JP7534627B2 - Light-emitting device and surface light source - Google Patents

Description

This disclosure relates to a light emitting device and a surface light source.

Light-emitting devices that include a light-emitting element and a phosphor are known.

JP 2007-080994 A

Light-emitting devices are required to have even greater light extraction efficiency.

A light-emitting device according to an embodiment of the present disclosure includes a light-emitting element having a first lower surface on which a pair of electrodes are provided, a first upper surface located opposite the first lower surface, and a first side surface located between the first upper surface and the first lower surface; a first translucent member containing a wavelength conversion material and covering at least a portion of the first side surface of the light-emitting element, the first translucent member having a second upper surface that does not overlap the first upper surface of the light-emitting element in a planar view; a second translucent member covering the first upper surface of the light-emitting element and the second upper surface of the first translucent member, the second translucent member having a third upper surface, the second translucent member substantially not containing a wavelength conversion material; and a first light-reflective member covering the third upper surface of the second translucent member.

Embodiments of the present disclosure can provide a light-emitting device with improved light extraction efficiency.

FIG. 1 is a schematic diagram illustrating an exemplary configuration of a light emitting device according to an embodiment of the present disclosure. 10 is a schematic cross-sectional view showing an exemplary configuration of a light-emitting device according to another embodiment of the present disclosure. FIG. 11 is a schematic cross-sectional view showing a modified example of the light emitting device. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 5A to 5C are schematic cross-sectional views for explaining exemplary manufacturing processes of the light emitting device according to the embodiment of the present disclosure. 13 is a schematic perspective view showing an exemplary configuration of a surface light source according to still another embodiment of the present disclosure. FIG. 13 is a schematic cross-sectional view showing an exemplary configuration of the light-emitting region shown in FIG. 12. FIG. 4 is a schematic plan view showing an example of an arrangement of partition grooves in a light guide plate of a surface light source. 13 is a schematic perspective view showing an exemplary configuration of a surface light source according to still another embodiment of the present disclosure. FIG. 16 is a schematic cross-sectional view showing an exemplary configuration of the light-emitting region shown in FIG. 15.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings. The following embodiments are merely examples, and the light-emitting device and surface light source according to the present disclosure are not limited to the following embodiments. For example, the numerical values, shapes, materials, steps, and the order of the steps shown in the following embodiments are merely examples, and various modifications are possible as long as no technical contradictions arise. Each embodiment described below is merely an example, and various combinations are possible as long as no technical contradictions arise.

The dimensions, shapes, etc. of components shown in the drawings may be exaggerated for clarity and may not reflect the dimensions, shapes, and size relationships between components in an actual light-emitting device or surface light source. Also, some elements may be omitted from the illustration to avoid overly complicating the drawings.

In the following description, components having substantially the same functions are indicated by common reference symbols, and descriptions may be omitted. In the following description, terms indicating a specific direction or position (for example, "up", "down", "right", "left", and other terms including these terms) may be used. However, these terms are merely used for the sake of clarity of the relative direction or position in the referenced drawings. As long as the relationship of the relative direction or position by terms such as "up" and "down" in the referenced drawings is the same, the arrangement in drawings other than this disclosure, actual products, manufacturing equipment, etc. may not be the same as in the referenced drawings. In this disclosure, "parallel" includes cases where two straight lines, sides, faces, etc. are in the range of about 0° to ±5°, unless otherwise specified. In addition, in this disclosure, "perpendicular" or "orthogonal" includes cases where two straight lines, sides, faces, etc. are in the range of about 90° to ±5°, unless otherwise specified.

(Embodiment 1 of the Light Emitting Device)
FIG. 1 shows an exemplary configuration of a light-emitting device according to an embodiment of the present disclosure. The light-emitting device 100A shown in FIG. 1 includes a light-emitting element 120 having an upper surface 120a (first upper surface) and a side surface 120c (first side surface), a first light-transmissive member 130A, a second light-transmissive member 140A, and a first light-reflective member 150. In the configuration shown in FIG. 1, the light-emitting device 100A further includes a covering member 110. FIG. 1 shows a schematic cross-section of the light-emitting device 100A cut perpendicularly to the upper surface 120a near the center of the light-emitting element 120, and a schematic appearance of the structure of the light-emitting device 100A excluding the second light-transmissive member 140A and the first light-reflective member 150 when viewed along the normal direction of the upper surface 120a.

In the configuration illustrated in FIG. 1, the first light-transmissive member 130A has a shape that surrounds the light-emitting element 120 in a planar view. The second light-transmissive member 140A has a plate-like shape and is located above the light-emitting element 120 and the first light-transmissive member 130A. The first light-reflective member 150 has light reflectivity, and in this example, the layer-like first light-reflective member 150 is disposed on the upper surface 140a (third upper surface) of the second light-transmissive member 140A. The shape of the light-emitting device 100A in a planar view is typically rectangular.

Of the light emitted from the light emitting element 120, most of the light emitted from the side surface 120c travels inside the first translucent member 130A and is emitted to the outside of the light emitting device 100A from the outer side surface 130c of the first translucent member 130A. In contrast, the light emitted from the upper surface 120a of the light emitting element 120 mainly travels inside the second translucent member 140A toward the upper surface 140a, and is reflected by the first light reflective member 150 and diffuses within the surface of the second translucent member 140A. A portion of the light reflected by the first light reflective member 150 travels to the outside of the light emitting device 100A from the outer side surface 140c of the second translucent member 140A, and the other portion travels inside the first translucent member 130A and is emitted to the outside of the light emitting device 100A from the outer side surface 130c of the first translucent member 130A.

In the embodiment of the present disclosure, the first light-transmissive member 130A contains a wavelength conversion material such as a phosphor, whereas the second light-transmissive member 140A does not substantially contain a wavelength conversion material. Therefore, compared to a configuration in which both the top and side surfaces of the light-emitting element are covered with a member containing a wavelength conversion material, the proportion of light passing through the member containing the wavelength conversion material can be reduced. This reduces the proportion of light that is absorbed by the light-emitting element after being scattered by the wavelength conversion material, improving the light extraction efficiency.

The components of the light emitting device 100A are described in more detail below.

[Light-emitting element 120]
A typical example of the light-emitting element 120 is an LED. The light-emitting element 120 has a light-transmitting substrate 12s such as sapphire or gallium nitride, a semiconductor laminate 12m, and a pair of positive and negative electrodes 124. In the example shown in FIG. 1, the substrate 12s is disposed on the upper surface of the semiconductor laminate 12m, and the upper surface of the substrate 12s constitutes the upper surface 120a of the light-emitting element 120. The electrode 124 is located on the lower surface of the semiconductor laminate 12m. In other words, the electrode 124 is located on the lower surface 120b (first lower surface) side of the light-emitting element 120 opposite to the upper surface 120a. Here, a configuration in which the light-emitting element 120 includes the substrate 12s is illustrated, but the light-emitting element 120 may also be composed of the semiconductor laminate 12m and the electrode 124.

The semiconductor laminate 12m includes an n-type semiconductor layer, a p-type semiconductor layer, and a light-emitting layer sandwiched between them. The light-emitting layer may have a structure such as a double heterojunction or a single quantum well (SQW), or may have a structure having a group of active layers such as a multiple quantum well (MQW). The semiconductor laminate 12m is configured to be capable of emitting visible light or ultraviolet light. The semiconductor laminate 12m including such a light-emitting layer may include, for example, In _x Al _y Ga _1-xy N (0≦x, 0≦y, x+y≦1).

