JP2021027129A - Light-emitting device - Google Patents

Abstract

To provide a light-emitting device that can suppress uneven brightness of light emitted from a light source and can be made thinner and smaller.SOLUTION: A light-emitting device 100 includes: a wiring board 10; a plurality of light emitting elements 20 arranged on the wiring board and electrically connected to a wiring layer 11 of the wiring board; a first light diffusing member 30 which is arranged on the wiring board, has a plurality of through holes 30h, and includes a light diffusing material, and in which each of the plurality of light emitting elements is arranged in a corresponding through hole among the plurality of through holes; and a plurality of second light diffusing members 50 which covers the plurality of light emitting elements and is arranged in the plurality of through holes, each of which includes a light diffusing material and a wavelength converting substance, and a content of the light diffusing member is higher than a content of the light diffusing material contained in the first light diffusing member.SELECTED DRAWING: Figure 1A

Description

The present disclosure relates to a light emitting device.

In recent years, a thin light emitting device in which a plurality of light emitting elements are arranged two-dimensionally has been developed. The thin light emitting device is used as a direct type backlight used in a display device such as a liquid crystal display device. Patent Documents 1 and 2 disclose a light emitting device including a light guide plate having a through hole and a plurality of light emitting diode (LED: Light Emitting Diode) elements mounted on a mounting substrate by a flip chip connection. Each of the plurality of light emitting diode elements is covered with a sealing material and is arranged in the corresponding through hole.

Japanese Unexamined Patent Publication No. 2011-204566 Japanese Unexamined Patent Publication No. 2011-21674

There is a further demand for thinner and smaller light emitting devices. An exemplary embodiment of the present disclosure provides a light emitting device capable of suppressing uneven brightness of light emitted from a light source and making it thinner and smaller.

In a non-limiting and exemplary embodiment, the light emitting device of the present disclosure includes a wiring board and a plurality of light emitting elements arranged on the wiring board and electrically connected to the wiring layer of the wiring board. A first light diffusing member having a plurality of through holes and containing a light diffusing material, which is arranged on the wiring substrate, and each of the plurality of light emitting elements is one of the plurality of through holes. A first light diffusing member arranged in the corresponding through hole and a plurality of second light diffusing members covering the plurality of light emitting elements and arranged in the plurality of through holes, each of which diffuses light. A plurality of second lights containing the material and the wavelength converting substance, and the content of the light diffusing material contained in each of them is higher than the content of the light diffusing material contained in the first light diffusing member. It includes a diffusion member.

According to an exemplary embodiment of the present disclosure, there is provided a novel light emitting device capable of suppressing uneven brightness of light emitted from a light source and making it thinner and smaller.

It is a schematic cross-sectional view which shows an example of the structure of the light emitting device 100 which concerns on embodiment. It is a schematic cross-sectional view which shows an example of the structure by variation of the light emitting device 100 which concerns on this embodiment. It is a schematic top view which shows an example of the structure of the light emitting device 100 which concerns on embodiment. It is a schematic top view which shows another example of the structure of the light emitting device 100 which concerns on embodiment. It is a schematic cross-sectional view which shows another example of the structure by variation of the light emitting device 100 which concerns on this embodiment. It is a schematic cross-sectional view which shows another example of the structure by variation of the light emitting device 100 which concerns on this embodiment. It is a schematic cross-sectional view which shows another example of the structure by variation of the light emitting device 100 which concerns on this embodiment. It is a process sectional view for demonstrating each manufacturing process included in the manufacturing method of a light emitting device 100. It is a process sectional view for demonstrating each manufacturing process included in the manufacturing method of a light emitting device 100. It is a process sectional view for demonstrating each manufacturing process included in the manufacturing method of a light emitting device 100. It is a process sectional view for demonstrating each manufacturing process included in the manufacturing method of a light emitting device 100. It is a process sectional view for demonstrating each manufacturing process included in the manufacturing method of a light emitting device 100.

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

The dimensions, shapes, etc. of the components shown in the drawings may be exaggerated for the sake of clarity, and may not reflect the dimensions, shapes, and magnitude relationships between the components in an actual light emitting device. In addition, some elements may be omitted in order to avoid overly complicated drawings.

