 11 and the XY plane in which the light-emitting device 20 is arranged changes, unevenness occurs in the light emitted from the surface light source device 10, and the quality of the image in a display device such as a liquid crystal display device may deteriorate.

[0006] An object of the present invention is to provide a surface light source device, a display device, and a light flux control member used in the surface light source device, in which deterioration of image quality is suppressed even when the distance between the light-reaching surface of a light diffusing plate and the plane on which a light-emitting device is arranged changes.

Means for Solving the Problems

[0007] The present invention relates to the following surface light source device, display device, and light flux control member. [1]In a surface light source device having a plurality of light emitting devices arranged on the XY plane of XYZ coordinates defining X, Y, and Z directions orthogonal to each other, and a light diffusion plate arranged at a distance from the XY plane in the Z direction, each of the plurality of light emitting devices has a light emitting element and a light flux control member for controlling the light from the light emitting element. The light flux control member has an incident surface on which the light from the light emitting element is incident, a total reflection surface on which a part of the light incident from the incident surface is reflected, and an exit surface arranged around the total reflection surface. The plurality of light emitting devices are arranged in rows in the X direction and the Y direction. When the center-to-center distance between adjacent light emitting devices among the plurality of light emitting devices arranged in the X direction is Px, and the center-to-center distance between adjacent light emitting devices among the plurality of light emitting devices arranged in the Y direction is Py, Py > Px. Among the plurality of light emitting devices, with a line along the optical axis OA of the light emitting element of an arbitrary light emitting device as a reference line L1, the intersection point of the reference line L1 and the light arrival surface located on the light emitting device side of the light diffusion plate is defined as a first reference point P1. When the angle of the light emitted from the light emitting element along the reference line L1 is set to 0°, for the light emitted from the light emitting element corresponding to the arbitrary light emitting device at an angle of 0° to 90°, in a graph showing the light distribution characteristics on the YZ cross-section regarding the light emission luminous intensity from the light emitting device, the position on the light arrival surface where the light ray corresponding to the luminous intensity peak arrives exists in the range of Py / 3 or more and Py or less from the first reference point P1. The light emitted from an arbitrary light emitting element, reflected by the total reflection surface, and reaching the exit surface is emitted from the exit surface at an angle greater than 90° with respect to the reference line L1. The intersection point of the reference line L1 and the XY plane is defined as a second reference point P2. Using the second reference point P2 as one vertex, when a rectangle having two sides of length Px and Py on the XY plane is divided by the diagonal of the rectangle passing through the second reference point P2, when comparing the amount of light reaching the total reflection surface in a triangular region A having the second reference point P2 at the end point of the side of length Px and a triangular region B having the second reference point P2 at the end point of the side of length Py, more light reaches the triangular region B than the triangular region A. In a graph of the luminance distribution showing the change in luminance on the straight line along the Y direction passing through the second reference point P2 for the light reflected by the total reflection surface and reaching the XY plane,(A) The position of the luminance peak top in the Y direction is farther from the second reference point than the distance D between the center of the light beam control member along the Y direction and the outer edge of the light beam control member, or (B) When a line segment corresponding to the half-value width of the luminance peak is divided into a first divided line segment W1 that is closer to the reference line L1 than the peak top in the Y direction and a second divided line segment W2 that is farther from the reference line L1 than the peak top in the Y direction, the length of the second divided line segment W2 is 1.5 times or more the length of the first divided line segment W1. A surface light source device. [2] The surface light source device according to [1], wherein a shoulder peak exists in the graph of the luminance distribution. [3] A display device having the surface light source device according to [1] or [2]. [4] A light beam control member used in the surface light source device according to [1] or [2].

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a surface light source device, a display device, and a light beam control member used in the surface light source device that suppress a decrease in image quality even when the distance between the light-reaching surface of the light diffusion plate and the plane on which the light-emitting device is disposed changes.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, as a representative example of the surface light source device according to the present invention, a surface light source device suitable for a backlight of a liquid crystal display device or the like will be described. These surface light source devices can be used as a display device 100' by combining with a display member 102 (for example, a liquid crystal panel) irradiated with light from the surface light source device (see FIG. 2B).

[0011] [Embodiment] (Surface Light Source Device and Light Emitting Device) FIGS. 2A and 2B are diagrams showing the configuration of a surface light source device 100 according to an embodiment of the present invention. FIG. 2A is a plan view, and FIG. 2B is a front view. FIG. 3A is a schematic cross-sectional view taken along line A-A shown in FIG. 2B, showing the schematic arrangement of the light emitting devices 200. FIG. 3B is a schematic cross-sectional view taken along line B-B of FIG. 2A.

[0012] As shown in FIGS. 2A to 3B, the surface light source device 100 according to the present embodiment includes a housing 110, a plurality of light emitting devices 200, and a light diffusing plate 120. As shown in FIG. 3A, a plurality of light emitting devices 200 are arranged on the bottom plate 112 of the housing 110. The inner surface of the bottom plate 112 functions as a diffusing reflection surface. An opening is provided in the top plate 114 of the housing 110. The light diffusing plate 120 is arranged so as to close this opening and functions as a light emitting surface. The size of the light emitting surface is not particularly limited, but is, for example, about 800 mm × about 1450 mm.

[0013] As shown in FIG. 3A, in the present embodiment, the light emitting device 200 is fixed on a substrate 210 fixed at a predetermined position on the bottom plate 112 of the housing 110. In the present embodiment, the substrate 210 is bar-shaped and long in the X direction. The shape of the substrate is not limited to bar-shaped. One substrate including a region where the light emitting device 200 that is not functionally required is not arranged may be used. From the viewpoint of weight reduction, it is preferable to eliminate unnecessary substrate regions. A part of a plurality of bar-shaped substrates arranged parallel to the X axis may be connected by a substrate on which no light emitting device is arranged to form a comb-shaped single substrate.

