JP2014187224A - Semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device capable of more efficiently obtaining light emission by exciting a phosphor by a laser light source.SOLUTION: A semiconductor light-emitting device comprises a base 2 having a through hole 6, a wavelength conversion unit 1 arranged on the base 2 so as to clog the through hole 6, and a semiconductor light-emitting element which irradiates the wavelength conversion unit 1 with light through the through hole 6. A translucent layer 8 is formed between the base 2 and the wavelength conversion unit 1.

Description

  The present invention relates to a semiconductor light emitting device. More specifically, the present invention relates to a light source device that excites a wavelength conversion material with light emitted from a semiconductor light emitting element, emits wavelength converted light, and uses the wavelength converted light.

  Conventionally, a light emitting device having a structure in which a semiconductor laser light source and a phosphor are combined has been proposed.

  For example, Patent Document 1 discloses a laser light source, a phosphor that is excited by laser light and emits light, a translucent heat conductive member that is disposed on the excitation light irradiation side of the phosphor, and a translucent heat conductive member. A light emitting device is described that is composed of a gap layer that fills the space between the phosphors. In this apparatus, the heat conductive particles are included in the gap layer so that the heat generated when the phosphor is excited by the laser light and emits light can be efficiently transmitted to the translucent heat conductive member.

JP2012-059452A

  An object of the present invention is to provide a device capable of obtaining light emission more efficiently in a light-emitting device that emits light by exciting a phosphor with a laser light source.

In order to solve the above problems, the present inventors have invented the following means after research. That is, a base having a through hole;
A wavelength converter disposed on the base so as to close the through hole;
A semiconductor light emitting element that irradiates light to the wavelength conversion unit through the through hole, and
A semiconductor light emitting device in which a light-transmitting layer having a thickness of 30 to 100 μm is formed between the base and the wavelength conversion unit.

  According to the present invention, it is possible to obtain a semiconductor light-emitting device with a high light emission rate.

It is explanatory drawing of 1st embodiment of this invention. It is explanatory drawing of 2nd embodiment of this invention. It is explanatory drawing of 3rd embodiment of this invention. It is explanatory drawing of 4th embodiment of this invention. It is explanatory drawing of 5th embodiment of this invention. It is a figure which shows the effect of this invention. It is explanatory drawing of a comparative example.

  In order to explain the problems of the present invention, a comparative example shown in FIG. 7 will be described first. FIG. 7A is a schematic view of a light emitting device related to the present invention, and FIG. 7B is an enlarged view of a portion surrounded by a dotted line in FIG. 7A. In this figure, the wavelength converter 1 is arranged on a base 2 having a through hole 6 so as to block the through hole 6. The wavelength conversion unit 1 is fixed to the base 2 with an adhesive or the like (not shown). Since this adhesive effectively transfers the heat generated in the wavelength conversion section 1 to the base 2, it is often suppressed to a thickness of about several μm to tens of μm. The outer periphery of the wavelength conversion unit 1 is covered with the reflective resin 4, and light that propagates inside the wavelength conversion unit 1 and reaches the outer periphery of the wavelength conversion unit 1 is returned to the inside. The reflective resin 4 fills the space between the outer wall 3 extending upward from the outer periphery of the base 2 and the wavelength conversion unit 1. The laser diode 5 and the lens 15 have their optical axes aligned with the center of the through hole 6 and are irradiated on the lower surface of the wavelength conversion unit 1 by applying power. Here, the wavelength conversion unit 1 is configured by laminating a scattering layer 12 on the lower layer side and a phosphor layer 11 on the upper layer side.

  When the emitted light 7 is incident on the wavelength conversion unit 1 from the laser diode 5 through the through-hole 6, the emitted light 7 is incident on the scattering layer 12, and the phosphor layer 11 is scattered while being guided in the scattering layer 12. Irradiate. Since the phosphor layer 11 includes a phosphor that is excited by the emitted light 7 and emits fluorescence, the phosphor layer 11 emits fluorescence, which is emitted to the outside from the upper surface of the wavelength conversion unit 1. In some cases, a part of the emitted light 7 is emitted from the upper surface as it is without exciting the phosphor of the phosphor layer 11, and a mixed light of the fluorescence and the emitted light is emitted.

  Here, not all of the outgoing light 7 incident from the laser diode 5 is incident on the scattering layer 12, and there is also return light 9 reflected to the laser diode 5 side. The amount of light that enters the wavelength conversion unit 1 and excites the phosphor by the amount of the return light 9 decreases, and the overall light emission rate decreases. The inventor of the present application has found that the ratio of the return light 9 to the total incident light flux is about 40 to 50%. Therefore, the inventor of the present application has found a problem that the decrease in efficiency due to the return light 9 is suppressed, and has obtained a method for solving this problem.