In the following description, components having substantially the same function are indicated by common reference numerals, and the description may be omitted. In the following description, terms indicating a specific direction or position (eg, "top", "bottom", "right", "left" and other terms including those terms) may be used. However, these terms use relative orientation or position in the referenced drawings for clarity only. If the relative directions or positional relationships in terms such as "upper" and "lower" in the referenced drawings are the same, they are the same as the referenced drawings in drawings other than the present disclosure, actual products, manufacturing equipment, etc. It does not have to be an arrangement. In the present disclosure, "parallel" includes the case where two straight lines, sides, surfaces, etc. are in the range of about 0 ° to ± 5 ° unless otherwise specified. Further, in the present disclosure, "vertical" or "orthogonal" includes a case where two straight lines, sides, surfaces, etc. are in the range of about 90 ° to ± 5 ° unless otherwise specified.

[1. Structure of light emitting device 100]
FIG. 1A is a cross-sectional view showing an example of the structure of the light emitting device 100 according to the present embodiment. The figure shows a three-dimensional coordinate system stretched by three axes, the x-axis, the y-axis, and the z-axis, which are orthogonal to each other. Similar three-dimensional coordinate systems are described in the other accompanying drawings, where the x-axis, y-axis, and z-axis each point to a common orientation in all drawings.

The light emitting device 100 includes a wiring substrate 10, a plurality of light emitting elements 20, a first light diffusing member 30, a first light reflecting layer 40, a second light diffusing member 50, and a third light reflecting layer 51. A typical example of the shape of the light emitting device 100 is a substantially rectangular shape in a plan view. For example, the thickness (height in the z direction) of the light emitting device 100 can be 0.5 mm or more and 0.8 mm or less. Hereinafter, each component will be described in detail.

(Wiring board 10)
The wiring board 10 has an upper surface 10a and a lower surface 10b. A plurality of light emitting elements 20 are arranged and supported on the upper surface 10a side of the wiring board 10. The wiring board 10 has a first conductor wiring layer 12a, a second conductor wiring layer 12b, and an insulating layer 11, and a plurality of light emitting elements 20 are electrically connected to the first conductor wiring layer 12a. The first conductor wiring layer 12a and the second conductor wiring layer 12b are insulated by the insulating layer 11 and are electrically connected via the via 13. The portion of the upper surface 10a of the wiring board 10 other than the region where the light emitting element 20 is mounted is covered with the insulating layer 11.

An example of the wiring board 10 is a flexible printed circuit board (FPC) that can be manufactured by a roll-to-roll method. The FPC has a film-like insulator (resin) and a conductor wiring layer made of, for example, copper. Examples of the resin material include phenol resin, epoxy resin, polyimide resin, BT resin, polyphthalamide (PPA), polyethylene terephthalate (PET) and the like. The thickness of the wiring board 10 can be appropriately selected. Its thickness h1 (height in the z direction in the figure) is, for example, about 0.195 mm. By adopting the FPC, the wiring board 10 can be made lighter and thinner.

Ceramics may be selected as the material of the wiring board 10 from the viewpoint of excellent heat resistance and light resistance. In that case, the wiring board 10 is a rigid board. The rigid substrate is preferably a thin bendable rigid substrate. Examples of the ceramics include alumina, mullite, forsterite, glass ceramics, nitride-based (for example, AlN), carbide-based (for example, SiC), and LTCC.

Further, the wiring board 10 may be formed of a composite material. Specifically, the above-mentioned resin may be mixed with an inorganic filler such as _{glass fiber, SiO 2} , TiO ₂ , and Al ₂ O _3. For example, a glass fiber reinforced resin (glass epoxy resin) and the like can be mentioned. As a result, the mechanical strength of the wiring board 10 can be improved, the coefficient of thermal expansion can be reduced, and the light reflectance can be improved. Further, the wiring board 10 may have a laminated structure as long as at least the upper surface 10a has an electrical insulating property.

The conductor wiring layer 11 is provided on the upper surface 10a side of the wiring board 10. The conductor wiring layer 11 has a wiring pattern for supplying electric power to a plurality of light emitting elements 20 from an external control circuit (not shown). The material of the conductor wiring layer 11 can be appropriately selected depending on the material used as the conductor wiring layer 11, the manufacturing method, and the like. For example, when an epoxy resin is used as the material of the wiring board 10, it is preferable to select a material that is easy to process as the material of the conductor wiring layer 11. For example, a metal layer such as copper or nickel formed by plating, sputtering, vapor deposition, or pasting by pressing can be used. The metal layer can be processed into a predetermined wiring pattern by masking and etching by printing, photolithography, or the like. By coating the solder resist on the wiring pattern, oxidation of the substrate surface is suppressed.