The semiconductor laminate 12m may have a structure including one or more light-emitting layers between an n-type semiconductor layer and a p-type semiconductor layer, or may have a structure in which a structure including an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer in sequence is repeated multiple times. When the semiconductor laminate 12m includes multiple light-emitting layers, the semiconductor laminate 12m may include light-emitting layers with different emission peak wavelengths, or may include light-emitting layers with the same emission peak wavelength. The same emission peak wavelength includes cases where there is a variation of about several nm. The combination of emission peak wavelengths between the multiple light-emitting layers can be appropriately selected. For example, when the semiconductor laminate 12m includes two light-emitting layers, the light-emitting layers can be selected from combinations such as blue light and blue light, green light and green light, red light and red light, ultraviolet light and ultraviolet light, blue light and green light, blue light and red light, or green light and red light. Each light-emitting layer may include multiple active layers with different emission peak wavelengths, or may include multiple active layers with the same emission peak wavelength.

In the example shown in FIG. 1, the electrode 124 has a pad portion 12p located on the semiconductor laminate 12m side and a conductive member 13 located on the underside of the pad portion 12p. The conductive member 13 is, for example, a columnar member made of Cu. The underside 13b of the conductive member 13 is exposed from the underside 110b of the covering member 110.

As shown in FIG. 1, the shape of the light emitting element 120 in a plan view is typically rectangular. The length of one side of the rectangular shape of the light emitting element 120 is, for example, 1000 μm or less. The length of one side of the rectangular shape of the light emitting element 120 may be 500 μm or less. Light emitting elements with a rectangular side length of 500 μm or less are easy to procure at low cost. Alternatively, the length of one side of the rectangular shape of the light emitting element 120 may be 200 μm or less. If the length of one side of the rectangular shape of the light emitting element 120 is small, it is advantageous for expressing high-definition images, local dimming operation, etc., when applied to a backlight unit of a liquid crystal display device. In particular, a light emitting element in which the length of all sides of the rectangular shape of the light emitting element 120 is 250 μm or less has a small area of the upper surface, so that the amount of light emitted from the side of the light emitting element is relatively large. In other words, it is easy to obtain a batwing-type light distribution characteristic. Here, the batwing-type light distribution characteristic refers, in a broad sense, to a light distribution characteristic that is defined by an emission intensity distribution in which the emission intensity is high at angles where the absolute value of the light distribution angle is greater than 0°, with the optical axis perpendicular to the top surface of the light-emitting element being 0°.

The side surface 120c of the light-emitting element 120 refers to the portion of the surface of the light-emitting element 120 that is located between the upper surface 120a and the lower surface 120b. When the shape of the upper surface 120a of the light-emitting element 120 is rectangular, the light-emitting element 120 has four side surfaces 120c. Note that in FIG. 1, the side surface 120c is shown as a flat surface perpendicular to the upper surface 120a, but in a cross-sectional view, the side surface 120c may have a shape that includes a curve or a step. The lower surface 120b may also have a shape that includes a curve or a step. The side surface 120c may be inclined with respect to a plane perpendicular to the upper surface 120a.

[First translucent member 130A]
The first light-transmissive member 130A is located on at least a part of the side surface 120c of the light-emitting element 120. When the light-emitting element 120 has a plurality of side surfaces 120c, the first light-transmissive member 130A is located on each of the side surfaces 120c (herein, In the example shown, the cover 120 covers part or all of each of the four sides 120c.

As shown in FIG. 1, the first light-transmissive member 130A does not have a portion that covers the upper surface 120a of the light-emitting element 120. The first light-transmissive member 130A is provided in the light-emitting device 100A so as to surround the light-emitting element 120 in a plan view. Therefore, the upper surface 130a (second upper surface) of the first light-transmissive member 130A has a ring shape that does not overlap with the upper surface 120a of the light-emitting element 120. In the example shown in FIG. 1, the upper surface 130a of the first light-transmissive member 130A is on the same plane as the upper surface 120a of the light-emitting element 120.

The material of the first translucent member 130A can be a resin material containing a transparent resin as a base material. The base material of the first translucent member 130A can be an epoxy resin, a silicone resin, a silicone modified resin, a phenol resin, a polycarbonate resin, an acrylic resin, a polymethylpentene resin, a polynorbornene resin, or a material containing two or more of these.

The first translucent member 130A contains a wavelength conversion material such as phosphor particles. The wavelength conversion material in the first translucent member 130A absorbs at least a portion of the light incident on the first translucent member 130A and emits light with a wavelength different from the wavelength of the light from the light emitting element 120. For example, a wavelength conversion material that converts the wavelength of a portion of the blue light from the light emitting element 120 to emit yellow light can be selected as the wavelength conversion material. With this configuration, white light is obtained by mixing the blue light that has passed through the first translucent member 130A and the yellow light emitted from the wavelength conversion material contained in the first translucent member 130A.

As the wavelength conversion material contained in the first light-transmissive member 130A, for example, a known phosphor can be applied. Examples of the phosphor include fluoride phosphors such as KSF phosphors (e.g., K ₂ SiF ₆ :Mn), KSAF phosphors (e.g., K ₂ (Si, Al) F ₆ :Mn), and nitride phosphors such as CASN (e.g., CaAlSiN ₃ :Eu, (Sr, Ca)AlSiN ₃ :Eu), YAG phosphors (e.g., Y ₃ (Al, Ga) ₅ O ₁₂ :Ce), and β-sialon phosphors (e.g., (Si, Al) ₃ (O, N) ₄ :Eu). KSF phosphors and CASN are examples of wavelength conversion materials that convert blue light to red light, and YAG phosphors are examples of wavelength conversion materials that convert blue light to yellow light. The β-sialon phosphor is an example of a wavelength conversion material that converts blue light into green light. The phosphor may be a phosphor having a perovskite structure (e.g., CsPb(F,Cl,Br,I) ₃ ) or a quantum dot phosphor (e.g., CdSe, InP, _AgInS2 , or _AgInSe2 ). The first light-transmitting member 130A may further contain a light diffusing material such as titanium dioxide or silicon oxide particles.

[Second translucent member 140A]
The second light-transmissive member 140A is provided in the light-emitting device 100A so as to cover the upper surface 120a of the light-emitting element 120 and the upper surface 130a of the first light-transmissive member 130A. The optical member 140A is in direct contact with the upper surface 120a of the light emitting element 120. In this example, the second optically transmissive member 140A is also in direct contact with the upper surface 130a of the first optically transmissive member 130A.

In the configuration illustrated in FIG. 1, each of the four outer surfaces 140c of the second translucent member 140A is flush with a corresponding one of the outer surfaces 130c of the first translucent member 130A. A light diffusion layer may be disposed on the outer surface 140c of the second translucent member 140A and the corresponding outer surface 130c of the first translucent member 130A. By disposing the light diffusion layer in this manner, the light from the light emitting element 120 can be diffused by the light diffusion layer.

The material of the second translucent member 140A can be the same as the base material of the first translucent member 130A. However, in the embodiment of the present disclosure, the second translucent member 140A does not substantially contain a wavelength conversion material such as phosphor particles. A part of the light (here, blue light) introduced from the upper surface 120a of the light emitting element 120 to the second translucent member 140A is reflected by the first light reflective member 150 described below and enters the first translucent member 130A through the upper surface 130a of the first translucent member 130A. A part of the blue light introduced from the second translucent member 140A to the first translucent member 130A is wavelength converted by the first translucent member 130A and is emitted to the outside of the light emitting device 100A.

