Illumination device and light-emitting device

Abstract

This illumination device comprises: a substrate; a first light-emitting element disposed on the main surface of the substrate; a second light-emitting element disposed on the main surface with the first light-emitting element interposed therebetween; an optical member having a convex surface, the optical member transmitting light from the first light-emitting element and the second light-emitting element and emitting the transmitted light from the convex surface; and a reflection member for reflecting some of the light from the second light-emitting element emitted from the convex surface.

Description

Illumination device and light-emitting device

[0001] The present disclosure relates to lighting devices and light emitting devices.

[0002] There are known lighting devices that change the atmosphere of a space by controlling the illumination light. For example, Japanese Patent Application Laid-Open No. 2016-170912 describes a lighting device that uses multiple LED modules that emit light of different color temperatures and applies different lens effects to the light emitted from each LED module to change the light distribution angle of the illumination light.

[0003] The lighting device described in JP 2016-170912 A includes multiple lenses with different shapes to impart different lens effects to the light from each LED module. However, there is a demand for a lighting device that can greatly change the light distribution angle of emitted light with a simpler structure.

[0004] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an illumination device and a light-emitting device that can greatly change the luminous intensity distribution angle of emitted light with a simple structure.

[0005] An illumination device according to an embodiment of the present disclosure includes a substrate, a first light-emitting element arranged on a main surface of the substrate, a second light-emitting element arranged on the main surface across the first light-emitting element, a wiring pattern that applies a voltage to the first light-emitting element and the second light-emitting element to independently drive the first light-emitting element and the second light-emitting element, an optical element having a convex surface that transmits light from the first light-emitting element and the second light-emitting element and emits the light from the convex surface, and a reflective element that reflects a portion of the light from the second light-emitting element that has emitted from the convex surface.

[0006] The optical member preferably satisfies the following formula: Here, T is the height of the apex of the convex surface relative to the main surface, L1 is the distance between the apex of the convex surface and the second light-emitting element in the direction along the main surface, and n is the refractive index of the optical member.

[0007] It is preferable that the optical member further satisfies the following formula:

[0008] The optical member preferably satisfies the following formula: Here, L1 is the distance from the apex of the convex surface to the second light-emitting element in the direction along the main surface, and L2 is the distance between the apex of the convex surface and the outer periphery in the direction along the main surface.

[0009] It is preferable that the lighting device further includes a structure disposed on the main surface and surrounding the first light-emitting element and the second light-emitting element, and that the optical member is disposed such that its outer periphery overlaps the structure.

[0010] The optical member preferably has a two-fold rotationally symmetric planar shape.

[0011] The reflecting member is preferably a lens that totally reflects and transmits the light from the second light-emitting element.

[0012] A light emitting device according to an embodiment of the present disclosure includes a substrate, a first light emitting element arranged on a main surface of the substrate, a second light emitting element arranged on the main surface across the first light emitting element, a wiring pattern that applies a voltage to the first light emitting element and the second light emitting element to drive the first light emitting element and the second light emitting element independently, and an optical element having a convex surface that transmits light from the first light emitting element and emits it from the convex surface, and transmits a portion of light from the second light emitting element and emits it from the convex surface to be reflected by a reflective element.

[0013] The lighting device and light-emitting device according to the present disclosure make it possible to greatly change the light distribution angle of emitted light with a simple structure.

[0014] Fig. 1 is a schematic perspective view of a lighting device according to an embodiment; Fig. 2 is a plan view of a light emitting device according to an embodiment; Fig. 3 is a plan view of a light emitting device according to an embodiment; Fig. 4 is a schematic cross-sectional view of a light emitting device according to an embodiment; Fig. 5 is a schematic diagram for explaining light distribution; Fig. 6 is a flow diagram showing a manufacturing method of a lighting device according to an embodiment; Fig. 7 is a diagram showing the relationship between the shape of an optical member and a light distribution angle;

[0015] Various embodiments of the present disclosure will be described below with reference to the drawings. Please note that the technical scope of the present invention is not limited to these embodiments, but extends to the inventions described in the claims and their equivalents.

[0016] 1 is a schematic perspective view of an illumination device 1 according to an embodiment of the present disclosure. The illumination device 1 includes a light-emitting device 2 and a reflecting member 3. The reflecting member 3 is held by a holding member (not shown) and fixed to the light-emitting device 2.