  Next, FIG. 1 shows an explanatory diagram of the first embodiment of the present invention. In this figure, the wavelength converter 1 is arranged on a base 2 having a through hole 6 so as to block the through hole 6. The outer periphery of the wavelength conversion unit 1 is covered with the reflective resin 4, and light that propagates inside the wavelength conversion unit 1 and reaches the outer periphery of the wavelength conversion unit 1 is returned to the inside. The reflective resin 4 fills the space between the outer wall 3 extending upward from the outer periphery of the base 2 and the wavelength conversion unit 1. The laser diode 5 has an optical axis aligned with the center of the through hole 6 and is irradiated on the lower surface of the wavelength conversion unit 1 by applying power. Here, the wavelength conversion unit 1 is configured by laminating a scattering layer 12 on the lower layer side and a phosphor layer 11 on the upper layer side. In addition, the wavelength conversion unit 1 is fixed to the base 2 via the light transmitting layer 8.

  The outgoing light 7 incident from the laser diode 5 is not incident on the scattering layer 12 in the same way as the comparative example. However, in the present invention, a part of the return light 9 reflected to the laser diode 5 side by the scattering layer 12 is incident on the light transmitting layer 8 from the end face facing the through hole 6 and is reflected by the base 2. Then, the wavelength conversion unit 1 is irradiated again. As a result, the return light 9 can be used for excitation of the phosphor more effectively, and the effect of improving the efficiency of the light emitting device can be obtained.

  In particular, the return light 9 incident on the light transmissive layer 8 spreads to every corner by the light guide in the light transmissive layer 8 and enters the wavelength conversion unit 1. In the comparative example, when the wavelength conversion unit 1 is viewed from the phosphor layer 12 side, it can be seen that the central portion is brightest, and the incident light is not evenly excited to the phosphor layer 12 even by the scattering layer 12. In the present invention, the phosphor layer 12 is excited almost uniformly by guiding the return light 9, and as a result, uneven brightness of the excitation light can be improved.

  The wavelength conversion unit 1 includes a phosphor layer 11 including a phosphor excited by light from the laser diode 5. However, as shown in FIG. 1, the phosphor layer 11 may further include a scattering layer 12. The scattering layer 12 can more effectively scatter light from the laser diode 5 and distribute the light to the entire phosphor layer 11.

  The phosphor layer 11 is formed by forming a resin containing a phosphor into a plate shape, molding a glass or ceramic containing the phosphor into a plate shape, sintering, and forming the phosphor itself into a plate shape and sintering. Can be used. When using a resin, it is desirable to use a silicone resin from the viewpoint of light resistance. When ceramic is used, alumina or the like is preferable because it needs to be translucent. When using the phosphor itself, a sintered body of YAG: Ce phosphor in which Ce is adjusted to a predetermined concentration is desirable. A sintered body of ceramic or phosphor itself is particularly preferable because it does not contain an organic substance that deteriorates due to light from the laser diode, and there is little risk of a decrease in light intensity during use.

  As the scattering layer 12, for example, a resin containing a scattering material formed in a plate shape, a glass containing a scattering material in a plate shape, a ceramic in a plate shape, or the like can be used. In the case of using ceramic, light entering through pores (holes) entering the material can be scattered and spread over the entire phosphor layer 11. The scattering layer 12 is bonded to the phosphor layer 11 via an adhesive or the like.

  The laser diode 5 may be selected as an appropriate light source that can excite the wavelength converter 1 in order to obtain light of a desired wavelength as an output. A blue light emitting laser is desirable if the wavelength converter 1 including a yellow phosphor is excited to emit yellow fluorescence and white light is output as an output together with the laser light. For example, an InGaN / GaN laser with an emission wavelength of 450 nm can be used.

  The light-transmitting layer 8 has a role as a spacer, and transparent glass, a resin sheet, a high-viscosity resin (1 Pa · s or more, preferably 5 Pa · s or more) by printing / stamping, or the like can be used. In particular, when using a highly viscous resin, the wavelength converting portion 1 is arranged from the top after the light transmitting layer 8 is formed on the base 2, but the press load from the wavelength converting portion 1 is adjusted. By doing so, the height of the high viscosity resin can be controlled with higher accuracy. When using a resin, a dimethyl silicone resin is preferable from the viewpoint of heat resistance and light resistance. In the resin, a filler is not mixed so that the laser light incident on the through-hole and back-scattered by the scattering layer 12 is easily guided to the light-transmitting layer 8. However, fine particles of 100 nm or less that do not contribute to optical scattering may be added. In addition, it is not always necessary to be filled with a substance such as a resin, and a gap in the air layer may be used.

