Light-emitting diode array

Abstract

To provide a light-emitting diode array whose light crosstalk phenomenon is inhibited.SOLUTION: According to an embodiment, a light-emitting diode array is provided which includes a substrate, a plurality of light-emitting diode elements disposed on the substrate, and a light shielding member of a two-layer structure which covers the light-emitting diode elements and has a plurality of openings. The light-emitting diode elements individually include a light-emitting electrode. The plurality of openings respectively overlap the light-emitting electrodes. A first optical reflectance of a first layer on a side of the light-emitting diode element in the light shielding member is lower than a second optical reflectance of a second layer on a rear side of the light shielding member with respect to the first layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a light emitting diode array. [Background technology]

[0002] Light source arrays, which are arrays of multiple light sources such as light-emitting diodes (LEDs), are used as light sources for display devices, such as backlights for display devices. To improve the resolution of displayed images and characters, efforts have been made to miniaturize the light sources on the arrays, and arrays using micro LEDs, for example, are becoming popular for use in display devices.

[0003] As light sources such as LED elements become increasingly miniaturized, high directivity is required for light source arrays such as LED arrays. When light emitted from a light source is not directional and is emitted radially, the light emitted from adjacent light sources interferes with each other, a phenomenon known as optical crosstalk. The more densely the fine light sources are arranged, the more pronounced the effects of optical crosstalk become. Ideally, the light emitted from each light source travels in a straight line perpendicular to the main surface of the array, preventing interference with adjacent light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-49326 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-103351 [Patent Document 3] Japanese Patent Application Publication No. 2019-152851 [Patent Document 4] Japanese Patent Publication No. 2020-88383 [Patent Document 5] Japanese Patent Publication No. 2020-181980 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of an embodiment of the present invention is to provide a light-emitting diode array in which the optical crosstalk phenomenon is suppressed. [Means for solving the problem]

[0006] According to an embodiment, there is provided a light-emitting diode array including a substrate, a plurality of light-emitting diode elements arranged on the substrate, and a two-layer light-shielding member covering the light-emitting diode elements and having a plurality of openings. The light-emitting diode elements include light-emitting electrodes. The plurality of openings overlap with the light-emitting electrodes, respectively. A first layer of the light-shielding member on the side of the light-emitting diode elements has a first reflectivity to light that is lower than a second reflectivity to light of a second layer located on the back side of the light-shielding member relative to the first layer. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a light-emitting diode array according to an embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view illustrating a portion of an example of a light-emitting diode array according to an embodiment. [Figure 3] FIG. 2 is a partial perspective view showing an example of a light-emitting diode element according to an embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view conceptually illustrating light emission in an example of a conventional light-emitting diode array. [Figure 5] FIG. 10 is a schematic cross-sectional view conceptually illustrating light emission in another example of a conventional light-emitting diode array. [Figure 6] FIG. 2 is a schematic cross-sectional view conceptually illustrating light emission in an example of a light-emitting diode array according to an embodiment. [Figure 7] FIG. 2 is a partially see-through view illustrating an example of a light-emitting diode array according to an embodiment. [Figure 8] FIG. 2 is a schematic cross-sectional view conceptually illustrating light emission in an example of a light-emitting diode array according to an embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional view conceptually illustrating light emission in another example of the light-emitting diode array according to the embodiment. [Figure 10]FIG. 10 is a schematic cross-sectional view showing a part of a modified example of the light-emitting diode array according to the embodiment. [Figure 11] FIG. 10 is a schematic cross-sectional view showing a part of another modified example of the light-emitting diode array according to the embodiment. [Figure 12] 3A to 3C are schematic cross-sectional views illustrating a step in an example of manufacturing a light-emitting diode array according to an embodiment. [Figure 13] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 14] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 15] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 16] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 17] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 18] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 19] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 20] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 21] 10A to 10C are schematic cross-sectional views illustrating other steps in the example of manufacturing the light-emitting diode array according to the embodiment. [Figure 22] 10A and 10B are schematic cross-sectional views showing a step in a modified example of the manufacturing method of the light-emitting diode array according to the embodiment. [Figure 23] 10A to 10C are schematic cross-sectional views illustrating other steps in the modified example of the manufacturing method of the light-emitting diode array according to the embodiment. [Figure 24] 10A to 10C are schematic cross-sectional views illustrating other steps in the modified example of the manufacturing method of the light-emitting diode array according to the embodiment. [Figure 25]10A to 10C are schematic cross-sectional views illustrating other steps in the modified example of the manufacturing method of the light-emitting diode array according to the embodiment. [Figure 26] 10A to 10C are schematic cross-sectional views illustrating other steps in the modified example of the manufacturing method of the light-emitting diode array according to the embodiment. [Figure 27] FIG. 10 is a schematic cross-sectional view illustrating a part of another modified example of the light-emitting diode element according to the embodiment. [Figure 28] 28 is a schematic cross-sectional view illustrating the concept of light emission in the modified example shown in FIG. 27. [Figure 29] FIG. 10 is a schematic cross-sectional view illustrating a part of another modified example of the light-emitting diode element according to the embodiment. [Figure 30] FIG. 10 is a schematic cross-sectional view illustrating a part of another modified example of the light-emitting diode element according to the embodiment. [Figure 31] FIG. 30 is a schematic cross-sectional view illustrating the concept of light emission in the modification shown in FIG. 29. [Figure 32] 31 is a schematic cross-sectional view illustrating the concept of light emission in the modified example shown in FIG. 30. [Figure 33] 10A and 10B are schematic cross-sectional views illustrating a step in another modified example of the manufacturing method of the light-emitting diode array according to the embodiment. [Figure 34] 10A and 10B are schematic cross-sectional views illustrating a step in another modified example of the manufacturing method of the light-emitting diode array according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Light-emitting diode (LED) arrays use light-blocking materials as a countermeasure against optical crosstalk of light emitted from LEDs. By providing a layer of light-blocking material on the surface of the LED array and creating an opening in the light-blocking material layer at the position of the LED light source, optical crosstalk can be reduced by allowing only emitted light with a certain degree of directivity to pass through the opening. In addition, covering the opening with a microlens can further increase the directivity of the light passing through the opening.

