JP2004111882A - Light emitting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting apparatus even with a tilted side wall capable of obtaining uniform color luminescence on a light emission observing face. <P>SOLUTION: A low concentration resin layer 24 filled with a translucent resin up to an upper face position of a blue LED 17 and a high concentration resin layer 25 filled with a translucent resin on the low concentration resin layer 24 are formed in a cup 12a acting as a reflecting mirror, and a phosphor 27 is mixed in the layers 24, 25 so that the phosphor concentration of the high concentration resin layer 25 is higher than that of the low concentration resin layer 24. Further, the concentration of the phosphor 27 mixed in the layers 24, 25 is distributed in a way that a value multiplying the concentration of the phosphor 27 with an optical path length of the light emitted from the blue LED 17 to reach the upper face of the high concentration resin layer 25 is almost constant. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting device having a light emitting element and a phosphor to emit light, and for example, to a light emitting device applied to an LED display, a backlight device, a traffic light, an illuminated switch, various sensors, various indicators, and the like.
[0002]
[Prior art]
As a conventional light emitting device that emits light having a light emitting element and a phosphor, for example, using a lead frame having a concave portion formed at the tip portion, mounting an LED that is a light emitting element on the bottom surface of the concave portion, further from the LED A phosphor that absorbs emitted light and converts the wavelength to light of another wavelength is mixed in a resin such as a transparent epoxy resin, and the phosphor-mixed resin is completely filled in the concave portion covering the LED. is there.
[0003]
In a light emitting device having such a configuration, for example, if a blue LED is used as an LED and a phosphor that converts the wavelength of blue light from the blue LED to yellow is used as the phosphor, a mixed color of both colors causes a light emission observation surface. It is possible to emit white light uniformly.
[0004]
However, in this light emitting device, the light emitted in the direction directly above the blue LED and the light emitted obliquely from the upper surface or side surface of the blue LED or reflected by the inner wall of the concave portion after the emission have an optical path passing through the resin. Lengths are different. If the optical path length is different, the amount of phosphor passing through the resin will be different, leading to external radiation, so when viewed from the light emission observation surface, the color directly above the blue LED is white and the surrounding area looks yellow. Occurs.
[0005]
In particular, recently, there is a strong need for miniaturization and thinning of a light emitting device such as a shell type or an SMD (Surface Mounted Device) type. In order to realize such a light emitting device, a resin filled in a concave portion covering an LED is required. The phosphor concentration must be increased. When the concentration of the fluorescent material is increased, the difference in the amount of light passing through the fluorescent material due to the difference in the optical path length becomes larger, so that more color unevenness occurs.
[0006]
As a light emitting device capable of eliminating such color unevenness, there is a light emitting device disclosed in Japanese Patent No. 3065263. In the light emitting device of this publication, a concave portion in which an LED is mounted on the bottom surface is filled with a first resin having a concave spherical shape that covers the LED and has a concave shape as viewed from a light emission observation surface, and further has a fluorescent material on the first resin. By filling the second resin into which the body is mixed, the difference in the amount of light passing through the phosphor is substantially reduced, and the color unevenness is reduced.
[0007]
[Problems to be solved by the invention]
By the way, in the light emitting device of the above-mentioned publication, the thickness of the second resin containing the phosphor is thickest immediately above the LED and becomes thinner toward the side wall. When the side wall is inclined, after the light is emitted from the LED, the light reflected by the inclined wall and traveling directly upward passes through the thin portion of the second resin, so that the amount of the phosphor passing therethrough is smaller than that of the other portions. Less. In other words, a difference occurs in the amount of light passing through the phosphor, so that color unevenness occurs. In other words, there is a problem that light emission of a uniform color cannot be obtained on the light emission observation surface.
