JP2008066365A - Method for forming light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a light emitting device with improved light extraction efficiency by electrophoretic deposition.
The present invention provides a method for forming a light emitting device including a light emitting element and a fluorescent material, wherein the light emitting element is placed in a first solution containing the fluorescent material and a light transmitting material. A first step of disposing, a second step of depositing a fluorescent substance on the light emitting element by electrophoresis in the first solution, and a second solution containing a translucent material as a main material. A third step of arranging the light emitting element on which the fluorescent material is deposited and electrophoresis in the second solution, the translucent material contained in the second solution is added to the deposit of the fluorescent material. And a fourth step of impregnation.
[Selection] Figure 1

Description

  The present invention relates to a light emitting device including a light emitting element and a fluorescent substance that emits light when excited by light from the light emitting element, and a method for forming the same.

  In recent years, a light-emitting device that emits white-color mixed light by combining a light-emitting element chip configured using a gallium nitride-based compound semiconductor and a fluorescent material has been developed. In this light emitting device, a part of blue light output from the light emitting element is wavelength-converted by a fluorescent material, and the wavelength-converted yellow light and blue light from the light emitting element chip are mixed. , White light is emitted.

  For example, a light emitting device described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-88013) includes a phosphor layer formed of a solution of a light-transmitting material including a particulate phosphor. Specifically, a particulate phosphor solution containing a light-transmitting material is dropped on the light-emitting element (potting), and then the light-transmitting material is cured, so that the particulate phosphor is transparent. A phosphor layer formed by fixing the light-sensitive material as a binder is formed. In the phosphor layer arranged in this manner, there may be a cavity in which no particulate phosphor or translucent material exists. Such a cavity attenuates light from the light emitting element or light from the phosphor. Therefore, the light-emitting device is a light-emitting device formed by impregnating substantially the same material as the light-transmitting material in the hollow portions scattered in the phosphor layer. As a result, there are no hollow portions scattered in the phosphor layer, and a light emitting device with improved light extraction efficiency can be obtained without losing light in the phosphor layer.

  Further, in a light emitting device including a light emitting element and a fluorescent material, the fluorescent material is disposed so as to cover the surface of the light emitting element in order to be efficiently excited by light from the light emitting element. Further, in order to allow the mixed color light from the light emitting device to be observed with uniform chromaticity in each direction, the fluorescent material needs to be arranged in the same amount as much as possible in each direction of the light emitting surface of the light emitting element.

  Therefore, the light emitting device disclosed in the following Patent Document 2 (Japanese Patent Laid-Open No. 2003-69086) is substantially uniform in which a fluorescent material is contained on the side of a light-transmitting substrate of a light emitting element flip-chip mounted on a support. It has a phosphor layer with a different thickness. This phosphor layer is formed by depositing a fluorescent substance and a binder for fixing the fluorescent substance on the surface of the light emitting element by electrophoretic deposition. Hereinafter, an outline of a method for forming a phosphor layer disclosed in this patent document will be described.

  First, a conductive film that covers a light-emitting element flip-chip mounted on a support is formed. Note that this conductive film is not necessary when a voltage is applied to the light emitting element itself when the surface of the light emitting element is already conductive. Next, the light-emitting element covered with the conductive film is immersed in an electrolytic solution containing a fluorescent material and a binder (for example, resin) that are charged in advance. Further, a voltage having a polarity different from the charging of the fluorescent material is applied to the conductive film. Accordingly, the fluorescent material and the binder are electrophoresed in the direction of the conductive film and are deposited on the light emitting element. Finally, the fluorescent material and the binder deposited on the light emitting element are dried to form a phosphor layer.

Japanese Patent Application Laid-Open No. 2004-88013.

JP2003-69086A.

  However, the impregnation method described in Japanese Patent Application Laid-Open No. 2004-88013 is based on a method that uses sedimentation and permeation due to the weight of the material to be impregnated, such as potting. Hateful. In particular, the phosphor layer formed by electrophoretic deposition is densely deposited with phosphors having a relatively small particle diameter. According to a conventional method such as potting, the material to be impregnated is the phosphor layer. There is a problem that it is difficult to penetrate to every corner. As a result, a cavity is generated in the phosphor layer, and a light emitting device with reduced light extraction efficiency is formed.

