JP2001177157A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device for obtaining a white light emission having a uniform chromaticity in total bearing from a light emitting element, even without accurate formation of a layer or a package of a resin containing a phosphor necessary for wavelength conversion of blue light. SOLUTION: The surface of the light emitting element 3 including at least a light emitting surface is covered with a wavelength conversion layer 6 for converting the light wavelength of the element 3 with the contained phosphor. Further, the surface of the layer 6 is covered with a light diffusion layer 7 for scattering the light directed from the layer 6 itself toward outward to return the part of the light to the layer 6. Thus, the wavelength converted light is diffused as it is by the layer 7, and radiated. The phosphor is re-stimulated by the partial light returned to the layer 6 and further expedited to obtain white light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light-emitting device in which light emitted by a blue light-emitting diode is converted into a wavelength to obtain white light, and more particularly, to a uniform color regardless of the direction of a light emission observation surface. The present invention relates to a semiconductor light emitting device capable of emitting white light at a temperature.

[0002]

2. Description of the Related Art Light emitting diodes emitting blue light (hereinafter referred to as "L").
ED ”) recently became GaN, GaAl
By using GaN-based compound semiconductors such as N, InGaN, and InAlGaN, products with high emission luminance can be obtained. And this blue (B) LED
With the combination of the conventional red (R) and green (G) light emitting LEDs, a high-quality full-color image using three of these LEDs as one dot can be formed.

In the field of LEDs, R, G, and B (blue) of the three primary colors of light are required for full-color support. Therefore, further development and improvement of LEDs of these luminescent colors are mainly performed.
On the other hand, attempts have already been made to achieve white light emission that can be obtained only by combining R, G, and B with a single LED. One such attempt is
For example, there is one disclosed in JP-A-7-99345.

The LED described in this publication is a so-called LED lamp which is sealed with a resin (not shown) including a mounting portion 51a of a lead frame 51 on which a light emitting chip 50 is mounted, as shown in a schematic diagram of FIG. Of the type. Then, in order to change the emission wavelength of the light emitting chip 50 to obtain a different emission color, the mounting portion 51a around the light emitting chip 50 is sealed with a resin 52 containing a fluorescent substance. In other words, instead of using a conventional LED lamp that is covered with a single layer of epoxy resin that also covers the tip of the lead frame on which the light-emitting chip is mounted and also functions as a lens, it is used for wavelength conversion around the light-emitting chip. Is formed, and the periphery thereof is sealed with an epoxy resin.

[0005] By sealing the light emitting chip 50 with such a resin 52 containing a fluorescent substance for wavelength conversion, the wavelength of blue light emitted from the light emitting chip 50 can be changed by the fluorescent substance, and a high-brightness GaN-based semiconductor can be obtained. The blue light emitting chip used can be used as a white light emitting device. That is, in the case of the blue light emitting chip 50 using a GaN-based compound semiconductor, the blue light emitting component itself has:
White light emission is obtained by mixing color with a yellow-green component whose wavelength has been converted by the fluorescent substance contained in the resin 52.

A semiconductor light emitting device in which a light emitting chip is surface-mounted on a printed wiring board and resin sealed is used instead of an LED lamp in which a light emitting chip is mounted on a mount portion and sealed with a shell-shaped resin. Similarly, white light emission can be obtained by a resin layer containing a fluorescent substance. As an example of such a semiconductor light emitting device, see, for example,
There is one described in Japanese Patent No. 1845. In this method, an adhesive layer is applied on a main light extraction surface of a light emitting chip mounted and mounted on a printed wiring board, and a phosphor layer is attached to the upper surface.

The applicant of the present application has disclosed a white light emitting semiconductor device in which a light emitting element mounted on a submount element with p-side and n-side electrodes facing downward is sealed with a resin package containing a fluorescent substance. Proposed and filed as Japanese Patent Application No. 11-3788. Also in the semiconductor light emitting device according to this application, white light can be emitted by converting the wavelength of blue light emitted from the light emitting element with a fluorescent substance.

