TWI502776B - Light emitting device - Google Patents

Description

Illuminating device

The present invention relates to a light-emitting device that uses a phosphor to output light.

A light-emitting device using a light-emitting element such as a light-emitting diode (LED) in 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 emit red light, green light, or blue light, or a blue LED and various blue-excited phosphors (yellow phosphor, green phosphor, Red phosphor) combined with a white LED.

In order to improve the brightness and the luminous efficiency, the light-emitting element is generally mounted on a light-transmitting substrate such as a sapphire substrate or a tantalum carbide (SiC) substrate (see, for example, Patent Document 1). Similarly, a crystal having a high light transmittance or a high light reflectance has been used for the adhesive which fixes the substrate to the package.

Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-207519

In the case where a light-emitting element is disposed on a substrate having light transmissivity, light emitted from the light-emitting element or the like is diffused. Therefore, the light emitted from the substrate is transmitted through the substrate and also output from the side surface of the substrate. The film thickness of the adhesive attached to the side surface of the substrate or the amount of climb (height) from the bottom surface changes by the amount of coating of the adhesive to mount the substrate on the package. The amount of light outputted from the side surface of the substrate is uneven due to the change in the amount of light blocking on the side surface of the substrate. As a result, the emitted light of the light-emitting element and the excitation light from the phosphor are generated. The color mixture produces a problem of uneven chromaticity of the white output light.

Furthermore, in the case where the package has a light reflecting portion, the reflectance of the light reflecting portion is deteriorated with time due to light energy. Therefore, the reliability of the light-emitting device is remarkably lowered, especially the chromaticity change is large.

In view of the above problems, it is an object of the present invention 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.

A light-emitting device according to one aspect of the present invention includes: (a) a light-emitting element; (b) a substrate on which a light-emitting element is mounted, and absorbs light emitted from the light-emitting element after the incident, so that the emitted light is not output from the side surface; a package having a concave portion for accommodating the light-emitting element and the substrate; (d) a die-bonding agent for fixing the substrate to the package on a bottom surface of the concave portion of the package; and (e) a phosphor layer containing the phosphor filled in the concave portion The fluorescent system emits excitation light by excitation of light emitted from the light-emitting element; and outputs mixed color light of the light emitted from the light-emitting element and the excitation light.

According to the present invention, it is possible to provide a light-emitting device capable of suppressing chromaticity variation and reliability deterioration due to fluctuations in output light from the side surface of the substrate.

Next, the first and second embodiments of the present invention will be described with reference to the drawings. In the following description, the same or similar parts are given the same or similar symbols. In addition, the embodiment shown below exemplifies the apparatus or method for embodying the technical idea of the present invention, and the technical idea of the present invention does not limit the shape, structure, arrangement, and the like of the component parts to the following description. In the embodiment of the present invention, various modifications can be made in the scope of the patent application.

(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, a substrate 20 on which the light-emitting element 10 is mounted, and the light emitted from the light-emitting element 10 after the incident light is absorbed. The package body 30 has a recess for receiving the light-emitting element 10 and the substrate 20, and the inner wall surface 31 of the recess is a light-reflecting surface. The adhesive 40 fixes the substrate 20 to the package 30 on the bottom surface of the recess of the package 30. And the phosphor layer 50 includes a phosphor 51 filled in the concave portion, and the phosphor 51 is excited by the light emitted from the light-emitting element 10 to emit excitation light. The light-emitting device 1 outputs the output light L after the light emitted from the light-emitting element 10 is mixed with the excitation light.

In the light-emitting device 1 shown in Fig. 1, a light-emitting element 10 is disposed on a bottom surface of a concave portion of a package 30 having a concave portion having a narrow bottom portion. The light-emitting element 10 can employ a semiconductor light-emitting element such as an LED or a laser diode.

The light-emitting element 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 laminated. The n-side electrode 110 is connected to the n-type cladding layer 11, and electrons are supplied from the external negative power source (not shown) to the n-side electrode 110 through a bonding wire or the like. Thereby, electrons are supplied from the n-type cladding layer 11 to the active layer 12.

The p-side electrode 130 is connected to the p-type cladding layer 13, and a hole is supplied from the external positive power source (not shown) to the p-side electrode 130 through a bonding wire or the like. Thereby, the hole is 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 an InGaN film and a GaN film are alternately laminated. The electrons supplied from the n-type cladding layer 11 and the holes supplied from the p-type cladding layer 13 are recoupled in the active layer 12 to generate light.