In this specification, "substantially free of" does not intend to exclude the inclusion of wavelength conversion material or light diffusing material due to unavoidable contamination during the manufacturing process, etc. The weight ratio of the wavelength conversion material unintentionally contaminated in the second light-transmissive member 140A to the entire second light-transmissive member 140A is preferably 0.05% by weight or less. Since the second light-transmissive member 140A is substantially free of light diffusing material, scattering within the second light-transmissive member 140A can be suppressed.

The second light-transmissive member 140A has a transmittance of, for example, 60% or more for light having the emission peak wavelength of the light-emitting element 120. From the viewpoint of increasing the light extraction efficiency, it is beneficial for the transmittance of the second light-transmissive member 140A at the emission peak wavelength of the light-emitting element 120 to be 70% or more, and more beneficial for it to be 80% or more.

[First light reflective member 150]
The first light reflective member 150 is provided on the upper surface 140a of the second light-transmitting member 140A. The first light reflective member 150 typically covers the entire upper surface 140a. The first light reflective member 150 can be formed from, for example, a white resin material. The white resin material typically includes a base material and a light reflective filler.

Examples of the base material of the first light-reflective member 150 include silicone resin, phenolic resin, epoxy resin, BT resin, polyphthalamide (PPA), etc. As the light-reflective filler, metal particles, or particles of inorganic or organic materials having a higher refractive index than the base material can be used. Examples of the light-reflective filler include particles of titanium dioxide, silicon oxide, zirconium dioxide, potassium titanate, aluminum oxide, magnesium oxide, aluminum nitride, boron nitride, mullite, niobium oxide, barium sulfate, or particles of various rare earth oxides such as yttrium oxide and gadolinium oxide.

In this specification, "light reflectivity" refers to a reflectivity of 60% or more at the emission peak wavelength of the light emitting element 120. The reflectivity of the first light reflective member 150 can be adjusted appropriately depending on the application of the light emitting device. It is sufficient for the first light reflective member 150 to appropriately reflect the light emitted from the light emitting element 120 and appropriately reduce the luminance directly above the light emitting element 120. It is not essential that the first light reflective member 150 completely blocks the light from the light emitting element 120.

The first light reflective member 150 is not limited to a white resin layer. The first light reflective member 150 may be a metal film such as an Ag film or an Al film, or a reflective film such as a dielectric multilayer film. The first light reflective member 150 may be a composite of a white resin layer and a reflective film. For example, the first light reflective member 150 may be a composite of a white resin layer and a metal film.

By disposing the first light-reflective member 150 above the light-emitting element 120, at least a portion of the light emitted upward from the light-emitting element 120 can be reflected by the first light-reflective member 150. Reflection at the interface between the first light-reflective member 150 and the second light-transmissive member 140A can suppress the luminance on the optical axis of the light-emitting element 120 while allowing more light to be emitted toward the side of the light-emitting device 100A. Such a configuration of the light-emitting device according to the embodiment of the present disclosure is advantageous for application as a light source optically coupled to a light guide plate, as described below.

The light extracted to the outside of the light emitting device 100A includes light that is guided between the first light reflective member 150 and the upper surface 120a of the light emitting element 120 or the upper surface 130a of the first translucent member 130A inside the second translucent member 140A and is emitted from the outer surface 140c of the second translucent member 140A. As described above, since the second translucent member 140A does not substantially contain a wavelength conversion material, when a blue LED is applied to the light emitting element 120, the light emitted from the outer surface 140c of the second translucent member 140A is basically blue light. In other words, according to this embodiment, more blue light can be emitted toward the side of the light emitting device 100A.

The light extracted to the outside of the light emitting device 100A also includes light that passes through the second light-transmitting member 140A and the first light-reflecting member 150 from the light emitting element 120 and is emitted from the upper surface 150a. Since the second light-transmitting member 140A does not substantially contain a wavelength conversion material, the light emitted from the upper surface 150a of the first light-reflecting member 150 is also basically blue light. That is, according to this embodiment, light containing a large amount of blue components can be emitted even toward the upper side of the light emitting device 100A. This means that in an application as a light source optically coupled to a light guide plate, more blue light or a light amount with an adjusted amount of blue light is emitted directly above the light source, and for example, the light emitting device according to the embodiment of the present disclosure can be used as a light source more advantageously in an application to a backlight combined with a light guide plate.

[Covering member 110]
As illustrated in Fig. 1, the light emitting device may have a light reflective covering member 110 on the lower surface 120b side of the light emitting element 120. In the example illustrated in Fig. 1, the covering member 110 covers the lower surface 130b (second lower surface) of the first light transmissive member 130A, which is located on the opposite side to the upper surface 130a. The covering member 110 covers the light emitting element 120 except for the lower surface of the electrode 124 (here, the lower surface 13b of the conductive member 13). In the example illustrated in Fig. 1, the lower surface 13b of the conductive member 13 is in the same plane as the lower surface 11b of the covering member 110.

The covering member 110 contains, for example, a base material and a light-reflective filler, similar to the first light-reflective member 150. In this case, the covering member 110 functions as a light-reflective layer. By providing the covering member 110 on the lower surface 120b side of the light-emitting element 120, it is possible to reduce light leakage from the lower surface 120b side of the light-emitting element 120, and to avoid a decrease in the light extraction efficiency.

(Embodiment 2 of the Light Emitting Device)
Fig. 2 shows an exemplary configuration of a light emitting device according to another embodiment of the present disclosure. Compared with the light emitting device 100A described with reference to Fig. 1, the light emitting device 100B shown in Fig. 2 has a first light transmissive member 130B and a second light transmissive member 140B instead of the first light transmissive member 130A and the second light transmissive member 140A, respectively.

In the configuration illustrated in FIG. 2, the upper surface 130a of the first translucent member 130B is located below the upper surface 120a of the light-emitting element 120. Therefore, in this example, the second translucent member 140B covers a part of the side surface 120c of the light-emitting element 120. By adjusting the proportion of the side surface 120c of the light-emitting element 120 covered by the second translucent member 140B, the amount of light extracted that has not been wavelength-converted can be adjusted. For example, by covering a larger portion of the side surface 120c of the light-emitting element 120 with the second translucent member 140B, the amount of light extracted that has not been wavelength-converted can be improved. Improving the amount of light extracted that has not been wavelength-converted also reduces the proportion of light that is scattered by the wavelength conversion material inside the first translucent member 130B and is ultimately absorbed by the light-emitting element 120. That is, the light extraction efficiency of the entire light-emitting device can also be improved. In addition, it becomes easier to obtain a batwing-type light distribution characteristic.

In the example shown in FIG. 2, the second translucent member 140B covers a portion of each side surface 12sc of the substrate 12s, which constitutes a portion of the side surface 120c of the light-emitting element 120. The second translucent member 140B may cover the entirety of each side surface 12sc of the substrate 12s, or may further cover a portion of the side surface of the semiconductor laminate 12m.

(Modification)
Fig. 3 shows a modified example of the light emitting device. Compared to the light emitting device 100A shown in Fig. 1, the light emitting device 100C shown in Fig. 3 has a wiring layer 170 connected to the electrode 124 of the light emitting element 120.

In this example, a wiring layer 170 is disposed across the lower surface 13b of the conductive member 13 and the lower surface 110b of the covering member 110. The wiring layer 170 is electrically connected to the electrode 124 of the light-emitting element 120, and functions as an external connection portion for supplying current to the light-emitting element 120. The wiring layer 170 may be provided in the light-emitting device 100A shown in FIG. 1 or the light-emitting device 100B shown in FIG. 2.