[0008]
The present invention has been made in view of such a point, and an object of the present invention is to provide a light emitting device that can obtain uniform color light emission on a light emission observation surface even in a light emitting device having inclined side walls. I do.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a light emitting device according to the present invention includes a light emitting element made of a nitride semiconductor fixed in a concave reflecting mirror, and light absorbed by the light emitting element. In a light-emitting device having a phosphor that emits light of different wavelengths, a light-transmitting resin is filled in the reflector to cover the light-emitting element, and the phosphor is mixed into the entire light-transmitting resin, The concentration of the mixed phosphor is distributed such that a value obtained by multiplying an optical path length of light emitted from the light emitting element to an upper surface of the translucent resin by the concentration is substantially constant. And
[0010]
In addition, the light emitting device of the present invention includes a light emitting element made of a nitride semiconductor fixed in a concave reflecting mirror, absorbing light emitted by the light emitting element, and emitting light having a different wavelength from the absorbed light. A first resin layer in which the reflecting mirror is filled with a translucent resin up to the upper surface of the light emitting element, and a translucent resin on the first resin layer. And a second resin layer filled with the first and second resin layers. The first and second resin layers are formed such that the phosphor concentration of the second resin layer is higher than that of the first resin layer. Is mixed.
[0011]
In addition, the concentration of the phosphor mixed in the first and second resin layers is a value obtained by multiplying the optical path length of light emitted from the light emitting element to the upper surface of the second resin layer by the concentration. Are distributed so as to be substantially constant.
[0012]
Further, the thickness of the first and second resin layers is adjusted so that a value obtained by multiplying the optical path length of light emitted by the light emitting element to the upper surface of the second resin layer by the concentration is substantially constant. It is characterized by being formed in.
[0013]
Also, the upper surface of the first resin layer is formed in an annular shape depressed in an arc from the edge of the upper surface of the light emitting element to the space between the inner walls of the reflecting mirror.
[0014]
Further, a reflection agent for irregularly reflecting light is mixed into the first resin layer.
[0015]
Further, the light-emitting element is a flip-chip type light-emitting diode.
[0016]
Further, the light-emitting element is a face-up type light-emitting diode, and a light reflection film is formed on a surface fixed with the adhesive.
[0017]
The light emitting element is characterized by being fixed by an adhesive mixed with the phosphor.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
(First Embodiment)
FIG. 1A is a cross-sectional view illustrating a configuration of an LED lamp according to a first embodiment of the present invention, and FIG. 1B illustrates an optical path length of light from a light emitting element (LED) used in the LED lamp. FIG.
[0020]
The LED lamp 10 shown in FIG. 1A is of a shell type, and is a metal having a cup 12a at the tip of one of the two electrically insulated lead frames 12, 13. A stem 14 is provided. The surface of the cup 12a is a reflecting mirror that reflects light. A flip-chip type LED in which a blue LED 17 is flip-chip mounted on the overvoltage protection element 16 is mounted on the bottom surface of the cup 12a. That is, the overvoltage protection element 16 is fixed to the bottom surface of the cup 12a by a mount 18 made of a conductive paste, and the blue LED 17 having a wavelength of 450 to 550 nm is flip-chip mounted on the overvoltage protection element 16.
[0021]
As shown in FIG. 2, the layer configuration of the blue LED 17 includes, for example, a sapphire substrate 17a as a transparent substrate, and on the sapphire substrate 17a, as a nitride semiconductor layer by MOCVD or the like, for example, a buffer layer 17b, an n-type contact. A layer 17c, an n-type cladding layer 17d, a layer 17e having a light emitting layer, a p-type cladding layer 17f, and a p-type contact layer 17g are sequentially formed, and are formed on the p-type contact layer 17g by a sputtering method, a vacuum deposition method, or the like. A non-light-transmitting light reflecting electrode 17h is formed on the entire surface, a p-electrode 17i is formed on a part of the non-light-transmitting light reflecting electrode 17h, and an n-electrode 17j is formed on a part of the n-type contact layer 17c.
[0022]
In the flip-chip mounting of the blue LED 17, as shown in FIG. 1, the lower surface of the sapphire substrate 17a is the uppermost surface, and the p-electrode 17i is connected to the electrode 16a on the n-layer of the overvoltage protection element 16 via the gold bump 19. , And the n-electrode 17j is connected to the electrode 16b on the p-layer of the overvoltage protection element 16 via the gold bump 20. The electrode 16b of the overvoltage protection element 16 is connected to the lead frame 13 by a bonding wire 22.
[0023]
Further, a low-concentration resin layer 24 described later is formed on the cup 12a up to the position of the uppermost surface of the blue LED 17, and a high-concentration resin layer 25 is formed on the low-concentration resin layer 24 so as to swell on the cup 12a. I have. More specifically, the upper surface of the low-concentration resin layer 24 formed in an annular shape around the uppermost surface of the blue LED 17 has a cross-sectionally concave shape. The upper surface of the high-concentration resin layer 25 has a convex shape in which the position immediately above the blue LED 17 is the highest.