[0009] However, when using LEDs that emit ultraviolet light, the ultraviolet light emitted from the LEDs can pass through the material behind the light-blocking material, and can reach the opening above the adjacent LED after repeated reflection and transmission. Therefore, simply using a light-blocking material is insufficient to suppress optical crosstalk in LED arrays that use ultraviolet LEDs. Furthermore, even when LEDs that emit visible light are used, there is a risk of light passing through when using LEDs that emit short-wavelength light and thin materials, and for the same reason, there is a concern about optical crosstalk.

[0010] According to an embodiment, a light-emitting diode array is provided. The light-emitting diode array includes a substrate, a plurality of light-emitting diode elements arranged on the substrate, and a two-layer light-shielding member covering the light-emitting diode elements. The light-emitting diode elements include light-emitting electrodes. The light-shielding member has a plurality of openings overlapping with the light-emitting electrodes. A first layer of the light-shielding member on the side of the light-emitting diode elements has a first reflectivity to light that is lower than a second reflectivity to light of a second layer located on the back side of the light-shielding member relative to the first layer.

[0011] In the light-emitting diode array having the above configuration, optical crosstalk between the light emitted from each light-emitting diode element is suppressed. In other words, the light-emitting diode array has high directivity of the emitted light. Therefore, the light-emitting diode array can satisfy the high directivity required for display applications, etc.

[0012] The light-shielding member has a two-layer structure including two layers with different reflectivities. The first layer, which is closer to the light-emitting diode element, has a low reflectivity (first reflectivity). Therefore, light is absorbed by the first layer, converted into heat, and is hardly reflected, so that light emitted from the light-emitting electrode does not reach the opening overlapping the light-emitting electrode of the adjacent light-emitting diode element. The first reflectivity of light by the first layer, particularly the reflectivity of light by the main surface of the first layer facing the light-emitting diode element, can be, for example, 30% or less. Examples of materials constituting the first layer include nickel (Ni), copper (Cu), silver (Ag), and alloys of these metals with other metals. A first layer made of such a material can exhibit a reflectivity of 30% or less for at least ultraviolet light.

[0013] The second layer of the two-layer structure of the light-shielding member, which is located opposite the first layer, exhibits high reflectivity (second reflectivity) for light. Most of the light emitted from the light-emitting electrode that strikes the side surface of the second layer located on the inner side surface of the opening of the light-shielding member is reflected, thereby increasing the efficiency of extracting light from the opening. The second reflectivity of light by the second layer, particularly the reflectivity of light by the side surface of the second layer exposed at the opening, can be, for example, 70% or more. Examples of materials constituting the second layer include aluminum (Al), and alloys of Al with other metals are also possible. A second layer made of such a material can exhibit a reflectivity of 70% or more for at least ultraviolet light.

[0014] The reflectivity of a material to light can vary greatly between the reflectivity to visible light (electromagnetic waves with a wavelength between approximately 360 nm and 400 nm and an upper limit between approximately 760 nm and 830 nm) and the reflectivity to ultraviolet light (electromagnetic waves with a wavelength between approximately 100 nm and 400 nm; for example, UV-C is an electromagnetic wave with a wavelength of approximately 260 nm). For example, among the above-mentioned examples of materials, Al has high reflectivity to ultraviolet light, while Ni, Cu, and Ag have low reflectivity to ultraviolet light. In contrast, Al, Ag, and gold (Au) are known to have high reflectivity to visible light. Therefore, the materials to be considered in terms of light reflectivity differ depending on whether a visible light source or an ultraviolet light source is used. Therefore, when selecting materials for the first and second layers to obtain the above-mentioned first and second reflectivities, appropriate selection is made depending on the light emitted from the light-emitting diode element. For example, when a light-emitting diode element that emits ultraviolet light is used, it is desirable to focus on the first reflectance for ultraviolet light and the second reflectance for ultraviolet light. Similarly, when a light-emitting diode element that emits visible light is used, it is desirable to focus on the first reflectance for visible light and the second reflectance for ultraviolet light.

[0015] Hereinafter, a light-emitting diode array according to an embodiment will be described in detail with reference to the drawings. Hereinafter, a light-emitting diode array having light-emitting diode elements that emit ultraviolet light will be described in detail as a specific example, but the light-emitting diode elements are not limited to those that emit ultraviolet light. The light-emitting diode array according to the embodiment includes not only an embodiment that emits ultraviolet light, but also an embodiment that emits visible light. Similar effects are exhibited in both an embodiment that uses ultraviolet light and an embodiment that uses visible light.

[0016] 1 is a schematic cross-sectional view showing an example of a light-emitting diode array according to an embodiment. The illustrated light-emitting diode array 1 includes a substrate 2, a plurality of light-emitting diode elements 10 arranged in parallel on the substrate 2, and a light-shielding member 17 covering the light-emitting diode elements 10.

