JP2010027704A - Production method of light-emitting device using phosphor ceramic board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a light-emitting device, which performs color control at a stage before colors are included in a light emitting element, thus producing a light-emitting device with uniform luminescent chromaticity by simple and few production steps. <P>SOLUTION: Provided is the production method of a light-emitting device which has: a semiconductor light-emitting element for emitting an excitation light; and a phosphor ceramic board composed of a fluorescent polycrystalline material, and emitting a light with a wavelength different from that of the excitation light, and which emits light compounded from the excitation light and the light emitted by the phosphor ceramic board. The method includes a step of adjusting the phosphor ceramic used for the light-emitting device by using an interrelationship between a product of the atomic concentration of a dopant contained in the fluorescent material and the thickness of the phosphor ceramic board and the chromaticity of the light emitted by the light-emitting device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a light emitting device combining a semiconductor light emitting element and a phosphor ceramic plate, and more particularly to a method for manufacturing a light emitting device that emits light with uniform chromaticity with good reproducibility.

  As a light emitting device, a white LED combining a blue light emitting diode such as GaN and a wavelength conversion material is widely used. Phosphor particles are generally used as wavelength conversion materials, and those in which phosphor particles are dispersed in a resin have been used, but in recent years, ceramics for polycrystalline phosphors have been developed for use as wavelength conversion materials, It has been proposed (Patent Document 1, Patent Document 2). However, since general phosphor ceramics contain scatterers such as pores and heterogeneous phases in the sintered body, the linear transmission is low, and the scatterers are usually distributed inhomogeneously, so the scattered light is inhomogeneous. There is a problem that color variation is likely to occur.

  Further, since the emission chromaticity of the light emitting device depends on the thickness of the phosphor ceramic plate, it is not easy to perform uniform color management for each individual white LED.

On the other hand, Patent Document 2 discloses a method of adjusting a light emitting device using a light conversion ceramic as a wavelength conversion material to a desired spectrum (chromaticity). In this method, a light conversion ceramic is bonded to an LED die or placed on the die, and light is actually emitted as a device. In this state, it is confirmed whether a desired emission spectrum is obtained. If the thickness is thick, the desired wavelength spectrum is generated by reducing the thickness by laser ablation or etching.
JP 2006-282447 A JP 2007-324608 A

  The above-described color management method requires expensive equipment such as laser ablation, and there is a problem that it takes a lot of labor and cost to adjust devices individually. Therefore, it is desirable to adjust the phosphor ceramic to achieve the desired chromaticity before incorporating the phosphor ceramic into the light emitting device. However, the chromaticity of the light emitting device is a combination of the LED element and the phosphor ceramic. Therefore, it is impossible to manage the color of the phosphor ceramic alone. On the other hand, the amount of ceramic cut by laser ablation of the above-described technique is measured in advance, and the amount of shaving of the phosphor ceramic is set to a predetermined fixed amount for each light emitting element, thereby realizing the phosphor ceramic. It is possible to make the chromaticity constant.

  However, handling when incorporating the phosphor ceramic into the light emitting device, for example, cutting to a predetermined size and placing it on the LED element, prevents cracking or chipping. For this reason, the thickness of the phosphor ceramic is naturally limited by the thickness, and there is a limit to color management only by the amount of shaving of the phosphor ceramic. Moreover, even if the amount of the raw material of the phosphor ceramic is the same, it is difficult to keep the composition constant depending on the purity of the raw material and the manufacturing conditions. In particular, since the dopant concentration that determines the luminescent color is very small, it is difficult to keep it constant, which causes the luminescent color to fluctuate.