[0024]
The low-concentration resin layer 24 is formed by mixing a phosphor 27 that absorbs blue light emitted by the blue LED 17 and emits yellow light at a low concentration into a translucent resin such as an epoxy resin or a silicone resin. The high-concentration resin layer 25 is obtained by mixing the phosphor 27 with a high concentration in a translucent resin. The phosphor 27 is made of Ce: YAG (a yttrium aluminum garnet phosphor).
[0025]
The concentration or shape of the phosphor 27 in each of the layers 24 and 25 is determined by the light path length of light emitted from the blue LED 17 reaching the interface between the high-concentration resin layer 25 and the external resin 29 and the concentration of the phosphor 27. The multiplied value is adjusted to be substantially constant.
For example, in the case of three optical paths A, B, and C shown in FIG. 1B, the optical path length × density is substantially constant. However, in (b), l _{1 to} l ₉ indicate an optical path length, d ₁ indicates a high density, d ₂ indicates a low density, C ₁ indicates an arc portion, and C ₂ indicates a convex portion. In this case, the optical path A of the light emitted directly upward blue LED 17, the A = _{l 1} × _{d 1.} In the optical path B of the light emitted from the side surface of the blue LED 17 and further reflected on the side wall of the cup 12a, B = (l ₂ + l ₃ ) d ₂ + l ₄ × d ₁ . Further, the light emitted from the side surface of the blue LED 17 passes through the low-concentration resin layer 24, then passes through the arc-shaped portion of the high-concentration resin layer 25, passes through the low-concentration resin layer 24, and passes through the side wall of the cup 12a. is reflected, the optical path C of the light the reflected light passing through the high density resin layer 25 via the low density resin layer _{24, C = (l 5 +} l 7 + l 8) d 2 + (l 6 + l 9) d 1 and Become. In this case, the relationship is A ≒ B ≒ C.
[0026]
In the case of preparing a resin mixed with the phosphor 27, for example, a base material and a curing agent, which are light-transmissive resins, are mixed at a predetermined ratio, then stirred and defoamed, and Aerosil + silane coupling agent is mixed with the resin. It is prepared by sufficiently kneading. When the layers 24 and 25 are formed of this resin, for example, assuming that the depth of the cup 12a is 0.35 mm and the height of the flip-chip type LED is 0.25 mm, the phosphor 27 of the low concentration resin layer 24 is formed. The layers 24 and 25 are formed by setting the concentration to 20% and the concentration of the high-concentration resin layer 25 to 60%, and setting each curing time to 120 ° C./1 hour.
[0027]
Further, the lead frame 12 on which the metal stem 14 having the cup 12a is formed and the other lead frame 13 are sealed with an external resin 29 which is a mold member. The external resin 29 is obtained by solidifying a translucent resin into a shell shape.
[0028]
In the LED lamp 10 configured as described above, when a voltage is applied to the lead frames 12 and 13, the blue LED 17 emits blue light. The blue light passes through the layers 24 and 25 between the light emitted directly above the blue LED 17 and the light emitted obliquely from the upper surface or side surface of the blue LED 17 or reflected by the inner wall of the cup 12a after the emission. The optical path length is different.
[0029]
However, in each of the layers 24 and 25, the concentration of the phosphor 27 or the shape of each of the layers 24 and 25 is adjusted so that the optical path length × the concentration of the phosphor 27 becomes substantially constant. As described above, the light emitted in each direction passes through the phosphor 27 almost in the same amount in the course of passing through the layers 24 and 25.
[0030]
For example, when light emitted from the blue LED 17 passes through the optical paths A, B, and C, the amount of light passing through the phosphor 27 becomes substantially the same in any of the optical paths A to C. Since the converted yellow light is mixed with blue light that has not passed through the phosphor 27, uniform white light emission can be obtained on the light emission observation surface of the LED lamp 10.
Although the non-light-transmitting light reflecting electrode 17h is formed on the entire surface of the blue LED 17 on the p-type contact layer 17g, the non-light-transmitting light reflecting electrode 17h can be replaced with a light-transmitting electrode.