[0008]

In the case of an LED lamp, since the inner surface of the mount portion 51a on which the light emitting chip 50 is mounted is used as a light reflecting surface, the mount portion 51a is formed in a mortar shape as shown in the example of FIG. Is valid. However, when the mount portion 51a has a mortar shape, the light emitting direction of the light emitting chip 50 and the thicknesses A and B of the resin 52 on the side are often different as shown in FIG. The difference between the thicknesses A and B varies depending on the shape of the mount portion 51a, the size of the light emitting chip 50, the filling thickness of the resin 52, and the like. Therefore, if these conditions can be optimized, the layer thickness of the resin 52 can be made uniform in all directions around the light emitting chip 50. However, since the resin 52 is injected into the mount portion 51a by the dispenser, it is very difficult to control the thickness with high precision.
At present, it is impossible to make the thickness of the resin 52 around the light emitting chip 50 uniform as well as the relationship between the thicknesses of A and B as shown in the figure.

If the thickness of the resin 52 around the light emitting chip 50 is different, the larger the thickness, the higher the rate of conversion of blue light emission from the light emitting chip 50 to yellow green. For this reason, even if good white light emission is obtained in the thickness A direction, the yellow-green component exceeds the white color in the portion near the inner peripheral surface of the mount portion 51a in the thickness B direction. Accordingly, since the light is emitted with the bottom surface and the inner peripheral surface of the mount portion 51a as the reflecting surfaces, white light is occupied at the center portion and yellowish light is emitted at the peripheral portion.

On the other hand, as described in the above-mentioned publication, a resin layer is formed so as to face a main light extraction surface of a light-emitting element, or a fluorescent material is applied around a flip-chip type light-emitting element of the earlier application by the present applicant. There is a similar problem in the case of sealing with a contained resin package. In other words, when applying a resin layer or encapsulating with a resin package, due to limitations in the manufacturing technology, a fluorescent substance is applied so as to have a uniform thickness on the main light extraction surface of the light emitting element or on the entire periphery thereof. It is difficult to form a layer that contains. For this reason, when the resin layer containing the fluorescent substance is thicker than a predetermined value, light from the light emitting element becomes greenish, and when the resin layer containing the fluorescent substance is thinner than the predetermined value, light emission becomes bluish,
When viewed from all observation planes, chromaticity variations become noticeable.

As described above, even when the area around the light emitting element emitting blue light is coated with a resin layer or a package containing a fluorescent substance, the wavelength conversion rate changes according to the thickness of these layers and the package. No white light emission is obtained. Therefore, there is a problem that a large difference in chromaticity appears depending on the viewing direction, and chromaticity unevenness occurs when incorporated in a backlight light source such as a liquid crystal display panel.

According to the present invention, even if molding of a resin layer or a package containing a fluorescent substance necessary for wavelength conversion of blue light emission cannot be obtained with high precision, white light emission of uniform chromaticity in all directions can be obtained from the light emitting element. It is an object to provide a semiconductor light emitting device obtained.

[0013]

SUMMARY OF THE INVENTION The present invention is a semiconductor light emitting device in which at least a surface including a light emitting surface of a light emitting element is covered with a wavelength conversion layer for converting a light emitting wavelength of the light emitting element with a contained fluorescent substance, The surface of the wavelength conversion layer is covered with a light diffusion layer that scatters light going outward from the wavelength conversion layer and returns a part of the light to the wavelength conversion layer.

In such a configuration, the light diffusion layer can be a molded layer in which SiO ₂ is mixed in a transparent resin,
Further, the light diffusion layer may be sealed with a transparent light transmitting resin.

[0015]

The invention according to claim 1 is a semiconductor light emitting device in which at least a surface including a light emitting surface of a light emitting element is covered with a wavelength conversion layer for converting a light emitting wavelength of the light emitting element with a contained fluorescent substance. There is provided a semiconductor light emitting device characterized in that the surface of the wavelength conversion layer is covered with a light diffusion layer that scatters light outward from the wavelength conversion layer and returns a part of the light to the wavelength conversion layer. In addition, the wavelength-converted light is diffused to the outside by the light diffusion layer and emitted, and at the same time, a part of the light is returned to the wavelength conversion layer, thereby re-exciting the fluorescent substance to promote whitening.