  An object of the present invention is to provide a manufacturing method capable of performing color management at a stage before being incorporated into a light emitting element, and capable of manufacturing a light emitting device having uniform emission chromaticity with simple and few manufacturing processes. And

  In order to solve the above problems, the present inventors have found that the chromaticity of light emitted from the phosphor ceramic plate when combined with a semiconductor light emitting element has a good correlation with the product of the dopant concentration and the thickness of the ceramic plate, By utilizing this correlation, it has been found that desired chromaticity can be realized with good reproducibility under conditions where the thickness of the ceramic plate is limited, and the present invention has been achieved.

  That is, the method for manufacturing a light emitting device of the present invention includes a semiconductor light emitting element that emits excitation light, a phosphor ceramic plate that is made of a phosphor polycrystalline material, and emits light having a wavelength different from that of the excitation light emitted from the semiconductor light emitting element. A light emitting device that emits light obtained by synthesizing the excitation light and the light emitted from the phosphor ceramic plate, the atomic concentration of the dopant contained in the phosphor and the thickness of the phosphor ceramic plate And a step of adjusting a phosphor ceramic used in the light emitting device using a relationship between the product of the above and the chromaticity of light emitted from the light emitting device.

  According to the present invention, by using the relationship between the product of the dopant concentration determined in advance and the thickness of the ceramic plate and the emission chromaticity, an expensive device and a light emitting device free from color variations can be obtained without going through complicated processes. It can be manufactured with good reproducibility.

Embodiments of a method for manufacturing a light emitting device according to the present invention will be described below.
The light-emitting device targeted by the present invention is a combination of a light-emitting element and a phosphor ceramic, and light synthesized from light emitted from the LED element and light emitted from the phosphor ceramic determines the chromaticity of the light-emitting device.

  As the light emitting element, a semiconductor light emitting element (LED element) that generates light having a wavelength of 440 to 460 nm is used. Specific examples include semiconductor light emitting devices that emit blue to ultraviolet light, such as gallium nitride compound semiconductor light emitting devices, zinc oxide compound semiconductor light emitting devices, and zinc selenide compound semiconductor light emitting devices.

The phosphor ceramic plate absorbs light emitted from the LED element and generates light having a longer wavelength. Various phosphor ceramics have been proposed and any of them can be employed. For example, a light emitting device that obtains white light in combination with an LED element that emits light having a wavelength of 440 to 460 nm is used. In order to obtain, a YAG phosphor having Ce as a dopant, (Ba, Sr, Ca) ₂ SiO ₄ : Eu, Ca _x (Si, Al) ₁₂ (O, N) ₁₆ : Eu, or the like is used.

  Although the form of the light-emitting device is not particularly limited, as an example, FIGS. 1 and 2 show a light-emitting device (dot matrix light source) including a package obtained by processing a Si wafer by photolithography and etching technology. 1A and 1B are a plan view and a side view of the light emitting device. FIG. 2 is a side view of one dot (light emitting element) constituting the light emitting device.

  The light emitting device 10 includes a substrate 11 on which a large number of through holes 12 are formed, a semiconductor light emitting element (hereinafter referred to as an LED element) 13 bonded to a position corresponding to each through hole 12, and an LED element. A phosphor ceramic plate 14 is provided, and a light emitting element is formed by the individual LED elements 13 and the phosphor ceramic plate 14 placed thereon. Each light emitting element is separated by a mold 15 fixed on the substrate 11. In the illustrated example, a dot matrix light source composed of a large number of light emitting elements arranged in a two-dimensional direction is shown, but it may be arranged in a one-dimensional direction or may be composed of a single light emitting element. .

  As shown in FIG. 2 for example, each light emitting element constituting the light emitting device has a p electrode 131 and an n electrode 132 provided on the LED element 13 through a through hole 12 made of a conductive metal such as copper. A lead (Cu wiring) 111 provided on the back surface of the substrate 11 is connected. By applying a voltage between these electrodes, the LED element 13 emits light of a predetermined wavelength. The mold 15 has, for example, a cylindrical shape, and is joined to the substrate 11 so as to surround the LED element 13. The inner surface of the mold 15 is composed of a reflecting member for reflecting light emitted from the LED element 13, and also serves as a reflecting ring. A step 151 for fixing the phosphor ceramic plate 14 is formed on the inner periphery of the upper end of the mold 15, and a fixing material (for example, an adhesive such as low-melting glass) 152 is formed on the step 151. A phosphor ceramic plate 14 is placed.