[0031]
(Second embodiment)
FIG. 3 is a sectional view showing the configuration of the LED lamp according to the second embodiment of the present invention. However, in FIG. 3, portions corresponding to the respective portions in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0032]
The LED lamp 30 shown in FIG. 3 is different from the flip-chip type LED described in the first embodiment in that a blue LED 42 having a light reflection film 42a formed on the lower surface of a sapphire substrate 17a of the blue LED 17 shown in FIG. Is fixed to the bottom surface of the cup 12a by a mount 18 in a face-up manner. The p-electrode 17i of the blue LED 42 and the lead frame 12 are connected by a bonding wire 21, and the n-electrode 17j and the lead frame 13 are connected by a bonding wire 22. In the blue LED 42, the light emitted in the downward direction is reflected by the reflection film 42a and emitted in the upward direction.
[0033]
Further, a low-concentration resin layer 24 is formed on the cup 12a up to the uppermost position of the blue LED 42, and a high-concentration resin layer 25 is formed on the low-concentration resin layer 24 so as to swell on the cup 12a.
[0034]
More specifically, the upper surface of the low-concentration resin layer 24 formed in an annular shape around the uppermost surface of the blue LED 42 has an arcuate cross section. The upper surface of the high-concentration resin layer 25 has a convex shape in which the position immediately above the blue LED 17 is the highest. The concentration and shape of the phosphor 27 in each of the layers 24 and 25 are determined by the light path length from the light emitted by the blue LED 42 to the interface between the high-concentration resin layer 25 and the external resin 29, and the shape of the phosphor 27. It is adjusted so that the value obtained by multiplying the density is substantially constant.
[0035]
The LED lamp 40 configured as described above has the same effect as the LED lamp 10 of the first embodiment.
[0036]
That is, when a voltage is applied to the lead frames 12 and 13, the blue LED 42 emits blue light. This blue light passes through the layers 24 and 25 between the light emitted directly above the blue LED 42 and the light emitted obliquely from the upper surface or side surface of the blue LED 42 or reflected by the inner wall of the cup 12a after the emission. The optical path length is different.
[0037]
However, in each of the layers 24 and 25, the concentration of the phosphor 27 and the shape of each of the layers 24 and 25 are adjusted so that the optical path length × the concentration of the phosphor 27 is substantially constant. As described above, the light emitted in each direction passes through the phosphor 27 almost in the same amount in the course of passing through the layers 24 and 25. The light whose wavelength has been converted into yellow by such passage is mixed with blue light that has not passed through the phosphor 27, so that uniform white light emission can be obtained on the emission observation surface of the LED lamp 30.
[0038]
(Third embodiment)
FIG. 4 is a sectional view showing the configuration of the LED lamp according to the third embodiment of the present invention. However, in FIG. 4, portions corresponding to the respective portions in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.
[0039]
In the LED lamp 50 shown in FIG. 4, the blue LED 17 shown in FIG. 2 is fixed to the bottom surface of the cup 12a by the mount 18 instead of the blue LED 42 described in the second embodiment, and the mount 18 contains an Ag filler. In addition, the phosphor 27 is mixed. That is, the blue light emitted by the blue LED 17 in the downward direction is converted into a yellow light by the phosphor 27 in the mount 18 and is reflected on the bottom surface of the cup 12a in the upward or oblique direction.
[0040]
Therefore, in addition to the same effects as described in the second embodiment, the following effects can be obtained. That is, the blue light emitted in the downward direction is once converted to yellow light by the phosphor 27 in the mount 18 and the converted light is reflected right above or obliquely on the bottom surface. There is no need to perform the wavelength conversion at 27, and the thickness of the high-concentration resin layer 25 can be reduced. If the thickness of the high-concentration resin layer 25 can be reduced in this way, it is possible to further reduce the thickness of the LED lamp, particularly of the SMD type.
[0041]
In the first to third embodiments described above, if a reflective agent such as spherical glass beads is mixed into the low-concentration resin layer 24, light is irregularly reflected, so that uniformity of light can be maintained. it can.
[0042]
In each embodiment, the light-transmitting resin layer 24 is divided into the low-concentration resin layer 24 and the high-concentration resin layer 25, but the single light-transmitting resin filling the cup 12a is not divided. A configuration in which the mixed concentration of the phosphor 27 is gradually changed so that the optical path length × the concentration of the phosphor 27 is substantially constant may be adopted.