[0017] 2 and 3 are plan views of the light-emitting device 2, and FIG. 4 is a schematic cross-sectional view of the light-emitting device 2 taken along the line IV-IV. The light-emitting device 2 includes a substrate 21, a wiring pattern 22, a first light-emitting element 23, a second light-emitting element 24, a structure 25, a sealing material 26, and an optical member 27. The structure 25, the sealing material 26, and the optical member 27 are not shown in FIG. 3. To facilitate distinction between the first light-emitting element 23 and the second light-emitting element 24, the first light-emitting element 23 is hatched in FIG. 3, but the second light-emitting element 24 is not hatched. The wiring pattern 22 is not shown in FIG. 4.

[0018] The substrate 21 is formed by bonding together a mounting substrate and a circuit board having a main surface 211. The circuit board is formed into a flat plate shape from an electrically insulating resin. For example, the electrically insulating resin is a phenol resin, an epoxy resin, a polyimide resin, a polyester resin, or the like. Other components of the light emitting device 2 are arranged on the main surface 211 of the substrate 21.

[0019] The wiring pattern 22 is formed of a conductive material such as gold, silver, copper, or aluminum. The wiring pattern 22 includes a first wiring 221, a second wiring 222, and a third wiring 223 that are arranged spaced apart from each other on the main surface 211 of the substrate 21. The wiring pattern 22 is connected to a power source (not shown) and applies a voltage to the first light-emitting element 23 and the second light-emitting element 24 to drive the first light-emitting element 23 and the second light-emitting element 24.

[0020] The first light-emitting element 23 and the second light-emitting element 24 are, for example, light-emitting diodes (LEDs) that emit light. For example, the first light-emitting element 23 and the second light-emitting element 24 are blue LEDs made of an InGaN-based compound semiconductor. The first light-emitting element 23 and the second light-emitting element 24 may be LEDs made of other compound semiconductors, such as GaAs-based compound semiconductors, GaN-based compound semiconductors, or GaP-based compound semiconductors. The first light-emitting element 23 and the second light-emitting element 24 may be LEDs that emit light in other wavelength bands, such as red LEDs or green LEDs.

[0021] The first light-emitting element 23 is disposed near the center of the main surface 211 of the substrate 21. The second light-emitting element 24 is disposed on the main surface 211 of the substrate 21, sandwiching the first light-emitting element 23 therebetween. In the example shown in FIG. 3 , the second light-emitting element 24 is disposed along the main surface 211, sandwiching the first light-emitting element 23 therebetween in both the X direction (the horizontal direction in FIG. 3 ) and the Y direction (the vertical direction in FIG. 3 ), which are orthogonal to each other. That is, the second light-emitting element 24 is disposed surrounding the first light-emitting element 23. The example shown in FIG. 3 is not limited to this, and the second light-emitting element 24 may be disposed sandwiching the first light-emitting element 23 in only one direction.

[0022] The first light-emitting elements 23 and the second light-emitting elements 24 may be connected in series by bonding wires W. The number of first light-emitting elements 23 connected in series may be equal to the number of second light-emitting elements 24 connected in series. This makes the drive voltages of the first light-emitting elements 23 and the second light-emitting elements 24 approximately equal, simplifying the circuit configuration. In the example shown in FIG. 3 , six first light-emitting elements 23 are connected in series, and twelve second light-emitting elements 24 are separated into two systems, with six second light-emitting elements 24 connected in series in each system.

[0023] The first light-emitting element 23 and the second light-emitting element 24 are connected to different power supply systems. In the example shown in Fig. 3 , both ends of the first light-emitting element 23 connected in series are connected to the first wiring 221 and the second wiring 222, respectively. Both ends of the second light-emitting element 24 connected in series are connected to the first wiring 221 and the third wiring 223, respectively. In other words, the wiring pattern 22 applies voltages to the first light-emitting element 23 and the second light-emitting element 24 independently, and drives the first light-emitting element 23 and the second light-emitting element 24 independently.

