JP2005191197A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device that can efficiently convert wavelength in a light emitting from a light emitting element by using a fluorescent substance and increase radiation intensity, and that is superior in optical characteristic such as axial luminous intensity, luminance, color rendering properties, etc. <P>SOLUTION: The light emitting device is provided with a substrate 1 having a placement part 1a wherein a light emitting element 5 is placed on its upper main surface; a frame 2 that is connected to the outer periphery of the upper main surface of the substrate 1 so as to surround the placement part 1a, and wherein an inner circumferential surface 2a works as a reflection surface for reflecting a light emitting from the light emitting element 5; a wiring conductor wherein one end formed on the upper main surface of the substrate 1 is electrically connected with an electrode of the light emitting element 5, and the other end thereof is led to the outer surface of the substrate 1; the light emitting element 5 that is placed on the placement part 1a and is electrically connected with the wiring conductor; a light transmitting member 3 that is formed inside the frame 1 so as to cover the light emitting element 5; and a fluorescent substance layer 7 that covers the light transmitting member 3 and includes a fluorescent substance for wavelength conversion of a light of the light emitting element 5. The upper surfaces of the light transmitting member 3 and the fluorescent substance layer 7 are roughened. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light emitting device that converts the wavelength of light emitted from a light emitting element with a phosphor and emits light to the outside.

  Light emission that emits white light by converting long wavelengths of light such as near-ultraviolet light and blue light emitted from a light emitting element 15 such as a conventional light emitting diode (LED) into a long wavelength with a plurality of phosphors 14 such as red, green, blue, and yellow. The apparatus is shown in FIG. In FIG. 2, the light emitting device has a mounting portion 11a for mounting the light emitting element 15 at the center of the upper surface, and leads that electrically connect the inside and outside of the light emitting device from the mounting portion 11a and its periphery. A base 11 made of an insulator on which a wiring conductor (not shown) made of a terminal, metallized wiring, or the like is formed, and a through hole that is bonded and fixed to the upper surface of the base 11 and whose upper opening is larger than the lower opening are formed. The frame 12 in which the inner peripheral surface 12a is a reflecting surface that reflects the light emitted from the light emitting element 15, and the fluorescence that excites the light emitted from the light emitting element 15 that is filled in the frame 12 to convert the light into a long wavelength. It is mainly composed of a translucent member 13 containing the body 14 and a light emitting element 15 mounted and fixed on the mounting portion 11a.

  The substrate 11 is made of an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, a mullite sintered body, ceramics such as glass ceramics, or a resin such as epoxy resin. When the substrate 11 is made of ceramic, the wiring conductor is formed on its upper surface by firing a metal paste made of tungsten (W), molybdenum (Mo) -manganese (Mn), etc. at a high temperature. When the base 11 is made of a resin, lead terminals made of copper (Cu), iron (Fe) -nickel (Ni) alloy, etc. are molded and fixed inside the base 11.

  Further, the frame body 12 has a frame shape in which a through hole having an upper opening larger than a lower opening is formed and a reflection surface for reflecting light is provided on the inner peripheral surface 12a. Specifically, it consists of metals such as aluminum (Al) and Fe-Ni-cobalt (Co) alloys, ceramics such as alumina ceramics or resins such as epoxy resins, and molding technologies such as cutting, die molding or extrusion molding. It is formed by.

  Further, the reflecting surface of the frame 12 is coated by polishing or flattening the inner peripheral surface 12a of the through hole, or by depositing a metal such as Al on the inner peripheral surface 12a of the through hole by vapor deposition or plating. It is formed by doing. The frame 12 is formed on the upper surface of the base 11 so that the mounting portion 11a is surrounded by the inner peripheral surface 12a of the frame 12 by a soldering material such as solder, silver (Ag) brazing, or a bonding material such as a resin adhesive. Be joined.

  Then, the wiring conductor arranged around the mounting portion 11a and the light emitting element 15 are electrically connected through the electrode 16 such as a bonding wire or a metal ball, and then an epoxy resin or silicone containing the phosphor 14 is used. A light-transmitting member 13 such as resin is filled into the frame body 12 so as to cover the light-emitting element 15 with an injection machine such as a dispenser, and is thermally cured in an oven. A light-emitting device capable of extracting light having a desired wavelength spectrum after wavelength conversion can be obtained.

