JP2013110154A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device capable of restraining chromaticity variation and deterioration of reliability due to variation of output light from a substrate side face.SOLUTION: The light emitting device comprises: a light emitting element 10; a substrate 20 on which the light emitting element 10 is mounted and that absorbs incident emission light of the light emitting element 10 to prevent the emission light from being outputted from a side face; a package 30 having a recess for housing the light emitting element 10 and the substrate 20; a die mounting agent 40 for fixing the substrate 20 to the package 30 on a bottom face of the recess of the package 30; and a phosphor layer 50 containing a phosphor 51 filled in the recess, excited by the emission light of the light emitting element 10 and radiating excitation light. Mixture light of the emission light and the excitation light of the light emitting element 10 is outputted.

Description

  The present invention relates to a light emitting device that outputs light using a phosphor.

  A light emitting device using a light emitting element such as a light emitting diode (LED) as a light source has been put into practical use. In order to realize a light emitting device that outputs white light, a plurality of LEDs that respectively emit red light, green light, and blue light are used, or blue LEDs and various blue excitation phosphors (yellow phosphor, green phosphor) , A red phosphor) is used in combination with a pseudo white LED.

  In order to improve brightness and luminous efficiency, the light-emitting element is generally mounted on a light-transmitting substrate such as a sapphire substrate or a silicon carbide (SiC) substrate (see, for example, Patent Document 1). Similarly, a die mount agent for fixing a substrate to a package uses a material having a high light transmittance or a white material having a high light reflectance.

JP 2004-207519 A

  In the case where a light-emitting element is provided over a light-transmitting substrate, light emitted from the light-emitting element spreads isotropically. Therefore, the outgoing light incident on the substrate is output from the side surface of the substrate after passing through the substrate. The film thickness of the die mount agent adhering to the side surface of the substrate and the amount of rise (height) from the bottom surface change due to fluctuations in the amount of die mount agent applied to mount the substrate on the package. The amount of light output from the side surface of the substrate varies due to the change in the light shielding amount on the side surface of the substrate. As a result, there arises a problem that chromaticity variation of white output light occurs due to color mixture of light emitted from the light emitting element and excitation light from the phosphor.

  Further, when the package has a light reflecting portion, the reflectance of the light reflecting portion is deteriorated with time due to light energy. For this reason, the reliability of the light-emitting device is significantly reduced, and the chromaticity change is particularly large.

  In view of the above problems, an object of the present invention is to provide a light-emitting device capable of suppressing chromaticity variation and reliability degradation due to fluctuations in output light from the side surface of a substrate.

  According to one aspect of the present invention, (a) a light emitting element, and (b) a light emitting element mounted thereon, the substrate that does not output the emitted light from the side surface by absorbing the emitted light of the incident light emitting element, C) a package having a recess for storing the light emitting element and the substrate; (d) a die mount agent for fixing the substrate to the package on the bottom surface of the recess of the package; and (e) the light emitted from the light emitting element filled in the recess. There is provided a light emitting device that includes a phosphor layer containing a phosphor that is excited and emits excitation light, and that outputs mixed color light emitted from the light emitting element and excitation light.

  ADVANTAGE OF THE INVENTION According to this invention, the light-emitting device which can suppress the chromaticity dispersion | variation by the fluctuation | variation of the output light from a board | substrate side surface, and the fall of reliability can be provided.

It is a schematic diagram which shows the structure of the light-emitting device which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the light-emitting device of a comparative example. It is a schematic diagram which shows the structure of the light-emitting device which concerns on the 1st modification of the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the light-emitting device which concerns on the 2nd modification of the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the light-emitting device which concerns on the 2nd Embodiment of this invention. 6A is an xy chromaticity diagram of output light of the light emitting device according to the second embodiment of the present invention, and FIG. 6B is an xy of output light of the light emitting device of the comparative example shown in FIG. It is a chromaticity diagram.

  Next, first and second embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes the shape, structure, arrangement, etc. of components. It is not specified to the following. The embodiment of the present invention can be variously modified within the scope of the claims.

(First embodiment)
As shown in FIG. 1, the light emitting device 1 according to the first embodiment of the present invention includes a light emitting element 10 and the light emitting element 10, and absorbs outgoing light from the incident light emitting element 10. The substrate 20 that does not output incident light from the side surface, the light-emitting element 10 and a recess for storing the substrate 20, the package 30 whose inner wall surface 31 is a light reflecting surface, and the substrate 20 on the bottom surface of the recess of the package 30 A die mount agent 40 that is fixed to the package 30 and a phosphor layer 50 that contains a phosphor 51 that is filled in the recess and is excited by the light emitted from the light emitting element 10 to emit excitation light. The light emitting device 1 outputs an output light L in which the light emitted from the light emitting element 10 and the excitation light are mixed.