  The LED element 13 has a structure in which light is emitted from the electrode side using a transparent electrode and a so-called flip chip type in which light is emitted from the transparent substrate side. A flip chip type having an excellent external take-out effect is particularly preferable.

As described above, the phosphor ceramic plate 14 is a YAG phosphor having Ce as a dopant, (Ba, Sr, Ca) ₂ SiO ₄ : Eu, Ca _x (Si, Al) ₁₂ (O, N) ₁₆ : Eu. It is a ceramic made of polycrystal such as. Since such a phosphor ceramic plate has a small refractive index difference at the grain boundary, light scattering at the grain boundary is substantially eliminated and the transparency is high. Therefore, the light emitted from the LED element 13 and the phosphor can be efficiently extracted outside the light emitting device.

  Next, a method for manufacturing the light emitting device having such a structure will be described. FIG. 3 is a diagram showing an outline of the manufacturing process. The method for manufacturing a light emitting device of the present invention is roughly divided into a step 300 for adjusting a phosphor ceramic plate that achieves a target chromaticity, and a light emitting device is assembled using the phosphor ceramic plate adjusted in step 300. It consists of step 310 and is characterized in that step 300 is provided.

  Before describing the process 300 for adjusting the phosphor ceramic plate, the process 310 will be briefly described first. Here, the step 310 will be described by taking the light emitting device shown in FIG. 1 as an example. However, the step 310 differs depending on the type of the light emitting device, and a known manufacturing method is adopted depending on the type of the light emitting device.

  First, using a Cu wiring embedding technique, the through hole 12 is formed in the Si substrate 11, and the Cu wiring 111 is turned to the back side. Separately, the Si plate is etched by a fine processing technique to form a mold for each dot (light emitting element), and the mold 15 is bonded to the Si substrate 11 in which the through holes 12 are formed. Both can be joined by heating, for example. By using a photolithography technique for forming dots, the dot spacing can be increased to about 100 μm, and crosstalk between adjacent dots can be reliably eliminated by the mold.

  Next, for example, a flip-chip LED element 13 having a p-electrode and an n-electrode formed on one side is bonded with an Au band. On the other hand, after the phosphor ceramic plate adjusted so that the chromaticity is in an appropriate range when combined with the LED element 13 in step 300 is diced in accordance with the size of the mold 15, Place and fix on top.

  The process 300 for adjusting the phosphor ceramic plate will be described. Details of step 300 are shown in FIG. Here, a case where the spectrum of the light emitting device to be achieved is white will be described as an example. In the present embodiment, the target white color is surrounded by four points (0.24, 0.30), (0.31, 0.26), (0.40, 0.44), and (0.34, 0.48) in the CIE1931 chromaticity diagram shown in FIG. Let it be an area (area enclosed by a square in the figure). For reference, a range defined as white in JIS Z8110 as a light source is generally indicated by a region surrounded by a dotted line.

  First, a calibration curve 40 of the product of the thickness of the phosphor ceramic and the dopant concentration ([thickness × concentration]) and chromaticity is prepared. The calibration curve is obtained by preparing various phosphor ceramics having different thicknesses and dopant concentrations, placing these phosphor ceramics on a predetermined LED element, and measuring the chromaticity when the LED element emits light. A calibration curve may be obtained for thickness and chromaticity for each different dopant concentration.