  Further, in addition to the structure of the light emitting device shown in FIG. 2, the light emitted from the light emitting element 25 is excited on the upper part of the translucent member 23 provided so as to cover the light emitting element 25 as shown in FIG. A configuration has been proposed in which a phosphor layer 23 containing a phosphor 24 to be converted to the wavelength side in a transparent resin 27 is formed (see Patent Document 1 below).

According to this configuration, the path length through which the light emitted from the light emitting element passes through the phosphor layer 23 can be made nearly constant, so that the wavelength conversion efficiency in the phosphor layer 23 is made uniform and uneven emission is reduced. Can do.
Japanese Patent No. 3052663

  In recent years, light emitting devices have been required to further increase the light emission intensity. However, when the current value is increased in order to increase the light emission intensity, heat generation of the light emitting element is increased, and as a result, the light emitting element is heated to a high temperature.

  Further, in the transparent resin 27 that covers the light-emitting element 25 and contains the phosphor 24 for wavelength-converting light from the light-emitting element 25, an attempt is made to improve the wavelength conversion efficiency by increasing the content of the phosphor 24. Then, since the light is easily disturbed by the phosphor 24, there is a problem that the intensity of the emitted light cannot be improved.

  Conversely, when the content of phosphor 24 is decreased, the proportion of phosphor 24 irradiated with light from light emitting element 25 decreases, the probability that phosphor 24 emits light is significantly deteriorated, and the efficiency of wavelength conversion decreases. As a result, there is a problem that light having a desired wavelength cannot be obtained, and as a result, the intensity of emitted light cannot be improved.

  Further, the difference in light intensity between the central portion and the edge portion of the phosphor layer 27 containing the phosphor 24 is increased, resulting in uneven color on the light emitting surface and uneven illumination distribution on the irradiated surface. .

  Furthermore, light that has not been wavelength-converted is emitted to the outside at the same wavelength, and when the light emitted from the light emitting element 25 is ultraviolet light, there is a problem that the human body may be affected.

  Accordingly, the present invention has been devised in view of such conventional problems, and the object thereof is to efficiently convert the wavelength of the light emitted from the light emitting element by using a phosphor and to increase the intensity of the emitted light. The object is to provide a light emitting device having excellent light characteristics such as brightness, luminance, and color rendering.

  The light emitting device of the present invention includes a base having a mounting portion on which the light emitting element is mounted on the upper main surface, and an outer peripheral portion of the upper main surface of the base that is joined so as to surround the mounting portion. A frame whose peripheral surface is a reflecting surface that reflects light emitted from the light emitting element, one end formed on the upper main surface of the base, and electrically connected to the electrode of the light emitting element A wiring conductor whose end is led out to the outer surface of the base body, a light emitting element placed on the mounting portion and electrically connected to the wiring conductor, and covering the light emitting element inside the frame body A translucent member provided on the phosphor, and a phosphor layer containing a phosphor that converts the wavelength of light of the light-emitting element that covers the translucent member, the translucent member and the translucent member The upper surface of the phosphor layer is a rough surface.

  In the light emitting device of the present invention, it is preferable that arithmetic mean roughness of the upper surfaces of the light transmissive member and the phosphor layer is 0.1 to 0.8 μm, respectively.

  In the light-emitting device of the present invention, the light-transmitting member has a rough upper surface. Therefore, the light emitted from the light-emitting element is scattered by the upper surface of the light-transmitting member and is irradiated with this light. The ratio of the phosphor in the phosphor layer can be increased. As a result, the probability that the phosphor emits light can be remarkably improved, and the output of light converted in wavelength by the phosphor can be improved. Moreover, since the upper surface of the phosphor layer is rough, the light whose wavelength is converted by the phosphor is totally reflected at the interface with the air outside the phosphor layer and is confined in the phosphor layer. The total reflection can be effectively reduced by the rough surface having various angles on the upper surface of the phosphor layer, and the light can be extracted to the outside very efficiently. Furthermore, the light intensity difference between the central portion and the outer peripheral portion of the phosphor layer can be further reduced by appropriately scattering light on the rough surface formed on the upper surface of the translucent member and the upper surface of the phosphor layer. it can. As a result, uneven color on the light emitting surface and uneven illumination distribution on the irradiated surface can be suppressed.