When ceramics are used as the material of the wiring board 10, the material of the conductor wiring layer 11 is formed of, for example, a refractory metal capable of simultaneous firing with the ceramics of the wiring board 10. For example, the conductor wiring layer 11 is formed of a refractory metal such as tungsten or molybdenum. The conductor wiring layer 11 may have a multi-layer structure. For example, the conductor wiring layer 11 includes a pattern of a refractory metal formed by the above-mentioned method and a metal layer containing other metals such as nickel, gold, and silver formed on the pattern by plating, sputtering, vapor deposition, or the like. , May be provided.

(Light emitting element 20)
The plurality of light emitting elements 20 are arranged on the upper surface 10a side of the wiring board 10 and are electrically connected to the conductor wiring layer 11. FIG. 2A is a top view of the light emitting device 100. In FIG. 2A, attention is paid to 3 × 3 light emitting elements 20, and they are enlarged and shown.

The plurality of light emitting elements 20 may be arranged one-dimensionally or two-dimensionally on the upper surface 10a of the wiring board 10. In the present embodiment, the plurality of light emitting elements 20 are arranged two-dimensionally along two orthogonal directions, that is, the x direction and the y direction, and the arrangement pitch px in the x direction and the arrangement pitch py in the y direction are equal. Here, the arrangement pitch of the light emitting elements means the distance between the optical axes of two adjacent light emitting elements.

If the size of the array pitch is too large, the brightness efficiency can be significantly reduced. According to the study of the present inventor, for example, the arrangement pitch px and py are each preferably 0.5 mm or more and 10.0 mm or less. From the viewpoint of improving the luminance efficiency, it is more preferable that each of the array pitch px and py is 0.5 mm or more and 2.0 mm or less. However, the arrangement direction is not limited to this. The arrangement pitches in the x-direction and the y-direction may be different, and the two directions of the arrangement may not be orthogonal to each other. Further, the arrangement pitch is not limited to equal intervals, and may be unequal intervals. For example, a plurality of light emitting elements 20 may be arranged so that the distance from the center of the wiring board 10 becomes wider toward the periphery.

The light emitting element 20 is a semiconductor light emitting element, and known light emitting elements such as a semiconductor laser and a light emitting diode can be used. In this embodiment, a light emitting diode is exemplified as the light emitting element 20. For the light emitting element 20, an element that emits light of an arbitrary wavelength can be selected. For example, blue, as the light-emitting element which emits light having a green wavelength, ZnSe, nitride semiconductor _{(In x Al y Ga 1-} x-y N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1), GaP An element using the above can be used. Further, as the light emitting device that emits light having a red wavelength, a semiconductor light emitting device containing a semiconductor such as GaAlAs or AlInGaP can be used. Further, a semiconductor light emitting device formed of a material other than these can also be used. The composition, emission color, size, number, etc. of the light emitting element to be used can be appropriately selected according to the purpose and design specifications.

The light emitting device 20 preferably includes a nitride semiconductor (In _x Al _y Ga _1-x-y N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) capable of emitting light having a short wavelength. As a result, the second light diffusing member 50, which will be described later, can be efficiently excited. Various emission wavelengths can be selected depending on the material of the semiconductor layer and / or the mixed crystalliteity thereof. It may have positive and negative electrodes on the same surface side, or it may have positive and negative electrodes on different surfaces.

The light emitting element 20 has, for example, a translucent substrate and a semiconductor laminated structure laminated on the substrate. The semiconductor laminated structure includes an active layer and an n-type semiconductor layer and a p-type semiconductor layer sandwiching the active layer, and the n-type electrode and the p-side electrode are electrically connected to the n-type semiconductor layer and the p-type semiconductor layer, respectively. There is. The light emitting element 20 has an upper surface (or emission surface) 20a that emits light and a lower surface 20b that is located on the opposite side of the upper surface 20a. In this embodiment, the n-side electrode and the p-side electrode are located on the lower surface 20b.

The n-side electrode and the p-side electrode of the light emitting element 20 are electrically connected to and fixed to the conductor wiring layer 11 provided on the upper surface 10a of the wiring board 10. In this embodiment, the wiring board 10 is an FPC, and the light emitting element 20 is directly mounted on the FPC.

The light emitting element 20 may include a lens or the like for widening the emission angle of the light emitted from the upper surface 20a. The height in the z direction from the upper surface 10a of the wiring board 10 to the upper surface 20a of the light emitting element 20 can be, for example, about 0.155 mm. Alternatively, the height h5 in the z direction from the upper surface of the first conductor wiring layer 12a of the wiring board 10 to the upper surface 20a of the light emitting element 20 may be, for example, about 0.205 mm.