[0043]
【The invention's effect】
As described above, according to the present invention, the light-emitting element fixed in the concave reflecting mirror with the light-transmitting adhesive is covered, and the reflecting mirror is filled with the light-transmitting resin. A phosphor is mixed into the entire resin, and the value obtained by multiplying the concentration of the mixed phosphor by the optical path length of the light emitted by the light emitting element to the upper surface of the translucent resin is substantially constant. , Light emitted in each direction from the light emitting element passes through the same amount of phosphor when passing through the translucent resin. Light that has been wavelength-converted by the phosphor due to such passage is mixed with blue light that has not passed through the phosphor, so that even in a light-emitting device having inclined side walls, the light is uniformly observed on the light emission observation surface of the light-emitting device. Light emission can be obtained.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view illustrating a configuration of an LED lamp according to a first embodiment of the present invention, and FIG. 1B is an optical path length of light from a light emitting element (LED) used in the LED lamp. FIG.
FIG. 2 is a diagram showing a layer structure of a blue LED used for the LED lamp.
FIG. 3 is a cross-sectional view illustrating a configuration of an LED lamp according to a second embodiment of the present invention.
FIG. 4 is a sectional view showing a configuration of an LED lamp according to a third embodiment of the present invention.
[Explanation of symbols]
10, 40, 50 LED lamp 12, 13 Lead frame 12a Cup 14 Metal stem 16 Overvoltage protection element 16a, 16b Electrode 17, 42 Blue LED
17a sapphire substrate 17b buffer layer 17c n-type contact layer 17d n-type cladding layer 17e MQW active layer 17f p-type cladding layer 17g p-type contact layer 17h p-electrode 17in n-electrode 17j translucent electrode 18 mount 19, 20 gold bump 21, 22 Bonding wire 24 Low concentration resin layer 25 High concentration resin layer 27 Phosphor 29 External resin 42a Reflective film

Claims (9)

In a light emitting device having a light emitting element made of a nitride semiconductor fixed in a concave reflecting mirror and a phosphor that absorbs light emitted by the light emitting element and emits light of a different wavelength from the absorbed light ,
The reflector is filled with a light-transmitting resin covering the light-emitting element, the phosphor is mixed into the entire light-transmitting resin, and the concentration of the mixed phosphor is emitted by the light-emitting element. A light emitting device characterized in that the light is distributed such that a value obtained by multiplying an optical path length of the light that reaches the upper surface of the translucent resin by the concentration becomes substantially constant. In a light emitting device having a light emitting element made of a nitride semiconductor fixed in a concave reflecting mirror and a phosphor that absorbs light emitted by the light emitting element and emits light of a different wavelength from the absorbed light ,
A first resin layer filled with a translucent resin up to the upper surface position of the light emitting element and a second resin layer filled with a translucent resin on the first resin layer are provided in the reflector. A light emitting device, wherein the phosphor is mixed into the first and second resin layers such that the phosphor concentration of the second resin layer is higher than that of the first resin layer. . The concentration of the phosphor mixed in the first and second resin layers is substantially equal to the value obtained by multiplying the optical path length of light emitted by the light emitting element to the upper surface of the second resin layer by the concentration. The light emitting device according to claim 2, wherein the light emitting device is distributed so as to be constant. The thicknesses of the first and second resin layers are formed such that a value obtained by multiplying an optical path length of light emitted by the light emitting element to an upper surface of the second resin layer by the concentration is substantially constant. The light emitting device according to claim 2, wherein: The light emitting device according to claim 2, wherein an upper surface of the first resin layer has an annular shape depressed in an arc shape between the inner wall of the reflector and an edge of the upper surface of the light emitting element. The light emitting device according to claim 2, wherein a reflective agent that irregularly reflects light is mixed into the first resin layer. The light emitting device according to claim 1, wherein the light emitting element is a flip-chip type light emitting diode. The light emitting device according to claim 1, wherein the light emitting element is a face-up type light emitting diode, and a light reflection film is formed on a surface fixed with the adhesive. . The light emitting device according to claim 1, wherein the light emitting element is fixed by an adhesive in which the phosphor is mixed.

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