  Therefore, an object of the present invention is to provide a method for forming a light emitting device by electrophoretic deposition without reducing the light extraction efficiency of the light emitting device.

  In order to achieve the above object, a method for forming a light emitting device according to the present invention is a first method in which a fluorescent substance is deposited on the light emitting element by electrophoresis in a first solution containing the fluorescent substance and a translucent material. And the second step of impregnating the fluorescent material deposit with the translucent material contained in the second solution by electrophoresis in a second solution containing the translucent material as a main material. And having.

  The translucent material contained in the first solution or the second solution is a material containing a metal alkoxide containing at least one element selected from Al, Sn, Si, Ti, Y, or Pb. preferable.

  It is preferable that the refractive indexes of the translucent materials respectively contained in the first solution and the second solution are substantially the same.

  It is preferable that the fluorescent substance has an average particle diameter of 1 μm to 10 μm and the translucent material has an average particle diameter of 1 nm to 200 nm.

  It is preferable that the refractive index of the fluorescent material and the refractive index of the translucent material are substantially the same.

  The present invention can easily form a light emitting device with improved light extraction efficiency from a phosphor layer formed by electrophoretic deposition.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the modes described below exemplify a method for forming a light emitting device for embodying the technical idea of the present invention, and the present invention does not limit the method for forming the light emitting device to the following.

  Light extraction efficiency has been improved for a method for forming a light-emitting device including a light-emitting element, a phosphor layer containing a phosphor that emits light having a wavelength different from that of the light-emitting element, and a support on which the light-emitting element is disposed. In order to easily obtain a light emitting device, the present inventors have made various studies. The method for forming a light emitting device according to the present invention includes a step of arranging a light emitting element in a first solution containing a fluorescent substance and a light transmissive material, and electrophoresis in the first solution. A step of depositing a substance on the light emitting element, a step of arranging the light emitting element on which the fluorescent material is deposited in a second solution containing a light-transmitting material as a main material, and an electricity in the second solution. Impregnating the fluorescent substance deposit with the translucent material contained in the second solution by electrophoresis. By impregnation by electrophoresis, a light emitting device with improved light extraction efficiency can be easily formed.

  That is, in the method for forming a light-emitting device according to the present invention, after a fluorescent material is deposited on a light-emitting element together with a light-transmitting material, the light-transmitting material is a main material and the electrolyte solution is substantially free of the fluorescent material. It is a particularly important structure to have a step of impregnating a light-transmitting material with a deposit of a fluorescent substance by electrophoresis in the above. Here, “electrolyte solution substantially free of fluorescent substance” means an electrophoretic deposition of a translucent material contained in the second electrolyte solution in addition to an electrolyte solution prepared without containing a fluorescent substance. The electrolyte solution contains a very small amount of fluorescent material to the extent that it does not affect

  When the surface of the light emitting element on which the fluorescent material is deposited is made of a conductive material, the charged fluorescent substance is electrophoresed and deposited on the light emitting element by applying a voltage to the light emitting element itself. Can be made. In addition, when a fluorescent material is deposited on a non-conductive portion of a light-emitting element in which a semiconductor is stacked on a light-transmitting substrate such as sapphire (for example, the surface of a light-transmitting substrate mounted with flip chip), After the non-conductive portion is covered with the conductive member, a voltage is applied to the conductive member, whereby the charged fluorescent substance can be electrophoresed and deposited on the light emitting element.

  In the method for forming a light-emitting device of this embodiment, when the light-emitting element is covered with a conductive member, it is preferable to include a step of converting a non-light-transmitting conductive member into a light-transmitting member. For example, by containing a material that dissolves the material of the conductive member in the electrolyte solution for electrophoresis deposition, the conductive member is dissolved and ionized, or the conductive member is heated to transmit light of the light emitting element. It is preferable to have the process of making it into the oxide which has property. When the conductive member is translucent, for example, when it is ITO (a composite oxide of indium and tin) which is a kind of translucent conductive member, such a step is not required.