(1st light diffusing member 30)
The first light diffusing member 30 is arranged on the wiring board 10. The first light diffusing member 30 has a plurality of through holes 30h and contains a light diffusing material. Each of the plurality of light emitting elements 20 is arranged in the corresponding through hole of the plurality of through holes 30h. The thickness h3 of the first light diffusing member 30 can be, for example, about 0.30 mm. The first light diffusing member 30 may contain a wavelength converting substance. Details of the wavelength conversion material will be described later.

The first light diffusing member 30 is a member that diffuses and transmits incident light. The first light diffusing member 30 is made of a material having little light absorption with respect to visible light, such as a polycarbonate resin, a polystyrene resin, an acrylic resin, and a polyethylene resin. By providing irregularities on the surface of the first light diffusing member 30, dispersing light diffusing materials having different refractive indexes in the first light diffusing member 30, or changing the particle size of the light diffusing material, light is diffused. It becomes possible to control the degree. As the light diffusing material, a material having a high refractive index such as silicon oxide, zirconium oxide, or titanium oxide can be used. As the light diffusing member, a member commercially available under the name of a light diffusing sheet, a diffuser film, or the like can be used.

As shown in FIG. 2A, in a plan view, an example of the shape of the through hole 30h is circular. However, the shape of the through hole 30h is not limited to this, and may be a rectangular shape shown in FIG. 2B, or an oval shape including an elliptical shape and an oval shape. For example, when the shape of the through hole 30h is circular, the length r of the diameter can be about 0.50 mm. FIG. 2B shows a structural example of the first light diffusing member 30 in which the shape of the through hole 30h is square. For example, the array pitch px in the x direction and the array pitch py in the y direction are equal, and the respective array pitches can be 0.5 mm or more and 10.0 mm or less. Further, the length r of one side of the through hole 30h may be about 1.0 mm. However, the arrangement direction is not limited to this. The plurality of through holes 30h are appropriately provided in the first light diffusing member 30 according to the arrangement of the plurality of light emitting elements 20. As mentioned above, the two directions of the array do not have to be orthogonal. Further, the arrangement pitch indicating the distance between the centers of the two adjacent through holes 30h is not limited to equal intervals, and may be unequal intervals.

(First light reflecting layer 40)
The first light reflecting layer 40 is located between the wiring board 10 and the first light diffusing member 30. As the light reflecting layer, for example, a highly reflective film having a multilayer structure formed of a polyester resin is used. When a highly reflective film is used as the light reflecting layer, it is preferable to have a through hole corresponding to the through hole 30h of the first light diffusing member 30. The highly reflective film has high reflectance in the wavelength range belonging to the visible light region (for example, 400 nm to 800 nm). The highly reflective film preferably has a high reflectance of, for example, 98% or more in the wavelength range. For the highly reflective film, for example, a reflective film (ESR 80v2) manufactured by 3M can be preferably used. However, the first light reflecting layer 40 is not limited to the highly reflective film, and may be a metal film or a dielectric multilayer film. The thickness h2 of the first light reflecting layer 40 can be, for example, about 0.065 mm.

The first light reflecting layer 40 reflects the incident light toward the first light diffusing member 30. By providing the first light reflecting layer 40 between the upper surface 10a of the wiring substrate 10 and the lower surface 30b of the first light diffusing member 30, the light directed to the lower surface 30b of the first light diffusing member 30 is directed to the first light reflecting layer 40. Therefore, it can be reflected. As a result, the utilization efficiency of the light emitted from the light emitting element 20 can be improved. In particular, by using a highly reflective film as the light reflecting layer and minimizing the loss of light energy during reflection, it is possible to improve the brightness of the light emitting device 100.

(Second light diffusing member 50)
The plurality of second light diffusing members 50 cover the plurality of light emitting elements 20 and are arranged in the plurality of through holes 30h of the first light diffusing member 30. Each of the second light diffusing members 50 has an inner surface 30s of the through hole 30h, a side surface 40c of the first light reflecting layer 40, a part of the upper surface 10a of the wiring board 10, and an upper surface 20a of the light emitting element 20 in the through hole 30h. Is in contact with the lower surface 20b and the side surface 20c. In other words, the second light diffusing member 50 covers the plurality of light emitting elements 20 and is in contact with the inner surface 30s of the through hole 30h, the side surface 40c of the first light reflecting layer 40, and a part of the upper surface 10a of the wiring board 10. The through hole 30h is filled. However, a partial or local void may be formed along the boundary between the inner surface 30s of the through hole 30h and / or the side surface 40c of the first light reflecting layer 40 and the second light diffusing member 50. Such voids can occur, for example, due to manufacturing. As will be described in detail later, another light reflecting layer different from the first light reflecting layer 40 may be located between the upper surface 10a of the wiring board 10 and the plurality of second light diffusing members 50.