As the phosphor layer 50, a neon resin containing the phosphor 51 or the like can be used. The phosphor 51 included in the phosphor layer 50 is determined in accordance with the light emitted from the light-emitting element 10. For example, in the case where the light-emitting element 10 emits blue light, yttrium aluminum garnet (YAG) or the like which is excited by blue light and emits yellow light is used as the phosphor 51. At this time, the phosphor 51 is partially excited by one of the blue light emitted from the light-emitting element 10, whereby the wavelength is converted into yellow light. The yellow light emitted from the phosphor 51 is mixed with the blue light emitted from the light-emitting element 10, whereby the white output light L is output from the light-emitting device 1. The light-emitting element 10 is placed on the bottom surface of the concave portion of the package 30 to improve the directivity of the output light L.

Further, by making the inner wall surface 31 of the package 30 a light reflecting surface, light is scattered inside the package 30, and the luminance or luminous efficiency of the light-emitting device 1 can be improved. For example, a silver (Ag) film or a white resin is applied to the inner wall surface 31 to make the inner wall surface 31 a light reflecting surface.

The substrate 20 shown in FIG. 1 has a structure in which the light reflecting layer 22 and the light absorbing layer 23 are disposed on the side surface layer of the light-transmitting substrate 21. Light that is incident on the light-transmitting substrate 21 from the light-emitting element 10 is reflected by the light-reflecting layer 22. Further, light that is emitted from the side surface of the light-transmitting substrate 21 to the outside is absorbed by the light absorbing layer 23. Therefore, it is possible to prevent the outgoing light of the light-emitting element 10 transmitted through the substrate 20 from being output from the side surface of the substrate 20.

The light-transmitting substrate 21 is a sapphire substrate, a SiC substrate, or the like. The light reflecting layer 22 may be a metal film such as aluminum (Al) or Au (gold). The light absorbing layer 23 is, for example, an interference layer in which a carbon coating layer, a cerium oxide (SiO ₂ ) film, and a zirconia (ZrO ₂ ) film are alternately laminated. The light absorbing layer 23 absorbs light such as the light emitted from the light-emitting element 10, the excitation light of the phosphor 51, and the mixed color light.

The thickness of the adhesive 40 adhering to the side surface of the substrate 20 or the amount of climb (height) from the bottom surface is changed by the variation of the coating amount of the bonding agent 40 between the substrate 20 and the package 30. As a result, as shown in FIG. 2, in Comparative Example 1A in which the light-reflecting layer 22 or the light-absorbing layer 23 is not disposed on the side surface of the light-transmitting substrate 21, depending on the amount of the bonding agent 40, the side surface of the substrate 20 is The amount of light blocking varies, and the amount of light output from the side of the substrate 20 is uneven. Therefore, the amount of light of the output light L differs for each light-emitting device, and the yield of the product is lowered.

However, in the light-emitting device 1 shown in FIG. 1, light is prevented from being output from the side surface of the substrate 20 by the light absorbing layer 23. Therefore, the amount of light of the output light L of each of the light-emitting devices is not uneven, and the yield can be improved.

Further, the light absorbing layer 23 has a function of outputting light from the side surface of the light-transmitting substrate 21 to the outside and a part of the light emitted from the light-emitting element 10 which is reflected by the inside of the package 30 and which is reflected from the outside to the side of the substrate 20. Therefore, it is possible to suppress light which is transmitted from the side surface after being transmitted through the substrate 20 and light reflected on the side surface of the substrate 20 from entering the light reflecting surface of the package 30.

The light reflectance of the inner wall surface 31 of the concave portion of the package 30 is deteriorated by the reaction with the resin constituting the phosphor 50 or the moisture immersed from the outside. This degradation is promoted by light energy. Therefore, in the portion of the inner wall surface 31 of the concave portion that faces the side surfaces of the light-emitting element 10 and the substrate 20, the light reflectance deteriorates with time.

However, in the light-emitting device 1 shown in Fig. 1, light incident on the side surface of the substrate 20 is absorbed as described above. Furthermore, light can be prevented from being output from the side surface of the substrate 20. Therefore, 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.