[0017] The substrate 2 is made of, for example, silicon or an organic material. An electrical circuit is constructed on the substrate 2 using an electrical insulating film 3 and a substrate-side electrode 4, and the substrate 2 can also serve as a control substrate. The substrate-side electrode 4 is electrically connected to the light-emitting diode element 10 via, for example, a solder-based metal bump for power supply. As a specific example, the light-emitting electrode 11 and the other electrode 12 included in each light-emitting diode element 10 are bonded to the substrate-side electrode 4 via an Au bump 14, an Sn bump 5a, and an Ni bump 5b. The solder is not limited to Sn; alloy solders widely available on the market can also be used. Furthermore, bonding between Au bumps or direct bonding between metal films such as Cu or Al without using bumps may also be used. The light-emitting electrode 11 includes an active layer 13 that emits light when powered. The light-emitting electrode 11 and the other electrode 12 are connected via a semiconductor layer 15 (e.g., AlGaN). A buffer layer 16 made of, for example, aluminum nitride (AlN), which is an insulating material, may be provided on the side of the light-emitting diode element 10 opposite the Sn bumps 5a and Ni bumps 5b. The AlN layer may be removed during the assembly process. A sealing resin 6 (for example, underfill or resin containing a reflective material) is filled in the spaces between adjacent light-emitting diode elements 10, between the light-emitting diode element 10 and the electrical insulating film 3, and between the metal bumps. The structure and constituent materials around each electrode in the light-emitting diode array according to the embodiment are not limited to the structure shown in the figure or the materials in the specific examples described above.

[0018] The light-shielding member 17 is provided on the buffer layer 16 via an adhesive layer 18. The adhesive layer 18 may be omitted, in which case the light-shielding member 17 may be in direct contact with the buffer layer 16. The adhesive layer 18 may be made of, for example, titanium (Ti), a combination of Ti and copper (Cu), a Ti-based alloy, chromium (Cr), a combination of Cr and Au, a Cr-based alloy, or the like.

[0019] The light-shielding member 17 has a two-layer structure including a first layer 17a, which is the lower layer on the light-emitting diode element 10 side, and a second layer 17b, which is the upper layer on the opposite side. The light-shielding member 17 has an opening 19 at a position overlapping the light-emitting electrode 11. The opening 19 penetrates the light-shielding member 17, allowing ultraviolet light emitted from the active layer 13 to exit the light-emitting diode array 1. In the illustrated example, grooves 20 are formed in the light-shielding member 17, dividing the light-shielding member 17 into multiple pieces corresponding to each light-emitting diode element 10. The light-shielding member 17 does not need to be divided; in that case, the grooves 20 are not formed in the light-shielding member 17. In the illustrated example, the opening 19 in the light-shielding member 17 is filled with a transparent resin, which forms a microlens 21 that covers the opening 19. The microlens 21 improves the focusing of ultraviolet light extracted from the light-emitting electrode 11 through the opening 19, thereby increasing the directivity. Furthermore, although the microlens 21 has the effect of protecting the element from dust and the like, it may be omitted. An example in which the microlens is omitted is shown in FIG. 2. FIG. 2 shows one light-emitting diode element 10 in the modular structure of the light-emitting diode array and the light-shielding member 17 (segment) above it, and omits other parts of the array. Furthermore, the microlens 21 does not have to have an outwardly curved lens shape as shown in FIG. 1, and may have a flat shape with the same height as the light-shielding member 17. In this case, the light-condensing effect of the microlens is not achieved, but the element is protected from dust and the like.

[0020] As shown in the figure, the light-emitting diode element 10 has a structure including a light-emitting electrode 11 that emits ultraviolet light and other electrodes that do not emit light, both of which are located on the same plane. The ultraviolet light emitted from the light-emitting electrode 11 is, for example, UV-C. UV-C refers to electromagnetic waves of ultraviolet light with a wavelength of 100 nm or more and 280 nm or less, and a specific example is ultraviolet light of 260 nm. The ultraviolet light emitted from the light-emitting electrode 11 is not limited to UV-C, but may be UV-B having a wavelength of 280 nm or more and less than 315 nm, or UV-A having a wavelength of 315 nm or more and less than 400 nm. The active layer 13, which is the light-emitting portion of the light-emitting electrode 11, is made of a semiconductor material that emits ultraviolet light when a voltage is applied, such as a nitride-based semiconductor.

[0021] FIG. 3 is a partially transparent view illustrating an example of a light-emitting diode element according to an embodiment. FIG. 3 may be, for example, a plan view of the light-emitting diode element 10 whose cross section is shown in FIG. 2 . However, the light-shielding member 17 is omitted. The light-emitting diode element 10 may have, for example, a rectangular planar shape as illustrated. In the illustrated example, the light-emitting electrode 11 and the other electrodes 12 are arranged biased toward one side of the planar shape. However, the arrangement of the light-emitting electrode 11 and the other electrodes 12 in the light-emitting diode element 10 is not limited to this example. Various arrangements are possible, such as an arrangement along a line passing through the center of the planar shape, or an arrangement in a horizontal, vertical, or diagonal direction. In addition, in the illustrated example, the light-emitting electrode 11 is depicted as a circle and the other electrodes 12 are depicted as a rectangle, but the shapes of the electrodes are not limited to those illustrated. The vertical distance DY of the planar shape of the light-emitting diode element 10 may be, for example, on the order of a dozen or so microns or several tens of microns. The horizontal distance DX of the planar shape may be, for example, on the order of several microns to several tens of microns. The active layer 13 of the light-emitting electrode 11 may have a diameter DA of, for example, several μm. The other electrode 12 may have a width WE of, for example, several μm. The diameter B1 and width B2 of the Au bumps on the bottom of each electrode may each be several μm. The spacing I between the Au bumps of each electrode may be, for example, several μm. The light-emitting diode device 10 may be, for example, a micro-LED light source.