In the configuration illustrated in FIG. 3, the light-emitting device 100C further includes a translucent bonding member 180. The bonding member 180 is a member formed by curing an adhesive containing, for example, a transparent resin. In this example, the light-emitting element 120 is fixed to the second translucent member 140A by the bonding member 180. As illustrated in FIG. 3, the bonding member 180 may have a portion located between the lower surface 140b of the second translucent member 140A and the upper surface 120a of the light-emitting element 120.

(Outline of manufacturing method of light emitting device)
An exemplary method for manufacturing a light emitting device according to an embodiment of the present disclosure will now be outlined with reference to FIGS.

First, as shown in FIG. 4, a support 62 is prepared. Here, a heat-resistant adhesive sheet attached to a ring frame is used as the support 62.

Next, the first resin material 110r in an uncured state is applied onto the support 62. Here, a ring-shaped shim 64 is placed on the upper surface 62a of the support 62, and then the first resin material 110r is applied to the area surrounded by the shim 64.

Next, the light emitting element 120 is prepared. The electrode 124 of the light emitting element 120 may be in a state where the conductive member 13 is arranged on the pad portion 12p. After preparing the light emitting element 120, the light emitting element 120 is arranged on the support 62 with the lower surface 120b of the light emitting element 120 facing the support 62. Here, a plurality of light emitting elements 120 are arranged on the support 62. At this time, by pressing the light emitting element 120 toward the support 62, the electrode 124 can be buried inside the first resin material 110r as shown in FIG. 5 by pressing the light emitting element 120 toward the support 62. Typically, the light emitting element 120 is pressed toward the support 62 until the lower surface of the electrode 124 contacts the upper surface 62a of the support 62. The thickness of the layer of the first resin material 110r can be adjusted by the thickness of the shim 64. The thickness of the layer of the first resin material 110r is, for example, in the range of 10 μm to 90 μm, and can be appropriately adjusted according to the thickness of the electrode 124.

Next, the first resin material 110r is cured. By curing the first resin material 110r, the first resin layer 110L can be formed on the support 62. After the first resin layer 110L is formed, as shown in FIG. 6, the second resin material 130r is applied to the area of the first resin layer 110L excluding the light emitting element 120. At this time, the supply amount of the second resin material 130r is adjusted so that the upper surface of the layer of the second resin material 130r is at the same height as the upper surface 120a of the light emitting element 120 when the surface of the second resin material 130r applied on the first resin layer 110L is flattened. The position of the upper surface of the layer of the second resin material 130r may be aligned with the position of the upper surface 120a of the light emitting element 120, or may be lower than the position of the upper surface 120a of the light emitting element 120. Then, the second resin material 130r is cured.

By hardening the second resin material 130r, as shown in FIG. 7, a second resin layer 130L can be formed around the light-emitting element 120. The second resin material 130r may be disposed up to a position higher than the position of the upper surface 120a of the light-emitting element 120 and hardened. In this case, by performing grinding after the second resin material 130r has hardened, the second resin layer 130L having an upper surface 130a that is flush with the upper surface 120a of the light-emitting element 120 can be obtained.

Next, a third resin material is applied to the upper surface 120a of the light-emitting element 120 and the upper surface 130a of the second resin layer 130L, and cured to form a third resin layer 140L that collectively covers the multiple light-emitting elements 120, as shown in FIG. 8. As the third resin material, a material that does not substantially contain a wavelength conversion material or a light diffusing material is used.

Then, a fourth resin material is applied to the upper surface 140a of the third resin layer 140L, and the fourth resin material is cured. By curing the fourth resin material, a light-reflective fourth resin layer 150L can be formed on the third resin layer 140L, as shown in FIG. 9. The fourth resin material may be the same material as the first resin material 110r.

Next, the support 62 and shim 64 are removed, and the structure separated from the support 62 is turned upside down and placed on a support 66 as shown in FIG. 10. A UV tape, whose adhesive strength decreases when exposed to ultraviolet light, can be applied to the support 66. The support 66 can be supported by a ring frame 68.

If necessary, the structure supported by the support 66 is ground from the first resin layer 110L side by, for example, about 20 μm to 40 μm. This grinding process can expose, for example, the lower surface of the electrode 124 (if the electrode 124 includes a conductive member 13, the lower surface 13b) from the ground surface. Also, if necessary, a metal film may be formed on the first resin layer 110L, and a conductive layer may be formed on the first resin layer 110L by patterning the metal film. For example, Ni, Ru, and Au may be deposited in order on the first resin layer 110L, and the laminated film on the first resin layer 110L may be patterned. Alternatively, Ti, Pt, and Au may be deposited in order on the first resin layer 110L, and the laminated film on the first resin layer 110L may be patterned. If the outermost surface of the conductive layer is an Au layer, the wettability to solder when mounting the light-emitting device is improved. It is beneficial if the conductive layer contains a high melting point metal layer such as a Ru layer, Mo layer, or Ta layer, as such a layer can function as a diffusion prevention layer that suppresses the diffusion of Sn in the solder to the electrode.

11, the first resin layer 110L, the second resin layer 130L, the third resin layer 140L, and the fourth resin layer 150L are cut at a position between two adjacent light emitting elements 120. This singulation process allows the covering member 110 and the first light reflective member 150 to be formed from the first resin layer 110L and the fourth resin layer 150L, respectively. In the process of applying the second resin material 130r shown in FIG. 6, if the position of the upper surface of the layer of the second resin material 130r is aligned with the position of the upper surface 120a of the light emitting element 120, the first translucent member 130A and the second translucent member 140A can be formed from the second resin layer 130L and the third resin layer 140L, respectively, and the light emitting device 100A shown in FIG. 1 can be obtained. In the step of applying the second resin material 130r, if the position of the upper surface of the layer of the second resin material 130r is made lower than the position of the upper surface 120a of the light emitting element 120, the first translucent member 130B and the second translucent member 140B can be formed from the second resin layer 130L and the third resin layer 140L, respectively, and the light emitting device 100B shown in FIG. 2 can be obtained. By forming a conductive layer on the first resin layer 110L and then performing a singulation step, a light emitting device having a wiring layer 170 on the covering member 110 (see FIG. 3) can be obtained. The formation of the wiring layer 170 may be omitted.

After the first resin layer 110L is formed, a resin sheet piece including a translucent resin layer and a light-reflective resin layer may be bonded to the upper surface 120a of each light-emitting element 120 using a translucent adhesive. After the translucent adhesive has hardened, a second resin material 130r is placed around each light-emitting element 120, and the second resin material 130r is hardened. Thereafter, a singulation process is performed to form a bonding member 180 from the translucent adhesive, thereby obtaining the light-emitting device 100C shown in FIG. 3.

(Application example 1 to a surface light source)
Next, an example of application of the above-mentioned light emitting devices 100A to 100C as a light source will be described. In the following, an example in which the light emitting device 100B of the light emitting devices 100A to 100C is applied to a surface light source will be described, but it is of course possible to apply the light emitting device 100A or 100C instead of the light emitting device 100B, and to mix the light emitting devices 100A, 100B, and 100C as light sources when the surface light source includes multiple light sources.

Figure 12 shows an exemplary configuration of a surface light source according to yet another embodiment of the present disclosure. The surface light source 300A shown in Figure 12 has a light guide plate 310A having an upper surface 310a, and a plurality of light emitting devices 100B. In this example, the surface light source 300A further has a wiring board 340 located below the light guide plate 310A. For ease of explanation, Figure 12 also shows arrows indicating the mutually orthogonal X, Y, and Z directions. Arrows indicating these directions may also be shown in other drawings of the present disclosure.