[0024] The arrangement area of ​​the first light-emitting elements 23 and the second light-emitting elements 24 may be substantially rectangular. In the example shown in FIG. 3 , two first light-emitting elements 23 are arranged in the X direction and three first light-emitting elements 23 are arranged in a grid pattern in the Y direction, and the arrangement area of ​​the first light-emitting elements 23 is a rectangle extending in the Y direction. Furthermore, three second light-emitting elements 24 are arranged along each of the four sides of the arrangement area of ​​the first light-emitting elements 23, and the arrangement area of ​​the second light-emitting elements 24 is a substantially rectangular shape extending in the Y direction. Since the arrangement area of ​​the first light-emitting elements 23 and the second light-emitting elements 24 is substantially rectangular, the bonding wires W connecting the first light-emitting elements 23 and the second light-emitting elements 24 arranged at both ends of the long side direction to the wiring pattern 22 are shortened, thereby reducing the possibility of the bonding wires W being damaged.

[0025] The structure 25 is disposed on the main surface 211, surrounding the first light-emitting element 23 and the second light-emitting element 24. The structure 25 may be formed of a material that reflects light from the first light-emitting element 23 and the second light-emitting element 24. For example, the structure 25 may be formed of a white resin in which titanium oxide particles are dispersed in a resin such as a silicone resin or an epoxy resin.

[0026] The sealing material 26 is translucent and is disposed in a space defined by the main surface 211 of the substrate 21 and the structure 25. The sealing material 26 is formed so that its upper surface is higher than the upper surfaces of the first light-emitting element 23 and the second light-emitting element 24, and seals the first light-emitting element 23 and the second light-emitting element 24. The sealing material 26 is formed of a translucent resin such as an epoxy resin or a silicone resin. The sealing material 26 may be formed so that its upper surface is higher than the bonding wires W. This protects the bonding wires W.

[0027] The encapsulant 26 may contain a phosphor that converts the wavelength band of light from at least one of the first light-emitting element 23 and the second light-emitting element 24. The phosphor may emit light that tends to become white light when mixed with light from at least one of the first light-emitting element 23 and the second light-emitting element 24. For example, if at least one of the first light-emitting element 23 and the second light-emitting element 24 is a blue LED, the phosphor may be a YAG (Yttrium Aluminum Garnet) yellow phosphor. This converts a portion of the blue light from the light-emitting element into yellow light, and the blue light and yellow light are mixed to generate white light. The phosphor may also be a CASN red phosphor or a LuAG green phosphor, etc.

[0028] When the sealing material 26 contains a phosphor, the structure 25 and the sealing material 26 may be formed into a substantially rectangular shape extending in the extension direction of the arrangement area of ​​the first light-emitting element 23 and the second light-emitting element 24. In the example shown in Fig. 2, the structure 25 and the sealing material 26 are formed into a substantially rectangular shape extending in the Y direction, which is the extension direction of the arrangement area of ​​the first light-emitting element 23 and the second light-emitting element 24. This reduces variation in the optical path length from the first light-emitting element 23 and the second light-emitting element 24 until it exits the sealing material 26, preventing the occurrence of color unevenness such as a yellow ring.

[0029] The optical member 27 is translucent and is disposed opposite the first light-emitting element 23 and the second light-emitting element 24 with the sealing material 26 sandwiched therebetween. For example, the optical member 27 is formed of a translucent resin such as epoxy resin or silicone resin, or glass. The optical member 27 has a convex surface 271 on the side opposite the surface facing the first light-emitting element 23 and the second light-emitting element 24. The convex surface 271 is, for example, a spherical surface or a parabolic surface, but is not limited to these examples and may be a surface having any convex shape.

[0030] The optical element 27 may be arranged so that its outer periphery overlaps the structure 25. That is, when the light-emitting device 2 is viewed in plan, the outer periphery of the optical element 27 may be located between the inner and outer peripheries of the structure 25. If the outer periphery of the optical element 27 is located inside the inner periphery of the structure 25, some of the light from the first light-emitting element 23 and the second light-emitting element 24 will be emitted to the outside without entering the optical element 27, resulting in uncontrolled light distribution. If the outer periphery of the optical element 27 is located outside the outer periphery of the structure 25, the light-collecting ability of the optical element 27 will be increased, thereby reducing the amount of change in the light distribution angle (described later). By arranging the optical element 27 so that its outer periphery overlaps the structure 25, these adverse effects are prevented. In this case, the optical element 27 has a substantially rectangular planar shape, similar to the structure 25.