Like the first light diffusing member 30, the second light diffusing member 50 is made of a material that absorbs less light with respect to visible light, such as polycarbonate resin, polystyrene resin, acrylic resin, and polyethylene resin. The second light diffusing member 50 contains a light diffusing material. As the light diffusing material, a high refractive index material (or high refractive index fine particles) such as silicon oxide, zirconium oxide, and titanium oxide can be used. For example, by blending a high refractive index material with an acrylic resin material, a material used for the second light diffusing member 50 can be obtained. Here, the content rate a of the light diffusing material contained in the second light diffusing member 50 is higher than the content rate b of the light diffusing material contained in the first light diffusing member 30. The content rate a is preferably 1.5 times or more and 3.0 times or less of the content rate b. Depending on the magnitude relationship of the content, the light emitted from the light emitting element 20 can be diffusely reflected by the second light diffusing member 50, and the reflected light can be guided to the first light diffusing member 30.

The second light diffusing member 50 further contains a wavelength converting substance. When the first light diffusing member 30 contains a wavelength converting substance, the content of the wavelength converting substance contained in the first light diffusing member 30 is the wavelength converting substance contained in each of the plurality of second light diffusing members 50. It is set lower than the content rate.

Wavelength converters are typically phosphor particles. That is, the second light diffusing member 50 is a member in which particles of a high refractive index material and a phosphor are dispersed (or blended) in a resin. The second light diffusing member 50 absorbs at least a part of the light emitted from the light emitting element 20 and emits light having a wavelength different from the wavelength of the light emitted from the light emitting element 20. For example, the second light diffusing member 50 emits yellow light by wavelength-converting a part of blue light from the light emitting element 20. According to such a configuration, white light is obtained by mixing the blue light that has passed through the second light diffusing member 50 and the yellow light emitted from the second light diffusing member 50. From the viewpoint of efficiently introducing light into the first light diffusing member 30, it is beneficial that the material of the second light diffusing member 50 has a lower refractive index than the material of the first light diffusing member 30.

A known material can be applied to the phosphor. Examples of phosphors include fluoride-based phosphors such as KSF-based phosphors, nitride-based phosphors such as CASN, YAG-based phosphors, and β-sialone phosphors. The YAG-based phosphor is an example of a wavelength-converting substance that converts blue light into yellow light, and the KSF-based phosphor and CASN are examples of wavelength-converting substances that convert blue light into red light, and β-sialone phosphors. Is an example of a wavelength converting substance that converts blue light into green light. The phosphor may be a quantum dot phosphor.

The second light diffusing member 50 may contain, for example, a wavelength converting substance that converts blue light into red light and green light, respectively. In that case, the light emitting device 100 may mix red, blue, and green light to emit white light by transmitting the blue light emitted from the light emitting element 20 through the second light diffusing member 50. Alternatively, the plurality of light emitting elements 20 may include two or more types of light emitting elements 20. The plurality of light emitting elements 20 may include, for example, a light emitting element that emits light having a blue wavelength, a light emitting element that emits light having a green wavelength, and a light emitting element that emits light having a red wavelength. In that case, the light emitting device 100 may emit white light by mixing red, blue, and green light and transmitting the light through the second light diffusing member 50. Further, the type of light emitting element used in the light emitting device 100 may be determined from the viewpoint of enhancing the color rendering property of the light emitted from the light emitting device 100.

(Second light reflecting layer 55)
As shown in FIG. 6E, the light emitting device 100 may further include a second light reflecting layer 55 located between the wiring board 10 and the plurality of second light diffusing members 50. The second light reflecting layer 55 can be formed of the same material as the third light reflecting layer 51. By providing the light reflecting layer on the back surface side of the light emitting element 20 in this way, the light directed to the upper surface 10a of the wiring substrate 10 can be reflected by the light reflecting layer and guided to the second light diffusing member 50. As a result, the utilization efficiency of the light emitted from the light emitting element 20 can be further improved.

(Third light reflecting layer 51)
The third light reflecting layer 51 is located between the plurality of second light diffusing members 50 and the translucent laminated body 60 described later. The third light reflecting layer 51 covers the plurality of second light diffusing members 50 arranged in the plurality of through holes 30h of the first light diffusing member 30, and fills the openings 30f of the plurality of through holes 30h. The height h6 in the z direction from the upper surface 20a of the light emitting element 20 to the opening 30f of the through hole 30h can be, for example, about 0.210 mm.