  By including the step of converting the non-light-transmitting conductive member into the light-transmitting member, a light-emitting device without loss of light extraction efficiency due to the non-light-transmitting conductive member can be obtained. In addition, after the electrophoretic deposition step, the conductive member has a significantly reduced conductivity. Therefore, when the light emitting element is driven, a current is not leaked and a highly reliable light emitting device is obtained. Can do.

  Note that the fluorescent material deposited on the conductive member is one that is disposed so as to be irradiated with light from the light emitting element, and is not limited to one that is disposed in direct contact with the surface of the conductive member. It shall include what is arrange | positioned through the other member etc. of translucency between a light emitting element and fluorescent substance. In addition, the fluorescent substance is charged by the process in which the voltage is applied by the fluorescent substance itself or by other chargeable materials contained in the electrolytic solution, such as a polar translucent material. Good.

  FIG. 1 is a schematic cross-sectional view of a light emitting device in this embodiment. The light-emitting device of this embodiment is a light-emitting device 100 including a light-emitting element 107 flip-chip mounted on a support, and a phosphor layer 102 that covers the light-emitting observation surface side of the light-emitting element. Note that the mounting mode of the light-emitting element according to the present embodiment is not limited to flip-chip mounting, but includes a mode in which the electrodes of the light-emitting element are mounted facing the light emission observation surface direction (the side opposite to the support).

  2 to 7 are schematic cross-sectional views showing respective steps in the method for manufacturing the light emitting device of the present embodiment. Hereinafter, a method for manufacturing a light-emitting device according to this embodiment will be described with reference to the drawings. The method for manufacturing a light-emitting device of this embodiment includes at least the following steps 1 to 5. When electrophoretic deposition is used as a method for forming the phosphor layer, a phosphor layer with a favorable phosphor distribution state can be formed around the light emitting element. Furthermore, by the impregnation method in this embodiment, a light-emitting device that does not reduce light extraction efficiency can be easily formed.

  Step 1. First, a first electrolytic solution 101a in which a fluorescent material is contained in a sol solution of an organometallic material is prepared. Thereby, the fluorescent material is charged. Here, the sol of the organometallic material in this embodiment also becomes a binder for the fluorescent substance by drying and gelling after electrophoresis deposition. Therefore, it is not necessary to charge the fluorescent substance in a separate process, and the fluorescent substance can be easily charged with the binder material itself, so that the light emitting device can be manufactured with good workability.

It is preferable that the electrolytic solution of this embodiment includes a substance that dissolves a conductive member described later. In another form, the sol solution itself made of an organic metal may dissolve the conductive member. For example, when the conductive member is made of aluminum, the electrolytic solution of the present embodiment is an sol made of an organic metal as an alumina sol made of an aluminum alcoholate, or an acid or alkali that dissolves aluminum in the electrolytic solution, for example, Nitric acid containing alkaline earth metal ions (such as Mg ²⁺ ) can be included.

  The metal alkoxide suitably used as the translucent material in this embodiment is an organometallic material containing an element selected from Al, Sn, Si, Ti, Y, Pb, or alkaline earth metal as a constituent element. By including such a metal alkoxide in the electrolytic solution, it has a good shape without generating bubbles such as hydrogen gas and without deteriorating optical properties, compared to conventional forming methods in which the electrolytic solution contains moisture. The phosphor layer can be formed. Further, such metal alkoxide is likely to become a sol solution or finally gel by hydrolysis or the like. Therefore, it is possible to easily form a phosphor layer in which the phosphor is fixed by a binder composed of an oxide or hydroxide containing one or more elements selected from the metal group.

  Hereinafter, aluminum alcoholate will be described as an example of a specific material contained in the electrolytic solution. A mixed liquid in which a phosphor is dispersed in an alumina sol obtained by mixing aluminum alcoholate or aluminum alkoxide and an organic solvent in a predetermined ratio is used as an electrolytic solution. Further, the electrolytic solution is preferably a mixed solution containing, for example, acetone as an organic solvent and alumina sol and a fluorescent substance as an organic metal material in a solution containing isopropyl alcohol as a mother liquid.