  It is desirable that the base 2 has a small reflection loss with respect to the light guided through the light transmitting layer 8 in addition to releasing the heat generated from the wavelength conversion unit 1. For this reason, what coated aluminum which was excellent in the reflectance on the upper surface of copper excellent in thermal conductivity, etc. can be used suitably. Preferably, the reflectance is improved by mirror-finishing the upper surface of the base.

The reflective resin 4 is made of, for example, a silicone resin mixed with a highly light-reflective resin such as TiO ₂ . The reflective resin 4 has a function of reflecting the light that has been guided through the scattering layer 12 and the phosphor layer 11 and reached its end face, and returned to the inside of the scattering layer 12 and the phosphor layer 11 again.

  FIG. 2 shows a second embodiment of the present invention. In FIG. 2, the basic configuration is the same as in FIG. The difference is that the resin-made translucent layer 8 has beads 13 (spacers) in order to keep the film thickness. Here, the beads 13 are spherical and translucent. Moreover, it is more desirable that the thermal conductivity is high. FIG. 2B is a view of the mounting portion of the wavelength conversion unit 1 of the light emitting device as viewed from the phosphor layer 11 side, and FIG. 2B, the place where the beads 13 are arranged is a place other than the through hole 6 provided in the base 2, and the corresponding arrangement place is indicated by a circle. If there are three or more beads 13, the thickness of the translucent layer 8 can be made constant.

The size of the wavelength conversion unit 1 when viewed from the phosphor layer 11 side is set to such an extent that it can be excited to some extent by the laser light and emit fluorescence. For this reason, the area of the wavelength converter 1 is about 800 μm × 400 μm. Therefore, the area of the translucent layer 8 formed under the wavelength converting portion 1 is a value obtained by subtracting the area of the through hole 6 from the above area. The through hole 6 has a circular shape of about φ200 μm, depending on the spot size of the laser beam. Here, the spherical diameter φ of the beads 13, that is, the thickness of the light transmitting layer 8 is about 30 μm to 100 μm. When three beads having a diameter of 30 μm are used, the ratio of the area of the beads 13 in the translucent layer 8 formed under the wavelength conversion unit 1 is 3 × ((30/2) ² × π) / {( 800 × 400) − (200/2) ² × π} ≈0.007, that is, not 1%. Therefore, if only three φ30 μm beads are used, the light guide in the light-transmitting layer 8 is hardly hindered.

  As the number of beads 13 arranged in the light-transmitting layer 8 (that is, the concentration of beads in the light-transmitting layer) increases, the interface between the light-transmitting layer 8 and the beads 13 increases. This begins to hinder light guiding in the translucent layer. Therefore, it is desirable that the number of beads 13 is minimal from the viewpoint of light guide. The ratio of the area of the beads to be included in the light-transmitting layer shown in the above calculation example should be 20% or less at most.

Here, as a modification of the second embodiment, a combination of substances in which the refractive indexes of the beads 13 and the light transmitting layer 8 are substantially matched may be used. For example, the refractive index of dimethyl silicone resin is about 1.41, while the refractive index of SiO ₂ beads is about the same. Moreover, since the refractive index of a phenyl-type silicone resin is 1.5-1.65, the material excellent in thermal conductivity like an alumina (n = 1.58-1.65) can be selected. With such a combination of resin and bead materials, the bead 13 can be included in the translucent layer 8 without worrying about the proportion of the area in the translucent layer 8 or the like. Here, the same refractive index means that the refractive index difference Δn between the two substances is within ± 0.05.

  FIG. 3 shows a third embodiment of the present invention. In FIG. 3, the basic configuration is the same as in FIGS. The difference is that the concave portion 14 is provided in order to maintain the film thickness of the resin-made translucent layer 8. The concave portion 14 is slightly smaller than the size of the wavelength converting portion 1, and the through hole 6 is formed at the bottom thereof. A translucent layer 8 is formed between the bottom surface of the recess 14 excluding the through-hole portion and the wavelength conversion unit 1, and the return light 9 is guided. In this configuration, the thickness of the light-transmitting layer 8 can be controlled only by the depth of the recess 14 and there is no need to worry about the refractive index of the beads, so that the controllability is good and simple.