  In the light emitting device according to the present invention, the upper surfaces of the translucent member and the phosphor layer have arithmetic average roughnesses of 0.1 to 0.8 μm, respectively. The light transmitted through the phosphor layer without being wavelength-converted from the light emitting element can be greatly suppressed. Therefore, for example, when the light emitted from the light emitting element is ultraviolet light, the wavelength of ultraviolet light is efficiently converted into visible light, and the ultraviolet light emitted without wavelength conversion is effectively reduced to reduce environmental impact. An excellent light-emitting device can be manufactured. Further, uneven color on the light emitting surface and uneven illumination distribution on the irradiated surface can be further suppressed.

  The light emitting device of the present invention will be described in detail below. FIG. 1 is a cross-sectional view showing an example of an embodiment of a light emitting device of the present invention. In this figure, 1 is a substrate, 2 is a frame, 3 is a translucent member provided so as to cover the light emitting element, and 7 is a phosphor layer containing the phosphor 4 in a transparent resin. A light emitting device capable of emitting light emitted from the light emitting element 5 to the outside with directionality is mainly constituted by these elements.

  The substrate 1 in the present invention is made of alumina ceramic, aluminum nitride sintered body, mullite sintered body, ceramic such as glass ceramic, or resin such as epoxy resin. The base body 1 has a mounting portion 1a for mounting the light emitting element 5 on the upper main surface.

  A wiring conductor (not shown) for electrically connecting the light emitting element 5 is formed on the mounting portion 1a. The wiring conductor is led out to the outer surface of the light emitting device through a wiring layer (not shown) formed inside the base 1 and connected to the external electric circuit board, whereby the light emitting element 5 and the external electric circuit board are connected. Are electrically connected.

  As a method of connecting the light emitting element 5 to the wiring conductor, a method of connecting via wire bonding, or a flip chip bonding method in which the lower surface of the light emitting element 5 shown in FIG. A method or the like is used. Preferably, the connection is made by a flip chip bonding method. Thereby, since the wiring conductor can be provided directly under the light emitting element 5, it is not necessary to provide a space for providing the wiring conductor on the upper surface of the base 1 around the light emitting element 5. Therefore, it is possible to effectively suppress the light emitted from the light emitting element 5 from being absorbed in the space of the wiring conductor of the base 1 and the on-axis luminous intensity from being lowered.

  In this wiring conductor, for example, a metallized layer of a metal powder such as W, Mo, Cu, or Ag is formed on the surface or inside of the base 1 to embed a lead terminal such as an Fe—Ni—Co alloy in the base 1. Or an input / output terminal made of an insulator on which a wiring conductor is formed is fitted and joined to a through-hole provided in the base 1.

  In addition, it is better to deposit a metal with excellent corrosion resistance, such as Ni or gold (Au), with a thickness of about 1 to 20 μm on the exposed surface of the wiring conductor, effectively preventing oxidative corrosion of the wiring conductor. In addition, the connection between the light emitting element 5 and the wiring conductor can be strengthened. Therefore, for example, an Ni plating layer having a thickness of about 1 to 10 μm and an Au plating layer having a thickness of about 0.1 to 3 μm are sequentially deposited on the exposed surface of the wiring conductor by an electrolytic plating method or an electroless plating method. Is more preferable.

  Further, the frame 2 is attached to the upper surface of the base 1 by a bonding material such as solder, a brazing material such as Ag brazing, or an adhesive such as an epoxy resin. The frame body 2 has a through hole formed in the center thereof, and the inner peripheral surface 2a is a reflection surface that reflects light emitted from the light emitting element 5.