[0031] As shown in Figure 4, light LS1 emitted from the second light-emitting element 24 and incident on the apex of the convex surface 271 of the optical member 27 (the highest point with respect to the main surface 211 of the substrate 21) at an incident angle θ1 has the largest exit angle θ2 of all the light emitted from the convex surface 271. If the incident angle θ1 is greater than the critical angle, the light from the second light-emitting element 24 is totally reflected at the apex of the convex surface 271, thereby reducing the light utilization efficiency. Therefore, it is preferable that the incident angle θ1 be equal to or less than the critical angle. When the optical member 27 satisfies the following formula, the incident angle θ1 is equal to or less than the critical angle. Here, T is the height of the apex of the convex surface 271 relative to the main surface 211, L1 is the distance in the direction along the main surface 211 between the apex of the convex surface 271 and the second light-emitting element 24, and n is the refractive index of the optical element 27.

[0032] Furthermore, the larger the value of T / L1, the thicker the optical member 27, and therefore the greater the light-collecting ability of the optical member 27. As will be described later with reference to Table 2, when the value of T / L1 is 2.67 or less, the difference between the light distribution angle when only the first light-emitting element 23 is driven and the light distribution angle when only the second light-emitting element 24 is driven, i.e., the amount of change in the light distribution angle, becomes large. Therefore, it is preferable that the optical member 27 satisfy the following formula. Furthermore, as will be described later with reference to Table 2, when the value of T / L1 is 2.0 or less, the amount of change in the light distribution angle increases as T / L1 increases, and the amount of change in the light distribution angle reaches a maximum when the value of T / L1 is approximately 2.0. Therefore, it is more preferable that the optical member 27 satisfy the following formula.

[0033] If the distance L2 between the vertex and the outer periphery of the optical member 27 in the direction along the main surface 211 is small, the outer periphery of the optical member 27 will be located inside the outermost second light-emitting elements 24, making it impossible to control the light distribution. On the other hand, if the distance L2 is large, the light collecting ability of the optical member 27 will increase, as described above, and the light distribution angle will become smaller. In order to prevent a decrease in the light utilization efficiency and to increase the light distribution angle, it is preferable that the optical member 27 satisfy the following formula:

[0034] 4 illustrates that the light LS1 is emitted only from the center of the upper surface of the second light-emitting element 24, and the distance L1 is illustrated as the distance in the direction along the main surface 211 between the apex of the convex surface 271 and the center of the upper surface of the second light-emitting element 24, but this is merely a schematic diagram. In reality, the light LS1 is emitted from at least a partial region of the upper surface of the second light-emitting element 24. In this case, the distance L1 may be the distance in the direction along the main surface 211 between the apex of the convex surface 271 and the point of the light-emitting region of the light LS1 on the upper surface of the second light-emitting element 24 that is farthest from the apex of the convex surface 271.

[0035] 4 also shows the relationship between the height T, the distance L1, and the distance L2 in the IV-IV cross section (i.e., the cross section in the X direction). It is preferable that the height T, the distance L1, and the distance L2 also satisfy the above-mentioned relationship in the cross section in the Y direction. It is also preferable that the height T, the distance L1, and the distance L2 also satisfy the above-mentioned relationship in any cross section passing through the apex of the convex surface of the optical member 27.

[0036] FIG. 5 is a schematic cross-sectional view of the lighting device 1 for explaining the light distribution angle of the light emitted from the lighting device 1.

[0037] The reflective member 3 is translucent and formed in a generally inverted truncated cone shape. For example, the reflective member 3 is made of a translucent resin such as an acrylic resin, an olefin resin, or a polycarbonate resin, or glass. A recess 33 defined by a bottom surface 31 and an inner peripheral surface 32 is formed on one bottom surface of the reflective member 3. The bottom surface 31 of the recess 33 may be formed to protrude toward the light-emitting device 2.