  FIG. 6 shows an example of a calibration curve when YAG using Ce as a light emitting dopant is used. The calibration curve in FIG. 6 is the case where the cerium atom concentration (dopant concentration) with respect to yttrium is varied in the range of 0.05 at% to 0.5 at%, and [thickness (mm) × concentration (at%)]. On the other hand, the x value of CIE chromaticity is plotted. When the x value is in the range of 0.30 to 0.39, the color is almost white. The larger the numerical value, the stronger the yellowness, and the smaller the value, the stronger the blueness. Thus, when the dopant concentration is relatively low, the x value increases with an increase in [thickness × concentration], and it can be seen that there is a correlation between [thickness × concentration] and the x value.

  However, when the dopant concentration is higher than a certain level, the x value becomes substantially constant without depending on the thickness. This is because the wavelength of light emitted from the phosphor ceramic plate becomes dominant because all light emitted from the LED element is absorbed when the dopant concentration is increased. FIG. 7 shows the relationship between [thickness × concentration] and x value when the Ce dopant concentration is 3.0 at%. As can be seen from FIG. 7, when the dopant concentration is high, the chromaticity is substantially constant even if [thickness × concentration] is changed. In this case, the chromaticity cannot be in the white range (x value is 0.40 or less) even if the thickness is reduced to the lower limit for handling the phosphor ceramic.

Therefore, in the first step of the process 300 for preparing the phosphor ceramic plate, a phosphor material having a dopant concentration in a predetermined range is prepared (step 41). For example, a light-emitting device using YAG using Ce as a light-emitting dopant and having a Ce concentration of 1 at% or less is prepared for the purpose of white light emission. By setting the Ce concentration to 1 at% or less, white can be realized within a thickness range that does not hinder handling.
The dopant concentration of the phosphor ceramic is determined by the ratio of raw materials (preparation amount) when the phosphor ceramic is manufactured.

  Next, the thickness of the phosphor ceramic is measured (step 42). A product of the measured thickness and the concentration of the phosphor ceramic is obtained, and using a calibration curve, it is determined whether or not this value is within a range of values that achieve a desired chromaticity (step 43). In the case of the calibration curve shown in FIG. 6, if [thickness (mm) × concentration (at%)] is in the range of 0.02 or more and 0.06 or less, the chromaticity (x value of CIE coordinates) is in the range of 0.31 to 0.39. The target white light emission can be realized.

  If the value obtained in step 23 is within a range where the target chromaticity can be realized, it is used for the device as it is (step 44). If the value obtained in step 43 is outside the range where the target chromaticity can be achieved, it is determined whether the thickness measured in step 42 is equal to or greater than the lower limit (step 45). If there is, it is polished to a predetermined thickness (step 46). The polishing method is performed by a known polishing technique, and polishing is performed until [thickness (mm) × concentration (at%)] is within a range obtained from a calibration curve.

  On the other hand, if the thickness measured in step 42 is thinner than the lower limit value, it is not preferable to make it thinner than that for handling. (Step 47). For the phosphors assigned to step 47, as in the case of the white light emitting device, the processing corresponding to steps 41 to 46 is performed as necessary, and the phosphor ceramic is adjusted to the target light emitting device. .

  If the phosphor ceramic plate to be used for the light emitting device is selected in the above steps 41 to 46, it is cut into a shape suitable for the target light emitting device, and then the target light emission is combined with the LED element by the above-described step 310. Get the device.

  As described above, the light emitting device manufactured according to the present embodiment is adjusted so that the emission color is in the target spectral range when the phosphor ceramic plate 14 is combined with the LED element. A matrix light source can be realized. Further, since it is only necessary to adjust the thickness by a normal polishing technique, the light emitting device can be manufactured by a simple process without requiring expensive equipment.