[0014] As shown in FIGS. 3A and 3B, the surface light source device 100 of the present embodiment includes a plurality of light emitting devices 200 arranged on the XY plane of the XYZ coordinates defining the X direction, Y direction, and Z direction orthogonal to each other, and a light diffusion plate 120 arranged at a distance in the Z direction from the XY plane.

[0015] In the surface light source device 100, as shown in FIG. 3A, the plurality of light emitting devices 200 are arranged in rows in the X direction and the Y direction. When the center-to-center distance between adjacent light emitting devices 200 among the plurality of light emitting devices 200 arranged in the X direction is Px, and the center-to-center distance between adjacent light emitting devices among the plurality of light emitting devices 200 arranged in the Y direction is Py, Py > Px.

[0016] FIG. 4A is a diagram showing a cross section of the light emitting device 200 and the progress of light. As shown in FIG. 4A, the light emitting device 200 includes a light emitting element 220 arranged on the XY plane and a light flux control member (lens) 300 for controlling the light from the light emitting element 220.

[0017] Hereinafter, the light emitting element 220 and the light flux control member 300 included in the light emitting device 200 will be described.

[0018] (Light Emitting Element) The light emitting element 220 is a light source of the surface light source device 100 and is mounted on the substrate 210. The light emitting element 220 is a light emitting diode (LED) such as a white light emitting diode, for example. Also, the type of the light emitting element 220 is not particularly limited, but a light emitting element 220 that emits light from the top surface and the side surface (for example, a COB type light emitting diode) is preferably used in the light emitting device 200 according to the present embodiment. The size of the light emitting element 220 is not particularly limited, but is preferably 0.1 mm to 1.6 mm, and more preferably 0.2 mm to 0.7 mm. The substrate 210 is a rectangular substrate having the X direction as the long side and the short side shorter than Py, and a plurality of light emitting devices 220 are arranged on the substrate 210 in the X direction. A plurality of substrates 210 having the X direction as the long side are arranged at intervals in the Y direction. Alternatively, a plurality of substrates 210 having the Y direction as the long side may be arranged at intervals in the X direction.

[0019] (Optical beam control member) The optical beam control member 300 is an optical member that controls the light distribution of the light emitted from the light-emitting element 220. In the present embodiment, the optical beam control member 300 is fixed on the substrate 210. As shown in FIG. 4A, the optical beam control member 300 has an incident surface 310 on which the light from the light-emitting element 220 is incident, a total reflection surface 320 on which a part of the light incident from the incident surface 310 is reflected, and an emission surface 330 disposed around the total reflection surface 320. When the line along the optical axis OA of the light-emitting device is used as the reference line L1, the light reflected by the total reflection surface 320 and reaching the emission surface 330 is emitted from the emission surface at an angle greater than 90° with respect to the reference line L1.

[0020] The optical beam control member 300 is disposed on the light-emitting element 220 such that the central axis CA of the incident surface 310 coincides with the optical axis OA of each light-emitting element 220. Note that the "optical axis OA of the light-emitting element 220" means the central ray of the three-dimensional emission light beam from the light-emitting element 220. A gap may or may not be formed between the substrate 210 on which the light-emitting element 220 is mounted and the back surface of the optical beam control member 300 to release the heat generated from the light-emitting element 220 to the outside.

[0021] The optical beam control member 300 is formed by integral molding. The material of the optical beam control member 300 is not particularly limited as long as it is a material that can transmit light of a desired wavelength. For example, the material of the optical beam control member 300 is a light-transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), epoxy resin (EP), polystyrene (PS), styrene-methyl methacrylate copolymer resin (MS), silicone, or glass.

[0022] The specific configuration of the optical beam control member 300 will be described in detail separately.

[0023] The light diffusing plate 120 is a plate-shaped member having light diffusing properties, and transmits the light emitted from the light emitting device 200 while diffusing it. Usually, the light diffusing plate 120 has substantially the same size as a display member such as a liquid crystal panel. For example, the light diffusing plate 120 is formed of a light transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), or styrene-methyl methacrylate copolymer resin (MS). In order to impart light diffusing properties, fine irregularities are formed on the surface of the light diffusing plate 120, or light diffusing particles such as beads are dispersed inside the light diffusing plate 120.

[0024] In the surface light source device 100 according to the present embodiment, the light emitted from each light emitting element 220 is expanded by the light flux control member 300 so as to illuminate a wide range of the light diffusing plate 120. The light emitted from each light flux control member 300 is further diffused by the light diffusing plate 120. Most of the light reaching the light diffusing plate 120 passes through the light diffusing plate 120, but a part of it is reflected by the light diffusing plate 120. Most of the light reflected by the light diffusing plate 120 is reflected by the inner surface of the bottom plate 112 or the substrate 210 that functions as a diffuse reflection surface and then heads back to the light diffusing plate 120. A part of the light reflected by the light diffusing plate 120 is reflected by the front surface or the back surface of the light flux control member 300 and then heads back to the light diffusing plate 120. As a result, the surface light source device 100 according to the present embodiment can uniformly illuminate a planar display member (for example, a liquid crystal panel). Note that it is preferable that a reflecting member (reflective sheet) is disposed on the bottom plate 112 of the surface light source device 100.