  In the light emitting device 1 shown in FIG. 1, the light emitting element 10 is disposed on the bottom surface of the recess of the package 30 having a recess whose bottom is narrower than the top. As the light emitting element 10, a semiconductor light emitting element such as an LED or a laser diode can be employed.

  The light emitting device 10 shown in FIG. 1 has a structure in which an n-type cladding layer 11, an active layer 12, and a p-type cladding layer 13 are stacked. An n-side electrode 110 is connected to the n-type cladding layer 11, and electrons are supplied to the n-side electrode 110 from an external negative power source (not shown) through a bonding wire or the like. As a result, electrons are supplied from the n-type cladding layer 11 to the active layer 12.

  A p-side electrode 130 is connected to the p-type cladding layer 13, and holes are supplied to the p-side electrode 130 from an external positive power supply (not shown) via a bonding wire or the like. As a result, holes are supplied from the p-type cladding layer 13 to the active layer 12.

  The active layer 12 has, for example, a multiple quantum well (MQW) structure in which InGaN films and GaN films are alternately stacked. The electrons supplied from the n-type cladding layer 11 and the holes supplied from the p-type cladding layer 13 are recombined in the active layer 12 to generate light.

  For the phosphor layer 50, a silicon resin containing the phosphor 51 can be used. The phosphor 51 contained in the phosphor layer 50 is determined according to the light emitted from the light emitting element 10. For example, when the light emitting element 10 emits blue light, yttrium aluminum garnet (YAG) or the like that emits yellow light when excited by the blue light is used as the phosphor 51. At this time, a part of the blue light emitted from the light emitting element 10 excites the phosphor 51, thereby converting the wavelength into yellow light. By mixing the yellow light emitted from the phosphor 51 and the blue light emitted from the light emitting element 10, white output light L is output from the light emitting device 1. By arranging the light emitting element 10 on the bottom surface of the recess of the package 30, the directivity of the output light L is improved.

  In addition, by using the inner wall surface 31 of the package 30 as a light reflecting surface, light is scattered inside the package 30, and the brightness and light emission efficiency of the light emitting device 1 can be improved. For example, by applying a silver (Ag) film or a white resin to the inner wall surface 31, the inner wall surface 31 is made a light reflecting surface.

  The substrate 20 shown in FIG. 1 has a structure in which a light reflecting layer 22 and a light absorbing layer 23 are stacked on the side surface of a light transmitting substrate 21. The light incident on the light transmissive substrate 21 from the light emitting element 10 is reflected by the light reflecting layer 22. Further, light traveling from the side surface of the translucent substrate 21 to the outside is absorbed by the light absorption layer 23. For this reason, the light emitted from the light emitting element 10 that has passed through the substrate 20 is prevented from being output from the side surface of the substrate 20.

The translucent substrate 21 is a sapphire substrate, a SiC substrate, or the like. For the light reflecting layer 22, for example, a metal film such as aluminum (Al) or Au (gold) can be used. The light absorption layer 23 is, for example, an interference layer in which a carbon coat, a silicon oxide (SiO ₂ ) film, and a zirconia (ZrO ₂ ) film are alternately stacked. The light absorption layer 23 absorbs light such as light emitted from the light emitting element 10, excitation light from the phosphor 51, and mixed color light thereof.

  The thickness of the die mount agent 40 adhering to the side surface of the substrate 20 and the amount of crawling (height) from the bottom surface change due to the variation in the amount of the die mount agent 40 that bonds the substrate 20 and the package 30. As a result, in Comparative Example 1A in which the light reflecting layer 22 and the light absorbing layer 23 are not disposed on the side surface of the light transmissive substrate 21 as illustrated in FIG. 2, the substrate 20 depends on the amount of adhesion of the die mount agent 40. The light shielding amount on the side surface changes, and the amount of light output from the side surface of the substrate 20 varies. For this reason, the light quantity of the output light L will differ for every light-emitting device, and the yield of a product will fall.

  However, in the light emitting device 1 illustrated in FIG. 1, the light absorption layer 23 prevents light from being output from the side surface of the substrate 20. For this reason, variation in the amount of the output light L for each light emitting device does not occur, and the yield can be improved.