[0022] Suppression of optical crosstalk in a light-emitting diode array according to an embodiment will be described with reference to Figs. 4 to 6. Figs. 4 and 5 are schematic cross-sectional views each showing the concept of light emission in a conventional light-emitting diode array. Fig. 6 is a schematic cross-sectional view showing the concept of light emission in an example of a light-emitting diode array according to an embodiment. In each figure, the array structure is simplified by simplifying the light-emitting electrode 11 and other electrodes 12 and omitting the adhesive layer. The structure shown in Fig. 6 is a simplified version of the structure shown in Fig. 1.

[0023] The conventional array structure shown in Fig. 4 does not have a light-shielding member. Without a light-shielding member, the ultraviolet light 100 emitted from each light-emitting electrode 11 spreads radially, and some of it interferes with the ultraviolet light 100 from the light-emitting electrodes 11 of other LED elements. In other words, the ultraviolet light 100 emitted from the LED elements has low directivity, resulting in optical crosstalk.

[0024] The light source array shown in FIG. 5 includes a single-layer light-shielding member 17 covering the LED elements. To increase the intensity of light extracted through the openings in the light-shielding member 17, the single-layer light-shielding member 17 is typically made of a highly reflective material. A portion of the ultraviolet light 100 emitted from the light-emitting electrode 11 is extracted to the outside of the array through an opening provided with a microlens 21, for example. Another portion of the ultraviolet light 100 is irradiated onto and reflected from the backside of the light-shielding member 17, outside the opening, with the main surface of the light-shielding member 17 facing the direction in which the ultraviolet light 100 is extracted serving as the front surface. Because the ultraviolet light 100 can pass through the constituent materials (e.g., resin, nitride, etc.) of the sealing resin 6 and the buffer layer 16, the ultraviolet light 100 is reflected by the backside of the light-shielding member 17 and reaches an opening corresponding to a light-emitting electrode 11 (e.g., a light-emitting electrode of an adjacent LED element) different from the light-emitting electrode 11 from which it was emitted, resulting in interference between the ultraviolet light beams 100. In other words, the optical crosstalk phenomenon occurs due to the reflected light inside the LED element. Furthermore, since the transmission of the ultraviolet light 100 causes deterioration of the sealing resin 6 and the buffer layer 16, it is undesirable for the ultraviolet light 100 to be repeatedly reflected on the back side of the light-shielding member 17.

[0025] In the example light-emitting diode array 1 according to the embodiment shown in FIG. 6, a two-layer light-shielding member 17 covers the light-emitting diode elements. As in the conventional example shown in FIG. 5, a portion of the ultraviolet light 100 emitted from the light-emitting electrode 11 is extracted to the outside of the array through, for example, an opening provided with a microlens 21. However, because the low-reflectivity first layer 17a is located on the backside of the two-layer light-shielding member 17, ultraviolet light 100 irradiated onto this surface with low ultraviolet reflectivity (e.g., 30% or less) is not reflected but is instead absorbed by the first layer 17a and converted into heat. This reduces the amount of light reflected from the backside of the light-shielding member 17, thereby suppressing optical crosstalk. Furthermore, even if the first layer 17a is thin and transmits only a small amount of light (ultraviolet rays), the second layer 17b can reflect the ultraviolet rays downward (toward the substrate 2) and return them. As a result, the repeatedly reflected ultraviolet rays are absorbed by the first layer 17a and do not exit the array module, causing crosstalk.

[0026] In the example of FIG. 6, the reflectance of the ultraviolet light 100 irradiated onto the side surface of the second layer 17b within the opening of the two-layer light-shielding member 17 is high (e.g., 70% or more), resulting in high light extraction efficiency outside the array. This improves the light intensity as an array light source. From the viewpoint of improving light extraction efficiency, it is preferable to make the thickness of the second layer 17b of the light-shielding member 17 thicker than the thickness of the first layer 17a. Although not illustrated in the drawings, a film made of the same material as the second layer 17b may be further provided to cover the side surface of the first layer 17a inside the opening. For example, the side surface of the second layer 17b may be extended so that a portion of the film covers the side surface of the first layer 17a. Covering the side surface of the low-reflectivity first layer 17a with a high-reflectivity film can also improve the reflectance of the ultraviolet light 100 irradiated onto the side surface of the first layer 17a within the opening. This further improves light extraction efficiency and light intensity.

[0027] It is desirable to use a material that has both high reflectivity and high thermal emissivity, such as a metal material, as the constituent material of the second layer 17b. For example, aluminum (Al) not only has high reflectivity for ultraviolet light as described above, but also has high thermal emissivity. As will be described later, the light-shielding member 17 may expand due to heat generated when ultraviolet light 100 is absorbed and converted by the first layer 17a, which has low reflectivity. The film stress caused by the expansion may cause warping, which may damage the joint. Therefore, it is desirable to stack the second layer 17b, which has excellent thermal emissivity, on the first layer 17a as a heat dissipation path.

[0028] 5 and 6 each include the microlens 21, but the microlens 21 may be omitted. Also, the shape of the microlens 21 is not limited to that shown in the drawings.