[0025] FIGS. 4B, 5A, and 5B are diagrams for explaining the light distribution characteristics in the surface light source device 100 as described above. Specifically, as shown in FIG. 4B, when a reference point and regions are defined as follows for any one of the plurality of light emitting devices in the surface light source device 100, the light is distributed as shown in the graphs of FIGS. 5A and 5B. Thereby, even when the distance OD changes, a decrease in the image quality is suppressed. Hereinafter, first, the reference point and the like will be described, and then the light distribution characteristics based on the reference point and the like will be described.

[0026] That is, as shown in FIG. 4B, a line along the optical axis OA (see FIG. 4A) of the light-emitting element 220 of the light-emitting device 200 is defined as a reference line L1. The intersection point of this reference line L1 and the light-reaching surface 120a located on the light-emitting device 200 side of the light-diffusing plate 120 is defined as a first reference point P1, and the intersection point of the reference line L1 and the XY plane is defined as a second reference point P2. Taking the second reference point P2 as one vertex, a rectangular region having two sides of lengths Px and Py on the XY plane is divided by the diagonal of the rectangle passing through the second reference point P2. A triangular region having the second reference point P2 at the end point of the side of length Px is defined as a triangular region A, and a triangular region having the second reference point P2 at the end point of the side of length Py is defined as a triangular region B.

[0027] Based on the reference points and the like defined as above, in the surface light source device 100, the light distribution of any light-emitting device 200 is performed as follows.

[0028] That is, as shown in FIG. 5A, when the angle of the light emitted from an arbitrarily selected light-emitting element 220 along the reference line L1 is set to 0°, for the light emitted from the light-emitting element 220 corresponding to the light-emitting device 200 at an angle of 0° to 90° and emitted along the YZ cross-section, the luminous intensity of the light emitted from the light-emitting device 200 is measured. In a graph with the distance from the first reference point P1 to the position where the light reaches the light-reaching surface 120a of the light emitted within the measurement angle range on the horizontal axis and the luminous intensity of the light emitted at the emission angle reaching that position on the vertical axis, the position on the light-reaching surface 120a where the light ray corresponding to the luminous intensity peak top reaches exists within the range of Py / 3 or more and Py or less from the first reference point P1. Hereinafter, this is referred to as condition 1 as appropriate.

[0029] In addition, when comparing the amount of light reaching the total reflection surface 320 between the triangular region A and the triangular region B, more light reaches the triangular region B than the triangular region A. Hereinafter, this is referred to as condition 2 as appropriate.

[0030] Also, as shown in FIG. 5B, consider a graph of the luminance distribution showing the change in luminance along the straight line in the Y direction passing through the second reference point P2 for the light reflected by the total reflection surface 320 and reaching the XY plane. In this graph, (A) the position in the Y direction indicating the value of the luminance peak top is farther from the second reference point P2 than the distance D between the center of the light flux control member 300 along the Y direction and the outer edge of the light flux control member, or (B) when a line segment corresponding to the half-value width of the luminance peak is divided into a first divided line segment W1, which is a portion closer to the reference line L1 than the peak top in the Y direction, and a second divided line segment W2, which is a portion farther from the reference line L1 than the peak top in the Y direction, the length of the second divided line segment W2 is 1.5 times or more the length of the first divided line segment W1. Hereinafter, the above (A) is referred to as condition 3-1 as appropriate, and (B) is referred to as condition 3-2 as appropriate.

[0031] By satisfying the above condition 1, condition 2, and condition 3-1 or condition 3-2, the surface light source device of the present invention can suppress a decrease in image quality even when the distance OD changes. Hereinafter, this is also referred to as having high OD robustness.

[0032] (Configuration of the light flux control member) Hereinafter, the light flux control members according to Embodiments 1 to 9 that can be used in the surface light source device as described above will be described.

[0033] The configuration of each light flux control member will be described assuming that the light flux control member is placed in the XYZ coordinates. Specifically, although the light flux control member has a rotation symmetry axis (two-fold symmetry axis), it is assumed that the rotation symmetry axis (two-fold symmetry axis) coincides with the Z axis, the back surface of the light flux control member is placed on the XY plane, and the major axis direction when the light flux control member 400 is viewed in plan is parallel to the Y direction. Note that the terms "coincide" and "be parallel" here include not only the cases of complete coincidence and complete parallelism but also the cases of being substantially coincident and substantially parallel within the accuracy range of the installation of the light flux control member. Hereinafter, hatching in the cross-sectional view of the light flux control member will be omitted.

[0034] <Beam control member according to Embodiment 1> Figs. 6A to 6E show a beam control member 400 according to Embodiment 1.

[0035] Fig. 6A is a perspective view of the beam control member 400 according to Embodiment 1 as viewed from the front side, Fig. 6B is a plan view, Fig. 6C is a bottom view, Fig. 6D is a front view, Fig. 6E is a side view, and Fig. 6F is a cross-sectional view taken along the line F-F of Fig. 6C.

[0036] As shown in Figs. 6A to 6F, the beam control member 400 has an incident surface 410, a total reflection surface 420, and an exit surface 430. The beam control member 400 has an elliptical shape having a major axis in the Y direction and a minor axis in the X direction when viewed in plan and from the bottom. The length of the major axis of the ellipse is 4.73 mm, and the length of the minor axis is 3.38 mm.

[0037] The incident surface 410 is the inner surface of a recess arranged on the back side of the beam control member 400 so as to intersect the optical axis OA of the light emitting element 220, and allows the light emitted from the light emitting element 220 to enter. The incident surface 410 has a minor axis in the Y direction and a major axis in the X direction when viewed from the bottom of the beam control member 400. The incident surface 410 is a curved surface. The incident surface 410 is a curved surface such that the tangent to the curved surface approaches parallel to the XY plane as it proceeds from the back surface 440 side of the beam control member 400 to the front side of the beam control member 400.