  Aluminum isopropoxide, aluminum ethoxide, or aluminum butoxide, which is a kind of aluminum alcoholate (or aluminum alkoxide), is a colorless and transparent liquid at room temperature, and produces aluminum hydroxide. Produces aluminum oxide.

  A phosphor can be contained in a sol solution containing aluminum isopropoxide to form an electrolytic solution, and the phosphor can be charged in the electrolytic solution. Furthermore, after electrophoretic deposition in the electrolytic solution, the phosphor can be fixed to the light-emitting element using an aluminum oxide or hydroxide generated by gelation as a binder. This gelation can be promoted by heating and drying.

  Next, a conductive member that covers the light emitting element with a predetermined thickness is formed. Here, the conductive member is provided to cause the charged fluorescent material to be electrophoresed on the light emitting element side. Therefore, the form in which the light emitting element is covered with the conductive member is not limited to the form in which the conductive member is disposed in direct contact with the light emitting element, and other members (for example, for example, between the conductive member and the light emitting element) It is assumed that the conductive member is disposed in the light-emitting element through a light-transmitting resin or glass.

  The thickness of the conductive member is contained in the electrolytic solution so that the conductive member has conductivity from the start to the end of the electrophoretic deposition, and is converted into a translucent member after the electrophoretic deposition step. The amount is determined in consideration of the amount of the substance that dissolves, the voltage in the electrophoresis deposition step, the application time of the voltage, and the like.

  As shown in FIG. 2, the light-emitting element in this embodiment is flip-chip mounted on the support 103 in advance so that the substrate 112 side becomes a light emission observation surface. That is, the light emitting element is welded by applying a load, an ultrasonic wave, and heat so that the electrode faces a conductor wiring provided on the support through a bump 106 made of a metal material such as gold or tin. .

  After the light emitting element is arranged on the support, as shown in FIG. 3, each part around the light emitting element 107 is masked with an insulating member 105 as necessary, such as on the conductor wiring 104 of the support 103. . The material of the insulating member 105 is preferably, for example, an inorganic material made of silicon dioxide, or a resin material such as a silicone resin or an epoxy resin.

  After applying a mask that exposes a predetermined portion where the fluorescent material is disposed, the conductive member 108 covers the side surface and the upper surface of the light emitting element 107 as shown in FIG. As an arrangement method of the conductive member 108 in this embodiment, for example, a vapor deposition method, sputtering, screen printing, inkjet coating, spray coating, or a combination thereof can be given.

  The material of the conductive member is a metal that is soluble in an electrolytic solution and has good contact resistance with the semiconductor material forming the light emitting element, or metal with good adhesion to the semiconductor substrate that forms the light emitting element. It is preferable that As a material of such a conductive member, for example, a metal material or an alloy including at least one selected from Al (aluminum), Ti (titanium), and W (tungsten), which has good contact resistance with a nitride semiconductor, can be given. In this manner, by using a material that can convert light from a light-emitting element into a material having a light-transmitting property, a light-emitting device with high light extraction efficiency can be obtained without loss of light from the light-emitting element. be able to.

  Step 2. A conductive member 108 covering the light emitting element is disposed in the first electrolytic solution 101a. Here, at least the conductive member 108 is sufficient as a member to be disposed in the electrolytic solution. In addition to the conductive member 108, the light emitting element 107 and the support 103 on which the light emitting element 107 is mounted are disposed in the electrolytic solution. May be. In this embodiment, as shown in FIG. 6, the conductive member 108, the light emitting element 107, and the support 103 on which the light emitting element is mounted are immersed in the first electrolytic solution 101a. Note that the conductive member 108 is electrically connected to an external power source.