[0029] Fig. 7 shows a partially see-through view illustrating an example of a light-emitting diode array according to an embodiment. Fig. 7 may be, for example, a plan view of the light-emitting diode array 1, the cross section of which is shown in Fig. 6, viewed from the front surface side (second layer 17b side) of the light-shielding member 17. The illustrated light-emitting diode array 1 is a light-emitting diode array module including 4 x 4 = 16 light-emitting diode elements 10. The number and arrangement of the light-emitting diode elements 10 included in the light-emitting diode array 1 are not limited to those shown in the drawing.

[0030] The light-emitting diode elements 10 are covered by a light-shielding member 17 having multiple openings 19 and divided into individual light-emitting diode elements 10 by grooves 20. The sealing resin 6 is visible through the gaps between the divided pieces of the light-shielding member 17 divided by the grooves 20. Although not illustrated in the drawings, the light-shielding member 17 may have a structure in which it is not divided into individual light-emitting diode elements 10. In other words, the grooves 20 may be omitted. If the light-shielding member 17 has a high thermal expansion coefficient, significant film stress may be generated due to thermal expansion caused by the first layer 17a absorbing ultraviolet light. This may result in warping of the array and damage to the joints. Alternatively, bending of the light-shielding member 17 may affect the linearity of light rays and change the direction of light propagation. Dividing the light-shielding member 17 by providing grooves 20 reduces film stress. Therefore, dividing the light-shielding member 17 into individual light-emitting diode elements 10 is preferable because it suppresses warping and bending and reduces damage to the joints. Even if the light-shielding member 17 is not divided, the buffer layer 16 below it is independent for each light-emitting diode element 10. Furthermore, each light-emitting diode element 10 is separated by the sealing resin 6.

[0031] For example, each light-emitting diode element 10 is assumed to have a light-emitting electrode and other electrodes 12 arranged in the same manner as the example shown in FIG. 3. In this case, although not shown because their positions would overlap, each opening 19 overlaps with the light-emitting electrode of each light-emitting diode element 10. In the example shown, each opening 19 is filled with transparent resin and a microlens 21 is formed on the top. It is desirable that the center positions of the light-emitting electrode, opening 19, and microlens 21 coincide with each other. At least in terms of design, these center positions should coincide with each other. The microlens 21 may be omitted.

[0032] It is common to provide microlenses on LED elements to prevent contamination and scratches caused by debris such as dust, and to obtain a light-condensing effect. Covering the opening of the light-shielding member with a microlens is desirable from the perspective of the reliability of the light-emitting diode array. The light-condensing effect of the microlens 21 will be explained with reference to FIGS. 8 and 9. FIG. 8 is a schematic cross-sectional view conceptually showing light emission in an example of the light-emitting diode array according to the embodiment in which the microlens is omitted. FIG. 9 is a schematic cross-sectional view conceptually showing light emission in an example of the light-emitting diode array according to the embodiment in which the microlens is provided.

[0033] 8, part of the light emitted from the active layer 13 of the light-emitting electrode 11 is reflected by the side surface of the second layer 17b at the opening 19 of the light-shielding member 17 and is extracted from the array as diffused light 101. Although the optical crosstalk phenomenon is suppressed compared to the conventional examples shown in FIGS. 4 and 5, the light that passes through the opening 19 includes diffused light 101, so the light extracted from the array appears to spread radially.

[0034] 9, the microlenses 21 provided in the openings of the light-shielding member 17 exert a light-collecting effect, thereby improving the directivity of the ultraviolet light 100 emitted from the active layer 13 and passing through the openings. Light reflected on the side surfaces of the second layer 17b is also collected by the microlenses 21. Therefore, providing the microlenses 21 is preferable from the viewpoints of further suppressing optical crosstalk and increasing optical energy.

[0035] FIG. 10 shows a modified example of the light-emitting diode array according to the embodiment. FIG. 10 is a schematic cross-sectional view showing a portion of the modified example. Specifically, the modified example shows the light-emitting diode elements 10 and the light-shielding member 17 included in the light-emitting diode array. As in FIG. 2, one of the multiple light-emitting diode elements 10 included in the light-emitting diode array and the light-shielding member 17 (segment) thereon are shown, while other parts of the array, such as the substrate and sealing resin, are omitted. Unlike the arrays shown in FIGS. 1 and 2, a sapphire plate 22 is provided on the buffer layer 16 of the light-emitting diode elements 10. The sapphire plate 22 may be, for example, a thinned sapphire substrate used in manufacturing the light-emitting diode elements 10. As in the illustrated example, an adhesive layer 18 may be provided between the sapphire plate 22 and the light-shielding member 17, but the adhesive layer 18 may be omitted. The sapphire plate 22 is covered with the light-shielding member 17, including the side surfaces, except for the portion of the sapphire plate 22 corresponding to the opening 19 and the contact surface with the buffer layer 16. The light-emitting diode array having the sapphire plate 22 between the light-emitting diode elements 10 and the light-shielding member 17 has high rigidity. As mentioned above, film stress can occur due to thermal expansion generated when the first layer 17a of the light-shielding member 17 absorbs ultraviolet light. However, the increased rigidity improves the array's resistance to the light-shielding member 17. This reduces warping of the array and damage to the joints, improving the reliability of the light-emitting diode array. Furthermore, for example, after mounting the light-emitting diode elements 10 on the substrate-side electrodes on the substrate via bonding bumps (e.g., Sn bumps and Ni bumps) by flip-chip mounting, the lift-off process of the sapphire substrate from the light-emitting diode elements 10 can be omitted. The lift-off process may be performed before the flip-chip mounting process, but in any case, this process can be omitted. Therefore, the assembly of an array including the sapphire plate 22 as shown in the figure is easy.