[0038] The total reflection surface 420 is the inner surface of a recess arranged on the front side of the beam control member 400 so as to intersect the optical axis OA of the light emitting element 220, and reflects a part of the light incident from the incident surface 410. In the present embodiment, the total reflection surface 420 is arranged on the opposite side of the incident surface 410 in the beam control member 400. In the present embodiment, the total reflection surface 420 is a curved surface whose intersection with the rotation symmetry axis of the beam control member is the deepest, and gradually becomes lower in the Z direction from the intersection toward the outer edge of the total reflection surface 420. The tangent to the curved surface gradually approaches parallel to the XY plane from the intersection toward the outer edge of the total reflection surface.

[0039] In addition, in the present embodiment, the total reflection surface 430 has a shape with a two-fold axis of symmetry, is symmetric with respect to the XZ plane, and is also symmetric with respect to the YZ plane. The maximum length of the total reflection surface 430 in the Y direction is substantially the same as the maximum length in the X direction. Substantially the same means within a range of ±5%.

[0040] The emission surface 430 is a surface disposed around the total reflection surface 420. The emission surface 430 has a first emission surface 431 and a second emission surface 432. The first emission surface 431 is on the inner side of the emission surface 430, and the second emission surface 432 is on the outer side of the emission surface 430. In the present embodiment, at the first emission surface 431, light is mainly emitted at a certain small angle from the optical axis OA of the light-emitting element 220, reaches the first emission surface 431 directly without reaching the total reflection surface 420. On the other hand, at the second emission surface 430, light reflected by the total reflection surface 420 and light emitted at a large angle from the optical axis OA are mainly emitted.

[0041] The inner edge of the first emission surface 431 is connected to the outer edge of the total reflection surface 420. The first emission surface 431 is a curved surface, and the tangent to the curved surface gradually approaches perpendicular to the XY plane as it moves away from the Z axis (as it moves from the inner edge to the outer edge of the first emission surface 431).

[0042] The second emission surface 432 is disposed around the first emission surface 431. In the present embodiment, the second emission surface 432 is perpendicular to the XY plane. The upper end of the second emission surface 432 is connected to the outer edge of the first emission surface 431, and the lower end of the second emission surface 432 is connected to the back surface 440 of the light beam control member 400.

[0043] <Light beam control member according to Embodiment 2> Figs. 7A to 7F show a light beam control member 500 according to Embodiment 2.

[0044] Fig. 7A is a perspective view of the light beam control member 500 according to Embodiment 2 as viewed from the front side, Fig. 7B is a plan view, Fig. 7C is a bottom view, Fig. 7D is a front view, Fig. 7E is a side view, and Fig. 7F is a cross-sectional view taken along the F-F line of Fig. 7C.

[0045] The light beam control member 500 according to Embodiment 2 is a modification of the light beam control member 400 according to Embodiment 1. For the light beam control member 500, the same components as those of the light beam control member 400 according to Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, the differences from the light beam control member 400 that are deformed will be mainly described for the light beam control member 500.

[0046] The light beam control member 500 has a total reflection surface 520, and the configuration of the total reflection surface 520 is different from that of the total reflection surface 420 of the light beam control member 400. As shown in FIG. 7A and the like, the total reflection surface 520 has a first reflection surface 521 and two second total reflection surfaces 522. The first total reflection surface 521 is the inner surface of a recess disposed on the front side of the light beam control member 500 so as to intersect the optical axis OA of the light emitting element 220. On the other hand, the second reflection surface 522 is a surface that is spaced apart in the Y direction so as to sandwich the first reflection surface 521. When the total reflection surface 520 having the above-described configuration is viewed in plan, the maximum length in the Y direction is longer than the maximum length in the X direction.

[0047] The total reflection surface 520 has a rotation symmetry (two-fold rotation symmetry) axis and is symmetric with respect to the XZ plane. The first reflection surface 521 is a curved surface such that its tangent gradually approaches parallel to the XY plane as it moves away from the XZ plane. The second reflection surface 522 is a plane substantially parallel to the XY plane. Substantially parallel means, for example, including within a range of ±5°.

[0048] The exit surface 530 is disposed around the total reflection surface 520 as described above and has a first exit surface 531 and a second exit surface 432. The first exit surface 531 is different from the first exit surface 431 in that it is a surface connecting the total reflection surface 520 and the second exit surface 432. The other configurations of the first exit surface 531 are the same as those of the first exit surface 431.

[0049] (Light beam control member according to Embodiment 3) FIGS. 8A to 8F show a light beam control member 600 according to Embodiment 3.

[0050] FIG. 8A is a perspective view of the light beam control member 600 according to Embodiment 3 as viewed from the front side, FIG. 8B is a plan view, FIG. 8C is a bottom view, FIG. 8D is a front view, FIG. 8E is a side view, and FIG. 8F is a cross-sectional view taken along line F-F of FIG. 8C.

[0051] The light beam control member 600 according to Embodiment 3 is a modification of Embodiment 2, and the same components as those of the light beam control member 500 according to Embodiment 2 are denoted by the same reference numerals and their description is omitted. Hereinafter, the light beam control member 600 will be described focusing on the points of deformation and difference from the light beam control member 500.

[0052] The light beam control member 600 has an incident surface 610, and the configuration of the incident surface 610 is different from that of the incident surface 510 of the light beam control member 500. As shown in FIG. 8F, the incident surface 610 has a first incident surface 611 and a second incident surface 612. The first incident surface 611 is connected to the back surface 440 of the light beam control member 600 and is close to the back surface 440. The second incident surface 612 is far from the back surface 440 of the light beam control member 600. The first incident surface 611 is a curved surface such that its tangent approaches parallel to the XY plane as it goes from the back surface 440 toward the front side of the light beam control member 600. The second incident surface 612 is a curved surface such that its tangent approaches perpendicular to the XY plane as it goes from the back surface 440 side toward the front side. The tangent to the first incident surface 611 has a slope that is closer to perpendicular to the XY plane than the tangent to the second incident surface 612.