  The frame body 2 is formed by performing a cutting process, mold forming, or the like. Alternatively, by forming a highly reflective metal thin film such as Al, Ag, Au, platinum (Pt), titanium (Ti), chromium (Cr), or Cu on the inner peripheral surface 2a by, for example, plating or vapor deposition. A reflective surface may be formed. When the reflecting surface is made of a metal that is easily discolored by oxidation such as Ag or Cu, for example, a Ni plating layer having a thickness of about 1 to 10 μm and an Au plating layer having a thickness of about 0.1 to 3 μm are formed on the surface. It is preferable that the electrodes are sequentially deposited by electrolytic plating or electroless plating. This improves the corrosion resistance of the reflective surface.

  The arithmetic average roughness Ra of the inner peripheral surface 2a of the frame body 2 is preferably 0.1 μm or less, so that the light emitted from the light emitting element 5 is favorably reflected to the upper side of the light emitting device. Can do. When Ra exceeds 0.1 μm, it becomes difficult to favorably reflect the light emitted from the light emitting element 5 to the upper side of the light emitting device on the inner peripheral surface 2a of the frame body 2 and to easily diffuse diffusely inside the light emitting device. . As a result, the loss of light inside the light emitting device tends to be large, and it becomes difficult to emit light outside the light emitting device at a desired radiation angle.

  Furthermore, the inner peripheral surface 2a has, for example, a linear inclined surface as shown in FIG. 1 that spreads outward as it goes upward, and a curved surface that spreads outward as it goes upward. Examples of the shape include an inclined surface.

  Furthermore, the frame body 2 may be attached to any part other than the mounting portion 1a on the upper surface of the base body 1. However, the frame body 2 has a desired surface accuracy around the light emitting element 5, for example, light emission in a longitudinal section of the light emitting device. It is preferable that the inner peripheral surface 2a provided on both sides of the light emitting element 5 is symmetric with the element 5 interposed therebetween. Thereby, the light emitted from the light emitting element 5 through the translucent member 3 in the lateral direction or the light emitted downward from the phosphor 4 can be uniformly and uniformly reflected by the inner peripheral surface 2a. In addition, the light can be uniformly incident on the phosphor layer 7 formed on the upper part of the translucent member 3, and the on-axis luminous intensity, luminance, color rendering, etc. can be effectively improved.

  The translucent member 3 is preferably made of a material having a small refractive index difference from the light emitting element 5 and having a high transmissivity with respect to light in the ultraviolet region to the visible light region. For example, the translucent member 3 is made of a transparent resin such as a silicone resin, an epoxy resin, or a urea resin, low-melting glass, sol-gel glass, or the like. Thereby, it is possible to effectively suppress the occurrence of light reflection loss due to the difference in refractive index between the light emitting element 5 and the translucent member 3, and desired radiation intensity and angular distribution with high efficiency to the outside of the light emitting device. A light emitting device that can emit light can be provided. Moreover, such a translucent member 3 is filled inside the frame body 2 so as to cover the light emitting element 5 with an injection machine such as a dispenser, and is thermally cured in an oven or the like.

  The phosphor layer 7 of the present invention is made of a transparent resin such as an epoxy resin or a silicone resin containing the phosphor 4 capable of converting the wavelength of light from the light emitting element 5. The phosphor layer 7 is filled inside the frame body 2 so as to cover the translucent member 3 with an injection machine such as a dispenser, and is thermally cured in an oven or the like, so that light from the light emitting element 5 is converted into the phosphor 4. The light having a desired wavelength spectrum can be extracted by converting the wavelength.

  Further, the upper surface of the translucent member 3 and the upper surface of the phosphor layer 7 are rough. Thereby, the light emitted from the light emitting element 5 passes through the translucent member 3 and enters the phosphor 4 included in the phosphor layer 7. At that time, since the upper surface of the translucent member 3 is rough, the incident light becomes scattered light, and the ratio of the phosphor 4 irradiated by this light can be increased. Moreover, by scattering light on the upper surface of the translucent member 3, the ratio of hitting the phosphor 4 increases, and light transmitted without wavelength conversion can be suppressed. Therefore, wavelength conversion can be performed with high efficiency, and as a result, the intensity of radiated light after wavelength conversion of the light emitting device can be increased, and optical characteristics such as on-axis luminous intensity and luminance can be improved. Furthermore, by making the upper surface of the phosphor layer 7 rough, it is possible to suppress the total reflection of light converted in wavelength by the phosphor 4 confined inside the phosphor layer 7 at the interface with air. .