  The light absorption layer 23 has a function of preventing light from being output to the outside from the side surface of the translucent substrate 21, and a part of the emitted light of the light emitting element 10 that is reflected in the package 30 and reaches the side surface of the substrate 20 from the outside. It has a function of absorbing water. For this reason, it can suppress that the light which permeate | transmitted the board | substrate 20 and was output from the side surface, and the light reflected on the side surface of the board | substrate 20 injects into the light reflection surface of the package 30. FIG.

  By reacting with the resin constituting the phosphor layer 50 and moisture entering from the outside, the light reflectance of the inner wall surface 31 of the recess of the package 30 is deteriorated. This deterioration is promoted by light energy. For this reason, the light reflectance deteriorates with time in the inner wall surface 31 of the recess, particularly in the portion facing the side surfaces of the light emitting element 10 and the substrate 20.

  However, in the light emitting device 1 shown in FIG. 1, the light incident on the side surface of the substrate 20 is absorbed as described above. Further, light is prevented from being output from the side surface of the substrate 20. For this reason, the amount of light between the side surface of the substrate 20 and the inner wall surface 31 of the package 30 is reduced. As a result, deterioration of the light reflectance of the inner wall surface 31 can be suppressed.

  In order to reduce the amount of light output from the side surface of the substrate 20 or reflected from the side surface of the substrate 20, the height of the side surface of the substrate 20, that is, the thickness of the substrate 20 is preferably thin. For this reason, for example, the thickness of the substrate 20 is set to 150 μm or less. Thereby, deterioration of the light reflectance of the inner wall surface 31 can be further suppressed.

  A part of the light emitted from the upper surface of the light emitting element 10 is reflected in the package 30 and reaches the side surface of the substrate 20. For this reason, the light quantity of the side surface of the substrate 20 can be reduced by using a material having a light absorption characteristic that absorbs light such as the emitted light of the light emitting element 10, the excitation light of the phosphor 51, and the mixed color light thereof for the die mount agent 40. Further reduction. For this purpose, the die mount agent 40 is not transparent or white. For example, a gray silver paste is used for the die mount agent 40. For the same reason, a material having light absorption characteristics (not transparent or not white) may be used for the package 30. For example, a package 30 made of a resin mixed with carbon can be used.

  As described above, in the light emitting device 1 according to the first embodiment of the present invention, the output of light from the side surface of the substrate 20 and the incidence of light on the substrate 20 from the side surface and the reflection of light from the side surface. Is prevented. As a result, in the light emitting device 1, variations in the light amount of the output light L and deterioration over time of the light reflecting surface of the package 30 are suppressed. Therefore, according to the light emitting device 1 shown in FIG. 1, variations in chromaticity and a decrease in reliability due to fluctuations in the output light L can be suppressed. In addition, the low-cost light emitting device 1 can be provided by improving the yield.

<First Modification>
FIG. 3 shows a light emitting device 1 according to a first modification of the first embodiment of the present invention. In the light emitting device 1 illustrated in FIG. 3, the light reflection layer 22 is not disposed on the side surface of the substrate 20, and only the light absorption layer 23 is disposed.

  Even without the light reflection layer 22, the light output from the side surface of the substrate 20 and the reflection of light from the side surface of the substrate 20 can be prevented only by the light absorption layer 23. By arranging only the light absorption layer 23 on the side surface of the substrate 20, it is possible to shorten the manufacturing process of the light emitting device 1 and reduce the manufacturing cost.

<Second Modification>
FIG. 4 shows a light emitting device 1 according to a second modification of the first embodiment of the present invention. In the light emitting device 1 shown in FIG. 4, the light reflecting layer 22 and the light absorbing layer 23 are formed on the side surface of the substrate 20 from the package base portion of the package 30 on which the substrate 20 is disposed to at least the height at which the die mount agent 40 is crawled up. Is arranged.

  Of the light output from the side surface of the substrate 20, the amount of light that does not pass through the die mount agent 40 varies little for each light emitting device 1. There is little variation in the amount of reflected light from the die mount agent 40. Therefore, when the die mount agent 40 is formed from the bottom surface of the substrate 20 to the lower portion of the side surface, the light reflection layer 22 and the light absorption layer 23 are disposed only in the region where the die mount agent 40 is attached on the side surface of the substrate 20. By doing so, the fluctuation | variation of the light quantity of the output light L can be suppressed. As in FIG. 3, only the light absorption layer 23 may be disposed instead of the light reflection layer 22 on the side surface of the substrate 20.