[0038] As shown in FIG. 5 , the reflecting member 3 is disposed so that at least a portion of the light-emitting device 2 is accommodated in the recess 33. A portion of the light emitted from the first light-emitting element 23 is incident on the bottom surface 31 of the recess 33 of the reflecting member 3 and emitted to the outside of the lighting device 1, as shown by light LS2 in FIG. 5 . At this time, because the bottom surface 31 is formed to protrude toward the light-emitting device 2, the range of the luminous intensity distribution angle (the angle with respect to the direction perpendicular to the main surface 211 of the substrate 21) of the light from the first light-emitting element 23 is narrowed. A portion of the light emitted from the second light-emitting element 24 is incident on the inner circumferential surface 32 of the recess 33 of the reflecting member 3, as shown by light LS3 in FIG. 5 , is totally reflected by the side surface 34, and is emitted to the outside of the lighting device 1. Because the optical element 27 has a convex surface 271, the luminous intensity distribution angle of the light emitted from the optical element 27 is increased, and therefore the range of the luminous intensity distribution angle of the light from the second light-emitting element 24 is widened. Therefore, when only the first light-emitting element 23 is driven, the range of the light distribution angle is narrow, and when the second light-emitting element 24 is driven, the range of the light distribution angle is wide, making it possible to change the light distribution angle greatly.

[0039] FIG. 6 is a flow diagram showing an example of the flow of a manufacturing method for the lighting device 1.

[0040] First, in a substrate preparation step S1, a substrate 21 having a wiring pattern 22 is prepared.

[0041] Next, in a light-emitting element arrangement step S2, the first light-emitting element 23 and the second light-emitting element 24 are arranged on the main surface 211 of the substrate 21. For example, the first light-emitting element 23 and the second light-emitting element 24 are arranged by being adhered to the inside of the structure 25 on the main surface 211 via a resin or metal adhesive member. The arranged first light-emitting element 23 and second light-emitting element 24 are connected to the wiring pattern 22 by bonding wires W.

[0042] Next, in the structure formation step S3, the structure 25 is formed. For example, the structure 25 is formed by applying a liquid thermosetting resin in a ring shape to the main surface 211 and curing the thermosetting resin by heating. The structure 25 may be formed in a ring shape in advance and then adhered to the main surface 211.

[0043] Next, in a sealing material disposing step S4, a sealing material 26 is disposed in the space defined by the main surface 211 and the structures 25. For example, the sealing material 26 is formed by filling the space defined by the main surface 211 and the structures 25 with a liquid thermosetting resin until the upper surfaces of the first light-emitting element 23 and the second light-emitting element 24 are immersed, and then curing the thermosetting resin by heating. The sealing material 26 may be formed by applying a liquid thermosetting resin only to the upper surfaces of the first light-emitting element 23 and the second light-emitting element 24 and curing it. The sealing material 26 may be formed by applying a liquid thermosetting resin to the upper surfaces and side surfaces of the first light-emitting element 23 and the second light-emitting element 24 and curing it.

[0044] Next, in an optical element placement step S5, the optical element 27 is placed. For example, the optical element 27 is formed by dropping droplets of a thermosetting resin onto the structure 25 and the sealing material 26, and then curing the thermosetting resin by heating in a state in which a convex surface is formed by the surface tension of the thermosetting resin. The optical element 27 may be placed on the structure 25 and the sealing material 26 in a state in which it has already been formed with a convex surface.

[0045] Next, in a reflecting member disposing step S6, the reflecting member 3 is disposed so that at least a portion of the light emitting device 2 is housed in the recess 33 of the reflecting member 3. In this way, the lighting device 1 is manufactured.

[0046] As described above, the lighting device 1 includes the first light-emitting element 23, the second light-emitting element 24 that is disposed on either side of the first light-emitting element 23 and is driven independently of the first light-emitting element 23, and the optical member 27 that transmits light from the first light-emitting element 23 and the second light-emitting element 24 and emits the light from the convex surface. This makes it possible to widen the luminous intensity distribution angle of the light from the second light-emitting element 24 and greatly change the luminous intensity distribution angle of the emitted light.

[0047] In the above-described embodiment, the reflective member 3 is a lens that reflects the light from the second light-emitting element 24 by total reflection. However, the reflective member 3 is not limited to this example, and may be a reflector having a reflective surface at a position corresponding to the side surface 34. The reflective surface may be formed of a metal such as aluminum that reflects the light from the second light-emitting element 24.