In the above description, the case where the target light emission chromaticity is white has been described. However, even in cases other than white, the phosphor ceramic can be adjusted in the same manner, so that the desired chromaticity can be adjusted. Thus, a light emitting device with extremely little color variation can be realized. For example, when the target chromaticity is yellow (in the CIE chromaticity diagram shown in FIG. 5, the region surrounded by (0.45,0.55), (0.40,0.50), (0.42,0.40), (0.55,0.45)). Provides a phosphor ceramic plate with a Ce concentration in the range of 1.5 to 3 at% and adjusts the product of the dopant concentration and thickness to be in the range of 0.2 to 2.0 to achieve the desired yellow color. can do.
Further, from the relationship between [thickness × concentration] and x value as shown in FIG. 7, by setting the Ce dopant concentration to 3.0 at% or more, there is no chromaticity change even if the thickness changes, and a very uniform yellow A light emitting device can be realized.

  Examples of the present invention will be described below.

<Example 1>
1. Preparation of phosphor ceramic plate A predetermined ratio of cerium oxide powder, yttrium oxide powder and aluminum oxide powder was weighed, ethanol and an acrylic binder were added thereto, and mixing was performed for 20 hours by a ball mill using nylon balls. A granulated powder having an average particle size of 70 μm was prepared from the obtained slurry using a spray dryer. The granulated powder was uniaxially molded at 20 MPa, and then subjected to 150 MPa cold isostatic pressing (CIP) to obtain a compact, which was degreased at 1000 ° C. in the atmosphere. The degreased body was fired at 1700 ° C. for 3 hours in a vacuum atmosphere (1 × 10 −2 Pa or less) to obtain a sintered body. The sintered body was processed into a double-side polished crystal with a predetermined thickness to obtain a phosphor ceramic having a thickness of 0.1 to 1.0 mm. Four types of phosphor ceramics were produced by changing the weighing ratio of the raw material powders so that the cerium concentrations were 0.05, 0.1, 0.15, and 0.5 at%.

2. Preparation of calibration curve The phosphor ceramic produced as described above was incorporated into a light-emitting device (structure shown in FIG. 2) equipped with a blue LED using a GaN chip, and light was emitted by passing an electric current (350 mA). The total luminous flux at this time was taken in with an integrating sphere, and its chromaticity was measured. The measured chromaticity (x value of CIE coordinates) is plotted against the product ([concentration × thickness]) of the thickness (mm) and cerium concentration (at%) of the phosphor ceramic used, as shown in FIG. A good calibration curve was obtained.

As can be seen from FIG. 6, in the range where the cerium concentration is 0.05 at% to 0.5 at%, a correlation was observed between [concentration × thickness] and the x value of the CIE coordinates.
Therefore, by adjusting the thickness of the plate so as to obtain a desired x value in accordance with the cerium concentration of the produced phosphor ceramic plate, a light emitting device having a desired chromaticity can be manufactured.

3. Production of Light-Emitting Device A white LED light source having the structure shown in FIG. 2 was produced using a phosphor ceramic plate having a cerium concentration of 0.05 at% and a thickness of 0.54 mm. As the blue LED, a GaN-based flip chip type LED element having a peak wavelength of 452 nm was used.
The chromaticity of the produced LED light source was measured. The results are shown in FIG. In FIG. 8, the horizontal axis represents the distance from the center of the LED light source, and the vertical axis represents the CIE x and y values. As can be seen from this result, almost uniform x value (= 0.33) and y value (= 0.38) can be achieved in the plane of the light source.

<Example 2>
1. Production of Phosphor Ceramic Plate A plurality of phosphor ceramics having different thicknesses were produced in the same manner as in Example 1 except that the weighing ratio of the raw material powder was cerium concentration of 3.0 at% (thickness (mm) = 0.1, 0.2, 0.3, 0.35, 0.5, 0.7).