The third light reflecting layer 51 is formed of a material containing a resin and particles of an oxide such as titanium oxide, aluminum oxide, and silicon oxide, which are particles of a reflective material dispersed in the resin. The average particle size of the oxide particles is, for example, about 30 nm or more and 250 nm or less. The third light reflecting layer 51 may further contain a pigment, a light absorbing material, a phosphor, and the like. As the resin material, a photocurable resin containing acrylate, epoxy, silicone or the like as a main component can be used. The particles of the reflector that scatter the light in the third light reflecting layer 51 may be uniformly distributed, and the absolute value of the light distribution angle is large in the region where the absolute value of the light distribution angle of the light emitting element 20 is small. It may be distributed at a higher density than the region.

By providing the third light reflecting layer 51 at a position directly above the light emitting element 20, the light directed directly above the light emitting element 20 is effectively diffused in the plane of the second light diffusing member 50 by the third light reflecting layer 51. Therefore, the brightness in a region other than directly above the light emitting element 20 can be improved. In other words, it is possible to effectively suppress the uneven brightness on the upper surface of the light emitting device 100 and obtain more uniform light.

(Translucent laminated body 60)
As shown in FIG. 1B, the light emitting device 100 may further include a translucent laminate 60 including a prism sheet 61. The translucent laminated body 60 has a substantially plate-like shape in a plan view.

The prism sheet 61 has a structure in which two prism array layers are laminated. In the present specification, a structure in which two prism array layers are laminated is referred to as a "prism sheet". Each of the two prism array layers has a structure in which a plurality of prisms extending in a predetermined direction are arranged. For example, in FIG. 1, one prism array layer has a plurality of prisms extending in the y direction, and the other prism array layer has a plurality of prisms extending in the x direction.

The prism sheet 61 refracts light incident from various directions in a direction (z direction) toward a display panel (not shown) facing the light emitting device 100. As a result, the light emitted from the upper surface 60a of the translucent laminate 60, which is the light emitting surface of the light emitting device 100, has a large amount of components perpendicular to the upper surface 60a (parallel to the z-axis), and the light emitting device 100 is moved to the front (z direction). It is possible to increase the brightness when viewed from. As the prism sheet 61, for example, 3M's Advanced Structural Optical Composite (ASOC) can be used. The thickness h4 of the prism sheet 61 may be about 0.08 mm.

By adopting the prism sheet 61, the light emitting device 100 can be further made thinner. Such a thin light emitting device 100 is particularly useful for applications such as smartphones.

The light emitting device 100 may further include a reflective polarizing layer (not shown) located above the prism sheet 61. The reflective polarizing layer selectively transmits light in a polarization direction that matches the polarization direction of a polarizing plate arranged on the backlight side of a display panel, for example, a liquid crystal display panel, and polarizes in a direction perpendicular to the polarization direction. It is reflected toward the prism sheet 61 side. A part of the polarized light returned from the reflective polarizing layer changes its polarization direction when it is reflected again by the prism sheet 61 and the first light diffusing member 30, and is converted into polarized light having the polarization direction of the polarizing plate of the liquid crystal display panel. , It enters the reflective polarizing layer again and exits to the display panel. As a result, the polarization directions of the light emitted from the light emitting device 100 are aligned, and light in the polarization direction effective for improving the brightness of the display panel can be obtained with high efficiency.

According to the light emitting device 100 according to the present embodiment, the first light diffusing member 30 is located above the first light diffusing member 30 in order to have both functions of the light guide plate and the light diffusing member. No light diffusing member is required. Further, since the second light diffusing member 50 has the functions of both the light diffusing member and the wavelength conversion member, the conventional wavelength conversion member located above the first light diffusing member 30 becomes unnecessary. Further, by adopting the prism sheet 61 as the translucent laminated body 60, the thickness of the light emitting device 100 can be reduced to 0.5 mm or less, and the light emitting device can be made thinner.

In recent years, the height specifications required in the market for smartphones and the like are less than 1.5 mm, and very strict specifications such as 0.5 mm or more and 1.0 mm or less may be required. The light emitting device 100 according to the present embodiment fully satisfies the requirement. Further, the light emitted from the light emitting element 20 is guided to the surrounding first light diffusing member 30 by the second light diffusing member 50 covering the light emitting element 20, so that the brightness of the light emitted from the light emitting device 100 is increased. It is possible to appropriately suppress unevenness.

3 to 5 are cross-sectional views showing an example of a structure according to a variation of the light emitting device 100 according to the present embodiment.