[0053] The light beam control member 600 has a total reflection surface 620, and the configuration of the total reflection surface 620 is different from that of the light beam control member 500. As shown in FIG. 8A, the total reflection surface 620 has a shape symmetric with respect to the XZ plane. The total reflection surface 620 is a curved surface that is inclined so that its tangent approaches the XY plane as it moves away from the XZ plane.

[0054] The connection surface 621 is a plane that connects the total reflection surface 620 and the exit surface 630.

[0055] The exit surface 630 has a first exit surface 631 and a second exit surface 432. The first exit surface 631 is disposed between the total reflection surface 620 and the second exit surface 432 and is connected to each of them.

[0056] (Light beam control member according to Embodiment 4) Figs. 9A to F show a light beam control member 700 according to Embodiment 4.

[0057] Fig. 9A is a perspective view of the light beam control member 700 according to Embodiment 4 as viewed from the front side, Fig. 9B is a plan view, Fig. 9C is a bottom view, Fig. 9D is a front view, Fig. 9E is a side view, and Fig. 9F is a cross-sectional view taken along the line F-F of Fig. 9C.

[0058] The light beam control member 700 according to Embodiment 4 is a modification of Embodiment 3, and the same components as those of the light beam control member 600 according to Embodiment 3 are denoted by the same reference numerals and their description is omitted. Hereinafter, the light beam control member 700 will be described focusing on the points different from the light beam control member 600 due to the modification.

[0059] The light beam control member 700 has a total reflection surface 720, and the configuration of the total reflection surface 720 is different from that of the light beam control member 600. As shown in Fig. 9A, the total reflection surface 720 is smoothly connected to the connection surface 721. The connection surface 721 is disposed between the total reflection surface 720 and the exit surface and is connected to each of them.

[0060] The exit surface 730 has a first exit surface 731 and a second exit surface 432. The first exit surface 731 is disposed between the total reflection surface 720 and the second exit surface and is connected to each of them.

[0061] (Light beam control member according to Embodiment 5) Figs. 10A to F show a light beam control member 800 according to Embodiment 5.

[0062] FIG. 10A is a perspective view of the light beam control member 800 according to Embodiment 5 as viewed from the front side, FIG. 10B is a plan view, FIG. 10C is a bottom view, FIG. 10D is a front view, FIG. 10E is a side view, and FIG. 10F is a cross-sectional view taken along the line F-F of FIG. 10C.

[0063] The light beam control member 800 according to Embodiment 5 is a modification of Embodiment 2, and the same components as those of the light beam control member 500 according to Embodiment 2 are denoted by the same reference numerals and the description thereof is omitted. Hereinafter, the light beam control member 800 will be described centering on the points that are different from the light beam control member 500 by deformation.

[0064] The light beam control member 800 has an elliptical shape in plan view. The elliptical shape is larger than the elliptical shape of Embodiment 2. Specifically, the major axis of the ellipse is 5.20 mm and the minor axis is 3.72 mm.

[0065] The light beam control member 800 has a total reflection surface 820, and the configuration of the total reflection surface 820 is different from that of the light beam control member 500. As shown in FIG. 10A, the total reflection surface 820 is a curved surface such that as it moves away from the XZ plane, its tangent approaches parallel to the XY plane. The total reflection surface 820 has a maximum length in the Y direction that is longer than the maximum length in the X direction in plan view.

[0066] The exit surface 830 has a first exit surface 831 and a second exit surface 832. The first exit surface 831 connects the total reflection surface 820 and the second exit surface 832. The second exit surface 832 is perpendicular to the XY plane.

[0067] (Light beam control member according to Embodiment 6) FIGS. 11A to F show the light beam control member 900 according to Embodiment 6.

[0068] FIG. 11A is a perspective view of the light beam control member 900 according to Embodiment 6 as viewed from the front side, FIG. 11B is a plan view, FIG. 11C is a bottom view, FIG. 11D is a front view, FIG. 11E is a side view, and FIG. 11F is a cross-sectional view taken along the line F-F of FIG. 11C.

[0069] The light beam control member 900 according to Embodiment 6 is a modification of the light beam control member 800 according to Embodiment 5. The same components as those in Embodiment 5 are denoted by the same reference numerals, and the description thereof is omitted.

[0070] The light beam control member 900 has an incident surface 910. The height of the incident surface 910 is slightly lower than that of the incident surface 410, and the diameter is the same.

[0071] The light beam control member 900 has a total reflection surface 920. The total reflection surface 920 is a curved surface such that its tangent approaches parallel to the XY plane as it moves away from the XZ plane. When viewed in plan view, the maximum length in the X direction of the total reflection surface 920 is longer than the maximum length in the Y direction.

[0072] The connection surface 921 is disposed between the total reflection surface 920 and the exit surface 930 and connects the two. The connection surface is a plane.

[0073] The exit surface 930 has a first exit surface 931 and a second exit surface 832. The first exit surface 931 is disposed between the total reflection surface 920 and the second exit surface 832 and connects the two.

[0074] (Light beam control member according to Embodiment 7) Figs. 12A to F show a light beam control member 1000 according to Embodiment 7.

[0075] Fig. 12A is a perspective view of the light beam control member 1000 according to Embodiment 7 as viewed from the front side, Fig. 12B is a plan view, Fig. 12C is a bottom view, Fig. 12D is a front view, Fig. 12E is a side view, and Fig. 12F is a cross-sectional view taken along the F - F line of Fig. 12C.