The surface light source 300A is generally plate-shaped. The upper surface 310a of the light guide plate 310A, which constitutes the light-emitting surface of the surface light source 300A, typically has a rectangular shape. Here, the above-mentioned X direction and Y direction respectively correspond to one side and the other side of the rectangular shape of the light guide plate 310A that are perpendicular to each other. The length of one side of the rectangular shape of the upper surface 310a is, for example, in the range of 20 cm to 40 cm.

In the configuration illustrated in FIG. 12, the surface light source 300A includes a plurality of light-emitting regions 200A, each having at least one light-emitting device 100B. As illustrated in FIG. 12, the surface light source 300A includes a total of 16 light-emitting regions 200A arranged in four rows and four columns in this example. The number of light-emitting regions included in the surface light source and the arrangement of these light-emitting regions are arbitrary and are not limited to the configuration illustrated in FIG. 12. For example, the surface light source may be configured with a one-dimensional array of two or more light-emitting regions. It is also possible for the surface light source to be configured from a single light-emitting region.

As shown in FIG. 12, each light-emitting region 200A has a through-hole 10 that includes an opening 10a located on the upper surface 310a of the light guide plate 310A. The light-emitting device 100B of each light-emitting region 200A is located inside a corresponding one of the multiple through-holes 10. In this example, the light-emitting regions 200A are arranged in four rows and four columns, and the light-emitting devices 100B are arranged in four rows and four columns on the wiring substrate 340 along the X and Y directions accordingly.

Figure 13 shows a schematic cross section of the light-emitting region 200A shown in Figure 12. The cross section shown in Figure 13 corresponds to a part of a cross section when the surface light source 300A is cut perpendicularly to the upper surface 310a of the light guide plate 310A.

The light-emitting region 200A generally includes a light guide plate 210A, a light source (here, the light-emitting device 100B), and a wiring board 240. The light guide plate 210A has an upper surface 210a and a lower surface 210b opposite to the upper surface 210a. The wiring board 240 is located on the lower surface 210b side of the light guide plate 210A. The light guide plate 210A is provided with a through hole 10 including an opening 10a located on the upper surface 210a. The light guide plate 210A is a part of the light guide plate 310A shown in FIG. 12, and the through hole 10 in FIG. 13 is one of the multiple through holes 10 shown in FIG. 12.

Here, the through hole 10 has a generally cylindrical shape. As shown in FIG. 13, in addition to the opening 10a, the through hole 10 includes an opening 10b located on the lower surface 210b of the light guide plate 210, and a side surface 10c located between the openings 10a and 10b. The side surface of the through hole is the inner side surface of the light guide plate that defines the shape of the through hole. The specific shape of the through hole 10 is not limited to this example. The shape of the through hole 10 may be a prism shape, a truncated cone shape, an inverted truncated cone shape, a truncated polygonal pyramid shape, etc.

The light emitting device 100B is located inside the through hole 10. In this example, the light emitting device 100B is covered by the third translucent member 23.

The wiring board 240 shown in FIG. 13 is a part of the wiring board 340 shown in FIG. 12, and includes one or more wiring layers 241 and an insulating part 244 such as resin. The wiring board 240 has an upper surface 240a and a lower surface 240b located opposite the upper surface 240a. Here, the light guide plate 210A is bonded to the wiring board 240 by an adhesive sheet 250 interposed between the upper surface 240a of the wiring board 240 and the lower surface 210b of the light guide plate 210A. The light emitting element 120 in the light emitting device 100B is electrically connected to the wiring layer 241 of the wiring board 240.

In this embodiment, the light emitting device 100A, the light emitting device 100B, or the light emitting device 100C can be used as the light source of each light emitting region. As described above, in the light emitting devices 100A to 100C, the upper surface 120a of the light emitting element 120 is covered with the second light transmissive member 140A or 140B that does not substantially contain a wavelength conversion material, thereby reducing the proportion of light that is scattered by the wavelength conversion material and then absorbed by the light emitting element. In addition, since the second light transmissive members 140A and 140B do not substantially contain a wavelength conversion material, the scattering of light traveling inside the second light transmissive member is reduced, and light emitted to the side of the light emitting device can be propagated further. Therefore, in applications in combination with a light guide plate, more light can reach the part of the light emitting region that is far from the light emitting device. As a result of improving the brightness of the areas of the light emitting surface of each light emitting region that tend to be relatively dark, it is possible to more effectively suppress brightness unevenness while suppressing an increase in the thickness of the light guide plate.

The following describes each component in the light-emitting area 200A in detail.

[Light guide plate 210A]
The light guide plate 210A is a generally plate-shaped member made of a thermoplastic resin such as acrylic, polycarbonate, cyclic polyolefin, polyethylene terephthalate, or polyester, or a thermosetting resin such as epoxy or silicone, and has light transmissivity. The light guide plate 210A has a function of propagating light from a light source (here, the light emitting device 100B) inside and emitting it from an upper surface 210a. The upper surface 210a of the light guide plate 210A typically has a rectangular shape similar to the upper surface 310a of the light guide plate 310. In this embodiment, a collection of the upper surfaces 210a of the multiple light guide plates 210A constitutes the light emitting surface of the planar light source 300A.

As can be seen from FIG. 1, the shape of the light-emitting device according to the embodiment of the present disclosure is typically rectangular in plan view. In this case, the light-emitting device (e.g., light-emitting device 100B) may be disposed in through-hole 10 so that one side of the rectangular shape is parallel to one side of the rectangular shape of light guide plate 210A, or may be disposed in through-hole 10 so that it is inclined with respect to one side of the rectangular shape of light guide plate 210A. For example, light-emitting device 100B may be disposed in through-hole 10 so that its rectangular shape is inclined 45° with respect to the rectangular shape of light guide plate 210A in plan view. In either arrangement, the center of the through-hole of light guide plate 210A is approximately aligned with the optical axis of light-emitting device 100B.

13, the light guide plate 210A may have one or more partition grooves 210g. The partition grooves 210g are provided, for example, at the boundary between two adjacent light emitting regions 200A in the surface light source 300A, and are arranged to surround the light emitting device 100B of each light emitting region 200A in a planar view. By providing the partition grooves 210g in the light guide plate 210A, for example, under local dimming drive, the contrast ratio between two adjacent light emitting regions 200A (the steepness of the luminance change between the light emitting region 200A in which the light emitting device 100B is turned on and the light emitting region 200A adjacent to the light emitting region 200A in which the light emitting device 100B is turned off) can be advantageously improved.

In this example, each partition groove 210g includes an opening located on the upper surface 210a of the light guide plate 210A and reaches the lower surface 210b. The depth of the partition groove 210g is, for example, in the range of 20% to 100% of the thickness of the light guide plate 210A. In the example shown in FIG. 13, the partition groove 210g penetrates the adhesive sheet 250 and reaches the light reflective sheet 255 described below. In this sense, it can be said that the partition groove 210g may have a depth greater than the thickness of the light guide plate. The shape of the partition groove 210g may be such that it does not have an opening on the upper surface 210a of the light guide plate 210A and opens on the lower surface 210b.

The inner surface 210c that defines the shape of the partition groove 210g may be perpendicular to the upper surface 210a of the light guide plate 210A in a cross-sectional view, or may be inclined with respect to the upper surface 210a. The inner surface 210c of the partition groove 210g may have a step in a cross-sectional view.