(Second Embodiment)
The light emitting device 1 according to the second embodiment of the present invention shown in FIG. 5 is different from the light emitting device 1 shown in FIG. 1 in that it includes a substrate 20 having light absorption characteristics. About another structure, it is the same as that of 1st Embodiment. As the substrate 20 shown in FIG. 5, a non-transparent substrate, a non-white substrate, or the like is used. For example, a silicon substrate or a germanium (Ge) substrate can be used as the substrate 20.

  By using the substrate 20 made of a light absorbing material, it is possible to prevent the light emitted from the light emitting element 10 from being transmitted through the substrate 20 and being output from the side surface. For this reason, even if the application amount of the die mount agent 40 on the side surface of the substrate 20 varies, the variation in the light amount of the output light L for each light-emitting device due to the variation in the amount of light output from the side surface of the substrate 20. Does not occur.

  Further, the light that is reflected in the package 30 and reaches the side surface of the substrate 20 from the outside is absorbed by the substrate 20. For this reason, the amount of light between the side surface of the substrate 20 and the inner wall surface 31 of the package 30 is reduced. As a result, deterioration of the light reflectance of the inner wall surface 31 can be suppressed.

  FIGS. 6A and 6B show chromaticity variations of the light emitting device 1 shown in FIG. 5 and the comparative example 1A shown in FIG. As is clear by comparing FIG. 6A and FIG. 6B, the light-emitting device 1 shown in FIG. 5 has less chromaticity variation than the comparative example 1A.

  As described above, according to the light emitting device 1 according to the second embodiment of the present invention, the chromaticity variation and the reliability decrease due to the fluctuation of the output light L are suppressed, and further, the yield is improved and the price is reduced. Can be provided.

  Others are substantially the same as those in the first embodiment, and redundant description is omitted. For example, a material having light absorption characteristics may be employed for the die mount agent 40 and the package 30.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the description of the embodiment described above, an example in which the number of light emitting elements 10 stored in the package 30 is one is shown. However, the light emitting device 1 may include a plurality of light emitting elements 10. Moreover, although the case where the emitted light of the light emitting element 10 is blue light and the excitation light of the phosphor contained in the phosphor layer 50 is yellow is shown, the combination of the emitted light of the light emitting element 10 and the phosphor is shown here. It is not limited. For example, the phosphor layer 50 may contain a light emitting element 10 that emits near ultraviolet light and a phosphor that emits red light, green light, and blue light when excited by the near ultraviolet light. Further, the output light L of the light emitting device 1 may be other than white light.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device 10 ... Light emitting element 11 ... N-type clad layer 12 ... Active layer 13 ... P-type clad layer 20 ... Substrate 21 ... Translucent substrate 22 ... Light reflection layer 23 ... Light absorption layer 30 ... Package 31 ... Inner wall surface 40 ... Die mount agent 50 ... Phosphor layer 51 ... Phosphor 110 ... n-side electrode 130 ... p-side electrode

Claims (8)

A light emitting element;
A substrate that mounts the light emitting element and does not output the emitted light from the side surface by absorbing the incident emitted light of the light emitting element;
A package having a recess for storing the light emitting element and the substrate;
A die mount agent for fixing the substrate to the package at the bottom of the recess of the package;
And a phosphor layer containing a phosphor that is excited by the light emitted from the light emitting element and emits excitation light, and that emits mixed light of the emitted light and the excitation light. apparatus.   The light emitting device according to claim 1, wherein a light absorption layer made of a light absorption material is disposed on a side surface of the substrate.   The light emitting device according to claim 2, wherein a light reflection layer is disposed between a side surface of the substrate and the light absorption layer.   When the die mount agent is disposed from the bottom surface of the substrate to the lower portion of the side surface, the light absorption layer is disposed from the bottom surface to a height at which the die mount agent is disposed on the side surface. The light emitting device according to claim 2 or 3.   The light emitting device according to claim 1, wherein the substrate is made of a light absorbing material.   The light emitting device according to claim 1, wherein the die mount agent is made of a light absorbing material.   The light emitting device according to claim 1, wherein the package is made of a light absorbing material.   The light emitting device according to any one of claims 1 to 7, wherein the emitted light of the light emitting element is blue light, and the excitation light is yellow light.

Images