  Moreover, the light intensity difference between the central portion and the edge portion of the phosphor layer 7 can be reduced by scattering light on the upper surface of the translucent member 3. As a result, the wavelength of light emitted to the outside can be controlled, and color characteristics such as color rendering can be improved.

The rough surface formed on the upper surface of the translucent member 3 and the upper surface of the phosphor layer 7 is an arithmetic average roughness.
Preferably, the arithmetic average roughness of the upper surface of the translucent member 3 and the upper surface of the phosphor layer 7 is 0.1 to 0.8 μm, respectively. When the thickness exceeds 0.8 μm, light is confined in the gap between the rough surfaces, and the ratio of the light entering the phosphor layer 7 from the translucent member 3 and the ratio of the light emitted from the phosphor layer 7 into the air easily decrease. Therefore, it is difficult to improve the on-axis luminous intensity of the light emitting device. On the other hand, when the thickness is less than 0.1 μm, the ratio of scattered light is likely to be reduced, and it is difficult to improve optical characteristics such as on-axis luminous intensity, luminance, and color rendering.

  The arithmetic average roughness of the upper surface of the translucent member 3 and the upper surface of the phosphor layer 7 may be the same or different. More preferably, the arithmetic average roughness of the rough surface formed on the upper surface of the translucent member 3 should be larger than the arithmetic average roughness of the rough surface formed on the upper surface of the phosphor layer 7. As a result, the scattering effect is increased on the upper surface of the translucent member 3 to improve the wavelength conversion efficiency, and the emission angle is suppressed from increasing on the upper surface of the phosphor layer 7 by making the scattering effect appropriate. It is possible to improve the axial luminous intensity by increasing the directivity of light.

  The phosphor layer 7 is formed of an inorganic or organic phosphor 4 that emits blue, red, green, yellow, or the like by recombination of electrons of the phosphor 4 excited by light emitted from the light emitting element 5. Since it is blended and filled in an arbitrary ratio, it is possible to output light having a desired emission spectrum and color.

  The light emitting element 5 may have any peak wavelength of radiated energy from the ultraviolet range to the infrared range. However, from the viewpoint of emitting white light and light of various colors with good visibility, the light emitting element 5 has a wavelength of about 300 to 500 nm. It is preferable that the element emits light from ultraviolet to blue. For example, a gallium nitride-based compound semiconductor such as GaN, GaAlN, InGaN, or InGaAlN, or a silicon carbide-based compound semiconductor or ZnSe (selenide) in which a buffer layer, an n-type layer, a light-emitting layer, and a p-type layer are sequentially stacked on a sapphire substrate. Zinc) or the like in which the light emitting layer is formed.

  Examples of the light-emitting device of the present invention will be described below with reference to FIG.

  First, an alumina ceramic substrate to be the base 1 was prepared. The substrate 1 has a mounting portion 1a, and the mounting portion 1a on which the light emitting element 5 is mounted is connected to an internal wiring in which the light emitting element 5 and an external electric circuit board are formed inside the substrate 1. Wiring conductors for electrical connection were formed. The wiring conductor is formed into a circular pad having a diameter of 0.1 mm by a metallized layer made of Mo—Mn powder, and a 3 μm thick Ni plating layer and a 2 μm thick Au plating layer are sequentially deposited on the surface. It was. Further, the internal wiring inside the substrate 1 was formed by an electrical connection portion made of a through conductor, so-called through hole. This through hole was also formed with a metallized conductor made of Mo-Mn powder in the same manner as the wiring conductor.

  Further, a metallization layer for bonding for bonding the frame body 2 with Au-tin (Sn) brazing was formed on the outer peripheral portion of the upper surface of the substrate 1. This bonding metallized layer was obtained by depositing a 3 μm thick Ni plating layer and a 2 μm thick Au plating layer on the surface of a metallized layer made of Mo—Mn powder.

  Furthermore, a frame 2 made of aluminum was prepared. The frame body 2 has a through hole having a linear inclined surface in which the longitudinal section shape spreads outward as it goes upward in the longitudinal section as shown in FIG. The surface of the inner peripheral surface 2a of the hole was a reflecting surface with Ra of 0.1 μm.