  Step 3. A voltage having a polarity different from that of charging of the fluorescent material is applied to the conductive member 108. The magnitude of the voltage to be applied and the time for applying the voltage are adjusted in consideration of the thickness of the phosphor layer for obtaining light of desired chromaticity and workability. Through this step, the fluorescent substance is electrophoresed in the first electrolytic solution 101a and deposited on the light emitting element. Further, when the conductive member 108 contains a component that dissolves the conductive member in the electrolytic solution, the conductive member 108 is gradually dissolved by the component.

  Specifically, as shown in FIG. 5, after the light emitting element 107 covered with the conductive member 108 is immersed in the first electrolytic solution 101 a containing a fluorescent material, Apply voltage. Here, it is preferable to apply a voltage to the conductive member 108 electrically connected thereto via a conductor wiring provided on the support. Accordingly, it is possible to easily apply a voltage to the conductive member 108, and the charged fluorescent substance is electrophoresed in the direction of the conductive member 108. The fluorescent material is deposited on the surface of the conductive member 108 together with the metal alkoxide sol.

  Note that an electrode 114 having a polarity different from the voltage applied to the conductive member 108 (that is, the same polarity as the charging of the fluorescent material) is provided above the conductive member 108 in the electrolytic solution 101a or the electrolytic solution 101b. Thereby, the charged fluorescent substance can be electrophoresed.

  Step 4. The second electrolyte solution 101b which contains an organic metal material as a main material and does not substantially contain a fluorescent material is prepared. That is, the second electrolyte solution 101b containing the same organometallic material as the first electrolyte solution 101a is prepared except that the fluorescent material is not contained in the sol solution of the organometallic material. Then, in the same manner as in the above steps 2 to 3, as shown in FIG. 6, electrophoretic deposition in the second electrolytic solution 101b is performed. Note that the voltage applied to the conductive member is different from the charge of the sol particles of the organometallic material. As a result, the material contained in the second electrolytic solution 101b is impregnated into the cavity of the phosphor layer deposited in the third step.

  When the average particle diameter of the fluorescent material is 1 μm to 10 μm, the average particle diameter of the particles made of the translucent material is preferably 1 nm to 200 nm, which is smaller than the average particle diameter of the fluorescent material. Thus, by adjusting the particle size of the light-transmitting material, the light-transmitting material can be easily impregnated into the cavity in the fluorescent substance deposit formed by electrophoresis.

  It is preferable that the refractive indexes of the translucent materials contained in the first electrolytic solution and the second electrolytic solution are substantially the same. Furthermore, it is preferable that the refractive index of the fluorescent material and the refractive index of the translucent material are substantially the same. This is because, by reducing the difference in refractive index between the materials, total reflection can be suppressed and the light extraction efficiency from the phosphor layer can be improved.

  Step 5. After the step 4, the light emitting element is taken out from the second electrolytic solution, and the conductive member covering the light emitting element or the deposit on the conductive member is naturally dried or heated. By heating under conditions containing high-temperature water vapor, conversion of the conductive member remaining after electrophoresis deposition to a light-transmitting member can be promoted. Further, by removing excess solvent contained in the deposit and promoting gelation of the sol solution, the phosphor is bound, and a phosphor layer can be formed on the light emitting element. Note that after this step, the conductive member may remain to some extent in such a distribution state or film thickness as long as the light of the light emitting element is transmitted.

  When the method for forming a light-emitting device according to this embodiment includes a step of converting a conductive member into a light-transmitting member, a change in the concentration of a substance in which the conductive member is made transparent in the thickness direction of the phosphor layer A region is formed. For example, if hydrochloric acid is contained in the electrolytic solution and the material of the conductive member is aluminum, a concentration change region of a component (for example, aluminum ions) in which aluminum is dissolved by hydrochloric acid is formed.

  As described above, the concentration changing region containing the translucent member of the conductive member has a concentration distribution in which the concentration is high on the light emitting element side and gradually decreases as the distance from the light emitting element increases. In addition, GDS (glow discharge emission spectroscopic analysis), SIMS (secondary ion mass spectrometry), etc. are employable as an analysis method of the density distribution in a density | concentration change area | region. Hereinafter, each structure of this form is explained in full detail.