Figure 14 shows an example of the arrangement of the partition grooves 210g in the light guide plate 310A of the surface light source 300A. In the configuration illustrated in Figure 14, each of the partition grooves 210g extends linearly in the X direction or Y direction between two adjacent light emitting regions 200A arranged two-dimensionally, or along the outer edge of the light guide plate 310A. That is, in this example, the partition grooves 210g include multiple grooves located at the boundary between two adjacent light emitting regions 200A, and a collection of the multiple partition grooves 210g forms a lattice-shaped groove structure provided on the light guide plate 310A. The width of each partition groove 210g in a top view is, for example, about 220 μm. Note that the partition grooves 210g located on the outer edge of the light guide plate 310A may be omitted.

[Partition member 21]
Referring again to Fig. 13, in the example shown in Fig. 13, a light-reflective partitioning member 21 is located inside the partitioning groove 210g. The partitioning member 21 is made of, for example, a resin material containing a resin as a base material and a light-reflective filler. The material of the partitioning member 21 may be the same as that of the first light-reflective member 150 or the covering member 110. The partitioning member 21 may be a white resin layer.

The material of the partition member 21 is not limited to a material having a resin as a base material. The partition member 21 may be a metal film (Ag film, Al film, etc.) or a reflective film such as a dielectric multilayer film. The partition member 21 may have a shape in which a part of it covers the upper surface 210a and/or the lower surface 210b of the light guide plate 210A.

[Third translucent member 23]
13, the light-emitting region 200A further includes a third light-transmissive member 23 disposed inside the through-hole 10 of the light guide plate 210A. In this example, the openings 10a and 10b and the side surface 10c and A third light-transmissive member 23 is disposed in the space defined by the arrows 21 and 22 excluding the light emitting device 100B.

The upper surface 23a of the third light-transmissive member 23 is the surface of the third light-transmissive member 23 that is located on the upper surface 210a side of the light guide plate 210A. The upper surface 23a of the third light-transmissive member 23 may be raised relative to the upper surface 210a of the light guide plate 210A, or may be recessed from the position of the upper surface 210a of the light guide plate 210A.

The material of the third light-transmissive member 23 may be a material containing a resin as a base material. Typical examples of the base material of the third light-transmissive member 23 are thermosetting resins such as epoxy resin and silicone resin. From the viewpoint of efficiently guiding the light from the light-emitting device 100B into the light guide plate 210A, it is advantageous for the third light-transmissive member 23 to have a refractive index equal to or higher than that of the material of the light guide plate 210A.

The third translucent member 23 may contain a wavelength conversion material. Alternatively, instead of or in addition to the wavelength conversion material, the third translucent member 23 may contain a light diffusing material. The light emitting device according to the embodiment of the present disclosure has a higher proportion of light that is not wavelength converted compared to a configuration in which the top surface as well as the side surfaces of the light emitting element are covered with a material containing a phosphor or the like. Therefore, even if the third translucent member 23 contains a wavelength conversion material, it is possible to suppress an unintended decrease in the color temperature of the light emitted from the top surface 23a of the third translucent member 23 (e.g., white light becoming yellowish).

In addition, after bonding the light guide plate 210A to the wiring board 240 and mounting the light emitting device on the wiring board 240 inside the through hole 10 of the light guide plate 210A, it may be found that the chromaticity of the light from the light emitting device deviates from the desired chromaticity. Even in such a case, by including a wavelength conversion material in the third light-transmissive member 23, the wavelength conversion material in the third light-transmissive member 23 can be excited by the light from the light emitting device (e.g., blue light) to obtain wavelength-converted light, so that the chromaticity of the upper surface 23a of the third light-transmissive member 23 when the light emitting device is turned on can be made uniform among the multiple light emitting regions 200A. Since color correction can be performed after the light emitting device is mounted on the wiring board 240, the yield of the surface light source 300A can be improved without replacing the light emitting device itself in which a deviation from the desired chromaticity is found.

[Second light reflective member 22]
13 , the light-emitting region 200A has a second light-reflective member 22 disposed on an upper surface 23a of the third light-transmissive member 23. The second light-reflective member 22 can be formed from the same material as the first light-reflective member 150 or the covering member 110.

The second light-reflective member 22 of each light-emitting region 200A covers the through-hole 10 on the upper surface 210a side of the light guide plate 210A. By disposing the second light-reflective member 22 above the light-emitting element 120, at least a portion of the light emitted upward from the light-emitting element 120 can be reflected by the second light-reflective member 22. Therefore, it is possible to prevent the brightness of the area located directly above the light-emitting element 120 from becoming extremely high compared to an area of the light-emitting surface of the light-emitting region 200A that is located away from the light-emitting element 120.

In addition, when a light-reflecting member made of a resin that easily absorbs blue light is placed directly above the light source, or when a light-reflecting member that contains a light-reflecting filler that easily reflects blue light and exhibits wavelength dependency such that the transmittance decreases on the short wavelength side is placed, the color temperature of the transmitted light from the light-reflecting member may be lowered (e.g., yellowish) compared to the direct light from the light source. In the example shown in FIG. 13, the second light-reflecting member 22 is also located above the light-emitting device 100B as a light source. However, as described above, according to the embodiment of the present disclosure, it is relatively easy to supply blue light with an adjusted amount of light toward the upper side of the light-emitting device. Therefore, even when the second light-reflecting member 22 is placed above the light-emitting device 100B, it is possible to prevent the transmitted light from the second light-reflecting member 22 from becoming yellowish. The same effect can be obtained by using the third light-reflecting member 50 in the planar light source 300B described later.

The second light-reflective member 22 may be selectively disposed on the upper surface 23a of the third light-transmissive member 23, which is part of the light-emitting surface of the light-emitting region 200A, or a part of it may be disposed on the upper surface 210a of the light guide plate 210A. The shape of the second light-reflective member 22 in a plan view is typically similar to the shape of the opening 10a of the through hole 10.

In addition, when the third light-transmissive member 23 contains a wavelength conversion member such as a YAG phosphor for color correction between multiple light-emitting devices, repeated reflections between the first light-reflecting member 150 and the second light-reflecting member 22 of the light-emitting device inside the through-hole 10 may cause the light emitted from the upper surface 23a of the third light-transmissive member 23 to be yellowish compared to the light emitted from the upper surface 210a of the light guide plate 210A. By configuring the first light-reflecting member 150 to be able to transmit at least a portion of the light from the light-emitting element 120, the proportion of light that has not been wavelength-converted (e.g., blue light) can be increased, and changes in the color of the emitted light caused by repeated reflections inside the through-hole 10 (i.e., the emitted light becomes more yellowish) can be suppressed.

[Wiring board 240]
The wiring board 240 is located on the lower surface 210b side of the light guide plate 210A and supports the light guide plate 210A. In other words, the light guide plate 210A is disposed on the wiring board 240. The wiring board 240 shown in FIG. 13 is a part of the wiring board 340 shown in FIG. 12, and typically includes one or more wiring layers and an insulating part such as a resin. Here, the wiring board 240 has a wiring layer 241, an insulating part 244, and a via 60. An example of the wiring board 240 is a flexible printed circuit board (FPC). The wiring board 240 may be a double-sided printed circuit board or a single-sided printed circuit board.

The majority of the wiring layer 241 of the wiring board 240 is disposed within the insulating portion 244. In the configuration illustrated in FIG. 13, the wiring layer 241 includes a first wiring layer 241a located on the upper surface 240a side of the wiring board 240 and a second wiring layer 241b located on the lower surface 240b side of the wiring board 240. The first wiring layer 241a and the second wiring layer 241b are made of a metal such as copper, and are electrically connected to each other inside the wiring board 240 by vias (not shown in FIG. 13).