[0076] The light beam control member 1000 according to Embodiment 7 is a modification of the light beam control member 800 according to Embodiment 5. The same components as those in Embodiment 5 are denoted by the same reference numerals, and the description thereof is omitted.

[0077] The exit surface 1030 has a first exit surface 831 and a second exit surface 1032. The first exit surface 831 is disposed between and connected to the total reflection surface 820 and the second exit surface 1032.

[0078] As shown in FIG. 12E, the second exit surface 1032 is inclined so as to move away from the Z axis as it moves away from the XY plane in the Z direction when viewed along the X direction.

[0079] (Beam control member according to Embodiment 8) FIGS. 13A to 13F show a beam control member 1100 according to Embodiment 8.

[0080] FIG. 13A is a perspective view of the beam control member 1100 according to Embodiment 8 as viewed from the front side, FIG. 13B is a plan view, FIG. 13C is a bottom view, FIG. 13D is a front view, FIG. 13E is a side view, and FIG. 13F is a cross-sectional view taken along line F-F of FIG. 13C.

[0081] The beam control member 1100 according to Embodiment 8 is a modification of the beam control member 800 according to Embodiment 5, and the same components as those in Embodiment 5 are denoted by the same reference numerals and their description is omitted.

[0082] The beam control member 1100 has an elliptical shape with a constriction at half the length in the Y direction when viewed in plan and from the bottom.

[0083] The beam control member 1100 has a total reflection surface 1120. The total reflection surface 1120 is a curved surface that approaches parallel to the XY plane as it moves away from the XZ plane. When the total reflection surface 1120 is viewed in plan, the maximum length in the Y direction and the maximum length in the X direction are substantially the same. Substantially the same means within a range of ±5%.

[0084] The beam control member 1100 has an exit surface 1130. The exit surface 1130 has a first exit surface 1131 and a second exit surface 1132. The first exit surface 1131 is a curved surface that approaches perpendicular to the XY plane as it moves away from the XZ plane. The second exit surface 1132 is a plane perpendicular to the XY plane.

[0085] (Light beam control member according to Comparative Example 1) Figures 14A to 14F show the light beam control member 1200 according to Comparative Example 1.

[0086] Figure 14A is a perspective view of the light beam control member 1200 according to the comparative example as viewed from the front side, Figure 14B is a plan view, Figure 14C is a bottom view, Figure 14D is a front view, Figure 14E is a side view, and Figure 14F is a cross-sectional view taken along the F-F line of Figure 14C.

[0087] The light beam control member 1200 has an incident surface 1210 and an exit surface 1230 but does not have a total reflection surface.

[0088] (Light beam control member according to Comparative Example 2) Figures 15A to 15F show the light beam control member 1300 according to Comparative Example 2.

[0089] Figure 15A is a perspective view of the light beam control member 1300 according to the comparative example as viewed from the front side, Figure 15B is a plan view, Figure 15C is a bottom view, Figure 15D is a front view, Figure 15E is a side view, and Figure 15F is a cross-sectional view taken along the F-F line of Figure 15C.

[0090] The light beam control member 1300 is a modification of the light beam control member 600 according to Embodiment 3. For the same configurations as those of the light beam control member 600 in the light beam control member 1300, the same reference numerals are given and the description thereof is omitted.

[0091] The light beam control member 1300 has a total reflection surface 1320. The total reflection surface 1320 has a first total reflection surface 1321 and a second total reflection surface 1322. The first total reflection surface 1321 is a curved surface such that its tangent approaches parallel to the XY plane as it moves away from the XZ plane. The second total reflection surface 1322 is a plane substantially parallel to the XY plane.

[0092] The light beam control member 1300 has an emission surface 1330. The emission surface 1330 has a first emission surface 1331 and a second emission surface 432. The first emission surface 1331 is disposed between and connected to the total reflection surface 1320 and the second emission surface 432.

[0093] [Simulation] A simulation was performed on the surface light source device having each of the above light beam control members to examine whether conditions 1 to 3-2 are satisfied. In the simulation, Py was set to 35 mm, Px was set to 14 mm, and OD was set to 5 mm.

[0094] (Condition 1) The simulation of Condition 1 was performed using the light beam control members according to the above Embodiments 1 to 8 and Comparative Examples 1 and 2. The simulation results are shown in Table 1. Condition 1 means that, for the light emitted from the light emitting element at 0° to 90°, in the graph showing the light distribution characteristics on the YZ cross section regarding the luminous intensity of the light emitted from the light emitting device, the position on the light arrival surface where the light ray corresponding to the luminous intensity peak top arrives is within the range of Py / 3 or more and Py or less from the first reference point P1. Here, Py is 35 mm, and Py / 3 is about 11.7 mm. Table 1 shows the distance (mm) from the first reference point P1 of the point where the light ray corresponding to the luminous intensity peak top arrives at the light arrival surface. If this distance is within the range of 11.7 mm to 35 mm, Condition 1 is satisfied.

[0095] Specifically, in the simulation, for the light emitted from the light-emitting element at angles from 0° to 90° as shown in FIG. 16A, a graph showing the light distribution characteristics on the YZ cross-section regarding the luminous intensity of the light emitted from the light-emitting device was obtained. Note that the simulation was performed under the conditions of only the light-emitting element and the light beam control member. Also, the light emitted from the light-emitting element had a Lambertian light distribution. Then, the luminous intensity peak top angle θ (°) was obtained from this graph. From this luminous intensity peak top angle θ (°), the distance L from the first reference point P1 of the point where the light ray corresponding to the peak top as shown in FIG. 16B reached the light arrival surface 120a was obtained from L = OD × tan θ. Table 1 shows the luminous intensity peak top angle θ (°), the distance L, and whether or not the condition 1 was satisfied for each example and each comparative example.