(Light emitting element)
An LED chip will be described as a light emitting element in this embodiment. Examples of the light-emitting element that constitutes the LED chip include semiconductor light-emitting elements formed of various semiconductors such as ZnSe and GaN. When a fluorescent substance is used, a short wavelength that can efficiently excite the fluorescent substance. There can emit light nitride semiconductor _{(in X Al Y Ga 1-} X-Y N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) is preferably exemplified. Various emission wavelengths can be selected depending on the semiconductor material and the degree of mixed crystal.

  Such an LED chip is formed by stacking a semiconductor material on a substrate. For example, an insulating substrate such as sapphire or spinel, or a conductive substrate such as GaN, SiC, Si, or ZnO is preferably used as the material for the substrate on which the nitride semiconductor is stacked. Since nitride semiconductors can be stacked with good crystallinity, a sapphire substrate is preferably used as an insulating substrate for stacking nitride semiconductors. The formation method according to this embodiment is also preferably used for a light-emitting element having such an insulating substrate. Further, a metal material having good adhesion to the substrate is selected as the conductive member according to this embodiment. For example, aluminum is selected as the conductive member for the sapphire substrate.

  The light-emitting element according to this embodiment may be a light-emitting element in which a nitride semiconductor is bonded to a conductive supporting substrate containing copper and tungsten, in addition to the above-described light-emitting element in which a semiconductor is stacked over a substrate. it can.

  The side surface of the substrate of the light emitting element may be inclined in consideration of the light extraction efficiency of the light emitting element. Compared with other forming methods such as potting and printing, the phosphor layer can be formed with a uniform film thickness on such an inclined surface by the forming method by electrophoretic deposition. About the light emitting element having such an inclined surface, the light emitting element in this embodiment is arranged so that the inclined surface faces upward with respect to the support, that is, the opposite side of the light emitting element mounting surface of the support. It is preferred that Accordingly, since the conductive member disposed on the inclined surface is directed toward the electrode 114, the electrophoresis of the fluorescent material in the side surface direction of the light emitting element is more efficient than the light emitting element whose side surface is not inclined. Done.

(Support)
The support body 103 (hereinafter referred to as “submount”) in this embodiment is provided with a conductor wiring 104 on at least a surface facing the electrode of the light-emitting element, and the light-emitting element 107 that is flip-chip mounted is provided. It is a member for holding.

The material of the support is preferably AlN, Al ₂ O ₃ , SiC, GaAs, BN, C (diamond) or the like. More preferably, aluminum nitride (AlN) is selected for a light-emitting element having a thermal expansion coefficient substantially equal to that of the light-emitting element 107, for example, a light-emitting element made of a nitride-based semiconductor. Thereby, the influence of the thermal stress which generate | occur | produces between a support body and a light emitting element can be relieve | moderated.

  The light emitting element 107 is flip-chip mounted on the submount 103. That is, after the bump 106 is disposed on the conductor wiring 104 of the submount 103, the pair of positive and negative electrodes 109 and 110 of the light emitting element 107 are opposed to the conductor wiring 104 through the bump 106. Next, the light emitting element 107 and the submount 103 are electrically and mechanically connected by applying ultrasonic waves, heat, and a load.

(Phosphor layer)
The phosphor layer 102 in this embodiment is a member that contains a fluorescent material 101 that emits light having different wavelengths by absorbing at least part of light from the light emitting element. The phosphor layer can be disposed on an optical element such as a lens, or can be disposed on the tip of an optical fiber. Such a phosphor layer 102 is formed of a fluorescent material and a binding material for fixing the fluorescent material. In particular, the binder in this embodiment can be a gelled product of a metal alkoxide sol solution. In order to strengthen the fixation of the phosphor layer to the light emitting element or to protect it from the external environment, the phosphor layer formed by electrophoretic deposition is made of a translucent resin such as epoxy resin or silicone resin, glass, etc. It is preferable to coat with other translucent members.