Further, in order to reduce the amount of light output from the side surface of the substrate 20 or the light reflected on the side surface of the substrate 20, it is preferable that the height of the side surface of the substrate 20, that is, the thickness of the substrate 20 is thin. Therefore, for example, the thickness of the substrate 20 is 150 μm or less. Thereby, deterioration of the light reflectance of the inner wall surface 31 can be further suppressed.

A portion 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. Therefore, by using the material having the light absorption characteristics of the light which absorbs the light emitted from the light-emitting element 10, the excitation light of the phosphor 51, and the light of the mixed color light, etc., in the adhesive 40, the side surface of the substrate 20 can be further reduced. The amount of light. To this end, the bonding agent 40 is made non-transparent or non-white. For example, a gray silver paste is used in the bonding agent 40. Further, for the same reason, a material having light absorbing properties (non-transparent or non-white) may be used for the package 30. For example, a package 30 made of a resin in which carbon is mixed may be employed.

As described above, in the light-emitting device 1 according to the first embodiment of the present invention, it is possible to prevent the light output from the side surface of the substrate 20 and the light incident from the side surface to the substrate 20 or the light reflected from the side surface. As a result, in the light-emitting device 1, it is possible to suppress unevenness in the amount of light of the output light L or deterioration of the light-reflecting surface of the package 30 over time. Therefore, according to the light-emitting device 1 shown in Fig. 1, it is possible to suppress a decrease in chromaticity and reliability due to fluctuations in the output light L. Further, since the yield is improved, the light-emitting device 1 of a low price can be provided.

(First Modification)

Fig. 3 is a view showing a light-emitting device 1 according to a first modification of the first embodiment of the present invention. In the light-emitting device 1 shown in FIG. 3, the side of the substrate 20 is not provided. The light-reflecting layer 22 is disposed, and only the light absorbing layer 23 is disposed.

Even with the light-reflecting layer 22, the light output from the side surface of the substrate 20 and the light reflected from the side surface of the substrate 20 can be prevented only by the light absorbing layer 23. By arranging only the light absorbing layer 23 on the side of the substrate 20, the process of the light-emitting device 1 can be shortened or the manufacturing cost can be reduced.

(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 are disposed on the side surface of the substrate 20 from the package base portion of the package 30 on which the substrate 20 is placed to at least the height at which the adhesive 40 is climbed up. Absorbing layer 23.

Among the light output from the side surface of the substrate 20, the amount of light that is not transmitted through the optical bonding agent 40 is less uneven in the respective light-emitting devices 1. The unevenness of the amount of light reflected by the bonding agent 40 is also small. Therefore, in the case where the die bond 40 is formed from the bottom surface of the substrate 20 to the lower side of the substrate, the light reflection layer 22 and the light absorbing layer 23 are disposed only in the region where the die bond 40 is adhered to the side surface of the substrate 20, thereby suppressing The variation in the amount of light of the output light L. Further, similarly to 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 may be disposed.

(Second embodiment)

The light-emitting device 1 according to the second embodiment of the present invention shown in Fig. 5 is provided with a substrate 20 having light absorption characteristics, which is different from the light-emitting device 1 shown in Fig. 1 . The other configuration is the same as that of the first embodiment. A non-transparent substrate, a non-white substrate, or the like is used for the substrate 20 shown in FIG. For example, the substrate 20 may be a tantalum substrate or a germanium (Ge) substrate or the like.

By using the substrate 20 composed 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 from the side. Therefore, even if the coating amount of the adhesive 40 on the side surface of the substrate 20 is changed, the amount of light of the output light L of each of the light-emitting devices caused by the unevenness of the amount of light output from the side surface of the substrate 20 does not occur.

Further, the light which is reflected in the package 30 and reaches the side surface of the substrate 20 from the outside is absorbed by the substrate 20. Therefore, 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.

6(a) and 6(b) show the chromaticity unevenness of the light-emitting device 1 shown in Fig. 5 and the comparative example 1A shown in Fig. 2, respectively. Comparing Fig. 6(a) with Fig. 6(b), it is clear that the illuminating device 1 shown in Fig. 5 has a smaller chromaticity unevenness than the comparative example 1A.

As described above, according to the light-emitting device 1 of the second embodiment of the present invention, it is possible to suppress a decrease in chromaticity and reliability due to fluctuations in the output light L, and further, it is possible to provide a low-cost light-emitting device due to an increase in productivity.