  Further, the frame body 2 was formed in a columnar shape having an outer diameter of 8 mm and a height of 5 mm, an upper opening having a diameter of 6 mm, and a lower opening having a diameter of 3 mm.

  Next, Au—Sn solder is provided on the wiring conductor on the mounting portion 1 a, and the 0.08 mm thick light emitting element 5 emitting near-ultraviolet light is joined to the wiring conductor through the Au—Sn solder, The frame 2 was bonded to the bonding metallization layer on the upper surface of the substrate 1 with Au—Sn brazing.

  Next, the middle stage of the inner peripheral surface 2a of the frame body 2 in the region surrounded by the base body 1 and the frame body 2 by using a dispenser with silicone resin (translucent member 3) (height from the top surface of the base body 1 is 4 mm) Until filled. And the rough surface whose arithmetic mean roughness is various values was formed by spraying the particle | grains of an alumina on the surface of the translucent member 3, and roughening it (refer Table 1).

  Next, a silicone resin (phosphor layer 7) containing three kinds of phosphors 4 that emit red light, green light, and blue light is removed from the uppermost end of the inner peripheral surface 2a of the frame 2 by about 0.2 mm using a dispenser. The remaining light-transmitting member 3 is filled (the phosphor layer 7 has a thickness of 0.8 mm), and further alumina particles are sprayed to make the surface of the phosphor layer 7 have various rough surfaces (tables). 1), a light emitting device as a sample was manufactured.

For this sample, the on-axis intensity when the light was emitted was measured to compare the emission intensity. The evaluation results are shown in Table 1.

  From the results shown in Table 1, it is possible to make the axis of the light-transmitting member 3 and the phosphor layer 7 rough by comparing the upper surface of the light-transmitting member 3 and the phosphor layer 7 with the rough surface of the sample 1 in which neither of the surfaces is the rough surface. It was found that the luminous intensity was improved (Samples 2 to 6). Furthermore, the arithmetic average roughness of the upper surfaces of the translucent member 3 and the phosphor layer 7 is in the range of 0.1 to 0.8 μm, respectively, and has a strength of 900 mcd or more, and the central portion and the outer peripheral portion of the light emitting device The color unevenness was not observed and was found to be excellent.

  It should be noted that the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present invention. For example, a plurality of light emitting elements 5 may be provided on the substrate 1 in order to improve the emitted light intensity. Further, the angle of the inner peripheral surface 2a and the thickness of the phosphor layer 7 can be arbitrarily adjusted, and a transparent member such as a glass substrate is further provided on the upper surface of the phosphor layer 7 including the phosphor 4. It can also be provided, and this leads to improved reliability because it is protected from the external environment.

It is sectional drawing which shows an example of embodiment of the light-emitting device of this invention. It is sectional drawing which shows the conventional light-emitting device. It is sectional drawing which shows an example of the conventional light-emitting device.

Explanation of symbols

1: Base 1a: Placement part 2: Frame body 2a: Inner peripheral surface 3: Translucent member 4: Phosphor 5: Light emitting element 7: Phosphor layer

Claims (2)

A base having a mounting portion on which the light emitting element is mounted on the upper main surface, and an outer peripheral portion of the upper main surface of the base are joined so as to surround the mounting portion, and an inner peripheral surface is separated from the light emitting element. A frame body that is a reflecting surface for reflecting emitted light, one end is formed on the upper main surface of the substrate, and is electrically connected to the electrode of the light emitting element, and the other end is formed on the outer surface of the substrate. A derived wiring conductor; a light emitting element placed on the mounting portion and electrically connected to the wiring conductor; and a translucent light provided inside the frame so as to cover the light emitting element And a phosphor layer containing a phosphor that converts the wavelength of the light of the light emitting element that covers the light transmissive member, and the light transmissive member and the phosphor layer have upper surfaces thereof. A light emitting device characterized by having a rough surface. 2. The light emitting device according to claim 1, wherein the translucent member and the upper surface of the phosphor layer each have an arithmetic average roughness of 0.1 to 0.8 μm.

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