  The fluorescent substance of this embodiment converts light from the light emitting element, and it is more efficient to convert light from the light emitting element to a longer wavelength. When the light from the light-emitting element is high-energy short-wavelength visible light, an yttrium-aluminum-garnet-based phosphor (YAG: Ce) activated by cerium, which is a kind of aluminum oxide-based phosphor, is preferably used. It is done. Particularly, the YAG: Ce phosphor absorbs part of the blue light from the LED chip depending on its content and emits a yellow light that is a complementary color. Therefore, a high-power light emitting diode that emits a white light mixture Can be formed relatively easily.

  It is preferable that the phosphor in the forming method of the present embodiment has a shape and size that facilitates electrophoresis in the electrolytic solution. In particular, for electrophoresis in an electrolytic solution, it is preferable that the phosphor has a substantially spherical particle shape.

  In addition, the particle size of the phosphor in the present specification is a value obtained by a volume-based particle size distribution curve, and the volume-based particle size distribution curve can be obtained by measuring the particle size distribution of the phosphor by a laser diffraction / scattering method. Is. Specifically, in an environment where the temperature is 25 ° C. and the humidity is 70%, the phosphor is dispersed in an aqueous solution of sodium hexametaphosphate having a concentration of 0.05%, and a laser diffraction particle size distribution analyzer (SALD-2000A) It was obtained by measuring in a particle size range of 0.03 μm to 700 μm.

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

  FIG. 1 is a schematic cross-sectional view of a light emitting device 100 according to this embodiment. The light-emitting device 100 of this embodiment includes a light-emitting element 107 formed using a gallium nitride-based semiconductor, a phosphor layer 102 containing an yttrium / aluminum / garnet-based phosphor, and a light-transmitting material that covers the phosphor layer 102. And a light emitting device provided with the conductive member 113. 2 to 7 are schematic cross-sectional views showing each step in the method for manufacturing the light emitting device of this example. Hereinafter, a method for forming the light emitting device of this example will be described.

  The light emitting element of this embodiment is an LED chip 107 formed by stacking a gallium nitride based semiconductor on a sapphire substrate which is an insulating translucent substrate 112. First, as shown in FIG. 2, the LED chip 107 is flip-chip mounted on the submount 103. That is, the positive electrode 109 and the negative electrode 110 of the light emitting element 107 are joined to the conductor wiring 104 provided on the submount 103 by Au bumps 106, respectively. In the LED chip 107 of this embodiment, a plurality of LED chips are mounted on the same submount substrate. A gap formed between the light emitting element and the support is filled with a silicone resin. In this manner, it is possible to insulate from a conductive film described later by filling a gap generated between the light emitting element and the support.

  As shown in FIG. 4, in order to form the conductive member 108 that covers the LED chip 107, sputtering using aluminum as a material is performed. In this embodiment, an Al conductive film having a thickness of 500 to 2000 mm is formed so as to cover the surface of the sapphire substrate 112 of the LED chip 107 and the exposed portion on the side surface of the semiconductor. The conductive film is also formed on the submount 103, and the conductive film on the submount 103 is electrically connected to the conductive film that covers the LED chip 107.

  The first electrolytic solution 101a of this example is composed of alumina sol (1% by weight) made of aluminum alcoholate, isopropyl alcohol (93% by weight) as an organic solvent, and magnesium nitrate (1% by weight) as a charging agent. And yttrium / aluminum / garnet phosphor (5% by weight) as a fluorescent substance. The yttrium / aluminum / garnet phosphor in this example has an average particle diameter of 3 μm and a refractive index of 1.8.

  As shown in FIG. 5, a phosphor substrate is mounted on the LED chip 107 by disposing a submount substrate on which the LED chip is mounted in the first electrolyte solution 101 a and applying a voltage to the conductive member 108. Is electrophoretically deposited. The applied voltage is 100 V, and the electrophoresis time is 1 minute. As a result, a phosphor layer having a thickness of about 20 μm is obtained on the light emitting element.