According to a second aspect of the present invention, in the semiconductor light emitting device according to the first aspect, the light diffusion layer is a molded layer in which SiO ₂ is mixed in a transparent resin.
The light diffusion layer can be formed at low cost.

The invention according to claim 3 is the semiconductor light emitting device according to claim 1 or 2, wherein the light diffusion layer is sealed with a transparent light transmitting resin. It has the effect of improving the durability by protecting, and improving the on-axis luminous intensity by making the light-transmitting resin into a lens shape.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic vertical sectional view of a semiconductor light emitting device according to one embodiment of the present invention.

As shown in the drawing, the semiconductor light emitting device of the present invention comprises a mounting substrate 1, a submount element 2 mounted thereon, a light emitting element 3 mounted thereon, The main component is a transparent resin package 4 sealed including the element 3. As will be described later, a resin layer of a fluorescent substance for whitening and a resin layer for uniforming chromaticity by light diffusion are formed around the light emitting element 3.

The mounting substrate 1 is insulative, and a slit is formed in a substrate material in a wafer state as in the case of a conventional flip-chip type semiconductor light emitting element. The electrodes 1a and 1b are formed by plating through the slits. It is formed on both sides of the mounting substrate 1. After the mounting of the sub-mount element 2 and the light-emitting element 3 and the wire bonding, the resin package 4 seals the surface of the substrate material in a wafer state with a resin, and the mounting board 1 and the resin package having the illustrated shapes by dicing in the final step. Created as 4.

The sub-mount element 2 uses an n-type silicon substrate 2a. On the bottom surface of the silicon substrate 2a, an n-electrode 2b which is electrically mounted on the electrode 1a of the mounting substrate 1 is formed. On the upper surface of the silicon substrate 2a, a p-side electrode 2c that contacts a p-type semiconductor region formed on a part of the silicon substrate 2a and an n-side electrode 2d that contacts an n-type semiconductor region are formed.

The light emitting element 3 is formed of Ga as described in the section of the prior art.
High-brightness blue light emitting LED using N-based compound semiconductor
It is. The light-emitting element 3 includes, for example, an n-type layer of GaN, InGaN, on a surface of a substrate 3a made of sapphire.
Of an active layer and a p-type layer of GaN. Then, as is well known in the art, a part of the p-type layer is etched to expose the n-type layer, an n-side electrode 3b is formed on the exposed surface of the n-type layer, and a p-type electrode is formed on the surface of the p-type layer. The side electrode 3c is formed, and the n-side electrode 3b is connected to the p-side electrode 2 of the submount element 2.
c and the p-side electrode 3c are joined to the n-side electrode 2d of the submount element 2 via bump electrodes.

Further, the p-side electrode 2c of the submount element 2
A wire 5 is bonded between the substrate 1 and the electrode 1b of the mounting board 1. The mounting substrate 1 is mounted on a wiring substrate of an electronic device or the like, and the electrodes 1a and 1b are mounted and mounted on the wiring pattern of the wiring substrate. Make it conductive. The resin package 4 is made of a light-transmissive epoxy resin conventionally used in the field of LED lamps.

Here, in the present invention, the periphery of the light emitting element 3 is coated with the wavelength conversion layer 6, and the entire surface of the wavelength conversion layer 6 is coated with the light diffusion layer 7. As described in the specification of Japanese Patent Application No. 11-3788, the wavelength conversion layer 6 is obtained by mixing a fluorescent substance for converting blue light emission of the light emitting element 3 into white light into the epoxy resin. Things. The fluorescent substance that converts the blue light emission to the white light emission may be any substance that has a complementary color relationship with the blue color that is the light emission color of the light emitting element 3, and a fluorescent dye, a fluorescent pigment, a fluorescent substance, or the like can be used. , Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce
Etc. are preferred. The light diffusion layer 7 is for scattering and irregularly reflecting the light whose wavelength has been converted by the wavelength conversion layer 6, returning a part of the light to the wavelength conversion layer 6, and then re-exciting the white light conversion by the phosphor. , Epoxy resin mixed with SiO ₂ .