[0036] Another modified example is shown in FIG. 11. FIG. 11 is a schematic cross-sectional view of a portion of this modified example. As with FIGS. 2 and 10, the modified example shows one of the multiple light-emitting diode elements 10 included in the light-emitting diode array and the light-shielding member 17 (segment) thereon, while other elements of the array, such as the substrate and encapsulation resin, are omitted. Unlike the arrays shown in FIGS. 1 and 2, an electrical insulating layer 24 is provided on the buffer layer 16. The buffer layer 16 is made of, for example, AlN, which is considered a highly insulating material. However, to ensure electrical insulation, it is preferable to further provide an electrical insulating layer 24 between the light-emitting diode element 10 and the light-shielding member 17. Furthermore, even if the buffer layer 16 is made of, for example, another material with less high electrical insulation properties, it is desirable to ensure electrical insulation using the electrical insulating layer 24. In other words, the use of the electrical insulating layer 24 broadens the range of materials available for the buffer layer 16 and, ultimately, for the light-emitting diode element 10. The electrical insulating layer 24 can be made of an inorganic material, such as SiO2 or SiN.

[0037] An example of manufacturing a light-emitting diode array according to this embodiment will be described with reference to FIGS.

[0038] First, a mounting substrate having light-emitting diode elements as shown in FIG. 12 and bonding bumps as shown in FIG. 13 is prepared. The structure of FIG. 12 is formed, for example, by forming a buffer layer 16 on a sapphire substrate 23 and then growing semiconductors to form the light-emitting electrode 11 and other electrodes 12 on the buffer layer 16. The buffer layer 16 can be obtained, for example, by growing AlN crystals on the sapphire substrate 23. Although not shown for simplified illustration, Au bumps are formed on the light-emitting electrode 11 and other electrodes 12 by, for example, soldering. Alternatively, thin-film metal layers such as Au formed by a film-forming device may be used. In this manner, multiple light-emitting diode elements 10 are formed on the sapphire substrate 23. The mounting substrate shown in FIG. 13 can be obtained, for example, by forming wiring on the substrate 2 by patterning the electrical insulating film 3 and the substrate-side electrode 4, and then sequentially forming Ni bumps 5b and Sn bumps 5a as appropriate on the substrate-side electrode 4. When directly bonding metal films, thin films may be laminated using a dry process.

[0039] The light-emitting diode element 10 on the sapphire substrate shown in Fig. 12 is bonded to the Sn bumps 5a and Ni bumps 5b on the mounting substrate shown in Fig. 13 by a mounting method such as flip-chip mounting (Figs. 14 and 15). Next, sealing resin 6 is filled into spaces such as gaps between the bonding bumps (Fig. 16).

[0040] The sapphire substrate 23 is removed by laser lift-off (LLO) using laser light L (FIG. 17). Note that this step may be performed before flip bonding.

[0041] Next, an adhesion layer 18 (seed layer) is formed on the surface exposed by lift-off of the sapphire substrate 23 (FIG. 18). Formation of the adhesion layer 18 may be omitted. For example, a seed layer is essential when the light-shielding film formation process is electroplating, but if the light-shielding member 17 is formed by another process such as electroless plating or injection of molten metal, the adhesion layer 18 may be unnecessary. Furthermore, the adhesion layer 18 may also be unnecessary if there are no structural concerns such as film peeling due to thermal stress generated in the light-shielding film.

[0042] Next, a resist 30 is provided by resist patterning (FIG. 19). The pattern of the resist 30 is set according to the positions where the openings and grooves are to be provided in the light-shielding member. In the areas where the resist 30 is not provided, a first layer 17a and a second layer 17b are sequentially formed by plating, thereby forming the light-shielding member 17 (FIG. 20). Next, the resist 30 is peeled off, and if an adhesive layer 18 is formed, the portion of it that was under the resist 30 is removed, thereby obtaining the light-emitting diode array 1. In the areas where the resist 30 and adhesive layer 18 have been removed, openings 19 and grooves 20 are formed in the light-shielding member 17.

[0043] Although not shown in the drawings, the openings 19 of the light blocking member 17 may be filled with a transparent resin to form microlenses.

[0044] The manufacturing of a light-emitting diode array having a sapphire plate 22 between the light-emitting diode elements 10 and the light-shielding member 17 as shown in Fig. 10 will be described with reference to the drawings. First, in the same manner as described above with reference to Figs. 12 to 16, the light-emitting diode elements are bonded to the mounting substrate, and then the sealing resin 6 is filled in. Next, instead of the method described above with reference to Figs. 17 to 21, the manufacturing is performed by the method described below with reference to Figs. 22 to 26.

[0045] Instead of lifting off the sapphire substrate 23 using LLO, the sapphire substrate 23 is thinned and divided using laser light L to form sapphire plates 22 for each light-emitting diode element (FIG. 22). This division process can be performed using a blade dicing method other than the laser method. Next, if an adhesion layer 18 is to be formed, the adhesion layer 18 is formed on the surface and between the sapphire plates 22 (FIG. 23), and resist 30 is then formed (FIG. 24). As described above, whether or not the adhesion layer 18 is formed depends on the light-shielding member formation process. A light-shielding member 17 is formed in the areas where the resist 30 was not formed (FIG. 25). Next, the resist 30 is peeled off, and if an adhesion layer 18 was formed, the portion under the resist 30 is removed, thereby obtaining a light-emitting diode array 1 including the sapphire plates 22 (FIG. 26). Note that the portions corresponding to the grooves 20 dividing the light-shielding member 17 can be omitted from the resist 30 pattern for the following reasons. The portions corresponding to the gaps between the sapphire plates 22 formed when the sapphire substrate 23 is divided by the laser light L become depressions in the light-shielding member 17 that are formed, and can function as grooves 20 in the light-shielding member 17 as they are.