  The second electrolytic solution 101b of this example is composed of alumina sol (3% by weight) made of aluminum alcoholate, isopropyl alcohol (96% by weight) as an organic solvent, and magnesium nitrate (1% by weight) as a charging agent. , Is contained. The alumina sol in this example has an average particle diameter of 2 to 20 nm and a refractive index of 1.8.

  As shown in FIG. 6, an alumina sol is electrophoretically deposited by disposing a submount in which a phosphor is deposited on the LED chip 107 and applying a voltage to the conductive member 108 in the second electrolyte solution 101b. Let The applied voltage is 100 V, and the electrophoresis time is 1 minute. Thereby, the phosphor layer is impregnated with the alumina sol, and the gap in the phosphor layer is filled.

  The substrate of the submount is taken out from the second electrolytic solution 101b, and the Al conductive film is made translucent under high temperature water vapor. That is, by leaving the Al conductive film for 12 hours under the conditions of 120 ° C. and 85% humidity in the reaction furnace, the aluminum of the non-light-transmitting Al conductive film is oxidized as a light-transmitting oxide. Convert to aluminum.

  As shown in FIG. 7, the phosphor layer 102 is covered with a translucent member 113 made of a silicone resin (refractive index 1.5). Note that when a silicone resin is disposed on the phosphor layer 102, a part of the silicone resin may be impregnated into a part of the phosphor layer 102. Here, comparing the refractive indexes of the silicone resin and the alumina sol, the refractive index difference with respect to the yttrium / aluminum / garnet phosphor is smaller in the alumina sol than in the silicone resin. Therefore, the light emitting device of this embodiment can be a light emitting device with higher light extraction efficiency than the light emitting device formed by impregnating the phosphor layer with a silicone resin instead of alumina sol.

  Finally, the substrate of the submount is divided into a desired size and separated into individual pieces, whereby the light emitting device 100 shown in FIG. 1 can be obtained. By mounting and dividing a plurality of light emitting elements on the same submount substrate, a large number of light emitting devices having substantially the same phosphor layer can be formed at a time.

  According to this embodiment, a light emitting device can be formed using electrophoretic deposition without causing a decrease in light extraction efficiency.

  The formation method according to the present invention can be used as a formation method of various light sources such as a signal, illumination, a display, an indicator, and a backlight of a mobile phone.

FIG. 1 is a schematic cross-sectional view of a light emitting device according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a method for forming a light emitting device according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a method for forming a light emitting device according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view illustrating a method for forming a light emitting device according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view illustrating a method for forming a light emitting device according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating a method for forming a light emitting device according to an embodiment of the present invention. FIG. 7 is a schematic cross-sectional view illustrating a method for forming a light emitting device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Light-emitting device 101a ... 1st electrolyte solution 101b ... 2nd electrolyte solution 102 ... Phosphor layer 103 ... Support body 104 ... Conductor wiring 105 ... Insulating member 106 ... Bump 107 ... Light emitting element 108 ... Conductive member 109 ... Positive electrode 110 ... Negative electrode 112 ... Translucent substrate 113 ... Translucent member 114 ... Electrode

Claims (5)

A method for forming a light emitting device comprising a light emitting element and a fluorescent material,
A first step of depositing the fluorescent substance on the light emitting element by electrophoresis in a first solution containing the fluorescent substance and a translucent material;
A second step of impregnating the fluorescent material deposit with the translucent material contained in the second solution by electrophoresis in the second solution containing the translucent material as a main material. A method for forming a light-emitting device.   The translucent material contained in said 1st solution or said 2nd solution contains the metal alkoxide containing at least 1 type of element selected from Al, Sn, Si, Ti, Y, or Pb. Method for forming the light emitting device.   3. The method for forming a light emitting device according to claim 1, wherein refractive indexes of the translucent materials contained in the first solution and the second solution are substantially the same.   4. The method for forming a light emitting device according to claim 1, wherein the fluorescent substance has an average particle diameter of 1 μm to 10 μm, and the translucent material has an average particle diameter of 1 nm to 200 nm.   The method for forming a light-emitting device according to claim 1, wherein a refractive index of the fluorescent material and a refractive index of the light-transmitting material are substantially the same.

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