As shown in FIG. 3, the light emitting device 100 may further include a light diffusing layer 52 located between the first light diffusing member 30 and the prism sheet 61. For example, the light diffusion layer 52 is formed on the upper surface 30a of the first light diffusion member 30 by applying a fine uneven structure to the surface of the upper surface 30a of the first light diffusion member 30 by surface treatment such as embossing or bead coating. can do. By providing the light diffusion layer 52, the diffusion effect of the light emitted from the light emitting element 20 can be further improved.

(Prism array layers 62, 63)
As shown in FIG. 4, the light emitting device 100 may include a translucent laminate 60 having prism array layers 62 and 63 instead of the prism sheet 61. For example, in FIG. 1, the prism array layer 62 has a plurality of prisms extending in the y direction, and the prism array layer 63 has a plurality of prisms extending in the x direction. As the prism array layers 62 and 63, commercially available optical members for backlights can be widely used. The total thickness 7 of the prism array layers 62 and 63 can be, for example, about 0.16 mm. However, since the thickness h4 of the prism sheet 61 can be suppressed to about half the thickness h7 of the prism sheet in which the prism array layers 62 and 63 are simply laminated, from the viewpoint of making the light emitting device 100 thinner. It is preferable to use the prism sheet 61 as the translucent laminated body 60.

As shown in FIG. 5, each inner surface 30s of the plurality of through holes 30h is an inclined surface (or an inclined surface) extending upward at a position higher than the upper surface 20a of the corresponding light emitting element among the plurality of light emitting elements 20. Inclined portion) 30c is included. The inclined surface 30c is inclined at a predetermined angle α with respect to the optical axis L extending in the direction perpendicular to the upper surface 20a of the light emitting element 20. A part of the second light diffusing member 50 and the third light reflecting layer 51 are in contact with the inclined surface 30c, and the third light reflecting layer 51 is a plurality of second light diffusing arranged in the plurality of through holes 30h. Covers member 50. By adjusting the angle α, it is possible to control the degree of diffusion of light in the first light diffusion member 30. The angle α can be set, for example, in the range of 5 ° or more and 45 ° or less. The thickness of the inclined portion 30c in the z direction is, for example, about 0.210 mm.

[2. Manufacturing method of light emitting device 100]
An example of a method for manufacturing the light emitting device 100 will be described with reference to FIGS. 6A to 6E. 6A to 6E are process cross-sectional views for explaining each manufacturing process included in the manufacturing method of the light emitting device 100.

As shown in FIG. 6A, the light emitting element 20 is mounted on the wiring board 10 which is an FPC. By mounting the light emitting element directly on the FPC, the reliability of LED mounting can be ensured and the variation in wiring resistance can be reduced. As a result, it is possible to reduce the brightness unevenness of the light emitting device 100 that may occur due to these.

The first light diffusing member 30 having a plurality of through holes 30h shown in FIG. 6B is manufactured. A thin light emitting device having a thickness of about 0.5 mm requires a light diffusing member having a thickness of about 0.3 mm. In the example of this manufacturing method, for example, Al is adhered to the surface of the light diffusing member by vapor deposition to form a light reflecting layer. The light reflecting layer can also be formed by attaching a sheet-shaped light reflecting layer, applying a resin in which a reflective material is dispersed, or the like. Then, an adhesive layer is formed by attaching a double-sided tape to the formed light-reflecting layer. After that, a plurality of through holes are punched in the light diffusing member by press working. Finally, by cutting the light diffusing member to a predetermined outer size, the first light reflecting layer 40 is formed on the lower surface 30b, and the first light diffusing member 30 having a plurality of through holes 30h (hereinafter, "diffusing"). Notated as "sheet".) Is obtained. By integrally forming the first light diffusing member 30 and the first light reflecting layer 40 in this way, the manufacturing process can be simplified, and as a result, the manufacturing cost can be suppressed.

As shown in FIG. 6C, a vacuum laminator is used to crimp the diffusion sheet to the wiring board 10 via the adhesive layer. The diffusion sheet is aligned so that each of the plurality of light emitting elements 20 is located in the corresponding through hole of the plurality of through holes 30h, and the diffusion sheet is arranged on the wiring board 10. At this time, even if the arrangement of the diffusion sheet is displaced, the displacement is absorbed by the plurality of through holes 30h. The optical effect can be reduced by adjusting the diffusivity (light scattering) of the diffusing sheet.