The via 60 penetrates from the upper surface 240a to the lower surface 240b of the wiring substrate 240, and electrically connects the electrode 124 of the light-emitting element 120 to the second wiring layer 241b of the wiring layer 241. In this example, the portion of the via 60 that is exposed on the lower surface 240b side of the wiring substrate 240 is covered with an insulating protective member 245. The protective member 245 is made of, for example, resin.

In the configuration illustrated in FIG. 13, the insulating section 244 includes a sheet-like insulating base material 244s that supports the first wiring layer 241a and the second wiring layer 241b, a first covering layer 244t that covers the first wiring layer 241a on the upper surface 240a side of the wiring board 240, a second covering layer 244u that covers the second wiring layer 241b on the lower surface 240b side of the wiring board 240, and the protective member 245 described above.

In this embodiment, the first light-transmissive members 130A and 130B containing the wavelength conversion material do not cover the top surface of the light-emitting element, but selectively cover the side surface of the light-emitting element, so that the light-emitting element is located closer to the wiring board 240 in the light-emitting device. Therefore, heat generated during wavelength conversion in the first light-transmissive members 130A and 130B can be easily released to the wiring board 240, improving the reliability of the surface light source 300A.

[Adhesive sheet 250]
A known resin sheet having an adhesive layer can be used as the adhesive sheet 250. For example, a sheet-shaped optically clear adhesive (OCA) can be applied to the adhesive sheet 250.

The adhesive sheet 250 may have light reflectivity, for example by containing a light-reflective filler. By making the adhesive sheet 250 light-reflective, the light guide plate 210A is guided from the light-emitting device 100B toward the lower surface 210b of the light guide plate 210A, and the light guide plate 210A is reflected toward the upper surface 210a of the light guide plate 210A by the adhesive sheet 250, improving the light extraction efficiency.

[Light-reflecting sheet 255]
13, the light-emitting region 200A further includes a light-reflecting sheet 255. In this example, the light-reflecting sheet 255 is located between the above-mentioned adhesive sheet 250 and an adhesive sheet 270 (described later) located on the wiring substrate 240.

The light reflecting sheet 255 is, for example, a white member, and improves the light extraction efficiency by reflecting the light traveling toward the wiring board 240 side inside the light guide plate 210A toward the upper surface 210a of the light guide plate. As with the material of the second light reflecting member 22 described above, a resin material containing a light reflective filler as a light diffusing material can be used as the material of the light reflecting sheet 255. The light reflecting sheet 255 can be, for example, a resin sheet containing polyethylene terephthalate as a base material. As the light diffusing material, for example, titanium dioxide particles can be used. Instead of forming the light reflecting sheet 255 from a material containing a light diffusing material in the base material, a white polyethylene terephthalate sheet containing a large number of air bubbles may be used as the light reflecting sheet 255.

[Adhesive sheet 270]
The adhesive sheet 270 is disposed between the wiring board 240 and the light reflecting sheet 255, and fixes the light reflecting sheet 255 to the upper surface 240a of the wiring board 240. The adhesive sheet 270 may be an adhesive layer made of a resin material such as acrylic. A known resin sheet having an adhesive layer, such as a bonding sheet, may be used as the adhesive sheet 270. Like the adhesive sheet 250 described above, the adhesive sheet 270 may have light reflectivity.

(Application example 2 to a surface light source)
Fig. 15 shows another exemplary configuration of a surface light source. The surface light source 300B shown in Fig. 15 includes a light guide plate 310B having an upper surface 310a and a plurality of light emitting devices 100B. In this example, the surface light source 300B further includes a generally layered light reflective member 360 located on the opposite side of the upper surface 310a of the light guide plate 310B. In the configuration shown in Fig. 15, the surface light source 300B is configured with an arrangement of 16 light emitting regions 200B in 4 rows and 4 columns.

Figure 16 shows a schematic cross section of the light-emitting region 200B shown in Figure 15. Compared to the light-emitting region 200A shown in Figure 13, the light-emitting region 200B includes a light-guiding plate 210B having a first recess 31 on the upper surface 210a instead of the light-guiding plate 210A having the through-hole 10. The material of the light-guiding plate 210B can be the same as that of the light-guiding plate 210A described above.

In the configuration illustrated in FIG. 16, the light-emitting region 200B has, in addition to the light guide plate 210B, a light-emitting device 100B, a third light-reflective member 50, and a fourth light-reflective member 260. The light guide plate 210B is part of the light guide plate 310B shown in FIG. 15, and the fourth light-reflective member 260 is part of the light-reflective member 360 shown in FIG. 15. Each component of the light-emitting region 200B will be described in more detail below.

[Light guide plate 210B]
The light guide plate 210B has a first recess 31 at approximately the center of the upper surface 210a. In this example, the first recess 31 has a first opening 31a located on the upper surface 210a, a first bottom surface 31b that is approximately parallel to the upper surface 210a of the light guide plate 210B, and a first side surface 31c that is inclined with respect to the upper surface 210a. The first side surface 31c of the first recess 31 is located between the first opening 31a and the first bottom surface 31b.

The first side surface 31c of the first recess 31 functions as a reflective surface for the light emitted from the light source (here, the light emitting device 100B) and introduced into the light guide plate 210B. The light emitted from the light emitting element 120 can be effectively diffused inside the light guide plate 210B by reflection at the first side surface 31c of the first recess 31. The first recess 31 of the light guide plate 210B functions as a light diffusion structure. By providing the light guide plate 210B with the first recess 31 as such a light diffusion structure, the brightness of the upper surface 210a in the region other than directly above the light emitting device 100B can be improved. In other words, the brightness unevenness on the upper surface of the light emitting region 200B can be suppressed.

As can be seen from Figures 15 and 16, here, the first recess 31 has an inverted truncated cone shape. However, the shape of the first recess 31 is not limited to this example, and may be other shapes such as an inverted truncated pyramid, an inverted cone, or an inverted pyramid. The shape of the first opening 31a and the shape of the first bottom surface 31b in a plan view are not limited to a perfect circle, and may be an ellipse, etc. Furthermore, the shape of the first side surface 31c in a cross-sectional view may be linear or curved. The shape of the first side surface 31c in a cross-sectional view may be a shape that includes a step and/or a bend.

As shown in FIG. 16, the light guide plate 210B has a second recess 32 on the lower surface 210b side. The second recess 32 has, for example, a quadrangular pyramid shape, and has a second bottom surface 32b facing the first bottom surface 31b of the first recess 31. Here, the second bottom surface 32b of the second recess 32 refers to the surface located at the bottom of the second recess 32 when the lower surface 210b of the light guide plate 210B is facing upward.

When the shape of the second recess 32 in a plan view is rectangular, the second recess 32 may be provided on the lower surface 210b of the light guide plate 210B so that one side of the rectangular shape is parallel to one side of the rectangular shape of the light guide plate 210B. Alternatively, the second recess 32 may be provided on the lower surface 210b so that one side of the rectangular outer shape is inclined with respect to the rectangular side of the light guide plate 210B. For example, the second recess 32 may be formed in the light guide plate 210B so that one side of the rectangular shape of the opening of the second recess 32 is approximately parallel to the diagonal of the rectangular shape of the light guide plate 210B. Other shapes such as a truncated cone shape, a cylindrical shape, or a prismatic shape may also be adopted as the shape of the second recess 32.

In the configuration illustrated in FIG. 16, the lower surface 210b of the light guide plate 210B has a shape that approaches the upper surface 210a as it approaches the outer edge of the light guide plate 210B. In other words, in this example, the light guide plate 210B has a shape that reduces in thickness as it approaches the outer edge. Thus, here, the lower surface 210b of the light guide plate 210B includes an inclined surface 210s that is provided to surround the light emitting device 100B.