The wavelength conversion layer 6 converts blue light emission from the light emitting element 3 into white light emission.
Depends on the thickness of the That is, as described above, when the wavelength conversion layer 6 is thicker than a predetermined value, a greenish emission color is obtained, and when the wavelength conversion layer 6 is thinner than the predetermined value, a bluish emission color is obtained. It is easy to have a color tone that deviates from light. Therefore, the thickness of the wavelength conversion layer 6 is
It is preferable to set the thickness so that it can be converted to white light with the same efficiency in all directions. However,
As described above, it is very difficult to form the wavelength conversion layer 6 to have a uniform thickness from the viewpoint of the current manufacturing technology.

On the other hand, in the present invention, since the surface of the wavelength conversion layer 6 is covered with the light diffusion layer 7, the light that has passed through the wavelength conversion layer 6 is diffused by SiO ₂ mixed in the light diffusion layer 7. Diffusely reflected. That is, the light incident on the light diffusion layer 7 from the wavelength conversion layer 6 is emitted as it is or
A component irradiated to the outside by diffusion by O ₂ and Si
The light is separated into components reflected by O ₂ and returned to the wavelength conversion layer 6. At this time, the light returned to the wavelength conversion layer 6 re-excites the fluorescent substance in the wavelength conversion layer 6 to further promote white conversion, and the converted white light enters the light diffusion layer 7. Released outside.

In the above configuration, when the light emitting element 3 is energized, light from the light emitting layer is emitted. In this case, in the blue light emitting element 3 of the GaN-based compound semiconductor using the transparent sapphire substrate 3a, the upper surface of the substrate 3a is used as the main light extraction surface, but the substrate 3a is formed on the bottom surface of the semiconductor thin film layer laminated thereon. Light is also emitted from the side and the light emitting element 3
Illuminates almost uniformly over the entire surface. Then, the light from the light emitting element 3 is wavelength-converted to white while passing through the wavelength conversion layer 6 containing a fluorescent substance, and is emitted from the light diffusion layer 7.

[0029] Here, since the light diffusion layer 7 is a resin layer obtained by mixing SiO _2, part of the light from the wavelength converting layer 6 as described above receives a diffused reflection SiO _2, is returned to the wavelength conversion layer 6. Therefore, a part of the light emitted from the light emitting element 3 is again wavelength-converted by the fluorescent substance of the wavelength conversion layer 6, and
Whitening is promoted. Therefore, even if the thickness of the wavelength conversion layer 6 is not uniform, highly efficient whitening can be achieved by returning light from the light diffusion layer 7 and re-exciting the fluorescent substance. Further, since light is diffused by the SiO ₂ mixed into the light diffusion layer 7, uniform white light emission is obtained in all directions of the light emitting element 3.

As described above, the provision of the light diffusion layer 7 around the wavelength conversion layer 6 makes it possible to promote white wavelength conversion and to diffuse outgoing light at the same time, so that the thickness of the wavelength conversion layer 6 can be reduced. It is possible to emit white light without unevenness in chromaticity without uniformity with high precision.

FIG. 2 is a schematic longitudinal sectional view of an example in which the LED lamp is mounted on a mount portion of a lead frame as in the conventional example of FIG. Note that the same components as those in the example of FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, a forked lead frame 1 is shown.
A mount portion 10b is formed on one of the leads 10a, and a composite light emitting device including a submount device 2 and a light emitting device 3 is mounted and mounted on the mount portion 10b, and is sealed with a resin package 11 made of epoxy resin. . The conduction structure between the submount element 2 and the light emitting element 3 is exactly the same as that of the example of FIG. 1. The n electrode 2 b on the bottom surface of the submount element 2 is conductively mounted on the mount portion 10 b, and the p Side electrode 2c and other lead 10c
Are bonded by a wire 12.

An epoxy resin mixed with a fluorescent substance is injected into the mount portion 10b by a dispenser in the same manner as in the previous example, whereby the wavelength conversion layer 13 covering the entire submount element 2 and light emitting element 3 is formed. Is formed. A light diffusion layer 14 made of epoxy resin mixed with SiO ₂ is formed on the surface of the wavelength conversion layer 13 by a dispenser or a coating tool.