As shown in FIG. 6C, the second light reflecting layer 55 may be formed so as to fill the gap between the upper surface 10a of the wiring board 10 and the lower surface 20b of the light emitting element 20. The second light reflecting layer 55 is formed of a material containing a resin and particles of an oxide such as titanium oxide, aluminum oxide, and silicon oxide, which are particles of a reflective material dispersed in the resin. For example, the second light reflecting layer 55 is formed by applying the above material so as to cover the upper surface 10a of the wiring board 10 located on the back surface side of the light emitting element 20 in the plurality of through holes 30h. Alternatively, the first light reflecting layer 40 and the second light reflecting layer 55 may be formed by using the same material as a common layer.

The method for producing the intermediate of the light emitting device shown in FIG. 6C is not limited to the method described above. First, the diffusion sheet may be crimped to the wiring board 10. After that, solder paste is printed on the conductor wiring layer 11 of the wiring board 10, a plurality of light emitting elements 20 are arranged in the plurality of through holes 30h, and the n-side electrode and the p-side electrode of the plurality of light emitting elements 20 are respectively placed. It is mounted on the conductor wiring layer 11. After that, the intermediate body of the light emitting device may be manufactured by electrically joining the plurality of light emitting elements 20 to the conductor wiring layer 11 via the solder paste by the reflow process.

As shown in FIG. 6D, for example, a material having low light absorption with respect to visible light, such as a polycarbonate resin, a polystyrene resin, an acrylic resin, a polyethylene resin, and a silicone resin, has a high refraction such as silicon oxide, zirconium oxide, and titanium oxide. A plurality of through holes 30h are filled with a diffusion resin containing a wavelength converting substance such as a rate material and particles of a phosphor, and the second light reflecting layer 55 and the light emitting element 20 are covered. Then, the diffusing resin is cured by irradiating it with ultraviolet rays or heating it.

As shown in FIG. 6E, on the upper surface 50a of the plurality of second light diffusing members 50, a resin and particles of oxides such as titanium oxide, aluminum oxide, and silicon oxide, which are particles of the reflective material dispersed in the resin, are formed. A material containing the above is applied to form a third light reflecting layer 51, whereby the plurality of through holes 30h are completely filled.

The light emitting device 100 is obtained through the above steps.

The light emitting device of the present disclosure can be used as a backlight source for a liquid crystal display, various lighting fixtures, and the like.

10: Wiring board 10a, 20a, 30a, 50a, 60a: Top surface 10b, 20b, 30b: Bottom surface 11: Insulation layer 12a: First conductor wiring layer 12b: Second conductor wiring layer 13: Via 20: Light emitting element 20c, 40c : Side surface 30: First light diffusing member 30c: Inclined surface 30f: Opening 30h: Through hole 30s: Inner surface 40: First light reflecting layer 50: Second light diffusing member 51: Third light reflecting layer 52: Light diffusing layer 55 : Second light reflecting layer 60: Translucent laminated body 61: Prism sheets 62, 63: Prism array layer 100: Light emitting device

Claims (9)

Wiring board and
A plurality of light emitting elements arranged on the wiring board and electrically connected to the wiring layer of the wiring board.
A first light diffusing member having a plurality of through holes and containing a light diffusing material, which is arranged on the wiring board, and each of the plurality of light emitting elements corresponds to the plurality of through holes. The first light diffusing member arranged in the through hole and
A plurality of second light diffusing members that cover the plurality of light emitting elements and are arranged in the plurality of through holes, each of which contains a light diffusing material and a wavelength converting substance, and each of which contains the above. The content of the light diffusing material is higher than the content of the light diffusing material contained in the first light diffusing member.
A light emitting device equipped with. The light emitting device according to claim 1, wherein the first light diffusing member contains a wavelength converting substance. The light emitting device according to claim 2, wherein the content of the wavelength converting substance contained in the first light diffusing member is lower than the content of the wavelength converting substance contained in each of the plurality of second light diffusing members. The light emitting device according to any one of claims 1 to 3, further comprising a first light reflecting layer located between the wiring board and the first light diffusing member. The light emitting device according to any one of claims 1 to 4, further comprising a second light reflecting layer located between the wiring board and the plurality of second light diffusing members. The light emitting device according to any one of claims 1 to 5, further comprising a prism sheet located above the first light diffusing member. The light emitting device according to claim 6, further comprising a light diffusing layer located between the first light diffusing member and the prism sheet. The light emitting device according to claim 6 or 7, further comprising a third light reflecting layer located between the plurality of second light diffusing members and the prism sheet. One of claims 1 to 8, wherein each inner surface of the plurality of through holes includes an inclined surface extending upward at a position higher than the upper surface of the corresponding light emitting element among the plurality of light emitting elements. The light emitting device described.

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