Since it is substantially the same as the first embodiment, the description thereof will not be repeated. For example, a material having light absorbing properties may be employed for the adhesive 40 or the package 30.

(Other embodiments)

As described above, the present invention is described by the embodiments, but it should be understood that the invention is not limited by the description and the drawings. It will be apparent to those skilled in the art from this disclosure that various alternative embodiments, embodiments, and operational techniques are apparent.

In the above description, although the light-emitting element 10 housed in the package 30 is shown as one example, the light-emitting device 1 may include a plurality of light-emitting elements 10. Further, although the light emitted from the light-emitting element 10 is blue light and the excitation light of the phosphor contained in the phosphor layer 50 is yellow, the combination of the light emitted from the light-emitting element 10 and the phosphor is not limited thereto. For example, a light-emitting element 10 that emits near-ultraviolet light and a phosphor that emits red light, green light, and blue light by being excited by near-ultraviolet light may be contained in the phosphor layer 50. 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 and the like which are not described herein. Therefore, the technical scope of the present invention is determined by the above-described description only by the specific matters of the invention of the scope of the patent application.

1‧‧‧Lighting device

10‧‧‧Lighting elements

11‧‧‧n type cladding

12‧‧‧Active layer

13‧‧‧p-type cladding

20‧‧‧Substrate

21‧‧‧Transmissive substrate

22‧‧‧Light reflection layer

23‧‧‧Light absorbing layer

30‧‧‧Package

31‧‧‧ inner wall

40‧‧‧Macking agent

50‧‧‧Fluorescent layer

51‧‧‧Fertior

110‧‧‧n side electrode

130‧‧‧p side electrode

Fig. 1 is a schematic view showing the configuration of a light-emitting device according to a first embodiment of the present invention.

Fig. 2 is a view showing the constitution of a light-emitting device of a comparative example.

Fig. 3 is a schematic view showing the configuration of a light-emitting device according to a first modification of the first embodiment of the present invention.

Fig. 4 is a schematic view showing the configuration of a light-emitting device according to a second modification of the first embodiment of the present invention.

Fig. 5 is a schematic view showing the configuration of a light-emitting device according to a second embodiment of the present invention.

Fig. 6(a) is an xy chromaticity diagram of output light of the illuminating device according to the second embodiment of the present invention, and Fig. 6(b) is an output of the illuminating device of the comparative example shown in Fig. 2. The xy chromaticity diagram of light.

L‧‧‧Output light

1‧‧‧Lighting device

10‧‧‧Lighting elements

11‧‧‧n type cladding

12‧‧‧Active layer

13‧‧‧p-type cladding

20‧‧‧Substrate

21‧‧‧Transmissive substrate

22‧‧‧Light reflection layer

23‧‧‧Light absorbing layer

30‧‧‧Package

31‧‧‧ inner wall

40‧‧‧Macking agent

50‧‧‧Fluorescent layer

51‧‧‧Fertior

110‧‧‧n side electrode

130‧‧‧p side electrode

Claims (7)

A light-emitting device comprising: a light-emitting element; a light-transmissive substrate on which the light-emitting element is mounted; and a package on which a light-absorbing layer formed of a light-absorbing material is disposed on a side surface of the substrate and the light-absorbing layer a light reflecting layer is disposed between the light emitting element and the recessed portion; the adhesive is fixed to the package on the bottom surface of the recess of the package; and the phosphor layer is provided. The light absorbing layer has a function of absorbing a portion of the light emitted from the package and reflected from the outside on the side of the substrate, and includes a phosphor filled in the recess, the fluorescent The system emits excitation light by excitation of the emitted light of the light-emitting element; it outputs mixed color light of the emitted light and the excitation light. The light-emitting device of claim 1, wherein the substrate has a thickness of 150 μm or less. The illuminating device according to claim 1 or 2, wherein, when the viscous agent is disposed from a bottom surface of the substrate to a lower portion of the side surface, the height of the adhesive is disposed from the bottom surface to the side surface The light absorbing layer is disposed. The illuminating device of claim 1, wherein the substrate is Made up of light absorbing material. The illuminating device according to any one of claims 1 to 2, wherein the viscous agent is composed of a light absorbing material. The light-emitting device according to any one of claims 1 to 2, wherein the package is made of a light absorbing material. The light-emitting device according to any one of claims 1 to 2, wherein the emitted light of the light-emitting element is blue light, and the excitation light is yellow light.