[0096]

Table 1

[0097] As can be seen from Table 1, all of Embodiments 1 to 8 and Comparative Examples 1 and 2 satisfied Condition 1.

[0098] (Condition 2) Using the light beam control members according to the above-described Embodiments 1 to 8 and Comparative Examples 1 and 2, the simulation of Condition 2 was performed. The simulation results are shown in FIGS. 17A to D and 18A to D for Embodiments 1 to 8, and FIGS. 19A and B for Comparative Examples 1 and 2, respectively. Also, the straight lines shown in each figure are the boundary lines dividing the aforementioned triangular regions A and B, and the curve in FIG. 19A shows the outer shape of the light beam control member in a plan view. Note that Condition 2 means that when comparing the amount of light reaching the triangular region A and the triangular region B after being reflected by the total reflection surface, more light reaches the triangular region B than the triangular region A.

[0099] In the graphs of FIGS. 17A to 17D, FIGS. 18A to 18D, and FIGS. 19A and 19B, each plot indicates the position where the light ray reflected by the total reflection surface reaches the triangular regions A and B. As can be seen from FIGS. 17A to 17D and FIGS. 18A to 18D, in Embodiments 1 to 8, more light rays reached the triangular region B than the triangular region A. On the other hand, as can be seen from FIG. 19A, in Comparative Example 1, no light rays reached the triangular regions A and B. Further, as can be seen from FIG. 19B, in Comparative Example 2, more light reached the triangular region B than the triangular region A. That is, Embodiments 1 to 8 and Comparative Example 2 satisfied Condition 2. On the other hand, Comparative Example 1 did not satisfy Condition 2.

[0100] (Condition 3-1, 3-2) Regarding Condition 3-1 and Condition 3-2, actual measurements were taken using the light beam control members according to Embodiments 1 to 8 and Comparative Examples 1 and 2 above. The actual measurement results (graphs of luminance distribution) are shown in FIGS. 20A and 20B. Note that Condition 3-1 is as follows: In a graph of luminance distribution showing the change in luminance along a straight line in the Y direction passing through the second reference point P2 for the light reflected by the total reflection surface and reaching the XY plane, (A) the position in the Y direction indicating the luminance peak top is farther from the second reference point than the distance D between the center of the light beam control member along the Y direction and the outer edge of the light beam control member. Also, Condition 3-2 is as follows: In a graph of luminance distribution showing the change in luminance along a straight line in the Y direction passing through the second reference point P2 for the light reflected by the total reflection surface and reaching the XY plane, (B) when a line segment corresponding to the half-value width of the luminance peak is divided into a first divided line segment W1 that is a portion closer to the reference line L1 than the peak top in the Y direction and a second divided line segment W2 that is a portion farther from the reference line L1 than the peak top in the Y direction in the Y direction, the length of the second divided line segment W2 is 1.5 times or more the length of the first divided line segment W1.

[0101] Specifically, as shown in FIG. 21, the luminance meter 1 was placed about 20 cm above the XY plane so that the optical axis OA overlapped with the center of the detection unit of the luminance meter 1. The light reflected by the total reflection surface 320 and scattered by the reflection surface 2 (reflection sheet 2) with a thickness of 0.2 mm arranged on the XY plane was measured. The light emitting device 200 was placed in the hole of the reflection sheet 2. The hole of the reflection sheet was circular with a diameter of 6.5 mm. The light emitting device was placed so that the optical axis OA overlapped with the center of this circle. Only one light emitting device 200 was lit. The measurement was performed under the condition without a light diffusing plate. The light emitted directly from the light emitting element and emitted from the emission surface was not measured.

[0102] As can be seen from FIG. 20A, in Embodiments 1 to 4, although Condition 3-1 was not satisfied, Condition 3-2 was satisfied. In Embodiments 1 to 4 and Comparative Examples 1 and 2, the distance D was 2.36 mm as shown in FIG. 20A. Also, as can be seen from FIG. 20A, Embodiment 1 had a shoulder peak. As can be seen from FIG. 20B, in Embodiments 5, 7, and 8, Condition 3-1 was satisfied. In addition, in Embodiment 6, although Condition 3-1 was not satisfied, Condition 3-2 was satisfied. In Embodiments 5 to 8, the distance D was 2.60 mm as shown in FIG. 20B. Here, the shoulder peak refers to a part where the skirt is drawn in the direction away from the reference line L1 of the top peak, and there is a part where the slope of the graph becomes gentle on the side away from the reference line L1 of the peak where the second divided line segment W2 is larger than the first divided line segment W1.

[0103] Note that the high peak near the distance of 0.5 mm in the Y direction shown in FIGS. 20A and 20B is an error value and is not a top peak or a shoulder peak.