Also in this example, when the light from the light emitting element 3 passes through the wavelength conversion layer 13, the wavelength is converted to white light,
A part of the light diffuses through the light diffusion layer 14 and is radiated, and the remaining part is irregularly reflected by SiO ₂ mixed into the light diffusion layer 14 and returns to the wavelength conversion layer 13. Therefore, as in the example of FIG. 1, uniform light emission without chromaticity unevenness is caused by the synergistic effect of whitening by re-excitation of the fluorescent substance in the wavelength conversion layer 13 and light diffusion by the SiO _{2 in the} light diffusion layer 14. Color can be emitted in all directions. In particular, the wavelength conversion layer 13 is formed by injecting a resin with a dispenser so that the wavelength conversion layer 13 is formed in a convex mountain shape as shown in the figure, and the difference between the thickness and the light extraction surface on the upper surface of the light emitting element 3 is not parallel. Even if big,
Good white light is obtained by the function of the light diffusion layer 14.

In the above embodiment, the wavelength conversion layers 6 and 13 are formed around the light emitting element 3 by mixing the epoxy resin with the fluorescent substance as the wavelength conversion layers 6 and 13. It may be attached to the surface. That is, (Y, Gd) ₃ (Al, Ga) ₅ O exemplified above.
₁₂ : The fluorescent layer may be formed by directly applying a fluorescent dye such as Ce, a fluorescent pigment, a fluorescent substance, or the like to the light emitting surface of the light emitting element 3, and the light emitting element 3 may be formed by such a fluorescent layer.
Can be converted to white light.

[0036]

According to the present invention, the wavelength-converted light can be converted into light by the light diffusion layer provided on the surface of the light-emitting element without forming the wavelength conversion layer having a uniform thickness. The phosphor is diffused to the outside and emitted, and at the same time, a part of the phosphor is returned to the wavelength conversion layer, whereby the fluorescent substance is re-excited and whitening can be promoted. Therefore, white light emission having uniform chromaticity and color tone can be obtained in all directions of the light emitting element by promoting diffusion and whitening, and can be effectively used as a light source for various applications.

Further, since the chromaticity can be controlled by changing the amount of the diffusing material such as SiO ₂ mixed in the light diffusion layer, the chromaticity of the color development can be finely adjusted and matched to the required emission color. Products can be created.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a semiconductor light emitting device of an example of an LED lamp type mounted on a mounting portion of a lead frame and sealed with a resin;

FIG. 3 is a conventional example in which a blue light emitting element is sealed with a wavelength conversion layer in which a fluorescent substance is mixed into a resin, and FIG.
Is a schematic vertical sectional view, and (b) is a schematic plan view.

[Explanation of symbols]

 Reference Signs List 1 mounting substrate 1a, 1b electrode 2 submount element 2a silicon substrate 2b n electrode 2c p-side electrode 2d n-side electrode 3 light-emitting element 3a substrate 3b n-side electrode 3c p-side electrode 4 resin package 5 wire 6 wavelength conversion layer 7 light diffusion Layer 10 Lead frame 10a Lead 10b Mounting part 10c Lead 11 Resin package 12 Wire 13 Wavelength conversion layer 14 Light diffusion layer

Claims (3)

[Claims] 1. A semiconductor light emitting device in which at least a surface including a light emitting surface of a light emitting element is coated with a wavelength conversion layer that converts an emission wavelength of the light emitting element with a contained fluorescent substance,
A semiconductor light emitting device, wherein a surface of the wavelength conversion layer is covered with a light diffusion layer that scatters light going outward from the wavelength conversion layer and returns a part of the light to the wavelength conversion layer. 2. The light diffusion layer according to claim 1, wherein said light diffusion layer comprises SiO _{2 in a} transparent resin.
2. The semiconductor light emitting device according to claim 1, wherein the molded layer is a molded layer containing a mixed material. 3. The semiconductor light emitting device according to claim 1, wherein said light diffusion layer is sealed with a transparent light transmitting resin.