As shown diagrammatically by the solid arrow Ry in FIG. 16, the inclined surface 210s functions as a reflecting surface, making it easier to extract light diffused within the plane of the light guide plate 210B from a region of the upper surface 210a of the light guide plate 210B that is distant from the light emitting device 100B. In other words, by making part of the lower surface 210b of the light guide plate 210B into an inclined surface 210s, it is possible to improve the brightness of the region of the upper surface 210a that is distant from the light emitting device 100B, which tends to be relatively dark, and to suppress uneven brightness on the light emitting surface.

The cross-sectional shape of the inclined surface 210s may be curved as shown in FIG. 16, or may be linear. The cross-sectional shape of the inclined surface 210s is not limited to these and may include steps, bends, etc.

[Joining member 40]
In this embodiment, the light emitting device 100B is located inside the second recess 32. The light emitting device 100B is disposed in the second recess 32 by a bonding member 40 that fills the inside of the second recess 32 except for the light emitting device 100B. The bonding member 40 may have a portion that is located between the second bottom surface 32b of the second recess 32 and the upper surface of the light emitting device 100B. As shown in FIG. 16 , at least a portion of the bonding member 40 is located inside the second recess 32.

The material of the joining member 40 can be, for example, a resin material containing a transparent resin as a base material. The joining member 40 typically has a refractive index lower than that of the light guide plate 210B. The joining member 40 may have a light diffusion function by, for example, containing a material having a refractive index different from that of the base material. As shown in FIG. 16, the joining member 40 may have a portion that is raised on the side opposite the upper surface 210a of the light guide plate 210B from the lower surface 210b.

[Third light reflective member 50]
The third light reflective member 50 can be formed from the same material as the above-mentioned second light reflective member 22, first light reflective member 150, etc. The third light reflective member 50 is located inside the first recess 31, and here occupies a part of the space defined by the first side surface 31c and the first bottom surface 31b.

By disposing the third light-reflective member 50 above the light-emitting element 120, the light traveling toward the upper surface 210a of the light-guiding plate 210A near the center of the light-guiding plate 210B can be reflected by the third light-reflective member 50. In other words, the light emitted from the light-emitting device 100B can be diffused more effectively within the surface of the light-guiding plate 210B. In addition, it is possible to prevent the brightness of the area of the upper surface 210a of the light-guiding plate 210B directly above the light-emitting element 120 from becoming extremely high locally.

[Fourth light reflective member 260]
Fourth light reflective member 260 is located on the side of lower surface 210b of light guide plate 210B, and covers lower surface 210b of light guide plate 210B and bonding member 40 disposed in second recess 32. Fourth light reflective member 260 is made of a light reflective resin material similar to third light reflective member 50.

By disposing the fourth light reflective member 260 on the lower surface 210b side of the light guide plate 210B, light heading toward the lower surface 210b in the light guide plate 210B can be reflected toward the upper surface 210a at the interface between the light guide plate 210B and the fourth light reflective member 260. Therefore, it is possible to more efficiently extract light from the upper surface 210a of the light guide plate 210B. In particular, here, the fourth light reflective member 260 covers the joint member 40 in addition to the lower surface 210b of the light guide plate 210B. By covering the joint member 40 with the fourth light reflective member 260, it is possible to suppress leakage of light from the joint member 40 to the lower surface 210b side of the light guide plate 210B.

By covering the lower surface 210b of the light guide plate 210B with the fourth light reflective member 260, it is possible to effectively reflect light at the interface between the light guide plate 210B and the fourth light reflective member 260 while suppressing leakage of light from the lower surface 210b of the light guide plate 210B. It is also possible to obtain the effect of reinforcing the light guide plate 210B. A wiring layer that is electrically connected to the light emitting device 100B may be formed on the lower surface 260b of the fourth light reflective member 260. If necessary, a wiring board may be disposed on the lower surface 260b side of the fourth light reflective member 260.

The light emitting device according to the embodiment of the present disclosure is useful as a light source for various illuminations, an in-vehicle light source, a display light source, etc., and is particularly advantageous for application to a surface light source combined with a light guide plate. The surface light source according to the embodiment of the present disclosure can be advantageously applied to a backlight unit for a liquid crystal display device, etc. The surface light source according to the embodiment of the present disclosure can be suitably used for a backlight for a display device of a mobile device that has strict requirements for reducing thickness, a surface light emitting device that requires local dimming, etc.

REFERENCE SIGNS LIST 10 through hole in light guide plate 21 partition member 22 second light reflective member 23 third light transmissive member 31 first recess in light guide plate 32 second recess in light guide plate 50 third light reflective member 100A to 100C light emitting device 110 covering member 120 light emitting element 130A, 130B first light transmissive member 140A, 140B second light transmissive member 150 first light reflective member 200A, 200B light emitting region 210A, 210B light guide plate 210g partition groove in light guide plate 240 wiring board 250 adhesive sheet 260 fourth light reflective member 300A, 300B surface light source 310A, 310B light guide plate 340 wiring board 360 light reflective member

Claims (13)

a light emitting element having a first lower surface on which a pair of electrodes are provided, a first upper surface located opposite to the first lower surface, and a first side surface located between the first upper surface and the first lower surface;
a first light-transmissive member that contains a wavelength converting material and covers at least a part of the first side surface of the light-emitting element, the first light-transmissive member having a second upper surface that does not overlap the first upper surface of the light-emitting element in a plan view;
a second light-transmissive member that covers the first upper surface of the light-emitting element and the second upper surface of the first light-transmissive member and has a third upper surface, the second light-transmissive member being substantially free of a wavelength converting material;
a first light reflective member covering the third upper surface of the second light transmissive member. The light emitting device according to claim 1, wherein the first translucent member has an outer surface flush with the outer surface of the second translucent member. The light-emitting device according to claim 1 or 2, further comprising a covering member that covers a second lower surface of the first translucent member that is located opposite the second upper surface, and covers the light-emitting element except for the lower surface of the electrode. The light-emitting device according to claim 3, wherein the covering member is a light-reflecting layer. The light emitting device according to any one of claims 1 to 4, wherein the second upper surface of the first translucent member is located below the first upper surface of the light emitting element. The light-emitting device according to claim 5, wherein the second translucent member covers a portion of the first side surface of the light-emitting element. The light-emitting element is
a substrate having the first top surface;
The light emitting device according to claim 1 , further comprising: a semiconductor layer located on a main surface of the substrate opposite to the first top surface. The light-emitting element is
a substrate having the first upper surface;
a semiconductor layer located on a major surface of the substrate opposite to the first upper surface,
The light emitting device according to claim 5 , wherein the second light transmissive member covers at least a part of a side surface of the substrate. A surface light source comprising a plurality of light emitting devices according to any one of claims 1 to 8,
The surface light source further includes a light guide plate having a plurality of through holes.
A surface light source, wherein each of the plurality of light emitting devices is positioned inside a corresponding one of the plurality of through holes. A wiring board electrically connected to each of the light emitting devices is further provided.
The surface light source according to claim 9 , wherein the light guide plate is disposed on the wiring board. Further comprising a plurality of second light reflective members;
The surface light source according to claim 10 , wherein each of the second light reflective members covers a corresponding one of the plurality of through holes on a main surface of the light guide plate opposite to the wiring board. The surface light source according to any one of claims 9 to 11, wherein the light guide plate has partition grooves that surround each of the plurality of light emitting devices in a plan view. Further comprising a plurality of third light-transmissive members containing a wavelength converting material;
The surface light source according to claim 9 , wherein each of the third light-transmissive members is disposed inside a corresponding one of the through holes.