[0104] Table 2 shows the OD robustness of the surface light source devices of Embodiments 1 to 8 and Comparative Examples 1 and 2. The OD robustness was simulated as follows. The luminance distribution on the light diffusion plate was actually measured with one of the light emitting devices lit. Assuming that the data of one light emitting device was arranged according to the pitch of the light emitting devices, the luminance of the overlapping part of the luminance distributions was added to assume a state where a plurality of light emitting devices were lit. The point directly above the light emitting element where the OA of the light emitting element overlaps the upper surface of the light diffusion plate is defined as the directly above point a. From the directly above point a, the point advanced by half of the center-to-center distance of the adjacent light emitting elements in the Y direction in the Y direction is defined as the intermediate point b in the Y direction. From the directly above point a, the point advanced by half of the center-to-center distance of the adjacent light emitting elements in the X direction in the X direction is defined as the intermediate point c in the X direction. The point advanced by half of the center-to-center distance of the adjacent light emitting elements in the X direction from the directly above point a in the X direction is defined as the relay point, and the point further advanced by half of the center-to-center distance of the adjacent light emitting elements in the Y direction from the relay point in the Y direction is defined as the intermediate point d. The luminance values of each point from points a to d were extracted. The luminance value of each point was divided by the luminance value of the directly above point a to calculate the relative luminance value of each position. Note that Px was set to 14 mm and Py was set to 35 mm. The OD was set to 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, and 10 mm. The relative luminance values of each point were calculated for each OD. The largest value of the maximum difference in the relative luminance values of each point for all ODs was used as the numerical value of the OD robustness. Also, the OD robustness was evaluated in four grades from A to D. A is the best and D is the worst. The passing line is C or higher.

[0105]

Table 2

[0106] As can be seen from Table 2, in Embodiments 1 to 8 that satisfy Condition 1, 2, and Condition 3-1 or Condition 3-2, the OD robustness was all evaluated as C or higher, and Comparative Examples 1 and 2 that did not satisfy it were evaluated as D. Also in the circular optical control member, it is expected that the OD robustness will be improved by forming the total reflection surface in 360-degree rotational symmetry so as to satisfy Condition 3-1 or Condition 3-2.

Industrial Applicability

[0107] The surface light source device of the present invention can be applied to, for example, the backlight of a liquid crystal display device or general lighting.

Description of Signs

[0108] 1 Luminance meter 2 Reflecting surface (reflective sheet) 10, 100 Surface light source device 11a, 120a Light-reaching surface 100’ Display device 102 Display member 110 Housing 112 Bottom plate 114 Top plate 11, 120 Light diffusing plate 20, 200 Light-emitting device 210 Substrate 220 Light-emitting element 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300 Light beam control member 310, 410, 610, 910, 1210 Incident surface 320, 420, 520, 620, 720, 820, 920, 1020, 1120, 1320 Total reflection surface 330, 430, 530, 630, 730, 830, 930, 1030, 1130, 1230, 1330 Exit surface 431, 531, 631, 731, 831, 931, 1031, 1131, 1231, 1331 First exit surface 432, 832, 1032, 1132, 1232 Second exit surface 440 Back surface 521 First reflecting surface 522 Second reflecting surface 611 First incident surface 612 Second incident surface 621, 721, 921 Connection surface

Claims

1. In a surface light source device having a plurality of light emitting devices arranged on the XY plane of XYZ coordinates defining X, Y, and Z directions orthogonal to each other, and a light diffusion plate arranged at a distance from the XY plane in the Z direction, each of the plurality of light emitting devices has a light emitting element and a light flux control member for controlling light from the light emitting element, the light flux control member has an incident surface on which light from the light emitting element is incident, a total reflection surface on which a part of the light incident from the incident surface is reflected, and an emission surface arranged around the total reflection surface, the plurality of light emitting devices are arranged in rows in the X direction and the Y direction, and when the center-to-center distance between adjacent light emitting devices among the plurality of light emitting devices arranged in the X direction is Px and the center-to-center distance between adjacent light emitting devices among the plurality of light emitting devices arranged in the Y direction is Py, Py > Px, among the plurality of light emitting devices, with a line along the optical axis OA of the light emitting element of an arbitrary light emitting device as a reference line L1, the intersection point of the reference line L1 and the light arrival surface located on the light emitting device side of the light diffusion plate is defined as a first reference point P1. When the angle of the light emitted from the light emitting element along the reference line L1 is set to 0°, for the light emitted from the light emitting element of the arbitrary light emitting device at an angle of 0° to 90°, in a graph showing the light distribution characteristics on the YZ cross-section regarding the light emission luminance from the light emitting device, the position on the light arrival surface where the light ray corresponding to the luminance peak top arrives exists in the range of not less than Py / 3 and not more than Py from the first reference point P1, the light emitted from an arbitrary light emitting element, reflected by the total reflection surface, and reaching the emission surface is emitted from the emission surface at an angle greater than 90° with respect to the reference line L1, with the intersection point of the reference line L1 and the XY plane as a second reference point P2, using the second reference point P2 as one vertex, when comparing the amount of light reaching the total reflection surface in a triangular region A having the second reference point P2 at an end point of the side with a length of Px and a triangular region B having the second reference point P2 at an end point of the side with a length of Py in a rectangle having two sides with lengths of Px and Py on the XY plane and divided by the diagonal of the rectangle passing through the second reference point P2, more light reaches the triangular region B than the triangular region A, In a graph of the luminance distribution showing the change in luminance along the straight line in the Y direction passing through the second reference point P2 for the light reflected by the total reflection surface and reaching the XY plane, (A) the position in the Y direction of the luminance peak top is farther from the second reference point than the distance D between the center of the light beam control member along the Y direction and the outer edge of the light beam control member, or (B) when a line segment corresponding to the half-value width of the luminance peak is divided into a first divided line segment W1 which is a portion closer to the reference line L1 than the peak top in the Y direction and a second divided line segment W2 which is a portion farther from the reference line L1 than the peak top in the Y direction, the length of the second divided line segment W2 is 1.5 times or more the length of the first divided line segment W1. Surface light source device.

2. The surface light source device according to claim 1, wherein a shoulder peak exists in the graph of the luminance distribution.

3. A display device having the surface light source device according to claim 1 or 2.

4. A light beam control member used in the surface light source device according to claim 1 or 2.

Images