2. Preparation of calibration curve The phosphor ceramic produced as described above was incorporated into a light-emitting device (structure shown in FIG. 2) equipped with a blue LED using a GaN chip, and light was emitted by passing an electric current (350 mA). The total luminous flux at this time was taken in with an integrating sphere, and its chromaticity was measured. The measured chromaticity (x value of CIE coordinates) is plotted against the product ([concentration × thickness]) of the thickness (mm) and cerium concentration (3.0 at%) of the phosphor ceramic used, and is shown in FIG. A calibration curve like this was obtained.
As can be seen from FIG. 7, when the cerium concentration is 3.0 at%, when the value of [concentration × thickness] exceeds 0.5 (that is, the thickness is about 170 μm or more), constant chromaticity is obtained regardless of the thickness.

3. Production of Light-Emitting Device A yellow-orange LED light source having the structure shown in FIG. 2 was produced using a phosphor ceramic plate having a cerium concentration of 3.0 at% and a thickness of 0.2 mm. As the blue LED, a GaN-based flip chip type LED element having a peak wavelength of 452 nm was used.
The chromaticity of the produced LED light source was measured. The results are shown in FIG. In FIG. 9, the horizontal axis represents the distance from the center of the LED light source, and the vertical axis represents the CIE x and y values. As can be seen from this result, almost uniform x value (= 0.47) and y value (= 0.5) could be achieved in the plane of the light source.

  With the manufacturing method of the present invention, the light emitting device is extremely excellent in color uniformity and reproducibility, and has excellent luminous efficiency because it uses a polycrystalline phosphor. This light emitting device can be used as a light source for various lighting devices such as a vehicle lighting device, a liquid crystal display lighting device, an indoor lighting device, and an outdoor lighting device.

The figure which shows an example of the light-emitting device to which this invention is applied The figure which shows an example of the light emitting element of the light-emitting device of FIG. The figure which shows the outline of the manufacturing method of a light-emitting device Diagram showing the procedure for adjusting the phosphor ceramic plate The figure which shows an example of the chromaticity range of a light-emitting device Diagram showing the relationship between the product of dopant concentration and phosphor ceramic plate and chromaticity Diagram showing the relationship between the product of dopant concentration and phosphor ceramic plate and chromaticity The figure which shows chromaticity distribution of the light-emitting device of Example 1. The figure which shows chromaticity distribution of the light-emitting device of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 13 ... LED element, 14 ... Phosphor ceramic board, 15 ... Formwork (reflection ring)

Claims (5)

A semiconductor light-emitting element that emits excitation light; and a phosphor ceramic plate that is made of a phosphor polycrystalline material and emits light having a wavelength different from that of the excitation light emitted from the semiconductor light-emitting element, the excitation light and the phosphor ceramic A method of manufacturing a light emitting device that emits light, which is obtained by combining light emitted by a plate,
Using the relationship between the product of the atomic concentration of the dopant contained in the phosphor and the thickness of the phosphor ceramic plate, and the chromaticity of the light emitted from the light emitting device, the phosphor ceramic used in the light emitting device is The manufacturing method of the light-emitting device characterized by including the process to adjust. A method of manufacturing a light emitting device according to claim 1,
The step of adjusting the phosphor ceramic comprises:
Selecting a phosphor ceramic plate having an atomic concentration of the dopant in a predetermined range;
About the selected phosphor ceramic plate, the product of the atomic concentration of the dopant and the thickness of the phosphor ceramic plate is in a range corresponding to a desired chromaticity from the relationship with the chromaticity. Adjusting the thickness of the phosphor ceramic plate. A method of manufacturing a light emitting device according to claim 1 or 2,
A method for manufacturing a light emitting device, wherein the chromaticity of light emitted from the light emitting device is defined by an x value and a y value of CIE chromaticity coordinates. A method of manufacturing a light emitting device according to any one of claims 1 to 3,
The phosphor ceramic plate is made of a YAG phosphor having Ce as a dopant, and the desired chromaticity is white (x and y values of CIE chromaticity coordinates are (0.24, 0.30), (0.31, 0.26), (A region surrounded by (0.40, 0.44) and (0.34, 0.48)).   A light emitting device manufactured by the manufacturing method according to claim 1.

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