[0046] A further modified example of the light-emitting diode array according to the embodiment will be described with reference to FIGS. 27 and 28. FIG. 27 is a schematic cross-sectional view illustrating a portion of the modified example. FIG. 28 conceptually illustrates light emission in the modified example. Similar to FIGS. 2, 10, and 11, one of the multiple light-emitting diode elements 10 included in the modified light-emitting diode array and the light-shielding member 17 (segment) thereon are shown, with other components of the array, such as the substrate and sealing resin, omitted. In the illustrated modified example, the side surfaces of the first layer 17a and the second layer 17b within the opening 19 of the light-shielding member 17 have an uneven structure. The uneven surface may be, for example, a spiky surface with an array of countless thorns ranging in size from submicron to several microns. Because the inner wall of the opening 19 has an uneven structure, ultraviolet light 100 emitted from the light-emitting electrode 11 is likely to be diffusely reflected when irradiated thereon. That is, in this modified example, the reflectivity of the inner wall of the opening 19 to the ultraviolet light 100 is lower than when the inner wall is flat. The ultraviolet light 100 is diffusely reflected by the uneven surface and becomes scattered light 102. The scattered light 102 is less likely to exit the array from the opening 19, and does not become diffused light. Alternatively, even if some of the scattered light 102 exits the array from the opening 19, the amount of light is reduced by diffuse reflection, so the impact is small. For these reasons, making the inner surface of the opening 19 an uneven surface increases the effect of suppressing optical crosstalk.

[0047] The surface roughness Ra (arithmetic roughness) of the surface having the uneven structure can be, for example, 70 nm or more, preferably 80 nm or more, and more preferably 120 nm or more.

[0048] The uneven structure can be formed by roughening or blackening the inner surface of the opening 19, i.e., the side surfaces of the opening 19 of the first layer 17a and the second layer 17b of the light-shielding member 17. Examples of such treatments include chemical etching or blasting. For example, the surface roughness Ra of a Ni material surface that has been roughened or blackened increases by approximately 1.5 to 3 times compared to the surface roughness Ra of a flat Ni film (Ra of a flat Ni film with a thickness of 3 μm: 46 nm; Ra of a roughened Ni film with a thickness of 3 μm: 125 nm; Ra of a roughened Ni film with a thickness of 0.5 μm: 78 nm). For example, by performing the roughening or blackening treatment after removing the resist 30 and the underlying adhesion layer 18 as shown in FIG. 21 using the manufacturing method described with reference to FIGS. 12 to 21, a light-emitting diode element according to the modified example shown in FIG. 27 can be obtained.

[0049] The modified examples shown in Figures 27 and 28 employ a structure that diffuses the ultraviolet light 100 to reduce reflectance. Therefore, it is desirable that the side surfaces of the low-reflectance first layer 17a of the two-layer light-blocking member 17 occupy a large portion of the inner wall of the opening 19, as shown in the figures. At least the side surfaces of the first layer 17a of the inner wall of the opening 19 are roughened to form an uneven structure. In this modified example, suppression of optical crosstalk takes priority over light emission intensity. However, the second layer 17b is not omitted. In this modified example, it is desirable to use a material with high thermal emissivity, typically a metal material, as the constituent material of the second layer 17b. As described above, the second layer 17b, which has excellent thermal emissivity, can function as a heat dissipation path for heat generated when the ultraviolet light 100 is absorbed and converted by the first layer 17a. To enhance the heat dissipation effect of the second layer 17b, it is preferable to make the second layer 17b thicker. Furthermore, as described above, the second layer 17b is also necessary to reflect and confine the ultraviolet light that has slightly passed through the first layer 17a of the light-shielding member downward (toward the substrate 2).

[0050] Two further modified examples of the light-emitting diode array according to the embodiment will be described with reference to FIGS. 29 to 32. FIGS. 29 and 30 are schematic cross-sectional views illustrating portions of these modified examples. FIGS. 31 and 32 conceptually illustrate the light emission patterns in each of these modified examples. Similar to FIGS. 2, 10, and 11, the diagram illustrates one of the multiple light-emitting diode elements 10 included in the modified light-emitting diode array and the light-shielding member 17 (segment) thereon, while other components of the array, such as the substrate and sealing resin, are omitted. In these modified examples, the diameter of the opening 19 on the first layer 17a side is larger than the diameter of the opening 19 on the second layer 17b side. Specifically, in the example shown in FIG. 29, the side surface of the light-shielding member 17 is inclined so that the opening 19 widens from the second layer 17b side toward the first layer 17a side. In other words, the cross-sectional shape of the light-shielding member 17 is similar to the cross-section of a reverse-tapered mold. In the example shown in FIG. 30, the inner surface of the light-shielding member 17 at the opening 19 has a curved shape. As a result, the cross section of light blocking member 17 in the thickness direction has a substantially arc shape at opening 19. In other words, opening 19 has a dome-like shape with a through-hole at the center of the top. Note that the curved shape of the inner surface of light blocking member 17 is not limited to the shape of curvature shown in FIG.