[0048] In the above-described embodiment, the placement area, the structure 25, and the sealing material 26 of the first light-emitting element 23 and the second light-emitting element 24 are formed in a substantially rectangular shape. However, this is not a limitation. The placement area, the structure 25, and the sealing material 26 may be formed in any two-fold rotationally symmetric shape, such as a rhombus or parallelogram, extending in a predetermined direction. This also reduces the possibility of damage to the bonding wire W and prevents color unevenness such as yellow rings. Furthermore, in this case, the optical member 27 may also have any two-fold rotationally symmetric planar shape. The placement area, the structure 25, the sealing material 26, and the optical member 27 may be formed in any other shape, such as a triangle or pentagon, extending in a predetermined direction.

[0049] In the above-described embodiment, the first light-emitting element 23 and the second light-emitting element 24 are connected to the wiring pattern 22 by bonding wires W. However, the present invention is not limited to this example, and the first light-emitting element 23 and the second light-emitting element 24 may be connected to the wiring pattern 22 by surface mounting, or may be connected to the wiring pattern 22 by any other method that allows the first light-emitting element 23 and the second light-emitting element 24 to be driven independently.

[0050] In the above-described embodiment, as shown in Fig. 4 , when viewed in cross section, one second light-emitting element 24 is arranged on each side of the first light-emitting element 23. However, the present invention is not limited to this example, and a plurality of second light-emitting elements 24 may be arranged on each side of the first light-emitting element 23. In this case, the above-described distance L1 is the distance in the direction along the main surface 211 between the apex of the convex surface 271 and the second light-emitting element 24 arranged outermost.

[0051] It should be understood by those skilled in the art that various changes, substitutions, and alterations can be made to the present invention without departing from the scope of the present invention. For example, the above-described embodiments and modifications may be appropriately combined within the scope of the present invention.

[0052] The light distribution angles of light emitted from four lighting devices (Examples 1-4) differing only in the shape of the optical member 27 were calculated by simulation. In the lighting device according to Example 1, the ratio L2 / L1 of the distance L1 between the apex of the optical member and the second light-emitting element in the direction along the main surface to the distance L2 between the apex of the optical member and the outer periphery in the direction along the main surface was 1.67. The L2 / L1 ratio of the lighting device according to Example 2 was 2.0. The L2 / L1 ratio of the lighting device according to Example 3 was 2.33. The L2 / L1 ratio of the lighting device according to Example 4 was 2.67. The distances L1 and L2 in Examples 1-4 were the distances along the X direction in FIGS. 2 and 3 , i.e., the short side direction of the structure having a rectangular planar shape. The outer periphery of the optical member of the lighting device according to Example 1 was located inside the inner periphery of the structure. The outer periphery of the optical member of the lighting device according to Example 2 overlapped with the structure. The outer periphery of the optical member of the lighting device according to Examples 3-4 was located outside the outer periphery of the structure. As a comparative example, the light distribution angle of a lighting device that does not have an optical member was calculated.

[0053] In Examples 1-4 and the Comparative Example, the light distribution angle (narrow angle) of light emitted from the lighting device when only the first light-emitting element 23 is driven, and the light distribution angle (wide angle) of light emitted from the lighting device when both the first light-emitting element 23 and the second light-emitting element 24 are driven were calculated. The light distribution angle is the half-width, i.e., the emission angle of light where the intensity is half of the intensity of light when the emission angle is 0 degrees. The calculated results are shown in Table 1.

[0054] As described above, the narrow and wide angles of Examples 1-4 were both wider than those of the comparative example, confirming that the optical element widened the light distribution angle. Furthermore, it was confirmed that the wide angle of Examples 1-4 was particularly widened compared to the comparative example, resulting in a large difference between the wide and narrow angles. Therefore, it was confirmed that the simple process of arranging an optical element having a convex surface makes it possible to significantly change the light distribution angle of the emitted light.

[0055] Furthermore, the wide angle of Example 2 was wider than the wide angle of Example 1. This is thought to be because in Example 1, the outer periphery of the optical element was located inside the inner periphery of the structure, and light emitted from near the outer periphery of the sealing material was not subjected to refraction by the optical element. Furthermore, the narrow angle and wide angle of Examples 1-2 were wider than the narrow angle and wide angle of Examples 3-4. This is thought to be because the optical element of Examples 3-4 was large and had high light-collecting properties. Therefore, it was confirmed that the distance L2 was equal to or less than twice the distance L1, and that the outer periphery of the optical element overlapped the structure, making it possible to change the light distribution angle more significantly.