  FIG. 4 shows a fourth embodiment of the present invention. In FIG. 4, the basic configuration is the same as in FIGS. The difference is that the scattering layer convex portion 16 is provided at the bottom portion of the scattering layer 12 in order to keep the film thickness of the resin-made translucent layer 8 and not overlapping the through-hole 6 when viewed from above. Three or more scattering layer convex portions 16 are formed at the same height on the bottom of the scattering layer 12. A translucent layer 8 is formed between the base 2 and the scattering layer 12 and has a function of guiding the return light 9 while adhering between the wavelength conversion unit 1 and the base 2. In this configuration, the thickness of the light-transmitting layer 8 can be controlled only by the height of the scattering layer projections 16 and there is no need to worry about the refractive index of the beads, so that the controllability is good and simple.

  FIG. 5 shows a fifth embodiment of the present invention. In FIG. 5, the basic configuration is the same as in FIGS. The difference is that the base 2 protrudes from the base 2 on the upper surface of the base 2 so as to maintain the film thickness of the resin-made translucent layer 8 and does not overlap with the through hole when viewed from above and contacts the bottom of the scattering layer 12. It has the convex part 17. Three or more base protrusions 17 are formed at the same height so as to be in contact with the bottom of the scattering layer 12, and the distance from the wavelength conversion unit 1 is kept constant. A translucent layer 8 is formed between the base 2 and the scattering layer 12 and has a function of guiding the return light 9 while adhering between the wavelength conversion unit 1 and the base 2. In this configuration, the thickness of the light-transmitting layer 8 can be controlled only by the height of the base convex portion 17, and there is no need to worry about the refractive index of the beads.

  FIG. 6 shows how much the luminous flux of the entire apparatus is improved with respect to the thickness of the light-transmitting layer 8 in the implementation of the present invention. In this figure, the translucent layer thickness of 0 μm is a value of a comparative example in which no translucent layer is provided. Further, the luminous flux improvement rate indicates the ratio of the improved luminous flux to the luminous flux in the comparative example having a thickness of 0 μm.

  Since the translucent layer 8 captures the return light 9 from the end surface portion facing the through-hole 6, the thicker the translucent layer 8 is, the larger the area of the end surface portion can be expected to increase the luminous flux improvement rate. On the other hand, if the light-transmitting layer 8 is too thick, the heat generated in the wavelength conversion unit 1 cannot be released through the light-transmitting layer 8, so that the light emission rate decreases due to the temperature quenching phenomenon of the phosphor layer 11. Therefore, from the viewpoint of the light emission intensity of the light emitting device as a whole, there is an optimum range in which the thickness of the light transmitting layer 8 can be well balanced.

  From FIG. 6, when the thickness of the translucent layer 8 is 30 μm, the luminous flux improvement rate is about 7%. In general, it is considered that there is an effect if the thickness exceeds this level. On the other hand, from the viewpoint of heat dissipation, the thickness of the translucent layer 8 is considered to be 100 μm or less when the translucent layer is a resin. In addition, when a material having higher thermal conductivity such as ceramic is used for the light-transmitting layer, it may be about 200 μm.

DESCRIPTION OF SYMBOLS 1 Wavelength conversion part 2 Base 3 Outer wall 4 Reflective resin 5 Laser diode 6 Through-hole 7 Outgoing light 8 Translucent layer 9 Return light 11 Phosphor layer 12 Scattering layer 13 Beads 14 Concave part 15 Lens

Claims (8)

A base having a through hole;
A wavelength converter disposed on the base so as to close the through hole;
A semiconductor light emitting element that irradiates light to the wavelength conversion unit through the through hole, and
A semiconductor light-emitting device in which a light-transmitting layer having a thickness of 30 μm or more is formed between the base and the wavelength conversion unit so that an end face is exposed in the through hole.   The semiconductor light emitting device according to claim 1, wherein the light transmissive layer is made of a resin including beads.   The semiconductor light emitting device according to claim 2, wherein the bead has a refractive index difference within ± 0.05 of the resin.   The said through-hole is formed in the recessed part bottom face formed in the said base, The said translucent layer is a resin layer arrange | positioned between the said wavelength conversion part and the said recessed part bottom face. The semiconductor light-emitting device as described.   The semiconductor light emitting device according to claim 1, wherein the light transmissive layer is formed of any one of glass and ceramic.   A convex portion that contacts the base is formed on a portion of the wavelength conversion portion that faces the through-hole side and does not overlap the through-hole in top view, thereby defining a thickness of the light-transmitting layer. Item 14. The semiconductor light emitting device according to Item 1.   A convex portion that contacts the wavelength conversion portion is formed on a portion of the upper surface of the base that faces the wavelength conversion portion and does not overlap the through hole when viewed from above, and defines the thickness of the light-transmitting layer The semiconductor light emitting device according to claim 1.   The semiconductor light-emitting device according to claim 1, wherein a side surface of the wavelength conversion unit is covered with a reflective resin.

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