[0051] 31 and 32, in either the case of the opening 19 having a reverse tapered cross section or the case of the dome-shaped opening 19, the ultraviolet light 100 emitted from the active layer 13 of the light-emitting electrode 11 is reflected by the inclined side surface and the curved side surface of the light-shielding member 17, and the reflected light 103 is unlikely to exit the array from the opening 19. This increases the effect of suppressing optical crosstalk.

[0052] 27 and 28, in the modified examples shown in Fig. 29 to Fig. 32, from the viewpoint of suppressing optical crosstalk, it is desirable that the side surface of the first layer 17a of the light-shielding member 17, which has low reflectivity, occupy a large portion of the inner wall of the opening 19. Similarly, it is desirable that the second layer 17b be made of a material with high thermal emissivity, such as metal. From the viewpoint of enhancing the heat emissivity of the second layer 17b, it is preferable to make the second layer 17b thicker.

[0053] The modified examples shown in FIGS. 31 and 32 , which have an opening 19 with a narrower diameter on the outlet side of the ultraviolet light 100, can be obtained, for example, by a manufacturing method including resist patterning, as shown in FIGS. 33 and 34 . After performing the steps up to FIG. 18 in the manufacturing method of the light-emitting diode array 1 described with reference to FIGS. 12 to 21 , patterning is performed to form a resist 30 with the shape shown in FIG. 33 or a resist 30 with the shape shown in FIG. 34 . Subsequently, the same steps as those shown in FIGS. 19 to 21 are performed to obtain a light-emitting diode array including the structure shown in FIG. 31 or the structure shown in FIG. 32 . Specifically, as shown in FIG. 33 , a taper is formed in the portion of the resist 30 for forming the opening 19. A plating process for forming the light-shielding member 17 is performed using the structure including the tapered resist 30, and then the resist 30 is removed, thereby obtaining a light-shielding member 17 having an opening 19 with a reverse tapered cross section. Alternatively, a resist material is dropped to form a resist 30 with the shape shown in FIG. 34 . A microlens array may be formed instead of the hill-shaped resist 30 shown in Fig. 34. A plating process for forming the light-shielding member 17 is performed using a structure including the resist 30 with a curved surface shape, and then the resist 30 is removed, thereby obtaining the light-shielding member 17 having the opening 19 with a curved cross section.

[0054] The light-emitting diode array according to the embodiment described above includes a substrate, a plurality of light-emitting diode elements arranged on the substrate, and a two-layer light-shielding member covering the light-emitting diode elements and having a plurality of openings. The light-emitting diode elements include light-emitting electrodes. The openings in the light-shielding member overlap with the light-emitting electrodes. A first reflectance to light of a first layer on the light-emitting diode element side of the light-shielding member is lower than a second reflectance to light of a second layer located on the back side of the light-shielding member relative to the first layer. The above configuration provides a light-emitting diode array in which optical crosstalk is suppressed.

[0055] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0056] 1...light-emitting diode array, 2...substrate, 3...electrical insulating film, 4...substrate-side electrode, 5a...Sn bump, 5b...Ni bump, 6...encapsulating resin, 10...light-emitting diode element, 11...light-emitting electrode, 12...electrode, 13...active layer, 14...Au bump, 15...semiconductor layer, 16...buffer layer, 17...light-shielding member, 17a...first layer, 17b...second layer, 18...adhesion layer, 19...opening, 20...groove, 21...microlens, 22...sapphire plate, 23...sapphire substrate, 24...electrical insulating layer, 30...resist, 100...ultraviolet light, 101...diffused light, 102...scattered light, 103...reflected light, L...laser light.

Claims

1. A substrate; a plurality of light-emitting diode elements each including a light-emitting electrode disposed on the substrate; a two-layered light-shielding member covering the light-emitting diode element and having a plurality of openings overlapping the light-emitting electrodes; Equipped with A light-emitting diode array in which a first layer on the light-shielding member's side has a first reflectivity to light that is lower than a second reflectivity to light of a second layer located on the back side of the light-shielding member relative to the first layer.

2. 2. The light-emitting diode array of claim 1, wherein the first reflectance is 30% or less and the second reflectance is 70% or more.

3. 3. The light-emitting diode array according to claim 1, further comprising a film made of the same material as the second layer, covering a side surface of the first layer inside the opening.

4. 3. The light-emitting diode array according to claim 1, further comprising a sapphire plate between said light-emitting diode elements and said light-shielding member.

5. 3. The light-emitting diode array according to claim 1, wherein the light-shielding member is divided into sections for each of the light-emitting diode elements.

6. 3. The light-emitting diode array according to claim 1, wherein a side surface of said first layer inside said opening has an uneven structure.

7. 3. The light-emitting diode array according to claim 1, wherein the diameter of the opening on the first layer side is larger than the diameter of the opening on the second layer side.

8. 8. The light-emitting diode array according to claim 7, wherein an inner surface of the light-shielding member is inclined so that the opening widens from the second layer side toward the first layer side.

9. The light-emitting diode array according to claim 7 , wherein the inner surface of the light-blocking member at the opening has a curved shape.

10. 3. The light-emitting diode array according to claim 1, further comprising an adhesive layer between said light-emitting diode elements and said light-shielding member.

11. 5. The light-emitting diode array according to claim 4, further comprising an adhesive layer between said light-emitting diode elements and said sapphire plate.

12. 3. The light-emitting diode array according to claim 1, further comprising a microlens made of a transparent resin covering the opening.

13. 3. The light-emitting diode array according to claim 1, further comprising an electrical insulating layer between the light-emitting diode elements and the light-shielding member.

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