[0056] The light distribution angles of light emitted from five lighting devices (Examples 5-9) differing only in the shape of the optical member 27 were calculated by simulation. In the lighting device according to Example 5, the ratio T / L1 of the distance L1 between the apex of the optical member and the second light-emitting element in the direction along the main surface to the height T of the apex of the convex surface relative to the main surface was 1.33. The T / L1 of the lighting device according to Example 6 was 1.67. The T / L1 of the lighting device according to Example 7 was 2.00. The T / L1 of the lighting device according to Example 8 was 2.33. The T / L1 of the lighting device according to Example 9 was 2.67. The distance L1 in Examples 5-9 was the distance along the X direction in FIGS. 2 and 3 , i.e., the short side direction of the structure having a rectangular planar shape.

[0057] In Examples 5-9, the light distribution angle (narrow angle) of light emitted from the lighting device when only the first light-emitting element 23 is driven and the light distribution angle (wide angle) of light emitted from the lighting device when only the second light-emitting element 24 is driven were calculated by simulation. The calculated results are shown in Table 2.

[0058] Fig. 7 is a diagram showing the relationship between T / L1 of the optical element and the narrow and wide angles. In the graph of Fig. 7, the horizontal axis is T / L1, and the vertical axis is the light distribution angle. In the graph of Fig. 7, the solid broken line L1 indicates the narrow angle of Examples 5-9, and the dashed broken line L2 indicates the wide angle of Examples 5-9. In addition, in the graph of Fig. 7, the narrow angle and wide angle of the comparative example not having the optical element are indicated by the solid line L3 and the dashed line L4, respectively.

[0059] As shown in Figure 7, the difference between the wide angle and the narrow angle in Examples 5-9, i.e., the change in the light distribution angle associated with switching between the wide angle and the narrow angle, was greater than the change in the light distribution angle in the comparative example. Therefore, it was confirmed that the inclusion of an optical element in a lighting device enables a significant change in the light distribution angle of the emitted light. In particular, in Examples 5-7, in which T / L1 was 2.0 or less, the change in the light distribution angle increased as T / L1 increased. Therefore, it was confirmed that a T / L1 of 2.0 or less enables a greater change in the light distribution angle of the emitted light, and that a T / L1 of 2.0 enables a particularly large change in the light distribution angle of the emitted light.

Claims

1. A lighting device comprising a substrate, a first light-emitting element disposed on a main surface of the substrate, a second light-emitting element disposed on the main surface with the first light-emitting element interposed therebetween, a wiring pattern for applying a voltage to the first light-emitting element and the second light-emitting element to independently drive the first light-emitting element and the second light-emitting element, an optical member having a convex surface and transmitting light from the first light-emitting element and the second light-emitting element to emit the light from the convex surface, and a reflecting member for reflecting a part of the light from the second light-emitting element emitted from the convex surface.

2. The optical member satisfies the following formula: Here, T is the height of the vertex of the convex surface with respect to the main surface, L1 is the distance in the direction along the main surface between the vertex of the convex surface and the second light-emitting element, and n is the refractive index of the optical member. The lighting device according to claim 1.

3. The optical member further satisfies the following equation: The lighting device according to claim 2.

4. The optical member satisfies the following formula: Here, L1 is the distance in the direction along the main surface from the vertex of the convex surface to the second light-emitting element, and L2 is the distance in the direction along the main surface between the vertex of the convex surface and the outer periphery. The lighting device according to claim 1.

5. The lighting device according to claim 1, further comprising a structure disposed on the main surface so as to surround the first light-emitting element and the second light-emitting element, wherein the optical member has an outer periphery overlapping with the structure.

6. The lighting device according to claim 1, wherein the optical member has a plane shape that is rotationally symmetric about an axis two times.

7. The lighting device according to claim 1, wherein the reflecting member is a lens that reflects light from the second light-emitting element by total reflection.

8. A light-emitting device comprising a substrate, a first light-emitting element disposed on a main surface of the substrate, a second light-emitting element disposed on the main surface with the first light-emitting element interposed therebetween, a wiring pattern for applying a voltage to the first light-emitting element and the second light-emitting element to independently drive the first light-emitting element and the second light-emitting element, and an optical member having a convex surface that transmits light from the first light-emitting element to emit the light from the convex surface and also transmits a part of the light from the second light-emitting element to emit the light from the convex surface so as to be reflected by a reflecting member.

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